dnl  ARM mpn_udiv_qrnnd -- divide a two limb dividend and a one limb divisor.
dnl  Return quotient and store remainder through a supplied pointer.

dnl  Copyright 2001 Free Software Foundation, Inc.

dnl  This file is part of the GNU MP Library.

dnl  The GNU MP Library is free software; you can redistribute it and/or modify
dnl  it under the terms of the GNU Lesser General Public License as published
dnl  by the Free Software Foundation; either version 3 of the License, or (at
dnl  your option) any later version.

dnl  The GNU MP Library is distributed in the hope that it will be useful, but
dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
dnl  License for more details.

dnl  You should have received a copy of the GNU Lesser General Public License
dnl  along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.

include(`../config.m4')

C INPUT PARAMETERS
define(`rem_ptr',`r0')
define(`n1',`r1')
define(`n0',`r2')
define(`d',`r3')

C divstep -- develop one quotient bit.  Dividend in $1$2, divisor in $3.
C Quotient bit is shifted into $2.
define(`divstep',
       `adcs	$2, $2, $2
	adc	$1, $1, $1
	cmp	$1, $3
	subcs	$1, $1, $3')

ASM_START()
PROLOGUE(mpn_udiv_qrnnd)
	mov	r12, #8			C loop counter for both loops below
	cmp	d, #0x80000000		C check divisor msb and clear carry
	bcs	L(_large_divisor)

L(oop):	divstep(n1,n0,d)
	divstep(n1,n0,d)
	divstep(n1,n0,d)
	divstep(n1,n0,d)
	sub	r12, r12, #1
	teq	r12, #0
	bne	L(oop)

	str	n1, [ rem_ptr ]		C store remainder
	adc	r0, n0, n0		C quotient: add last carry from divstep
	mov	pc, lr

L(_large_divisor):
	stmfd	sp!, { r8, lr }

	and	r8, n0, #1		C save lsb of dividend
	mov	lr, n1, lsl #31
	orrs	n0, lr, n0, lsr #1	C n0 = lo(n1n0 >> 1)
	mov	n1, n1, lsr #1		C n1 = hi(n1n0 >> 1)

	and	lr, d, #1		C save lsb of divisor
	movs	d, d, lsr #1		C d = floor(orig_d / 2)
	adc	d, d, #0		C d = ceil(orig_d / 2)

L(oop2):
	divstep(n1,n0,d)
	divstep(n1,n0,d)
	divstep(n1,n0,d)
	divstep(n1,n0,d)
	sub	r12, r12, #1
	teq	r12, #0
	bne	L(oop2)

	adc	n0, n0, n0		C shift and add last carry from divstep
	add	n1, r8, n1, lsl #1	C shift in omitted dividend lsb
	tst	lr, lr			C test saved divisor lsb
	beq	L(_even_divisor)

	rsb	d, lr, d, lsl #1	C restore orig d value
	adds	n1, n1, n0		C fix remainder for omitted divisor lsb
	addcs	n0, n0, #1		C adjust quotient if rem. fix carried
	subcs	n1, n1, d		C adjust remainder accordingly
	cmp	n1, d			C remainder >= divisor?
	subcs	n1, n1, d		C adjust remainder
	addcs	n0, n0, #1		C adjust quotient

L(_even_divisor):
	str	n1, [ rem_ptr ]		C store remainder
	mov	r0, n0			C quotient
	ldmfd	sp!, { r8, pc }
EPILOGUE(mpn_udiv_qrnnd)