Add range to kBIT_AND with positive constants. Use that range to eliminate compares in left shifts.

runtime/vm/intermediate_language.cc

 // Copyright (c) 2012, 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/bit_vector.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph_allocator.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 2495 matching lines @@
       }
 
       if (!SymbolicSub(left_max, right_range->min(), &max)) {
         max =
           RangeBoundary::Sub(Range::ConstantMax(left_range),
                              Range::ConstantMin(right_range),
                              RangeBoundary::OverflowedMaxSmi());
       }
       break;
 
+    case Token::kBIT_AND:
+      if (Range::ConstantMin(right_range).value() >= 0) {
+        min = RangeBoundary::FromConstant(0);
+        max = Range::ConstantMax(right_range);
+        break;
+      }
+      if (Range::ConstantMin(left_range).value() >= 0) {
+        min = RangeBoundary::FromConstant(0);
+        max = Range::ConstantMax(left_range);
+        break;
+      }
+
+      if (range_ == NULL) {
+        range_ = Range::Unknown();
+      }
+      return;
+
     default:
       if (range_ == NULL) {
         range_ = Range::Unknown();
       }
       return;
   }
 
   ASSERT(!min.IsUnknown() && !max.IsUnknown());
   set_overflow(min.LowerBound().Overflowed() || max.UpperBound().Overflowed());
 
   if (min.IsConstant()) min.Clamp();
   if (max.IsConstant()) max.Clamp();
 
   range_ = new Range(min, max);
 }
 
 
+// Inclusive.
+bool Range::IsWithin(intptr_t min_int, intptr_t max_int) const {
+  if (min().LowerBound().value() < min_int) return false;
+  if (max().UpperBound().value() > max_int) return false;
+  return true;
+}
+
+
 bool CheckArrayBoundInstr::IsRedundant(RangeBoundary length) {
   // Check that array has an immutable length.
   if ((array_type() != kArrayCid) && (array_type() != kImmutableArrayCid)) {
     return false;
   }
 
   Range* index_range = index()->definition()->range();
 
   // Range of the index is unknown can't decide if the check is redundant.
   if (index_range == NULL) return false;
@@ skipping 20 matching lines @@
   } while (CanonicalizeMaxBoundary(&max) || CanonicalizeMinBoundary(&length));
 
   // Failed to prove that maximum is bounded with array length.
   return false;
 }
 
 
 #undef __
 
 }  // namespace dart