[llvm] [llvm][InstCombine] Fold signum(x) into scmp(x, 0) (PR #143445)

[via llvm-commits]

AZero13 wrote:

if you're looking at `sbb eax, eax`, then (1) that's probably special-cased by the CPU, and (2) even if not, `eax` isn't touched before that point, so it's very unlikely that the value is still in flight

I don't know if LLVM is aware of special cases like that though. Or if it's worth teaching LLVM that

https://github.com/llvm/llvm-project/pull/143445