Move flow graph and helper classes to their own file.

src/flow-graph.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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_FLOW_GRAPH_H_
+#define V8_FLOW_GRAPH_H_
+
+#include "v8.h"
+
+#include "data-flow.h"
+#include "zone.h"
+
+namespace v8 {
+namespace internal {
+
+// Flow-graph nodes.
+class Node: public ZoneObject {
+ public:
+  Node() : number_(-1), mark_(false) {}
+
+  virtual ~Node() {}
+
+  virtual bool IsExitNode() { return false; }
+  virtual bool IsBlockNode() { return false; }
+  virtual bool IsBranchNode() { 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; }
+
+  // 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; }
+
+  // Functions used by data-flow analyses.
+  virtual void InitializeReachingDefinitions(int definition_count,
+                                             List<BitVector*>* variables,
+                                             WorkList<Node>* worklist,
+                                             bool mark);
+  virtual void ComputeRDOut(BitVector* result) = 0;
+  virtual void UpdateRDIn(WorkList<Node>* worklist, bool mark) = 0;
+  virtual void PropagateReachingDefinitions(List<BitVector*>* variables);
+
+  // Functions used by dead-code elimination.
+  virtual void MarkCriticalInstructions(
+      List<AstNode*>* stack,
+      ZoneList<Expression*>* body_definitions,
+      int variable_count);
+
+#ifdef DEBUG
+  void AssignNodeNumber();
+  void PrintReachingDefinitions();
+  virtual void PrintText() = 0;
+#endif
+
+ protected:
+  ReachingDefinitionsData rd_;
+
+ private:
+  int number_;
+  bool mark_;
+
+  DISALLOW_COPY_AND_ASSIGN(Node);
+};
+
+
+// An exit node has a arbitrarily many predecessors and no successors.
+class ExitNode: public Node {
+ public:
+  ExitNode() : predecessors_(4) {}
+
+  virtual bool IsExitNode() { return true; }
+
+  virtual void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor != NULL);
+    predecessors_.Add(predecessor);
+  }
+
+  virtual void AddSuccessor(Node* successor) { UNREACHABLE(); }
+
+  virtual void Traverse(bool mark,
+                        ZoneList<Node*>* preorder,
+                        ZoneList<Node*>* postorder);
+
+  virtual void ComputeRDOut(BitVector* result);
+  virtual void UpdateRDIn(WorkList<Node>* worklist, bool mark);
+
+#ifdef DEBUG
+  virtual 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);
+  }
+
+  virtual bool IsBlockNode() { return true; }
+
+  bool is_empty() { return instructions_.is_empty(); }
+
+  ZoneList<AstNode*>* instructions() { return &instructions_; }
+
+  virtual void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor_ == NULL && predecessor != NULL);
+    predecessor_ = predecessor;
+  }
+
+  virtual void AddSuccessor(Node* successor) {
+    ASSERT(successor_ == NULL && successor != NULL);
+    successor_ = successor;
+  }
+
+  void AddInstruction(AstNode* instruction) {
+    instructions_.Add(instruction);
+  }
+
+  virtual void Traverse(bool mark,
+                        ZoneList<Node*>* preorder,
+                        ZoneList<Node*>* postorder);
+
+  virtual void InitializeReachingDefinitions(int definition_count,
+                                             List<BitVector*>* variables,
+                                             WorkList<Node>* worklist,
+                                             bool mark);
+  virtual void ComputeRDOut(BitVector* result);
+  virtual void UpdateRDIn(WorkList<Node>* worklist, bool mark);
+  virtual void PropagateReachingDefinitions(List<BitVector*>* variables);
+
+  virtual void MarkCriticalInstructions(
+      List<AstNode*>* stack,
+      ZoneList<Expression*>* body_definitions,
+      int variable_count);
+
+#ifdef DEBUG
+  virtual 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) {}
+
+  virtual bool IsBranchNode() { return true; }
+
