Id's fo Expr-inherited classes

ast.h

@@ -48,8 +48,9 @@
     (Expr) and statements (Stmt) inherit from this class.
 */
 class ASTNode {
+    const unsigned char SubclassID;   // Subclass identifier (for isa/dyn_cast)
 public:
-    ASTNode(SourcePos p) : pos(p) { }
+    ASTNode(SourcePos p, unsigned scid) : SubclassID(scid), pos(p) { }
     virtual ~ASTNode();
 
     /** The Optimize() method should perform any appropriate early-stage
@@ -74,12 +75,24 @@ public:
     /** All AST nodes must track the file position where they are
         defined. */
     SourcePos pos;
+   
+    /** An enumeration for keeping track of the concrete subclass of Value 
+        that is actually instantiated.*/
+    enum ASTNodeTy {
+        ExprID,
+        StmtID
+    };
+   
+    /** Return an ID for the concrete type of this object. This is used to
+        implement the classof checks.  This should not be used for any 
+        other purpose, as the values may change as ISPC evolves */
+    unsigned getValueID() const {
+        return SubclassID;
+    }
+
+    static inline bool classof(ASTNode const*) { return true; }
 };
 
-
-/** Simple representation of the abstract syntax trees for all of the
-    functions declared in a compilation unit.
- */
 class AST {
 public:
     /** Add the AST for a function described by the given declaration