[turbofan] Introduce explicit loop exits markers.

src/compiler/control-builders.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_CONTROL_BUILDERS_H_
 #define V8_COMPILER_CONTROL_BUILDERS_H_
 
 #include "src/compiler/ast-graph-builder.h"
 #include "src/compiler/node.h"
 
@@ skipping 45 matching lines @@
 };
 
 
 // Tracks control flow for an iteration statement.
 class LoopBuilder final : public ControlBuilder {
  public:
   explicit LoopBuilder(AstGraphBuilder* builder)
       : ControlBuilder(builder),
         loop_environment_(nullptr),
         continue_environment_(nullptr),
-        break_environment_(nullptr) {}
+        break_environment_(nullptr),
+        assigned_(nullptr) {}
 
   // Primitive control commands.
   void BeginLoop(BitVector* assigned, bool is_osr = false);
   void Continue();
   void EndBody();
   void EndLoop();
 
   // Primitive support for break.
   void Break() final;
 
+  // Loop exit support. Used to introduce explicit loop exit control
+  // node and variable markers.
+  void ExitLoop(Node** extra_value_to_rename = nullptr);
+
   // Compound control commands for conditional break.
   void BreakUnless(Node* condition);
   void BreakWhen(Node* condition);
 
  private:
   Environment* loop_environment_;      // Environment of the loop header.
   Environment* continue_environment_;  // Environment after the loop body.
   Environment* break_environment_;     // Environment after the loop exits.
+  BitVector* assigned_;                // Assigned values in the environment.
 };
 
 
 // Tracks control flow for a switch statement.
 class SwitchBuilder final : public ControlBuilder {
  public:
   explicit SwitchBuilder(AstGraphBuilder* builder, int case_count)
       : ControlBuilder(builder),
         body_environment_(nullptr),
         label_environment_(nullptr),
@@ skipping 95 matching lines @@
   Environment* finally_environment_;  // Environment for the 'finally' body.
   Node* token_node_;                  // Node for token in 'finally' body.
   Node* value_node_;                  // Node for value in 'finally' body.
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_CONTROL_BUILDERS_H_