RFR: 8285301: C2: assert(!requires_atomic_access) failed: can't ensure atomicity

[Vladimir Kozlov]

On Wed, 27 Apr 2022 10:25:36 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> We hit asserts in `BarrierSetC2::load_at_resolved` and `BarrierSetC2::store_at_resolved` when running with `-XX:+AlwaysAtomicAccesses` because the corresponding code paths have not been implemented yet. Although the assert triggers on all platforms, it only affects long and double accesses on 32-bit systems (everything else is atomic anyway).
> 
> I moved the `requires_atomic_access` logic into `LoadNode::make` and `StoreNode::make` and refactored related code.
> 
> I noticed that `LoadNode::convert_to_reinterpret_load` and `StoreNode::convert_to_reinterpret_store` did not properly check for `requires_atomic_access` and fixed that as well.
> 
> I'm currently running all tests with `-XX:+AlwaysAtomicAccesses`.
> 
> Thanks,
> Tobias

src/hotspot/share/opto/memnode.hpp line 610:

> 608:   static StoreNode* make(PhaseGVN& gvn, Node* c, Node* mem, Node* adr,
> 609:                          const TypePtr* at, Node* val, BasicType bt,
> 610:                          MemOrd mo = MemNode::unordered, bool require_atomic_access = false);

I think it was intentionally `MemOrd mo` parameter did not specify default value so that value is always specified at all call sites. I think this change is not required for the fix.

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PR: https://git.openjdk.java.net/jdk/pull/8422