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55 lines
1.7 KiB
55 lines
1.7 KiB
/* SPDX-License-Identifier: GPL-2.0-or-later */ |
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/* |
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* Divide a 64-bit unsigned number by a 32-bit unsigned number. |
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* This routine assumes that the top 32 bits of the dividend are |
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* non-zero to start with. |
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* On entry, r3 points to the dividend, which get overwritten with |
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* the 64-bit quotient, and r4 contains the divisor. |
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* On exit, r3 contains the remainder. |
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* |
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* Copyright (C) 2002 Paul Mackerras, IBM Corp. |
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*/ |
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#include <asm/ppc_asm.h> |
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#include <asm/processor.h> |
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_GLOBAL(__div64_32) |
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lwz r5,0(r3) # get the dividend into r5/r6 |
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lwz r6,4(r3) |
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cmplw r5,r4 |
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li r7,0 |
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li r8,0 |
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blt 1f |
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divwu r7,r5,r4 # if dividend.hi >= divisor, |
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mullw r0,r7,r4 # quotient.hi = dividend.hi / divisor |
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subf. r5,r0,r5 # dividend.hi %= divisor |
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beq 3f |
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1: mr r11,r5 # here dividend.hi != 0 |
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andis. r0,r5,0xc000 |
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bne 2f |
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cntlzw r0,r5 # we are shifting the dividend right |
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li r10,-1 # to make it < 2^32, and shifting |
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srw r10,r10,r0 # the divisor right the same amount, |
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addc r9,r4,r10 # rounding up (so the estimate cannot |
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andc r11,r6,r10 # ever be too large, only too small) |
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andc r9,r9,r10 |
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addze r9,r9 |
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or r11,r5,r11 |
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rotlw r9,r9,r0 |
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rotlw r11,r11,r0 |
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divwu r11,r11,r9 # then we divide the shifted quantities |
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2: mullw r10,r11,r4 # to get an estimate of the quotient, |
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mulhwu r9,r11,r4 # multiply the estimate by the divisor, |
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subfc r6,r10,r6 # take the product from the divisor, |
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add r8,r8,r11 # and add the estimate to the accumulated |
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subfe. r5,r9,r5 # quotient |
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bne 1b |
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3: cmplw r6,r4 |
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blt 4f |
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divwu r0,r6,r4 # perform the remaining 32-bit division |
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mullw r10,r0,r4 # and get the remainder |
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add r8,r8,r0 |
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subf r6,r10,r6 |
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4: stw r7,0(r3) # return the quotient in *r3 |
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stw r8,4(r3) |
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mr r3,r6 # return the remainder in r3 |
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blr
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