M_PI_2l
: M_PI_2l), __imag__ x);
__imag__ res = copysignl (M_PI_2l, __imag__ x);
__real__ res = M_PI_2l - __real__ y;
__imag__ res = copysignl (rcls >= FP_ZERO ? M_PI_2l : M_PI_4l,