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* [Bug tree-optimization/96681] New: Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables
@ 2020-08-18 16:36 gabravier at gmail dot com
2020-08-25 10:47 ` [Bug tree-optimization/96681] " rguenth at gcc dot gnu.org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: gabravier at gmail dot com @ 2020-08-18 16:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96681
Bug ID: 96681
Summary: Failure to optimize xor of comparisons with specific
constants to comparison of xor-ed of compared
variables
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
int f(int x, int y)
{
return (x < 0) ^ (y < 0);
}
This can be optimized to `return (x ^ y) < 0;`. LLVM does this transformation,
but GCC does not. This transformation can also be done with `return (x > -1) ^
(y > -1);`. There is also a similar transformation with `return (x > -1) ^ (y <
0);`, which can be optimized to `return ~(x ^ y) < 0;`.
^ permalink raw reply [flat|nested] 6+ messages in thread* [Bug tree-optimization/96681] Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables 2020-08-18 16:36 [Bug tree-optimization/96681] New: Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables gabravier at gmail dot com @ 2020-08-25 10:47 ` rguenth at gcc dot gnu.org 2021-01-15 13:22 ` jakub at gcc dot gnu.org ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: rguenth at gcc dot gnu.org @ 2020-08-25 10:47 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96681 Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Last reconfirmed| |2020-08-25 ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/96681] Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables 2020-08-18 16:36 [Bug tree-optimization/96681] New: Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables gabravier at gmail dot com 2020-08-25 10:47 ` [Bug tree-optimization/96681] " rguenth at gcc dot gnu.org @ 2021-01-15 13:22 ` jakub at gcc dot gnu.org 2021-01-15 20:11 ` cvs-commit at gcc dot gnu.org ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: jakub at gcc dot gnu.org @ 2021-01-15 13:22 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96681 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org Status|NEW |ASSIGNED --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Created attachment 49972 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49972&action=edit gcc11-pr96681.patch Untested fix. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/96681] Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables 2020-08-18 16:36 [Bug tree-optimization/96681] New: Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables gabravier at gmail dot com 2020-08-25 10:47 ` [Bug tree-optimization/96681] " rguenth at gcc dot gnu.org 2021-01-15 13:22 ` jakub at gcc dot gnu.org @ 2021-01-15 20:11 ` cvs-commit at gcc dot gnu.org 2021-01-15 20:14 ` jakub at gcc dot gnu.org 2022-11-28 22:42 ` pinskia at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: cvs-commit at gcc dot gnu.org @ 2021-01-15 20:11 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96681 --- Comment #2 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:5c046034e3ea61dd68965154a398f8f813daf8f2 commit r11-6738-g5c046034e3ea61dd68965154a398f8f813daf8f2 Author: Jakub Jelinek <jakub@redhat.com> Date: Fri Jan 15 21:10:44 2021 +0100 match.pd: Optimize (x < 0) ^ (y < 0) to (x ^ y) < 0 etc. [PR96681] This patch simplifies comparisons that test the sign bit xored together. If the comparisons are both < 0 or both >= 0, then we should xor the operands together and compare the result to < 0, if the comparisons are different, we should compare to >= 0. 2021-01-15 Jakub Jelinek <jakub@redhat.com> PR tree-optimization/96681 * match.pd ((x < 0) ^ (y < 0) to (x ^ y) < 0): New simplification. ((x >= 0) ^ (y >= 0) to (x ^ y) < 0): Likewise. ((x < 0) ^ (y >= 0) to (x ^ y) >= 0): Likewise. ((x >= 0) ^ (y < 0) to (x ^ y) >= 0): Likewise. * gcc.dg/tree-ssa/pr96681.c: New test. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/96681] Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables 2020-08-18 16:36 [Bug tree-optimization/96681] New: Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables gabravier at gmail dot com ` (2 preceding siblings ...) 2021-01-15 20:11 ` cvs-commit at gcc dot gnu.org @ 2021-01-15 20:14 ` jakub at gcc dot gnu.org 2022-11-28 22:42 ` pinskia at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: jakub at gcc dot gnu.org @ 2021-01-15 20:14 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96681 Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Status|ASSIGNED |RESOLVED --- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Fixed. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/96681] Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables 2020-08-18 16:36 [Bug tree-optimization/96681] New: Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables gabravier at gmail dot com ` (3 preceding siblings ...) 2021-01-15 20:14 ` jakub at gcc dot gnu.org @ 2022-11-28 22:42 ` pinskia at gcc dot gnu.org 4 siblings, 0 replies; 6+ messages in thread From: pinskia at gcc dot gnu.org @ 2022-11-28 22:42 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96681 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Target Milestone|--- |11.0 ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-11-28 22:42 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-08-18 16:36 [Bug tree-optimization/96681] New: Failure to optimize xor of comparisons with specific constants to comparison of xor-ed of compared variables gabravier at gmail dot com 2020-08-25 10:47 ` [Bug tree-optimization/96681] " rguenth at gcc dot gnu.org 2021-01-15 13:22 ` jakub at gcc dot gnu.org 2021-01-15 20:11 ` cvs-commit at gcc dot gnu.org 2021-01-15 20:14 ` jakub at gcc dot gnu.org 2022-11-28 22:42 ` pinskia at gcc dot gnu.org
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