projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| f24c459c JH |
1 | /* |
| 2 | * poly_2xm1.c | |
| 3 | * | |
| 4 | * Function to compute 2^x-1 by a polynomial approximation. | |
| 5 | * | |
| 6 | * | |
| 7 | * Copyright (C) 1992, 1993 W. Metzenthen, 22 Parker St, Ormond, | |
| 8 | * Vic 3163, Australia. | |
| 9 | * E-mail apm233m@vaxc.cc.monash.edu.au | |
| 10 | * All rights reserved. | |
| 11 | * | |
| 12 | * This copyright notice covers the redistribution and use of the | |
| 13 | * FPU emulator developed by W. Metzenthen. It covers only its use | |
| 14 | * in the 386BSD operating system. Any other use is not permitted | |
| 15 | * under this copyright. | |
| 16 | * | |
| 17 | * Redistribution and use in source and binary forms, with or without | |
| 18 | * modification, are permitted provided that the following conditions | |
| 19 | * are met: | |
| 20 | * 1. Redistributions of source code must retain the above copyright | |
| 21 | * notice, this list of conditions and the following disclaimer. | |
| 22 | * 2. Redistributions in binary form must include information specifying | |
| 23 | * that source code for the emulator is freely available and include | |
| 24 | * either: | |
| 25 | * a) an offer to provide the source code for a nominal distribution | |
| 26 | * fee, or | |
| 27 | * b) list at least two alternative methods whereby the source | |
| 28 | * can be obtained, e.g. a publically accessible bulletin board | |
| 29 | * and an anonymous ftp site from which the software can be | |
| 30 | * downloaded. | |
| 31 | * 3. All advertising materials specifically mentioning features or use of | |
| 32 | * this emulator must acknowledge that it was developed by W. Metzenthen. | |
| 33 | * 4. The name of W. Metzenthen may not be used to endorse or promote | |
| 34 | * products derived from this software without specific prior written | |
| 35 | * permission. | |
| 36 | * | |
| 37 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, | |
| 38 | * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY | |
| 39 | * AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL | |
| 40 | * W. METZENTHEN BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, | |
| 41 | * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, | |
| 42 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR | |
| 43 | * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF | |
| 44 | * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING | |
| 45 | * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS | |
| 46 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 47 | * | |
| 48 | */ | |
| 49 | ||
| 50 | #include "exception.h" | |
| 51 | #include "reg_constant.h" | |
| 52 | #include "fpu_emu.h" | |
| 53 | ||
| 54 | ||
| 55 | ||
| 56 | #define HIPOWER 13 | |
| 57 | static unsigned short lterms[HIPOWER][4] = | |
| 58 | { | |
| 59 | {0x79b5, 0xd1cf, 0x17f7, 0xb172}, | |
| 60 | {0x1b56, 0x058b, 0x7bff, 0x3d7f}, | |
| 61 | {0x8bb0, 0x8250, 0x846b, 0x0e35}, | |
| 62 | {0xbc65, 0xf747, 0x556d, 0x0276}, | |
| 63 | {0x17cb, 0x9e39, 0x61ff, 0x0057}, | |
| 64 | {0xe018, 0x9776, 0x1848, 0x000a}, | |
| 65 | {0x66f2, 0xff30, 0xffe5, 0x0000}, | |
| 66 | {0x682f, 0xffb6, 0x162b, 0x0000}, | |
| 67 | {0xb7ca, 0x2956, 0x01b5, 0x0000}, | |
| 68 | {0xcd3e, 0x4817, 0x001e, 0x0000}, | |
| 69 | {0xb7e2, 0xecbe, 0x0001, 0x0000}, | |
| 70 | {0x0ed5, 0x1a27, 0x0000, 0x0000}, | |
| 71 | {0x101d, 0x0222, 0x0000, 0x0000}, | |
| 72 | }; | |
| 73 | ||
| 74 | ||
| 75 | /*--- poly_2xm1() -----------------------------------------------------------+ | |
| 76 | | | | |
| 77 | +---------------------------------------------------------------------------*/ | |
| 78 | int | |
| 79 | poly_2xm1(FPU_REG * arg, FPU_REG * result) | |
| 80 | { | |
| 81 | short exponent; | |
| 82 | long long Xll; | |
| 83 | FPU_REG accum; | |
| 84 | ||
| 85 | ||
| 86 | exponent = arg->exp - EXP_BIAS; | |
| 87 | ||
| 88 | if (arg->tag == TW_Zero) { | |
| 89 | /* Return 0.0 */ | |
| 90 | reg_move(&CONST_Z, result); | |
| 91 | return 0; | |
| 92 | } | |
| 93 | if (exponent >= 0) { /* Can't hack a number >= 1.0 */ | |
| 94 | arith_invalid(result); /* Number too large */ | |
| 95 | return 1; | |
| 96 | } | |
| 97 | if (arg->sign != SIGN_POS) { /* Can't hack a number < 0.0 */ | |
| 98 | arith_invalid(result); /* Number negative */ | |
| 99 | return 1; | |
| 100 | } | |
| 101 | if (exponent < -64) { | |
| 102 | reg_move(&CONST_LN2, result); | |
| 103 | return 0; | |
| 104 | } | |
| 105 | *(unsigned *) &Xll = arg->sigl; | |
| 106 | *(((unsigned *) &Xll) + 1) = arg->sigh; | |
| 107 | if (exponent < -1) { | |
| 108 | /* shift the argument right by the required places */ | |
| 109 | if (shrx(&Xll, -1 - exponent) >= (unsigned)0x80000000) | |
| 110 | Xll++; /* round up */ | |
| 111 | } | |
| 112 | *(short *) &(accum.sign) = 0; /* will be a valid positive nr with | |
| 113 | * expon = 0 */ | |
| 114 | accum.exp = 0; | |
| 115 | ||
| 116 | /* Do the basic fixed point polynomial evaluation */ | |
| 117 | polynomial((unsigned *) &accum.sigl, (unsigned *) &Xll, lterms, HIPOWER - 1); | |
| 118 | ||
| 119 | /* Convert to 64 bit signed-compatible */ | |
| 120 | accum.exp += EXP_BIAS - 1; | |
| 121 | ||
| 122 | reg_move(&accum, result); | |
| 123 | ||
| 124 | normalize(result); | |
| 125 | ||
| 126 | return 0; | |
| 127 | ||
| 128 | } |