RFR: 8339910: RISC-V: crc32 intrinsic with carry-less multiplication [v3]

[Hamlin Li]

On Thu, 5 Dec 2024 15:27:35 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> src/hotspot/cpu/riscv/vm_version_riscv.cpp line 360:
>> 
>>> 358:   // UseZvbc (depends on RVV).
>>> 359:   if (UseZvbc && !UseRVV) {
>>> 360:     FLAG_SET_DEFAULT(UseZvbc, false);
>> 
>> If Zvbc is picked up via hwprobe and user uses:
>> `java -XX:-UseRVV ...`
>> wouldn't they get the warning forcing them to add -UseZvbc?
>
> I tested:
> 
> qemu-riscv64 -cpu "rv64,v=true,vext_spec=v1.0,zvbc=true" java -XX:-UseRVV -version
> 
> Gives me this warning about zvcb.
> 
> I think if zvcb is default, just turn it off if rvv is off.

Thanks for the suggestion!
It makes sense to me, fixed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22475#discussion_r1871768650