[llvm] [SCEV] Collect and merge loop guards through PHI nodes with multiple incoming values (PR #113915)

[Nikita Popov via llvm-commits]

nikic wrote:

Haven't looked at the implementation yet, but this change has some compile-time impact: https://llvm-compile-time-tracker.com/compare.php?from=a256e89fd1b9f42d3f29df42d4f21ea823476ff3&to=24ca499a1d02f88bee077c2a3135dfae8f1094fe&stat=instructions:u

https://github.com/llvm/llvm-project/pull/113915