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  1. JDK
  2. JDK-8248742

Add VM option for AArch64 to optionally select SVE feature

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    Details

    • Type: CSR
    • Status: Closed
    • Priority: P4
    • Resolution: Approved
    • Fix Version/s: 16
    • Component/s: hotspot
    • Labels:
      None
    • Subcomponent:
    • Compatibility Kind:
      behavioral
    • Compatibility Risk:
      minimal
    • Interface Kind:
      add/remove/modify command line option
    • Scope:
      Implementation

      Description

      Summary

      Add VM option for AArch64 to optionally select SVE feature

      Problem

      Arm SVE [1] and SVE2 [2] are optional extentions to Arm architecture. VM needs to detect SVE version in running hardware and generate code for non-SVE, SVE1 and SVE2 to get best performance. And we can also enable or disable SVE based on different applications or use cases.

      [1] https://developer.arm.com/architectures/cpu-architecture/a-profile/docs/arm-architecture-reference-manual-supplement-armv8-a [2] https://developer.arm.com/tools-and-software/server-and-hpc/compile/arm-instruction-emulator/resources/tutorials/sve/sve-vs-sve2/introduction-to-sve2

      Solution

      We add a VM option UseSVE to control which SVE version is going to be used or not using SVE at all. This is similar to x86 UseAVX option.

      Specification

      We add a new VM option, UseSVE, which is an integer with the following valid values:

      0: Do not use SVE, even when the hardware supports SVE.

      1: Use SVE version 1

      2: Use SVE version 2

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              Assignee:
              njian Ningsheng Jian
              Reporter:
              njian Ningsheng Jian
              Reviewed By:
              Nick Gasson
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                Dates

                Created:
                Updated:
                Resolved: