Fix folding of == when a type defines operator=.

lib/compiler/implementation/ssa/optimize.dart

 // Copyright (c) 2011, 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.
 
 interface OptimizationPhase {
   String get name();
   void visitGraph(HGraph graph);
 }
 
 class SsaOptimizerTask extends CompilerTask {
@@ skipping 227 matching lines @@
   }
 
   HInstruction visitEquals(HEquals node) {
     HInstruction left = node.left;
     HInstruction right = node.right;
 
     if (left.isConstant() && right.isConstant()) {
       return visitInvokeBinary(node);
     }
 
+    if (left.isNonPrimitive()) {
+      HNonPrimitiveType type = left.propagatedType;
+      Element element = type.lookupMember(Namer.OPERATOR_EQUALS);
+      if (element !== null) {
+        // If the left-hand side is guaranteed to be a non-primitive
+        // type and and it defines operator==, we emit a call to that
+        // operator.
+        return visitInvokeBinary(node);
+      } else if (right.isConstantNull()) {
+        return graph.addConstantBool(false);
+      } else {
+        // We can just emit an identity check because the type does
+        // not implement operator=.
+        // TODO(floitsch): cache interceptors.
+        HStatic target = new HStatic(
+            compiler.builder.interceptors.getTripleEqualsInterceptor());
+        return new HIdentity(target, left, right);
+      }
+    }
+
+
     if (right.isConstantNull()) {
       if (left.propagatedType.isUseful()) {
         return graph.addConstantBool(false);
       } else {
         // TODO(floitsch): cache interceptors.
         HStatic target = new HStatic(
             compiler.builder.interceptors.getEqualsNullInterceptor());
         node.block.addBefore(node,target);
         return new HEquals(target, node.left, node.right);
       }
     }
 
-    if (left.isNonPrimitive()) {
-      // If the left-hand side is guaranteed to be a non-primitive
-      // type and and it does not define operator==, we can just emit
-      // an identity check.
-      HNonPrimitiveType type = left.propagatedType;
-      Element element = type.lookupMember(Namer.OPERATOR_EQUALS);
-      if (element === null) {
-        // TODO(floitsch): cache interceptors.
-        HStatic target = new HStatic(
-            compiler.builder.interceptors.getTripleEqualsInterceptor());
-        return new HIdentity(target, left, right);
-      }
-    }
-
     // All other cases are dealt with by the [visitInvokeBinary].
     return visitInvokeBinary(node);
   }
 
   HInstruction visitTypeGuard(HTypeGuard node) {
     HInstruction value = node.guarded;
     HType combinedType = value.propagatedType.combine(node.propagatedType);
     return (combinedType == value.propagatedType) ? value : node;
   }
 
@@ skipping 520 matching lines @@
         }
       }
       if (!canBeMoved) continue;
 
       // This is safe because we are running after GVN.
       // TODO(ngeoffray): ensure GVN has been run.
       set_.add(current);
     }
   }
 }