Add a performance assert that we do not emit a null check for smi class-ids. Instead we should use …

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/bigint_operations.h"
 #include "vm/bit_vector.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
@@ skipping 115 matching lines @@
   return externalizable ? EffectSet::Externalization() : EffectSet::None();
 }
 
 
 bool CheckClassInstr::IsNullCheck() const {
   if (unary_checks().NumberOfChecks() != 1) {
     return false;
   }
   CompileType* in_type = value()->Type();
   const intptr_t cid = unary_checks().GetCidAt(0);
+  // Performance check: use CheckSmiInstr instead.
+  ASSERT(cid != kSmiCid);
   return in_type->is_nullable() && (in_type->ToNullableCid() == cid);
 }
 
 
 bool GuardFieldInstr::AttributesEqual(Instruction* other) const {
   return field().raw() == other->AsGuardField()->field().raw();
 }
 
 
 bool AssertAssignableInstr::AttributesEqual(Instruction* other) const {
@@ skipping 2453 matching lines @@
     default:
       UNREACHABLE();
   }
   return kPowRuntimeEntry;
 }
 
 
 #undef __
 
 }  // namespace dart