RFR: 8357258: x86: Improve receiver type profiling reliability [v9]

[Vladimir Ivanov]

On Wed, 10 Dec 2025 08:33:30 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> 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 with a new target base due to a merge or a rebase. The pull request now contains 22 commits:
> 
>  - Merge branch 'master' into JDK-8357258-x86-c1-optimize-virt-calls
>  - Merge branch 'master' into JDK-8357258-x86-c1-optimize-virt-calls
>  - More comments
>  - Tighten up the comments
>  - 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
>  - Merge branch 'master' into JDK-8357258-x86-c1-optimize-virt-calls
>  - Tighten up some more
>  - Offset is always rscratch1, no need to save it
>  - ... and 12 more: https://git.openjdk.org/jdk/compare/1bbbce75...c28810e3

Looks good.

Thanks for the clarifications, Aleksey. Just wanted to get a sense how much performance-wise we leave on the table and whether it is worth to spend more time on it later.

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Marked as reviewed by vlivanov (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25305#pullrequestreview-3564254380
PR Comment: https://git.openjdk.org/jdk/pull/25305#issuecomment-3638717818