Added a simple dead code removal phase.

src/hydrogen-instructions.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 1836 matching lines @@
   stream->Add("[");
   key()->PrintNameTo(stream);
   stream->Add("] ");
   dependency()->PrintNameTo(stream);
   if (RequiresHoleCheck()) {
     stream->Add(" check_hole");
   }
 }
 
 
-bool HLoadKeyedFastElement::RequiresHoleCheck() {
+bool HLoadKeyedFastElement::RequiresHoleCheck() const {
   if (IsFastPackedElementsKind(elements_kind())) {
     return false;
   }
 
   for (HUseIterator it(uses()); !it.Done(); it.Advance()) {
     HValue* use = it.value();
     if (!use->IsChange()) return true;
   }
 
   return false;
@@ skipping 215 matching lines @@
 }
 
 
 void HLoadGlobalCell::PrintDataTo(StringStream* stream) {
   stream->Add("[%p]", *cell());
   if (!details_.IsDontDelete()) stream->Add(" (deleteable)");
   if (details_.IsReadOnly()) stream->Add(" (read-only)");
 }
 
 
-bool HLoadGlobalCell::RequiresHoleCheck() {
+bool HLoadGlobalCell::RequiresHoleCheck() const {
   if (details_.IsDontDelete() && !details_.IsReadOnly()) return false;
   for (HUseIterator it(uses()); !it.Done(); it.Advance()) {
     HValue* use = it.value();
     if (!use->IsChange()) return true;
   }
   return false;
 }
 
 
 void HLoadGlobalGeneric::PrintDataTo(StringStream* stream) {
@@ skipping 523 matching lines @@
 
 
 void HCheckPrototypeMaps::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal