kolibrios/programs/develop/open watcom/trunk/clib/convert/mdfd386.asm
Sergey Semyonov (Serge) 43bd1e645f Clib char & math functions
git-svn-id: svn://kolibrios.org@554 a494cfbc-eb01-0410-851d-a64ba20cac60
2007-06-26 11:19:49 +00:00

106 lines
4.0 KiB
NASM

;*****************************************************************************
;*
;* 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 mdfd386
xdefp "C",_dmsbintoieee
defpe _dmsbintoieee
ifdef __STACK__
mov eax,dword ptr +4H[esp]
mov edx,dword ptr +8H[esp]
else
push ecx
endif
; At this point:
; eax - ptr to MBF source double
; edx - ptr to IEEE dest double
; ecx - spare register
; Check for and process MBF 0.0 first
mov ecx,+4h[eax] ; load MBF double (hi)
test ecx,0ff000000h ; MBF exponent = 0 ?
jne MBFNonZero ; no, jump
; MBF 0.0, store IEEE 0.0
xor eax,eax ; make 0
mov [edx],eax ; store IEEE 0.0 (lo)
mov +4h[edx],eax ; store IEEE 0.0 (hi)
ifndef __STACK__
pop ecx ; clean up
endif
ret ; return 0 (no overflow)
MBFNonZero: mov eax,[eax] ; load MBF double (lo)
; At this point:
; ecx:eax - MBF source double
; edx - ptr to IEEE dest double
rol ecx,9 ; rotate exponent & sign bit low
shr ecx,1 ; move sign bit before exponent
rcr cl,1 ; :
adc ecx,ecx ; :
ror ecx,9 ; rotate exponent & sign bit back
; shift mantissa into place
shrd eax,ecx,2 ; shift mantissa
sar ecx,3 ; shift exponent & mantissa, save sign bit
rcr eax,1 ; shift mantissa
jc MBFRound ; jump if rounding up
and ecx,8FFFFFFFh ; mask out surplus sign bits
add ecx,37e00000h ; convert MBF to IEEE exponent
IEEEStore:
mov [edx],eax ; store IEEE double (lo)
mov +4h[edx],ecx ; store IEEE double (hi)
xor eax,eax ; 0
ifndef __STACK__
pop ecx ; clean up
endif
ret ; return 0 (no overflow)
; add rounding bit
MBFRound: and ecx,8FFFFFFFh ; mask out surplus sign bits
add eax,1 ; add round bit
adc ecx,37e00000h ; convert MBF to IEEE exponent
jmp IEEEStore ; store result
endproc _dmsbintoieee
endmod
end