On Fri, 13 May 2022 01:35:40 GMT, Xiaohong Gong <xg...@openjdk.org> wrote:

>> Checking whether the indexes of masked lanes are inside of the valid memory 
>> boundary is necessary for masked vector memory access. However, this could 
>> be saved if the given offset is inside of the vector range that could make 
>> sure no IOOBE (IndexOutOfBoundaryException) happens. The masked load APIs 
>> have saved this kind of check for common cases. And this patch did the 
>> similar optimization for the masked vector store.
>> The performance for the new added store masked benchmarks improves about 
>> `1.83x ~ 2.62x` on a x86 system:
>> Benchmark                                   Before    After     Gain Units
>> StoreMaskedBenchmark.byteStoreArrayMask   12757.936 23291.118  1.826 ops/ms
>> StoreMaskedBenchmark.doubleStoreArrayMask  1520.932  3921.616  2.578 ops/ms
>> StoreMaskedBenchmark.floatStoreArrayMask   2713.031  7122.535  2.625 ops/ms
>> StoreMaskedBenchmark.intStoreArrayMask     4113.772  8220.206  1.998 ops/ms
>> StoreMaskedBenchmark.longStoreArrayMask    1993.986  4874.148  2.444 ops/ms
>> StoreMaskedBenchmark.shortStoreArrayMask   8543.593 17821.086  2.086 ops/ms
>> Similar performane gain can also be observed on ARM hardware.
> Xiaohong Gong has updated the pull request incrementally with one additional 
> commit since the last revision:
>   Wrap the offset check into a static method

Thanks for the explanation! Yeah, the main problem is Java doesn't have the 
direct unsigned comparison. We need the function call. From the two ways you 
provided, I think the second `Integer.lessThanUnsigned` looks better. But I'm 
not sure whether this could improve the performance a lot, although the first 
check `a.length - vsp.length() > 0` can be hosited out side of the loop. And 
this might make the codes more complex for me. Maybe we can do a pre research 
to find a better implementation to the unsigned comparison first. Do you think 


PR: https://git.openjdk.java.net/jdk/pull/8620

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