[build, lto] Only accept -fuse-linker-plugin if linker supports -plugin (PR lto/46944)

[Richard Guenther]

On Mon, 21 Mar 2011, Rainer Orth wrote:

> Richard Guenther <rguenther@suse.de> writes:
> 
> > On Fri, 18 Mar 2011, Rainer Orth wrote:
> >
> >> Richard Guenther <richard.guenther@gmail.com> writes:
> >> 
> >> > It seemed to have disabled linker-plugin support for old binutils
> >> > with --with-plugin-ld=/usr/local/bin/gold, explicit -fuse-linker-plugin says
> >> > it is not supported.  The system linker does not have plugin support
> >> > (nor gold).  /usr/local has gold from binutils 2.20.50.xxx.  So it seems that
> >> >
> >> >     # Allow -fuse-linker-plugin to enable plugin support in GNU gold 2.20.
> >> >     elif test "$ld_is_gold" = yes -a "$ld_vers_major" -eq 2 -a
> >> > "$ld_vers_minor" -eq 20; then
> >> >       gcc_cv_lto_plugin=1
> >> >     fi
> >> >
> >> > only allows explicit -fuse-linker-plugin for recent gold but based on checking
> >> > the system linker version (instead of that of --with-plugin-ld).  I'd say
> >> > allow explicit -fuse-linker-plugin always if --with-plugin-ld is specified.
> >> 
> >> Agreed.  I'll have a look and refrain from installing on 4.6 until this
> >> is resolved.  I wasn't even aware of --with-plugin-ld, which isn't
> >> documented in install.texi ;-(  This stuff seems insanely complicated to
> >> me, though: which user is supposed to deal with such complications?
> >
> > It's sort of historic ... with plugin support for GNU ld we can probably
> > drop this flag for 4.7 (eventually I'd even like to enforce the use
> > of the plugin all the time or disable LTO, just for the sake of reducing
> > the testing and bugreporting matrix ...).
> >
> > I just noticed the above with the LTO setup of our SPEC testers
> > which are using somewhat old system tools.
> 
> Here's the patch I came up with.  It is on top of the previous one, so
> if we want to backport to 4.6 later, both are necessary.
> 
> It also fixes a typo in the in_tree_ld case, which can never have worked.
> 
> Tested by i386-pc-solaris2.11 bootstraps with either Sun ld or gld 2.21,
> and by configuring with Sun ld --with-plugin-ld=gld-2.21 and obvserving
> HAVE_LTO_PLUGIN being set to 1.
> 
> Ok for mainline now and 4.6 after some soak time?

Ok for trunk and 4.6.1.

Thanks,
Richard.

> Thanks.
> 	Rainer
> 
> 
> 2011-03-19  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
> 
> 	* configure.ac (gcc_cv_lto_plugin): Fix typo.
> 	Allow -fuse-linker-plugin for non-default plugin linker.
> 	* configure: Regenerate.
> 
> diff -r 916a52719d80 gcc/configure.ac
> --- a/gcc/configure.ac	Sat Mar 19 08:54:19 2011 +0100
> +++ b/gcc/configure.ac	Sun Mar 20 13:37:38 2011 +0100
> @@ -3192,14 +3192,14 @@
>  AC_MSG_CHECKING(linker plugin support)
>  gcc_cv_lto_plugin=0
>  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 $in_tree_ld = yes -a x"$ORIGINAL_PLUGIN_LD_FOR_TARGET" = x"$gcc_cv_ld"; then
>      if test "$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=2
>      elif test "$ld_is_gold" = yes -a "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -eq 20; then
>        gcc_cv_lto_plugin=1
>  
>      fi
> -  elif echo "$ld_ver" | grep GNU > /dev/null; then
> +  elif test x"$ORIGINAL_PLUGIN_LD_FOR_TARGET" = x"$gcc_cv_ld" && echo "$ld_ver" | grep GNU > /dev/null; then
>      # Require GNU ld or gold 2.21+ for plugin support by default.
>      if test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 21; then
>        gcc_cv_lto_plugin=2
> @@ -3207,6 +3207,10 @@
>      elif test "$ld_is_gold" = yes -a "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -eq 20; then
>        gcc_cv_lto_plugin=1
>      fi
> +  elif test x"$ORIGINAL_PLUGIN_LD_FOR_TARGET" != x"$gcc_cv_ld"; then
> +    # Allow -fuse-linker-plugin if plugin linker differs from
> +    # default/specified linker.
> +    gcc_cv_lto_plugin=1
>    fi
>  fi
>  AC_DEFINE_UNQUOTED(HAVE_LTO_PLUGIN, $gcc_cv_lto_plugin,
> 
> 
> 

-- 
Richard Guenther <rguenther@suse.de>
Novell / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746 - GF: Markus Rex