1/* k_tanf.c -- float version of k_tan.c
2 */
3
4/*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15#if defined(LIBM_SCCS) && !defined(lint)
16static char rcsid[] = "$NetBSD: k_tanf.c,v 1.4 1995/05/10 20:46:39 jtc Exp $";
17#endif
18
19#include <float.h>
20#include <math.h>
21#include <math_private.h>
22#include <math-underflow.h>
23static const float
24one = 1.0000000000e+00, /* 0x3f800000 */
25pio4 = 7.8539812565e-01, /* 0x3f490fda */
26pio4lo= 3.7748947079e-08, /* 0x33222168 */
27T[] = {
28 3.3333334327e-01, /* 0x3eaaaaab */
29 1.3333334029e-01, /* 0x3e088889 */
30 5.3968254477e-02, /* 0x3d5d0dd1 */
31 2.1869488060e-02, /* 0x3cb327a4 */
32 8.8632395491e-03, /* 0x3c11371f */
33 3.5920790397e-03, /* 0x3b6b6916 */
34 1.4562094584e-03, /* 0x3abede48 */
35 5.8804126456e-04, /* 0x3a1a26c8 */
36 2.4646313977e-04, /* 0x398137b9 */
37 7.8179444245e-05, /* 0x38a3f445 */
38 7.1407252108e-05, /* 0x3895c07a */
39 -1.8558637748e-05, /* 0xb79bae5f */
40 2.5907305826e-05, /* 0x37d95384 */
41};
42
43float __kernel_tanf(float x, float y, int iy)
44{
45 float z,r,v,w,s;
46 int32_t ix,hx;
47 GET_FLOAT_WORD(hx,x);
48 ix = hx&0x7fffffff; /* high word of |x| */
49 if(ix<0x39000000) /* x < 2**-13 */
50 {if((int)x==0) { /* generate inexact */
51 if((ix|(iy+1))==0) return one/fabsf(x);
52 else if (iy == 1)
53 {
54 math_check_force_underflow (x);
55 return x;
56 }
57 else
58 return -one / x;
59 }
60 }
61 if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
62 if(hx<0) {x = -x; y = -y;}
63 z = pio4-x;
64 w = pio4lo-y;
65 x = z+w; y = 0.0;
66 if (fabsf (x) < 0x1p-13f)
67 return (1 - ((hx >> 30) & 2)) * iy * (1.0f - 2 * iy * x);
68 }
69 z = x*x;
70 w = z*z;
71 /* Break x^5*(T[1]+x^2*T[2]+...) into
72 * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
73 * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
74 */
75 r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
76 v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
77 s = z*x;
78 r = y + z*(s*(r+v)+y);
79 r += T[0]*s;
80 w = x+r;
81 if(ix>=0x3f2ca140) {
82 v = (float)iy;
83 return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
84 }
85 if(iy==1) return w;
86 else { /* if allow error up to 2 ulp,
87 simply return -1.0/(x+r) here */
88 /* compute -1.0/(x+r) accurately */
89 float a,t;
90 int32_t i;
91 z = w;
92 GET_FLOAT_WORD(i,z);
93 SET_FLOAT_WORD(z,i&0xfffff000);
94 v = r-(z - x); /* z+v = r+x */
95 t = a = -(float)1.0/w; /* a = -1.0/w */
96 GET_FLOAT_WORD(i,t);
97 SET_FLOAT_WORD(t,i&0xfffff000);
98 s = (float)1.0+t*z;
99 return t+a*(s+t*v);
100 }
101}
102