RFR: JDK-8318228: RISC-V: C2 ConvF2HF [v2]

[Hamlin Li]

On Thu, 18 Jan 2024 07:10:58 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   replace fclass with feq as performance optimization.
>
> Hi, Thanks for this change. I have a small question.

@RealFYang
Based on the [latest confirmation](https://bugs.openjdk.org/browse/JDK-8324212), we don't have to implemented in the same way as [Float.java]([1] https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/lang/Float.java#L1112-L1113). 

And per performance and test consideration, it's convenient for us to implement in current way.

But, for long term and performance consideration, I filed a bug to re-visit all the NaN related intrinsics in riscv: [JDK-8324303](https://bugs.openjdk.org/browse/JDK-8324303)

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PR Comment: https://git.openjdk.org/jdk/pull/17450#issuecomment-1905536920