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Date: | 1997-03-28 (11:13) |
From: | Mark Hayden <hayden@c...> |
Subject: | Re: ocaml inlining |
>> In the recent versions of Ocaml, are functions inlined >> across modules? Across files? > >Yes to both. (Remember: this applies only to the native-code compiler.) >The body of an inlinable function is stored in the .cmx file for its >defining module, thus it can be inlined from other modules. > >> If so, what is the effect of >> compiling several files with different levels of inlining? > >The inlining level (-inline n) is taken into account when compiling a >function definition, but not when compiling a call to this function. >If the function is small enough (w.r.t. the inlining level at that >time), it is marked inlinable, and all uses of this function will >inline its body, regardless of the value of -inline at the time of use. Doing things in this fashion seems to prevent functions in the standard library from being inlined (other than with the default level). It would seem that there could be many advantages to inlining functions such as List.iter. Is there any way to get around this limitation without recompiling & reinstalling the standard library or compiling private versions of the standard library modules? Also, I tried compiling the following to see what assembly code was being generated: let rec map f = function (* from List module *) [] -> [] | a::l -> let r = f a in r :: map f l let list_incr l = map (fun i -> succ i) l Unfortunately, no matter how large an inlining level was used, the map function would not be inlined. When I looked at the compiler sources, I found that "let rec" expressions are never inlined. Is there a reason for this? As a final note, I ran some tests to see the effect of inlining on the size of Ensemble, the system I'm working on. Ensemble is a distributed communication system with around 30,000 lines of ML code. With varying levels of inlining, I compiled, linked, and stripped all of Ensemble, and then printed the size of the resulting executable. inline executable level size 0 757024 1 757424 2 765584 3 769776 4 772928 8 782032 16 787488 20 792064 24 795136 28 803056 32 803056 --Mark