1dnl ARM mpn_udiv_qrnnd -- divide a two limb dividend and a one limb divisor. 2dnl Return quotient and store remainder through a supplied pointer. 3 4dnl Copyright 2001, 2012 Free Software Foundation, Inc. 5 6dnl This file is part of the GNU MP Library. 7dnl 8dnl The GNU MP Library is free software; you can redistribute it and/or modify 9dnl it under the terms of either: 10dnl 11dnl * the GNU Lesser General Public License as published by the Free 12dnl Software Foundation; either version 3 of the License, or (at your 13dnl option) any later version. 14dnl 15dnl or 16dnl 17dnl * the GNU General Public License as published by the Free Software 18dnl Foundation; either version 2 of the License, or (at your option) any 19dnl later version. 20dnl 21dnl or both in parallel, as here. 22dnl 23dnl The GNU MP Library is distributed in the hope that it will be useful, but 24dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 25dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 26dnl for more details. 27dnl 28dnl You should have received copies of the GNU General Public License and the 29dnl GNU Lesser General Public License along with the GNU MP Library. If not, 30dnl see https://www.gnu.org/licenses/. 31 32include(`../config.m4') 33 34C INPUT PARAMETERS 35define(`rem_ptr',`r0') 36define(`n1',`r1') 37define(`n0',`r2') 38define(`d',`r3') 39 40C divstep -- develop one quotient bit. Dividend in $1$2, divisor in $3. 41C Quotient bit is shifted into $2. 42define(`divstep', 43 `adcs $2, $2, $2 44 adc $1, $1, $1 45 cmp $1, $3 46 subcs $1, $1, $3') 47 48ASM_START() 49PROLOGUE(mpn_udiv_qrnnd) 50 mov r12, #8 C loop counter for both loops below 51 cmp d, #0x80000000 C check divisor msb and clear carry 52 bcs L(_large_divisor) 53 54L(oop): divstep(n1,n0,d) 55 divstep(n1,n0,d) 56 divstep(n1,n0,d) 57 divstep(n1,n0,d) 58 sub r12, r12, #1 59 teq r12, #0 60 bne L(oop) 61 62 str n1, [rem_ptr] C store remainder 63 adc r0, n0, n0 C quotient: add last carry from divstep 64 return lr 65 66L(_large_divisor): 67 stmfd sp!, { r8, lr } 68 69 and r8, n0, #1 C save lsb of dividend 70 mov lr, n1, lsl #31 71 orrs n0, lr, n0, lsr #1 C n0 = lo(n1n0 >> 1) 72 mov n1, n1, lsr #1 C n1 = hi(n1n0 >> 1) 73 74 and lr, d, #1 C save lsb of divisor 75 movs d, d, lsr #1 C d = floor(orig_d / 2) 76 adc d, d, #0 C d = ceil(orig_d / 2) 77 78L(oop2): 79 divstep(n1,n0,d) 80 divstep(n1,n0,d) 81 divstep(n1,n0,d) 82 divstep(n1,n0,d) 83 sub r12, r12, #1 84 teq r12, #0 85 bne L(oop2) 86 87 adc n0, n0, n0 C shift and add last carry from divstep 88 add n1, r8, n1, lsl #1 C shift in omitted dividend lsb 89 tst lr, lr C test saved divisor lsb 90 beq L(_even_divisor) 91 92 rsb d, lr, d, lsl #1 C restore orig d value 93 adds n1, n1, n0 C fix remainder for omitted divisor lsb 94 addcs n0, n0, #1 C adjust quotient if rem. fix carried 95 subcs n1, n1, d C adjust remainder accordingly 96 cmp n1, d C remainder >= divisor? 97 subcs n1, n1, d C adjust remainder 98 addcs n0, n0, #1 C adjust quotient 99 100L(_even_divisor): 101 str n1, [rem_ptr] C store remainder 102 mov r0, n0 C quotient 103 ldmfd sp!, { r8, pc } 104EPILOGUE(mpn_udiv_qrnnd) 105