[LV] Apply sink-after & interleave-groups as VPlan transformations (NFCI)

This recommits 100e797adb (reverted in
009e032634 for failing an assert). While the
root cause was independently reverted in eaff300401,
this commit includes a LIT to make sure IVDescriptor's SinkAfter logic does not
try to sink branch instructions.

llvm/include/llvm/Analysis/VectorUtils.h

@@ -542,13 +542,10 @@ public:
   /// formation for predicated accesses, we may be able to relax this limitation
   /// in the future once we handle more complicated blocks.
   void reset() {
-    SmallPtrSet<InterleaveGroup<Instruction> *, 4> DelSet;
-    // Avoid releasing a pointer twice.
-    for (auto &I : InterleaveGroupMap)
-      DelSet.insert(I.second);
-    for (auto *Ptr : DelSet)
-      delete Ptr;
     InterleaveGroupMap.clear();
+    for (auto *Ptr : InterleaveGroups)
+      delete Ptr;
+    InterleaveGroups.clear();
     RequiresScalarEpilogue = false;
   }
 

llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h

@@ -201,6 +201,9 @@ class LoopVectorizationPlanner {
   /// The profitability analysis.
   LoopVectorizationCostModel &CM;
 
+  /// The interleaved access analysis.
+  InterleavedAccessInfo &IAI;
+
   SmallVector<VPlanPtr, 4> VPlans;
 
   /// This class is used to enable the VPlan to invoke a method of ILV. This is
@@ -223,8 +226,10 @@ public:
   LoopVectorizationPlanner(Loop *L, LoopInfo *LI, const TargetLibraryInfo *TLI,
                            const TargetTransformInfo *TTI,
                            LoopVectorizationLegality *Legal,
-                           LoopVectorizationCostModel &CM)
+                           LoopVectorizationCostModel &CM,
-      : OrigLoop(L), LI(LI), TLI(TLI), TTI(TTI), Legal(Legal), CM(CM) {}
+                           InterleavedAccessInfo &IAI)
+      : OrigLoop(L), LI(LI), TLI(TLI), TTI(TTI), Legal(Legal), CM(CM),
+        IAI(IAI) {}
 
   /// Plan how to best vectorize, return the best VF and its cost, or None if
   /// vectorization and interleaving should be avoided up front.

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -6710,37 +6710,6 @@ VPValue *VPRecipeBuilder::createBlockInMask(BasicBlock *BB, VPlanPtr &Plan) {
   return BlockMaskCache[BB] = BlockMask;
 }
 
-VPInterleaveRecipe *VPRecipeBuilder::tryToInterleaveMemory(Instruction *I,
-                                                           VFRange &Range,
-                                                           VPlanPtr &Plan) {
-  const InterleaveGroup<Instruction> *IG = CM.getInterleavedAccessGroup(I);
-  if (!IG)
-    return nullptr;
-
-  // Now check if IG is relevant for VF's in the given range.
-  auto isIGMember = [&](Instruction *I) -> std::function<bool(unsigned)> {
-    return [=](unsigned VF) -> bool {
-      return (VF >= 2 && // Query is illegal for VF == 1
-              CM.getWideningDecision(I, VF) ==
-                  LoopVectorizationCostModel::CM_Interleave);
-    };
-  };
-  if (!LoopVectorizationPlanner::getDecisionAndClampRange(isIGMember(I), Range))
-    return nullptr;
-
-  // I is a member of an InterleaveGroup for VF's in the (possibly trimmed)
-  // range. If it's the primary member of the IG construct a VPInterleaveRecipe.
-  // Otherwise, it's an adjunct member of the IG, do not construct any Recipe.
-  assert(I == IG->getInsertPos() &&
-         "Generating a recipe for an adjunct member of an interleave group");
-
-  VPValue *Mask = nullptr;
-  if (Legal->isMaskRequired(I))
-    Mask = createBlockInMask(I->getParent(), Plan);
-
-  return new VPInterleaveRecipe(IG, Mask);
-}
-
 VPWidenMemoryInstructionRecipe *
 VPRecipeBuilder::tryToWidenMemory(Instruction *I, VFRange &Range,
                                   VPlanPtr &Plan) {
@@ -6757,8 +6726,6 @@ VPRecipeBuilder::tryToWidenMemory(Instruction *I, VFRange &Range,
         CM.getWideningDecision(I, VF);
     assert(Decision != LoopVectorizationCostModel::CM_Unknown &&
            "CM decision should be taken at this point.");
-    assert(Decision != LoopVectorizationCostModel::CM_Interleave &&
-           "Interleave memory opportunity should be caught earlier.");
     return Decision != LoopVectorizationCostModel::CM_Scalarize;
   };
 
