Initial implementation of an edge-labeled instruction flow graph.

src/data-flow.cc

 // 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:
 //
 //     * 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 15 matching lines @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "v8.h"
 
 #include "data-flow.h"
 
 namespace v8 {
 namespace internal {
 
 
+void FlowGraph::Append(AstNode* instruction) {
+  ASSERT(instruction != NULL);
+  if (is_empty() || !exit()->IsBlockNode()) {
+    Append(new BlockNode());
+  }
+  BlockNode::cast(exit())->AddInstruction(instruction);
+}
+
+
+void FlowGraph::Append(Node* node) {
+  ASSERT(node != NULL);
+  if (is_empty()) {
+    entry_ = exit_ = node;
+  } else {
+    exit()->AddSuccessor(node);
+    node->AddPredecessor(exit());
+    exit_ = node;
+  }
+}
+
+
+void FlowGraph::Append(FlowGraph* graph) {
+  ASSERT(!graph->is_empty());
+  if (is_empty()) {
+    entry_ = graph->entry();
+    exit_ = graph->exit();
+  } else {
+    exit()->AddSuccessor(graph->entry());
+    graph->entry()->AddPredecessor(exit());
+    exit_ = graph->exit();
+  }
+}
+
+
+void FlowGraph::Split(BranchNode* branch,
+                      FlowGraph* left,
+                      FlowGraph* right,
+                      JoinNode* merge) {
+  // Graphs are in edge split form.  Add empty blocks if necessary.
+  if (left->is_empty()) left->Append(new BlockNode());
+  if (right->is_empty()) right->Append(new BlockNode());
+
+  // Add the branch, left flowgraph and merge.
+  Append(branch);
+  Append(left);
+  Append(merge);
+
+  // Splice in the right flowgraph.
+  right->Append(merge);
+  branch->AddSuccessor(right->entry());
+  right->entry()->AddPredecessor(branch);
+}
+
+
+void FlowGraph::Loop(JoinNode* merge,
+                     FlowGraph* condition,
+                     BranchNode* branch,
+                     FlowGraph* body) {
+  // Add the merge, condition and branch.  Add merge's predecessors in
+  // left-to-right order.
+  Append(merge);
+  body->Append(merge);
+  Append(condition);
+  Append(branch);
+
+  // Splice in the body flowgraph.
+  branch->AddSuccessor(body->entry());
+  body->entry()->AddPredecessor(branch);
+}
+
+
+void EntryNode::Traverse(bool mark,
+                         ZoneList<Node*>* preorder,
+                         ZoneList<Node*>* postorder) {
+  ASSERT(successor_ != NULL);
+  preorder->Add(this);
+  if (!successor_->IsMarkedWith(mark)) {
+    successor_->MarkWith(mark);
+    successor_->Traverse(mark, preorder, postorder);
+  }
+  postorder->Add(this);
+}
+
+
+void ExitNode::Traverse(bool mark,
+                        ZoneList<Node*>* preorder,
+                        ZoneList<Node*>* postorder) {
+  preorder->Add(this);
+  postorder->Add(this);
+}
+
+
+void BlockNode::Traverse(bool mark,
+                         ZoneList<Node*>* preorder,
+                         ZoneList<Node*>* postorder) {
+  ASSERT(successor_ != NULL);
+  preorder->Add(this);
+  if (!successor_->IsMarkedWith(mark)) {
+    successor_->MarkWith(mark);
+    successor_->Traverse(mark, preorder, postorder);
+  }
+  postorder->Add(this);
+}
+
+
+void BranchNode::Traverse(bool mark,
+                          ZoneList<Node*>* preorder,
+                          ZoneList<Node*>* postorder) {
+  ASSERT(successor0_ != NULL && successor1_ != NULL);
+  preorder->Add(this);
+  if (!successor0_->IsMarkedWith(mark)) {
+    successor0_->MarkWith(mark);
+    successor0_->Traverse(mark, preorder, postorder);
+  }
+  if (!successor1_->IsMarkedWith(mark)) {
+    successor1_->MarkWith(mark);
+    successor1_->Traverse(mark, preorder, postorder);
+  }
+  postorder->Add(this);
+}
+
+
+void JoinNode::Traverse(bool mark,
+                        ZoneList<Node*>* preorder,
+                        ZoneList<Node*>* postorder) {
+  ASSERT(successor_ != NULL);
+  preorder->Add(this);
+  if (!successor_->IsMarkedWith(mark)) {
+    successor_->MarkWith(mark);
+    successor_->Traverse(mark, preorder, postorder);
+  }
+  postorder->Add(this);
+}
+
+
+void FlowGraphBuilder::Build(FunctionLiteral* lit) {
+  graph_ = FlowGraph::Empty();
+  graph_.Append(new EntryNode());
+  global_exit_ = new ExitNode();
+  VisitStatements(lit->body());
+
+  if (HasStackOverflow()) {
+    graph_ = FlowGraph::Empty();
+    return;
+  }
+
+  graph_.Append(global_exit_);
+
+  // Build preorder and postorder traversal orders.  All the nodes in
+  // the graph have the same mark flag.  For the traversal, use that
