[VPlan] Unroll VPRedplicateRecipes by VF.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -7557,6 +7557,7 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
   // cost model is complete for better cost estimates.
   VPlanTransforms::runPass(VPlanTransforms::unrollByUF, BestVPlan, BestUF,
                            OrigLoop->getHeader()->getContext());
+  VPlanTransforms::runPass(VPlanTransforms::unrollByVF, BestVPlan, BestVF);
   VPlanTransforms::runPass(VPlanTransforms::materializeBroadcasts, BestVPlan);
   VPlanTransforms::optimizeForVFAndUF(BestVPlan, BestVF, BestUF, PSE);
   VPlanTransforms::simplifyRecipes(BestVPlan, *Legal->getWidestInductionType());

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -261,6 +261,14 @@ Value *VPTransformState::get(const VPValue *Def, const VPLane &Lane) {
     return Data.VPV2Scalars[Def][0];
   }
 
+  // Look through BuildVector to avoid redundant extracts.
+  // TODO: Remove once replicate regions are unrolled explicitly.
+  auto *BV = dyn_cast<VPInstruction>(Def);
+  if (Lane.getKind() == VPLane::Kind::First && BV &&
+      BV->getOpcode() == VPInstruction::BuildVector) {
+    return get(BV->getOperand(Lane.getKnownLane()), true);
+  }
+
   assert(hasVectorValue(Def));
   auto *VecPart = Data.VPV2Vector[Def];
   if (!VecPart->getType()->isVectorTy()) {

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -907,6 +907,12 @@ class VPInstruction : public VPRecipeWithIRFlags,
     BranchOnCount,
     BranchOnCond,
     Broadcast,
+    /// Creates a vector containing all operands. The vector element count
+    /// matches the number of operands.
+    BuildVector,
+    /// Creates a struct of vectors containing all operands. The vector element
+    /// count matches the number of operands.
+    BuildStructVector,
     ComputeFindLastIVResult,
     ComputeReductionResult,
     // Extracts the last lane from its operand if it is a vector, or the last

llvm/lib/Transforms/Vectorize/VPlanAnalysis.cpp

@@ -104,6 +104,8 @@ Type *VPTypeAnalysis::inferScalarTypeForRecipe(const VPInstruction *R) {
   case VPInstruction::CalculateTripCountMinusVF:
   case VPInstruction::CanonicalIVIncrementForPart:
   case VPInstruction::AnyOf:
+  case VPInstruction::BuildVector:
+  case VPInstruction::BuildStructVector:
     return SetResultTyFromOp();
   case VPInstruction::FirstActiveLane:
     return Type::getIntNTy(Ctx, 64);

