Fixed printing of LInstructions in the presence of optional arguments

src/x64/lithium-x64.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 96 matching lines @@
     stream->Add(" ");
     pointer_map()->PrintTo(stream);
   }
 }
 
 
 void LInstruction::PrintDataTo(StringStream* stream) {
   stream->Add("= ");
   for (int i = 0; i < InputCount(); i++) {
     if (i > 0) stream->Add(" ");
-    InputAt(i)->PrintTo(stream);
+    if (InputAt(i) == NULL) {
+      stream->Add("NULL");
+    } else {
+      InputAt(i)->PrintTo(stream);
+    }
   }
 }
 
 
 void LInstruction::PrintOutputOperandTo(StringStream* stream) {
   if (HasResult()) result()->PrintTo(stream);
 }
 
 
 void LLabel::PrintDataTo(StringStream* stream) {
@@ skipping 2225 matching lines @@
 LInstruction* LChunkBuilder::DoLoadFieldByIndex(HLoadFieldByIndex* instr) {
   LOperand* object = UseRegister(instr->object());
   LOperand* index = UseTempRegister(instr->index());
   return DefineSameAsFirst(new(zone()) LLoadFieldByIndex(object, index));
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64