95 lines
2.5 KiB
C
95 lines
2.5 KiB
C
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// Emacs style mode select -*- C++ -*-
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//-----------------------------------------------------------------------------
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//
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// $Id$
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//
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// Copyright (C) 1993-1996 by id Software, Inc.
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// DESCRIPTION:
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// Fixed point arithemtics, implementation.
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//
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//-----------------------------------------------------------------------------
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#ifndef __M_FIXED__
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#define __M_FIXED__
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#ifdef __GNUG__
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#pragma interface
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#endif
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#include "doomtype.h"
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#include "rockmacros.h"
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//
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// Fixed point, 32bit as 16.16.
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//
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#define FRACBITS 16
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#define FRACUNIT (1<<FRACBITS)
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#define D_abs(x) ({fixed_t _t = (x), _s = _t >> (8*sizeof _t-1); (_t^_s)-_s;})
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typedef int fixed_t;
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inline static int FixedMul( int a, int b )
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{
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#if defined(CPU_COLDFIRE) && !defined(SIMULATOR)
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// Code contributed by Thom Johansen
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register int result;
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asm volatile (
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"mac.l %[x],%[y],%%acc0 \n" /* multiply */
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"move.l %[y],%%d2 \n"
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"mulu.l %[x],%%d2 \n" /* get lower half, avoid emac stall */
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"movclr.l %%acc0,%[result] \n" /* get higher half */
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"moveq.l #15,%%d1 \n"
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"asl.l %%d1,%[result] \n" /* hi <<= 15, plus one free */
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"moveq.l #16,%%d1 \n"
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"lsr.l %%d1,%%d2 \n" /* (unsigned)lo >>= 16 */
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"or.l %%d2 ,%[result] \n" /* combine result */
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: /* outputs */
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[result]"=&d"(result)
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: /* inputs */
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[x] "d" (a),
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[y] "d" (b)
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: /* clobbers */
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"d1", "d2"
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);
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return result;
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#else
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return (fixed_t)((long long) a*b >> FRACBITS);
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#endif
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}
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inline static fixed_t FixedDiv( fixed_t a, fixed_t b )
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{
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return (D_abs(a)>>14) >= D_abs(b) ? ((a^b)>>31) ^ MAXINT :
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(fixed_t)(((long long) a << FRACBITS) / b);
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}
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/* CPhipps -
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* FixedMod - returns a % b, guaranteeing 0<=a<b
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* (notice that the C standard for % does not guarantee this)
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*/
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inline static fixed_t FixedMod(fixed_t a, fixed_t b)
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{
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if (b & (b-1)) {
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fixed_t r = a % b;
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return ((r<0) ? r+b : r);
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} else
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return (a & (b-1));
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}
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#endif
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