| Issue |
109718
|
| Summary |
[clang] Missed optimization: dead store to thread-local not optimized out
|
| Labels |
clang
|
| Assignees |
|
| Reporter |
tavianator
|
For this code
```c
void foo(void **ptr) {
static _Thread_local void *tmp;
tmp = *ptr;
*ptr = 0;
}
```
Clang generates
```asm
foo:
movq (%rdi), %rax
movq %rax, %fs:foo.tmp@TPOFF
movq $0, (%rdi)
retq
```
I think it's an alias analysis issue, because a `_Thread_local int` is optimized out. But even without alias analysis, we know that `tmp` hasn't had its address taken.
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