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. */
20static const double c1pio2 = 1 * M_PI_2, /* 0x3FF921FB, 0x54442D18 */
21    c2pio2 = 2 * M_PI_2,                 /* 0x400921FB, 0x54442D18 */
22    c3pio2 = 3 * M_PI_2,                 /* 0x4012D97C, 0x7F3321D2 */
23    c4pio2 = 4 * M_PI_2;                 /* 0x401921FB, 0x54442D18 */
24
25float cosf(float x) {
26    double y;
27    uint32_t ix;
28    unsigned n, sign;
29
30    GET_FLOAT_WORD(ix, x);
31    sign = ix >> 31;
32    ix &= 0x7fffffff;
33
34    if (ix <= 0x3f490fda) {    /* |x| ~<= pi/4 */
35        if (ix < 0x39800000) { /* |x| < 2**-12 */
36            /* raise inexact if x != 0 */
37            FORCE_EVAL(x + 0x1p120f);
38            return 1.0f;
39        }
40        return __cosdf(x);
41    }
42    if (ix <= 0x407b53d1) {  /* |x| ~<= 5*pi/4 */
43        if (ix > 0x4016cbe3) /* |x|  ~> 3*pi/4 */
44            return -__cosdf(sign ? x + c2pio2 : x - c2pio2);
45        else {
46            if (sign)
47                return __sindf(x + c1pio2);
48            else
49                return __sindf(c1pio2 - x);
50        }
51    }
52    if (ix <= 0x40e231d5) {  /* |x| ~<= 9*pi/4 */
53        if (ix > 0x40afeddf) /* |x| ~> 7*pi/4 */
54            return __cosdf(sign ? x + c4pio2 : x - c4pio2);
55        else {
56            if (sign)
57                return __sindf(-x - c3pio2);
58            else
59                return __sindf(x - c3pio2);
60        }
61    }
62
63    /* cos(Inf or NaN) is NaN */
64    if (ix >= 0x7f800000)
65        return x - x;
66
67    /* general argument reduction needed */
68    n = __rem_pio2f(x, &y);
69    switch (n & 3) {
70    case 0:
71        return __cosdf(y);
72    case 1:
73        return __sindf(-y);
74    case 2:
75        return -__cosdf(y);
76    default:
77        return __sindf(y);
78    }
79}
80