RFR: 8333793: Improve BootstrapMethodInvoker for ConstantBootstraps and ProxyGenerator

[Chen Liang]

On Fri, 7 Jun 2024 12:12:44 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> This PR refactors type matching in BootstrapMethodInvoker and adds a few types, seeking to improve bootstrap overheads of some ConstantBootstraps and in particular the ProxyGenerator condys generated for e.g. annotation proxies since [JDK-8332457](https://bugs.openjdk.org/browse/JDK-8332457)
> 
> I've adjusted the micro-benchmark added by JDK-8332457 to not only generate a proxy but also call into one of the proxied methodt (`Object::hashCode`). 
> 
> Running org.openjdk.bench.java.lang.reflect.ProxyGenBench as a one-off startup benchmark sees significant improvement (-9% instructions, -6% cycles):
> 
> Name             Cnt           Base          Error            Test          Error         Unit  Change
> Perfstartup-JMH   20        154,000 ±        8,165         148,000 ±       23,164        ms/op   1,04x (p = 0,352 )
>   :.cycles            925335973,200 ± 47147600,262   842221278,800 ± 46836254,964       cycles   0,91x (p = 0,000*)
>   :.instructions     2101588857,600 ± 81105850,361  1966307798,400 ± 22011043,908 instructions   0,94x (p = 0,000*)
>   :.taskclock               291,500 ±       16,494         262,000 ±       15,328           ms   0,90x (p = 0,000*)
>   * = significant
> 
> Number of classes loaded drops from 1096 to 1092
> 
> Running the micro regularly shows no significant difference:
> 
> Name                              Cnt   Base   Error    Test   Error  Unit  Change
> ProxyGenBench.generateAndProxy100  10 26,827 ± 8,954  26,855 ± 7,531 ms/op   1,00x (p = 0,991 )
>   * = significant

I recommend considering the `MethodHandle, Object[]` signature used by `ConstantBootstrap.invoke`: There had been previous proposals to use any method as a bootstrap method, and that API in particular can bridge that gap.

src/java.base/share/classes/java/lang/invoke/BootstrapMethodInvoker.java line 289:

> 287:      * bootstrap method.
> 288:      */
> 289:     private static final MethodType CONDY_GET_STATIC_FINAL_MT = MethodType.methodType(Object.class,

This type should just be called `CONDY_NO_ARG` as it's the most common form of condy that doesn't take any arg (`nullConstant` `primitiveClass` etc.)

src/java.base/share/classes/java/lang/invoke/BootstrapMethodInvoker.java line 296:

> 294:      * bootstrap method.
> 295:      */
> 296:     private static final MethodType CONDY_GET_STATIC_FINAL_CLASS_MT = MethodType.methodType(Object.class,

I recommend calling this `CONDY_EXTRA_CLASS`, as this is the type of `arrayVarHandle`.

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PR Review: https://git.openjdk.org/jdk/pull/19598#pullrequestreview-2104617832
PR Review Comment: https://git.openjdk.org/jdk/pull/19598#discussion_r1631241317
PR Review Comment: https://git.openjdk.org/jdk/pull/19598#discussion_r1631250689