Add tool to visualize machine code/lithium.

src/hydrogen-representation-changes.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 43 matching lines @@
       Maybe<HConstant*> res = constant->CopyToTruncatedInt32(graph()->zone());
       if (res.has_value) new_value = res.value;
     } else {
       new_value = constant->CopyToRepresentation(to, graph()->zone());
     }
   }
 
   if (new_value == NULL) {
     new_value = new(graph()->zone()) HChange(
         value, to, is_truncating_to_smi, is_truncating_to_int);
+    if (use_value->position() != RelocInfo::kNoPosition) {
+      new_value->set_position(use_value->position());
+    } else {
+      ASSERT(!FLAG_opt_code_positions || !graph()->info()->IsOptimizing());
+    }
   }
 
   new_value->InsertBefore(next);
   use_value->SetOperandAt(use_index, new_value);
 }
 
 
 void HRepresentationChangesPhase::InsertRepresentationChangesForValue(
     HValue* value) {
   Representation r = value->representation();
@@ skipping 109 matching lines @@
     // Process normal instructions.
     for (HInstruction* current = block->first(); current != NULL; ) {
       HInstruction* next = current->next();
       InsertRepresentationChangesForValue(current);
       current = next;
     }
   }
 }
 
 } }  // namespace v8::internal