308 lines
15 KiB
NASM
308 lines
15 KiB
NASM
;*****************************************************************************
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;*
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;* Open Watcom Project
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;*
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;* Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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;*
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;* ========================================================================
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;*
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;* This file contains Original Code and/or Modifications of Original
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;* Code as defined in and that are subject to the Sybase Open Watcom
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;* Public License version 1.0 (the 'License'). You may not use this file
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;* except in compliance with the License. BY USING THIS FILE YOU AGREE TO
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;* ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
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;* provided with the Original Code and Modifications, and is also
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;* available at www.sybase.com/developer/opensource.
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;*
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;* The Original Code and all software distributed under the License are
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;* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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;* EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
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;* ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
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;* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
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;* NON-INFRINGEMENT. Please see the License for the specific language
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;* governing rights and limitations under the License.
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;*
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;* ========================================================================
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;*
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;* Description: WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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;* DESCRIBE IT HERE!
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;*
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;*****************************************************************************
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;
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include mdef.inc
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include struct.inc
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.8087
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modstart div386
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xref __8087 ; indicate that NDP instructions are present
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datasegment
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extrn __real87 : byte ; 8087.asm
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extrn __chipbug: byte
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enddata
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xref F8DivZero ; Fstatus
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xref F8OverFlow ; Fstatus
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xref F8UnderFlow ; Fstatus
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xref __fdiv_m64
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xdefp __FDD
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; double __FDD( double , double )
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sign equ -12
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den equ sign-8
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quot equ den-12
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lo equ 0
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hi equ 4
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defpe __FDD
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or EBX,EBX ; if low word of divisor is 0
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_if e ; then
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_shl ECX,1 ; - shift sign of divisor into carry
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_if e ; - if divisor is zero
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jmp F8DivZero ; - - handle divide by zero
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_endif ; - endif
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rcr ECX,1 ; - restore sign of divisor
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_endif ; endif
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or EAX,EAX ; check dividend for zero
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_if e ; if so then
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_shl EDX,1 ; - save sign of dividend
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_if e ; - if dividend is 0
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ret ; - - return
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_endif ; - endif
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rcr EDX,1 ; - restore sign of dividend
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_endif ; endif
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cmp byte ptr __real87,0 ; if no 80x87 is present
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je short __FDDemu ; then emulate
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__FDD87:
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push EDX ; push operand 1
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push EAX ; . . .
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fld qword ptr [ESP] ; load operand 1
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push ECX ; push operand 2
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push EBX ; . . .
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test byte ptr __chipbug,1 ; have we got a bad divider?
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_if ne ; then
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call __fdiv_m64 ; - call support rtn for divide
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_else ; else
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fdiv qword ptr [ESP] ; - divide operand 1 by operand 2
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add ESP,8 ; - clean up stack
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_endif ; endif
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fstp qword ptr [ESP] ; store result
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fwait ; wait
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pop EAX ; load result into DX:AX
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pop EDX ; . . .
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cmp EDX,80000000H ; is it a negative zero?
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_if e ; if it is then
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sub EDX,EDX ; - make it positive 0.0
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mov EAX,EDX ; - ...
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_endif ; endif
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ret ; return
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__FDDemu:
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push EBP ; save EBP
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mov EBP,ESP ; get access to stack
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push EDI ; save EDI
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push ESI ; and ESI
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mov EDI,EDX ; get high part of op1
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mov ESI,ECX ; get high part of op2
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sar EDI,20 ; shift exponent to bottom, duplicating sign
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sar ECX,20 ; shift exponent to bottom, duplicating sign
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and EDI,0800007FFh ; isolate signs and exponent
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and ECX,0800007FFh ; ...
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rol EDI,16 ; rotate signs to bottom
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rol ECX,16 ; ...
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add DI,CX ; calc sign of result
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rol EDI,16 ; rotate signs to top
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rol ECX,16 ; ...
