VM: Fix imprecision in array bounds check elimination.

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 3108 matching lines @@
     ASSERT(!Range::IsUnknown(&range));
     index()->definition()->set_range(range);
     index_range = index()->definition()->range();
   }
 
   // Range of the index is not positive. Check can't be redundant.
   if (Range::ConstantMinSmi(index_range).ConstantValue() < 0) {
     return false;
   }
 
-  RangeBoundary max = CanonicalizeBoundary(
-      RangeBoundary::FromDefinition(index()->definition()),
-      RangeBoundary::PositiveInfinity());
-
-  if (max.OverflowedSmi()) {
-    return false;
-  }
-
+  RangeBoundary max = RangeBoundary::FromDefinition(index()->definition());
 
   RangeBoundary max_upper = max.UpperBound();
   RangeBoundary length_lower = length.LowerBound();
 
   if (max_upper.OverflowedSmi() || length_lower.OverflowedSmi()) {
     return false;
   }
 
   // Try to compare constant boundaries.
   if (max_upper.ConstantValue() < length_lower.ConstantValue()) {
@@ skipping 13 matching lines @@
     }
   } while (CanonicalizeMaxBoundary(&max) ||
            CanonicalizeMinBoundary(&canonical_length));
 
   // Failed to prove that maximum is bounded with array length.
   return false;
 }
 
 
 }  // namespace dart