[turbofan] Introduce a SpeculativeToNumber operator.

src/compiler/js-type-hint-lowering.h

 // Copyright 2017 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_JS_TYPE_HINT_LOWERING_H_
 #define V8_COMPILER_JS_TYPE_HINT_LOWERING_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/graph-reducer.h"
 #include "src/deoptimize-reason.h"
@@ skipping 37 matching lines @@
 
   JSTypeHintLowering(JSGraph* jsgraph, Handle<FeedbackVector> feedback_vector,
                      Flags flags);
 
   // Potential reduction of binary (arithmetic, logical, shift and relational
   // comparison) operations.
   Reduction ReduceBinaryOperation(const Operator* op, Node* left, Node* right,
                                   Node* effect, Node* control,
                                   FeedbackSlot slot) const;
 
+  // Potential reduction to ToNumber operations
+  Reduction ReduceToNumberOperation(Node* value, Node* effect, Node* control,
+                                    FeedbackSlot slot) const;
+
   // Potential reduction of property access operations.
   Reduction ReduceLoadNamedOperation(const Operator* op, Node* obj,
                                      Node* effect, Node* control,
                                      FeedbackSlot slot) const;
   Reduction ReduceLoadKeyedOperation(const Operator* op, Node* obj, Node* key,
                                      Node* effect, Node* control,
                                      FeedbackSlot slot) const;
   Reduction ReduceStoreNamedOperation(const Operator* op, Node* obj, Node* val,
                                       Node* effect, Node* control,
                                       FeedbackSlot slot) const;
@@ skipping 17 matching lines @@
   Handle<FeedbackVector> feedback_vector_;
 
   DISALLOW_COPY_AND_ASSIGN(JSTypeHintLowering);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_TYPE_HINT_LOWERING_H_