Tree-shaking: use a hash set for tracking live selectors, drop uncompiled functions.

runtime/vm/precompiler.h

 // Copyright (c) 2015, 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_PRECOMPILER_H_
 #define VM_PRECOMPILER_H_
 
 #include "vm/allocation.h"
+#include "vm/hash_map.h"
+#include "vm/object.h"
 
 namespace dart {
 
 // Forward declarations.
 class Class;
 class Error;
 class Field;
 class Function;
 class GrowableObjectArray;
 class RawError;
 class String;
 
+class SymbolPair {
+ public:
+  // Typedefs needed for the DirectChainedHashMap template.
+  typedef const String* Key;
+  typedef bool Value;

[Florian Schneider, 2015/08/06 08:21:19]

I think you can do something simpler:

typedef String* Key;
typedef String* Value;
typedef String* Pair;

See PointerLeyValueTrait in hash_map.h.

NULL means non-existent in this case.

+  typedef SymbolPair Pair;
+
+  SymbolPair() : key_(NULL), value_(false) {}
+  SymbolPair(Key key, Value value) : key_(key), value_(value) {
+    ASSERT(key->IsNotTemporaryScopedHandle());
+  }
+
+  static Key KeyOf(Pair kv) { return kv.key_; }
+
+  static Value ValueOf(Pair kv) { return kv.value_; }
+
+  static inline intptr_t Hashcode(Key key) {
+    return key->Hash();
+  }
+
+  static inline bool IsKeyEqual(Pair pair, Key key) {
+    return pair.key_->raw() == key->raw();
+  }
+
+ private:
+  Key key_;
+  Value value_;
+};
+
+
+class SymbolSet : public ValueObject {
+ public:
+  explicit SymbolSet(Zone* zone) : zone_(zone), map_() {}
+
+  void Add(const String& symbol) {
+    ASSERT(symbol.IsSymbol());
+    if (symbol.IsNotTemporaryScopedHandle()) {
+      SymbolPair pair(&symbol, true);
+      map_.Insert(pair);
+    } else {
+      SymbolPair pair(&String::ZoneHandle(zone_, symbol.raw()), true);
+      map_.Insert(pair);
+    }
+  }
+
+  bool Includes(const String& symbol) {
+    ASSERT(symbol.IsSymbol());
+    return map_.Lookup(&symbol);
+  }
+
+ private:
+  Zone* zone_;
+  DirectChainedHashMap<SymbolPair> map_;
+};
+
+
 class Precompiler : public ValueObject {
  public:
   static RawError* CompileAll();
 
  private:
   explicit Precompiler(Thread* thread);
 
   void DoCompileAll();
   void ClearAllCode();
   void AddRoots();
   void Iterate();
   void CleanUp();
 
   void AddCalleesOf(const Function& function);
   void AddField(const Field& field);
   void AddFunction(const Function& function);
   void AddClass(const Class& cls);
   void AddSelector(const String& selector);
   bool IsSent(const String& selector);
 
   void ProcessFunction(const Function& function);
   void CheckForNewDynamicFunctions();
 
+  void DropUncompiledFunctions();
+
   Thread* thread() const { return thread_; }
   Zone* zone() const { return zone_; }
   Isolate* isolate() const { return isolate_; }
 
   Thread* thread_;
   Zone* zone_;
   Isolate* isolate_;
 
   bool changed_;
   intptr_t function_count_;
   intptr_t class_count_;
+  intptr_t selector_count_;
+  intptr_t dropped_function_count_;
 
   const GrowableObjectArray& libraries_;
   const GrowableObjectArray& pending_functions_;
   const GrowableObjectArray& collected_closures_;
-  const GrowableObjectArray& sent_selectors_;
+  SymbolSet sent_selectors_;
   Error& error_;
 };
 
 }  // namespace dart
 
 #endif  // VM_PRECOMPILER_H_