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diff --git a/docs/LangRef.html b/docs/LangRef.html deleted file mode 100644 index b4782c273d..0000000000 --- a/docs/LangRef.html +++ /dev/null @@ -1,9099 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" - "http://www.w3.org/TR/html4/strict.dtd"> -<html> -<head> - <title>LLVM Assembly Language Reference Manual</title> - <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> - <meta name="author" content="Chris Lattner"> - <meta name="description" - content="LLVM Assembly Language Reference Manual."> - <link rel="stylesheet" href="_static/llvm.css" type="text/css"> -</head> - -<body> - -<h1>LLVM Language Reference Manual</h1> -<ol> - <li><a href="#abstract">Abstract</a></li> - <li><a href="#introduction">Introduction</a></li> - <li><a href="#identifiers">Identifiers</a></li> - <li><a href="#highlevel">High Level Structure</a> - <ol> - <li><a href="#modulestructure">Module Structure</a></li> - <li><a href="#linkage">Linkage Types</a> - <ol> - <li><a href="#linkage_private">'<tt>private</tt>' Linkage</a></li> - <li><a href="#linkage_linker_private">'<tt>linker_private</tt>' Linkage</a></li> - <li><a href="#linkage_linker_private_weak">'<tt>linker_private_weak</tt>' Linkage</a></li> - <li><a href="#linkage_internal">'<tt>internal</tt>' Linkage</a></li> - <li><a href="#linkage_available_externally">'<tt>available_externally</tt>' Linkage</a></li> - <li><a href="#linkage_linkonce">'<tt>linkonce</tt>' Linkage</a></li> - <li><a href="#linkage_common">'<tt>common</tt>' Linkage</a></li> - <li><a href="#linkage_weak">'<tt>weak</tt>' Linkage</a></li> - <li><a href="#linkage_appending">'<tt>appending</tt>' Linkage</a></li> - <li><a href="#linkage_externweak">'<tt>extern_weak</tt>' Linkage</a></li> - <li><a href="#linkage_linkonce_odr">'<tt>linkonce_odr</tt>' Linkage</a></li> - <li><a href="#linkage_linkonce_odr_auto_hide">'<tt>linkonce_odr_auto_hide</tt>' Linkage</a></li> - <li><a href="#linkage_weak">'<tt>weak_odr</tt>' Linkage</a></li> - <li><a href="#linkage_external">'<tt>external</tt>' Linkage</a></li> - <li><a href="#linkage_dllimport">'<tt>dllimport</tt>' Linkage</a></li> - <li><a href="#linkage_dllexport">'<tt>dllexport</tt>' Linkage</a></li> - </ol> - </li> - <li><a href="#callingconv">Calling Conventions</a></li> - <li><a href="#namedtypes">Named Types</a></li> - <li><a href="#globalvars">Global Variables</a></li> - <li><a href="#functionstructure">Functions</a></li> - <li><a href="#aliasstructure">Aliases</a></li> - <li><a href="#namedmetadatastructure">Named Metadata</a></li> - <li><a href="#paramattrs">Parameter Attributes</a></li> - <li><a href="#fnattrs">Function Attributes</a></li> - <li><a href="#gc">Garbage Collector Names</a></li> - <li><a href="#moduleasm">Module-Level Inline Assembly</a></li> - <li><a href="#datalayout">Data Layout</a></li> - <li><a href="#pointeraliasing">Pointer Aliasing Rules</a></li> - <li><a href="#volatile">Volatile Memory Accesses</a></li> - <li><a href="#memmodel">Memory Model for Concurrent Operations</a></li> - <li><a href="#ordering">Atomic Memory Ordering Constraints</a></li> - <li><a href="#fastmath">Fast-Math Flags</a></li> - </ol> - </li> - <li><a href="#typesystem">Type System</a> - <ol> - <li><a href="#t_classifications">Type Classifications</a></li> - <li><a href="#t_primitive">Primitive Types</a> - <ol> - <li><a href="#t_integer">Integer Type</a></li> - <li><a href="#t_floating">Floating Point Types</a></li> - <li><a href="#t_x86mmx">X86mmx Type</a></li> - <li><a href="#t_void">Void Type</a></li> - <li><a href="#t_label">Label Type</a></li> - <li><a href="#t_metadata">Metadata Type</a></li> - </ol> - </li> - <li><a href="#t_derived">Derived Types</a> - <ol> - <li><a href="#t_aggregate">Aggregate Types</a> - <ol> - <li><a href="#t_array">Array Type</a></li> - <li><a href="#t_struct">Structure Type</a></li> - <li><a href="#t_opaque">Opaque Structure Types</a></li> - <li><a href="#t_vector">Vector Type</a></li> - </ol> - </li> - <li><a href="#t_function">Function Type</a></li> - <li><a href="#t_pointer">Pointer Type</a></li> - </ol> - </li> - </ol> - </li> - <li><a href="#constants">Constants</a> - <ol> - <li><a href="#simpleconstants">Simple Constants</a></li> - <li><a href="#complexconstants">Complex Constants</a></li> - <li><a href="#globalconstants">Global Variable and Function Addresses</a></li> - <li><a href="#undefvalues">Undefined Values</a></li> - <li><a href="#poisonvalues">Poison Values</a></li> - <li><a href="#blockaddress">Addresses of Basic Blocks</a></li> - <li><a href="#constantexprs">Constant Expressions</a></li> - </ol> - </li> - <li><a href="#othervalues">Other Values</a> - <ol> - <li><a href="#inlineasm">Inline Assembler Expressions</a></li> - <li><a href="#metadata">Metadata Nodes and Metadata Strings</a> - <ol> - <li><a href="#tbaa">'<tt>tbaa</tt>' Metadata</a></li> - <li><a href="#tbaa.struct">'<tt>tbaa.struct</tt>' Metadata</a></li> - <li><a href="#fpmath">'<tt>fpmath</tt>' Metadata</a></li> - <li><a href="#range">'<tt>range</tt>' Metadata</a></li> - </ol> - </li> - </ol> - </li> - <li><a href="#module_flags">Module Flags Metadata</a> - <ol> - <li><a href="#objc_gc_flags">Objective-C Garbage Collection Module Flags Metadata</a></li> - </ol> - </li> - <li><a href="#intrinsic_globals">Intrinsic Global Variables</a> - <ol> - <li><a href="#intg_used">The '<tt>llvm.used</tt>' Global Variable</a></li> - <li><a href="#intg_compiler_used">The '<tt>llvm.compiler.used</tt>' - Global Variable</a></li> - <li><a href="#intg_global_ctors">The '<tt>llvm.global_ctors</tt>' - Global Variable</a></li> - <li><a href="#intg_global_dtors">The '<tt>llvm.global_dtors</tt>' - Global Variable</a></li> - </ol> - </li> - <li><a href="#instref">Instruction Reference</a> - <ol> - <li><a href="#terminators">Terminator Instructions</a> - <ol> - <li><a href="#i_ret">'<tt>ret</tt>' Instruction</a></li> - <li><a href="#i_br">'<tt>br</tt>' Instruction</a></li> - <li><a href="#i_switch">'<tt>switch</tt>' Instruction</a></li> - <li><a href="#i_indirectbr">'<tt>indirectbr</tt>' Instruction</a></li> - <li><a href="#i_invoke">'<tt>invoke</tt>' Instruction</a></li> - <li><a href="#i_resume">'<tt>resume</tt>' Instruction</a></li> - <li><a href="#i_unreachable">'<tt>unreachable</tt>' Instruction</a></li> - </ol> - </li> - <li><a href="#binaryops">Binary Operations</a> - <ol> - <li><a href="#i_add">'<tt>add</tt>' Instruction</a></li> - <li><a href="#i_fadd">'<tt>fadd</tt>' Instruction</a></li> - <li><a href="#i_sub">'<tt>sub</tt>' Instruction</a></li> - <li><a href="#i_fsub">'<tt>fsub</tt>' Instruction</a></li> - <li><a href="#i_mul">'<tt>mul</tt>' Instruction</a></li> - <li><a href="#i_fmul">'<tt>fmul</tt>' Instruction</a></li> - <li><a href="#i_udiv">'<tt>udiv</tt>' Instruction</a></li> - <li><a href="#i_sdiv">'<tt>sdiv</tt>' Instruction</a></li> - <li><a href="#i_fdiv">'<tt>fdiv</tt>' Instruction</a></li> - <li><a href="#i_urem">'<tt>urem</tt>' Instruction</a></li> - <li><a href="#i_srem">'<tt>srem</tt>' Instruction</a></li> - <li><a href="#i_frem">'<tt>frem</tt>' Instruction</a></li> - </ol> - </li> - <li><a href="#bitwiseops">Bitwise Binary Operations</a> - <ol> - <li><a href="#i_shl">'<tt>shl</tt>' Instruction</a></li> - <li><a href="#i_lshr">'<tt>lshr</tt>' Instruction</a></li> - <li><a href="#i_ashr">'<tt>ashr</tt>' Instruction</a></li> - <li><a href="#i_and">'<tt>and</tt>' Instruction</a></li> - <li><a href="#i_or">'<tt>or</tt>' Instruction</a></li> - <li><a href="#i_xor">'<tt>xor</tt>' Instruction</a></li> - </ol> - </li> - <li><a href="#vectorops">Vector Operations</a> - <ol> - <li><a href="#i_extractelement">'<tt>extractelement</tt>' Instruction</a></li> - <li><a href="#i_insertelement">'<tt>insertelement</tt>' Instruction</a></li> - <li><a href="#i_shufflevector">'<tt>shufflevector</tt>' Instruction</a></li> - </ol> - </li> - <li><a href="#aggregateops">Aggregate Operations</a> - <ol> - <li><a href="#i_extractvalue">'<tt>extractvalue</tt>' Instruction</a></li> - <li><a href="#i_insertvalue">'<tt>insertvalue</tt>' Instruction</a></li> - </ol> - </li> - <li><a href="#memoryops">Memory Access and Addressing Operations</a> - <ol> - <li><a href="#i_alloca">'<tt>alloca</tt>' Instruction</a></li> - <li><a href="#i_load">'<tt>load</tt>' Instruction</a></li> - <li><a href="#i_store">'<tt>store</tt>' Instruction</a></li> - <li><a href="#i_fence">'<tt>fence</tt>' Instruction</a></li> - <li><a href="#i_cmpxchg">'<tt>cmpxchg</tt>' Instruction</a></li> - <li><a href="#i_atomicrmw">'<tt>atomicrmw</tt>' Instruction</a></li> - <li><a href="#i_getelementptr">'<tt>getelementptr</tt>' Instruction</a></li> - </ol> - </li> - <li><a href="#convertops">Conversion Operations</a> - <ol> - <li><a href="#i_trunc">'<tt>trunc .. to</tt>' Instruction</a></li> - <li><a href="#i_zext">'<tt>zext .. to</tt>' Instruction</a></li> - <li><a href="#i_sext">'<tt>sext .. to</tt>' Instruction</a></li> - <li><a href="#i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a></li> - <li><a href="#i_fpext">'<tt>fpext .. to</tt>' Instruction</a></li> - <li><a href="#i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a></li> - <li><a href="#i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a></li> - <li><a href="#i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a></li> - <li><a href="#i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a></li> - <li><a href="#i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a></li> - <li><a href="#i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a></li> - <li><a href="#i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a></li> - </ol> - </li> - <li><a href="#otherops">Other Operations</a> - <ol> - <li><a href="#i_icmp">'<tt>icmp</tt>' Instruction</a></li> - <li><a href="#i_fcmp">'<tt>fcmp</tt>' Instruction</a></li> - <li><a href="#i_phi">'<tt>phi</tt>' Instruction</a></li> - <li><a href="#i_select">'<tt>select</tt>' Instruction</a></li> - <li><a href="#i_call">'<tt>call</tt>' Instruction</a></li> - <li><a href="#i_va_arg">'<tt>va_arg</tt>' Instruction</a></li> - <li><a href="#i_landingpad">'<tt>landingpad</tt>' Instruction</a></li> - </ol> - </li> - </ol> - </li> - <li><a href="#intrinsics">Intrinsic Functions</a> - <ol> - <li><a href="#int_varargs">Variable Argument Handling Intrinsics</a> - <ol> - <li><a href="#int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a></li> - <li><a href="#int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a></li> - <li><a href="#int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_gc">Accurate Garbage Collection Intrinsics</a> - <ol> - <li><a href="#int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a></li> - <li><a href="#int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a></li> - <li><a href="#int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_codegen">Code Generator Intrinsics</a> - <ol> - <li><a href="#int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a></li> - <li><a href="#int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a></li> - <li><a href="#int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a></li> - <li><a href="#int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a></li> - <li><a href="#int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a></li> - <li><a href="#int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a></li> - <li><a href="#int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_libc">Standard C Library Intrinsics</a> - <ol> - <li><a href="#int_memcpy">'<tt>llvm.memcpy.*</tt>' Intrinsic</a></li> - <li><a href="#int_memmove">'<tt>llvm.memmove.*</tt>' Intrinsic</a></li> - <li><a href="#int_memset">'<tt>llvm.memset.*</tt>' Intrinsic</a></li> - <li><a href="#int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a></li> - <li><a href="#int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a></li> - <li><a href="#int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a></li> - <li><a href="#int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a></li> - <li><a href="#int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a></li> - <li><a href="#int_exp">'<tt>llvm.exp.*</tt>' Intrinsic</a></li> - <li><a href="#int_exp2">'<tt>llvm.exp2.*</tt>' Intrinsic</a></li> - <li><a href="#int_log">'<tt>llvm.log.*</tt>' Intrinsic</a></li> - <li><a href="#int_log10">'<tt>llvm.log10.*</tt>' Intrinsic</a></li> - <li><a href="#int_log2">'<tt>llvm.log2.*</tt>' Intrinsic</a></li> - <li><a href="#int_fma">'<tt>llvm.fma.*</tt>' Intrinsic</a></li> - <li><a href="#int_fabs">'<tt>llvm.fabs.*</tt>' Intrinsic</a></li> - <li><a href="#int_floor">'<tt>llvm.floor.*</tt>' Intrinsic</a></li> - <li><a href="#int_ceil">'<tt>llvm.ceil.*</tt>' Intrinsic</a></li> - <li><a href="#int_trunc">'<tt>llvm.trunc.*</tt>' Intrinsic</a></li> - <li><a href="#int_rint">'<tt>llvm.rint.*</tt>' Intrinsic</a></li> - <li><a href="#int_nearbyint">'<tt>llvm.nearbyint.*</tt>' Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_manip">Bit Manipulation Intrinsics</a> - <ol> - <li><a href="#int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a></li> - <li><a href="#int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic </a></li> - <li><a href="#int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic </a></li> - <li><a href="#int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic </a></li> - </ol> - </li> - <li><a href="#int_overflow">Arithmetic with Overflow Intrinsics</a> - <ol> - <li><a href="#int_sadd_overflow">'<tt>llvm.sadd.with.overflow.*</tt> Intrinsics</a></li> - <li><a href="#int_uadd_overflow">'<tt>llvm.uadd.with.overflow.*</tt> Intrinsics</a></li> - <li><a href="#int_ssub_overflow">'<tt>llvm.ssub.with.overflow.*</tt> Intrinsics</a></li> - <li><a href="#int_usub_overflow">'<tt>llvm.usub.with.overflow.*</tt> Intrinsics</a></li> - <li><a href="#int_smul_overflow">'<tt>llvm.smul.with.overflow.*</tt> Intrinsics</a></li> - <li><a href="#int_umul_overflow">'<tt>llvm.umul.with.overflow.*</tt> Intrinsics</a></li> - </ol> - </li> - <li><a href="#spec_arithmetic">Specialised Arithmetic Intrinsics</a> - <ol> - <li><a href="#fmuladd">'<tt>llvm.fmuladd</tt> Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_fp16">Half Precision Floating Point Intrinsics</a> - <ol> - <li><a href="#int_convert_to_fp16">'<tt>llvm.convert.to.fp16</tt>' Intrinsic</a></li> - <li><a href="#int_convert_from_fp16">'<tt>llvm.convert.from.fp16</tt>' Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_debugger">Debugger intrinsics</a></li> - <li><a href="#int_eh">Exception Handling intrinsics</a></li> - <li><a href="#int_trampoline">Trampoline Intrinsics</a> - <ol> - <li><a href="#int_it">'<tt>llvm.init.trampoline</tt>' Intrinsic</a></li> - <li><a href="#int_at">'<tt>llvm.adjust.trampoline</tt>' Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_memorymarkers">Memory Use Markers</a> - <ol> - <li><a href="#int_lifetime_start">'<tt>llvm.lifetime.start</tt>' Intrinsic</a></li> - <li><a href="#int_lifetime_end">'<tt>llvm.lifetime.end</tt>' Intrinsic</a></li> - <li><a href="#int_invariant_start">'<tt>llvm.invariant.start</tt>' Intrinsic</a></li> - <li><a href="#int_invariant_end">'<tt>llvm.invariant.end</tt>' Intrinsic</a></li> - </ol> - </li> - <li><a href="#int_general">General intrinsics</a> - <ol> - <li><a href="#int_var_annotation"> - '<tt>llvm.var.annotation</tt>' Intrinsic</a></li> - <li><a href="#int_annotation"> - '<tt>llvm.annotation.*</tt>' Intrinsic</a></li> - <li><a href="#int_trap"> - '<tt>llvm.trap</tt>' Intrinsic</a></li> - <li><a href="#int_debugtrap"> - '<tt>llvm.debugtrap</tt>' Intrinsic</a></li> - <li><a href="#int_stackprotector"> - '<tt>llvm.stackprotector</tt>' Intrinsic</a></li> - <li><a href="#int_objectsize"> - '<tt>llvm.objectsize</tt>' Intrinsic</a></li> - <li><a href="#int_expect"> - '<tt>llvm.expect</tt>' Intrinsic</a></li> - <li><a href="#int_donothing"> - '<tt>llvm.donothing</tt>' Intrinsic</a></li> - </ol> - </li> - </ol> - </li> -</ol> - -<div class="doc_author"> - <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> - and <a href="mailto:vadve@cs.uiuc.edu">Vikram Adve</a></p> -</div> - -<!-- *********************************************************************** --> -<h2><a name="abstract">Abstract</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>This document is a reference manual for the LLVM assembly language. LLVM is - a Static Single Assignment (SSA) based representation that provides type - safety, low-level operations, flexibility, and the capability of representing - 'all' high-level languages cleanly. It is the common code representation - used throughout all phases of the LLVM compilation strategy.</p> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="introduction">Introduction</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>The LLVM code representation is designed to be used in three different forms: - as an in-memory compiler IR, as an on-disk bitcode representation (suitable - for fast loading by a Just-In-Time compiler), and as a human readable - assembly language representation. This allows LLVM to provide a powerful - intermediate representation for efficient compiler transformations and - analysis, while providing a natural means to debug and visualize the - transformations. The three different forms of LLVM are all equivalent. This - document describes the human readable representation and notation.</p> - -<p>The LLVM representation aims to be light-weight and low-level while being - expressive, typed, and extensible at the same time. It aims to be a - "universal IR" of sorts, by being at a low enough level that high-level ideas - may be cleanly mapped to it (similar to how microprocessors are "universal - IR's", allowing many source languages to be mapped to them). By providing - type information, LLVM can be used as the target of optimizations: for - example, through pointer analysis, it can be proven that a C automatic - variable is never accessed outside of the current function, allowing it to - be promoted to a simple SSA value instead of a memory location.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="wellformed">Well-Formedness</a> -</h4> - -<div> - -<p>It is important to note that this document describes 'well formed' LLVM - assembly language. There is a difference between what the parser accepts and - what is considered 'well formed'. For example, the following instruction is - syntactically okay, but not well formed:</p> - -<pre class="doc_code"> -%x = <a href="#i_add">add</a> i32 1, %x -</pre> - -<p>because the definition of <tt>%x</tt> does not dominate all of its uses. The - LLVM infrastructure provides a verification pass that may be used to verify - that an LLVM module is well formed. This pass is automatically run by the - parser after parsing input assembly and by the optimizer before it outputs - bitcode. The violations pointed out by the verifier pass indicate bugs in - transformation passes or input to the parser.</p> - -</div> - -</div> - -<!-- Describe the typesetting conventions here. --> - -<!-- *********************************************************************** --> -<h2><a name="identifiers">Identifiers</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>LLVM identifiers come in two basic types: global and local. Global - identifiers (functions, global variables) begin with the <tt>'@'</tt> - character. Local identifiers (register names, types) begin with - the <tt>'%'</tt> character. Additionally, there are three different formats - for identifiers, for different purposes:</p> - -<ol> - <li>Named values are represented as a string of characters with their prefix. - For example, <tt>%foo</tt>, <tt>@DivisionByZero</tt>, - <tt>%a.really.long.identifier</tt>. The actual regular expression used is - '<tt>[%@][a-zA-Z$._][a-zA-Z$._0-9]*</tt>'. Identifiers which require - other characters in their names can be surrounded with quotes. Special - characters may be escaped using <tt>"\xx"</tt> where <tt>xx</tt> is the - ASCII code for the character in hexadecimal. In this way, any character - can be used in a name value, even quotes themselves.</li> - - <li>Unnamed values are represented as an unsigned numeric value with their - prefix. For example, <tt>%12</tt>, <tt>@2</tt>, <tt>%44</tt>.</li> - - <li>Constants, which are described in a <a href="#constants">section about - constants</a>, below.</li> -</ol> - -<p>LLVM requires that values start with a prefix for two reasons: Compilers - don't need to worry about name clashes with reserved words, and the set of - reserved words may be expanded in the future without penalty. Additionally, - unnamed identifiers allow a compiler to quickly come up with a temporary - variable without having to avoid symbol table conflicts.</p> - -<p>Reserved words in LLVM are very similar to reserved words in other - languages. There are keywords for different opcodes - ('<tt><a href="#i_add">add</a></tt>', - '<tt><a href="#i_bitcast">bitcast</a></tt>', - '<tt><a href="#i_ret">ret</a></tt>', etc...), for primitive type names - ('<tt><a href="#t_void">void</a></tt>', - '<tt><a href="#t_primitive">i32</a></tt>', etc...), and others. These - reserved words cannot conflict with variable names, because none of them - start with a prefix character (<tt>'%'</tt> or <tt>'@'</tt>).</p> - -<p>Here is an example of LLVM code to multiply the integer variable - '<tt>%X</tt>' by 8:</p> - -<p>The easy way:</p> - -<pre class="doc_code"> -%result = <a href="#i_mul">mul</a> i32 %X, 8 -</pre> - -<p>After strength reduction:</p> - -<pre class="doc_code"> -%result = <a href="#i_shl">shl</a> i32 %X, i8 3 -</pre> - -<p>And the hard way:</p> - -<pre class="doc_code"> -%0 = <a href="#i_add">add</a> i32 %X, %X <i>; yields {i32}:%0</i> -%1 = <a href="#i_add">add</a> i32 %0, %0 <i>; yields {i32}:%1</i> -%result = <a href="#i_add">add</a> i32 %1, %1 -</pre> - -<p>This last way of multiplying <tt>%X</tt> by 8 illustrates several important - lexical features of LLVM:</p> - -<ol> - <li>Comments are delimited with a '<tt>;</tt>' and go until the end of - line.</li> - - <li>Unnamed temporaries are created when the result of a computation is not - assigned to a named value.</li> - - <li>Unnamed temporaries are numbered sequentially</li> -</ol> - -<p>It also shows a convention that we follow in this document. When - demonstrating instructions, we will follow an instruction with a comment that - defines the type and name of value produced. Comments are shown in italic - text.</p> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="highlevel">High Level Structure</a></h2> -<!-- *********************************************************************** --> -<div> -<!-- ======================================================================= --> -<h3> - <a name="modulestructure">Module Structure</a> -</h3> - -<div> - -<p>LLVM programs are composed of <tt>Module</tt>s, each of which is a - translation unit of the input programs. Each module consists of functions, - global variables, and symbol table entries. Modules may be combined together - with the LLVM linker, which merges function (and global variable) - definitions, resolves forward declarations, and merges symbol table - entries. Here is an example of the "hello world" module:</p> - -<pre class="doc_code"> -<i>; Declare the string constant as a global constant.</i> -<a href="#identifiers">@.str</a> = <a href="#linkage_private">private</a> <a href="#globalvars">unnamed_addr</a> <a href="#globalvars">constant</a> <a href="#t_array">[13 x i8]</a> c"hello world\0A\00" - -<i>; External declaration of the puts function</i> -<a href="#functionstructure">declare</a> i32 @puts(i8* <a href="#nocapture">nocapture</a>) <a href="#fnattrs">nounwind</a> - -<i>; Definition of main function</i> -define i32 @main() { <i>; i32()* </i> - <i>; Convert [13 x i8]* to i8 *...</i> - %cast210 = <a href="#i_getelementptr">getelementptr</a> [13 x i8]* @.str, i64 0, i64 0 - - <i>; Call puts function to write out the string to stdout.</i> - <a href="#i_call">call</a> i32 @puts(i8* %cast210) - <a href="#i_ret">ret</a> i32 0 -} - -<i>; Named metadata</i> -!1 = metadata !{i32 42} -!foo = !{!1, null} -</pre> - -<p>This example is made up of a <a href="#globalvars">global variable</a> named - "<tt>.str</tt>", an external declaration of the "<tt>puts</tt>" function, - a <a href="#functionstructure">function definition</a> for - "<tt>main</tt>" and <a href="#namedmetadatastructure">named metadata</a> - "<tt>foo</tt>".</p> - -<p>In general, a module is made up of a list of global values (where both - functions and global variables are global values). Global values are - represented by a pointer to a memory location (in this case, a pointer to an - array of char, and a pointer to a function), and have one of the - following <a href="#linkage">linkage types</a>.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="linkage">Linkage Types</a> -</h3> - -<div> - -<p>All Global Variables and Functions have one of the following types of - linkage:</p> - -<dl> - <dt><tt><b><a name="linkage_private">private</a></b></tt></dt> - <dd>Global values with "<tt>private</tt>" linkage are only directly accessible - by objects in the current module. In particular, linking code into a - module with an private global value may cause the private to be renamed as - necessary to avoid collisions. Because the symbol is private to the - module, all references can be updated. This doesn't show up in any symbol - table in the object file.</dd> - - <dt><tt><b><a name="linkage_linker_private">linker_private</a></b></tt></dt> - <dd>Similar to <tt>private</tt>, but the symbol is passed through the - assembler and evaluated by the linker. Unlike normal strong symbols, they - are removed by the linker from the final linked image (executable or - dynamic library).</dd> - - <dt><tt><b><a name="linkage_linker_private_weak">linker_private_weak</a></b></tt></dt> - <dd>Similar to "<tt>linker_private</tt>", but the symbol is weak. Note that - <tt>linker_private_weak</tt> symbols are subject to coalescing by the - linker. The symbols are removed by the linker from the final linked image - (executable or dynamic library).</dd> - - <dt><tt><b><a name="linkage_internal">internal</a></b></tt></dt> - <dd>Similar to private, but the value shows as a local symbol - (<tt>STB_LOCAL</tt> in the case of ELF) in the object file. This - corresponds to the notion of the '<tt>static</tt>' keyword in C.</dd> - - <dt><tt><b><a name="linkage_available_externally">available_externally</a></b></tt></dt> - <dd>Globals with "<tt>available_externally</tt>" linkage are never emitted - into the object file corresponding to the LLVM module. They exist to - allow inlining and other optimizations to take place given knowledge of - the definition of the global, which is known to be somewhere outside the - module. Globals with <tt>available_externally</tt> linkage are allowed to - be discarded at will, and are otherwise the same as <tt>linkonce_odr</tt>. - This linkage type is only allowed on definitions, not declarations.</dd> - - <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt></dt> - <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of - the same name when linkage occurs. This can be used to implement - some forms of inline functions, templates, or other code which must be - generated in each translation unit that uses it, but where the body may - be overridden with a more definitive definition later. Unreferenced - <tt>linkonce</tt> globals are allowed to be discarded. Note that - <tt>linkonce</tt> linkage does not actually allow the optimizer to - inline the body of this function into callers because it doesn't know if - this definition of the function is the definitive definition within the - program or whether it will be overridden by a stronger definition. - To enable inlining and other optimizations, use "<tt>linkonce_odr</tt>" - linkage.</dd> - - <dt><tt><b><a name="linkage_weak">weak</a></b></tt></dt> - <dd>"<tt>weak</tt>" linkage has the same merging semantics as - <tt>linkonce</tt> linkage, except that unreferenced globals with - <tt>weak</tt> linkage may not be discarded. This is used for globals that - are declared "weak" in C source code.</dd> - - <dt><tt><b><a name="linkage_common">common</a></b></tt></dt> - <dd>"<tt>common</tt>" linkage is most similar to "<tt>weak</tt>" linkage, but - they are used for tentative definitions in C, such as "<tt>int X;</tt>" at - global scope. - Symbols with "<tt>common</tt>" linkage are merged in the same way as - <tt>weak symbols</tt>, and they may not be deleted if unreferenced. - <tt>common</tt> symbols may not have an explicit section, - must have a zero initializer, and may not be marked '<a - href="#globalvars"><tt>constant</tt></a>'. Functions and aliases may not - have common linkage.</dd> - - - <dt><tt><b><a name="linkage_appending">appending</a></b></tt></dt> - <dd>"<tt>appending</tt>" linkage may only be applied to global variables of - pointer to array type. When two global variables with appending linkage - are linked together, the two global arrays are appended together. This is - the LLVM, typesafe, equivalent of having the system linker append together - "sections" with identical names when .o files are linked.</dd> - - <dt><tt><b><a name="linkage_externweak">extern_weak</a></b></tt></dt> - <dd>The semantics of this linkage follow the ELF object file model: the symbol - is weak until linked, if not linked, the symbol becomes null instead of - being an undefined reference.</dd> - - <dt><tt><b><a name="linkage_linkonce_odr">linkonce_odr</a></b></tt></dt> - <dt><tt><b><a name="linkage_weak_odr">weak_odr</a></b></tt></dt> - <dd>Some languages allow differing globals to be merged, such as two functions - with different semantics. Other languages, such as <tt>C++</tt>, ensure - that only equivalent globals are ever merged (the "one definition rule" - — "ODR"). Such languages can use the <tt>linkonce_odr</tt> - and <tt>weak_odr</tt> linkage types to indicate that the global will only - be merged with equivalent globals. These linkage types are otherwise the - same as their non-<tt>odr</tt> versions.</dd> - - <dt><tt><b><a name="linkage_linkonce_odr_auto_hide">linkonce_odr_auto_hide</a></b></tt></dt> - <dd>Similar to "<tt>linkonce_odr</tt>", but nothing in the translation unit - takes the address of this definition. For instance, functions that had an - inline definition, but the compiler decided not to inline it. - <tt>linkonce_odr_auto_hide</tt> may have only <tt>default</tt> visibility. - The symbols are removed by the linker from the final linked image - (executable or dynamic library).</dd> - - <dt><tt><b><a name="linkage_external">external</a></b></tt></dt> - <dd>If none of the above identifiers are used, the global is externally - visible, meaning that it participates in linkage and can be used to - resolve external symbol references.</dd> -</dl> - -<p>The next two types of linkage are targeted for Microsoft Windows platform - only. They are designed to support importing (exporting) symbols from (to) - DLLs (Dynamic Link Libraries).</p> - -<dl> - <dt><tt><b><a name="linkage_dllimport">dllimport</a></b></tt></dt> - <dd>"<tt>dllimport</tt>" linkage causes the compiler to reference a function - or variable via a global pointer to a pointer that is set up by the DLL - exporting the symbol. On Microsoft Windows targets, the pointer name is - formed by combining <code>__imp_</code> and the function or variable - name.</dd> - - <dt><tt><b><a name="linkage_dllexport">dllexport</a></b></tt></dt> - <dd>"<tt>dllexport</tt>" linkage causes the compiler to provide a global - pointer to a pointer in a DLL, so that it can be referenced with the - <tt>dllimport</tt> attribute. On Microsoft Windows targets, the pointer - name is formed by combining <code>__imp_</code> and the function or - variable name.</dd> -</dl> - -<p>For example, since the "<tt>.LC0</tt>" variable is defined to be internal, if - another module defined a "<tt>.LC0</tt>" variable and was linked with this - one, one of the two would be renamed, preventing a collision. Since - "<tt>main</tt>" and "<tt>puts</tt>" are external (i.e., lacking any linkage - declarations), they are accessible outside of the current module.</p> - -<p>It is illegal for a function <i>declaration</i> to have any linkage type - other than <tt>external</tt>, <tt>dllimport</tt> - or <tt>extern_weak</tt>.</p> - -<p>Aliases can have only <tt>external</tt>, <tt>internal</tt>, <tt>weak</tt> - or <tt>weak_odr</tt> linkages.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="callingconv">Calling Conventions</a> -</h3> - -<div> - -<p>LLVM <a href="#functionstructure">functions</a>, <a href="#i_call">calls</a> - and <a href="#i_invoke">invokes</a> can all have an optional calling - convention specified for the call. The calling convention of any pair of - dynamic caller/callee must match, or the behavior of the program is - undefined. The following calling conventions are supported by LLVM, and more - may be added in the future:</p> - -<dl> - <dt><b>"<tt>ccc</tt>" - The C calling convention</b>:</dt> - <dd>This calling convention (the default if no other calling convention is - specified) matches the target C calling conventions. This calling - convention supports varargs function calls and tolerates some mismatch in - the declared prototype and implemented declaration of the function (as - does normal C).</dd> - - <dt><b>"<tt>fastcc</tt>" - The fast calling convention</b>:</dt> - <dd>This calling convention attempts to make calls as fast as possible - (e.g. by passing things in registers). This calling convention allows the - target to use whatever tricks it wants to produce fast code for the - target, without having to conform to an externally specified ABI - (Application Binary Interface). - <a href="CodeGenerator.html#id80">Tail calls can only be optimized - when this, the GHC or the HiPE convention is used.</a> This calling - convention does not support varargs and requires the prototype of all - callees to exactly match the prototype of the function definition.</dd> - - <dt><b>"<tt>coldcc</tt>" - The cold calling convention</b>:</dt> - <dd>This calling convention attempts to make code in the caller as efficient - as possible under the assumption that the call is not commonly executed. - As such, these calls often preserve all registers so that the call does - not break any live ranges in the caller side. This calling convention - does not support varargs and requires the prototype of all callees to - exactly match the prototype of the function definition.</dd> - - <dt><b>"<tt>cc <em>10</em></tt>" - GHC convention</b>:</dt> - <dd>This calling convention has been implemented specifically for use by the - <a href="http://www.haskell.org/ghc">Glasgow Haskell Compiler (GHC)</a>. - It passes everything in registers, going to extremes to achieve this by - disabling callee save registers. This calling convention should not be - used lightly but only for specific situations such as an alternative to - the <em>register pinning</em> performance technique often used when - implementing functional programming languages. At the moment only X86 - supports this convention and it has the following limitations: - <ul> - <li>On <em>X86-32</em> only supports up to 4 bit type parameters. No - floating point types are supported.</li> - <li>On <em>X86-64</em> only supports up to 10 bit type parameters and - 6 floating point parameters.</li> - </ul> - This calling convention supports - <a href="CodeGenerator.html#id80">tail call optimization</a> but - requires both the caller and callee are using it. - </dd> - - <dt><b>"<tt>cc <em>11</em></tt>" - The HiPE calling convention</b>:</dt> - <dd>This calling convention has been implemented specifically for use by the - <a href="http://www.it.uu.se/research/group/hipe/">High-Performance Erlang - (HiPE)</a> compiler, <em>the</em> native code compiler of the - <a href="http://www.erlang.org/download.shtml">Ericsson's Open Source - Erlang/OTP system</a>. It uses more registers for argument passing than - the ordinary C calling convention and defines no callee-saved registers. - The calling convention properly supports - <a href="CodeGenerator.html#id80">tail call optimization</a> but requires - that both the caller and the callee use it. It uses a <em>register - pinning</em> mechanism, similar to GHC's convention, for keeping - frequently accessed runtime components pinned to specific hardware - registers. At the moment only X86 supports this convention (both 32 and 64 - bit).</dd> - - <dt><b>"<tt>cc <<em>n</em>></tt>" - Numbered convention</b>:</dt> - <dd>Any calling convention may be specified by number, allowing - target-specific calling conventions to be used. Target specific calling - conventions start at 64.</dd> -</dl> - -<p>More calling conventions can be added/defined on an as-needed basis, to - support Pascal conventions or any other well-known target-independent - convention.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="visibility">Visibility Styles</a> -</h3> - -<div> - -<p>All Global Variables and Functions have one of the following visibility - styles:</p> - -<dl> - <dt><b>"<tt>default</tt>" - Default style</b>:</dt> - <dd>On targets that use the ELF object file format, default visibility means - that the declaration is visible to other modules and, in shared libraries, - means that the declared entity may be overridden. On Darwin, default - visibility means that the declaration is visible to other modules. Default - visibility corresponds to "external linkage" in the language.</dd> - - <dt><b>"<tt>hidden</tt>" - Hidden style</b>:</dt> - <dd>Two declarations of an object with hidden visibility refer to the same - object if they are in the same shared object. Usually, hidden visibility - indicates that the symbol will not be placed into the dynamic symbol - table, so no other module (executable or shared library) can reference it - directly.</dd> - - <dt><b>"<tt>protected</tt>" - Protected style</b>:</dt> - <dd>On ELF, protected visibility indicates that the symbol will be placed in - the dynamic symbol table, but that references within the defining module - will bind to the local symbol. That is, the symbol cannot be overridden by - another module.</dd> -</dl> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="namedtypes">Named Types</a> -</h3> - -<div> - -<p>LLVM IR allows you to specify name aliases for certain types. This can make - it easier to read the IR and make the IR more condensed (particularly when - recursive types are involved). An example of a name specification is:</p> - -<pre class="doc_code"> -%mytype = type { %mytype*, i32 } -</pre> - -<p>You may give a name to any <a href="#typesystem">type</a> except - "<a href="#t_void">void</a>". Type name aliases may be used anywhere a type - is expected with the syntax "%mytype".</p> - -<p>Note that type names are aliases for the structural type that they indicate, - and that you can therefore specify multiple names for the same type. This - often leads to confusing behavior when dumping out a .ll file. Since LLVM IR - uses structural typing, the name is not part of the type. When printing out - LLVM IR, the printer will pick <em>one name</em> to render all types of a - particular shape. This means that if you have code where two different - source types end up having the same LLVM type, that the dumper will sometimes - print the "wrong" or unexpected type. This is an important design point and - isn't going to change.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="globalvars">Global Variables</a> -</h3> - -<div> - -<p>Global variables define regions of memory allocated at compilation time - instead of run-time. Global variables may optionally be initialized, may - have an explicit section to be placed in, and may have an optional explicit - alignment specified.