| Issue |
53374
|
| Summary |
LLVM fails to detect/remove unreachable branch
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
y21
|
First issue here, so not sure if this is a duplicate, but
```c
#include <stdlib.h>
int divide(int x, int y) {
y += (y == 0);
if (y == 0) {
// unreachable
abort();
}
return x / y;
}
```
`y` can logically never be zero past the first line (if `y == 0`, then it will be set to 1), [yet the abort branch is still emitted](https://gcc.godbolt.org/z/MPPao4Koq). Replacing `abort();` with `__builtin_unreachable();` gets rid of it.
Originally found this in Rust code, where the `rhs == 0` check is [implicitly inserted due to the division](https://godbolt.org/z/fbxqs7s6n)
```rs
pub fn divide(x: u32, mut y: u32) -> u32 {
y += (y == 0) as u32;
x / y
}
```
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