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author | Jing Yu <jingyu@google.com> | 2009-11-05 15:11:04 -0800 |
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committer | Jing Yu <jingyu@google.com> | 2009-11-05 15:11:04 -0800 |
commit | df62c1c110e8532b995b23540b7e3695729c0779 (patch) | |
tree | dbbd4cbdb50ac38011e058a2533ee4c3168b0205 /gcc-4.3.1/gcc/doc/fragments.texi | |
parent | 8d401cf711539af5a2f78d12447341d774892618 (diff) | |
download | toolchain_gcc-df62c1c110e8532b995b23540b7e3695729c0779.tar.gz toolchain_gcc-df62c1c110e8532b995b23540b7e3695729c0779.tar.bz2 toolchain_gcc-df62c1c110e8532b995b23540b7e3695729c0779.zip |
Check in gcc sources for prebuilt toolchains in Eclair.
Diffstat (limited to 'gcc-4.3.1/gcc/doc/fragments.texi')
-rw-r--r-- | gcc-4.3.1/gcc/doc/fragments.texi | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/gcc-4.3.1/gcc/doc/fragments.texi b/gcc-4.3.1/gcc/doc/fragments.texi new file mode 100644 index 000000000..450fd50f4 --- /dev/null +++ b/gcc-4.3.1/gcc/doc/fragments.texi @@ -0,0 +1,214 @@ +@c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, +@c 1999, 2000, 2001, 2003, 2004, 2005 Free Software Foundation, Inc. +@c This is part of the GCC manual. +@c For copying conditions, see the file gcc.texi. + +@node Fragments +@chapter Makefile Fragments +@cindex makefile fragment + +When you configure GCC using the @file{configure} script, it will +construct the file @file{Makefile} from the template file +@file{Makefile.in}. When it does this, it can incorporate makefile +fragments from the @file{config} directory. These are used to set +Makefile parameters that are not amenable to being calculated by +autoconf. The list of fragments to incorporate is set by +@file{config.gcc} (and occasionally @file{config.build} +and @file{config.host}); @xref{System Config}. + +Fragments are named either @file{t-@var{target}} or @file{x-@var{host}}, +depending on whether they are relevant to configuring GCC to produce +code for a particular target, or to configuring GCC to run on a +particular host. Here @var{target} and @var{host} are mnemonics +which usually have some relationship to the canonical system name, but +no formal connection. + +If these files do not exist, it means nothing needs to be added for a +given target or host. Most targets need a few @file{t-@var{target}} +fragments, but needing @file{x-@var{host}} fragments is rare. + +@menu +* Target Fragment:: Writing @file{t-@var{target}} files. +* Host Fragment:: Writing @file{x-@var{host}} files. +@end menu + +@node Target Fragment +@section Target Makefile Fragments +@cindex target makefile fragment +@cindex @file{t-@var{target}} + +Target makefile fragments can set these Makefile variables. + +@table @code +@findex LIBGCC2_CFLAGS +@item LIBGCC2_CFLAGS +Compiler flags to use when compiling @file{libgcc2.c}. + +@findex LIB2FUNCS_EXTRA +@item LIB2FUNCS_EXTRA +A list of source file names to be compiled or assembled and inserted +into @file{libgcc.a}. + +@findex Floating Point Emulation +@item Floating Point Emulation +To have GCC include software floating point libraries in @file{libgcc.a} +define @code{FPBIT} and @code{DPBIT} along with a few rules as follows: +@smallexample +# We want fine grained libraries, so use the new code +# to build the floating point emulation libraries. +FPBIT = fp-bit.c +DPBIT = dp-bit.c + + +fp-bit.c: $(srcdir)/config/fp-bit.c + echo '#define FLOAT' > fp-bit.c + cat $(srcdir)/config/fp-bit.c >> fp-bit.c + +dp-bit.c: $(srcdir)/config/fp-bit.c + cat $(srcdir)/config/fp-bit.c > dp-bit.c +@end smallexample + +You may need to provide additional #defines at the beginning of @file{fp-bit.c} +and @file{dp-bit.c} to control target endianness and other options. + + +@findex CRTSTUFF_T_CFLAGS +@item CRTSTUFF_T_CFLAGS +Special flags used when compiling @file{crtstuff.c}. +@xref{Initialization}. + +@findex CRTSTUFF_T_CFLAGS_S +@item CRTSTUFF_T_CFLAGS_S +Special flags used when compiling @file{crtstuff.c} for shared +linking. Used if you use @file{crtbeginS.o} and @file{crtendS.o} +in @code{EXTRA-PARTS}. +@xref{Initialization}. + +@findex MULTILIB_OPTIONS +@item MULTILIB_OPTIONS +For some targets, invoking GCC in different ways produces objects +that can not be linked together. For example, for some targets GCC +produces both big and little endian code. For these targets, you must +arrange for multiple versions of @file{libgcc.a} to be compiled, one for +each set of incompatible options. When GCC invokes the linker, it +arranges to link in the right version of @file{libgcc.a}, based on +the command line options used. + +The @code{MULTILIB_OPTIONS} macro lists the set of options for which +special versions of @file{libgcc.a} must be built. Write options that +are mutually incompatible side by side, separated by a slash. Write +options that may be used together separated by a space. The build +procedure will build all combinations of compatible options. + +For example, if you set @code{MULTILIB_OPTIONS} to @samp{m68000/m68020 +msoft-float}, @file{Makefile} will build special versions of +@file{libgcc.a} using the following sets of options: @option{-m68000}, +@option{-m68020}, @option{-msoft-float}, @samp{-m68000 -msoft-float}, and +@samp{-m68020 -msoft-float}. + +@findex MULTILIB_DIRNAMES +@item MULTILIB_DIRNAMES +If @code{MULTILIB_OPTIONS} is used, this variable specifies the +directory names that should be used to hold the various libraries. +Write one element in @code{MULTILIB_DIRNAMES} for each element in +@code{MULTILIB_OPTIONS}. If @code{MULTILIB_DIRNAMES} is not used, the +default value will be @code{MULTILIB_OPTIONS}, with all slashes treated +as spaces. + +For example, if @code{MULTILIB_OPTIONS} is set to @samp{m68000/m68020 +msoft-float}, then the default value of @code{MULTILIB_DIRNAMES} is +@samp{m68000 m68020 msoft-float}. You may specify a different value if +you desire a different set of directory names. + +@findex MULTILIB_MATCHES +@item MULTILIB_MATCHES +Sometimes the same option may be written in two different ways. If an +option is listed in @code{MULTILIB_OPTIONS}, GCC needs to know about +any synonyms. In that case, set @code{MULTILIB_MATCHES} to a list of +items of the form @samp{option=option} to describe all relevant +synonyms. For example, @samp{m68000=mc68000 m68020=mc68020}. + +@findex MULTILIB_EXCEPTIONS +@item MULTILIB_EXCEPTIONS +Sometimes when there are multiple sets of @code{MULTILIB_OPTIONS} being +specified, there are combinations that should not be built. In that +case, set @code{MULTILIB_EXCEPTIONS} to be all of the switch exceptions +in shell case syntax that should not be built. + +For example the ARM processor cannot execute both hardware floating +point instructions and the reduced size THUMB instructions at the same +time, so there is no need to build libraries with both of these +options enabled. Therefore @code{MULTILIB_EXCEPTIONS} is set to: +@smallexample +*mthumb/*mhard-float* +@end smallexample + +@findex MULTILIB_EXTRA_OPTS +@item MULTILIB_EXTRA_OPTS +Sometimes it is desirable that when building multiple versions of +@file{libgcc.a} certain options should always be passed on to the +compiler. In that case, set @code{MULTILIB_EXTRA_OPTS} to be the list +of options to be used for all builds. If you set this, you should +probably set @code{CRTSTUFF_T_CFLAGS} to a dash followed by it. + +@findex NATIVE_SYSTEM_HEADER_DIR +@item NATIVE_SYSTEM_HEADER_DIR +If the default location for system headers is not @file{/usr/include}, +you must set this to the directory containing the headers. This value +should match the value of the @code{SYSTEM_INCLUDE_DIR} macro. + +@findex SPECS +@item SPECS +Unfortunately, setting @code{MULTILIB_EXTRA_OPTS} is not enough, since +it does not affect the build of target libraries, at least not the +build of the default multilib. One possible work-around is to use +@code{DRIVER_SELF_SPECS} to bring options from the @file{specs} file +as if they had been passed in the compiler driver command line. +However, you don't want to be adding these options after the toolchain +is installed, so you can instead tweak the @file{specs} file that will +be used during the toolchain build, while you still install the +original, built-in @file{specs}. The trick is to set @code{SPECS} to +some other filename (say @file{specs.install}), that will then be +created out of the built-in specs, and introduce a @file{Makefile} +rule to generate the @file{specs} file that's going to be used at +build time out of your @file{specs.install}. +@end table + +@node Host Fragment +@section Host Makefile Fragments +@cindex host makefile fragment +@cindex @file{x-@var{host}} + +The use of @file{x-@var{host}} fragments is discouraged. You should do +so only if there is no other mechanism to get the behavior desired. +Host fragments should never forcibly override variables set by the +configure script, as they may have been adjusted by the user. + +Variables provided for host fragments to set include: + +@table @code + +@item X_CFLAGS +@itemx X_CPPFLAGS +These are extra flags to pass to the C compiler and preprocessor, +respectively. They are used both when building GCC, and when compiling +things with the just-built GCC@. + +@item XCFLAGS +These are extra flags to use when building the compiler. They are not +used when compiling @file{libgcc.a}. However, they @emph{are} used when +recompiling the compiler with itself in later stages of a bootstrap. + +@item BOOT_LDFLAGS +Flags to be passed to the linker when recompiling the compiler with +itself in later stages of a bootstrap. You might need to use this if, +for instance, one of the front ends needs more text space than the +linker provides by default. + +@item EXTRA_PROGRAMS +A list of additional programs required to use the compiler on this host, +which should be compiled with GCC and installed alongside the front +ends. If you set this variable, you must also provide rules to build +the extra programs. + +@end table |