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  1. JDK
  2. JDK-8277178

Reduce the priority of data dependent nodes when OptoScheduling enabled

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    Details

    • Type: Enhancement
    • Status: Open
    • Priority: P4
    • Resolution: Unresolved
    • Affects Version/s: 18
    • Fix Version/s: tbd
    • Component/s: hotspot
    • Labels:

      Description

      when doing gcm/lcm, We should not only consider the height of nodes(latency), but also consider whether there is data dependency between nodes. When there is data dependency between two nodes and the delay of the previous node is large, another node without data dependency can be considered inserting between the two nodes. For example:

      sequence 1:
      ldrd V16, [R15, #16] # double
      fmuld V18, V16, V17
      faddd V16, V18, V16
      strd V16, [R15, #16] # double
      ldrw R2, [R13, #16] # int
      addw R1, R2, R2
      addw R1, R1, #2
      strw R1, [R13, #16] # int

      sequence 2:
      ldrd V16, [R15, #16] # double
      ldrw R2, [R13, #16] # int
      fmuld V18, V16, V17
      addw R1, R2, R2
      faddd V16, V18, V16
      strd V16, [R15, #16] # double
      addw R1, R1, #2
      strw R1, [R13, #16] # int

      Sequence 2 is more efficient than sequence 1 for aarch64 and MIPS architectures.

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              Assignee:
              sguoyun Sun Guoyun
              Reporter:
              sguoyun Sun Guoyun
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                Created:
                Updated: