Add range analysis for left-shift smi operations.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
===================================================================
--- runtime/vm/intermediate_language.cc	(revision 37229)
+++ runtime/vm/intermediate_language.cc	(working copy)
@@ -3112,6 +3112,10 @@
       }
       return;
     }
+    case Token::kSHL: {
+      Range::Shl(left_range, right_range, &min, &max);
+      break;
+    }
     case Token::kBIT_AND:
       if (Range::ConstantMin(right_range).value() >= 0) {
         min = RangeBoundary::FromConstant(0);
@@ -3236,6 +3240,35 @@
 }
 
 
+void Range::Shl(Range* left,
+                Range* right,
+                RangeBoundary* result_min,
+                RangeBoundary* result_max) {
+  RangeBoundary left_max = Range::ConstantMax(left);
+  RangeBoundary left_min = Range::ConstantMin(left);
+  // Ignore negative values of shift count because shift by a negative shift
+  // count does give a result.
+  intptr_t right_max = Range::ConstantMax(right).value() > 0

[Vyacheslav Egorov (Google), 2014/06/12 14:59:00]

Can be written as Max(Range::ConstantMax(right).value(), 0)

[Florian Schneider, 2014/06/12 15:12:42]

Done.

+      ? Range::ConstantMax(right).value() : 0;
+  intptr_t right_min = Range::ConstantMin(right).value() > 0

[Vyacheslav Egorov (Google), 2014/06/12 14:59:00]

ditto

[Florian Schneider, 2014/06/12 15:12:42]

Done.

+      ? Range::ConstantMin(right).value() : 0;
+
+  *result_min = RangeBoundary::Shl(
+      left_min,
+      left_min.value() > 0 ? right_min : right_max,
+      left_min.value() > 0
+          ? RangeBoundary::PositiveInfinity()
+          : RangeBoundary::NegativeInfinity());
+
+  *result_max = RangeBoundary::Shl(
+      left_max,
+      left_max.value() > 0 ? right_max : right_min,
+      left_max.value() > 0
+          ? RangeBoundary::PositiveInfinity()
+          : RangeBoundary::NegativeInfinity());
+}
+
+
 bool CheckArrayBoundInstr::IsFixedLengthArrayType(intptr_t cid) {
   return LoadFieldInstr::IsFixedLengthArrayCid(cid);
 }