https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127012
Bug ID: 127012
Summary: Missed X86 optimization of or to use lea when x < CST
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: kaelfandrew at gmail dot com
Target Milestone: ---
https://godbolt.org/z/EKszhKeE6
```c
#define TYPE unsigned
#define N 4
#define CST ((TYPE)1 << N)
TYPE
src (TYPE x)
{
if (x >= CST)
__builtin_unreachable ();
return x | CST;
}
```
With -O2, GCC produce this assembly:
```
"src":
mov eax, edi
or eax, 16
ret
```
While Clang -O2:
```
src:
lea eax, [rdi + 16]
ret
```
Clang on x86_64 does this for TYPEs u8, u32, u64, u128.
