[PATCH] D30826: [DAG] vector div/rem with any zero element in divisor is undef

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
Herald added a subscriber: mcrosier.

This is the backend counterpart to: 
https://reviews.llvm.org/rL297390
https://reviews.llvm.org/rL297409
and follow-up to:
https://reviews.llvm.org/rL297384

It surprised me that we need to duplicate the check in FoldConstantArithmetic and FoldConstantVectorArithmetic, but one or the other doesn't catch all of the test cases. There is an existing code comment about merging those someday. If we fix more cases like this to properly recognize undef (signed overflow in sdiv, oversized shifts, etc), we should fix the code structure or at least make a helper function to avoid repeating code.


https://reviews.llvm.org/D30826

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  lib/CodeGen/SelectionDAG/SelectionDAG.cpp
  test/CodeGen/X86/div-rem-simplify.ll
  test/CodeGen/X86/vec_sdiv_to_shift.ll

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