Our first test looking at the generated binary performance of GCC and LLVM was with Apache via the Phoronix Test Suite. LLVM-GCC proved to run at about the same speed as GCC 4.3/4.4/4.5, but surprisingly Clang was the fastest! The Apple-backed compiler was able to handle delivering 9% more requests per second with the Apache server than with GCC. For servers under heavy load this performance boost could be rather welcomed.
LLVM-GCC had a rather strange performance issue with 7-Zip that basically killed its numbers, but Clang was performing on par with GCC 4.4.0, which is slightly behind where GCC 4.5 is running.
Building the LAME program under LLVM-GCC and Clang led to it running slower at encoding WAV files to MP3 than when built with any of the past three GCC releases. This SVN snapshot of Clang was 12% slower than GCC 4.5.0.