s_tanf.c revision 152596 
1/* s_tanf.c -- float version of s_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#ifndef lint
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/s_tanf.c 152596 2005-11-19 02:38:27Z bde $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23/* Small multiples of pi/2 rounded to double precision. */
24static const double
25t1pio2 = 1*M_PI_2,			/* 0x3FF921FB, 0x54442D18 */
26t2pio2 = 2*M_PI_2,			/* 0x400921FB, 0x54442D18 */
27t3pio2 = 3*M_PI_2,			/* 0x4012D97C, 0x7F3321D2 */
28t4pio2 = 4*M_PI_2;			/* 0x401921FB, 0x54442D18 */
29
30static inline float
31__kernel_tandf(double x, int iy)
32{
33	return __kernel_tanf((float)x, x - (float)x, iy);
34}
35
36float
37tanf(float x)
38{
39	float y[2],z=0.0;
40	int32_t n, hx, ix;
41
42	GET_FLOAT_WORD(hx,x);
43	ix = hx & 0x7fffffff;
44
45	if(ix <= 0x3f490fda) {		/* |x| ~<= pi/4 */
46	    if(ix<0x39800000)		/* |x| < 2**-12 */
47		if(((int)x)==0) return x;	/* x with inexact if x != 0 */
48	    return __kernel_tanf(x,z,1);
49	}
50	if(ix<=0x407b53d1) {		/* |x| ~<= 5*pi/4 */
51	    if(ix<=0x4016cbe3)		/* |x| ~<= 3pi/4 */
52		return __kernel_tandf(x + (hx>0 ? -t1pio2 : t1pio2), -1);
53	    else
54		return __kernel_tandf(x + (hx>0 ? -t2pio2 : t2pio2), 1);
55	}
56	if(ix<=0x40e231d5) {		/* |x| ~<= 9*pi/4 */
57	    if(ix<=0x40afeddf)		/* |x| ~<= 7*pi/4 */
58		return __kernel_tandf(x + (hx>0 ? -t3pio2 : t3pio2), -1);
59	    else
60		return __kernel_tandf(x + (hx>0 ? -t4pio2 : t4pio2), 1);
61	}
62
63    /* tan(Inf or NaN) is NaN */
64	else if (ix>=0x7f800000) return x-x;
65
66    /* general argument reduction needed */
67	else {
68	    n = __ieee754_rem_pio2f(x,y);
69	    /* integer parameter: 1 -- n even; -1 -- n odd */
70	    return __kernel_tanf(y[0],y[1],1-((n&1)<<1));
71	}
72}
73