[LLVMdev] cfrontend building

Chris Lattner sabre at nondot.org
Tue Aug 9 09:22:04 PDT 2005

On Tue, 9 Aug 2005, Stephan Wienczny wrote:
> I found the problem. The gcc sources are older than those on my system. I've
> got some CFLAGS that the old gcc does not know, eg. -march=pentium-m. Are
> these flags filtered out everything works fine ;-)

Ok, great!

> What are the differences between the cfrontends.tar.gz and the corresponding
> gcc release?

It's a pretty big diff.  All of the code for translating to llvm form, 
plus minor patches here and there to cause GCC to produce more type-safe 
LLVM code (e.g. not lowering address arithmetic etc).  Total it's probably 
about 15K LOC.

> What would have to be done to get a new version of gcc working as 
> frontend?

It's a pretty significant job.  You could try to merging in new bits from 
GCC mainline, but it's a nasty job: debugging failures requires pretty 
strong understanding of how GCC works.  Easier would be to patch the 
llvm-gcc X86 configuration stuff to accept and ignore that switch.

If it's any consolation, it seems fairly likely that there will be a new 
llvm-gcc in development in the next couple of months, based on GCC 



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