1 | /* ef_acos.c -- float version of e_acos.c. |
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2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
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3 | */ |
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4 | |
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5 | /* |
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6 | * ==================================================== |
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7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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8 | * |
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9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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10 | * Permission to use, copy, modify, and distribute this |
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11 | * software is freely granted, provided that this notice |
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12 | * is preserved. |
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13 | * ==================================================== |
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14 | */ |
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15 | |
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16 | #include "fdlibm.h" |
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17 | |
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18 | #ifdef __STDC__ |
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19 | static const float |
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20 | #else |
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21 | static float |
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22 | #endif |
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23 | one = 1.0000000000e+00, /* 0x3F800000 */ |
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24 | pi = 3.1415925026e+00, /* 0x40490fda */ |
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25 | pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */ |
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26 | pio2_lo = 7.5497894159e-08, /* 0x33a22168 */ |
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27 | pS0 = 1.6666667163e-01, /* 0x3e2aaaab */ |
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28 | pS1 = -3.2556581497e-01, /* 0xbea6b090 */ |
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29 | pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */ |
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30 | pS3 = -4.0055535734e-02, /* 0xbd241146 */ |
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31 | pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */ |
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32 | pS5 = 3.4793309169e-05, /* 0x3811ef08 */ |
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33 | qS1 = -2.4033949375e+00, /* 0xc019d139 */ |
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34 | qS2 = 2.0209457874e+00, /* 0x4001572d */ |
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35 | qS3 = -6.8828397989e-01, /* 0xbf303361 */ |
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36 | qS4 = 7.7038154006e-02; /* 0x3d9dc62e */ |
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37 | |
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38 | #ifdef __STDC__ |
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39 | float __ieee754_acosf(float x) |
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40 | #else |
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41 | float __ieee754_acosf(x) |
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42 | float x; |
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43 | #endif |
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44 | { |
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45 | float z,p,q,r,w,s,c,df; |
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46 | __int32_t hx,ix; |
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47 | GET_FLOAT_WORD(hx,x); |
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48 | ix = hx&0x7fffffff; |
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49 | if(ix==0x3f800000) { /* |x|==1 */ |
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50 | if(hx>0) return 0.0; /* acos(1) = 0 */ |
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51 | else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */ |
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52 | } else if(ix>0x3f800000) { /* |x| >= 1 */ |
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53 | return (x-x)/(x-x); /* acos(|x|>1) is NaN */ |
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54 | } |
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55 | if(ix<0x3f000000) { /* |x| < 0.5 */ |
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56 | if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/ |
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57 | z = x*x; |
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58 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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59 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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60 | r = p/q; |
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61 | return pio2_hi - (x - (pio2_lo-x*r)); |
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62 | } else if (hx<0) { /* x < -0.5 */ |
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63 | z = (one+x)*(float)0.5; |
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64 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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65 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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66 | s = __ieee754_sqrtf(z); |
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67 | r = p/q; |
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68 | w = r*s-pio2_lo; |
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69 | return pi - (float)2.0*(s+w); |
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70 | } else { /* x > 0.5 */ |
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71 | __int32_t idf; |
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72 | z = (one-x)*(float)0.5; |
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73 | s = __ieee754_sqrtf(z); |
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74 | df = s; |
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75 | GET_FLOAT_WORD(idf,df); |
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76 | SET_FLOAT_WORD(df,idf&0xfffff000); |
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77 | c = (z-df*df)/(s+df); |
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78 | p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5))))); |
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79 | q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4))); |
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80 | r = p/q; |
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81 | w = r*s+c; |
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82 | return (float)2.0*(df+w); |
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83 | } |
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84 | } |
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