[llvm] [SCEV] Prove implied conditions via matching SCEV differences (PR #201839)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Thanks, I think this approach makes more sense.

An issue is that this causes a compile-time regression: https://llvm-compile-time-tracker.com/compare.php?from=745a8e0f1cd2b783b2039617a3880b40f6405ec1&to=b5fd8424d21213ca504123bff938df54d552d1f5&stat=instructions:u

We can slightly improve it by adjusting the conditions: https://github.com/llvm/llvm-project/commit/bd8ecf010c3cb35626370e161b4956bbda1d3112 At least I think that's the intent behind the check. This doesn't fully recover the regression though.

https://github.com/llvm/llvm-project/pull/201839