Fix context register allocation in LTransitionElementsKind.

src/x64/lithium-codegen-x64.cc

 // Copyright 2013 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 4345 matching lines @@
   __ j(not_equal, &not_applicable);
   if (IsSimpleMapChangeTransition(from_kind, to_kind)) {
     Register new_map_reg = ToRegister(instr->new_map_temp());
     __ movq(new_map_reg, to_map, RelocInfo::EMBEDDED_OBJECT);
     __ movq(FieldOperand(object_reg, HeapObject::kMapOffset), new_map_reg);
     // Write barrier.
     ASSERT_NE(instr->temp(), NULL);
     __ RecordWriteField(object_reg, HeapObject::kMapOffset, new_map_reg,
                         ToRegister(instr->temp()), kDontSaveFPRegs);
   } else {
+    ASSERT(ToRegister(instr->context()).is(rsi));
     PushSafepointRegistersScope scope(this);
     if (!object_reg.is(rax)) {
       __ movq(rax, object_reg);
     }
-    LoadContextFromDeferred(instr->context());
     __ Move(rbx, to_map);
     TransitionElementsKindStub stub(from_kind, to_kind);
     __ CallStub(&stub);
     RecordSafepointWithRegisters(
         instr->pointer_map(), 0, Safepoint::kNoLazyDeopt);
   }
   __ bind(&not_applicable);
 }
 
 
@@ skipping 1258 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64