+  // flag's negation.  Traversal will flip all the flags.
+  bool mark = graph_.entry()->IsMarkedWith(false);
+  graph_.entry()->MarkWith(mark);
+  graph_.entry()->Traverse(mark, &preorder_, &postorder_);
+}
+
+
+void FlowGraphBuilder::VisitDeclaration(Declaration* decl) {
+  UNREACHABLE();
+}
+
+
+void FlowGraphBuilder::VisitBlock(Block* stmt) {
+  VisitStatements(stmt->statements());
+}
+
+
+void FlowGraphBuilder::VisitExpressionStatement(ExpressionStatement* stmt) {
+  Visit(stmt->expression());
+}
+
+
+void FlowGraphBuilder::VisitEmptyStatement(EmptyStatement* stmt) {
+  // Nothing to do.
+}
+
+
+void FlowGraphBuilder::VisitIfStatement(IfStatement* stmt) {
+  Visit(stmt->condition());
+
+  BranchNode* branch = new BranchNode();
+  FlowGraph original = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->then_statement());
+
+  FlowGraph left = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->else_statement());
+
+  JoinNode* join = new JoinNode();
+  original.Split(branch, &left, &graph_, join);
+  graph_ = original;
+}
+
+
+void FlowGraphBuilder::VisitContinueStatement(ContinueStatement* stmt) {
+  SetStackOverflow();
+}
+
+
+void FlowGraphBuilder::VisitBreakStatement(BreakStatement* stmt) {
+  SetStackOverflow();
+}
+
+
+void FlowGraphBuilder::VisitReturnStatement(ReturnStatement* stmt) {
+  Visit(stmt->expression());
+  graph_.Append(stmt);
+  graph_.Append(global_exit());
+}
+
+
+void FlowGraphBuilder::VisitWithEnterStatement(WithEnterStatement* stmt) {
+  Visit(stmt->expression());
+  graph_.Append(stmt);
+}
+
+
+void FlowGraphBuilder::VisitWithExitStatement(WithExitStatement* stmt) {
+  graph_.Append(stmt);
+}
+
+
+void FlowGraphBuilder::VisitSwitchStatement(SwitchStatement* stmt) {
+  SetStackOverflow();
+}
+
+
+void FlowGraphBuilder::VisitDoWhileStatement(DoWhileStatement* stmt) {
+  JoinNode* join = new JoinNode();
+  FlowGraph original = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->body());
+
+  FlowGraph body = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->cond());
+
+  BranchNode* branch = new BranchNode();
+
+  // Add body, condition and branch.
+  original.Append(join);
+  original.Append(&body);
+  original.Append(&graph_);  // The condition.
+  original.Append(branch);
+
+  // Tie the knot.
+  branch->AddSuccessor(join);
+  join->AddPredecessor(branch);
+
+  graph_ = original;
+}
+
+
+void FlowGraphBuilder::VisitWhileStatement(WhileStatement* stmt) {
+  JoinNode* join = new JoinNode();
+  FlowGraph original = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->cond());
+
+  BranchNode* branch = new BranchNode();
+  FlowGraph condition = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->body());
+
+  original.Loop(join, &condition, branch, &graph_);
+  graph_ = original;
+}
+
+
+void FlowGraphBuilder::VisitForStatement(ForStatement* stmt) {
+  if (stmt->init() != NULL) Visit(stmt->init());
+
+  JoinNode* join = new JoinNode();
+  FlowGraph original = graph_;
+  graph_ = FlowGraph::Empty();
+  if (stmt->cond() != NULL) Visit(stmt->cond());
+
+  BranchNode* branch = new BranchNode();
+  FlowGraph condition = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->body());
+
+  if (stmt->next() != NULL) Visit(stmt->next());
+
+  original.Loop(join, &condition, branch, &graph_);
+  graph_ = original;
+}
+
+
+void FlowGraphBuilder::VisitForInStatement(ForInStatement* stmt) {
+  Visit(stmt->enumerable());
+
+  JoinNode* join = new JoinNode();
+  FlowGraph empty;
+  BranchNode* branch = new BranchNode();
+  FlowGraph original = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(stmt->body());
+
+  original.Loop(join, &empty, branch, &graph_);
+  graph_ = original;
+}
+
+
+void FlowGraphBuilder::VisitTryCatchStatement(TryCatchStatement* stmt) {
+  SetStackOverflow();
+}
+
+
+void FlowGraphBuilder::VisitTryFinallyStatement(TryFinallyStatement* stmt) {
+  SetStackOverflow();
+}
+
+
+void FlowGraphBuilder::VisitDebuggerStatement(DebuggerStatement* stmt) {
+  graph_.Append(stmt);
+}
+
+
+void FlowGraphBuilder::VisitFunctionLiteral(FunctionLiteral* expr) {
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitFunctionBoilerplateLiteral(
+    FunctionBoilerplateLiteral* expr) {
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitConditional(Conditional* expr) {
+  Visit(expr->condition());
+
+  BranchNode* branch = new BranchNode();
+  FlowGraph original = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(expr->then_expression());
+
+  FlowGraph left = graph_;
+  graph_ = FlowGraph::Empty();
+  Visit(expr->else_expression());
+
+  JoinNode* join = new JoinNode();
+  original.Split(branch, &left, &graph_, join);
+  graph_ = original;
+}
+
+
+void FlowGraphBuilder::VisitSlot(Slot* expr) {
+  UNREACHABLE();
+}
+
+
+void FlowGraphBuilder::VisitVariableProxy(VariableProxy* expr) {
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitLiteral(Literal* expr) {
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitRegExpLiteral(RegExpLiteral* expr) {
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitObjectLiteral(ObjectLiteral* expr) {
+  ZoneList<ObjectLiteral::Property*>* properties = expr->properties();
+  for (int i = 0, len = properties->length(); i < len; i++) {
+    Visit(properties->at(i)->value());
+  }
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitArrayLiteral(ArrayLiteral* expr) {
+  ZoneList<Expression*>* values = expr->values();
+  for (int i = 0, len = values->length(); i < len; i++) {
+    Visit(values->at(i));
+  }
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitCatchExtensionObject(CatchExtensionObject* expr) {
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitAssignment(Assignment* expr) {
+  Variable* var = expr->target()->AsVariableProxy()->AsVariable();
+  Property* prop = expr->target()->AsProperty();
+  // Left-hand side can be a variable or property (or reference error) but
+  // not both.
+  ASSERT(var == NULL || prop == NULL);
+  if (prop != NULL) {
+    Visit(prop->obj());
+    if (!prop->key()->IsPropertyName()) Visit(prop->key());
+  }
+  if (var != NULL || prop != NULL) {
+    Visit(expr->value());
+  }
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitThrow(Throw* expr) {
+  Visit(expr->exception());
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitProperty(Property* expr) {
+  Visit(expr->obj());
+  if (!expr->key()->IsPropertyName()) Visit(expr->key());
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitCall(Call* expr) {
+  Visit(expr->expression());
+  ZoneList<Expression*>* arguments = expr->arguments();
+  for (int i = 0, len = arguments->length(); i < len; i++) {
+    Visit(arguments->at(i));
+  }
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitCallNew(CallNew* expr) {
+  Visit(expr->expression());
+  ZoneList<Expression*>* arguments = expr->arguments();
+  for (int i = 0, len = arguments->length(); i < len; i++) {
+    Visit(arguments->at(i));
+  }
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitCallRuntime(CallRuntime* expr) {
+  ZoneList<Expression*>* arguments = expr->arguments();
+  for (int i = 0, len = arguments->length(); i < len; i++) {
+    Visit(arguments->at(i));
+  }
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitUnaryOperation(UnaryOperation* expr) {
+  Visit(expr->expression());
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitCountOperation(CountOperation* expr) {
+  Visit(expr->expression());
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitBinaryOperation(BinaryOperation* expr) {
+  Visit(expr->left());
+
+  switch (expr->op()) {
+    case Token::COMMA:
+      Visit(expr->right());
+      break;
+
+    case Token::OR: {
+      BranchNode* branch = new BranchNode();
+      FlowGraph original = graph_;
+      graph_ = FlowGraph::Empty();
+      Visit(expr->right());
+      FlowGraph empty;
+      JoinNode* join = new JoinNode();
+      original.Split(branch, &empty, &graph_, join);
+      graph_ = original;
+      break;
+    }
+
+    case Token::AND: {
+      BranchNode* branch = new BranchNode();
+      FlowGraph original = graph_;
+      graph_ = FlowGraph::Empty();
+      Visit(expr->right());
+      FlowGraph empty;
+      JoinNode* join = new JoinNode();
+      original.Split(branch, &graph_, &empty, join);
+      graph_ = original;
+      break;
+    }
+
+    case Token::BIT_OR:
+    case Token::BIT_XOR:
+    case Token::BIT_AND:
+    case Token::SHL:
+    case Token::SAR:
+    case Token::SHR:
+    case Token::ADD:
+    case Token::SUB:
+    case Token::MUL:
+    case Token::DIV:
+    case Token::MOD:
+      Visit(expr->right());
+      graph_.Append(expr);
+      break;
+
+    default:
+      UNREACHABLE();
+  }
+}
+
+
+void FlowGraphBuilder::VisitCompareOperation(CompareOperation* expr) {
+  Visit(expr->left());
+  Visit(expr->right());
+  graph_.Append(expr);
+}
+
+
+void FlowGraphBuilder::VisitThisFunction(ThisFunction* expr) {
+  graph_.Append(expr);
+}
+
+
 void AstLabeler::Label(CompilationInfo* info) {
   info_ = info;
   VisitStatements(info_->function()->body());
 }
 
