https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127082
Bug ID: 127082
Summary: [Missed optimization] 96 % [-96, -65] yields [0, 95]
instead of [0, 31]
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: apowenq at gmail dot com
Target Milestone: ---
cat prog.c
int src(int v0_i8) {
if (!((-96 <= v0_i8) && (v0_i8 <= -65))) __builtin_unreachable();
int i0_i8 = (int)96 % v0_i8;
int i1_i8 = i0_i8 | -96;
return i1_i8;
}
```
# RANGE [irange] int [-96, -65] MASK 0x1f VALUE 0xffffffa0
int v0_i8_3(D) = v0_i8;
# RANGE [irange] int [0, 95] MASK 0x7f VALUE 0x0
i0_i8_4 = 96 % v0_i8_3(D);
```
GCC at O3:
"src":
xor edx, edx
mov eax, 96
idiv edi
mov eax, edx
or eax, -96
ret
LLVM at O3:
src:
mov eax, edi
ret
