Last change
on this file since 535 was
444,
checked in by satin@…, 6 years ago
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add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc
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File size:
2.4 KB
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Line | |
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1 | |
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2 | /* @(#)z_powf.c 1.0 98/08/13 */ |
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3 | #include <float.h> |
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4 | #include "fdlibm.h" |
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5 | #include "zmath.h" |
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6 | |
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7 | float powf (float x, float y) |
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8 | { |
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9 | float d, k, t, r = 1.0; |
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10 | int n, sign, exponent_is_even_int = 0; |
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11 | __int32_t px; |
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12 | |
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13 | GET_FLOAT_WORD (px, x); |
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14 | |
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15 | k = modff (y, &d); |
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16 | |
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17 | if (k == 0.0) |
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18 | { |
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19 | /* Exponent y is an integer. */ |
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20 | if (modff (ldexpf (y, -1), &t)) |
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21 | { |
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22 | /* y is odd. */ |
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23 | exponent_is_even_int = 0; |
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24 | } |
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25 | else |
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26 | { |
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27 | /* y is even. */ |
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28 | exponent_is_even_int = 1; |
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29 | } |
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30 | } |
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31 | |
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32 | if (x == 0.0) |
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33 | { |
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34 | if (y <= 0.0) |
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35 | errno = EDOM; |
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36 | } |
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37 | else if ((t = y * log (fabsf (x))) >= BIGX) |
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38 | { |
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39 | errno = ERANGE; |
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40 | if (px & 0x80000000) |
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41 | { |
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42 | /* x is negative. */ |
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43 | if (k) |
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44 | { |
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45 | /* y is not an integer. */ |
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46 | errno = EDOM; |
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47 | x = 0.0; |
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48 | } |
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49 | else if (exponent_is_even_int) |
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50 | x = z_infinity_f.f; |
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51 | else |
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52 | x = -z_infinity_f.f; |
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53 | } |
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54 | else |
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55 | { |
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56 | x = z_infinity_f.f; |
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57 | } |
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58 | } |
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59 | else if (t < SMALLX) |
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60 | { |
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61 | errno = ERANGE; |
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62 | x = 0.0; |
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63 | } |
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64 | else |
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65 | { |
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66 | if ( !k && fabsf (d) <= 32767 ) |
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67 | { |
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68 | n = (int) d; |
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69 | |
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70 | if ((sign = (n < 0))) |
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71 | n = -n; |
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72 | |
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73 | while ( n > 0 ) |
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74 | { |
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75 | if ((unsigned int) n % 2) |
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76 | r *= x; |
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77 | x *= x; |
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78 | n = (unsigned int) n / 2; |
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79 | } |
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80 | |
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81 | if (sign) |
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82 | r = 1.0 / r; |
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83 | |
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84 | return r; |
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85 | } |
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86 | else |
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87 | { |
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88 | if ( px & 0x80000000 ) |
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89 | { |
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90 | /* x is negative. */ |
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91 | if (k) |
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92 | { |
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93 | /* y is not an integer. */ |
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94 | errno = EDOM; |
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95 | return 0.0; |
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96 | } |
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97 | } |
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98 | |
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99 | x = exp (t); |
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100 | |
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101 | if (!exponent_is_even_int) |
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102 | { |
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103 | if (px & 0x80000000) |
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104 | { |
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105 | /* y is an odd integer, and x is negative, |
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106 | so the result is negative. */ |
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107 | GET_FLOAT_WORD (px, x); |
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108 | px |= 0x80000000; |
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109 | SET_FLOAT_WORD (x, px); |
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110 | } |
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111 | } |
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112 | } |
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113 | } |
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114 | |
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115 | return x; |
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116 | } |
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117 | |
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118 | #ifdef _DOUBLE_IS_32BITS |
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119 | |
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120 | double pow (double x, double y) |
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121 | { |
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122 | return (double) powf ((float) x, (float) y); |
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123 | } |
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124 | |
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125 | #endif /* defined(_DOUBLE_IS_32BITS) */ |
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