Update.
[glibc.git] / sysdeps / libm-ieee754 / k_tanf.c
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1 /* k_tanf.c -- float version of k_tan.c
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 */
5 /*
6 * ====================================================
7 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 * ====================================================
16 #if defined(LIBM_SCCS) && !defined(lint)
17 static char rcsid[] = "$NetBSD: k_tanf.c,v 1.4 1995/05/10 20:46:39 jtc Exp $";
18 #endif
20 #include "math.h"
21 #include "math_private.h"
22 #ifdef __STDC__
23 static const float
24 #else
25 static float
26 #endif
27 one = 1.0000000000e+00, /* 0x3f800000 */
28 pio4 = 7.8539812565e-01, /* 0x3f490fda */
29 pio4lo= 3.7748947079e-08, /* 0x33222168 */
30 T[] = {
31 3.3333334327e-01, /* 0x3eaaaaab */
32 1.3333334029e-01, /* 0x3e088889 */
33 5.3968254477e-02, /* 0x3d5d0dd1 */
34 2.1869488060e-02, /* 0x3cb327a4 */
35 8.8632395491e-03, /* 0x3c11371f */
36 3.5920790397e-03, /* 0x3b6b6916 */
37 1.4562094584e-03, /* 0x3abede48 */
38 5.8804126456e-04, /* 0x3a1a26c8 */
39 2.4646313977e-04, /* 0x398137b9 */
40 7.8179444245e-05, /* 0x38a3f445 */
41 7.1407252108e-05, /* 0x3895c07a */
42 -1.8558637748e-05, /* 0xb79bae5f */
43 2.5907305826e-05, /* 0x37d95384 */
46 #ifdef __STDC__
47 float __kernel_tanf(float x, float y, int iy)
48 #else
49 float __kernel_tanf(x, y, iy)
50 float x,y; int iy;
51 #endif
53 float z,r,v,w,s;
54 int32_t ix,hx;
55 GET_FLOAT_WORD(hx,x);
56 ix = hx&0x7fffffff; /* high word of |x| */
57 if(ix<0x31800000) /* x < 2**-28 */
58 {if((int)x==0) { /* generate inexact */
59 if((ix|(iy+1))==0) return one/fabsf(x);
60 else return (iy==1)? x: -one/x;
63 if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
64 if(hx<0) {x = -x; y = -y;}
65 z = pio4-x;
66 w = pio4lo-y;
67 x = z+w; y = 0.0;
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]))
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)));
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);