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 #define BIAS (LDBL_MAX_EXP - 1) 36 37 static const float 38 shift[2] = { 39 #if LDBL_MANT_DIG == 64 40 0x1.0p63, -0x1.0p63 41 #elif LDBL_MANT_DIG == 113 42 0x1.0p112, -0x1.0p112 43 #else 44 #error "Unsupported long double format" 45 #endif 46 }; 47 48 long double 49 rintl(long double x) 50 { 51 union IEEEl2bits u; 52 short sign; 53 54 u.e = x; 55 56 if (u.bits.exp >= BIAS + LDBL_MANT_DIG - 1) { 57 /* 58 * The biased exponent is greater than the number of digits 59 * in the mantissa, so x is inf, NaN, or an integer. 60 */ 61 return (x); 62 } 63 sign = u.bits.sign; 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 may occur, and if they are 69 * evaluated in less precision (as on i386), results will be 70 * wildly incorrect. 71 */ 72 x += shift[sign]; 73 x -= shift[sign]; 74 75 /* 76 * If the result is +-0, then it must have the same sign as x, but 77 * the above calculation doesn't always give this. Fix up the sign. 78 */ 79 if (x == 0.0L) 80 return (sign ? -0.0L : 0.0L); 81 return (x); 82 } 83