Refactor Reference so that SetValue and GetValue pop the reference state.

Review URL: http://codereview.chromium.org/487017

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3720 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/codegen-arm.cc

-// Copyright 2006-2009 the V8 project authors. All rights reserved.
+// Copyright 2010 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:
@@ -605,14 +605,19 @@ void CodeGenerator::LoadTypeofExpression(Expression* expr) {
 }
 
 
-Reference::Reference(CodeGenerator* cgen, Expression* expression)
-    : cgen_(cgen), expression_(expression), type_(ILLEGAL) {
+Reference::Reference(CodeGenerator* cgen,
+                     Expression* expression,
+                     bool persist_after_get)
+    : cgen_(cgen),
+      expression_(expression),
+      type_(ILLEGAL),
+      persist_after_get_(persist_after_get) {
   cgen->LoadReference(this);
 }
 
 
 Reference::~Reference() {
-  cgen_->UnloadReference(this);
+  ASSERT(is_unloaded() || is_illegal());
 }
 
 
@@ -661,6 +666,7 @@ void CodeGenerator::UnloadReference(Reference* ref) {
     frame_->Drop(size);
     frame_->EmitPush(r0);
   }
+  ref->set_unloaded();
 }
 
 
@@ -1244,8 +1250,6 @@ void CodeGenerator::VisitDeclaration(Declaration* node) {
       Reference target(this, node->proxy());
       LoadAndSpill(val);
       target.SetValue(NOT_CONST_INIT);
-      // The reference is removed from the stack (preserving TOS) when
-      // it goes out of scope.
     }
     // Get rid of the assigned value (declarations are statements).
     frame_->Drop();
@@ -1932,25 +1936,17 @@ void CodeGenerator::VisitForInStatement(ForInStatement* node) {
       if (each.size() > 0) {
         __ ldr(r0, frame_->ElementAt(each.size()));
         frame_->EmitPush(r0);
-      }
-      // If the reference was to a slot we rely on the convenient property
-      // that it doesn't matter whether a value (eg, r3 pushed above) is
-      // right on top of or right underneath a zero-sized reference.
-      each.SetValue(NOT_CONST_INIT);
-      if (each.size() > 0) {
-        // It's safe to pop the value lying on top of the reference before
-        // unloading the reference itself (which preserves the top of stack,
-        // ie, now the topmost value of the non-zero sized reference), since
-        // we will discard the top of stack after unloading the reference
-        // anyway.
-        frame_->EmitPop(r0);
+        each.SetValue(NOT_CONST_INIT);
+        frame_->Drop(2);
+      } else {
+        // If the reference was to a slot we rely on the convenient property
+        // that it doesn't matter whether a value (eg, r3 pushed above) is
+        // right on top of or right underneath a zero-sized reference.
+        each.SetValue(NOT_CONST_INIT);
+        frame_->Drop();
       }
     }
   }
-  // Discard the i'th entry pushed above or else the remainder of the
-  // reference, whichever is currently on top of the stack.
-  frame_->Drop();
-
   // Body.
   CheckStack();  // TODO(1222600): ignore if body contains calls.
   VisitAndSpill(node->body());
@@ -2844,7 +2840,7 @@ void CodeGenerator::VisitAssignment(Assignment* node) {
   VirtualFrame::SpilledScope spilled_scope;
   Comment cmnt(masm_, "[ Assignment");
 
-  { Reference target(this, node->target());
+  { Reference target(this, node->target(), node->is_compound());
     if (target.is_illegal()) {
       // Fool the virtual frame into thinking that we left the assignment's
       // value on the frame.
@@ -2859,8 +2855,7 @@ void CodeGenerator::VisitAssignment(Assignment* node) {
         node->op() == Token::INIT_CONST) {
       LoadAndSpill(node->value());
 
-    } else {
-      // +=, *= and similar binary assignments.
+    } else {  // Assignment is a compound assignment.
       // Get the old value of the lhs.
       target.GetValueAndSpill();
       Literal* literal = node->value()->AsLiteral();
@@ -2881,13 +2876,12 @@ void CodeGenerator::VisitAssignment(Assignment* node) {
         frame_->EmitPush(r0);
       }
     }
-
     Variable* var = node->target()->AsVariableProxy()->AsVariable();
     if (var != NULL &&
         (var->mode() == Variable::CONST) &&
         node->op() != Token::INIT_VAR && node->op() != Token::INIT_CONST) {
       // Assignment ignored - leave the value on the stack.
-
+      UnloadReference(&target);
     } else {
       CodeForSourcePosition(node->position());
       if (node->op() == Token::INIT_CONST) {
@@ -3097,16 +3091,20 @@ void CodeGenerator::VisitCall(Call* node) {
       // JavaScript example: 'array[index](1, 2, 3)'
       // -------------------------------------------
 
