[lworld] RFR: 8363846: [lworld] Make Class.isIdentityClass() non-native [v4]

[Roger Riggs]

On Wed, 23 Jul 2025 17:24:54 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This moves isIdentityClass() implementation to Class.java, and checks within the JVM that is_identity_class() doesn't check the access flags for an ArrayKlass, since AccessFlags aren't initialized in ArrayKlasses.  The AccessFlags should be moved from Klass.hpp to InstanceKlass.cpp in mainline but that's a more complicated change and has several pieces.
>> Added a test.
>> Tested with tier1 locally.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Minimize the test.

test/jdk/valhalla/valuetypes/IsIdentityClassTest.java line 27:

> 25:  * @test
> 26:  * @summary Test that IsIdentityClass and modifiers return true for arrays that can be flattened.
> 27:  * @library /test/lib

You'll need to add `@enablePreview false` to counteract the setting in TEST.properties.
Its still running both tests as enablePreview = true.

test/jdk/valhalla/valuetypes/IsIdentityClassTest.java line 41:

> 39: 
> 40: import jdk.internal.misc.PreviewFeatures;
> 41: import jdk.internal.value.ValueClass;

Unused import

test/jdk/valhalla/valuetypes/IsIdentityClassTest.java line 62:

> 60:         assertFalseIfPreview(Modifier.isIdentity(imod), "Modifier of Integer should not have IDENTITY set");
> 61:         int amod = Integer[].class.getModifiers();
> 62:         assertTrue(Modifier.isIdentity(amod), "Modifier of array of inline types should have IDENTITY set");

Suggestion:

        assertEquals(PreviewFeatures.isPreviewEnabled(), Modifier.isIdentity(amod), "Modifier of array should have IDENTITY set");

Before Valhalla, Arrays had identity but did not have a modifier bit set.
When --enable-preview, the IDENTITY modifier bit is set.

test/jdk/valhalla/valuetypes/IsIdentityClassTest.java line 68:

> 66:     void testAccessFlags() {
> 67:         Set<AccessFlag> iacc = Integer.class.accessFlags();
> 68:         assertFalseIfPreview(iacc.contains(Modifier.IDENTITY), "Access flags should not contain IDENTITY");

Suggestion:

        if (PreviewFeatures.isEnabled()) {
            Set<AccessFlag> iacc = Integer.class.accessFlags();
            assertFalse(iacc.contains(AccessFlag.IDENTITY), "Access flags should not contain IDENTITY");
        }
Without --enable-preview (before Valhalla), there was no IDENTITY accessflag.

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

PR Review Comment: https://git.openjdk.org/valhalla/pull/1514#discussion_r2226254970
PR Review Comment: https://git.openjdk.org/valhalla/pull/1514#discussion_r2226225014
PR Review Comment: https://git.openjdk.org/valhalla/pull/1514#discussion_r2226322924
PR Review Comment: https://git.openjdk.org/valhalla/pull/1514#discussion_r2226336992