[llvm] [LAA] Use PSE::getSymbolicMaxBackedgeTakenCount. (PR #93499)

[Florian Hahn via llvm-commits]

================
@@ -1506,6 +1506,16 @@ bool LoopVectorizationLegality::canVectorize(bool UseVPlanNativePath) {
       return false;
   }
 
+  if (isa<SCEVCouldNotCompute>(PSE.getBackedgeTakenCount())) {
----------------
fhahn wrote:

I checked `LoopVersioningLICM`, `LoopDistribute.cpp` & `LoopLoadElimination.cpp`, they all check for a single exiting block, which should be sufficient I think. I also added tests for loop-distribute & loop-load-elim.

https://github.com/llvm/llvm-project/pull/93499