GCC options for optimization on given CPU architecture

I am working on Nehalam/westmere Intel micro architecture CPU. I want to optimize my code for this Architecture. Are there any specialized compilation flags or C functions by GCC which will help me improve my code's run time performance?

I am already using -o3.

Language of the Code - C
Platform - Linux
GCC Version - 4.4.6 20110731 (Red Hat 4.4.6-3) (GCC)

In my code I have some floating point comparison and they are done over a million time.

Please assume the code is already best optimized.