[llvm] [ConstantRange] Expand makeAllowedICmpRegion to use samesign to give tighter range (PR #174355)

[Adar Dagan via llvm-commits]

Adar-Dagan wrote:

> > @dtcxzyw could you run the compilation time check again? I don't have permission
> 
> [dtcxzyw/llvm-opt-benchmark-nightly#106](https://github.com/dtcxzyw/llvm-opt-benchmark-nightly/pull/106) https://llvm-compile-time-tracker.com/compare.php?from=0b7f01ad515d83f1f3144a44a1b0145187eff484&to=67794ea9c094ffd93690daf7ff6ffdd1a676d213&stat=instructions:u

The regression source is the call to `intersectsWith` it is a heavy function that doesn't utilize the knowledge we have about the source of the two ranges being from a different signed version of the same cmp, but that being said the current implementation is much simpler than my original one.

What do you all think? Which version would you prefer we continue with?

https://github.com/llvm/llvm-project/pull/174355