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* [Bug c/108818] New: [aarch64] use a extra mov instruction compare to llvm
@ 2023-02-16 10:30 zhongyunde at huawei dot com
2023-02-16 17:31 ` [Bug rtl-optimization/108818] " pinskia at gcc dot gnu.org
2023-02-16 17:42 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: zhongyunde at huawei dot com @ 2023-02-16 10:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108818
Bug ID: 108818
Summary: [aarch64] use a extra mov instruction compare to llvm
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: zhongyunde at huawei dot com
Target Milestone: ---
* test:https://gcc.godbolt.org/z/res6aTYqP
```
unsigned sel(unsigned X) {
return X == 6 ? 6 : 8;
}
```
* gcc:
```
sel:
cmp w0, 6
mov w1, 8
mov w0, 6
csel w0, w1, w0, ne
ret
```
* llvm:
```
sel: // @sel
mov w8, #8
cmp w0, #6
csel w0, w0, w8, eq
ret
```
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/108818] [aarch64] use a extra mov instruction compare to llvm
2023-02-16 10:30 [Bug c/108818] New: [aarch64] use a extra mov instruction compare to llvm zhongyunde at huawei dot com
@ 2023-02-16 17:31 ` pinskia at gcc dot gnu.org
2023-02-16 17:42 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-02-16 17:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108818
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |rtl-optimization
Keywords| |missed-optimization
Severity|normal |enhancement
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug rtl-optimization/108818] [aarch64] use a extra mov instruction compare to llvm
2023-02-16 10:30 [Bug c/108818] New: [aarch64] use a extra mov instruction compare to llvm zhongyunde at huawei dot com
2023-02-16 17:31 ` [Bug rtl-optimization/108818] " pinskia at gcc dot gnu.org
@ 2023-02-16 17:42 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-02-16 17:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108818
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2023-02-16
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed, note it is only related to return/argument passing really.
That is the following does not produce any extra mov's:
```
void sel(unsigned *X) {
*X = *X == 6 ? 6 : 8;
}
```
Was this a reducation of a bigger application? Or was it found by making
testcases?
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-02-16 10:30 [Bug c/108818] New: [aarch64] use a extra mov instruction compare to llvm zhongyunde at huawei dot com
2023-02-16 17:31 ` [Bug rtl-optimization/108818] " pinskia at gcc dot gnu.org
2023-02-16 17:42 ` pinskia at gcc dot gnu.org
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