Clang: now available from a SVN server near you!

[Erik Cederstrand]

Den 04/06/2009 kl. 11.38 skrev Ed Schouten:

> You can now build your very own version of FreeBSD with Clang  
> installed
> as /usr/bin/cc as follows:

Thanks for your hard work, Ed. This is great news!

You might want to mention that a few parts are still GCC-compiled due  
to bugs in Clang ( see http://wiki.freebsd.org/ 
BuildingFreeBSDWithClang). Also, it's very encouraging that the ports  
run you did with Erwin (http://lists.cs.uiuc.edu/pipermail/cfe-dev/2009-June/005274.html 
) compiles over 7000 ports with Clang.

I've asked in the Clang list, but I'd like an opinion from FreeBSD  
folks, too: Clang supports LTO (http://llvm.org/docs/LinkTimeOptimization.html 
), which has a potential for performance improvements. It doesn't work  
on FreeBSD because the linker we have (in binutils) doesn't know about  
the libLTO that LLVM provides. There's a new linker from GNU called  
Gold, but as far as I know it's GPLv3 licensed and therefore  
undesirable at least to have in base. LLVM provides a linker (http://llvm.org/cmds/llvm-ld.html 
) but "it doesn't interact correctly with conventional nm/ar/etc" (http://lists.cs.uiuc.edu/pipermail/cfe-dev/2009-June/005296.html 
). There's the ELF toolchain project (elftoolchain.sourceforge.net/)  
but a BSD-licensed ld hasn't been developed yet.

What would be the best way to get LTO to work on FreeBSD?

Thanks,
Erik