1 | /* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */
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2 | /*
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3 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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4 | * Optimized by Bruce D. Evans.
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5 | */
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6 | /*
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7 | * ====================================================
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8 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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9 | *
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10 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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11 | * Permission to use, copy, modify, and distribute this
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12 | * software is freely granted, provided that this notice
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13 | * is preserved.
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14 | * ====================================================
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15 | */
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16 |
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17 | #include "libm.h"
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18 |
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19 | /* Small multiples of pi/2 rounded to double precision. */
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20 | static const double
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21 | t1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
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22 | t2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
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23 | t3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
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24 | t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
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25 |
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26 | float tanf(float x)
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27 | {
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28 | double y;
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29 | uint32_t ix;
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30 | unsigned n, sign;
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31 |
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32 | GET_FLOAT_WORD(ix, x);
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33 | sign = ix >> 31;
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34 | ix &= 0x7fffffff;
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35 |
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36 | if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */
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37 | if (ix < 0x39800000) { /* |x| < 2**-12 */
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38 | /* raise inexact if x!=0 and underflow if subnormal */
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39 | FORCE_EVAL(ix < 0x00800000 ? x/0x1p120f : x+0x1p120f);
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40 | return x;
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41 | }
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42 | return __tandf(x, 0);
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43 | }
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44 | if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */
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45 | if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */
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46 | return __tandf((sign ? x+t1pio2 : x-t1pio2), 1);
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47 | else
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48 | return __tandf((sign ? x+t2pio2 : x-t2pio2), 0);
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49 | }
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50 | if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */
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51 | if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */
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52 | return __tandf((sign ? x+t3pio2 : x-t3pio2), 1);
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53 | else
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54 | return __tandf((sign ? x+t4pio2 : x-t4pio2), 0);
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55 | }
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56 |
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57 | /* tan(Inf or NaN) is NaN */
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58 | if (ix >= 0x7f800000)
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59 | return x - x;
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60 |
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61 | /* argument reduction */
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62 | n = __rem_pio2f(x, &y);
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63 | return __tandf(y, n&1);
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64 | }
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