I've been working on combining LLVM, clang, the NetBSD standard C library, compiler-rt, QEMU, GDB, and GNU binutils as a cross compilation environment. My goal is to target small embedded systems, but I think that what I'm working on may be of interest to other LLVM/clang developers as I have been able to use the environment to fix several code generation issues in LLVM.
As of today, I can compile non-trivial programs for ARM, i386, Mips, Microblaze, PowerPC, PowerPC64, and X86_64. These programs can be run with the modified NetBSD C library under QEMU in Linux user space emulation mode on my X86_64 Linux box. If anyone is interested in trying it out it is at http://ellcc.org.
Some important notes:
* I have built this on a X86_64 Linux system only. Linux is required to get the QEMU Linux user mode support.
* The SVN checkout is huge, since it has everything mentioned above in it.
* This is a work in progress: There are things that don't work. Not for the faint of heart!
* It is fairly easy to build the complete package, see http://ellcc.org/installation.html and http://ellcc.org/targetsupport.html
* Not all of the NetBSD standard library has been ported. There are a lot of system calls, etc. that have not been tested. I've been adding things as needed, not in any systematic way.
* It is currently based on a fairly recent version of LLVM/clang: r122956.
* Processor support is currently limited to those that are supported by QEMU, just because I wanted to have a common run/debug environment.
Feel free to check it out.