[llvm] [CodeGen] Combine two loops in SlotIndexes.cpp file (PR #127631)

[via llvm-commits]

Rifet-c wrote:

Oh well, "Some checks were not successful", does it mean that there indeed is a problem with the changes?
If so, then should I revert the commit and investigate it or what else should I do?
@arsenm (sorry for pinging you so often, if it creates discomfort, please, feel free to tell me so)

https://github.com/llvm/llvm-project/pull/127631