Re: [PATCH] x86-64: Compile branred.c with -mprefer-vector-width=128 [BZ #24603]

[Joseph Myers <joseph at codesourcery dot com>]

On Mon, 17 Jun 2019, H.J. Lu wrote:

> On Mon, Jun 17, 2019 at 12:12 PM Florian Weimer <fweimer@redhat.com> wrote:
> >
> > * Jeff Law:
> >
> > > ISTM that 8, 9, 10 would use the new flag.  11 would issue an error
> > > which would trigger a reinvestigation roughly a year from now.
> >
> > Do you suggest to put in a #warning for GCC 11, so that people can
> > configure with --disable-werror and still build with GCC 11?
> >
> > Given that GCC 11 will probably add other warnings that break the build,
> > this proposal isn't entirely unreasonable (even though I generally
> > dislike such time bombs).
> >
> 
> Since there is no issue in source, this requires an artificial warning
> purely based on GCC version.   We can place GCC version check in
> configure script with explicit -mprefer-vector-width=128 support.
> 
> --enable-mprefer-vector-width:
> 
> 1.  Default.  For GCC 8, 9, 10, use -mprefer-vector-width=128.
> For GCC 11 and above, issue a configure error.

I don't think anything causing the build to break with newer GCC versions 
is appropriate.

-- 
Joseph S. Myers
joseph@codesourcery.com