[PATCH] D106358: [InstCombine] Add more complex folds for extractelement + stepvector

[David Sherwood via Phabricator via llvm-commits]

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I have updated cheapToScalarize to also consider the case when
extracting lanes from a stepvector intrinsic. This required removing
the existing 'bool IsConstantExtractIndex' and passing in the actual
index as a Value instead. We do this because we need to know if the
index is <= known minimum number of elements returned by the stepvector
intrinsic. Effectively, when extracting lane X from a stepvector we
know the value returned is also X.

New tests added here:

  Transforms/InstCombine/vscale_extractelement.ll


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D106358

Files:
  llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
  llvm/test/Transforms/InstCombine/vscale_extractelement.ll

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