PR middle-end/81657
	* expr.h (enum block_op_methods): Add BLOCK_OP_NO_LIBCALL_RET.
	* expr.c (emit_block_move_hints): Handle BLOCK_OP_NO_LIBCALL_RET.
	* builtins.c (expand_builtin_memory_copy_args): Use
	BLOCK_OP_NO_LIBCALL_RET method for mempcpy with non-ignored target,
	handle dest_addr == pc_rtx.

	* gcc.dg/string-opt-1.c: Remove bogus comment.  Expect a mempcpy
	call.

Co-Authored-By: Jakub Jelinek <jakub@redhat.com>

From-SVN: r259366