1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2008 David Schultz <das@FreeBSD.ORG> 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 #include <float.h> 33 #include <math.h> 34 35 #include "fpmath.h" 36 37 #if LDBL_MAX_EXP != 0x4000 38 /* We also require the usual bias, min exp and expsign packing. */ 39 #error "Unsupported long double format" 40 #endif 41 42 #define BIAS (LDBL_MAX_EXP - 1) 43 44 static const float 45 shift[2] = { 46 #if LDBL_MANT_DIG == 64 47 0x1.0p63, -0x1.0p63 48 #elif LDBL_MANT_DIG == 113 49 0x1.0p112, -0x1.0p112 50 #else 51 #error "Unsupported long double format" 52 #endif 53 }; 54 static const float zero[2] = { 0.0, -0.0 }; 55 56 long double 57 rintl(long double x) 58 { 59 union IEEEl2bits u; 60 uint32_t expsign; 61 int ex, sign; 62 63 u.e = x; 64 expsign = u.xbits.expsign; 65 ex = expsign & 0x7fff; 66 67 if (ex >= BIAS + LDBL_MANT_DIG - 1) { 68 if (ex == BIAS + LDBL_MAX_EXP) 69 return (x + x); /* Inf, NaN, or unsupported format */ 70 return (x); /* finite and already an integer */ 71 } 72 sign = expsign >> 15; 73 74 /* 75 * The following code assumes that intermediate results are 76 * evaluated in long double precision. If they are evaluated in 77 * greater precision, double rounding may occur, and if they are 78 * evaluated in less precision (as on i386), results will be 79 * wildly incorrect. 80 */ 81 x += shift[sign]; 82 x -= shift[sign]; 83 84 /* 85 * If the result is +-0, then it must have the same sign as x, but 86 * the above calculation doesn't always give this. Fix up the sign. 87 */ 88 if (ex < BIAS && x == 0.0L) 89 return (zero[sign]); 90 91 return (x); 92 } 93