Use range information to omit checks in TRUNCDIV/MOD operations.

runtime/vm/intermediate_language.cc

Index: runtime/vm/intermediate_language.cc
===================================================================
--- runtime/vm/intermediate_language.cc	(revision 30671)
+++ runtime/vm/intermediate_language.cc	(working copy)
@@ -1114,6 +1114,10 @@
       }
       return true;
     }
+    case Token::kMOD: {
+      Range* right_range = this->right()->definition()->range();
+      return (right_range == NULL) || right_range->Overlaps(0, 0);
+    }
     default:
       return overflow_;
   }
@@ -2686,6 +2690,16 @@
 }
 
 
+bool Range::Overlaps(intptr_t min_int, intptr_t max_int) const {
+  const intptr_t this_min = min().LowerBound().value();
+  const intptr_t this_max = max().UpperBound().value();
+  if ((this_min <= min_int) && (min_int <= this_max)) return true;
+  if ((this_min <= max_int) && (max_int <= this_max)) return true;
+  if ((min_int < this_min) && (max_int > this_max)) return true;
+  return false;
+}
+
+
 bool Range::IsUnsatisfiable() const {
   // Constant case: For example [0, -1].
   if (Range::ConstantMin(this).value() > Range::ConstantMax(this).value()) {