move int8/16/32 type conversions to index_class_helper.pxi.in

Author: topper-123

pandas/_libs/index.pyx

@@ -266,8 +266,6 @@ cdef class IndexEngine:
         if not self.is_mapping_populated:
 
             values = self._get_index_values()
-            if values.dtype in {'int8', 'int16', 'int32'}:
-                values = algos.ensure_int64(values)
             self.mapping = self._make_hash_table(len(values))
             self._call_map_locations(values)
 

pandas/_libs/index_class_helper.pxi.in

@@ -46,6 +46,13 @@ cdef class {{name}}Engine(IndexEngine):
         return _hash.{{name}}HashTable(n)
         {{endif}}
 
+    {{if name in {'Int8', 'Int16', 'Int32'} }}
+    cpdef _call_map_locations(self, values):
+        # we don't have Int8/16/32HashTable, so use Int64HashTable
+        # and need to pass int64 values to it
+        self.mapping.map_locations(algos.ensure_int64(values))
+    {{endif}}
+
     {{if name != 'Float64' and name != 'Object'}}
     cdef _check_type(self, object val):
         hash(val)