[turbofan] Introduce explicit loop exits markers.

src/compiler/ast-graph-builder.h

 // Copyright 2014 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_AST_GRAPH_BUILDER_H_
 #define V8_COMPILER_AST_GRAPH_BUILDER_H_
 
 #include "src/ast/ast.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/liveness-analyzer.h"
@@ skipping 31 matching lines @@
   bool CreateGraph(bool stack_check = true);
 
   // Helpers to create new control nodes.
   Node* NewIfTrue() { return NewNode(common()->IfTrue()); }
   Node* NewIfFalse() { return NewNode(common()->IfFalse()); }
   Node* NewMerge() { return NewNode(common()->Merge(1), true); }
   Node* NewLoop() { return NewNode(common()->Loop(1), true); }
   Node* NewBranch(Node* condition, BranchHint hint = BranchHint::kNone) {
     return NewNode(common()->Branch(hint), condition);
   }
+  void BuildLoopExit(Node* loop, BitVector* assigned_variables,
+                     Node** extra_value_to_rename);
 
  protected:
 #define DECLARE_VISIT(type) void Visit##type(type* node) override;
   // Visiting functions for AST nodes make this an AstVisitor.
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
   // Visiting function for declarations list is overridden.
   void VisitDeclarations(ZoneList<Declaration*>* declarations) override;
 
@@ skipping 470 matching lines @@
     int depth = stack_height() - trim_to_height;
     DCHECK(depth >= 0 && depth <= stack_height());
     values()->erase(values()->end() - depth, values()->end());
   }
 
   // Preserve a checkpoint of the environment for the IR graph. Any
   // further mutation of the environment will not affect checkpoints.
   Node* Checkpoint(BailoutId ast_id, OutputFrameStateCombine combine =
                                          OutputFrameStateCombine::Ignore(),
                    bool node_has_exception = false);
+  void RenameForLoopExit(Node* loop, BitVector* assigned_variables);

[Michael Starzinger, 2016/07/14 12:13:36]

nit: Needs a short comment explaining purpose of method. Also, can we call it
"PrepareForLoopExit" instead?

[Jarin, 2016/07/14 12:51:34]

Done.

 
   // Control dependency tracked by this environment.
   Node* GetControlDependency() { return control_dependency_; }
   void UpdateControlDependency(Node* dependency) {
     control_dependency_ = dependency;
   }
 
   // Effect dependency tracked by this environment.
   Node* GetEffectDependency() { return effect_dependency_; }
   void UpdateEffectDependency(Node* dependency) {
@@ skipping 51 matching lines @@
 
   // Prepare environment to be used as loop header.
   void PrepareForLoop(BitVector* assigned, bool is_osr = false);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_AST_GRAPH_BUILDER_H_