dart2js cps: Share interceptors by default and propagate to use later.

pkg/compiler/lib/src/js_backend/codegen/unsugar.dart

Index: pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
diff --git a/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart b/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
index bbe998f1f396f742fb02e2570ed10aa6e2a32156..110d156acc756a234b9a77331c9cf80e70068a9f 100644
--- a/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
+++ b/pkg/compiler/lib/src/js_backend/codegen/unsugar.dart
@@ -5,12 +5,7 @@ import '../../cps_ir/cps_ir_nodes.dart';
 import '../../cps_ir/optimizers.dart' show ParentVisitor;
 import '../../constants/expressions.dart';
 import '../../constants/values.dart';
-import '../../elements/elements.dart' show
-    ClassElement,
-    FieldElement,
-    FunctionElement,
-    Local,
-    ExecutableElement;
+import '../../elements/elements.dart';
 import '../../js_backend/codegen/glue.dart';
 import '../../dart2jslib.dart' show Selector, World;
 import '../../cps_ir/cps_ir_builder.dart' show ThisParameterLocal;
@@ -22,6 +17,16 @@ class ExplicitReceiverParameterEntity implements Local {
   toString() => 'ExplicitReceiverParameterEntity($executableContext)';
 }
 
+/// Suggested name for an interceptor.
+class InterceptorEntity extends Entity {
+  Entity interceptedVariable;
+
+  InterceptorEntity(this.interceptedVariable);
+
+  String get name => interceptedVariable.name + '_';
+}
+
+
 /// Rewrites the initial CPS IR to make Dart semantics explicit and inserts
 /// special nodes that respect JavaScript behavior.
 ///
@@ -38,6 +43,8 @@ class UnsugarVisitor extends RecursiveVisitor {
   Parameter thisParameter;
   Parameter explicitReceiverParameter;
 
+  Map<Primitive, Interceptor> interceptors = <Primitive, Interceptor>{};
+
   // In a catch block, rethrow implicitly throws the block's exception
   // parameter.  This is the exception parameter when nested in a catch
   // block and null otherwise.
@@ -227,6 +234,32 @@ class UnsugarVisitor extends RecursiveVisitor {
     // worry about unlinking.
   }
 
+  /// Returns an interceptor for the given value, capable of responding to
+  /// [selector].
+  /// 
+  /// A single getInterceptor call will be created per primitive, bound
+  /// immediately after the primitive is bound.
+  /// 
+  /// The type propagation pass will later narrow the set of interceptors
+  /// based on the input type, and the let sinking pass will propagate the
+  /// getInterceptor call closer to its use when this is profitable.
+  Interceptor getInterceptorFor(Primitive prim, Selector selector) {
+    Interceptor interceptor = interceptors[prim];
+    if (interceptor == null) {
+      interceptor = new Interceptor(prim);
+      interceptors[prim] = interceptor;
+      InteriorNode parent = prim.parent;
+      insertLetPrim(interceptor, parent.body);
+      if (prim.hint != null) {
+        interceptor.hint = new InterceptorEntity(prim.hint);
+      }
+    }
+    // Add the interceptor classes that can respond to the given selector.
+    interceptor.interceptedClasses.addAll(
+        _glue.getInterceptedClassesOn(selector));
+    return interceptor;
+  }
+
   processInvokeMethod(InvokeMethod node) {
     Selector selector = node.selector;
     if (!_glue.isInterceptedSelector(selector)) return;
@@ -240,13 +273,7 @@ class UnsugarVisitor extends RecursiveVisitor {
       //  Change 'receiver.foo()'  to  'this.foo(receiver)'.
       newReceiver = thisParameter;
     } else {
-      // TODO(sra): Move the computation of interceptedClasses to a much later
-      // phase and take into account the remaining uses of the interceptor.
-      Set<ClassElement> interceptedClasses =
-        _glue.getInterceptedClassesOn(selector);
-      _glue.registerSpecializedGetInterceptor(interceptedClasses);
-      newReceiver = new Interceptor(receiver, interceptedClasses);
-      insertLetPrim(newReceiver, node);
+      newReceiver = getInterceptorFor(receiver, node.selector);
     }
 
     node.arguments.insert(0, node.receiver);