Cache lookups at megamorphic call sites in optimized code.

runtime/vm/megamorphic_cache_table.h

+// 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.
+
+#ifndef VM_MEGAMORPHIC_CACHE_TABLE_H_
+#define VM_MEGAMORPHIC_CACHE_TABLE_H_
+
+#include "vm/allocation.h"
+
+namespace dart {
+
+class Array;
+class Function;
+class ObjectPointerVisitor;
+class RawArray;
+class RawFunction;
+class RawMegamorphicCache;
+class RawString;
+class String;
+
+class MegamorphicCacheTable : public ValueObject {

[srdjan, 2012/12/03 19:10:46]

Don't make it a ValueObject as this indicates to me that it can be used anywhere
as regular class. See also definition of classes ClassTable and StoreBuffer

[Kevin Millikin (Google), 2012/12/06 14:03:11]

Done.

+ public:
+  MegamorphicCacheTable();
+  ~MegamorphicCacheTable();
+
+  RawFunction* miss_handler() const { return miss_handler_; }
+  void InitMissHandler();
+
+  RawMegamorphicCache* Lookup(const String& name, const Array& descriptor);
+
+  void VisitObjectPointers(ObjectPointerVisitor* visitor);
+
+  void PrintSizes();
+
+ private:
+  struct Entry {
+    RawString* name;
+    RawArray* descriptor;
+    RawMegamorphicCache* cache;
+  };
+
+  static const int kInitialCapacity = 128;
+  static const int kCapacityIncrement = 128;
+
+  RawFunction* miss_handler_;
+  intptr_t capacity_;
+  intptr_t length_;
+  Entry* table_;

[srdjan, 2012/12/03 19:10:46]

DISALLOW_YADYADA...

[Kevin Millikin (Google), 2012/12/06 14:03:11]

Done.

+};

[srdjan, 2012/12/03 19:10:46]

You can use RawGrowableObjectArray* table_, then you do not need to implement
another growing algorithm.

[Kevin Millikin (Google), 2012/12/06 14:03:11]

Thanks for the good idea.  I'll hold that off for another change to get this one
landed.

The Entries are not heap objects now.  Making them their own class is a somewhat
painful and representing structured data in an array (e.g., ArgumentsDescriptor)
is also a lot of busy work in C++.

+
+}  // namespace dart
+
+#endif  // VM_MEGAMORPHIC_CACHE_TABLE_H_