[PATCH] D35700: DAGCombiner: Extend reduceBuildVecToTrunc to handle non-zero offset

[Zvi Rackover via Phabricator via llvm-commits]

zvi updated this revision to Diff 108027.
zvi added a comment.

Follow Simon's suggestion to generalize isDesirableToCombineBuildVectorToShuffleTruncate() to allow it to handle more cases.
The patch still only handles monotonically increasing indices - added TODO's to be revisited in follow-up work.


https://reviews.llvm.org/D35700

Files:
  include/llvm/Target/TargetLowering.h
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  lib/Target/X86/X86ISelLowering.cpp
  lib/Target/X86/X86ISelLowering.h
  test/CodeGen/X86/shuffle-strided-with-offset-256.ll
  test/CodeGen/X86/shuffle-strided-with-offset-512.ll
  test/CodeGen/X86/vector-shuffle-512-v32.ll

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