| Issue |
108906
|
| Summary |
Missed optimization for a loop with dead code
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
dcci
|
Godbolt link:
https://godbolt.org/z/Kaq3sbsr9
Inline code:
```
long patatino() {
long x = 0;
for (int i = 0; i < 5; ++i) {
while (x < 10) {
if (x % 2 == 0) {
x += 2;
} else {
x += 1;
}
// Dead while loop
while ((x > 20) && (i % 3 == 0) && (x % 5 == 0)) {
x -= 5;
}
// Dead while loop
while ((x < -5) && (i % 2 == 0) && (x % 3 == 0)) {
x += 3;
}
}
}
return x;
}
```
If you remove the two 'dead while loops' then LLVM is able to optimize this down to a constant.
For comparison, GCC trunk seems to do better, but also doesn't optimize this fully
cc: @fhahn/@nikic
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