[PATCH] D16022: AMDGPU: Pattern match ffbh pattern to instruction.

[Matt Arsenault via llvm-commits]

arsenm created this revision.
arsenm added a reviewer: tstellarAMD.
arsenm added a subscriber: llvm-commits.
Herald added subscribers: rampitec, arsenm.

The hardware instruction's output on 0 is -1 rather than 32.
Eliminate a test and select to -1. This removes an extra instruction
from the compatability function with HSAIL's firstbit instruction.

http://reviews.llvm.org/D16022

Files:
  lib/Target/AMDGPU/AMDGPUISelLowering.cpp
  lib/Target/AMDGPU/AMDGPUISelLowering.h
  lib/Target/AMDGPU/AMDGPUInstrInfo.td
  lib/Target/AMDGPU/EvergreenInstructions.td
  lib/Target/AMDGPU/SIISelLowering.cpp
  lib/Target/AMDGPU/SIInstructions.td
  test/CodeGen/AMDGPU/ctlz.ll
  test/CodeGen/AMDGPU/ctlz_zero_undef.ll

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