</p> - -<p>A variable may be defined as <tt>thread_local</tt>, which - means that it will not be shared by threads (each thread will have a - separated copy of the variable). Not all targets support thread-local - variables. Optionally, a TLS model may be specified:</p> - -<dl> - <dt><b><tt>localdynamic</tt></b>:</dt> - <dd>For variables that are only used within the current shared library.</dd> - - <dt><b><tt>initialexec</tt></b>:</dt> - <dd>For variables in modules that will not be loaded dynamically.</dd> - - <dt><b><tt>localexec</tt></b>:</dt> - <dd>For variables defined in the executable and only used within it.</dd> -</dl> - -<p>The models correspond to the ELF TLS models; see - <a href="http://people.redhat.com/drepper/tls.pdf">ELF - Handling For Thread-Local Storage</a> for more information on under which - circumstances the different models may be used. The target may choose a - different TLS model if the specified model is not supported, or if a better - choice of model can be made.</p> - -<p>A variable may be defined as a global - "constant," which indicates that the contents of the variable - will <b>never</b> be modified (enabling better optimization, allowing the - global data to be placed in the read-only section of an executable, etc). - Note that variables that need runtime initialization cannot be marked - "constant" as there is a store to the variable.</p> - -<p>LLVM explicitly allows <em>declarations</em> of global variables to be marked - constant, even if the final definition of the global is not. This capability - can be used to enable slightly better optimization of the program, but - requires the language definition to guarantee that optimizations based on the - 'constantness' are valid for the translation units that do not include the - definition.</p> - -<p>As SSA values, global variables define pointer values that are in scope - (i.e. they dominate) all basic blocks in the program. Global variables - always define a pointer to their "content" type because they describe a - region of memory, and all memory objects in LLVM are accessed through - pointers.</p> - -<p>Global variables can be marked with <tt>unnamed_addr</tt> which indicates - that the address is not significant, only the content. Constants marked - like this can be merged with other constants if they have the same - initializer. Note that a constant with significant address <em>can</em> - be merged with a <tt>unnamed_addr</tt> constant, the result being a - constant whose address is significant.</p> - -<p>A global variable may be declared to reside in a target-specific numbered - address space. For targets that support them, address spaces may affect how - optimizations are performed and/or what target instructions are used to - access the variable. The default address space is zero. The address space - qualifier must precede any other attributes.</p> - -<p>LLVM allows an explicit section to be specified for globals. If the target - supports it, it will emit globals to the section specified.</p> - -<p>An explicit alignment may be specified for a global, which must be a power - of 2. If not present, or if the alignment is set to zero, the alignment of - the global is set by the target to whatever it feels convenient. If an - explicit alignment is specified, the global is forced to have exactly that - alignment. Targets and optimizers are not allowed to over-align the global - if the global has an assigned section. In this case, the extra alignment - could be observable: for example, code could assume that the globals are - densely packed in their section and try to iterate over them as an array, - alignment padding would break this iteration.</p> - -<p>For example, the following defines a global in a numbered address space with - an initializer, section, and alignment:</p> - -<pre class="doc_code"> -@G = addrspace(5) constant float 1.0, section "foo", align 4 -</pre> - -<p>The following example defines a thread-local global with - the <tt>initialexec</tt> TLS model:</p> - -<pre class="doc_code"> -@G = thread_local(initialexec) global i32 0, align 4 -</pre> - -</div> - - -<!-- ======================================================================= --> -<h3> - <a name="functionstructure">Functions</a> -</h3> - -<div> - -<p>LLVM function definitions consist of the "<tt>define</tt>" keyword, an - optional <a href="#linkage">linkage type</a>, an optional - <a href="#visibility">visibility style</a>, an optional - <a href="#callingconv">calling convention</a>, - an optional <tt>unnamed_addr</tt> attribute, a return type, an optional - <a href="#paramattrs">parameter attribute</a> for the return type, a function - name, a (possibly empty) argument list (each with optional - <a href="#paramattrs">parameter attributes</a>), optional - <a href="#fnattrs">function attributes</a>, an optional section, an optional - alignment, an optional <a href="#gc">garbage collector name</a>, an opening - curly brace, a list of basic blocks, and a closing curly brace.</p> - -<p>LLVM function declarations consist of the "<tt>declare</tt>" keyword, an - optional <a href="#linkage">linkage type</a>, an optional - <a href="#visibility">visibility style</a>, an optional - <a href="#callingconv">calling convention</a>, - an optional <tt>unnamed_addr</tt> attribute, a return type, an optional - <a href="#paramattrs">parameter attribute</a> for the return type, a function - name, a possibly empty list of arguments, an optional alignment, and an - optional <a href="#gc">garbage collector name</a>.</p> - -<p>A function definition contains a list of basic blocks, forming the CFG - (Control Flow Graph) for the function. Each basic block may optionally start - with a label (giving the basic block a symbol table entry), contains a list - of instructions, and ends with a <a href="#terminators">terminator</a> - instruction (such as a branch or function return).</p> - -<p>The first basic block in a function is special in two ways: it is immediately - executed on entrance to the function, and it is not allowed to have - predecessor basic blocks (i.e. there can not be any branches to the entry - block of a function). Because the block can have no predecessors, it also - cannot have any <a href="#i_phi">PHI nodes</a>.</p> - -<p>LLVM allows an explicit section to be specified for functions. If the target - supports it, it will emit functions to the section specified.</p> - -<p>An explicit alignment may be specified for a function. If not present, or if - the alignment is set to zero, the alignment of the function is set by the - target to whatever it feels convenient. If an explicit alignment is - specified, the function is forced to have at least that much alignment. All - alignments must be a power of 2.</p> - -<p>If the <tt>unnamed_addr</tt> attribute is given, the address is know to not - be significant and two identical functions can be merged.</p> - -<h5>Syntax:</h5> -<pre class="doc_code"> -define [<a href="#linkage">linkage</a>] [<a href="#visibility">visibility</a>] - [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] - <ResultType> @<FunctionName> ([argument list]) - [<a href="#fnattrs">fn Attrs</a>] [section "name"] [align N] - [<a href="#gc">gc</a>] { ... } -</pre> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="aliasstructure">Aliases</a> -</h3> - -<div> - -<p>Aliases act as "second name" for the aliasee value (which can be either - function, global variable, another alias or bitcast of global value). Aliases - may have an optional <a href="#linkage">linkage type</a>, and an - optional <a href="#visibility">visibility style</a>.</p> - -<h5>Syntax:</h5> -<pre class="doc_code"> -@<Name> = alias [Linkage] [Visibility] <AliaseeTy> @<Aliasee> -</pre> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="namedmetadatastructure">Named Metadata</a> -</h3> - -<div> - -<p>Named metadata is a collection of metadata. <a href="#metadata">Metadata - nodes</a> (but not metadata strings) are the only valid operands for - a named metadata.</p> - -<h5>Syntax:</h5> -<pre class="doc_code"> -; Some unnamed metadata nodes, which are referenced by the named metadata. -!0 = metadata !{metadata !"zero"} -!1 = metadata !{metadata !"one"} -!2 = metadata !{metadata !"two"} -; A named metadata. -!name = !{!0, !1, !2} -</pre> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="paramattrs">Parameter Attributes</a> -</h3> - -<div> - -<p>The return type and each parameter of a function type may have a set of - <i>parameter attributes</i> associated with them. Parameter attributes are - used to communicate additional information about the result or parameters of - a function. Parameter attributes are considered to be part of the function, - not of the function type, so functions with different parameter attributes - can have the same function type.</p> - -<p>Parameter attributes are simple keywords that follow the type specified. If - multiple parameter attributes are needed, they are space separated. For - example:</p> - -<pre class="doc_code"> -declare i32 @printf(i8* noalias nocapture, ...) -declare i32 @atoi(i8 zeroext) -declare signext i8 @returns_signed_char() -</pre> - -<p>Note that any attributes for the function result (<tt>nounwind</tt>, - <tt>readonly</tt>) come immediately after the argument list.</p> - -<p>Currently, only the following parameter attributes are defined:</p> - -<dl> - <dt><tt><b>zeroext</b></tt></dt> - <dd>This indicates to the code generator that the parameter or return value - should be zero-extended to the extent required by the target's ABI (which - is usually 32-bits, but is 8-bits for a i1 on x86-64) by the caller (for a - parameter) or the callee (for a return value).</dd> - - <dt><tt><b>signext</b></tt></dt> - <dd>This indicates to the code generator that the parameter or return value - should be sign-extended to the extent required by the target's ABI (which - is usually 32-bits) by the caller (for a parameter) or the callee (for a - return value).</dd> - - <dt><tt><b>inreg</b></tt></dt> - <dd>This indicates that this parameter or return value should be treated in a - special target-dependent fashion during while emitting code for a function - call or return (usually, by putting it in a register as opposed to memory, - though some targets use it to distinguish between two different kinds of - registers). Use of this attribute is target-specific.</dd> - - <dt><tt><b><a name="byval">byval</a></b></tt></dt> - <dd><p>This indicates that the pointer parameter should really be passed by - value to the function. The attribute implies that a hidden copy of the - pointee - is made between the caller and the callee, so the callee is unable to - modify the value in the caller. This attribute is only valid on LLVM - pointer arguments. It is generally used to pass structs and arrays by - value, but is also valid on pointers to scalars. The copy is considered - to belong to the caller not the callee (for example, - <tt><a href="#readonly">readonly</a></tt> functions should not write to - <tt>byval</tt> parameters). This is not a valid attribute for return - values.</p> - - <p>The byval attribute also supports specifying an alignment with - the align attribute. It indicates the alignment of the stack slot to - form and the known alignment of the pointer specified to the call site. If - the alignment is not specified, then the code generator makes a - target-specific assumption.</p></dd> - - <dt><tt><b><a name="sret">sret</a></b></tt></dt> - <dd>This indicates that the pointer parameter specifies the address of a - structure that is the return value of the function in the source program. - This pointer must be guaranteed by the caller to be valid: loads and - stores to the structure may be assumed by the callee to not to trap and - to be properly aligned. This may only be applied to the first parameter. - This is not a valid attribute for return values. </dd> - - <dt><tt><b><a name="noalias">noalias</a></b></tt></dt> - <dd>This indicates that pointer values - <a href="#pointeraliasing"><i>based</i></a> on the argument or return - value do not alias pointer values which are not <i>based</i> on it, - ignoring certain "irrelevant" dependencies. - For a call to the parent function, dependencies between memory - references from before or after the call and from those during the call - are "irrelevant" to the <tt>noalias</tt> keyword for the arguments and - return value used in that call. - The caller shares the responsibility with the callee for ensuring that - these requirements are met. - For further details, please see the discussion of the NoAlias response in - <a href="AliasAnalysis.html#MustMayNo">alias analysis</a>.<br> -<br> - Note that this definition of <tt>noalias</tt> is intentionally - similar to the definition of <tt>restrict</tt> in C99 for function - arguments, though it is slightly weaker. -<br> - For function return values, C99's <tt>restrict</tt> is not meaningful, - while LLVM's <tt>noalias</tt> is. - </dd> - - <dt><tt><b><a name="nocapture">nocapture</a></b></tt></dt> - <dd>This indicates that the callee does not make any copies of the pointer - that outlive the callee itself. This is not a valid attribute for return - values.</dd> - - <dt><tt><b><a name="nest">nest</a></b></tt></dt> - <dd>This indicates that the pointer parameter can be excised using the - <a href="#int_trampoline">trampoline intrinsics</a>. This is not a valid - attribute for return values.</dd> -</dl> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="gc">Garbage Collector Names</a> -</h3> - -<div> - -<p>Each function may specify a garbage collector name, which is simply a - string:</p> - -<pre class="doc_code"> -define void @f() gc "name" { ... } -</pre> - -<p>The compiler declares the supported values of <i>name</i>. Specifying a - collector which will cause the compiler to alter its output in order to - support the named garbage collection algorithm.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="fnattrs">Function Attributes</a> -</h3> - -<div> - -<p>Function attributes are set to communicate additional information about a - function. Function attributes are considered to be part of the function, not - of the function type, so functions with different function attributes can - have the same function type.</p> - -<p>Function attributes are simple keywords that follow the type specified. If - multiple attributes are needed, they are space separated. For example:</p> - -<pre class="doc_code"> -define void @f() noinline { ... } -define void @f() alwaysinline { ... } -define void @f() alwaysinline optsize { ... } -define void @f() optsize { ... } -</pre> - -<dl> - <dt><tt><b>address_safety</b></tt></dt> - <dd>This attribute indicates that the address safety analysis - is enabled for this function. </dd> - - <dt><tt><b>alignstack(<<em>n</em>>)</b></tt></dt> - <dd>This attribute indicates that, when emitting the prologue and epilogue, - the backend should forcibly align the stack pointer. Specify the - desired alignment, which must be a power of two, in parentheses. - - <dt><tt><b>alwaysinline</b></tt></dt> - <dd>This attribute indicates that the inliner should attempt to inline this - function into callers whenever possible, ignoring any active inlining size - threshold for this caller.</dd> - - <dt><tt><b>nonlazybind</b></tt></dt> - <dd>This attribute suppresses lazy symbol binding for the function. This - may make calls to the function faster, at the cost of extra program - startup time if the function is not called during program startup.</dd> - - <dt><tt><b>inlinehint</b></tt></dt> - <dd>This attribute indicates that the source code contained a hint that inlining - this function is desirable (such as the "inline" keyword in C/C++). It - is just a hint; it imposes no requirements on the inliner.</dd> - - <dt><tt><b>naked</b></tt></dt> - <dd>This attribute disables prologue / epilogue emission for the function. - This can have very system-specific consequences.</dd> - - <dt><tt><b>noimplicitfloat</b></tt></dt> - <dd>This attributes disables implicit floating point instructions.</dd> - - <dt><tt><b>noinline</b></tt></dt> - <dd>This attribute indicates that the inliner should never inline this - function in any situation. This attribute may not be used together with - the <tt>alwaysinline</tt> attribute.</dd> - - <dt><tt><b>noredzone</b></tt></dt> - <dd>This attribute indicates that the code generator should not use a red - zone, even if the target-specific ABI normally permits it.</dd> - - <dt><tt><b>noreturn</b></tt></dt> - <dd>This function attribute indicates that the function never returns - normally. This produces undefined behavior at runtime if the function - ever does dynamically return.</dd> - - <dt><tt><b>nounwind</b></tt></dt> - <dd>This function attribute indicates that the function never returns with an - unwind or exceptional control flow. If the function does unwind, its - runtime behavior is undefined.</dd> - - <dt><tt><b>optsize</b></tt></dt> - <dd>This attribute suggests that optimization passes and code generator passes - make choices that keep the code size of this function low, and otherwise - do optimizations specifically to reduce code size.</dd> - - <dt><tt><b>readnone</b></tt></dt> - <dd>This attribute indicates that the function computes its result (or decides - to unwind an exception) based strictly on its arguments, without - dereferencing any pointer arguments or otherwise accessing any mutable - state (e.g. memory, control registers, etc) visible to caller functions. - It does not write through any pointer arguments - (including <tt><a href="#byval">byval</a></tt> arguments) and never - changes any state visible to callers. This means that it cannot unwind - exceptions by calling the <tt>C++</tt> exception throwing methods.</dd> - - <dt><tt><b><a name="readonly">readonly</a></b></tt></dt> - <dd>This attribute indicates that the function does not write through any - pointer arguments (including <tt><a href="#byval">byval</a></tt> - arguments) or otherwise modify any state (e.g. memory, control registers, - etc) visible to caller functions. It may dereference pointer arguments - and read state that may be set in the caller. A readonly function always - returns the same value (or unwinds an exception identically) when called - with the same set of arguments and global state. It cannot unwind an - exception by calling the <tt>C++</tt> exception throwing methods.</dd> - - <dt><tt><b><a name="returns_twice">returns_twice</a></b></tt></dt> - <dd>This attribute indicates that this function can return twice. The - C <code>setjmp</code> is an example of such a function. The compiler - disables some optimizations (like tail calls) in the caller of these - functions.</dd> - - <dt><tt><b><a name="ssp">ssp</a></b></tt></dt> - <dd>This attribute indicates that the function should emit a stack smashing - protector. It is in the form of a "canary"—a random value placed on - the stack before the local variables that's checked upon return from the - function to see if it has been overwritten. A heuristic is used to - determine if a function needs stack protectors or not.<br> -<br> - If a function that has an <tt>ssp</tt> attribute is inlined into a - function that doesn't have an <tt>ssp</tt> attribute, then the resulting - function will have an <tt>ssp</tt> attribute.</dd> - - <dt><tt><b>sspreq</b></tt></dt> - <dd>This attribute indicates that the function should <em>always</em> emit a - stack smashing protector. This overrides - the <tt><a href="#ssp">ssp</a></tt> function attribute.<br> -<br> - If a function that has an <tt>sspreq</tt> attribute is inlined into a - function that doesn't have an <tt>sspreq</tt> attribute or which has - an <tt>ssp</tt> attribute, then the resulting function will have - an <tt>sspreq</tt> attribute.</dd> - - <dt><tt><b><a name="uwtable">uwtable</a></b></tt></dt> - <dd>This attribute indicates that the ABI being targeted requires that - an unwind table entry be produce for this function even if we can - show that no exceptions passes by it. This is normally the case for - the ELF x86-64 abi, but it can be disabled for some compilation - units.</dd> -</dl> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="moduleasm">Module-Level Inline Assembly</a> -</h3> - -<div> - -<p>Modules may contain "module-level inline asm" blocks, which corresponds to - the GCC "file scope inline asm" blocks. These blocks are internally - concatenated by LLVM and treated as a single unit, but may be separated in - the <tt>.ll</tt> file if desired. The syntax is very simple:</p> - -<pre class="doc_code"> -module asm "inline asm code goes here" -module asm "more can go here" -</pre> - -<p>The strings can contain any character by escaping non-printable characters. - The escape sequence used is simply "\xx" where "xx" is the two digit hex code - for the number.</p> - -<p>The inline asm code is simply printed to the machine code .s file when - assembly code is generated.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="datalayout">Data Layout</a> -</h3> - -<div> - -<p>A module may specify a target specific data layout string that specifies how - data is to be laid out in memory. The syntax for the data layout is - simply:</p> - -<pre class="doc_code"> -target datalayout = "<i>layout specification</i>" -</pre> - -<p>The <i>layout specification</i> consists of a list of specifications - separated by the minus sign character ('-'). Each specification starts with - a letter and may include other information after the letter to define some - aspect of the data layout. The specifications accepted are as follows:</p> - -<dl> - <dt><tt>E</tt></dt> - <dd>Specifies that the target lays out data in big-endian form. That is, the - bits with the most significance have the lowest address location.</dd> - - <dt><tt>e</tt></dt> - <dd>Specifies that the target lays out data in little-endian form. That is, - the bits with the least significance have the lowest address - location.</dd> - - <dt><tt>S<i>size</i></tt></dt> - <dd>Specifies the natural alignment of the stack in bits. Alignment promotion - of stack variables is limited to the natural stack alignment to avoid - dynamic stack realignment. The stack alignment must be a multiple of - 8-bits. If omitted, the natural stack alignment defaults to "unspecified", - which does not prevent any alignment promotions.</dd> - - <dt><tt>p[n]:<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> - <dd>This specifies the <i>size</i> of a pointer and its <i>abi</i> and - <i>preferred</i> alignments for address space <i>n</i>. All sizes are in - bits. Specifying the <i>pref</i> alignment is optional. If omitted, the - preceding <tt>:</tt> should be omitted too. The address space, - <i>n</i> is optional, and if not specified, denotes the default address - space 0. The value of <i>n</i> must be in the range [1,2^23).</dd> - - <dt><tt>i<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> - <dd>This specifies the alignment for an integer type of a given bit - <i>size</i>. The value of <i>size</i> must be in the range [1,2^23).</dd> - - <dt><tt>v<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> - <dd>This specifies the alignment for a vector type of a given bit - <i>size</i>.</dd> - - <dt><tt>f<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> - <dd>This specifies the alignment for a floating point type of a given bit - <i>size</i>. Only values of <i>size</i> that are supported by the target - will work. 32 (float) and 64 (double) are supported on all targets; - 80 or 128 (different flavors of long double) are also supported on some - targets. - - <dt><tt>a<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> - <dd>This specifies the alignment for an aggregate type of a given bit - <i>size</i>.</dd> - - <dt><tt>s<i>size</i>:<i>abi</i>:<i>pref</i></tt></dt> - <dd>This specifies the alignment for a stack object of a given bit - <i>size</i>.</dd> - - <dt><tt>n<i>size1</i>:<i>size2</i>:<i>size3</i>...</tt></dt> - <dd>This specifies a set of native integer widths for the target CPU - in bits. For example, it might contain "n32" for 32-bit PowerPC, - "n32:64" for PowerPC 64, or "n8:16:32:64" for X86-64. Elements of - this set are considered to support most general arithmetic - operations efficiently.</dd> -</dl> - -<p>When constructing the data layout for a given target, LLVM starts with a - default set of specifications which are then (possibly) overridden by the - specifications in the <tt>datalayout</tt> keyword. The default specifications - are given in this list:</p> - -<ul> - <li><tt>E</tt> - big endian</li> - <li><tt>p:64:64:64</tt> - 64-bit pointers with 64-bit alignment</li> - <li><tt>p1:32:32:32</tt> - 32-bit pointers with 32-bit alignment for - address space 1</li> - <li><tt>p2:16:32:32</tt> - 16-bit pointers with 32-bit alignment for - address space 2</li> - <li><tt>i1:8:8</tt> - i1 is 8-bit (byte) aligned</li> - <li><tt>i8:8:8</tt> - i8 is 8-bit (byte) aligned</li> - <li><tt>i16:16:16</tt> - i16 is 16-bit aligned</li> - <li><tt>i32:32:32</tt> - i32 is 32-bit aligned</li> - <li><tt>i64:32:64</tt> - i64 has ABI alignment of 32-bits but preferred - alignment of 64-bits</li> - <li><tt>f32:32:32</tt> - float is 32-bit aligned</li> - <li><tt>f64:64:64</tt> - double is 64-bit aligned</li> - <li><tt>v64:64:64</tt> - 64-bit vector is 64-bit aligned</li> - <li><tt>v128:128:128</tt> - 128-bit vector is 128-bit aligned</li> - <li><tt>a0:0:1</tt> - aggregates are 8-bit aligned</li> - <li><tt>s0:64:64</tt> - stack objects are 64-bit aligned</li> -</ul> - -<p>When LLVM is determining the alignment for a given type, it uses the - following rules:</p> - -<ol> - <li>If the type sought is an exact match for one of the specifications, that - specification is used.</li> - - <li>If no match is found, and the type sought is an integer type, then the - smallest integer type that is larger than the bitwidth of the sought type - is used. If none of the specifications are larger than the bitwidth then - the largest integer type is used. For example, given the default - specifications above, the i7 type will use the alignment of i8 (next - largest) while both i65 and i256 will use the alignment of i64 (largest - specified).</li> - - <li>If no match is found, and the type sought is a vector type, then the - largest vector type that is smaller than the sought vector type will be - used as a fall back. This happens because <128 x double> can be - implemented in terms of 64 <2 x double>, for example.</li> -</ol> - -<p>The function of the data layout string may not be what you expect. Notably, - this is not a specification from the frontend of what alignment the code - generator should use.</p> - -<p>Instead, if specified, the target data layout is required to match what the - ultimate <em>code generator</em> expects. This string is used by the - mid-level optimizers to - improve code, and this only works if it matches what the ultimate code - generator uses. If you would like to generate IR that does not embed this - target-specific detail into the IR, then you don't have to specify the - string. This will disable some optimizations that require precise layout - information, but this also prevents those optimizations from introducing - target specificity into the IR.</p> - - - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="pointeraliasing">Pointer Aliasing Rules</a> -</h3> - -<div> - -<p>Any memory access must be done through a pointer value associated -with an address range of the memory access, otherwise the behavior -is undefined. Pointer values are associated with address ranges -according to the following rules:</p> - -<ul> - <li>A pointer value is associated with the addresses associated with - any value it is <i>based</i> on. - <li>An address of a global variable is associated with the address - range of the variable's storage.</li> - <li>The result value of an allocation instruction is associated with - the address range of the allocated storage.</li> - <li>A null pointer in the default address-space is associated with - no address.</li> - <li>An integer constant other than zero or a pointer value returned - from a function not defined within LLVM may be associated with address - ranges allocated through mechanisms other than those provided by - LLVM. Such ranges shall not overlap with any ranges of addresses - allocated by mechanisms provided by LLVM.</li> -</ul> - -<p>A pointer value is <i>based</i> on another pointer value according - to the following rules:</p> - -<ul> - <li>A pointer value formed from a - <tt><a href="#i_getelementptr">getelementptr</a></tt> operation - is <i>based</i> on the first operand of the <tt>getelementptr</tt>.</li> - <li>The result value of a - <tt><a href="#i_bitcast">bitcast</a></tt> is <i>based</i> on the operand - of the <tt>bitcast</tt>.</li> - <li>A pointer value formed by an - <tt><a href="#i_inttoptr">inttoptr</a></tt> is <i>based</i> on all - pointer values that contribute (directly or indirectly) to the - computation of the pointer's value.</li> - <li>The "<i>based</i> on" relationship is transitive.</li> -</ul> - -<p>Note that this definition of <i>"based"</i> is intentionally - similar to the definition of <i>"based"</i> in C99, though it is - slightly weaker.</p> - -<p>LLVM IR does not associate types with memory. The result type of a -<tt><a href="#i_load">load</a></tt> merely indicates the size and -alignment of the memory from which to load, as well as the -interpretation of the value. The first operand type of a -<tt><a href="#i_store">store</a></tt> similarly only indicates the size -and alignment of the store.</p> - -<p>Consequently, type-based alias analysis, aka TBAA, aka -<tt>-fstrict-aliasing</tt>, is not applicable to general unadorned -LLVM IR. <a href="#metadata">Metadata</a> may be used to encode -additional information which specialized optimization passes may use -to implement type-based alias analysis.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="volatile">Volatile Memory Accesses</a> -</h3> - -<div> - -<p>Certain memory accesses, such as <a href="#i_load"><tt>load</tt></a>s, <a -href="#i_store"><tt>store</tt></a>s, and <a -href="#int_memcpy"><tt>llvm.memcpy</tt></a>s may be marked <tt>volatile</tt>. -The optimizers must not change the number of volatile operations or change their -order of execution relative to other volatile operations. The optimizers -<i>may</i> change the order of volatile operations relative to non-volatile -operations. This is not Java's "volatile" and has no cross-thread -synchronization behavior.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="memmodel">Memory Model for Concurrent Operations</a> -</h3> - -<div> - -<p>The LLVM IR does not define any way to start parallel threads of execution -or to register signal handlers. Nonetheless, there are platform-specific -ways to create them, and we define LLVM IR's behavior in their presence. This -model is inspired by the C++0x memory model.</p> - -<p>For a more informal introduction to this model, see the -<a href="Atomics.html">LLVM Atomic Instructions and Concurrency Guide</a>. - -<p>We define a <i>happens-before</i> partial order as the least partial order -that</p> -<ul> - <li>Is a superset of single-thread program order, and</li> - <li>When a <i>synchronizes-with</i> <tt>b</tt>, includes an edge from - <tt>a</tt> to <tt>b</tt>. <i>Synchronizes-with</i> pairs are introduced - by platform-specific techniques, like pthread locks, thread - creation, thread joining, etc., and by atomic instructions. - (See also <a href="#ordering">Atomic Memory Ordering Constraints</a>). - </li> -</ul> - -<p>Note that program order does not introduce <i>happens-before</i> edges -between a thread and signals executing inside that thread.</p> - -<p>Every (defined) read operation (load instructions, memcpy, atomic -loads/read-modify-writes, etc.) <var>R</var> reads a series of bytes written by -(defined) write operations (store instructions, atomic -stores/read-modify-writes, memcpy, etc.). For the purposes of this section, -initialized globals are considered to have a write of the initializer which is -atomic and happens before any other read or write of the memory in question. -For each byte of a read <var>R</var>, <var>R<sub>byte</sub></var> may see -any write to the same byte, except:</p> - -<ul> - <li>If <var>write<sub>1</sub></var> happens before - <var>write<sub>2</sub></var>, and <var>write<sub>2</sub></var> happens - before <var>R<sub>byte</sub></var>, then <var>R<sub>byte</sub></var> - does not see <var>write<sub>1</sub></var>. - <li>If <var>R<sub>byte</sub></var> happens before - <var>write<sub>3</sub></var>, then <var>R<sub>byte</sub></var> does not - see <var>write<sub>3</sub></var>. -</ul> - -<p>Given that definition, <var>R<sub>byte</sub></var> is defined as follows: -<ul> - <li>If <var>R</var> is volatile, the result is target-dependent. (Volatile - is supposed to give guarantees which can support - <code>sig_atomic_t</code> in C/C++, and may be used for accesses to - addresses which do not behave like normal memory. It does not generally - provide cross-thread synchronization.) - <li>Otherwise, if there is no write to the same byte that happens before - <var>R<sub>byte</sub></var>, <var>R<sub>byte</sub></var> returns - <tt>undef</tt> for that byte. - <li>Otherwise, if <var>R<sub>byte</sub></var> may see exactly one write, - <var>R<sub>byte</sub></var> returns the value written by that - write.</li> - <li>Otherwise, if <var>R</var> is atomic, and all the writes - <var>R<sub>byte</sub></var> may see are atomic, it chooses one of the - values written. See the <a href="#ordering">Atomic Memory Ordering - Constraints</a> section for additional constraints on how the choice - is made. - <li>Otherwise <var>R<sub>byte</sub></var> returns <tt>undef</tt>.</li> -</ul> - -<p><var>R</var> returns the value composed of the series of bytes it read. -This implies that some bytes within the value may be <tt>undef</tt> -<b>without</b> the entire value being <tt>undef</tt>. Note that this only -defines the semantics of the operation; it doesn't mean that targets will -emit more than one instruction to read the series of bytes.</p> - -<p>Note that in cases where none of the atomic intrinsics are used, this model -places only one restriction on IR transformations on top of what is required -for single-threaded execution: introducing a store to a byte which might not -otherwise be stored is not allowed in general. (Specifically, in the case -where another thread might write to and read from an address, introducing a -store can change a load that may see exactly one write into a load that may -see multiple writes.)</p> - -<!-- FIXME: This model assumes all targets where concurrency is relevant have -a byte-size store which doesn't affect adjacent bytes. As far as I can tell, -none of the backends currently in the tree fall into this category; however, -there might be targets which care. If there are, we want a paragraph -like the following: - -Targets may specify that stores narrower than a certain width are not -available; on such a target, for the purposes of this model, treat any -non-atomic write with an alignment or width less than the minimum width -as if it writes to the relevant surrounding bytes. ---> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="ordering">Atomic Memory Ordering Constraints</a> -</h3> - -<div> - -<p>Atomic instructions (<a href="#i_cmpxchg"><code>cmpxchg</code></a>, -<a href="#i_atomicrmw"><code>atomicrmw</code></a>, -<a href="#i_fence"><code>fence</code></a>, -<a href="#i_load"><code>atomic load</code></a>, and -<a href="#i_store"><code>atomic store</code></a>) take an ordering parameter -that determines which other atomic instructions on the same address they -<i>synchronize with</i>. These semantics are borrowed from Java and C++0x, -but are somewhat more colloquial. If these descriptions aren't precise enough, -check those specs (see spec references in the -<a href="Atomics.html#introduction">atomics guide</a>). -<a href="#i_fence"><code>fence</code></a> instructions -treat these orderings somewhat differently since they don't take an address. -See that instruction's documentation for details.</p> - -<p>For a simpler introduction to the ordering constraints, see the -<a href="Atomics.html">LLVM Atomic Instructions and Concurrency Guide</a>.</p> - -<dl> -<dt><code>unordered</code></dt> -<dd>The set of values that can be read is governed by the happens-before -partial order. A value cannot be read unless some operation wrote it. -This is intended to provide a guarantee strong enough to model Java's -non-volatile shared variables. This ordering cannot be specified for -read-modify-write operations; it is not strong enough to make them atomic -in any interesting way.</dd> -<dt><code>monotonic</code></dt> -<dd>In addition to the guarantees of <code>unordered</code>, there is a single -total order for modifications by <code>monotonic</code> operations on each -address. All modification orders must be compatible with the happens-before -order. There is no guarantee that the modification orders can be combined to -a global total order for the whole program (and this often will not be -possible). The read in an atomic read-modify-write operation -(<a href="#i_cmpxchg"><code>cmpxchg</code></a> and -<a href="#i_atomicrmw"><code>atomicrmw</code></a>) -reads the value in the modification order immediately before the value it -writes. If one atomic read happens before another atomic read of the same -address, the later read must see the same value or a later value in the -address's modification order. This disallows reordering of -<code>monotonic</code> (or stronger) operations on the same address. If an -address is written <code>monotonic</code>ally by one thread, and other threads -<code>monotonic</code>ally read that address repeatedly, the other threads must -eventually see the write. This corresponds to the C++0x/C1x -<code>memory_order_relaxed</code>.</dd> -<dt><code>acquire</code></dt> -<dd>In addition to the guarantees of <code>monotonic</code>, -a <i>synchronizes-with</i> edge may be formed with a <code>release</code> -operation. This is intended to model C++'s <code>memory_order_acquire</code>.</dd> -<dt><code>release</code></dt> -<dd>In addition to the guarantees of <code>monotonic</code>, if this operation -writes a value which is subsequently read by an <code>acquire</code> operation, -it <i>synchronizes-with</i> that operation. (This isn't a complete -description; see the C++0x definition of a release sequence.) This corresponds -to the C++0x/C1x <code>memory_order_release</code>.</dd> -<dt><code>acq_rel</code> (acquire+release)</dt><dd>Acts as both an -<code>acquire</code> and <code>release</code> operation on its address. -This corresponds to the C++0x/C1x <code>memory_order_acq_rel</code>.</dd> -<dt><code>seq_cst</code> (sequentially consistent)</dt><dd> -<dd>In addition to the guarantees of <code>acq_rel</code> -(<code>acquire</code> for an operation which only reads, <code>release</code> -for an operation which only writes), there is a global total order on all -sequentially-consistent operations on all addresses, which is consistent with -the <i>happens-before</i> partial order and with the modification orders of -all the affected addresses. Each sequentially-consistent read sees the last -preceding write to the same address in this global order. This corresponds -to the C++0x/C1x <code>memory_order_seq_cst</code> and Java volatile.</dd> -</dl> - -<p id="singlethread">If an atomic operation is marked <code>singlethread</code>, -it only <i>synchronizes with</i> or participates in modification and seq_cst -total orderings with other operations running in the same thread (for example, -in signal handlers).