1/* k_tanf.c -- float version of k_tan.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
4
5/*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8 *
9 * Developed at SunPro, a Sun Microsystems, Inc. business.
10 * Permission to use, copy, modify, and distribute this
11 * software is freely granted, provided that this notice
12 * is preserved.
13 * ====================================================
14 */
15
16#if defined(LIBM_SCCS) && !defined(lint)
17static char rcsid[] = "$NetBSD: k_tanf.c,v 1.4 1995/05/10 20:46:39 jtc Exp $";
18#endif
19
20#include <float.h>
21#include <math.h>
22#include <math_private.h>
23#include <math-underflow.h>
24static const float
25one = 1.0000000000e+00, /* 0x3f800000 */
26pio4 = 7.8539812565e-01, /* 0x3f490fda */
27pio4lo= 3.7748947079e-08, /* 0x33222168 */
28T[] = {
29 3.3333334327e-01, /* 0x3eaaaaab */
30 1.3333334029e-01, /* 0x3e088889 */
31 5.3968254477e-02, /* 0x3d5d0dd1 */
32 2.1869488060e-02, /* 0x3cb327a4 */
33 8.8632395491e-03, /* 0x3c11371f */
34 3.5920790397e-03, /* 0x3b6b6916 */
35 1.4562094584e-03, /* 0x3abede48 */
36 5.8804126456e-04, /* 0x3a1a26c8 */
37 2.4646313977e-04, /* 0x398137b9 */
38 7.8179444245e-05, /* 0x38a3f445 */
39 7.1407252108e-05, /* 0x3895c07a */
40 -1.8558637748e-05, /* 0xb79bae5f */
41 2.5907305826e-05, /* 0x37d95384 */
42};
43
44float __kernel_tanf(float x, float y, int iy)
45{
46 float z,r,v,w,s;
47 int32_t ix,hx;
48 GET_FLOAT_WORD(hx,x);
49 ix = hx&0x7fffffff; /* high word of |x| */
50 if(ix<0x39000000) /* x < 2**-13 */
51 {if((int)x==0) { /* generate inexact */
52 if((ix|(iy+1))==0) return one/fabsf(x);
53 else if (iy == 1)
54 {
55 math_check_force_underflow (x);
56 return x;
57 }
58 else
59 return -one / x;
60 }
61 }
62 if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
63 if(hx<0) {x = -x; y = -y;}
64 z = pio4-x;
65 w = pio4lo-y;
66 x = z+w; y = 0.0;
67 if (fabsf (x) < 0x1p-13f)
68 return (1 - ((hx >> 30) & 2)) * iy * (1.0f - 2 * iy * x);
69 }
70 z = x*x;
71 w = z*z;
72 /* Break x^5*(T[1]+x^2*T[2]+...) into
73 * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
74 * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
75 */
76 r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
77 v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
78 s = z*x;
79 r = y + z*(s*(r+v)+y);
80 r += T[0]*s;
81 w = x+r;
82 if(ix>=0x3f2ca140) {
83 v = (float)iy;
84 return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
85 }
86 if(iy==1) return w;
87 else { /* if allow error up to 2 ulp,
88 simply return -1.0/(x+r) here */
89 /* compute -1.0/(x+r) accurately */
90 float a,t;
91 int32_t i;
92 z = w;
93 GET_FLOAT_WORD(i,z);
94 SET_FLOAT_WORD(z,i&0xfffff000);
95 v = r-(z - x); /* z+v = r+x */
96 t = a = -(float)1.0/w; /* a = -1.0/w */
97 GET_FLOAT_WORD(i,t);
98 SET_FLOAT_WORD(t,i&0xfffff000);
99 s = (float)1.0+t*z;
100 return t+a*(s+t*v);
101 }
102}
103