| Issue |
122388
|
| Summary |
[InstCombine] Missed fold: `umax(x *nuw 2, x + 1)` => `x == 0 ? 1 : x *nuw 2`
|
| Labels |
llvm:instcombine,
missed-optimization
|
| Assignees |
|
| Reporter |
Kmeakin
|
https://godbolt.org/z/TEzxx8vbj
```rust
#[inline(never)]
pub unsafe fn src(x: usize) -> usize {
std::cmp::max(x.unchecked_mul(2), x + 1)
}
#[inline(never)]
pub unsafe fn tgt(x: usize) -> usize {
match x {
0 => 1,
_ => x.unchecked_mul(2),
}
}
```
https://alive2.llvm.org/ce/z/ijq6ZJ
```llvm
define noundef i64 @src(i64 noundef %x) {
%x2 = shl nuw i64 %x, 1
%x1 = add i64 %x, 1
%max = tail call noundef i64 @llvm.umax.i64(i64 %x2, i64 %x1)
ret i64 %max
}
define noundef range(i64 1, 0) i64 @tgt(i64 noundef %x) {
%eq = icmp eq i64 %x, 0
%x2 = shl nuw i64 %x, 1
%max = select i1 %eq, i64 1, i64 %x2
ret i64 %max
}
```
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