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

#include <math.h>
#include <stdint.h>

int __fpclassify(double x) {
    union {
        double f;
        uint64_t i;
    } u = {x};
    int e = u.i >> 52 & 0x7ff;
    if (!e)
        return u.i << 1 ? FP_SUBNORMAL : FP_ZERO;
    if (e == 0x7ff)
        return u.i << 12 ? FP_NAN : FP_INFINITE;
    return FP_NORMAL;
}