RFR: 8354996: Reduce dynamic code generation for a single downcall [v2]

[Jorn Vernee]

On Fri, 18 Apr 2025 18:25:54 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Perf numbers for simple main:
>> Linking of `Class::forName0` down from ~152 to ~83
>> 
>> For calling little color management system https://bugs.openjdk.org/browse/JDK-8313344:
>> JNI: ~45
>> baseline panama: ~164
>> patch: ~103
>> 
>> Also see #24705.
>
> Chen Liang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Simplify FFM linker warmup

make/jdk/src/classes/build/tools/classlist/HelloClasslist.java line 184:

> 182:                 ADDRESS, ADDRESS, ADDRESS,
> 183:                 JAVA_BOOLEAN, ADDRESS, ADDRESS);
> 184:         Linker.nativeLinker().downcallHandle(signature);

Why do we care specifically about this shape, but not about others?

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PR Review Comment: https://git.openjdk.org/jdk/pull/24742#discussion_r2063684813