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  1. JDK
  2. JDK-8217909 Make unused r12 register (without compressed oops) available to regalloc in C2
  3. JDK-8226473

Release Note: More Registers Available When Running Without Compressed References on x86_64

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    Details

    • Type: Sub-task
    • Status: Closed
    • Priority: P4
    • Resolution: Fixed
    • Affects Version/s: 13
    • Fix Version/s: 13
    • Component/s: hotspot
    • Labels:

      Description

      When running with compressed references on x86_64, one of the CPU registers holds the heap base pointer to be used for references encoding/decoding. This register is not available for register allocation.

      Simple implementations before this release made this register unavailable (and thus unused) even if compressed references were disabled. In this release, the implementation was revised to put this unused register back into the available registers pool. Configurations with large heaps and/or `-XX:-UseCompressedOops` benefit from this improvement.

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            Assignee:
            shade Aleksey Shipilev
            Reporter:
            shade Aleksey Shipilev
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