 
 void AstLabeler::VisitStatements(ZoneList<Statement*>* stmts) {
   for (int i = 0, len = stmts->length(); i < len; i++) {
     Visit(stmts->at(i));
   }
@@ skipping 151 matching lines @@
 
 
 void AstLabeler::VisitAssignment(Assignment* expr) {
   Property* prop = expr->target()->AsProperty();
   ASSERT(prop != NULL);
   ASSERT(prop->key()->IsPropertyName());
   VariableProxy* proxy = prop->obj()->AsVariableProxy();
   USE(proxy);
   ASSERT(proxy != NULL && proxy->var()->is_this());
   info()->set_has_this_properties(true);
+
+  prop->obj()->set_num(AstNode::kNoNumber);

[fschneider, 2010/03/08 12:14:27]

We should remove depending on certain nodes having no number as a separate
change.

+  prop->key()->set_num(AstNode::kNoNumber);
   Visit(expr->value());
   expr->set_num(next_number_++);
 }
 
 
 void AstLabeler::VisitThrow(Throw* expr) {
   UNREACHABLE();
 }
 
 
 void AstLabeler::VisitProperty(Property* expr) {
   ASSERT(expr->key()->IsPropertyName());
   VariableProxy* proxy = expr->obj()->AsVariableProxy();
   USE(proxy);
   ASSERT(proxy != NULL && proxy->var()->is_this());
   info()->set_has_this_properties(true);
+
+  expr->obj()->set_num(AstNode::kNoNumber);
+  expr->key()->set_num(AstNode::kNoNumber);
   expr->set_num(next_number_++);
 }
 
 
 void AstLabeler::VisitCall(Call* expr) {
   UNREACHABLE();
 }
 
 
 void AstLabeler::VisitCallNew(CallNew* expr) {
@@ skipping 318 matching lines @@
 void LivenessAnalyzer::VisitCompareOperation(CompareOperation* expr) {
   UNREACHABLE();
 }
 
 
 void LivenessAnalyzer::VisitThisFunction(ThisFunction* expr) {
   UNREACHABLE();
 }
 
