[turbofan] Fix value output count for the Start node.

src/compiler/ast-graph-builder.cc

 // 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.
 
 #include "src/compiler/ast-graph-builder.h"
 
 #include "src/compiler.h"
 #include "src/compiler/ast-loop-assignment-analyzer.h"
 #include "src/compiler/control-builders.h"
 #include "src/compiler/js-type-feedback.h"
@@ skipping 484 matching lines @@
   const Operator* op =
       common()->Parameter(info()->num_parameters_including_this(), "%context");
   return NewNode(op, graph()->start());
 }
 
 
 bool AstGraphBuilder::CreateGraph(bool constant_context, bool stack_check) {
   Scope* scope = info()->scope();
   DCHECK(graph() != NULL);
 
-  // Set up the basic structure of the graph.
-  int parameter_count = info()->num_parameters();
-  graph()->SetStart(graph()->NewNode(common()->Start(parameter_count)));
+  // Set up the basic structure of the graph. Outputs for {Start} are the formal
+  // parameters (including the receiver) plus context and closure.
+  int actual_parameter_count = info()->num_parameters_including_this() + 2;
+  graph()->SetStart(graph()->NewNode(common()->Start(actual_parameter_count)));
 
   // Initialize the top-level environment.
   Environment env(this, scope, graph()->start());
   set_environment(&env);
 
   if (info()->is_osr()) {
     // Use OSR normal entry as the start of the top-level environment.
     // It will be replaced with {Dead} after typing and optimizations.
     NewNode(common()->OsrNormalEntry());
   }
@@ skipping 3652 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8