RFR: 8357258: x86: Improve receiver type profiling reliability [v5]

[Andrew Haley]

On Wed, 26 Nov 2025 15:55:38 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 15 commits:
> 
>  - Merge branch 'master' into JDK-8357258-x86-c1-optimize-virt-calls
>  - Tighten up some more
>  - Offset is always rscratch1, no need to save it
>  - Grossly simplify register shuffling
>  - More asserts
>  - More comment touchups
>  - Inline code comments
>  - Mention the updater in ReceiverTypeData
>  - type_profile -> profile_receiver_type
>  - Stylistic: remove redundant assert
>  - ... and 5 more: https://git.openjdk.org/jdk/compare/c028369d...c441209a

I'm seeing minor performance regressions in `InterfaceCalls.test2ndInt5Types`, before and after this PR:

Mainline:

Benchmark                                                (randomized)  Mode  Cnt    Score   Error      Units
InterfaceCalls.test2ndInt5Types                                 false  avgt    4   28.185 ± 0.538      ns/op
InterfaceCalls.test2ndInt5Types:IPC                             false  avgt         2.232          insns/clk
InterfaceCalls.test2ndInt5Types:branch-misses:u                 false  avgt         0.342               #/op
InterfaceCalls.test2ndInt5Types:instructions:u                  false  avgt       206.028               #/op


This PR:

Benchmark                                                (randomized)  Mode  Cnt    Score   Error      Units
InterfaceCalls.test2ndInt5Types                                 false  avgt    4   32.247 ± 0.109      ns/op
InterfaceCalls.test2ndInt5Types:IPC                             false  avgt         2.231          insns/clk
InterfaceCalls.test2ndInt5Types:branch-misses:u                 false  avgt         0.561               #/op
InterfaceCalls.test2ndInt5Types:instructions:u                  false  avgt       238.324               #/op



model name	: Intel(R) Xeon(R) Platinum 8275CL CPU @ 3.00GHz
java -XX:+UnlockExperimentalVMOptions -XX:ProfileCaptureRatio=1 -jar /home/aph/theRealAph-jdk/build/linux-x86_64-server-release/images/test/micro/benchmarks.jar test2ndInt5Types -p randomized=false -f 1 -jvmArgs ' -XX:TieredStopAtLevel=3' -t 1 -prof perfnorm

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PR Comment: https://git.openjdk.org/jdk/pull/25305#issuecomment-3589699041