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 __scalblnf = scalblnf
  32 
  33 #include "libm.h"
  34 #include <float.h>                        /* FLT_MAX, FLT_MIN */
  35 
  36 static const float twom25f = 2.98023223876953125e-8F;
  37 
  38 #if defined(__x86)
  39 static const float two23f = 8388608.0F;
  40 #else
  41 /*
  42  * v: a non-zero subnormal |x|; returns [-22, 0]
  43  */
  44 static int
  45 ilogbf_biased(unsigned v)
  46 {
  47         int r = -22;
  48 
  49         if (v & 0xffff0000)
  50                 r += 16, v >>= 16;
  51 
  52         if (v & 0xff00)
  53                 r += 8, v >>= 8;
  54 
  55         if (v & 0xf0)
  56                 r += 4, v >>= 4;
  57 
  58         v <<= 1;
  59         return (r + ((0xffffaa50 >> v) & 0x3));
  60 }
  61 #endif /* defined(__x86) */
  62 
  63 float
  64 scalblnf(float x, long n)
  65 {
  66         int *px = (int *)&x, ix, k;
  67 
  68         ix = *px & ~0x80000000;
  69         k = ix >> 23;
  70 
  71         if (k == 0xff)
  72 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
  73                 return (ix > 0x7f800000 ? x * x : x);
  74 #else
  75                 return (x + x);
  76 #endif
  77 
  78         if (ix == 0 || n == 0)
  79                 return (x);
  80 
  81         if (k == 0) {
  82 #if defined(__x86)
  83                 x *= two23f;
  84                 k = ((*px & ~0x80000000) >> 23) - 23;
  85 #else
  86                 k = ilogbf_biased(ix);
  87                 *px = (*px & 0x80000000) | (ix << (-k + 1));
  88 #endif
  89         }
  90 
  91         k += (int)n;
  92 
  93         if (n > 5000 || k > 0xfe)
  94                 return (FLT_MAX * copysignf(FLT_MAX, x));
  95 
  96         if (n < -5000 || k <= -25)
  97                 return (FLT_MIN * copysignf(FLT_MIN, x));
  98 
  99         if (k > 0) {
 100                 *px = (*px & ~0x7f800000) | (k << 23);
 101                 return (x);
 102         }
 103 
 104         k += 25;
 105         *px = (*px & ~0x7f800000) | (k << 23);
 106         return (x * twom25f);
 107 }