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 #include <sys/cdefs.h>
17 #if defined(LIBM_SCCS) && !defined(lint)
18 __RCSID("$NetBSD: k_tanf.c,v 1.7 2002/05/26 22:01:54 wiz Exp $");
19 #endif
20
21 #include "math.h"
22 #include "math_private.h"
23 static const float
24 one = 1.0000000000e+00, /* 0x3f800000 */
25 pio4 = 7.8539812565e-01, /* 0x3f490fda */
26 pio4lo= 3.7748947079e-08, /* 0x33222168 */
27 T[] = {
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
43 float
__kernel_tanf(float x,float y,int iy)44 __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<0x31800000) /* x < 2**-28 */
51 {if((int)x==0) { /* generate inexact */
52 if((ix|(iy+1))==0) return one/fabsf(x);
53 else return (iy==1)? x: -one/x;
54 }
55 }
56 if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
57 if(hx<0) {x = -x; y = -y;}
58 z = pio4-x;
59 w = pio4lo-y;
60 x = z+w; y = 0.0;
61 }
62 z = x*x;
63 w = z*z;
64 /* Break x^5*(T[1]+x^2*T[2]+...) into
65 * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
66 * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
67 */
68 r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
69 v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
70 s = z*x;
71 r = y + z*(s*(r+v)+y);
72 r += T[0]*s;
73 w = x+r;
74 if(ix>=0x3f2ca140) {
75 v = (float)iy;
76 return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
77 }
78 if(iy==1) return w;
79 else { /* if allow error up to 2 ulp,
80 simply return -1.0/(x+r) here */
81 /* compute -1.0/(x+r) accurately */
82 float a,t;
83 int32_t i;
84 z = w;
85 GET_FLOAT_WORD(i,z);
86 SET_FLOAT_WORD(z,i&0xfffff000);
87 v = r-(z - x); /* z+v = r+x */
88 t = a = -(float)1.0/w; /* a = -1.0/w */
89 GET_FLOAT_WORD(i,t);
90 SET_FLOAT_WORD(t,i&0xfffff000);
91 s = (float)1.0+t*z;
92 return t+a*(s+t*v);
93 }
94 }
95