[build, lto] Only accept -fuse-linker-plugin if linker supports -plugin (PR lto/46944)
Richard Guenther
rguenther@suse.de
Thu Mar 10 12:26:00 GMT 2011
On Thu, 10 Mar 2011, Rainer Orth wrote:
> After considerable discussion in this thread
>
> Unreviewed build, lto patch
> http://gcc.gnu.org/ml/gcc-patches/2011-02/msg00868.html
>
> Richard's recommendation was to only use the lto-plugin with known-good
> linkers supporting -plugin, i.e. GNU ld or gold >= 2.21.
>
> I'm extracting the binutils version number from gold --version since
> it's more familiar than the separate gold version number and provides a
> higher resolution than the gold version number that only changes once
> per binutils release.
>
> Here's the reworked patch that implements this suggestion. I couldn't
> check with gold yet since it doesn't work on Solaris so far, but
> i386-pc-solaris2.11 bootstraps with Sun ld and GNU ld 2.21 work as
> expected, i.e. the failure described in PR lto/46944 is gone.
>
> Ok for mainline?
If I read this patch correctly then
1) it doesn't change the condition under which lto-plugin/ is built
(good)
2) it makes -fuse-linker-plugin the default for and only for
known good linkers (GNU binutils >= 2.21) (good)
3) it makes it impossible to use -fuse-linker-plugin explicitly
for other linkers or linkers that were not installed during
configuring gcc (bad - esp. the latter)
can you please try avoiding 3) at this stage? Or is the whole
point of this patch 3) to be able to fix PR46944?
Ideally we'd reject broken linkers at runtime, but that would
require some major collect2 massaging (eventually falling back
to collect2 or simply reporting an error).
That said, I'm not 100% happy with 3) at this point (though
2) is very desirable).
Can we to fix 46944 change the dejagnu require-linker-plugin
to check if a linker plugin is used by default and not add
-fuse-linker-plugin?
Thanks,
Richard.
> Rainer
>
>
> 2011-02-05 Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
>
> PR lto/46944
> * configure.ac (gcc_cv_gld_major_version, gcc_cv_gld_minor):
> Handle in-tree gold.
> (ld_vers): Extract binutils version for gold.
> (gcc_cv_ld_hidden): Handle gold here.
> (gcc_cv_lto_plugin): Require gld or gold 2.21.
> * configure: Regenerate.
> * gcc.c [HAVE_LTO_PLUGIN] (PLUGIN_COND, PLUGIN_COND_CLOSE): Remove.
> (LINK_PLUGIN_SPEC): Define.
> Extract from LINK_COMMAND_SPEC, integrate PLUGIN_COND,
> PLUGIN_COND_CLOSE.
> [!HAVE_LTO_PLUGIN] (LINK_PLUGIN_SPEC): Define, reject
> -fuse-linker-plugin.
> (LINK_COMMAND_SPEC): Use it.
>
> diff -r bbab4a602b6f gcc/configure.ac
> --- a/gcc/configure.ac Sat Feb 26 09:27:25 2011 +0100
> +++ b/gcc/configure.ac Sat Mar 05 09:36:08 2011 +0100
> @@ -1967,7 +1967,8 @@
> esac
>
> AC_MSG_CHECKING(what linker to use)
> -if test "$gcc_cv_ld" = ../ld/ld-new$build_exeext; then
> +if test "$gcc_cv_ld" = ../ld/ld-new$build_exeext \
> + || test "$gcc_cv_ld" = ../gold/ld-new$build_exeext; then
> # Single tree build which includes ld. We want to prefer it
> # over whatever linker top-level may have detected, since
> # we'll use what we're building after installation anyway.
> @@ -1978,6 +1979,8 @@
> || grep 'EMUL = .*linux' ../ld/Makefile \
> || grep 'EMUL = .*lynx' ../ld/Makefile) > /dev/null; then
> in_tree_ld_is_elf=yes
> + elif test "$ld_is_gold" = yes; then
> + in_tree_ld_is_elf=yes
> fi
> for f in $gcc_cv_ld_bfd_srcdir/configure $gcc_cv_ld_gld_srcdir/configure $gcc_cv_ld_gld_srcdir/configure.in $gcc_cv_ld_gld_srcdir/Makefile.in
> do
> @@ -2192,11 +2195,23 @@
> changequote(,)dnl
> if test $in_tree_ld != yes ; then
> ld_ver=`$gcc_cv_ld --version 2>/dev/null | sed 1q`
> - if test x"$ld_is_gold" = xyes; then
> - gcc_cv_ld_hidden=yes
> - elif echo "$ld_ver" | grep GNU > /dev/null; then
> - ld_vers=`echo $ld_ver | sed -n \
> - -e 's,^.*[ ]\([0-9][0-9]*\.[0-9][0-9]*.*\)$,\1,p'`
> + if echo "$ld_ver" | grep GNU > /dev/null; then
> + if test x"$ld_is_gold" = xyes; then
> + # GNU gold --version looks like this:
> + #
> + # GNU gold (GNU Binutils 2.21.51.20110225) 1.11
> + #
> + # We extract the binutils version which is more familiar and specific
> + # than the gold version.
