Reapply "Reapply "[VPlan] Compute cost of more replicating loads/stores in ::computeCost. (llvm#160053)" (llvm#161724)"

fhahn · fhahn · commit 770cb1686db5 · 2025-10-06T18:26:02.000+01:00
This reverts commit f80c0ba.
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -3903,7 +3903,8 @@ void LoopVectorizationPlanner::emitInvalidCostRemarks(
       if (VF.isScalar())
         continue;
 
-      VPCostContext CostCtx(CM.TTI, *CM.TLI, *Plan, CM, CM.CostKind);
+      VPCostContext CostCtx(CM.TTI, *CM.TLI, *Plan, CM, CM.CostKind,
+                            *CM.PSE.getSE());
       precomputeCosts(*Plan, VF, CostCtx);
       auto Iter = vp_depth_first_deep(Plan->getVectorLoopRegion()->getEntry());
       for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(Iter)) {
@@ -4160,7 +4161,8 @@ VectorizationFactor LoopVectorizationPlanner::selectVectorizationFactor() {
 
       // Add on other costs that are modelled in VPlan, but not in the legacy
       // cost model.
-      VPCostContext CostCtx(CM.TTI, *CM.TLI, *P, CM, CM.CostKind);
+      VPCostContext CostCtx(CM.TTI, *CM.TLI, *P, CM, CM.CostKind,
+                            *CM.PSE.getSE());
       VPRegionBlock *VectorRegion = P->getVectorLoopRegion();
       assert(VectorRegion && "Expected to have a vector region!");
       for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
@@ -6852,7 +6854,7 @@ LoopVectorizationPlanner::precomputeCosts(VPlan &Plan, ElementCount VF,
 
 InstructionCost LoopVectorizationPlanner::cost(VPlan &Plan,
                                                ElementCount VF) const {
-  VPCostContext CostCtx(CM.TTI, *CM.TLI, Plan, CM, CM.CostKind);
+  VPCostContext CostCtx(CM.TTI, *CM.TLI, Plan, CM, CM.CostKind, *PSE.getSE());
   InstructionCost Cost = precomputeCosts(Plan, VF, CostCtx);
 
   // Now compute and add the VPlan-based cost.
@@ -7085,7 +7087,8 @@ VectorizationFactor LoopVectorizationPlanner::computeBestVF() {
   // simplifications not accounted for in the legacy cost model. If that's the
   // case, don't trigger the assertion, as the extra simplifications may cause a
   // different VF to be picked by the VPlan-based cost model.
-  VPCostContext CostCtx(CM.TTI, *CM.TLI, BestPlan, CM, CM.CostKind);
+  VPCostContext CostCtx(CM.TTI, *CM.TLI, BestPlan, CM, CM.CostKind,
+                        *CM.PSE.getSE());
   precomputeCosts(BestPlan, BestFactor.Width, CostCtx);
   // Verify that the VPlan-based and legacy cost models agree, except for VPlans
   // with early exits and plans with additional VPlan simplifications. The
@@ -8418,7 +8421,8 @@ VPlanPtr LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(
   // TODO: Enable following transform when the EVL-version of extended-reduction
   // and mulacc-reduction are implemented.
   if (!CM.foldTailWithEVL()) {
-    VPCostContext CostCtx(CM.TTI, *CM.TLI, *Plan, CM, CM.CostKind);
+    VPCostContext CostCtx(CM.TTI, *CM.TLI, *Plan, CM, CM.CostKind,
+                          *CM.PSE.getSE());
     VPlanTransforms::runPass(VPlanTransforms::convertToAbstractRecipes, *Plan,
                              CostCtx, Range);
   }
@@ -9874,7 +9878,7 @@ bool LoopVectorizePass::processLoop(Loop *L) {
     bool ForceVectorization =
         Hints.getForce() == LoopVectorizeHints::FK_Enabled;
     VPCostContext CostCtx(CM.TTI, *CM.TLI, LVP.getPlanFor(VF.Width), CM,
-                          CM.CostKind);
+                          CM.CostKind, *CM.PSE.getSE());
     if (!ForceVectorization &&
         !isOutsideLoopWorkProfitable(Checks, VF, L, PSE, CostCtx,
                                      LVP.getPlanFor(VF.Width), SEL,
diff --git a/llvm/lib/Transforms/Vectorize/VPlan.cpp b/llvm/lib/Transforms/Vectorize/VPlan.cpp
@@ -1772,7 +1772,8 @@ VPCostContext::getOperandInfo(VPValue *V) const {
 }
 
