RFR: 8357258: x86: Improve receiver type profiling reliability [v6]
Aleksey Shipilev
shade at openjdk.org
Mon Dec 1 13:04:08 UTC 2025
> See the bug for discussion what issues current machinery has.
>
> This PR executes the plan outlined in the bug:
> 1. Common the receiver type profiling code in interpreter and C1
> 2. Rewrite receiver type profiling code to only do atomic receiver slot installations
> 3. Trim `C1OptimizeVirtualCallProfiling` to only claim slots when receiver is installed
>
> This PR does _not_ do atomic counter updates themselves, as it may have much wider performance implications, including regressions. This PR should be at least performance neutral.
>
> Additional testing:
> - [x] Linux x86_64 server fastdebug, `compiler/`
> - [x] Linux x86_64 server fastdebug, `all`
Aleksey Shipilev has updated the pull request incrementally with three additional commits since the last revision:
- Simplify third case: no need to loop, just restart the search
- Actually have a second "fast" case: receiver is not found in the table, and the table is full
- Pushing/popping for rare CAS path is counter-productive
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/25305/files
- new: https://git.openjdk.org/jdk/pull/25305/files/c441209a..f3e0fa4d
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=25305&range=05
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=25305&range=04-05
Stats: 157 lines in 1 file changed: 85 ins; 52 del; 20 mod
Patch: https://git.openjdk.org/jdk/pull/25305.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/25305/head:pull/25305
PR: https://git.openjdk.org/jdk/pull/25305
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