[m-rev.] for review: Make link-time optimisation with gcc work.

[Peter Wang]

On Tue, 28 Jan 2020 15:12:46 +1100 (AEDT), Julien Fischer <jfischer at opturion.com> wrote:
> 
> Hi Peter,
> 
> On Tue, 28 Jan 2020, Peter Wang wrote:
> 
> > configure.ac:
> >    Add -flto to LINK_SHARED_OBJ and LINK_SHARED_OBJ_SH commands
> >    when LTO is enabled with gcc.
> >
> >    Search for and use LTO-aware gcc-ar, gcc-ranlib and gcc-nm
> >    programs in place of the normal tools.
> >
> > diff --git a/configure.ac b/configure.ac
> > index 3e7e10c09..6dbee8860 100644
> > --- a/configure.ac
> > +++ b/configure.ac
> > @@ -5348,7 +5348,19 @@ if test "$mercury_cv_lto" = "yes"; then
> >             CFLAGS_FOR_LTO="-GL"
> >             LDFLAGS_FOR_LTO="-LTCG"
> >             ;;
> > -        gcc*|clang*)
> > +        gcc*)
> > +            CFLAGS_FOR_LTO="-flto"
> > +            LDFLAGS_FOR_LTO="-flto"
> > +            LINK_SHARED_OBJ="$LINK_SHARED_OBJ -flto"
> > +            LINK_SHARED_OBJ_SH="$LINK_SHARED_OBJ_SH -flto"
> > +            AC_CHECK_TOOL([GCC_AR], [gcc-ar], [])
> > +            AC_CHECK_TOOL([GCC_RANLIB], [gcc-ranlib], [])
> > +            AC_CHECK_TOOL([GCC_NM], [gcc-nm], [])
> 
> 
> Is that going to work in situations where the gcc executable is not
> named gcc.  (For Homebrew, it is named gcc-9, gcc-8 etc.)
> (We don't need to support that case now however.)

I don't know. As long as gcc-ar etc. are still available without the
version suffix, otherwise I assume they won't be found.

Peter