The optimization to determine index bounds from a regular expression, which works by checking whether the regex is left-anchored and contains a constant prefix, is not applied when the regex has any option other than "m" or "x" (see index_bounds_builder.cpp).

There is no reason why the optimization shouldn't work for the option "s", which only changes the behavior of the . operator, and . can never be part of the constant prefix anyway.

So the suggestion is to perform the optimization even when "s" is present, just as with "m" and "x".