Fix LoadFieldByIndex to take mutable heap-numbers into account.

src/arm64/lithium-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
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@@ skipping 2543 matching lines @@
   LOperand* value = UseRegisterAtStart(instr->value());
   LOperand* map = UseRegister(instr->map());
   LOperand* temp = TempRegister();
   return AssignEnvironment(new(zone()) LCheckMapValue(value, map, temp));
 }
 
 
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegisterAtStart(instr->object());
   LOperand* index = UseRegister(instr->index());
-  return DefineAsRegister(new(zone()) LLoadFieldByIndex(object, index));
+  LLoadFieldByIndex* load = new(zone()) LLoadFieldByIndex(object, index);
+  LInstruction* result = DefineSameAsFirst(load);
+  return AssignPointerMap(result);
 }
 
 
 LInstruction* LChunkBuilder::DoWrapReceiver(HWrapReceiver* instr) {
   LOperand* receiver = UseRegister(instr->receiver());
   LOperand* function = UseRegister(instr->function());
   LWrapReceiver* result = new(zone()) LWrapReceiver(receiver, function);
   return AssignEnvironment(DefineAsRegister(result));
 }
 
 
 } }  // namespace v8::internal