RFR: 8354996: Reduce dynamic code generation for a single downcall [v3]

[Chen Liang]

On Sun, 4 May 2025 19:35:15 GMT, Luca Kellermann <duke at openjdk.org> wrote:

>> Chen Liang 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 five additional commits since the last revision:
>> 
>>  - Merge branch 'master' of https://github.com/openjdk/jdk into exp/ffm-lcms
>>  - Use more simple function descriptor
>>  - Simplify FFM linker warmup
>>  - Merge branch 'master' of https://github.com/openjdk/jdk into exp/ffm-lcms
>>  - Wip work trying to speed up FFM
>
> src/java.base/share/classes/java/lang/foreign/Linker.java line 866:
> 
>> 864:                     .map(CapturableState::forName)
>> 865:                     .mapToInt(state -> 1 << state.ordinal())
>> 866:                     .sum();
> 
> Using `sum` means the result will be incorrect if `capturedState` contains a valid name multiple times:
> 
> var option = (LinkerOptions.CaptureCallState)Linker.Option.captureCallState("WSAGetLastError", "WSAGetLastError");
> 
> // will print [ERRNO] on Windows
> System.out.println(option.saved());
> 
> 
> option = (LinkerOptions.CaptureCallState)Linker.Option.captureCallState("errno", "errno");
> 
> // will throw IndexOutOfBoundsException on all platforms
> option.saved();

Hmm, I intentionally checked `toSet` does not reject duplicates but forgot about this part. Anyways this stream code is problematic; will fix this in a patch that removes this stream code wholesale.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24742#discussion_r2072703688