| Elliott Hughes | a0ee078 | 2013-01-30 19:06:37 -0800 | [diff] [blame] | 1 | /*- |
| 2 | * Copyright (c) 2008 David Schultz <das@FreeBSD.ORG> |
| 3 | * All rights reserved. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions |
| 7 | * are met: |
| 8 | * 1. Redistributions of source code must retain the above copyright |
| 9 | * notice, this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright |
| 11 | * notice, this list of conditions and the following disclaimer in the |
| 12 | * documentation and/or other materials provided with the distribution. |
| 13 | * |
| 14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| 15 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 16 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 17 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| 18 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| 19 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| 20 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 21 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| 22 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| 23 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| 24 | * SUCH DAMAGE. |
| 25 | */ |
| 26 | |
| 27 | #include <sys/cdefs.h> |
| 28 | __FBSDID("$FreeBSD$"); |
| 29 | |
| 30 | #include <float.h> |
| 31 | #include <math.h> |
| 32 | |
| 33 | #include "fpmath.h" |
| 34 | |
| 35 | #if LDBL_MAX_EXP != 0x4000 |
| 36 | /* We also require the usual bias, min exp and expsign packing. */ |
| 37 | #error "Unsupported long double format" |
| 38 | #endif |
| 39 | |
| 40 | #define BIAS (LDBL_MAX_EXP - 1) |
| 41 | |
| 42 | static const float |
| 43 | shift[2] = { |
| 44 | #if LDBL_MANT_DIG == 64 |
| 45 | 0x1.0p63, -0x1.0p63 |
| 46 | #elif LDBL_MANT_DIG == 113 |
| 47 | 0x1.0p112, -0x1.0p112 |
| 48 | #else |
| 49 | #error "Unsupported long double format" |
| 50 | #endif |
| 51 | }; |
| 52 | static const float zero[2] = { 0.0, -0.0 }; |
| 53 | |
| 54 | long double |
| 55 | rintl(long double x) |
| 56 | { |
| 57 | union IEEEl2bits u; |
| 58 | uint32_t expsign; |
| 59 | int ex, sign; |
| 60 | |
| 61 | u.e = x; |
| 62 | expsign = u.xbits.expsign; |
| 63 | ex = expsign & 0x7fff; |
| 64 | |
| 65 | if (ex >= BIAS + LDBL_MANT_DIG - 1) { |
| 66 | if (ex == BIAS + LDBL_MAX_EXP) |
| 67 | return (x + x); /* Inf, NaN, or unsupported format */ |
| 68 | return (x); /* finite and already an integer */ |
| 69 | } |
| 70 | sign = expsign >> 15; |
| 71 | |
| 72 | /* |
| 73 | * The following code assumes that intermediate results are |
| 74 | * evaluated in long double precision. If they are evaluated in |
| 75 | * greater precision, double rounding may occur, and if they are |
| 76 | * evaluated in less precision (as on i386), results will be |
| 77 | * wildly incorrect. |
| 78 | */ |
| 79 | x += shift[sign]; |
| 80 | x -= shift[sign]; |
| 81 | |
| 82 | /* |
| 83 | * If the result is +-0, then it must have the same sign as x, but |
| 84 | * the above calculation doesn't always give this. Fix up the sign. |
| 85 | */ |
| 86 | if (ex < BIAS && x == 0.0L) |
| 87 | return (zero[sign]); |
| 88 | |
| 89 | return (x); |
| 90 | } |