For megamorphic calls (IC calls in optimized code), use a stub without attempting to count usage of…

runtime/vm/stub_code.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_STUB_CODE_H_
 #define VM_STUB_CODE_H_
 
 #include "vm/allocation.h"
 #include "vm/assembler.h"
 
@@ skipping 37 matching lines @@
 
 // List of stubs created per isolate, these stubs could potentially contain
 // embedded objects and hence cannot be shared across isolates.
 #define STUB_CODE_LIST(V)                                                      \
   V(InvokeDartCode)                                                            \
   V(AllocateContext)                                                           \
   V(UpdateStoreBuffer)                                                         \
   V(OneArgCheckInlineCache)                                                    \
   V(TwoArgsCheckInlineCache)                                                   \
   V(ThreeArgsCheckInlineCache)                                                 \
+  V(MegamorphicCall)                                                           \
   V(BreakpointDynamic)                                                         \
   V(EqualityWithNullArg)                                                       \
 
 // class StubEntry is used to describe stub methods generated in dart to
 // abstract out common code executed from generated dart code.
 class StubEntry {
  public:
   StubEntry(const char* name, const Code& code);
   ~StubEntry() {}
 
@@ skipping 108 matching lines @@
   // code executable area.
   static RawCode* Generate(const char* name,
                            void (*GenerateStub)(Assembler* assembler));
 
   static void GenerateAllocationStubForClass(Assembler* assembler,
                                              const Class& cls);
   static void GenerateAllocationStubForClosure(Assembler* assembler,
                                                const Function& func);
   static void GenerateNArgsCheckInlineCacheStub(Assembler* assembler,
                                                 intptr_t num_args);
+  static void GenerateUsageCounterIncrement(Assembler* assembler,
+                                            Register ic_reg,
+                                            Register temp_reg);
 };
 
 }  // namespace dart
 
 #endif  // VM_STUB_CODE_H_