RFR: JDK-8290137: riscv: small refactoring for add_memory_int32/64

[Fei Yang]

On Mon, 18 Jul 2022 11:43:03 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> @shipilev : Yes, the type of _generic_arraycopystub_cnt is int and it occupies 32-bit in memory on Linux/RISC-V. That's why we use incrementw here which increments a 32-bit memory operand. Note that incrementl works for 64-bit memory operand. Hope that explains. Thanks.
>
> Is this RISC-V specific postfix naming? On x86, there is `b`/`w`/`l`/`q` for 1/2/4/8-byte ops, respectively. This is just my curiosity, it does not block the integration.

Yes, default is for 8-byte ops and we use 'w' post-fix for 4-byte ops on RISC-V. And I think this is hangover from the aarch64 port [1]. 

[1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/aarch64/macroAssembler_aarch64.cpp#L1917

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PR: https://git.openjdk.org/jdk/pull/9461