-      // Load the function to call from the property through a reference.
-      Reference ref(this, property);
-      ref.GetValueAndSpill();  // receiver
-
-      // Pass receiver to called function.
+      LoadAndSpill(property->obj());
+      LoadAndSpill(property->key());
+      EmitKeyedLoad(false);
+      frame_->Drop();  // key
+      // Put the function below the receiver.
       if (property->is_synthetic()) {
+        // Use the global receiver.
+        frame_->Drop();
+        frame_->EmitPush(r0);
         LoadGlobalReceiver(r0);
       } else {
-        __ ldr(r0, frame_->ElementAt(ref.size()));
-        frame_->EmitPush(r0);
+        frame_->EmitPop(r1);  // receiver
+        frame_->EmitPush(r0);  // function
+        frame_->EmitPush(r1);  // receiver
       }
 
       // Call the function.
@@ -3807,7 +3805,9 @@ void CodeGenerator::VisitCountOperation(CountOperation* node) {
      frame_->EmitPush(r0);
   }
 
-  { Reference target(this, node->expression());
+  // A constant reference is not saved to, so a constant reference is not a
+  // compound assignment reference.
+  { Reference target(this, node->expression(), !is_const);
     if (target.is_illegal()) {
       // Spoof the virtual frame to have the expected height (one higher
       // than on entry).
@@ -4268,6 +4268,16 @@ void CodeGenerator::VisitCompareOperation(CompareOperation* node) {
 }
 
 
+void CodeGenerator::EmitKeyedLoad(bool is_global) {
+  Comment cmnt(masm_, "[ Load from keyed Property");
+  Handle<Code> ic(Builtins::builtin(Builtins::KeyedLoadIC_Initialize));
+  RelocInfo::Mode rmode = is_global
+                          ? RelocInfo::CODE_TARGET_CONTEXT
+                          : RelocInfo::CODE_TARGET;
+  frame_->CallCodeObject(ic, rmode, 0);
+}
+
+
 #ifdef DEBUG
 bool CodeGenerator::HasValidEntryRegisters() { return true; }
 #endif
@@ -4334,23 +4344,21 @@ void Reference::GetValue() {
     case KEYED: {
       // TODO(181): Implement inlined version of array indexing once
       // loop nesting is properly tracked on ARM.
-      VirtualFrame* frame = cgen_->frame();
-      Comment cmnt(masm, "[ Load from keyed Property");
       ASSERT(property != NULL);
-      Handle<Code> ic(Builtins::builtin(Builtins::KeyedLoadIC_Initialize));
       Variable* var = expression_->AsVariableProxy()->AsVariable();
       ASSERT(var == NULL || var->is_global());
-      RelocInfo::Mode rmode = (var == NULL)
-                            ? RelocInfo::CODE_TARGET
-                            : RelocInfo::CODE_TARGET_CONTEXT;
-      frame->CallCodeObject(ic, rmode, 0);
-      frame->EmitPush(r0);
+      cgen_->EmitKeyedLoad(var != NULL);
+      cgen_->frame()->EmitPush(r0);
       break;
     }
 
     default:
       UNREACHABLE();
   }
+
+  if (!persist_after_get_) {
+    cgen_->UnloadReference(this);
+  }
 }
 
 
@@ -4412,6 +4420,7 @@ void Reference::SetValue(InitState init_state) {
     default:
       UNREACHABLE();
   }
+  cgen_->UnloadReference(this);
 }
 
 

src/arm/codegen-arm.h

-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2010 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:
@@ -43,57 +43,69 @@ enum TypeofState { INSIDE_TYPEOF, NOT_INSIDE_TYPEOF };
 // -------------------------------------------------------------------------
 // Reference support
 
