[PATCH] D12561: [X86][SSE] Match zero/any extension shuffles that don't start from the first element

[Simon Pilgrim via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: chandlerc, qcolombet, andreadb.
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This patch generalizes the lowering of shuffles as zero extensions to allow extensions that don't start from the first element. It now recognises extensions starting anywhere in the lower 128-bits or at the start of any higher 128-bit lane.

The motivation was to reduce the number of high cost pshufb calls, but it also improves the SSE2 case as well.

Repository:
  rL LLVM

http://reviews.llvm.org/D12561

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/machine-cp.ll
  test/CodeGen/X86/vec_cast2.ll
  test/CodeGen/X86/vec_int_to_fp.ll
  test/CodeGen/X86/vector-shuffle-256-v16.ll
  test/CodeGen/X86/vector-shuffle-256-v32.ll
  test/CodeGen/X86/vector-shuffle-sse4a.ll
  test/CodeGen/X86/vector-zext.ll

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