Reapply "[LV] Don't add blocks to loop in GeneratedRTChecks (NFC)."

This reverts commit 46a2f41.

Recommits 2fd6f8f with corresponding VPlan change to ensure
LoopInfo is updated for all blocks during VPlan execution if needed.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -2082,9 +2082,6 @@ class GeneratedRTChecks {
 
     auto *Pred = LoopVectorPreHeader->getSinglePredecessor();
     BranchInst::Create(LoopVectorPreHeader, SCEVCheckBlock);
-    // Create new preheader for vector loop.
-    if (OuterLoop)
-      OuterLoop->addBasicBlockToLoop(SCEVCheckBlock, *LI);
 
     SCEVCheckBlock->getTerminator()->eraseFromParent();
     SCEVCheckBlock->moveBefore(LoopVectorPreHeader);
@@ -2122,9 +2119,6 @@ class GeneratedRTChecks {
     DT->changeImmediateDominator(LoopVectorPreHeader, MemCheckBlock);
     MemCheckBlock->moveBefore(LoopVectorPreHeader);
 
-    if (OuterLoop)
-      OuterLoop->addBasicBlockToLoop(MemCheckBlock, *LI);
-
     BranchInst &BI =
         *BranchInst::Create(Bypass, LoopVectorPreHeader, MemRuntimeCheckCond);
     if (AddBranchWeights) {

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -432,6 +432,19 @@ BasicBlock *VPBasicBlock::createEmptyBasicBlock(VPTransformState &State) {
 void VPBasicBlock::connectToPredecessors(VPTransformState &State) {
   auto &CFG = State.CFG;
   BasicBlock *NewBB = CFG.VPBB2IRBB[this];
+
+  // Register NewBB in its loop. In innermost loops its the same for all
+  // BB's.
+  Loop *ParentLoop = State.CurrentParentLoop;
+  // If this block has a sole successor that is an exit block then it needs
+  // adding to the same parent loop as the exit block.
+  VPBlockBase *SuccVPBB = getSingleSuccessor();
+  if (SuccVPBB && State.Plan->isExitBlock(SuccVPBB))
+    ParentLoop =
+        State.LI->getLoopFor(cast<VPIRBasicBlock>(SuccVPBB)->getIRBasicBlock());
+  if (ParentLoop && !State.LI->getLoopFor(NewBB))
+    ParentLoop->addBasicBlockToLoop(NewBB, *State.LI);
+
   // Hook up the new basic block to its predecessors.
   for (VPBlockBase *PredVPBlock : getHierarchicalPredecessors()) {
     VPBasicBlock *PredVPBB = PredVPBlock->getExitingBasicBlock();
@@ -517,17 +530,6 @@ void VPBasicBlock::execute(VPTransformState *State) {
     State->Builder.SetInsertPoint(NewBB);
     // Temporarily terminate with unreachable until CFG is rewired.
     UnreachableInst *Terminator = State->Builder.CreateUnreachable();
-    // Register NewBB in its loop. In innermost loops its the same for all
-    // BB's.
-    Loop *ParentLoop = State->CurrentParentLoop;
-    // If this block has a sole successor that is an exit block then it needs
-    // adding to the same parent loop as the exit block.
-    VPBlockBase *SuccVPBB = getSingleSuccessor();
-    if (SuccVPBB && State->Plan->isExitBlock(SuccVPBB))
-      ParentLoop = State->LI->getLoopFor(
-          cast<VPIRBasicBlock>(SuccVPBB)->getIRBasicBlock());
-    if (ParentLoop)
-      ParentLoop->addBasicBlockToLoop(NewBB, *State->LI);
     State->Builder.SetInsertPoint(Terminator);
 
     State->CFG.PrevBB = NewBB;