aboutsummaryrefslogtreecommitdiff
path: root/math/s_clog10f.c
blob: ca2cdf4f8086ea0ca0e85a0a8da2ee7eff1a54c6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/* Compute complex base 10 logarithm.
   Copyright (C) 1997-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <http://www.gnu.org/licenses/>.  */

#include <complex.h>
#include <math.h>
#include <math_private.h>
#include <float.h>

/* log_10 (2).  */
#define M_LOG10_2f 0.3010299956639811952137388947244930267682f

/* pi * log10 (e).  */
#define M_PI_LOG10Ef 1.364376353841841347485783625431355770210f

__complex__ float
__clog10f (__complex__ float x)
{
  __complex__ float result;
  int rcls = fpclassify (__real__ x);
  int icls = fpclassify (__imag__ x);

  if (__glibc_unlikely (rcls == FP_ZERO && icls == FP_ZERO))
    {
      /* Real and imaginary part are 0.0.  */
      __imag__ result = signbit (__real__ x) ? M_PI_LOG10Ef : 0.0;
      __imag__ result = __copysignf (__imag__ result, __imag__ x);
      /* Yes, the following line raises an exception.  */
      __real__ result = -1.0 / fabsf (__real__ x);
    }
  else if (__glibc_likely (rcls != FP_NAN && icls != FP_NAN))
    {
      /* Neither real nor imaginary part is NaN.  */
      float absx = fabsf (__real__ x), absy = fabsf (__imag__ x);
      int scale = 0;

      if (absx < absy)
	{
	  float t = absx;
	  absx = absy;
	  absy = t;
	}

      if (absx > FLT_MAX / 2.0f)
	{
	  scale = -1;
	  absx = __scalbnf (absx, scale);
	  absy = (absy >= FLT_MIN * 2.0f ? __scalbnf (absy, scale) : 0.0f);
	}
      else if (absx < FLT_MIN && absy < FLT_MIN)
	{
	  scale = FLT_MANT_DIG;
	  absx = __scalbnf (absx, scale);
	  absy = __scalbnf (absy, scale);
	}

      if (absx == 1.0f && scale == 0)
	{
	  float absy2 = absy * absy;
	  if (absy2 <= FLT_MIN * 2.0f * (float) M_LN10)
	    {
#if __FLT_EVAL_METHOD__ == 0
	      __real__ result
		= (absy2 / 2.0f - absy2 * absy2 / 4.0f) * (float) M_LOG10E;
#else
	      volatile float force_underflow = absy2 * absy2 / 4.0f;
	      __real__ result
		= (absy2 / 2.0f - force_underflow) * (float) M_LOG10E;
#endif
	    }
	  else
	    __real__ result = __log1pf (absy2) * ((float) M_LOG10E / 2.0f);
	}
      else if (absx > 1.0f && absx < 2.0f && absy < 1.0f && scale == 0)
	{
	  float d2m1 = (absx - 1.0f) * (absx + 1.0f);
	  if (absy >= FLT_EPSILON)
	    d2m1 += absy * absy;
	  __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
	}
      else if (absx < 1.0f
	       && absx >= 0.75f
	       && absy < FLT_EPSILON / 2.0f
	       && scale == 0)
	{
	  float d2m1 = (absx - 1.0f) * (absx + 1.0f);
	  __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
	}
      else if (absx < 1.0f && (absx >= 0.75f || absy >= 0.5f) && scale == 0)
	{
	  float d2m1 = __x2y2m1f (absx, absy);
	  __real__ result = __log1pf (d2m1) * ((float) M_LOG10E / 2.0f);
	}
      else
	{
	  float d = __ieee754_hypotf (absx, absy);
	  __real__ result = __ieee754_log10f (d) - scale * M_LOG10_2f;
	}

      __imag__ result = M_LOG10E * __ieee754_atan2f (__imag__ x, __real__ x);
    }
  else
    {
      __imag__ result = __nanf ("");
      if (rcls == FP_INFINITE || icls == FP_INFINITE)
	/* Real or imaginary part is infinite.  */
	__real__ result = HUGE_VALF;
      else
	__real__ result = __nanf ("");
    }

  return result;
}
#ifndef __clog10f
weak_alias (__clog10f, clog10f)
#endif