| Issue |
151078
|
| Summary |
Checked range of variables is forgotten after a slightly non-trivial condition
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
kornelski
|
```c
#include <assert.h>
int choose(int v[], int len, int a, int b, int cond) {
if (a >= len || b >= len) {
return 0;
}
int res = v[a] > cond || v[b] > cond ? a : b;
assert(res < len);
return res;
}
```
I would expect `assert` to be optimized out, because the only possible values for `res` are either `a` or `b`, and both had their range checked at the beginning of the function.
What is really weird about this is that changing `||` to `|` makes this optimization work (`int res = v[a] > cond | v[b] > cond ? a : b`). I [originally](https://github.com/rust-lang/rust/issues/144522) thought it was related to reading two different memory locations, but in this minimized example it seems to be caused by having an extra branch in the short-circuiting condition.
https://gcc.godbolt.org/z/jx8zje6v8
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