| 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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