Thierry Manfe has a post at the Sun HPC blogs helping beginners navigate the esoterica of compiler options in the Sun Studio compilers
Sun Studio offers a unique set of optimization features dedicated to processor instruction set that help me squeeze out the best perf out of C, C++ or Fortran code. Yet these options are so numerous that it can be a bit daunting to look into them.
If you are in a rush, you can use the -fast option. What it really does is triggering a set of other options for maximum runtime performance.
What I like about the post is that it talks about options, and gives those just learning enough information to make their own decisions. To whit
Yet -fast has its own drawbacks. First, the options triggered might change from one compiler release to another. Also, the values for -xarch -xcache -xchip specify the processor for which to optimize, and -fast decides of these values based on the processor on which the compiler runs, which can deffer from the processor on which the code will eventually be executed. This is why I usually stay away from -fast.