\input{umtest-preamble}
\usepackage{unicode-math}
\setmathfont{Asana Math}
\begin{document}
[$x_{x}'$]
[$x_{x}′$]
[$x_{x}\prime$]
[$x_{x}`$]
[$x_{x}\backprime$]

[$x'_x$]
[$x′_x$]
[$x\prime_x$]
[$x`_x$]
[$x\backprime_x$]

[$x_{x'}$]
[$x_{x′}$]
[$x_{x\prime}$]
[$x_{x`}$]
[$x_{x\backprime}$]
   
\end{document}
