linux/arch/powerpc/lib/div64.S
Thomas Gleixner 2874c5fd28 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>
2019-05-30 11:26:32 -07:00

56 lines
1.7 KiB
ArmAsm

/* 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