Fix bug in 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 1804 matching lines @@
     // expand the minimum.
     range->set_min(other.min());
   } else {
     // Can't compare ranges as whole. Join minimum and maximum separately.
     *range = Range(RangeBoundary::JoinMin(range->min(), other.min(), size),
                    RangeBoundary::JoinMax(range->max(), other.max(), size));
   }
 }
 
 
+// A definition dominates a phi if its block dominates the phi's block
+// and the two blocks are different.
+static bool DominatesPhi(BlockEntryInstr* a, BlockEntryInstr* phi_block) {
+  return a->Dominates(phi_block) && (a != phi_block);

[Vyacheslav Egorov (Google), 2014/09/10 18:33:41]

You reoder (a != phi_block) && ...

+}
+
+
 // When assigning range to a phi we must take care to avoid self-reference
 // cycles when phi's range depends on the phi itself.
 // To prevent such cases we impose additional restriction on symbols that
 // can be used as boundaries for phi's range: they must dominate
 // phi's definition.
 static RangeBoundary EnsureAcyclicSymbol(BlockEntryInstr* phi_block,
                                          const RangeBoundary& a,
                                          const RangeBoundary& limit) {
-  if (!a.IsSymbol() || a.symbol()->GetBlock()->Dominates(phi_block)) {
+  if (!a.IsSymbol() || DominatesPhi(a.symbol()->GetBlock(), phi_block)) {
     return a;
   }
 
   // Symbol does not dominate phi. Try unwrapping constraint and check again.
   Definition* unwrapped = UnwrapConstraint(a.symbol());
   if ((unwrapped != a.symbol()) &&
-      unwrapped->GetBlock()->Dominates(phi_block)) {
+      DominatesPhi(unwrapped->GetBlock(), phi_block)) {
     return RangeBoundary::FromDefinition(unwrapped, a.offset());
   }
 
   return limit;
 }
 
 
 void PhiInstr::InferRange(RangeAnalysis* analysis, Range* range) {
   ASSERT((Type()->ToCid() == kSmiCid) || (representation() == kUnboxedInt32));
   const RangeBoundary::RangeSize size = (Type()->ToCid() == kSmiCid) ?
@@ skipping 367 matching lines @@
     }
   } while (CanonicalizeMaxBoundary(&max) ||
            CanonicalizeMinBoundary(&canonical_length));
 
   // Failed to prove that maximum is bounded with array length.
   return false;
 }
 
 
 }  // namespace dart