RFR: 8312425: [vectorapi] AArch64: Optimize vector math operations with SLEEF [v2]

[Magnus Ihse Bursie]

On Thu, 14 Mar 2024 09:14:04 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Hi,
>> Can you help to review this patch?
>> Thanks
>> 
>> This is a continuation of work based on [1] by @XiaohongGong, most work was done in that pr. In this new pr, just rebased the code in [1], then added some minor changes (renaming of calling method, add libsleef as extra lib in CI cross-build on aarch64 in github workflow); I aslo tested the combination of following scenarios:
>> * at build time
>>   * with/without sleef
>>   * with/without sve support 
>> * at runtime
>>   * with/without sleef
>>   * with/without sve support 
>> 
>> [1] https://github.com/openjdk/jdk/pull/16234
>> 
>> ## Regression Test
>> * test/jdk/jdk/incubator/vector/
>> * test/hotspot/jtreg/compiler/vectorapi/
>> 
>> ## Performance Test
>> Previously, @XiaohongGong has shared the data: https://github.com/openjdk/jdk/pull/16234#issuecomment-1767727028
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix variable name in github workflow

make/autoconf/flags-cflags.m4 line 994:

> 992:   # for SVE. Set SVE_CFLAGS to -march=armv8-a+sve if it does. Empty otherwise.
> 993:   # ACLE and this flag are required to build the Arm SVE related functions in
> 994:   # libvmath.

Suggestion:

  # Check whether the compiler supports the Arm C Language Extensions (ACLE)
  # for SVE. Set SVE_CFLAGS to -march=armv8-a+sve if it does.
  # ACLE and this flag are required to build the aarch64 SVE related functions in
  # libvectormath.

src/jdk.incubator.vector/linux/native/libvmath/vect_math.h line 1:

> 1: /*

I'd just like to raise the question of naming. Right now the terms "vmath", "vect_math" and "vector_math" seems to be used interchangeably. I think it would be good to standardize on one name, and my suggestion is to go with the complete name -- that fits with a general theme in Java. It has the benefit that if there are many ways to abbreviate a term, there is only one way to not abbreviate it.

On the other hand, using `_` in library names is not really that common, so I'd suggest this file should be named `libvectormath/vector_math.h`. (And correspondingly for the other files.)

src/jdk.incubator.vector/linux/native/libvmath/vect_math.h line 31:

> 29: #endif
> 30: 
> 31: #ifndef VMATH_EXPORT

You can just use `JNIEXPORT` instead of trying to brew your own solution.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18294#discussion_r1524748090
PR Review Comment: https://git.openjdk.org/jdk/pull/18294#discussion_r1524745947
PR Review Comment: https://git.openjdk.org/jdk/pull/18294#discussion_r1524746666