+++ /dev/null
-/*
- * COPYRIGHT: See COPYING in the top level directory
- * PROJECT: ReactOS kernel
- * PURPOSE: Run-Time Library
- * FILE: lib/sdk/crt/math/i386/aulldvrm_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 <asm.inc>
-
-PUBLIC __aulldvrm
-
-/* FUNCTIONS ***************************************************************/
-.code
-
-__aulldvrm:
-
-// ulldvrm - unsigned long divide and remainder
-//
-// Purpose:
-// Does a unsigned long divide and remainder 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)
-// EBX:ECX contains the remainder (divided % divisor)
-// NOTE: this routine removes the parameters from the stack.
-//
-// Uses:
-// ECX
-//
- push esi
-
-// 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 aulldvrm(a, b)):
-//
-// -----------------
-// | |
-// |---------------|
-// | |
-// |--divisor (b)--|
-// | |
-// |---------------|
-// | |
-// |--dividend (a)-|
-// | |
-// |---------------|
-// | return addr** |
-// |---------------|
-// ESP---->| ESI |
-// -----------------
-//
-
-#undef DVNDLO
-#undef DVNDHI
-#undef DVSRLO
-#undef DVSRHI
-#define DVNDLO [esp + 8] // stack address of dividend (a)
-#define DVNDHI [esp + 12] // stack address of dividend (a)
-#define DVSRLO [esp + 16] // stack address of divisor (b)
-#define DVSRHI [esp + 20] // stack address of divisor (b)
-
-//
-// 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.
-//
-
- mov eax,DVSRHI // check to see if divisor < 4194304K
- or eax,eax
- jnz short .L1 // 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 // get 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 // get low order bits of quotient
- mov esi,eax // ebx:esi <- quotient
-
-//
-// Now we need to do a multiply so that we can compute the remainder.
-//
- mov eax,ebx // set up high word of quotient
- mul dword ptr DVSRLO // HIWORD(QUOT) * DVSR
- mov ecx,eax // save the result in ecx
- mov eax,esi // set up low word of quotient
- mul dword ptr DVSRLO // LOWORD(QUOT) * DVSR
- add edx,ecx // EDX:EAX = QUOT * DVSR
- jmp short .L2 // complete remainder calculation
-
-//
-// Here we do it the hard way. Remember, eax contains DVSRHI
-//
-
-.L1:
- mov ecx,eax // ecx:ebx <- divisor
- mov ebx,DVSRLO
- mov edx,DVNDHI // edx:eax <- dividend
- mov eax,DVNDLO
-.L3:
- shr ecx,1 // shift divisor right one bit// hi bit <- 0
- rcr ebx,1
- shr edx,1 // shift dividend right one bit// hi bit <- 0
- rcr eax,1
- or ecx,ecx
- jnz short .L3 // loop until divisor < 4194304K
- div ebx // 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 .L4 // 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 .L4 // if result > original, do subtract
- jb short .L5 // if result < original, we are ok
- cmp eax,DVNDLO // hi words are equal, compare lo words
- jbe short .L5 // if less or equal we are ok, else subtract
-.L4:
- dec esi // subtract 1 from quotient
- sub eax,DVSRLO // subtract divisor from result
- sbb edx,DVSRHI
-.L5:
- xor ebx,ebx // ebx:esi <- quotient
-
-.L2:
-//
-// Calculate remainder by subtracting the result from the original dividend.
-// Since the result is already in a register, we will do the subtract in the
-// opposite direction and negate the result.
-//
-
- sub eax,DVNDLO // subtract dividend from result
- sbb edx,DVNDHI
- neg edx // otherwise, negate the result
- neg eax
- sbb edx,0
-
-//
-// Now we need to get the quotient into edx:eax and the remainder into ebx:ecx.
-//
- mov ecx,edx
- mov edx,ebx
- mov ebx,ecx
- mov ecx,eax
- mov eax,esi
-//
-// Just the cleanup left to do. edx:eax contains the quotient.
-// Restore the saved registers and return.
-//
-
- pop esi
-
- ret 16
-
-END
projects / reactos.git / blobdiff