VM: Fix issue with optimizing compiler's range analysis.

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 603 matching lines @@
 
 // Given the current range of a phi and a newly computed range check
 // if we can perform narrowing: use newly computed minimum to improve precision
 // of the computed range. We do it only if current minimum was widened and is
 // equal to MinSmi.
 // Newly computed minimum is expected to be greater or equal than old one as
 // we are running after widening phase.
 static RangeBoundary NarrowMin(const Range* range,
                                const Range* new_range,
                                RangeBoundary::RangeSize size) {
-#ifdef DEBUG
   const RangeBoundary min = Range::ConstantMin(range, size);
   const RangeBoundary new_min = Range::ConstantMin(new_range, size);
-  ASSERT(min.ConstantValue() <= new_min.ConstantValue());
-#endif
+  if (min.ConstantValue() > new_min.ConstantValue()) return range->min();
+
   // TODO(vegorov): consider using negative infinity to indicate widened bound.
   return range->min().IsMinimumOrBelow(size) ? new_range->min() : range->min();
 }
 
 
 // Given the current range of a phi and a newly computed range check
 // if we can perform narrowing: use newly computed maximum to improve precision
 // of the computed range. We do it only if current maximum was widened and is
 // equal to MaxSmi.
 // Newly computed maximum is expected to be less or equal than old one as
 // we are running after widening phase.
 static RangeBoundary NarrowMax(const Range* range,
                                const Range* new_range,
                                RangeBoundary::RangeSize size) {
-#ifdef DEBUG
   const RangeBoundary max = Range::ConstantMax(range, size);
   const RangeBoundary new_max = Range::ConstantMax(new_range, size);
-  ASSERT(max.ConstantValue() >= new_max.ConstantValue());
-#endif
+  if (max.ConstantValue() < new_max.ConstantValue()) return range->max();
+
   // TODO(vegorov): consider using positive infinity to indicate widened bound.
   return range->max().IsMaximumOrAbove(size) ? new_range->max() : range->max();
 }
 
 
 char RangeAnalysis::OpPrefix(JoinOperator op) {
   switch (op) {
     case WIDEN: return 'W';
     case NARROW: return 'N';
     case NONE: return 'I';
@@ skipping 2504 matching lines @@
     }
   } while (CanonicalizeMaxBoundary(&max) ||
            CanonicalizeMinBoundary(&canonical_length));
 
   // Failed to prove that maximum is bounded with array length.
   return false;
 }
 
 
 }  // namespace dart