-// A reference is a C++ stack-allocated object that keeps an ECMA
-// reference on the execution stack while in scope. For variables
-// the reference is empty, indicating that it isn't necessary to
-// store state on the stack for keeping track of references to those.
-// For properties, we keep either one (named) or two (indexed) values
-// on the execution stack to represent the reference.
-
+// A reference is a C++ stack-allocated object that puts a
+// reference on the virtual frame.  The reference may be consumed
+// by GetValue, TakeValue, SetValue, and Codegen::UnloadReference.
+// When the lifetime (scope) of a valid reference ends, it must have
+// been consumed, and be in state UNLOADED.
 class Reference BASE_EMBEDDED {
  public:
   // The values of the types is important, see size().
-  enum Type { ILLEGAL = -1, SLOT = 0, NAMED = 1, KEYED = 2 };
-  Reference(CodeGenerator* cgen, Expression* expression);
+  enum Type { UNLOADED = -2, ILLEGAL = -1, SLOT = 0, NAMED = 1, KEYED = 2 };
+  Reference(CodeGenerator* cgen,
+            Expression* expression,
+            bool persist_after_get = false);
   ~Reference();
 
   Expression* expression() const { return expression_; }
   Type type() const { return type_; }
   void set_type(Type value) {
-    ASSERT(type_ == ILLEGAL);
+    ASSERT_EQ(ILLEGAL, type_);
     type_ = value;
   }
 
+  void set_unloaded() {
+    ASSERT_NE(ILLEGAL, type_);
+    ASSERT_NE(UNLOADED, type_);
+    type_ = UNLOADED;
+  }
   // The size the reference takes up on the stack.
-  int size() const { return (type_ == ILLEGAL) ? 0 : type_; }
+  int size() const {
+    return (type_ < SLOT) ? 0 : type_;
+  }
 
   bool is_illegal() const { return type_ == ILLEGAL; }
   bool is_slot() const { return type_ == SLOT; }
   bool is_property() const { return type_ == NAMED || type_ == KEYED; }
+  bool is_unloaded() const { return type_ == UNLOADED; }
 
   // Return the name.  Only valid for named property references.
   Handle<String> GetName();
 
   // Generate code to push the value of the reference on top of the
   // expression stack.  The reference is expected to be already on top of
-  // the expression stack, and it is left in place with its value above it.
+  // the expression stack, and it is consumed by the call unless the
+  // reference is for a compound assignment.
+  // If the reference is not consumed, it is left in place under its value.
   void GetValue();
 
-  // Generate code to push the value of a reference on top of the expression
-  // stack and then spill the stack frame.  This function is used temporarily
-  // while the code generator is being transformed.
+  // Generate code to pop a reference, push the value of the reference,
+  // and then spill the stack frame.
   inline void GetValueAndSpill();
 
   // Generate code to store the value on top of the expression stack in the
   // reference.  The reference is expected to be immediately below the value
-  // on the expression stack.  The stored value is left in place (with the
-  // reference intact below it) to support chained assignments.
+  // on the expression stack.  The  value is stored in the location specified
+  // by the reference, and is left on top of the stack, after the reference
+  // is popped from beneath it (unloaded).
   void SetValue(InitState init_state);
 
  private:
   CodeGenerator* cgen_;
   Expression* expression_;
   Type type_;
+  // Keep the reference on the stack after get, so it can be used by set later.
+  bool persist_after_get_;
 };
 
 
@@ -274,6 +286,9 @@ class CodeGenerator: public AstVisitor {
   void LoadFromSlot(Slot* slot, TypeofState typeof_state);
   // Store the value on top of the stack to a slot.
   void StoreToSlot(Slot* slot, InitState init_state);
+  // Load a keyed property, leaving it in r0.  The receiver and key are
+  // passed on the stack, and remain there.
+  void EmitKeyedLoad(bool is_global);
 
   void LoadFromGlobalSlotCheckExtensions(Slot* slot,
                                          TypeofState typeof_state,

src/ia32/codegen-ia32.h

-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2010 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:
@@ -43,57 +43,70 @@ enum TypeofState { INSIDE_TYPEOF, NOT_INSIDE_TYPEOF };
 // -------------------------------------------------------------------------
 // Reference support
 