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -493,6 +493,9 @@ Value *VPInstruction::generate(VPTransformState &State) {
   }
   case Instruction::ExtractElement: {
     assert(State.VF.isVector() && "Only extract elements from vectors");
+    return State.get(getOperand(0),
+                     VPLane(cast<ConstantInt>(getOperand(1)->getLiveInIRValue())
+                                ->getZExtValue()));
     Value *Vec = State.get(getOperand(0));
     Value *Idx = State.get(getOperand(1), /*IsScalar=*/true);
     return Builder.CreateExtractElement(Vec, Idx, Name);
@@ -604,6 +607,34 @@ Value *VPInstruction::generate(VPTransformState &State) {
     return Builder.CreateVectorSplat(
         State.VF, State.get(getOperand(0), /*IsScalar*/ true), "broadcast");
   }
+  case VPInstruction::BuildVector: {
+    auto *ScalarTy = State.TypeAnalysis.inferScalarType(getOperand(0));
+    Value *Res = PoisonValue::get(
+        toVectorizedTy(ScalarTy, ElementCount::getFixed(getNumOperands())));
+    for (const auto &[Idx, Op] : enumerate(operands()))
+      Res = State.Builder.CreateInsertElement(Res, State.get(Op, true),
+                                              State.Builder.getInt32(Idx));
+    return Res;
+  }
+  case VPInstruction::BuildStructVector: {
+    // For struct types, we need to build a new 'wide' struct type, where each
+    // element is widened.
+    auto *STy =
+        cast<StructType>(State.TypeAnalysis.inferScalarType(getOperand(0)));
+    Value *Res = PoisonValue::get(
+        toVectorizedTy(STy, ElementCount::getFixed(getNumOperands())));
+    for (const auto &[Idx, Op] : enumerate(operands())) {
+      for (unsigned I = 0, E = STy->getNumElements(); I != E; I++) {
+        Value *ScalarValue = Builder.CreateExtractValue(State.get(Op, true), I);
+        Value *VectorValue = Builder.CreateExtractValue(Res, I);
+        VectorValue =
+            Builder.CreateInsertElement(VectorValue, ScalarValue, Idx);
+        Res = Builder.CreateInsertValue(Res, VectorValue, I);
+      }
+    }
+    return Res;
+  }
+
   case VPInstruction::ComputeFindLastIVResult: {
     // FIXME: The cross-recipe dependency on VPReductionPHIRecipe is temporary
     // and will be removed by breaking up the recipe further.
@@ -864,10 +895,11 @@ void VPInstruction::execute(VPTransformState &State) {
   if (!hasResult())
     return;
   assert(GeneratedValue && "generate must produce a value");
-  assert(
-      (GeneratedValue->getType()->isVectorTy() == !GeneratesPerFirstLaneOnly ||
-       State.VF.isScalar()) &&
-      "scalar value but not only first lane defined");
+  assert((((GeneratedValue->getType()->isVectorTy() ||
+            GeneratedValue->getType()->isStructTy()) ==
+           !GeneratesPerFirstLaneOnly) ||
+          State.VF.isScalar()) &&
+         "scalar value but not only first lane defined");
   State.set(this, GeneratedValue,
             /*IsScalar*/ GeneratesPerFirstLaneOnly);
 }
@@ -881,6 +913,8 @@ bool VPInstruction::opcodeMayReadOrWriteFromMemory() const {
   case Instruction::ICmp:
   case Instruction::Select:
   case VPInstruction::AnyOf:
+  case VPInstruction::BuildVector:
+  case VPInstruction::BuildStructVector:
   case VPInstruction::CalculateTripCountMinusVF:
   case VPInstruction::CanonicalIVIncrementForPart:
   case VPInstruction::ExtractLastElement:
@@ -999,6 +1033,12 @@ void VPInstruction::print(raw_ostream &O, const Twine &Indent,
   case VPInstruction::Broadcast:
     O << "broadcast";
     break;
+  case VPInstruction::BuildVector:
+    O << "buildvector";
+    break;
+  case VPInstruction::BuildStructVector:
+    O << "buildstructvector";
+    break;
   case VPInstruction::ExtractLastElement:
     O << "extract-last-element";
     break;
@@ -2758,20 +2798,6 @@ void VPReplicateRecipe::execute(VPTransformState &State) {
     scalarizeInstruction(UI, this, VPLane(0), State);
     return;
   }
-
-  // A store of a loop varying value to a uniform address only needs the last
-  // copy of the store.
-  if (isa<StoreInst>(UI) && vputils::isSingleScalar(getOperand(1))) {
-    auto Lane = VPLane::getLastLaneForVF(State.VF);
-    scalarizeInstruction(UI, this, VPLane(Lane), State);
-    return;
-  }
-
-  // Generate scalar instances for all VF lanes.
-  assert(!State.VF.isScalable() && "Can't scalarize a scalable vector");
-  const unsigned EndLane = State.VF.getKnownMinValue();
-  for (unsigned Lane = 0; Lane < EndLane; ++Lane)
-    scalarizeInstruction(UI, this, VPLane(Lane), State);
 }
 
 bool VPReplicateRecipe::shouldPack() const {

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -1142,6 +1142,22 @@ static void simplifyRecipe(VPRecipeBase &R, VPTypeAnalysis &TypeInfo) {
     return;
   }
 
