A few days ago, the ARM Software Dev Tools blog posted their 2015Q2 update on their use of Open Source Toolchains. The post talks about ARM changes in GNU GCC as well as LLVM. It appears they’re getting ready to present at GNU Cauldron in August. Look at their blog for more information. They’ve got some YouTube video and presentation slides, as well.
One thing this blog post clarified to me was what codebase ARM’s C compiler was based on: LLVM Clang:
“The commercial toolchain we offer to our customers, ARM Compiler 6, is in fact based on open source clang.”