For the Himeno Poisson Pressure Solver, the LLVM/Clang performance is competitive with GCC 4.8.0.
When it comes to measuring the time needed to build the ImageMagick program from source, the compile times for LLVM/Clang continue to be dramatically faster than with the GNU Compiler Collection.
Another test done was measuring the compilation time for the widely deployed PHP package. Like the ImageMagick result, the PHP compilation time was dramatically shorter with LLVM/Clang over GCC.
GCC 4.8.0 still maintains a slight performance edge over LLVM/Clang 3.3 with the C-Ray multi-threaded ray-tracer.