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 | |