Upstream folding instanceof on a constant.

runtime/vm/constant_propagator.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/constant_propagator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/flow_graph_range_analysis.h"
@@ skipping 722 matching lines @@
       ASSERT(((rep == kUnboxedFloat32x4) && (value_cid == kFloat32x4Cid)) ||
              ((rep == kUnboxedInt32x4) && (value_cid == kInt32x4Cid)) ||
              ((rep == kUnboxedDouble) && (value_cid == kDoubleCid)) ||
              ((rep == kUnboxedMint) && (value_cid == kMintCid)));
       // The representation guarantees the type check to be true.
       SetValue(instr, instr->negate_result() ? Bool::False() : Bool::True());
     } else {
       SetValue(instr, non_constant_);
     }
   } else if (IsConstant(value)) {
-    // TODO(kmillikin): Handle instanceof on constants.
+    if (value.IsInstance()) {
+      const Instance& instance = Instance::Cast(value);
+      const AbstractType& checked_type = instr->type();
+      if (instr->instantiator()->BindsToConstantNull() &&
+        instr->instantiator_type_arguments()->BindsToConstantNull()) {
+        const TypeArguments& checked_type_arguments = TypeArguments::Handle();
+        Error& bound_error = Error::Handle();
+        bool is_instance = instance.IsInstanceOf(checked_type,
+                                                 checked_type_arguments,
+                                                 &bound_error);
+        // Can only have bound error with generics.
+        ASSERT(bound_error.IsNull());
+        SetValue(instr, Bool::Get(instr->negate_result()
+                                  ? !is_instance : is_instance));
+        return;
+      }
+    }
     SetValue(instr, non_constant_);
   }
 }
 
 
 void ConstantPropagator::VisitCreateArray(CreateArrayInstr* instr) {
   SetValue(instr, non_constant_);
 }
 
 
@@ skipping 883 matching lines @@
   graph_->ComputeDominators(&dominance_frontier);
 
   if (FLAG_trace_constant_propagation) {
     OS::Print("\n==== After constant propagation ====\n");
     FlowGraphPrinter printer(*graph_);
     printer.PrintBlocks();
   }
 }
 
 }  // namespace dart