[PATCH] D29053: [InstSimplify] try to eliminate icmp Pred (add nsw X, C1), C2

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
Herald added a subscriber: mcrosier.

I was surprised to see that we're missing icmp folds based on 'add nsw' in InstCombine, but I think we should handle the 'InstSimplify' cases first because that could make the InstCombine code simpler.

Here's an attempt to prove the logic with Alive:
http://rise4fun.com/Alive/g5Q

gcc has had these kinds of folds since at least v4.4 based on:
https://godbolt.org/g/J1nh5Q


https://reviews.llvm.org/D29053

Files:
  lib/Analysis/InstructionSimplify.cpp
  test/Transforms/InstSimplify/icmp-constant.ll

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