https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114489
Bug ID: 114489
Summary: introduced redundant load facing different branches
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: absoler at smail dot nju.edu.cn
Target Milestone: ---
similar with https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107050, but without
function call.
```
int f = 1;
int g1, g2, arr[10];
int func_1() {
int a = 4;
int *p1 = &g1;
if (f) {
arr[0] = g2;
int *p2 = &a;
a = 1;
}
*p1 &= (a > 9) - 5;
return a;
}
int main() {
func_1();
}
```
gcc-13.2.0 -O1 generates:
```
func_1():
401106: mov 0x2f80(%rip),%eax # 40408c <g1> # first load
40110c: mov $0x4,%edx
401111: cmpl $0x0,0x2f10(%rip) # 404028 <f>
401118: je 401131 <func_1+0x2b>
40111a: mov 0x2f68(%rip),%eax # 404088 <g2>
401120: mov %eax,0x2f3a(%rip) # 404060 <arr>
401126: mov 0x2f60(%rip),%eax # 40408c <g1> # second load
40112c: mov $0x1,%edx
401131: and $0xfffffffb,%eax
401134: mov %eax,0x2f52(%rip) # 40408c <g1>
40113a: mov %edx,%eax
40113c: retq
```
I wonder why compiler won't use another register to hold `g2`, so that the
second load is unnecessary.
