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 __scalblnl = scalblnl
  32 
  33 #include "libm.h"
  34 #include <float.h>                        /* LDBL_MAX, LDBL_MIN */
  35 
  36 #if defined(__sparc)
  37 #define XSET_EXP(k, x)                  ((int *)&x)[0] = (((int *)&x)[0] & \
  38             ~0x7fff0000) | (k << 16)
  39 #define ISINFNANL(k, x)                 (k == 0x7fff)
  40 #define XTWOT_OFFSET                    113
  41 
  42 static const long double
  43         xtwot = 10384593717069655257060992658440192.0L, /* 2^113 */
  44         twomtm1 = 4.814824860968089632639944856462318296E-35L;  /* 2^-114 */
  45 #elif defined(__x86)
  46 #define XSET_EXP(k, x)                  ((int *)&x)[2] = (((int *)&x)[2] & \
  47             ~0x7fff) | k
  48 #if defined(HANDLE_UNSUPPORTED)
  49 #define ISINFNANL(k, x)         (k == 0x7fff || (k != 0 && \
  50         (((int *)&x)[1] & 0x80000000) == 0))
  51 #else
  52 #define ISINFNANL(k, x)                 (k == 0x7fff)
  53 #endif
  54 #define XTWOT_OFFSET                    64
  55 
  56 static const long double xtwot = 18446744073709551616.0L,       /* 2^64 */
  57         twomtm1 = 2.7105054312137610850186E-20L;                /* 2^-65 */
  58 #endif
  59 
  60 long double
  61 scalblnl(long double x, long n)
  62 {
  63         int k = XBIASED_EXP(x);
  64 
  65         if (ISINFNANL(k, x))
  66                 return (x + x);
  67 
  68         if (ISZEROL(x) || n == 0)
  69                 return (x);
  70 
  71         if (k == 0) {
  72                 x *= xtwot;
  73                 k = XBIASED_EXP(x) - XTWOT_OFFSET;
  74         }
  75 
  76         k += (int)n;
  77 
  78         if (n > 50000 || k > 0x7ffe)
  79                 return (LDBL_MAX * copysignl(LDBL_MAX, x));
  80 
  81         if (n < -50000 || k <= -XTWOT_OFFSET - 1)
  82                 return (LDBL_MIN * copysignl(LDBL_MIN, x));
  83 
  84         if (k > 0) {
  85                 XSET_EXP(k, x);
  86                 return (x);
  87         }
  88 
  89         k += XTWOT_OFFSET + 1;
  90         XSET_EXP(k, x);
  91         return (x * twomtm1);
  92 }