Calculating $(x_1^{x_2})(x_2^{x_1})$ in a quadratic equation

Question

Supposing $S=x_1+x_2$ and $P=x_1x_2$ where $x_1$ and $x_2$ are the roots of the quadratic equation $ax^2+bx+c=0$ (it's clear the equation is equivalent to $x^2-Sx+P=0$ where $S=-b/a$ and $P=c/a$), how we can calculate $(x_1^{x_2})(x_2^{x_1})$?