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* [Bug tree-optimization/114797] New: Missed optimization : fail to merge memset with unrelated clobber
@ 2024-04-21 17:20 xxs_chy at outlook dot com
2024-04-21 19:26 ` [Bug tree-optimization/114797] " pinskia at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: xxs_chy at outlook dot com @ 2024-04-21 17:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114797
Bug ID: 114797
Summary: Missed optimization : fail to merge memset with
unrelated clobber
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: xxs_chy at outlook dot com
Target Milestone: ---
Godbolt link: https://godbolt.org/z/E581jvaPs
Code like:
```
void src(char* config){
char stack[208];
memset(stack, 0, 184);
*config = 0;
memset(stack + 184, 0, 8);
use(stack);
}
```
can be transformed to
```
void tgt(char* config){
char stack[208];
memset(stack, 0, 192);
*config = 0;
use(stack);
}
```
GCC doesn't merge them even both memsets overlap:
https://godbolt.org/z/ffc6b8zqs
^ permalink raw reply [flat|nested] 4+ messages in thread* [Bug tree-optimization/114797] Missed optimization : fail to merge memset with unrelated clobber 2024-04-21 17:20 [Bug tree-optimization/114797] New: Missed optimization : fail to merge memset with unrelated clobber xxs_chy at outlook dot com @ 2024-04-21 19:26 ` pinskia at gcc dot gnu.org 2024-04-21 19:55 ` xxs_chy at outlook dot com 2024-04-21 19:58 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-04-21 19:26 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114797 Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |DUPLICATE --- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> --- GCC does not even merge without an unrelated clobber yet. *** This bug has been marked as a duplicate of bug 49872 *** ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/114797] Missed optimization : fail to merge memset with unrelated clobber 2024-04-21 17:20 [Bug tree-optimization/114797] New: Missed optimization : fail to merge memset with unrelated clobber xxs_chy at outlook dot com 2024-04-21 19:26 ` [Bug tree-optimization/114797] " pinskia at gcc dot gnu.org @ 2024-04-21 19:55 ` xxs_chy at outlook dot com 2024-04-21 19:58 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: xxs_chy at outlook dot com @ 2024-04-21 19:55 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114797 --- Comment #2 from XChy <xxs_chy at outlook dot com> --- It looks like for completely overlapped memset, it's merged: https://godbolt.org/z/4r7Eqr1Ee With clobber, that's not the case: https://godbolt.org/z/8jhaEbKqo ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/114797] Missed optimization : fail to merge memset with unrelated clobber 2024-04-21 17:20 [Bug tree-optimization/114797] New: Missed optimization : fail to merge memset with unrelated clobber xxs_chy at outlook dot com 2024-04-21 19:26 ` [Bug tree-optimization/114797] " pinskia at gcc dot gnu.org 2024-04-21 19:55 ` xxs_chy at outlook dot com @ 2024-04-21 19:58 ` pinskia at gcc dot gnu.org 2 siblings, 0 replies; 4+ messages in thread From: pinskia at gcc dot gnu.org @ 2024-04-21 19:58 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114797 --- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to XChy from comment #2) > It looks like for completely overlapped memset, it's merged: > https://godbolt.org/z/4r7Eqr1Ee > With clobber, that's not the case: https://godbolt.org/z/8jhaEbKqo Yes for the secondary memset that is completely overlapping can be removed. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2024-04-21 19:58 UTC | newest] Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2024-04-21 17:20 [Bug tree-optimization/114797] New: Missed optimization : fail to merge memset with unrelated clobber xxs_chy at outlook dot com 2024-04-21 19:26 ` [Bug tree-optimization/114797] " pinskia at gcc dot gnu.org 2024-04-21 19:55 ` xxs_chy at outlook dot com 2024-04-21 19:58 ` pinskia at gcc dot gnu.org
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