[PATCH] D80658: [InstCombine] enhance vector demanded elements for select condition operand

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: lebedev.ri, efriedma, nlopes, nikic, RKSimon, craig.topper.
Herald added subscribers: hiraditya, kristof.beyls, mcrosier.
Herald added a project: LLVM.

This is part of reducing IR in PR42755:
https://bugs.llvm.org/show_bug.cgi?id=42755

If we can determine that both arms of a given element of a vector select are the same value, then the select's condition operand is not demanded at that element.

Alive2 examples based on the regression tests:
http://volta.cs.utah.edu:8080/z/2PCSs2
http://volta.cs.utah.edu:8080/z/s4hWra
http://volta.cs.utah.edu:8080/z/Jgexop


https://reviews.llvm.org/D80658

Files:
  llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
  llvm/test/Transforms/InstCombine/vec_demanded_elts.ll

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