If you have some performance-critical part of the code, you can help the compiler to optimize the code with [[likely]] and [[unlikely]] attributes.
auto f(int i) -> int
{
switch (i)
{
case 1: [[fallthrough]];
[[likely]] case 2: return 1;
}
return 2;
}
https://en.cppreference.com/w/cpp/language/attributes/likely