fix potentially wrong-sign zero in cproj functions at infinity

[musl] / src / math / s390x / fma.c

#include <math.h>

double fma(double x, double y, double z)
{
        __asm__ ("madbr %0, %1, %2" : "+f"(z) : "f"(x), "f"(y));
        return z;
}