The reaction $\frac{1}{2}{\mathrm{H}}_2\left(\mathrm{g}\right)+\mathrm{AgCl}\left(\mathrm{s}\right)\to {\mathrm{H}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)+\mathrm{Ag}\left(\mathrm{s}\right)$ occurs in the galvanic cell

${\mathrm{H}}_2$ is oxidized to ${\mathrm{H}}^{+}$ and thus it will occur at anode, i.e., left side electrode is $\text{ Pt }\left|{\mathrm{H}}_2\left(\mathrm{g}\right)\right|\mathrm{HCl}\left(\mathrm{aq}\right) \mathrm{Agcl}$ s reduced to Ag and thus it will occur at cathode, i.e., right side electrode is $\mathrm{HCl}\left(\mathrm{aq}\right)\left|\mathrm{AgCl}\right(\mathrm{s}\left)\right|\mathrm{Ag}\left(\mathrm{s}\right)$