1  /*
 2   * Copyright (C) 2008-2020 Advanced Micro Devices, Inc. All rights reserved.
 3   *
 4   * Redistribution and use in source and binary forms, with or without modification,
 5   * are permitted provided that the following conditions are met:
 6   * 1. Redistributions of source code must retain the above copyright notice,
 7   *    this list of conditions and the following disclaimer.
 8   * 2. Redistributions in binary form must reproduce the above copyright notice,
 9   *    this list of conditions and the following disclaimer in the documentation
10   *    and/or other materials provided with the distribution.
11   * 3. Neither the name of the copyright holder nor the names of its contributors
12   *    may be used to endorse or promote products derived from this software without
13   *    specific prior written permission.
14   *
15   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
16   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
17   * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18   * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
19   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
20   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
21   * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
22   * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
23   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
24   * POSSIBILITY OF SUCH DAMAGE.
25   *
26   */
27  
28  #include "libm_amd.h"
29  #include "libm_util_amd.h"
30  #include "libm_special.h"
31  
32  
33  float FN_PROTOTYPE_REF(logbf)(float x)
34  {
35    unsigned int ux;
36    int u;
37    GET_BITS_SP32(x, ux);
38    u = ((ux & EXPBITS_SP32) >> EXPSHIFTBITS_SP32) - EXPBIAS_SP32;
39    if ((ux & ~SIGNBIT_SP32) == 0)
40      /* x is +/-zero. Return -infinity with div-by-zero flag. */
41  	return __amd_handle_errorf("logbf", __amd_logb, NINFBITPATT_SP32, _SING, AMD_F_DIVBYZERO, ERANGE, x, 0.0, 1);
42    else if (EMIN_SP32 <= u && u <= EMAX_SP32)
43      /* x is a normal number */
44      return (float)u;
45    else if (u > EMAX_SP32)
46      {
47        /* x is infinity or NaN */
48        if ((ux & MANTBITS_SP32) == 0)
49        {
50          /* x is +/-infinity. return +ve inf. */
51  #ifdef WINDOWS 
52          PUT_BITS_SP32(ux,x);
53  #else              
54          PUT_BITS_SP32(ux & (~SIGNBIT_SP32), x);
55  #endif
56          return x;
57        }
58        else
59        {
60          /* x is NaN, result is NaN */
61  #ifdef WINDOWS
62            return __amd_handle_errorf("logbf", __amd_logb, ux|0x00400000, _DOMAIN, AMD_F_NONE, EDOM, x, 0.0, 1);
63  #else
64            return x+x;
65  #endif
66        }
67      }
68    else
69      {
70        /* x is denormalized. */
71  #ifdef FOLLOW_IEEE754_LOGB
72        /* Return the value of the minimum exponent to ensure that
73  	         the relationship between logb and scalb, defined in
74           IEEE 754, holds. */
75        return EMIN_SP32;
76  #else
77        /* Follow the rule set by IEEE 854 for logb */
78        ux &= MANTBITS_SP32;
79        u = EMIN_SP32;
80        while (ux < IMPBIT_SP32)
81          {
82            ux <<= 1;
83            u--;
84          }
85        return (float)u;
86  #endif
87      }
88  }
89  
90