RFR: 8340456: Reduce overhead of proxying Object methods in ProxyGenerator

[Claes Redestad]

On Thu, 19 Sep 2024 14:14:59 GMT, Chen Liang <liach at openjdk.org> wrote:

>> This PR changes proxy code gen to avoid generating `Class.forName("java.lang.Object")`, instead emitting an ldc for the class literal, `ldc(CD_Object)`, java code equivalent `Object.class`. 
>> 
>> More types could profitably use `ldc(ClassDesc/-Entry)`, taking cues from `InvokerBytecodeGenerator.isStaticallyInvocable`, but just addressing the `Object` methods gets rid of most `Class.forName` emits. It's not terribly important for throughput performance since these are called in the generated `clinit`, so getting a quick win with few additional checks is a good starting point.
>> 
>> Added a few unrelated minor refactors/improvements, guided by diagnostic runs of the now fixed microbenchmark.
>
> src/java.base/share/classes/java/lang/reflect/ProxyGenerator.java line 833:
> 
>> 831:                 cob.ldc(objectCE);
>> 832:             } else {
>> 833:                 cob.ldc(cl.getName())
> 
> This `Class.forName` is only necessary in a very small number of cases, namely when the overridden interface method has an unaccessible parameter type, usually a package-private type not accessible to the implementing class. Maybe we can always directly ldc if the class is `public`.

Yeah, I'm just not sure what rules are quite right here. Wouldn't want to inadvertently regress this again, and not sure we have tests for all eventualities, so I started this off with the most conservative yet most beneficial improvement.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21090#discussion_r1766973606