1/* s_tanf.c -- float version of s_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: s_tanf.c,v 1.4 1995/05/10 20:48:20 jtc Exp $";
17#endif
18
19#include <errno.h>
20#include <math.h>
21#include <math_private.h>
22#include <libm-alias-float.h>
23#include "s_sincosf.h"
24
25/* Reduce range of X to a multiple of PI/2. The modulo result is between
26 -PI/4 and PI/4 and returned as a high part y[0] and a low part y[1].
27 The low bit in the return value indicates the first or 2nd half of tanf. */
28static inline int32_t
29rem_pio2f (float x, float *y)
30{
31 double dx = x;
32 int n;
33 const sincos_t *p = &__sincosf_table[0];
34
35 if (__glibc_likely (abstop12 (x) < abstop12 (120.0f)))
36 dx = reduce_fast (dx, p, &n);
37 else
38 {
39 uint32_t xi = asuint (x);
40 int sign = xi >> 31;
41
42 dx = reduce_large (xi, &n);
43 dx = sign ? -dx : dx;
44 }
45
46 y[0] = dx;
47 y[1] = dx - y[0];
48 return n;
49}
50
51float __tanf(float x)
52{
53 float y[2],z=0.0;
54 int32_t n, ix;
55
56 GET_FLOAT_WORD(ix,x);
57
58 /* |x| ~< pi/4 */
59 ix &= 0x7fffffff;
60 if(ix <= 0x3f490fda) return __kernel_tanf(x,z,1);
61
62 /* tan(Inf or NaN) is NaN */
63 else if (ix>=0x7f800000) {
64 if (ix==0x7f800000)
65 __set_errno (EDOM);
66 return x-x; /* NaN */
67 }
68
69 /* argument reduction needed */
70 else {
71 n = rem_pio2f(x,y);
72 return __kernel_tanf(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even
73 -1 -- n odd */
74 }
75}
76libm_alias_float (__tan, tan)
77