RFR: 8310268: RISC-V: misaligned memory access in String.Compare intrinsic [v3]

[Vladimir Kempik]

On Mon, 24 Jul 2023 05:54:43 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Vladimir Kempik has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Simplify case for long LU UL compares
>
> src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 2315:
> 
>> 2313:   void compare_string_8_x_LU(Register tmpL, Register tmpU, Register strL, Register strU, Label& DIFF) {
>> 2314:     const Register tmp = x30;
>> 2315:     __ ld(tmpL, Address(strL));
> 
> Could we make use of another tmp register (maybe `x7`) and use that as the destination register for `ld` instead? Then we could inflate_lo32/hi32 from this tmp register and put the result in `tmpL`. That way would help remove the two `mv` instructions here in this function and the one located at label `DIFF`.

I have done it in a slightly different way, still removing all "mv"s you have mentioned

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PR Review Comment: https://git.openjdk.org/jdk/pull/14534#discussion_r1272022286