-// A reference is a C++ stack-allocated object that keeps an ECMA
-// reference on the execution stack while in scope. For variables
-// the reference is empty, indicating that it isn't necessary to
-// store state on the stack for keeping track of references to those.
-// For properties, we keep either one (named) or two (indexed) values
-// on the execution stack to represent the reference.
-
+// A reference is a C++ stack-allocated object that puts a
+// reference on the virtual frame.  The reference may be consumed
+// by GetValue, TakeValue, SetValue, and Codegen::UnloadReference.
+// When the lifetime (scope) of a valid reference ends, it must have
+// been consumed, and be in state UNLOADED.
 class Reference BASE_EMBEDDED {
  public:
   // The values of the types is important, see size().
-  enum Type { ILLEGAL = -1, SLOT = 0, NAMED = 1, KEYED = 2 };
-  Reference(CodeGenerator* cgen, Expression* expression);
+  enum Type { UNLOADED = -2, ILLEGAL = -1, SLOT = 0, NAMED = 1, KEYED = 2 };
+  Reference(CodeGenerator* cgen,
+            Expression* expression,
+            bool persist_after_get = false);
   ~Reference();
 
   Expression* expression() const { return expression_; }
   Type type() const { return type_; }
   void set_type(Type value) {
-    ASSERT(type_ == ILLEGAL);
+    ASSERT_EQ(ILLEGAL, type_);
     type_ = value;
   }
 
+  void set_unloaded() {
+    ASSERT_NE(ILLEGAL, type_);
+    ASSERT_NE(UNLOADED, type_);
+    type_ = UNLOADED;
+  }
   // The size the reference takes up on the stack.
-  int size() const { return (type_ == ILLEGAL) ? 0 : type_; }
+  int size() const {
+    return (type_ < SLOT) ? 0 : type_;
+  }
 
   bool is_illegal() const { return type_ == ILLEGAL; }
   bool is_slot() const { return type_ == SLOT; }
   bool is_property() const { return type_ == NAMED || type_ == KEYED; }
+  bool is_unloaded() const { return type_ == UNLOADED; }
 
   // Return the name.  Only valid for named property references.
   Handle<String> GetName();
 
   // Generate code to push the value of the reference on top of the
   // expression stack.  The reference is expected to be already on top of
-  // the expression stack, and it is left in place with its value above it.
+  // the expression stack, and it is consumed by the call unless the
+  // reference is for a compound assignment.
+  // If the reference is not consumed, it is left in place under its value.
   void GetValue();
 
   // Like GetValue except that the slot is expected to be written to before
-  // being read from again.  Thae value of the reference may be invalidated,
+  // being read from again.  The value of the reference may be invalidated,
   // causing subsequent attempts to read it to fail.
   void TakeValue();
 
   // Generate code to store the value on top of the expression stack in the
   // reference.  The reference is expected to be immediately below the value
-  // on the expression stack.  The stored value is left in place (with the
-  // reference intact below it) to support chained assignments.
+  // on the expression stack.  The  value is stored in the location specified
+  // by the reference, and is left on top of the stack, after the reference
+  // is popped from beneath it (unloaded).
   void SetValue(InitState init_state);
 
  private:
   CodeGenerator* cgen_;
   Expression* expression_;
   Type type_;
+  // Keep the reference on the stack after get, so it can be used by set later.
+  bool persist_after_get_;
 };
 
 
@@ -420,6 +433,11 @@ class CodeGenerator: public AstVisitor {
   // value in place.
   void StoreToSlot(Slot* slot, InitState init_state);
 
+  // Load a property of an object, returning it in a Result.
+  // The object and the property name are passed on the stack, and
+  // not changed.
+  Result EmitKeyedLoad(bool is_global);
+
   // Special code for typeof expressions: Unfortunately, we must
   // be careful when loading the expression in 'typeof'
   // expressions. We are not allowed to throw reference errors for
@@ -479,10 +497,10 @@ class CodeGenerator: public AstVisitor {
                          CallFunctionFlags flags,
                          int position);
 
-  // Use an optimized version of Function.prototype.apply that avoid
-  // allocating the arguments object and just copies the arguments
-  // from the stack.
-  void CallApplyLazy(Property* apply,
+  // An optimized implementation of expressions of the form
+  // x.apply(y, arguments).  We call x the applicand and y the receiver.
+  // The optimization avoids allocating an arguments object if possible.
+  void CallApplyLazy(Expression* applicand,
                      Expression* receiver,
                      VariableProxy* arguments,
                      int position);

src/x64/codegen-x64.h

-// Copyright 2009 the V8 project authors. All rights reserved.
+// Copyright 2010 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:
@@ -43,57 +43,70 @@ enum TypeofState { INSIDE_TYPEOF, NOT_INSIDE_TYPEOF };
 // -------------------------------------------------------------------------
 // Reference support
 
