Add --dump-megamorphic-stats. Lower megamorphic cache load factor to 50%.

runtime/vm/object.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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 147 matching lines @@
     reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::subtypetestcache_class_ =
     reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::api_error_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::language_error_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::unhandled_exception_class_ =
     reinterpret_cast<RawClass*>(RAW_NULL);
 RawClass* Object::unwind_error_class_ = reinterpret_cast<RawClass*>(RAW_NULL);
 
 
-const double MegamorphicCache::kLoadFactor = 0.75;
+const double MegamorphicCache::kLoadFactor = 0.50;
 
 
 static void AppendSubString(Zone* zone,
                             GrowableArray<const char*>* segments,
                             const char* name,
                             intptr_t start_pos, intptr_t len) {
   char* segment = zone->Alloc<char>(len + 1);  // '\0'-terminated.
   memmove(segment, name + start_pos, len);
   segment[len] = '\0';
   segments->Add(segment);
@@ skipping 22430 matching lines @@
   return UserTag::null();
 }
 
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart