We cannot use the value stored in a typed array for load elimination, but we should still kill save…

sdk/lib/_internal/compiler/implementation/ssa/optimize.dart

Index: sdk/lib/_internal/compiler/implementation/ssa/optimize.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/ssa/optimize.dart	(revision 30353)
+++ sdk/lib/_internal/compiler/implementation/ssa/optimize.dart	(working copy)
@@ -1649,9 +1649,6 @@
 
   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);
   }
@@ -1832,6 +1829,10 @@
       }
     });
 
+    JavaScriptBackend backend = compiler.backend;
+    // Typed arrays may narrow incoming values.
+    if (backend.couldBeTypedArray(receiver.instructionType)) return;
+
     Map<HInstruction, HInstruction> map = keyedValues.putIfAbsent(
         receiver, () => <HInstruction, HInstruction> {});
     map[index] = value;