[foreign-abi] RFR: 8254156: Simplify ABI classification logic

[Chris Vest]

On Wed, 7 Oct 2020 11:39:50 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch reverts recent changes to introduce a public CValueLayout class; the realization here is that, after all,
> CValueLayout exposes a public `Type` enum which is used by ABI classification. So, instead of using subclassing (which
> is messy and tedious with immutable data structures with covariant overrides), let's just double down on layout
> attributes, get rid of CValueLayout and simply expose the Type enum (now renamed to TypeKind).

src/jdk.incubator.foreign/share/classes/jdk/incubator/foreign/CLinker.java line 749:

> 747:          * A kind corresponding to the a C pointer type
> 748:          */
> 749:         POINTER(false);

Pointer or pointer-sized? We'd also use this one for `size_t` for instance, right?

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PR: https://git.openjdk.java.net/panama-foreign/pull/371