basic bloc chaining: using dominance

[Pierre Vittet]

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?