1 /* $NetBSD: s_scalbnl.c,v 1.1 2011/07/26 16:10:16 joerg Exp $ */
4 * Copyright (c) 2011 The NetBSD Foundation, Inc.
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Joerg Sonnenberger.
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
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.
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.
34 #include <machine/ieee.h>
36 #ifdef __HAVE_LONG_DOUBLE
38 #if LDBL_MANT_DIG == 64
39 #define FROM_UNDERFLOW 0x1p65L
40 #define TO_UNDERFLOW 0x1p-65L
41 #elif LDBL_MANT_DIG == 113
42 #define FROM_UNDERFLOW 0x1p114L
43 #define TO_UNDERFLOW 0x1p-114L
45 #error Unsupported long double format
49 scalbnl(long double x, int n)
53 /* Trivial cases first */
54 if (n == 0 || x == 0.0L)
59 /* NaN and infinite don't change either, but trigger exception */
60 if (u.extu_ext.ext_exp == EXT_EXP_INFNAN)
63 /* Protect against integer overflow in calculation of new exponent */
64 if (n > LDBL_MAX_EXP - LDBL_MIN_EXP + LDBL_MANT_DIG)
66 if (n < LDBL_MAX_EXP - LDBL_MIN_EXP + LDBL_MANT_DIG)
69 /* Scale denormalized numbers slightly, so that they are normal */
70 if (u.extu_ext.ext_exp == 0) {
71 u.extu_ld *= FROM_UNDERFLOW;
72 n -= LDBL_MANT_DIG + 1;
75 n += u.extu_ext.ext_exp;
76 if (n >= LDBL_MAX_EXP + EXT_EXP_BIAS)
78 /* Positive exponent (incl. bias) means normal result */
80 u.extu_ext.ext_exp = n;
83 /* Shift the exponent and let the multiply below handle subnormal */
84 n += LDBL_MANT_DIG + 1;
87 u.extu_ext.ext_exp = n;
88 return u.extu_ld * TO_UNDERFLOW;
91 return LDBL_MIN * copysignl(LDBL_MIN, x);
94 return LDBL_MAX * copysignl(LDBL_MAX, x);