kolibrios/programs/develop/open watcom/trunk/clib/cgsupp/fsfd386.asm

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;*****************************************************************************
;*
;* Open Watcom Project
;*
;* Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
;*
;* ========================================================================
;*
;* This file contains Original Code and/or Modifications of Original
;* Code as defined in and that are subject to the Sybase Open Watcom
;* Public License version 1.0 (the 'License'). You may not use this file
;* except in compliance with the License. BY USING THIS FILE YOU AGREE TO
;* ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
;* provided with the Original Code and Modifications, and is also
;* available at www.sybase.com/developer/opensource.
;*
;* The Original Code and all software distributed under the License are
;* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
;* EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
;* ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
;* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
;* NON-INFRINGEMENT. Please see the License for the specific language
;* governing rights and limitations under the License.
;*
;* ========================================================================
;*
;* Description: WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
;* DESCRIBE IT HERE!
;*
;*****************************************************************************
;=========================================================================
;== Name: FSFD ==
;== Operation: Float single to float double conversion ==
;== Inputs: EAX single precision float ==
;== Outputs: EDX:EAX double precision float ==
;== Volatile: none ==
;=========================================================================
include mdef.inc
include struct.inc
modstart fsfd386
xdefp __FSFD
defpe __FSFD
_guess ; guess: number is 0.0 or -0.0
mov EDX,EAX ; - get float
and EAX,7fffffffh ; - remove sign
_quif ne ; - quit if number is not +0.0 or -0.0
_admit ; guess: number is +-infinity
cmp EAX,7f800000h ; - quit if not +-infinity
_quif ne ; - ...
or EDX,7ff00000h ; - set double precision infinity
sub EAX,EAX ; - ...
_admit ; admit: not a special number
test EAX,7f800000h ; - if exponent is 0 (denormal number)
_if e ; - then
or EDX,7F800000h ; - - set exponent to 0xFF
_loop ; - - loop (normalize the fraction)
sub EDX,00800000h ; - - - subtract 1 from exponent adjustment
_shl EAX,1 ; - - - shift fraction left
test EAX,00800000h ; - - - check to see if fraction is normalized
_until ne ; - - until normalized
and EDX,0FF800000h ; - - copy fraction back to EDX
and EAX,007FFFFFh ; - - ...
or EDX,EAX ; - - ...
sar EDX,3 ; - shift over 3
and EDX,8FFFFFFFh ; - reset exponent extended bits
add EDX,28200000h ; - adjust exponent by (3FF - FF -7F + 1) shl 20
_else ; - else
sar EDX,3 ; - shift over 3
and EDX,8FFFFFFFh ; - reset exponent extended bits
cmp EAX,7F800000h ; - if number is not number (NaN)
_if a ;
or EDX,7FF00000h; - adjust exponent to NaN 7FF shl 20
_else
add EDX,38000000h; - adjust exponent by (3FF-7F) shl 20
_endif
_endif ; - endif
and EAX,7 ; - get bottom 3 bits of fraction
ror EAX,3 ; - shift them to the top
_endguess ; endguess
ret ; return
endproc __FSFD
endmod
end