This document contains information on how to cross-compile the compiler-rt builtins library for several flavours of Arm target and how to test the libraries using qemu.
I've written this HowTo to try and document my experiences of cross-compiling and testing compiler-rt for Arm targets. Starting with no knowledge of how compiler-rt was built I found this quite hard to do given the existing documentation. I've done most of my testing using just an unpacked linaro gcc or GNU embedded toolchain directory as my sysroot.
I think that the approach will work for other targets that a qemu user-mode emulator exists for but I haven't tested to make sure that they work.
I've documented an abstraction of the scripts that I found worked for me. I'm sure that there are many other ways of doing this, most likely better ones, so if you do have anything that you'd like to add, or have different ideas please let me know and I'll be happy to write them up.