Refine typing of addition, subtraction, multiplication, and division.

src/types.h

Index: src/types.h
diff --git a/src/types.h b/src/types.h
index 8490cbb2ed1ecb74493d8f9d20cc8bc9f7443af9..bd96ddefce08f4935b9ddb4788b761bb259b47d1 100644
--- a/src/types.h
+++ b/src/types.h
@@ -787,6 +787,7 @@ class TypeImpl<Config>::RangeType : public StructuralType {
 
   static RangeHandle New(
       i::Handle<i::Object> min, i::Handle<i::Object> max, Region* region) {
+    DCHECK(IsInteger(min->Number()) && IsInteger(max->Number()));
     DCHECK(min->Number() <= max->Number());
     RangeHandle type = Config::template cast<RangeType>(
         StructuralType::New(StructuralType::kRangeTag, 3, region));
@@ -801,6 +802,18 @@ class TypeImpl<Config>::RangeType : public StructuralType {
     return New(lim.min, lim.max, region);
   }
 
+  // Returns the least integers-only supertype that's not a range.  If there is
+  // no such supertype, it returns Range(-inf, +inf) instead.
+  TypeHandle Weaken(Region* region) {
+    bitset lub = this->BitsetLub();
+    if (BitsetType::Is(SEMANTIC(BitsetType::kOtherNumber), lub)) {
+      return New(
+          Config::factory(region)->NewNumber(-V8_INFINITY),
+          Config::factory(region)->NewNumber(+V8_INFINITY), region);
+    }
+    return BitsetType::New(lub, region);
+  }
+
   static RangeType* cast(TypeImpl* type) {
     DCHECK(type->IsRange());
     return static_cast<RangeType*>(type);
@@ -947,6 +960,10 @@ struct ZoneTypeConfig {
   static inline i::Handle<V> struct_get_value(Struct* structure, int i);
   template<class V> static inline void struct_set_value(
       Struct* structure, int i, i::Handle<V> x);
+
+  static inline Factory* factory(Zone* zone) {
+    return zone->isolate()->factory();
+  }
 };
 
 typedef TypeImpl<ZoneTypeConfig> Type;
@@ -995,6 +1012,10 @@ struct HeapTypeConfig {
   template<class V>
   static inline void struct_set_value(
       i::Handle<Struct> structure, int i, i::Handle<V> x);
+
+  static inline Factory* factory(Isolate* isolate) {
+    return isolate->factory();
+  }
 };
 
 typedef TypeImpl<HeapTypeConfig> HeapType;