JDK-8365290 : [perf] x86 ArrayFill intrinsic generates SPLIT_STORE for unaligned arrays
  • Type: Bug
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 26
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • OS: generic
  • CPU: x86
  • Submitted: 2025-08-11
  • Updated: 2025-10-13
  • Resolved: 2025-10-05
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JDK 26
26 b19Fixed
Related Reports
Causes :  
JDK-8363858 - [perf] OptimizeFill may use wide set of intrinsics
Relates :  
JDK-8367158 - C2: create better fill and copy benchmarks, taking alignment into account
Description
For the SRF platform the ArrayFill test reports ~2x score drop for runs with intrinsic vs generated code. For the ArraysFill.testIntFill test with size=8195 on the Xeon 6740E reported score looks as:
no issue: 2774.537 
issue reproduced: 1302.243

CPUs with the AVX3 support not affected while it use different intrinsic.
Comments
Changeset: ba7bf43c Branch: master Author: Vladimir Ivanov <vaivanov@openjdk.org> Committer: Sandhya Viswanathan <sviswanathan@openjdk.org> Date: 2025-10-05 23:55:53 +0000 URL: https://git.openjdk.org/jdk/commit/ba7bf43c76c94bea85dbbd865794184b7ee0cc86
05-10-2025
ILW = Performance regression, with array fill intrinsic, -XX:-OptimizeFill = MML = P4
09-09-2025
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk/pull/26747 Date: 2025-08-12 14:54:22 +0000
12-08-2025