@@ -6923,15 +6890,21 @@ bool VPRecipeBuilder::tryToWiden(Instruction *I, VPBasicBlock *VPBB,
   if (!LoopVectorizationPlanner::getDecisionAndClampRange(willWiden, Range))
     return false;
 
+  // If this ingredient's recipe is to be recorded, keep its recipe a singleton
+  // to avoid having to split recipes later.
+  bool IsSingleton = Ingredient2Recipe.count(I);
+
   // Success: widen this instruction. We optimize the common case where
   // consecutive instructions can be represented by a single recipe.
-  if (!VPBB->empty()) {
+  if (!IsSingleton && !VPBB->empty() && LastExtensibleRecipe == &VPBB->back() &&
-    VPWidenRecipe *LastWidenRecipe = dyn_cast<VPWidenRecipe>(&VPBB->back());
+      LastExtensibleRecipe->appendInstruction(I))
-    if (LastWidenRecipe && LastWidenRecipe->appendInstruction(I))
+    return true;
-      return true;
-  }
 
-  VPBB->appendRecipe(new VPWidenRecipe(I));
+  VPWidenRecipe *WidenRecipe = new VPWidenRecipe(I);
+  if (!IsSingleton)
+    LastExtensibleRecipe = WidenRecipe;
+  setRecipe(I, WidenRecipe);
+  VPBB->appendRecipe(WidenRecipe);
   return true;
 }
 
@@ -6947,6 +6920,7 @@ VPBasicBlock *VPRecipeBuilder::handleReplication(
       [&](unsigned VF) { return CM.isScalarWithPredication(I, VF); }, Range);
 
   auto *Recipe = new VPReplicateRecipe(I, IsUniform, IsPredicated);
+  setRecipe(I, Recipe);
 
   // Find if I uses a predicated instruction. If so, it will use its scalar
   // value. Avoid hoisting the insert-element which packs the scalar value into
@@ -7005,36 +6979,20 @@ VPRegionBlock *VPRecipeBuilder::createReplicateRegion(Instruction *Instr,
 bool VPRecipeBuilder::tryToCreateRecipe(Instruction *Instr, VFRange &Range,
                                         VPlanPtr &Plan, VPBasicBlock *VPBB) {
   VPRecipeBase *Recipe = nullptr;
-  // Check if Instr should belong to an interleave memory recipe, or already
+
-  // does. In the latter case Instr is irrelevant.
+  // First, check for specific widening recipes that deal with memory
-  if ((Recipe = tryToInterleaveMemory(Instr, Range, Plan))) {
+  // operations, inductions and Phi nodes.
+  if ((Recipe = tryToWidenMemory(Instr, Range, Plan)) ||
+      (Recipe = tryToOptimizeInduction(Instr, Range)) ||
+      (Recipe = tryToBlend(Instr, Plan)) ||
+      (isa<PHINode>(Instr) &&
+       (Recipe = new VPWidenPHIRecipe(cast<PHINode>(Instr))))) {
+    setRecipe(Instr, Recipe);
     VPBB->appendRecipe(Recipe);
     return true;
   }
 
-  // Check if Instr is a memory operation that should be widened.
+  // Check if Instr is to be widened by a general VPWidenRecipe.
-  if ((Recipe = tryToWidenMemory(Instr, Range, Plan))) {
-    VPBB->appendRecipe(Recipe);
-    return true;
-  }
-
-  // Check if Instr should form some PHI recipe.
-  if ((Recipe = tryToOptimizeInduction(Instr, Range))) {
-    VPBB->appendRecipe(Recipe);
-    return true;
-  }
-  if ((Recipe = tryToBlend(Instr, Plan))) {
-    VPBB->appendRecipe(Recipe);
-    return true;
-  }
-  if (PHINode *Phi = dyn_cast<PHINode>(Instr)) {
-    VPBB->appendRecipe(new VPWidenPHIRecipe(Phi));
-    return true;
-  }
-
-  // Check if Instr is to be widened by a general VPWidenRecipe, after
-  // having first checked for specific widening recipes that deal with
-  // Interleave Groups, Inductions and Phi nodes.
   if (tryToWiden(Instr, VPBB, Range))
     return true;
 
