What is the purpose of the *** family of GCC optimization options?

Question

Reading the gcc manual, I see the -ftree-*** optimization options family. What is the purpose of these options? What are these "trees"?

Answer 1

They are optimizer packages that work with trees (SSA) inside the compiler, and not at the RTL level (translation language).

For what it is, see the GCC internal docs documentation: http://gcc.gnu.org/onlinedocs/gccint/

For an introduction about SSA, see http://en.wikipedia.org/wiki/Static_single_assignment_form