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* [Bug tree-optimization/114702] New: Missed optimization: fail to infer c - b != if a + b != c
@ 2024-04-12 13:50 xxs_chy at outlook dot com
2024-04-12 22:33 ` [Bug tree-optimization/114702] " pinskia at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: xxs_chy at outlook dot com @ 2024-04-12 13:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114702
Bug ID: 114702
Summary: Missed optimization: fail to infer c - b != if a + b
!= c
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/58rxGaabW
```
void src(int a, int b){
if(b + a == 32){
return;
}else{
if(32 - b == a)
dummy();
else
dummy1();
}
}
```
Obviously, "32 - b == a" is false. We can get:
```
void tgt(int a, int b){
if(b + a == 32){
return;
}else{
dummy1();
}
}
```
This is a real-world dead code after inlining functions in QEMU.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/114702] Missed optimization: fail to infer c - b != if a + b != c
2024-04-12 13:50 [Bug tree-optimization/114702] New: Missed optimization: fail to infer c - b != if a + b != c xxs_chy at outlook dot com
@ 2024-04-12 22:33 ` pinskia at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-04-12 22:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114702
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Ever confirmed|0 |1
Last reconfirmed| |2024-04-12
Severity|normal |enhancement
Status|UNCONFIRMED |NEW
Blocks| |85316
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
VRP does some of this but I am not sure if it can be expanded to be handle more
general value relations here
Folding statement: if (_2 == a_5(D))
Registering value_relation (_2 == a_5(D)) on (3->4)
Registering value_relation (_2 != a_5(D)) on (3->5)
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85316
[Bug 85316] [meta-bug] VRP range propagation missed cases
^ permalink raw reply [flat|nested] 2+ messages in thread
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2024-04-12 13:50 [Bug tree-optimization/114702] New: Missed optimization: fail to infer c - b != if a + b != c xxs_chy at outlook dot com
2024-04-12 22:33 ` [Bug tree-optimization/114702] " pinskia at gcc dot gnu.org
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