Review of JEP draft

[Julian Waters]

The idea of adding opcodes specifically meaning the one after it should be
extended had not occurred to me while writing the JEP, I'll update the
proposal in a while to reflect this possibility. I actually think this
might be a better idea than the one I came up with.

best regards,
Julian

On Thu, Mar 17, 2022 at 9:57 PM David Lloyd <david.lloyd at redhat.com> wrote:

> The proposal seems to imply that the only alternative would be to pad all
> existing opcodes. But at the same time, it indicates that having the
> `ExtendedOpcodes` attribute be present - on a per-Code-attribute basis -
> would require not only the extra bytes for the attribute but that the code
> attribute itself must be padded.
>
> What about alternatives such as reserving one (or more) bytecode(s) to
> mean "extended instruction"?  This would be similar to how `WIDE` modifies
> the next bytecode, and would immediately make another 256 bytecodes
> available without impacting the size of any other bytecode in the method,
> nor requiring any extra attributes.
>
> This idea could be extended as far as one is willing to add prefix
> bytecodes. For example one could reserve 16 aligned and consecutive
> bytecodes for this purpose, creating a 12 bit space for up to 4096 more
> bytecodes with a minimum of impact on space or on producers or consumers of
> bytecodes, at the cost of 16 "small" bytecodes.
>
> While there might (or might not) be good reasons to not pursue this
> approach, if you're talking about extending the bytecode space in a JEP,
> you should probably at least explain why such a scheme should not be
> considered or else list it under the "Alternatives" heading.
>
>
> On Thu, Mar 17, 2022 at 7:19 AM Julian Waters <tanksherman27 at gmail.com>
> wrote:
>
>> Hi everyone,
>>
>> If you don't mind a little reading, can I get a review of the following
>> JEP
>> draft at
>>
>> https://bugs.openjdk.java.net/projects/JDK/issues/JDK-8283291?filter=allissues&orderby=created+DESC%2C+priority+DESC%2C+updated+DESC
>> ?
>> Apologies if this is not the proper way to submit a JEP, I'm a little new
>> to this.
>>
>> Have a great day!
>>
>> best regards,
>> Julian
>>
>>
>
> --
> - DML • he/him
>