+  // Look through Extract(Last|Penultimate)Element (BuildVector ....).
+  if (match(&R,
+            m_VPInstruction<VPInstruction::ExtractLastElement>(m_VPValue(A))) ||
+      match(&R, m_VPInstruction<VPInstruction::ExtractPenultimateElement>(
+                    m_VPValue(A)))) {
+    unsigned Offset = cast<VPInstruction>(&R)->getOpcode() ==
+                              VPInstruction::ExtractLastElement
+                          ? 1
+                          : 2;
+    auto *BV = dyn_cast<VPInstruction>(A);
+    if (BV && BV->getOpcode() == VPInstruction::BuildVector) {
+      Def->replaceAllUsesWith(BV->getOperand(BV->getNumOperands() - Offset));
+      return;
+    }
+  }
+
   // Some simplifications can only be applied after unrolling. Perform them
   // below.
   if (!Plan->isUnrolled())

llvm/lib/Transforms/Vectorize/VPlanTransforms.h

@@ -99,6 +99,10 @@ struct VPlanTransforms {
   /// Explicitly unroll \p Plan by \p UF.
   static void unrollByUF(VPlan &Plan, unsigned UF, LLVMContext &Ctx);
 
+  /// Explicitly unroll VPReplicateRecipes outside of replicate regions by \p
+  /// VF.
+  static void unrollByVF(VPlan &Plan, ElementCount VF);
+
   /// Optimize \p Plan based on \p BestVF and \p BestUF. This may restrict the
   /// resulting plan to \p BestVF and \p BestUF.
   static void optimizeForVFAndUF(VPlan &Plan, ElementCount BestVF,

llvm/lib/Transforms/Vectorize/VPlanUnroll.cpp

@@ -15,6 +15,7 @@
 #include "VPlan.h"
 #include "VPlanAnalysis.h"
 #include "VPlanCFG.h"
+#include "VPlanHelpers.h"
 #include "VPlanPatternMatch.h"
 #include "VPlanTransforms.h"
 #include "VPlanUtils.h"
@@ -428,3 +429,83 @@ void VPlanTransforms::unrollByUF(VPlan &Plan, unsigned UF, LLVMContext &Ctx) {
 
