[LLVMdev] Would DosBox benefit from LLVM JIT? (original) (raw)
Jacek Wielemborek d33tah at gmail.com
Wed Jul 22 06:36:36 PDT 2015
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W dniu 22.07.2015 o 15:21, David Chisnall pisze:
A sequence of 32 instruction is not very likely to have many optimisation opportunities that LLVM can take advantage of.
I don't know the codebase, but perhaps it's as easy as increasing the number here and maybe adjusting some relevant buffers:
https://github.com/wjp/dosbox/blob/idados/src/cpu/core_dynrec.cpp#L212
You may get a speedup from longer traces, though of course the LLVM JITing time is likely to be longer, so you’d want to make sure that it’s done in a separate thread. If you can get longer traces (and DOSBox has the infrastructure already for invalidating on self-modifying code) then you may be able to get some speedup.
Introducing another thread sounds like a difficult task, though it definitely makes sense and could be worth it, though...
There was a similar project to use LLVM in QEMU a few years ago that failed to provide a speedup.
David
Why did it fail?
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