[all-commits] [llvm/llvm-project] 47aaa9: [VectorCombine] allow peeking through GEPs when cr...

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  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 47aaa99c0e1e28573bf24d95c5540005ee734531
      https://github.com/llvm/llvm-project/commit/47aaa99c0e1e28573bf24d95c5540005ee734531
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2020-12-18 (Fri, 18 Dec 2020)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/VectorCombine.cpp
    M llvm/test/Transforms/VectorCombine/X86/load.ll

  Log Message:
  -----------
  [VectorCombine] allow peeking through GEPs when creating a vector load

This is an enhancement motivated by https://llvm.org/PR16739
(see D92858 for another).

We can look through a GEP to find a base pointer that may be
safe to use for a vector load. If so, then we shuffle (shift)
the necessary vector element over to index 0.

Alive2 proof based on 1 of the regression tests:
https://alive2.llvm.org/ce/z/yPJLkh

The vector translation is independent of endian (verify by
changing to leading 'E' in the datalayout string).

Differential Revision: https://reviews.llvm.org/D93229