[PATCH] D51696: [SelectionDAG] enhance vector demanded elements to look at a vector select condition operand

[Sanjay Patel via Phabricator via llvm-commits]

spatel updated this revision to Diff 164216.
spatel added a comment.

Patch updated:
No functional change from the last rev, but updated the TODO comment based on finding the answer to the select-condition-is-undef question. For reference, this is how we handle it in IR-level constant folding:

  if (isa<UndefValue>(Cond)) {
    if (isa<UndefValue>(V1)) return V1;
    return V2;
  }


https://reviews.llvm.org/D51696

Files:
  lib/CodeGen/SelectionDAG/TargetLowering.cpp
  test/CodeGen/X86/horizontal-reduce-smax.ll
  test/CodeGen/X86/horizontal-reduce-smin.ll
  test/CodeGen/X86/horizontal-reduce-umax.ll
  test/CodeGen/X86/horizontal-reduce-umin.ll
  test/CodeGen/X86/pr34592.ll
  test/CodeGen/X86/vector-reduce-smax.ll
  test/CodeGen/X86/vector-reduce-smin.ll
  test/CodeGen/X86/vector-reduce-umax.ll
  test/CodeGen/X86/vector-reduce-umin.ll

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