[PATCH] D74691: [Attributor] Detect SCCs with unbounded cycles

[omar ahmed via Phabricator via llvm-commits]

omarahmed added a comment.

In D74691#1888396 <https://reviews.llvm.org/D74691#1888396>, @baziotis wrote:

> @omarahmed @jdoerfert
>
> I'm in the unpleasant position to tell you that the method I proposed is wrong. `SCCIterator` uses Tarjan's algorithm which for some reason, I remembered it finds all strongly-connected components but actually, it finds only maximal.
>  That means, if a loop has an SCC inside it, we'll never find it since the loop is the maximal SCC. That probably means that we have to fall-back to the method that Johannes had proposed:
>
>   As before, we identify all cycles via the depth-first search and the visited set. If a cycles is found we did bail before but now we ask LI & SE instead. If they say we found a proper loop header of a loop with a bounded trip count we can ignore that cycles and continue exploring.
>
>
> I'm really sorry for that. I'll try to think if anything better can be done.
>
> Edit: Let's not forget of course: A big thanks to @Meinersbur for pointing this out.


that's fine , no problem :D
I think i can move faster now as i know the small mistakes i have done till now from the great reviews :)

But if it finds only the maximum ones why it hadn't returned willreturn here , as it shouldn't have seen the while inside

  ; int non_loop_inside_loop(int n) {
  ;   int ans = 0;
  ;   for (int i = 0; i < n; i++) {
  ;     while (1)
  ;       ans++;
  ;   }
  ;   return ans;
  ; } 




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