[PATCH] D55819: [SelectionDAG] Optional handling of UNDEF elements in matchUnaryPredicate

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: andreadb, spatel, craig.topper.

Now that SimplifyDemandedBits/SimplifyDemandedVectorElts is simplifying vector elements, we're seeing more constant BUILD_VECTOR containing UNDEFs.

This patch provides opt-in handling of UNDEF elements in matchUnaryPredicate, passing NULL instead of the result ConstantSDNode* argument.

I've updated SelectionDAG::simplifyShift to demonstrate its use.

An equivalent matchBinaryPredicate patch is in progress.


Repository:
  rL LLVM

https://reviews.llvm.org/D55819

Files:
  include/llvm/CodeGen/SelectionDAGNodes.h
  lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  test/CodeGen/X86/combine-shl.ll
  test/CodeGen/X86/combine-sra.ll
  test/CodeGen/X86/combine-srl.ll

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