[all-commits] [llvm/llvm-project] 2ed914: [X86][SSE] getFauxShuffleMask - handle PACKSS(SRAI...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2ed914cb7e9c0737bdf60a0b1fd48b6499973325
      https://github.com/llvm/llvm-project/commit/2ed914cb7e9c0737bdf60a0b1fd48b6499973325
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2021-01-12 (Tue, 12 Jan 2021)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/psubus.ll

  Log Message:
  -----------
  [X86][SSE] getFauxShuffleMask - handle PACKSS(SRAI(),SRAI()) shuffle patterns.

We can't easily treat ASHR a faux shuffle, but if it was just feeding a PACKSS then it was likely being used as sign-extension for a truncation, so just peek through and adjust the mask accordingly.