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Re: local data flow


Joern RENNECKE wrote:
> Kenneth Zadeck wrote:
>
>>  
>>
>> you can have def-use chains, you can have use-def chains or you can have
>> both.
>> It seems like what you are asking for are use-def chains,
>>
> No, I want to know if there exists a path from the current *use* of a
> register to
> some other *use* of the same register without going through a def.
>
The right way to do this is not to build chains but to define your own
dataflow problem to do this. 

I think that what you want is something like the reaching uses problem
but you want a forwards version of this rather than a backwards version
as is defined in df-problems.c.
However, you may find that that problem does provide the info you are
looking for.

If this is what you want, I can help you define it.



>> i.e. the list
>> of defs that can reach each use.  If the set is empty, this is equiv to
>> a reg-dead note.
>>  
>>
> Huh?  If the set is empty, the use is either uninitialized or
> unreachable.
yes, I am sorry


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