Fix compiler warning with shift of negative value.

runtime/vm/flow_graph_range_analysis.cc

 // 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.
 
 #include "vm/flow_graph_range_analysis.h"
 
 #include "vm/bit_vector.h"
 #include "vm/il_printer.h"
 
 namespace dart {
@@ skipping 2330 matching lines @@
 void Range::BitwiseOp(const Range* left_range,
                       const Range* right_range,
                       RangeBoundary* result_min,
                       RangeBoundary* result_max) {
   const int bitsize = Utils::Maximum(BitSize(left_range), BitSize(right_range));
 
   if (left_range->IsPositive() && right_range->IsPositive()) {
     *result_min = RangeBoundary::FromConstant(0);
   } else {
     *result_min =
-        RangeBoundary::FromConstant(static_cast<int64_t>(-1) << bitsize);
+        RangeBoundary::FromConstant(-(static_cast<int64_t>(1) << bitsize));
   }
 
   *result_max =
       RangeBoundary::FromConstant((static_cast<uint64_t>(1) << bitsize) - 1);
 }
 
 
 static bool IsArrayLength(Definition* defn) {
   if (defn == NULL) {
     return false;
@@ skipping 684 matching lines @@
     }
   } while (CanonicalizeMaxBoundary(&max) ||
            CanonicalizeMinBoundary(&canonical_length));
 
   // Failed to prove that maximum is bounded with array length.
   return false;
 }
 
 
 }  // namespace dart