On Thu, 24 Aug 2023 13:56:12 GMT, Martin Doerr <[email protected]> wrote:
> I've found a way to solve the remaining FFI problem on linux PPC64 Big
> Endian. Large structs (>8 Bytes) which are passed in registers or on stack
> require shifting the Bytes in the last slot if the size is not a multiple of
> 8. This PR adds the required functionality to the Java code.
>
> Please review and provide feedback. There may be better ways to implement it.
> I just found one which works and makes the tests pass:
>
> Test summary
> ==============================
> TEST TOTAL PASS FAIL ERROR
>
> jtreg:test/jdk/java/foreign 88 88 0 0
>
>
>
> Note: This PR should be considered as preparation work for AIX which also
> uses ABIv1.
Overall these changes look good - as commented I'd like to learn a bit more of
the underlying ABI, to get a sense of whether adding a new binding is ok. But
overall it's great to see support for a big-endian ABI - apart from the linker,
I am pleased to see that you did not encounter too many issues in the
memory-side of the FFM API.
src/java.base/share/classes/jdk/internal/foreign/abi/Binding.java line 695:
> 693: * Negative [shiftAmount] shifts right and converts to int if
> needed.
> 694: */
> 695: record ShiftLeft(int shiftAmount, Class<?> type) implements Binding {
Given the situation you are facing, perhaps adding the new binding here is
unavoidable. Let's wait to hear from @JornVernee. In the meantime, can you
point me to a document which explains this behavior? I'm curious and I'd like
to know more :-)
-------------
PR Review: https://git.openjdk.org/jdk/pull/15417#pullrequestreview-1594603192
PR Review Comment: https://git.openjdk.org/jdk/pull/15417#discussion_r1304967438
