[llvm] VT: teach a special-case optz about samesign (PR #122590)

[Nikita Popov via llvm-commits]

nikic wrote:

This caused a compile-time regression: https://llvm-compile-time-tracker.com/compare.php?from=26b4a0ac7ed3f04f10bd1c043e2cf9c52da7fc47&to=66badf224ade6e78d5da005f6a9819092fd8767b&stat=instructions:u

I think we should add a more efficient variant of getMatching() for the case where we just want to check for equality. getMatching() does this in a really inefficient way.

https://github.com/llvm/llvm-project/pull/122590