[LLVMdev] llvm-qemu. (Was: Newbie)

Ralph Corderoy ralph at inputplus.co.uk
Sun Apr 6 04:11:44 PDT 2008

Hi Tilmann,

> Nevertheless, it is unlikely that llvm-qemu will ever be much faster
> than regular qemu (by replacing its code generator completely, which
> it currently does), which is due to the fact that regular qemu has a
> very lightweight code generator (it basically only copies blocks of
> memory and performs some patching to them and only does static
> register allocation) which generates reasonably good code, with a very
> low overhead for compilation time. In contrast the LLVM JIT generates
> really high quality code (in fact the JIT and the static compiler
> share the same code generator), but at a higher price in terms of
> compilation time.

How about storing generated code on disc?  Or the intermediate IR?  I'd
typically use the same things under qemu day after day and would be
happy to slowly build up a cache on disc.  Perhaps starting qemu with a
'spend time and add to cache' option when I'm getting it to learn and a
'use only what's in the cache already' when I having got the time to



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