dart2js cps: Hoist loop-invariant branches from loop entry.

pkg/compiler/lib/src/cps_ir/optimizers.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 dart2js.cps_ir.optimizers;
 
 import 'cps_ir_nodes.dart';
 import '../constants/values.dart';
 import '../common/names.dart';
 import '../universe/selector.dart';
 
 export 'type_propagation.dart' show TypePropagator;
 export 'scalar_replacement.dart' show ScalarReplacer;
 export 'redundant_phi.dart' show RedundantPhiEliminator;
 export 'redundant_join.dart' show RedundantJoinEliminator;
 export 'shrinking_reductions.dart' show ShrinkingReducer;
 export 'mutable_ssa.dart' show MutableVariableEliminator;
 export 'insert_refinements.dart' show InsertRefinements;
 export 'update_refinements.dart' show UpdateRefinements;
 export 'redundant_refinement.dart' show RedundantRefinementEliminator;
 export 'optimize_interceptors.dart' show OptimizeInterceptors;
 export 'bounds_checker.dart' show BoundsChecker;
 export 'backward_null_check_remover.dart' show BackwardNullCheckRemover;
 export 'gvn.dart' show GVN;
 export 'inline.dart' show Inliner;
 export 'eagerly_load_statics.dart' show EagerlyLoadStatics;
+export 'loop_invariant_branch.dart' show LoopInvariantBranchMotion;
 export 'parent_visitor.dart' show ParentVisitor;
 
 /// An optimization pass over the CPS IR.
 abstract class Pass {
   /// Applies optimizations to root, rewriting it in the process.
   void rewrite(FunctionDefinition root);
 
   String get passName;
 }
 
@@ skipping 15 matching lines @@
 /// For non-strict, this is the opposite of [isFalsyConstant].
 bool isTruthyConstant(ConstantValue value, {bool strict: false}) {
   return strict ? value.isTrue : !isFalsyConstant(value);
 }
 
 /// Selectors that do not throw when invoked on the null value.
 final List<Selector> selectorsOnNull = <Selector>[
     Selectors.equals, Selectors.hashCode_, Selectors.runtimeType_,
     Selectors.toString_, Selectors.toStringGetter,
     Selectors.noSuchMethodGetter];