RFR: 8322753: RISC-V: C2 ReverseBytesV

[Hamlin Li]

On Tue, 7 May 2024 18:00:37 GMT, Ludovic Henry <luhenry at openjdk.org> wrote:

>> Hi,
>> Can you review this patch to add ReverseBytesV intrinsic?
>> Thanks.
>
> src/hotspot/cpu/riscv/globals_riscv.hpp line 118:
> 
>> 116:   product(bool, UseZihintpause, false, EXPERIMENTAL,                             \
>> 117:           "Use Zihintpause instructions")                                        \
>> 118:   product(bool, UseZvbb, false, "Use Zvbb instructions")                         \
> 
> That'll conflict with https://github.com/openjdk/jdk/pull/19065, but same, we'd want to have `EXPERIMENTAL`

Yes, this will be fixed after https://github.com/openjdk/jdk/pull/19065 by merging from master.

> src/hotspot/os_cpu/linux_riscv/riscv_hwprobe.cpp line 182:
> 
>> 180:   }
>> 181:   if (is_set(RISCV_HWPROBE_KEY_IMA_EXT_0, RISCV_HWPROBE_EXT_ZVBB)) {
>> 182:     VM_Version::ext_Zvbb.enable_feature();
> 
> Same as https://github.com/openjdk/jdk/pull/19065, we don't want to enable experimental extensions via hwprobe.

Same as above. Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/19120#discussion_r1593001036
PR Review Comment: https://git.openjdk.org/jdk/pull/19120#discussion_r1593001423