When beginning with our Apache web-server benchmark, there was not a whole lot of difference in performance between the eight tested compilers. The only exception is when using LLVM DragonEgg on the AMD Opteron Quad-Core where its performance strangely plummeted.
The Gcrypt library performance when built with the different GCC and LLVM compilers was more interesting. On all three systems, GCC 4.3.0 had regressed rather significantly compared to GCC 4.2.1, but fortunately, that regression was addressed in GCC 4.4.0. With all three systems, the GCC 4.6.0 development snapshot from 2010-10-30 was the fastest, which makes us excited for this next GNU Compiler Collection release coming in 2011. While LLVM-GCC had no problems building the Gcrypt test, DragonEgg and Clang both failed. LLVM-GCC provided no real performance gains in this benchmark over using a normal GCC build.
The OpenSSL performance had not fluctuated much between the different compilers and GCC versions. However, GCC 4.5.1 with DragonEgg failed to build OpenSSL.