Hi, On Mon, 28 Nov 2011, Jiangning Liu wrote:
> > > One more question... > > > > > > Can " i = i.6_18;" be sinked out of loop, because it doesn't have > > memory > > > dependence with others? > > > > With current trunk the stores to i, a_p, b_p and k are sunken after the > > loop. (There are no aliasing problems because the decls can't > > conflict). > > > > What isn't sunken is the calculation of the &a[D.2248_7] expression. > > First, the number of iterations of the inner loop can't be determined > > by > > current code (replacing i+=k with e.g. i++ could be handled for > > instance). > > Hi Michael, > > Do you know what the essential problem is in the case of loop iteration > uncertainty? Yes, the number of iterations of the i loop simply is too difficult for our loop iteration calculator to comprehend: for (i=k; i<500; i+=k) iterates for roundup((500-k)/k) time. In particular if the step is non-constant our nr-of-iteration calculator gives up. > I thought it was still an aliasing problem. No. All accesses are resolved to final objects (i.e. no pointers), and hence can be trivially disambiguated. Ciao, Michael.
