Stack allocating block scoped variables.

src/scopes.h

 // Copyright 2011 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
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   // Current number of var or const locals.
   int num_var_or_const() { return num_var_or_const_; }
 
   // Result of variable allocation.
   int num_stack_slots() const { return num_stack_slots_; }
   int num_heap_slots() const { return num_heap_slots_; }
 
   int StackLocalCount() const;
   int ContextLocalCount() const;
 
+  // Computed during code generation; for block scopes only. The depth
+  // above the function locals on the stack at which the stack locals
+  // of the block start.
+  int stack_slots_depth() const {
+    return stack_slots_depth_;
+  }
+  void set_stack_slots_depth(int stack_slots_depth) {
+    stack_slots_depth_ = stack_slots_depth;
+  }
+
   // Make sure this scope and all outer scopes are eagerly compiled.
   void ForceEagerCompilation()  { force_eager_compilation_ = true; }
 
   // Determine if we can use lazy compilation for this scope.
   bool AllowsLazyCompilation() const;
 
   // True if the outer context of this scope is always the global context.
   bool HasTrivialOuterContext() const;
 
   // The number of contexts between this and scope; zero if this == scope.
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   // constructed based on a serialized scope info or a catch context).
   bool already_resolved_;
 
   // Computed as variables are declared.
   int num_var_or_const_;
 
   // Computed via AllocateVariables; function, block and catch scopes only.
   int num_stack_slots_;
   int num_heap_slots_;
 
+  // Computed during code generation; for block scopes only.
+  int stack_slots_depth_;
+
   // Serialized scope info support.
   Handle<ScopeInfo> scope_info_;
   bool already_resolved() { return already_resolved_; }
 
   // Create a non-local variable with a given name.
   // These variables are looked up dynamically at runtime.
   Variable* NonLocal(Handle<String> name, VariableMode mode);
 
   // Variable resolution.
   // Possible results of a recursive variable lookup telling if and how a
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   }
 
   void SetDefaults(ScopeType type,
                    Scope* outer_scope,
                    Handle<ScopeInfo> scope_info);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_SCOPES_H_