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kolibrios/programs/develop/open watcom/trunk/clib/cgsupp/fdi8386.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!
;*
;*****************************************************************************
;
; from double to signed/unsigned int64
;
include mdef.inc
include struct.inc
modstart fdi8386
xref __U8LS
xref __U8RS
; Convert double precision float to unsigned 64-bit integer with truncation
; Input: [EDX, EAX] = 64-bit float
; Output: [EDX, EAX] = 64-bit integer
xdefp __FDU8
defp __FDU8
push ECX ; save ECX
mov CX,3ffh+64 ; maximum number 2^64-1
call __FDU ; convert float to unsigned __int64
pop ECX ; restore ECX
ret ; return
endproc __FDU8
; Convert double precision float to signed 64-bit integer with truncation
; Input: [EDX, EAX] = 64-bit float
; Output: [EDX, EAX] = 64-bit integer
xdefp __FDI8
defp __FDI8
push ECX ; save ECX
mov CX,3ffh+63 ; maximum number 2^63-1
call __FDI ; convert float to signed __int64
pop ECX ; restore ECX
ret ; return
endproc __FDI8
__FDI proc near
__FDU: ; what? they both do the same thing
or EDX,EDX ; check sign bit
jns short __FDAbs ; treat as unsigned if positive
call __FDAbs ; otherwise convert number
neg EDX ; negate the result
neg EAX ;
sbb EDX,0 ;
ret ; return
endproc __FDI
__FDAbs proc near
or EAX,EAX ; check if number 0
jne short notzero ;
or EDX,EDX ; check if number 0
jne short notzero ;
ret
notzero:
push EBX ; save EBX
_shl EDX,1 ; shift mantissa over
rol EDX,11 ; get exponent to bottom
mov BX,DX ; copy and isolate
and BX,07ffh ; exponent
cmp BX,3ffh ; quit if number < 1.0
jb short dbluflow ; ...
stc ; set carry for implied bit
rcr EDX,1 ; put implied '1' bit in
shr EDX,11 ; remove exponent and extra bit
cmp BX,CX ; check if exponent exceeds maximum
jae short dblmax ; return maximum value if so
sub BX,3ffh+52 ; calculate amount to shift (+ve -> left)
jae short dblm_left ; jump if left shift/no shift
neg BX ; make positive
call __U8RS ; shift mantissa right
pop EBX ; restore EBX
ret ; return
dblm_left:
_if ne ; done if exponent exactly 55
call __U8LS ; - shift mantissa left
_endif ; endif
pop EBX ; restore EBX
ret ; return
; CX = 3ffh+64 for unsigned
; 3ffh+63 for signed
dblmax:
mov EAX,0FFFFFFFFh ; return maximum value
mov EDX,EAX ;
sub CX,3fFh+64 ; subtract bias + 64, results in 0 or -1
neg CX ; get shift count
mov BX,CX ; set shift count
call __U8RS ; shift mantissa right 1 bit for signed
pop EBX ; restore EBX
ret ; return
dbluflow:
sub EAX,EAX ; ensure entire number 0
sub EDX,EDX ;
pop EBX ; restore EBX
ret ; return
endproc __FDAbs
; Convert double precision float to unsigned 64-bit integer with rounding
; Input: [EDX, EAX] = 64-bit float
; xdefp __RDU8
; defp __RDU8
; not implemented
; endproc __RDU8
; Convert double precision float to signed 64-bit integer with rounding
; Input: [EDX, EAX] = 64-bit float
; xdefp __RDI8
; defp __RDI8
; not implemented
; endproc __RDI8
endmod
end