RFR: 8354242: VectorAPI: combine vector not operation with compare [v6]

[erifan]

On Thu, 29 May 2025 07:55:06 GMT, erifan <duke at openjdk.org> wrote:

>> Also: You now cast `(VectorMaskCmpNode*) in1` twice. Can we not do `as_VectorMaskCmp()`? Or could we at least cast it only once, and then use it as `in1_mask_cmp` instead?
>
>> What is the hard-coded ^ 4 here?
> 
> This is to negate the comparison condition. We can't use `BoolTest::negate()` here because the comparison condition may be **unsigned** comparison. Since there's already a `negate()` function in `BoolTest`, so I tend to add a new function `get_negative_predicate` for this into class `VectorMaskCmpNode`.
> 
>> Also: You now cast (VectorMaskCmpNode*) in1 twice. Can we not do as_VectorMaskCmp()? Or could we at least cast it only once, and then use it as in1_mask_cmp instead?
> 
> For the first cast, I think you mean
> 
>   if (in1->Opcode() != Op_VectorMaskCmp ||
>       in1->outcnt() > 1 ||
>       !((VectorMaskCmpNode*) in1)->predicate_can_be_negated() ||
>       !VectorNode::is_all_ones_vector(in2)) {
>     return nullptr;
>   }
> 
> To remove one cast, then we have to split the above `if` because `in1` may not be a `VectorMaskCmpNode`.
> 
>   if (in1->Opcode() != Op_VectorMaskCmp) {
>     return nullptr;
>   }
>   VectorMaskCmpNode* in1_as_mask_cmp = (VectorMaskCmpNode*) in1;
>   if (in1->outcnt() > 1 ||
>       !in1_as_mask_cmp->predicate_can_be_negated() ||
>       !VectorNode::is_all_ones_vector(in2)) {
>     return nullptr;
>   }
>  BoolTest::mask neg_cond = (BoolTest::mask) (in1_as_mask_cmp->get_predicate() ^ 4);
> 
> Does this look better to you ?

For now I kept the current approach, as I feel it's a little more compact. Thanks!

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PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2128358563