RFR: 8337780: RISC-V: C2: Change C calling convention for sp to NS

[Feilong Jiang]

On Mon, 5 Aug 2024 01:07:11 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Hi, please review this patch that changes the C calling convention for sp to NS as sp is always saved and restored by the prolog/epilog code..
>> This could reduce the frame size by 16 bytes for those C2 runtime stubs [1] as we do not have to save sp on the method entry.
>> 
>> I also checked the calling convention type for sp on other platforms (AArch64, PPC, x86, x64, S390), and they are all treated as NS.
>> 
>> 
>> Testing:
>> - [x] tier1~3 & hotspot:tier4 with release build
>> 
>> 1: https://github.com/openjdk/jdk/blob/367e0a65561f95aad61b40930d5f46843fee3444/src/hotspot/share/opto/runtime.cpp#L147-L167
>
> Looks good. Thanks.

@RealFYang @robehn  -- Thanks for the review!

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PR Comment: https://git.openjdk.org/jdk/pull/20449#issuecomment-2271371090