[llvm] [VPlan][NFC] Add new getMiddleBlock interface to VPlan (PR #113558)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: David Sherwood (david-arm)

<details>
<summary>Changes</summary>

This work is in preparation for PRs #<!-- -->112138 and #<!-- -->88385 where
the middle block is not guaranteed to be the immediate successor
to the region block. I've simply add new getMiddleBlock()
interfaces to VPlan that for now just return

cast<VPBasicBlock>(VectorRegion->getSingleSuccessor())

Once PR #<!-- -->112138 lands we'll need to do more work to discover
the middle block.

---
Full diff: https://github.com/llvm/llvm-project/pull/113558.diff


5 Files Affected:

- (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+6-11) 
- (modified) llvm/lib/Transforms/Vectorize/VPlan.cpp (+2-2) 
- (modified) llvm/lib/Transforms/Vectorize/VPlan.h (+8) 
- (modified) llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp (+1-2) 
- (modified) llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp (+1-2) 


``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index e8653498d32a12..9647267c217172 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7692,8 +7692,7 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
   BestVPlan.execute(&State);
 
   // 2.5 Collect reduction resume values.
-  auto *ExitVPBB =
-      cast<VPBasicBlock>(BestVPlan.getVectorLoopRegion()->getSingleSuccessor());
+  auto *ExitVPBB = BestVPlan.getMiddleBlock();
   for (VPRecipeBase &R : *ExitVPBB) {
     createAndCollectMergePhiForReduction(
         dyn_cast<VPInstruction>(&R), State, OrigLoop,
@@ -8778,8 +8777,7 @@ static void addCanonicalIVRecipes(VPlan &Plan, Type *IdxTy, bool HasNUW,
 static SetVector<VPIRInstruction *> collectUsersInExitBlock(
     Loop *OrigLoop, VPRecipeBuilder &Builder, VPlan &Plan,
     const MapVector<PHINode *, InductionDescriptor> &Inductions) {
-  auto *MiddleVPBB =
-      cast<VPBasicBlock>(Plan.getVectorLoopRegion()->getSingleSuccessor());
+  auto *MiddleVPBB = Plan.getMiddleBlock();
   // No edge from the middle block to the unique exit block has been inserted
   // and there is nothing to fix from vector loop; phis should have incoming
   // from scalar loop only.
@@ -8825,8 +8823,7 @@ addUsersInExitBlock(VPlan &Plan,
   if (ExitUsersToFix.empty())
     return;
 
-  auto *MiddleVPBB =
-      cast<VPBasicBlock>(Plan.getVectorLoopRegion()->getSingleSuccessor());
+  auto *MiddleVPBB = Plan.getMiddleBlock();
   VPBuilder B(MiddleVPBB, MiddleVPBB->getFirstNonPhi());
 
