1#include "libm.h"
2
3#if FLT_EVAL_METHOD == 0 || FLT_EVAL_METHOD == 1
4#define EPS DBL_EPSILON
5#elif FLT_EVAL_METHOD == 2
6#define EPS LDBL_EPSILON
7#endif
8static const double_t toint = 1 / EPS;
9
10double round(double x) {
11    union {
12        double f;
13        uint64_t i;
14    } u = {x};
15    int e = u.i >> 52 & 0x7ff;
16    double_t y;
17
18    if (e >= 0x3ff + 52)
19        return x;
20    if (u.i >> 63)
21        x = -x;
22    if (e < 0x3ff - 1) {
23        /* raise inexact if x!=0 */
24        FORCE_EVAL(x + toint);
25        return 0 * u.f;
26    }
27    y = x + toint - toint - x;
28    if (y > 0.5)
29        y = y + x - 1;
30    else if (y <= -0.5)
31        y = y + x + 1;
32    else
33        y = y + x;
34    if (u.i >> 63)
35        y = -y;
36    return y;
37}
38