Allow bound check elimination to eliminate checks when both array length and index boundaries are e…

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index ccb0b2def5266170f6e7ddce541763bb2937540c..5402e9a23069c7b738c389cfdef8cdd3788ef049 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -1607,7 +1607,7 @@ class RangeBoundary : public ValueObject {
   static RangeBoundary Max(RangeBoundary a, RangeBoundary b);
 
   bool Overflowed() const {
-    return !Smi::IsValid(value());
+    return IsConstant() && !Smi::IsValid(value());
   }
 
   RangeBoundary Clamp() const {
@@ -2367,7 +2367,8 @@ class StaticCallInstr : public TemplateDefinition<0> {
         function_(function),
         argument_names_(argument_names),
         arguments_(arguments),
-        result_cid_(kDynamicCid) {
+        result_cid_(kDynamicCid),
+        is_known_constructor_(false) {
     ASSERT(function.IsZoneHandle());
     ASSERT(argument_names.IsZoneHandle());
   }
@@ -2394,6 +2395,11 @@ class StaticCallInstr : public TemplateDefinition<0> {
   virtual intptr_t ResultCid() const { return result_cid_; }
   void set_result_cid(intptr_t value) { result_cid_ = value; }
 
+  bool is_known_constructor() const { return is_known_constructor_; }
+  void set_is_known_constructor(bool is_known_constructor) {
+    is_known_constructor_ = is_known_constructor;
+  }
+
  private:
   const intptr_t token_pos_;
   const Function& function_;
@@ -2401,6 +2407,10 @@ class StaticCallInstr : public TemplateDefinition<0> {
   ZoneGrowableArray<PushArgumentInstr*>* arguments_;
   intptr_t result_cid_;  // For some library functions we know the result.
 
+  // Some library constructors have known semantics.
+  bool is_known_constructor_;
+
+
   DISALLOW_COPY_AND_ASSIGN(StaticCallInstr);
 };
 
@@ -3956,7 +3966,7 @@ class CheckArrayBoundInstr : public TemplateInstruction<2> {
 
   intptr_t array_type() const { return array_type_; }
 
-  bool IsRedundant();
+  bool IsRedundant(RangeBoundary length);
 
  private:
   intptr_t array_type_;