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

[Vladimir Ivanov]

On Wed, 23 Apr 2025 08:43:47 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> 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?

Does the following check catch `UseRVV == false` case on RISC-V? 

public boolean isSupported(Operator op, VectorSpecies<?> vspecies) {
...
            int maxLaneCount = VectorSupport.getMaxLaneCount(vspecies.elementType());
            if (vspecies.length() > maxLaneCount) {
                return false; // lacking vector support
            }
...

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

PR Review Comment: https://git.openjdk.org/jdk/pull/24462#discussion_r2056642914