Use kind to speed up dtype decision

Author: hmaarrfk

pandas/core/indexes/base.py

@@ -591,20 +591,20 @@ def _dtype_to_subclass(cls, dtype: DtypeObj):
 
             return TimedeltaIndex
 
-        elif is_float_dtype(dtype):
+        elif dtype.kind == "f":
             from pandas.core.api import Float64Index
 
             return Float64Index
-        elif is_unsigned_integer_dtype(dtype):
+        elif dtype.kind == "u":
             from pandas.core.api import UInt64Index
 
             return UInt64Index
-        elif is_signed_integer_dtype(dtype):
+        elif dtype.kind == "i":
             from pandas.core.api import Int64Index
 
             return Int64Index
 
-        elif dtype == _dtype_obj:
+        elif dtype.kind == "O":
             # NB: assuming away MultiIndex
             return Index