Make sure floating phi nodes are coupled to their control.

src/compiler/scheduler.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_COMPILER_SCHEDULER_H_
 #define V8_COMPILER_SCHEDULER_H_
 
 #include "src/v8.h"
 
 #include "src/compiler/opcodes.h"
 #include "src/compiler/schedule.h"
 #include "src/zone-containers.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 // Computes a schedule from a graph, placing nodes into basic blocks and
 // ordering the basic blocks in the special RPO order.
 class Scheduler {
  public:
   // The complete scheduling algorithm. Creates a new schedule and places all
   // nodes from the graph into it.
   static Schedule* ComputeSchedule(Graph* graph);
 
   // Compute the RPO of blocks in an existing schedule.
   static BasicBlockVector* ComputeSpecialRPO(Schedule* schedule);
 
  private:
-  enum Placement { kUnknown, kSchedulable, kFixed };
+  enum Placement { kUnknown, kSchedulable, kFixed, kCoupled };
 
   // Per-node data tracked during scheduling.
   struct SchedulerData {
     BasicBlock* minimum_block_;  // Minimum legal RPO placement.
     int unscheduled_count_;      // Number of unscheduled uses of this node.
     bool is_connected_control_;  // {true} if control-connected to the end node.
     bool is_floating_control_;   // {true} if control, but not control-connected
                                  // to the end node.
-    Placement placement_ : 3;    // Whether the node is fixed, schedulable,
-                                 // or not yet known.
+    Placement placement_ : 2;    // Whether the node is fixed, schedulable,
+                                 // coupled to another node, or not yet known.
   };
 
   Zone* zone_;
   Graph* graph_;
   Schedule* schedule_;
   NodeVectorVector scheduled_nodes_;
   NodeVector schedule_root_nodes_;
   ZoneVector<SchedulerData> node_data_;
   bool has_floating_control_;
 
   Scheduler(Zone* zone, Graph* graph, Schedule* schedule);
 
-  SchedulerData DefaultSchedulerData();
-
-  SchedulerData* GetData(Node* node) {
-    DCHECK(node->id() < static_cast<int>(node_data_.size()));
-    return &node_data_[node->id()];
-  }
+  inline SchedulerData DefaultSchedulerData();
+  inline SchedulerData* GetData(Node* node);
 
   Placement GetPlacement(Node* node);
 
-  int GetRPONumber(BasicBlock* block) {
-    DCHECK(block->rpo_number() >= 0 &&
-           block->rpo_number() <
-               static_cast<int>(schedule_->rpo_order_.size()));
-    DCHECK(schedule_->rpo_order_[block->rpo_number()] == block);
-    return block->rpo_number();
-  }
+  void IncrementUnscheduledUseCount(Node* node, Node* from);
+  void DecrementUnscheduledUseCount(Node* node, Node* from);
 
+  inline int GetRPONumber(BasicBlock* block);
   BasicBlock* GetCommonDominator(BasicBlock* b1, BasicBlock* b2);
 
   // Phase 1: Build control-flow graph and dominator tree.
   friend class CFGBuilder;
   void BuildCFG();
   void GenerateImmediateDominatorTree();
 
   // Phase 2: Prepare use counts for nodes.
   friend class PrepareUsesVisitor;
   void PrepareUses();
 
   // Phase 3: Schedule nodes early.
   friend class ScheduleEarlyNodeVisitor;
   void ScheduleEarly();
 
   // Phase 4: Schedule nodes late.
   friend class ScheduleLateNodeVisitor;
   void ScheduleLate();
 
   bool ConnectFloatingControl();
   void ConnectFloatingControlSubgraph(BasicBlock* block, Node* node);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_SCHEDULER_H_