1 /* $NetBSD: s_ilogbl.c,v 1.2 2013/02/09 22:56:00 matt Exp $ */ 2 3 /*- 4 * Copyright (c) 2011 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Joerg Sonnenberger. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __RCSID("$NetBSD: s_ilogbl.c,v 1.2 2013/02/09 22:56:00 matt Exp $"); 34 35 #include "namespace.h" 36 37 #include <float.h> 38 #include <math.h> 39 #include <machine/ieee.h> 40 41 #ifdef __HAVE_LONG_DOUBLE 42 43 #if LDBL_MANT_DIG == 64 44 #define FROM_UNDERFLOW 0x1p65L 45 #elif LDBL_MANT_DIG == 113 46 #define FROM_UNDERFLOW 0x1p114L 47 #else 48 #error Unsupported long double format 49 #endif 50 51 int 52 ilogbl(long double x) 53 { 54 union ieee_ext_u u; 55 56 if (x == 0.0L) 57 return FP_ILOGB0; /* ilogbl(0) = 0x80000001 */ 58 59 u.extu_ld = x; 60 61 if (u.extu_ext.ext_exp == EXT_EXP_INFNAN) 62 return FP_ILOGBNAN; /* inf too */ 63 64 if (u.extu_ext.ext_exp == 0) { 65 /* 66 * Scale denormalized numbers slightly, 67 * so that they are normal. 68 */ 69 u.extu_ld *= FROM_UNDERFLOW; 70 return u.extu_ext.ext_exp - EXT_EXP_BIAS - LDBL_MANT_DIG - 1; 71 } 72 return u.extu_ext.ext_exp - EXT_EXP_BIAS; 73 74 } 75 76 #endif 77