[all-commits] [llvm/llvm-project] ab29f0: [InstCombine] propagate 'nsw' on pointer differenc...

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  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: ab29f091eb64c8608ba943df604b218bcff41a26
      https://github.com/llvm/llvm-project/commit/ab29f091eb64c8608ba943df604b218bcff41a26
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2020-11-23 (Mon, 23 Nov 2020)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    M llvm/test/Transforms/InstCombine/sub-gep.ll
    M llvm/test/Transforms/InstCombine/sub.ll

  Log Message:
  -----------
  [InstCombine] propagate 'nsw' on pointer difference of 'inbounds' geps

This is a retry of 324a53205. I cautiously reverted that at 6aa3fc4
because the rules about gep math were not clear. Since then, we
have added this line to LangRef for gep inbounds:
"The successive addition of offsets (without adding the base address)
does not wrap the pointer index type in a signed sense (nsw)."

See D90708 and post-commit comments on the revert patch for more details.