RFR: 8346567: Make Class.getModifiers() non-native

[ExE Boss]

On Mon, 9 Dec 2024 19:26:53 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> The Class.getModifiers() method is implemented as a native method in java.lang.Class to access a field that we've calculated when creating the mirror.  The field is final after that point. The VM doesn't need it anymore, so there's no real need for the jdk code to call into the VM to get it.  This moves the field to Java and removes the intrinsic code.  I promoted the compute_modifiers() functions to return int since that's how java.lang.Class uses the value.  It should really be an unsigned short though.
> 
> There's a couple of JMH benchmarks added with this change.  One does show that for array classes for non-bootstrap class loader, this results in one extra load which in a long loop of just that, is observable.  I don't think this is real life code. The other benchmarks added show no regression.
> 
> Tested with tier1-8.

src/java.base/share/classes/java/lang/Class.java line 1005:

> 1003:     private transient Object[] signers; // Read by VM, mutable
> 1004: 
> 1005:     @Stable

The `modifiers` field doesn’t need to be `@Stable`:
Suggestion:

test/micro/org/openjdk/bench/java/lang/reflect/Clazz.java line 65:

> 63:      */
> 64:     @Benchmark
> 65:     public int getModifiers() throws NoSuchMethodException {

The only `Throwable`s that can be thrown by calling `Class::getModifiers()` are `Error`s (e.g.: `StackOverflowError`) and `RuntimeException`s (e.g.: `NullPointerException`):
Suggestion:

    public int getModifiers() {

test/micro/org/openjdk/bench/java/lang/reflect/Clazz.java line 71:

> 69:     Clazz[] clazzArray = new Clazz[1];
> 70:     @Benchmark
> 71:     public int getAppArrayModifiers() throws NoSuchMethodException {

Suggestion:

    public int getAppArrayModifiers() {

test/micro/org/openjdk/bench/java/lang/reflect/Clazz.java line 81:

> 79:      */
> 80:     @Benchmark
> 81:     public int getArrayModifiers() throws NoSuchMethodException {

Suggestion:

    public int getArrayModifiers() {

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PR Review Comment: https://git.openjdk.org/jdk/pull/22652#discussion_r1888757754
PR Review Comment: https://git.openjdk.org/jdk/pull/22652#discussion_r1888760732
PR Review Comment: https://git.openjdk.org/jdk/pull/22652#discussion_r1888760967
PR Review Comment: https://git.openjdk.org/jdk/pull/22652#discussion_r1888761412