</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="fastmath">Fast-Math Flags</a> -</h3> - -<div> - -<p> LLVM IR floating-point binary ops (<a href="#i_fadd"><code>fadd</code></a>, -<a href="#i_fsub"><code>fsub</code></a>, <a - href="#i_fmul"><code>fmul</code></a>, <a href="#i_fdiv"><code>fdiv</code></a>, -<a href="#i_frem"><code>frem</code></a>) have the following flags -that can set to enable otherwise unsafe floating point operations</p> - -<dt><code>nnan</dt></code> -<dd> - No NaNs - Allow optimizations to assume the arguments and result are not -NaN. Such optimizations are required to retain defined behavior over NaNs, but -the value of the result is undefined. -</dd> - -<dt><code>ninf</code></dt> -<dd> - No Infs - Allow optimizations to assume the arguments and result are not -+/-Inf. Such optimizations are required to retain defined behavior over +/-Inf, -but the value of the result is undefined. -</dd> - -<dt><code>nsz</code></dt> -<dd> - No Signed Zeros - Allow optimizations to treat the sign of a zero argument or -result as insignificant. -</dd> - -<dt><code>arcp</code></dt> -<dd> - Allow Reciprocal - Allow optimizations to use the reciprocal of an argument -rather than perform division. -</dd> - -<dt><code>fast</code></TD> -<dd> - Fast - Allow algebraically equivalent transformations that may dramatically -change results in floating point (e.g. reassociate). This flag implies all the -others. -</dd> - -</div> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="typesystem">Type System</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>The LLVM type system is one of the most important features of the - intermediate representation. Being typed enables a number of optimizations - to be performed on the intermediate representation directly, without having - to do extra analyses on the side before the transformation. A strong type - system makes it easier to read the generated code and enables novel analyses - and transformations that are not feasible to perform on normal three address - code representations.</p> - -<!-- ======================================================================= --> -<h3> - <a name="t_classifications">Type Classifications</a> -</h3> - -<div> - -<p>The types fall into a few useful classifications:</p> - -<table border="1" cellspacing="0" cellpadding="4"> - <tbody> - <tr><th>Classification</th><th>Types</th></tr> - <tr> - <td><a href="#t_integer">integer</a></td> - <td><tt>i1, i2, i3, ... i8, ... i16, ... i32, ... i64, ... </tt></td> - </tr> - <tr> - <td><a href="#t_floating">floating point</a></td> - <td><tt>half, float, double, x86_fp80, fp128, ppc_fp128</tt></td> - </tr> - <tr> - <td><a name="t_firstclass">first class</a></td> - <td><a href="#t_integer">integer</a>, - <a href="#t_floating">floating point</a>, - <a href="#t_pointer">pointer</a>, - <a href="#t_vector">vector</a>, - <a href="#t_struct">structure</a>, - <a href="#t_array">array</a>, - <a href="#t_label">label</a>, - <a href="#t_metadata">metadata</a>. - </td> - </tr> - <tr> - <td><a href="#t_primitive">primitive</a></td> - <td><a href="#t_label">label</a>, - <a href="#t_void">void</a>, - <a href="#t_integer">integer</a>, - <a href="#t_floating">floating point</a>, - <a href="#t_x86mmx">x86mmx</a>, - <a href="#t_metadata">metadata</a>.</td> - </tr> - <tr> - <td><a href="#t_derived">derived</a></td> - <td><a href="#t_array">array</a>, - <a href="#t_function">function</a>, - <a href="#t_pointer">pointer</a>, - <a href="#t_struct">structure</a>, - <a href="#t_vector">vector</a>, - <a href="#t_opaque">opaque</a>. - </td> - </tr> - </tbody> -</table> - -<p>The <a href="#t_firstclass">first class</a> types are perhaps the most - important. Values of these types are the only ones which can be produced by - instructions.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="t_primitive">Primitive Types</a> -</h3> - -<div> - -<p>The primitive types are the fundamental building blocks of the LLVM - system.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_integer">Integer Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The integer type is a very simple type that simply specifies an arbitrary - bit width for the integer type desired. Any bit width from 1 bit to - 2<sup>23</sup>-1 (about 8 million) can be specified.</p> - -<h5>Syntax:</h5> -<pre> - iN -</pre> - -<p>The number of bits the integer will occupy is specified by the <tt>N</tt> - value.</p> - -<h5>Examples:</h5> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt>i1</tt></td> - <td class="left">a single-bit integer.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>i32</tt></td> - <td class="left">a 32-bit integer.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>i1942652</tt></td> - <td class="left">a really big integer of over 1 million bits.</td> - </tr> -</table> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_floating">Floating Point Types</a> -</h4> - -<div> - -<table> - <tbody> - <tr><th>Type</th><th>Description</th></tr> - <tr><td><tt>half</tt></td><td>16-bit floating point value</td></tr> - <tr><td><tt>float</tt></td><td>32-bit floating point value</td></tr> - <tr><td><tt>double</tt></td><td>64-bit floating point value</td></tr> - <tr><td><tt>fp128</tt></td><td>128-bit floating point value (112-bit mantissa)</td></tr> - <tr><td><tt>x86_fp80</tt></td><td>80-bit floating point value (X87)</td></tr> - <tr><td><tt>ppc_fp128</tt></td><td>128-bit floating point value (two 64-bits)</td></tr> - </tbody> -</table> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_x86mmx">X86mmx Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The x86mmx type represents a value held in an MMX register on an x86 machine. The operations allowed on it are quite limited: parameters and return values, load and store, and bitcast. User-specified MMX instructions are represented as intrinsic or asm calls with arguments and/or results of this type. There are no arrays, vectors or constants of this type.</p> - -<h5>Syntax:</h5> -<pre> - x86mmx -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_void">Void Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The void type does not represent any value and has no size.</p> - -<h5>Syntax:</h5> -<pre> - void -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_label">Label Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The label type represents code labels.</p> - -<h5>Syntax:</h5> -<pre> - label -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_metadata">Metadata Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The metadata type represents embedded metadata. No derived types may be - created from metadata except for <a href="#t_function">function</a> - arguments. - -<h5>Syntax:</h5> -<pre> - metadata -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="t_derived">Derived Types</a> -</h3> - -<div> - -<p>The real power in LLVM comes from the derived types in the system. This is - what allows a programmer to represent arrays, functions, pointers, and other - useful types. Each of these types contain one or more element types which - may be a primitive type, or another derived type. For example, it is - possible to have a two dimensional array, using an array as the element type - of another array.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_aggregate">Aggregate Types</a> -</h4> - -<div> - -<p>Aggregate Types are a subset of derived types that can contain multiple - member types. <a href="#t_array">Arrays</a> and - <a href="#t_struct">structs</a> are aggregate types. - <a href="#t_vector">Vectors</a> are not considered to be aggregate types.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_array">Array Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The array type is a very simple derived type that arranges elements - sequentially in memory. The array type requires a size (number of elements) - and an underlying data type.</p> - -<h5>Syntax:</h5> -<pre> - [<# elements> x <elementtype>] -</pre> - -<p>The number of elements is a constant integer value; <tt>elementtype</tt> may - be any type with a size.</p> - -<h5>Examples:</h5> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt>[40 x i32]</tt></td> - <td class="left">Array of 40 32-bit integer values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>[41 x i32]</tt></td> - <td class="left">Array of 41 32-bit integer values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>[4 x i8]</tt></td> - <td class="left">Array of 4 8-bit integer values.</td> - </tr> -</table> -<p>Here are some examples of multidimensional arrays:</p> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt>[3 x [4 x i32]]</tt></td> - <td class="left">3x4 array of 32-bit integer values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>[12 x [10 x float]]</tt></td> - <td class="left">12x10 array of single precision floating point values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>[2 x [3 x [4 x i16]]]</tt></td> - <td class="left">2x3x4 array of 16-bit integer values.</td> - </tr> -</table> - -<p>There is no restriction on indexing beyond the end of the array implied by - a static type (though there are restrictions on indexing beyond the bounds - of an allocated object in some cases). This means that single-dimension - 'variable sized array' addressing can be implemented in LLVM with a zero - length array type. An implementation of 'pascal style arrays' in LLVM could - use the type "<tt>{ i32, [0 x float]}</tt>", for example.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_function">Function Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The function type can be thought of as a function signature. It consists of - a return type and a list of formal parameter types. The return type of a - function type is a first class type or a void type.</p> - -<h5>Syntax:</h5> -<pre> - <returntype> (<parameter list>) -</pre> - -<p>...where '<tt><parameter list></tt>' is a comma-separated list of type - specifiers. Optionally, the parameter list may include a type <tt>...</tt>, - which indicates that the function takes a variable number of arguments. - Variable argument functions can access their arguments with - the <a href="#int_varargs">variable argument handling intrinsic</a> - functions. '<tt><returntype></tt>' is any type except - <a href="#t_label">label</a>.</p> - -<h5>Examples:</h5> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt>i32 (i32)</tt></td> - <td class="left">function taking an <tt>i32</tt>, returning an <tt>i32</tt> - </td> - </tr><tr class="layout"> - <td class="left"><tt>float (i16, i32 *) * - </tt></td> - <td class="left"><a href="#t_pointer">Pointer</a> to a function that takes - an <tt>i16</tt> and a <a href="#t_pointer">pointer</a> to <tt>i32</tt>, - returning <tt>float</tt>. - </td> - </tr><tr class="layout"> - <td class="left"><tt>i32 (i8*, ...)</tt></td> - <td class="left">A vararg function that takes at least one - <a href="#t_pointer">pointer</a> to <tt>i8 </tt> (char in C), - which returns an integer. This is the signature for <tt>printf</tt> in - LLVM. - </td> - </tr><tr class="layout"> - <td class="left"><tt>{i32, i32} (i32)</tt></td> - <td class="left">A function taking an <tt>i32</tt>, returning a - <a href="#t_struct">structure</a> containing two <tt>i32</tt> values - </td> - </tr> -</table> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_struct">Structure Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The structure type is used to represent a collection of data members together - in memory. The elements of a structure may be any type that has a size.</p> - -<p>Structures in memory are accessed using '<tt><a href="#i_load">load</a></tt>' - and '<tt><a href="#i_store">store</a></tt>' by getting a pointer to a field - with the '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction. - Structures in registers are accessed using the - '<tt><a href="#i_extractvalue">extractvalue</a></tt>' and - '<tt><a href="#i_insertvalue">insertvalue</a></tt>' instructions.</p> - -<p>Structures may optionally be "packed" structures, which indicate that the - alignment of the struct is one byte, and that there is no padding between - the elements. In non-packed structs, padding between field types is inserted - as defined by the DataLayout string in the module, which is required to match - what the underlying code generator expects.</p> - -<p>Structures can either be "literal" or "identified". A literal structure is - defined inline with other types (e.g. <tt>{i32, i32}*</tt>) whereas identified - types are always defined at the top level with a name. Literal types are - uniqued by their contents and can never be recursive or opaque since there is - no way to write one. Identified types can be recursive, can be opaqued, and are - never uniqued. -</p> - -<h5>Syntax:</h5> -<pre> - %T1 = type { <type list> } <i>; Identified normal struct type</i> - %T2 = type <{ <type list> }> <i>; Identified packed struct type</i> -</pre> - -<h5>Examples:</h5> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt>{ i32, i32, i32 }</tt></td> - <td class="left">A triple of three <tt>i32</tt> values</td> - </tr> - <tr class="layout"> - <td class="left"><tt>{ float, i32 (i32) * }</tt></td> - <td class="left">A pair, where the first element is a <tt>float</tt> and the - second element is a <a href="#t_pointer">pointer</a> to a - <a href="#t_function">function</a> that takes an <tt>i32</tt>, returning - an <tt>i32</tt>.</td> - </tr> - <tr class="layout"> - <td class="left"><tt><{ i8, i32 }></tt></td> - <td class="left">A packed struct known to be 5 bytes in size.</td> - </tr> -</table> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_opaque">Opaque Structure Types</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>Opaque structure types are used to represent named structure types that do - not have a body specified. This corresponds (for example) to the C notion of - a forward declared structure.</p> - -<h5>Syntax:</h5> -<pre> - %X = type opaque - %52 = type opaque -</pre> - -<h5>Examples:</h5> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt>opaque</tt></td> - <td class="left">An opaque type.</td> - </tr> -</table> - -</div> - - - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_pointer">Pointer Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>The pointer type is used to specify memory locations. - Pointers are commonly used to reference objects in memory.</p> - -<p>Pointer types may have an optional address space attribute defining the - numbered address space where the pointed-to object resides. The default - address space is number zero. The semantics of non-zero address - spaces are target-specific.</p> - -<p>Note that LLVM does not permit pointers to void (<tt>void*</tt>) nor does it - permit pointers to labels (<tt>label*</tt>). Use <tt>i8*</tt> instead.</p> - -<h5>Syntax:</h5> -<pre> - <type> * -</pre> - -<h5>Examples:</h5> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt>[4 x i32]*</tt></td> - <td class="left">A <a href="#t_pointer">pointer</a> to <a - href="#t_array">array</a> of four <tt>i32</tt> values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>i32 (i32*) *</tt></td> - <td class="left"> A <a href="#t_pointer">pointer</a> to a <a - href="#t_function">function</a> that takes an <tt>i32*</tt>, returning an - <tt>i32</tt>.</td> - </tr> - <tr class="layout"> - <td class="left"><tt>i32 addrspace(5)*</tt></td> - <td class="left">A <a href="#t_pointer">pointer</a> to an <tt>i32</tt> value - that resides in address space #5.</td> - </tr> -</table> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="t_vector">Vector Type</a> -</h4> - -<div> - -<h5>Overview:</h5> -<p>A vector type is a simple derived type that represents a vector of elements. - Vector types are used when multiple primitive data are operated in parallel - using a single instruction (SIMD). A vector type requires a size (number of - elements) and an underlying primitive data type. Vector types are considered - <a href="#t_firstclass">first class</a>.</p> - -<h5>Syntax:</h5> -<pre> - < <# elements> x <elementtype> > -</pre> - -<p>The number of elements is a constant integer value larger than 0; elementtype - may be any integer or floating point type, or a pointer to these types. - Vectors of size zero are not allowed. </p> - -<h5>Examples:</h5> -<table class="layout"> - <tr class="layout"> - <td class="left"><tt><4 x i32></tt></td> - <td class="left">Vector of 4 32-bit integer values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt><8 x float></tt></td> - <td class="left">Vector of 8 32-bit floating-point values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt><2 x i64></tt></td> - <td class="left">Vector of 2 64-bit integer values.</td> - </tr> - <tr class="layout"> - <td class="left"><tt><4 x i64*></tt></td> - <td class="left">Vector of 4 pointers to 64-bit integer values.</td> - </tr> -</table> - -</div> - -</div> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="constants">Constants</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>LLVM has several different basic types of constants. This section describes - them all and their syntax.</p> - -<!-- ======================================================================= --> -<h3> - <a name="simpleconstants">Simple Constants</a> -</h3> - -<div> - -<dl> - <dt><b>Boolean constants</b></dt> - <dd>The two strings '<tt>true</tt>' and '<tt>false</tt>' are both valid - constants of the <tt><a href="#t_integer">i1</a></tt> type.</dd> - - <dt><b>Integer constants</b></dt> - <dd>Standard integers (such as '4') are constants of - the <a href="#t_integer">integer</a> type. Negative numbers may be used - with integer types.</dd> - - <dt><b>Floating point constants</b></dt> - <dd>Floating point constants use standard decimal notation (e.g. 123.421), - exponential notation (e.g. 1.23421e+2), or a more precise hexadecimal - notation (see below). The assembler requires the exact decimal value of a - floating-point constant. For example, the assembler accepts 1.25 but - rejects 1.3 because 1.3 is a repeating decimal in binary. Floating point - constants must have a <a href="#t_floating">floating point</a> type. </dd> - - <dt><b>Null pointer constants</b></dt> - <dd>The identifier '<tt>null</tt>' is recognized as a null pointer constant - and must be of <a href="#t_pointer">pointer type</a>.</dd> -</dl> - -<p>The one non-intuitive notation for constants is the hexadecimal form of - floating point constants. For example, the form '<tt>double - 0x432ff973cafa8000</tt>' is equivalent to (but harder to read than) - '<tt>double 4.5e+15</tt>'. The only time hexadecimal floating point - constants are required (and the only time that they are generated by the - disassembler) is when a floating point constant must be emitted but it cannot - be represented as a decimal floating point number in a reasonable number of - digits. For example, NaN's, infinities, and other special values are - represented in their IEEE hexadecimal format so that assembly and disassembly - do not cause any bits to change in the constants.</p> - -<p>When using the hexadecimal form, constants of types half, float, and double are - represented using the 16-digit form shown above (which matches the IEEE754 - representation for double); half and float values must, however, be exactly - representable as IEE754 half and single precision, respectively. - Hexadecimal format is always used - for long double, and there are three forms of long double. The 80-bit format - used by x86 is represented as <tt>0xK</tt> followed by 20 hexadecimal digits. - The 128-bit format used by PowerPC (two adjacent doubles) is represented - by <tt>0xM</tt> followed by 32 hexadecimal digits. The IEEE 128-bit format - is represented by <tt>0xL</tt> followed by 32 hexadecimal digits; no - currently supported target uses this format. Long doubles will only work if - they match the long double format on your target. The IEEE 16-bit format - (half precision) is represented by <tt>0xH</tt> followed by 4 hexadecimal - digits. All hexadecimal formats are big-endian (sign bit at the left).</p> - -<p>There are no constants of type x86mmx.</p> -</div> - -<!-- ======================================================================= --> -<h3> -<a name="aggregateconstants"></a> <!-- old anchor --> -<a name="complexconstants">Complex Constants</a> -</h3> - -<div> - -<p>Complex constants are a (potentially recursive) combination of simple - constants and smaller complex constants.</p> - -<dl> - <dt><b>Structure constants</b></dt> - <dd>Structure constants are represented with notation similar to structure - type definitions (a comma separated list of elements, surrounded by braces - (<tt>{}</tt>)). For example: "<tt>{ i32 4, float 17.0, i32* @G }</tt>", - where "<tt>@G</tt>" is declared as "<tt>@G = external global i32</tt>". - Structure constants must have <a href="#t_struct">structure type</a>, and - the number and types of elements must match those specified by the - type.</dd> - - <dt><b>Array constants</b></dt> - <dd>Array constants are represented with notation similar to array type - definitions (a comma separated list of elements, surrounded by square - brackets (<tt>[]</tt>)). For example: "<tt>[ i32 42, i32 11, i32 74 - ]</tt>". Array constants must have <a href="#t_array">array type</a>, and - the number and types of elements must match those specified by the - type.</dd> - - <dt><b>Vector constants</b></dt> - <dd>Vector constants are represented with notation similar to vector type - definitions (a comma separated list of elements, surrounded by - less-than/greater-than's (<tt><></tt>)). For example: "<tt>< i32 - 42, i32 11, i32 74, i32 100 ></tt>". Vector constants must - have <a href="#t_vector">vector type</a>, and the number and types of - elements must match those specified by the type.</dd> - - <dt><b>Zero initialization</b></dt> - <dd>The string '<tt>zeroinitializer</tt>' can be used to zero initialize a - value to zero of <em>any</em> type, including scalar and - <a href="#t_aggregate">aggregate</a> types. - This is often used to avoid having to print large zero initializers - (e.g. for large arrays) and is always exactly equivalent to using explicit - zero initializers.</dd> - - <dt><b>Metadata node</b></dt> - <dd>A metadata node is a structure-like constant with - <a href="#t_metadata">metadata type</a>. For example: "<tt>metadata !{ - i32 0, metadata !"test" }</tt>". Unlike other constants that are meant to - be interpreted as part of the instruction stream, metadata is a place to - attach additional information such as debug info.</dd> -</dl> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="globalconstants">Global Variable and Function Addresses</a> -</h3> - -<div> - -<p>The addresses of <a href="#globalvars">global variables</a> - and <a href="#functionstructure">functions</a> are always implicitly valid - (link-time) constants. These constants are explicitly referenced when - the <a href="#identifiers">identifier for the global</a> is used and always - have <a href="#t_pointer">pointer</a> type. For example, the following is a - legal LLVM file:</p> - -<pre class="doc_code"> -@X = global i32 17 -@Y = global i32 42 -@Z = global [2 x i32*] [ i32* @X, i32* @Y ] -</pre> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="undefvalues">Undefined Values</a> -</h3> - -<div> - -<p>The string '<tt>undef</tt>' can be used anywhere a constant is expected, and - indicates that the user of the value may receive an unspecified bit-pattern. - Undefined values may be of any type (other than '<tt>label</tt>' - or '<tt>void</tt>') and be used anywhere a constant is permitted.</p> - -<p>Undefined values are useful because they indicate to the compiler that the - program is well defined no matter what value is used. This gives the - compiler more freedom to optimize. Here are some examples of (potentially - surprising) transformations that are valid (in pseudo IR):</p> - - -<pre class="doc_code"> - %A = add %X, undef - %B = sub %X, undef - %C = xor %X, undef -Safe: - %A = undef - %B = undef - %C = undef -</pre> - -<p>This is safe because all of the output bits are affected by the undef bits. - Any output bit can have a zero or one depending on the input bits.</p> - -<pre class="doc_code"> - %A = or %X, undef - %B = and %X, undef -Safe: - %A = -1 - %B = 0 -Unsafe: - %A = undef - %B = undef -</pre> - -<p>These logical operations have bits that are not always affected by the input. - For example, if <tt>%X</tt> has a zero bit, then the output of the - '<tt>and</tt>' operation will always be a zero for that bit, no matter what - the corresponding bit from the '<tt>undef</tt>' is. As such, it is unsafe to - optimize or assume that the result of the '<tt>and</tt>' is '<tt>undef</tt>'. - However, it is safe to assume that all bits of the '<tt>undef</tt>' could be - 0, and optimize the '<tt>and</tt>' to 0. Likewise, it is safe to assume that - all the bits of the '<tt>undef</tt>' operand to the '<tt>or</tt>' could be - set, allowing the '<tt>or</tt>' to be folded to -1.</p> - -<pre class="doc_code"> - %A = select undef, %X, %Y - %B = select undef, 42, %Y - %C = select %X, %Y, undef -Safe: - %A = %X (or %Y) - %B = 42 (or %Y) - %C = %Y -Unsafe: - %A = undef - %B = undef - %C = undef -</pre> - -<p>This set of examples shows that undefined '<tt>select</tt>' (and conditional - branch) conditions can go <em>either way</em>, but they have to come from one - of the two operands. In the <tt>%A</tt> example, if <tt>%X</tt> and - <tt>%Y</tt> were both known to have a clear low bit, then <tt>%A</tt> would - have to have a cleared low bit. However, in the <tt>%C</tt> example, the - optimizer is allowed to assume that the '<tt>undef</tt>' operand could be the - same as <tt>%Y</tt>, allowing the whole '<tt>select</tt>' to be - eliminated.</p> - -<pre class="doc_code"> - %A = xor undef, undef - - %B = undef - %C = xor %B, %B - - %D = undef - %E = icmp lt %D, 4 - %F = icmp gte %D, 4 - -Safe: - %A = undef - %B = undef - %C = undef - %D = undef - %E = undef - %F = undef -</pre> - -<p>This example points out that two '<tt>undef</tt>' operands are not - necessarily the same. This can be surprising to people (and also matches C - semantics) where they assume that "<tt>X^X</tt>" is always zero, even - if <tt>X</tt> is undefined. This isn't true for a number of reasons, but the - short answer is that an '<tt>undef</tt>' "variable" can arbitrarily change - its value over its "live range". This is true because the variable doesn't - actually <em>have a live range</em>. Instead, the value is logically read - from arbitrary registers that happen to be around when needed, so the value - is not necessarily consistent over time. In fact, <tt>%A</tt> and <tt>%C</tt> - need to have the same semantics or the core LLVM "replace all uses with" - concept would not hold.</p> - -<pre class="doc_code"> - %A = fdiv undef, %X - %B = fdiv %X, undef -Safe: - %A = undef -b: unreachable -</pre> - -<p>These examples show the crucial difference between an <em>undefined - value</em> and <em>undefined behavior</em>. An undefined value (like - '<tt>undef</tt>') is allowed to have an arbitrary bit-pattern. This means that - the <tt>%A</tt> operation can be constant folded to '<tt>undef</tt>', because - the '<tt>undef</tt>' could be an SNaN, and <tt>fdiv</tt> is not (currently) - defined on SNaN's. However, in the second example, we can make a more - aggressive assumption: because the <tt>undef</tt> is allowed to be an - arbitrary value, we are allowed to assume that it could be zero. Since a - divide by zero has <em>undefined behavior</em>, we are allowed to assume that - the operation does not execute at all. This allows us to delete the divide and - all code after it. Because the undefined operation "can't happen", the - optimizer can assume that it occurs in dead code.</p> - -<pre class="doc_code"> -a: store undef -> %X -b: store %X -> undef -Safe: -a: <deleted> -b: unreachable -</pre> - -<p>These examples reiterate the <tt>fdiv</tt> example: a store <em>of</em> an - undefined value can be assumed to not have any effect; we can assume that the - value is overwritten with bits that happen to match what was already there. - However, a store <em>to</em> an undefined location could clobber arbitrary - memory, therefore, it has undefined behavior.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="poisonvalues">Poison Values</a> -</h3> - -<div> - -<p>Poison values are similar to <a href="#undefvalues">undef values</a>, however - they also represent the fact that an instruction or constant expression which - cannot evoke side effects has nevertheless detected a condition which results - in undefined behavior.</p> - -<p>There is currently no way of representing a poison value in the IR; they - only exist when produced by operations such as - <a href="#i_add"><tt>add</tt></a> with the <tt>nsw</tt> flag.</p> - -<p>Poison value behavior is defined in terms of value <i>dependence</i>:</p> - -<ul> -<li>Values other than <a href="#i_phi"><tt>phi</tt></a> nodes depend on - their operands.</li> - -<li><a href="#i_phi"><tt>Phi</tt></a> nodes depend on the operand corresponding - to their dynamic predecessor basic block.</li> - -<li>Function arguments depend on the corresponding actual argument values in - the dynamic callers of their functions.</li> - -<li><a href="#i_call"><tt>Call</tt></a> instructions depend on the - <a href="#i_ret"><tt>ret</tt></a> instructions that dynamically transfer - control back to them.</li> - -<li><a href="#i_invoke"><tt>Invoke</tt></a> instructions depend on the - <a href="#i_ret"><tt>ret</tt></a>, <a href="#i_resume"><tt>resume</tt></a>, - or exception-throwing call instructions that dynamically transfer control - back to them.</li> - -<li>Non-volatile loads and stores depend on the most recent stores to all of the - referenced memory addresses, following the order in the IR - (including loads and stores implied by intrinsics such as - <a href="#int_memcpy"><tt>@llvm.memcpy</tt></a>.)</li> - -<!-- TODO: In the case of multiple threads, this only applies if the store - "happens-before" the load or store. --> - -<!-- TODO: floating-point exception state --> - -<li>An instruction with externally visible side effects depends on the most - recent preceding instruction with externally visible side effects, following - the order in the IR. (This includes - <a href="#volatile">volatile operations</a>.)</li> - -<li>An instruction <i>control-depends</i> on a - <a href="#terminators">terminator instruction</a> - if the terminator instruction has multiple successors and the instruction - is always executed when control transfers to one of the successors, and - may not be executed when control is transferred to another.</li> - -<li>Additionally, an instruction also <i>control-depends</i> on a terminator - instruction if the set of instructions it otherwise depends on would be - different if the terminator had transferred control to a different - successor.</li> - -<li>Dependence is transitive.</li> - -</ul> - -<p>Poison Values have the same behavior as <a href="#undefvalues">undef values</a>, - with the additional affect that any instruction which has a <i>dependence</i> - on a poison value has undefined behavior.</p> - -<p>Here are some examples:</p> - -<pre class="doc_code"> -entry: - %poison = sub nuw i32 0, 1 ; Results in a poison value. - %still_poison = and i32 %poison, 0 ; 0, but also poison. - %poison_yet_again = getelementptr i32* @h, i32 %still_poison - store i32 0, i32* %poison_yet_again ; memory at @h[0] is poisoned - - store i32 %poison, i32* @g ; Poison value stored to memory. - %poison2 = load i32* @g ; Poison value loaded back from memory. - - store volatile i32 %poison, i32* @g ; External observation; undefined behavior. - - %narrowaddr = bitcast i32* @g to i16* - %wideaddr = bitcast i32* @g to i64* - %poison3 = load i16* %narrowaddr ; Returns a poison value. - %poison4 = load i64* %wideaddr ; Returns a poison value. - - %cmp = icmp slt i32 %poison, 0 ; Returns a poison value. - br i1 %cmp, label %true, label %end ; Branch to either destination. - -true: - store volatile i32 0, i32* @g ; This is control-dependent on %cmp, so - ; it has undefined behavior. - br label %end - -end: - %p = phi i32 [ 0, %entry ], [ 1, %true ] - ; Both edges into this PHI are - ; control-dependent on %cmp, so this - ; always results in a poison value. - - store volatile i32 0, i32* @g ; This would depend on the store in %true - ; if %cmp is true, or the store in %entry - ; otherwise, so this is undefined behavior. - - br i1 %cmp, label %second_true, label %second_end - ; The same branch again, but this time the - ; true block doesn't have side effects. - -second_true: - ; No side effects! - ret void - -second_end: - store volatile i32 0, i32* @g ; This time, the instruction always depends - ; on the store in %end. Also, it is - ; control-equivalent to %end, so this is - ; well-defined (ignoring earlier undefined - ; behavior in this example). -</pre> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="blockaddress">Addresses of Basic Blocks</a> -</h3> - -<div> - -<p><b><tt>blockaddress(@function, %block)</tt></b></p> - -<p>The '<tt>blockaddress</tt>' constant computes the address of the specified - basic block in the specified function, and always has an i8* type. Taking - the address of the entry block is illegal.</p> - -<p>This value only has defined behavior when used as an operand to the - '<a href="#i_indirectbr"><tt>indirectbr</tt></a>' instruction, or for - comparisons against null. Pointer equality tests between labels addresses - results in undefined behavior — though, again, comparison against null - is ok, and no label is equal to the null pointer. This may be passed around - as an opaque pointer sized value as long as the bits are not inspected. This - allows <tt>ptrtoint</tt> and arithmetic to be performed on these values so - long as the original value is reconstituted before the <tt>indirectbr</tt> - instruction.</p> - -<p>Finally, some targets may provide defined semantics when using the value as - the operand to an inline assembly, but that is target specific.</p> - -</div> - - -<!-- ======================================================================= --> -<h3> - <a name="constantexprs">Constant Expressions</a> -</h3> - -<div> - -<p>Constant expressions are used to allow expressions involving other constants - to be used as constants. Constant expressions may be of - any <a href="#t_firstclass">first class</a> type and may involve any LLVM - operation that does not have side effects (e.g. load and call are not - supported). The following is the syntax for constant expressions:</p> - -<dl> - <dt><b><tt>trunc (CST to TYPE)</tt></b></dt> - <dd>Truncate a constant to another type. The bit size of CST must be larger - than the bit size of TYPE. Both types must be integers.</dd> - - <dt><b><tt>zext (CST to TYPE)</tt></b></dt> - <dd>Zero extend a constant to another type. The bit size of CST must be - smaller than the bit size of TYPE. Both types must be integers.</dd> - - <dt><b><tt>sext (CST to TYPE)</tt></b></dt> - <dd>Sign extend a constant to another type. The bit size of CST must be - smaller than the bit size of TYPE. Both types must be integers.</dd> - - <dt><b><tt>fptrunc (CST to TYPE)</tt></b></dt> - <dd>Truncate a floating point constant to another floating point type. The - size of CST must be larger than the size of TYPE. Both types must be - floating point.</dd> - - <dt><b><tt>fpext (CST to TYPE)</tt></b></dt> - <dd>Floating point extend a constant to another type. The size of CST must be - smaller or equal to the size of TYPE. Both types must be floating - point.</dd> - - <dt><b><tt>fptoui (CST to TYPE)</tt></b></dt> - <dd>Convert a floating point constant to the corresponding unsigned integer - constant. TYPE must be a scalar or vector integer type. CST must be of - scalar or vector floating point type. Both CST and TYPE must be scalars, - or vectors of the same number of elements. If the value won't fit in the - integer type, the results are undefined.</dd> - - <dt><b><tt>fptosi (CST to TYPE)</tt></b></dt> - <dd>Convert a floating point constant to the corresponding signed integer - constant. TYPE must be a scalar or vector integer type. CST must be of - scalar or vector floating point type. Both CST and TYPE must be scalars, - or vectors of the same number of elements. If the value won't fit in the - integer type, the results are undefined.</dd> - - <dt><b><tt>uitofp (CST to TYPE)</tt></b></dt> - <dd>Convert an unsigned integer constant to the corresponding floating point - constant. TYPE must be a scalar or vector floating point type. CST must be - of scalar or vector integer type. Both CST and TYPE must be scalars, or - vectors of the same number of elements. If the value won't fit in the - floating point type, the results are undefined.</dd> - - <dt><b><tt>sitofp (CST to TYPE)</tt></b></dt> - <dd>Convert a signed integer constant to the corresponding floating point - constant. TYPE must be a scalar or vector floating point type. CST must be - of scalar or vector integer type. Both CST and TYPE must be scalars, or - vectors of the same number of elements. If the value won't fit in the - floating point type, the results are undefined.</dd> - - <dt><b><tt>ptrtoint (CST to TYPE)</tt></b></dt> - <dd>Convert a pointer typed constant to the corresponding integer constant - <tt>TYPE</tt> must be an integer type. <tt>CST</tt> must be of pointer - type. The <tt>CST</tt> value is zero extended, truncated, or unchanged to - make it fit in <tt>TYPE</tt>.</dd> - - <dt><b><tt>inttoptr (CST to TYPE)</tt></b></dt> - <dd>Convert an integer constant to a pointer constant. TYPE must be a pointer - type. CST must be of integer type. The CST value is zero extended, - truncated, or unchanged to make it fit in a pointer size. This one is - <i>really</i> dangerous!</dd> - - <dt><b><tt>bitcast (CST to TYPE)</tt></b></dt> - <dd>Convert a constant, CST, to another TYPE. The constraints of the operands - are the same as those for the <a href="#i_bitcast">bitcast - instruction</a>.</dd> - - <dt><b><tt>getelementptr (CSTPTR, IDX0, IDX1, ...)</tt></b></dt> - <dt><b><tt>getelementptr inbounds (CSTPTR, IDX0, IDX1, ...)</tt></b></dt> - <dd>Perform the <a href="#i_getelementptr">getelementptr operation</a> on - constants. As with the <a href="#i_getelementptr">getelementptr</a> - instruction, the index list may have zero or more indexes, which are - required to make sense for the type of "CSTPTR".</dd> - - <dt><b><tt>select (COND, VAL1, VAL2)</tt></b></dt> - <dd>Perform the <a href="#i_select">select operation</a> on constants.</dd> - - <dt><b><tt>icmp COND (VAL1, VAL2)</tt></b></dt> - <dd>Performs the <a href="#i_icmp">icmp operation</a> on constants.</dd> - - <dt><b><tt>fcmp COND (VAL1, VAL2)</tt></b></dt> - <dd>Performs the <a href="#i_fcmp">fcmp operation</a> on constants.</dd> - - <dt><b><tt>extractelement (VAL, IDX)</tt></b></dt> - <dd>Perform the <a href="#i_extractelement">extractelement operation</a> on - constants.</dd> - - <dt><b><tt>insertelement (VAL, ELT, IDX)</tt></b></dt> - <dd>Perform the <a href="#i_insertelement">insertelement operation</a> on - constants.</dd> - - <dt><b><tt>shufflevector (VEC1, VEC2, IDXMASK)</tt></b></dt> - <dd>Perform the <a href="#i_shufflevector">shufflevector operation</a> on - constants.</dd> - - <dt><b><tt>extractvalue (VAL, IDX0, IDX1, ...)</tt></b></dt> - <dd>Perform the <a href="#i_extractvalue">extractvalue operation</a> on - constants. The index list is interpreted in a similar manner as indices in - a '<a href="#i_getelementptr">getelementptr</a>' operation. At least one - index value must be specified.</dd> - - <dt><b><tt>insertvalue (VAL, ELT, IDX0, IDX1, ...)</tt></b></dt> - <dd>Perform the <a href="#i_insertvalue">insertvalue operation</a> on - constants. The index list is interpreted in a similar manner as indices in - a '<a href="#i_getelementptr">getelementptr</a>' operation. At least one - index value must be specified.</dd> - - <dt><b><tt>OPCODE (LHS, RHS)</tt></b></dt> - <dd>Perform the specified operation of the LHS and RHS constants. OPCODE may - be any of the <a href="#binaryops">binary</a> - or <a href="#bitwiseops">bitwise binary</a> operations. The constraints - on operands are the same as those for the corresponding instruction - (e.g. no bitwise operations on floating point values are allowed).