PR middle-end/23484
	* builtins.c (fold_builtin_memory_chk, fold_builtin_stxcpy_chk,
	fold_builtin_strncpy_chk, fold_builtin_snprintf_chk): If len is
	not constant, but maxlen is, don't set len to maxlen, rather
	set maxlen to len if len is a constant.

	* gcc.c-torture/execute/builtins/pr23484-chk.c: New test.
	* gcc.c-torture/execute/builtins/pr23484-chk-lib.c: New file.

From-SVN: r103594