Due to the common ion effect of chloride, the solubility of silver chloride is less in $\mathrm{HCl}$ and $\mathrm{KCl}$, compared to solubility in water. In deionized water no common ion effect will take place so maximum solubility

$AgCl\left(\mathrm{s}\right)\rightleftharpoons {\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)$