</dd> -</dl> - -</div> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="othervalues">Other Values</a></h2> -<!-- *********************************************************************** --> -<div> -<!-- ======================================================================= --> -<h3> -<a name="inlineasm">Inline Assembler Expressions</a> -</h3> - -<div> - -<p>LLVM supports inline assembler expressions (as opposed - to <a href="#moduleasm">Module-Level Inline Assembly</a>) through the use of - a special value. This value represents the inline assembler as a string - (containing the instructions to emit), a list of operand constraints (stored - as a string), a flag that indicates whether or not the inline asm - expression has side effects, and a flag indicating whether the function - containing the asm needs to align its stack conservatively. An example - inline assembler expression is:</p> - -<pre class="doc_code"> -i32 (i32) asm "bswap $0", "=r,r" -</pre> - -<p>Inline assembler expressions may <b>only</b> be used as the callee operand of - a <a href="#i_call"><tt>call</tt></a> or an - <a href="#i_invoke"><tt>invoke</tt></a> instruction. - Thus, typically we have:</p> - -<pre class="doc_code"> -%X = call i32 asm "<a href="#int_bswap">bswap</a> $0", "=r,r"(i32 %Y) -</pre> - -<p>Inline asms with side effects not visible in the constraint list must be - marked as having side effects. This is done through the use of the - '<tt>sideeffect</tt>' keyword, like so:</p> - -<pre class="doc_code"> -call void asm sideeffect "eieio", ""() -</pre> - -<p>In some cases inline asms will contain code that will not work unless the - stack is aligned in some way, such as calls or SSE instructions on x86, - yet will not contain code that does that alignment within the asm. - The compiler should make conservative assumptions about what the asm might - contain and should generate its usual stack alignment code in the prologue - if the '<tt>alignstack</tt>' keyword is present:</p> - -<pre class="doc_code"> -call void asm alignstack "eieio", ""() -</pre> - -<p>Inline asms also support using non-standard assembly dialects. The assumed - dialect is ATT. When the '<tt>inteldialect</tt>' keyword is present, the - inline asm is using the Intel dialect. Currently, ATT and Intel are the - only supported dialects. An example is:</p> - -<pre class="doc_code"> -call void asm inteldialect "eieio", ""() -</pre> - -<p>If multiple keywords appear the '<tt>sideeffect</tt>' keyword must come - first, the '<tt>alignstack</tt>' keyword second and the - '<tt>inteldialect</tt>' keyword last.</p> - -<!-- -<p>TODO: The format of the asm and constraints string still need to be - documented here. Constraints on what can be done (e.g. duplication, moving, - etc need to be documented). This is probably best done by reference to - another document that covers inline asm from a holistic perspective.</p> - --> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="inlineasm_md">Inline Asm Metadata</a> -</h4> - -<div> - -<p>The call instructions that wrap inline asm nodes may have a - "<tt>!srcloc</tt>" MDNode attached to it that contains a list of constant - integers. If present, the code generator will use the integer as the - location cookie value when report errors through the <tt>LLVMContext</tt> - error reporting mechanisms. This allows a front-end to correlate backend - errors that occur with inline asm back to the source code that produced it. - For example:</p> - -<pre class="doc_code"> -call void asm sideeffect "something bad", ""()<b>, !srcloc !42</b> -... -!42 = !{ i32 1234567 } -</pre> - -<p>It is up to the front-end to make sense of the magic numbers it places in the - IR. If the MDNode contains multiple constants, the code generator will use - the one that corresponds to the line of the asm that the error occurs on.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="metadata">Metadata Nodes and Metadata Strings</a> -</h3> - -<div> - -<p>LLVM IR allows metadata to be attached to instructions in the program that - can convey extra information about the code to the optimizers and code - generator. One example application of metadata is source-level debug - information. There are two metadata primitives: strings and nodes. All - metadata has the <tt>metadata</tt> type and is identified in syntax by a - preceding exclamation point ('<tt>!</tt>').</p> - -<p>A metadata string is a string surrounded by double quotes. It can contain - any character by escaping non-printable characters with "<tt>\xx</tt>" where - "<tt>xx</tt>" is the two digit hex code. For example: - "<tt>!"test\00"</tt>".</p> - -<p>Metadata nodes are represented with notation similar to structure constants - (a comma separated list of elements, surrounded by braces and preceded by an - exclamation point). Metadata nodes can have any values as their operand. For - example:</p> - -<div class="doc_code"> -<pre> -!{ metadata !"test\00", i32 10} -</pre> -</div> - -<p>A <a href="#namedmetadatastructure">named metadata</a> is a collection of - metadata nodes, which can be looked up in the module symbol table. For - example:</p> - -<div class="doc_code"> -<pre> -!foo = metadata !{!4, !3} -</pre> -</div> - -<p>Metadata can be used as function arguments. Here <tt>llvm.dbg.value</tt> - function is using two metadata arguments:</p> - -<div class="doc_code"> -<pre> -call void @llvm.dbg.value(metadata !24, i64 0, metadata !25) -</pre> -</div> - -<p>Metadata can be attached with an instruction. Here metadata <tt>!21</tt> is - attached to the <tt>add</tt> instruction using the <tt>!dbg</tt> - identifier:</p> - -<div class="doc_code"> -<pre> -%indvar.next = add i64 %indvar, 1, !dbg !21 -</pre> -</div> - -<p>More information about specific metadata nodes recognized by the optimizers - and code generator is found below.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="tbaa">'<tt>tbaa</tt>' Metadata</a> -</h4> - -<div> - -<p>In LLVM IR, memory does not have types, so LLVM's own type system is not - suitable for doing TBAA. Instead, metadata is added to the IR to describe - a type system of a higher level language. This can be used to implement - typical C/C++ TBAA, but it can also be used to implement custom alias - analysis behavior for other languages.</p> - -<p>The current metadata format is very simple. TBAA metadata nodes have up to - three fields, e.g.:</p> - -<div class="doc_code"> -<pre> -!0 = metadata !{ metadata !"an example type tree" } -!1 = metadata !{ metadata !"int", metadata !0 } -!2 = metadata !{ metadata !"float", metadata !0 } -!3 = metadata !{ metadata !"const float", metadata !2, i64 1 } -</pre> -</div> - -<p>The first field is an identity field. It can be any value, usually - a metadata string, which uniquely identifies the type. The most important - name in the tree is the name of the root node. Two trees with - different root node names are entirely disjoint, even if they - have leaves with common names.</p> - -<p>The second field identifies the type's parent node in the tree, or - is null or omitted for a root node. A type is considered to alias - all of its descendants and all of its ancestors in the tree. Also, - a type is considered to alias all types in other trees, so that - bitcode produced from multiple front-ends is handled conservatively.</p> - -<p>If the third field is present, it's an integer which if equal to 1 - indicates that the type is "constant" (meaning - <tt>pointsToConstantMemory</tt> should return true; see - <a href="AliasAnalysis.html#OtherItfs">other useful - <tt>AliasAnalysis</tt> methods</a>).</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="tbaa.struct">'<tt>tbaa.struct</tt>' Metadata</a> -</h4> - -<div> - -<p>The <a href="#int_memcpy"><tt>llvm.memcpy</tt></a> is often used to implement -aggregate assignment operations in C and similar languages, however it is -defined to copy a contiguous region of memory, which is more than strictly -necessary for aggregate types which contain holes due to padding. Also, it -doesn't contain any TBAA information about the fields of the aggregate.</p> - -<p><tt>!tbaa.struct</tt> metadata can describe which memory subregions in a memcpy -are padding and what the TBAA tags of the struct are.</p> - -<p>The current metadata format is very simple. <tt>!tbaa.struct</tt> metadata nodes - are a list of operands which are in conceptual groups of three. For each - group of three, the first operand gives the byte offset of a field in bytes, - the second gives its size in bytes, and the third gives its - tbaa tag. e.g.:</p> - -<div class="doc_code"> -<pre> -!4 = metadata !{ i64 0, i64 4, metadata !1, i64 8, i64 4, metadata !2 } -</pre> -</div> - -<p>This describes a struct with two fields. The first is at offset 0 bytes - with size 4 bytes, and has tbaa tag !1. The second is at offset 8 bytes - and has size 4 bytes and has tbaa tag !2.</p> - -<p>Note that the fields need not be contiguous. In this example, there is a - 4 byte gap between the two fields. This gap represents padding which - does not carry useful data and need not be preserved.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="fpmath">'<tt>fpmath</tt>' Metadata</a> -</h4> - -<div> - -<p><tt>fpmath</tt> metadata may be attached to any instruction of floating point - type. It can be used to express the maximum acceptable error in the result of - that instruction, in ULPs, thus potentially allowing the compiler to use a - more efficient but less accurate method of computing it. ULP is defined as - follows:</p> - -<blockquote> - -<p>If <tt>x</tt> is a real number that lies between two finite consecutive - floating-point numbers <tt>a</tt> and <tt>b</tt>, without being equal to one - of them, then <tt>ulp(x) = |b - a|</tt>, otherwise <tt>ulp(x)</tt> is the - distance between the two non-equal finite floating-point numbers nearest - <tt>x</tt>. Moreover, <tt>ulp(NaN)</tt> is <tt>NaN</tt>.</p> - -</blockquote> - -<p>The metadata node shall consist of a single positive floating point number - representing the maximum relative error, for example:</p> - -<div class="doc_code"> -<pre> -!0 = metadata !{ float 2.5 } ; maximum acceptable inaccuracy is 2.5 ULPs -</pre> -</div> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="range">'<tt>range</tt>' Metadata</a> -</h4> - -<div> -<p><tt>range</tt> metadata may be attached only to loads of integer types. It - expresses the possible ranges the loaded value is in. The ranges are - represented with a flattened list of integers. The loaded value is known to - be in the union of the ranges defined by each consecutive pair. Each pair - has the following properties:</p> -<ul> - <li>The type must match the type loaded by the instruction.</li> - <li>The pair <tt>a,b</tt> represents the range <tt>[a,b)</tt>.</li> - <li>Both <tt>a</tt> and <tt>b</tt> are constants.</li> - <li>The range is allowed to wrap.</li> - <li>The range should not represent the full or empty set. That is, - <tt>a!=b</tt>. </li> -</ul> -<p> In addition, the pairs must be in signed order of the lower bound and - they must be non-contiguous.</p> - -<p>Examples:</p> -<div class="doc_code"> -<pre> - %a = load i8* %x, align 1, !range !0 ; Can only be 0 or 1 - %b = load i8* %y, align 1, !range !1 ; Can only be 255 (-1), 0 or 1 - %c = load i8* %z, align 1, !range !2 ; Can only be 0, 1, 3, 4 or 5 - %d = load i8* %z, align 1, !range !3 ; Can only be -2, -1, 3, 4 or 5 -... -!0 = metadata !{ i8 0, i8 2 } -!1 = metadata !{ i8 255, i8 2 } -!2 = metadata !{ i8 0, i8 2, i8 3, i8 6 } -!3 = metadata !{ i8 -2, i8 0, i8 3, i8 6 } -</pre> -</div> -</div> -</div> - -</div> - -<!-- *********************************************************************** --> -<h2> - <a name="module_flags">Module Flags Metadata</a> -</h2> -<!-- *********************************************************************** --> - -<div> - -<p>Information about the module as a whole is difficult to convey to LLVM's - subsystems. The LLVM IR isn't sufficient to transmit this - information. The <tt>llvm.module.flags</tt> named metadata exists in order to - facilitate this. These flags are in the form of key / value pairs — - much like a dictionary — making it easy for any subsystem who cares - about a flag to look it up.</p> - -<p>The <tt>llvm.module.flags</tt> metadata contains a list of metadata - triplets. Each triplet has the following form:</p> - -<ul> - <li>The first element is a <i>behavior</i> flag, which specifies the behavior - when two (or more) modules are merged together, and it encounters two (or - more) metadata with the same ID. The supported behaviors are described - below.</li> - - <li>The second element is a metadata string that is a unique ID for the - metadata. How each ID is interpreted is documented below.</li> - - <li>The third element is the value of the flag.</li> -</ul> - -<p>When two (or more) modules are merged together, the resulting - <tt>llvm.module.flags</tt> metadata is the union of the - modules' <tt>llvm.module.flags</tt> metadata. The only exception being a flag - with the <i>Override</i> behavior, which may override another flag's value - (see below).</p> - -<p>The following behaviors are supported:</p> - -<table border="1" cellspacing="0" cellpadding="4"> - <tbody> - <tr> - <th>Value</th> - <th>Behavior</th> - </tr> - <tr> - <td>1</td> - <td align="left"> - <dl> - <dt><b>Error</b></dt> - <dd>Emits an error if two values disagree. It is an error to have an ID - with both an Error and a Warning behavior.</dd> - </dl> - </td> - </tr> - <tr> - <td>2</td> - <td align="left"> - <dl> - <dt><b>Warning</b></dt> - <dd>Emits a warning if two values disagree.</dd> - </dl> - </td> - </tr> - <tr> - <td>3</td> - <td align="left"> - <dl> - <dt><b>Require</b></dt> - <dd>Emits an error when the specified value is not present or doesn't - have the specified value. It is an error for two (or more) - <tt>llvm.module.flags</tt> with the same ID to have the Require - behavior but different values. There may be multiple Require flags - per ID.</dd> - </dl> - </td> - </tr> - <tr> - <td>4</td> - <td align="left"> - <dl> - <dt><b>Override</b></dt> - <dd>Uses the specified value if the two values disagree. It is an - error for two (or more) <tt>llvm.module.flags</tt> with the same - ID to have the Override behavior but different values.</dd> - </dl> - </td> - </tr> - </tbody> -</table> - -<p>An example of module flags:</p> - -<pre class="doc_code"> -!0 = metadata !{ i32 1, metadata !"foo", i32 1 } -!1 = metadata !{ i32 4, metadata !"bar", i32 37 } -!2 = metadata !{ i32 2, metadata !"qux", i32 42 } -!3 = metadata !{ i32 3, metadata !"qux", - metadata !{ - metadata !"foo", i32 1 - } -} -!llvm.module.flags = !{ !0, !1, !2, !3 } -</pre> - -<ul> - <li><p>Metadata <tt>!0</tt> has the ID <tt>!"foo"</tt> and the value '1'. The - behavior if two or more <tt>!"foo"</tt> flags are seen is to emit an - error if their values are not equal.</p></li> - - <li><p>Metadata <tt>!1</tt> has the ID <tt>!"bar"</tt> and the value '37'. The - behavior if two or more <tt>!"bar"</tt> flags are seen is to use the - value '37' if their values are not equal.</p></li> - - <li><p>Metadata <tt>!2</tt> has the ID <tt>!"qux"</tt> and the value '42'. The - behavior if two or more <tt>!"qux"</tt> flags are seen is to emit a - warning if their values are not equal.</p></li> - - <li><p>Metadata <tt>!3</tt> has the ID <tt>!"qux"</tt> and the value:</p> - -<pre class="doc_code"> -metadata !{ metadata !"foo", i32 1 } -</pre> - - <p>The behavior is to emit an error if the <tt>llvm.module.flags</tt> does - not contain a flag with the ID <tt>!"foo"</tt> that has the value - '1'. If two or more <tt>!"qux"</tt> flags exist, then they must have - the same value or an error will be issued.</p></li> -</ul> - - -<!-- ======================================================================= --> -<h3> -<a name="objc_gc_flags">Objective-C Garbage Collection Module Flags Metadata</a> -</h3> - -<div> - -<p>On the Mach-O platform, Objective-C stores metadata about garbage collection - in a special section called "image info". The metadata consists of a version - number and a bitmask specifying what types of garbage collection are - supported (if any) by the file. If two or more modules are linked together - their garbage collection metadata needs to be merged rather than appended - together.</p> - -<p>The Objective-C garbage collection module flags metadata consists of the - following key-value pairs:</p> - -<table border="1" cellspacing="0" cellpadding="4"> - <col width="30%"> - <tbody> - <tr> - <th>Key</th> - <th>Value</th> - </tr> - <tr> - <td><tt>Objective-C Version</tt></td> - <td align="left"><b>[Required]</b> — The Objective-C ABI - version. Valid values are 1 and 2.</td> - </tr> - <tr> - <td><tt>Objective-C Image Info Version</tt></td> - <td align="left"><b>[Required]</b> — The version of the image info - section. Currently always 0.</td> - </tr> - <tr> - <td><tt>Objective-C Image Info Section</tt></td> - <td align="left"><b>[Required]</b> — The section to place the - metadata. Valid values are <tt>"__OBJC, __image_info, regular"</tt> for - Objective-C ABI version 1, and <tt>"__DATA,__objc_imageinfo, regular, - no_dead_strip"</tt> for Objective-C ABI version 2.</td> - </tr> - <tr> - <td><tt>Objective-C Garbage Collection</tt></td> - <td align="left"><b>[Required]</b> — Specifies whether garbage - collection is supported or not. Valid values are 0, for no garbage - collection, and 2, for garbage collection supported.</td> - </tr> - <tr> - <td><tt>Objective-C GC Only</tt></td> - <td align="left"><b>[Optional]</b> — Specifies that only garbage - collection is supported. If present, its value must be 6. This flag - requires that the <tt>Objective-C Garbage Collection</tt> flag have the - value 2.</td> - </tr> - </tbody> -</table> - -<p>Some important flag interactions:</p> - -<ul> - <li>If a module with <tt>Objective-C Garbage Collection</tt> set to 0 is - merged with a module with <tt>Objective-C Garbage Collection</tt> set to - 2, then the resulting module has the <tt>Objective-C Garbage - Collection</tt> flag set to 0.</li> - - <li>A module with <tt>Objective-C Garbage Collection</tt> set to 0 cannot be - merged with a module with <tt>Objective-C GC Only</tt> set to 6.</li> -</ul> - -</div> - -</div> - -<!-- *********************************************************************** --> -<h2> - <a name="intrinsic_globals">Intrinsic Global Variables</a> -</h2> -<!-- *********************************************************************** --> -<div> -<p>LLVM has a number of "magic" global variables that contain data that affect -code generation or other IR semantics. These are documented here. All globals -of this sort should have a section specified as "<tt>llvm.metadata</tt>". This -section and all globals that start with "<tt>llvm.</tt>" are reserved for use -by LLVM.</p> - -<!-- ======================================================================= --> -<h3> -<a name="intg_used">The '<tt>llvm.used</tt>' Global Variable</a> -</h3> - -<div> - -<p>The <tt>@llvm.used</tt> global is an array with i8* element type which has <a -href="#linkage_appending">appending linkage</a>. This array contains a list of -pointers to global variables and functions which may optionally have a pointer -cast formed of bitcast or getelementptr. For example, a legal use of it is:</p> - -<div class="doc_code"> -<pre> -@X = global i8 4 -@Y = global i32 123 - -@llvm.used = appending global [2 x i8*] [ - i8* @X, - i8* bitcast (i32* @Y to i8*) -], section "llvm.metadata" -</pre> -</div> - -<p>If a global variable appears in the <tt>@llvm.used</tt> list, then the - compiler, assembler, and linker are required to treat the symbol as if there - is a reference to the global that it cannot see. For example, if a variable - has internal linkage and no references other than that from - the <tt>@llvm.used</tt> list, it cannot be deleted. This is commonly used to - represent references from inline asms and other things the compiler cannot - "see", and corresponds to "<tt>attribute((used))</tt>" in GNU C.</p> - -<p>On some targets, the code generator must emit a directive to the assembler or - object file to prevent the assembler and linker from molesting the - symbol.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="intg_compiler_used"> - The '<tt>llvm.compiler.used</tt>' Global Variable - </a> -</h3> - -<div> - -<p>The <tt>@llvm.compiler.used</tt> directive is the same as the - <tt>@llvm.used</tt> directive, except that it only prevents the compiler from - touching the symbol. On targets that support it, this allows an intelligent - linker to optimize references to the symbol without being impeded as it would - be by <tt>@llvm.used</tt>.</p> - -<p>This is a rare construct that should only be used in rare circumstances, and - should not be exposed to source languages.</p> - -</div> - -<!-- ======================================================================= --> -<h3> -<a name="intg_global_ctors">The '<tt>llvm.global_ctors</tt>' Global Variable</a> -</h3> - -<div> - -<div class="doc_code"> -<pre> -%0 = type { i32, void ()* } -@llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @ctor }] -</pre> -</div> - -<p>The <tt>@llvm.global_ctors</tt> array contains a list of constructor - functions and associated priorities. The functions referenced by this array - will be called in ascending order of priority (i.e. lowest first) when the - module is loaded. The order of functions with the same priority is not - defined.</p> - -</div> - -<!-- ======================================================================= --> -<h3> -<a name="intg_global_dtors">The '<tt>llvm.global_dtors</tt>' Global Variable</a> -</h3> - -<div> - -<div class="doc_code"> -<pre> -%0 = type { i32, void ()* } -@llvm.global_dtors = appending global [1 x %0] [%0 { i32 65535, void ()* @dtor }] -</pre> -</div> - -<p>The <tt>@llvm.global_dtors</tt> array contains a list of destructor functions - and associated priorities. The functions referenced by this array will be - called in descending order of priority (i.e. highest first) when the module - is loaded. The order of functions with the same priority is not defined.</p> - -</div> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="instref">Instruction Reference</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>The LLVM instruction set consists of several different classifications of - instructions: <a href="#terminators">terminator - instructions</a>, <a href="#binaryops">binary instructions</a>, - <a href="#bitwiseops">bitwise binary instructions</a>, - <a href="#memoryops">memory instructions</a>, and - <a href="#otherops">other instructions</a>.</p> - -<!-- ======================================================================= --> -<h3> - <a name="terminators">Terminator Instructions</a> -</h3> - -<div> - -<p>As mentioned <a href="#functionstructure">previously</a>, every basic block - in a program ends with a "Terminator" instruction, which indicates which - block should be executed after the current block is finished. These - terminator instructions typically yield a '<tt>void</tt>' value: they produce - control flow, not values (the one exception being the - '<a href="#i_invoke"><tt>invoke</tt></a>' instruction).</p> - -<p>The terminator instructions are: - '<a href="#i_ret"><tt>ret</tt></a>', - '<a href="#i_br"><tt>br</tt></a>', - '<a href="#i_switch"><tt>switch</tt></a>', - '<a href="#i_indirectbr"><tt>indirectbr</tt></a>', - '<a href="#i_invoke"><tt>invoke</tt></a>', - '<a href="#i_resume"><tt>resume</tt></a>', and - '<a href="#i_unreachable"><tt>unreachable</tt></a>'.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_ret">'<tt>ret</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - ret <type> <value> <i>; Return a value from a non-void function</i> - ret void <i>; Return from void function</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>ret</tt>' instruction is used to return control flow (and optionally - a value) from a function back to the caller.</p> - -<p>There are two forms of the '<tt>ret</tt>' instruction: one that returns a - value and then causes control flow, and one that just causes control flow to - occur.</p> - -<h5>Arguments:</h5> -<p>The '<tt>ret</tt>' instruction optionally accepts a single argument, the - return value. The type of the return value must be a - '<a href="#t_firstclass">first class</a>' type.</p> - -<p>A function is not <a href="#wellformed">well formed</a> if it it has a - non-void return type and contains a '<tt>ret</tt>' instruction with no return - value or a return value with a type that does not match its type, or if it - has a void return type and contains a '<tt>ret</tt>' instruction with a - return value.</p> - -<h5>Semantics:</h5> -<p>When the '<tt>ret</tt>' instruction is executed, control flow returns back to - the calling function's context. If the caller is a - "<a href="#i_call"><tt>call</tt></a>" instruction, execution continues at the - instruction after the call. If the caller was an - "<a href="#i_invoke"><tt>invoke</tt></a>" instruction, execution continues at - the beginning of the "normal" destination block. If the instruction returns - a value, that value shall set the call or invoke instruction's return - value.</p> - -<h5>Example:</h5> -<pre> - ret i32 5 <i>; Return an integer value of 5</i> - ret void <i>; Return from a void function</i> - ret { i32, i8 } { i32 4, i8 2 } <i>; Return a struct of values 4 and 2</i> -</pre> - -</div> -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_br">'<tt>br</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - br i1 <cond>, label <iftrue>, label <iffalse> - br label <dest> <i>; Unconditional branch</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>br</tt>' instruction is used to cause control flow to transfer to a - different basic block in the current function. There are two forms of this - instruction, corresponding to a conditional branch and an unconditional - branch.</p> - -<h5>Arguments:</h5> -<p>The conditional branch form of the '<tt>br</tt>' instruction takes a single - '<tt>i1</tt>' value and two '<tt>label</tt>' values. The unconditional form - of the '<tt>br</tt>' instruction takes a single '<tt>label</tt>' value as a - target.</p> - -<h5>Semantics:</h5> -<p>Upon execution of a conditional '<tt>br</tt>' instruction, the '<tt>i1</tt>' - argument is evaluated. If the value is <tt>true</tt>, control flows to the - '<tt>iftrue</tt>' <tt>label</tt> argument. If "cond" is <tt>false</tt>, - control flows to the '<tt>iffalse</tt>' <tt>label</tt> argument.</p> - -<h5>Example:</h5> -<pre> -Test: - %cond = <a href="#i_icmp">icmp</a> eq i32 %a, %b - br i1 %cond, label %IfEqual, label %IfUnequal -IfEqual: - <a href="#i_ret">ret</a> i32 1 -IfUnequal: - <a href="#i_ret">ret</a> i32 0 -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_switch">'<tt>switch</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - switch <intty> <value>, label <defaultdest> [ <intty> <val>, label <dest> ... ] -</pre> - -<h5>Overview:</h5> -<p>The '<tt>switch</tt>' instruction is used to transfer control flow to one of - several different places. It is a generalization of the '<tt>br</tt>' - instruction, allowing a branch to occur to one of many possible - destinations.</p> - -<h5>Arguments:</h5> -<p>The '<tt>switch</tt>' instruction uses three parameters: an integer - comparison value '<tt>value</tt>', a default '<tt>label</tt>' destination, - and an array of pairs of comparison value constants and '<tt>label</tt>'s. - The table is not allowed to contain duplicate constant entries.</p> - -<h5>Semantics:</h5> -<p>The <tt>switch</tt> instruction specifies a table of values and - destinations. When the '<tt>switch</tt>' instruction is executed, this table - is searched for the given value. If the value is found, control flow is - transferred to the corresponding destination; otherwise, control flow is - transferred to the default destination.</p> - -<h5>Implementation:</h5> -<p>Depending on properties of the target machine and the particular - <tt>switch</tt> instruction, this instruction may be code generated in - different ways. For example, it could be generated as a series of chained - conditional branches or with a lookup table.</p> - -<h5>Example:</h5> -<pre> - <i>; Emulate a conditional br instruction</i> - %Val = <a href="#i_zext">zext</a> i1 %value to i32 - switch i32 %Val, label %truedest [ i32 0, label %falsedest ] - - <i>; Emulate an unconditional br instruction</i> - switch i32 0, label %dest [ ] - - <i>; Implement a jump table:</i> - switch i32 %val, label %otherwise [ i32 0, label %onzero - i32 1, label %onone - i32 2, label %ontwo ] -</pre> - -</div> - - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_indirectbr">'<tt>indirectbr</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - indirectbr <somety>* <address>, [ label <dest1>, label <dest2>, ... ] -</pre> - -<h5>Overview:</h5> - -<p>The '<tt>indirectbr</tt>' instruction implements an indirect branch to a label - within the current function, whose address is specified by - "<tt>address</tt>". Address must be derived from a <a - href="#blockaddress">blockaddress</a> constant.</p> - -<h5>Arguments:</h5> - -<p>The '<tt>address</tt>' argument is the address of the label to jump to. The - rest of the arguments indicate the full set of possible destinations that the - address may point to. Blocks are allowed to occur multiple times in the - destination list, though this isn't particularly useful.</p> - -<p>This destination list is required so that dataflow analysis has an accurate - understanding of the CFG.</p> - -<h5>Semantics:</h5> - -<p>Control transfers to the block specified in the address argument. All - possible destination blocks must be listed in the label list, otherwise this - instruction has undefined behavior. This implies that jumps to labels - defined in other functions have undefined behavior as well.</p> - -<h5>Implementation:</h5> - -<p>This is typically implemented with a jump through a register.</p> - -<h5>Example:</h5> -<pre> - indirectbr i8* %Addr, [ label %bb1, label %bb2, label %bb3 ] -</pre> - -</div> - - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_invoke">'<tt>invoke</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = invoke [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ptr to function ty> <function ptr val>(<function args>) [<a href="#fnattrs">fn attrs</a>] - to label <normal label> unwind label <exception label> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>invoke</tt>' instruction causes control to transfer to a specified - function, with the possibility of control flow transfer to either the - '<tt>normal</tt>' label or the '<tt>exception</tt>' label. If the callee - function returns with the "<tt><a href="#i_ret">ret</a></tt>" instruction, - control flow will return to the "normal" label. If the callee (or any - indirect callees) returns via the "<a href="#i_resume"><tt>resume</tt></a>" - instruction or other exception handling mechanism, control is interrupted and - continued at the dynamically nearest "exception" label.</p> - -<p>The '<tt>exception</tt>' label is a - <i><a href="ExceptionHandling.html#overview">landing pad</a></i> for the - exception. As such, '<tt>exception</tt>' label is required to have the - "<a href="#i_landingpad"><tt>landingpad</tt></a>" instruction, which contains - the information about the behavior of the program after unwinding - happens, as its first non-PHI instruction. The restrictions on the - "<tt>landingpad</tt>" instruction's tightly couples it to the - "<tt>invoke</tt>" instruction, so that the important information contained - within the "<tt>landingpad</tt>" instruction can't be lost through normal - code motion.</p> - -<h5>Arguments:</h5> -<p>This instruction requires several arguments:</p> - -<ol> - <li>The optional "cconv" marker indicates which <a href="#callingconv">calling - convention</a> the call should use. If none is specified, the call - defaults to using C calling conventions.</li> - - <li>The optional <a href="#paramattrs">Parameter Attributes</a> list for - return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and - '<tt>inreg</tt>' attributes are valid here.</li> - - <li>'<tt>ptr to function ty</tt>': shall be the signature of the pointer to - function value being invoked. In most cases, this is a direct function - invocation, but indirect <tt>invoke</tt>s are just as possible, branching - off an arbitrary pointer to function value.</li> - - <li>'<tt>function ptr val</tt>': An LLVM value containing a pointer to a - function to be invoked. </li> - - <li>'<tt>function args</tt>': argument list whose types match the function - signature argument types and parameter attributes. All arguments must be - of <a href="#t_firstclass">first class</a> type. If the function - signature indicates the function accepts a variable number of arguments, - the extra arguments can be specified.</li> - - <li>'<tt>normal label</tt>': the label reached when the called function - executes a '<tt><a href="#i_ret">ret</a></tt>' instruction. </li> - - <li>'<tt>exception label</tt>': the label reached when a callee returns via - the <a href="#i_resume"><tt>resume</tt></a> instruction or other exception - handling mechanism.</li> - - <li>The optional <a href="#fnattrs">function attributes</a> list. Only - '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and - '<tt>readnone</tt>' attributes are valid here.</li> -</ol> - -<h5>Semantics:</h5> -<p>This instruction is designed to operate as a standard - '<tt><a href="#i_call">call</a></tt>' instruction in most regards. The - primary difference is that it establishes an association with a label, which - is used by the runtime library to unwind the stack.</p> - -<p>This instruction is used in languages with destructors to ensure that proper - cleanup is performed in the case of either a <tt>longjmp</tt> or a thrown - exception. Additionally, this is important for implementation of - '<tt>catch</tt>' clauses in high-level languages that support them.</p> - -<p>For the purposes of the SSA form, the definition of the value returned by the - '<tt>invoke</tt>' instruction is deemed to occur on the edge from the current - block to the "normal" label. If the callee unwinds then no return value is - available.</p> - -<h5>Example:</h5> -<pre> - %retval = invoke i32 @Test(i32 15) to label %Continue - unwind label %TestCleanup <i>; {i32}:retval set</i> - %retval = invoke <a href="#callingconv">coldcc</a> i32 %Testfnptr(i32 15) to label %Continue - unwind label %TestCleanup <i>; {i32}:retval set</i> -</pre> - -</div> - - <!-- _______________________________________________________________________ --> - -<h4> - <a name="i_resume">'<tt>resume</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - resume <type> <value> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>resume</tt>' instruction is a terminator instruction that has no - successors.</p> - -<h5>Arguments:</h5> -<p>The '<tt>resume</tt>' instruction requires one argument, which must have the - same type as the result of any '<tt>landingpad</tt>' instruction in the same - function.</p> - -<h5>Semantics:</h5> -<p>The '<tt>resume</tt>' instruction resumes propagation of an existing - (in-flight) exception whose unwinding was interrupted with - a <a href="#i_landingpad"><tt>landingpad</tt></a> instruction.</p> - -<h5>Example:</h5> -<pre> - resume { i8*, i32 } %exn -</pre> - -</div> - -<!-- _______________________________________________________________________ --> - -<h4> - <a name="i_unreachable">'<tt>unreachable</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - unreachable -</pre> - -<h5>Overview:</h5> -<p>The '<tt>unreachable</tt>' instruction has no defined semantics. This - instruction is used to inform the optimizer that a particular portion of the - code is not reachable. This can be used to indicate that the code after a - no-return function cannot be reached, and other facts.</p> - -<h5>Semantics:</h5> -<p>The '<tt>unreachable</tt>' instruction has no defined semantics.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="binaryops">Binary Operations</a> -</h3> - -<div> - -<p>Binary operators are used to do most of the computation in a program. They - require two operands of the same type, execute an operation on them, and - produce a single value. The operands might represent multiple data, as is - the case with the <a href="#t_vector">vector</a> data type. The result value - has the same type as its operands.</p> - -<p>There are several different binary operators:</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_add">'<tt>add</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = add <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = add nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = add nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = add nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>add</tt>' instruction returns the sum of its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>add</tt>' instruction must - be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of - integer values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The value produced is the integer sum of the two operands.</p> - -<p>If the sum has unsigned overflow, the result returned is the mathematical - result modulo 2<sup>n</sup>, where n is the bit width of the result.</p> - -<p>Because LLVM integers use a two's complement representation, this instruction - is appropriate for both signed and unsigned integers.</p> - -<p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap" - and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or - <tt>nsw</tt> keywords are present, the result value of the <tt>add</tt> - is a <a href="#poisonvalues">poison value</a> if unsigned and/or signed overflow, - respectively, occurs.</p> - -<h5>Example:</h5> -<pre> - <result> = add i32 4, %var <i>; yields {i32}:result = 4 + %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fadd">'<tt>fadd</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fadd [fast-math flags]* <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fadd</tt>' instruction returns the sum of its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>fadd</tt>' instruction must be - <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of - floating point values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> - <p>The value produced is the floating point sum of the two operands. This - instruction can also take any number of <a href="#fastmath">fast-math - flags</a>, which are optimization hints to enable otherwise unsafe floating - point optimizations:</p> - -<h5>Example:</h5> -<pre> - <result> = fadd float 4.0, %var <i>; yields {float}:result = 4.0 + %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_sub">'<tt>sub</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = sub <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = sub nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = sub nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = sub nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>sub</tt>' instruction returns the difference of its two - operands.</p> - -<p>Note that the '<tt>sub</tt>' instruction is used to represent the - '<tt>neg</tt>' instruction present in most other intermediate - representations.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>sub</tt>' instruction must - be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of - integer values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The value produced is the integer difference of the two operands.</p> - -<p>If the difference has unsigned overflow, the result returned is the - mathematical result modulo 2<sup>n</sup>, where n is the bit width of the - result.