RFR: 8338023: Support two vector selectFrom API [v13]

[Sandhya Viswanathan]

On Mon, 30 Sep 2024 22:51:57 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Handling NPOT vector length for AArch64 SVE with vector sizes varying b/w 128 and 2048 bits at 128 bit increments.
>
> src/hotspot/share/opto/vectorIntrinsics.cpp line 2689:
> 
>> 2687:         !arch_supports_vector(cast_vopc, num_elem, T_BYTE, VecMaskNotUsed)                   ||
>> 2688:         !arch_supports_vector(Op_VectorLoadShuffle, num_elem, index_elem_bt, VecMaskNotUsed) ||
>> 2689:         !arch_supports_vector(Op_Replicate, num_elem, T_BYTE, VecMaskNotUsed)) {
> 
> Where SelectFromTwoVector is not supported, the alternate implementation is as part of SelectFromTwoVectorNode::Ideal() instead of right here.  A comment both here as well as in the Ideal() implementation is needed to keep these checks in sync.

We need to add VectorMaskCast here in the checks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20508#discussion_r1781886783