RFR: 8353786: Migrate Vector API math library support to FFM API [v13]

[Vladimir Ivanov]

On Thu, 24 Apr 2025 18:57:11 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   CPUFeatures: RISC-V support
>
> src/hotspot/share/opto/vectorIntrinsics.cpp line 563:
> 
>> 561:     debug_name = debug_name_oop->const_oop()->as_instance()->java_lang_String_str(buf, buflen);
>> 562:   }
>> 563:   Node* vcall = make_runtime_call(RC_VECTOR,
> 
> By generating an upfront CallLeafVectorNode, we may miss out on performing any GVN-style optimization for trigonometric identities like the following. do you think creating a macro node which can lazily be expanded to call node during macro expansion will help.
> 
> arcsin(sin(x)) => x
> arccos(cos(x)) => x
> sin(arcsin(x) => x
> cos(arccos(x) => x

It does look attractive, but macro expansion-based solution requires JVM to internalize such operations and their properties. 

IMO a higher-level solution based on more generic JVM primitives would enable libraries to properly annotate their operations in Java bytecodes/class files, so C2 can perform such type of transformations without the need to intrinsify each individual operation first. (Think of [JDK-8218414](https://bugs.openjdk.org/browse/JDK-8218414) / [JDK-8347901](https://bugs.openjdk.org/browse/JDK-8347901) on steroids.)

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

PR Review Comment: https://git.openjdk.org/jdk/pull/24462#discussion_r2059356271