RFR(S): 8243670: Unexpected test result caused by C2 MergeMemNode::Ideal

[Roland Westrelin]

Hi Felix,

> So I guess it might be safer to go with the initially proposed patch.  

What about a PhiNode::Identity transformation that, for a memory phi,
looks for phis with identical inputs and if it finds one that has type
TypePtr::BOTTOM, replaces the current phi with the bottom phi? Wouldn't
that result in both the LoadI and the MergeMem with the same memory
input which would fix the problem?

Roland.