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and EDX,000FFFFFh ; isolate fraction
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and ESI,000FFFFFh ; isolate fraction
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or DI,DI ; if op1 is not a denormal
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_if ne ; then
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or EDX,00100000h ; - turn on implied 1 bit
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_else ; else (denormal)
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_loop ; - loop (normalize it)
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_shl EAX,1 ; - - shift fraction left
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_rcl EDX,1 ; - - . . .
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dec DI ; - - decrement exponent
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test EDX,00100000h ; - - until implied 1 bit is on
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_until ne ; - until implied 1 bit is on
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_endif ; endif
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or CX,CX ; if op2 is not a denormal
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_if ne ; then
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or ESI,00100000h ; - turn on implied 1 bit
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_else ; else (denormal)
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_loop ; - loop (normalize it)
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_shl EBX,1 ; - - shift fraction left
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_rcl ESI,1 ; - - . . .
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dec CX ; - - decrement exponent
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test ESI,00100000h ; - - until implied 1 bit is on
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_until ne ; - until implied 1 bit is on
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_endif ; endif
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sub DI,CX ; calculate exponent of result
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add DI,03ffh ; add in removed bias
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_guess ; guess: overflow
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_quif s ; - quit if exponent is negative
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cmp DI,07FFh ; - quit if not overflow
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_quif b ; - . . .
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mov EAX,ECX ; - put sign into EAX
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pop ESI ; - restore ESI
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pop EDI ; - restore EDI
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pop EBP ; - restore EBP
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jmp F8OverFlow ; - handle overflow
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_endguess ; endguess
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cmp DI,-52 ; if exponent is too small
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_if l ; then underflow
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pop ESI ; - restore ESI
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pop EDI ; - restore EDI
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pop EBP ; - restore EBP
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jmp F8UnderFlow ; - handle underflow
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_endif ; endif
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push EDI ; save sign and exponent
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mov CL,11 ; shift fractions to top of registers
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shld EDX,EAX,CL ; ...
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shld EAX,EBP,CL ; ...
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and EAX,0FFFFF800h ; ...
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shld ESI,EBX,CL ; ...
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shld EBX,EBP,CL ; ...
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and EBX,0FFFFF800h ; ...
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push ESI ; save divisor
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push EBX ; ...
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mov ECX,ESI ; get top part of divisor
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mov EDI,EDX ; get dividend
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mov ESI,EAX ; ...
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sub EAX,EAX ; assume top bit is 0
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cmp ECX,EDX ; check high parts
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_if be ; if hi(divisor) <= hi(dividend)
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sub EDX,ECX ; - subtract divisor from dividend
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inc EAX ; - set quotient to 1
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_endif ; endif
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push EAX ; save high word of quotient
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mov EAX,ESI ; get low part of dividend
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div ECX ; estimate next word of quotient
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push EAX ; save estimate of quotient (quot+4[EBP])
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xchg EAX,EBX ; save quot., get low word of divisor
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mul EBX ; calc. estimate * lo(divisor)
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xchg EAX,ECX ; ...
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xchg EBX,EDX ; save partial product
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mul EDX ; calc. estimate * hi(divisor)
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add EAX,EBX ; add to partial product
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adc EDX,0 ; ...
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mov EBX,den+lo[EBP] ; get low word of divisor
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test byte ptr quot+8[EBP],1 ; if high word of quot is 1
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_if ne ; then
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add EAX,EBX ; - add in divisor
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adc EDX,den+hi[EBP] ; - ...
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_endif ; endif
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; subtract estimate * divisor from dividend
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neg ECX ; 0 - ECX
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sbb ESI,EAX ; ...
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sbb EDI,EDX ; ...
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_if ne ; if high word not 0 (quotient too big)
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_loop ; - loop (find correct quotient)
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sub dword ptr quot+4[EBP],1; - - decrement quotient
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sbb dword ptr quot+8[EBP],0; - - ...
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add ECX,EBX ; - - add divisor back to dividend
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adc ESI,den+hi[EBP] ; - - ...
