Integrated: 7903586: Revisit jextract constant classes

[Maurizio Cimadamore]

On Wed, 29 Nov 2023 10:58:56 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This PR removes the use of jextract constant classes, and falls back to a simpler code generation strategies which move the various constants closer to where they belong:
> 
> * for structs and callbacks, the constants are added to the class/interface being generated;
> * for the header class, we use a local holder class per function to hold the method handle and function descriptor constants.
> 
> This scheme results in much less generated code (as no constant class is emitted), but with the same performance and laziness as the old scheme.
> 
> When working with the code, I've decided to simplify the handling of constant generation, in the spirit of what was recently done with the introduction of string templates. That is, instead of using a magic `Constant` class, which has methods to generate getters/setters for a given constant, I converted much of the code into "static" string templates, so that it's easier to see which code gets generated when staring at the jextract code. As a result, the `Constant` class has been removed.

This pull request has now been integrated.

Changeset: e3a489c4
Author:    Maurizio Cimadamore <mcimadamore at openjdk.org>
URL:       https://git.openjdk.org/jextract/commit/e3a489c4a48f2813ed7fe1245133ec9c56766ab7
Stats:     922 lines in 7 files changed: 291 ins; 577 del; 54 mod

7903586: Revisit jextract constant classes

Reviewed-by: jvernee

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PR: https://git.openjdk.org/jextract/pull/145