PR tree-optimization/57230
	* tree-ssa-strlen.c (handle_char_store): Add missing integer_zerop
	check.

	* gcc.dg/strlenopt-23.c: New test.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@198813 138bc75d-0d04-0410-961f-82ee72b054a4