usr/src/lib/libm/common/LD/scalbl.c

   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  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29
  30 #pragma weak __scalbl = scalbl
  31
  32 /*
  33  * scalbl(x,n): return x * 2**n by manipulating exponent.
  34  */
  35
  36 #include "libm.h"
  37 #include "longdouble.h"
  38
  39 #include <sys/isa_defs.h>
  40
  41 long double
  42 scalbl(long double x, long double fn) {
  43         int *py = (int *) &fn, n;
  44         long double z;
  45
  46         if (isnanl(x) || isnanl(fn))
  47                 return x * fn;
  48
  49         /* fn is +/-Inf */
  50 #if defined(_BIG_ENDIAN)
  51         if ((py[0] & 0x7fff0000) == 0x7fff0000) {
  52                 if ((py[0] & 0x80000000) != 0)
  53 #else
  54         if ((py[2] & 0x7fff) == 0x7fff) {
  55                 if ((py[2] & 0x8000) != 0)
  56 #endif
  57                         return x / (-fn);
  58                 else
  59                         return x * fn;
  60         }
  61         if (rintl(fn) != fn)
  62                 return (fn - fn) / (fn - fn);
  63         if (fn > 65000.0L)
  64                 z = scalbnl(x, 65000);
  65         else if (-fn > 65000.0L)
  66                 z = scalbnl(x, -65000);
  67         else {
  68                 n = (int) fn;
  69                 z = scalbnl(x, n);
  70         }
  71         return z;
  72 }