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

[Richard Guenther <rguenther@suse.de>]

On Mon, 30 May 2011, Rainer Orth wrote:

> Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> writes:
> 
> > Richard Guenther <richard.guenther@gmail.com> writes:
> >
> >> I think we should do the linker version checks which relate to linker-plugin
> >> use on the plugin-linker instead.  So if I specify a separate but known
> >> buggy linker I don't want it to be used by default.
> >
> > Here's a patch that does this.  I'm not at all happy with the patch
> > since it partially duplicates the logic to determine linker version
> > numbers.  While this could (and probably should) be generalized along
> > the lines of gcc_GAS_CHECK_FEATURE and gcc_GAS_VERSION_GTE_IFELSE, even
> > that wouldn't help immediately since such autoconf macros would still
> > $gcc_cv_ld.  As far as I can see, all those linker checks could
> > massively benefit from an overhaul to use gcc_LD_CHECK_FEATURE
> > etc.macros, but that's not something I want to attack.  It's especially
> > messy that there are two sets of version variables for in-tree and
> > external linkers.  Probably fodder for the build maintainers.
> >
> > Anyway, here's what I've got.  Tested by configuring with
> >
> > * no --with-ld arg (i.e. /usr/ccs/bin/ld)
> >
> > * --with-ld=/path/to/gld-2.21 --with-gnu-ld
> >
> > * --with-plugin-ld=/path/to/gld-2.21
> >
> > * --with-ld=/path/to/gld-2.21 --with-gnu-ld --with-plugin-ld=/usr/ccs/bin/ld
> >
> > and checking HAVE_LTO_PLUGIN in auto-host.h (0, 2, 2, 0).
> >
> > I haven't found if there are provisions for in-tree gold, though, and
> > still cannot test that.
> [...]
> > Could the whole bunch eventually be backported to the 4.6 branch?
> >
> > 	http://gcc.gnu.org/ml/gcc-patches/2011-03/msg00759.html
> >         http://gcc.gnu.org/ml/gcc-patches/2011-03/msg01890.html
> >         http://gcc.gnu.org/ml/gcc-patches/2011-03/msg01250.html
> >
> > and this one?
> 
> This question remains: is this series appropriate for the 4.6 branch or
> should it stay on mainline only?

I think it should stay on mainline for now.

Richard.