ld	h, -1
	ld	l, 0
	push	hl
		sra	h
		rr	l
		ld	d, h
		ld	e, l
		call	_FP_Mul
		push	hl			; x^2/4
			sra	h
			rr	l
			ld	d, h
			ld	e, l
			call	_FP_Mul
			sra	h
			rr	l
			inc	h
			ex	(sp), hl	; x^4/128+1 is on stack, HL=x^2/4
			xor	a, a
			ld	d, a
			ld	b, h
			ld	c, l
			add.s	hl, hl \ rla
			add.s	hl, hl \ rla
			add.s	hl, bc \ adc a, d
			ld	b, h
			ld	c, l
			add.s	hl, hl \ rla
			add.s	hl, hl \ rla
			add.s	hl, hl \ rla
			add.s	hl, hl \ rla
			add.s	hl, bc \ adc a, d
			ld	e, l
			ld	l, h
			ld	h, a
			rl	e
			adc.s	hl, hl
			rl	e
			jr	nc, $+3
			inc	hl
		pop	de
		ex	de, hl
		or	a, a
		sbc	hl, de
	pop	de
_FP_Mul:
; Inputs: H.L * D.E
; Output: H.L
; Speed:
;   154 cycles
	ld	a, e
	push	hl
	ld	b, l
	ld	c, d
	ld	l, d
	ld	d, h
	mlt	hl
	mlt	de
	mlt	bc
	add	hl, hl
	add	hl, hl
	add	hl, hl
	add	hl, hl
	add	hl, hl
	add	hl, hl
	add	hl, hl
	add	hl, hl
	add	hl, de
	add	hl, bc
	pop	de
	ld	d, a
	mlt	de
	ld	e, d
	ld	d, 0
	add	hl, de
	ret