Better dependency tracking

sdk/lib/_internal/compiler/implementation/dump_info.dart

Index: sdk/lib/_internal/compiler/implementation/dump_info.dart
diff --git a/sdk/lib/_internal/compiler/implementation/dump_info.dart b/sdk/lib/_internal/compiler/implementation/dump_info.dart
index c5d0db85679d36d8849478deaa078147bb2f338c..51787fe2bd2a8a0dd2d30290cd1d440906c77fc5 100644
--- a/sdk/lib/_internal/compiler/implementation/dump_info.dart
+++ b/sdk/lib/_internal/compiler/implementation/dump_info.dart
@@ -18,11 +18,11 @@ import 'dart2jslib.dart' show
     CodeBuffer;
 import 'dart_types.dart' show DartType;
 import 'types/types.dart' show TypeMask;
-import 'util/util.dart' show modifiersToString;
+import 'util/util.dart' show modifiersToString, SpannableAssertionFailure;
 import 'deferred_load.dart' show OutputUnit;
 import 'js_backend/js_backend.dart' show JavaScriptBackend;
 import 'js/js.dart' as jsAst;
-import 'compilation_info.dart' show CompilationInformation;
+import 'dependency_info.dart' show DependencyInformation;
 
 /// Maps elements to an id.  Supports lookups in
 /// both directions.
@@ -34,6 +34,8 @@ class ElementMapper {
 
   ElementMapper(this.name);
 
+  Iterable<Element> get elements => _elementToId.keys;
+
   String add(Element e) {
     if (_elementToId.containsKey(e)) {
       return name + "/${_elementToId[e]}";
@@ -54,6 +56,8 @@ class DividedElementMapper {
   ElementMapper _class = new ElementMapper('class');
   ElementMapper _function = new ElementMapper('function');
 
+  Iterable<Element> get functions => _function.elements;
+
   // Convert this database of elements into JSON for rendering
   Map<String, dynamic> _toJson(ElementToJsonVisitor elementToJson) {
     Map<String, dynamic> json = {};
@@ -78,7 +82,7 @@ class ElementToJsonVisitor extends ElementVisitor<Map<String, dynamic>> {
   DividedElementMapper mapper = new DividedElementMapper();
   Compiler compiler;
 
-  CompilationInformation compilationInfo;
+  DependencyInformation dependencyInfo;
 
   Map<Element, Map<String, dynamic>> jsonCache = {};
   Map<Element, jsAst.Expression> codeCache;
@@ -91,7 +95,7 @@ class ElementToJsonVisitor extends ElementVisitor<Map<String, dynamic>> {
 
   ElementToJsonVisitor(Compiler compiler) {
     this.compiler = compiler;
-    this.compilationInfo = compiler.enqueuer.codegen.compilationInfo;
+    this.dependencyInfo = compiler.enqueuer.codegen.dependencyInfo;
 
     programSize = compiler.assembledCode.length;
     compilationMoment = new DateTime.now();
@@ -108,8 +112,7 @@ class ElementToJsonVisitor extends ElementVisitor<Map<String, dynamic>> {
   // If keeping the element is in question (like if a function has a size
   // of zero), only keep it if it holds dependencies to elsewhere.
   bool shouldKeep(Element element) {
-    return compilationInfo.addsToWorkListMap.containsKey(element) ||
-           compilationInfo.enqueuesMap.containsKey(element);
+    return dependencyInfo.selectorsFromElement.containsKey(element);
   }
 
   Map<String, dynamic> toJson() {
@@ -121,6 +124,14 @@ class ElementToJsonVisitor extends ElementVisitor<Map<String, dynamic>> {
     return jsonCache.putIfAbsent(element, () => element.accept(this));
   }
 
+  String idOf(Element element) {
+    if (jsonCache.containsKey(element) && jsonCache[element] != null) {
+      return jsonCache[element]['id'];
+    } else {
+      return null;
+    }
+  }
+
   Map<String, dynamic> visitElement(Element element) {
     return null;
   }
@@ -464,34 +475,24 @@ class DumpInfoTask extends CompilerTask {
   void dumpInfoJson(StringSink buffer) {
     JsonEncoder encoder = const JsonEncoder();
 
-    // `A` uses and depends on the functions `Bs`.
-    //     A         Bs
-    Map<String, List<String>> holding = <String, List<String>>{};
-
     DateTime startToJsonTime = new DateTime.now();
 
-    CompilationInformation compilationInfo =
-      infoCollector.compiler.enqueuer.codegen.compilationInfo;
-    compilationInfo.addsToWorkListMap.forEach((func, deps) {
-      if (func != null) {
-        var funcJson = infoCollector.process(func);
-        if (funcJson != null) {
-          var funcId = funcJson['id'];
-
-          List<String> heldList = <String>[];
-
-          for (var held in deps) {
-            // "process" to get the ids of the elements.
-            var heldJson = infoCollector.process(held);
-            if (heldJson != null) {
-              var heldId = heldJson['id'];
-              heldList.add(heldId);
-            }
-          }
-          holding[funcId] = heldList;
+    DependencyInformation dependencyInfo =
+      infoCollector.compiler.enqueuer.codegen.dependencyInfo;
+
+    Map<String, List<String>> holding = <String, List<String>>{};
+    for (Element fn in infoCollector.mapper.functions) {
+      Iterable<Element> pulling = dependencyInfo.getRetaining(fn, compiler);
+      if (pulling.length > 0) {
+        String fnId = infoCollector.idOf(fn);
+        if (fnId != null) {
+          holding[fnId] = pulling
+            .map((a) => infoCollector.idOf(a))
+            .where((a) => a != null)
+            .toList();
         }
       }
-    });
+    }
 
     Map<String, dynamic> outJson = {
       'elements': infoCollector.toJson(),