RFR: 8312425: [vectorapi] AArch64: Optimize vector math operations with SLEEF [v4]

[Xiaohong Gong]

On Thu, 23 Nov 2023 15:43:34 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Address review comments in build system
>
> make/autoconf/lib-vmath.m4 line 94:
> 
>> 92:           # Check the ARM SVE feature
>> 93:           SVE_CFLAGS="-march=armv8-a+sve"
>> 94: 
> 
> What's this about? We're building a standard binary, and all SVE detection is to be deferred to runtime.

We have to use this c-compiler option to build out the SVE ABIs (e.g. `svfloat32_t sinfx_u10sve(svfloat32_t input)`) in `libvmath.so`. Without this option, at build time, all the sve related featues like `arm_sve.h / __ARM_FEATURE_SVE` are missing, together with the sve symbols in `libvmath.so` we needed at runtime.  That means at runtime, hotspot cannot find out the sve symbols and the vector operations will fall back to the default java implementation.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16234#discussion_r1405529521