GCC 4.9 vs. GCC 5.3 vs. GCC 6.1 On A Debian Xeon E5 Linux System

From this Debian box powered by an Intel Xeon E5-2687W v3 + MSI X99S SLI PLUS, I was using Debian testing and did clean builds of the GCC 4.9.3, GCC 5.3.0, and GCC 6.0.0 for Linux x86_64. Following that I ran a range of primarily C/C++ benchmarks using the open-source Phoronix Test Suite.