[all-commits] [llvm/llvm-project] 3d3c0e: [InstSimplify] fold extractelement of splat with v...

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  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3d3c0ed9323ba387dd6030337c672d2c9c4816f0
      https://github.com/llvm/llvm-project/commit/3d3c0ed9323ba387dd6030337c672d2c9c4816f0
  Author: Sanjay Patel <spatel at rotateright.com>
  Date:   2021-07-05 (Mon, 05 Jul 2021)

  Changed paths:
    M llvm/lib/Analysis/InstructionSimplify.cpp
    M llvm/test/Transforms/InstSimplify/extract-element.ll
    M llvm/test/Transforms/InstSimplify/vscale-inseltpoison.ll
    M llvm/test/Transforms/InstSimplify/vscale.ll

  Log Message:
  -----------
  [InstSimplify] fold extractelement of splat with variable extract index

We already have a fold for variable index with constant vector,
but if we can determine a scalar splat value, then it does not
matter whether that value is constant or not.

We overlooked this fold in D102404 and earlier patches,
but the fixed vector variant is shown in:
https://llvm.org/PR50817

Alive2 agrees on that:
https://alive2.llvm.org/ce/z/HpijPC

The same logic applies to scalable vectors.

Differential Revision: https://reviews.llvm.org/D104867