[all-commits] [llvm/llvm-project] ac0929: [SelectionDAG] Widen cttz to cttz_zero_undef (#92514)

[Jay Foad via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ac092925c3fa61144e606c7a9d0d375b96e1abda
      https://github.com/llvm/llvm-project/commit/ac092925c3fa61144e606c7a9d0d375b96e1abda
  Author: Jay Foad <jay.foad at amd.com>
  Date:   2024-05-17 (Fri, 17 May 2024)

  Changed paths:
    M llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
    M llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
    M llvm/test/CodeGen/AMDGPU/cttz.ll
    M llvm/test/CodeGen/AMDGPU/cttz_zero_undef.ll
    M llvm/test/CodeGen/RISCV/rvv/cttz-vp.ll

  Log Message:
  -----------
  [SelectionDAG] Widen cttz to cttz_zero_undef (#92514)

Instead of widening e.g. i8 cttz(x) to i16 cttz(x | 0x100), use the more
optimizable form cttz_zero_undef(x | 0x100) since the widened operand is
definitely not zero.



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