RFR: 8318650: Optimized subword gather for x86 targets. [v3]

[Jatin Bhateja]

On Fri, 3 Nov 2023 20:00:30 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Restricting masked sub-word gather to AVX512 target to align with integral gather support.
>
> src/hotspot/share/opto/matcher.cpp line 2495:
> 
>> 2493:         n->del_req(MemNode::ValueIn+1);
>> 2494:         break;
>> 2495:       }
> 
> The "break;" should be after the "}".

Its placed appropriately, we intend take fall-through path for non sub-word case.

> src/hotspot/share/opto/vectorIntrinsics.cpp line 1551:
> 
>> 1549:   Node* index_vect = nullptr;
>> 1550:   const TypeInstPtr* vbox_idx_type = TypeInstPtr::make_exact(TypePtr::NotNull, vbox_idx_klass);
>> 1551:   if (!is_subword_type(elem_bt)) {
> 
> This could check for argument(8) to be not null instead.

Sub-word type check makes the intent more explicit.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16354#discussion_r1382572989
PR Review Comment: https://git.openjdk.org/jdk/pull/16354#discussion_r1382572622