Thoughts about semantics of BB_VISITED

[Diego Novillo]

Zdenek Dvorak wrote:
> Hello,
> 
> 
>>>If the state of the mark would be undefined, you would need either to
>>>clean them up first (over whole cfg), or use bitmaps for the marks.
>>>Both of these approaches bring a risk of quadratic behavior.
>>>
>>
>>Quadratic behaviour?  How?
> 
> 
> because the places where it is used now (most notably, get_loop_body)
> do not look at whole cfg, but just at the loop body.
 >
Oh, I see.  So, this is inside a helper, not a pass.  How unfortunate. 
Perhaps get_loop_body should not use BB_VISITED.  What if the pass 
calling get_loop_body is using BB_VISITED for its own processing?

In any case, I agree that we should assert this inside verify_flow_info. 
  I'll prepare a patch.


Diego.