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From: "cvs-commit at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/78794] [7 Regression] We noticed ~9% regression in 32-bit mode for 462.libquntum on Avoton after r243202
Date: Wed, 28 Jun 2023 10:08:54 +0000 [thread overview]
Message-ID: <bug-78794-4-tt9NPJn4jV@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-78794-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78794
--- Comment #12 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Roger Sayle <sayle@gcc.gnu.org>:
https://gcc.gnu.org/g:c027592d39b2968005aa28bc84a946bab2668db8
commit r14-2158-gc027592d39b2968005aa28bc84a946bab2668db8
Author: Roger Sayle <roger@nextmovesoftware.com>
Date: Wed Jun 28 11:07:47 2023 +0100
i386: Fix FAIL of gcc.target/i386/pr78794.c on ia32.
This patch fixes that FAIL of gcc.target/i386/pr78794.c on ia32, which
is caused by minor STV rtx_cost differences with -march=silvermont.
It turns out that generic tuning results in pandn, but the lack of
accurate parameterization for COMPARE in compute_convert_gain combined
with small differences in scalar<->SSE costs on silvermont results in
this DImode chain not being converted.
The solution is to provide more accurate costs/gains for converting
(DImode and SImode) comparisons.
I'd been holding off of doing this as I'd thought it would be possible
to turn pandn;ptestz into ptestc (for an even bigger scalar-to-vector
win) but I've recently realized that these optimizations (as I've
implemented them) occur in the wrong order (stv2 occurs after
combine), so it isn't easy for STV to convert CCZmode into CCCmode.
Doh! Perhaps something can be done in peephole2.
2023-06-28 Roger Sayle <roger@nextmovesoftware.com>
gcc/ChangeLog
PR target/78794
* config/i386/i386-features.cc (compute_convert_gain): Provide
more accurate gains for conversion of scalar comparisons to
PTEST.
parent reply other threads:[~2023-06-28 10:08 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <bug-78794-4@http.gcc.gnu.org/bugzilla/>]
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