</p> - -<p>Because LLVM integers use a two's complement representation, this instruction - is appropriate for both signed and unsigned integers.</p> - -<p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap" - and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or - <tt>nsw</tt> keywords are present, the result value of the <tt>sub</tt> - is a <a href="#poisonvalues">poison value</a> if unsigned and/or signed overflow, - respectively, occurs.</p> - -<h5>Example:</h5> -<pre> - <result> = sub i32 4, %var <i>; yields {i32}:result = 4 - %var</i> - <result> = sub i32 0, %val <i>; yields {i32}:result = -%var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fsub">'<tt>fsub</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fsub [fast-math flags]* <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fsub</tt>' instruction returns the difference of its two - operands.</p> - -<p>Note that the '<tt>fsub</tt>' instruction is used to represent the - '<tt>fneg</tt>' instruction present in most other intermediate - representations.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>fsub</tt>' instruction must be - <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of - floating point values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> - <p>The value produced is the floating point difference of the two operands. - This instruction can also take any number of <a href="#fastmath">fast-math - flags</a>, which are optimization hints to enable otherwise unsafe floating - point optimizations:</p> - -<h5>Example:</h5> -<pre> - <result> = fsub float 4.0, %var <i>; yields {float}:result = 4.0 - %var</i> - <result> = fsub float -0.0, %val <i>; yields {float}:result = -%var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_mul">'<tt>mul</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = mul <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = mul nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = mul nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = mul nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>mul</tt>' instruction returns the product of its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>mul</tt>' instruction must - be <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of - integer values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The value produced is the integer product of the two operands.</p> - -<p>If the result of the multiplication has unsigned overflow, the result - returned is the mathematical result modulo 2<sup>n</sup>, where n is the bit - width of the result.</p> - -<p>Because LLVM integers use a two's complement representation, and the result - is the same width as the operands, this instruction returns the correct - result for both signed and unsigned integers. If a full product - (e.g. <tt>i32</tt>x<tt>i32</tt>-><tt>i64</tt>) is needed, the operands should - be sign-extended or zero-extended as appropriate to the width of the full - product.</p> - -<p><tt>nuw</tt> and <tt>nsw</tt> stand for "No Unsigned Wrap" - and "No Signed Wrap", respectively. If the <tt>nuw</tt> and/or - <tt>nsw</tt> keywords are present, the result value of the <tt>mul</tt> - is a <a href="#poisonvalues">poison value</a> if unsigned and/or signed overflow, - respectively, occurs.</p> - -<h5>Example:</h5> -<pre> - <result> = mul i32 4, %var <i>; yields {i32}:result = 4 * %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fmul">'<tt>fmul</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fmul [fast-math flags]* <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fmul</tt>' instruction returns the product of its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>fmul</tt>' instruction must be - <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of - floating point values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> - <p>The value produced is the floating point product of the two operands. This - instruction can also take any number of <a href="#fastmath">fast-math - flags</a>, which are optimization hints to enable otherwise unsafe floating - point optimizations:</p> - -<h5>Example:</h5> -<pre> - <result> = fmul float 4.0, %var <i>; yields {float}:result = 4.0 * %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_udiv">'<tt>udiv</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = udiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = udiv exact <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>udiv</tt>' instruction returns the quotient of its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>udiv</tt>' instruction must be - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The value produced is the unsigned integer quotient of the two operands.</p> - -<p>Note that unsigned integer division and signed integer division are distinct - operations; for signed integer division, use '<tt>sdiv</tt>'.</p> - -<p>Division by zero leads to undefined behavior.</p> - -<p>If the <tt>exact</tt> keyword is present, the result value of the - <tt>udiv</tt> is a <a href="#poisonvalues">poison value</a> if %op1 is not a - multiple of %op2 (as such, "((a udiv exact b) mul b) == a").</p> - - -<h5>Example:</h5> -<pre> - <result> = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_sdiv">'<tt>sdiv</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = sdiv <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = sdiv exact <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>sdiv</tt>' instruction returns the quotient of its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>sdiv</tt>' instruction must be - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The value produced is the signed integer quotient of the two operands rounded - towards zero.</p> - -<p>Note that signed integer division and unsigned integer division are distinct - operations; for unsigned integer division, use '<tt>udiv</tt>'.</p> - -<p>Division by zero leads to undefined behavior. Overflow also leads to - undefined behavior; this is a rare case, but can occur, for example, by doing - a 32-bit division of -2147483648 by -1.</p> - -<p>If the <tt>exact</tt> keyword is present, the result value of the - <tt>sdiv</tt> is a <a href="#poisonvalues">poison value</a> if the result would - be rounded.</p> - -<h5>Example:</h5> -<pre> - <result> = sdiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fdiv">'<tt>fdiv</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fdiv [fast-math flags]* <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fdiv</tt>' instruction returns the quotient of its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>fdiv</tt>' instruction must be - <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of - floating point values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> - <p>The value produced is the floating point quotient of the two operands. This - instruction can also take any number of <a href="#fastmath">fast-math - flags</a>, which are optimization hints to enable otherwise unsafe floating - point optimizations:</p> -</p> - -<h5>Example:</h5> -<pre> - <result> = fdiv float 4.0, %var <i>; yields {float}:result = 4.0 / %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_urem">'<tt>urem</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = urem <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>urem</tt>' instruction returns the remainder from the unsigned - division of its two arguments.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>urem</tt>' instruction must be - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>This instruction returns the unsigned integer <i>remainder</i> of a division. - This instruction always performs an unsigned division to get the - remainder.</p> - -<p>Note that unsigned integer remainder and signed integer remainder are - distinct operations; for signed integer remainder, use '<tt>srem</tt>'.</p> - -<p>Taking the remainder of a division by zero leads to undefined behavior.</p> - -<h5>Example:</h5> -<pre> - <result> = urem i32 4, %var <i>; yields {i32}:result = 4 % %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_srem">'<tt>srem</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = srem <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>srem</tt>' instruction returns the remainder from the signed - division of its two operands. This instruction can also take - <a href="#t_vector">vector</a> versions of the values in which case the - elements must be integers.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>srem</tt>' instruction must be - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>This instruction returns the <i>remainder</i> of a division (where the result - is either zero or has the same sign as the dividend, <tt>op1</tt>), not the - <i>modulo</i> operator (where the result is either zero or has the same sign - as the divisor, <tt>op2</tt>) of a value. - For more information about the difference, - see <a href="http://mathforum.org/dr.math/problems/anne.4.28.99.html">The - Math Forum</a>. For a table of how this is implemented in various languages, - please see <a href="http://en.wikipedia.org/wiki/Modulo_operation"> - Wikipedia: modulo operation</a>.</p> - -<p>Note that signed integer remainder and unsigned integer remainder are - distinct operations; for unsigned integer remainder, use '<tt>urem</tt>'.</p> - -<p>Taking the remainder of a division by zero leads to undefined behavior. - Overflow also leads to undefined behavior; this is a rare case, but can - occur, for example, by taking the remainder of a 32-bit division of - -2147483648 by -1. (The remainder doesn't actually overflow, but this rule - lets srem be implemented using instructions that return both the result of - the division and the remainder.)</p> - -<h5>Example:</h5> -<pre> - <result> = srem i32 4, %var <i>; yields {i32}:result = 4 % %var</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_frem">'<tt>frem</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = frem [fast-math flags]* <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>frem</tt>' instruction returns the remainder from the division of - its two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>frem</tt>' instruction must be - <a href="#t_floating">floating point</a> or <a href="#t_vector">vector</a> of - floating point values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> - <p>This instruction returns the <i>remainder</i> of a division. The remainder - has the same sign as the dividend. This instruction can also take any number - of <a href="#fastmath">fast-math flags</a>, which are optimization hints to - enable otherwise unsafe floating point optimizations:</p> - -<h5>Example:</h5> -<pre> - <result> = frem float 4.0, %var <i>; yields {float}:result = 4.0 % %var</i> -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="bitwiseops">Bitwise Binary Operations</a> -</h3> - -<div> - -<p>Bitwise binary operators are used to do various forms of bit-twiddling in a - program. They are generally very efficient instructions and can commonly be - strength reduced from other instructions. They require two operands of the - same type, execute an operation on them, and produce a single value. The - resulting value is the same type as its operands.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_shl">'<tt>shl</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = shl <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = shl nuw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = shl nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = shl nuw nsw <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>shl</tt>' instruction returns the first operand shifted to the left - a specified number of bits.</p> - -<h5>Arguments:</h5> -<p>Both arguments to the '<tt>shl</tt>' instruction must be the - same <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of - integer type. '<tt>op2</tt>' is treated as an unsigned value.</p> - -<h5>Semantics:</h5> -<p>The value produced is <tt>op1</tt> * 2<sup><tt>op2</tt></sup> mod - 2<sup>n</sup>, where <tt>n</tt> is the width of the result. If <tt>op2</tt> - is (statically or dynamically) negative or equal to or larger than the number - of bits in <tt>op1</tt>, the result is undefined. If the arguments are - vectors, each vector element of <tt>op1</tt> is shifted by the corresponding - shift amount in <tt>op2</tt>.</p> - -<p>If the <tt>nuw</tt> keyword is present, then the shift produces a - <a href="#poisonvalues">poison value</a> if it shifts out any non-zero bits. If - the <tt>nsw</tt> keyword is present, then the shift produces a - <a href="#poisonvalues">poison value</a> if it shifts out any bits that disagree - with the resultant sign bit. As such, NUW/NSW have the same semantics as - they would if the shift were expressed as a mul instruction with the same - nsw/nuw bits in (mul %op1, (shl 1, %op2)).</p> - -<h5>Example:</h5> -<pre> - <result> = shl i32 4, %var <i>; yields {i32}: 4 << %var</i> - <result> = shl i32 4, 2 <i>; yields {i32}: 16</i> - <result> = shl i32 1, 10 <i>; yields {i32}: 1024</i> - <result> = shl i32 1, 32 <i>; undefined</i> - <result> = shl <2 x i32> < i32 1, i32 1>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 2, i32 4></i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_lshr">'<tt>lshr</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = lshr <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = lshr exact <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>lshr</tt>' instruction (logical shift right) returns the first - operand shifted to the right a specified number of bits with zero fill.</p> - -<h5>Arguments:</h5> -<p>Both arguments to the '<tt>lshr</tt>' instruction must be the same - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - type. '<tt>op2</tt>' is treated as an unsigned value.</p> - -<h5>Semantics:</h5> -<p>This instruction always performs a logical shift right operation. The most - significant bits of the result will be filled with zero bits after the shift. - If <tt>op2</tt> is (statically or dynamically) equal to or larger than the - number of bits in <tt>op1</tt>, the result is undefined. If the arguments are - vectors, each vector element of <tt>op1</tt> is shifted by the corresponding - shift amount in <tt>op2</tt>.</p> - -<p>If the <tt>exact</tt> keyword is present, the result value of the - <tt>lshr</tt> is a <a href="#poisonvalues">poison value</a> if any of the bits - shifted out are non-zero.</p> - - -<h5>Example:</h5> -<pre> - <result> = lshr i32 4, 1 <i>; yields {i32}:result = 2</i> - <result> = lshr i32 4, 2 <i>; yields {i32}:result = 1</i> - <result> = lshr i8 4, 3 <i>; yields {i8}:result = 0</i> - <result> = lshr i8 -2, 1 <i>; yields {i8}:result = 0x7FFFFFFF </i> - <result> = lshr i32 1, 32 <i>; undefined</i> - <result> = lshr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 2> <i>; yields: result=<2 x i32> < i32 0x7FFFFFFF, i32 1></i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_ashr">'<tt>ashr</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = ashr <ty> <op1>, <op2> <i>; yields {ty}:result</i> - <result> = ashr exact <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>ashr</tt>' instruction (arithmetic shift right) returns the first - operand shifted to the right a specified number of bits with sign - extension.</p> - -<h5>Arguments:</h5> -<p>Both arguments to the '<tt>ashr</tt>' instruction must be the same - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - type. '<tt>op2</tt>' is treated as an unsigned value.</p> - -<h5>Semantics:</h5> -<p>This instruction always performs an arithmetic shift right operation, The - most significant bits of the result will be filled with the sign bit - of <tt>op1</tt>. If <tt>op2</tt> is (statically or dynamically) equal to or - larger than the number of bits in <tt>op1</tt>, the result is undefined. If - the arguments are vectors, each vector element of <tt>op1</tt> is shifted by - the corresponding shift amount in <tt>op2</tt>.</p> - -<p>If the <tt>exact</tt> keyword is present, the result value of the - <tt>ashr</tt> is a <a href="#poisonvalues">poison value</a> if any of the bits - shifted out are non-zero.</p> - -<h5>Example:</h5> -<pre> - <result> = ashr i32 4, 1 <i>; yields {i32}:result = 2</i> - <result> = ashr i32 4, 2 <i>; yields {i32}:result = 1</i> - <result> = ashr i8 4, 3 <i>; yields {i8}:result = 0</i> - <result> = ashr i8 -2, 1 <i>; yields {i8}:result = -1</i> - <result> = ashr i32 1, 32 <i>; undefined</i> - <result> = ashr <2 x i32> < i32 -2, i32 4>, < i32 1, i32 3> <i>; yields: result=<2 x i32> < i32 -1, i32 0></i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_and">'<tt>and</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = and <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>and</tt>' instruction returns the bitwise logical and of its two - operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>and</tt>' instruction must be - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The truth table used for the '<tt>and</tt>' instruction is:</p> - -<table border="1" cellspacing="0" cellpadding="4"> - <tbody> - <tr> - <th>In0</th> - <th>In1</th> - <th>Out</th> - </tr> - <tr> - <td>0</td> - <td>0</td> - <td>0</td> - </tr> - <tr> - <td>0</td> - <td>1</td> - <td>0</td> - </tr> - <tr> - <td>1</td> - <td>0</td> - <td>0</td> - </tr> - <tr> - <td>1</td> - <td>1</td> - <td>1</td> - </tr> - </tbody> -</table> - -<h5>Example:</h5> -<pre> - <result> = and i32 4, %var <i>; yields {i32}:result = 4 & %var</i> - <result> = and i32 15, 40 <i>; yields {i32}:result = 8</i> - <result> = and i32 4, 8 <i>; yields {i32}:result = 0</i> -</pre> -</div> -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_or">'<tt>or</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = or <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>or</tt>' instruction returns the bitwise logical inclusive or of its - two operands.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>or</tt>' instruction must be - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The truth table used for the '<tt>or</tt>' instruction is:</p> - -<table border="1" cellspacing="0" cellpadding="4"> - <tbody> - <tr> - <th>In0</th> - <th>In1</th> - <th>Out</th> - </tr> - <tr> - <td>0</td> - <td>0</td> - <td>0</td> - </tr> - <tr> - <td>0</td> - <td>1</td> - <td>1</td> - </tr> - <tr> - <td>1</td> - <td>0</td> - <td>1</td> - </tr> - <tr> - <td>1</td> - <td>1</td> - <td>1</td> - </tr> - </tbody> -</table> - -<h5>Example:</h5> -<pre> - <result> = or i32 4, %var <i>; yields {i32}:result = 4 | %var</i> - <result> = or i32 15, 40 <i>; yields {i32}:result = 47</i> - <result> = or i32 4, 8 <i>; yields {i32}:result = 12</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_xor">'<tt>xor</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = xor <ty> <op1>, <op2> <i>; yields {ty}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>xor</tt>' instruction returns the bitwise logical exclusive or of - its two operands. The <tt>xor</tt> is used to implement the "one's - complement" operation, which is the "~" operator in C.</p> - -<h5>Arguments:</h5> -<p>The two arguments to the '<tt>xor</tt>' instruction must be - <a href="#t_integer">integer</a> or <a href="#t_vector">vector</a> of integer - values. Both arguments must have identical types.</p> - -<h5>Semantics:</h5> -<p>The truth table used for the '<tt>xor</tt>' instruction is:</p> - -<table border="1" cellspacing="0" cellpadding="4"> - <tbody> - <tr> - <th>In0</th> - <th>In1</th> - <th>Out</th> - </tr> - <tr> - <td>0</td> - <td>0</td> - <td>0</td> - </tr> - <tr> - <td>0</td> - <td>1</td> - <td>1</td> - </tr> - <tr> - <td>1</td> - <td>0</td> - <td>1</td> - </tr> - <tr> - <td>1</td> - <td>1</td> - <td>0</td> - </tr> - </tbody> -</table> - -<h5>Example:</h5> -<pre> - <result> = xor i32 4, %var <i>; yields {i32}:result = 4 ^ %var</i> - <result> = xor i32 15, 40 <i>; yields {i32}:result = 39</i> - <result> = xor i32 4, 8 <i>; yields {i32}:result = 12</i> - <result> = xor i32 %V, -1 <i>; yields {i32}:result = ~%V</i> -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="vectorops">Vector Operations</a> -</h3> - -<div> - -<p>LLVM supports several instructions to represent vector operations in a - target-independent manner. These instructions cover the element-access and - vector-specific operations needed to process vectors effectively. While LLVM - does directly support these vector operations, many sophisticated algorithms - will want to use target-specific intrinsics to take full advantage of a - specific target.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_extractelement">'<tt>extractelement</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = extractelement <n x <ty>> <val>, i32 <idx> <i>; yields <ty></i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>extractelement</tt>' instruction extracts a single scalar element - from a vector at a specified index.</p> - - -<h5>Arguments:</h5> -<p>The first operand of an '<tt>extractelement</tt>' instruction is a value - of <a href="#t_vector">vector</a> type. The second operand is an index - indicating the position from which to extract the element. The index may be - a variable.</p> - -<h5>Semantics:</h5> -<p>The result is a scalar of the same type as the element type of - <tt>val</tt>. Its value is the value at position <tt>idx</tt> of - <tt>val</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the - results are undefined.</p> - -<h5>Example:</h5> -<pre> - <result> = extractelement <4 x i32> %vec, i32 0 <i>; yields i32</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_insertelement">'<tt>insertelement</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = insertelement <n x <ty>> <val>, <ty> <elt>, i32 <idx> <i>; yields <n x <ty>></i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>insertelement</tt>' instruction inserts a scalar element into a - vector at a specified index.</p> - -<h5>Arguments:</h5> -<p>The first operand of an '<tt>insertelement</tt>' instruction is a value - of <a href="#t_vector">vector</a> type. The second operand is a scalar value - whose type must equal the element type of the first operand. The third - operand is an index indicating the position at which to insert the value. - The index may be a variable.</p> - -<h5>Semantics:</h5> -<p>The result is a vector of the same type as <tt>val</tt>. Its element values - are those of <tt>val</tt> except at position <tt>idx</tt>, where it gets the - value <tt>elt</tt>. If <tt>idx</tt> exceeds the length of <tt>val</tt>, the - results are undefined.</p> - -<h5>Example:</h5> -<pre> - <result> = insertelement <4 x i32> %vec, i32 1, i32 0 <i>; yields <4 x i32></i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_shufflevector">'<tt>shufflevector</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = shufflevector <n x <ty>> <v1>, <n x <ty>> <v2>, <m x i32> <mask> <i>; yields <m x <ty>></i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>shufflevector</tt>' instruction constructs a permutation of elements - from two input vectors, returning a vector with the same element type as the - input and length that is the same as the shuffle mask.</p> - -<h5>Arguments:</h5> -<p>The first two operands of a '<tt>shufflevector</tt>' instruction are vectors - with the same type. The third argument is a shuffle mask whose - element type is always 'i32'. The result of the instruction is a vector - whose length is the same as the shuffle mask and whose element type is the - same as the element type of the first two operands.</p> - -<p>The shuffle mask operand is required to be a constant vector with either - constant integer or undef values.</p> - -<h5>Semantics:</h5> -<p>The elements of the two input vectors are numbered from left to right across - both of the vectors. The shuffle mask operand specifies, for each element of - the result vector, which element of the two input vectors the result element - gets. The element selector may be undef (meaning "don't care") and the - second operand may be undef if performing a shuffle from only one vector.</p> - -<h5>Example:</h5> -<pre> - <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2, - <4 x i32> <i32 0, i32 4, i32 1, i32 5> <i>; yields <4 x i32></i> - <result> = shufflevector <4 x i32> %v1, <4 x i32> undef, - <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - Identity shuffle. - <result> = shufflevector <8 x i32> %v1, <8 x i32> undef, - <4 x i32> <i32 0, i32 1, i32 2, i32 3> <i>; yields <4 x i32></i> - <result> = shufflevector <4 x i32> %v1, <4 x i32> %v2, - <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7 > <i>; yields <8 x i32></i> -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="aggregateops">Aggregate Operations</a> -</h3> - -<div> - -<p>LLVM supports several instructions for working with - <a href="#t_aggregate">aggregate</a> values.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_extractvalue">'<tt>extractvalue</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = extractvalue <aggregate type> <val>, <idx>{, <idx>}* -</pre> - -<h5>Overview:</h5> -<p>The '<tt>extractvalue</tt>' instruction extracts the value of a member field - from an <a href="#t_aggregate">aggregate</a> value.</p> - -<h5>Arguments:</h5> -<p>The first operand of an '<tt>extractvalue</tt>' instruction is a value - of <a href="#t_struct">struct</a> or - <a href="#t_array">array</a> type. The operands are constant indices to - specify which value to extract in a similar manner as indices in a - '<tt><a href="#i_getelementptr">getelementptr</a></tt>' instruction.</p> - <p>The major differences to <tt>getelementptr</tt> indexing are:</p> - <ul> - <li>Since the value being indexed is not a pointer, the first index is - omitted and assumed to be zero.</li> - <li>At least one index must be specified.</li> - <li>Not only struct indices but also array indices must be in - bounds.</li> - </ul> - -<h5>Semantics:</h5> -<p>The result is the value at the position in the aggregate specified by the - index operands.</p> - -<h5>Example:</h5> -<pre> - <result> = extractvalue {i32, float} %agg, 0 <i>; yields i32</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_insertvalue">'<tt>insertvalue</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = insertvalue <aggregate type> <val>, <ty> <elt>, <idx>{, <idx>}* <i>; yields <aggregate type></i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>insertvalue</tt>' instruction inserts a value into a member field - in an <a href="#t_aggregate">aggregate</a> value.</p> - -<h5>Arguments:</h5> -<p>The first operand of an '<tt>insertvalue</tt>' instruction is a value - of <a href="#t_struct">struct</a> or - <a href="#t_array">array</a> type. The second operand is a first-class - value to insert. The following operands are constant indices indicating - the position at which to insert the value in a similar manner as indices in a - '<tt><a href="#i_extractvalue">extractvalue</a></tt>' instruction. The - value to insert must have the same type as the value identified by the - indices.</p> - -<h5>Semantics:</h5> -<p>The result is an aggregate of the same type as <tt>val</tt>. Its value is - that of <tt>val</tt> except that the value at the position specified by the - indices is that of <tt>elt</tt>.</p> - -<h5>Example:</h5> -<pre> - %agg1 = insertvalue {i32, float} undef, i32 1, 0 <i>; yields {i32 1, float undef}</i> - %agg2 = insertvalue {i32, float} %agg1, float %val, 1 <i>; yields {i32 1, float %val}</i> - %agg3 = insertvalue {i32, {float}} %agg1, float %val, 1, 0 <i>; yields {i32 1, float %val}</i> -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="memoryops">Memory Access and Addressing Operations</a> -</h3> - -<div> - -<p>A key design point of an SSA-based representation is how it represents - memory. In LLVM, no memory locations are in SSA form, which makes things - very simple. This section describes how to read, write, and allocate - memory in LLVM.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_alloca">'<tt>alloca</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = alloca <type>[, <ty> <NumElements>][, align <alignment>] <i>; yields {type*}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>alloca</tt>' instruction allocates memory on the stack frame of the - currently executing function, to be automatically released when this function - returns to its caller. The object is always allocated in the generic address - space (address space zero).</p> - -<h5>Arguments:</h5> -<p>The '<tt>alloca</tt>' instruction - allocates <tt>sizeof(<type>)*NumElements</tt> bytes of memory on the - runtime stack, returning a pointer of the appropriate type to the program. - If "NumElements" is specified, it is the number of elements allocated, - otherwise "NumElements" is defaulted to be one. If a constant alignment is - specified, the value result of the allocation is guaranteed to be aligned to - at least that boundary. If not specified, or if zero, the target can choose - to align the allocation on any convenient boundary compatible with the - type.</p> - -<p>'<tt>type</tt>' may be any sized type.</p> - -<h5>Semantics:</h5> -<p>Memory is allocated; a pointer is returned. The operation is undefined if - there is insufficient stack space for the allocation. '<tt>alloca</tt>'d - memory is automatically released when the function returns. The - '<tt>alloca</tt>' instruction is commonly used to represent automatic - variables that must have an address available. When the function returns - (either with the <tt><a href="#i_ret">ret</a></tt> - or <tt><a href="#i_resume">resume</a></tt> instructions), the memory is - reclaimed. Allocating zero bytes is legal, but the result is undefined. - The order in which memory is allocated (ie., which way the stack grows) is - not specified.</p> - -<p> - -<h5>Example:</h5> -<pre> - %ptr = alloca i32 <i>; yields {i32*}:ptr</i> - %ptr = alloca i32, i32 4 <i>; yields {i32*}:ptr</i> - %ptr = alloca i32, i32 4, align 1024 <i>; yields {i32*}:ptr</i> - %ptr = alloca i32, align 1024 <i>; yields {i32*}:ptr</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_load">'<tt>load</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = load [volatile] <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>][, !invariant.load !<index>] - <result> = load atomic [volatile] <ty>* <pointer> [singlethread] <ordering>, align <alignment> - !<index> = !{ i32 1 } -</pre> - -<h5>Overview:</h5> -<p>The '<tt>load</tt>' instruction is used to read from memory.</p> - -<h5>Arguments:</h5> -<p>The argument to the '<tt>load</tt>' instruction specifies the memory address - from which to load. The pointer must point to - a <a href="#t_firstclass">first class</a> type. If the <tt>load</tt> is - marked as <tt>volatile</tt>, then the optimizer is not allowed to modify the - number or order of execution of this <tt>load</tt> with other <a - href="#volatile">volatile operations</a>.</p> - -<p>If the <code>load</code> is marked as <code>atomic</code>, it takes an extra - <a href="#ordering">ordering</a> and optional <code>singlethread</code> - argument. The <code>release</code> and <code>acq_rel</code> orderings are - not valid on <code>load</code> instructions. Atomic loads produce <a - href="#memorymodel">defined</a> results when they may see multiple atomic - stores. The type of the pointee must be an integer type whose bit width - is a power of two greater than or equal to eight and less than or equal - to a target-specific size limit. <code>align</code> must be explicitly - specified on atomic loads, and the load has undefined behavior if the - alignment is not set to a value which is at least the size in bytes of - the pointee. <code>!nontemporal</code> does not have any defined semantics - for atomic loads.</p> - -<p>The optional constant <tt>align</tt> argument specifies the alignment of the - operation (that is, the alignment of the memory address). A value of 0 or an - omitted <tt>align</tt> argument means that the operation has the abi - alignment for the target. It is the responsibility of the code emitter to - ensure that the alignment information is correct. Overestimating the - alignment results in undefined behavior. Underestimating the alignment may - produce less efficient code. An alignment of 1 is always safe.</p> - -<p>The optional <tt>!nontemporal</tt> metadata must reference a single - metatadata name <index> corresponding to a metadata node with - one <tt>i32</tt> entry of value 1. The existence of - the <tt>!nontemporal</tt> metatadata on the instruction tells the optimizer - and code generator that this load is not expected to be reused in the cache. - The code generator may select special instructions to save cache bandwidth, - such as the <tt>MOVNT</tt> instruction on x86.</p> - -<p>The optional <tt>!invariant.load</tt> metadata must reference a single - metatadata name <index> corresponding to a metadata node with no - entries. The existence of the <tt>!invariant.load</tt> metatadata on the - instruction tells the optimizer and code generator that this load address - points to memory which does not change value during program execution. - The optimizer may then move this load around, for example, by hoisting it - out of loops using loop invariant code motion.</p> - -<h5>Semantics:</h5> -<p>The location of memory pointed to is loaded. If the value being loaded is of - scalar type then the number of bytes read does not exceed the minimum number - of bytes needed to hold all bits of the type. For example, loading an - <tt>i24</tt> reads at most three bytes. When loading a value of a type like - <tt>i20</tt> with a size that is not an integral number of bytes, the result - is undefined if the value was not originally written using a store of the - same type.</p> - -<h5>Examples:</h5> -<pre> - %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i> - <a href="#i_store">store</a> i32 3, i32* %ptr <i>; yields {void}</i> - %val = load i32* %ptr <i>; yields {i32}:val = i32 3</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_store">'<tt>store</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - store [volatile] <ty> <value>, <ty>* <pointer>[, align <alignment>][, !nontemporal !<index>] <i>; yields {void}</i> - store atomic [volatile] <ty> <value>, <ty>* <pointer> [singlethread] <ordering>, align <alignment> <i>; yields {void}</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>store</tt>' instruction is used to write to memory.</p> - -<h5>Arguments:</h5> -<p>There are two arguments to the '<tt>store</tt>' instruction: a value to store - and an address at which to store it. The type of the - '<tt><pointer></tt>' operand must be a pointer to - the <a href="#t_firstclass">first class</a> type of the - '<tt><value></tt>' operand. If the <tt>store</tt> is marked as - <tt>volatile</tt>, then the optimizer is not allowed to modify the number or - order of execution of this <tt>store</tt> with other <a - href="#volatile">volatile operations</a>.</p> - -<p>If the <code>store</code> is marked as <code>atomic</code>, it takes an extra - <a href="#ordering">ordering</a> and optional <code>singlethread</code> - argument. The <code>acquire</code> and <code>acq_rel</code> orderings aren't - valid on <code>store</code> instructions. Atomic loads produce <a - href="#memorymodel">defined</a> results when they may see multiple atomic - stores. The type of the pointee must be an integer type whose bit width - is a power of two greater than or equal to eight and less than or equal - to a target-specific size limit. <code>align</code> must be explicitly - specified on atomic stores, and the store has undefined behavior if the - alignment is not set to a value which is at least the size in bytes of - the pointee. <code>!nontemporal</code> does not have any defined semantics - for atomic stores.</p> - -<p>The optional constant "align" argument specifies the alignment of the - operation (that is, the alignment of the memory address). A value of 0 or an - omitted "align" argument means that the operation has the abi - alignment for the target. It is the responsibility of the code emitter to - ensure that the alignment information is correct. Overestimating the - alignment results in an undefined behavior. Underestimating the alignment may - produce less efficient code. An alignment of 1 is always safe.</p> - -<p>The optional !nontemporal metadata must reference a single metatadata - name <index> corresponding to a metadata node with one i32 entry of - value 1. The existence of the !nontemporal metatadata on the - instruction tells the optimizer and code generator that this load is - not expected to be reused in the cache. The code generator may - select special instructions to save cache bandwidth, such as the - MOVNT instruction on x86.</p> - - -<h5>Semantics:</h5> -<p>The contents of memory are updated to contain '<tt><value></tt>' at the - location specified by the '<tt><pointer></tt>' operand. If - '<tt><value></tt>' is of scalar type then the number of bytes written - does not exceed the minimum number of bytes needed to hold all bits of the - type. For example, storing an <tt>i24</tt> writes at most three bytes. When - writing a value of a type like <tt>i20</tt> with a size that is not an - integral number of bytes, it is unspecified what happens to the extra bits - that do not belong to the type, but they will typically be overwritten.</p> - -<h5>Example:</h5> -<pre> - %ptr = <a href="#i_alloca">alloca</a> i32 <i>; yields {i32*}:ptr</i> - store i32 3, i32* %ptr <i>; yields {void}</i> - %val = <a href="#i_load">load</a> i32* %ptr <i>; yields {i32}:val = i32 3</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> -<a name="i_fence">'<tt>fence</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - fence [singlethread] <ordering> <i>; yields {void}</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fence</tt>' instruction is used to introduce happens-before edges -between operations.</p> - -<h5>Arguments:</h5> <p>'<code>fence</code>' instructions take an <a -href="#ordering">ordering</a> argument which defines what -<i>synchronizes-with</i> edges they add. They can only be given -<code>acquire</code>, <code>release</code>, <code>acq_rel</code>, and -<code>seq_cst</code> orderings.</p> - -<h5>Semantics:</h5> -<p>A fence <var>A</var> which has (at least) <code>release</code> ordering -semantics <i>synchronizes with</i> a fence <var>B</var> with (at least) -<code>acquire</code> ordering semantics if and only if there exist atomic -operations <var>X</var> and <var>Y</var>, both operating on some atomic object -<var>M</var>, such that <var>A</var> is sequenced before <var>X</var>, -<var>X</var> modifies <var>M</var> (either directly or through some side effect -of a sequence headed by <var>X</var>), <var>Y</var> is sequenced before -<var>B</var>, and <var>Y</var> observes <var>M</var>. This provides a -<i>happens-before</i> dependency between <var>A</var> and <var>B</var>. Rather -than an explicit <code>fence</code>, one (but not both) of the atomic operations -<var>X</var> or <var>Y</var> might provide a <code>release</code> or -<code>acquire</code> (resp.) ordering constraint and still -<i>synchronize-with</i> the explicit <code>fence</code> and establish the -<i>happens-before</i> edge.</p> - -<p>A <code>fence</code> which has <code>seq_cst</code> ordering, in addition to -having both <code>acquire</code> and <code>release</code> semantics specified -above, participates in the global program order of other <code>seq_cst</code> -operations and/or fences.</p> - -<p>The optional "<a href="#singlethread"><code>singlethread</code></a>" argument -specifies that the fence only synchronizes with other fences in the same -thread. (This is useful for interacting with signal handlers.)