1/* 2 * COPYRIGHT: See COPYING in the top level directory 3 * PROJECT: ReactOS kernel 4 * PURPOSE: Run-Time Library 5 * FILE: lib/sdk/crt/math/i386/aulldiv_asm.s 6 * PROGRAMER: Alex Ionescu (alex@relsoft.net) 7 * 8 * Copyright (C) 2002 Michael Ringgaard. 9 * All rights reserved. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. Neither the name of the project nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 24 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES// LOSS OF USE, DATA, OR PROFITS// OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 */ 36 37#include <asm.inc> 38 39PUBLIC __aulldiv 40 41/* FUNCTIONS ***************************************************************/ 42.code 43 44// 45// ulldiv - unsigned long divide 46// 47// Purpose: 48// Does a unsigned long divide of the arguments. Arguments are 49// not changed. 50// 51// Entry: 52// Arguments are passed on the stack: 53// 1st pushed: divisor (QWORD) 54// 2nd pushed: dividend (QWORD) 55// 56// Exit: 57// EDX:EAX contains the quotient (dividend/divisor) 58// NOTE: this routine removes the parameters from the stack. 59// 60// Uses: 61// ECX 62// 63 64__aulldiv: 65 66 push ebx 67 push esi 68 69// Set up the local stack and save the index registers. When this is done 70// the stack frame will look as follows (assuming that the expression a/b will 71// generate a call to uldiv(a, b)): 72// 73// ----------------- 74// | | 75// |---------------| 76// | | 77// |--divisor (b)--| 78// | | 79// |---------------| 80// | | 81// |--dividend (a)-| 82// | | 83// |---------------| 84// | return addr** | 85// |---------------| 86// | EBX | 87// |---------------| 88// ESP---->| ESI | 89// ----------------- 90// 91 92#undef DVNDLO 93#undef DVNDHI 94#undef DVSRLO 95#undef DVSRHI 96#define DVNDLO [esp + 12] // stack address of dividend (a) 97#define DVNDHI [esp + 16] // stack address of dividend (a) 98#define DVSRLO [esp + 20] // stack address of divisor (b) 99#define DVSRHI [esp + 24] // stack address of divisor (b) 100 101// 102// Now do the divide. First look to see if the divisor is less than 4194304K. 103// If so, then we can use a simple algorithm with word divides, otherwise 104// things get a little more complex. 105// 106 107 mov eax,DVSRHI // check to see if divisor < 4194304K 108 or eax,eax 109 jnz short .L1 // nope, gotta do this the hard way 110 mov ecx,DVSRLO // load divisor 111 mov eax,DVNDHI // load high word of dividend 112 xor edx,edx 113 div ecx // get high order bits of quotient 114 mov ebx,eax // save high bits of quotient 115 mov eax,DVNDLO // edx:eax <- remainder:lo word of dividend 116 div ecx // get low order bits of quotient 117 mov edx,ebx // edx:eax <- quotient hi:quotient lo 118 jmp short .L2 // restore stack and return 119 120// 121// Here we do it the hard way. Remember, eax contains DVSRHI 122// 123 124.L1: 125 mov ecx,eax // ecx:ebx <- divisor 126 mov ebx,DVSRLO 127 mov edx,DVNDHI // edx:eax <- dividend 128 mov eax,DVNDLO 129.L3: 130 shr ecx,1 // shift divisor right one bit// hi bit <- 0 131 rcr ebx,1 132 shr edx,1 // shift dividend right one bit// hi bit <- 0 133 rcr eax,1 134 or ecx,ecx 135 jnz short .L3 // loop until divisor < 4194304K 136 div ebx // now divide, ignore remainder 137 mov esi,eax // save quotient 138 139// 140// We may be off by one, so to check, we will multiply the quotient 141// by the divisor and check the result against the orignal dividend 142// Note that we must also check for overflow, which can occur if the 143// dividend is close to 2**64 and the quotient is off by 1. 144// 145 146 mul dword ptr DVSRHI // QUOT * DVSRHI 147 mov ecx,eax 148 mov eax,DVSRLO 149 mul esi // QUOT * DVSRLO 150 add edx,ecx // EDX:EAX = QUOT * DVSR 151 jc short .L4 // carry means Quotient is off by 1 152 153// 154// do long compare here between original dividend and the result of the 155// multiply in edx:eax. If original is larger or equal, we are ok, otherwise 156// subtract one (1) from the quotient. 157// 158 159 cmp edx,DVNDHI // compare hi words of result and original 160 ja short .L4 // if result > original, do subtract 161 jb short .L5 // if result < original, we are ok 162 cmp eax,DVNDLO // hi words are equal, compare lo words 163 jbe short .L5 // if less or equal we are ok, else subtract 164.L4: 165 dec esi // subtract 1 from quotient 166.L5: 167 xor edx,edx // edx:eax <- quotient 168 mov eax,esi 169 170// 171// Just the cleanup left to do. edx:eax contains the quotient. 172// Restore the saved registers and return. 173// 174 175.L2: 176 177 pop esi 178 pop ebx 179 180 ret 16 181 182END 183