local data flow

[Joern RENNECKE]

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.

> 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.