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  1. JDK
  2. JDK-8165058

aarch64: should support CPU_NOT_MULTIPLE_COPY_ATOMIC dynamically

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    • Type: Bug
    • Status: Resolved
    • Priority: P5
    • Resolution: Not an Issue
    • Affects Version/s: 9
    • Fix Version/s: 10
    • Component/s: hotspot
    • Labels:

      Description

      Architecturally the ARMv8 spec says that it is not multi-copy-atomic, but I believe currently that all implementations ARE multi-copy-atomic.

      The current aarch64 port does not define CPU_NOT_MULTIPLE_COPY_ATOMIC, so it could fail on future hardware.

      The fix is NOT to require all aarch64 hardware to unnecessarily pay the price for some future HW, but to change CPU_NOT_MULTIPLE_COPY_ATOMIC and/or support_IRIW_for_not_multiple_copy_atomic_cpu to be dynamically set in VM_Version::get_processor_features().

      [I really don't want someone in the future to define CPU_NOT_MULTIPLE_COPY_ATOMIC in a panic for all aarch64 chips!]

      e.g. globalDefintions.hpp can define support_IRIW_for_not_multiple_copy_atomic_cpu to be a constant in the non-aarch64 case , otherwise it's defined as a variable in global_definitions_aarch64.hpp.

      I think some discussion about this issue should be in aarch64 port somewhere, perhaps vm_version_aarch64.cpp.

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              Assignee:
              aph Andrew Haley
              Reporter:
              drwhite Derek White
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