1dnl AMD K6 mpn_mod_34lsub1 -- mpn remainder modulo 2**24-1. 2 3dnl Copyright 2000-2002 Free Software Foundation, Inc. 4 5dnl This file is part of the GNU MP Library. 6dnl 7dnl The GNU MP Library is free software; you can redistribute it and/or modify 8dnl it under the terms of either: 9dnl 10dnl * the GNU Lesser General Public License as published by the Free 11dnl Software Foundation; either version 3 of the License, or (at your 12dnl option) any later version. 13dnl 14dnl or 15dnl 16dnl * the GNU General Public License as published by the Free Software 17dnl Foundation; either version 2 of the License, or (at your option) any 18dnl later version. 19dnl 20dnl or both in parallel, as here. 21dnl 22dnl The GNU MP Library is distributed in the hope that it will be useful, but 23dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 24dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 25dnl for more details. 26dnl 27dnl You should have received copies of the GNU General Public License and the 28dnl GNU Lesser General Public License along with the GNU MP Library. If not, 29dnl see https://www.gnu.org/licenses/. 30 31include(`../config.m4') 32 33 34C K6: 2.66 cycles/limb 35 36 37C mp_limb_t mpn_mod_34lsub1 (mp_srcptr src, mp_size_t size) 38C 39C An attempt was made to use a loop like 40C 41C L(top): 42C adcl (%edx), %eax 43C adcl 4(%edx), %ebx 44C adcl 8(%edx), %esi 45C leal 12(%edx), %edx 46C loop L(top) 47C 48C with %ecx starting from floor(size/3), but it still measured 2.66 c/l. 49C The form used instead can save about 6 cycles by not dividing by 3. 50C 51C In the code used, putting the "leal"s at the top of the loop is necessary 52C for the claimed speed, anywhere else costs an extra cycle per loop. 53C Perhaps a tight loop like this needs short decode instructions at the 54C branch target, which would explain the leal/loop form above taking 8 55C cycles instead of 7 too. 56 57defframe(PARAM_SIZE, 8) 58defframe(PARAM_SRC, 4) 59 60dnl re-use parameter space 61define(SAVE_EBX, `PARAM_SIZE') 62define(SAVE_ESI, `PARAM_SRC') 63 64 TEXT 65 ALIGN(16) 66PROLOGUE(mpn_mod_34lsub1) 67deflit(`FRAME',0) 68 69 movl PARAM_SIZE, %eax 70 movl PARAM_SRC, %edx 71 72 subl $2, %eax 73 ja L(three_or_more) 74 75Zdisp( movl, 0,(%edx), %eax) C avoid code cache line boundary 76 jne L(one) 77 78 movl %eax, %ecx 79 movl 4(%edx), %edx 80 81 shrl $24, %eax C src[0] high 82 andl $0x00FFFFFF, %ecx C src[0] low 83 84 addl %ecx, %eax 85 movl %edx, %ecx 86 87 shll $8, %edx 88 andl $0x00FFFF00, %edx C src[1] high 89 90 shrl $16, %ecx C src[1] low 91 addl %ecx, %eax 92 93 addl %edx, %eax 94 95L(one): 96 ret 97 98 99L(three_or_more): 100 C eax size-2 101 C ebx 102 C ecx 103 C edx src 104 105 movl %ebx, SAVE_EBX 106 xorl %ebx, %ebx 107 108 movl %esi, SAVE_ESI 109 pushl %edi FRAME_pushl() 110 111 xorl %esi, %esi 112 xorl %edi, %edi C and clear carry flag 113 114L(top): 115 C eax counter, limbs 116 C ebx acc 0mod3 117 C ecx 118 C edx src, incrementing 119 C esi acc 1mod3 120 C edi acc 2mod3 121 C ebp 122 123 leal -2(%eax), %eax 124 leal 12(%edx), %edx 125 126 adcl -12(%edx), %ebx 127 adcl -8(%edx), %esi 128 adcl -4(%edx), %edi 129 130 decl %eax 131 jg L(top) 132 133 134 C ecx is -3, -2 or -1 representing 0, 1 or 2 more limbs, respectively 135 136 movb $0, %cl 137 incl %eax 138 139 js L(combine) C 0 more 140 141Zdisp( adcl, 0,(%edx), %ebx) C avoid code cache line crossings 142 143 movb $8, %cl 144 decl %eax 145 146 js L(combine) C 1 more 147 148 adcl 4(%edx), %esi 149 150 movb $16, %cl 151 152 153L(combine): 154 sbbl %edx, %edx 155 156 shll %cl, %edx C carry 157 movl %ebx, %eax C 0mod3 158 159 shrl $24, %eax C 0mod3 high 160 andl $0x00FFFFFF, %ebx C 0mod3 low 161 162 subl %edx, %eax C apply carry 163 movl %esi, %ecx C 1mod3 164 165 shrl $16, %esi C 1mod3 high 166 addl %ebx, %eax C apply 0mod3 low 167 168 andl $0x0000FFFF, %ecx 169 addl %esi, %eax C apply 1mod3 high 170 171 shll $8, %ecx C 1mod3 low 172 movl %edi, %edx C 2mod3 173 174 shrl $8, %edx C 2mod3 high 175 addl %ecx, %eax C apply 1mod3 low 176 177 addl %edx, %eax C apply 2mod3 high 178 andl $0x000000FF, %edi 179 180 shll $16, %edi C 2mod3 low 181 movl SAVE_EBX, %ebx 182 183 addl %edi, %eax C apply 2mod3 low 184 movl SAVE_ESI, %esi 185 186 popl %edi 187 188 ret 189 190EPILOGUE() 191