</p> - -<h5>Example:</h5> -<pre> - fence acquire <i>; yields {void}</i> - fence singlethread seq_cst <i>; yields {void}</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> -<a name="i_cmpxchg">'<tt>cmpxchg</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - cmpxchg [volatile] <ty>* <pointer>, <ty> <cmp>, <ty> <new> [singlethread] <ordering> <i>; yields {ty}</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>cmpxchg</tt>' instruction is used to atomically modify memory. -It loads a value in memory and compares it to a given value. If they are -equal, it stores a new value into the memory.</p> - -<h5>Arguments:</h5> -<p>There are three arguments to the '<code>cmpxchg</code>' instruction: an -address to operate on, a value to compare to the value currently be at that -address, and a new value to place at that address if the compared values are -equal. The type of '<var><cmp></var>' must be an integer type whose -bit width is a power of two greater than or equal to eight and less than -or equal to a target-specific size limit. '<var><cmp></var>' and -'<var><new></var>' must have the same type, and the type of -'<var><pointer></var>' must be a pointer to that type. If the -<code>cmpxchg</code> is marked as <code>volatile</code>, then the -optimizer is not allowed to modify the number or order of execution -of this <code>cmpxchg</code> with other <a href="#volatile">volatile -operations</a>.</p> - -<!-- FIXME: Extend allowed types. --> - -<p>The <a href="#ordering"><var>ordering</var></a> argument specifies how this -<code>cmpxchg</code> synchronizes with other atomic operations.</p> - -<p>The optional "<code>singlethread</code>" argument declares that the -<code>cmpxchg</code> is only atomic with respect to code (usually signal -handlers) running in the same thread as the <code>cmpxchg</code>. Otherwise the -cmpxchg is atomic with respect to all other code in the system.</p> - -<p>The pointer passed into cmpxchg must have alignment greater than or equal to -the size in memory of the operand. - -<h5>Semantics:</h5> -<p>The contents of memory at the location specified by the -'<tt><pointer></tt>' operand is read and compared to -'<tt><cmp></tt>'; if the read value is the equal, -'<tt><new></tt>' is written. The original value at the location -is returned. - -<p>A successful <code>cmpxchg</code> is a read-modify-write instruction for the -purpose of identifying <a href="#release_sequence">release sequences</a>. A -failed <code>cmpxchg</code> is equivalent to an atomic load with an ordering -parameter determined by dropping any <code>release</code> part of the -<code>cmpxchg</code>'s ordering.</p> - -<!-- -FIXME: Is compare_exchange_weak() necessary? (Consider after we've done -optimization work on ARM.) - -FIXME: Is a weaker ordering constraint on failure helpful in practice? ---> - -<h5>Example:</h5> -<pre> -entry: - %orig = atomic <a href="#i_load">load</a> i32* %ptr unordered <i>; yields {i32}</i> - <a href="#i_br">br</a> label %loop - -loop: - %cmp = <a href="#i_phi">phi</a> i32 [ %orig, %entry ], [%old, %loop] - %squared = <a href="#i_mul">mul</a> i32 %cmp, %cmp - %old = cmpxchg i32* %ptr, i32 %cmp, i32 %squared <i>; yields {i32}</i> - %success = <a href="#i_icmp">icmp</a> eq i32 %cmp, %old - <a href="#i_br">br</a> i1 %success, label %done, label %loop - -done: - ... -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> -<a name="i_atomicrmw">'<tt>atomicrmw</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - atomicrmw [volatile] <operation> <ty>* <pointer>, <ty> <value> [singlethread] <ordering> <i>; yields {ty}</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>atomicrmw</tt>' instruction is used to atomically modify memory.</p> - -<h5>Arguments:</h5> -<p>There are three arguments to the '<code>atomicrmw</code>' instruction: an -operation to apply, an address whose value to modify, an argument to the -operation. The operation must be one of the following keywords:</p> -<ul> - <li>xchg</li> - <li>add</li> - <li>sub</li> - <li>and</li> - <li>nand</li> - <li>or</li> - <li>xor</li> - <li>max</li> - <li>min</li> - <li>umax</li> - <li>umin</li> -</ul> - -<p>The type of '<var><value></var>' must be an integer type whose -bit width is a power of two greater than or equal to eight and less than -or equal to a target-specific size limit. The type of the -'<code><pointer></code>' operand must be a pointer to that type. -If the <code>atomicrmw</code> is marked as <code>volatile</code>, then the -optimizer is not allowed to modify the number or order of execution of this -<code>atomicrmw</code> with other <a href="#volatile">volatile - operations</a>.</p> - -<!-- FIXME: Extend allowed types. --> - -<h5>Semantics:</h5> -<p>The contents of memory at the location specified by the -'<tt><pointer></tt>' operand are atomically read, modified, and written -back. The original value at the location is returned. The modification is -specified by the <var>operation</var> argument:</p> - -<ul> - <li>xchg: <code>*ptr = val</code></li> - <li>add: <code>*ptr = *ptr + val</code></li> - <li>sub: <code>*ptr = *ptr - val</code></li> - <li>and: <code>*ptr = *ptr & val</code></li> - <li>nand: <code>*ptr = ~(*ptr & val)</code></li> - <li>or: <code>*ptr = *ptr | val</code></li> - <li>xor: <code>*ptr = *ptr ^ val</code></li> - <li>max: <code>*ptr = *ptr > val ? *ptr : val</code> (using a signed comparison)</li> - <li>min: <code>*ptr = *ptr < val ? *ptr : val</code> (using a signed comparison)</li> - <li>umax: <code>*ptr = *ptr > val ? *ptr : val</code> (using an unsigned comparison)</li> - <li>umin: <code>*ptr = *ptr < val ? *ptr : val</code> (using an unsigned comparison)</li> -</ul> - -<h5>Example:</h5> -<pre> - %old = atomicrmw add i32* %ptr, i32 1 acquire <i>; yields {i32}</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_getelementptr">'<tt>getelementptr</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = getelementptr <pty>* <ptrval>{, <ty> <idx>}* - <result> = getelementptr inbounds <pty>* <ptrval>{, <ty> <idx>}* - <result> = getelementptr <ptr vector> ptrval, <vector index type> idx -</pre> - -<h5>Overview:</h5> -<p>The '<tt>getelementptr</tt>' instruction is used to get the address of a - subelement of an <a href="#t_aggregate">aggregate</a> data structure. - It performs address calculation only and does not access memory.</p> - -<h5>Arguments:</h5> -<p>The first argument is always a pointer or a vector of pointers, - and forms the basis of the - calculation. The remaining arguments are indices that indicate which of the - elements of the aggregate object are indexed. The interpretation of each - index is dependent on the type being indexed into. The first index always - indexes the pointer value given as the first argument, the second index - indexes a value of the type pointed to (not necessarily the value directly - pointed to, since the first index can be non-zero), etc. The first type - indexed into must be a pointer value, subsequent types can be arrays, - vectors, and structs. Note that subsequent types being indexed into - can never be pointers, since that would require loading the pointer before - continuing calculation.</p> - -<p>The type of each index argument depends on the type it is indexing into. - When indexing into a (optionally packed) structure, only <tt>i32</tt> - integer <b>constants</b> are allowed (when using a vector of indices they - must all be the <b>same</b> <tt>i32</tt> integer constant). When indexing - into an array, pointer or vector, integers of any width are allowed, and - they are not required to be constant. These integers are treated as signed - values where relevant.</p> - -<p>For example, let's consider a C code fragment and how it gets compiled to - LLVM:</p> - -<pre class="doc_code"> -struct RT { - char A; - int B[10][20]; - char C; -}; -struct ST { - int X; - double Y; - struct RT Z; -}; - -int *foo(struct ST *s) { - return &s[1].Z.B[5][13]; -} -</pre> - -<p>The LLVM code generated by Clang is:</p> - -<pre class="doc_code"> -%struct.RT = <a href="#namedtypes">type</a> { i8, [10 x [20 x i32]], i8 } -%struct.ST = <a href="#namedtypes">type</a> { i32, double, %struct.RT } - -define i32* @foo(%struct.ST* %s) nounwind uwtable readnone optsize ssp { -entry: - %arrayidx = getelementptr inbounds %struct.ST* %s, i64 1, i32 2, i32 1, i64 5, i64 13 - ret i32* %arrayidx -} -</pre> - -<h5>Semantics:</h5> -<p>In the example above, the first index is indexing into the - '<tt>%struct.ST*</tt>' type, which is a pointer, yielding a - '<tt>%struct.ST</tt>' = '<tt>{ i32, double, %struct.RT }</tt>' type, a - structure. The second index indexes into the third element of the structure, - yielding a '<tt>%struct.RT</tt>' = '<tt>{ i8 , [10 x [20 x i32]], i8 }</tt>' - type, another structure. The third index indexes into the second element of - the structure, yielding a '<tt>[10 x [20 x i32]]</tt>' type, an array. The - two dimensions of the array are subscripted into, yielding an '<tt>i32</tt>' - type. The '<tt>getelementptr</tt>' instruction returns a pointer to this - element, thus computing a value of '<tt>i32*</tt>' type.</p> - -<p>Note that it is perfectly legal to index partially through a structure, - returning a pointer to an inner element. Because of this, the LLVM code for - the given testcase is equivalent to:</p> - -<pre class="doc_code"> -define i32* @foo(%struct.ST* %s) { - %t1 = getelementptr %struct.ST* %s, i32 1 <i>; yields %struct.ST*:%t1</i> - %t2 = getelementptr %struct.ST* %t1, i32 0, i32 2 <i>; yields %struct.RT*:%t2</i> - %t3 = getelementptr %struct.RT* %t2, i32 0, i32 1 <i>; yields [10 x [20 x i32]]*:%t3</i> - %t4 = getelementptr [10 x [20 x i32]]* %t3, i32 0, i32 5 <i>; yields [20 x i32]*:%t4</i> - %t5 = getelementptr [20 x i32]* %t4, i32 0, i32 13 <i>; yields i32*:%t5</i> - ret i32* %t5 -} -</pre> - -<p>If the <tt>inbounds</tt> keyword is present, the result value of the - <tt>getelementptr</tt> is a <a href="#poisonvalues">poison value</a> if the - base pointer is not an <i>in bounds</i> address of an allocated object, - or if any of the addresses that would be formed by successive addition of - the offsets implied by the indices to the base address with infinitely - precise signed arithmetic are not an <i>in bounds</i> address of that - allocated object. The <i>in bounds</i> addresses for an allocated object - are all the addresses that point into the object, plus the address one - byte past the end. - In cases where the base is a vector of pointers the <tt>inbounds</tt> keyword - applies to each of the computations element-wise. </p> - -<p>If the <tt>inbounds</tt> keyword is not present, the offsets are added to - the base address with silently-wrapping two's complement arithmetic. If the - offsets have a different width from the pointer, they are sign-extended or - truncated to the width of the pointer. The result value of the - <tt>getelementptr</tt> may be outside the object pointed to by the base - pointer. The result value may not necessarily be used to access memory - though, even if it happens to point into allocated storage. See the - <a href="#pointeraliasing">Pointer Aliasing Rules</a> section for more - information.</p> - -<p>The getelementptr instruction is often confusing. For some more insight into - how it works, see <a href="GetElementPtr.html">the getelementptr FAQ</a>.</p> - -<h5>Example:</h5> -<pre> - <i>; yields [12 x i8]*:aptr</i> - %aptr = getelementptr {i32, [12 x i8]}* %saptr, i64 0, i32 1 - <i>; yields i8*:vptr</i> - %vptr = getelementptr {i32, <2 x i8>}* %svptr, i64 0, i32 1, i32 1 - <i>; yields i8*:eptr</i> - %eptr = getelementptr [12 x i8]* %aptr, i64 0, i32 1 - <i>; yields i32*:iptr</i> - %iptr = getelementptr [10 x i32]* @arr, i16 0, i16 0 -</pre> - -<p>In cases where the pointer argument is a vector of pointers, each index must - be a vector with the same number of elements. For example: </p> -<pre class="doc_code"> - %A = getelementptr <4 x i8*> %ptrs, <4 x i64> %offsets, -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="convertops">Conversion Operations</a> -</h3> - -<div> - -<p>The instructions in this category are the conversion instructions (casting) - which all take a single operand and a type. They perform various bit - conversions on the operand.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_trunc">'<tt>trunc .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = trunc <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>trunc</tt>' instruction truncates its operand to the - type <tt>ty2</tt>.</p> - -<h5>Arguments:</h5> -<p>The '<tt>trunc</tt>' instruction takes a value to trunc, and a type to trunc it to. - Both types must be of <a href="#t_integer">integer</a> types, or vectors - of the same number of integers. - The bit size of the <tt>value</tt> must be larger than - the bit size of the destination type, <tt>ty2</tt>. - Equal sized types are not allowed.</p> - -<h5>Semantics:</h5> -<p>The '<tt>trunc</tt>' instruction truncates the high order bits - in <tt>value</tt> and converts the remaining bits to <tt>ty2</tt>. Since the - source size must be larger than the destination size, <tt>trunc</tt> cannot - be a <i>no-op cast</i>. It will always truncate bits.</p> - -<h5>Example:</h5> -<pre> - %X = trunc i32 257 to i8 <i>; yields i8:1</i> - %Y = trunc i32 123 to i1 <i>; yields i1:true</i> - %Z = trunc i32 122 to i1 <i>; yields i1:false</i> - %W = trunc <2 x i16> <i16 8, i16 7> to <2 x i8> <i>; yields <i8 8, i8 7></i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_zext">'<tt>zext .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = zext <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>zext</tt>' instruction zero extends its operand to type - <tt>ty2</tt>.</p> - - -<h5>Arguments:</h5> -<p>The '<tt>zext</tt>' instruction takes a value to cast, and a type to cast it to. - Both types must be of <a href="#t_integer">integer</a> types, or vectors - of the same number of integers. - The bit size of the <tt>value</tt> must be smaller than - the bit size of the destination type, - <tt>ty2</tt>.</p> - -<h5>Semantics:</h5> -<p>The <tt>zext</tt> fills the high order bits of the <tt>value</tt> with zero - bits until it reaches the size of the destination type, <tt>ty2</tt>.</p> - -<p>When zero extending from i1, the result will always be either 0 or 1.</p> - -<h5>Example:</h5> -<pre> - %X = zext i32 257 to i64 <i>; yields i64:257</i> - %Y = zext i1 true to i32 <i>; yields i32:1</i> - %Z = zext <2 x i16> <i16 8, i16 7> to <2 x i32> <i>; yields <i32 8, i32 7></i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_sext">'<tt>sext .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = sext <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>sext</tt>' sign extends <tt>value</tt> to the type <tt>ty2</tt>.</p> - -<h5>Arguments:</h5> -<p>The '<tt>sext</tt>' instruction takes a value to cast, and a type to cast it to. - Both types must be of <a href="#t_integer">integer</a> types, or vectors - of the same number of integers. - The bit size of the <tt>value</tt> must be smaller than - the bit size of the destination type, - <tt>ty2</tt>.</p> - -<h5>Semantics:</h5> -<p>The '<tt>sext</tt>' instruction performs a sign extension by copying the sign - bit (highest order bit) of the <tt>value</tt> until it reaches the bit size - of the type <tt>ty2</tt>.</p> - -<p>When sign extending from i1, the extension always results in -1 or 0.</p> - -<h5>Example:</h5> -<pre> - %X = sext i8 -1 to i16 <i>; yields i16 :65535</i> - %Y = sext i1 true to i32 <i>; yields i32:-1</i> - %Z = sext <2 x i16> <i16 8, i16 7> to <2 x i32> <i>; yields <i32 8, i32 7></i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fptrunc">'<tt>fptrunc .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fptrunc <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fptrunc</tt>' instruction truncates <tt>value</tt> to type - <tt>ty2</tt>.</p> - -<h5>Arguments:</h5> -<p>The '<tt>fptrunc</tt>' instruction takes a <a href="#t_floating">floating - point</a> value to cast and a <a href="#t_floating">floating point</a> type - to cast it to. The size of <tt>value</tt> must be larger than the size of - <tt>ty2</tt>. This implies that <tt>fptrunc</tt> cannot be used to make a - <i>no-op cast</i>.</p> - -<h5>Semantics:</h5> -<p>The '<tt>fptrunc</tt>' instruction truncates a <tt>value</tt> from a larger - <a href="#t_floating">floating point</a> type to a smaller - <a href="#t_floating">floating point</a> type. If the value cannot fit - within the destination type, <tt>ty2</tt>, then the results are - undefined.</p> - -<h5>Example:</h5> -<pre> - %X = fptrunc double 123.0 to float <i>; yields float:123.0</i> - %Y = fptrunc double 1.0E+300 to float <i>; yields undefined</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fpext">'<tt>fpext .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fpext <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fpext</tt>' extends a floating point <tt>value</tt> to a larger - floating point value.</p> - -<h5>Arguments:</h5> -<p>The '<tt>fpext</tt>' instruction takes a - <a href="#t_floating">floating point</a> <tt>value</tt> to cast, and - a <a href="#t_floating">floating point</a> type to cast it to. The source - type must be smaller than the destination type.</p> - -<h5>Semantics:</h5> -<p>The '<tt>fpext</tt>' instruction extends the <tt>value</tt> from a smaller - <a href="#t_floating">floating point</a> type to a larger - <a href="#t_floating">floating point</a> type. The <tt>fpext</tt> cannot be - used to make a <i>no-op cast</i> because it always changes bits. Use - <tt>bitcast</tt> to make a <i>no-op cast</i> for a floating point cast.</p> - -<h5>Example:</h5> -<pre> - %X = fpext float 3.125 to double <i>; yields double:3.125000e+00</i> - %Y = fpext double %X to fp128 <i>; yields fp128:0xL00000000000000004000900000000000</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fptoui">'<tt>fptoui .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fptoui <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fptoui</tt>' converts a floating point <tt>value</tt> to its - unsigned integer equivalent of type <tt>ty2</tt>.</p> - -<h5>Arguments:</h5> -<p>The '<tt>fptoui</tt>' instruction takes a value to cast, which must be a - scalar or vector <a href="#t_floating">floating point</a> value, and a type - to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> - type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a - vector integer type with the same number of elements as <tt>ty</tt></p> - -<h5>Semantics:</h5> -<p>The '<tt>fptoui</tt>' instruction converts its - <a href="#t_floating">floating point</a> operand into the nearest (rounding - towards zero) unsigned integer value. If the value cannot fit - in <tt>ty2</tt>, the results are undefined.</p> - -<h5>Example:</h5> -<pre> - %X = fptoui double 123.0 to i32 <i>; yields i32:123</i> - %Y = fptoui float 1.0E+300 to i1 <i>; yields undefined:1</i> - %Z = fptoui float 1.04E+17 to i8 <i>; yields undefined:1</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fptosi">'<tt>fptosi .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fptosi <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fptosi</tt>' instruction converts - <a href="#t_floating">floating point</a> <tt>value</tt> to - type <tt>ty2</tt>.</p> - -<h5>Arguments:</h5> -<p>The '<tt>fptosi</tt>' instruction takes a value to cast, which must be a - scalar or vector <a href="#t_floating">floating point</a> value, and a type - to cast it to <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> - type. If <tt>ty</tt> is a vector floating point type, <tt>ty2</tt> must be a - vector integer type with the same number of elements as <tt>ty</tt></p> - -<h5>Semantics:</h5> -<p>The '<tt>fptosi</tt>' instruction converts its - <a href="#t_floating">floating point</a> operand into the nearest (rounding - towards zero) signed integer value. If the value cannot fit in <tt>ty2</tt>, - the results are undefined.</p> - -<h5>Example:</h5> -<pre> - %X = fptosi double -123.0 to i32 <i>; yields i32:-123</i> - %Y = fptosi float 1.0E-247 to i1 <i>; yields undefined:1</i> - %Z = fptosi float 1.04E+17 to i8 <i>; yields undefined:1</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_uitofp">'<tt>uitofp .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = uitofp <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>uitofp</tt>' instruction regards <tt>value</tt> as an unsigned - integer and converts that value to the <tt>ty2</tt> type.</p> - -<h5>Arguments:</h5> -<p>The '<tt>uitofp</tt>' instruction takes a value to cast, which must be a - scalar or vector <a href="#t_integer">integer</a> value, and a type to cast - it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a> - type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector - floating point type with the same number of elements as <tt>ty</tt></p> - -<h5>Semantics:</h5> -<p>The '<tt>uitofp</tt>' instruction interprets its operand as an unsigned - integer quantity and converts it to the corresponding floating point - value. If the value cannot fit in the floating point value, the results are - undefined.</p> - -<h5>Example:</h5> -<pre> - %X = uitofp i32 257 to float <i>; yields float:257.0</i> - %Y = uitofp i8 -1 to double <i>; yields double:255.0</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_sitofp">'<tt>sitofp .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = sitofp <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>sitofp</tt>' instruction regards <tt>value</tt> as a signed integer - and converts that value to the <tt>ty2</tt> type.</p> - -<h5>Arguments:</h5> -<p>The '<tt>sitofp</tt>' instruction takes a value to cast, which must be a - scalar or vector <a href="#t_integer">integer</a> value, and a type to cast - it to <tt>ty2</tt>, which must be an <a href="#t_floating">floating point</a> - type. If <tt>ty</tt> is a vector integer type, <tt>ty2</tt> must be a vector - floating point type with the same number of elements as <tt>ty</tt></p> - -<h5>Semantics:</h5> -<p>The '<tt>sitofp</tt>' instruction interprets its operand as a signed integer - quantity and converts it to the corresponding floating point value. If the - value cannot fit in the floating point value, the results are undefined.</p> - -<h5>Example:</h5> -<pre> - %X = sitofp i32 257 to float <i>; yields float:257.0</i> - %Y = sitofp i8 -1 to double <i>; yields double:-1.0</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_ptrtoint">'<tt>ptrtoint .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = ptrtoint <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>ptrtoint</tt>' instruction converts the pointer or a vector of - pointers <tt>value</tt> to - the integer (or vector of integers) type <tt>ty2</tt>.</p> - -<h5>Arguments:</h5> -<p>The '<tt>ptrtoint</tt>' instruction takes a <tt>value</tt> to cast, which - must be a a value of type <a href="#t_pointer">pointer</a> or a vector of - pointers, and a type to cast it to - <tt>ty2</tt>, which must be an <a href="#t_integer">integer</a> or a vector - of integers type.</p> - -<h5>Semantics:</h5> -<p>The '<tt>ptrtoint</tt>' instruction converts <tt>value</tt> to integer type - <tt>ty2</tt> by interpreting the pointer value as an integer and either - truncating or zero extending that value to the size of the integer type. If - <tt>value</tt> is smaller than <tt>ty2</tt> then a zero extension is done. If - <tt>value</tt> is larger than <tt>ty2</tt> then a truncation is done. If they - are the same size, then nothing is done (<i>no-op cast</i>) other than a type - change.</p> - -<h5>Example:</h5> -<pre> - %X = ptrtoint i32* %P to i8 <i>; yields truncation on 32-bit architecture</i> - %Y = ptrtoint i32* %P to i64 <i>; yields zero extension on 32-bit architecture</i> - %Z = ptrtoint <4 x i32*> %P to <4 x i64><i>; yields vector zero extension for a vector of addresses on 32-bit architecture</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_inttoptr">'<tt>inttoptr .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = inttoptr <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>inttoptr</tt>' instruction converts an integer <tt>value</tt> to a - pointer type, <tt>ty2</tt>.</p> - -<h5>Arguments:</h5> -<p>The '<tt>inttoptr</tt>' instruction takes an <a href="#t_integer">integer</a> - value to cast, and a type to cast it to, which must be a - <a href="#t_pointer">pointer</a> type.</p> - -<h5>Semantics:</h5> -<p>The '<tt>inttoptr</tt>' instruction converts <tt>value</tt> to type - <tt>ty2</tt> by applying either a zero extension or a truncation depending on - the size of the integer <tt>value</tt>. If <tt>value</tt> is larger than the - size of a pointer then a truncation is done. If <tt>value</tt> is smaller - than the size of a pointer then a zero extension is done. If they are the - same size, nothing is done (<i>no-op cast</i>).</p> - -<h5>Example:</h5> -<pre> - %X = inttoptr i32 255 to i32* <i>; yields zero extension on 64-bit architecture</i> - %Y = inttoptr i32 255 to i32* <i>; yields no-op on 32-bit architecture</i> - %Z = inttoptr i64 0 to i32* <i>; yields truncation on 32-bit architecture</i> - %Z = inttoptr <4 x i32> %G to <4 x i8*><i>; yields truncation of vector G to four pointers</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_bitcast">'<tt>bitcast .. to</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = bitcast <ty> <value> to <ty2> <i>; yields ty2</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type - <tt>ty2</tt> without changing any bits.</p> - -<h5>Arguments:</h5> -<p>The '<tt>bitcast</tt>' instruction takes a value to cast, which must be a - non-aggregate first class value, and a type to cast it to, which must also be - a non-aggregate <a href="#t_firstclass">first class</a> type. The bit sizes - of <tt>value</tt> and the destination type, <tt>ty2</tt>, must be - identical. If the source type is a pointer, the destination type must also be - a pointer. This instruction supports bitwise conversion of vectors to - integers and to vectors of other types (as long as they have the same - size).</p> - -<h5>Semantics:</h5> -<p>The '<tt>bitcast</tt>' instruction converts <tt>value</tt> to type - <tt>ty2</tt>. It is always a <i>no-op cast</i> because no bits change with - this conversion. The conversion is done as if the <tt>value</tt> had been - stored to memory and read back as type <tt>ty2</tt>. - Pointer (or vector of pointers) types may only be converted to other pointer - (or vector of pointers) types with this instruction. To convert - pointers to other types, use the <a href="#i_inttoptr">inttoptr</a> or - <a href="#i_ptrtoint">ptrtoint</a> instructions first.</p> - -<h5>Example:</h5> -<pre> - %X = bitcast i8 255 to i8 <i>; yields i8 :-1</i> - %Y = bitcast i32* %x to sint* <i>; yields sint*:%x</i> - %Z = bitcast <2 x int> %V to i64; <i>; yields i64: %V</i> - %Z = bitcast <2 x i32*> %V to <2 x i64*> <i>; yields <2 x i64*></i> -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="otherops">Other Operations</a> -</h3> - -<div> - -<p>The instructions in this category are the "miscellaneous" instructions, which - defy better classification.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_icmp">'<tt>icmp</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = icmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>icmp</tt>' instruction returns a boolean value or a vector of - boolean values based on comparison of its two integer, integer vector, - pointer, or pointer vector operands.</p> - -<h5>Arguments:</h5> -<p>The '<tt>icmp</tt>' instruction takes three operands. The first operand is - the condition code indicating the kind of comparison to perform. It is not a - value, just a keyword. The possible condition code are:</p> - -<ol> - <li><tt>eq</tt>: equal</li> - <li><tt>ne</tt>: not equal </li> - <li><tt>ugt</tt>: unsigned greater than</li> - <li><tt>uge</tt>: unsigned greater or equal</li> - <li><tt>ult</tt>: unsigned less than</li> - <li><tt>ule</tt>: unsigned less or equal</li> - <li><tt>sgt</tt>: signed greater than</li> - <li><tt>sge</tt>: signed greater or equal</li> - <li><tt>slt</tt>: signed less than</li> - <li><tt>sle</tt>: signed less or equal</li> -</ol> - -<p>The remaining two arguments must be <a href="#t_integer">integer</a> or - <a href="#t_pointer">pointer</a> or integer <a href="#t_vector">vector</a> - typed. They must also be identical types.</p> - -<h5>Semantics:</h5> -<p>The '<tt>icmp</tt>' compares <tt>op1</tt> and <tt>op2</tt> according to the - condition code given as <tt>cond</tt>. The comparison performed always yields - either an <a href="#t_integer"><tt>i1</tt></a> or vector of <tt>i1</tt> - result, as follows:</p> - -<ol> - <li><tt>eq</tt>: yields <tt>true</tt> if the operands are equal, - <tt>false</tt> otherwise. No sign interpretation is necessary or - performed.</li> - - <li><tt>ne</tt>: yields <tt>true</tt> if the operands are unequal, - <tt>false</tt> otherwise. No sign interpretation is necessary or - performed.</li> - - <li><tt>ugt</tt>: interprets the operands as unsigned values and yields - <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li> - - <li><tt>uge</tt>: interprets the operands as unsigned values and yields - <tt>true</tt> if <tt>op1</tt> is greater than or equal - to <tt>op2</tt>.</li> - - <li><tt>ult</tt>: interprets the operands as unsigned values and yields - <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li> - - <li><tt>ule</tt>: interprets the operands as unsigned values and yields - <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> - - <li><tt>sgt</tt>: interprets the operands as signed values and yields - <tt>true</tt> if <tt>op1</tt> is greater than <tt>op2</tt>.</li> - - <li><tt>sge</tt>: interprets the operands as signed values and yields - <tt>true</tt> if <tt>op1</tt> is greater than or equal - to <tt>op2</tt>.</li> - - <li><tt>slt</tt>: interprets the operands as signed values and yields - <tt>true</tt> if <tt>op1</tt> is less than <tt>op2</tt>.</li> - - <li><tt>sle</tt>: interprets the operands as signed values and yields - <tt>true</tt> if <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> -</ol> - -<p>If the operands are <a href="#t_pointer">pointer</a> typed, the pointer - values are compared as if they were integers.</p> - -<p>If the operands are integer vectors, then they are compared element by - element. The result is an <tt>i1</tt> vector with the same number of elements - as the values being compared. Otherwise, the result is an <tt>i1</tt>.</p> - -<h5>Example:</h5> -<pre> - <result> = icmp eq i32 4, 5 <i>; yields: result=false</i> - <result> = icmp ne float* %X, %X <i>; yields: result=false</i> - <result> = icmp ult i16 4, 5 <i>; yields: result=true</i> - <result> = icmp sgt i16 4, 5 <i>; yields: result=false</i> - <result> = icmp ule i16 -4, 5 <i>; yields: result=false</i> - <result> = icmp sge i16 4, 5 <i>; yields: result=false</i> -</pre> - -<p>Note that the code generator does not yet support vector types with - the <tt>icmp</tt> instruction.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_fcmp">'<tt>fcmp</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = fcmp <cond> <ty> <op1>, <op2> <i>; yields {i1} or {<N x i1>}:result</i> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>fcmp</tt>' instruction returns a boolean value or vector of boolean - values based on comparison of its operands.</p> - -<p>If the operands are floating point scalars, then the result type is a boolean -(<a href="#t_integer"><tt>i1</tt></a>).</p> - -<p>If the operands are floating point vectors, then the result type is a vector - of boolean with the same number of elements as the operands being - compared.</p> - -<h5>Arguments:</h5> -<p>The '<tt>fcmp</tt>' instruction takes three operands. The first operand is - the condition code indicating the kind of comparison to perform. It is not a - value, just a keyword. The possible condition code are:</p> - -<ol> - <li><tt>false</tt>: no comparison, always returns false</li> - <li><tt>oeq</tt>: ordered and equal</li> - <li><tt>ogt</tt>: ordered and greater than </li> - <li><tt>oge</tt>: ordered and greater than or equal</li> - <li><tt>olt</tt>: ordered and less than </li> - <li><tt>ole</tt>: ordered and less than or equal</li> - <li><tt>one</tt>: ordered and not equal</li> - <li><tt>ord</tt>: ordered (no nans)</li> - <li><tt>ueq</tt>: unordered or equal</li> - <li><tt>ugt</tt>: unordered or greater than </li> - <li><tt>uge</tt>: unordered or greater than or equal</li> - <li><tt>ult</tt>: unordered or less than </li> - <li><tt>ule</tt>: unordered or less than or equal</li> - <li><tt>une</tt>: unordered or not equal</li> - <li><tt>uno</tt>: unordered (either nans)</li> - <li><tt>true</tt>: no comparison, always returns true</li> -</ol> - -<p><i>Ordered</i> means that neither operand is a QNAN while - <i>unordered</i> means that either operand may be a QNAN.</p> - -<p>Each of <tt>val1</tt> and <tt>val2</tt> arguments must be either - a <a href="#t_floating">floating point</a> type or - a <a href="#t_vector">vector</a> of floating point type. They must have - identical types.</p> - -<h5>Semantics:</h5> -<p>The '<tt>fcmp</tt>' instruction compares <tt>op1</tt> and <tt>op2</tt> - according to the condition code given as <tt>cond</tt>. If the operands are - vectors, then the vectors are compared element by element. Each comparison - performed always yields an <a href="#t_integer">i1</a> result, as - follows:</p> - -<ol> - <li><tt>false</tt>: always yields <tt>false</tt>, regardless of operands.</li> - - <li><tt>oeq</tt>: yields <tt>true</tt> if both operands are not a QNAN and - <tt>op1</tt> is equal to <tt>op2</tt>.</li> - - <li><tt>ogt</tt>: yields <tt>true</tt> if both operands are not a QNAN and - <tt>op1</tt> is greater than <tt>op2</tt>.</li> - - <li><tt>oge</tt>: yields <tt>true</tt> if both operands are not a QNAN and - <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> - - <li><tt>olt</tt>: yields <tt>true</tt> if both operands are not a QNAN and - <tt>op1</tt> is less than <tt>op2</tt>.</li> - - <li><tt>ole</tt>: yields <tt>true</tt> if both operands are not a QNAN and - <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> - - <li><tt>one</tt>: yields <tt>true</tt> if both operands are not a QNAN and - <tt>op1</tt> is not equal to <tt>op2</tt>.</li> - - <li><tt>ord</tt>: yields <tt>true</tt> if both operands are not a QNAN.</li> - - <li><tt>ueq</tt>: yields <tt>true</tt> if either operand is a QNAN or - <tt>op1</tt> is equal to <tt>op2</tt>.</li> - - <li><tt>ugt</tt>: yields <tt>true</tt> if either operand is a QNAN or - <tt>op1</tt> is greater than <tt>op2</tt>.</li> - - <li><tt>uge</tt>: yields <tt>true</tt> if either operand is a QNAN or - <tt>op1</tt> is greater than or equal to <tt>op2</tt>.</li> - - <li><tt>ult</tt>: yields <tt>true</tt> if either operand is a QNAN or - <tt>op1</tt> is less than <tt>op2</tt>.</li> - - <li><tt>ule</tt>: yields <tt>true</tt> if either operand is a QNAN or - <tt>op1</tt> is less than or equal to <tt>op2</tt>.</li> - - <li><tt>une</tt>: yields <tt>true</tt> if either operand is a QNAN or - <tt>op1</tt> is not equal to <tt>op2</tt>.</li> - - <li><tt>uno</tt>: yields <tt>true</tt> if either operand is a QNAN.</li> - - <li><tt>true</tt>: always yields <tt>true</tt>, regardless of operands.</li> -</ol> - -<h5>Example:</h5> -<pre> - <result> = fcmp oeq float 4.0, 5.0 <i>; yields: result=false</i> - <result> = fcmp one float 4.0, 5.0 <i>; yields: result=true</i> - <result> = fcmp olt float 4.0, 5.0 <i>; yields: result=true</i> - <result> = fcmp ueq double 1.0, 2.0 <i>; yields: result=false</i> -</pre> - -<p>Note that the code generator does not yet support vector types with - the <tt>fcmp</tt> instruction.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_phi">'<tt>phi</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = phi <ty> [ <val0>, <label0>], ... -</pre> - -<h5>Overview:</h5> -<p>The '<tt>phi</tt>' instruction is used to implement the φ node in the - SSA graph representing the function.</p> - -<h5>Arguments:</h5> -<p>The type of the incoming values is specified with the first type field. After - this, the '<tt>phi</tt>' instruction takes a list of pairs as arguments, with - one pair for each predecessor basic block of the current block. Only values - of <a href="#t_firstclass">first class</a> type may be used as the value - arguments to the PHI node. Only labels may be used as the label - arguments.</p> - -<p>There must be no non-phi instructions between the start of a basic block and - the PHI instructions: i.e. PHI instructions must be first in a basic - block.</p> - -<p>For the purposes of the SSA form, the use of each incoming value is deemed to - occur on the edge from the corresponding predecessor block to the current - block (but after any definition of an '<tt>invoke</tt>' instruction's return - value on the same edge).</p> - -<h5>Semantics:</h5> -<p>At runtime, the '<tt>phi</tt>' instruction logically takes on the value - specified by the pair corresponding to the predecessor basic block that - executed just prior to the current block.</p> - -<h5>Example:</h5> -<pre> -Loop: ; Infinite loop that counts from 0 on up... - %indvar = phi i32 [ 0, %LoopHeader ], [ %nextindvar, %Loop ] - %nextindvar = add i32 %indvar, 1 - br label %Loop -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_select">'<tt>select</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = select <i>selty</i> <cond>, <ty> <val1>, <ty> <val2> <i>; yields ty</i> - - <i>selty</i> is either i1 or {<N x i1>} -</pre> - -<h5>Overview:</h5> -<p>The '<tt>select</tt>' instruction is used to choose one value based on a - condition, without branching.</p> - - -<h5>Arguments:</h5> -<p>The '<tt>select</tt>' instruction requires an 'i1' value or a vector of 'i1' - values indicating the condition, and two values of the - same <a href="#t_firstclass">first class</a> type. If the val1/val2 are - vectors and the condition is a scalar, then entire vectors are selected, not - individual elements.</p> - -<h5>Semantics:</h5> -<p>If the condition is an i1 and it evaluates to 1, the instruction returns the - first value argument; otherwise, it returns the second value argument.</p> - -<p>If the condition is a vector of i1, then the value arguments must be vectors - of the same size, and the selection is done element by element.</p> - -<h5>Example:</h5> -<pre> - %X = select i1 true, i8 17, i8 42 <i>; yields i8:17</i> -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_call">'<tt>call</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <result> = [tail] call [<a href="#callingconv">cconv</a>] [<a href="#paramattrs">ret attrs</a>] <ty> [<fnty>*] <fnptrval>(<function args>) [<a href="#fnattrs">fn attrs</a>] -</pre> - -<h5>Overview:</h5> -<p>The '<tt>call</tt>' instruction represents a simple function call.</p> - -<h5>Arguments:</h5> -<p>This instruction requires several arguments:</p> - -<ol> - <li>The optional "tail" marker indicates that the callee function does not - access any allocas or varargs in the caller. Note that calls may be - marked "tail" even if they do not occur before - a <a href="#i_ret"><tt>ret</tt></a> instruction. If the "tail" marker is - present, the function call is eligible for tail call optimization, - but <a href="CodeGenerator.html#tailcallopt">might not in fact be - optimized into a jump</a>. The code generator may optimize calls marked - "tail" with either 1) automatic <a href="CodeGenerator.html#sibcallopt"> - sibling call optimization</a> when the caller and callee have - matching signatures, or 2) forced tail call optimization when the - following extra requirements are met: - <ul> - <li>Caller and callee both have the calling - convention <tt>fastcc</tt>.</li> - <li>The call is in tail position (ret immediately follows call and ret - uses value of call or is void).</li> - <li>Option <tt>-tailcallopt</tt> is enabled, - or <code>llvm::GuaranteedTailCallOpt</code> is <code>true</code>.</li> - <li><a href="CodeGenerator.html#tailcallopt">Platform specific - constraints are met.</a></li> - </ul> - </li> - - <li>The optional "cconv" marker indicates which <a href="#callingconv">calling - convention</a> the call should use. If none is specified, the call - defaults to using C calling conventions. The calling convention of the - call must match the calling convention of the target function, or else the - behavior is undefined.