[foreign-memaccess+abi] RFR: 8275647: Enable multi-register return values for optimized upcall stubs

[Jorn Vernee]

On Tue, 2 Nov 2021 19:07:45 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

> Hi,
> 
> After we've added multi-register return support to native invokers, this patch does the same for optimized upcall stubs. The strategy is very similar: the caller (in this case the upcall stub) allocates a return buffer in which the return values are stored, and then after the upcall shuffles the return values from the buffer into the right registers.
> 
> This patch also removes the buffered invocation strategy for upcalls, and all related code, such as BufferLayout.
> 
> ~Note, in it's current state this patch will disable regress AArch64 since optimized upcalls are not implemented there yet. i.e. this PR is blocked by: https://bugs.openjdk.java.net/browse/JDK-8275646~
> 
> Jorn

src/hotspot/cpu/x86/foreign_globals_x86.cpp line 96:

> 94: }
> 95: 
> 96: const CallRegs ForeignGlobals::parse_call_regs_impl(jobject jconv) const {

This is now also moved to shared code.

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PR: https://git.openjdk.java.net/panama-foreign/pull/608