Nested n-th root under XeTeX makes compilation extremely slow

[stone-zeng]

Description

Nested n-th root under XeTeX makes compilation extremely slow. However, when using LuaTeX, the compilation time seems normal (in my computer only 1/7 time of xetex).

Check/indicate

• [x] Relevant for XeTeX
• [ ] Relevant for LuaTeX
• [x] Issue tracker has been searched for similar issues?
• [ ] Links to discussion if appropriate

Minimal example demonstrating the issue

\documentclass{article}
\usepackage{unicode-math}

\begin{document}
\[ \sqrt[x]{y} \]
\[ \sqrt[x]{\sqrt[x]{\sqrt[x]{\sqrt[x]{\sqrt[x]{\sqrt[x]{\sqrt[x]{\sqrt[x]{y}}}}}}}} \]
\end{document}

Further details