RFR: 8331187: Optimize MethodTypeDesc and ClassDesc.ofDescriptor for primitive types [v3]

[Mandy Chung]

On Fri, 26 Apr 2024 18:41:18 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> src/java.base/share/classes/sun/invoke/util/Wrapper.java line 384:
>> 
>>> 382: 
>>> 383:     /** A nominal descriptor of the primitive type */
>>> 384:     public ClassDesc primitiveClassDescriptor() { return primitiveTypeDesc; }
>> 
>> As this method is named as `primitiveClassDescriptor`, I expect this should either throw or return null for `OBJECT` and even `VOID` wrapper.   Or should be named "classDescriptor".
>
> While I agree it may seem non-sensical to define `CD_Object` for `Object`, there's precedent in that `Wrapper.primitiveType` is `Object.class` - so for consistency I wired it up the same way. For the usage patterns introduced with this patch we'll never call `primitiveClassDescriptor()` on `Wrapper.OBJECT`, though - and `Wrapper.forPrimitiveType` will throw an `IAE` if you try - so we can always revisit this. 
>  
> `void.class` is the primitive type for `Void.class`, allowed as a return type and recognized by `Wrapper.forPrimitiveType`. There are checks in for example `ConstantUtils.parseMethodDescriptor` which disallows `void.class` anywhere but as a return type.

I know it'll never call `primitiveClassDescriptor()` besides primitive types.   While `void.class.isPrimitive()` returns true, `void` is not a primitive type and called out explicitly in the spec.

My point is about the behavior does not match the method name.  It may be better to rename it to `classDescriptor` instead.  It's okay to clean up in your other performance fix (perhaps #18945).

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

PR Review Comment: https://git.openjdk.org/jdk/pull/18971#discussion_r1581507425