Replace guarded list length field loads with constants

runtime/vm/intermediate_language.cc

 // Copyright (c) 2013, 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/intermediate_language.h"
 
 #include "vm/bigint_operations.h"
 #include "vm/bit_vector.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
@@ skipping 2501 matching lines @@
     return false;
   }
 
   RangeBoundary max = CanonicalizeBoundary(index_range->max(),
                                            RangeBoundary::OverflowedMaxSmi());
 
   if (max.Overflowed()) {
     return false;
   }
 
+  intptr_t known_array_length = GetGuardedArrayLength();
+  if (max.UpperBound().value() < known_array_length) {

[srdjan, 2013/08/27 15:50:33]

How about "max.UpperBound().value() < GetGuardedArrayLength()"?

+    return true;
+  }
+
   // Try to compare constant boundaries.
   if (max.UpperBound().value() < length.LowerBound().value()) {
     return true;
   }
 
   length = CanonicalizeBoundary(length, RangeBoundary::OverflowedMaxSmi());
   if (length.Overflowed()) {
     return false;
   }
 
@@ skipping 119 matching lines @@
     default:
       UNREACHABLE();
   }
   return kPowRuntimeEntry;
 }
 
 
 #undef __
 
 }  // namespace dart