@@ -7090,19 +7048,57 @@ void LoopVectorizationPlanner::buildVPlansWithVPRecipes(unsigned MinVF,
 VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
     VFRange &Range, SmallPtrSetImpl<Value *> &NeedDef,
     SmallPtrSetImpl<Instruction *> &DeadInstructions) {
+
   // Hold a mapping from predicated instructions to their recipes, in order to
   // fix their AlsoPack behavior if a user is determined to replicate and use a
   // scalar instead of vector value.
   DenseMap<Instruction *, VPReplicateRecipe *> PredInst2Recipe;
 
   DenseMap<Instruction *, Instruction *> &SinkAfter = Legal->getSinkAfter();
-  DenseMap<Instruction *, Instruction *> SinkAfterInverse;
+
+  SmallPtrSet<const InterleaveGroup<Instruction> *, 1> InterleaveGroups;
+
+  VPRecipeBuilder RecipeBuilder(OrigLoop, TLI, Legal, CM, Builder);
+
+  // ---------------------------------------------------------------------------
+  // Pre-construction: record ingredients whose recipes we'll need to further
+  // process after constructing the initial VPlan.
+  // ---------------------------------------------------------------------------
+
+  // Mark instructions we'll need to sink later and their targets as
+  // ingredients whose recipe we'll need to record.
+  for (auto &Entry : SinkAfter) {
+    RecipeBuilder.recordRecipeOf(Entry.first);
+    RecipeBuilder.recordRecipeOf(Entry.second);
+  }
+
+  // For each interleave group which is relevant for this (possibly trimmed)
+  // Range, add it to the set of groups to be later applied to the VPlan and add
+  // placeholders for its members' Recipes which we'll be replacing with a
+  // single VPInterleaveRecipe.
+  for (InterleaveGroup<Instruction> *IG : IAI.getInterleaveGroups()) {
+    auto applyIG = [IG, this](unsigned VF) -> bool {
+      return (VF >= 2 && // Query is illegal for VF == 1
+              CM.getWideningDecision(IG->getInsertPos(), VF) ==
+                  LoopVectorizationCostModel::CM_Interleave);
+    };
+    if (!getDecisionAndClampRange(applyIG, Range))
+      continue;
+    InterleaveGroups.insert(IG);
+    for (unsigned i = 0; i < IG->getFactor(); i++)
+      if (Instruction *Member = IG->getMember(i))
+        RecipeBuilder.recordRecipeOf(Member);
+  };
+
+  // ---------------------------------------------------------------------------
+  // Build initial VPlan: Scan the body of the loop in a topological order to
+  // visit each basic block after having visited its predecessor basic blocks.
+  // ---------------------------------------------------------------------------
 
   // Create a dummy pre-entry VPBasicBlock to start building the VPlan.
   VPBasicBlock *VPBB = new VPBasicBlock("Pre-Entry");
   auto Plan = std::make_unique<VPlan>(VPBB);
 
-  VPRecipeBuilder RecipeBuilder(OrigLoop, TLI, Legal, CM, Builder);
   // Represent values that will have defs inside VPlan.
   for (Value *V : NeedDef)
     Plan->addVPValue(V);
@@ -7123,8 +7119,7 @@ VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
 
     std::vector<Instruction *> Ingredients;
 
-    // Organize the ingredients to vectorize from current basic block in the
+    // Introduce each ingredient into VPlan.
-    // right order.
     for (Instruction &I : BB->instructionsWithoutDebug()) {
       Instruction *Instr = &I;
 
@@ -7134,43 +7129,6 @@ VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
           DeadInstructions.find(Instr) != DeadInstructions.end())
         continue;
 
