use simple memcpy() instead of explicit C array copying

Cython/Compiler/ExprNodes.py

@@ -4072,30 +4072,13 @@ class SliceIndexNode(ExprNode):
             else:
                 array_length = '%s - %s' % (self.stop_code(), start_offset)
 
-            def copy_carray(dst, src, item_type, start, count, depth):
-                var_name = Naming.quick_temp_cname
-                if depth:
-                    var_name += str(depth)
-                dst_item, src_item = '{dst}[{i}+{start}] = {src}[{i}]'.format(
-                    src=src,
-                    dst=dst,
-                    start=start,
-                    i=var_name
-                ).split(' = ')
-
-                code.putln('{')
-                code.putln('Py_ssize_t %s;' % var_name)
-                code.put('for ({i}=0; {i} < {count}; {i}++) '.format(
-                    i=var_name,
-                    count=count))
-                if item_type.is_array:
-                    copy_carray(dst_item, src_item, item_type.base_type, 0, item_type.size, depth + 1)
-                else:
-                    code.putln('%s = %s;' % (dst_item, src_item))
-                code.putln('}')
+            code.globalstate.use_utility_code(UtilityCode.load_cached("IncludeStringH", "StringTools.c"))
+            code.putln("memcpy(&(%s[%s]), %s, sizeof(%s[0]) * (%s));" % (
+                self.base.result(), start_offset,
+                rhs.result(),
+                self.base.result(), array_length
+            ))
 
-            copy_carray(self.base.result(), rhs.result(), rhs.type.base_type,
-                        start_offset, array_length, 0)
         self.generate_subexpr_disposal_code(code)
         self.free_subexpr_temps(code)
         rhs.generate_disposal_code(code)