RFR: 8309413: General improvements to MethodTypeDesc implementation [v5]

[Mandy Chung]

On Mon, 5 Jun 2023 22:34:23 GMT, Chen Liang <liach at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/constant/MethodTypeDescImpl.java line 84:
>> 
>>> 82:             paramTypes = new ClassDesc[paramCount];
>>> 83:             for (int i = 0; i < paramCount; i++) {
>>> 84:                 paramTypes[i] = validateParameter(ClassDesc.ofDescriptor(types.get(i + 1)));
>> 
>> It seems useful to have a static factory method to take a trusted copy of parameter types and it will validate the parameters before constructing `MethodTypeDescImpl` instance.   Parameter validation in one single place.    Several methods doing the validation can simply call this factory method and the code would be cleaner.
>> 
>> `insertParameterTypes` can call it as well and overhead of re-validating existing parameter types isn't a big issue.
>
> Should I just keep track of the slot count of MethodTypeDesc instead? Having a slot count implicitly requires validating the parameters, and the slot count can be used to eagerly reject `resolveConstantDesc` on MTD with over 255 slots.

I don't think `resolveConstantDesc` is performance-sensitive that needs the eager checking of the number of parameter slots.  Also the common case is to resolve a good MethodType with <= 255 parameter slots.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13186#discussion_r1218681876