 
+#ifdef DEBUG
+
+// Print a textual representation of an instruction in a flow graph.  Using
+// the AstVisitor is overkill because there is no recursion here.  It is
+// only used for printing in debug mode.
+class TextInstructionPrinter: public AstVisitor {
+ public:
+  TextInstructionPrinter() {}
+
+ private:
+  // AST node visit functions.
+#define DECLARE_VISIT(type) virtual void Visit##type(type* node);
+  AST_NODE_LIST(DECLARE_VISIT)
+#undef DECLARE_VISIT
+
+  DISALLOW_COPY_AND_ASSIGN(TextInstructionPrinter);
+};
+
+
+void TextInstructionPrinter::VisitDeclaration(Declaration* decl) {
+  UNREACHABLE();
+}
+
+
+void TextInstructionPrinter::VisitBlock(Block* stmt) {
+  PrintF("Block");
+}
+
+
+void TextInstructionPrinter::VisitExpressionStatement(ExpressionStatement* stmt) {
+  PrintF("ExpressionStatement");
+}
+
+
+void TextInstructionPrinter::VisitEmptyStatement(EmptyStatement* stmt) {
+  PrintF("EmptyStatement");
+}
+
+
+void TextInstructionPrinter::VisitIfStatement(IfStatement* stmt) {
+  PrintF("IfStatement");
+}
+
+
+void TextInstructionPrinter::VisitContinueStatement(ContinueStatement* stmt) {
+  UNREACHABLE();
+}
+
+
+void TextInstructionPrinter::VisitBreakStatement(BreakStatement* stmt) {
+  UNREACHABLE();
+}
+
+
+void TextInstructionPrinter::VisitReturnStatement(ReturnStatement* stmt) {
+  PrintF("return @%d", stmt->expression()->num());
+}
+
+
+void TextInstructionPrinter::VisitWithEnterStatement(WithEnterStatement* stmt) {
+  PrintF("WithEnterStatement");
+}
+
+
+void TextInstructionPrinter::VisitWithExitStatement(WithExitStatement* stmt) {
+  PrintF("WithExitStatement");
+}
+
+
+void TextInstructionPrinter::VisitSwitchStatement(SwitchStatement* stmt) {
+  UNREACHABLE();
+}
+
+
+void TextInstructionPrinter::VisitDoWhileStatement(DoWhileStatement* stmt) {
+  PrintF("DoWhileStatement");
+}
+
+
+void TextInstructionPrinter::VisitWhileStatement(WhileStatement* stmt) {
+  PrintF("WhileStatement");
+}
+
+
+void TextInstructionPrinter::VisitForStatement(ForStatement* stmt) {
+  PrintF("ForStatement");
+}
+
+
+void TextInstructionPrinter::VisitForInStatement(ForInStatement* stmt) {
+  PrintF("ForInStatement");
+}
+
+
+void TextInstructionPrinter::VisitTryCatchStatement(TryCatchStatement* stmt) {
+  UNREACHABLE();
+}
+
+
+void TextInstructionPrinter::VisitTryFinallyStatement(
+    TryFinallyStatement* stmt) {
+  UNREACHABLE();
+}
+
+
+void TextInstructionPrinter::VisitDebuggerStatement(DebuggerStatement* stmt) {
+  PrintF("DebuggerStatement");
+}
+
+
+void TextInstructionPrinter::VisitFunctionLiteral(FunctionLiteral* expr) {
+  PrintF("FunctionLiteral");
+}
+
+
+void TextInstructionPrinter::VisitFunctionBoilerplateLiteral(
+    FunctionBoilerplateLiteral* expr) {
+  PrintF("FunctionBoilerplateLiteral");
+}
+
+
+void TextInstructionPrinter::VisitConditional(Conditional* expr) {
+  PrintF("Conditional");
+}
+
+
+void TextInstructionPrinter::VisitSlot(Slot* expr) {
+  UNREACHABLE();
+}
+
+
+void TextInstructionPrinter::VisitVariableProxy(VariableProxy* expr) {
+  Variable* var = expr->AsVariable();
