1 /* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */
2 /*
3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
4 * Optimized by Bruce D. Evans.
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 "libm.h"
18
19 /* Small multiples of pi/2 rounded to double precision. */
20 static const double
21 c1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
22 c2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
23 c3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
24 c4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
25
cosf(float x)26 float cosf(float x)
27 {
28 double y;
29 uint32_t ix;
30 unsigned n, sign;
31
32 GET_FLOAT_WORD(ix, x);
33 sign = ix >> 31;
34 ix &= 0x7fffffff;
35
36 if (ix <= 0x3f490fda) { /* |x| ~<= pi/4 */
37 if (ix < 0x39800000) { /* |x| < 2**-12 */
38 /* raise inexact if x != 0 */
39 FORCE_EVAL(x + 0x1p120f);
40 return 1.0f;
41 }
42 return __cosdf(x);
43 }
44 if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */
45 if (ix > 0x4016cbe3) /* |x| ~> 3*pi/4 */
46 return -__cosdf(sign ? x+c2pio2 : x-c2pio2);
47 else {
48 if (sign)
49 return __sindf(x + c1pio2);
50 else
51 return __sindf(c1pio2 - x);
52 }
53 }
54 if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */
55 if (ix > 0x40afeddf) /* |x| ~> 7*pi/4 */
56 return __cosdf(sign ? x+c4pio2 : x-c4pio2);
57 else {
58 if (sign)
59 return __sindf(-x - c3pio2);
60 else
61 return __sindf(x - c3pio2);
62 }
63 }
64
65 /* cos(Inf or NaN) is NaN */
66 if (ix >= 0x7f800000)
67 return x-x;
68
69 /* general argument reduction needed */
70 n = __rem_pio2f(x,&y);
71 switch (n&3) {
72 case 0: return __cosdf(y);
73 case 1: return __sindf(-y);
74 case 2: return -__cosdf(y);
75 default:
76 return __sindf(y);
77 }
78 }
79