On Tue, 8 Jul 2025 10:21:03 GMT, erifan <d...@openjdk.org> wrote:
>>> predicate cannot be negated AND the vector is all ones. Can you explain
>>> this condition?
>>
>> Ok, I'll add a comment for it.
>>
>>> Why do you guard against VectorNode::is_all_ones_vector(in2) at all?
>>
>> Because one of the nodes in the supported patterns by this PR needs to be
>> `MaskAll` or `Replicate`. And this function `VectorNode::is_all_ones_vector`
>> just meets our check for `MaskAll` and `Replicate`. Actually I don't quite
>> understand your question. I have two understandings:
>> 1. Not all nodes that `VectorNode::is_all_ones_vector` returns true are
>> `MaskAll` or `Replicate`, but other nodes that do not meet the conditions.
>> 2. Here, it does not need to be a vector with every bit 1, it only needs to
>> be an `all true` mask.
>>
>> Which one do you mean? Or something else? Thanks~
>
> The purpose of this PR is optimizing the following kinds of patterns:
>
> XXXVector va, vb;
> va.compare(EQ, vb).not()
>
> And the generated IR of `va.compare(EQ, vb).not()` is `(XorVMask
> (VectorMaskCmp va vb EQ) (MaskAll -1))`. On platforms like aarch64 NEON,
> `MaskAll` is `Replicate`. And `MaskAll` and `Replicate` are both all ones
> vectors, so we do this check `VectorNode::is_all_ones_vector(in2)`
Oh wow, my bad. I misunderstood the brackets!
Instead of:
!(in1->as_VectorMaskCmp())->predicate_can_be_negated() ||
!VectorNode::is_all_ones_vector(in2)) {
I read:
!(in1->as_VectorMaskCmp()->predicate_can_be_negated() ||
!VectorNode::is_all_ones_vector(in2))) {
That confused me a lot... absolutely my bad.
Well actually then my indentation suggestion was terrible!
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/24674#discussion_r2192261081
