Something general (beginner related)

[Nils Pipenbrinck <n dot pipenbrinck at cubic dot org>]

Hi folks.

Maybe the one or another remembers the post I've wrote more than a month 
ago. I was (and still am) new to the GCC codebase and had the evil plan 
to add an optimization pass to do byte permutations (capturing all 
home-brewed bswap things and all the other 23 possible byte-permutations 
as well).

Well - I had a lot of time to kill during the last weeks, and I had a 
lot of timeto read into the source. Business trips without internet 
access are a perfect opportunity to read such stuf...

Anyway, after all this passive read-work, I've been able to add the 
humble beginnings of my pass. I'm now able to  and I've been able to run 
a code that does a printf as soon as I find an structure in the SSA tree 
that is a potential candidate for my optimization.

However, approaching this point has been very painfull and I'm far away 
from chainging anything in the SSA.

Let's get to the point: The documentation sucks. If you want to learn 
how things work the wiki and the documentation is of little help. You 
have to read other code, step through other optimizations  and do a lot 
of reverse-engineering and code-reading to understand how all the 
different things fit and relate to each other.

I think a well commented pseudo-pass (well document as: talk to someone 
who know C but has no idea about the GCC magic..) that does something 
stupid but valid like re-inventing the neg-operator by using not and 
subtraction could act as be a very nice boilerplate code for people like me.

For someone who is into the SSA structures and the gcc internals should 
be able to write up something within a day or an half.

Just an idea.. And just to let you know how hard it can be: Finding out 
what GTY means *can* take half a day...

  Nils