RFR: 8303040: linux PPC64le: Implementation of Foreign Function & Memory API (Preview) [v3]

[Martin Doerr]

On Mon, 13 Mar 2023 16:37:18 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> > I'm currently wondering about the TestArrayStructs failures. Passing arrays with up to 7 elements seems to work fine. When I pass 8 elements, the last element of capturedArgs gets observed as 0. When I pass more than 8 elements, element 5 and 6 of capturedArgs get observed as 0.
> > DowncallLinker.invokeInterpBindings has the correct args, but UpcallLinker.invokeInterpBindings doesn't receive the correct values as lowLevelArgs. They contain the wrong zeros. The remaining elements look correct.
> > Do you have an idea what could be going wrong? Otherwise, I'll have to continue debugging.
> 
> This sounds like there might be a mismatch between the Java and native side. I suggest looking at the assembly generated for the native function for the failing case, and seeing if it matches what is generated by CallArranger. Here is also where adding a CallArranger test can be useful (in test/jdk/java/foreign/callarranger), to test whether the resulting bindings match your expectation for that function descriptor.
> 
> Also, you might want to check the layout the native compiler uses for the particular struct, and verify that it matches the Java side. (i.e. there's no weird padding or something, it's just a struct of 8 bytes).

Note that argument and return value passing works. I'm getting all values back. So, the native side seems to be ok. Only (one or two) values in `returnBox` are broken.

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PR: https://git.openjdk.org/jdk/pull/12708