</li> - - <li>The optional <a href="#paramattrs">Parameter Attributes</a> list for - return values. Only '<tt>zeroext</tt>', '<tt>signext</tt>', and - '<tt>inreg</tt>' attributes are valid here.</li> - - <li>'<tt>ty</tt>': the type of the call instruction itself which is also the - type of the return value. Functions that return no value are marked - <tt><a href="#t_void">void</a></tt>.</li> - - <li>'<tt>fnty</tt>': shall be the signature of the pointer to function value - being invoked. The argument types must match the types implied by this - signature. This type can be omitted if the function is not varargs and if - the function type does not return a pointer to a function.</li> - - <li>'<tt>fnptrval</tt>': An LLVM value containing a pointer to a function to - be invoked. In most cases, this is a direct function invocation, but - indirect <tt>call</tt>s are just as possible, calling an arbitrary pointer - to function value.</li> - - <li>'<tt>function args</tt>': argument list whose types match the function - signature argument types and parameter attributes. All arguments must be - of <a href="#t_firstclass">first class</a> type. If the function - signature indicates the function accepts a variable number of arguments, - the extra arguments can be specified.</li> - - <li>The optional <a href="#fnattrs">function attributes</a> list. Only - '<tt>noreturn</tt>', '<tt>nounwind</tt>', '<tt>readonly</tt>' and - '<tt>readnone</tt>' attributes are valid here.</li> -</ol> - -<h5>Semantics:</h5> -<p>The '<tt>call</tt>' instruction is used to cause control flow to transfer to - a specified function, with its incoming arguments bound to the specified - values. Upon a '<tt><a href="#i_ret">ret</a></tt>' instruction in the called - function, control flow continues with the instruction after the function - call, and the return value of the function is bound to the result - argument.</p> - -<h5>Example:</h5> -<pre> - %retval = call i32 @test(i32 %argc) - call i32 (i8*, ...)* @printf(i8* %msg, i32 12, i8 42) <i>; yields i32</i> - %X = tail call i32 @foo() <i>; yields i32</i> - %Y = tail call <a href="#callingconv">fastcc</a> i32 @foo() <i>; yields i32</i> - call void %foo(i8 97 signext) - - %struct.A = type { i32, i8 } - %r = call %struct.A @foo() <i>; yields { 32, i8 }</i> - %gr = extractvalue %struct.A %r, 0 <i>; yields i32</i> - %gr1 = extractvalue %struct.A %r, 1 <i>; yields i8</i> - %Z = call void @foo() noreturn <i>; indicates that %foo never returns normally</i> - %ZZ = call zeroext i32 @bar() <i>; Return value is %zero extended</i> -</pre> - -<p>llvm treats calls to some functions with names and arguments that match the -standard C99 library as being the C99 library functions, and may perform -optimizations or generate code for them under that assumption. This is -something we'd like to change in the future to provide better support for -freestanding environments and non-C-based languages.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_va_arg">'<tt>va_arg</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <resultval> = va_arg <va_list*> <arglist>, <argty> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>va_arg</tt>' instruction is used to access arguments passed through - the "variable argument" area of a function call. It is used to implement the - <tt>va_arg</tt> macro in C.</p> - -<h5>Arguments:</h5> -<p>This instruction takes a <tt>va_list*</tt> value and the type of the - argument. It returns a value of the specified argument type and increments - the <tt>va_list</tt> to point to the next argument. The actual type - of <tt>va_list</tt> is target specific.</p> - -<h5>Semantics:</h5> -<p>The '<tt>va_arg</tt>' instruction loads an argument of the specified type - from the specified <tt>va_list</tt> and causes the <tt>va_list</tt> to point - to the next argument. For more information, see the variable argument - handling <a href="#int_varargs">Intrinsic Functions</a>.</p> - -<p>It is legal for this instruction to be called in a function which does not - take a variable number of arguments, for example, the <tt>vfprintf</tt> - function.</p> - -<p><tt>va_arg</tt> is an LLVM instruction instead of - an <a href="#intrinsics">intrinsic function</a> because it takes a type as an - argument.</p> - -<h5>Example:</h5> -<p>See the <a href="#int_varargs">variable argument processing</a> section.</p> - -<p>Note that the code generator does not yet fully support va_arg on many - targets. Also, it does not currently support va_arg with aggregate types on - any target.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="i_landingpad">'<tt>landingpad</tt>' Instruction</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - <resultval> = landingpad <resultty> personality <type> <pers_fn> <clause>+ - <resultval> = landingpad <resultty> personality <type> <pers_fn> cleanup <clause>* - - <clause> := catch <type> <value> - <clause> := filter <array constant type> <array constant> -</pre> - -<h5>Overview:</h5> -<p>The '<tt>landingpad</tt>' instruction is used by - <a href="ExceptionHandling.html#overview">LLVM's exception handling - system</a> to specify that a basic block is a landing pad — one where - the exception lands, and corresponds to the code found in the - <i><tt>catch</tt></i> portion of a <i><tt>try/catch</tt></i> sequence. It - defines values supplied by the personality function (<tt>pers_fn</tt>) upon - re-entry to the function. The <tt>resultval</tt> has the - type <tt>resultty</tt>.</p> - -<h5>Arguments:</h5> -<p>This instruction takes a <tt>pers_fn</tt> value. This is the personality - function associated with the unwinding mechanism. The optional - <tt>cleanup</tt> flag indicates that the landing pad block is a cleanup.</p> - -<p>A <tt>clause</tt> begins with the clause type — <tt>catch</tt> - or <tt>filter</tt> — and contains the global variable representing the - "type" that may be caught or filtered respectively. Unlike the - <tt>catch</tt> clause, the <tt>filter</tt> clause takes an array constant as - its argument. Use "<tt>[0 x i8**] undef</tt>" for a filter which cannot - throw. The '<tt>landingpad</tt>' instruction must contain <em>at least</em> - one <tt>clause</tt> or the <tt>cleanup</tt> flag.</p> - -<h5>Semantics:</h5> -<p>The '<tt>landingpad</tt>' instruction defines the values which are set by the - personality function (<tt>pers_fn</tt>) upon re-entry to the function, and - therefore the "result type" of the <tt>landingpad</tt> instruction. As with - calling conventions, how the personality function results are represented in - LLVM IR is target specific.</p> - -<p>The clauses are applied in order from top to bottom. If two - <tt>landingpad</tt> instructions are merged together through inlining, the - clauses from the calling function are appended to the list of clauses. - When the call stack is being unwound due to an exception being thrown, the - exception is compared against each <tt>clause</tt> in turn. If it doesn't - match any of the clauses, and the <tt>cleanup</tt> flag is not set, then - unwinding continues further up the call stack.</p> - -<p>The <tt>landingpad</tt> instruction has several restrictions:</p> - -<ul> - <li>A landing pad block is a basic block which is the unwind destination of an - '<tt>invoke</tt>' instruction.</li> - <li>A landing pad block must have a '<tt>landingpad</tt>' instruction as its - first non-PHI instruction.</li> - <li>There can be only one '<tt>landingpad</tt>' instruction within the landing - pad block.</li> - <li>A basic block that is not a landing pad block may not include a - '<tt>landingpad</tt>' instruction.</li> - <li>All '<tt>landingpad</tt>' instructions in a function must have the same - personality function.</li> -</ul> - -<h5>Example:</h5> -<pre> - ;; A landing pad which can catch an integer. - %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0 - catch i8** @_ZTIi - ;; A landing pad that is a cleanup. - %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0 - cleanup - ;; A landing pad which can catch an integer and can only throw a double. - %res = landingpad { i8*, i32 } personality i32 (...)* @__gxx_personality_v0 - catch i8** @_ZTIi - filter [1 x i8**] [@_ZTId] -</pre> - -</div> - -</div> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="intrinsics">Intrinsic Functions</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>LLVM supports the notion of an "intrinsic function". These functions have - well known names and semantics and are required to follow certain - restrictions. Overall, these intrinsics represent an extension mechanism for - the LLVM language that does not require changing all of the transformations - in LLVM when adding to the language (or the bitcode reader/writer, the - parser, etc...).</p> - -<p>Intrinsic function names must all start with an "<tt>llvm.</tt>" prefix. This - prefix is reserved in LLVM for intrinsic names; thus, function names may not - begin with this prefix. Intrinsic functions must always be external - functions: you cannot define the body of intrinsic functions. Intrinsic - functions may only be used in call or invoke instructions: it is illegal to - take the address of an intrinsic function. Additionally, because intrinsic - functions are part of the LLVM language, it is required if any are added that - they be documented here.</p> - -<p>Some intrinsic functions can be overloaded, i.e., the intrinsic represents a - family of functions that perform the same operation but on different data - types. Because LLVM can represent over 8 million different integer types, - overloading is used commonly to allow an intrinsic function to operate on any - integer type. One or more of the argument types or the result type can be - overloaded to accept any integer type. Argument types may also be defined as - exactly matching a previous argument's type or the result type. This allows - an intrinsic function which accepts multiple arguments, but needs all of them - to be of the same type, to only be overloaded with respect to a single - argument or the result.</p> - -<p>Overloaded intrinsics will have the names of its overloaded argument types - encoded into its function name, each preceded by a period. Only those types - which are overloaded result in a name suffix. Arguments whose type is matched - against another type do not. For example, the <tt>llvm.ctpop</tt> function - can take an integer of any width and returns an integer of exactly the same - integer width. This leads to a family of functions such as - <tt>i8 @llvm.ctpop.i8(i8 %val)</tt> and <tt>i29 @llvm.ctpop.i29(i29 - %val)</tt>. Only one type, the return type, is overloaded, and only one type - suffix is required. Because the argument's type is matched against the return - type, it does not require its own name suffix.</p> - -<p>To learn how to add an intrinsic function, please see the - <a href="ExtendingLLVM.html">Extending LLVM Guide</a>.</p> - -<!-- ======================================================================= --> -<h3> - <a name="int_varargs">Variable Argument Handling Intrinsics</a> -</h3> - -<div> - -<p>Variable argument support is defined in LLVM with - the <a href="#i_va_arg"><tt>va_arg</tt></a> instruction and these three - intrinsic functions. These functions are related to the similarly named - macros defined in the <tt><stdarg.h></tt> header file.</p> - -<p>All of these functions operate on arguments that use a target-specific value - type "<tt>va_list</tt>". The LLVM assembly language reference manual does - not define what this type is, so all transformations should be prepared to - handle these functions regardless of the type used.</p> - -<p>This example shows how the <a href="#i_va_arg"><tt>va_arg</tt></a> - instruction and the variable argument handling intrinsic functions are - used.</p> - -<pre class="doc_code"> -define i32 @test(i32 %X, ...) { - ; Initialize variable argument processing - %ap = alloca i8* - %ap2 = bitcast i8** %ap to i8* - call void @llvm.va_start(i8* %ap2) - - ; Read a single integer argument - %tmp = va_arg i8** %ap, i32 - - ; Demonstrate usage of llvm.va_copy and llvm.va_end - %aq = alloca i8* - %aq2 = bitcast i8** %aq to i8* - call void @llvm.va_copy(i8* %aq2, i8* %ap2) - call void @llvm.va_end(i8* %aq2) - - ; Stop processing of arguments. - call void @llvm.va_end(i8* %ap2) - ret i32 %tmp -} - -declare void @llvm.va_start(i8*) -declare void @llvm.va_copy(i8*, i8*) -declare void @llvm.va_end(i8*) -</pre> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_va_start">'<tt>llvm.va_start</tt>' Intrinsic</a> -</h4> - - -<div> - -<h5>Syntax:</h5> -<pre> - declare void %llvm.va_start(i8* <arglist>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.va_start</tt>' intrinsic initializes <tt>*<arglist></tt> - for subsequent use by <tt><a href="#i_va_arg">va_arg</a></tt>.</p> - -<h5>Arguments:</h5> -<p>The argument is a pointer to a <tt>va_list</tt> element to initialize.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.va_start</tt>' intrinsic works just like the <tt>va_start</tt> - macro available in C. In a target-dependent way, it initializes - the <tt>va_list</tt> element to which the argument points, so that the next - call to <tt>va_arg</tt> will produce the first variable argument passed to - the function. Unlike the C <tt>va_start</tt> macro, this intrinsic does not - need to know the last argument of the function as the compiler can figure - that out.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_va_end">'<tt>llvm.va_end</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.va_end(i8* <arglist>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.va_end</tt>' intrinsic destroys <tt>*<arglist></tt>, - which has been initialized previously - with <tt><a href="#int_va_start">llvm.va_start</a></tt> - or <tt><a href="#i_va_copy">llvm.va_copy</a></tt>.</p> - -<h5>Arguments:</h5> -<p>The argument is a pointer to a <tt>va_list</tt> to destroy.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.va_end</tt>' intrinsic works just like the <tt>va_end</tt> - macro available in C. In a target-dependent way, it destroys - the <tt>va_list</tt> element to which the argument points. Calls - to <a href="#int_va_start"><tt>llvm.va_start</tt></a> - and <a href="#int_va_copy"> <tt>llvm.va_copy</tt></a> must be matched exactly - with calls to <tt>llvm.va_end</tt>.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_va_copy">'<tt>llvm.va_copy</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.va_copy(i8* <destarglist>, i8* <srcarglist>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.va_copy</tt>' intrinsic copies the current argument position - from the source argument list to the destination argument list.</p> - -<h5>Arguments:</h5> -<p>The first argument is a pointer to a <tt>va_list</tt> element to initialize. - The second argument is a pointer to a <tt>va_list</tt> element to copy - from.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.va_copy</tt>' intrinsic works just like the <tt>va_copy</tt> - macro available in C. In a target-dependent way, it copies the - source <tt>va_list</tt> element into the destination <tt>va_list</tt> - element. This intrinsic is necessary because - the <tt><a href="#int_va_start"> llvm.va_start</a></tt> intrinsic may be - arbitrarily complex and require, for example, memory allocation.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_gc">Accurate Garbage Collection Intrinsics</a> -</h3> - -<div> - -<p>LLVM support for <a href="GarbageCollection.html">Accurate Garbage -Collection</a> (GC) requires the implementation and generation of these -intrinsics. These intrinsics allow identification of <a href="#int_gcroot">GC -roots on the stack</a>, as well as garbage collector implementations that -require <a href="#int_gcread">read</a> and <a href="#int_gcwrite">write</a> -barriers. Front-ends for type-safe garbage collected languages should generate -these intrinsics to make use of the LLVM garbage collectors. For more details, -see <a href="GarbageCollection.html">Accurate Garbage Collection with -LLVM</a>.</p> - -<p>The garbage collection intrinsics only operate on objects in the generic - address space (address space zero).</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_gcroot">'<tt>llvm.gcroot</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.gcroot(i8** %ptrloc, i8* %metadata) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.gcroot</tt>' intrinsic declares the existence of a GC root to - the code generator, and allows some metadata to be associated with it.</p> - -<h5>Arguments:</h5> -<p>The first argument specifies the address of a stack object that contains the - root pointer. The second pointer (which must be either a constant or a - global value address) contains the meta-data to be associated with the - root.</p> - -<h5>Semantics:</h5> -<p>At runtime, a call to this intrinsic stores a null pointer into the "ptrloc" - location. At compile-time, the code generator generates information to allow - the runtime to find the pointer at GC safe points. The '<tt>llvm.gcroot</tt>' - intrinsic may only be used in a function which <a href="#gc">specifies a GC - algorithm</a>.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_gcread">'<tt>llvm.gcread</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i8* @llvm.gcread(i8* %ObjPtr, i8** %Ptr) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.gcread</tt>' intrinsic identifies reads of references from heap - locations, allowing garbage collector implementations that require read - barriers.</p> - -<h5>Arguments:</h5> -<p>The second argument is the address to read from, which should be an address - allocated from the garbage collector. The first object is a pointer to the - start of the referenced object, if needed by the language runtime (otherwise - null).</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.gcread</tt>' intrinsic has the same semantics as a load - instruction, but may be replaced with substantially more complex code by the - garbage collector runtime, as needed. The '<tt>llvm.gcread</tt>' intrinsic - may only be used in a function which <a href="#gc">specifies a GC - algorithm</a>.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_gcwrite">'<tt>llvm.gcwrite</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.gcwrite(i8* %P1, i8* %Obj, i8** %P2) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.gcwrite</tt>' intrinsic identifies writes of references to heap - locations, allowing garbage collector implementations that require write - barriers (such as generational or reference counting collectors).</p> - -<h5>Arguments:</h5> -<p>The first argument is the reference to store, the second is the start of the - object to store it to, and the third is the address of the field of Obj to - store to. If the runtime does not require a pointer to the object, Obj may - be null.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.gcwrite</tt>' intrinsic has the same semantics as a store - instruction, but may be replaced with substantially more complex code by the - garbage collector runtime, as needed. The '<tt>llvm.gcwrite</tt>' intrinsic - may only be used in a function which <a href="#gc">specifies a GC - algorithm</a>.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_codegen">Code Generator Intrinsics</a> -</h3> - -<div> - -<p>These intrinsics are provided by LLVM to expose special features that may - only be implemented with code generator support.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_returnaddress">'<tt>llvm.returnaddress</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i8 *@llvm.returnaddress(i32 <level>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.returnaddress</tt>' intrinsic attempts to compute a - target-specific value indicating the return address of the current function - or one of its callers.</p> - -<h5>Arguments:</h5> -<p>The argument to this intrinsic indicates which function to return the address - for. Zero indicates the calling function, one indicates its caller, etc. - The argument is <b>required</b> to be a constant integer value.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.returnaddress</tt>' intrinsic either returns a pointer - indicating the return address of the specified call frame, or zero if it - cannot be identified. The value returned by this intrinsic is likely to be - incorrect or 0 for arguments other than zero, so it should only be used for - debugging purposes.</p> - -<p>Note that calling this intrinsic does not prevent function inlining or other - aggressive transformations, so the value returned may not be that of the - obvious source-language caller.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_frameaddress">'<tt>llvm.frameaddress</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i8* @llvm.frameaddress(i32 <level>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.frameaddress</tt>' intrinsic attempts to return the - target-specific frame pointer value for the specified stack frame.</p> - -<h5>Arguments:</h5> -<p>The argument to this intrinsic indicates which function to return the frame - pointer for. Zero indicates the calling function, one indicates its caller, - etc. The argument is <b>required</b> to be a constant integer value.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.frameaddress</tt>' intrinsic either returns a pointer - indicating the frame address of the specified call frame, or zero if it - cannot be identified. The value returned by this intrinsic is likely to be - incorrect or 0 for arguments other than zero, so it should only be used for - debugging purposes.</p> - -<p>Note that calling this intrinsic does not prevent function inlining or other - aggressive transformations, so the value returned may not be that of the - obvious source-language caller.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_stacksave">'<tt>llvm.stacksave</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i8* @llvm.stacksave() -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.stacksave</tt>' intrinsic is used to remember the current state - of the function stack, for use - with <a href="#int_stackrestore"> <tt>llvm.stackrestore</tt></a>. This is - useful for implementing language features like scoped automatic variable - sized arrays in C99.</p> - -<h5>Semantics:</h5> -<p>This intrinsic returns a opaque pointer value that can be passed - to <a href="#int_stackrestore"><tt>llvm.stackrestore</tt></a>. When - an <tt>llvm.stackrestore</tt> intrinsic is executed with a value saved - from <tt>llvm.stacksave</tt>, it effectively restores the state of the stack - to the state it was in when the <tt>llvm.stacksave</tt> intrinsic executed. - In practice, this pops any <a href="#i_alloca">alloca</a> blocks from the - stack that were allocated after the <tt>llvm.stacksave</tt> was executed.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_stackrestore">'<tt>llvm.stackrestore</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.stackrestore(i8* %ptr) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.stackrestore</tt>' intrinsic is used to restore the state of - the function stack to the state it was in when the - corresponding <a href="#int_stacksave"><tt>llvm.stacksave</tt></a> intrinsic - executed. This is useful for implementing language features like scoped - automatic variable sized arrays in C99.</p> - -<h5>Semantics:</h5> -<p>See the description - for <a href="#int_stacksave"><tt>llvm.stacksave</tt></a>.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_prefetch">'<tt>llvm.prefetch</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.prefetch(i8* <address>, i32 <rw>, i32 <locality>, i32 <cache type>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.prefetch</tt>' intrinsic is a hint to the code generator to - insert a prefetch instruction if supported; otherwise, it is a noop. - Prefetches have no effect on the behavior of the program but can change its - performance characteristics.</p> - -<h5>Arguments:</h5> -<p><tt>address</tt> is the address to be prefetched, <tt>rw</tt> is the - specifier determining if the fetch should be for a read (0) or write (1), - and <tt>locality</tt> is a temporal locality specifier ranging from (0) - no - locality, to (3) - extremely local keep in cache. The <tt>cache type</tt> - specifies whether the prefetch is performed on the data (1) or instruction (0) - cache. The <tt>rw</tt>, <tt>locality</tt> and <tt>cache type</tt> arguments - must be constant integers.</p> - -<h5>Semantics:</h5> -<p>This intrinsic does not modify the behavior of the program. In particular, - prefetches cannot trap and do not produce a value. On targets that support - this intrinsic, the prefetch can provide hints to the processor cache for - better performance.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_pcmarker">'<tt>llvm.pcmarker</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.pcmarker(i32 <id>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.pcmarker</tt>' intrinsic is a method to export a Program - Counter (PC) in a region of code to simulators and other tools. The method - is target specific, but it is expected that the marker will use exported - symbols to transmit the PC of the marker. The marker makes no guarantees - that it will remain with any specific instruction after optimizations. It is - possible that the presence of a marker will inhibit optimizations. The - intended use is to be inserted after optimizations to allow correlations of - simulation runs.</p> - -<h5>Arguments:</h5> -<p><tt>id</tt> is a numerical id identifying the marker.</p> - -<h5>Semantics:</h5> -<p>This intrinsic does not modify the behavior of the program. Backends that do - not support this intrinsic may ignore it.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_readcyclecounter">'<tt>llvm.readcyclecounter</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i64 @llvm.readcyclecounter() -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.readcyclecounter</tt>' intrinsic provides access to the cycle - counter register (or similar low latency, high accuracy clocks) on those - targets that support it. On X86, it should map to RDTSC. On Alpha, it - should map to RPCC. As the backing counters overflow quickly (on the order - of 9 seconds on alpha), this should only be used for small timings.</p> - -<h5>Semantics:</h5> -<p>When directly supported, reading the cycle counter should not modify any - memory. Implementations are allowed to either return a application specific - value or a system wide value. On backends without support, this is lowered - to a constant 0.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_libc">Standard C Library Intrinsics</a> -</h3> - -<div> - -<p>LLVM provides intrinsics for a few important standard C library functions. - These intrinsics allow source-language front-ends to pass information about - the alignment of the pointer arguments to the code generator, providing - opportunity for more efficient code generation.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_memcpy">'<tt>llvm.memcpy</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.memcpy</tt> on any - integer bit width and for different address spaces. Not all targets support - all bit widths however.</p> - -<pre> - declare void @llvm.memcpy.p0i8.p0i8.i32(i8* <dest>, i8* <src>, - i32 <len>, i32 <align>, i1 <isvolatile>) - declare void @llvm.memcpy.p0i8.p0i8.i64(i8* <dest>, i8* <src>, - i64 <len>, i32 <align>, i1 <isvolatile>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the - source location to the destination location.</p> - -<p>Note that, unlike the standard libc function, the <tt>llvm.memcpy.*</tt> - intrinsics do not return a value, takes extra alignment/isvolatile arguments - and the pointers can be in specified address spaces.</p> - -<h5>Arguments:</h5> - -<p>The first argument is a pointer to the destination, the second is a pointer - to the source. The third argument is an integer argument specifying the - number of bytes to copy, the fourth argument is the alignment of the - source and destination locations, and the fifth is a boolean indicating a - volatile access.</p> - -<p>If the call to this intrinsic has an alignment value that is not 0 or 1, - then the caller guarantees that both the source and destination pointers are - aligned to that boundary.</p> - -<p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the - <tt>llvm.memcpy</tt> call is a <a href="#volatile">volatile operation</a>. - The detailed access behavior is not very cleanly specified and it is unwise - to depend on it.</p> - -<h5>Semantics:</h5> - -<p>The '<tt>llvm.memcpy.*</tt>' intrinsics copy a block of memory from the - source location to the destination location, which are not allowed to - overlap. It copies "len" bytes of memory over. If the argument is known to - be aligned to some boundary, this can be specified as the fourth argument, - otherwise it should be set to 0 or 1.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_memmove">'<tt>llvm.memmove</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use llvm.memmove on any integer bit - width and for different address space. Not all targets support all bit - widths however.</p> - -<pre> - declare void @llvm.memmove.p0i8.p0i8.i32(i8* <dest>, i8* <src>, - i32 <len>, i32 <align>, i1 <isvolatile>) - declare void @llvm.memmove.p0i8.p0i8.i64(i8* <dest>, i8* <src>, - i64 <len>, i32 <align>, i1 <isvolatile>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.memmove.*</tt>' intrinsics move a block of memory from the - source location to the destination location. It is similar to the - '<tt>llvm.memcpy</tt>' intrinsic but allows the two memory locations to - overlap.</p> - -<p>Note that, unlike the standard libc function, the <tt>llvm.memmove.*</tt> - intrinsics do not return a value, takes extra alignment/isvolatile arguments - and the pointers can be in specified address spaces.</p> - -<h5>Arguments:</h5> - -<p>The first argument is a pointer to the destination, the second is a pointer - to the source. The third argument is an integer argument specifying the - number of bytes to copy, the fourth argument is the alignment of the - source and destination locations, and the fifth is a boolean indicating a - volatile access.</p> - -<p>If the call to this intrinsic has an alignment value that is not 0 or 1, - then the caller guarantees that the source and destination pointers are - aligned to that boundary.</p> - -<p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the - <tt>llvm.memmove</tt> call is a <a href="#volatile">volatile operation</a>. - The detailed access behavior is not very cleanly specified and it is unwise - to depend on it.</p> - -<h5>Semantics:</h5> - -<p>The '<tt>llvm.memmove.*</tt>' intrinsics copy a block of memory from the - source location to the destination location, which may overlap. It copies - "len" bytes of memory over. If the argument is known to be aligned to some - boundary, this can be specified as the fourth argument, otherwise it should - be set to 0 or 1.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_memset">'<tt>llvm.memset.*</tt>' Intrinsics</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use llvm.memset on any integer bit - width and for different address spaces. However, not all targets support all - bit widths.</p> - -<pre> - declare void @llvm.memset.p0i8.i32(i8* <dest>, i8 <val>, - i32 <len>, i32 <align>, i1 <isvolatile>) - declare void @llvm.memset.p0i8.i64(i8* <dest>, i8 <val>, - i64 <len>, i32 <align>, i1 <isvolatile>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.memset.*</tt>' intrinsics fill a block of memory with a - particular byte value.</p> - -<p>Note that, unlike the standard libc function, the <tt>llvm.memset</tt> - intrinsic does not return a value and takes extra alignment/volatile - arguments. Also, the destination can be in an arbitrary address space.</p> - -<h5>Arguments:</h5> -<p>The first argument is a pointer to the destination to fill, the second is the - byte value with which to fill it, the third argument is an integer argument - specifying the number of bytes to fill, and the fourth argument is the known - alignment of the destination location.</p> - -<p>If the call to this intrinsic has an alignment value that is not 0 or 1, - then the caller guarantees that the destination pointer is aligned to that - boundary.</p> - -<p>If the <tt>isvolatile</tt> parameter is <tt>true</tt>, the - <tt>llvm.memset</tt> call is a <a href="#volatile">volatile operation</a>. - The detailed access behavior is not very cleanly specified and it is unwise - to depend on it.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.memset.*</tt>' intrinsics fill "len" bytes of memory starting - at the destination location. If the argument is known to be aligned to some - boundary, this can be specified as the fourth argument, otherwise it should - be set to 0 or 1.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_sqrt">'<tt>llvm.sqrt.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.sqrt</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.sqrt.f32(float %Val) - declare double @llvm.sqrt.f64(double %Val) - declare x86_fp80 @llvm.sqrt.f80(x86_fp80 %Val) - declare fp128 @llvm.sqrt.f128(fp128 %Val) - declare ppc_fp128 @llvm.sqrt.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.sqrt</tt>' intrinsics return the sqrt of the specified operand, - returning the same value as the libm '<tt>sqrt</tt>' functions would. - Unlike <tt>sqrt</tt> in libm, however, <tt>llvm.sqrt</tt> has undefined - behavior for negative numbers other than -0.0 (which allows for better - optimization, because there is no need to worry about errno being - set). <tt>llvm.sqrt(-0.0)</tt> is defined to return -0.0 like IEEE sqrt.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the sqrt of the specified operand if it is a - nonnegative floating point number.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_powi">'<tt>llvm.powi.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.powi</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.powi.f32(float %Val, i32 %power) - declare double @llvm.powi.f64(double %Val, i32 %power) - declare x86_fp80 @llvm.powi.f80(x86_fp80 %Val, i32 %power) - declare fp128 @llvm.powi.f128(fp128 %Val, i32 %power) - declare ppc_fp128 @llvm.powi.ppcf128(ppc_fp128 %Val, i32 %power) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.powi.*</tt>' intrinsics return the first operand raised to the - specified (positive or negative) power. The order of evaluation of - multiplications is not defined. When a vector of floating point type is - used, the second argument remains a scalar integer value.</p> - -<h5>Arguments:</h5> -<p>The second argument is an integer power, and the first is a value to raise to - that power.</p> - -<h5>Semantics:</h5> -<p>This function returns the first value raised to the second power with an - unspecified sequence of rounding operations.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_sin">'<tt>llvm.sin.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.sin</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.sin.f32(float %Val) - declare double @llvm.sin.f64(double %Val) - declare x86_fp80 @llvm.sin.f80(x86_fp80 %Val) - declare fp128 @llvm.sin.f128(fp128 %Val) - declare ppc_fp128 @llvm.sin.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.sin.*</tt>' intrinsics return the sine of the operand.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the sine of the specified operand, returning the same - values as the libm <tt>sin</tt> functions would, and handles error conditions - in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_cos">'<tt>llvm.cos.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.cos</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.cos.f32(float %Val) - declare double @llvm.cos.f64(double %Val) - declare x86_fp80 @llvm.cos.f80(x86_fp80 %Val) - declare fp128 @llvm.cos.f128(fp128 %Val) - declare ppc_fp128 @llvm.cos.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.cos.*</tt>' intrinsics return the cosine of the operand.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the cosine of the specified operand, returning the same - values as the libm <tt>cos</tt> functions would, and handles error conditions - in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_pow">'<tt>llvm.pow.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.pow</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.pow.f32(float %Val, float %Power) - declare double @llvm.pow.f64(double %Val, double %Power) - declare x86_fp80 @llvm.pow.f80(x86_fp80 %Val, x86_fp80 %Power) - declare fp128 @llvm.pow.f128(fp128 %Val, fp128 %Power) - declare ppc_fp128 @llvm.pow.ppcf128(ppc_fp128 %Val, ppc_fp128 Power) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.pow.*</tt>' intrinsics return the first operand raised to the - specified (positive or negative) power.</p> - -<h5>Arguments:</h5> -<p>The second argument is a floating point power, and the first is a value to - raise to that power.</p> - -<h5>Semantics:</h5> -<p>This function returns the first value raised to the second power, returning - the same values as the libm <tt>pow</tt> functions would, and handles error - conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_exp">'<tt>llvm.exp.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.exp</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.exp.f32(float %Val) - declare double @llvm.exp.f64(double %Val) - declare x86_fp80 @llvm.exp.f80(x86_fp80 %Val) - declare fp128 @llvm.exp.f128(fp128 %Val) - declare ppc_fp128 @llvm.exp.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.exp.*</tt>' intrinsics perform the exp function.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>exp</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_exp2">'<tt>llvm.exp2.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.exp2</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.exp2.f32(float %Val) - declare double @llvm.exp2.f64(double %Val) - declare x86_fp80 @llvm.exp2.f80(x86_fp80 %Val) - declare fp128 @llvm.exp2.f128(fp128 %Val) - declare ppc_fp128 @llvm.exp2.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.exp2.*</tt>' intrinsics perform the exp2 function.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>exp2</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_log">'<tt>llvm.log.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.log</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.log.f32(float %Val) - declare double @llvm.log.f64(double %Val) - declare x86_fp80 @llvm.log.f80(x86_fp80 %Val) - declare fp128 @llvm.log.f128(fp128 %Val) - declare ppc_fp128 @llvm.log.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.log.*</tt>' intrinsics perform the log function.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>log</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_log10">'<tt>llvm.log10.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.log10</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.log10.f32(float %Val) - declare double @llvm.log10.f64(double %Val) - declare x86_fp80 @llvm.log10.f80(x86_fp80 %Val) - declare fp128 @llvm.log10.f128(fp128 %Val) - declare ppc_fp128 @llvm.log10.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.log10.*</tt>' intrinsics perform the log10 function.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>log10</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_log2">'<tt>llvm.log2.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.log2</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.log2.f32(float %Val) - declare double @llvm.log2.f64(double %Val) - declare x86_fp80 @llvm.log2.f80(x86_fp80 %Val) - declare fp128 @llvm.log2.f128(fp128 %Val) - declare ppc_fp128 @llvm.log2.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.log2.*</tt>' intrinsics perform the log2 function.