RFR: 8322753: RISC-V: C2 ReverseBytesV

[Ludovic Henry]

On Tue, 7 May 2024 13:29:33 GMT, Hamlin Li <mli 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`

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.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19120#discussion_r1592872466
PR Review Comment: https://git.openjdk.org/jdk/pull/19120#discussion_r1592873103