[vectorIntrinsics] RFR: Load store memory segment

[Xiaohong Gong]

On Wed, 30 Mar 2022 02:14:52 GMT, Xiaohong Gong <xgong at openjdk.org> wrote:

>> This is the initial implementation for loading/storing vectors from/to memory segments.
>> 
>> Some of the changes are related to `int` -> `long` for the offset. I had to change the load/store intrinsic signatures to accept an offset as a `long`. This does not affect the C2 implementation, only the fallback lambdas. So in some cases there is a downcast to `int`, which is safe because the original input was an `int` e.g. the offset for primitive array access. 
>> 
>> Some changes related to module dependency and memory segment proxies will go away when the Memory Segment API is integrated into `java.base` as a preview API.
>>  
>> There is still more work to do but i wanted to get this in now and iterate:
>> - I will remove the `byte[]` and `ByteBuffer` accepting load/store methods in a following PR.
>> - some additional negative tests are required, specifically if a scope of segment is not alive, or the segment covers a heap array other than `byte[]`.
>
> src/jdk.incubator.vector/share/classes/jdk/incubator/vector/ByteVector.java line 3369:
> 
>> 3367:     /**
>> 3368:      * Loads a vector from a {@linkplain ByteBuffer byte buffer}
>> 3369:      * starting at an offset into the byte buffer
> 
> Should be `{@linkplain MemorySegment memory segment}` and the `memory segment buffer` ?

Please ignore my comments since it is fixed in the second commit. Thanks!

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PR: https://git.openjdk.java.net/panama-vector/pull/187