> + ld_vers=`echo $ld_ver | sed -n \
> + -e 's,^.*[ ]\([0-9][0-9]*\.[0-9][0-9]*.*\)) .*$,\1,p'`
> + else
> + # GNU ld --version looks like this:
> + #
> + # GNU ld (GNU Binutils) 2.21.51.20110225
> + ld_vers=`echo $ld_ver | sed -n \
> + -e 's,^.*[ ]\([0-9][0-9]*\.[0-9][0-9]*.*\)$,\1,p'`
> + fi
> ld_date=`echo $ld_ver | sed -n 's,^.*\([2-9][0-9][0-9][0-9]\)[-]*\([01][0-9]\)[-]*\([0-3][0-9]\).*$,\1\2\3,p'`
> ld_vers_major=`expr "$ld_vers" : '\([0-9]*\)'`
> ld_vers_minor=`expr "$ld_vers" : '[0-9]*\.\([0-9]*\)'`
> @@ -2235,7 +2250,9 @@
> fi
> else
> gcc_cv_ld_hidden=yes
> - if echo "$ld_ver" | grep GNU > /dev/null; then
> + if test x"$ld_is_gold" = xyes; then
> + :
> + elif echo "$ld_ver" | grep GNU > /dev/null; then
> if test 0"$ld_date" -lt 20020404; then
> if test -n "$ld_date"; then
> # If there was date string, but was earlier than 2002-04-04, fail
> @@ -3176,14 +3193,14 @@
> gcc_cv_lto_plugin=no
> if test -f liblto_plugin.la; then
> if test $in_tree_ld = yes -a x"$ORIGINAL_PLUGIN_LD_FOR_TARGET=" = x"$gcc_cv_ld"; then
> - if test x"$ld_is_gold" = xyes; then
> - gcc_cv_lto_plugin=yes
> - elif test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 21 -o "$gcc_cv_gld_major_version" -gt 2; then \
> + if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 21 -o "$gcc_cv_gld_major_version" -gt 2; then
> gcc_cv_lto_plugin=yes
> fi
> - # Check if the linker supports --plugin-opt option
> - elif $ORIGINAL_PLUGIN_LD_FOR_TARGET --help 2>/dev/null | grep plugin-opt > /dev/null; then
> - gcc_cv_lto_plugin=yes
> + elif echo "$ld_ver" | grep GNU > /dev/null; then
> + # Require GNU ld or gold 2.21 for plugin support.
> + if test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 21; then
> + gcc_cv_lto_plugin=yes
> + fi
> fi
> fi
> if test x"$gcc_cv_lto_plugin" = xyes; then
> diff -r bbab4a602b6f gcc/gcc.c
> --- a/gcc/gcc.c Sat Feb 26 09:27:25 2011 +0100
> +++ b/gcc/gcc.c Sat Mar 05 09:36:08 2011 +0100
> @@ -623,16 +623,20 @@
>
> /* Conditional to test whether plugin is used or not.
> FIXME: For slim LTO we will need to enable plugin unconditionally. This
> - still cause problems with PLUGIN_LD != LD and when plugin is built but
> + still causes problems with PLUGIN_LD != LD and when plugin is built but
> not useable. For GCC 4.6 we don't support slim LTO and thus we can enable
> - plugin only when LTO is enabled. We still honor explicit
> - -fuse-linker-plugin. */
> + plugin only when LTO is enabled. */
> #ifdef HAVE_LTO_PLUGIN
> -#define PLUGIN_COND "!fno-use-linker-plugin:%{flto|flto=*|fuse-linker-plugin"
> -#define PLUGIN_COND_CLOSE "}"
> +#define LINK_PLUGIN_SPEC \
> + "%{!fno-use-linker-plugin:%{flto|flto=*|fuse-linker-plugin: \
> + -plugin %(linker_plugin_file) \
> + -plugin-opt=%(lto_wrapper) \
> + -plugin-opt=-fresolution=%u.res \
> + %{!nostdlib:%{!nodefaultlibs:%:pass-through-libs(%(link_gcc_c_sequence))}} \
> + }}"
> #else
> -#define PLUGIN_COND "fuse-linker-plugin"
> -#define PLUGIN_COND_CLOSE ""
> +#define LINK_PLUGIN_SPEC "%{fuse-linker-plugin:\
> + %e-fuse-linker-plugin is not supported in this configuration}"
> #endif
>
>
> @@ -648,14 +652,9 @@
> #ifndef LINK_COMMAND_SPEC
> #define LINK_COMMAND_SPEC "\
> %{!fsyntax-only:%{!c:%{!M:%{!MM:%{!E:%{!S:\
> - %(linker) \
> - %{"PLUGIN_COND": \
> - -plugin %(linker_plugin_file) \
> - -plugin-opt=%(lto_wrapper) \
> - -plugin-opt=-fresolution=%u.res \
> - %{!nostdlib:%{!nodefaultlibs:%:pass-through-libs(%(link_gcc_c_sequence))}} \
> - }"PLUGIN_COND_CLOSE" \
> - %{flto|flto=*:%<fcompare-debug*} \
> + %(linker) " \
> + LINK_PLUGIN_SPEC \
> + "%{flto|flto=*:%<fcompare-debug*} \
> %{flto} %{flto=*} %l " LINK_PIE_SPEC \
> "%X %{o*} %{e*} %{N} %{n} %{r}\
> %{s} %{t} %{u*} %{z} %{Z} %{!nostdlib:%{!nostartfiles:%S}}\
>
>
>
--
Richard Guenther <rguenther@suse.de>
Novell / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 - GF: Markus Rex
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