On Mon, May 23, 2022 at 10:00 AM Uros Bizjak <ubiz...@gmail.com> wrote:
>
> On Mon, May 23, 2022 at 9:16 AM Roger Sayle <ro...@nextmovesoftware.com>
> wrote:
> >
> >
> > This patch is an alternate/supplementary fix to PR tree-optimization/105668
> > that provides a vcond_mask_v1titi optab/define_expand to the i386 backend.
> > An undocumented feature/bug of GCC's vectorization is that any target that
> > provides a vec_cmpeq<mode><mode> has to also provide a matching
> > vcond_mask<mode><mode>. This backend patch preserves the status quo,
> > rather than fixes the underlying problem.
>
> IIRC, I also hit this issue a while ago. I was under impression it was
> fixed in the meantime, but looks I was wrong.
It's generally prefered to have vec_cmp* and vcond_mask over
vcond when the target will end up doing the compare and select
in different instructions (IIRC the x86 ISA has no combined
compare & select instructions).
So it might be interesting to see if we can remove the vcond{,u,eq}
expanders (and fill in missing vec_cmp and vcond_mask patterns).
Richard.
> > One aspect of this clean-up is that ix86_expand_sse_movcc provides
> > fallback implementations using pand/pandn/por that effectively make
> > V2DImode and V1TImode vcond_mask available on any TARGET_SSE2, not
> > just TARGET_SSE4_2. This allows a simplification as V2DI mode can
> > be handled by using a VI_128 mode iterator instead of a VI124_128
> > mode iterator, and instead this define_expand is effectively renamed
> > to provide a V1TImode vcond_mask expander (as V1TI isn't in VI_128).
> >
> > This patch has been tested on x86_64-pc-linux-gnu with make bootstrap
> > and make -k check, both with and without --target_board=unix{-m32} with
> > no new failures. The new test case is identical to the middle-end patch,
> > so if both patches are approved, this'll be committed only once.
> > Ok for mainline?
>
> OK.
>
> Thanks,
> Uros.
>
> >
> >
> > 2022-05-23 Roger Sayle <ro...@nextmovesoftware.com>
> >
> > gcc/ChangeLog
> > PR tree-optimization/105668
> > * config/i386/i386-expand.cc (ix86_expand_sse_movcc): Support
> > V1TImode, just like V2DImode.
> > * config/i386/sse.md (vcond_mask_<mode>Msseintvecmodelower>):
> > Use VI_128 mode iterator instead of VI124_128 to include V2DI.
> > (vcond_mask_v2div2di): Delete.
> > (vcond_mask_v1tiv1ti): New define_expand.
> >
> > gcc/testsuite/ChangeLog
> > PR tree-optimization/105668
> > * gcc.target/i386/pr105668.c: New test case.
> >
> >
> > Roger
> > --
> >
