Fix https://code.google.com/p/dart/issues/detail?id=15132, by not doing load elimination on typed a…

sdk/lib/_internal/compiler/implementation/ssa/optimize.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.
 
 part of ssa;
 
 abstract class OptimizationPhase {
   String get name;
   void visitGraph(HGraph graph);
 }
@@ skipping 1631 matching lines @@
     if (existing != null) {
       instruction.block.rewriteWithBetterUser(instruction, existing);
       instruction.block.remove(instruction);
     } else {
       memorySet.registerKeyedValue(receiver, instruction.index, instruction);
     }
   }
 
   void visitIndexAssign(HIndexAssign instruction) {
     HInstruction receiver = instruction.receiver.nonCheck();
+    JavaScriptBackend backend = compiler.backend;
+    // Typed arrays may narrow incoming values.
+    if (backend.couldBeTypedArray(receiver.instructionType)) return;
     memorySet.registerKeyedValueUpdate(
         receiver, instruction.index, instruction.value);
   }
 }
 
 /**
  * Holds values of memory places.
  */
 class MemorySet {
   final Compiler compiler;
@@ skipping 218 matching lines @@
 
     keyedValues.forEach((receiver, values) {
       result.keyedValues[receiver] =
           new Map<HInstruction, HInstruction>.from(values);
     });
 
     result.nonEscapingReceivers.addAll(nonEscapingReceivers);
     return result;
   }
 }