If i take $v\in H^1(\Omega)$ where $$ H^1(\Omega)=\{u\in L^2(\Omega), \frac{\partial u}{\partial x_i}\in L^2(\Omega), i=1,\ldots,N\} $$

$\Omega$ is bounded open set from $\mathbb{R}^N$

What is the sufficient condition for a real function $f:\mathbb{R}\rightarrow \mathbb{R}$ to have that $f\circ v\in H^1(\Omega)$

Thank you