[PATCH] D50840: [InstCombine] Extend collectShuffleElements to support extract/zext/insert patterns

[Joey Gouly via Phabricator via llvm-commits]

joey created this revision.

collectShuffleElements already handles combining the following into a single shufflevector:

  %elt0 = extractelement <8 x i16> %in, i32 3
  %elt1 = extractelement <8 x i16> %in, i32 1
  %elt2 = extractelement <8 x i16> %in2, i32 0
  %elt3 = extractelement <8 x i16> %in, i32 2
  
  %vec.0 = insertelement <4 x i16> undef, i16 %elt0, i32 0
  %vec.1 = insertelement <4 x i16> %vec.0, i16 %elt1, i32 1
  %vec.2 = insertelement <4 x i16> %vec.1, i16 %elt2, i32 2
  %vec.3 = insertelement <4 x i16> %vec.2, i16 %elt3, i32 3

This patch extends it to handle the following, by turning it into shufflevector + ext.

  %elt0e = extractelement <8 x i16> %in, i32 3
  %elt1e = extractelement <8 x i16> %in, i32 1
  %elt2e = extractelement <8 x i16> %in, i32 0
  %elt3e = extractelement <8 x i16> %in, i32 3
  
  %elt0 = zext i16 %elt0e to i32
  %elt1 = zext i16 %elt1e to i32
  %elt2 = zext i16 %elt2e to i32
  %elt3 = zext i16 %elt3e to i32
  
  %vec.0 = insertelement <4 x i32> undef, i32 %elt0, i32 0
  %vec.1 = insertelement <4 x i32> %vec.0, i32 %elt1, i32 1
  %vec.2 = insertelement <4 x i32> %vec.1, i32 %elt2, i32 2
  %vec.3 = insertelement <4 x i32> %vec.2, i32 %elt3, i32 3


Repository:
  rL LLVM

https://reviews.llvm.org/D50840

Files:
  lib/Transforms/InstCombine/InstCombineVectorOps.cpp
  test/Transforms/InstCombine/insert-extract-shuffle.ll

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