https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102473
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |marxin at gcc dot gnu.org
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Hongtao.liu from comment #2)
> (In reply to Richard Biener from comment #1)
> > Looks like at least on Zen movs[hl]dup is on the integer domain so we'l see
> > a domain crossing penalty here(?). But since this is a generic arch/tuning
> > regression the SSE2 code path should be what matters - on the committed
> > testcase I see
> >
> > foo:
> > .LFB572:
> > .cfi_startproc
> > pxor %xmm0, %xmm0
> > addss (%rdi), %xmm0
> > addss 4(%rdi), %xmm0
> > addss 8(%rdi), %xmm0
> > addss 12(%rdi), %xmm0
> > ret
> >
> > where it seems that the vectorizer doesn't pick up the reduction pattern.
> >
> Guess you're use O3, -ffast-math is needed for v4sf reduction
> https://godbolt.org/z/sjf4Pncna
I was looking at the testcase as compiled by the testsuite.
It seems that adding __attribute__((optimize("tree-vectorize"))) makes the
loop no longer vectorized as it at the moment cancels -ffast-math.
IIRC when Martin commits his optimize() re-org it will no longer do that.
