RFR: 8354242: VectorAPI: combine vector not operation with compare [v8]

[erifan]

On Wed, 11 Jun 2025 09:09:57 GMT, erifan <duke at openjdk.org> wrote:

>> src/hotspot/share/opto/vectornode.cpp line 2221:
>> 
>>> 2219:   // XorV/XorVMask is commutative, swap VectorMaskCmp/VectorMaskCast to in1.
>>> 2220:   if (in2->Opcode() == Op_VectorMaskCmp ||
>>> 2221:       (in2->Opcode() == Op_VectorMaskCast && in2->in(1)->Opcode() == Op_VectorMaskCmp)) {
>> 
>> We may need to consider cases that a `VectorMaskCast` is generated between `compare + not`, such as `compare + cast + not`. For such cases, the element size maybe different for input and output of a `cast`.  Although this patch's intention is not for the latter pattern, current change have also covered it well. Could you please add more test/jmh for all kinds of `cast` pattern here? And I think the scope of this PR could be also extended to `compare + cast + not`. WDYT?
>
> Good catch, I'll add more tests and check the correctness. Thanks~

Added more tests for this, thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2166350143