[foreign-memaccess+abi] RFR: 8317324: Add an overload to bind a memory segment var handle at an offset

[Maurizio Cimadamore]

On Fri, 29 Sep 2023 16:09:24 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This PR adds an overload which binds a memory segment var handle offset coordinate to a provided constant value.
> 
> This is useful when the client knows that the accessed offset will be e.g. zero, or some other known constant value, thus reducing the number of coordinates that var handles clients will have to provide on each access.

Looking more (and after some offline discussions), it we go down this path (e.g. that of having simple ways for developers to avoid var handle combinators for common cases), we'll need to do the same for several other methods:

* scaleHandle
* sliceHandle
* offsetHandle

And, we will probably need to add a new method like:

* arrayElementVarHandle

Which composes the var handle with the scale handle. And that would also be required in two variants. So, that's a total of 5 new methods, which while not a big deal (after all, the new methods are rather straightforwardly obtained from calling combinators on plain var handles), it makes me wonder a bit how much value there really is in making the MemoryLayout that much bigger.

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PR Comment: https://git.openjdk.org/panama-foreign/pull/900#issuecomment-1741269639