On Fri, 13 Oct 2023 13:39:11 GMT, Martin Doerr <mdo...@openjdk.org> wrote:
>> Just to clarify, is the ABI equal to what is described in this table: >> https://www.ibm.com/docs/en/xl-c-and-cpp-aix/16.1?topic=data-using-alignment-modes >> ? >> >> This shows `double` having 8-byte alignment, but being 4-byte aligned when >> not the first member of an aggregate. > >> Okay, so it sounds like Java double on AIX is still 8-byte aligned, but the >> native double is 4-byte aligned? > > Correct within structures. I believe they are always 8-byte aligned except in > structures which are packed more densely. > >> In that case, I'd say that passing `JAVA_DOUBLE` as an argument resulting in >> an exception, is expected behavior. > > Hmm... Should we disallow to pass 8-byte aligned double values? Fixing the > tests is a good thing. But, I have a different concern: I guess many > developers may use them without testing on AIX. This would cause problems > which we could avoid by supporting 8-byte aligned doubles in addition. > > What about adding > > layouts.put("jdouble", ValueLayout.JAVA_DOUBLE.withByteAlignment(4)); > layouts.put("aligneddouble", ValueLayout.JAVA_DOUBLE); // allowed for usage > outside of structures > > ? > Just to clarify, is the ABI equal to what is described in this table: > https://www.ibm.com/docs/en/xl-c-and-cpp-aix/16.1?topic=data-using-alignment-modes > ? > > This shows `double` having 8-byte alignment, but being 4-byte aligned when > not the first member of an aggregate. Interesting! This matches my understanding. I can see that doubles are 4-byte aligned within structures. The 8-byte alignment of the first member is already established by the allocation alignment. I have only read the ABI documentation for linux. IBM will have to cover AIX specific details if there are more questions. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/16179#discussion_r1358313306
