https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113487
Bug ID: 113487
Summary: Missed optimization:simplify demanded bits on
multi-use instructions like select
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 example: https://godbolt.org/z/EfKrTbK77
Based on common demanded bits from s&8 and s&16,
```
void src(bool c, unsigned a, unsigned b) {
unsigned s = c ? a & 24 : b & 25;
use(s & 8);
use(s & 16);
}
```
can be folded to:
```
void tgt(bool c, unsigned a, unsigned b) {
unsigned s = c ? a : b ;
use(s & 8);
use(s & 16);
}
```
Both LLVM and GCC missed this optimization opportunity.
