Initial implementation of an edge-labeled instruction flow graph.

src/data-flow.h

 // 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 77 matching lines @@
   int length() const { return length_; }
 
  private:
   int length_;
   Vector<uint32_t> bits_;
 
   DISALLOW_COPY_AND_ASSIGN(BitVector);
 };
 
 
+// Forward declarations of Node types.
+class Node;
+class BranchNode;
+class JoinNode;
+
+// Flow graphs have a single entry and single exit.  The empty flowgraph is
+// represented by both entry and exit being NULL.
+class FlowGraph BASE_EMBEDDED {
+ public:
+  FlowGraph() : entry_(NULL), exit_(NULL) {}
+
+  static FlowGraph Empty() { return FlowGraph(); }
+
+  bool is_empty() const { return entry_ == NULL; }
+  Node* entry() const { return entry_; }
+  Node* exit() const { return exit_; }
+
+  // Add a single instruction to the end of this flowgraph.
+  void Append(AstNode* instruction);

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

I'm not sure if overloading the name Append helps readability. I'd prefer using
AppendInstruction, AppendNode, AppendFlowGraph.

+
+  // Add a single node to the end of this flow graph.
+  void Append(Node* node);
+
+  // Add a flow graph fragment to the end of this one.
+  void Append(FlowGraph* graph);
+
+  // Concatenate an if-then-else flow-graph to this one.  Control is split
+  // and merged, so the graph remains single-entry, single-exit.

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

Maybe mentions that left is always the true-branch and right is the false
branch.

+  void Split(BranchNode* branch,
+             FlowGraph* left,
+             FlowGraph* right,
+             JoinNode* merge);
+
+  // Concatenate a forward loop (e.g., while or for loop) flow-graph to this
+  // one.  Control is split by the condition and merged back from the back
+  // edge at end of the body to the beginning of the condition.  The single
+  // (free) exit of the result graph is the right (false) arm of the branch
+  // node.
+  void Loop(JoinNode* merge,
+            FlowGraph* condition,
+            BranchNode* branch,
+            FlowGraph* body);
+
+#ifdef DEBUG
+  void PrintText(ZoneList<Node*>* postorder);
+#endif
+
+ private:
+  Node* entry_;
+  Node* exit_;
+};
+
+
+// Flow-graph nodes.
+class Node: public ZoneObject {
+ public:
+  Node() : number_(-1), mark_(false) {}
+
+  virtual ~Node() {}
+
+  virtual bool IsBlockNode() { return false; }
+  virtual bool IsJoinNode() { return false; }
+
+  virtual void AddPredecessor(Node* predecessor) = 0;
+  virtual void AddSuccessor(Node* successor) = 0;
+
+  bool IsMarkedWith(bool mark) { return mark_ == mark; }
+  void MarkWith(bool mark) { mark_ = mark; }

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

Name this functions consistently with other accessors mark() and set_mark()

