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  1. JDK
  2. JDK-8308172

[Lilliput/JDK17] Revert disabling vzeroupper

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    • Icon: Bug Bug
    • Resolution: Fixed
    • Icon: P3 P3
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    • repo-lilliput-17
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    • generic
    • generic

      While looking through the diff between Lilliput/JDK17 and upstream JDK17, I noticed one change in library_call.cpp that should not be there, it probably slipped through from debugging.

          void clear_upper_avx() {
        #ifdef X86
      - if (UseAVX >= 2) {
      + if (false && UseAVX >= 2) {
              C->set_clear_upper_avx(true);
            }
        #endif
          }

      This prevents emitting vzeroupper instructions on x86_64. I believe this will have performance impact when transitioning between AVX and SSE code. We should revert this.

            rkennke Roman Kennke
            rkennke Roman Kennke
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