Run-time monomorphization

Some compilers like Stalin (for Scheme) and MLton (for SML) use
whole-program optimizations to completely remove the run-time cost of
polymorphism. In contrast, languages like OCaml often suffer a 2x slowdown
due to polymorphism in performance critical functions (due to run-time
dispatch inserted into inner loops and not hoisted) that must then be
optimized manually.


If I'm using LLVM to JIT compile code for an OCaml-like language, can I
monomorphize function definitions on the fly easily?


May I conjecture how:


. Fetching a handle to a function "f" at its call site uses a
function "get".


. The application "get f" is memoized with respect to the instantiations of
the type variables of "f" used at its call site.


Consider the example:


    val List.fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a
    let sum_int = List.fold_left (+) 0
    let sum_float = List.fold_left (+.) 0.


The call to "List.fold_left" inside "sum_int" uses 'a = 'b = int and a
version of "List.fold_left" is JIT compiled specifically for those types.


Similarly for "sum_float" with 'a = 'b = float.


--
Dr Jon D Harrop, Flying Frog Consultancy Ltd.
http://www.ffconsultancy.com/products/?u

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