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Diffstat (limited to 'sys/gnu/fpemul/poly_2xm1.c')
| -rw-r--r-- | sys/gnu/fpemul/poly_2xm1.c | 141 |
1 files changed, 141 insertions, 0 deletions
diff --git a/sys/gnu/fpemul/poly_2xm1.c b/sys/gnu/fpemul/poly_2xm1.c new file mode 100644 index 0000000000000..d4da1bb815270 --- /dev/null +++ b/sys/gnu/fpemul/poly_2xm1.c @@ -0,0 +1,141 @@ +/* + * 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 1.3 1994/06/10 07:44:32 rich Exp $ + * + */ + +#include "exception.h" +#include "reg_constant.h" +#include "fpu_emu.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; + +} |