Fix equality instruction to switch from checked (polymorphic) to megamorphic state. This helps da…

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2012, 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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/hash_map.h"
 #include "vm/il_printer.h"
 #include "vm/intermediate_language.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/resolver.h"
 #include "vm/scopes.h"
 #include "vm/symbols.h"
 
 namespace dart {
 
 DECLARE_FLAG(bool, eliminate_type_checks);
 DECLARE_FLAG(bool, enable_type_checks);
 DEFINE_FLAG(bool, trace_optimization, false, "Print optimization details.");
 DECLARE_FLAG(bool, trace_type_check_elimination);
 DEFINE_FLAG(bool, use_cha, true, "Use class hierarchy analysis.");
 DEFINE_FLAG(bool, load_cse, true, "Use redundant load elimination.");
 DEFINE_FLAG(bool, trace_range_analysis, false, "Trace range analysis progress");
 DEFINE_FLAG(bool, trace_constant_propagation, false,
-            "Print constant propagation and useless code elimination.");
+    "Print constant propagation and useless code elimination.");
 DEFINE_FLAG(bool, array_bounds_check_elimination, true,
-            "Eliminate redundant bounds checks.");
+    "Eliminate redundant bounds checks.");
+DEFINE_FLAG(int, max_polymorphic_checks, 4,
+    "Maximum number of polymorphic check, otherwise it is megamorphic.");
 
 
 void FlowGraphOptimizer::ApplyICData() {
   VisitBlocks();
 }
 
 
 // Attempts to convert an instance call (IC call) using propagated class-ids,
 // e.g., receiver class id.
 void FlowGraphOptimizer::ApplyClassIds() {
@@ skipping 1107 matching lines @@
     const ICData& unary_checks =
         ICData::ZoneHandle(instr->ic_data()->AsUnaryClassChecks());
     if (!InstanceCallNeedsClassCheck(instr)) {
       const bool call_with_checks = false;
       PolymorphicInstanceCallInstr* call =
           new PolymorphicInstanceCallInstr(instr, unary_checks,
                                            call_with_checks);
       instr->ReplaceWith(call, current_iterator());
       return;
     }
-    const intptr_t kMaxChecks = 4;
-    if (instr->ic_data()->NumberOfChecks() <= kMaxChecks) {
+    if (instr->ic_data()->NumberOfChecks() <= FLAG_max_polymorphic_checks) {
       bool call_with_checks;
       if (unary_checks.HasOneTarget()) {
         // Type propagation has not run yet, we cannot eliminate the check.
         AddCheckClass(instr, instr->ArgumentAt(0)->value()->Copy());
         // Call can still deoptimize, do not detach environment from instr.
         call_with_checks = false;
       } else {
         call_with_checks = true;
       }
       PolymorphicInstanceCallInstr* call =
@@ skipping 2470 matching lines @@
 
   if (FLAG_trace_constant_propagation) {
     OS::Print("\n==== After constant propagation ====\n");
     FlowGraphPrinter printer(*graph_);
     printer.PrintBlocks();
   }
 }
 
 
 }  // namespace dart