[LLVMdev] Using LLVM on an embedded device

Evan Cheng evan.cheng at apple.com
Mon Jun 29 16:48:49 PDT 2009

On Jun 26, 2009, at 3:11 PM, Anna Zaks wrote:

> Hi Evan,
> Sorry for the delayed reply. We've compiled llvm on Linux with only  
> the x86 target, which produced an lli executable that's about 5.5MB.  
> The LLVMX86CodeGen.o alone is 1.7MB. We've configured with
> --disable-assertions --enable-optimized --enable-targets=x86 -- 
> disable-debug-runtime --enable-bindings=none --disable-ltdl-install  
> --disable-shared --enable-static
> Are there any tips on making them even smaller? It seems that the  
> ARM backend would be smaller but I am not sure if we could get it  
> under 2MB. Also I guess, the interpreter could be removed, but it is  
> quite small (145KB).

Size of lli is a poor indicator for dynamic memory footprint. You  
really have to measure in a JIT environment. That said, there are  
definitely possibilities for reducing the size. But I don't think  
there is anyone actively working on it.

> Thank you,
> Anna.
> > Hi,
> >
> > I am researching a possibility of running LLVM components (such as
> > JIT) on an embedded device, where the memory footprint and RAM usage
> > are the main concerns. So I was wondering if anyone could share
> > their experience with running LLVM on an embedded device. What is
> > the approximate code footprint that we are looking at? For example,
> > on an x86 with a minimum set of optimizations and with only the x86
> > backend, it seems difficult to get the LLVM JIT occupy less than
> > 5MB. Is there any performance and memory usage data available?
> That seems too high. I would think it's more in the 2MB range. How did
> you come about that figure? x86 instruction selector itself is quite
> large due to the complex selection patterns. I would expect ARM's
> footprint to be smaller.
> There are ways to reduce memory foot print further. But it will
> require someone to drive the effort. One of the (very rough) idea is
> to switch to a table driven instruction selector.
> Evan
> >
> > Thank you!
> > Anna.
> >
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