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 __scalblnf = scalblnf
  31 
  32 #include "libm.h"
  33 #include <float.h>                /* FLT_MAX, FLT_MIN */
  34 
  35 static const float twom25f = 2.98023223876953125e-8F;
  36 #if defined(__x86)
  37 static const float two23f = 8388608.0F;
  38 #else
  39 /*
  40  * v: a non-zero subnormal |x|; returns [-22, 0]
  41  */
  42 static int
  43 ilogbf_biased(unsigned v) {
  44         int r = -22;
  45 
  46         if (v & 0xffff0000)
  47                 r += 16, v >>= 16;
  48         if (v & 0xff00)
  49                 r += 8, v >>= 8;
  50         if (v & 0xf0)
  51                 r += 4, v >>= 4;
  52         v <<= 1;
  53         return (r + ((0xffffaa50 >> v) & 0x3));
  54 }
  55 #endif  /* defined(__x86) */
  56 
  57 float
  58 scalblnf(float x, long n) {
  59         int *px = (int *) &x, ix, k;
  60 
  61         ix = *px & ~0x80000000;
  62         k = ix >> 23;
  63         if (k == 0xff)
  64 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
  65                 return (ix > 0x7f800000 ? x * x : x);
  66 #else
  67                 return (x + x);
  68 #endif
  69         if (ix == 0 || n == 0)
  70                 return (x);
  71         if (k == 0) {
  72 #if defined(__x86)
  73                 x *= two23f;
  74                 k = ((*px & ~0x80000000) >> 23) - 23;
  75 #else
  76                 k = ilogbf_biased(ix);
  77                 *px = (*px & 0x80000000) | (ix << (-k + 1));
  78 #endif
  79         }
  80         k += (int) n;
  81         if (n > 5000 || k > 0xfe)
  82                 return (FLT_MAX * copysignf(FLT_MAX, x));
  83         if (n < -5000 || k <= -25)
  84                 return (FLT_MIN * copysignf(FLT_MIN, x));
  85         if (k > 0) {
  86                 *px = (*px & ~0x7f800000) | (k << 23);
  87                 return (x);
  88         }
  89         k += 25;
  90         *px = (*px & ~0x7f800000) | (k << 23);
  91         return (x * twom25f);
  92 }