s_tanf.c revision 176569 
1/* s_tanf.c -- float version of s_tan.c.
2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3 * Optimized by Bruce D. Evans.
4 */
5
6/*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
9 *
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
15 */
16
17#include <sys/cdefs.h>
18__FBSDID("$FreeBSD: head/lib/msun/src/s_tanf.c 176569 2008-02-25 22:19:17Z bde $");
19
20#include <float.h>
21
22#include "math.h"
23#define	INLINE_KERNEL_TANDF
24#define INLINE_REM_PIO2F
25#include "math_private.h"
26#include "e_rem_pio2f.c"
27#include "k_tanf.c"
28
29/* Small multiples of pi/2 rounded to double precision. */
30static const double
31t1pio2 = 1*M_PI_2,			/* 0x3FF921FB, 0x54442D18 */
32t2pio2 = 2*M_PI_2,			/* 0x400921FB, 0x54442D18 */
33t3pio2 = 3*M_PI_2,			/* 0x4012D97C, 0x7F3321D2 */
34t4pio2 = 4*M_PI_2;			/* 0x401921FB, 0x54442D18 */
35
36float
37tanf(float x)
38{
39	double y;
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_tandf(x,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_tandf(y,1-((n&1)<<1));
71	}
72}
73