RFR: 8353786: Migrate Vector API math library support to FFM API [v12]

[Hamlin Li]

On Wed, 23 Apr 2025 08:40:44 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Avoid thread state transition in VectorSupport_GetCPUFeatures
>
> src/jdk.incubator.vector/share/classes/jdk/incubator/vector/VectorMathLibrary.java line 288:
> 
>> 286:                   IntFunction<VectorSupport.UnaryOperation<V,?>> implSupplier,
>> 287:                   V v) {
>> 288:         var entry = lookup(op, opc, vspecies, implSupplier);
> 
> Seems there is another issue for riscv here.
> If the rvv extension is not supported on the running machine, it will still generate the code using rvv, this should lead to a crash at runtime?

In previous code, we use `UseRVV` to detect if rvv extension is supported.

On the other hand, user can choose to disable UseRVV if they want even if rvv extension is supported on the running machine. In this sense, there could be similar issue on other platforms?

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PR Review Comment: https://git.openjdk.org/jdk/pull/24462#discussion_r2055556734