More precise type lub for numbers

src/types.cc

Index: src/types.cc
diff --git a/src/types.cc b/src/types.cc
index 70ddccd6a74eeebf9f3ee0c3b3ceb941f2c80ca8..0086313eee83970539e77644ad930ab5b6eaef1c 100644
--- a/src/types.cc
+++ b/src/types.cc
@@ -128,11 +128,18 @@ int Type::LubBitset() {
       Handle<v8::internal::Object> value = this->as_constant();
       if (value->IsSmi()) return kSmi;
       map = HeapObject::cast(*value)->map();
+      if (map->instance_type() == HEAP_NUMBER_TYPE) {
+        int32_t i;
+        uint32_t u;
+        if (value->ToInt32(&i)) return Smi::IsValid(i) ? kSmi : kOtherSigned32;
+        if (value->ToUint32(&u)) return kUnsigned32;
+        return kDouble;
+      }
       if (map->instance_type() == ODDBALL_TYPE) {
         if (value->IsUndefined()) return kUndefined;
         if (value->IsNull()) return kNull;
         if (value->IsTrue() || value->IsFalse()) return kBoolean;
-        if (value->IsTheHole()) return kAny;
+        if (value->IsTheHole()) return kAny;  // TODO(rossberg): kNone?
       }
     }
     switch (map->instance_type()) {
@@ -162,9 +169,8 @@ int Type::LubBitset() {
       case SYMBOL_TYPE:
         return kSymbol;
       case ODDBALL_TYPE:
-        return kOddball;
       case HEAP_NUMBER_TYPE:
-        return kDouble;
+        UNREACHABLE();
       case JS_VALUE_TYPE:
       case JS_DATE_TYPE:
       case JS_OBJECT_TYPE: