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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/97707] avx512 math function invoked even if -mprefer-vector-width=256 specified
Date: Wed, 04 Nov 2020 08:24:04 +0000 [thread overview]
Message-ID: <bug-97707-4-EcjYL4T75M@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-97707-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97707
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
CC| |jakub at gcc dot gnu.org
Blocks| |53947
Target| |x86_64-*-* i?86-*-*
Ever confirmed|0 |1
Last reconfirmed| |2020-11-04
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
-mprefer-vector-width=256 means it _prefers_ AVX256 but then in case
vectorization fails (for whatever bogus reason) with AVX256 it will still try
AVX512:
static unsigned int
ix86_autovectorize_vector_modes (vector_modes *modes, bool all)
{
if (TARGET_AVX512F && !TARGET_PREFER_AVX256)
{
modes->safe_push (V64QImode);
modes->safe_push (V32QImode);
modes->safe_push (V16QImode);
}
else if (TARGET_AVX512F && all)
{
modes->safe_push (V32QImode);
modes->safe_push (V16QImode);
modes->safe_push (V64QImode);
}
the odd thing is that the dumps suggest we use V4DFmode. We use a VF of 8
because of V8SI and it seems that call vectorization then chooses the
larger vector mode because it is supported - it seems to have its own
idea of costing there (probably reasonable).
Do you think this is a bad idea?
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations
next prev parent reply other threads:[~2020-11-04 8:24 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-03 18:05 [Bug tree-optimization/97707] New: avx12 " vincenzo.innocente at cern dot ch
2020-11-04 8:24 ` rguenth at gcc dot gnu.org [this message]
2020-11-04 8:47 ` [Bug tree-optimization/97707] avx512 " jakub at gcc dot gnu.org
2020-11-04 8:57 ` vincenzo.innocente at cern dot ch
2020-11-04 8:59 ` jakub at gcc dot gnu.org
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