   VPlanTransforms::removeDeadRecipes(Plan);
 }
+
+/// Create a single-scalar clone of RepR for lane \p Lane.
+static VPReplicateRecipe *cloneForLane(VPlan &Plan, VPBuilder &Builder,
+                                       Type *IdxTy, VPReplicateRecipe *RepR,
+                                       VPLane Lane) {
+  // Collect the operands at Lane, creating extracts as needed.
+  SmallVector<VPValue *> NewOps;
+  for (VPValue *Op : RepR->operands()) {
+    if (vputils::isSingleScalar(Op)) {
+      NewOps.push_back(Op);
+      continue;
+    }
+    VPValue *Ext;
+    if (Lane.getKind() == VPLane::Kind::ScalableLast) {
+      Ext = Builder.createNaryOp(VPInstruction::ExtractLastElement, {Op});
+    } else {
+      // Look through buildvector to avoid unnecessary extracts.
+      auto *BV = dyn_cast<VPInstruction>(Op);
+      if (BV && BV->getOpcode() == VPInstruction::BuildVector) {
+        NewOps.push_back(BV->getOperand(Lane.getKnownLane()));
+        continue;
+      }
+      VPValue *Idx =
+          Plan.getOrAddLiveIn(ConstantInt::get(IdxTy, Lane.getKnownLane()));
+      Ext = Builder.createNaryOp(Instruction::ExtractElement, {Op, Idx});
+    }
+    NewOps.push_back(Ext);
+  }
+
+  auto *New =
+      new VPReplicateRecipe(RepR->getUnderlyingInstr(), NewOps,
+                            /*IsSingleScalar=*/true, /*Mask=*/nullptr, *RepR);
+  New->insertBefore(RepR);
+  return New;
+}
+
+void VPlanTransforms::unrollByVF(VPlan &Plan, ElementCount VF) {
+  Type *IdxTy = IntegerType::get(
+      Plan.getScalarHeader()->getIRBasicBlock()->getContext(), 32);
+  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
+           vp_depth_first_shallow(Plan.getVectorLoopRegion()->getEntry()))) {
+    for (VPRecipeBase &R : make_early_inc_range(*VPBB)) {
+      auto *RepR = dyn_cast<VPReplicateRecipe>(&R);
+      if (!RepR || RepR->isSingleScalar())
+        continue;
+
+      VPBuilder Builder(RepR);
+      SmallVector<VPValue *> LaneDefs;
+      // Stores to invariant addresses only need to store the last lane.
+      if (isa<StoreInst>(RepR->getUnderlyingInstr()) &&
+          vputils::isSingleScalar(RepR->getOperand(1))) {
+        cloneForLane(Plan, Builder, IdxTy, RepR, VPLane::getLastLaneForVF(VF));
+        RepR->eraseFromParent();
+        continue;
+      }
+
+      /// Create single-scalar version of RepR for all lanes.
+      for (unsigned I = 0; I != VF.getKnownMinValue(); ++I)
+        LaneDefs.push_back(cloneForLane(Plan, Builder, IdxTy, RepR, VPLane(I)));
+
+      /// Users that only demand the first lane can use the definition for lane
+      /// 0.
+      RepR->replaceUsesWithIf(LaneDefs[0], [RepR](VPUser &U, unsigned) {
+        return U.onlyFirstLaneUsed(RepR);
+      });
+
+      Type *ResTy = RepR->getUnderlyingInstr()->getType();
+      // If needed, create a Build(Struct)Vector recipe to insert the scalar
+      // lane values into a vector.
+      if (!ResTy->isVoidTy()) {
+        VPValue *VecRes = Builder.createNaryOp(
+            ResTy->isStructTy() ? VPInstruction::BuildStructVector
+                                : VPInstruction::BuildVector,
+            LaneDefs);
+        RepR->replaceAllUsesWith(VecRes);
+      }
+      RepR->eraseFromParent();
+    }
+  }
+}

llvm/test/Transforms/LoopVectorize/X86/fixed-order-recurrence.ll

@@ -398,12 +398,6 @@ define void @test_for_tried_to_force_scalar(ptr noalias %A, ptr noalias %B, ptr
 ; CHECK-NEXT:    [[STRIDED_VEC:%.*]] = shufflevector <12 x float> [[WIDE_VEC]], <12 x float> poison, <4 x i32> <i32 0, i32 3, i32 6, i32 9>
 ; CHECK-NEXT:    [[TMP30:%.*]] = extractelement <4 x float> [[STRIDED_VEC]], i32 3
 ; CHECK-NEXT:    store float [[TMP30]], ptr [[C:%.*]], align 4
-; CHECK-NEXT:    [[TMP31:%.*]] = extractelement <4 x ptr> [[TMP29]], i32 0
-; CHECK-NEXT:    [[TMP38:%.*]] = load float, ptr [[TMP31]], align 4
-; CHECK-NEXT:    [[TMP33:%.*]] = extractelement <4 x ptr> [[TMP29]], i32 1
-; CHECK-NEXT:    [[TMP32:%.*]] = load float, ptr [[TMP33]], align 4
-; CHECK-NEXT:    [[TMP35:%.*]] = extractelement <4 x ptr> [[TMP29]], i32 2
-; CHECK-NEXT:    [[TMP34:%.*]] = load float, ptr [[TMP35]], align 4
 ; CHECK-NEXT:    [[TMP37:%.*]] = extractelement <4 x ptr> [[TMP29]], i32 3
 ; CHECK-NEXT:    [[TMP36:%.*]] = load float, ptr [[TMP37]], align 4
 ; CHECK-NEXT:    store float [[TMP36]], ptr [[B:%.*]], align 4