On Thu, 7 Dec 2023 09:30:01 GMT, Xiaohong Gong <xg...@openjdk.org> wrote:

>> Currently the vector floating-point math APIs like 
>> `VectorOperators.SIN/COS/TAN...` are not intrinsified on AArch64 platform, 
>> which causes large performance gap on AArch64. Note that those APIs are 
>> optimized by C2 compiler on X86 platforms by calling Intel's SVML code [1]. 
>> To close the gap, we would like to optimize these APIs for AArch64 by 
>> calling a third-party vector library called libsleef [2], which are 
>> available in mainstream Linux distros (e.g. [3] [4]).
>> 
>> SLEEF supports multiple accuracies. To match Vector API's requirement and 
>> implement the math ops on AArch64, we 1) call 1.0 ULP accuracy with FMA 
>> instructions used stubs in libsleef for most of the operations by default, 
>> and 2) add the vector calling convention to apply with the runtime calls to 
>> stub code in libsleef. Note that for those APIs that libsleef does not 
>> support 1.0 ULP, we choose 0.5 ULP instead.
>> 
>> To help loading the expected libsleef library, this patch also adds an 
>> experimental JVM option (i.e. `-XX:UseSleefLib`) for AArch64 platforms. 
>> People can use it to denote the libsleef path/name explicitly. By default, 
>> it points to the system installed library. If the library does not exist or 
>> the dynamic loading of it in runtime fails, the math vector ops will 
>> fall-back to use the default scalar version without error. But a warning is 
>> printed out if people specifies a nonexistent library explicitly.
>> 
>> Note that this is a part of the original proposed patch in panama-dev [5], 
>> just with some initial review comments addressed. And now we'd like to get 
>> some wider feedbacks from more hotspot experts.
>> 
>> [1] https://github.com/openjdk/jdk/pull/3638
>> [2] https://sleef.org/
>> [3] https://packages.fedoraproject.org/pkgs/sleef/sleef/
>> [4] https://packages.debian.org/bookworm/libsleef3
>> [5] https://mail.openjdk.org/pipermail/panama-dev/2022-December/018172.html
>
> Xiaohong Gong has updated the pull request incrementally with one additional 
> commit since the last revision:
> 
>   Fix potential attribute issue

> Build changes finally look good. Great, actually! Thanks for persisting, 
> despite the many rounds of review.
> 
> You will still need the 2 hotspot reviews for the hotspot part of the patch.
> 
> /reviewers 3

Thanks for the review and all the comments!

-------------

PR Comment: https://git.openjdk.org/jdk/pull/16234#issuecomment-1846330893

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