Experimental: introduce a helper class to delmite a scope where the...

src/virtual-frame-ia32.h

 // Copyright 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
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 // Virtual frames
 //
 // The virtual frame is an abstraction of the physical stack frame.  It
 // encapsulates the parameters, frame-allocated locals, and the expression
 // stack.  It supports push/pop operations on the expression stack, as well
 // as random access to the expression stack elements, locals, and
 // parameters.
 
 class VirtualFrame : public Malloced {
  public:
+  // A utility class to introduce a scope where the virtual frame is
+  // expected to remain spilled.  The constructor spills the code
+  // generator's current frame, but no attempt is made to require it to stay
+  // stay spilled.  It is intended as documentation while the code generator
+  // is being transformed.
+  class SpilledScope BASE_EMBEDDED {
+   public:
+    explicit SpilledScope(CodeGenerator* cgen);
+
+    ~SpilledScope();
+
+   private:
+    CodeGenerator* cgen_;
+    bool previous_state_;
+  };
+
   // Construct an initial virtual frame on entry to a JS function.
   explicit VirtualFrame(CodeGenerator* cgen);
 
   // Construct a virtual frame as a clone of an existing one.
   explicit VirtualFrame(VirtualFrame* original);
 
   // The height of the virtual expression stack.
   int height() const {
     return elements_.length() - expression_base_index();
   }
@@ skipping 276 matching lines @@
   // This is because some new memory-to-register moves are
   // created in order to break cycles of register moves.
   // Used in the implementation of MergeTo().
   void MergeMoveRegistersToRegisters(VirtualFrame *expected);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_VIRTUAL_FRAME_IA32_H_