[turbofan] Do not rename context for loop exits in bytecode graph builder.

src/compiler/bytecode-graph-builder.cc

 // Copyright 2015 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/bytecode-graph-builder.h"
 
 #include "src/compiler/bytecode-branch-analysis.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/operator-properties.h"
 #include "src/interpreter/bytecodes.h"
@@ skipping 395 matching lines @@
 
   // Create the loop exit node.
   Node* loop_exit = graph()->NewNode(common()->LoopExit(), control, loop);
   UpdateControlDependency(loop_exit);
 
   // Rename the effect.
   Node* effect_rename = graph()->NewNode(common()->LoopExitEffect(),
                                          GetEffectDependency(), loop_exit);
   UpdateEffectDependency(effect_rename);
 
-  // Rename the current context.
-  context_ = graph()->NewNode(common()->LoopExitValue(), context_, loop_exit);
+  // TODO(jarin) We should also rename context here. However, uncoditional
+  // renaming confuses global object and native context specialization.
+  // We should only rename if the context is assigned in the loop.
 
   // Rename the environmnent values.
   for (size_t i = 0; i < values_.size(); i++) {
     Node* rename =
         graph()->NewNode(common()->LoopExitValue(), values_[i], loop_exit);
     values_[i] = rename;
   }
 }
 
 void BytecodeGraphBuilder::Environment::UpdateStateValues(Node** state_values,
@@ skipping 1463 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