float copysign1(float  x, float y)
{
        bool t = __builtin_signbit(x) == 0;
        bool t1 = __builtin_signbit(y) == 0;
        return (t == t1) ? y : -y;
}
float copysign2(float  x, float y)
{
        bool t = __builtin_signbit(x) != 0;
        bool t1 = __builtin_signbit(y) != 0;
        return (t == t1) ? y : -y;
}
float copysign3(float  x, float y)
{
        bool t = __builtin_signbit(x) != 0;
        bool t1 = __builtin_signbit(y) == 0;
        return (t != t1) ? y : -y;
}
float copysign4(float  x, float y)
{
        bool t = __builtin_signbit(x) == 0;
        bool t1 = __builtin_signbit(y) != 0;
        return (t != t1) ? y : -y;
}
float copysign5(float  x, float y)
{
        return __builtin_copysignf(x, y);
}

These all should end up being the same code.
Hopefully I didn't mess these up.