Improve and simplify removal of unreachable code

src/lithium.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 472 matching lines @@
         spill_slot_count_ += 2;
       } else {
         spill_slot_count_++;
       }
     }
     iterator.Advance();
   }
 }
 
 
+LInstruction* LChunkBuilder::CheckElideControlInstruction(
+    HControlInstruction* instr) {
+  HBasicBlock* successor;
+  if (!instr->KnownSuccessorBlock(&successor)) return NULL;
+  return new(zone()) LGoto(successor);
+}
+
+
 LPhase::~LPhase() {
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceLithium(name(), chunk_);
   }
 }
 
 
 } }  // namespace v8::internal