Handle Symbols in the LBranch instruction on x64.

src/code-stubs.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 451 matching lines @@
     state_.Add(GENERIC);
   } else {
     state_.Add(MONOMORPHIC_MAP);
   }
   TraceTransition(old_state, state_);
 }
 
 
 template<class StateType>
 void HydrogenCodeStub::TraceTransition(StateType from, StateType to) {
+  // Note: Although a no-op transition is semantically OK, it is hinting at a
+  // bug somewhere in our state transition machinery.
+  ASSERT(from != to);
   #ifdef DEBUG
   if (!FLAG_trace_ic) return;
   char buffer[100];
   NoAllocationStringAllocator allocator(buffer,
                                         static_cast<unsigned>(sizeof(buffer)));
   StringStream stream(&allocator);
   stream.Add("[");
   PrintBaseName(&stream);
   stream.Add(": ");
   from.Print(&stream);
@@ skipping 314 matching lines @@
   InstallDescriptor(isolate, &stub3);
 }
 
 InternalArrayConstructorStub::InternalArrayConstructorStub(
     Isolate* isolate) {
   InternalArrayConstructorStubBase::GenerateStubsAheadOfTime(isolate);
 }
 
 
 } }  // namespace v8::internal