third_party/ulib/musl/src/math/trunc.c

#include "libm.h"

double trunc(double x) {
    union {
        double f;
        uint64_t i;
    } u = {x};
    int e = (int)(u.i >> 52 & 0x7ff) - 0x3ff + 12;
    uint64_t m;

    if (e >= 52 + 12)
        return x;
    if (e < 12)
        e = 1;
    m = -1ULL >> e;
    if ((u.i & m) == 0)
        return x;
    FORCE_EVAL(x + 0x1p120f);
    u.i &= ~m;
    return u.f;
}