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Diffstat (limited to 'gcc-4.2.1-5666.3/gcc/tree-ssa-ccp.c')
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diff --git a/gcc-4.2.1-5666.3/gcc/tree-ssa-ccp.c b/gcc-4.2.1-5666.3/gcc/tree-ssa-ccp.c new file mode 100644 index 000000000..6e74f35f2 --- /dev/null +++ b/gcc-4.2.1-5666.3/gcc/tree-ssa-ccp.c @@ -0,0 +1,2632 @@ +/* Conditional constant propagation pass for the GNU compiler. + Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 + Free Software Foundation, Inc. + Adapted from original RTL SSA-CCP by Daniel Berlin <dberlin@dberlin.org> + Adapted to GIMPLE trees by Diego Novillo <dnovillo@redhat.com> + +This file is part of GCC. + +GCC is free software; you can redistribute it and/or modify it +under the terms of the GNU General Public License as published by the +Free Software Foundation; either version 2, or (at your option) any +later version. + +GCC is distributed in the hope that it will be useful, but WITHOUT +ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or +FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received a copy of the GNU General Public License +along with GCC; see the file COPYING. If not, write to the Free +Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA +02110-1301, USA. */ + +/* Conditional constant propagation (CCP) is based on the SSA + propagation engine (tree-ssa-propagate.c). Constant assignments of + the form VAR = CST are propagated from the assignments into uses of + VAR, which in turn may generate new constants. The simulation uses + a four level lattice to keep track of constant values associated + with SSA names. Given an SSA name V_i, it may take one of the + following values: + + UNINITIALIZED -> This is the default starting value. V_i + has not been processed yet. + + UNDEFINED -> V_i is a local variable whose definition + has not been processed yet. Therefore we + don't yet know if its value is a constant + or not. + + CONSTANT -> V_i has been found to hold a constant + value C. + + VARYING -> V_i cannot take a constant value, or if it + does, it is not possible to determine it + at compile time. + + The core of SSA-CCP is in ccp_visit_stmt and ccp_visit_phi_node: + + 1- In ccp_visit_stmt, we are interested in assignments whose RHS + evaluates into a constant and conditional jumps whose predicate + evaluates into a boolean true or false. When an assignment of + the form V_i = CONST is found, V_i's lattice value is set to + CONSTANT and CONST is associated with it. This causes the + propagation engine to add all the SSA edges coming out the + assignment into the worklists, so that statements that use V_i + can be visited. + + If the statement is a conditional with a constant predicate, we + mark the outgoing edges as executable or not executable + depending on the predicate's value. This is then used when + visiting PHI nodes to know when a PHI argument can be ignored. + + + 2- In ccp_visit_phi_node, if all the PHI arguments evaluate to the + same constant C, then the LHS of the PHI is set to C. This + evaluation is known as the "meet operation". Since one of the + goals of this evaluation is to optimistically return constant + values as often as possible, it uses two main short cuts: + + - If an argument is flowing in through a non-executable edge, it + is ignored. This is useful in cases like this: + + if (PRED) + a_9 = 3; + else + a_10 = 100; + a_11 = PHI (a_9, a_10) + + If PRED is known to always evaluate to false, then we can + assume that a_11 will always take its value from a_10, meaning + that instead of consider it VARYING (a_9 and a_10 have + different values), we can consider it CONSTANT 100. + + - If an argument has an UNDEFINED value, then it does not affect + the outcome of the meet operation. If a variable V_i has an + UNDEFINED value, it means that either its defining statement + hasn't been visited yet or V_i has no defining statement, in + which case the original symbol 'V' is being used + uninitialized. Since 'V' is a local variable, the compiler + may assume any initial value for it. + + + After propagation, every variable V_i that ends up with a lattice + value of CONSTANT will have the associated constant value in the + array CONST_VAL[i].VALUE. That is fed into substitute_and_fold for + final substitution and folding. + + + Constant propagation in stores and loads (STORE-CCP) + ---------------------------------------------------- + + While CCP has all the logic to propagate constants in GIMPLE + registers, it is missing the ability to associate constants with + stores and loads (i.e., pointer dereferences, structures and + global/aliased variables). We don't keep loads and stores in + SSA, but we do build a factored use-def web for them (in the + virtual operands). + + For instance, consider the following code fragment: + + struct A a; + const int B = 42; + + void foo (int i) + { + if (i > 10) + a.a = 42; + else + { + a.b = 21; + a.a = a.b + 21; + } + + if (a.a != B) + never_executed (); + } + + We should be able to deduce that the predicate 'a.a != B' is always + false. To achieve this, we associate constant values to the SSA + names in the V_MAY_DEF and V_MUST_DEF operands for each store. + Additionally, since we also glob partial loads/stores with the base + symbol, we also keep track of the memory reference where the + constant value was stored (in the MEM_REF field of PROP_VALUE_T). + For instance, + + # a_5 = V_MAY_DEF <a_4> + a.a = 2; + + # VUSE <a_5> + x_3 = a.b; + + In the example above, CCP will associate value '2' with 'a_5', but + it would be wrong to replace the load from 'a.b' with '2', because + '2' had been stored into a.a. + + To support STORE-CCP, it is necessary to add a new value to the + constant propagation lattice. When evaluating a load for a memory + reference we can no longer assume a value of UNDEFINED if we + haven't seen a preceding store to the same memory location. + Consider, for instance global variables: + + int A; + + foo (int i) + { + if (i_3 > 10) + A_4 = 3; + # A_5 = PHI (A_4, A_2); + + # VUSE <A_5> + A.0_6 = A; + + return A.0_6; + } + + The value of A_2 cannot be assumed to be UNDEFINED, as it may have + been defined outside of foo. If we were to assume it UNDEFINED, we + would erroneously optimize the above into 'return 3;'. Therefore, + when doing STORE-CCP, we introduce a fifth lattice value + (UNKNOWN_VAL), which overrides any other value when computing the + meet operation in PHI nodes. + + Though STORE-CCP is not too expensive, it does have to do more work + than regular CCP, so it is only enabled at -O2. Both regular CCP + and STORE-CCP use the exact same algorithm. The only distinction + is that when doing STORE-CCP, the boolean variable DO_STORE_CCP is + set to true. This affects the evaluation of statements and PHI + nodes. + + References: + + Constant propagation with conditional branches, + Wegman and Zadeck, ACM TOPLAS 13(2):181-210. + + Building an Optimizing Compiler, + Robert Morgan, Butterworth-Heinemann, 1998, Section 8.9. + + Advanced Compiler Design and Implementation, + Steven Muchnick, Morgan Kaufmann, 1997, Section 12.6 */ + +#include "config.h" +#include "system.h" +#include "coretypes.h" +#include "tm.h" +#include "tree.h" +#include "flags.h" +#include "rtl.h" +#include "tm_p.h" +#include "ggc.h" +#include "basic-block.h" +#include "output.h" +#include "expr.h" +#include "function.h" +#include "diagnostic.h" +#include "timevar.h" +#include "tree-dump.h" +#include "tree-flow.h" +#include "tree-pass.h" +#include "tree-ssa-propagate.h" +#include "langhooks.h" +#include "target.h" +#include "toplev.h" + + +/* Possible lattice values. */ +typedef enum +{ + UNINITIALIZED = 0, + UNDEFINED, + UNKNOWN_VAL, + CONSTANT, + VARYING +} ccp_lattice_t; + +/* Array of propagated constant values. After propagation, + CONST_VAL[I].VALUE holds the constant value for SSA_NAME(I). If + the constant is held in an SSA name representing a memory store + (i.e., a V_MAY_DEF or V_MUST_DEF), CONST_VAL[I].MEM_REF will + contain the actual memory reference used to store (i.e., the LHS of + the assignment doing the store). */ +static prop_value_t *const_val; + +/* True if we are also propagating constants in stores and loads. */ +static bool do_store_ccp; + +/* Dump constant propagation value VAL to file OUTF prefixed by PREFIX. */ + +static void +dump_lattice_value (FILE *outf, const char *prefix, prop_value_t val) +{ + switch (val.lattice_val) + { + case UNINITIALIZED: + fprintf (outf, "%sUNINITIALIZED", prefix); + break; + case UNDEFINED: + fprintf (outf, "%sUNDEFINED", prefix); + break; + case VARYING: + fprintf (outf, "%sVARYING", prefix); + break; + case UNKNOWN_VAL: + fprintf (outf, "%sUNKNOWN_VAL", prefix); + break; + case CONSTANT: + fprintf (outf, "%sCONSTANT ", prefix); + print_generic_expr (outf, val.value, dump_flags); + break; + default: + gcc_unreachable (); + } +} + + +/* Print lattice value VAL to stderr. */ + +void debug_lattice_value (prop_value_t val); + +void +debug_lattice_value (prop_value_t val) +{ + dump_lattice_value (stderr, "", val); + fprintf (stderr, "\n"); +} + + +/* The regular is_gimple_min_invariant does a shallow test of the object. + It assumes that full gimplification has happened, or will happen on the + object. For a value coming from DECL_INITIAL, this is not true, so we + have to be more strict ourselves. */ + +static bool +ccp_decl_initial_min_invariant (tree t) +{ + if (!is_gimple_min_invariant (t)) + return false; + if (TREE_CODE (t) == ADDR_EXPR) + { + /* Inline and unroll is_gimple_addressable. */ + while (1) + { + t = TREE_OPERAND (t, 0); + if (is_gimple_id (t)) + return true; + if (!handled_component_p (t)) + return false; + } + } + return true; +} + + +/* Compute a default value for variable VAR and store it in the + CONST_VAL array. The following rules are used to get default + values: + + 1- Global and static variables that are declared constant are + considered CONSTANT. + + 2- Any other value is considered UNDEFINED. This is useful when + considering PHI nodes. PHI arguments that are undefined do not + change the constant value of the PHI node, which allows for more + constants to be propagated. + + 3- If SSA_NAME_VALUE is set and it is a constant, its value is + used. + + 4- Variables defined by statements other than assignments and PHI + nodes are considered VARYING. + + 5- Variables that are not GIMPLE registers are considered + UNKNOWN_VAL, which is really a stronger version of UNDEFINED. + It's used to avoid the short circuit evaluation implied by + UNDEFINED in ccp_lattice_meet. */ + +static prop_value_t +get_default_value (tree var) +{ + tree sym = SSA_NAME_VAR (var); + prop_value_t val = { UNINITIALIZED, NULL_TREE, NULL_TREE }; + + if (!do_store_ccp && !is_gimple_reg (var)) + { + /* Short circuit for regular CCP. We are not interested in any + non-register when DO_STORE_CCP is false. */ + val.lattice_val = VARYING; + } + else if (SSA_NAME_VALUE (var) + && is_gimple_min_invariant (SSA_NAME_VALUE (var))) + { + val.lattice_val = CONSTANT; + val.value = SSA_NAME_VALUE (var); + } + else if (TREE_STATIC (sym) + && TREE_READONLY (sym) + && !MTAG_P (sym) + && DECL_INITIAL (sym) + && ccp_decl_initial_min_invariant (DECL_INITIAL (sym))) + { + /* Globals and static variables declared 'const' take their + initial value. */ + val.lattice_val = CONSTANT; + val.value = DECL_INITIAL (sym); + val.mem_ref = sym; + } + else + { + tree stmt = SSA_NAME_DEF_STMT (var); + + if (IS_EMPTY_STMT (stmt)) + { + /* Variables defined by an empty statement are those used + before being initialized. If VAR is a local variable, we + can assume initially that it is UNDEFINED. If we are + doing STORE-CCP, function arguments and non-register + variables are initially UNKNOWN_VAL, because we cannot + discard the value incoming from outside of this function + (see ccp_lattice_meet for details). */ + if (is_gimple_reg (sym) && TREE_CODE (sym) != PARM_DECL) + val.lattice_val = UNDEFINED; + else if (do_store_ccp) + val.lattice_val = UNKNOWN_VAL; + else + val.lattice_val = VARYING; + } + else if (TREE_CODE (stmt) == MODIFY_EXPR + || TREE_CODE (stmt) == PHI_NODE) + { + /* Any other variable defined by an assignment or a PHI node + is considered UNDEFINED (or UNKNOWN_VAL if VAR is not a + GIMPLE register). */ + val.lattice_val = is_gimple_reg (sym) ? UNDEFINED : UNKNOWN_VAL; + } + else + { + /* Otherwise, VAR will never take on a constant value. */ + val.lattice_val = VARYING; + } + } + + return val; +} + + +/* Get the constant value associated with variable VAR. If + MAY_USE_DEFAULT_P is true, call get_default_value on variables that + have the lattice value UNINITIALIZED. */ + +static prop_value_t * +get_value (tree var, bool may_use_default_p) +{ + prop_value_t *val = &const_val[SSA_NAME_VERSION (var)]; + if (may_use_default_p && val->lattice_val == UNINITIALIZED) + *val = get_default_value (var); + + return val; +} + + +/* Set the value for variable VAR to NEW_VAL. Return true if the new + value is different from VAR's previous value. */ + +static bool +set_lattice_value (tree var, prop_value_t new_val) +{ + prop_value_t *old_val = get_value (var, false); + + /* Lattice transitions must always be monotonically increasing in + value. We allow two exceptions: + + 1- If *OLD_VAL and NEW_VAL are the same, return false to + inform the caller that this was a non-transition. + + 2- If we are doing store-ccp (i.e., DOING_STORE_CCP is true), + allow CONSTANT->UNKNOWN_VAL. The UNKNOWN_VAL state is a + special type of UNDEFINED state which prevents the short + circuit evaluation of PHI arguments (see ccp_visit_phi_node + and ccp_lattice_meet). */ + gcc_assert (old_val->lattice_val <= new_val.lattice_val + || (old_val->lattice_val == new_val.lattice_val + && old_val->value == new_val.value + && old_val->mem_ref == new_val.mem_ref) + || (do_store_ccp + && old_val->lattice_val == CONSTANT + && new_val.lattice_val == UNKNOWN_VAL)); + + if (old_val->lattice_val != new_val.lattice_val) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + { + dump_lattice_value (dump_file, "Lattice value changed to ", new_val); + fprintf (dump_file, ". %sdding SSA edges to worklist.\n", + new_val.lattice_val != UNDEFINED ? "A" : "Not a"); + } + + *old_val = new_val; + + /* Transitions UNINITIALIZED -> UNDEFINED are never interesting + for propagation purposes. In these cases return false to + avoid doing useless work. */ + return (new_val.lattice_val != UNDEFINED); + } + + return false; +} + + +/* Return the likely CCP lattice value for STMT. + + If STMT has no operands, then return CONSTANT. + + Else if any operands of STMT are undefined, then return UNDEFINED. + + Else if any operands of STMT are constants, then return CONSTANT. + + Else return VARYING. */ + +static ccp_lattice_t +likely_value (tree stmt) +{ + bool found_constant; + stmt_ann_t ann; + tree use; + ssa_op_iter iter; + + ann = stmt_ann (stmt); + + /* If the statement has volatile operands, it won't fold to a + constant value. */ + if (ann->has_volatile_ops) + return VARYING; + + /* If we are not doing store-ccp, statements with loads + and/or stores will never fold into a constant. */ + if (!do_store_ccp + && !ZERO_SSA_OPERANDS (stmt, SSA_OP_ALL_VIRTUALS)) + return VARYING; + + + /* A CALL_EXPR is assumed to be varying. NOTE: This may be overly + conservative, in the presence of const and pure calls. */ + if (get_call_expr_in (stmt) != NULL_TREE) + return VARYING; + + /* Anything other than assignments and conditional jumps are not + interesting for CCP. */ + if (TREE_CODE (stmt) != MODIFY_EXPR + && TREE_CODE (stmt) != COND_EXPR + && TREE_CODE (stmt) != SWITCH_EXPR) + return VARYING; + + if (is_gimple_min_invariant (get_rhs (stmt))) + return CONSTANT; + + found_constant = false; + FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE|SSA_OP_VUSE) + { + prop_value_t *val = get_value (use, true); + + if (val->lattice_val == VARYING) + return VARYING; + + if (val->lattice_val == UNKNOWN_VAL) + { + /* UNKNOWN_VAL is invalid when not doing STORE-CCP. */ + gcc_assert (do_store_ccp); + return UNKNOWN_VAL; + } + + if (val->lattice_val == CONSTANT) + found_constant = true; + } + + if (found_constant + || ZERO_SSA_OPERANDS (stmt, SSA_OP_USE) + || ZERO_SSA_OPERANDS (stmt, SSA_OP_VUSE)) + return CONSTANT; + + return UNDEFINED; +} + + +/* Initialize local data structures for CCP. */ + +static void +ccp_initialize (void) +{ + basic_block bb; + + const_val = XNEWVEC (prop_value_t, num_ssa_names); + memset (const_val, 0, num_ssa_names * sizeof (*const_val)); + + /* Initialize simulation flags for PHI nodes and statements. */ + FOR_EACH_BB (bb) + { + block_stmt_iterator i; + + for (i = bsi_start (bb); !bsi_end_p (i); bsi_next (&i)) + { + bool is_varying = false; + tree stmt = bsi_stmt (i); + + if (likely_value (stmt) == VARYING) + + { + tree def; + ssa_op_iter iter; + + /* If the statement will not produce a constant, mark + all its outputs VARYING. */ + FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) + get_value (def, false)->lattice_val = VARYING; + + /* Never mark conditional jumps with DONT_SIMULATE_AGAIN, + otherwise the propagator will never add the outgoing + control edges. */ + if (TREE_CODE (stmt) != COND_EXPR + && TREE_CODE (stmt) != SWITCH_EXPR) + is_varying = true; + } + + DONT_SIMULATE_AGAIN (stmt) = is_varying; + } + } + + /* Now process PHI nodes. */ + FOR_EACH_BB (bb) + { + tree phi; + + for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) + { + int i; + tree arg; + prop_value_t *val = get_value (PHI_RESULT (phi), false); + + for (i = 0; i < PHI_NUM_ARGS (phi); i++) + { + arg = PHI_ARG_DEF (phi, i); + + if (TREE_CODE (arg) == SSA_NAME + && get_value (arg, false)->lattice_val == VARYING) + { + val->lattice_val = VARYING; + break; + } + } + + DONT_SIMULATE_AGAIN (phi) = (val->lattice_val == VARYING); + } + } +} + + +/* Do final substitution of propagated values, cleanup the flowgraph and + free allocated storage. */ + +static void +ccp_finalize (void) +{ + /* Perform substitutions based on the known constant values. */ + substitute_and_fold (const_val, false); + + free (const_val); +} + + +/* Compute the meet