On Fri, 27 Oct 2023 05:09:23 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:
>> src/hotspot/share/opto/vectorIntrinsics.cpp line 1486:
>>
>>> 1484: // Check whether the predicated gather/scatter node is supported
>>> by architecture.
>>> 1485: VectorMaskUseType mask = (is_scatter ||
>>> !is_subword_type(elem_bt)) ? (VectorMaskUseType) (VecMaskUseLoad |
>>> VecMaskUsePred) : VecMaskUseLoad;
>>> 1486: if (!arch_supports_vector(is_scatter ?
>>> Op_StoreVectorScatterMasked : Op_LoadVectorGatherMasked, num_elem, elem_bt,
>>> mask)) {
>>
>> What is the difference between subword-type load gather and others? It seems
>> only check `VecMaskUseLoad` is enough for all kinds of masked
>> gather/scatter. Only checking `is_match_rule_supported_vector` for these ops
>> are ok. WDYT?
>
> sub-word gather do not emit any predicated instructions, thus only
> VectorMaskUseLoad is relevant in this context, however AVX512 and SVE does
> have a direct predicated gather instructions for 32/64 bit types.
I see, thanks! `VecMaskUsePred` is added to check
`match_rule_supported_vector_masked` for normal vector ops. That's because we
may add an additional mask input for those vector ops. But
`Load|StoreVectorScatterMasked` are different. They point to the masked
operations no matter how they are implemented. So just `VecMaskUseLoad` is fine
for all these two ops for me.
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PR Review Comment: https://git.openjdk.org/jdk/pull/16354#discussion_r1374135147
