1 /* $NetBSD: s_ilogbl.c,v 1.3 2016/08/24 10:03:32 christos 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 1.3 2016/08/24 10:03:32 christos Exp $"); 34 35 #include "namespace.h" 36 37 #include <float.h> 38 #include <math.h> 39 #include <fenv.h> 40 #include <machine/ieee.h> 41 42 #ifdef __HAVE_LONG_DOUBLE 43 44 #if LDBL_MANT_DIG == 64 45 #define FROM_UNDERFLOW 0x1p65L 46 #elif LDBL_MANT_DIG == 113 47 #define FROM_UNDERFLOW 0x1p114L 48 #else 49 #error Unsupported long double format 50 #endif 51 52 int 53 ilogbl(long double x) 54 { 55 union ieee_ext_u u; 56 57 if (x == 0.0L) { 58 feraiseexcept(FE_INVALID); 59 return FP_ILOGB0; /* ilogbl(0) = 0x80000001 */ 60 } 61 62 u.extu_ld = x; 63 64 if (u.extu_ext.ext_exp == EXT_EXP_INFNAN) { 65 feraiseexcept(FE_INVALID); 66 return isnan(x) ? FP_ILOGBNAN : INT_MAX; 67 } 68 69 if (u.extu_ext.ext_exp == 0) { 70 /* 71 * Scale denormalized numbers slightly, 72 * so that they are normal. 73 */ 74 u.extu_ld *= FROM_UNDERFLOW; 75 return u.extu_ext.ext_exp - EXT_EXP_BIAS - LDBL_MANT_DIG - 1; 76 } 77 return u.extu_ext.ext_exp - EXT_EXP_BIAS; 78 79 } 80 81 #endif 82