-// A reference is a C++ stack-allocated object that keeps an ECMA
-// reference on the execution stack while in scope. For variables
-// the reference is empty, indicating that it isn't necessary to
-// store state on the stack for keeping track of references to those.
-// For properties, we keep either one (named) or two (indexed) values
-// on the execution stack to represent the reference.
-
+// A reference is a C++ stack-allocated object that puts a
+// reference on the virtual frame.  The reference may be consumed
+// by GetValue, TakeValue, SetValue, and Codegen::UnloadReference.
+// When the lifetime (scope) of a valid reference ends, it must have
+// been consumed, and be in state UNLOADED.
 class Reference BASE_EMBEDDED {
  public:
   // The values of the types is important, see size().
-  enum Type { ILLEGAL = -1, SLOT = 0, NAMED = 1, KEYED = 2 };
-  Reference(CodeGenerator* cgen, Expression* expression);
+  enum Type { UNLOADED = -2, ILLEGAL = -1, SLOT = 0, NAMED = 1, KEYED = 2 };
+
+  Reference(CodeGenerator* cgen,
+            Expression* expression,
+            bool persist_after_get = false);
   ~Reference();
 
   Expression* expression() const { return expression_; }
   Type type() const { return type_; }
   void set_type(Type value) {
-    ASSERT(type_ == ILLEGAL);
+    ASSERT_EQ(ILLEGAL, type_);
     type_ = value;
   }
 
+  void set_unloaded() {
+    ASSERT_NE(ILLEGAL, type_);
+    ASSERT_NE(UNLOADED, type_);
+    type_ = UNLOADED;
+  }
   // The size the reference takes up on the stack.
-  int size() const { return (type_ == ILLEGAL) ? 0 : type_; }
+  int size() const {
+    return (type_ < SLOT) ? 0 : type_;
+  }
 
   bool is_illegal() const { return type_ == ILLEGAL; }
   bool is_slot() const { return type_ == SLOT; }
   bool is_property() const { return type_ == NAMED || type_ == KEYED; }
+  bool is_unloaded() const { return type_ == UNLOADED; }
 
   // Return the name.  Only valid for named property references.
   Handle<String> GetName();
 
   // Generate code to push the value of the reference on top of the
   // expression stack.  The reference is expected to be already on top of
-  // the expression stack, and it is left in place with its value above it.
+  // the expression stack, and it is consumed by the call unless the
+  // reference is for a compound assignment.
+  // If the reference is not consumed, it is left in place under its value.
   void GetValue();
 
   // Like GetValue except that the slot is expected to be written to before
-  // being read from again.  Thae value of the reference may be invalidated,
+  // being read from again.  The value of the reference may be invalidated,
   // causing subsequent attempts to read it to fail.
   void TakeValue();
 
   // Generate code to store the value on top of the expression stack in the
   // reference.  The reference is expected to be immediately below the value
-  // on the expression stack.  The stored value is left in place (with the
-  // reference intact below it) to support chained assignments.
+  // on the expression stack.  The  value is stored in the location specified
+  // by the reference, and is left on top of the stack, after the reference
+  // is popped from beneath it (unloaded).
   void SetValue(InitState init_state);
 
  private:
   CodeGenerator* cgen_;
   Expression* expression_;
   Type type_;
+  bool persist_after_get_;
 };
 
 
@@ -422,6 +435,11 @@ class CodeGenerator: public AstVisitor {
   // value in place.
   void StoreToSlot(Slot* slot, InitState init_state);
 
+  // Load a property of an object, returning it in a Result.
+  // The object and the property name are passed on the stack, and
+  // not changed.
+  Result EmitKeyedLoad(bool is_global);
+
   // Special code for typeof expressions: Unfortunately, we must
   // be careful when loading the expression in 'typeof'
   // expressions. We are not allowed to throw reference errors for
@@ -478,10 +496,10 @@ class CodeGenerator: public AstVisitor {
                          CallFunctionFlags flags,
                          int position);
 
-  // Use an optimized version of Function.prototype.apply that avoid
-  // allocating the arguments object and just copies the arguments
-  // from the stack.
-  void CallApplyLazy(Property* apply,
+  // An optimized implementation of expressions of the form
+  // x.apply(y, arguments).  We call x the applicand and y the receiver.
+  // The optimization avoids allocating an arguments object if possible.
+  void CallApplyLazy(Expression* applicand,
                      Expression* receiver,
                      VariableProxy* arguments,
                      int position);