Profiling gcc itself

[Jeff Evarts]

I posted this question at irc://irc.oftc.net/#gcc and they suggested
that I pose it here instead.

I do some "large-ish" builds (linux, gcc itself, etc) on a too-regular
basis, and I was wondering what could be done to speed things up. A
little printf-style checking hints to me that I might be spending the
majority of my time in CPP rather g++, gasm, ld, etc. Has anyone
(ever, regularly, or recently) built gcc (g++, gcpp) with profiling
turned on? Is it hard? Did you get good results?

Specifically I'm wondering what percentage of a g++ compile is spent
in one of three places:

1) opening/reading header files
2) opening/reading source files
3) doing everything else

Thanks in advance for any pointers, results, or thoughts.
-Jeff