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| /* 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
|
|