-      // I is a member of an InterleaveGroup for Range.Start. If it's an adjunct
-      // member of the IG, do not construct any Recipe for it.
-      const InterleaveGroup<Instruction> *IG =
-          CM.getInterleavedAccessGroup(Instr);
-      if (IG && Instr != IG->getInsertPos() &&
-          Range.Start >= 2 && // Query is illegal for VF == 1
-          CM.getWideningDecision(Instr, Range.Start) ==
-              LoopVectorizationCostModel::CM_Interleave) {
-        auto SinkCandidate = SinkAfterInverse.find(Instr);
-        if (SinkCandidate != SinkAfterInverse.end())
-          Ingredients.push_back(SinkCandidate->second);
-        continue;
-      }
-
-      // Move instructions to handle first-order recurrences, step 1: avoid
-      // handling this instruction until after we've handled the instruction it
-      // should follow.
-      auto SAIt = SinkAfter.find(Instr);
-      if (SAIt != SinkAfter.end()) {
-        LLVM_DEBUG(dbgs() << "Sinking" << *SAIt->first << " after"
-                          << *SAIt->second
-                          << " to vectorize a 1st order recurrence.\n");
-        SinkAfterInverse[SAIt->second] = Instr;
-        continue;
-      }
-
-      Ingredients.push_back(Instr);
-
-      // Move instructions to handle first-order recurrences, step 2: push the
-      // instruction to be sunk at its insertion point.
-      auto SAInvIt = SinkAfterInverse.find(Instr);
-      if (SAInvIt != SinkAfterInverse.end())
-        Ingredients.push_back(SAInvIt->second);
-    }
-
-    // Introduce each ingredient into VPlan.
-    for (Instruction *Instr : Ingredients) {
       if (RecipeBuilder.tryToCreateRecipe(Instr, Range, Plan, VPBB))
         continue;
 
@@ -7195,6 +7153,32 @@ VPlanPtr LoopVectorizationPlanner::buildVPlanWithVPRecipes(
   VPBlockUtils::disconnectBlocks(PreEntry, Entry);
   delete PreEntry;
 
+  // ---------------------------------------------------------------------------
+  // Transform initial VPlan: Apply previously taken decisions, in order, to
+  // bring the VPlan to its final state.
+  // ---------------------------------------------------------------------------
+
+  // Apply Sink-After legal constraints.
+  for (auto &Entry : SinkAfter) {
+    VPRecipeBase *Sink = RecipeBuilder.getRecipe(Entry.first);
+    VPRecipeBase *Target = RecipeBuilder.getRecipe(Entry.second);
+    Sink->moveAfter(Target);
+  }
+
+  // Interleave memory: for each Interleave Group we marked earlier as relevant
+  // for this VPlan, replace the Recipes widening its memory instructions with a
+  // single VPInterleaveRecipe at its insertion point.
+  for (auto IG : InterleaveGroups) {
+    auto *Recipe = cast<VPWidenMemoryInstructionRecipe>(
+        RecipeBuilder.getRecipe(IG->getInsertPos()));
+    (new VPInterleaveRecipe(IG, Recipe->getMask()))->insertBefore(Recipe);
+
+    for (unsigned i = 0; i < IG->getFactor(); ++i)
+      if (Instruction *Member = IG->getMember(i)) {
+        RecipeBuilder.getRecipe(Member)->eraseFromParent();
+      }
+  }
+
   // Finally, if tail is folded by masking, introduce selects between the phi
   // and the live-out instruction of each reduction, at the end of the latch.
   if (CM.foldTailByMasking()) {
@@ -7427,12 +7411,11 @@ void VPPredInstPHIRecipe::execute(VPTransformState &State) {
 }
 
 void VPWidenMemoryInstructionRecipe::execute(VPTransformState &State) {
-  if (!User)
+  VPValue *Mask = getMask();
+  if (!Mask)
     return State.ILV->vectorizeMemoryInstruction(&Instr);
 
-  // Last (and currently only) operand is a mask.
   InnerLoopVectorizer::VectorParts MaskValues(State.UF);
-  VPValue *Mask = User->getOperand(User->getNumOperands() - 1);
   for (unsigned Part = 0; Part < State.UF; ++Part)
     MaskValues[Part] = State.get(Mask, Part);
   State.ILV->vectorizeMemoryInstruction(&Instr, &MaskValues);
@@ -7481,7 +7464,7 @@ static bool processLoopInVPlanNativePath(
   // Use the planner for outer loop vectorization.
   // TODO: CM is not used at this point inside the planner. Turn CM into an
   // optional argument if we don't need it in the future.
-  LoopVectorizationPlanner LVP(L, LI, TLI, TTI, LVL, CM);
+  LoopVectorizationPlanner LVP(L, LI, TLI, TTI, LVL, CM, IAI);
 
   // Get user vectorization factor.
   const unsigned UserVF = Hints.getWidth();
@@ -7641,7 +7624,7 @@ bool LoopVectorizePass::processLoop(Loop *L) {
   CM.collectValuesToIgnore();
 
   // Use the planner for vectorization.
-  LoopVectorizationPlanner LVP(L, LI, TLI, TTI, &LVL, CM);
+  LoopVectorizationPlanner LVP(L, LI, TLI, TTI, &LVL, CM, IAI);
 
