RFR: 8317121: vector_masked_load instruction is moved too early after JDK-8286941 [v2]

[Aleksey Shipilev]

On Tue, 3 Oct 2023 16:10:27 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> [JDK-8286941](https://bugs.openjdk.org/browse/JDK-8286941) changed how masked vector operations are created and processed. It calls `LoadNode::Ideal()` which tries to find best place in code for it.
>> Unfortunately some places do not expect to have vector access to modified memory.
>> In `LoadNode::find_previous_arraycopy()` the call to `ArrayCopyNode::modifies()` assumes that it access only one element and did not take into account that a vector may access wider memory.
>> The same issue exists with Unsafe mismatching (bigger size) access.
>> 
>> The fix is to take into account size of memory access.
>> 
>> New regression test is added which show the issue.
>> 
>> Tested tier1-5. xcomp, stress. Testing tier6-7 in progress.
>
> Vladimir Kozlov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Be more specific in exception message which test failed

I think the original JBS issue got closed somehow, could it be open again?
https://bugs.openjdk.org/browse/JDK-8317121

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PR Comment: https://git.openjdk.org/jdk/pull/16015#issuecomment-1758130307