[all-commits] [llvm/llvm-project] e82e17: [X86] Add lowerShuffleAsBitRotate (PR44379)

[Simon Pilgrim via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: e82e17d4d4cac8b2df00094e80d5e1cb22795664
      https://github.com/llvm/llvm-project/commit/e82e17d4d4cac8b2df00094e80d5e1cb22795664
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2020-02-09 (Sun, 09 Feb 2020)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/vector-shuffle-128-v16.ll
    M llvm/test/CodeGen/X86/vector-shuffle-128-v8.ll
    M llvm/test/CodeGen/X86/vector-shuffle-256-v16.ll
    M llvm/test/CodeGen/X86/vector-shuffle-256-v32.ll
    M llvm/test/CodeGen/X86/vector-shuffle-512-v32.ll
    M llvm/test/CodeGen/X86/vector-shuffle-512-v64.ll

  Log Message:
  -----------
  [X86] Add lowerShuffleAsBitRotate (PR44379)

As noted on PR44379, we didn't attempt to lower vector shuffles using bit rotations on XOP/AVX512F targets.

This patch lowers to uniform ISD:ROTL nodes - ROTR isn't supported by XOP and they are interchangeable for constant values anyway.

There might be cases where targets without ISD:ROTL support would benefit from this (expanding to SRL+SHL+OR), which I'll investigate in a future patch.

Also, non-AVX512BW targets fail to concatenate 256-bit rotations back to 512-bits (split during shuffle lowering as they don't have v32i16/v64i8 types).