Optimize getField by caching a closure generated from eval.

runtime/lib/mirrors_impl.dart

 // 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.
 
 // VM-specific implementation of the dart:mirrors library.
 
 import "dart:collection";
 
 final emptyList = new UnmodifiableListView([]);
 final emptyMap = new _UnmodifiableMapView({});
@@ skipping 314 matching lines @@
       }
     }
     if (!found) {
       throw new ArgumentError(
           "${MirrorSystem.getName(type.simpleName)} has no instance method "
           "${MirrorSystem.getName(selector)}");
     }
     return new _InvocationTrampoline(this, selector);
   }
 
+  // TODO(16539): Make these weak or soft.
+  static var _getFieldClosures = new HashMap();
+  static var _setFieldClosures = new HashMap();
+  static var _getFieldCallCounts = new HashMap();
+  static var _setFieldCallCounts = new HashMap();
+
+  _getFieldSlow(unwrapped) {
+    // Slow path factored out to give the fast path a better chance at being
+    // inlined.
+    var callCount = _getFieldCallCounts[unwrapped];
+    if (callCount == null) {
+      callCount = 0;
+    }
+    if (callCount == 20) {

[Ivan Posva, 2014/02/05 22:23:44]

How about naming this arbitrary constant and pulling it out of the functions.

[rmacnak, 2014/02/05 22:56:31]

Done.

+      // We've seen a success getter invocation a few times: time to invest in a
+      // closure.
+      var f;
+      var atPosition = unwrapped.indexOf('@');
+      if (atPosition == -1) {
+        // Public symbol.
+        f = _eval('(x) => x.$unwrapped', null);
+      } else {
+        // Private symbol.
+        var withoutKey = unwrapped.substring(0, atPosition);
+        var privateKey = unwrapped.substring(atPosition);
+        f = _eval('(x) => x.$withoutKey', privateKey);
+      }
+      _getFieldClosures[unwrapped] = f;
+      _getFieldCallCounts.remove(unwrapped);  // We won't look for this again.
+      return reflect(f(_reflectee));
+    }
+    var result = reflect(_invokeGetter(_reflectee, unwrapped));
+    // Only update call count if we don't throw to avoid creating closures for
+    // non-existent getters.
+    _getFieldCallCounts[unwrapped] = callCount + 1;
+    return result;
+  }
+
+  InstanceMirror getField(Symbol memberName) {
+    var unwrapped = _n(memberName);
+    var f = _getFieldClosures[unwrapped];
+    return (f == null)

[Ivan Posva, 2014/02/05 22:23:44]

return (f == null) ?
      _getFieldSlow(unwrapped) : reflect(f(_reflectee));

[rmacnak, 2014/02/05 22:56:31]

Done.

+        ? _getFieldSlow(unwrapped)
+        : reflect(f(_reflectee));
+  }
+
+  _setFieldSlow(unwrapped, arg) {
+    // Slow path factored out to give the fast path a better chance at being
+    // inlined.
+    var callCount = _setFieldCallCounts[unwrapped];
+    if (callCount == null) {
+      callCount = 0;
+    }
+    if (callCount == 20) {
+      // We've seen a success getter invocation a few times: time to invest in a
+      // closure.
+      var f;
+      var atPosition = unwrapped.indexOf('@');
+      if (atPosition == -1) {
+        // Public symbol.
+        f = _eval('(x, v) => x.$unwrapped = v', null);
+      } else {
+        // Private symbol.
+        var withoutKey = unwrapped.substring(0, atPosition);
+        var privateKey = unwrapped.substring(atPosition);
+        f = _eval('(x, v) => x.$withoutKey = v', privateKey);
+      }
+      _setFieldClosures[unwrapped] = f;
+      _setFieldCallCounts.remove(unwrapped);
+      return reflect(f(_reflectee, arg));
+    }
+    _invokeSetter(_reflectee, unwrapped, arg);
+    var result = reflect(arg);
+    // Only update call count if we don't throw to avoid creating closures for
+    // non-existent setters.
+    _setFieldCallCounts[unwrapped] = callCount + 1;
+    return result;
+  }
+
+  InstanceMirror setField(Symbol memberName, arg) {
+    var unwrapped = _n(memberName);
+    var f = _setFieldClosures[unwrapped];
+    return (f == null)
+        ? _setFieldSlow(unwrapped, arg)
+        : reflect(f(_reflectee, arg));
+  }
+
+  static _eval(expression, privateKey)
+      native "Mirrors_evalInLibraryWithPrivateKey";
+
   // Override to include the receiver in the arguments.
   InstanceMirror invoke(Symbol memberName,
                         List positionalArguments,
                         [Map<Symbol, dynamic> namedArguments]) {
     int numPositionalArguments = positionalArguments.length + 1;  // Receiver.
     int numNamedArguments = namedArguments != null ? namedArguments.length : 0;
     int numArguments = numPositionalArguments + numNamedArguments;
     List arguments = new List(numArguments);
     arguments[0] = _reflectee;  // Receiver.
     arguments.setRange(1, numPositionalArguments, positionalArguments);
@@ skipping 1147 matching lines @@
     if (typeMirror == null) {
       typeMirror = makeLocalTypeMirror(key);
       _instanitationCache[key] = typeMirror;
       if (typeMirror is ClassMirror && !typeMirror._isGeneric) {
         _declarationCache[key] = typeMirror;
       }
     }
     return typeMirror;
   }
 }