VM compiler: Remove dead strict-compare instructions in optimized code.

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/intermediate_language.h"
 
 #include "vm/bit_vector.h"
 #include "vm/bootstrap.h"
 #include "vm/compiler.h"
 #include "vm/constant_propagator.h"
@@ skipping 2504 matching lines @@
       flow_graph->CopyDeoptTarget(this, bit_and);
       SetComparison(test);
       bit_and->RemoveFromGraph();
     }
   }
   return this;
 }
 
 
 Definition* StrictCompareInstr::Canonicalize(FlowGraph* flow_graph) {
+  if (!HasUses()) return NULL;
   bool negated = false;
   Definition* replacement = CanonicalizeStrictCompare(this, &negated);
   if (negated && replacement->IsComparison()) {
     ASSERT(replacement != this);
     replacement->AsComparison()->NegateComparison();
   }
   return replacement;
 }
 
 
@@ skipping 1143 matching lines @@
   set_native_c_function(native_function);
   function().SetIsNativeAutoSetupScope(auto_setup_scope);
   Dart_NativeEntryResolver resolver = library.native_entry_resolver();
   bool is_bootstrap_native = Bootstrap::IsBootstapResolver(resolver);
   set_is_bootstrap_native(is_bootstrap_native);
 }
 
 #undef __
 
 }  // namespace dart