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OCamlJIT2 vs. OCamlJIT
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Date: 2010-11-30 (08:36)
From: Benedikt Meurer <benedikt.meurer@g...>
Subject: OCamlJIT2 vs. OCamlJIT
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):


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).

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.

Therefore, as suggested earlier, I'll try to get my hands on the native top-level now (already contacted Alain for the emitter code). Additionally, the linear scan register allocation will be implemented by a student as part of his diploma thesis.