linux/arch/powerpc/lib/div64.S

/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Divide a 64-bit unsigned number by a 32-bit unsigned number.
 * This routine assumes that the top 32 bits of the dividend are
 * non-zero to start with.
 * On entry, r3 points to the dividend, which get overwritten with
 * the 64-bit quotient, and r4 contains the divisor.
 * On exit, r3 contains the remainder.
 *
 * Copyright (C) 2002 Paul Mackerras, IBM Corp.
 */
#include <asm/ppc_asm.h>
#include <asm/processor.h>

_GLOBAL(__div64_32)
	lwz	r5,0(r3)	# get the dividend into r5/r6
	lwz	r6,4(r3)
	cmplw	r5,r4
	li	r7,0
	li	r8,0
	blt	1f
	divwu	r7,r5,r4	# if dividend.hi >= divisor,
	mullw	r0,r7,r4	# quotient.hi = dividend.hi / divisor
	subf.	r5,r0,r5	# dividend.hi %= divisor
	beq	3f
1:	mr	r11,r5		# here dividend.hi != 0
	andis.	r0,r5,0xc000
	bne	2f
	cntlzw	r0,r5		# we are shifting the dividend right
	li	r10,-1		# to make it < 2^32, and shifting
	srw	r10,r10,r0	# the divisor right the same amount,
	addc	r9,r4,r10	# rounding up (so the estimate cannot
	andc	r11,r6,r10	# ever be too large, only too small)
	andc	r9,r9,r10
	addze	r9,r9
	or	r11,r5,r11
	rotlw	r9,r9,r0
	rotlw	r11,r11,r0
	divwu	r11,r11,r9	# then we divide the shifted quantities
2:	mullw	r10,r11,r4	# to get an estimate of the quotient,
	mulhwu	r9,r11,r4	# multiply the estimate by the divisor,
	subfc	r6,r10,r6	# take the product from the divisor,
	add	r8,r8,r11	# and add the estimate to the accumulated
	subfe.	r5,r9,r5	# quotient
	bne	1b
3:	cmplw	r6,r4
	blt	4f
	divwu	r0,r6,r4	# perform the remaining 32-bit division
	mullw	r10,r0,r4	# and get the remainder
	add	r8,r8,r0
	subf	r6,r10,r6
4:	stw	r7,0(r3)	# return the quotient in *r3
	stw	r8,4(r3)
	mr	r3,r6		# return the remainder in r3
	blr
treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation either version 2 of the license or at your option any later version extracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-later has been chosen to replace the boilerplate/reference in 3029 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 2019-05-27 06:55:01 +00:00			`/* SPDX-License-Identifier: GPL-2.0-or-later */`
powerpc: Merge enough to start building in arch/powerpc. This creates the directory structure under arch/powerpc and a bunch of Kconfig files. It does a first-cut merge of arch/powerpc/mm, arch/powerpc/lib and arch/powerpc/platforms/powermac. This is enough to build a 32-bit powermac kernel with ARCH=powerpc. For now we are getting some unmerged files from arch/ppc/kernel and arch/ppc/syslib, or arch/ppc64/kernel. This makes some minor changes to files in those directories and files outside arch/powerpc. The boot directory is still not merged. That's going to be interesting. Signed-off-by: Paul Mackerras <paulus@samba.org> 2005-09-26 06:04:21 +00:00			`/*`
			`* Divide a 64-bit unsigned number by a 32-bit unsigned number.`
			`* This routine assumes that the top 32 bits of the dividend are`
			`* non-zero to start with.`
			`* On entry, r3 points to the dividend, which get overwritten with`
			`* the 64-bit quotient, and r4 contains the divisor.`
			`* On exit, r3 contains the remainder.`
			`*`
			`* Copyright (C) 2002 Paul Mackerras, IBM Corp.`
			`*/`
			`#include <asm/ppc_asm.h>`
			`#include <asm/processor.h>`

