[PATCH] D17680: [X86][SSE] Lower 128-bit MOVDDUP with existing VBROADCAST mechanisms

[Simon Pilgrim via llvm-commits]

RKSimon created this revision.
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We have a number of useful lowering strategies for VBROADCAST instructions (both from memory and register element 0) which the 128-bit form of the MOVDDUP instruction can make use of.

This patch tweaks lowerVectorShuffleAsBroadcast to enable it to broadcast 2f64 args using MOVDDUP as well.

It does require a slight tweak to the lowerVectorShuffleAsBroadcast mechanism as the existing MOVDDUP lowering uses isShuffleEquivalent which can match binary shuffles that can lower to (unary) broadcasts.

Repository:
  rL LLVM

http://reviews.llvm.org/D17680

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/avx-splat.ll
  test/CodeGen/X86/avx-vbroadcast.ll
  test/CodeGen/X86/avx2-vbroadcast.ll
  test/CodeGen/X86/extractelement-load.ll
  test/CodeGen/X86/vec_extract-sse4.ll

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