operator between *VAL1 and *VAL2. Store the result + in VAL1. + + any M UNDEFINED = any + any M UNKNOWN_VAL = UNKNOWN_VAL + any M VARYING = VARYING + Ci M Cj = Ci if (i == j) + Ci M Cj = VARYING if (i != j) + + Lattice values UNKNOWN_VAL and UNDEFINED are similar but have + different semantics at PHI nodes. Both values imply that we don't + know whether the variable is constant or not. However, UNKNOWN_VAL + values override all others. For instance, suppose that A is a + global variable: + + +------+ + | | + | / \ + | / \ + | | A_1 = 4 + | \ / + | \ / + | A_3 = PHI (A_2, A_1) + | ... = A_3 + | | + +----+ + + If the edge into A_2 is not executable, the first visit to A_3 will + yield the constant 4. But the second visit to A_3 will be with A_2 + in state UNKNOWN_VAL. We can no longer conclude that A_3 is 4 + because A_2 may have been set in another function. If we had used + the lattice value UNDEFINED, we would have had wrongly concluded + that A_3 is 4. */ + + +static void +ccp_lattice_meet (prop_value_t *val1, prop_value_t *val2) +{ + if (val1->lattice_val == UNDEFINED) + { + /* UNDEFINED M any = any */ + *val1 = *val2; + } + else if (val2->lattice_val == UNDEFINED) + { + /* any M UNDEFINED = any + Nothing to do. VAL1 already contains the value we want. */ + ; + } + else if (val1->lattice_val == UNKNOWN_VAL + || val2->lattice_val == UNKNOWN_VAL) + { + /* UNKNOWN_VAL values are invalid if we are not doing STORE-CCP. */ + gcc_assert (do_store_ccp); + + /* any M UNKNOWN_VAL = UNKNOWN_VAL. */ + val1->lattice_val = UNKNOWN_VAL; + val1->value = NULL_TREE; + val1->mem_ref = NULL_TREE; + } + else if (val1->lattice_val == VARYING + || val2->lattice_val == VARYING) + { + /* any M VARYING = VARYING. */ + val1->lattice_val = VARYING; + val1->value = NULL_TREE; + val1->mem_ref = NULL_TREE; + } + else if (val1->lattice_val == CONSTANT + && val2->lattice_val == CONSTANT + && simple_cst_equal (val1->value, val2->value) == 1 + && (!do_store_ccp + || (val1->mem_ref && val2->mem_ref + && operand_equal_p (val1->mem_ref, val2->mem_ref, 0)))) + { + /* Ci M Cj = Ci if (i == j) + Ci M Cj = VARYING if (i != j) + + If these two values come from memory stores, make sure that + they come from the same memory reference. */ + val1->lattice_val = CONSTANT; + val1->value = val1->value; + val1->mem_ref = val1->mem_ref; + } + else + { + /* Any other combination is VARYING. */ + val1->lattice_val = VARYING; + val1->value = NULL_TREE; + val1->mem_ref = NULL_TREE; + } +} + + +/* Loop through the PHI_NODE's parameters for BLOCK and compare their + lattice values to determine PHI_NODE's lattice value. The value of a + PHI node is determined calling ccp_lattice_meet with all the arguments + of the PHI node that are incoming via executable edges. */ + +static enum ssa_prop_result +ccp_visit_phi_node (tree phi) +{ + int i; + prop_value_t *old_val, new_val; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "\nVisiting PHI node: "); + print_generic_expr (dump_file, phi, dump_flags); + } + + old_val = get_value (PHI_RESULT (phi), false); + switch (old_val->lattice_val) + { + case VARYING: + return SSA_PROP_VARYING; + + case CONSTANT: + new_val = *old_val; + break; + + case UNKNOWN_VAL: + /* To avoid the default value of UNKNOWN_VAL overriding + that of its possible constant arguments, temporarily + set the PHI node's default lattice value to be + UNDEFINED. If the PHI node's old value was UNKNOWN_VAL and + the new value is UNDEFINED, then we prevent the invalid + transition by not calling set_lattice_value. */ + gcc_assert (do_store_ccp); + + /* FALLTHRU */ + + case UNDEFINED: + case UNINITIALIZED: + new_val.lattice_val = UNDEFINED; + new_val.value = NULL_TREE; + new_val.mem_ref = NULL_TREE; + break; + + default: + gcc_unreachable (); + } + + for (i = 0; i < PHI_NUM_ARGS (phi); i++) + { + /* Compute the meet operator over all the PHI arguments flowing + through executable edges. */ + edge e = PHI_ARG_EDGE (phi, i); + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, + "\n Argument #%d (%d -> %d %sexecutable)\n", + i, e->src->index, e->dest->index, + (e->flags & EDGE_EXECUTABLE) ? "" : "not "); + } + + /* If the incoming edge is executable, Compute the meet operator for + the existing value of the PHI node and the current PHI argument. */ + if (e->flags & EDGE_EXECUTABLE) + { + tree arg = PHI_ARG_DEF (phi, i); + prop_value_t arg_val; + + if (is_gimple_min_invariant (arg)) + { + arg_val.lattice_val = CONSTANT; + arg_val.value = arg; + arg_val.mem_ref = NULL_TREE; + } + else + arg_val = *(get_value (arg, true)); + + ccp_lattice_meet (&new_val, &arg_val); + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "\t"); + print_generic_expr (dump_file, arg, dump_flags); + dump_lattice_value (dump_file, "\tValue: ", arg_val); + fprintf (dump_file, "\n"); + } + + if (new_val.lattice_val == VARYING) + break; + } + } + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + dump_lattice_value (dump_file, "\n PHI node value: ", new_val); + fprintf (dump_file, "\n\n"); + } + + /* Check for an invalid change from UNKNOWN_VAL to UNDEFINED. */ + if (do_store_ccp + && old_val->lattice_val == UNKNOWN_VAL + && new_val.lattice_val == UNDEFINED) + return SSA_PROP_NOT_INTERESTING; + + /* Otherwise, make the transition to the new value. */ + if (set_lattice_value (PHI_RESULT (phi), new_val)) + { + if (new_val.lattice_val == VARYING) + return SSA_PROP_VARYING; + else + return SSA_PROP_INTERESTING; + } + else + return SSA_PROP_NOT_INTERESTING; +} + + +/* CCP specific front-end to the non-destructive constant folding + routines. + + Attempt to simplify the RHS of STMT knowing that one or more + operands are constants. + + If simplification is possible, return the simplified RHS, + otherwise return the original RHS. */ + +static tree +ccp_fold (tree stmt) +{ + tree rhs = get_rhs (stmt); + enum tree_code code = TREE_CODE (rhs); + enum tree_code_class kind = TREE_CODE_CLASS (code); + tree retval = NULL_TREE; + + if (TREE_CODE (rhs) == SSA_NAME) + { + /* If the RHS is an SSA_NAME, return its known constant value, + if any. */ + return get_value (rhs, true)->value; + } + else if (do_store_ccp && stmt_makes_single_load (stmt)) + { + /* If the RHS is a memory load, see if the VUSEs associated with + it are a valid constant for that memory load. */ + prop_value_t *val = get_value_loaded_by (stmt, const_val); + if (val && val->mem_ref) + { + if (operand_equal_p (val->mem_ref, rhs, 0)) + return val->value; + + /* If RHS is extracting REALPART_EXPR or IMAGPART_EXPR of a + complex type with a known constant value, return it. */ + if ((TREE_CODE (rhs) == REALPART_EXPR + || TREE_CODE (rhs) == IMAGPART_EXPR) + && operand_equal_p (val->mem_ref, TREE_OPERAND (rhs, 0), 0)) + return fold_build1 (TREE_CODE (rhs), TREE_TYPE (rhs), val->value); + } + return NULL_TREE; + } + + /* Unary operators. Note that we know the single operand must + be a constant. So this should almost always return a + simplified RHS. */ + if (kind == tcc_unary) + { + /* Handle unary operators which can appear in GIMPLE form. */ + tree op0 = TREE_OPERAND (rhs, 0); + + /* Simplify the operand down to a constant. */ + if (TREE_CODE (op0) == SSA_NAME) + { + prop_value_t *val = get_value (op0, true); + if (val->lattice_val == CONSTANT) + op0 = get_value (op0, true)->value; + } + + if ((code == NOP_EXPR || code == CONVERT_EXPR) + && tree_ssa_useless_type_conversion_1 (TREE_TYPE (rhs), + TREE_TYPE (op0))) + return op0; + return fold_unary (code, TREE_TYPE (rhs), op0); + } + + /* Binary and comparison operators. We know one or both of the + operands are constants. */ + else if (kind == tcc_binary + || kind == tcc_comparison + || code == TRUTH_AND_EXPR + || code == TRUTH_OR_EXPR + || code == TRUTH_XOR_EXPR) + { + /* Handle binary and comparison operators that can appear in + GIMPLE form. */ + tree op0 = TREE_OPERAND (rhs, 0); + tree op1 = TREE_OPERAND (rhs, 1); + + /* Simplify the operands down to constants when appropriate. */ + if (TREE_CODE (op0) == SSA_NAME) + { + prop_value_t *val = get_value (op0, true); + if (val->lattice_val == CONSTANT) + op0 = val->value; + } + + if (TREE_CODE (op1) == SSA_NAME) + { + prop_value_t *val = get_value (op1, true); + if (val->lattice_val == CONSTANT) + op1 = val->value; + } + + return fold_binary (code, TREE_TYPE (rhs), op0, op1); + } + + /* We may be able to fold away calls to builtin functions if their + arguments are constants. */ + else if (code == CALL_EXPR + && TREE_CODE (TREE_OPERAND (rhs, 0)) == ADDR_EXPR + && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)) + == FUNCTION_DECL) + && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0))) + { + if (!ZERO_SSA_OPERANDS (stmt, SSA_OP_USE)) + { + tree *orig, var; + tree fndecl, arglist; + size_t i = 0; + ssa_op_iter iter; + use_operand_p var_p; + + /* Preserve the original values of every operand. */ + orig = XNEWVEC (tree, NUM_SSA_OPERANDS (stmt, SSA_OP_USE)); + FOR_EACH_SSA_TREE_OPERAND (var, stmt, iter, SSA_OP_USE) + orig[i++] = var; + + /* Substitute operands with their values and try to fold. */ + replace_uses_in (stmt, NULL, const_val); + fndecl = get_callee_fndecl (rhs); + arglist = TREE_OPERAND (rhs, 1); + retval = fold_builtin (fndecl, arglist, false); + + /* Restore operands to their original form. */ + i = 0; + FOR_EACH_SSA_USE_OPERAND (var_p, stmt, iter, SSA_OP_USE) + SET_USE (var_p, orig[i++]); + free (orig); + } + } + else + return rhs; + + /* If we got a simplified form, see if we need to convert its type. */ + if (retval) + return fold_convert (TREE_TYPE (rhs), retval); + + /* No simplification was possible. */ + return rhs; +} + + +/* Return the tree representing the element referenced by T if T is an + ARRAY_REF or COMPONENT_REF into constant aggregates. Return + NULL_TREE otherwise. */ + +static tree +fold_const_aggregate_ref (tree t) +{ + prop_value_t *value; + tree base, ctor, idx, field; + unsigned HOST_WIDE_INT cnt; + tree cfield, cval; + + switch (TREE_CODE (t)) + { + case ARRAY_REF: + /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its + DECL_INITIAL. If BASE is a nested reference into another + ARRAY_REF or COMPONENT_REF, make a recursive call to resolve + the inner reference. */ + base = TREE_OPERAND (t, 0); + switch (TREE_CODE (base)) + { + case VAR_DECL: + if (!TREE_READONLY (base) + || TREE_CODE (TREE_TYPE (base)) != ARRAY_TYPE + || !targetm.binds_local_p (base)) + return NULL_TREE; + + ctor = DECL_INITIAL (base); + break; + + case ARRAY_REF: + case COMPONENT_REF: + ctor = fold_const_aggregate_ref (base); + break; + + default: + return NULL_TREE; + } + + if (ctor == NULL_TREE + || (TREE_CODE (ctor) != CONSTRUCTOR + && TREE_CODE (ctor) != STRING_CST) + || !TREE_STATIC (ctor)) + return NULL_TREE; + + /* Get the index. If we have an SSA_NAME, try to resolve it + with the current lattice value for the SSA_NAME. */ + idx = TREE_OPERAND (t, 1); + switch (TREE_CODE (idx)) + { + case SSA_NAME: + if ((value = get_value (idx, true)) + && value->lattice_val == CONSTANT + && TREE_CODE (value->value) == INTEGER_CST) + idx = value->value; + else + return NULL_TREE; + break; + + case INTEGER_CST: + break; + + default: + return NULL_TREE; + } + + /* Fold read from constant string. */ + if (TREE_CODE (ctor) == STRING_CST) + { + if ((TYPE_MODE (TREE_TYPE (t)) + == TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) + && (GET_MODE_CLASS (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) + == MODE_INT) + && GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (TREE_TYPE (ctor)))) == 1 + && compare_tree_int (idx, TREE_STRING_LENGTH (ctor)) < 0) + return build_int_cst (TREE_TYPE (t), (TREE_STRING_POINTER (ctor) + [TREE_INT_CST_LOW (idx)])); + return NULL_TREE; + } + + /* Whoo-hoo! I'll fold ya baby. Yeah! */ + FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval) + if (tree_int_cst_equal (cfield, idx)) + return cval; + break; + + case COMPONENT_REF: + /* Get a CONSTRUCTOR. If BASE is a VAR_DECL, get its + DECL_INITIAL. If BASE is a nested reference into another + ARRAY_REF or COMPONENT_REF, make a recursive call to resolve + the inner reference. */ + base = TREE_OPERAND (t, 0); + switch (TREE_CODE (base)) + { + case VAR_DECL: + if (!TREE_READONLY (base) + || TREE_CODE (TREE_TYPE (base)) != RECORD_TYPE + || !targetm.binds_local_p (base)) + return NULL_TREE; + + ctor = DECL_INITIAL (base); + break; + + case ARRAY_REF: + case COMPONENT_REF: + ctor = fold_const_aggregate_ref (base); + break; + + default: + return NULL_TREE; + } + + if (ctor == NULL_TREE + || TREE_CODE (ctor) != CONSTRUCTOR + || !TREE_STATIC (ctor)) + return NULL_TREE; + + field = TREE_OPERAND (t, 1); + + FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (ctor), cnt, cfield, cval) + if (cfield == field + /* FIXME: Handle bit-fields. */ + && ! DECL_BIT_FIELD (cfield)) + return cval; + break; + + case REALPART_EXPR: + case IMAGPART_EXPR: + { + tree c = fold_const_aggregate_ref (TREE_OPERAND (t, 0)); + if (c && TREE_CODE (c) == COMPLEX_CST) + return fold_build1 (TREE_CODE (t), TREE_TYPE (t), c); + break; + } + + default: + break; + } + + return NULL_TREE; +} + +/* Evaluate statement STMT. */ + +static prop_value_t +evaluate_stmt (tree stmt) +{ + prop_value_t val; + tree simplified = NULL_TREE; + ccp_lattice_t likelyvalue = likely_value (stmt); + bool is_constant; + + val.mem_ref = NULL_TREE; + + fold_defer_overflow_warnings (); + + /* If the statement is likely to have a CONSTANT result, then try + to fold the statement to determine the constant value. */ + if (likelyvalue == CONSTANT) + simplified = ccp_fold (stmt); + /* If the statement is likely to have a VARYING result, then do not + bother folding the statement. */ + if (likelyvalue == VARYING) + simplified = get_rhs (stmt); + /* If the statement is an ARRAY_REF or COMPONENT_REF into constant + aggregates, extract the referenced constant. Otherwise the + statement is likely to have an UNDEFINED value, and there will be + nothing to do. Note that fold_const_aggregate_ref returns + NULL_TREE if the first case does not match. */ + else if (!simplified) + simplified = fold_const_aggregate_ref (get_rhs (stmt)); + + is_constant = simplified && is_gimple_min_invariant (simplified); + + fold_undefer_overflow_warnings (is_constant, stmt, 0); + + if (is_constant) + { + /* The statement produced a constant value. */ + val.lattice_val = CONSTANT; + val.value = simplified; + } + else + { + /* The statement produced a nonconstant value. If the statement + had UNDEFINED operands, then the result of the statement + should be UNDEFINED. Otherwise, the statement is VARYING. */ + if (likelyvalue == UNDEFINED || likelyvalue == UNKNOWN_VAL) + val.lattice_val = likelyvalue; + else + val.lattice_val = VARYING; + + val.value = NULL_TREE; + } + + return val; +} + + +/* Visit the assignment statement STMT. Set the value of its LHS to the + value computed by the RHS and store LHS in *OUTPUT_P. If STMT + creates virtual definitions, set the value of each new name to that + of the RHS (if we can derive a constant out of the RHS). */ + +static enum ssa_prop_result +visit_assignment (tree stmt, tree *output_p) +{ + prop_value_t val; + tree lhs, rhs; + enum ssa_prop_result retval; + + lhs = TREE_OPERAND (stmt, 0); + rhs = TREE_OPERAND (stmt, 1); + + if (TREE_CODE (rhs) == SSA_NAME) + { + /* For a simple copy operation, we copy the lattice values. */ + prop_value_t *nval = get_value (rhs, true); + val = *nval; + } + else if (do_store_ccp && stmt_makes_single_load (stmt)) + { + /* Same as above, but the RHS is not a gimple register and yet + has a known VUSE. If STMT is loading from the same memory + location that created the SSA_NAMEs for the virtual operands, + we can propagate the value on the RHS. */ + prop_value_t *nval = get_value_loaded_by (stmt, const_val); + + if (nval && nval->mem_ref + && operand_equal_p (nval->mem_ref, rhs, 0)) + val = *nval; + else + val = evaluate_stmt (stmt); + } + else + /* Evaluate the statement. */ + val = evaluate_stmt (stmt); + + /* If the original LHS was a VIEW_CONVERT_EXPR, modify the constant + value to be a VIEW_CONVERT_EXPR of the old constant value. + + ??? Also, if this was a definition of a bitfield, we need to widen + the constant value into the type of the destination variable. This + should not be necessary if GCC represented bitfields properly. */ + { + tree orig_lhs = TREE_OPERAND (stmt, 0); + + if (TREE_CODE (orig_lhs) == VIEW_CONVERT_EXPR + && val.lattice_val == CONSTANT) + { + tree w = fold_unary (VIEW_CONVERT_EXPR, + TREE_TYPE (TREE_OPERAND (orig_lhs, 0)), + val.value); + + orig_lhs = TREE_OPERAND (orig_lhs, 0); + if (w && is_gimple_min_invariant (w)) + val.value = w; + else + { + val.lattice_val = VARYING; + val.value = NULL; + } + } + + if (val.lattice_val == CONSTANT + && TREE_CODE (orig_lhs) == COMPONENT_REF + && DECL_BIT_FIELD (TREE_OPERAND (orig_lhs, 1))) + { + tree w = widen_bitfield (val.value, TREE_OPERAND (orig_lhs, 1), + orig_lhs); + + if (w && is_gimple_min_invariant (w)) + val.value = w; + else + { + val.lattice_val = VARYING; + val.value = NULL_TREE; + val.mem_ref = NULL_TREE; + } + } + } + + retval = SSA_PROP_NOT_INTERESTING; + + /* Set the lattice value of the statement's output. */ + if (TREE_CODE (lhs) == SSA_NAME) + { + /* If STMT is an assignment to an SSA_NAME, we only have one + value to set. */ + if (set_lattice_value (lhs, val)) + { + *output_p = lhs; + if (val.lattice_val == VARYING) + retval = SSA_PROP_VARYING; + else + retval = SSA_PROP_INTERESTING; + } + } + else if (do_store_ccp && stmt_makes_single_store (stmt)) + { + /* Otherwise, set the names in V_MAY_DEF/V_MUST_DEF operands + to the new constant value and mark the LHS as the memory + reference associated with VAL. */ + ssa_op_iter i; + tree vdef; + bool changed; + + /* Stores cannot take on an UNDEFINED value. */ + if (val.lattice_val == UNDEFINED) + val.lattice_val = UNKNOWN_VAL; + + /* Mark VAL as stored in the LHS of this assignment. */ + val.mem_ref = lhs; + + /* Set the value of every VDEF to VAL. */ + changed = false; + FOR_EACH_SSA_TREE_OPERAND (vdef, stmt, i, SSA_OP_VIRTUAL_DEFS) + changed |= set_lattice_value (vdef, val); + + /* Note that for propagation purposes, we are only interested in + visiting