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

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
===================================================================
--- runtime/vm/intermediate_language.cc	(revision 14103)
+++ runtime/vm/intermediate_language.cc	(working copy)
@@ -2187,26 +2187,43 @@
   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();
@@ -2221,6 +2238,14 @@
 }
 
 
+// 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