 InstructionCost VPCostContext::getScalarizationOverhead(
-    Type *ResultTy, ArrayRef<const VPValue *> Operands, ElementCount VF) {
+    Type *ResultTy, ArrayRef<const VPValue *> Operands, ElementCount VF,
+    bool AlwaysIncludeReplicatingR) {
   if (VF.isScalar())
     return 0;
 
@@ -1792,7 +1793,11 @@ InstructionCost VPCostContext::getScalarizationOverhead(
   SmallPtrSet<const VPValue *, 4> UniqueOperands;
   SmallVector<Type *> Tys;
   for (auto *Op : Operands) {
-    if (Op->isLiveIn() || isa<VPReplicateRecipe, VPPredInstPHIRecipe>(Op) ||
+    if (Op->isLiveIn() ||
+        (!AlwaysIncludeReplicatingR &&
+         isa<VPReplicateRecipe, VPPredInstPHIRecipe>(Op)) ||
+        (isa<VPReplicateRecipe>(Op) &&
+         cast<VPReplicateRecipe>(Op)->getOpcode() == Instruction::Load) ||
         !UniqueOperands.insert(Op).second)
       continue;
     Tys.push_back(toVectorizedTy(Types.inferScalarType(Op), VF));
diff --git a/llvm/lib/Transforms/Vectorize/VPlanHelpers.h b/llvm/lib/Transforms/Vectorize/VPlanHelpers.h
@@ -349,12 +349,14 @@ struct VPCostContext {
   LoopVectorizationCostModel &CM;
   SmallPtrSet<Instruction *, 8> SkipCostComputation;
   TargetTransformInfo::TargetCostKind CostKind;
+  ScalarEvolution &SE;
 
   VPCostContext(const TargetTransformInfo &TTI, const TargetLibraryInfo &TLI,
                 const VPlan &Plan, LoopVectorizationCostModel &CM,
-                TargetTransformInfo::TargetCostKind CostKind)
+                TargetTransformInfo::TargetCostKind CostKind,
+                ScalarEvolution &SE)
       : TTI(TTI), TLI(TLI), Types(Plan), LLVMCtx(Plan.getContext()), CM(CM),
-        CostKind(CostKind) {}
+        CostKind(CostKind), SE(SE) {}
 
   /// Return the cost for \p UI with \p VF using the legacy cost model as
   /// fallback until computing the cost of all recipes migrates to VPlan.
@@ -374,10 +376,12 @@ struct VPCostContext {
 
   /// Estimate the overhead of scalarizing a recipe with result type \p ResultTy
   /// and \p Operands with \p VF. This is a convenience wrapper for the
-  /// type-based getScalarizationOverhead API.
-  InstructionCost getScalarizationOverhead(Type *ResultTy,
-                                           ArrayRef<const VPValue *> Operands,
-                                           ElementCount VF);
+  /// type-based getScalarizationOverhead API. If \p AlwaysIncludeReplicatingR
+  /// is true, always compute the cost of scalarizing replicating operands.
+  InstructionCost
+  getScalarizationOverhead(Type *ResultTy, ArrayRef<const VPValue *> Operands,
+                           ElementCount VF,
+                           bool AlwaysIncludeReplicatingR = false);
 };
 
 /// This class can be used to assign names to VPValues. For VPValues without
diff --git a/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp b/llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp
@@ -40,6 +40,7 @@
 #include <cassert>
 
 using namespace llvm;
+using namespace llvm::VPlanPatternMatch;
 
 using VectorParts = SmallVector<Value *, 2>;
 
@@ -303,7 +304,6 @@ VPPartialReductionRecipe::computeCost(ElementCount VF,
   VPRecipeBase *OpR = Op->getDefiningRecipe();
 
   // If the partial reduction is predicated, a select will be operand 0
-  using namespace llvm::VPlanPatternMatch;
   if (match(getOperand(1), m_Select(m_VPValue(), m_VPValue(Op), m_VPValue()))) {
     OpR = Op->getDefiningRecipe();
   }
@@ -1963,7 +1963,6 @@ InstructionCost VPWidenSelectRecipe::computeCost(ElementCount VF,
   Type *VectorTy = toVectorTy(Ctx.Types.inferScalarType(this), VF);
 
   VPValue *Op0, *Op1;
-  using namespace llvm::VPlanPatternMatch;
   if (!ScalarCond && ScalarTy->getScalarSizeInBits() == 1 &&
       (match(this, m_LogicalAnd(m_VPValue(Op0), m_VPValue(Op1))) ||
        match(this, m_LogicalOr(m_VPValue(Op0), m_VPValue(Op1))))) {
@@ -3111,6 +3110,62 @@ bool VPReplicateRecipe::shouldPack() const {
   });
 }
 
+/// Returns true if \p Ptr is a pointer computation for which the legacy cost
+/// model computes a SCEV expression when computing the address cost.
+static bool shouldUseAddressAccessSCEV(const VPValue *Ptr) {
+  auto *PtrR = Ptr->getDefiningRecipe();
+  if (!PtrR || !((isa<VPReplicateRecipe>(PtrR) &&
+                  cast<VPReplicateRecipe>(PtrR)->getOpcode() ==
+                      Instruction::GetElementPtr) ||
+                 isa<VPWidenGEPRecipe>(PtrR) ||
+                 match(Ptr, m_GetElementPtr(m_VPValue(), m_VPValue()))))
+    return false;
+
+  // We are looking for a GEP where all indices are either loop invariant or
+  // inductions.
+  for (VPValue *Opd : drop_begin(PtrR->operands())) {
+    if (!Opd->isDefinedOutsideLoopRegions() &&
+        !isa<VPScalarIVStepsRecipe, VPWidenIntOrFpInductionRecipe>(Opd))
+      return false;
+  }
+
+  return true;
+}
+
+/// Returns true if \p V is used as part of the address of another load or
+/// store.
+static bool isUsedByLoadStoreAddress(const VPUser *V) {
+  SmallPtrSet<const VPUser *, 4> Seen;
+  SmallVector<const VPUser *> WorkList = {V};
+
+  while (!WorkList.empty()) {
+    auto *Cur = dyn_cast<VPSingleDefRecipe>(WorkList.pop_back_val());
+    if (!Cur || !Seen.insert(Cur).second)
+      continue;
+
+    for (VPUser *U : Cur->users()) {
+      if (auto *InterleaveR = dyn_cast<VPInterleaveBase>(U))
+        if (InterleaveR->getAddr() == Cur)
+          return true;
+      if (auto *RepR = dyn_cast<VPReplicateRecipe>(U)) {
+        if (RepR->getOpcode() == Instruction::Load &&
+            RepR->getOperand(0) == Cur)
+          return true;
+        if (RepR->getOpcode() == Instruction::Store &&
+            RepR->getOperand(1) == Cur)
+          return true;
+      }
+      if (auto *MemR = dyn_cast<VPWidenMemoryRecipe>(U)) {
+        if (MemR->getAddr() == Cur && MemR->isConsecutive())
+          return true;
+      }
+    }
+
+    append_range(WorkList, cast<VPSingleDefRecipe>(Cur)->users());
+  }
+  return false;
+}
+
 InstructionCost VPReplicateRecipe::computeCost(ElementCount VF,
                                                VPCostContext &Ctx) const {
   Instruction *UI = cast<Instruction>(getUnderlyingValue());
@@ -3218,21 +3273,58 @@ InstructionCost VPReplicateRecipe::computeCost(ElementCount VF,
   }
