local data flow

[Joern RENNECKE]

Kenneth Zadeck wrote:

>  
>
>The right way to do this is not to build chains but to define your own
>dataflow problem to do this. 
>  
>
But wouldn't I need to update the problem solution every time a change a 
bit of the
program - which would be much more costly then doing a local update of some
local def-firstuse or use-nextuse chains?

>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.
>  
>
It is reaching uses, but the starting point is not necessarily a 
definition, but is more
often a use.  I want to know about uses that are forward of the current 
site in the
control flow, but I suppose this is best computed with a backward 
propagation of
lifeness data.  AFAICT that's the same direction that the current 
reaching use problem
has.