https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114591
Bug ID: 114591
Summary: rtl-reload introduce an extra load operation since
gcc-12
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: absoler at smail dot nju.edu.cn
Target Milestone: ---
Hi, I found such a case:
```
unsigned v1;
long long v2;
short func_1() {
v2 = v1;
return v2;
}
```
gcc-12 and gcc-13 would produce under -O2:
```
func_1:
mov 0x0(%rip),%eax # v1
mov %rax,0x0(%rip) # v2
movzwl 0x0(%rip),%eax # v1
```
and gcc-11's:
```
func_1:
mov 0x0(%rip),%edx # v1
mov %rdx,0x0(%rip) # v2
mov %rdx,%rax
```
I guess the latter is better? the second load of `v1` was introduced in
RTL-reload pass, maybe this pessimize the performance.
