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 2169 matching lines @@
   if ((left_range == NULL) || (right_range == NULL)) {
     range_ = new Range(RangeBoundary::MinSmi(), RangeBoundary::MaxSmi());
     return;
   }
 
   RangeBoundary new_min;
   RangeBoundary new_max;
   switch (op_kind()) {
     case Token::kADD:
       new_min =
-        RangeBoundary::Add(Range::ConstantMin(left_range),
-                           Range::ConstantMin(right_range),
-                           RangeBoundary::OverflowedMinSmi());
+          RangeBoundary::Add(Range::ConstantMin(left_range),
+                             Range::ConstantMin(right_range),
+                             RangeBoundary::OverflowedMinSmi());
       new_max =
-        RangeBoundary::Add(Range::ConstantMax(left_range),
-                           Range::ConstantMax(right_range),
-                           RangeBoundary::OverflowedMaxSmi());
+          RangeBoundary::Add(Range::ConstantMax(left_range),
+                             Range::ConstantMax(right_range),
+                             RangeBoundary::OverflowedMaxSmi());
       break;
 
     case Token::kSUB:
       new_min =
-        RangeBoundary::Sub(Range::ConstantMin(left_range),
-                           Range::ConstantMax(right_range),
-                           RangeBoundary::OverflowedMinSmi());
+          RangeBoundary::Sub(Range::ConstantMin(left_range),
+                             Range::ConstantMax(right_range),
+                             RangeBoundary::OverflowedMinSmi());
       new_max =
-        RangeBoundary::Sub(Range::ConstantMax(left_range),
-                           Range::ConstantMin(right_range),
-                           RangeBoundary::OverflowedMaxSmi());
+          RangeBoundary::Sub(Range::ConstantMax(left_range),
+                             Range::ConstantMin(right_range),
+                             RangeBoundary::OverflowedMaxSmi());
       break;
 
+    case Token::kBIT_AND:
+      if (Range::ConstantMin(right_range).value() >= 0) {
+        new_min = RangeBoundary::FromConstant(0);
+        new_max = Range::ConstantMax(right_range);
+        break;
+      }
+      if (Range::ConstantMin(left_range).value() >= 0) {
+        new_min = RangeBoundary::FromConstant(0);
+        new_max = Range::ConstantMax(left_range);
+        break;
+      }
+
+      if (range_ == NULL) {
+        range_ = Range::Unknown();
+      }
+      return;
+
     default:
       if (range_ == NULL) {
         range_ = Range::Unknown();
       }
       return;
   }
 
   ASSERT(!new_min.IsUnknown() && !new_max.IsUnknown());
   set_overflow(new_min.Overflowed() || new_max.Overflowed());
 
   range_ = new Range(new_min.Clamp(), new_max.Clamp());
 }
 
 
+// Inclusive.
+bool Range::IsWithin(intptr_t min_int, intptr_t max_int) const {
+  if (!min().IsConstant() || (min().value() < min_int)) return false;

[Vyacheslav Egorov (Google), 2012/10/26 12:21:42]

I suggest using LowerBound() and UpperBound() here instead of limiting function
to constant boundaries.

[srdjan, 2012/10/30 18:21:13]

Done.

+  if (!max().IsConstant() || (max().value() > max_int)) return false;
+  return true;
+}
+
+
 #undef __
 
 }  // namespace dart