RFR: 8318227: RISC-V: C2 ConvHF2F [v3]

[Fei Yang]

On Wed, 29 Nov 2023 11:15:23 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Hi,
>> Can you review the patch to add ConvHF2F intrinsic to JDK for riscv？
>> Thanks!
>> 
>> (By latest kernel patch, `#define		RISCV_HWPROBE_EXT_ZFH		(1 << 27)`
>> https://lore.kernel.org/lkml/20231114141256.126749-11-cleger@rivosinc.com/)
>> 
>> ## Test
>> ### Functionality
>> #### hotspot tests
>> test/hotspot/jtreg/compiler/intrinsics/ 
>> test/hotspot/jtreg/compiler/c2/irTests
>> 
>> #### jdk tests
>> test/jdk/java/lang/Float/Binary16Conversion*.java
>> 
>> ### Performance
>> tested on licheepi.
>> 
>> #### with UseZfh enabled & stub out-of-band
>> 
>> Benchmark                                     (size)  Mode  Cnt      Score     Error  Units
>> Fp16ConversionBenchmark.float16ToFloat          2048  avgt   10   3493.376 ?  18.631  ns/op
>> Fp16ConversionBenchmark.float16ToFloatMemory    2048  avgt   10     19.819 ?   0.193  ns/op
>> 
>> 
>> #### with UseZfh enabled only
>> (i.e. enable the intrinsic)
>> 
>> Benchmark                                     (size)  Mode  Cnt      Score     Error  Units
>> Fp16ConversionBenchmark.float16ToFloat          2048  avgt   10   4659.796 ?  13.262  ns/op
>> Fp16ConversionBenchmark.float16ToFloatMemory    2048  avgt   10     22.957 ?   0.098  ns/op
>> 
>> 
>> #### with UseZfh disabled
>> (i.e. disable the intrinsic)
>> 
>> Benchmark                                     (size)  Mode  Cnt      Score    Error  Units
>> Fp16ConversionBenchmark.float16ToFloat          2048  avgt   10  22930.591 ? 72.595  ns/op
>> Fp16ConversionBenchmark.float16ToFloatMemory    2048  avgt   10     25.970 ?  0.063  ns/op
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix pipeline cost in ad; Add comments

Hi Hamlin, updated change looks good to me. Please wait a while for the kernel patch to land. Thanks.

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Marked as reviewed by fyang (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16802#pullrequestreview-1761527566