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  1. JDK
  2. JDK-8001336

C2: Implement Bitwise Liveness Analysis

    Details

    • Type: Enhancement
    • Status: Open
    • Priority: P4
    • Resolution: Unresolved
    • Affects Version/s: hs25, 9, 10
    • Fix Version/s: tbd
    • Component/s: hotspot
    • Labels:

      Description

      In the long term, we should think about adding bitwise liveness analysis into the system, instead of using pattern matching. If the live bits out of a LoadB are contained in 0xFF, then we can transform to LoadUB.

      Doing this would require a type system that can represent per-bit liveness, and an analysis phase that pushes such types backwards through the graph. That is a straightforward extension of our existing type system, augmenting the existing arithmetic range endpoints with corresponding bit masks.

      — John

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              • Assignee:
                Unassigned
                Reporter:
                vlivanov Vladimir Ivanov
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                • Created:
                  Updated: