[VPlan] Add abstract base class for header phi recipes (NFC).

[fhahn]

Summary

Not all header phis widen the phi, e.g. like the new
VPCanonicalIVPHIRecipe in D113223. To let those recipes also inherit
from a phi-like base class, add a more generic VPHeaderPHIRecipe
abstract base class.

[Ayal]

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

586

This could be applied independently.

llvm/lib/Transforms/Vectorize/VPlan.h

1061–1062

Keep IncomingBlocks in VPWidenPHIRecipe?

1062

A [pure virtual] base class

inductions[.]and

1089–1090

phi/select >> phi

1099

it one >> if one

1104

"if there is one" - getOperand(1) asserts that there is one...

1172

Indep, of this patch, but why not have one constructor:

VPWidenPHIRecipe(PHINode *Phi, VPValue *Start = nullptr)
    : VPHeaderPHIRecipe(VPVWidenPHISC, VPWidenPHISC, Phi, Start) {}

[fhahn]

Address latest comments, thanks!

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

586

I'll push it as a separate commit

llvm/lib/Transforms/Vectorize/VPlan.h

1061–1062

Sounds good, thanks! Let's keep the base class as lightweight as possible.

1062

Adjusted, thanks!

1104

Removed.

1172

Good point! I rather remove the (single?) users of the constructor without start value as follow-up

[fhahn]

Add back missing VPWidenPHIRecipe constructor.

[Ayal]

Looks good to me, with a last nit.

llvm/lib/Transforms/Vectorize/VPlan.h

1154

Leave getIncomingValue() in VPWidenPHIRecipe, for VPlan native? It seems to complement getIncomingBlock() and addIncoming(), and is synonymous with getOperand(),,,

[fhahn]

llvm/lib/Transforms/Vectorize/VPlan.h

1154

Thanks, I moved it back to VPWidenPHIRecipe in the committed version.

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

PHINode *createInductionVariable(Loop *L, Value *Start, Value *End,
                                    Value *Step, Instruction *DL);
 
   /// Handle all cross-iteration phis in the header.
   void fixCrossIterationPHIs(VPTransformState &State);
 
   /// Create the exit value of first order recurrences in the middle block and
   /// update their users.
   void fixFirstOrderRecurrence(VPFirstOrderRecurrencePHIRecipe *PhiR,
                                VPTransformState &State);
 
   /// Create code for the loop exit value of the reduction.
   void fixReduction(VPReductionPHIRecipe *Phi, VPTransformState &State);
 
   /// Clear NSW/NUW flags from reduction instructions if necessary.
   void clearReductionWrapFlags(const RecurrenceDescriptor &RdxDesc,
                                VPTransformState &State);
 
if (!IsVectorizableOpcode(I->getOpcode()))
     return nullptr;
 
   // Success: widen this instruction.
   return new VPWidenRecipe(*I, make_range(Operands.begin(), Operands.end()));
 }
 
 void VPRecipeBuilder::fixHeaderPhis() {
   BasicBlock *OrigLatch = OrigLoop->getLoopLatch();
-  for (VPWidenPHIRecipe *R : PhisToFix) {
+  for (VPHeaderPHIRecipe *R : PhisToFix) {
     auto *PN = cast<PHINode>(R->getUnderlyingValue());
     VPRecipeBase *IncR =
         getRecipe(cast<Instruction>(PN->getIncomingValueForBlock(OrigLatch)));
     R->addOperand(IncR->getVPSingleValue());
   }
 }
 
 VPBasicBlock *VPRecipeBuilder::handleReplication(
VPRecipeBuilder::tryToCreateWidenRecipe(Instruction *Instr,
 
   VPRecipeBase *Recipe;
   if (auto Phi = dyn_cast<PHINode>(Instr)) {
     if (Phi->getParent() != OrigLoop->getHeader())
       return tryToBlend(Phi, Operands, Plan);
     if ((Recipe = tryToOptimizeInductionPHI(Phi, Operands)))
       return toVPRecipeResult(Recipe);
 
-    VPWidenPHIRecipe *PhiRecipe = nullptr;
+    VPHeaderPHIRecipe *PhiRecipe = nullptr;
     if (Legal->isReductionVariable(Phi) || Legal->isFirstOrderRecurrence(Phi)) {
       VPValue *StartV = Operands[0];
       if (Legal->isReductionVariable(Phi)) {
         const RecurrenceDescriptor &RdxDesc =
             Legal->getReductionVars().find(Phi)->second;
         assert(RdxDesc.getRecurrenceStartValue() ==
                Phi->getIncomingValueForBlock(OrigLoop->getLoopPreheader()));
         PhiRecipe = new VPReductionPHIRecipe(Phi, RdxDesc, *StartV,

llvm/lib/Transforms/Vectorize/VPRecipeBuilder.h

class VPRecipeBuilder {
   // 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.
   DenseMap<Instruction *, VPRecipeBase *> Ingredient2Recipe;
 
   /// Cross-iteration reduction & first-order recurrence phis for which we need
   /// to add the incoming value from the backedge after all recipes have been
   /// created.
-  SmallVector<VPWidenPHIRecipe *, 4> PhisToFix;
+  SmallVector<VPHeaderPHIRecipe *, 4> PhisToFix;
 
   /// Check if \p I can be widened at the start of \p Range and possibly
   /// decrease the range such that the returned value holds for the entire \p
   /// Range. The function should not be called for memory instructions or calls.
   bool shouldWiden(Instruction *I, VFRange &Range) const;
 
   /// Check if the load or store instruction \p I should widened for \p
   /// Range.Start and potentially masked. Such instructions are handled by a

llvm/lib/Transforms/Vectorize/VPlan.h

#endif
   }
   const TruncInst *getTruncInst() const {
     return dyn_cast_or_null<TruncInst>(getVPValue(0)->getUnderlyingValue());
   }
 
   /// Returns the induction descriptor for the recipe.
   const InductionDescriptor &getInductionDescriptor() const { return IndDesc; }
 };
 
-/// A recipe for handling first order recurrences and pointer inductions. For
-/// first-order recurrences, the start value is the first operand of the recipe
-/// and the incoming value from the backedge is the second operand. It also
-/// serves as base class for VPReductionPHIRecipe. In the VPlan native path, all
-/// incoming VPValues & VPBasicBlock pairs are managed in the recipe directly.
-class VPWidenPHIRecipe : public VPRecipeBase, public VPValue {
-  /// List of incoming blocks. Only used in the VPlan native path.
-  SmallVector<VPBasicBlock *, 2> IncomingBlocks;
-
+/// A pure virtual base class for all recipes modeling header phis, including
+/// phis for first order recurrences, pointer inductions and reductions. The
+/// start value is the first operand of the recipe and the incoming value from
+/// the backedge is the second operand.
+class VPHeaderPHIRecipe : public VPRecipeBase, public VPValue {
 protected:
-  VPWidenPHIRecipe(unsigned char VPVID, unsigned char VPDefID, PHINode *Phi,
+  VPHeaderPHIRecipe(unsigned char VPVID, unsigned char VPDefID, PHINode *Phi,
                     VPValue *Start = nullptr)
       : VPRecipeBase(VPDefID, {}), VPValue(VPVID, Phi, this) {
     if (Start)
       addOperand(Start);
   }
 
 public:
-  /// Create a VPWidenPHIRecipe for \p Phi
-  VPWidenPHIRecipe(PHINode *Phi)
-      : VPWidenPHIRecipe(VPVWidenPHISC, VPWidenPHISC, Phi) {}
-
-  /// Create a new VPWidenPHIRecipe for \p Phi with start value \p Start.
-  VPWidenPHIRecipe(PHINode *Phi, VPValue &Start) : VPWidenPHIRecipe(Phi) {
-    addOperand(&Start);
-  }
-
-  ~VPWidenPHIRecipe() override = default;
+  ~VPHeaderPHIRecipe() override = default;
 
   /// Method to support type inquiry through isa, cast, and dyn_cast.
   static inline bool classof(const VPRecipeBase *B) {
     return B->getVPDefID() == VPRecipeBase::VPWidenPHISC ||
            B->getVPDefID() == VPRecipeBase::VPFirstOrderRecurrencePHISC ||
            B->getVPDefID() == VPRecipeBase::VPReductionPHISC;
   }
   static inline bool classof(const VPValue *V) {
     return V->getVPValueID() == VPValue::VPVWidenPHISC ||
            V->getVPValueID() == VPValue::VPVFirstOrderRecurrencePHISC ||
            V->getVPValueID() == VPValue::VPVReductionPHISC;
   }
 
-  /// Generate the phi/select nodes.
-  void execute(VPTransformState &State) override;
+  /// Generate the phi nodes.
+  void execute(VPTransformState &State) override = 0;
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   /// Print the recipe.
   void print(raw_ostream &O, const Twine &Indent,
-             VPSlotTracker &SlotTracker) const override;
+             VPSlotTracker &SlotTracker) const override = 0;
 #endif
 
-  /// Returns the start value of the phi, if it is a reduction or first-order
-  /// recurrence.
+  /// Returns the start value of the phi, if one is set.
   VPValue *getStartValue() {
     return getNumOperands() == 0 ? nullptr : getOperand(0);
   }
 
-  /// Returns the incoming value from the loop backedge, if it is a reduction or
-  /// first-order recurrence.
+  /// Returns the incoming value from the loop backedge.
   VPValue *getBackedgeValue() {
     return getOperand(1);
   }
 
   /// Returns the backedge value as a recipe. The backedge value is guaranteed
   /// to be a recipe.
   VPRecipeBase *getBackedgeRecipe() {
     return cast<VPRecipeBase>(getBackedgeValue()->getDef());
   }
+};
+
+/// A recipe for handling header phis that are widened in the vector loop.
+/// In the VPlan native path, all incoming VPValues & VPBasicBlock pairs are
+/// managed in the recipe directly.
+class VPWidenPHIRecipe : public VPHeaderPHIRecipe {
+  /// List of incoming blocks. Only used in the VPlan native path.
+  SmallVector<VPBasicBlock *, 2> IncomingBlocks;
+
+public:
+  /// Create a VPWidenPHIRecipe for \p Phi
+  VPWidenPHIRecipe(PHINode *Phi)
+      : VPHeaderPHIRecipe(VPVWidenPHISC, VPWidenPHISC, Phi) {}
+
+  /// Create a new VPWidenPHIRecipe for \p Phi with start value \p Start.
+  VPWidenPHIRecipe(PHINode *Phi, VPValue &Start) : VPWidenPHIRecipe(Phi) {
+    addOperand(&Start);
+  }
+
+  ~VPWidenPHIRecipe() override = default;
+
+  /// Method to support type inquiry through isa, cast, and dyn_cast.
+  static inline bool classof(const VPRecipeBase *B) {
+    return B->getVPDefID() == VPRecipeBase::VPWidenPHISC;
+  }
+  static inline bool classof(const VPValue *V) {
+    return V->getVPValueID() == VPValue::VPVWidenPHISC;
+  }
+
+  /// Generate the phi/select nodes.
+  void execute(VPTransformState &State) override;
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+  /// Print the recipe.
+  void print(raw_ostream &O, const Twine &Indent,
+             VPSlotTracker &SlotTracker) const override;
+#endif
 
   /// Adds a pair (\p IncomingV, \p IncomingBlock) to the phi.
   void addIncoming(VPValue *IncomingV, VPBasicBlock *IncomingBlock) {
     addOperand(IncomingV);
     IncomingBlocks.push_back(IncomingBlock);
   }
 
-  /// Returns the \p I th incoming VPValue.
-  VPValue *getIncomingValue(unsigned I) { return getOperand(I); }
-
   /// Returns the \p I th incoming VPBasicBlock.
   VPBasicBlock *getIncomingBlock(unsigned I) { return IncomingBlocks[I]; }
+
+  /// Returns the \p I th incoming VPValue.
+  VPValue *getIncomingValue(unsigned I) { return getOperand(I); }
 };
 
 /// A recipe for handling first-order recurrence phis. The start value is the
 /// first operand of the recipe and the incoming value from the backedge is the
 /// second operand.
-struct VPFirstOrderRecurrencePHIRecipe : public VPWidenPHIRecipe {
+struct VPFirstOrderRecurrencePHIRecipe : public VPHeaderPHIRecipe {
   VPFirstOrderRecurrencePHIRecipe(PHINode *Phi, VPValue &Start)
-      : VPWidenPHIRecipe(VPVFirstOrderRecurrencePHISC,
+      : VPHeaderPHIRecipe(VPVFirstOrderRecurrencePHISC,
                           VPFirstOrderRecurrencePHISC, Phi, &Start) {}
 
