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 static const long double 36 shift[2]={ 37 #if LDBL_MANT_DIG == 64 38 0x1.0p63, -0x1.0p63 39 #elif LDBL_MANT_DIG == 113 40 0x1.0p112, -0x1.0p112 41 #else 42 #error "Unsupported long double format" 43 #endif 44 }; 45 46 long double 47 rintl(long double x) 48 { 49 union IEEEl2bits u; 50 short sign; 51 52 u.e = x; 53 54 if (u.bits.exp >= LDBL_MANT_DIG + LDBL_MAX_EXP - 2) { 55 /* 56 * The biased exponent is greater than the number of digits 57 * in the mantissa, so x is inf, NaN, or an integer. 58 */ 59 if (u.bits.exp == 2 * LDBL_MAX_EXP - 1) 60 return (x + x); /* inf or NaN */ 61 else 62 return (x); 63 } 64 65 /* 66 * The following code assumes that intermediate results are 67 * evaluated in long double precision. If they are evaluated in 68 * greater precision, double rounding will occur, and if they are 69 * evaluated in less precision (as on i386), results will be 70 * wildly incorrect. 71 */ 72 sign = u.bits.sign; 73 u.e = shift[sign] + x; 74 u.e -= shift[sign]; 75 u.bits.sign = sign; 76 return (u.e); 77 } 78