RFR: 8310190: C2 SuperWord: AlignVector is broken, generates misaligned packs [v3]

[Emanuel Peter]

On Fri, 6 Oct 2023 23:44:02 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Emanuel Peter has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix up TestVectorizationMismatchedAccess.java
>
> src/hotspot/share/opto/compile.cpp line 3668:
> 
>> 3666: 
>> 3667:   case Op_LoadVector:
>> 3668:   case Op_StoreVector:
> 
> What about Masked Load and Store vectors?

@vnkozlov for now, I only mark the vectors produced from SuperWord. And SuperWord only produces LoadVector/StoreVector, and nothing masked.
The masked vector memops come from the VectorAPI. But the VectorAPI does not respect AlignVector, and may generate misaligned vector ops - and then the verification fails.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14785#discussion_r1355108445