Take representation into account in ConstantPropagator::VisitInstanceOfInstr

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
diff --git a/runtime/vm/flow_graph_optimizer.cc b/runtime/vm/flow_graph_optimizer.cc
index b9f6bd448cddce363f24ede44848f46bd9aa0e07..ef6b36f75c2b7be44b8e138b610ea8fd282c4945 100644
--- a/runtime/vm/flow_graph_optimizer.cc
+++ b/runtime/vm/flow_graph_optimizer.cc
@@ -6324,9 +6324,20 @@ void ConstantPropagator::VisitBooleanNegate(BooleanNegateInstr* instr) {
 
 
 void ConstantPropagator::VisitInstanceOf(InstanceOfInstr* instr) {
-  const Object& value = instr->value()->definition()->constant_value();
+  const Definition* def = instr->value()->definition();
+  const Object& value = def->constant_value();
   if (IsNonConstant(value)) {
-    SetValue(instr, non_constant_);
+    const AbstractType& checked_type = instr->type();
+    Representation rep = def->representation();
+    if ((checked_type.IsFloat32x4Type() && (rep == kUnboxedFloat32x4)) ||
+        (checked_type.IsUint32x4Type() && (rep == kUnboxedUint32x4))   ||
+        (checked_type.IsDoubleType() && (rep == kUnboxedDouble))       ||
+        (checked_type.IsIntType() && (rep == kUnboxedMint))) {
+      // The representation guarantees the type check to be true.

[Florian Schneider, 2013/10/03 09:06:55]

Maybe add an ASSERT that the compile-type of instr->value()->Type() matches with
the representation.

You could also use the type here - it should be slightly more general - i.e.
type checks on boxed values with a known type could be optimized as well: e.g.
smis

[Cutch, 2013/11/06 23:04:43]

Done.
I'll save that for a follow up CL.

+      SetValue(instr, instr->negate_result() ? Bool::False() : Bool::True());
+    } else {
+      SetValue(instr, non_constant_);
+    }
   } else if (IsConstant(value)) {
     // TODO(kmillikin): Handle instanceof on constants.
     SetValue(instr, non_constant_);