Last change
on this file since 444 was
444,
checked in by satin@…, 6 years ago
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add newlib,libalmos-mkh, restructure shared_syscalls.h and mini-libc
|
File size:
2.4 KB
|
Rev | Line | |
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[444] | 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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