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 __ilogbl = ilogbl
  32 
  33 #include "libm.h"
  34 #include "xpg6.h"                               /* __xpg6 */
  35 
  36 #if defined(__sparc)
  37 #define ISNORMALL(k, x)         (k != 0x7fff)   /* assuming k != 0 */
  38 #define X86PDNRM(k, x)
  39 #define XSCALE_OFFSET           0x406f          /* 0x3fff + 112 */
  40 
  41 static const long double xscale = 5192296858534827628530496329220096.0L;
  42 
  43 /* 2^112 */
  44 #elif defined(__x86)
  45 /*
  46  * if pseudo-denormal, replace by the equivalent normal
  47  */
  48 #define X86PDNRM(k, x)  \
  49         if (k == 0 && (((int *)&x)[1] & 0x80000000) !=  0) \
  50                 ((int *)&x)[2] |= k = 1
  51 #if defined(HANDLE_UNSUPPORTED)         /* assuming k != 0 */
  52 #define ISNORMALL(k, x) (k != 0x7fff && (((int *)&x)[1] & 0x80000000) != \
  53         0)
  54 #else
  55 #define ISNORMALL(k, x)         (k != 0x7fff)
  56 #endif
  57 #define XSCALE_OFFSET   0x403e                          /* 0x3fff + 63 */
  58 static const long double xscale = 9223372036854775808.0L;       /* 2^63 */
  59 #endif
  60 
  61 static int
  62 raise_invalid(int v)   /* SUSv3 requires ilogbl(0,+/-Inf,NaN) raise invalid */
  63 {
  64 #ifndef lint
  65         if ((__xpg6 & _C99SUSv3_ilogb_0InfNaN_raises_invalid) != 0) {
  66                 static const double zero = 0.0;
  67                 volatile double dummy;
  68 
  69                 dummy = zero / zero;
  70         }
  71 #endif
  72         return (v);
  73 }
  74 
  75 int
  76 ilogbl(long double x)
  77 {
  78         int k = XBIASED_EXP(x);
  79 
  80         X86PDNRM(k, x);
  81 
  82         if (k == 0) {
  83                 if (ISZEROL(x)) {
  84                         return (raise_invalid(0x80000001));
  85                 } else {
  86                         x *= xscale;    /* scale up by 2^112 or 2^63 */
  87                         return (XBIASED_EXP(x) - XSCALE_OFFSET);
  88                 }
  89         } else if (ISNORMALL(k, x)) {
  90                 return (k - 0x3fff);
  91         } else {
  92                 return (raise_invalid(0x7fffffff));
  93         }
  94 }