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

[Andrey Turbanov]

On Tue, 19 Aug 2025 08:22:59 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!

test/hotspot/jtreg/compiler/intrinsics/float16/Binary16ConversionNaN_2.java line 144:

> 142: 
> 143:     private static float testRoundTrip(float f) {
> 144:         short s =  Float.floatToFloat16(f);

Suggestion:

        short s = Float.floatToFloat16(f);

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PR Review Comment: https://git.openjdk.org/jdk/pull/26838#discussion_r2285438166