dart2js cps: Rewrite iterator/moveNext/current into JS array accesses.

pkg/compiler/lib/src/cps_ir/cps_fragment.dart

 // Copyright (c) 2015, 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 cps_ir.cps_fragment;
 
 import 'cps_ir_nodes.dart';
 import '../constants/values.dart';
 import '../universe/universe.dart' show Selector;
 import '../types/types.dart' show TypeMask;
@@ skipping 42 matching lines @@
   Expression root;
 
   /// Node whose body is the hole in this CPS fragment. May be null.
   InteriorNode context;
 
   /// Source information to attach to every IR node created in the fragment.
   SourceInformation sourceInformation;
 
   CpsFragment([this.sourceInformation, this.context]);
 
-  /// Asserts that the fragment is closed and returns the IR that was built.
+  bool get isOpen => root == null || context != null;
+  bool get isClosed => !isOpen;
+  bool get isEmpty => root == null;
+
+  /// Asserts that the fragment is non-empty and closed and returns the IR that
+  /// was built.
   Expression get result {
-    assert(context == null);
-    assert(root != null);
+    assert(!isEmpty);
+    assert(isClosed);
     return root;
   }
 
   /// Put the given expression into the fragment's hole.
   ///
   /// Afterwards the fragment is closed and cannot be extended until a new
   /// [context] is set.
   void put(Expression node) {
     assert(root == null || context != null); // We must put the node somewhere.
     if (root == null) {
@@ skipping 15 matching lines @@
   }
 
   /// Bind a constant value.
   Primitive makeConstant(ConstantValue constant) {
     return letPrim(new Constant(constant));
   }
 
   Primitive makeZero() => makeConstant(new IntConstantValue(0));
   Primitive makeOne() => makeConstant(new IntConstantValue(1));
   Primitive makeNull() => makeConstant(new NullConstantValue());
+  Primitive makeTrue() => makeConstant(new TrueConstantValue());
+  Primitive makeFalse() => makeConstant(new FalseConstantValue());
 
   /// Invoke a built-in operator.
   Primitive applyBuiltin(BuiltinOperator op, List<Primitive> args) {
     return letPrim(new ApplyBuiltinOperator(op, args));
   }
 
   /// Inserts an invocation. binds its continuation, and returns the
   /// continuation parameter (i.e. the return value of the invocation).
   ///
   /// The continuation body becomes the new hole.
@@ skipping 144 matching lines @@
   /// in this fragment.
   /// 
   /// [other] is reset to an empty fragment after this.
   void append(CpsFragment other) {
     if (other.root == null) return;
     put(other.root);
     context = other.context;
     other.context = null;
     other.root = null;
   }
+
+  /// Reads the value of the given mutable variable.
+  Primitive getMutable(MutableVariable variable) {
+    return letPrim(new GetMutableVariable(variable));
+  }
+
+  /// Sets the value of the given mutable variable.
+  void setMutable(MutableVariable variable, Primitive value) {
+    SetMutableVariable setter = new SetMutableVariable(variable, value);
+    put(setter);
+    context = setter;
+  }
+
+  /// Declare a new mutable variable.
+  void letMutable(MutableVariable variable, Primitive initialValue) {
+    LetMutable let = new LetMutable(variable, initialValue);
+    put(let);
+    context = let;
+  }
 }