[foreign-memaccess+abi] RFR: 8255902: Enable stack arguments for native invokers & optimized upcall stubs [v2]

[Jorn Vernee]

On Tue, 19 Oct 2021 11:10:45 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> Jorn Vernee has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fold TestDown/UpcallStack into TestDown/Upcall to reduce code duplication
>
> src/hotspot/cpu/x86/macroAssembler_x86.hpp line 217:
> 
>> 215: 
>> 216:   // bias in bytes
>> 217:   void move32_64(VMRegPair src, VMRegPair dst, Register tmp = rax, int in_stk_bias = 0, int out_stk_bias = 0);
> 
> I was about to ask if you needed to preserve current code semantics - and I see you did that by adding default parameters - I'd check with some HS engineer to see what the code guidelines are here.

FWIW, the style guide doesn't mention these. I've asked around and other people say they actively use them as well (and there are plenty of existing uses). There doesn't seem to be a canonical advice on the use of parameter default values currently.

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PR: https://git.openjdk.java.net/panama-foreign/pull/600