Use the new introduced block's reachable flag.

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 4019 matching lines @@
   return r;
 }
 
 
 // Returns a representation if all uses agree on the same representation.
 // Integer32 is also returned when some uses are Smi but others are Integer32.
 Representation HValue::RepresentationFromUseRequirements() {
   Representation rep = Representation::None();
   for (HUseIterator it(uses()); !it.Done(); it.Advance()) {
     // Ignore the use requirement from never run code
-    if (it.value()->block()->IsDeoptimizing()) continue;
+    if (it.value()->block()->IsUnreachable()) continue;
 
     // We check for observed_input_representation elsewhere.
     Representation use_rep =
         it.value()->RequiredInputRepresentation(it.index());
     if (rep.IsNone()) {
       rep = use_rep;
       continue;
     }
     if (use_rep.IsNone() || rep.Equals(use_rep)) continue;
     if (rep.generalize(use_rep).IsInteger32()) {
@@ skipping 220 matching lines @@
       break;
     case kExternalMemory:
       stream->Add("[external-memory]");
       break;
   }
 
   stream->Add("@%d", offset());
 }
 
 } }  // namespace v8::internal