RFR: 8333793: Improve BootstrapMethodInvoker for ConstantBootstraps and ProxyGenerator

[Jorn Vernee]

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

src/java.base/share/classes/java/lang/invoke/BootstrapMethodInvoker.java line 145:

> 143:                             .invokeExact(caller, name, (MethodType)type, (MethodType)argv[0],
> 144:                                     (MethodHandle)argv[1], (MethodType)argv[2]);
> 145:                 } else if (argv.length >= 1 && bsmType == SCF_MT) {

It seems that these `argv.length` comparisons were here for cases where the wrong number of arguments are passed to a bootstrap method?

I don't see why check `argv.length > 1` is still required here... Some of the other cases are also happy to just access `argv`, (which we also do here on the next line).

If you don't think this extract check is needed, please remove this source of confusion.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19598#discussion_r1631232730