RFR: 8332586: Avoid cloning empty arrays in java.lang.reflect.{Method,Constructor} [v2]

[Aleksey Shipilev]

On Fri, 31 May 2024 16:21:36 GMT, jengebr <duke at openjdk.org> wrote:

>> Improve `java/lang/reflect/Method.java`  by eliminating needless cloning of Class[0] instances.  This cloning is intended to prevent callers from changing array contents, but smany Methods have zero exceptions or zero parameters, and returning the original `Class[0]` is sufficient.
>
> jengebr has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Adding JMH benchmark

Let's bikeshed about the benchmark a little :)

test/micro/org/openjdk/bench/java/lang/reflect/ExecutableParameterAndExceptionTypesBenchmark.java line 49:

> 47: @Warmup(iterations = 3, time = 2, timeUnit = TimeUnit.SECONDS)
> 48: @Measurement(iterations = 5, time = 2, timeUnit = TimeUnit.SECONDS)
> 49: public class ExecutableParameterAndExceptionTypesBenchmark {

I think we want to have two benchmark classes, like we already have `Clazz` as sibling.

Something like:
 MethodBenchmark.getExceptionTypes
 MethodBenchmark.getExceptionTypesEmpty
 MethodBenchmark.getParameterTypes
 MethodBenchmark.getParameterTypesEmtpy
 ConstructorBenchmark.getExceptionTypes
 ConstructorBenchmark.getExceptionTypesEmpty
 ConstructorBenchmark.getParameterTypes
 ConstructorBenchmark.getParameterTypesEmtpy

test/micro/org/openjdk/bench/java/lang/reflect/ExecutableParameterAndExceptionTypesBenchmark.java line 66:

> 64:     public void constructorExceptionsWithNoExceptions(Blackhole bh) throws Exception {
> 65:         bh.consume(objectConstructor.getExceptionTypes());
> 66:     }

Here and later, the common shape for these is:


    @Benchmark
    public Object[] constructorExceptionsWithNoExceptions() {
        return objectConstructor.getExceptionTypes();
    }

-------------

PR Review: https://git.openjdk.org/jdk/pull/19327#pullrequestreview-2091270415
PR Review Comment: https://git.openjdk.org/jdk/pull/19327#discussion_r1622686626
PR Review Comment: https://git.openjdk.org/jdk/pull/19327#discussion_r1622682560