1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 * Divide a 64-bit unsigned number by a 32-bit unsigned number. 4 * This routine assumes that the top 32 bits of the dividend are 5 * non-zero to start with. 6 * On entry, r3 points to the dividend, which get overwritten with 7 * the 64-bit quotient, and r4 contains the divisor. 8 * On exit, r3 contains the remainder. 9 * 10 * Copyright (C) 2002 Paul Mackerras, IBM Corp. 11 */ 12 #include <asm/ppc_asm.h> 13 #include <asm/processor.h> 14 15 _GLOBAL(__div64_32) 16 lwz r5,0(r3) # get the dividend into r5/r6 17 lwz r6,4(r3) 18 cmplw r5,r4 19 li r7,0 20 li r8,0 21 blt 1f 22 divwu r7,r5,r4 # if dividend.hi >= divisor, 23 mullw r0,r7,r4 # quotient.hi = dividend.hi / divisor 24 subf. r5,r0,r5 # dividend.hi %= divisor 25 beq 3f 26 1: mr r11,r5 # here dividend.hi != 0 27 andis. r0,r5,0xc000 28 bne 2f 29 cntlzw r0,r5 # we are shifting the dividend right 30 li r10,-1 # to make it < 2^32, and shifting 31 srw r10,r10,r0 # the divisor right the same amount, 32 addc r9,r4,r10 # rounding up (so the estimate cannot 33 andc r11,r6,r10 # ever be too large, only too small) 34 andc r9,r9,r10 35 addze r9,r9 36 or r11,r5,r11 37 rotlw r9,r9,r0 38 rotlw r11,r11,r0 39 divwu r11,r11,r9 # then we divide the shifted quantities 40 2: mullw r10,r11,r4 # to get an estimate of the quotient, 41 mulhwu r9,r11,r4 # multiply the estimate by the divisor, 42 subfc r6,r10,r6 # take the product from the divisor, 43 add r8,r8,r11 # and add the estimate to the accumulated 44 subfe. r5,r9,r5 # quotient 45 bne 1b 46 3: cmplw r6,r4 47 blt 4f 48 divwu r0,r6,r4 # perform the remaining 32-bit division 49 mullw r10,r0,r4 # and get the remainder 50 add r8,r8,r0 51 subf r6,r10,r6 52 4: stw r7,0(r3) # return the quotient in *r3 53 stw r8,4(r3) 54 mr r3,r6 # return the remainder in r3 55 blr 56