[llvm] [VPlan] Delay adding canonical IV increment and exit branches. (PR #82270)

[Florian Hahn via llvm-commits]

================
@@ -1235,16 +1235,10 @@ void VPlanTransforms::optimize(VPlan &Plan, ScalarEvolution &SE) {
 static VPActiveLaneMaskPHIRecipe *addVPLaneMaskPhiAndUpdateExitBranch(
     VPlan &Plan, bool DataAndControlFlowWithoutRuntimeCheck) {
   VPRegionBlock *TopRegion = Plan.getVectorLoopRegion();
-  VPBasicBlock *EB = TopRegion->getExitingBasicBlock();
   auto *CanonicalIVPHI = Plan.getCanonicalIV();
   VPValue *StartV = CanonicalIVPHI->getStartValue();
 
-  auto *CanonicalIVIncrement =
-      cast<VPInstruction>(CanonicalIVPHI->getBackedgeValue());
-  // TODO: Check if dropping the flags is needed if
-  // !DataAndControlFlowWithoutRuntimeCheck.
-  CanonicalIVIncrement->dropPoisonGeneratingFlags();
-  DebugLoc DL = CanonicalIVIncrement->getDebugLoc();
+  DebugLoc DL = CanonicalIVPHI->getDebugLoc();
----------------
fhahn wrote:

Yes I think so, the DL from the CanonicalIV should be the closest accurate debug location

https://github.com/llvm/llvm-project/pull/82270