[VPlan] Disconnect VPValue and VPUser.

This refactors VPuser to not inherit from VPValue to facilitate
introducing operations that introduce multiple VPValues (e.g.
VPInterleaveRecipe).

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D84679

docs/Proposals/VectorizationPlan.rst

@@ -151,10 +151,8 @@ The low-level design of VPlan comprises of the following classes.
   VPUser, but no operands.
 
 :VPUser:
-  A VPValue representing a general vertex in the def-use graph of VPlan. It has
-  operands which are of type VPValue. When instantiated, it represents a
-  live-out Instruction that exists outside VPlan. VPUser is similar in some
-  aspects to LLVM's User class.
+  A VPUser represents an entity that uses a number of VPValues as operands.
+  VPUser is similar in some aspects to LLVM's User class.
 
 :VPInstruction:
   A VPInstruction is both a VPRecipe and a VPUser. It models a single

lib/Transforms/Vectorize/VPlan.h

@@ -682,7 +682,7 @@ public:
 /// While as any Recipe it may generate a sequence of IR instructions when
 /// executed, these instructions would always form a single-def expression as
 /// the VPInstruction is also a single def-use vertex.
-class VPInstruction : public VPUser, public VPRecipeBase {
+class VPInstruction : public VPUser, public VPValue, public VPRecipeBase {
   friend class VPlanSlp;
 
 public:
@@ -712,7 +712,7 @@ protected:
 
 public:
   VPInstruction(unsigned Opcode, ArrayRef<VPValue *> Operands)
-      : VPUser(VPValue::VPInstructionSC, Operands),
+      : VPUser(Operands), VPValue(VPValue::VPInstructionSC),
         VPRecipeBase(VPRecipeBase::VPInstructionSC), Opcode(Opcode) {}
 
   VPInstruction(unsigned Opcode, std::initializer_list<VPValue *> Operands)

lib/Transforms/Vectorize/VPlanSLP.cpp

@@ -161,7 +161,8 @@ static SmallVector<VPValue *, 4> getOperands(ArrayRef<VPValue *> Values,
                                              unsigned OperandIndex) {
   SmallVector<VPValue *, 4> Operands;
   for (VPValue *V : Values) {
-    auto *U = cast<VPUser>(V);
+    // Currently we only support VPInstructions.
+    auto *U = cast<VPInstruction>(V);
     Operands.push_back(U->getOperand(OperandIndex));
   }
   return Operands;
@@ -222,18 +223,20 @@ static bool areConsecutiveOrMatch(VPInstruction *A, VPInstruction *B,
 /// Traverses and compares operands of V1 and V2 to MaxLevel.
 static unsigned getLAScore(VPValue *V1, VPValue *V2, unsigned MaxLevel,
                            VPInterleavedAccessInfo &IAI) {
-  if (!isa<VPInstruction>(V1) || !isa<VPInstruction>(V2))
+  auto *I1 = dyn_cast<VPInstruction>(V1);
+  auto *I2 = dyn_cast<VPInstruction>(V2);
+  // Currently we only support VPInstructions.
+  if (!I1 || !I2)
     return 0;
 
   if (MaxLevel == 0)
-    return (unsigned)areConsecutiveOrMatch(cast<VPInstruction>(V1),
-                                           cast<VPInstruction>(V2), IAI);
+    return (unsigned)areConsecutiveOrMatch(I1, I2, IAI);
 
   unsigned Score = 0;
-  for (unsigned I = 0, EV1 = cast<VPUser>(V1)->getNumOperands(); I < EV1; ++I)
-    for (unsigned J = 0, EV2 = cast<VPUser>(V2)->getNumOperands(); J < EV2; ++J)
-      Score += getLAScore(cast<VPUser>(V1)->getOperand(I),
-                          cast<VPUser>(V2)->getOperand(J), MaxLevel - 1, IAI);
+  for (unsigned I = 0, EV1 = I1->getNumOperands(); I < EV1; ++I)
+    for (unsigned J = 0, EV2 = I2->getNumOperands(); J < EV2; ++J)
+      Score +=
+          getLAScore(I1->getOperand(I), I2->getOperand(J), MaxLevel - 1, IAI);
   return Score;
 }
 

lib/Transforms/Vectorize/VPlanValue.h

@@ -10,9 +10,9 @@
 /// This file contains the declarations of the entities induced by Vectorization
 /// Plans, e.g. the instructions the VPlan intends to generate if executed.
 /// VPlan models the following entities:
-/// VPValue
-///  |-- VPUser
-///  |    |-- VPInstruction
+/// VPValue   VPUser
+///    |        |
+///   VPInstruction
 /// These are documented in docs/VectorizationPlan.rst.
 ///
 //===----------------------------------------------------------------------===//
@@ -76,7 +76,7 @@ public:
   /// are actually instantiated. Values of this enumeration are kept in the
   /// SubclassID field of the VPValue objects. They are used for concrete
   /// type identification.
-  enum { VPValueSC, VPUserSC, VPInstructionSC };
+  enum { VPValueSC, VPInstructionSC };
 
   VPValue(Value *UV = nullptr) : VPValue(VPValueSC, UV) {}
   VPValue(const VPValue &) = delete;
@@ -132,23 +132,19 @@ raw_ostream &operator<<(raw_ostream &OS, const VPValue &V);
 
 /// This class augments VPValue with operands which provide the inverse def-use
 /// edges from VPValue's users to their defs.
-class VPUser : public VPValue {
+class VPUser {
   SmallVector<VPValue *, 2> Operands;
 
-protected:
-  VPUser(const unsigned char SC) : VPValue(SC) {}
-  VPUser(const unsigned char SC, ArrayRef<VPValue *> Operands) : VPValue(SC) {
+public:
+  VPUser() {}
+  VPUser(ArrayRef<VPValue *> Operands) {
     for (VPValue *Operand : Operands)
       addOperand(Operand);
   }
 
-public:
-  VPUser() : VPValue(VPValue::VPUserSC) {}
-  VPUser(ArrayRef<VPValue *> Operands) : VPUser(VPValue::VPUserSC, Operands) {}
   VPUser(std::initializer_list<VPValue *> Operands)
       : VPUser(ArrayRef<VPValue *>(Operands)) {}
-  template <typename IterT>
-  VPUser(iterator_range<IterT> Operands) : VPValue(VPValue::VPUserSC) {
+  template <typename IterT> VPUser(iterator_range<IterT> Operands) {
     for (VPValue *Operand : Operands)
       addOperand(Operand);
   }
@@ -156,12 +152,6 @@ public:
   VPUser(const VPUser &) = delete;
   VPUser &operator=(const VPUser &) = delete;
 
-  /// Method to support type inquiry through isa, cast, and dyn_cast.
-  static inline bool classof(const VPValue *V) {
-    return V->getVPValueID() >= VPUserSC &&
-           V->getVPValueID() <= VPInstructionSC;
-  }
-
   void addOperand(VPValue *Operand) {
     Operands.push_back(Operand);
     Operand->addUser(*this);