xref: /freebsd/lib/msun/src/s_tanf.c (revision 3fb8f1272b50cb87cb624b321f7b81e76627c437)
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 <float.h>
18 
19 #include "math.h"
20 #define	INLINE_KERNEL_TANDF
21 #define INLINE_REM_PIO2F
22 #include "math_private.h"
23 #include "e_rem_pio2f.c"
24 #include "k_tanf.c"
25 
26 /* Small multiples of pi/2 rounded to double precision. */
27 static const double
28 t1pio2 = 1*M_PI_2,			/* 0x3FF921FB, 0x54442D18 */
29 t2pio2 = 2*M_PI_2,			/* 0x400921FB, 0x54442D18 */
30 t3pio2 = 3*M_PI_2,			/* 0x4012D97C, 0x7F3321D2 */
31 t4pio2 = 4*M_PI_2;			/* 0x401921FB, 0x54442D18 */
32 
33 float
34 tanf(float x)
35 {
36 	double y;
37 	int32_t n, hx, ix;
38 
39 	GET_FLOAT_WORD(hx,x);
40 	ix = hx & 0x7fffffff;
41 
42 	if(ix <= 0x3f490fda) {		/* |x| ~<= pi/4 */
43 	    if(ix<0x39800000)		/* |x| < 2**-12 */
44 		if(((int)x)==0) return x;	/* x with inexact if x != 0 */
45 	    return __kernel_tandf(x,1);
46 	}
47 	if(ix<=0x407b53d1) {		/* |x| ~<= 5*pi/4 */
48 	    if(ix<=0x4016cbe3)		/* |x| ~<= 3pi/4 */
49 		return __kernel_tandf(x + (hx>0 ? -t1pio2 : t1pio2), -1);
50 	    else
51 		return __kernel_tandf(x + (hx>0 ? -t2pio2 : t2pio2), 1);
52 	}
53 	if(ix<=0x40e231d5) {		/* |x| ~<= 9*pi/4 */
54 	    if(ix<=0x40afeddf)		/* |x| ~<= 7*pi/4 */
55 		return __kernel_tandf(x + (hx>0 ? -t3pio2 : t3pio2), -1);
56 	    else
57 		return __kernel_tandf(x + (hx>0 ? -t4pio2 : t4pio2), 1);
58 	}
59 
60     /* tan(Inf or NaN) is NaN */
61 	else if (ix>=0x7f800000) return x-x;
62 
63     /* general argument reduction needed */
64 	else {
65 	    n = __ieee754_rem_pio2f(x,&y);
66 	    /* integer parameter: 1 -- n even; -1 -- n odd */
67 	    return __kernel_tandf(y,1-((n&1)<<1));
68 	}
69 }
70