dart2js: Inhibit code motion of indexing

pkg/compiler/lib/src/ssa/nodes.dart

 // Copyright (c) 2012, 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.
 
 import '../closure.dart';
 import '../common.dart';
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../dart_types.dart';
@@ skipping 2605 matching lines @@
     sideEffects.setDependsOnIndexStore();
     setUseGvn();
   }
 
   String toString() => 'index operator';
   accept(HVisitor visitor) => visitor.visitIndex(this);
 
   HInstruction get receiver => inputs[0];
   HInstruction get index => inputs[1];
 
+  // Implicit dependency on HBoundsCheck or constraints on index.

[Siggi Cherem (dart-lang), 2016/09/07 14:27:01]

maybe add a TODO to make this more precise & refer to the bug?

+  bool get isMovable => false;
+
   HInstruction getDartReceiver(Compiler compiler) => receiver;
   bool onlyThrowsNSM() => true;
   bool canThrow() => receiver.canBeNull();
 
   int typeCode() => HInstruction.INDEX_TYPECODE;
   bool typeEquals(HInstruction other) => other is HIndex;
   bool dataEquals(HIndex other) => true;
 }
 
 /**
@@ skipping 10 matching lines @@
     sideEffects.clearAllDependencies();
     sideEffects.setChangesIndex();
   }
   String toString() => 'index assign operator';
   accept(HVisitor visitor) => visitor.visitIndexAssign(this);
 
   HInstruction get receiver => inputs[0];
   HInstruction get index => inputs[1];
   HInstruction get value => inputs[2];
 
+  // Implicit dependency on HBoundsCheck or constraints on index.
+  bool get isMovable => false;
+
   HInstruction getDartReceiver(Compiler compiler) => receiver;
   bool onlyThrowsNSM() => true;
   bool canThrow() => receiver.canBeNull();
 }
 
 class HIs extends HInstruction {
   /// A check against a raw type: 'o is int', 'o is A'.
   static const int RAW_CHECK = 0;
 
   /// A check against a type with type arguments: 'o is List<int>', 'o is C<T>'.
@@ skipping 763 matching lines @@
 class HDynamicType extends HRuntimeType {
   HDynamicType(DynamicType dartType, TypeMask instructionType)
       : super(const <HInstruction>[], dartType, instructionType);
 
   accept(HVisitor visitor) => visitor.visitDynamicType(this);
 
   int typeCode() => HInstruction.DYNAMIC_TYPE_TYPECODE;
 
   bool typeEquals(HInstruction other) => other is HDynamicType;
 }