103 lines
4.2 KiB
NASM
103 lines
4.2 KiB
NASM
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;*****************************************************************************
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;*
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;* Open Watcom Project
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;*
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;* Portions Copyright (c) 1983-2002 Sybase, Inc. All Rights Reserved.
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;*
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;* ========================================================================
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;*
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;* This file contains Original Code and/or Modifications of Original
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;* Code as defined in and that are subject to the Sybase Open Watcom
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;* Public License version 1.0 (the 'License'). You may not use this file
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;* except in compliance with the License. BY USING THIS FILE YOU AGREE TO
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;* ALL TERMS AND CONDITIONS OF THE LICENSE. A copy of the License is
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;* provided with the Original Code and Modifications, and is also
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;* available at www.sybase.com/developer/opensource.
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;*
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;* The Original Code and all software distributed under the License are
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;* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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;* EXPRESS OR IMPLIED, AND SYBASE AND ALL CONTRIBUTORS HEREBY DISCLAIM
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;* ALL SUCH WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF
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;* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR
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;* NON-INFRINGEMENT. Please see the License for the specific language
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;* governing rights and limitations under the License.
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;*
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;* ========================================================================
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;*
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;* Description: WHEN YOU FIGURE OUT WHAT THIS FILE DOES, PLEASE
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;* DESCRIBE IT HERE!
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;*
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;*****************************************************************************
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include mdef.inc
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include struct.inc
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modstart i8fs386
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xref __I8LS
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xref __I8RS
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; Convert signed 64-bit integer to single precision float
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; Input: [EDX, EAX] = 64-bit integer
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; Output: [EAX] = 32-bit float
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xdefp __I8FS
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defp __I8FS
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or EDX,EDX ; check sign
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jns __U8FS ; if positive, just convert
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neg EDX ;
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neg EAX ; take absolute value of number
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sbb EDX,0 ;
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call __U8FS ; convert to FS
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or EAX,80000000h ; set sign bit on
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ret ; return
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endproc __I8FS
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; Convert unsigned 64-bit integer to single precision float
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; Input: [EDX, EAX] = 64-bit integer
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; Output: [EAX] = 32-bit float
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xdefp __U8FS
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defp __U8FS
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or EAX,EAX ; if lo is zero
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_if e ;
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or EDX,EDX ; and if hi is zero
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_if e ;
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ret ; - return
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_endif
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_endif ; endif
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push ECX ; save ECX
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push EBX ; save EBX
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bsr ECX,EDX ; find most significant non-zero bit in hi
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_if e ; if all zero bits
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bsr ECX,EAX ; - find most significant non-zero bit in lo
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_else ; else
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add CL,32 ; - adjust shift count since hi was not 0
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_endif ; endif
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push ECX ; save shift count
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neg CL ; calculate # of bits to shift by
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add CL,63-8 ; ...
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mov EBX,ECX ; set up for call
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or CL,CL ; if mantissa should move left
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_if ge ; then
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call __I8LS ; - shift left
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_else ; else
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neg BL ; - make positive
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call __I8RS ; - shift right
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_endif ; endif
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pop ECX ; restore shift count
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and EDX,007FFFFFh ; mask out sign and exponent bits
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add CL,127 ; calculate exponent (excess 127)
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; and ECX,0FFh ; isolate exponent (not required)
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shl ECX,23 ; shift exponent into position
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or EDX,ECX ; place into result
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mov EAX,EDX ; single precision is only 32 bits
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pop EBX ; restore EBX
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pop ECX ; restore ECX
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ret ; return
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endproc __U8FS
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endmod
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end
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