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kolibrios/programs/develop/open watcom/trunk/clib/cgsupp/i8fs386.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!
;*
;*****************************************************************************
include mdef.inc
include struct.inc
modstart i8fs386
xref __I8LS
xref __I8RS
; Convert signed 64-bit integer to single precision float
; Input: [EDX, EAX] = 64-bit integer
; Output: [EAX] = 32-bit float
xdefp __I8FS
defp __I8FS
or EDX,EDX ; check sign
jns __U8FS ; if positive, just convert
neg EDX ;
neg EAX ; take absolute value of number
sbb EDX,0 ;
call __U8FS ; convert to FS
or EAX,80000000h ; set sign bit on
ret ; return
endproc __I8FS
; Convert unsigned 64-bit integer to single precision float
; Input: [EDX, EAX] = 64-bit integer
; Output: [EAX] = 32-bit float
xdefp __U8FS
defp __U8FS
or EAX,EAX ; if lo is zero
_if e ;
or EDX,EDX ; and if hi is zero
_if e ;
ret ; - return
_endif
_endif ; endif
push ECX ; save ECX
push EBX ; save EBX
bsr ECX,EDX ; find most significant non-zero bit in hi
_if e ; if all zero bits
bsr ECX,EAX ; - find most significant non-zero bit in lo
_else ; else
add CL,32 ; - adjust shift count since hi was not 0
_endif ; endif
push ECX ; save shift count
neg CL ; calculate # of bits to shift by
add CL,63-8 ; ...
mov EBX,ECX ; set up for call
or CL,CL ; if mantissa should move left
_if ge ; then
call __I8LS ; - shift left
_else ; else
neg BL ; - make positive
call __I8RS ; - shift right
_endif ; endif
pop ECX ; restore shift count
and EDX,007FFFFFh ; mask out sign and exponent bits
add CL,127 ; calculate exponent (excess 127)
; and ECX,0FFh ; isolate exponent (not required)
shl ECX,23 ; shift exponent into position
or EDX,ECX ; place into result
mov EAX,EDX ; single precision is only 32 bits
pop EBX ; restore EBX
pop ECX ; restore ECX
ret ; return
endproc __U8FS
endmod
end