[all-commits] [llvm/llvm-project] 35b35a: [X86] Prevent shuffle combining from creating an i...

[topperc via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 35b35a373d013df8e80c0c9840c085aa6a79c4dc
      https://github.com/llvm/llvm-project/commit/35b35a373d013df8e80c0c9840c085aa6a79c4dc
  Author: Craig Topper <craig.topper at intel.com>
  Date:   2020-09-04 (Fri, 04 Sep 2020)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/vector-shuffle-512-v16.ll

  Log Message:
  -----------
  [X86] Prevent shuffle combining from creating an identical X86ISD::SHUF128.

This can cause an infinite loop if SimplifiedDemandedElts asks
for the node to replace itself.

A similar protection exists in other places in shuffle combining.

Fixes ISPC https://github.com/ispc/ispc/issues/1864