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adc EDI,0 ; - - ...
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_until e ; - until done
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_endif ; endif
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mov EDI,ESI ; get new dividend
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mov ESI,ECX ; ...
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mov ECX,den+hi[EBP] ; get divisor
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cmp ECX,EDI ; check high parts 13-aug-90
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_if be ; if hi(divisor) <= hi(dividend)
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sub EDI,ECX ; - subtract divisor from dividend
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add dword ptr quot+4[EBP],1 ; - increment quotient
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adc dword ptr quot+8[EBP],0 ; - ...
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_endif ; endif
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mov EDX,EDI ; get dividend into EDX:EAX
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mov EAX,ESI ; ...
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div ECX ; estimate next word of quotient
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push EAX ; save estimate of quotient (-4[EBP])
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or EAX,EAX ; if quotient non-zero
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_if ne ; then
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xchg EAX,EBX ; - save quot., get low word of divisor
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mul EBX ; - calc. estimate * lo(divisor)
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xchg EAX,ECX ; - ...
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xchg EBX,EDX ; - save partial product
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mul EDX ; - calc. estimate * hi(divisor)
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add EAX,EBX ; - add to partial product
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adc EDX,0 ; - ...
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; - subtract estimate * divisor from dividend
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neg ECX ; - 0 - ECX
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sbb ESI,EAX ; - ...
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sbb EDI,EDX ; - ...
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_if ne ; - if high word not 0 (quotient too big)
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_loop ; - - loop (find correct quotient)
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sub dword ptr quot+0[EBP],1; - - - decrement quotient
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sbb dword ptr quot+4[EBP],0; - - - ...
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sbb dword ptr quot+8[EBP],0; - - - ...
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add ECX,den+lo[EBP] ; - - - add divisor back to dividend
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adc ESI,den+hi[EBP] ; - - - ...
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adc EDI,0 ; - - - ...
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_until e ; - - until done
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_endif ; - endif
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_endif ; endif
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pop EAX ; get quotient
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pop EDX ; ...
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pop EBX ; get high bit
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add ESP,8 ; remove divisor
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pop EDI ; restore sign and exponent
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dec DI ; decrement exponent
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shr EBX,1 ; if non-zero
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_if c ; then
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rcr EDX,1 ; - shift answer right
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rcr EAX,1 ; - ...
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inc EDI ; - increment exponent
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_endif ; endif
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sub ESI,ESI ; get zero for zero fill
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mov CL,11 ; shift result over
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shrd EAX,EDX,CL ; ...
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rcr ESI,1 ; save carry
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shrd EDX,ESI,CL ; ...
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or EDX,0FFF00000h ; turn top bits all on
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_shl ESI,1 ; get guard bit
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adc EAX,0 ; round up
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adc EDX,0 ; ...
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adc EDI,0 ; increment exponent if required
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or DI,DI ; if exponent <= 0
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_if le ; then (denormal result)
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_if e ; - if exponent = 0
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mov CL,1 ; - - set shift count to 1
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_else ; - else
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neg DI ; - - negate to get shift count
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mov CX,DI ; - - ...
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_endif ; - endif
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and EDX,001FFFFFh ; - isolate fraction
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sub EBX,EBX ; - for zero fill
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shrd EAX,EDX,CL ; - align the fraction
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shrd EDX,EBX,CL ; - ...
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sub DI,DI ; - set exponent to 0
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_endif ; endif
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and EDX,000FFFFFh ; isolate fraction
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mov ESI,EDI ; get copy of sign
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ror EDI,11 ; get exponent
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_shl ESI,1 ; get sign
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rcr EDI,1 ; put it in
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and EDI,0FFF00000h ; isolate sign and exponent
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or EDX,EDI ; place it in result
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pop ESI ; restore registers
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pop EDI ; ...
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pop EBP ; ...
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ret ; return
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endproc __FDD
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endmod
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end
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