RFR: 8316694: Implement relocation of nmethod within CodeCache [v31]

Chad Rakoczy duke at openjdk.org
Thu Jun 19 22:06:31 UTC 2025


> This PR introduces a new function to replace nmethods, addressing [JDK-8316694](https://bugs.openjdk.org/browse/JDK-8316694). It enables the creation of new nmethods from existing ones, allowing method relocation in the code heap and supporting [JDK-8328186](https://bugs.openjdk.org/browse/JDK-8328186).
> 
> When an nmethod is replaced, a deep copy is performed. The corresponding Java method is updated to reference the new nmethod, while the old one is marked as unused. The garbage collector handles final cleanup and deallocation.
> 
> This change does not modify existing code paths and therefore does not benefit much from existing tests. New tests were created and confirmed to pass on x64/aarch64 for slowdebug/fastdebug/release.

Chad Rakoczy has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 88 commits:

 - Merge remote-tracking branch 'origin/master' into JDK-8316694-Final
 - Fix pointer printing
 - Use set_destination_mt_safe
 - Print address as pointer
 - Use new _metadata_size instead of _jvmci_data_size
 - Merge remote-tracking branch 'origin/master' into JDK-8316694-Final
 - Only check branch distance for aarch64 and riscv
 - Move far branch fix to fix_relocation_after_move
 - Move far branch fix to fix_relocation_after_move
 - Add test to verify JVMTI events during nmethod relocation
 - ... and 78 more: https://git.openjdk.org/jdk/compare/0dd50dbb...e51a1a09

-------------

Changes: https://git.openjdk.org/jdk/pull/23573/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23573&range=30
  Stats: 1604 lines in 25 files changed: 1563 ins; 2 del; 39 mod
  Patch: https://git.openjdk.org/jdk/pull/23573.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23573/head:pull/23573

PR: https://git.openjdk.org/jdk/pull/23573


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