56 lines
1.7 KiB
ArmAsm
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
|