Fix a bad merge that lead to unused optimization: implement the dataEquals in HInterceptor in order…

sdk/lib/_internal/compiler/implementation/ssa/optimize.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/optimize.dart	(revision 15445)
+++ sdk/lib/_internal/compiler/implementation/ssa/optimize.dart	(working copy)
@@ -45,6 +45,7 @@
           new SsaDeadPhiEliminator(),
           new SsaConstantFolder(constantSystem, backend, work, types),
           new SsaTypePropagator(compiler, types),
+          new SsaReceiverSpecialization(compiler),
           new SsaGlobalValueNumberer(compiler, types),
           new SsaCodeMotion(),
           new SsaValueRangeAnalyzer(constantSystem, types, work),
@@ -1416,3 +1417,32 @@
     });
   }
 }
+
+/**
+ * This phase specializes dominated uses of a call, where the call
+ * can give us some type information of what the receiver might be.
+ * For example, after a call to [:a.foo():], if [:foo:] is only
+ * in class [:A:], a can be of type [:A:].
+ */
+class SsaReceiverSpecialization extends HBaseVisitor
+    implements OptimizationPhase {
+  final String name = "SsaReceiverSpecialization";
+  final Compiler compiler;
+
+  SsaReceiverSpecialization(this.compiler);
+
+  void visitGraph(HGraph graph) {
+    visitDominatorTree(graph);
+  }
+
+  void visitInterceptor(HInterceptor interceptor) {
+    HInstruction receiver = interceptor.receiver;
+    for (var user in receiver.usedBy) {
+      if (user is HInterceptor && interceptor.dominates(user)) {

[kasperl, 2012/11/29 08:22:27]

This is probably fine, but an alternative implementation would be to keep a
scoped mapping from interceptor receivers to intercepted classes -- and let the
dominator tree walk eliminate the need for calling interceptor.dominates(user).

[ngeoffray, 2012/11/29 08:31:56]

Good point. Filed http://code.google.com/p/dart/issues/detail?id=7022 to not
forget about it.

+        user.interceptedClasses = interceptor.interceptedClasses;
+      }
+    }
+  }
+
+  // TODO(ngeoffray): Also implement it for non-intercepted calls.
+}