qbe/test/tail.ssa

function w $factorial (w %n, w %acc) {
@start
	jnz %n, @z, @nz
@z
	ret %acc
@nz
	%n_next =w sub %n, 1
	%acc_next =w mul %n, %acc
	tail $factorial (w %n_next, w %acc)
}