RFR: 8357258: x86: Improve receiver type profiling reliability [v2]

[Dean Long]

On Mon, 15 Sep 2025 14:27:28 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/`
>>   - [ ] 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 incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8357258-x86-c1-optimize-virt-calls
>  - Drop atomic counters
>  - Initial version

src/hotspot/cpu/x86/macroAssembler_x86.cpp line 4853:

> 4851:       } else {
> 4852:         // Nothing to do, just go with defaults.
> 4853:         assert_different_registers(rax, mdp, recv, offset);

Can't we do all register shuffling and push/pop outside the loop?

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PR Review Comment: https://git.openjdk.org/jdk/pull/25305#discussion_r2356988910