statements that load the exact same memory reference + stored here. Those statements will have the exact same list + of virtual uses, so it is enough to set the output of this + statement to be its first virtual definition. */ + *output_p = first_vdef (stmt); + if (changed) + { + if (val.lattice_val == VARYING) + retval = SSA_PROP_VARYING; + else + retval = SSA_PROP_INTERESTING; + } + } + + return retval; +} + + +/* Visit the conditional statement STMT. Return SSA_PROP_INTERESTING + if it can determine which edge will be taken. Otherwise, return + SSA_PROP_VARYING. */ + +static enum ssa_prop_result +visit_cond_stmt (tree stmt, edge *taken_edge_p) +{ + prop_value_t val; + basic_block block; + + block = bb_for_stmt (stmt); + val = evaluate_stmt (stmt); + + /* Find which edge out of the conditional block will be taken and add it + to the worklist. If no single edge can be determined statically, + return SSA_PROP_VARYING to feed all the outgoing edges to the + propagation engine. */ + *taken_edge_p = val.value ? find_taken_edge (block, val.value) : 0; + if (*taken_edge_p) + return SSA_PROP_INTERESTING; + else + return SSA_PROP_VARYING; +} + + +/* Evaluate statement STMT. If the statement produces an output value and + its evaluation changes the lattice value of its output, return + SSA_PROP_INTERESTING and set *OUTPUT_P to the SSA_NAME holding the + output value. + + If STMT is a conditional branch and we can determine its truth + value, set *TAKEN_EDGE_P accordingly. If STMT produces a varying + value, return SSA_PROP_VARYING. */ + +static enum ssa_prop_result +ccp_visit_stmt (tree stmt, edge *taken_edge_p, tree *output_p) +{ + tree def; + ssa_op_iter iter; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "\nVisiting statement:\n"); + print_generic_stmt (dump_file, stmt, dump_flags); + fprintf (dump_file, "\n"); + } + + if (TREE_CODE (stmt) == MODIFY_EXPR) + { + /* If the statement is an assignment that produces a single + output value, evaluate its RHS to see if the lattice value of + its output has changed. */ + return visit_assignment (stmt, output_p); + } + else if (TREE_CODE (stmt) == COND_EXPR || TREE_CODE (stmt) == SWITCH_EXPR) + { + /* If STMT is a conditional branch, see if we can determine + which branch will be taken. */ + return visit_cond_stmt (stmt, taken_edge_p); + } + + /* Any other kind of statement is not interesting for constant + propagation and, therefore, not worth simulating. */ + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "No interesting values produced. Marked VARYING.\n"); + + /* Definitions made by statements other than assignments to + SSA_NAMEs represent unknown modifications to their outputs. + Mark them VARYING. */ + FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS) + { + prop_value_t v = { VARYING, NULL_TREE, NULL_TREE }; + set_lattice_value (def, v); + } + + return SSA_PROP_VARYING; +} + + +/* Main entry point for SSA Conditional Constant Propagation. */ + +static void +execute_ssa_ccp (bool store_ccp) +{ + do_store_ccp = store_ccp; + ccp_initialize (); + ssa_propagate (ccp_visit_stmt, ccp_visit_phi_node); + ccp_finalize (); +} + + +static unsigned int +do_ssa_ccp (void) +{ + execute_ssa_ccp (false); + return 0; +} + + +static bool +gate_ccp (void) +{ + return flag_tree_ccp != 0; +} + + +struct tree_opt_pass pass_ccp = +{ + "ccp", /* name */ + gate_ccp, /* gate */ + do_ssa_ccp, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_TREE_CCP, /* tv_id */ + PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ + 0, /* properties_provided */ + PROP_smt_usage, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_cleanup_cfg | TODO_dump_func | TODO_update_ssa + | TODO_ggc_collect | TODO_verify_ssa + | TODO_verify_stmts | TODO_update_smt_usage, /* todo_flags_finish */ + 0 /* letter */ +}; + + +static unsigned int +do_ssa_store_ccp (void) +{ + /* If STORE-CCP is not enabled, we just run regular CCP. */ + execute_ssa_ccp (flag_tree_store_ccp != 0); + return 0; +} + +static bool +gate_store_ccp (void) +{ + /* STORE-CCP is enabled only with -ftree-store-ccp, but when + -fno-tree-store-ccp is specified, we should run regular CCP. + That's why the pass is enabled with either flag. */ + return flag_tree_store_ccp != 0 || flag_tree_ccp != 0; +} + + +struct tree_opt_pass pass_store_ccp = +{ + "store_ccp", /* name */ + gate_store_ccp, /* gate */ + do_ssa_store_ccp, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + TV_TREE_STORE_CCP, /* tv_id */ + PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ + 0, /* properties_provided */ + PROP_smt_usage, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_dump_func | TODO_update_ssa + | TODO_ggc_collect | TODO_verify_ssa + | TODO_cleanup_cfg + | TODO_verify_stmts | TODO_update_smt_usage, /* todo_flags_finish */ + 0 /* letter */ +}; + +/* Given a constant value VAL for bitfield FIELD, and a destination + variable VAR, return VAL appropriately widened to fit into VAR. If + FIELD is wider than HOST_WIDE_INT, NULL is returned. */ + +tree +widen_bitfield (tree val, tree field, tree var) +{ + unsigned HOST_WIDE_INT var_size, field_size; + tree wide_val; + unsigned HOST_WIDE_INT mask; + unsigned int i; + + /* We can only do this if the size of the type and field and VAL are + all constants representable in HOST_WIDE_INT. */ + if (!host_integerp (TYPE_SIZE (TREE_TYPE (var)), 1) + || !host_integerp (DECL_SIZE (field), 1) + || !host_integerp (val, 0)) + return NULL_TREE; + + var_size = tree_low_cst (TYPE_SIZE (TREE_TYPE (var)), 1); + field_size = tree_low_cst (DECL_SIZE (field), 1); + + /* Give up if either the bitfield or the variable are too wide. */ + if (field_size > HOST_BITS_PER_WIDE_INT || var_size > HOST_BITS_PER_WIDE_INT) + return NULL_TREE; + + gcc_assert (var_size >= field_size); + + /* If the sign bit of the value is not set or the field's type is unsigned, + just mask off the high order bits of the value. */ + if (DECL_UNSIGNED (field) + || !(tree_low_cst (val, 0) & (((HOST_WIDE_INT)1) << (field_size - 1)))) + { + /* Zero extension. Build a mask with the lower 'field_size' bits + set and a BIT_AND_EXPR node to clear the high order bits of + the value. */ + for (i = 0, mask = 0; i < field_size; i++) + mask |= ((HOST_WIDE_INT) 1) << i; + + wide_val = fold_build2 (BIT_AND_EXPR, TREE_TYPE (var), val, + build_int_cst (TREE_TYPE (var), mask)); + } + else + { + /* Sign extension. Create a mask with the upper 'field_size' + bits set and a BIT_IOR_EXPR to set the high order bits of the + value. */ + for (i = 0, mask = 0; i < (var_size - field_size); i++) + mask |= ((HOST_WIDE_INT) 1) << (var_size - i - 1); + + wide_val = fold_build2 (BIT_IOR_EXPR, TREE_TYPE (var), val, + build_int_cst (TREE_TYPE (var), mask)); + } + + return wide_val; +} + + +/* A subroutine of fold_stmt_r. Attempts to fold *(A+O) to A[X]. + BASE is an array type. OFFSET is a byte displacement. ORIG_TYPE + is the desired result type. */ + +static tree +maybe_fold_offset_to_array_ref (tree base, tree offset, tree orig_type) +{ + tree min_idx, idx, elt_offset = integer_zero_node; + tree array_type, elt_type, elt_size; + + /* If BASE is an ARRAY_REF, we can pick up another offset (this time + measured in units of the size of elements type) from that ARRAY_REF). + We can't do anything if either is variable. + + The case we handle here is *(&A[N]+O). */ + if (TREE_CODE (base) == ARRAY_REF) + { + tree low_bound = array_ref_low_bound (base); + + elt_offset = TREE_OPERAND (base, 1); + if (TREE_CODE (low_bound) != INTEGER_CST + || TREE_CODE (elt_offset) != INTEGER_CST) + return NULL_TREE; + + elt_offset = int_const_binop (MINUS_EXPR, elt_offset, low_bound, 0); + base = TREE_OPERAND (base, 0); + } + + /* Ignore stupid user tricks of indexing non-array variables. */ + array_type = TREE_TYPE (base); + if (TREE_CODE (array_type) != ARRAY_TYPE) + return NULL_TREE; + elt_type = TREE_TYPE (array_type); + if (!lang_hooks.types_compatible_p (orig_type, elt_type)) + return NULL_TREE; + + /* If OFFSET and ELT_OFFSET are zero, we don't care about the size of the + element type (so we can use the alignment if it's not constant). + Otherwise, compute the offset as an index by using a division. If the + division isn't exact, then don't do anything. */ + elt_size = TYPE_SIZE_UNIT (elt_type); + if (integer_zerop (offset)) + { + if (TREE_CODE (elt_size) != INTEGER_CST) + elt_size = size_int (TYPE_ALIGN (elt_type)); + + idx = integer_zero_node; + } + else + { + unsigned HOST_WIDE_INT lquo, lrem; + HOST_WIDE_INT hquo, hrem; + + if (TREE_CODE (elt_size) != INTEGER_CST + || div_and_round_double (TRUNC_DIV_EXPR, 1, + TREE_INT_CST_LOW (offset), + TREE_INT_CST_HIGH (offset), + TREE_INT_CST_LOW (elt_size), + TREE_INT_CST_HIGH (elt_size), + &lquo, &hquo, &lrem, &hrem) + || lrem || hrem) + return NULL_TREE; + + idx = build_int_cst_wide (NULL_TREE, lquo, hquo); + } + + /* Assume the low bound is zero. If there is a domain type, get the + low bound, if any, convert the index into that type, and add the + low bound. */ + min_idx = integer_zero_node; + if (TYPE_DOMAIN (array_type)) + { + if (TYPE_MIN_VALUE (TYPE_DOMAIN (array_type))) + min_idx = TYPE_MIN_VALUE (TYPE_DOMAIN (array_type)); + else + min_idx = fold_convert (TYPE_DOMAIN (array_type), min_idx); + + if (TREE_CODE (min_idx) != INTEGER_CST) + return NULL_TREE; + + idx = fold_convert (TYPE_DOMAIN (array_type), idx); + elt_offset = fold_convert (TYPE_DOMAIN (array_type), elt_offset); + } + + if (!integer_zerop (min_idx)) + idx = int_const_binop (PLUS_EXPR, idx, min_idx, 0); + if (!integer_zerop (elt_offset)) + idx = int_const_binop (PLUS_EXPR, idx, elt_offset, 0); + + return build4 (ARRAY_REF, orig_type, base, idx, min_idx, + size_int (tree_low_cst (elt_size, 1) + / (TYPE_ALIGN_UNIT (elt_type)))); +} + + +/* A subroutine of fold_stmt_r. Attempts to fold *(S+O) to S.X. + BASE is a record type. OFFSET is a byte displacement. ORIG_TYPE + is the desired result type. */ +/* ??? This doesn't handle class inheritance. */ + +static tree +maybe_fold_offset_to_component_ref (tree record_type, tree base, tree offset, + tree orig_type, bool base_is_ptr) +{ + tree f, t, field_type, tail_array_field, field_offset; + + if (TREE_CODE (record_type) != RECORD_TYPE + && TREE_CODE (record_type) != UNION_TYPE + && TREE_CODE (record_type) != QUAL_UNION_TYPE) + return NULL_TREE; + + /* Short-circuit silly cases. */ + if (lang_hooks.types_compatible_p (record_type, orig_type)) + return NULL_TREE; + + tail_array_field = NULL_TREE; + for (f = TYPE_FIELDS (record_type); f ; f = TREE_CHAIN (f)) + { + int cmp; + + if (TREE_CODE (f) != FIELD_DECL) + continue; + if (DECL_BIT_FIELD (f)) + continue; + + field_offset = byte_position (f); + if (TREE_CODE (field_offset) != INTEGER_CST) + continue; + + /* ??? Java creates "interesting" fields for representing base classes. + They have no name, and have no context. With no context, we get into + trouble with nonoverlapping_component_refs_p. Skip them. */ + if (!DECL_FIELD_CONTEXT (f)) + continue; + + /* The previous array field isn't at the end. */ + tail_array_field = NULL_TREE; + + /* Check to see if this offset overlaps with the field. */ + cmp = tree_int_cst_compare (field_offset, offset); + if (cmp > 0) + continue; + + field_type = TREE_TYPE (f); + + /* Here we exactly match the offset being checked. If the types match, + then we can return that field. */ + if (cmp == 0 + && lang_hooks.types_compatible_p (orig_type, field_type)) + { + if (base_is_ptr) + base = build1 (INDIRECT_REF, record_type, base); + t = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE); + return t; + } + + /* Don't care about offsets into the middle of scalars. */ + if (!AGGREGATE_TYPE_P (field_type)) + continue; + + /* Check for array at the end of the struct. This is often + used as for flexible array members. We should be able to + turn this into an array access anyway. */ + if (TREE_CODE (field_type) == ARRAY_TYPE) + tail_array_field = f; + + /* Check the end of the field against the offset. */ + if (!DECL_SIZE_UNIT (f) + || TREE_CODE (DECL_SIZE_UNIT (f)) != INTEGER_CST) + continue; + t = int_const_binop (MINUS_EXPR, offset, field_offset, 1); + if (!tree_int_cst_lt (t, DECL_SIZE_UNIT (f))) + continue; + + /* If we matched, then set offset to the displacement into + this field. */ + offset = t; + goto found; + } + + if (!tail_array_field) + return NULL_TREE; + + f = tail_array_field; + field_type = TREE_TYPE (f); + offset = int_const_binop (MINUS_EXPR, offset, byte_position (f), 1); + + found: + /* If we get here, we've got an aggregate field, and a possibly + nonzero offset into them. Recurse and hope for a valid match. */ + if (base_is_ptr) + base = build1 (INDIRECT_REF, record_type, base); + base = build3 (COMPONENT_REF, field_type, base, f, NULL_TREE); + + t = maybe_fold_offset_to_array_ref (base, offset, orig_type); + if (t) + return t; + return maybe_fold_offset_to_component_ref (field_type, base, offset, + orig_type, false); +} + + +/* A subroutine of fold_stmt_r. Attempt to simplify *(BASE+OFFSET). + Return the simplified expression, or NULL if nothing could be done. */ + +static tree +maybe_fold_stmt_indirect (tree expr, tree base, tree offset) +{ + tree t; + + /* We may well have constructed a double-nested PLUS_EXPR via multiple + substitutions. Fold that down to one. Remove NON_LVALUE_EXPRs that + are sometimes added. */ + base = fold (base); + STRIP_TYPE_NOPS (base); + TREE_OPERAND (expr, 0) = base; + + /* One possibility is that the address reduces to a string constant. */ + t = fold_read_from_constant_string (expr); + if (t) + return t; + + /* Add in any offset from a PLUS_EXPR. */ + if (TREE_CODE (base) == PLUS_EXPR) + { + tree offset2; + + offset2 = TREE_OPERAND (base, 1); + if (TREE_CODE (offset2) != INTEGER_CST) + return NULL_TREE; + base = TREE_OPERAND (base, 0); + + offset = int_const_binop (PLUS_EXPR, offset, offset2, 1); + } + + if (TREE_CODE (base) == ADDR_EXPR) + { + /* Strip the ADDR_EXPR. */ + base = TREE_OPERAND (base, 0); + + /* Fold away CONST_DECL to its value, if the type is scalar. */ + if (TREE_CODE (base) == CONST_DECL + && ccp_decl_initial_min_invariant (DECL_INITIAL (base))) + return DECL_INITIAL (base); + + /* Try folding *(&B+O) to B[X]. */ + t = maybe_fold_offset_to_array_ref (base, offset, TREE_TYPE (expr)); + if (t) + return t; + + /* Try folding *(&B+O) to B.X. */ + t = maybe_fold_offset_to_component_ref (TREE_TYPE (base), base, offset, + TREE_TYPE (expr), false); + if (t) + return t; + + /* Fold *&B to B. We can only do this if EXPR is the same type + as BASE. We can't do this if EXPR is the element type of an array + and BASE is the array. */ + if (integer_zerop (offset) + && lang_hooks.types_compatible_p (TREE_TYPE (base), + TREE_TYPE (expr))) + return base; + } + else + { + /* We can get here for out-of-range string constant accesses, + such as "_"[3]. Bail out of the entire substitution search + and arrange for the entire statement to be replaced by a + call to __builtin_trap. In all likelihood this will all be + constant-folded away, but in the meantime we can't leave with + something that get_expr_operands can't understand. */ + + t = base; + STRIP_NOPS (t); + if (TREE_CODE (t) == ADDR_EXPR + && TREE_CODE (TREE_OPERAND (t, 0)) == STRING_CST) + { + /* FIXME: Except that this causes problems elsewhere with dead + code not being deleted, and we die in the rtl expanders + because we failed to remove some ssa_name. In the meantime, + just return zero. */ + /* FIXME2: This condition should be signaled by + fold_read_from_constant_string directly, rather than + re-checking for it here. */ + return integer_zero_node; + } + + /* Try folding *(B+O) to B->X. Still an improvement. */ + if (POINTER_TYPE_P (TREE_TYPE (base))) + { + t = maybe_fold_offset_to_component_ref (TREE_TYPE (TREE_TYPE (base)), + base, offset, + TREE_TYPE (expr), true); + if (t) + return t; + } + } + + /* Otherwise we had an offset that we could not simplify. */ + return NULL_TREE; +} + + +/* A subroutine of fold_stmt_r. EXPR is a PLUS_EXPR. + + A quaint feature extant in our address arithmetic is that there + can be hidden type changes here. The type of the result need + not be the same as the type of the input pointer. + + What we're after here is an expression of the form + (T *)(&array + const) + where the cast doesn't actually exist, but is implicit in the + type of the PLUS_EXPR. We'd like to turn this into + &array[x] + which may be able to propagate further. */ + +static tree +maybe_fold_stmt_addition (tree expr) +{ + tree op0 = TREE_OPERAND (expr, 0); + tree op1 = TREE_OPERAND (expr, 1); + tree ptr_type = TREE_TYPE (expr); + tree ptd_type; + tree t; + bool subtract = (TREE_CODE (expr) == MINUS_EXPR); + + /* We're only interested in pointer arithmetic. */ + if (!POINTER_TYPE_P (ptr_type)) + return NULL_TREE; + /* Canonicalize the integral operand to op1. */ + if (INTEGRAL_TYPE_P (TREE_TYPE (op0))) + { + if (subtract) + return NULL_TREE; + t = op0, op0 = op1, op1 = t; + } + /* It had better be a constant. */ + if (TREE_CODE (op1) != INTEGER_CST) + return NULL_TREE; + /* The first operand should be an ADDR_EXPR. */ + if (TREE_CODE (op0) != ADDR_EXPR) + return NULL_TREE; + op0 = TREE_OPERAND (op0, 0); + + /* If the first operand is an ARRAY_REF, expand it so that we can fold + the offset into it. */ + while (TREE_CODE (op0) == ARRAY_REF) + { + tree array_obj = TREE_OPERAND (op0, 0); + tree array_idx = TREE_OPERAND (op0, 1); + tree elt_type = TREE_TYPE (op0); + tree elt_size = TYPE_SIZE_UNIT (elt_type); + tree min_idx; + + if (TREE_CODE (array_idx) != INTEGER_CST) + break; + if (TREE_CODE (elt_size) != INTEGER_CST) + break; + + /* Un-bias the index by the min index of the array type. */ + min_idx = TYPE_DOMAIN (TREE_TYPE (array_obj)); + if (min_idx) + { + min_idx = TYPE_MIN_VALUE (min_idx); + if (min_idx) + { + if (TREE_CODE (min_idx) != INTEGER_CST) + break; + + array_idx = fold_convert (TREE_TYPE (min_idx), array_idx); + if (!integer_zerop (min_idx)) + array_idx = int_const_binop (MINUS_EXPR, array_idx, + min_idx, 0); + } + } + + /* Convert the index to a byte offset. */ + array_idx = fold_convert (sizetype, array_idx); + array_idx = int_const_binop (MULT_EXPR, array_idx, elt_size, 0); + + /* Update the operands for the next round, or for folding. */ + /* If we're manipulating unsigned types, then folding into negative + values can produce incorrect results. Particularly if the type + is smaller than the width of the pointer. */ + if (subtract + && TYPE_UNSIGNED (TREE_TYPE (op1)) + && tree_int_cst_lt (array_idx, op1)) + return NULL; + op1 = int_const_binop (subtract ? MINUS_EXPR : PLUS_EXPR, + array_idx, op1, 0); + subtract = false; + op0 = array_obj; + } + + /* If we weren't able to fold the subtraction into another array reference, + canonicalize the integer for passing to the array and component ref + simplification functions. */ + if (subtract) + { + if (TYPE_UNSIGNED (TREE_TYPE (op1))) + return NULL; + op1 = fold_unary (NEGATE_EXPR, TREE_TYPE (op1), op1); + /* ??? In theory fold should always produce another integer. */ + if (op1 == NULL || TREE_CODE (op1) != INTEGER_CST) + return NULL; + } + + ptd_type = TREE_TYPE (ptr_type); + + /* At which point we can try some of the same things as for indirects. */ + t = maybe_fold_offset_to_array_ref (op0, op1, ptd_type); + if (!t) + t = maybe_fold_offset_to_component_ref (TREE_TYPE (op0), op0, op1, + ptd_type, false); + if (t) + t = build1 (ADDR_EXPR, ptr_type, t); + + return t; +} + +/* For passing state through walk_tree into fold_stmt_r and its + children. */ + +struct fold_stmt_r_data +{ + tree stmt; + bool *changed_p; + bool *inside_addr_expr_p; +}; + +/* Subroutine of fold_stmt called via walk_tree. We perform several + simplifications of EXPR_P, mostly having to do with pointer arithmetic. */ + +static tree +fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data) +{ + struct fold_stmt_r_data *fold_stmt_r_data = (struct fold_stmt_r_data *) data; + bool *inside_addr_expr_p = fold_stmt_r_data->inside_addr_expr_p; + bool *changed_p = fold_stmt_r_data->changed_p; + tree expr = *expr_p, t; + + /* ??? It'd be nice if walk_tree had a pre-order option. */ + switch (TREE_CODE (expr)) + { + case INDIRECT_REF: + t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); + if (t) + return t; + *walk_subtrees = 0; + + t = maybe_fold_stmt_indirect (expr, TREE_OPERAND (expr, 0), + integer_zero_node); + break; + + /* ??? Could handle more ARRAY_REFs here, as a variant of INDIRECT_REF. + We'd only want to bother decomposing an existing ARRAY_REF if + the base array is found to have another offset contained within. + Otherwise we'd be wasting time. */ + case ARRAY_REF: + /* If we are not processing expressions found within an + ADDR_EXPR, then we can fold constant array references. */ + if (!*inside_addr_expr_p) + t = fold_read_from_constant_string (expr); + else + t = NULL; + break; + + case ADDR_EXPR: + *inside_addr_expr_p = true; + t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); + *inside_addr_expr_p = false; + if (t) + return t; + *walk_subtrees = 0; + + /* Set TREE_INVARIANT properly so that the value is properly + considered constant, and so gets propagated as expected. */ + if (*changed_p) + recompute_tree_invariant_for_addr_expr (expr); + return NULL_TREE; + + case PLUS_EXPR: + case MINUS_EXPR: + t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); + if (t) + return t; + t = walk_tree (&TREE_OPERAND (expr, 1), fold_stmt_r, data, NULL); + if (t) + return t; + *walk_subtrees = 0; + + t = maybe_fold_stmt_addition (expr); + break; + + case COMPONENT_REF: + t = walk_tree (&TREE_OPERAND (expr, 0), fold_stmt_r, data, NULL); + if (t) + return t; + *walk_subtrees = 0; + + /* Make sure the FIELD_DECL is actually a field in the type on the lhs. + We've already checked that the records are compatible, so we should + come up with a set of compatible fields. */ + { + tree expr_record = TREE_TYPE (TREE_OPERAND (expr, 0)); + tree expr_field = TREE_OPERAND (expr, 1); + + if (DECL_FIELD_CONTEXT (expr_field) != TYPE_MAIN_VARIANT (expr_record)) + { + expr_field = find_compatible_field (expr_record, expr_field); + TREE_OPERAND (expr, 1) = expr_field; + } + } + break; + + case TARGET_MEM_REF: + t = maybe_fold_tmr (expr); + break; + + case COND_EXPR: + if (COMPARISON_CLASS_P (TREE_OPERAND (expr, 0))) + { + tree op0 = TREE_OPERAND (expr, 0); + tree tem; + bool set; + + fold_defer_overflow_warnings (); + tem = fold_binary (TREE_CODE (op0), TREE_TYPE (op0), + TREE_OPERAND (op0, 0), + TREE_OPERAND (op0, 1)); + set = tem && is_gimple_condexpr (tem); + fold_undefer_overflow_warnings (set, fold_stmt_r_data->stmt, 0); + if (set) + TREE_OPERAND (expr, 0) = tem; + t = expr; + break; + } + + default: + return NULL_TREE; + } + + if (t) + { + *expr_p = t; + *changed_p = true; + } + + return NULL_TREE; +} + + +/* Return the string length, maximum string length or maximum value of + ARG in LENGTH. + If ARG is an SSA name variable, follow its use-def chains. If LENGTH + is not NULL and, for TYPE == 0, its value is not equal to the length + we determine or if we are unable to determine the length or value, + return false. VISITED is a bitmap of visited variables. + TYPE is 0 if string length should be returned, 1 for maximum string + length and 2 for maximum value ARG can have. */ + +static bool +get_maxval_strlen (tree arg, tree *length, bitmap visited, int type) +{ + tree var, def_stmt, val; + + if (TREE_CODE (arg) != SSA_NAME) + { + if (type == 2) + { + val = arg; + if (TREE_CODE (val) != INTEGER_CST + || tree_int_cst_sgn (val) < 0) + return false; + } + else + val = c_strlen (arg, 1); + if (!val) + return false; + + if (*length) + { + if (type > 0) + { + if (TREE_CODE (*length) != INTEGER_CST + || TREE_CODE (val) != INTEGER_CST) + return false; + + if (tree_int_cst_lt (*length, val)) + *length = val; + return true; + } + else if (simple_cst_equal (val, *length) != 1) + return false; + } + + *length = val; + return true; + } + + /* If we were already here, break the infinite cycle. */ + if (bitmap_bit_p (visited, SSA_NAME_VERSION (arg))) + return true; + bitmap_set_bit (visited, SSA_NAME_VERSION (arg)); + + var = arg; + def_stmt = SSA_NAME_DEF_STMT (var); + + switch (TREE_CODE (def_stmt)) + { + case MODIFY_EXPR: + { + tree rhs; + + /* The RHS of the statement defining VAR must either have a + constant length or come from another SSA_NAME with a constant + length. */ + rhs = TREE_OPERAND (def_stmt, 1); + STRIP_NOPS (rhs); + return get_maxval_strlen (rhs, length, visited, type); + } + + case PHI_NODE: + { + /* All the arguments of the PHI node must have the same constant + length. */ + int i; + + for (i = 0; i < PHI_NUM_ARGS (def_stmt); i++) + { + tree arg = PHI_ARG_DEF (def_stmt, i); + + /* If this PHI has itself as an argument, we cannot + determine the string length of this argument. However, + if we can find a constant string length for the other + PHI args then we can still be sure that this is a + constant string length. So be optimistic and just + continue with the next argument. */ + if (arg == PHI_RESULT (def_stmt)) + continue; + + if (!get_maxval_strlen (arg, length, visited, type)) + return false; + } + + return true; + } + + default: + break; + } + + + return false; +} + + +/* Fold builtin call FN in statement STMT. If it cannot be folded into a + constant, return NULL_TREE. Otherwise, return its constant value. */ + +static tree +ccp_fold_builtin (tree stmt, tree fn) +{ + tree result, val[3]; + tree callee, arglist, a; + int arg_mask, i, type; + bitmap visited; + bool ignore; + + ignore = TREE_CODE (stmt) != MODIFY_EXPR; + + /* First try the generic builtin folder. If that succeeds, return the + result directly. */ + callee = get_callee_fndecl (fn); + arglist = TREE_OPERAND (fn, 1); + result = fold_builtin (callee, arglist, ignore); + if (result) + { + if (ignore) + STRIP_NOPS (result); + return result; + } + + /* Ignore MD builtins. */ + if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_MD) + return NULL_TREE; + + /* If the builtin could not be folded, and it has no argument list, + we're done. */ + if (!arglist) + return NULL_TREE; + + /* Limit the work only for builtins we know how to simplify. */ + switch (DECL_FUNCTION_CODE (callee)) + { + case BUILT_IN_STRLEN: + case BUILT_IN_FPUTS: + case BUILT_IN_FPUTS_UNLOCKED: + arg_mask = 1; + type = 0; + break; + case BUILT_IN_STRCPY: + case BUILT_IN_STRNCPY: + arg_mask = 2; + type = 0; + break; + case BUILT_IN_MEMCPY_CHK: + case BUILT_IN_MEMPCPY_CHK: + case BUILT_IN_MEMMOVE_CHK: + case BUILT_IN_MEMSET_CHK: + case BUILT_IN_STRNCPY_CHK: + arg_mask = 4; + type = 2; + break; + case BUILT_IN_STRCPY_CHK: + case BUILT_IN_STPCPY_CHK: + arg_mask = 2; + type = 1; + break; + case BUILT_IN_SNPRINTF_CHK: + case BUILT_IN_VSNPRINTF_CHK: + arg_mask = 2; + type = 2; + break; + default: + return NULL_TREE; + } + + /* Try to use the dataflow information gathered by the CCP process. */ + visited = BITMAP_ALLOC (NULL); + + memset (val, 0, sizeof (val)); + for (i = 0, a = arglist; + arg_mask; + i++, arg_mask >>= 1, a = TREE_CHAIN (a)) + if (arg_mask & 1) + { + bitmap_clear (visited); + if (!get_maxval_strlen (TREE_VALUE (a), &val[i], visited, type)) + val[i] = NULL_TREE; + } + + BITMAP_FREE (visited); + + result = NULL_TREE; + switch (DECL_FUNCTION_CODE (callee)) + { + case BUILT_IN_STRLEN: + if (val[0]) + { + tree new = fold_convert (TREE_TYPE (fn), val[0]); + + /* If the result is not a valid gimple value, or not a cast + of a valid gimple value, then we can not use the result. */ + if (is_gimple_val (new) + || (is_gimple_cast (new) + && is_gimple_val (TREE_OPERAND (new, 0)))) + return new; + } + break; + + case BUILT_IN_STRCPY: + if (val[1] && is_gimple_val (val[1])) + result = fold_builtin_strcpy (callee, arglist, val[1]); + break; + + case BUILT_IN_STRNCPY: + if (val[1] && is_gimple_val (val[1])) + result = fold_builtin_strncpy (callee, arglist, val[1]); + break; + + case BUILT_IN_FPUTS: + result = fold_builtin_fputs (arglist, + TREE_CODE (stmt) != MODIFY_EXPR, 0, + val[0]); + break; + + case BUILT_IN_FPUTS_UNLOCKED: + result = fold_builtin_fputs (arglist, + TREE_CODE (stmt) != MODIFY_EXPR, 1, + val[0]); + break; + + case BUILT_IN_MEMCPY_CHK: + case BUILT_IN_MEMPCPY_CHK: + case BUILT_IN_MEMMOVE_CHK: + case BUILT_IN_MEMSET_CHK: + if (val[2] && is_gimple_val (val[2])) + result = fold_builtin_memory_chk (callee, arglist, val[2], ignore, + DECL_FUNCTION_CODE (callee)); + break; + + case BUILT_IN_STRCPY_CHK: + case BUILT_IN_STPCPY_CHK: + if (val[1] && is_gimple_val (val[1])) + result = fold_builtin_stxcpy_chk (callee, arglist, val[1], ignore, + DECL_FUNCTION_CODE (callee)); + break; + + case BUILT_IN_STRNCPY_CHK: + if (val[2] && is_gimple_val (val[2])) + result = fold_builtin_strncpy_chk (arglist, val[2]); + break; + + case BUILT_IN_SNPRINTF_CHK: + case BUILT_IN_VSNPRINTF_CHK: + if (val[1] && is_gimple_val (val[1])) + result = fold_builtin_snprintf_chk (arglist, val[1], + DECL_FUNCTION_CODE (callee)); + break; + + default: + gcc_unreachable (); + } + + if (result && ignore) + result = fold_ignored_result (result); + return result; +} + + +/* Fold the statement pointed to by STMT_P. In some cases, this function may + replace the whole statement with a new one. Returns true iff folding + makes any changes. */ + +bool +fold_stmt (tree *stmt_p) +{ + tree rhs, result, stmt; + struct fold_stmt_r_data fold_stmt_r_data; + bool changed = false; + bool inside_addr_expr = false; + + stmt = *stmt_p; + + fold_stmt_r_data.stmt = stmt; + fold_stmt_r_data.changed_p = &changed; + fold_stmt_r_data.inside_addr_expr_p = &inside_addr_expr; + + /* If we replaced constants and the statement makes pointer dereferences, + then we may need to fold instances of *&VAR into VAR, etc. */ + if (walk_tree (stmt_p, fold_stmt_r, &fold_stmt_r_data, NULL)) + { + *stmt_p + = build_function_call_expr (implicit_built_in_decls[BUILT_IN_TRAP], + NULL); + return true; + } + + rhs = get_rhs (stmt); + if (!rhs) + return changed; + result = NULL_TREE; + + if (TREE_CODE (rhs) == CALL_EXPR) + { + tree callee; + + /* Check for builtins that CCP can handle using information not + available in the generic fold routines. */ + callee = get_callee_fndecl (rhs); + if (callee && DECL_BUILT_IN (callee)) + result = ccp_fold_builtin (stmt, rhs); + else + { + /* Check for resolvable OBJ_TYPE_REF. The only sorts we can resolve + here are when we've propagated the address of a decl into the + object slot. */ + /* ??? Should perhaps do this in fold proper. However, doing it + there requires that we create a new CALL_EXPR, and that requires + copying EH region info to the new node. Easier to just do it + here where we can just smash the call operand. Also + CALL_EXPR_RETURN_SLOT_OPT needs to be handled correctly and + copied, fold_ternary does not have not information. */ + callee = TREE_OPERAND (rhs, 0); + if (TREE_CODE (callee) == OBJ_TYPE_REF + && lang_hooks.fold_obj_type_ref + && TREE_CODE (OBJ_TYPE_REF_OBJECT (callee)) == ADDR_EXPR + && DECL_P (TREE_OPERAND + (OBJ_TYPE_REF_OBJECT (callee), 0))) + { + tree t; + + /* ??? Caution: Broken ADDR_EXPR semantics means that + looking at the type of the operand of the addr_expr + can yield an array type. See silly exception in + check_pointer_types_r. */ + + t = TREE_TYPE (TREE_TYPE (OBJ_TYPE_REF_OBJECT (callee))); + t = lang_hooks.fold_obj_type_ref (callee, t); + if (t) + { + TREE_OPERAND (rhs, 0) = t; + changed = true; + } + } + } + } + + /* If we couldn't fold the RHS, hand over to the generic fold routines. */ + if (result == NULL_TREE) + result = fold (rhs); + + /* Strip away useless type conversions. Both the NON_LVALUE_EXPR that + may have been added by fold, and "useless" type conversions that might + now be apparent due to propagation. */ + STRIP_USELESS_TYPE_CONVERSION (result); + + if (result != rhs) + changed |= set_rhs (stmt_p, result); + + return changed; +} + +/* Perform the minimal folding on statement STMT. Only operations like + *&x created by constant propagation are handled. The statement cannot + be replaced with a new one. */ + +bool +fold_stmt_inplace (tree stmt) +{ + tree old_stmt = stmt, rhs, new_rhs; + struct fold_stmt_r_data fold_stmt_r_data; + bool changed = false; + bool inside_addr_expr = false; + + fold_stmt_r_data.stmt = stmt; + fold_stmt_r_data.changed_p = &changed; + fold_stmt_r_data.inside_addr_expr_p = &inside_addr_expr; + + walk_tree (&stmt, fold_stmt_r, &fold_stmt_r_data, NULL); + gcc_assert (stmt == old_stmt); + + rhs = get_rhs (stmt); + if (!rhs || rhs == stmt) + return changed; + + new_rhs = fold (rhs); + STRIP_USELESS_TYPE_CONVERSION (new_rhs); + if (new_rhs == rhs) + return changed; + + changed |= set_rhs (&stmt, new_rhs); + gcc_assert (stmt == old_stmt); + + return changed; +} + +/* Convert EXPR into a GIMPLE value suitable for substitution on the + RHS of an assignment. Insert the necessary statements before + iterator *SI_P. */ + +static tree +convert_to_gimple_builtin (block_stmt_iterator *si_p, tree expr) +{ + tree_stmt_iterator ti; + tree stmt = bsi_stmt (*si_p); + tree tmp, stmts = NULL; + + push_gimplify_context (); + tmp = get_initialized_tmp_var (expr, &stmts, NULL); + pop_gimplify_context (NULL); + + if (EXPR_HAS_LOCATION (stmt)) + annotate_all_with_locus (&stmts, EXPR_LOCATION (stmt)); + + /* The replacement can expose previously unreferenced variables. */ + for (ti = tsi_start (stmts); !tsi_end_p (ti); tsi_next (&ti)) + { + tree new_stmt = tsi_stmt (ti); + find_new_referenced_vars (tsi_stmt_ptr (ti)); + bsi_insert_before (si_p, new_stmt, BSI_NEW_STMT); + mark_new_vars_to_rename (bsi_stmt (*si_p)); + bsi_next (si_p); + } + + return tmp; +} + + +/* A simple pass that attempts to fold all builtin functions. This pass + is run after we've propagated as many constants as we can. */ + +static unsigned int +execute_fold_all_builtins (void) +{ + bool cfg_changed = false; + basic_block bb; + FOR_EACH_BB (bb) + { + block_stmt_iterator i; + for (i = bsi_start (bb); !bsi_end_p (i); ) + { + tree *stmtp = bsi_stmt_ptr (i); + tree old_stmt = *stmtp; + tree call = get_rhs (*stmtp); + tree callee, result; + enum built_in_function fcode; + + if (!call || TREE_CODE (call) != CALL_EXPR) + { + bsi_next (&i); + continue; + } + callee = get_callee_fndecl (call); + if (!callee || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL) + { + bsi_next (&i); + continue; + } + fcode = DECL_FUNCTION_CODE (callee); + + result = ccp_fold_builtin (*stmtp, call); + if (!result) + switch (DECL_FUNCTION_CODE (callee)) + { + case BUILT_IN_CONSTANT_P: + /* Resolve __builtin_constant_p. If it hasn't been + folded to integer_one_node by now, it's fairly + certain that the value simply isn't constant. */ + result = integer_zero_node; + break; + + default: + bsi_next (&i); + continue; + } + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "Simplified\n "); + print_generic_stmt (dump_file, *stmtp, dump_flags); + } + + if (!set_rhs (stmtp, result)) + { + result = convert_to_gimple_builtin (&i, result); + if (result) + { + bool ok = set_rhs (stmtp, result); + + gcc_assert (ok); + } + } + mark_new_vars_to_rename (*stmtp); + if (maybe_clean_or_replace_eh_stmt (old_stmt, *stmtp) + && tree_purge_dead_eh_edges (bb)) + cfg_changed = true; + + if (dump_file && (dump_flags & TDF_DETAILS)) + { + fprintf (dump_file, "to\n "); + print_generic_stmt (dump_file, *stmtp, dump_flags); + fprintf (dump_file, "\n"); + } + + /* Retry the same statement if it changed into another + builtin, there might be new opportunities now. */ + call = get_rhs (*stmtp); + if (!call || TREE_CODE (call) != CALL_EXPR) + { + bsi_next (&i); + continue; + } + callee = get_callee_fndecl (call); + if (!callee + || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL + || DECL_FUNCTION_CODE (callee) == fcode) + bsi_next (&i); + } + } + + /* Delete unreachable blocks. */ + if (cfg_changed) + cleanup_tree_cfg (); + return 0; +} + + +struct tree_opt_pass pass_fold_builtins = +{ + "fab", /* name */ + NULL, /* gate */ + execute_fold_all_builtins, /* execute */ + NULL, /* sub */ + NULL, /* next */ + 0, /* static_pass_number */ + 0, /* tv_id */ + PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */ + 0, /* properties_provided */ + 0, /* properties_destroyed */ + 0, /* todo_flags_start */ + TODO_dump_func + | TODO_verify_ssa + | TODO_update_ssa, /* todo_flags_finish */ + 0 /* letter */ +}; |