Profiling compilation time

[Yang Zhang <yanghatespam@xxxxxxxxx>]

Hi, are there any tools or hooks available that would help with 
profiling compilation time within g++?  I'd like to gain a better 
understanding of where the time goes, primarily on two dimensions:

- Which files does the compiler spend most of its time working with?

- What stages of compilation are most expensive?

Thanks!
--
Yang Zhang
http://www.mit.edu/~y_z/