kolibrios/programs/develop/open watcom/trunk/clib/cgsupp/i4fs386.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: I4FS, U4FS ==
;== Operation: Convert Integer types to single precision ==
;== Inputs: EAX, unsigned or signed integer ==
;== Outputs: EAX single precision floating point ==
;== Volatile: none ==
;== ==
;========================================================================
include mdef.inc
include struct.inc
modstart i4fs386
xdefp __I4FS
xdefp __U4FS
defpe __U4FS
or EAX,EAX ; if number is not zero
_if ne ; then
push ECX ; - save ECX
bsr ECX,EAX ; - find most significant non-zero bit
mov CH,CL ; - save shift count
neg CL ; - calculate # of bits to rotate by
add CL,23 ; - ...
and CL,1fh ; - just keep last 5 bits
rol EAX,CL ; - shift bits into position
and EAX,007FFFFFh ; - mask out sign and exponent bits
mov CL,CH ; - get shift count
add CL,7Fh ; - calculate exponent
and ECX,0FFh ; - isolate exponent
shl ECX,23 ; - shift exponent into position
or EAX,ECX ; - place into result
pop ECX ; - restore ECX
_endif ; endif
ret ; return
endproc __U4FS
defpe __I4FS
or EAX,EAX ; check sign
jns __U4FS ; if positive, just convert
neg EAX ; take absolute value of number
call __U4FS ; convert to FS
or EAX,80000000h ; set sign bit on
ret ; and return
endproc __I4FS
endmod
end