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

[Claes Redestad]

On Fri, 26 Apr 2024 17:57:52 GMT, Mandy Chung <mchung at openjdk.org> wrote:

>> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Copyrights and other comments from @JornVernee
>
> 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.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18971#discussion_r1581404597