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, 2012 Free Software Foundation, Inc.

dnl  This file is part of the GNU MP Library.

dnl

dnl  The GNU MP Library is free software; you can redistribute it and/or modify

dnl  it under the terms of either:

dnl

dnl    * the GNU Lesser General Public License as published by the Free

dnl      Software Foundation; either version 3 of the License, or (at your

dnl      option) any later version.

dnl

dnl  or

dnl

dnl    * the GNU General Public License as published by the Free Software

dnl      Foundation; either version 2 of the License, or (at your option) any

dnl      later version.

dnl

dnl  or both in parallel, as here.

dnl

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 General Public License

dnl  for more details.

dnl

dnl  You should have received copies of the GNU General Public License and the

dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,

dnl  see https://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

	ret	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)