[LLVMdev] Cross compilation question

[Jim Grosbach]

Hi Rafal,

LLVM's bitcode is not target independent in the manner you're hoping for. You can't take bitcode generated for x86 and use it on ARM, for example, or bitcode generated for Linux and use it on Darwin.

-Jim


On Jun 18, 2011, at 4:10 PM, Rafal Rusin wrote:

> Hello,
> 
> I wonder if it's possible to cross compile regular linux packages
> (autotools based) into llvm bitcode.
> Such bitcode could run on multiple target platforms using lli.
> So for example if we take 'tar' sources and compile them, we have
> 'tar' bitcode.
> We can run it using 'lli tar'.
> 
> If it was possible in general, then probably building lots of linux
> packages could be easy
> using for example openembedded distribution.
> 
> BTW. This question is more theoretical than actually needed for
> something particular.
> 
> So I tried to do something like this or 'tar' sources:
> ./configure --host none-llvm --target none-llvm
> 
> I had to rename llvm-gcc etc into none-llvm-*, because autotools complained on
> non recognized architecture when I used 'llvm'.
> 
> But I got an error later:
>  GEN    rmt-command.h
> make  all-am
> make[3]: Entering directory `/home/joker/tar-1.23/lib'
>  CC     rtapelib.o
>  AR     libtar.a
> make[3]: Leaving directory `/home/joker/tar-1.23/lib'
> make[2]: Leaving directory `/home/joker/tar-1.23/lib'
> Making all in rmt
> make[2]: Entering directory `/home/joker/tar-1.23/rmt'
>  CCLD   rmt
> ../gnu/libgnu.a: could not read symbols: Malformed archive
> collect2: ld returned 1 exit status
> make[2]: *** [rmt] Error 1
> make[2]: Leaving directory `/home/joker/tar-1.23/rmt'
> make[1]: *** [all-recursive] Error 1
> make[1]: Leaving directory `/home/joker/tar-1.23'
> make: *** [all] Error 2
> 
> 
> The other problem is that probably linker (llvm-ld) generates
> platform specific executable instead of bitcode in this case.
> 
> So if you had any clues how I could fix this, then
> it would be great.
> 
> BTW. I'm not sure also if that would work for technical reasons, like
> binary compatibility.
> 
> -- 
> Regards,
> Rafał Rusin
> 
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