1 | /* origin: FreeBSD /usr/src/lib/msun/src/e_acosl.c */
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2 | /*
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3 | * ====================================================
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4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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5 | *
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6 | * Developed at SunSoft, a Sun Microsystems, Inc. business.
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7 | * Permission to use, copy, modify, and distribute this
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8 | * software is freely granted, provided that this notice
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9 | * is preserved.
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10 | * ====================================================
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11 | */
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12 | /*
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13 | * See comments in acos.c.
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14 | * Converted to long double by David Schultz <das@FreeBSD.ORG>.
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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 | #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
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20 | long double acosl(long double x)
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21 | {
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22 | return acos(x);
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23 | }
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24 | #elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
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25 | #include "__invtrigl.h"
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26 | #if LDBL_MANT_DIG == 64
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27 | #define CLEARBOTTOM(u) (u.i.m &= -1ULL << 32)
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28 | #elif LDBL_MANT_DIG == 113
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29 | #define CLEARBOTTOM(u) (u.i.lo = 0)
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30 | #endif
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31 |
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32 | long double acosl(long double x)
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33 | {
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34 | union ldshape u = {x};
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35 | long double z, s, c, f;
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36 | uint16_t e = u.i.se & 0x7fff;
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37 |
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38 | /* |x| >= 1 or nan */
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39 | if (e >= 0x3fff) {
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40 | if (x == 1)
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41 | return 0;
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42 | if (x == -1)
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43 | return 2*pio2_hi + 0x1p-120f;
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44 | return 0/(x-x);
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45 | }
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46 | /* |x| < 0.5 */
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47 | if (e < 0x3fff - 1) {
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48 | if (e < 0x3fff - LDBL_MANT_DIG - 1)
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49 | return pio2_hi + 0x1p-120f;
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50 | return pio2_hi - (__invtrigl_R(x*x)*x - pio2_lo + x);
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51 | }
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52 | /* x < -0.5 */
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53 | if (u.i.se >> 15) {
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54 | z = (1 + x)*0.5;
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55 | s = sqrtl(z);
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56 | return 2*(pio2_hi - (__invtrigl_R(z)*s - pio2_lo + s));
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57 | }
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58 | /* x > 0.5 */
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59 | z = (1 - x)*0.5;
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60 | s = sqrtl(z);
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61 | u.f = s;
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62 | CLEARBOTTOM(u);
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63 | f = u.f;
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64 | c = (z - f*f)/(s + f);
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65 | return 2*(__invtrigl_R(z)*s + c + f);
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66 | }
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67 | #endif
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