Exactly. It's just like SQL: different queries end up as different entries in the query cache; although SQL is beneficially fuzzy in this case, if only the constants differ you should get a cache hit.

The "safe" and fast way to use eval for JIT is to get it to return a function, with all user inputs as parameters (like like the safe and fast way to do SQL is with parameters):

    var f = eval("(function (a, b) { return a + b })");
    f("a", "b");

Why not just do:

var f = new Function('a', 'b', 'return a + b')

I had no idea that was possible. The concept still applies though.