[SelectionDAG] Optional handling of UNDEF elements in matchBinaryPredicate (part 1 of 2)

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

This patch provides opt-in support for UNDEF elements in matchBinaryPredicate, passing NULL instead of the result ConstantSDNode* argument.

Differential Revision: https://reviews.llvm.org/D55822

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@349628 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed