[foreign-memaccess+abi] RFR: Rework PlatformLayout

[Jorn Vernee]

On Tue, 14 Feb 2023 17:14:52 GMT, Per Minborg <pminborg at openjdk.org> wrote:

> This PR suggests slightly reworking the class `PlatformLayout`. This reduces the number of objects created and aggregates common functionality in a support method.

I've been thinking for a while now that `PlatformLayouts` should just be removed: https://bugs.openjdk.org/browse/JDK-8291499 It is a remnant of a time where we exposed layout constant for each platform.

In the implementation we only use one or two layouts for each platform. I think `PlatformLayouts` should just be removed, and the needed layouts moved to the particular `CallArranger` class where they are needed. So, if you want to work on `PlatformLayouts` I suggest removing it instead :)

Last time I looked into this, the tricky part was that there was a test that used these layouts as test values. That test will have to do something else.

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PR: https://git.openjdk.org/panama-foreign/pull/794