/* 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
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