+  virtual void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor_ == NULL && predecessor != NULL);
+    predecessor_ = predecessor;
+  }
+
+  virtual void AddSuccessor(Node* successor) {
+    ASSERT(successor1_ == NULL && successor != NULL);
+    if (successor0_ == NULL) {
+      successor0_ = successor;
+    } else {
+      successor1_ = successor;
+    }
+  }
+
+  virtual void Traverse(bool mark,
+                        ZoneList<Node*>* preorder,
+                        ZoneList<Node*>* postorder);
+
+  virtual void ComputeRDOut(BitVector* result);
+  virtual void UpdateRDIn(WorkList<Node>* worklist, bool mark);
+
+#ifdef DEBUG
+  virtual 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);
+  }
+
+  virtual bool IsJoinNode() { return true; }
+
+  virtual void AddPredecessor(Node* predecessor) {
+    ASSERT(predecessor != NULL);
+    predecessors_.Add(predecessor);
+  }
+
+  virtual void AddSuccessor(Node* successor) {
+    ASSERT(successor_ == NULL && successor != NULL);
+    successor_ = successor;
+  }
+
+  virtual void Traverse(bool mark,
+                        ZoneList<Node*>* preorder,
+                        ZoneList<Node*>* postorder);
+
+  virtual void ComputeRDOut(BitVector* result);
+  virtual void UpdateRDIn(WorkList<Node>* worklist, bool mark);
+
+#ifdef DEBUG
+  virtual void PrintText();
+#endif
+
+ private:
+  ZoneList<Node*> predecessors_;
+  Node* successor_;
+
+  DISALLOW_COPY_AND_ASSIGN(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:
+  static FlowGraph Empty() {
+    FlowGraph graph;
+    graph.entry_ = new BlockNode();
+    graph.exit_ = graph.entry_;
+    return graph;
+  }
+
+  bool is_empty() const {
+    return entry_ == exit_ && BlockNode::cast(entry_)->is_empty();
+  }
+  Node* entry() const { return entry_; }
+  Node* exit() const { return exit_; }
+
+  // Add a single instruction to the end of this flowgraph.
+  void AppendInstruction(AstNode* instruction);
+
+  // Add a single node to the end of this flow graph.
+  void AppendNode(Node* node);
+
+  // Add a flow graph fragment to the end of this one.
+  void AppendGraph(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.
+  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(FunctionLiteral* fun, ZoneList<Node*>* postorder);
+#endif
+
+ private:
+  FlowGraph() : entry_(NULL), exit_(NULL) {}
+
+  Node* entry_;
+  Node* exit_;
+};
+
+
+// Construct a flow graph from a function literal.  Build pre- and postorder
+// traversal orders as a byproduct.
+class FlowGraphBuilder: public AstVisitor {
+ public:
+  explicit FlowGraphBuilder(int variable_count)
+      : graph_(FlowGraph::Empty()),
+        global_exit_(NULL),
+        preorder_(4),
+        postorder_(4),
+        variable_count_(variable_count),
+        body_definitions_(4) {
+  }
+
+  void Build(FunctionLiteral* lit);
+
+  FlowGraph* graph() { return &graph_; }
+  ZoneList<Node*>* preorder() { return &preorder_; }
+  ZoneList<Node*>* postorder() { return &postorder_; }
+  ZoneList<Expression*>* body_definitions() { return &body_definitions_; }
+
+ private:
+  ExitNode* global_exit() { return global_exit_; }
+
+  // Helpers to allow tranforming the ast during flow graph construction.
+  void VisitStatements(ZoneList<Statement*>* stmts);
+  Statement* ProcessStatement(Statement* stmt);
+
+  // 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_;
+
+  // The flow graph builder collects a list of explicit definitions
+  // (assignments and count operations) to stack-allocated variables to use
+  // for reaching definitions analysis.  It does not count the implicit
+  // definition at function entry.  AST node numbers in the AST are used to
+  // refer into this list.
+  int variable_count_;
+  ZoneList<Expression*> body_definitions_;
+
+  DISALLOW_COPY_AND_ASSIGN(FlowGraphBuilder);
+};
+
+
+} }  // namespace v8::internal
+
+#endif  // V8_FLOW_GRAPH_H_