Generalize bounds checks.

runtime/vm/flow_graph_range_analysis.h

Index: runtime/vm/flow_graph_range_analysis.h
diff --git a/runtime/vm/flow_graph_range_analysis.h b/runtime/vm/flow_graph_range_analysis.h
index fa07e6037826d31a0915fa74e35026a9d06e51f5..8383adc70429d7898de7351120626b82b7ada7bb 100644
--- a/runtime/vm/flow_graph_range_analysis.h
+++ b/runtime/vm/flow_graph_range_analysis.h
@@ -490,6 +490,10 @@ class RangeUtils : public AllStatic  {
   static bool IsWithin(Range* range, int64_t min, int64_t max) {
     return !Range::IsUnknown(range) && range->IsWithin(min, max);
   }
+
+  static bool IsPositive(Range* range) {
+    return !Range::IsUnknown(range) && range->IsPositive();
+  }
 };
 
 
@@ -510,6 +514,14 @@ class RangeAnalysis : public ValueObject {
   // as a reaching type.
   const Range* GetSmiRange(Value* value) const;
 
+  static bool IsIntegerDefinition(Definition* defn) {
+    return (defn->Type()->ToCid() == kSmiCid) ||
+        defn->IsMintDefinition() ||
+        defn->IsInt32Definition();
+  }
+
+  void AssignRangesRecursively(Definition* defn);
+
  private:
   enum JoinOperator {
     NONE,
@@ -539,7 +551,7 @@ class RangeAnalysis : public ValueObject {
                                        Range* constraint,
                                        Instruction* after);
 
-  void ConstrainValueAfterBranch(Value* use, Definition* defn);
+  bool ConstrainValueAfterBranch(Value* use, Definition* defn);
   void ConstrainValueAfterCheckArrayBound(Value* use, Definition* defn);
 
   // Replace uses of the definition def that are dominated by instruction dom
@@ -553,7 +565,7 @@ class RangeAnalysis : public ValueObject {
   void InferRanges();
 
   // Collect integer definition in the reverse postorder.
-  void CollectDefinitions(BlockEntryInstr* block, BitVector* set);
+  void CollectDefinitions(BitVector* set);
 
   // Recompute ranges of all definitions until they stop changing.
   // Apply the given JoinOperator when computing Phi ranges.
@@ -570,6 +582,8 @@ class RangeAnalysis : public ValueObject {
   // Convert mint operations that stay within int32 range into Int32 operations.
   void NarrowMintToInt32();
 
+  void DiscoverSimpleInductionVariables();
+
   // Remove artificial Constraint instructions and replace them with actual
   // unconstrained definitions.
   void RemoveConstraints();