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* [Bug tree-optimization/113176] New: `(n / 4) ? n / 4 : 0` is not optimized to just `n /4`
@ 2023-12-30 4:29 pinskia at gcc dot gnu.org
2023-12-30 4:44 ` [Bug tree-optimization/113176] " pinskia at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-30 4:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113176
Bug ID: 113176
Summary: `(n / 4) ? n / 4 : 0` is not optimized to just `n /4`
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take:
```
int unopt(int n) {
if (n / 4)
return n / 4;
else
return 0;
}
int unopt1(int n) {
return (n / 4) ? n / 4 : 0;
}
int opt(int n) {
return n / 4;
}
```
I would have expected unopt be transformed into opt but currently it is not.
This is because GCC decides to transform `(n / 4) != 0` into `(unsigned int) n
+ 3 > 6`.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/113176] `(n / 4) ? n / 4 : 0` is not optimized to just `n /4`
2023-12-30 4:29 [Bug tree-optimization/113176] New: `(n / 4) ? n / 4 : 0` is not optimized to just `n /4` pinskia at gcc dot gnu.org
@ 2023-12-30 4:44 ` pinskia at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-30 4:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113176
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I should note the non-constant case is already handled:
```
int unopt(int n, int c) {
if (n / c)
return n / c;
else
return 0;
}
```
It is just the constant case that has issues.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-12-30 4:29 [Bug tree-optimization/113176] New: `(n / 4) ? n / 4 : 0` is not optimized to just `n /4` pinskia at gcc dot gnu.org
2023-12-30 4:44 ` [Bug tree-optimization/113176] " pinskia at gcc dot gnu.org
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