[PATCH] Extend LoopVectorizationLegality::isConsecutivePtr to handle multiple level GEPs

[Wei Mi]

repaste the patch using SCEV in phabricator.

One problem I noticed about using SCEV to check consecutiveness is that it may add a new case that: both pointer operand of gep and one operand of gep are variant. For this case, InnerLoopVectorizer::vectorizeMemoryInstruction may generate incorrect code. Previously, isConsecutive only return true for the case either pointer operand of gep is invariant, or all the other operands of gep are invariant. If we simply check SCEV in isConsecutive, It is like we move the complexity from isConsecutive to vectorizeMemoryInstruction.


REPOSITORY
  rL LLVM

http://reviews.llvm.org/D10281

Files:
  lib/Transforms/Vectorize/LoopVectorize.cpp
  test/Transforms/LoopVectorize/pr23580.ll

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