   // Get user vectorization factor.
   unsigned UserVF = Hints.getWidth();

llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h

@@ -47,6 +47,24 @@ class VPRecipeBuilder {
   EdgeMaskCacheTy EdgeMaskCache;
   BlockMaskCacheTy BlockMaskCache;
 
+  // VPlan-VPlan transformations support: Hold a mapping from ingredients to
+  // their recipe. To save on memory, only do so for selected ingredients,
+  // marked by having a nullptr entry in this map. If those ingredients get a
+  // VPWidenRecipe, also avoid compressing other ingredients into it to avoid
+  // having to split such recipes later.
+  DenseMap<Instruction *, VPRecipeBase *> Ingredient2Recipe;
+  VPWidenRecipe *LastExtensibleRecipe = nullptr;
+
+  /// Set the recipe created for given ingredient. This operation is a no-op for
+  /// ingredients that were not marked using a nullptr entry in the map.
+  void setRecipe(Instruction *I, VPRecipeBase *R) {
+    if (!Ingredient2Recipe.count(I))
+      return;
+    assert(Ingredient2Recipe[I] == nullptr &&
+           "Recipe already set for ingredient");
+    Ingredient2Recipe[I] = R;
+  }
+
 public:
   /// A helper function that computes the predicate of the block BB, assuming
   /// that the header block of the loop is set to True. It returns the *entry*
@@ -57,16 +75,22 @@ public:
   /// and DST.
   VPValue *createEdgeMask(BasicBlock *Src, BasicBlock *Dst, VPlanPtr &Plan);
 
-  /// Check if \I belongs to an Interleave Group within the given VF \p Range,
+  /// Mark given ingredient for recording its recipe once one is created for
-  /// \return true in the first returned value if so and false otherwise.
+  /// it.
-  /// Build a new VPInterleaveGroup Recipe if \I is the primary member of an IG
+  void recordRecipeOf(Instruction *I) {
-  /// for \p Range.Start, and provide it as the second returned value.
+    assert((!Ingredient2Recipe.count(I) || Ingredient2Recipe[I] == nullptr) &&
-  /// Note that if \I is an adjunct member of an IG for \p Range.Start, the
+           "Recipe already set for ingredient");
-  /// \return value is <true, nullptr>, as it is handled by another recipe.
+    Ingredient2Recipe[I] = nullptr;
-  /// \p Range.End may be decreased to ensure same decision from \p Range.Start
+  }
-  /// to \p Range.End.
+
-  VPInterleaveRecipe *tryToInterleaveMemory(Instruction *I, VFRange &Range,
+  /// Return the recipe created for given ingredient.
-                                            VPlanPtr &Plan);
+  VPRecipeBase *getRecipe(Instruction *I) {
+    assert(Ingredient2Recipe.count(I) &&
+           "Recording this ingredients recipe was not requested");
+    assert(Ingredient2Recipe[I] != nullptr &&
+           "Ingredient doesn't have a recipe");
+    return Ingredient2Recipe[I];
+  }
 
   /// Check if \I is a memory instruction to be widened for \p Range.Start and
   /// potentially masked. Such instructions are handled by a recipe that takes

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -275,18 +275,35 @@ void VPRegionBlock::execute(VPTransformState *State) {
 }
 
 void VPRecipeBase::insertBefore(VPRecipeBase *InsertPos) {
+  assert(!Parent && "Recipe already in some VPBasicBlock");
+  assert(InsertPos->getParent() &&
+         "Insertion position not in any VPBasicBlock");
   Parent = InsertPos->getParent();
   Parent->getRecipeList().insert(InsertPos->getIterator(), this);
 }
 
+void VPRecipeBase::insertAfter(VPRecipeBase *InsertPos) {
+  assert(!Parent && "Recipe already in some VPBasicBlock");
+  assert(InsertPos->getParent() &&
+         "Insertion position not in any VPBasicBlock");
+  Parent = InsertPos->getParent();
+  Parent->getRecipeList().insertAfter(InsertPos->getIterator(), this);
+}
+
+void VPRecipeBase::removeFromParent() {
+  assert(getParent() && "Recipe not in any VPBasicBlock");
+  getParent()->getRecipeList().remove(getIterator());
+  Parent = nullptr;
+}
+
 iplist<VPRecipeBase>::iterator VPRecipeBase::eraseFromParent() {
+  assert(getParent() && "Recipe not in any VPBasicBlock");
   return getParent()->getRecipeList().erase(getIterator());
 }
 
