Extending GCC with new optimization

[Tomasz Jankowski]

Hello,

I'm investigating where to start and I'm overwhelmed with compilation
process, so I'd like to ask you on which passes I should focus and
where I actually should start.

I have to find arithmetical operations in input source code and
implement them using specific processor instructions on my CPU.

First of all I don't see any pass related to RTL representation in GCC
plugin events (file plugin.def), so is it possible to create GC plugin
modifying RTL representation at all?

Anyway, I should:

1. Add somehow (so far I don't know how) custom CPU instructions to GCC code.
2. Operate on RTL representation of basic blocks (I can modify RTL
representations by adding and removing instructions?).