Re: Definition of Data Dependence Distance

In article 91-12-041 pugh@cs.umd.edu (Bill Pugh) writes:
>
> Does dependence distance represent the difference in the values of
> the loop variables, or the difference in the loop trip counts?


I think the answer depends on why the compiler needs to know the dependence
distance. If one is interested in doing software pipelining or loop
unrolling, then you would care about the "iteration distance", becuase you
are interested in scheduling as many iterations as possible without
encountering a dependence.


If, on the other and, you are interested in doing a data-locality
transformation, you care about the "index-variable distance". Essentially
this requires knowing the distance between memory references.


Many compilers just normalize the loop and punt the whole issue.




Vinod Grover
--

Return to the comp.compilers page.
Search the comp.compilers archives again.