I actually had to crack open the man page for a few seconds since I couldn't find a flag I was wanting... and found something rather delightful... information about the compiler in general! It applies to almost all compilers and it's a good summary that can help people understand how the process goes:
http://www.manpagez.com/man/1/clang/
Specifically, the description section but reading some of the flags can also help you understand what a tool like clang/gcc is capable of.