   case Instruction::Load:
   case Instruction::Store: {
-    if (isSingleScalar()) {
-      bool IsLoad = UI->getOpcode() == Instruction::Load;
-      Type *ValTy = Ctx.Types.inferScalarType(IsLoad ? this : getOperand(0));
-      Type *ScalarPtrTy = Ctx.Types.inferScalarType(getOperand(IsLoad ? 0 : 1));
-      const Align Alignment = getLoadStoreAlignment(UI);
-      unsigned AS = getLoadStoreAddressSpace(UI);
-      TTI::OperandValueInfo OpInfo = TTI::getOperandInfo(UI->getOperand(0));
-      InstructionCost ScalarMemOpCost = Ctx.TTI.getMemoryOpCost(
-          UI->getOpcode(), ValTy, Alignment, AS, Ctx.CostKind, OpInfo, UI);
-      return ScalarMemOpCost + Ctx.TTI.getAddressComputationCost(
-                                   ScalarPtrTy, nullptr, nullptr, Ctx.CostKind);
-    }
+    if (VF.isScalable() && !isSingleScalar())
+      return InstructionCost::getInvalid();
+
     // TODO: See getMemInstScalarizationCost for how to handle replicating and
     // predicated cases.
-    break;
+    const VPRegionBlock *ParentRegion = getParent()->getParent();
+    if (ParentRegion && ParentRegion->isReplicator())
+      break;
+
+    bool IsLoad = UI->getOpcode() == Instruction::Load;
+    const VPValue *PtrOp = getOperand(!IsLoad);
+    // TODO: Handle cases where we need to pass a SCEV to
+    // getAddressComputationCost.
+    if (shouldUseAddressAccessSCEV(PtrOp))
+      break;
+
+    Type *ValTy = Ctx.Types.inferScalarType(IsLoad ? this : getOperand(0));
+    Type *ScalarPtrTy = Ctx.Types.inferScalarType(PtrOp);
+    const Align Alignment = getLoadStoreAlignment(UI);
+    unsigned AS = getLoadStoreAddressSpace(UI);
+    TTI::OperandValueInfo OpInfo = TTI::getOperandInfo(UI->getOperand(0));
+    InstructionCost ScalarMemOpCost = Ctx.TTI.getMemoryOpCost(
+        UI->getOpcode(), ValTy, Alignment, AS, Ctx.CostKind, OpInfo);
+
+    Type *PtrTy = isSingleScalar() ? ScalarPtrTy : toVectorTy(ScalarPtrTy, VF);
+
+    InstructionCost ScalarCost =
+        ScalarMemOpCost + Ctx.TTI.getAddressComputationCost(
+                              PtrTy, &Ctx.SE, nullptr, Ctx.CostKind);
+    if (isSingleScalar())
+      return ScalarCost;
+
+    SmallVector<const VPValue *> OpsToScalarize;
+    Type *ResultTy = Type::getVoidTy(PtrTy->getContext());
+    // Set ResultTy and OpsToScalarize, if scalarization is needed. Currently we
+    // don't assign scalarization overhead in general, if the target prefers
+    // vectorized addressing or the loaded value is used as part of an address
+    // of another load or store.
+    bool PreferVectorizedAddressing = Ctx.TTI.prefersVectorizedAddressing();
+    if (PreferVectorizedAddressing || !isUsedByLoadStoreAddress(this)) {
+      bool EfficientVectorLoadStore =
+          Ctx.TTI.supportsEfficientVectorElementLoadStore();
+      if (!(IsLoad && !PreferVectorizedAddressing) &&
+          !(!IsLoad && EfficientVectorLoadStore))
+        append_range(OpsToScalarize, operands());
+
+      if (!EfficientVectorLoadStore)
+        ResultTy = Ctx.Types.inferScalarType(this);
+    }
+
+    return (ScalarCost * VF.getFixedValue()) +
+           Ctx.getScalarizationOverhead(ResultTy, OpsToScalarize, VF, true);
   }
   }
 
