140 lines
4.6 KiB
C
140 lines
4.6 KiB
C
/*
|
|
* poly_2xm1.c
|
|
*
|
|
* Function to compute 2^x-1 by a polynomial approximation.
|
|
*
|
|
*
|
|
* Copyright (C) 1992,1993,1994
|
|
* W. Metzenthen, 22 Parker St, Ormond, Vic 3163,
|
|
* Australia. E-mail billm@vaxc.cc.monash.edu.au
|
|
* All rights reserved.
|
|
*
|
|
* This copyright notice covers the redistribution and use of the
|
|
* FPU emulator developed by W. Metzenthen. It covers only its use
|
|
* in the 386BSD, FreeBSD and NetBSD operating systems. Any other
|
|
* use is not permitted under this copyright.
|
|
*
|
|
* 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 include information specifying
|
|
* that source code for the emulator is freely available and include
|
|
* either:
|
|
* a) an offer to provide the source code for a nominal distribution
|
|
* fee, or
|
|
* b) list at least two alternative methods whereby the source
|
|
* can be obtained, e.g. a publically accessible bulletin board
|
|
* and an anonymous ftp site from which the software can be
|
|
* downloaded.
|
|
* 3. All advertising materials specifically mentioning features or use of
|
|
* this emulator must acknowledge that it was developed by W. Metzenthen.
|
|
* 4. The name of W. Metzenthen may not be used to endorse or promote
|
|
* products derived from this software without specific prior written
|
|
* permission.
|
|
*
|
|
* THIS SOFTWARE IS PROVIDED ``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
|
|
* W. METZENTHEN 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.
|
|
*
|
|
*
|
|
* The purpose of this copyright, based upon the Berkeley copyright, is to
|
|
* ensure that the covered software remains freely available to everyone.
|
|
*
|
|
* The software (with necessary differences) is also available, but under
|
|
* the terms of the GNU copyleft, for the Linux operating system and for
|
|
* the djgpp ms-dos extender.
|
|
*
|
|
* W. Metzenthen June 1994.
|
|
*
|
|
*
|
|
* $Id: poly_2xm1.c,v 1.6 1997/02/22 09:29:14 peter Exp $
|
|
*
|
|
*/
|
|
|
|
#include <gnu/i386/fpemul/reg_constant.h>
|
|
|
|
|
|
|
|
#define HIPOWER 13
|
|
static unsigned short lterms[HIPOWER][4] =
|
|
{
|
|
{0x79b5, 0xd1cf, 0x17f7, 0xb172},
|
|
{0x1b56, 0x058b, 0x7bff, 0x3d7f},
|
|
{0x8bb0, 0x8250, 0x846b, 0x0e35},
|
|
{0xbc65, 0xf747, 0x556d, 0x0276},
|
|
{0x17cb, 0x9e39, 0x61ff, 0x0057},
|
|
{0xe018, 0x9776, 0x1848, 0x000a},
|
|
{0x66f2, 0xff30, 0xffe5, 0x0000},
|
|
{0x682f, 0xffb6, 0x162b, 0x0000},
|
|
{0xb7ca, 0x2956, 0x01b5, 0x0000},
|
|
{0xcd3e, 0x4817, 0x001e, 0x0000},
|
|
{0xb7e2, 0xecbe, 0x0001, 0x0000},
|
|
{0x0ed5, 0x1a27, 0x0000, 0x0000},
|
|
{0x101d, 0x0222, 0x0000, 0x0000},
|
|
};
|
|
|
|
|
|
/*--- poly_2xm1() -----------------------------------------------------------+
|
|
| |
|
|
+---------------------------------------------------------------------------*/
|
|
int
|
|
poly_2xm1(FPU_REG * arg, FPU_REG * result)
|
|
{
|
|
short exponent;
|
|
long long Xll;
|
|
FPU_REG accum;
|
|
|
|
|
|
exponent = arg->exp - EXP_BIAS;
|
|
|
|
if (arg->tag == TW_Zero) {
|
|
/* Return 0.0 */
|
|
reg_move(&CONST_Z, result);
|
|
return 0;
|
|
}
|
|
if (exponent >= 0) { /* Can't hack a number >= 1.0 */
|
|
arith_invalid(result); /* Number too large */
|
|
return 1;
|
|
}
|
|
if (arg->sign != SIGN_POS) { /* Can't hack a number < 0.0 */
|
|
arith_invalid(result); /* Number negative */
|
|
return 1;
|
|
}
|
|
if (exponent < -64) {
|
|
reg_move(&CONST_LN2, result);
|
|
return 0;
|
|
}
|
|
*(unsigned *) &Xll = arg->sigl;
|
|
*(((unsigned *) &Xll) + 1) = arg->sigh;
|
|
if (exponent < -1) {
|
|
/* shift the argument right by the required places */
|
|
if (shrx(&Xll, -1 - exponent) >= (unsigned)0x80000000)
|
|
Xll++; /* round up */
|
|
}
|
|
*(short *) &(accum.sign) = 0; /* will be a valid positive nr with
|
|
* expon = 0 */
|
|
accum.exp = 0;
|
|
|
|
/* Do the basic fixed point polynomial evaluation */
|
|
polynomial((unsigned *) &accum.sigl, (unsigned *) &Xll, lterms, HIPOWER - 1);
|
|
|
|
/* Convert to 64 bit signed-compatible */
|
|
accum.exp += EXP_BIAS - 1;
|
|
|
|
reg_move(&accum, result);
|
|
|
|
normalize(result);
|
|
|
|
return 0;
|
|
|
|
}
|