[all-commits] [llvm/llvm-project] 522b4b: [DAG] Fold bitreverse(shl/srl(bitreverse(x), y)) ->...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 522b4bfe5b140068a7f9b3d899740a460aa0e715
      https://github.com/llvm/llvm-project/commit/522b4bfe5b140068a7f9b3d899740a460aa0e715
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2024-05-06 (Mon, 06 May 2024)

  Changed paths:
    M llvm/include/llvm/CodeGen/SDPatternMatch.h
    M llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    M llvm/test/CodeGen/RISCV/bitreverse-shift.ll
    M llvm/test/CodeGen/X86/combine-bitreverse.ll

  Log Message:
  -----------
  [DAG] Fold bitreverse(shl/srl(bitreverse(x),y)) -> srl/shl(x,y) (#89897)

Noticed while investigating GFNI per-element vector shifts (we can form SHL but not SRL/SRA)

Alive2: https://alive2.llvm.org/ce/z/fSH-rf



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