+
+  // Perform a depth first search and record preorder and postorder
+  // traversal orders.
+  virtual void Traverse(bool mark,
+                        ZoneList<Node*>* preorder,
+                        ZoneList<Node*>* postorder) = 0;
+
+  int number() { return number_; }
+  void set_number(int number) { number_ = number; }
+
+#ifdef DEBUG
+  virtual void AssignNumbers();
+  virtual void PrintText() = 0;
+#endif
+
+ private:
+  int number_;
+  bool mark_;
+
+  DISALLOW_COPY_AND_ASSIGN(Node);
+};
+
+
+// An entry node has no predecessors and a single successor.
+class EntryNode: public Node {
+ public:
+  EntryNode() : successor_(NULL) {}
+
+  void AddPredecessor(Node* predecessor) { UNREACHABLE(); }
+
+  void AddSuccessor(Node* successor) {
+    ASSERT(successor_ == NULL && successor != NULL);
+    successor_ = successor;
+  }
+
+  void Traverse(bool mark,
+                ZoneList<Node*>* preorder,
+                ZoneList<Node*>* postorder);
+
+#ifdef DEBUG
+  void PrintText();
+#endif
+
+ private:
+  Node* successor_;
+
+  DISALLOW_COPY_AND_ASSIGN(EntryNode);
+};
+
+
+// An exit node has a arbitrarily many predecessors and no successors.
+class ExitNode: public Node {
+ public:
+  ExitNode() : predecessors_(4) {}
+
+  void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor != NULL);
+    predecessors_.Add(predecessor);
+  }
+
+  void AddSuccessor(Node* successor) { /* Do nothing. */ }
+
+  void Traverse(bool mark,
+                ZoneList<Node*>* preorder,
+                ZoneList<Node*>* postorder);
+
+#ifdef DEBUG
+  void PrintText();
+#endif
+
+ private:
+  ZoneList<Node*> predecessors_;
+
+  DISALLOW_COPY_AND_ASSIGN(ExitNode);
+};
+
+
+// Block nodes have a single successor and predecessor and a list of
+// instructions.
+class BlockNode: public Node {
+ public:
+  BlockNode() : predecessor_(NULL), successor_(NULL), instructions_(4) {}
+
+  static BlockNode* cast(Node* node) {
+    ASSERT(node->IsBlockNode());
+    return reinterpret_cast<BlockNode*>(node);
+  }
+
+  bool IsBlockNode() { return true; }
+
+  void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor_ == NULL && predecessor != NULL);
+    predecessor_ = predecessor;
+  }
+
+  void AddSuccessor(Node* successor) {
+    ASSERT(successor_ == NULL && successor != NULL);
+    successor_ = successor;
+  }
+
+  void AddInstruction(AstNode* instruction) {
+    instructions_.Add(instruction);
+  }
+
+  void Traverse(bool mark,
+                ZoneList<Node*>* preorder,
+                ZoneList<Node*>* postorder);
+
+#ifdef DEBUG
+  void AssignNumbers();
+  void PrintText();
+#endif
+
+ private:
+  Node* predecessor_;
+  Node* successor_;
+  ZoneList<AstNode*> instructions_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlockNode);
+};
+
+
+// Branch nodes have a single predecessor and a pair of successors.
+class BranchNode: public Node {
+ public:
+  BranchNode() : predecessor_(NULL), successor0_(NULL), successor1_(NULL) {}
+
+  void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor_ == NULL && predecessor != NULL);
+    predecessor_ = predecessor;
+  }
+
+  void AddSuccessor(Node* successor) {
+    ASSERT(successor1_ == NULL && successor != NULL);
+    if (successor0_ == NULL) {
+      successor0_ = successor;
+    } else {
+      successor1_ = successor;
+    }
+  }
+
+  void Traverse(bool mark,
+                ZoneList<Node*>* preorder,
+                ZoneList<Node*>* postorder);
+
+#ifdef DEBUG
+  void PrintText();
+#endif
+
+ private:
+  Node* predecessor_;
+  Node* successor0_;
+  Node* successor1_;
+
+  DISALLOW_COPY_AND_ASSIGN(BranchNode);
+};
+
+
+// Join nodes have arbitrarily many predecessors and a single successor.
+class JoinNode: public Node {
+ public:
+  JoinNode() : predecessors_(2), successor_(NULL) {}
+
+  static JoinNode* cast(Node* node) {
+    ASSERT(node->IsJoinNode());
+    return reinterpret_cast<JoinNode*>(node);
+  }
+
+  bool IsJoinNode() { return true; }
+
+  void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor != NULL);
+    predecessors_.Add(predecessor);
+  }
+
+  void AddSuccessor(Node* successor) {
+    ASSERT(successor_ == NULL && successor != NULL);
+    successor_ = successor;
+  }
+
+  void Traverse(bool mark,
+                ZoneList<Node*>* preorder,
+                ZoneList<Node*>* postorder);
+
+#ifdef DEBUG
+  void PrintText();
+#endif
+
+ private:
+  ZoneList<Node*> predecessors_;
+  Node* successor_;
+
+  DISALLOW_COPY_AND_ASSIGN(JoinNode);
+};
+
+
+// Construct a flow graph from a function literal.  Build pre- and postorder
+// traversal orders as a byproduct.
+class FlowGraphBuilder: public AstVisitor {
+ public:
+  FlowGraphBuilder() : global_exit_(NULL), preorder_(4), postorder_(4) {}
+
+  void Build(FunctionLiteral* lit);
+
+  FlowGraph* graph() { return &graph_; }
+
+  ZoneList<Node*>* postorder() { return &postorder_; }
+
+ private:
+  ExitNode* global_exit() { return global_exit_; }
+
+  // AST node visit functions.
+#define DECLARE_VISIT(type) virtual void Visit##type(type* node);
+  AST_NODE_LIST(DECLARE_VISIT)
+#undef DECLARE_VISIT
+
+  FlowGraph graph_;
+  ExitNode* global_exit_;
+  ZoneList<Node*> preorder_;
+  ZoneList<Node*> postorder_;
+
+  DISALLOW_COPY_AND_ASSIGN(FlowGraphBuilder);
+};
+
+
 // This class is used to number all expressions in the AST according to
 // their evaluation order (post-order left-to-right traversal).
 class AstLabeler: public AstVisitor {
  public:
   AstLabeler() : next_number_(0) {}
 
   void Label(CompilationInfo* info);
 
  private:
   CompilationInfo* info() { return info_; }
@@ skipping 61 matching lines @@
   VarUseMap live_vars_;
 
   DISALLOW_COPY_AND_ASSIGN(LivenessAnalyzer);
 };
 
 
 } }  // namespace v8::internal
 
 
 #endif  // V8_DATAFLOW_H_