90 lines
4.3 KiB
NASM
90 lines
4.3 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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;== Name: FSFD ==
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;== Operation: Float single to float double conversion ==
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;== Inputs: EAX single precision float ==
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;== Outputs: EDX:EAX double precision float ==
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;== Volatile: none ==
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;=========================================================================
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include mdef.inc
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include struct.inc
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modstart fsfd386
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xdefp __FSFD
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defpe __FSFD
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_guess ; guess: number is 0.0 or -0.0
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mov EDX,EAX ; - get float
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and EAX,7fffffffh ; - remove sign
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_quif ne ; - quit if number is not +0.0 or -0.0
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_admit ; guess: number is +-infinity
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cmp EAX,7f800000h ; - quit if not +-infinity
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_quif ne ; - ...
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or EDX,7ff00000h ; - set double precision infinity
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sub EAX,EAX ; - ...
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_admit ; admit: not a special number
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test EAX,7f800000h ; - if exponent is 0 (denormal number)
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_if e ; - then
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or EDX,7F800000h ; - - set exponent to 0xFF
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_loop ; - - loop (normalize the fraction)
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sub EDX,00800000h ; - - - subtract 1 from exponent adjustment
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_shl EAX,1 ; - - - shift fraction left
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test EAX,00800000h ; - - - check to see if fraction is normalized
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_until ne ; - - until normalized
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and EDX,0FF800000h ; - - copy fraction back to EDX
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and EAX,007FFFFFh ; - - ...
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or EDX,EAX ; - - ...
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sar EDX,3 ; - shift over 3
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and EDX,8FFFFFFFh ; - reset exponent extended bits
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add EDX,28200000h ; - adjust exponent by (3FF - FF -7F + 1) shl 20
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_else ; - else
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sar EDX,3 ; - shift over 3
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and EDX,8FFFFFFFh ; - reset exponent extended bits
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cmp EAX,7F800000h ; - if number is not number (NaN)
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_if a ;
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or EDX,7FF00000h; - adjust exponent to NaN 7FF shl 20
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_else
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add EDX,38000000h; - adjust exponent by (3FF-7F) shl 20
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_endif
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_endif ; - endif
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and EAX,7 ; - get bottom 3 bits of fraction
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ror EAX,3 ; - shift them to the top
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_endguess ; endguess
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ret ; return
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endproc __FSFD
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endmod
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end
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