Begin using the virtual frame for assignment statements of the form:...

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
@@ skipping 52 matching lines @@
   // Construct a frame element whose value is known at compile time.
   FrameElement(Handle<Object> value, SyncFlag is_synced) {
     type_ = TypeField::encode(CONSTANT) | SyncField::encode(is_synced);
     data_.handle_ = value.location();
   }
 
   bool is_synced() const { return SyncField::decode(type_) == SYNCED; }
 
   void set_sync() {
     ASSERT(type() != MEMORY);
-    type_ = type_ | SyncField::encode(SYNCED);
+    type_ = (type_ & ~SyncField::mask()) | SyncField::encode(SYNCED);

[William Hesse, 2008/11/28 10:32:45]

Why isn't there a set_field accessor for bit fields?  Is this the way we always
set bit fields?

[Kevin Millikin (Chromium), 2008/11/28 12:19:08]

I don't know why there isn't such an accessor.  It's not something we do very
often, I guess (we don't have a lot of mutable bit fields).

This seems like a safe way to set/clear it that doesn't rely on knowing which
other fields are packed in with it or which sense the flag is.

It's the same way we do it in AccessorInfo::set_property_attributes, for
instance.

   }
 
   void clear_sync() {
     ASSERT(type() != MEMORY);
-    type_ = type_ & ~SyncField::mask();
+    type_ = (type_ & ~SyncField::mask()) | SyncField::encode(NOT_SYNCED);
   }
 
+  bool is_memory() const { return type() == MEMORY; }
   bool is_register() const { return type() == REGISTER; }
   bool is_constant() const { return type() == CONSTANT; }
 
   Register reg() const {
     ASSERT(type() == REGISTER);
     return data_.reg_;
   }
 
   Handle<Object> handle() const {
     ASSERT(type() == CONSTANT);
@@ skipping 87 matching lines @@
     return Operand(esp, index * kPointerSize);
   }
 
   // A frame-allocated local as an assembly operand.
   Operand LocalAt(int index) const {
     ASSERT(0 <= index);
     ASSERT(index < local_count_);
     return Operand(ebp, kLocal0Offset - index * kPointerSize);
   }
 
+  // Store the top value on the virtual frame into a local frame slot.  The
+  // value is left in place on top of the frame.
+  void StoreToLocalAt(int index) {
+    StoreToFrameSlotAt(local0_index() + index);
+  }
+
   // The function frame slot.
   Operand Function() const { return Operand(ebp, kFunctionOffset); }
 
   // The context frame slot.
   Operand Context() const { return Operand(ebp, kContextOffset); }
 
   // A parameter as an assembly operand.
   Operand ParameterAt(int index) const {
     ASSERT(-1 <= index);  // -1 is the receiver.
     ASSERT(index < parameter_count_);
     return Operand(ebp, (1 + parameter_count_ - index) * kPointerSize);
   }
 
+  // Store the top value on the virtual frame into a parameter frame slot.
+  // The value is left in place on top of the frame.
+  void StoreToParameterAt(int index) {
+    StoreToFrameSlotAt(param0_index() + index);
+  }
+
   // The receiver frame slot.
   Operand Receiver() const { return ParameterAt(-1); }
 
   // Push a try-catch or try-finally handler on top of the virtual frame.
   void PushTryHandler(HandlerType type);
 
   // Call a code stub, given the number of arguments it expects on (and
   // removes from) the top of the physical frame.
   void CallStub(CodeStub* stub, int frame_arg_count);
 
@@ skipping 30 matching lines @@
   // Push an element on top of the expression stack and emit a corresponding
   // push instruction.
   void EmitPush(Register reg);
   void EmitPush(Operand operand);
   void EmitPush(Immediate immediate);
 
   // Push an element on the virtual frame.
   void Push(Register reg);
   void Push(Handle<Object> value);
 
+#ifdef DEBUG
+  bool IsSpilled();
+#endif
+
  private:
   // An illegal index into the virtual frame.
   static const int kIllegalIndex = -1;
 
   static const int kLocal0Offset = JavaScriptFrameConstants::kLocal0Offset;
   static const int kFunctionOffset = JavaScriptFrameConstants::kFunctionOffset;
   static const int kContextOffset = StandardFrameConstants::kContextOffset;
 
   static const int kHandlerSize = StackHandlerConstants::kSize / kPointerSize;
 
@@ skipping 68 matching lines @@
 
   // Spill the element at a particular index---write it to memory if
   // necessary, free any associated register, and forget its value if
   // constant.  Space should have already been allocated in the actual frame
   // for all the elements below this one (at least).
   void SpillElementAt(int index);
 
   // Sync all elements in the frame.
   void SyncAll();
 
+  // Store the value on top of the frame to a frame slot (typically a local
+  // or parameter).
+  void StoreToFrameSlotAt(int index);
+
   // Spill the topmost elements of the frame to memory (eg, they are the
   // arguments to a call) and all registers.
   void PrepareForCall(int count);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_VIRTUAL_FRAME_IA32_H_