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      1 /*	$NetBSD: s_ilogbl.c,v 1.4 2016/08/26 08:20:31 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 1.4 2016/08/26 08:20:31 christos Exp $");
     34 
     35 #include "namespace.h"
     36 
     37 #include <float.h>
     38 #include <math.h>
     39 #define __TEST_FENV
     40 #include <fenv.h>
     41 #ifndef __HAVE_FENV
     42 #define feraiseexcept(a)
     43 #endif
     44 #include <machine/ieee.h>
     45 
     46 #ifdef __HAVE_LONG_DOUBLE
     47 
     48 #if LDBL_MANT_DIG == 64
     49 #define	FROM_UNDERFLOW	0x1p65L
     50 #elif LDBL_MANT_DIG == 113
     51 #define	FROM_UNDERFLOW	0x1p114L
     52 #else
     53 #error Unsupported long double format
     54 #endif
     55 
     56 int
     57 ilogbl(long double x)
     58 {
     59 	union ieee_ext_u u;
     60 
     61 	if (x == 0.0L) {
     62 		feraiseexcept(FE_INVALID);
     63 		return FP_ILOGB0;	/* ilogbl(0) = 0x80000001 */
     64 	}
     65 
     66 	u.extu_ld = x;
     67 
     68 	if (u.extu_ext.ext_exp == EXT_EXP_INFNAN) {
     69 		feraiseexcept(FE_INVALID);
     70 		return isnan(x) ? FP_ILOGBNAN : INT_MAX;
     71 	}
     72 
     73 	if (u.extu_ext.ext_exp == 0) {
     74 		/*
     75 		 * Scale denormalized numbers slightly,
     76 		 * so that they are normal.
     77 		 */
     78 		u.extu_ld *= FROM_UNDERFLOW;
     79 		return u.extu_ext.ext_exp - EXT_EXP_BIAS - LDBL_MANT_DIG - 1;
     80 	}
     81 	return u.extu_ext.ext_exp - EXT_EXP_BIAS;
     82 
     83 }
     84 
     85 #endif
     86