| Issue |
80275
|
| Summary |
[PRE] reuse the value to avoid double loading
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
vfdff
|
* test: https://gcc.godbolt.org/z/7eKGbndfK
```
void foo(dComplex* __restrict__ bb, bool flag) {
*aa = *bb;
//memcpy(aa, bb, sizeof(dComplex));
if (flag)
{
*aa = aa->conj();
// bb->neg();
}
}
void foo1(dComplex* __restrict__ bb, bool flag) {
aa->real = bb->real; aa->imag = bb->imag;
if (flag)
{
*aa = aa->conj();
}
}
```
* llvm of **foo**: ldr often has large cost because of long latency, so reuse of the part value of q0 will be more efficient, which is similar to **foo1**
```
foo(dComplex*, bool): // @foo(dComplex*, bool)
adrp x8, aa
ldr q0, [x0]
ldr x8, [x8, :lo12:aa]
str q0, [x8]
tbz w1, #0, .LBB0_2
ldr d0, [x8, #8] --- expect reuse the result of q0 （d0 is low part of q0）
fneg d0, d0
str d0, [x8, #8]
.LBB0_2:
ret
```
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