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Date: -- (:)
From: Török Edwin <edwintorok@g...>
Subject: Re: [Caml-list] OCamlJIT2 vs. OCamlJIT
On Tue, 30 Nov 2010 09:36:07 +0100
Benedikt Meurer <benedikt.meurer@googlemail.com> wrote:

> Hello everybody,
> 
> I did some final work on OCamlJIT2, and compared the result to
> OCamlJIT. The performance measures are presented in the following
> tech report (skip straight to section 4 for the performance results):
> 
> http://arxiv.org/abs/1011.6223
> 
> In short: Performance measured on a P4 "Northwood" (no long mode,
> plain x86) 2.4GHz. OCamlJIT2 beats OCamlJIT by a factor of 1.1 to 2.0
> in every benchmark, and - rather surprising - was even able to beat
> ocamlopt in the number crunching benchmark (probably an issue with
> the x86 backend of ocamlopt).

Looks like this happens only on Pentium4: on Core2 and Xeon ocamlopt
is still faster on almabench.unsafe, or did I miss something?

> 
> As mentioned by Xavier Leroy and others previously, we probably went
> as far as we could go in the direction of JITting the byte-code
> virtual machine, while preserving its general stack-based nature and
> instruction set. Moving even further means translating the byte-code
> to some intermediate form suitable for use with standard compilation
> techniques; but as we saw earlier, in an LLVM-based prototype, the
> compilation overhead increases dramatically and the benefit of JIT
> compilation vanishes.

An LLVM-based backend would still be interesting for static
compilation, where compile times don't matter much.
Did you try comparing an LLVM-based backend with ocamlopt?
If it is faster could some of the LLVM passes be ported to ocamlopt's
backend?

Best regards,
--Edwin