Track whether a node or variable are likely to be a Smi value. Propagate that...

src/variables.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 43 matching lines @@
 #ifdef DEBUG
   void Print();
 #endif
 
  private:
   int nreads_;
   int nwrites_;
 };
 
 
+// Variables and AST expression nodes can track their "type" to enable
+// optimizations and removal of redundant checks when generating code.
+
+class StaticType BASE_EMBEDDED {
+ public:
+  enum Kind {
+    UNKNOWN,
+    LIKELY_SMI
+  };
+
+  StaticType() : kind_(UNKNOWN) {}
+
+  bool Is(Kind kind) const { return kind_ == kind; }
+
+  bool IsKnown() const { return !Is(UNKNOWN); }
+  bool IsUnknown() const { return Is(UNKNOWN); }
+  bool IsLikelySmi() const { return Is(LIKELY_SMI); }
+
+  void CopyFrom(StaticType* other) {
+    kind_ = other->kind_;
+  }
+
+  static char* Type2String(StaticType* type);
+
+  // LIKELY_SMI accessors
+  void SetAsLikelySmi() {
+    kind_ = LIKELY_SMI;
+  }
+
+  void SetAsLikelySmiIfUnknown() {
+    if (IsUnknown()) {
+      SetAsLikelySmi();
+    }
+  }
+
+ private:
+  Kind kind_;
+
+  DISALLOW_COPY_AND_ASSIGN(StaticType);
+};
+
+
 // The AST refers to variables via VariableProxies - placeholders for the actual
 // variables. Variables themselves are never directly referred to from the AST,
 // they are maintained by scopes, and referred to from VariableProxies and Slots
 // after binding and variable allocation.
 
 class Variable: public ZoneObject {
  public:
   enum Mode {
     // User declared variables:
     VAR,       // declared via 'var', and 'function' declarations
@@ skipping 33 matching lines @@
   bool IsVariable(Handle<String> n) {
     return !is_this() && name().is_identical_to(n);
   }
 
   bool is_global() const;
   bool is_this() const { return is_this_; }
 
   Expression* rewrite() const  { return rewrite_; }
   Slot* slot() const;
 
+  StaticType* type() { return &type_; }
+
  private:
   Variable(Scope* scope, Handle<String> name, Mode mode, bool is_valid_LHS,
       bool is_this);
 
   Scope* scope_;
   Handle<String> name_;
   Mode mode_;
   bool is_valid_LHS_;
   bool is_this_;
 
   // Usage info.
   bool is_accessed_from_inner_scope_;  // set by variable resolver
   UseCount var_uses_;  // uses of the variable value
   UseCount obj_uses_;  // uses of the object the variable points to
 
+  // Static type information
+  StaticType type_;
+
   // Code generation.
   // rewrite_ is usually a Slot or a Property, but maybe any expression.
   Expression* rewrite_;
 
   friend class VariableProxy;
   friend class Scope;
   friend class LocalsMap;
   friend class AstBuildingParser;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_VARIABLES_H_