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

pkg/compiler/lib/src/tree_ir/optimization/statement_rewriter.dart

 // Copyright (c) 2014, 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.
 
 library tree_ir.optimization.statement_rewriter;
 
 import 'optimization.dart' show Pass;
 import '../tree_ir_nodes.dart';
 import '../../io/source_information.dart';
 
@@ skipping 147 matching lines @@
   /// Assignments with constant right-hand sides (see [isEffectivelyConstant])
   /// are not considered impure and are put in [constantEnvironment] instead.
   ///
   /// Except for [Conditional]s, expressions in the environment have
   /// not been processed, and all their subexpressions must therefore be
   /// variables uses.
   List<Expression> environment = <Expression>[];
 
   /// Binding environment for variables that are assigned to effectively
   /// constant expressions (see [isEffectivelyConstant]).
-  final Map<Variable, Expression> constantEnvironment;
+  Map<Variable, Expression> constantEnvironment;
 
   /// Substitution map for labels. Any break to a label L should be substituted
   /// for a break to L' if L maps to L'.
   Map<Label, Jump> labelRedirects = <Label, Jump>{};
 
   /// Number of uses of the given variable that are still unseen.
   /// Used to detect the first use of a variable (since we do backwards
   /// traversal, the first use is the last one seen).
   Map<Variable, int> unseenUses = <Variable, int>{};
 
@@ skipping 23 matching lines @@
 
   /// Returns the redirect target of [jump] or [jump] itself if it should not
   /// be redirected.
   Jump redirect(Jump jump) {
     Jump newJump = labelRedirects[jump.target];
     return newJump != null ? newJump : jump;
   }
 
   void inEmptyEnvironment(void action()) {
     List oldEnvironment = environment;
+    Map oldConstantEnvironment = constantEnvironment;
     environment = <Expression>[];
+    constantEnvironment = <Variable, Expression>{};
     action();
     assert(environment.isEmpty);
     environment = oldEnvironment;
+    constantEnvironment = oldConstantEnvironment;
   }
 
   /// Left-hand side of the given assignment, or `null` if not an assignment.
   Variable getLeftHand(Expression e) {
     return e is Assign ? e.variable : null;
   }
 
   /// If the given expression always returns the value of one of its
   /// subexpressions, returns that subexpression, otherwise `null`.
   Expression getValueSubexpression(Expression e) {
@@ skipping 119 matching lines @@
   /// Returns true if [exp] has no side effects and has a constant value within
   /// any given activation of the enclosing method.
   bool isEffectivelyConstant(Expression exp) {
     // TODO(asgerf): Can be made more aggressive e.g. by checking conditional
     // expressions recursively. Determine if that is a valuable optimization
     // and/or if it is better handled at the CPS level.
     return exp is Constant ||
            exp is This ||
            exp is CreateInvocationMirror ||
            exp is GetStatic && exp.element.isFunction ||
+           exp is GetField && exp.objectIsNotNull && exp.field.isFinal ||
            exp is Interceptor ||
            exp is ApplyBuiltinOperator ||
            exp is VariableUse && constantEnvironment.containsKey(exp.variable);
   }
 
   /// True if [node] is an assignment that can be propagated as a constant.
   bool isEffectivelyConstantAssignment(Expression node) {
     return node is Assign &&
            node.variable.writeCount == 1 &&
            isEffectivelyConstant(node.value);
@@ skipping 800 matching lines @@
   VariableUseVisitor(this.callback);
 
   visitVariableUse(VariableUse use) => callback(use);
 
   visitInnerFunction(FunctionDefinition node) {}
 
   static void visit(Expression node, VariableUseCallback callback) {
     new VariableUseVisitor(callback).visitExpression(node);
   }
 }