LLVM 18 issue: tests/codegen/pow_of_two.rs broken after https://github.com/rust-lang/rust/commit/9dccd5dce11f2fcce81fc77f4271eaf2359e2626

[krasimirgg]

Seems like the updated test expectations don't quite match up with LLVM 18, first failing check is:

 // CHECK: %{{[^ ]+}} = zext i32 %exp to i64

Found over at our experimental rust + LLVM @ HEAD build bot:
https://buildkite.com/llvm-project/rust-llvm-integrate-prototype/builds/25504#018d4612-a220-458b-84c9-1d8f56b6fbde/724-725

Looks like LLVM 18 adds some extra nneg-s, testing a PR to fix this: #120380

[krasimirgg]

@rustbot label: +A-LLVM