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 __ilogbl = ilogbl
  31 
  32 #include "libm.h"
  33 #include "xpg6.h"       /* __xpg6 */
  34 
  35 #if defined(__sparc)
  36 #define ISNORMALL(k, x) (k != 0x7fff)                   /* assuming k != 0 */
  37 #define X86PDNRM(k, x)
  38 #define XSCALE_OFFSET   0x406f                          /* 0x3fff + 112 */
  39 static const long double xscale = 5192296858534827628530496329220096.0L;
  40                                                                 /* 2^112 */
  41 #elif defined(__x86)
  42 /*
  43  * if pseudo-denormal, replace by the equivalent normal
  44  */
  45 #define X86PDNRM(k, x)  if (k == 0 && (((int *) &x)[1] & 0x80000000) != 0) \
  46                                 ((int *) &x)[2] |= k = 1
  47 #if defined(HANDLE_UNSUPPORTED)                         /* assuming k != 0 */
  48 #define ISNORMALL(k, x) (k != 0x7fff && (((int *) &x)[1] & 0x80000000) != 0)
  49 #else
  50 #define ISNORMALL(k, x) (k != 0x7fff)
  51 #endif
  52 #define XSCALE_OFFSET   0x403e                          /* 0x3fff + 63 */
  53 static const long double xscale = 9223372036854775808.0L;       /* 2^63 */
  54 #endif
  55 
  56 static int
  57 raise_invalid(int v) {  /* SUSv3 requires ilogbl(0,+/-Inf,NaN) raise invalid */
  58 #ifndef lint
  59         if ((__xpg6 & _C99SUSv3_ilogb_0InfNaN_raises_invalid) != 0) {
  60                 static const double zero = 0.0;
  61                 volatile double dummy;
  62 
  63                 dummy = zero / zero;
  64         }
  65 #endif
  66         return (v);
  67 }
  68 
  69 int
  70 ilogbl(long double x) {
  71         int k = XBIASED_EXP(x);
  72 
  73         X86PDNRM(k, x);
  74         if (k == 0) {
  75                 if (ISZEROL(x))
  76                         return (raise_invalid(0x80000001));
  77                 else {
  78                         x *= xscale;            /* scale up by 2^112 or 2^63 */
  79                         return (XBIASED_EXP(x) - XSCALE_OFFSET);
  80                 }
  81         } else if (ISNORMALL(k, x))
  82                 return (k - 0x3fff);
  83         else
  84                 return (raise_invalid(0x7fffffff));
  85 }