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  1. JDK
  2. JDK-8055394

x86 popcnt: false dependency on destination register

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      Originally found here:
      http://stackoverflow.com/questions/25078285/replacing-a-32-bit-loop-count-variable-with-64-bit-introduces-crazy-performance

      It seems newish Intel x86 processors treat the destination register for popcnt as the input, and wait for it to be ready in order to continue execution.

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            • Assignee:
              Unassigned
              Reporter:
              shade Aleksey Shipilev
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              • Created:
                Updated: