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/* $OpenBSD: fpu_explode.c,v 1.2 1996/05/09 22:20:45 niklas Exp $ */
/* $NetBSD: fpu_explode.c,v 1.2 1996/04/30 11:52:18 briggs Exp $ */
/*
* Copyright (c) 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This software was developed by the Computer Systems Engineering group
* at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
* contributed to Berkeley.
*
* All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Lawrence Berkeley Laboratory.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)fpu_explode.c 8.1 (Berkeley) 6/11/93
*/
/*
* FPU subroutines: `explode' the machine's `packed binary' format numbers
* into our internal format.
*/
#include <sys/types.h>
#include <sys/systm.h>
#include "ieee.h"
#include <machine/reg.h>
#include "fpu_arith.h"
#include "fpu_emulate.h"
/* Conversion to internal format -- note asymmetry. */
static int fpu_itof __P((struct fpn *fp, u_int i));
static int fpu_stof __P((struct fpn *fp, u_int i));
static int fpu_dtof __P((struct fpn *fp, u_int i, u_int j));
static int fpu_xtof __P((struct fpn *fp, u_int i, u_int j, u_int k));
/*
* N.B.: in all of the following, we assume the FP format is
*
* ---------------------------
* | s | exponent | fraction |
* ---------------------------
*
* (which represents -1**s * 1.fraction * 2**exponent), so that the
* sign bit is way at the top (bit 31), the exponent is next, and
* then the remaining bits mark the fraction. A zero exponent means
* zero or denormalized (0.fraction rather than 1.fraction), and the
* maximum possible exponent, 2bias+1, signals inf (fraction==0) or NaN.
*
* Since the sign bit is always the topmost bit---this holds even for
* integers---we set that outside all the *tof functions. Each function
* returns the class code for the new number (but note that we use
* FPC_QNAN for all NaNs; fpu_explode will fix this if appropriate).
*/
/*
* int -> fpn.
*/
static int
fpu_itof(fp, i)
register struct fpn *fp;
register u_int i;
{
if (i == 0)
return (FPC_ZERO);
/*
* The value FP_1 represents 2^FP_LG, so set the exponent
* there and let normalization fix it up. Convert negative
* numbers to sign-and-magnitude. Note that this relies on
* fpu_norm()'s handling of `supernormals'; see fpu_subr.c.
*/
fp->fp_exp = FP_LG;
fp->fp_mant[0] = (int)i < 0 ? -i : i;
fp->fp_mant[1] = 0;
fp->fp_mant[2] = 0;
fp->fp_mant[3] = 0;
fpu_norm(fp);
return (FPC_NUM);
}
#define mask(nbits) ((1 << (nbits)) - 1)
/*
* All external floating formats convert to internal in the same manner,
* as defined here. Note that only normals get an implied 1.0 inserted.
*/
#define FP_TOF(exp, expbias, allfrac, f0, f1, f2, f3) \
if (exp == 0) { \
if (allfrac == 0) \
return (FPC_ZERO); \
fp->fp_exp = 1 - expbias; \
fp->fp_mant[0] = f0; \
fp->fp_mant[1] = f1; \
fp->fp_mant[2] = f2; \
fp->fp_mant[3] = f3; \
fpu_norm(fp); \
return (FPC_NUM); \
} \
if (exp == (2 * expbias + 1)) { \
if (allfrac == 0) \
return (FPC_INF); \
fp->fp_mant[0] = f0; \
fp->fp_mant[1] = f1; \
fp->fp_mant[2] = f2; \
fp->fp_mant[3] = f3; \
return (FPC_QNAN); \
} \
fp->fp_exp = exp - expbias; \
fp->fp_mant[0] = FP_1 | f0; \
fp->fp_mant[1] = f1; \
fp->fp_mant[2] = f2; \
fp->fp_mant[3] = f3; \
return (FPC_NUM)
/*
* 32-bit single precision -> fpn.
* We assume a single occupies at most (64-FP_LG) bits in the internal
* format: i.e., needs at most fp_mant[0] and fp_mant[1].
*/
static int
fpu_stof(fp, i)
register struct fpn *fp;
register u_int i;
{
register int exp;
register u_int frac, f0, f1;
#define SNG_SHIFT (SNG_FRACBITS - FP_LG)
exp = (i >> (32 - 1 - SNG_EXPBITS)) & mask(SNG_EXPBITS);
frac = i & mask(SNG_FRACBITS);
f0 = frac >> SNG_SHIFT;
f1 = frac << (32 - SNG_SHIFT);
FP_TOF(exp, SNG_EXP_BIAS, frac, f0, f1, 0, 0);
}
/*
* 64-bit double -> fpn.
* We assume this uses at most (96-FP_LG) bits.
*/
static int
fpu_dtof(fp, i, j)
register struct fpn *fp;
register u_int i, j;
{
register int exp;
register u_int frac, f0, f1, f2;
#define DBL_SHIFT (DBL_FRACBITS - 32 - FP_LG)
exp = (i >> (32 - 1 - DBL_EXPBITS)) & mask(DBL_EXPBITS);
frac = i & mask(DBL_FRACBITS - 32);
f0 = frac >> DBL_SHIFT;
f1 = (frac << (32 - DBL_SHIFT)) | (j >> DBL_SHIFT);
f2 = j << (32 - DBL_SHIFT);
frac |= j;
FP_TOF(exp, DBL_EXP_BIAS, frac, f0, f1, f2, 0);
}
/*
* 96-bit extended -> fpn.
*/
static int
fpu_xtof(fp, i, j, k)
register struct fpn *fp;
register u_int i, j, k;
{
register int exp;
register u_int frac, f0, f1, f2;
#define EXT_SHIFT (EXT_FRACBITS - 1 - 32 - FP_LG)
exp = (i >> (32 - 1 - EXT_EXPBITS)) & mask(EXT_EXPBITS);
f0 = j >> EXT_SHIFT;
f1 = (j << (32 - EXT_SHIFT)) | (k >> EXT_SHIFT);
f2 = k << (32 - EXT_SHIFT);
frac = j | k;
/* m68k extended does not imply denormal by exp==0 */
if (exp == 0) {
if (frac == 0)
return (FPC_ZERO);
fp->fp_exp = - EXT_EXP_BIAS;
fp->fp_mant[0] = f0;
fp->fp_mant[1] = f1;
fp->fp_mant[2] = f2;
fp->fp_mant[3] = 0;
fpu_norm(fp);
return (FPC_NUM);
}
if (exp == (2 * EXT_EXP_BIAS + 1)) {
if (frac == 0)
return (FPC_INF);
fp->fp_mant[0] = f0;
fp->fp_mant[1] = f1;
fp->fp_mant[2] = f2;
fp->fp_mant[3] = 0;
return (FPC_QNAN);
}
fp->fp_exp = exp - EXT_EXP_BIAS;
fp->fp_mant[0] = FP_1 | f0;
fp->fp_mant[1] = f1;
fp->fp_mant[2] = f2;
fp->fp_mant[3] = 0;
return (FPC_NUM);
}
/*
* Explode the contents of a memory operand.
*/
void
fpu_explode(fe, fp, type, space)
register struct fpemu *fe;
register struct fpn *fp;
int type;
register u_int *space;
{
register u_int s;
s = space[0];
fp->fp_sign = s >> 31;
fp->fp_sticky = 0;
switch (type) {
case FTYPE_BYT:
s >>= 8;
case FTYPE_WRD:
s >>= 16;
case FTYPE_LNG:
s = fpu_itof(fp, s);
break;
case FTYPE_SNG:
s = fpu_stof(fp, s);
break;
case FTYPE_DBL:
s = fpu_dtof(fp, s, space[1]);
break;
case FTYPE_EXT:
s = fpu_xtof(fp, s, space[1], space[2]);
break;
default:
panic("fpu_explode");
}
if (s == FPC_QNAN && (fp->fp_mant[0] & FP_QUIETBIT) == 0) {
/*
* Input is a signalling NaN. All operations that return
* an input NaN operand put it through a ``NaN conversion'',
* which basically just means ``turn on the quiet bit''.
* We do this here so that all NaNs internally look quiet
* (we can tell signalling ones by their class).
*/
fp->fp_mant[0] |= FP_QUIETBIT;
fe->fe_fpsr |= FPSR_SNAN; /* assert SNAN exception */
s = FPC_SNAN;
}
fp->fp_class = s;
}
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