RFR: 8290249: Vectorize signum on AArch64 [v4]

[Andrew Haley]

On Fri, 19 Aug 2022 13:21:35 GMT, Bhavana-Kilambi <duke at openjdk.org> wrote:

>> This patch auto-vectorizes Math.signum intrinsic for float and  double
>> types on aarch64 (Neon and SVE). On SVE supporting machines, if the
>> MaxVectorSize <=16 the Neon code would be emitted and if the
>> MaxVectorSize > 16, the SVE code for the intrinsic would be emitted.
>> 
>> Following is the performance data for the micro test here -
>> test/micro/org/openjdk/bench/vm/compiler/VectorSignum.java
>> 
>> 
>> Benchmark	                Size    A	B       C
>> VectorSignum.doubleSignum	256	1.79	1.70	3.18
>> VectorSignum.doubleSignum	512	1.86	1.73	3.69
>> VectorSignum.doubleSignum	1024	1.89	1.74	2.98
>> VectorSignum.doubleSignum	2048	1.92	1.75	3.04
>> VectorSignum.floatSignum	256	3.34	3.06	3.92
>> VectorSignum.floatSignum	512	3.63	3.22	5.27
>> VectorSignum.floatSignum	1024	3.76	3.35	4.77
>> VectorSignum.floatSignum	2048	3.85	3.47	5.59
>> 
>> 
>> A, B , C machine descriptions given below -
>> A : 128-bit Neon machine
>> B : 256-bit SVE machine
>> C : 512-bit SVE machine
>> 
>> The numbers in the table are the gain ratios between the runtime (ns/op)
>> of the scalar, non-vectorized intrinsic code and the vectorized version
>> of the intrinsic (this patch).
>
> Bhavana-Kilambi has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add parantheses in aarch_assembler.hpp code to fix operator precedence error

Marked as reviewed by aph (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/9807