JDK-8343541 : C1: Plain memory accesses are emitted with membars with +AlwaysAtomicAccesses
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: compiler
  • Affected Version: 17,21,23,24
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2024-11-04
  • Updated: 2024-11-27
  • Resolved: 2024-11-20
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JDK 24
24 b25Fixed
Related Reports
Relates :  
JDK-8033380 - Experimental VM flag to enforce access atomicity
Description
Noticed this while looking at current AlwaysAtomicAccesses uses. This flag is useful to experiment with Valhalla flattening and generically with long atomicity.

See for example here: https://github.com/openjdk/jdk/blob/895a7b64f01dec7248549b127875edcf006457cf/src/hotspot/share/gc/shared/c1/barrierSetC1.cpp#L143 -- we set `is_volatile` when `+AlwaysAtomicAccesses`, so it emit barriers.
Comments
Changeset: afee7405 Branch: master Author: Xiaolong Peng <xpeng@openjdk.org> Committer: Aleksey Shipilev <shade@openjdk.org> Date: 2024-11-20 10:34:07 +0000 URL: https://git.openjdk.org/jdk/commit/afee7405bd13cbe1cb829dd150a9de7e6faf49ae
20-11-2024
A pull request was submitted for review. Branch: master URL: https://git.openjdk.org/jdk/pull/22191 Date: 2024-11-18 07:27:03 +0000
18-11-2024