/* * COPYRIGHT: See COPYING in the top level directory * PROJECT: ReactOS kernel * PURPOSE: Run-Time Library * FILE: lib/sdk/crt/math/i386/alldiv_asm.s * PROGRAMER: Alex Ionescu (alex@relsoft.net) * * Copyright (C) 2002 Michael Ringgaard. * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the project nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES// LOSS OF USE, DATA, OR PROFITS// OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include PUBLIC __alldiv /* FUNCTIONS ***************************************************************/ .code // // lldiv - signed long divide // // Purpose: // Does a signed long divide of the arguments. Arguments are // not changed. // // Entry: // Arguments are passed on the stack: // 1st pushed: divisor (QWORD) // 2nd pushed: dividend (QWORD) // // Exit: // EDX:EAX contains the quotient (dividend/divisor) // NOTE: this routine removes the parameters from the stack. // // Uses: // ECX // __alldiv: push edi push esi push ebx // Set up the local stack and save the index registers. When this is done // the stack frame will look as follows (assuming that the expression a/b will // generate a call to lldiv(a, b)): // // ----------------- // | | // |---------------| // | | // |--divisor (b)--| // | | // |---------------| // | | // |--dividend (a)-| // | | // |---------------| // | return addr** | // |---------------| // | EDI | // |---------------| // | ESI | // |---------------| // ESP---->| EBX | // ----------------- // #define DVNDLO [esp + 16] // stack address of dividend (a) #define DVNDHI [esp + 20] // stack address of dividend (a) #define DVSRLO [esp + 24] // stack address of divisor (b) #define DVSRHI [esp + 28] // stack address of divisor (b) // Determine sign of the result (edi = 0 if result is positive, non-zero // otherwise) and make operands positive. xor edi,edi // result sign assumed positive mov eax,DVNDHI // hi word of a or eax,eax // test to see if signed jge short L1 // skip rest if a is already positive inc edi // complement result sign flag mov edx,DVNDLO // lo word of a neg eax // make a positive neg edx sbb eax,0 mov DVNDHI,eax // save positive value mov DVNDLO,edx L1: mov eax,DVSRHI // hi word of b or eax,eax // test to see if signed jge short L2 // skip rest if b is already positive inc edi // complement the result sign flag mov edx,DVSRLO // lo word of a neg eax // make b positive neg edx sbb eax,0 mov DVSRHI,eax // save positive value mov DVSRLO,edx L2: // // Now do the divide. First look to see if the divisor is less than 4194304K. // If so, then we can use a simple algorithm with word divides, otherwise // things get a little more complex. // // NOTE - eax currently contains the high order word of DVSR // or eax,eax // check to see if divisor < 4194304K jnz short L3 // nope, gotta do this the hard way mov ecx,DVSRLO // load divisor mov eax,DVNDHI // load high word of dividend xor edx,edx div ecx // eax <- high order bits of quotient mov ebx,eax // save high bits of quotient mov eax,DVNDLO // edx:eax <- remainder:lo word of dividend div ecx // eax <- low order bits of quotient mov edx,ebx // edx:eax <- quotient jmp short L4 // set sign, restore stack and return // // Here we do it the hard way. Remember, eax contains the high word of DVSR // L3: mov ebx,eax // ebx:ecx <- divisor mov ecx,DVSRLO mov edx,DVNDHI // edx:eax <- dividend mov eax,DVNDLO L5: shr ebx,1 // shift divisor right one bit rcr ecx,1 shr edx,1 // shift dividend right one bit rcr eax,1 or ebx,ebx jnz short L5 // loop until divisor < 4194304K div ecx // now divide, ignore remainder mov esi,eax // save quotient // // We may be off by one, so to check, we will multiply the quotient // by the divisor and check the result against the orignal dividend // Note that we must also check for overflow, which can occur if the // dividend is close to 2**64 and the quotient is off by 1. // mul dword ptr DVSRHI // QUOT * DVSRHI mov ecx,eax mov eax,DVSRLO mul esi // QUOT * DVSRLO add edx,ecx // EDX:EAX = QUOT * DVSR jc short L6 // carry means Quotient is off by 1 // // do long compare here between original dividend and the result of the // multiply in edx:eax. If original is larger or equal, we are ok, otherwise // subtract one (1) from the quotient. // cmp edx,DVNDHI // compare hi words of result and original ja short L6 // if result > original, do subtract jb short L7 // if result < original, we are ok cmp eax,DVNDLO // hi words are equal, compare lo words jbe short L7 // if less or equal we are ok, else subtract L6: dec esi // subtract 1 from quotient L7: xor edx,edx // edx:eax <- quotient mov eax,esi // // Just the cleanup left to do. edx:eax contains the quotient. Set the sign // according to the save value, cleanup the stack, and return. // L4: dec edi // check to see if result is negative jnz short L8 // if EDI == 0, result should be negative neg edx // otherwise, negate the result neg eax sbb edx,0 // // Restore the saved registers and return. // L8: pop ebx pop esi pop edi ret 16 END