RFR: 8365206: RISC-V: compiler/c2/irTests/TestFloat16ScalarOperations.java is failing on riscv64 [v4]

[Dingli Zhang]

On Wed, 20 Aug 2025 12:35:47 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Hi,
>> Can you help to review this patch?
>> 
>> Currently implementation of conversion from float to float16 only preserve some significant bits of a NaN, which is not right in some cases.
>> As this (NaN conversion from float to float16) is already in the slow path, so I'll just fix it by preserving all significant bits in the same way as j.l.Float.floatToFloat16.
>> As current tests does not catch the issue, except of TestFloat16ScalarOperations.java, so add another test.
>> 
>> There is also the similar issue in vector version of conversion from float to float16, I'll address it in another pr [JDK-8365772](https://bugs.openjdk.org/browse/JDK-8365772)
>> 
>> Thanks!
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   comments

src/hotspot/cpu/riscv/macroAssembler_riscv.cpp line 5972:

> 5970:   // Check j.l.Float.floatToFloat16 for more information.
> 5971:   // 10 bits
> 5972:   slli(tmp1, dst, 9+32);

Suggestion for adding some whitespace:
Suggestion:

  slli(tmp1, dst, 9 + 32);

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PR Review Comment: https://git.openjdk.org/jdk/pull/26838#discussion_r2290133418