| Issue |
98017
|
| Summary |
[InstCombine] Missed optimization for `zext(trunc nuw(x))`
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Il-Capitano
|
Godbolt link: https://godbolt.org/z/Ws1jPz4rE
Instcombine transforms this function:
```llvm
define i64 @test(i64 %n) {
%trunc = trunc nuw i64 %n to i32
%zext = zext i32 %trunc to i64
ret i64 %zext
}
```
into this:
```llvm
define i64 @test(i64 %n) {
%zext = and i64 %n, 4294967295
ret i64 %zext
}
```
However, because of the `nuw` flag on `trunc`, this could be simplified into this instead:
```llvm
define i64 @test(i64 %n) {
ret i64 %n
}
```
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