 void VPRecipeBase::moveAfter(VPRecipeBase *InsertPos) {
-  InsertPos->getParent()->getRecipeList().splice(
+  removeFromParent();
-      std::next(InsertPos->getIterator()), getParent()->getRecipeList(),
+  insertAfter(InsertPos);
-      getIterator());
 }
 
 void VPInstruction::generateInstruction(VPTransformState &State,

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -567,6 +567,7 @@ public:
 /// instructions.
 class VPRecipeBase : public ilist_node_with_parent<VPRecipeBase, VPBasicBlock> {
   friend VPBasicBlock;
+  friend class VPBlockUtils;
 
 private:
   const unsigned char SubclassID; ///< Subclass identifier (for isa/dyn_cast).
@@ -615,10 +616,18 @@ public:
   /// the specified recipe.
   void insertBefore(VPRecipeBase *InsertPos);
 
+  /// Insert an unlinked Recipe into a basic block immediately after
+  /// the specified Recipe.
+  void insertAfter(VPRecipeBase *InsertPos);
+
   /// Unlink this recipe from its current VPBasicBlock and insert it into
   /// the VPBasicBlock that MovePos lives in, right after MovePos.
   void moveAfter(VPRecipeBase *MovePos);
 
+  /// This method unlinks 'this' from the containing basic block, but does not
+  /// delete it.
+  void removeFromParent();
+
   /// This method unlinks 'this' from the containing basic block and deletes it.
   ///
   /// \returns an iterator pointing to the element after the erased one
@@ -973,6 +982,13 @@ public:
     return V->getVPRecipeID() == VPRecipeBase::VPWidenMemoryInstructionSC;
   }
 
+  /// Return the mask used by this recipe. Note that a full mask is represented
+  /// by a nullptr.
+  VPValue *getMask() {
+    // Mask is the last operand.
+    return User ? User->getOperand(User->getNumOperands() - 1) : nullptr;
+  }
+
   /// Generate the wide load/store.
   void execute(VPTransformState &State) override;
 

llvm/test/Transforms/LoopVectorize/first-order-recurrence.ll

@@ -572,3 +572,38 @@ for.body:
 for.end:
   ret void
 }
+
+; Do not sink branches: While branches are if-converted and do not require
+; sinking, instructions with side effects (e.g. loads) conditioned by those
+; branches will become users of the condition bit after vectorization and would
+; need to be sunk if the loop is vectorized.
+define void @do_not_sink_branch(i32 %x, i32* %in, i32* %out, i32 %tc) local_unnamed_addr #0 {
+; NO-SINK-AFTER-LABEL: do_not_sink_branch
+; NO-SINK-AFTER-NOT:   vector.ph:
+; NO-SINK-AFTER:       }
+entry:
+  %cmp530 = icmp slt i32 0, %tc
+  br label %for.body4
+
+for.body4:                                        ; preds = %cond.end, %entry
+  %indvars.iv = phi i32 [ 0, %entry ], [ %indvars.iv.next, %cond.end ]
+  %cmp534 = phi i1 [ %cmp530, %entry ], [ %cmp5, %cond.end ]
+  br i1 %cmp534, label %cond.true, label %cond.end
+
+cond.true:                                        ; preds = %for.body4
+  %arrayidx7 = getelementptr inbounds i32, i32* %in, i32 %indvars.iv
+  %in.val = load i32, i32* %arrayidx7, align 4
+  br label %cond.end
+
+cond.end:                                         ; preds = %for.body4, %cond.true
+  %cond = phi i32 [ %in.val, %cond.true ], [ 0, %for.body4 ]
+  %arrayidx8 = getelementptr inbounds i32, i32* %out, i32 %indvars.iv
+  store i32 %cond, i32* %arrayidx8, align 4
+  %indvars.iv.next = add nuw nsw i32 %indvars.iv, 1
+  %cmp5 = icmp slt i32 %indvars.iv.next, %tc
+  %exitcond = icmp eq i32 %indvars.iv.next, %x
+  br i1 %exitcond, label %for.end12.loopexit, label %for.body4
+
+for.end12.loopexit:                               ; preds = %cond.end
+  ret void
+}

llvm/unittests/Transforms/Vectorize/VPlanTest.cpp

@@ -83,6 +83,7 @@ TEST(VPInstructionTest, moveAfter) {
 
   CHECK_ITERATOR(VPBB1, I2, I1);
   CHECK_ITERATOR(VPBB2, I4, I3, I5);
+  EXPECT_EQ(I3->getParent(), I4->getParent());
 }
 
 } // namespace