k_tanf.c - vx32 - Local 9vx git repository for patches.
(HTM) git clone git://r-36.net/vx32
(DIR) Log
(DIR) Files
(DIR) Refs
---
k_tanf.c (2963B)
---
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 2004 Sun Microsystems, Inc. All Rights Reserved.
8 *
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 #ifndef lint
16 static char rcsid[] = "$FreeBSD: src/lib/msun/src/k_tanf.c,v 1.8 2004/06/02 04:39:44 das Exp $";
17 #endif
18
19 #include "math.h"
20 #include "math_private.h"
21 static const float
22 one = 1.0000000000e+00, /* 0x3f800000 */
23 pio4 = 7.8539812565e-01, /* 0x3f490fda */
24 pio4lo= 3.7748947079e-08, /* 0x33222168 */
25 T[] = {
26 3.3333334327e-01, /* 0x3eaaaaab */
27 1.3333334029e-01, /* 0x3e088889 */
28 5.3968254477e-02, /* 0x3d5d0dd1 */
29 2.1869488060e-02, /* 0x3cb327a4 */
30 8.8632395491e-03, /* 0x3c11371f */
31 3.5920790397e-03, /* 0x3b6b6916 */
32 1.4562094584e-03, /* 0x3abede48 */
33 5.8804126456e-04, /* 0x3a1a26c8 */
34 2.4646313977e-04, /* 0x398137b9 */
35 7.8179444245e-05, /* 0x38a3f445 */
36 7.1407252108e-05, /* 0x3895c07a */
37 -1.8558637748e-05, /* 0xb79bae5f */
38 2.5907305826e-05, /* 0x37d95384 */
39 };
40
41 float
42 __kernel_tanf(float x, float y, int iy)
43 {
44 float z,r,v,w,s;
45 int32_t ix,hx;
46 GET_FLOAT_WORD(hx,x);
47 ix = hx&0x7fffffff; /* high word of |x| */
48 if(ix<0x31800000) { /* x < 2**-28 */
49 if ((int) x == 0) { /* generate inexact */
50 if ((ix | (iy + 1)) == 0)
51 return one / fabsf(x);
52 else {
53 if (iy == 1)
54 return x;
55 else { /* compute -1 / (x+y) carefully */
56 double a, t;
57
58 z = w = x + y;
59 GET_FLOAT_WORD(ix, z);
60 SET_FLOAT_WORD(z, ix & 0xfffff000);
61 v = y - (z - x);
62 t = a = -one / w;
63 GET_FLOAT_WORD(ix, t);
64 SET_FLOAT_WORD(t, ix & 0xfffff000);
65 s = one + t * z;
66 return t + a * (s + t * v);
67 }
68 }
69 }
70 }
71 if(ix>=0x3f2ca140) { /* |x|>=0.6744 */
72 if(hx<0) {x = -x; y = -y;}
73 z = pio4-x;
74 w = pio4lo-y;
75 x = z+w; y = 0.0;
76 }
77 z = x*x;
78 w = z*z;
79 /* Break x^5*(T[1]+x^2*T[2]+...) into
80 * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) +
81 * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12]))
82 */
83 r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11]))));
84 v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12])))));
85 s = z*x;
86 r = y + z*(s*(r+v)+y);
87 r += T[0]*s;
88 w = x+r;
89 if(ix>=0x3f2ca140) {
90 v = (float)iy;
91 return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r)));
92 }
93 if(iy==1) return w;
94 else { /* if allow error up to 2 ulp,
95 simply return -1.0/(x+r) here */
96 /* compute -1.0/(x+r) accurately */
97 float a,t;
98 int32_t i;
99 z = w;
100 GET_FLOAT_WORD(i,z);
101 SET_FLOAT_WORD(z,i&0xfffff000);
102 v = r-(z - x); /* z+v = r+x */
103 t = a = -(float)1.0/w; /* a = -1.0/w */
104 GET_FLOAT_WORD(i,t);
105 SET_FLOAT_WORD(t,i&0xfffff000);
106 s = (float)1.0+t*z;
107 return t+a*(s+t*v);
108 }
109 }