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Diffstat (limited to 'arch/powerpc/boot/div64.S')
| -rw-r--r-- | arch/powerpc/boot/div64.S | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/arch/powerpc/boot/div64.S b/arch/powerpc/boot/div64.S new file mode 100644 index 000000000..4354928ed --- /dev/null +++ b/arch/powerpc/boot/div64.S @@ -0,0 +1,107 @@ +/* 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 "ppc_asm.h" + + .globl __div64_32 +__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 + +/* + * Extended precision shifts. + * + * Updated to be valid for shift counts from 0 to 63 inclusive. + * -- Gabriel + * + * R3/R4 has 64 bit value + * R5 has shift count + * result in R3/R4 + * + * ashrdi3: arithmetic right shift (sign propagation) + * lshrdi3: logical right shift + * ashldi3: left shift + */ + .globl __ashrdi3 +__ashrdi3: + subfic r6,r5,32 + srw r4,r4,r5 # LSW = count > 31 ? 0 : LSW >> count + addi r7,r5,32 # could be xori, or addi with -32 + slw r6,r3,r6 # t1 = count > 31 ? 0 : MSW << (32-count) + rlwinm r8,r7,0,32 # t3 = (count < 32) ? 32 : 0 + sraw r7,r3,r7 # t2 = MSW >> (count-32) + or r4,r4,r6 # LSW |= t1 + slw r7,r7,r8 # t2 = (count < 32) ? 0 : t2 + sraw r3,r3,r5 # MSW = MSW >> count + or r4,r4,r7 # LSW |= t2 + blr + + .globl __ashldi3 +__ashldi3: + subfic r6,r5,32 + slw r3,r3,r5 # MSW = count > 31 ? 0 : MSW << count + addi r7,r5,32 # could be xori, or addi with -32 + srw r6,r4,r6 # t1 = count > 31 ? 0 : LSW >> (32-count) + slw r7,r4,r7 # t2 = count < 32 ? 0 : LSW << (count-32) + or r3,r3,r6 # MSW |= t1 + slw r4,r4,r5 # LSW = LSW << count + or r3,r3,r7 # MSW |= t2 + blr + + .globl __lshrdi3 +__lshrdi3: + subfic r6,r5,32 + srw r4,r4,r5 # LSW = count > 31 ? 0 : LSW >> count + addi r7,r5,32 # could be xori, or addi with -32 + slw r6,r3,r6 # t1 = count > 31 ? 0 : MSW << (32-count) + srw r7,r3,r7 # t2 = count < 32 ? 0 : MSW >> (count-32) + or r4,r4,r6 # LSW |= t1 + srw r3,r3,r5 # MSW = MSW >> count + or r4,r4,r7 # LSW |= t2 + blr |