1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 
  26 /*
  27  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 #pragma weak __scalbnl = scalbnl
  32 
  33 #include "libm.h"
  34 #include <float.h>                        /* LDBL_MAX, LDBL_MIN */
  35 #include <stdlib.h>                       /* abs */
  36 
  37 #if defined(__sparc)
  38 #define XSET_EXP(k, x)          ((int *)&x)[0] = (((int *)&x)[0] & \
  39             ~0x7fff0000) | (k << 16)
  40 #define ISINFNANL(k, x)         (k == 0x7fff)
  41 #define XTWOT_OFFSET            113
  42 
  43 /* 2^113 */
  44 static const long double xtwot = 10384593717069655257060992658440192.0L;
  45 /* 2^-114 */
  46 static const long double twomtm1 = 4.814824860968089632639944856462318296E-35L;
  47 #elif defined(__x86)
  48 #define XSET_EXP(k, x)          ((int *)&x)[2] = (((int *)&x)[2] & ~0x7fff) | k
  49 #if defined(HANDLE_UNSUPPORTED)
  50 #define ISINFNANL(k, x)         (k == 0x7fff || k != 0 && (((int *)&x)[1] & \
  51         0x80000000) == 0)
  52 #else
  53 #define ISINFNANL(k, x)         (k == 0x7fff)
  54 #endif
  55 #define XTWOT_OFFSET            64
  56 
  57 static const long double xtwot = 18446744073709551616.0L,       /* 2^64 */
  58         twomtm1 = 2.7105054312137610850186E-20L;                /* 2^-65 */
  59 #endif
  60 
  61 long double
  62 scalbnl(long double x, int n)
  63 {
  64         int k = XBIASED_EXP(x);
  65 
  66         if (ISINFNANL(k, x))
  67                 return (x + x);
  68 
  69         if (ISZEROL(x) || n == 0)
  70                 return (x);
  71 
  72         if (k == 0) {
  73                 x *= xtwot;
  74                 k = XBIASED_EXP(x) - XTWOT_OFFSET;
  75         }
  76 
  77         if ((unsigned)abs(n) >= 131072)      /* cast to unsigned for -2^31 */
  78                 n >>= 1;          /* avoid subsequent integer overflow */
  79 
  80         k += n;
  81 
  82         if (k > 0x7ffe)
  83                 return (LDBL_MAX * copysignl(LDBL_MAX, x));
  84 
  85         if (k <= -XTWOT_OFFSET - 1)
  86                 return (LDBL_MIN * copysignl(LDBL_MIN, x));
  87 
  88         if (k > 0) {
  89                 XSET_EXP(k, x);
  90                 return (x);
  91         }
  92 
  93         k += XTWOT_OFFSET + 1;
  94         XSET_EXP(k, x);
  95         return (x * twomtm1);
  96 }