RFR: 8345298: RISC-V: Add riscv backend for Float16 operations - scalar [v2]

[Hamlin Li]

On Thu, 6 Mar 2025 05:44:36 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Hamlin Li has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:
>> 
>>  - clean
>>  - merge master
>>  - merge master
>>  - clean 2
>>  - clean
>>  - initial commit
>
> src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 6624:
> 
>> 6622: 
>> 6623:     if (vmIntrinsics::is_intrinsic_available(vmIntrinsics::_float16ToFloat) &&
>> 6624:         vmIntrinsics::is_intrinsic_available(vmIntrinsics::_floatToFloat16)) {
> 
> Since this stub uses instructions from the Zfh extension which is not always available, do we need a similar checking like x86 [1] (https://bugs.openjdk.org/browse/JDK-8303415)? I see `vmIntrinsics::is_intrinsic_available` delegates work to `VM_Version::is_intrinsic_supported` [2].
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/vm_version_x86.cpp#L3333
> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/share/classfile/vmIntrinsics.cpp#L671

Thanks for catching!

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PR Review Comment: https://git.openjdk.org/jdk/pull/23844#discussion_r1983456182