RFR: 8294588: Auto vectorize half precision floating point conversion APIs [v2]

[Xiaohong Gong]

On Tue, 6 Dec 2022 02:09:59 GMT, Smita Kamath <svkamath at openjdk.org> wrote:

>> Hi All, 
>> 
>> I have added changes for autovectorizing Float.float16ToFloat and Float.floatToFloat16 API's.
>> Following are the performance numbers of JMH micro Fp16ConversionBenchmark:
>> Before code changes:
>> Benchmark | (size) | Mode | Cnt | Score | Error | Units
>> Fp16ConversionBenchmark.float16ToFloat | 2048 | thrpt | 3 | 1044.653 | ±     0.041 | ops/ms
>> Fp16ConversionBenchmark.float16ToFloatMemory | 2048 | thrpt | 3 | 2341529.9 | ± 11765.453 | ops/ms
>> Fp16ConversionBenchmark.floatToFloat16 | 2048 | thrpt | 3 | 2156.662 | ±     0.653 | ops/ms
>> Fp16ConversionBenchmark.floatToFloat16Memory | 2048 | thrpt | 3 | 2007988.1 | ±   361.696 | ops/ms
>> 
>> After:
>> Benchmark | (size) | Mode |  Cnt | Score | Error |   Units
>> Fp16ConversionBenchmark.float16ToFloat  | 2048 | thrpt | 3 |  20460.349 |±  372.327 |  ops/ms
>> Fp16ConversionBenchmark.float16ToFloatMemory | 2048 |  thrpt | 3 | 2342125.200 |± 9250.899  |ops/ms
>> Fp16ConversionBenchmark.floatToFloat16  |  2048 | thrpt  |  3 |   22553.977 |±  483.034 | ops/ms
>> Fp16ConversionBenchmark.floatToFloat16Memory | 2048 | thrpt |  3 |  2007899.797 |±  150.296 | ops/ms
>> 
>> Kindly review and share your feedback.
>> 
>> Thanks.
>> Smita
>
> Smita Kamath has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Updated code as per review comments

src/hotspot/share/opto/vectornode.cpp line 263:

> 261:     return Op_SignumVD;
> 262:   case Op_ConvHF2F:
> 263:     return Op_VectorCastH2F;

Could we use the same name style with the scalar op, i.e. `"Op_VectorCastHF2F"` ?

src/hotspot/share/opto/vectornode.cpp line 265:

> 263:     return Op_VectorCastH2F;
> 264:   case Op_ConvF2HF:
> 265:     return Op_VectorCastF2H;

Same with "Op_VectorCastHF2F"

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PR: https://git.openjdk.org/jdk/pull/11471