| Issue |
152788
|
| Summary |
Missed optimization: max(max(x<<C1, x+C2), C3) -> max(x<<C1, C3) when C2 <= (2^C1-1)/2^C1*C3
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
zxt5
|
```
define i64 @src(i32 %0) {
%v0 = add nsw i32 %0, 1
%v1 = shl nsw i32 %0, 1
%v2 = tail call i32 @llvm.smax.i32(i32 %v1, i32 %v0)
%v3 = tail call i32 @llvm.smax.i32(i32 %v2, i32 4)
%v4 = zext nneg i32 %v3 to i64
%v5 = shl nuw nsw i64 %v4, 3
ret i64 %v5
}
define i64 @tgt(i32 %0) {
%v1 = shl nsw i32 %0, 1
%v2 = tail call i32 @llvm.smax.i32(i32 %v1, i32 4)
%v3 = zext nneg i32 %v2 to i64
%v4 = shl nuw nsw i64 %v3, 3
ret i64 %v4
}
```
alive2: https://alive2.llvm.org/ce/z/BbxTr2
godbolt: https://godbolt.org/z/d557qnq49
Found this pattern in https://github.com/dtcxzyw/llvm-opt-benchmark/blob/main/bench/opencv/optimized/repeated_ptr_field.ll
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