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>log2</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_fma">'<tt>llvm.fma.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.fma</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.fma.f32(float %a, float %b, float %c) - declare double @llvm.fma.f64(double %a, double %b, double %c) - declare x86_fp80 @llvm.fma.f80(x86_fp80 %a, x86_fp80 %b, x86_fp80 %c) - declare fp128 @llvm.fma.f128(fp128 %a, fp128 %b, fp128 %c) - declare ppc_fp128 @llvm.fma.ppcf128(ppc_fp128 %a, ppc_fp128 %b, ppc_fp128 %c) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.fma.*</tt>' intrinsics perform the fused multiply-add - operation.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>fma</tt> functions - would.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_fabs">'<tt>llvm.fabs.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.fabs</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.fabs.f32(float %Val) - declare double @llvm.fabs.f64(double %Val) - declare x86_fp80 @llvm.fabs.f80(x86_fp80 %Val) - declare fp128 @llvm.fabs.f128(fp128 %Val) - declare ppc_fp128 @llvm.fabs.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.fabs.*</tt>' intrinsics return the absolute value of - the operand.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>fabs</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_floor">'<tt>llvm.floor.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.floor</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.floor.f32(float %Val) - declare double @llvm.floor.f64(double %Val) - declare x86_fp80 @llvm.floor.f80(x86_fp80 %Val) - declare fp128 @llvm.floor.f128(fp128 %Val) - declare ppc_fp128 @llvm.floor.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.floor.*</tt>' intrinsics return the floor of - the operand.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>floor</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_ceil">'<tt>llvm.ceil.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.ceil</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.ceil.f32(float %Val) - declare double @llvm.ceil.f64(double %Val) - declare x86_fp80 @llvm.ceil.f80(x86_fp80 %Val) - declare fp128 @llvm.ceil.f128(fp128 %Val) - declare ppc_fp128 @llvm.ceil.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.ceil.*</tt>' intrinsics return the ceiling of - the operand.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>ceil</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_trunc">'<tt>llvm.trunc.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.trunc</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.trunc.f32(float %Val) - declare double @llvm.trunc.f64(double %Val) - declare x86_fp80 @llvm.trunc.f80(x86_fp80 %Val) - declare fp128 @llvm.trunc.f128(fp128 %Val) - declare ppc_fp128 @llvm.trunc.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.trunc.*</tt>' intrinsics returns the operand rounded to the - nearest integer not larger in magnitude than the operand.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>trunc</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_rint">'<tt>llvm.rint.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.rint</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.rint.f32(float %Val) - declare double @llvm.rint.f64(double %Val) - declare x86_fp80 @llvm.rint.f80(x86_fp80 %Val) - declare fp128 @llvm.rint.f128(fp128 %Val) - declare ppc_fp128 @llvm.rint.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.rint.*</tt>' intrinsics returns the operand rounded to the - nearest integer. It may raise an inexact floating-point exception if the - operand isn't an integer.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>rint</tt> functions - would, and handles error conditions in the same way.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_nearbyint">'<tt>llvm.nearbyint.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.nearbyint</tt> on any - floating point or vector of floating point type. Not all targets support all - types however.</p> - -<pre> - declare float @llvm.nearbyint.f32(float %Val) - declare double @llvm.nearbyint.f64(double %Val) - declare x86_fp80 @llvm.nearbyint.f80(x86_fp80 %Val) - declare fp128 @llvm.nearbyint.f128(fp128 %Val) - declare ppc_fp128 @llvm.nearbyint.ppcf128(ppc_fp128 %Val) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.nearbyint.*</tt>' intrinsics returns the operand rounded to the - nearest integer.</p> - -<h5>Arguments:</h5> -<p>The argument and return value are floating point numbers of the same - type.</p> - -<h5>Semantics:</h5> -<p>This function returns the same values as the libm <tt>nearbyint</tt> - functions would, and handles error conditions in the same way.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_manip">Bit Manipulation Intrinsics</a> -</h3> - -<div> - -<p>LLVM provides intrinsics for a few important bit manipulation operations. - These allow efficient code generation for some algorithms.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_bswap">'<tt>llvm.bswap.*</tt>' Intrinsics</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic function. You can use bswap on any integer - type that is an even number of bytes (i.e. BitWidth % 16 == 0).</p> - -<pre> - declare i16 @llvm.bswap.i16(i16 <id>) - declare i32 @llvm.bswap.i32(i32 <id>) - declare i64 @llvm.bswap.i64(i64 <id>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.bswap</tt>' family of intrinsics is used to byte swap integer - values with an even number of bytes (positive multiple of 16 bits). These - are useful for performing operations on data that is not in the target's - native byte order.</p> - -<h5>Semantics:</h5> -<p>The <tt>llvm.bswap.i16</tt> intrinsic returns an i16 value that has the high - and low byte of the input i16 swapped. Similarly, - the <tt>llvm.bswap.i32</tt> intrinsic returns an i32 value that has the four - bytes of the input i32 swapped, so that if the input bytes are numbered 0, 1, - 2, 3 then the returned i32 will have its bytes in 3, 2, 1, 0 order. - The <tt>llvm.bswap.i48</tt>, <tt>llvm.bswap.i64</tt> and other intrinsics - extend this concept to additional even-byte lengths (6 bytes, 8 bytes and - more, respectively).</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_ctpop">'<tt>llvm.ctpop.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use llvm.ctpop on any integer bit - width, or on any vector with integer elements. Not all targets support all - bit widths or vector types, however.</p> - -<pre> - declare i8 @llvm.ctpop.i8(i8 <src>) - declare i16 @llvm.ctpop.i16(i16 <src>) - declare i32 @llvm.ctpop.i32(i32 <src>) - declare i64 @llvm.ctpop.i64(i64 <src>) - declare i256 @llvm.ctpop.i256(i256 <src>) - declare <2 x i32> @llvm.ctpop.v2i32(<2 x i32> <src>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.ctpop</tt>' family of intrinsics counts the number of bits set - in a value.</p> - -<h5>Arguments:</h5> -<p>The only argument is the value to be counted. The argument may be of any - integer type, or a vector with integer elements. - The return type must match the argument type.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.ctpop</tt>' intrinsic counts the 1's in a variable, or within each - element of a vector.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_ctlz">'<tt>llvm.ctlz.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.ctlz</tt> on any - integer bit width, or any vector whose elements are integers. Not all - targets support all bit widths or vector types, however.</p> - -<pre> - declare i8 @llvm.ctlz.i8 (i8 <src>, i1 <is_zero_undef>) - declare i16 @llvm.ctlz.i16 (i16 <src>, i1 <is_zero_undef>) - declare i32 @llvm.ctlz.i32 (i32 <src>, i1 <is_zero_undef>) - declare i64 @llvm.ctlz.i64 (i64 <src>, i1 <is_zero_undef>) - declare i256 @llvm.ctlz.i256(i256 <src>, i1 <is_zero_undef>) - declase <2 x i32> @llvm.ctlz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.ctlz</tt>' family of intrinsic functions counts the number of - leading zeros in a variable.</p> - -<h5>Arguments:</h5> -<p>The first argument is the value to be counted. This argument may be of any - integer type, or a vectory with integer element type. The return type - must match the first argument type.</p> - -<p>The second argument must be a constant and is a flag to indicate whether the - intrinsic should ensure that a zero as the first argument produces a defined - result. Historically some architectures did not provide a defined result for - zero values as efficiently, and many algorithms are now predicated on - avoiding zero-value inputs.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.ctlz</tt>' intrinsic counts the leading (most significant) - zeros in a variable, or within each element of the vector. - If <tt>src == 0</tt> then the result is the size in bits of the type of - <tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise. - For example, <tt>llvm.ctlz(i32 2) = 30</tt>.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_cttz">'<tt>llvm.cttz.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.cttz</tt> on any - integer bit width, or any vector of integer elements. Not all targets - support all bit widths or vector types, however.</p> - -<pre> - declare i8 @llvm.cttz.i8 (i8 <src>, i1 <is_zero_undef>) - declare i16 @llvm.cttz.i16 (i16 <src>, i1 <is_zero_undef>) - declare i32 @llvm.cttz.i32 (i32 <src>, i1 <is_zero_undef>) - declare i64 @llvm.cttz.i64 (i64 <src>, i1 <is_zero_undef>) - declare i256 @llvm.cttz.i256(i256 <src>, i1 <is_zero_undef>) - declase <2 x i32> @llvm.cttz.v2i32(<2 x i32> <src>, i1 <is_zero_undef>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.cttz</tt>' family of intrinsic functions counts the number of - trailing zeros.</p> - -<h5>Arguments:</h5> -<p>The first argument is the value to be counted. This argument may be of any - integer type, or a vectory with integer element type. The return type - must match the first argument type.</p> - -<p>The second argument must be a constant and is a flag to indicate whether the - intrinsic should ensure that a zero as the first argument produces a defined - result. Historically some architectures did not provide a defined result for - zero values as efficiently, and many algorithms are now predicated on - avoiding zero-value inputs.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.cttz</tt>' intrinsic counts the trailing (least significant) - zeros in a variable, or within each element of a vector. - If <tt>src == 0</tt> then the result is the size in bits of the type of - <tt>src</tt> if <tt>is_zero_undef == 0</tt> and <tt>undef</tt> otherwise. - For example, <tt>llvm.cttz(2) = 1</tt>.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_overflow">Arithmetic with Overflow Intrinsics</a> -</h3> - -<div> - -<p>LLVM provides intrinsics for some arithmetic with overflow operations.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_sadd_overflow"> - '<tt>llvm.sadd.with.overflow.*</tt>' Intrinsics - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.sadd.with.overflow</tt> - on any integer bit width.</p> - -<pre> - declare {i16, i1} @llvm.sadd.with.overflow.i16(i16 %a, i16 %b) - declare {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b) - declare {i64, i1} @llvm.sadd.with.overflow.i64(i64 %a, i64 %b) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform - a signed addition of the two arguments, and indicate whether an overflow - occurred during the signed summation.</p> - -<h5>Arguments:</h5> -<p>The arguments (%a and %b) and the first element of the result structure may - be of integer types of any bit width, but they must have the same bit - width. The second element of the result structure must be of - type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will - undergo signed addition.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.sadd.with.overflow</tt>' family of intrinsic functions perform - a signed addition of the two variables. They return a structure — the - first element of which is the signed summation, and the second element of - which is a bit specifying if the signed summation resulted in an - overflow.</p> - -<h5>Examples:</h5> -<pre> - %res = call {i32, i1} @llvm.sadd.with.overflow.i32(i32 %a, i32 %b) - %sum = extractvalue {i32, i1} %res, 0 - %obit = extractvalue {i32, i1} %res, 1 - br i1 %obit, label %overflow, label %normal -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_uadd_overflow"> - '<tt>llvm.uadd.with.overflow.*</tt>' Intrinsics - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.uadd.with.overflow</tt> - on any integer bit width.</p> - -<pre> - declare {i16, i1} @llvm.uadd.with.overflow.i16(i16 %a, i16 %b) - declare {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b) - declare {i64, i1} @llvm.uadd.with.overflow.i64(i64 %a, i64 %b) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform - an unsigned addition of the two arguments, and indicate whether a carry - occurred during the unsigned summation.</p> - -<h5>Arguments:</h5> -<p>The arguments (%a and %b) and the first element of the result structure may - be of integer types of any bit width, but they must have the same bit - width. The second element of the result structure must be of - type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will - undergo unsigned addition.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.uadd.with.overflow</tt>' family of intrinsic functions perform - an unsigned addition of the two arguments. They return a structure — - the first element of which is the sum, and the second element of which is a - bit specifying if the unsigned summation resulted in a carry.</p> - -<h5>Examples:</h5> -<pre> - %res = call {i32, i1} @llvm.uadd.with.overflow.i32(i32 %a, i32 %b) - %sum = extractvalue {i32, i1} %res, 0 - %obit = extractvalue {i32, i1} %res, 1 - br i1 %obit, label %carry, label %normal -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_ssub_overflow"> - '<tt>llvm.ssub.with.overflow.*</tt>' Intrinsics - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.ssub.with.overflow</tt> - on any integer bit width.</p> - -<pre> - declare {i16, i1} @llvm.ssub.with.overflow.i16(i16 %a, i16 %b) - declare {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b) - declare {i64, i1} @llvm.ssub.with.overflow.i64(i64 %a, i64 %b) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform - a signed subtraction of the two arguments, and indicate whether an overflow - occurred during the signed subtraction.</p> - -<h5>Arguments:</h5> -<p>The arguments (%a and %b) and the first element of the result structure may - be of integer types of any bit width, but they must have the same bit - width. The second element of the result structure must be of - type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will - undergo signed subtraction.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.ssub.with.overflow</tt>' family of intrinsic functions perform - a signed subtraction of the two arguments. They return a structure — - the first element of which is the subtraction, and the second element of - which is a bit specifying if the signed subtraction resulted in an - overflow.</p> - -<h5>Examples:</h5> -<pre> - %res = call {i32, i1} @llvm.ssub.with.overflow.i32(i32 %a, i32 %b) - %sum = extractvalue {i32, i1} %res, 0 - %obit = extractvalue {i32, i1} %res, 1 - br i1 %obit, label %overflow, label %normal -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_usub_overflow"> - '<tt>llvm.usub.with.overflow.*</tt>' Intrinsics - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.usub.with.overflow</tt> - on any integer bit width.</p> - -<pre> - declare {i16, i1} @llvm.usub.with.overflow.i16(i16 %a, i16 %b) - declare {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b) - declare {i64, i1} @llvm.usub.with.overflow.i64(i64 %a, i64 %b) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform - an unsigned subtraction of the two arguments, and indicate whether an - overflow occurred during the unsigned subtraction.</p> - -<h5>Arguments:</h5> -<p>The arguments (%a and %b) and the first element of the result structure may - be of integer types of any bit width, but they must have the same bit - width. The second element of the result structure must be of - type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will - undergo unsigned subtraction.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.usub.with.overflow</tt>' family of intrinsic functions perform - an unsigned subtraction of the two arguments. They return a structure — - the first element of which is the subtraction, and the second element of - which is a bit specifying if the unsigned subtraction resulted in an - overflow.</p> - -<h5>Examples:</h5> -<pre> - %res = call {i32, i1} @llvm.usub.with.overflow.i32(i32 %a, i32 %b) - %sum = extractvalue {i32, i1} %res, 0 - %obit = extractvalue {i32, i1} %res, 1 - br i1 %obit, label %overflow, label %normal -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_smul_overflow"> - '<tt>llvm.smul.with.overflow.*</tt>' Intrinsics - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.smul.with.overflow</tt> - on any integer bit width.</p> - -<pre> - declare {i16, i1} @llvm.smul.with.overflow.i16(i16 %a, i16 %b) - declare {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b) - declare {i64, i1} @llvm.smul.with.overflow.i64(i64 %a, i64 %b) -</pre> - -<h5>Overview:</h5> - -<p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform - a signed multiplication of the two arguments, and indicate whether an - overflow occurred during the signed multiplication.</p> - -<h5>Arguments:</h5> -<p>The arguments (%a and %b) and the first element of the result structure may - be of integer types of any bit width, but they must have the same bit - width. The second element of the result structure must be of - type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will - undergo signed multiplication.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.smul.with.overflow</tt>' family of intrinsic functions perform - a signed multiplication of the two arguments. They return a structure — - the first element of which is the multiplication, and the second element of - which is a bit specifying if the signed multiplication resulted in an - overflow.</p> - -<h5>Examples:</h5> -<pre> - %res = call {i32, i1} @llvm.smul.with.overflow.i32(i32 %a, i32 %b) - %sum = extractvalue {i32, i1} %res, 0 - %obit = extractvalue {i32, i1} %res, 1 - br i1 %obit, label %overflow, label %normal -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_umul_overflow"> - '<tt>llvm.umul.with.overflow.*</tt>' Intrinsics - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use <tt>llvm.umul.with.overflow</tt> - on any integer bit width.</p> - -<pre> - declare {i16, i1} @llvm.umul.with.overflow.i16(i16 %a, i16 %b) - declare {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b) - declare {i64, i1} @llvm.umul.with.overflow.i64(i64 %a, i64 %b) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform - a unsigned multiplication of the two arguments, and indicate whether an - overflow occurred during the unsigned multiplication.</p> - -<h5>Arguments:</h5> -<p>The arguments (%a and %b) and the first element of the result structure may - be of integer types of any bit width, but they must have the same bit - width. The second element of the result structure must be of - type <tt>i1</tt>. <tt>%a</tt> and <tt>%b</tt> are the two values that will - undergo unsigned multiplication.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.umul.with.overflow</tt>' family of intrinsic functions perform - an unsigned multiplication of the two arguments. They return a structure - — the first element of which is the multiplication, and the second - element of which is a bit specifying if the unsigned multiplication resulted - in an overflow.</p> - -<h5>Examples:</h5> -<pre> - %res = call {i32, i1} @llvm.umul.with.overflow.i32(i32 %a, i32 %b) - %sum = extractvalue {i32, i1} %res, 0 - %obit = extractvalue {i32, i1} %res, 1 - br i1 %obit, label %overflow, label %normal -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="spec_arithmetic">Specialised Arithmetic Intrinsics</a> -</h3> - -<!-- _______________________________________________________________________ --> - -<h4> - <a name="fmuladd">'<tt>llvm.fmuladd.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare float @llvm.fmuladd.f32(float %a, float %b, float %c) - declare double @llvm.fmuladd.f64(double %a, double %b, double %c) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.fmuladd.*</tt>' intrinsic functions represent multiply-add -expressions that can be fused if the code generator determines that the fused -expression would be legal and efficient.</p> - -<h5>Arguments:</h5> -<p>The '<tt>llvm.fmuladd.*</tt>' intrinsics each take three arguments: two -multiplicands, a and b, and an addend c.</p> - -<h5>Semantics:</h5> -<p>The expression:</p> -<pre> - %0 = call float @llvm.fmuladd.f32(%a, %b, %c) -</pre> -<p>is equivalent to the expression a * b + c, except that rounding will not be -performed between the multiplication and addition steps if the code generator -fuses the operations. Fusion is not guaranteed, even if the target platform -supports it. If a fused multiply-add is required the corresponding llvm.fma.* -intrinsic function should be used instead.</p> - -<h5>Examples:</h5> -<pre> - %r2 = call float @llvm.fmuladd.f32(float %a, float %b, float %c) ; yields {float}:r2 = (a * b) + c -</pre> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_fp16">Half Precision Floating Point Intrinsics</a> -</h3> - -<div> - -<p>For most target platforms, half precision floating point is a storage-only - format. This means that it is - a dense encoding (in memory) but does not support computation in the - format.</p> - -<p>This means that code must first load the half-precision floating point - value as an i16, then convert it to float with <a - href="#int_convert_from_fp16"><tt>llvm.convert.from.fp16</tt></a>. - Computation can then be performed on the float value (including extending to - double etc). To store the value back to memory, it is first converted to - float if needed, then converted to i16 with - <a href="#int_convert_to_fp16"><tt>llvm.convert.to.fp16</tt></a>, then - storing as an i16 value.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_convert_to_fp16"> - '<tt>llvm.convert.to.fp16</tt>' Intrinsic - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i16 @llvm.convert.to.fp16(f32 %a) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs - a conversion from single precision floating point format to half precision - floating point format.</p> - -<h5>Arguments:</h5> -<p>The intrinsic function contains single argument - the value to be - converted.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.convert.to.fp16</tt>' intrinsic function performs - a conversion from single precision floating point format to half precision - floating point format. The return value is an <tt>i16</tt> which - contains the converted number.</p> - -<h5>Examples:</h5> -<pre> - %res = call i16 @llvm.convert.to.fp16(f32 %a) - store i16 %res, i16* @x, align 2 -</pre> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_convert_from_fp16"> - '<tt>llvm.convert.from.fp16</tt>' Intrinsic - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare f32 @llvm.convert.from.fp16(i16 %a) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs - a conversion from half precision floating point format to single precision - floating point format.</p> - -<h5>Arguments:</h5> -<p>The intrinsic function contains single argument - the value to be - converted.</p> - -<h5>Semantics:</h5> -<p>The '<tt>llvm.convert.from.fp16</tt>' intrinsic function performs a - conversion from half single precision floating point format to single - precision floating point format. The input half-float value is represented by - an <tt>i16</tt> value.</p> - -<h5>Examples:</h5> -<pre> - %a = load i16* @x, align 2 - %res = call f32 @llvm.convert.from.fp16(i16 %a) -</pre> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_debugger">Debugger Intrinsics</a> -</h3> - -<div> - -<p>The LLVM debugger intrinsics (which all start with <tt>llvm.dbg.</tt> - prefix), are described in - the <a href="SourceLevelDebugging.html#format_common_intrinsics">LLVM Source - Level Debugging</a> document.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_eh">Exception Handling Intrinsics</a> -</h3> - -<div> - -<p>The LLVM exception handling intrinsics (which all start with - <tt>llvm.eh.</tt> prefix), are described in - the <a href="ExceptionHandling.html#format_common_intrinsics">LLVM Exception - Handling</a> document.</p> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_trampoline">Trampoline Intrinsics</a> -</h3> - -<div> - -<p>These intrinsics make it possible to excise one parameter, marked with - the <a href="#nest"><tt>nest</tt></a> attribute, from a function. - The result is a callable - function pointer lacking the nest parameter - the caller does not need to - provide a value for it. Instead, the value to use is stored in advance in a - "trampoline", a block of memory usually allocated on the stack, which also - contains code to splice the nest value into the argument list. This is used - to implement the GCC nested function address extension.</p> - -<p>For example, if the function is - <tt>i32 f(i8* nest %c, i32 %x, i32 %y)</tt> then the resulting function - pointer has signature <tt>i32 (i32, i32)*</tt>. It can be created as - follows:</p> - -<pre class="doc_code"> - %tramp = alloca [10 x i8], align 4 ; size and alignment only correct for X86 - %tramp1 = getelementptr [10 x i8]* %tramp, i32 0, i32 0 - call i8* @llvm.init.trampoline(i8* %tramp1, i8* bitcast (i32 (i8*, i32, i32)* @f to i8*), i8* %nval) - %p = call i8* @llvm.adjust.trampoline(i8* %tramp1) - %fp = bitcast i8* %p to i32 (i32, i32)* -</pre> - -<p>The call <tt>%val = call i32 %fp(i32 %x, i32 %y)</tt> is then equivalent - to <tt>%val = call i32 %f(i8* %nval, i32 %x, i32 %y)</tt>.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_it"> - '<tt>llvm.init.trampoline</tt>' Intrinsic - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.init.trampoline(i8* <tramp>, i8* <func>, i8* <nval>) -</pre> - -<h5>Overview:</h5> -<p>This fills the memory pointed to by <tt>tramp</tt> with executable code, - turning it into a trampoline.</p> - -<h5>Arguments:</h5> -<p>The <tt>llvm.init.trampoline</tt> intrinsic takes three arguments, all - pointers. The <tt>tramp</tt> argument must point to a sufficiently large and - sufficiently aligned block of memory; this memory is written to by the - intrinsic. Note that the size and the alignment are target-specific - LLVM - currently provides no portable way of determining them, so a front-end that - generates this intrinsic needs to have some target-specific knowledge. - The <tt>func</tt> argument must hold a function bitcast to - an <tt>i8*</tt>.</p> - -<h5>Semantics:</h5> -<p>The block of memory pointed to by <tt>tramp</tt> is filled with target - dependent code, turning it into a function. Then <tt>tramp</tt> needs to be - passed to <a href="#int_at">llvm.adjust.trampoline</a> to get a pointer - which can be <a href="#int_trampoline">bitcast (to a new function) and - called</a>. The new function's signature is the same as that of - <tt>func</tt> with any arguments marked with the <tt>nest</tt> attribute - removed. At most one such <tt>nest</tt> argument is allowed, and it must be of - pointer type. Calling the new function is equivalent to calling <tt>func</tt> - with the same argument list, but with <tt>nval</tt> used for the missing - <tt>nest</tt> argument. If, after calling <tt>llvm.init.trampoline</tt>, the - memory pointed to by <tt>tramp</tt> is modified, then the effect of any later call - to the returned function pointer is undefined.</p> -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_at"> - '<tt>llvm.adjust.trampoline</tt>' Intrinsic - </a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i8* @llvm.adjust.trampoline(i8* <tramp>) -</pre> - -<h5>Overview:</h5> -<p>This performs any required machine-specific adjustment to the address of a - trampoline (passed as <tt>tramp</tt>).</p> - -<h5>Arguments:</h5> -<p><tt>tramp</tt> must point to a block of memory which already has trampoline code - filled in by a previous call to <a href="#int_it"><tt>llvm.init.trampoline</tt> - </a>.</p> - -<h5>Semantics:</h5> -<p>On some architectures the address of the code to be executed needs to be - different to the address where the trampoline is actually stored. This - intrinsic returns the executable address corresponding to <tt>tramp</tt> - after performing the required machine specific adjustments. - The pointer returned can then be <a href="#int_trampoline"> bitcast and - executed</a>. -</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_memorymarkers">Memory Use Markers</a> -</h3> - -<div> - -<p>This class of intrinsics exists to information about the lifetime of memory - objects and ranges where variables are immutable.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_lifetime_start">'<tt>llvm.lifetime.start</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.lifetime.start(i64 <size>, i8* nocapture <ptr>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.lifetime.start</tt>' intrinsic specifies the start of a memory - object's lifetime.</p> - -<h5>Arguments:</h5> -<p>The first argument is a constant integer representing the size of the - object, or -1 if it is variable sized. The second argument is a pointer to - the object.</p> - -<h5>Semantics:</h5> -<p>This intrinsic indicates that before this point in the code, the value of the - memory pointed to by <tt>ptr</tt> is dead. This means that it is known to - never be used and has an undefined value. A load from the pointer that - precedes this intrinsic can be replaced with - <tt>'<a href="#undefvalues">undef</a>'</tt>.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_lifetime_end">'<tt>llvm.lifetime.end</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.lifetime.end(i64 <size>, i8* nocapture <ptr>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.lifetime.end</tt>' intrinsic specifies the end of a memory - object's lifetime.</p> - -<h5>Arguments:</h5> -<p>The first argument is a constant integer representing the size of the - object, or -1 if it is variable sized. The second argument is a pointer to - the object.</p> - -<h5>Semantics:</h5> -<p>This intrinsic indicates that after this point in the code, the value of the - memory pointed to by <tt>ptr</tt> is dead. This means that it is known to - never be used and has an undefined value. Any stores into the memory object - following this intrinsic may be removed as dead. - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_invariant_start">'<tt>llvm.invariant.start</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare {}* @llvm.invariant.start(i64 <size>, i8* nocapture <ptr>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.invariant.start</tt>' intrinsic specifies that the contents of - a memory object will not change.</p> - -<h5>Arguments:</h5> -<p>The first argument is a constant integer representing the size of the - object, or -1 if it is variable sized. The second argument is a pointer to - the object.</p> - -<h5>Semantics:</h5> -<p>This intrinsic indicates that until an <tt>llvm.invariant.end</tt> that uses - the return value, the referenced memory location is constant and - unchanging.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_invariant_end">'<tt>llvm.invariant.end</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.invariant.end({}* <start>, i64 <size>, i8* nocapture <ptr>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.invariant.end</tt>' intrinsic specifies that the contents of - a memory object are mutable.</p> - -<h5>Arguments:</h5> -<p>The first argument is the matching <tt>llvm.invariant.start</tt> intrinsic. - The second argument is a constant integer representing the size of the - object, or -1 if it is variable sized and the third argument is a pointer - to the object.</p> - -<h5>Semantics:</h5> -<p>This intrinsic indicates that the memory is mutable again.</p> - -</div> - -</div> - -<!-- ======================================================================= --> -<h3> - <a name="int_general">General Intrinsics</a> -</h3> - -<div> - -<p>This class of intrinsics is designed to be generic and has no specific - purpose.</p> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_var_annotation">'<tt>llvm.var.annotation</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.var.annotation(i8* <val>, i8* <str>, i8* <str>, i32 <int>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.var.annotation</tt>' intrinsic.</p> - -<h5>Arguments:</h5> -<p>The first argument is a pointer to a value, the second is a pointer to a - global string, the third is a pointer to a global string which is the source - file name, and the last argument is the line number.</p> - -<h5>Semantics:</h5> -<p>This intrinsic allows annotation of local variables with arbitrary strings. - This can be useful for special purpose optimizations that want to look for - these annotations. These have no other defined use; they are ignored by code - generation and optimization.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_annotation">'<tt>llvm.annotation.*</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<p>This is an overloaded intrinsic. You can use '<tt>llvm.annotation</tt>' on - any integer bit width.</p> - -<pre> - declare i8 @llvm.annotation.i8(i8 <val>, i8* <str>, i8* <str>, i32 <int>) - declare i16 @llvm.annotation.i16(i16 <val>, i8* <str>, i8* <str>, i32 <int>) - declare i32 @llvm.annotation.i32(i32 <val>, i8* <str>, i8* <str>, i32 <int>) - declare i64 @llvm.annotation.i64(i64 <val>, i8* <str>, i8* <str>, i32 <int>) - declare i256 @llvm.annotation.i256(i256 <val>, i8* <str>, i8* <str>, i32 <int>) -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.annotation</tt>' intrinsic.</p> - -<h5>Arguments:</h5> -<p>The first argument is an integer value (result of some expression), the - second is a pointer to a global string, the third is a pointer to a global - string which is the source file name, and the last argument is the line - number. It returns the value of the first argument.</p> - -<h5>Semantics:</h5> -<p>This intrinsic allows annotations to be put on arbitrary expressions with - arbitrary strings. This can be useful for special purpose optimizations that - want to look for these annotations. These have no other defined use; they - are ignored by code generation and optimization.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_trap">'<tt>llvm.trap</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.trap() noreturn nounwind -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.trap</tt>' intrinsic.</p> - -<h5>Arguments:</h5> -<p>None.</p> - -<h5>Semantics:</h5> -<p>This intrinsic is lowered to the target dependent trap instruction. If the - target does not have a trap instruction, this intrinsic will be lowered to - a call of the <tt>abort()</tt> function.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_debugtrap">'<tt>llvm.debugtrap</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.debugtrap() nounwind -</pre> - -<h5>Overview:</h5> -<p>The '<tt>llvm.debugtrap</tt>' intrinsic.</p> - -<h5>Arguments:</h5> -<p>None.</p> - -<h5>Semantics:</h5> -<p>This intrinsic is lowered to code which is intended to cause an execution - trap with the intention of requesting the attention of a debugger.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_stackprotector">'<tt>llvm.stackprotector</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.stackprotector(i8* <guard>, i8** <slot>) -</pre> - -<h5>Overview:</h5> -<p>The <tt>llvm.stackprotector</tt> intrinsic takes the <tt>guard</tt> and - stores it onto the stack at <tt>slot</tt>. The stack slot is adjusted to - ensure that it is placed on the stack before local variables.</p> - -<h5>Arguments:</h5> -<p>The <tt>llvm.stackprotector</tt> intrinsic requires two pointer - arguments. The first argument is the value loaded from the stack - guard <tt>@__stack_chk_guard</tt>. The second variable is an <tt>alloca</tt> - that has enough space to hold the value of the guard.</p> - -<h5>Semantics:</h5> -<p>This intrinsic causes the prologue/epilogue inserter to force the position of - the <tt>AllocaInst</tt> stack slot to be before local variables on the - stack. This is to ensure that if a local variable on the stack is - overwritten, it will destroy the value of the guard. When the function exits, - the guard on the stack is checked against the original guard. If they are - different, then the program aborts by calling the <tt>__stack_chk_fail()</tt> - function.</p> - -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_objectsize">'<tt>llvm.objectsize</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i32 @llvm.objectsize.i32(i8* <object>, i1 <min>) - declare i64 @llvm.objectsize.i64(i8* <object>, i1 <min>) -</pre> - -<h5>Overview:</h5> -<p>The <tt>llvm.objectsize</tt> intrinsic is designed to provide information to - the optimizers to determine at compile time whether a) an operation (like - memcpy) will overflow a buffer that corresponds to an object, or b) that a - runtime check for overflow isn't necessary. An object in this context means - an allocation of a specific class, structure, array, or other object.</p> - -<h5>Arguments:</h5> -<p>The <tt>llvm.objectsize</tt> intrinsic takes two arguments. The first - argument is a pointer to or into the <tt>object</tt>. The second argument - is a boolean and determines whether <tt>llvm.objectsize</tt> returns 0 (if - true) or -1 (if false) when the object size is unknown. - The second argument only accepts constants.</p> - -<h5>Semantics:</h5> -<p>The <tt>llvm.objectsize</tt> intrinsic is lowered to a constant representing - the size of the object concerned. If the size cannot be determined at compile - time, <tt>llvm.objectsize</tt> returns <tt>i32/i64 -1 or 0</tt> - (depending on the <tt>min</tt> argument).</p> - -</div> -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_expect">'<tt>llvm.expect</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare i32 @llvm.expect.i32(i32 <val>, i32 <expected_val>) - declare i64 @llvm.expect.i64(i64 <val>, i64 <expected_val>) -</pre> - -<h5>Overview:</h5> -<p>The <tt>llvm.expect</tt> intrinsic provides information about expected (the - most probable) value of <tt>val</tt>, which can be used by optimizers.</p> - -<h5>Arguments:</h5> -<p>The <tt>llvm.expect</tt> intrinsic takes two arguments. The first - argument is a value. The second argument is an expected value, this needs to - be a constant value, variables are not allowed.</p> - -<h5>Semantics:</h5> -<p>This intrinsic is lowered to the <tt>val</tt>.</p> -</div> - -<!-- _______________________________________________________________________ --> -<h4> - <a name="int_donothing">'<tt>llvm.donothing</tt>' Intrinsic</a> -</h4> - -<div> - -<h5>Syntax:</h5> -<pre> - declare void @llvm.donothing() nounwind readnone -</pre> - -<h5>Overview:</h5> -<p>The <tt>llvm.donothing</tt> intrinsic doesn't perform any operation. It's the -only intrinsic that can be called with an invoke instruction.</p> - -<h5>Arguments:</h5> -<p>None.</p> - -<h5>Semantics:</h5> -<p>This intrinsic does nothing, and it's removed by optimizers and ignored by -codegen.</p> -</div> - -</div> - -</div> -<!-- *********************************************************************** --> -<hr> -<address> - <a href="http://jigsaw.w3.org/css-validator/check/referer"><img - src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a> - <a href="http://validator.w3.org/check/referer"><img - src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a> - - <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> - <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br> - Last modified: $Date$ -</address> - -</body> -</html> |