Copy-on-write arrays.

src/codegen.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 163 matching lines @@
   static CodeGenerator* Current() {
     ASSERT(top_ != NULL);
     return top_;
   }
 
  private:
   static CodeGenerator* top_;
   CodeGenerator* previous_;
 };
 
+
 #if V8_TARGET_ARCH_IA32 || V8_TARGET_ARCH_X64
 
 // State of used registers in a virtual frame.
 class FrameRegisterState {
  public:
   // Captures the current state of the given frame.
   explicit FrameRegisterState(VirtualFrame* frame);
 
   // Saves the state in the stack.
   void Save(MacroAssembler* masm) const;
@@ skipping 194 matching lines @@
   int slots_;
 
   const char* GetName() { return "FastNewContextStub"; }
   Major MajorKey() { return FastNewContext; }
   int MinorKey() { return slots_; }
 };
 
 
 class FastCloneShallowArrayStub : public CodeStub {
  public:
-  static const int kMaximumLength = 8;
+  // Maximum length of copied elements array.
+  static const int kMaximumClonedLength = 8;
 
-  explicit FastCloneShallowArrayStub(int length) : length_(length) {
-    ASSERT(length >= 0 && length <= kMaximumLength);
+  enum Mode {
+    CLONE_ELEMENTS,
+    COPY_ON_WRITE_ELEMENTS
+  };
+
+  FastCloneShallowArrayStub(Mode mode, int length)
+      : mode_(mode),
+        length_((mode == COPY_ON_WRITE_ELEMENTS) ? 0 : length) {
+    ASSERT(length_ >= 0);
+    ASSERT(length_ <= kMaximumClonedLength);
   }
 
   void Generate(MacroAssembler* masm);
 
  private:
+  Mode mode_;
   int length_;
 
   const char* GetName() { return "FastCloneShallowArrayStub"; }
   Major MajorKey() { return FastCloneShallowArray; }
-  int MinorKey() { return length_; }
+  int MinorKey() {
+    ASSERT(mode_ == 0 || mode_ == 1);
+    return (length_ << 1) | mode_;
+  }
 };
 
 
 class InstanceofStub: public CodeStub {
  public:
   InstanceofStub() { }
 
   void Generate(MacroAssembler* masm);
 
  private:
@@ skipping 475 matching lines @@
   StringCharFromCodeGenerator char_from_code_generator_;
 
   DISALLOW_COPY_AND_ASSIGN(StringCharAtGenerator);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_CODEGEN_H_