RFR: 8314949: linux PPC64 Big Endian: Implementation of Foreign Function & Memory API

[Martin Doerr]

On Fri, 25 Aug 2023 00:10:11 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> 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.
>
> src/java.base/share/classes/jdk/internal/foreign/abi/Binding.java line 717:
> 
>> 715:         public void interpret(Deque<Object> stack, StoreFunc storeFunc,
>> 716:                               LoadFunc loadFunc, SegmentAllocator allocator) {
>> 717:             if (shiftAmount > 0) {
> 
> Why do we assume we can only deal with ints or longs?

I have inserted casts into `public Binding.Builder shiftLeft(int shiftAmount, Class<?> type)` (similar to other bindings). The VM handles integral types smaller than `int` like `int` and uses 4 Bytes for arithmetic operations.

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PR Review Comment: https://git.openjdk.org/jdk/pull/15417#discussion_r1305321446