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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 tree-optimization/90693] Missing popcount simplifications
Date: Mon, 20 Nov 2023 09:04:13 +0000 [thread overview]
Message-ID: <bug-90693-4-M7OQDVxJng@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-90693-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90693
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:d0b6b7f8a6b8115b033441590a6304fb088d193c
commit r14-5612-gd0b6b7f8a6b8115b033441590a6304fb088d193c
Author: Jakub Jelinek <jakub@redhat.com>
Date: Mon Nov 20 10:00:09 2023 +0100
tree-ssa-math-opts: popcount (X) == 1 to (X ^ (X - 1)) > (X - 1)
optimization [PR90693]
Per the earlier discussions on this PR, the following patch folds
popcount (x) == 1 (and != 1) into (x ^ (x - 1)) > x - 1 (or <=)
if the corresponding popcount optab isn't implemented (I think any
double-word popcount or call will be necessarily slower than the
above cheap 3 op check and even for -Os larger or same size).
I've noticed e.g. C++ aligned new starts with std::has_single_bit
which does popcount (x) == 1.
As a follow-up, I'm considering changing in this routine the popcount
call to IFN_POPCOUNT with 2 arguments and during expansion test costs.
2023-11-20 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/90693
* tree-ssa-math-opts.cc (match_single_bit_test): New function.
(math_opts_dom_walker::after_dom_children): Call it for EQ_EXPR
and NE_EXPR assignments and GIMPLE_CONDs.
* gcc.target/i386/pr90693.c: New test.
next prev parent reply other threads:[~2023-11-20 9:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <bug-90693-4@http.gcc.gnu.org/bugzilla/>
2021-08-10 23:15 ` pinskia at gcc dot gnu.org
2023-11-20 9:04 ` cvs-commit at gcc dot gnu.org [this message]
2023-11-20 9:04 ` cvs-commit at gcc dot gnu.org
2023-11-20 14:10 ` wilco at gcc dot gnu.org
2023-11-20 17:01 ` jakub at gcc dot gnu.org
2024-01-01 12:41 ` piotrsiupa at gmail dot com
2024-01-03 15:34 ` jakub at gcc dot gnu.org
2024-01-05 10:17 ` cvs-commit at gcc dot gnu.org
2024-01-07 12:56 ` piotrsiupa at gmail dot com
2024-03-04 7:42 ` pinskia at gcc dot gnu.org
2024-03-04 16:41 ` pinskia at gcc dot gnu.org
2024-03-04 22:55 ` pinskia at gcc dot gnu.org
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