The bottom line result seems to be that GCC 4 generates slightly slower code:
I updated my previous benchmark of PHP 5.1. This time around I built PHP with GCC 3.4.5, GCC 4.0.2, and GCC 4.1.0.
When I have more time, I will investigate this further using alternative optimizations, including profiling-guided ones.
The detailed results are also included, showing how he came to each point mentioned above. They include the specs for the machine, how the testing was set up, and the detailed breakdown of the stats for each GCC version.
