Fix bug in graph copy while inlining loops.

src/compiler/js-inlining.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/ast.h"
 #include "src/ast-numbering.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/ast-graph-builder.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/generic-node-inl.h"
@@ skipping 191 matching lines @@
     for (NodeId id = 0; id < source_graph_->NodeCount(); ++id) {
       Node* sentinel = sentinels_[id];
       if (sentinel == NULL) continue;
       Node* copy = copies_[id];
       DCHECK_NE(NULL, copy);
       sentinel->ReplaceUses(copy);
     }
   }
 
   Node* GetSentinel(Node* original) {
-    Node* sentinel = sentinels_[original->id()];
-    if (sentinel == NULL) {
-      sentinel = target_graph_->NewNode(&sentinel_op_);
+    if (sentinels_[original->id()] == NULL) {
+      sentinels_[original->id()] = target_graph_->NewNode(&sentinel_op_);
     }
-    return sentinel;
+    return sentinels_[original->id()];
   }
 
   NodeVector copies_;
   NodeVector sentinels_;
   Graph* source_graph_;
   Graph* target_graph_;
   Zone* temp_zone_;
   Operator sentinel_op_;
 };
 
@@ skipping 259 matching lines @@
              info_->shared_info()->DebugName()->ToCString().get());
     }
     NodeProperties::ReplaceWithValue(call_node, r.first, r.second);
     call_node->RemoveAllInputs();
     DCHECK_EQ(0, call_node->UseCount());
   }
 }
 }
 }
 }  // namespace v8::internal::compiler