• Hao Xu's avatar
    [turbofan][x64] Avoid TruncateInt64ToInt32 when possible · 59c55c1c
    Hao Xu authored
    Turbofan optimizes TruncateInt64ToInt32 by trying to merge it into
    its input. This can avoid generating a movl instruction. However, when
    the input is BitcastTaggedToWordForTagAndSmiBits, it fails to apply
    this optimization and this results in a redundant move:
    
      Turbofan IR:
      149: Load[kRepTaggedSigned|kTypeInt32](...)
      150: BitcastTaggedToWordForTagAndSmiBits(149)
      151: TruncateInt64ToInt32(150)
      152: Word32And(151, 558)
    
      Assembly:
      103  movl r11,[r8+0x1f]
      107  movl r11,r11
      10a  andl r11,0x4
    
    This CL fixes this and avoids the redundant movl instruction.
    
    Change-Id: Id59d1ce1e3b139344f750e903726dd9f338cfdba
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3787681Reviewed-by: 's avatarTobias Tebbi <tebbi@chromium.org>
    Commit-Queue: Hao A Xu <hao.a.xu@intel.com>
    Cr-Commit-Position: refs/heads/main@{#82156}
    59c55c1c
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