   /// Method to support type inquiry through isa, cast, and dyn_cast.
   static inline bool classof(const VPRecipeBase *R) {
     return R->getVPDefID() == VPRecipeBase::VPFirstOrderRecurrencePHISC;
   }
   static inline bool classof(const VPWidenPHIRecipe *D) {
     return D->getVPDefID() == VPRecipeBase::VPFirstOrderRecurrencePHISC;
   }
   static inline bool classof(const VPValue *V) {
     return V->getVPValueID() == VPValue::VPVFirstOrderRecurrencePHISC;
   }
 
   void execute(VPTransformState &State) override;
 
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
   /// Print the recipe.
   void print(raw_ostream &O, const Twine &Indent,
              VPSlotTracker &SlotTracker) const override;
 #endif
 };
 
 /// A recipe for handling reduction phis. The start value is the first operand
 /// of the recipe and the incoming value from the backedge is the second
 /// operand.
-class VPReductionPHIRecipe : public VPWidenPHIRecipe {
+class VPReductionPHIRecipe : public VPHeaderPHIRecipe {
   /// Descriptor for the reduction.
   const RecurrenceDescriptor &RdxDesc;
 
   /// The phi is part of an in-loop reduction.
   bool IsInLoop;
 
   /// The phi is part of an ordered reduction. Requires IsInLoop to be true.
   bool IsOrdered;
 
 public:
   /// Create a new VPReductionPHIRecipe for the reduction \p Phi described by \p
   /// RdxDesc.
   VPReductionPHIRecipe(PHINode *Phi, const RecurrenceDescriptor &RdxDesc,
                        VPValue &Start, bool IsInLoop = false,
                        bool IsOrdered = false)
-      : VPWidenPHIRecipe(VPVReductionPHISC, VPReductionPHISC, Phi, &Start),
+      : VPHeaderPHIRecipe(VPVReductionPHISC, VPReductionPHISC, Phi, &Start),
         RdxDesc(RdxDesc), IsInLoop(IsInLoop), IsOrdered(IsOrdered) {
     assert((!IsOrdered || IsInLoop) && "IsOrdered requires IsInLoop");
   }
 
   ~VPReductionPHIRecipe() override = default;
 
   /// Method to support type inquiry through isa, cast, and dyn_cast.
   static inline bool classof(const VPRecipeBase *R) {

llvm/lib/Transforms/Vectorize/VPlan.cpp

void VPlan::execute(VPTransformState *State) {
 
   for (VPBlockBase *Block : depth_first(Entry))
     Block->execute(State);
 
   // Fix the latch value of reduction and first-order recurrences phis in the
   // vector loop.
   VPBasicBlock *Header = Entry->getEntryBasicBlock();
   for (VPRecipeBase &R : Header->phis()) {
-    auto *PhiR = dyn_cast<VPWidenPHIRecipe>(&R);
+    auto *PhiR = dyn_cast<VPHeaderPHIRecipe>(&R);
     if (!PhiR || !(isa<VPFirstOrderRecurrencePHIRecipe>(&R) ||
                    isa<VPReductionPHIRecipe>(&R)))
       continue;
     // For first-order recurrences and in-order reduction phis, only a single
     // part is generated, which provides the last part from the previous
     // iteration. Otherwise all UF parts are generated.
     bool SinglePartNeeded = isa<VPFirstOrderRecurrencePHIRecipe>(&R) ||
                             cast<VPReductionPHIRecipe>(&R)->isOrdered();
for (VPBlockBase *Base : RPOT) {
     visitBlock(Base, Old2New, IAI);
   }
 }
 
 void VPInterleavedAccessInfo::visitBlock(VPBlockBase *Block, Old2NewTy &Old2New,
                                          InterleavedAccessInfo &IAI) {
   if (VPBasicBlock *VPBB = dyn_cast<VPBasicBlock>(Block)) {
     for (VPRecipeBase &VPI : *VPBB) {
-      if (isa<VPWidenPHIRecipe>(&VPI))
+      if (isa<VPHeaderPHIRecipe>(&VPI))
         continue;
       assert(isa<VPInstruction>(&VPI) && "Can only handle VPInstructions");
       auto *VPInst = cast<VPInstruction>(&VPI);
       auto *Inst = cast<Instruction>(VPInst->getUnderlyingValue());
       auto *IG = IAI.getInterleaveGroup(Inst);
       if (!IG)
         continue;