+  if (var != NULL) {
+    SmartPointer<char> name = var->name()->ToCString();
+    PrintF("%s", *name);
+  } else {
+    ASSERT(expr->AsProperty() != NULL);
+    VisitProperty(expr->AsProperty());
+  }
+}
+
+
+void TextInstructionPrinter::VisitLiteral(Literal* expr) {
+  expr->handle()->ShortPrint();
+}
+
+
+void TextInstructionPrinter::VisitRegExpLiteral(RegExpLiteral* expr) {
+  PrintF("RegExpLiteral");
+}
+
+
+void TextInstructionPrinter::VisitObjectLiteral(ObjectLiteral* expr) {
+  PrintF("ObjectLiteral");
+}
+
+
+void TextInstructionPrinter::VisitArrayLiteral(ArrayLiteral* expr) {
+  PrintF("ArrayLiteral");
+}
+
+
+void TextInstructionPrinter::VisitCatchExtensionObject(
+    CatchExtensionObject* expr) {
+  PrintF("CatchExtensionObject");
+}
+
+
+void TextInstructionPrinter::VisitAssignment(Assignment* expr) {
+  Variable* var = expr->target()->AsVariableProxy()->AsVariable();
+  Property* prop = expr->target()->AsProperty();
+
+  if (var != NULL) {
+    SmartPointer<char> name = var->name()->ToCString();
+    PrintF("%s %s @%d",
+           *name,
+           Token::String(expr->op()),
+           expr->value()->num());
+  } else if (prop != NULL) {
+    if (prop->key()->IsPropertyName()) {
+      PrintF("@%d.", prop->obj()->num());
+      ASSERT(prop->key()->AsLiteral() != NULL);
+      prop->key()->AsLiteral()->handle()->Print();
+      PrintF(" %s @%d",
+             Token::String(expr->op()),
+             expr->value()->num());
+    } else {
+      PrintF("@%d[@%d] %s @%d",
+             prop->obj()->num(),
+             prop->key()->num(),
+             Token::String(expr->op()),
+             expr->value()->num());
+    }
+  } else {
+    // Throw reference error.
+    Visit(expr->target());
+  }
+}
+
+
+void TextInstructionPrinter::VisitThrow(Throw* expr) {
+  PrintF("throw @%d", expr->exception()->num());
+}
+
+
+void TextInstructionPrinter::VisitProperty(Property* expr) {
+  if (expr->key()->IsPropertyName()) {
+    PrintF("@%d.", expr->obj()->num());
+    ASSERT(expr->key()->AsLiteral() != NULL);
+    expr->key()->AsLiteral()->handle()->Print();
+  } else {
+    PrintF("@%d[@%d]", expr->obj()->num(), expr->key()->num());
+  }
+}
+
+
+void TextInstructionPrinter::VisitCall(Call* expr) {
+  PrintF("@%d(", expr->expression()->num());
+  ZoneList<Expression*>* arguments = expr->arguments();
+  for (int i = 0, len = arguments->length(); i < len; i++) {
+    if (i != 0) PrintF(", ");
+    PrintF("@%d", arguments->at(i)->num());
+  }
+  PrintF(")");
+}
+
+
+void TextInstructionPrinter::VisitCallNew(CallNew* expr) {
+  PrintF("new @%d(", expr->expression()->num());
+  ZoneList<Expression*>* arguments = expr->arguments();
+  for (int i = 0, len = arguments->length(); i < len; i++) {
+    if (i != 0) PrintF(", ");
+    PrintF("@%d", arguments->at(i)->num());
+  }
+  PrintF(")");
+}
+
+
+void TextInstructionPrinter::VisitCallRuntime(CallRuntime* expr) {
+  SmartPointer<char> name = expr->name()->ToCString();
+  PrintF("%s(", *name);
+  ZoneList<Expression*>* arguments = expr->arguments();
