Do not GVN HLocalGet. If the local is final, the GVN thinks it can loop hoist accesses to it (which…

lib/compiler/implementation/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.
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
@@ skipping 1539 matching lines @@
   bool isJsStatement(HTypeMap types) => true;
   String toString() => "FieldSet $element";
 }
 
 class HLocalGet extends HFieldGet {
   HLocalGet(Element element, HLocalValue local) : super(element, local);
 
   accept(HVisitor visitor) => visitor.visitLocalGet(this);
 
   HLocalValue get local => inputs[0];
+
+  void prepareGvn(HTypeMap types) {
+    // No need to use GVN for a [HLocalGet], it is just a local
+    // access.
+    clearAllSideEffects();
+  }
 }
 
 class HLocalSet extends HFieldSet {
   HLocalSet(Element element, HLocalValue local, HInstruction value)
       : super(element, local, value);
 
   accept(HVisitor visitor) => visitor.visitLocalSet(this);
 
   HLocalValue get local => inputs[0];
 }
@@ skipping 1402 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty());
     return statements.last().end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }