Optimize instanceof: if all results are true and tests can be done using class only replace instanc…

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
===================================================================
--- runtime/vm/flow_graph_optimizer.cc	(revision 16610)
+++ runtime/vm/flow_graph_optimizer.cc	(working copy)
@@ -1249,6 +1249,37 @@
 }
 
 
+// Returns a Boolean constant if all classes in ic_data yield the same type-test
+// result and the type tests do not depend on type arguments. Otherwise return
+// Bool::null().
+RawBool* FlowGraphOptimizer::InstanceOfAsBool(const ICData& ic_data,
+                                              const AbstractType& type) const {
+  ASSERT(ic_data.num_args_tested() == 1);  // Unary checks only.
+  if (!type.IsInstantiated()) return Bool::null();

[regis, 2013/01/03 23:35:26]

I suppose there is no need to check that !type.IsMalformed()?

[srdjan, 2013/01/04 00:10:55]

Added it, just in case.

+  const Class& type_class = Class::Handle(type.type_class());
+  if (type_class.HasTypeArguments()) return Bool::null();
+  const ClassTable& class_table = *Isolate::Current()->class_table();
+  Bool& prev = Bool::Handle();
+  Class& cls = Class::Handle();
+  for (int i = 0; i < ic_data.NumberOfChecks(); i++) {
+    cls = class_table.At(ic_data.GetReceiverClassIdAt(i));
+    if (cls.HasTypeArguments()) return Bool::null();
+    const bool is_subtype = cls.IsNullClass() ?
+        false :

[regis, 2013/01/03 23:35:26]

I do not think this is correct, because null is an instance of Object and of
dynamic.

[srdjan, 2013/01/04 00:10:55]

Fixed.

+        cls.IsSubtypeOf(TypeArguments::Handle(),
+                        type_class,
+                        TypeArguments::Handle(),
+                        NULL);
+    if (prev.IsNull()) {
+      prev = is_subtype ? Bool::True() : Bool::False();
+    } else {
+      if (is_subtype != prev.value()) return Bool::null();
+    }
+  }
+  return prev.raw();
+}
+
+
 // TODO(srdjan): Use ICData to check if always true or false.
 void FlowGraphOptimizer::ReplaceWithInstanceOf(InstanceCallInstr* call) {
   ASSERT(Token::IsTypeTestOperator(call->token_kind()));
@@ -1259,6 +1290,21 @@
       AbstractType::Cast(call->ArgumentAt(3)->value()->BoundConstant());
   const Bool& negate =
       Bool::Cast(call->ArgumentAt(4)->value()->BoundConstant());
+  const ICData& unary_checks =
+      ICData::ZoneHandle(call->ic_data()->AsUnaryClassChecks());
+  if (unary_checks.NumberOfChecks() <= FLAG_max_polymorphic_checks) {
+    Bool& as_bool = Bool::ZoneHandle(InstanceOfAsBool(unary_checks, type));
+    if (!as_bool.IsNull()) {
+      AddCheckClass(call, left_val->Copy());
+      if (negate.value()) {
+        as_bool = as_bool.value() ? Bool::False() : Bool::True();
+      }
+      ConstantInstr* bool_const = new ConstantInstr(as_bool);
+      call->ReplaceWith(bool_const, current_iterator());
+      RemovePushArguments(call);
+      return;
+    }
+  }
   InstanceOfInstr* instance_of =
       new InstanceOfInstr(call->token_pos(),
                           left_val,