Arr, I'm not happy with the topic, but while reading through Agner Fog's recent thoughts on Intel compiler and software, it seems that the reason why the GNU compiler was slower than Intel compiler is that the GNU compiler has sub-par performance in Windows environment compared to Linux environment. Since most of the code is in C, the GCC should actually be faster than Intel C compiler, while Intel may be slightly ahead with their C++ compiler.

Here's the actual quote:
Quote Originally Posted by Agner Fog
In my test of the optimizing performance of C++ compilers, the Intel compiler and the Gnu compiler for Linux shared the first place. Unfortunately, the Gnu compiler for Windows is not up to date so we still need a good replacement for the Intel compiler for Windows.
So, if there's ever going to be linux version compiled with GCC, it could potentially mean that there might be some performance gain for AMD users.