On Sun, Jul 29, 2012 at 11:43 AM, Erick Tryzelaar <erick.tryzel...@gmail.com> wrote: > Unfortunately there are some pretty severe performance issues at the moment. > Ragel supports two state machine styles, table-driven and goto-driven. My > backend uses tables, but since Rust doesn't yet support global constant > vectors, I need to malloc the state machine table on every function call. This > results in the [ragel-based url > parser](https://github.com/erickt/ragel/blob/rust/examples/rust/url.rl) > being about > 10 times slower than the equivalent table-based parser in OCaml. You can see > the generated code [here](https://gist.github.com/3200980).
There's an open bug on vector constants: https://github.com/mozilla/rust/issues/571 It's assigned to me (though I haven't done anything on it yet), so feel free to bug me about it :-) > > The `goto` route could be promising to explore. We could simulate it using > mutually recursive function calls. OCaml does this. But again, since Rust > doesn't support tailcalls (and may > [ever](https://github.com/mozilla/rust/issues/217)), we could run into a stack > explosion. It may work well for small grammars though, and maybe LLVM could > optimize calls into tailcalls. This sounds like the open bug on labelled break and continue, as Patrick said: https://github.com/mozilla/rust/issues/2216 which is currently unassigned. As per #217, we decided not to support general tail calls, but that doesn't mean we can't support tail calls just for the special labelled break/continue form. Cheers, Tim -- Tim Chevalier * http://catamorphism.org/ * Often in error, never in doubt "Debate is useless when one participant denies the full dignity of the other." -- Eric Berndt _______________________________________________ Rust-dev mailing list Rust-dev@mozilla.org https://mail.mozilla.org/listinfo/rust-dev
