1 | /* kf_tan.c -- float version of k_tan.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 | #ifdef __STDC__ |
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18 | static const float |
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19 | #else |
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20 | static float |
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21 | #endif |
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22 | one = 1.0000000000e+00, /* 0x3f800000 */ |
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23 | pio4 = 7.8539812565e-01, /* 0x3f490fda */ |
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24 | pio4lo= 3.7748947079e-08, /* 0x33222168 */ |
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25 | T[] = { |
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26 | 3.3333334327e-01, /* 0x3eaaaaab */ |
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27 | 1.3333334029e-01, /* 0x3e088889 */ |
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28 | 5.3968254477e-02, /* 0x3d5d0dd1 */ |
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29 | 2.1869488060e-02, /* 0x3cb327a4 */ |
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30 | 8.8632395491e-03, /* 0x3c11371f */ |
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31 | 3.5920790397e-03, /* 0x3b6b6916 */ |
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32 | 1.4562094584e-03, /* 0x3abede48 */ |
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33 | 5.8804126456e-04, /* 0x3a1a26c8 */ |
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34 | 2.4646313977e-04, /* 0x398137b9 */ |
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35 | 7.8179444245e-05, /* 0x38a3f445 */ |
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36 | 7.1407252108e-05, /* 0x3895c07a */ |
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37 | -1.8558637748e-05, /* 0xb79bae5f */ |
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38 | 2.5907305826e-05, /* 0x37d95384 */ |
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39 | }; |
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40 | |
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41 | #ifdef __STDC__ |
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42 | float __kernel_tanf(float x, float y, int iy) |
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43 | #else |
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44 | float __kernel_tanf(x, y, iy) |
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45 | float x,y; int iy; |
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46 | #endif |
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47 | { |
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48 | float z,r,v,w,s; |
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49 | __int32_t ix,hx; |
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50 | GET_FLOAT_WORD(hx,x); |
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51 | ix = hx&0x7fffffff; /* high word of |x| */ |
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52 | if(ix<0x31800000) /* x < 2**-28 */ |
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53 | {if((int)x==0) { /* generate inexact */ |
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54 | if((ix|(iy+1))==0) return one/fabsf(x); |
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55 | else return (iy==1)? x: -one/x; |
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56 | } |
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57 | } |
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58 | if(ix>=0x3f2ca140) { /* |x|>=0.6744 */ |
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59 | if(hx<0) {x = -x; y = -y;} |
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60 | z = pio4-x; |
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61 | w = pio4lo-y; |
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62 | x = z+w; y = 0.0; |
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63 | } |
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64 | z = x*x; |
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65 | w = z*z; |
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66 | /* Break x^5*(T[1]+x^2*T[2]+...) into |
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67 | * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) + |
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68 | * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12])) |
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69 | */ |
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70 | r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11])))); |
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71 | v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12]))))); |
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72 | s = z*x; |
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73 | r = y + z*(s*(r+v)+y); |
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74 | r += T[0]*s; |
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75 | w = x+r; |
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76 | if(ix>=0x3f2ca140) { |
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77 | v = (float)iy; |
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78 | return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r))); |
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79 | } |
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80 | if(iy==1) return w; |
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81 | else { /* if allow error up to 2 ulp, |
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82 | simply return -1.0/(x+r) here */ |
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83 | /* compute -1.0/(x+r) accurately */ |
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84 | float a,t; |
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85 | __int32_t i; |
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86 | z = w; |
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87 | GET_FLOAT_WORD(i,z); |
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88 | SET_FLOAT_WORD(z,i&0xfffff000); |
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89 | v = r-(z - x); /* z+v = r+x */ |
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90 | t = a = -(float)1.0/w; /* a = -1.0/w */ |
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91 | GET_FLOAT_WORD(i,t); |
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92 | SET_FLOAT_WORD(t,i&0xfffff000); |
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93 | s = (float)1.0+t*z; |
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94 | return t+a*(s+t*v); |
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95 | } |
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96 | } |
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