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: src/lib/msun/src/s_rintl.c,v 1.5 2008/02/22 11:59:05 bde Exp $"); 29 30 #include <float.h> 31 #include <openlibm.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 u_int32_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 } 91