			`_GLOBAL(__div64_32)`
			`lwz r5,0(r3) # get the dividend into r5/r6`
			`lwz r6,4(r3)`
			`cmplw r5,r4`
			`li r7,0`
			`li r8,0`
			`blt 1f`
			`divwu r7,r5,r4 # if dividend.hi >= divisor,`
			`mullw r0,r7,r4 # quotient.hi = dividend.hi / divisor`
			`subf. r5,r0,r5 # dividend.hi %= divisor`
			`beq 3f`
			`1: mr r11,r5 # here dividend.hi != 0`
			`andis. r0,r5,0xc000`
			`bne 2f`
			`cntlzw r0,r5 # we are shifting the dividend right`
			`li r10,-1 # to make it < 2^32, and shifting`
			`srw r10,r10,r0 # the divisor right the same amount,`
powerpc: Fix a corner case in __div64_32 The code was incorrectly doing a division by 0 in the case where the denominator was 0x100000000 and the divisor was 0xffffffff. Thanks to Fred Liu of Motorola for pointing this out. Signed-off-by: Paul Mackerras <paulus@samba.org> 2005-10-19 23:37:02 +00:00			`addc r9,r4,r10 # rounding up (so the estimate cannot`
powerpc: Merge enough to start building in arch/powerpc. This creates the directory structure under arch/powerpc and a bunch of Kconfig files. It does a first-cut merge of arch/powerpc/mm, arch/powerpc/lib and arch/powerpc/platforms/powermac. This is enough to build a 32-bit powermac kernel with ARCH=powerpc. For now we are getting some unmerged files from arch/ppc/kernel and arch/ppc/syslib, or arch/ppc64/kernel. This makes some minor changes to files in those directories and files outside arch/powerpc. The boot directory is still not merged. That's going to be interesting. Signed-off-by: Paul Mackerras <paulus@samba.org> 2005-09-26 06:04:21 +00:00			`andc r11,r6,r10 # ever be too large, only too small)`
			`andc r9,r9,r10`
powerpc: Fix a corner case in __div64_32 The code was incorrectly doing a division by 0 in the case where the denominator was 0x100000000 and the divisor was 0xffffffff. Thanks to Fred Liu of Motorola for pointing this out. Signed-off-by: Paul Mackerras <paulus@samba.org> 2005-10-19 23:37:02 +00:00			`addze r9,r9`
powerpc: Merge enough to start building in arch/powerpc. This creates the directory structure under arch/powerpc and a bunch of Kconfig files. It does a first-cut merge of arch/powerpc/mm, arch/powerpc/lib and arch/powerpc/platforms/powermac. This is enough to build a 32-bit powermac kernel with ARCH=powerpc. For now we are getting some unmerged files from arch/ppc/kernel and arch/ppc/syslib, or arch/ppc64/kernel. This makes some minor changes to files in those directories and files outside arch/powerpc. The boot directory is still not merged. That's going to be interesting. Signed-off-by: Paul Mackerras <paulus@samba.org> 2005-09-26 06:04:21 +00:00			`or r11,r5,r11`
			`rotlw r9,r9,r0`
			`rotlw r11,r11,r0`
			`divwu r11,r11,r9 # then we divide the shifted quantities`
			`2: mullw r10,r11,r4 # to get an estimate of the quotient,`
			`mulhwu r9,r11,r4 # multiply the estimate by the divisor,`
			`subfc r6,r10,r6 # take the product from the divisor,`
			`add r8,r8,r11 # and add the estimate to the accumulated`
			`subfe. r5,r9,r5 # quotient`
			`bne 1b`
			`3: cmplw r6,r4`
			`blt 4f`
			`divwu r0,r6,r4 # perform the remaining 32-bit division`
			`mullw r10,r0,r4 # and get the remainder`
			`add r8,r8,r0`
			`subf r6,r10,r6`
			`4: stw r7,0(r3) # return the quotient in *r3`
			`stw r8,4(r3)`
			`mr r3,r6 # return the remainder in r3`
			`blr`