JDK-8346664 : C2: Optimize mask check with constant offset
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 25
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2024-12-19
  • Updated: 2025-02-24
  • Resolved: 2025-02-17
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JDK 25
25 b11Fixed
Related Reports
Causes :  
JDK-8350563 - C2 compilation fails because PhaseCCP does not reach a fixpoint
Relates :  
JDK-8277850 - C2: optimize mask checks in counted loops
Relates :  
JDK-8349128 - C2 SuperWord: generalize PopulateIndex patterns with constant vector
Description
Found this while looking at: https://mail.openjdk.org/pipermail/panama-dev/2024-December/020835.html

I believe the issue is that we optimize the pattern (base + offset) & mask when offset is a left shift but we miss the cases when offset is a constant.
Comments
Changeset: 7f3ecb4d Branch: master Author: Matthias Ernst <mernst-github@mernst.org> Date: 2025-02-17 13:07:23 +0000 URL: https://git.openjdk.org/jdk/commit/7f3ecb4d92fdb084ce632cab484cf4578487b090
17-02-2025
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk/pull/22856 Date: 2024-12-21 14:08:02 +0000
17-01-2025