[vectorIntrinsics+mask] RFR: 8268154: Add masking support for vector load intrinsics

[Xiaohong Gong]

On Mon, 7 Jun 2021 09:05:44 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

> This patch adds the predicate support for masked load vector operation, including the Vector API java implementation and hotspot intrinsics changes. The main changes contain:
>   - Adding a new hotspot intrinsic method (`loadMasked`), which can transform the vector mask class and value to hotspot. It is called by the masked `"fromArray"` API in JAVA level. The compiler will generate the masked vector load node if the current platform supports the predicate feature and backend has implemented it. Otherwise, the vector blend pattern will be generated like before.
>   - Adding the similar masked support for load/store boolean/char array.
> 
> Note that the intrinsification when there is the array range bailout is not implemented in this patch. We are considering making it vectorized with predicate feature for SVE/AVX-512 as well, and will create a separate patch for it in future.
> 
> Also note that this patch doesn't contain any backend changes.

> > Currently there following assertion check in both LoadVectorMaskedNode and StoreVectorMaskedNode
> > `assert(mask->bottom_type()->is_vectmask(), "sanity");`
> > This should be relaxed since mask argument will be VectorUnboxNode until macro expansion.
> > I added following static routine in VectorNode class to get over it in my local sandbox, and adjusted the assertion to use it. If suitable maybe we can integrate it in this patch.
> > ```
> > bool VectorNode::is_vector_mask(Node* n) {
> >   if (n->bottom_type()->is_vectmask()) {
> >     return true;
> >   }
> >   if (n->Opcode() == Op_VectorUnbox) {
> >     const TypeInstPtr* vector_klass_from = n->as_VectorUnbox()->obj()->bottom_type()->isa_instptr();
> >     ciKlass* vbox_klass_from = vector_klass_from->const_oop()->as_instance()->java_lang_Class_klass();
> >     return vbox_klass_from->is_subclass_of(ciEnv::current()->vector_VectorMask_klass());
> >   }
> >   return false;
> > }
> > ```
> 
> Thanks so for your suggestion @jatin-bhateja ! This looks ok to me. So that I can also revert the type changes to VectorBox/VectorUnbox in PR #78.

Regarding to merge it, do you think it's better to fix it in https://github.com/openjdk/panama-vector/pull/78 instead of this PR? One reason is that there are other mask IRs that also contains the same assertion, we can update them together. Another one is that I can revert the type changes for `VectorBox/VectorUnbox` and have a test together. Thanks!

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PR: https://git.openjdk.java.net/panama-vector/pull/90