On the Samsung Series 3 Chromebook with Exynos 5 Dual, I've upgraded the operating system to Ubuntu 13.10 and was doing some trial runs of GCC 4.8.1 and LLVM/Clang 3.3 as packaged in the Ubuntu "Saucy" archive for ARM.
For those curious about the performance, the C/C++ benchmark results can be found on OpenBenchmarking.org within 1309037-SO-SAMSUNGCH72. Via the open-source Phoronix Test Suite software you can also carry out your own tests by simply executing phoronix-test-suite benchmark 1309037-SO-SAMSUNGCH72.
If you are more interested in x86/x86_64 than ARM, see my Intel Core i7 LLVM vs. GCC benchmarks on a Haswell CPU and AMD compiler benchmarks from a Richland APU.
Embedded below are just a few of the GCC vs. Clang results on the Cortex-A15 system, so hit up the OpenBenchmarking.org link for all of the results and data in full.