+  for (int i = 0, len = arguments->length(); i < len; i++) {
+    if (i != 0) PrintF(", ");
+    PrintF("@%d", arguments->at(i)->num());
+  }
+  PrintF(")");
+}
+
+
+void TextInstructionPrinter::VisitUnaryOperation(UnaryOperation* expr) {
+  PrintF("%s(@%d)", Token::String(expr->op()), expr->expression()->num());
+}
+
+
+void TextInstructionPrinter::VisitCountOperation(CountOperation* expr) {
+  if (expr->is_prefix()) {
+    PrintF("%s@%d", Token::String(expr->op()), expr->expression()->num());
+  } else {
+    PrintF("@%d%s", expr->expression()->num(), Token::String(expr->op()));
+  }
+}
+
+
+void TextInstructionPrinter::VisitBinaryOperation(BinaryOperation* expr) {
+  ASSERT(expr->op() != Token::COMMA);
+  ASSERT(expr->op() != Token::OR);
+  ASSERT(expr->op() != Token::AND);
+  PrintF("@%d %s @%d",
+         expr->left()->num(),
+         Token::String(expr->op()),
+         expr->right()->num());
+}
+
+
+void TextInstructionPrinter::VisitCompareOperation(CompareOperation* expr) {
+  PrintF("@%d %s @%d",
+         expr->left()->num(),
+         Token::String(expr->op()),
+         expr->right()->num());
+}
+
+
+void TextInstructionPrinter::VisitThisFunction(ThisFunction* expr) {
+  PrintF("ThisFunction");
+}
+
+
+static int node_count = 0;
+static int instruction_count = 0;
+
+
+void Node::AssignNumbers() {
+  set_number(node_count++);
+}
+
+
+void BlockNode::AssignNumbers() {
+  set_number(node_count++);
+  for (int i = 0, len = instructions_.length(); i < len; i++) {
+    instructions_[i]->set_num(instruction_count++);
+  }
+}
+
+
+void EntryNode::PrintText() {
+  PrintF("L%d: Entry\n", number());
+  PrintF("goto L%d\n\n", successor_->number());
+}
+
+void ExitNode::PrintText() {
+  PrintF("L%d: Exit\n\n", number());
+}
+
+
+void BlockNode::PrintText() {
+  // Print the instructions in the block.
+  PrintF("L%d: Block\n", number());
+  TextInstructionPrinter printer;
+  for (int i = 0, len = instructions_.length(); i < len; i++) {
+    PrintF("%d ", instructions_[i]->num());
+    printer.Visit(instructions_[i]);
+    PrintF("\n");
+  }
+  PrintF("goto L%d\n\n", successor_->number());
+}
+
+
+void BranchNode::PrintText() {
+  PrintF("L%d: Branch\n", number());
+  PrintF("goto (L%d, L%d)\n\n", successor0_->number(), successor1_->number());
+}
+
+
+void JoinNode::PrintText() {
+  PrintF("L%d: Join(", number());
+  for (int i = 0, len = predecessors_.length(); i < len; i++) {
+    if (i != 0) PrintF(", ");
+    PrintF("L%d", predecessors_[i]->number());
+  }
+  PrintF(")\ngoto L%d\n\n", successor_->number());
+}
+
+
+void FlowGraph::PrintText(ZoneList<Node*>* postorder) {
+  PrintF("\n========\n");
+
+  // Number nodes and instructions in reverse postorder.
+  node_count = 0;
+  instruction_count = 0;
+  for (int i = postorder->length() - 1; i >= 0; i--) {
+    postorder->at(i)->AssignNumbers();
+  }
+
+  // Print basic blocks in reverse postorder.
+  for (int i = postorder->length() - 1; i >= 0; i--) {
+    postorder->at(i)->PrintText();
+  }
+}
+
+
+#endif  // defined(DEBUG)
+
+
 } }  // namespace v8::internal