Thoughts about semantics of BB_VISITED

[Zdenek Dvorak]

Hello,

> >because get_loop_body is often used on places where (lots of) new blocks
> >get created (like unroller).  Resizing the sbitmap would be quite
> >annoying.
> 
> Also, it's quite annoying to have to keep resetting these flags.  I don't 
> think a simple read-only helper should be altering the basic block flags.
> All i did was ask for the loop body.

it does not change them -- they must be clear on the entry, and they are
clear on the exit.  Aand this is by far the simplest way.  On contrary,
I believe that the optimization passes should not use these flags.
While inside the shared utility there is at least some justification for
it (it saves you passing bitmap to it and other trouble), I see no
justification why for example PRE cannot use sbitmap instead of touching
BB_VISITED.

Zdenek