[vectorIntrinsics] RFR: RFC: Vector API masking support proposal for Arm SVE [v3]

[Vladimir Ivanov]

On Thu, 18 Mar 2021 11:26:43 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Xiaohong Gong has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add mask support for masked binary operations
>
> src/hotspot/share/opto/vectorIntrinsics.cpp line 583:
> 
>> 581:       const TypeVMask* vmask_type = TypeVMask::make(elem_bt, num_elem);
>> 582:       mask = gvn().transform(new VectorToMaskNode(mask, vmask_type));
>> 583:       operation->add_req(mask);
> 
> We are adding a new input to a nary operation with existing opcodes
> Eg. following will be graph shapes with or w/o mask node for an add integer vector operation:-
>    AddVI SRC1 SRC2
>    AddVI SRC1 SRC2 MASK
> 
> Creating a new VectorMaskedOperNode by folding blend + vector pattern will remove lots of redundant instruction patterns from the AD files, this has been a cause of concern for us(X86) in past.

One downside of `AddVI SRC1 SRC2 MASK` shape is that the operation is not commutative anymore:
AddVI SRC1 SRC2 MASK = VectorBlend SRC1 (AddVI SRC1 SRC2) MASK
AddVI SRC2 SRC1 MASK = VectorBlend SRC2 (AddVI SRC2 SRC1) MASK

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PR: https://git.openjdk.java.net/panama-vector/pull/40