Various caches for incremental compilation.

dart/sdk/lib/_internal/compiler/implementation/enqueue.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.
 
 part of dart2js;
 
 typedef ItemCompilationContext ItemCompilationContextCreator();
 
 class EnqueueTask extends CompilerTask {
   final ResolutionEnqueuer resolution;
@@ skipping 703 matching lines @@
     log('Resolved ${resolvedElements.length} elements.');
   }
 }
 
 /// [Enqueuer] which is specific to code generation.
 class CodegenEnqueuer extends Enqueuer {
   final Queue<CodegenWorkItem> queue;
   final Map<Element, js.Expression> generatedCode =
       new Map<Element, js.Expression>();
 
+  final Set<Element> newlyEnqueuedElements = new HashSet<Element>.identity();

[Johnni Winther, 2014/06/19 09:22:32]

Element equality is object identity so why do you need HashSet.identity ? 

[ahe, 2014/06/19 09:36:19]

Good point. I'll investigate if it matters. I doubt it will for elements.

[ahe, 2014/06/19 13:50:10]

I'm not sure I have specific evidence for this particular place, but in other
places, identity sets and maps had superior performance.

This is now encapsulated in a strategy.

+
   CodegenEnqueuer(Compiler compiler,
                   ItemCompilationContext itemCompilationContextCreator())
       : super('codegen enqueuer', compiler, itemCompilationContextCreator),
         queue = new Queue<CodegenWorkItem>();
 
   bool isProcessed(Element member) =>
       member.isAbstract || generatedCode.containsKey(member);
 
   void internalAddToWorkList(Element element) {
+    if (compiler.hasIncrementalSupport) {
+      newlyEnqueuedElements.add(element);
+    }
     // Don't generate code for foreign elements.
     if (element.isForeign(compiler)) return;
 
     // Codegen inlines field initializers. It only needs to generate
     // code for checked setters.
     if (element.isField && element.isInstanceMember) {
       if (!compiler.enableTypeAssertions
           || element.enclosingElement.isClosure) {
         return;
       }
     }
 
     if (queueIsClosed) {
       throw new SpannableAssertionFailure(element,
           "Codegen work list is closed. Trying to add $element");
     }
     CodegenWorkItem workItem = new CodegenWorkItem(
         element, itemCompilationContextCreator());
     queue.add(workItem);
   }
 
   void _logSpecificSummary(log(message)) {
     log('Compiled ${generatedCode.length} methods.');
   }
 }