Re: basic bloc chaining: using dominance

[Pierre Vittet <piervit at pvittet dot com>]

On 10/05/2011 16:23, Ian Lance Taylor wrote:
> Pierre Vittet<piervit@pvittet.com>  writes:
>
>    
> > I am working on a plugin at the GIMPLE state, I am parsing basic
> > blocks and I need to check that a call to foo() is only present once
> > in a function. Howerver, it can be present several times if it is in
> > different basic blocks and only one is executed at execution time.
> >
> > I think the most convenient way is to use dominance relation between
> > the basic blocks: I can warn in a basic block A calling the foo()
> > function only if there is a block B calling foo and dominating A. In
> > others cases, I cannot be sure that there is several calls to foo().
> >
> > In the file gcc/dominance.c, there is a dominated_by_p function which
> > allows to test dominance between 2 basic blocks and I would like to
> > use it to solve this problem.
> >
> > I would like to have your opinion, does it looks the google solution
> > to the problem or is there another way to do this?
> >
> > If this is a good solution, I will implement a primitive in MELT
> > allowing to use dominated_by_p function in MELT.
> >      
> Yes, dominated_by_p and friends are the right way to test for basic
> block dominance.  Note that you have to build the graph first; see uses
> of calculate_dominance_info.
>
> Ian
>
>    
First, thanks for your help. I have looked at several function using 
calculate_dominance_info(). From what I understand, when you have finish 
to use it, you have to clear the structure by making a 
free_dominance_info().
In the function flow_loops_find (file gcc/cfgloop.c), there is a call to 
calculate_dominance_info() without call to free_dominance_info(). I feel 
it is a bug, no?