   // Introduce extract for exiting values and update the VPIRInstructions
@@ -8863,7 +8860,7 @@ static void addLiveOutsForFirstOrderRecurrences(
   // TODO: Should be replaced by
   // Plan->getScalarLoopRegion()->getSinglePredecessor() in the future once the
   // scalar region is modeled as well.
-  auto *MiddleVPBB = cast<VPBasicBlock>(VectorRegion->getSingleSuccessor());
+  auto *MiddleVPBB = Plan.getMiddleBlock();
   VPBasicBlock *ScalarPHVPBB = nullptr;
   if (MiddleVPBB->getNumSuccessors() == 2) {
     // Order is strict: first is the exit block, second is the scalar preheader.
@@ -9065,8 +9062,7 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
         bool NeedsBlends = BB != HeaderBB && !BB->phis().empty();
         return Legal->blockNeedsPredication(BB) || NeedsBlends;
       });
-  auto *MiddleVPBB =
-      cast<VPBasicBlock>(Plan->getVectorLoopRegion()->getSingleSuccessor());
+  auto *MiddleVPBB = Plan->getMiddleBlock();
   VPBasicBlock::iterator MBIP = MiddleVPBB->getFirstNonPhi();
   for (BasicBlock *BB : make_range(DFS.beginRPO(), DFS.endRPO())) {
     // Relevant instructions from basic block BB will be grouped into VPRecipe
@@ -9277,8 +9273,7 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
   using namespace VPlanPatternMatch;
   VPRegionBlock *VectorLoopRegion = Plan->getVectorLoopRegion();
   VPBasicBlock *Header = VectorLoopRegion->getEntryBasicBlock();
-  VPBasicBlock *MiddleVPBB =
-      cast<VPBasicBlock>(VectorLoopRegion->getSingleSuccessor());
+  VPBasicBlock *MiddleVPBB = Plan->getMiddleBlock();
   for (VPRecipeBase &R : Header->phis()) {
     auto *PhiR = dyn_cast<VPReductionPHIRecipe>(&R);
     if (!PhiR || !PhiR->isInLoop() || (MinVF.isScalar() && !PhiR->isOrdered()))
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp
index c1b97791331bcf..deeeca57357e26 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlan.cpp
@@ -1030,8 +1030,8 @@ void VPlan::execute(VPTransformState *State) {
   // skeleton creation, so we can only create the VPIRBasicBlocks now during
   // VPlan execution rather than earlier during VPlan construction.
   BasicBlock *MiddleBB = State->CFG.ExitBB;
-  VPBasicBlock *MiddleVPBB =
-      cast<VPBasicBlock>(getVectorLoopRegion()->getSingleSuccessor());
+  VPBasicBlock *MiddleVPBB = getMiddleBlock();
+
   // Find the VPBB for the scalar preheader, relying on the current structure
   // when creating the middle block and its successrs: if there's a single
   // predecessor, it must be the scalar preheader. Otherwise, the second
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.h b/llvm/lib/Transforms/Vectorize/VPlan.h
index 59a084401cc9bf..8ea50767aa783f 100644
--- a/llvm/lib/Transforms/Vectorize/VPlan.h
+++ b/llvm/lib/Transforms/Vectorize/VPlan.h
@@ -3689,6 +3689,14 @@ class VPlan {
   VPBasicBlock *getEntry() { return Entry; }
   const VPBasicBlock *getEntry() const { return Entry; }
 
+  /// Methods to support access to the middle block.
+  const VPBasicBlock *getMiddleBlock() const {
+    return cast<VPBasicBlock>(getVectorLoopRegion()->getSingleSuccessor());
+  }
+  VPBasicBlock *getMiddleBlock() {
+    return cast<VPBasicBlock>(getVectorLoopRegion()->getSingleSuccessor());
+  }
+
   /// The trip count of the original loop.
   VPValue *getTripCount() const {
     assert(TripCount && "trip count needs to be set before accessing it");
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
index 41f13cc2d9a978..19c1a910b49c66 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -212,8 +212,7 @@ bool VPRecipeBase::mayHaveSideEffects() const {
 
 void VPLiveOut::fixPhi(VPlan &Plan, VPTransformState &State) {
   VPValue *ExitValue = getOperand(0);
-  VPBasicBlock *MiddleVPBB =
-      cast<VPBasicBlock>(Plan.getVectorLoopRegion()->getSingleSuccessor());
+  VPBasicBlock *MiddleVPBB = Plan.getMiddleBlock();
   VPRecipeBase *ExitingRecipe = ExitValue->getDefiningRecipe();
   auto *ExitingVPBB = ExitingRecipe ? ExitingRecipe->getParent() : nullptr;
   // Values leaving the vector loop reach live out phi's in the exiting block
diff --git a/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp b/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
index 7ea5ee341cc547..1cccd8a5bab7fe 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp
@@ -248,8 +248,7 @@ bool VPlanVerifier::verifyVPBasicBlock(const VPBasicBlock *VPBB) {
     return false;
   }
 
-  VPBlockBase *MiddleBB =
-      IRBB->getPlan()->getVectorLoopRegion()->getSingleSuccessor();
+  const VPBasicBlock *MiddleBB = IRBB->getPlan()->getMiddleBlock();
   if (IRBB != IRBB->getPlan()->getPreheader() &&
       IRBB->getSinglePredecessor() != MiddleBB) {
     errs() << "VPIRBasicBlock can only be used as pre-header or a successor of "

``````````

</details>


https://github.com/llvm/llvm-project/pull/113558