151 lines
5.6 KiB
NASM
151 lines
5.6 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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;
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; from float to signed/unsigned int64
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;
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include mdef.inc
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include struct.inc
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modstart fsi8386
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xref __U8LS
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xref __U8RS
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; Convert single precision float to unsigned 64-bit integer with truncation
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; Input: [EAX] = 32-bit float
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; Output: [EDX, EAX] = 64-bit integer
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xdefp __FSU8
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defp __FSU8
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push ECX ; save ECX
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mov CL,7fh+64 ; maximum number 2^64-1
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call __FSU ; convert float to unsigned __int64
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pop ECX ; restore ECX
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ret ; return
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endproc __FSU8
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; Convert single precision float to signed 64-bit integer with truncation
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; Input: [EAX] = 32-bit float
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; Output: [EDX, EAX] = 64-bit integer
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xdefp __FSI8
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defp __FSI8
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push ECX ; save ECX
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mov CL,7fh+63 ; maximum number 2^63-1
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call __FSI ; convert float to signed __int64
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pop ECX ; restore ECX
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ret ; return
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endproc __FSI8
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__FSI proc near
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__FSU: ; what? they both do the same thing
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or EAX,EAX ; check sign bit
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jns short __FSAbs ; treat as unsigned if positive
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call __FSAbs ; otherwise convert number
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neg EDX ; negate the result
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neg EAX ;
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sbb EDX,0 ;
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ret ; return
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endproc __FSI
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__FSAbs proc near
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or EAX,EAX ; check if number 0
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je short fltzero ; if so, just return 0
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_shl EAX,1 ; shift mantissa over
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rol EAX,8 ; get exponent to bottom
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cmp AL,7fh ; quit if number < 1.0
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jb short fltuflow ; ...
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push EBX ; save EBX
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mov CH,AL ; save exponent
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stc ; set carry for implied bit
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rcr EAX,1 ; put implied '1' bit in
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shr EAX,8 ; remove exponent and extra bit
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mov EDX,EAX ; put into 64-bit hi part
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xor EAX,EAX ; zero 64-bit lo part
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cmp CH,CL ; check if exponent exceeds maximum
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jae short fltmax ; return maximum value if so
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sub CH,7fh+55 ; calculate amount to shift (+ve -> left)
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jae short fltm_left ; jump if left shift/no shift
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xchg CH,CL ; get shift count
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neg CL ; make positive
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mov BX,CX
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call __U8RS ; shift mantissa right
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pop EBX ; restore EBX
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ret ; return
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fltm_left:
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_if ne ; done if exponent exactly 55
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mov BL,CH ; - get shift count
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call __U8LS ; - shift mantissa left
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_endif ; endif
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pop EBX ; restore EBX
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ret ; return
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; CL = 7fh+64 for unsigned
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; 7fh+63 for signed
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fltmax:
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mov EAX,0FFFFFFFFh ; return maximum value
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mov EDX,EAX ;
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sub CL,7fh+64 ; subtract bias + 64, results in 0 or -1
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neg CL ; get shift count
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mov BL,CL ; set shift count
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call __U8RS ; shift mantissa right 1 bit for signed
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pop EBX ; restore EBX
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ret ; return
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fltuflow:
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sub EAX,EAX ; ensure entire number 0
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fltzero:
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sub EDX,EDX ;
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ret ; return
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endproc __FSAbs
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; Convert single precision float to unsigned 64-bit integer with rounding
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; Input: [EAX] = 32-bit float
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; xdefp __RSU8
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; defp __RSU8
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; not implemented
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; endproc __RSU8
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; Convert single precision float to signed 64-bit integer with rounding
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; Input: [EAX] = 32-bit float
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; xdefp __RSI8
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; defp __RSI8
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; not implemented
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; endproc __RSI8
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endmod
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end
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