RFR: 8293409: [vectorapi] Intrinsify VectorSupport.indexVector [v2]

[Jatin Bhateja]

On Tue, 18 Oct 2022 01:44:21 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> "`VectorSupport.indexVector()`" is used to compute a vector that contains the index values based on a given vector and a scale value (`i.e. index = vec + iota * scale`). This function is widely used in other APIs like "`VectorMask.indexInRange`" which is useful to the tail loop vectorization. And it can be easily implemented with the vector instructions.
>> 
>> This patch adds the vector intrinsic implementation of it. The steps are:
>> 
>>   1) Load the const "iota" vector.
>> 
>>   We extend the "`vector_iota_indices`" stubs from byte to other integral types. For floating point vectors, it needs an additional vector cast to get the right iota values.
>> 
>>   2) Compute indexes with "`vec + iota * scale`"
>> 
>> Here is the performance result to the new added micro benchmark on ARM NEON:
>> 
>> Benchmark                              Gain
>> IndexVectorBenchmark.byteIndexVector   1.477
>> IndexVectorBenchmark.doubleIndexVector 5.031
>> IndexVectorBenchmark.floatIndexVector  5.342
>> IndexVectorBenchmark.intIndexVector    5.529
>> IndexVectorBenchmark.longIndexVector   3.177
>> IndexVectorBenchmark.shortIndexVector  5.841
>> 
>> 
>> Please help to review and share the feedback! Thanks in advance!
>
> Xiaohong Gong has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Add the floating point support for VectorLoadConst and remove the VectorCast
>  - Merge branch 'master' into JDK-8293409
>  - 8293409: [vectorapi] Intrinsify VectorSupport.indexVector

Hi @XiaohongGong , patch now shows significant gains on both AVX512 and legacy X86 targets. 

X86 and common IR changes LGTM,  thanks!

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Marked as reviewed by jbhateja (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10332