Add TR::MemoryReference::create API with trivial implementation

This API is meant to be overridden in downstream projects who wish to
have custom logic for generating memory references. Typical examples of
this is for handling unresolved memory references.

Signed-off-by: Filip Jeremic <fjeremic@ca.ibm.com>

compiler/z/codegen/OMRMemoryReference.cpp

@@ -3300,6 +3300,12 @@ OMR::Z::MemoryReference::doEvaluate(TR::Node * subTree, TR::CodeGenerator * cg)
    return false;
    }
 
+TR::MemoryReference*
+OMR::Z::MemoryReference::create(TR::CodeGenerator* cg, TR::Node* node)
+   {
+   return generateS390MemoryReference(node, cg);
+   }
+
 ///////////////////////////////////////////
 // Generate Routines
 ///////////////////////////////////////////

compiler/z/codegen/OMRMemoryReference.hpp

@@ -465,6 +465,21 @@ void createPatchableDataInLitpool(TR::Node * node, TR::CodeGenerator * cg, TR::R
 
 bool symRefHasTemporaryNegativeOffset() {return false;}
 void setMemRefAndGetUnresolvedData(TR::Snippet *& snippet) {}
+
+/**
+ * \brief
+ *   Create a MemoryReference from a given node. 
+ *
+ * \param[in] node
+ *   The node which describes the memory reference.
+ *
+ * \param[in] cg
+ *   The code generator used to generate the instructions.
+ *
+ * \return
+ *   The \c TR::MemoryReference representing this node.
+ */
+static TR::MemoryReference* create(TR::CodeGenerator* cg, TR::Node* node);
 };
 }
 }