search for: scevpotentiallyinfinit

...use nsw to fix this, in spite of the fact that this is exactly what nsw was designed for. We know the answer even for the unsigned case, and we should just use that. Add a new SCEV node which lets us return that it's infinite in this case, and trip count X in the other; along the lines of "SCEVPotentiallyInfinite(m > int_max-3, sdiv(m, 4))". I've proposed this previously: http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120917/151250.html Nick -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/2...

On Thu, Aug 22, 2013 at 6:40 PM, Nick Lewycky <nlewycky at google.com> wrote: > It's a known limitation, see ScalarEvolution.cpp:5568. > > The fundamental problem is that len in your example could be (unsigned) > -1, -2 or -3, in which case your loop is infinite. > Unless I'm missing something, if len is -1 (or otherwise less than 0) the loop has 0 trip count. Did