Adds meta information to control graph

Meta info is very useful during type analysis.
It helps to make decisions based on graph structure.

In future, more flags will be added.

Issue: #17

include/analysis.h

@@ -461,6 +461,13 @@ class ControlGraph {
         return iDomain->second;
     }
 
+    struct TMetaInfo {
+        bool hasLoops;
+        bool hasBackEdgeTau;
+    };
+
+    TMetaInfo& getMeta() { return m_metaInfo; }
+
 private:
     ParsedMethod* m_parsedMethod;
     ParsedBlock*  m_parsedBlock;
@@ -471,6 +478,8 @@ class ControlGraph {
 
     typedef std::map<BasicBlock*, ControlDomain*> TDomainMap;
     TDomainMap    m_blocksToDomains;
+
+    TMetaInfo     m_metaInfo;
 };
 
 template<> InstructionNode* ControlNode::cast<InstructionNode>();

src/ControlGraph.cpp

@@ -747,6 +747,8 @@ class TauLinker : private BackEdgeDetector {
             }
         }
 
+        getGraph().getMeta().hasLoops = !getBackEdges().empty();
+
         // When all nodes visited, process the pending list
         TInstructionSet::iterator iNode = m_pendingNodes.begin();
         for (; iNode != m_pendingNodes.end(); ++iNode)
@@ -923,6 +925,9 @@ class TauLinker : private BackEdgeDetector {
             TauNode* const assignType = assignTemporary->getTauNode();
             assert(inheritedType);
 
+            if ((*iAssignSite).byBackEdge)
+                getGraph().getMeta().hasBackEdgeTau = true;
+
             if (! instruction.getTauNode()) {
                 // FIXME Could it be that the only incoming is accessible by back edge?
                 //       Possbible scenario: push default nil, assigned later, branch up