RFR: JDK-8316756: C2 EA fails with "missing memory path" when encountering unsafe_arraycopy stub call [v3]

[Christian Hagedorn]

On Tue, 16 Jan 2024 17:02:55 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>>> Could we somehow assert here that we have a call with an intended narrow memory input? Directly asserting that this is an unsafe arraycopy might be too specific. But maybe we can add the following sanity check?
>>> 
>>> ```
>>> n->as_CallLeaf()->adr_type()->is_rawptr()
>>> ```
>> 
>> @vnkozlov what do you think?
>
> If it is not Narrow memory you will get `MergeMem` node as Call's memory input which we put on`mergemem_worklist` and not processing it or its users in this part of code. We have `assert(mergemem_worklist.contains(m->as_MergeMem())` instead here.
> 
> You can add `assert(!n->in(TypeFunc::Memory)->as_MergeMem(), "only narrow memory expected here");` if you want.

Right, we could add this assert as well for expecting a narrow memory input in general. What are your thoughts about explicitly asserting for an unsafe arraycopy when visiting this call?

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PR Review Comment: https://git.openjdk.org/jdk/pull/17347#discussion_r1453772091