| //===-- VPlanTransforms.cpp - Utility VPlan to VPlan transforms -----------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| /// |
| /// \file |
| /// This file implements a set of utility VPlan to VPlan transformations. |
| /// |
| //===----------------------------------------------------------------------===// |
| |
| #include "VPlanTransforms.h" |
| #include "llvm/ADT/PostOrderIterator.h" |
| |
| using namespace llvm; |
| |
| void VPlanTransforms::VPInstructionsToVPRecipes( |
| Loop *OrigLoop, VPlanPtr &Plan, |
| LoopVectorizationLegality::InductionList &Inductions, |
| SmallPtrSetImpl<Instruction *> &DeadInstructions, ScalarEvolution &SE) { |
| |
| auto *TopRegion = cast<VPRegionBlock>(Plan->getEntry()); |
| ReversePostOrderTraversal<VPBlockBase *> RPOT(TopRegion->getEntry()); |
| |
| for (VPBlockBase *Base : RPOT) { |
| // Do not widen instructions in pre-header and exit blocks. |
| if (Base->getNumPredecessors() == 0 || Base->getNumSuccessors() == 0) |
| continue; |
| |
| VPBasicBlock *VPBB = Base->getEntryBasicBlock(); |
| // Introduce each ingredient into VPlan. |
| for (VPRecipeBase &Ingredient : llvm::make_early_inc_range(*VPBB)) { |
| VPValue *VPV = Ingredient.getVPSingleValue(); |
| Instruction *Inst = cast<Instruction>(VPV->getUnderlyingValue()); |
| if (DeadInstructions.count(Inst)) { |
| VPValue DummyValue; |
| VPV->replaceAllUsesWith(&DummyValue); |
| Ingredient.eraseFromParent(); |
| continue; |
| } |
| |
| VPRecipeBase *NewRecipe = nullptr; |
| if (auto *VPPhi = dyn_cast<VPWidenPHIRecipe>(&Ingredient)) { |
| auto *Phi = cast<PHINode>(VPPhi->getUnderlyingValue()); |
| InductionDescriptor II = Inductions.lookup(Phi); |
| if (II.getKind() == InductionDescriptor::IK_IntInduction || |
| II.getKind() == InductionDescriptor::IK_FpInduction) { |
| VPValue *Start = Plan->getOrAddVPValue(II.getStartValue()); |
| NewRecipe = new VPWidenIntOrFpInductionRecipe(Phi, Start, nullptr); |
| } else { |
| Plan->addVPValue(Phi, VPPhi); |
| continue; |
| } |
| } else { |
| assert(isa<VPInstruction>(&Ingredient) && |
| "only VPInstructions expected here"); |
| assert(!isa<PHINode>(Inst) && "phis should be handled above"); |
| // Create VPWidenMemoryInstructionRecipe for loads and stores. |
| if (LoadInst *Load = dyn_cast<LoadInst>(Inst)) { |
| NewRecipe = new VPWidenMemoryInstructionRecipe( |
| *Load, Plan->getOrAddVPValue(getLoadStorePointerOperand(Inst)), |
| nullptr /*Mask*/, false /*Consecutive*/, false /*Reverse*/); |
| } else if (StoreInst *Store = dyn_cast<StoreInst>(Inst)) { |
| NewRecipe = new VPWidenMemoryInstructionRecipe( |
| *Store, Plan->getOrAddVPValue(getLoadStorePointerOperand(Inst)), |
| Plan->getOrAddVPValue(Store->getValueOperand()), nullptr /*Mask*/, |
| false /*Consecutive*/, false /*Reverse*/); |
| } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) { |
| NewRecipe = new VPWidenGEPRecipe( |
| GEP, Plan->mapToVPValues(GEP->operands()), OrigLoop); |
| } else if (CallInst *CI = dyn_cast<CallInst>(Inst)) { |
| NewRecipe = |
| new VPWidenCallRecipe(*CI, Plan->mapToVPValues(CI->args())); |
| } else if (SelectInst *SI = dyn_cast<SelectInst>(Inst)) { |
| bool InvariantCond = |
| SE.isLoopInvariant(SE.getSCEV(SI->getOperand(0)), OrigLoop); |
| NewRecipe = new VPWidenSelectRecipe( |
| *SI, Plan->mapToVPValues(SI->operands()), InvariantCond); |
| } else { |
| NewRecipe = |
| new VPWidenRecipe(*Inst, Plan->mapToVPValues(Inst->operands())); |
| } |
| } |
| |
| NewRecipe->insertBefore(&Ingredient); |
| if (NewRecipe->getNumDefinedValues() == 1) |
| VPV->replaceAllUsesWith(NewRecipe->getVPSingleValue()); |
| else |
| assert(NewRecipe->getNumDefinedValues() == 0 && |
| "Only recpies with zero or one defined values expected"); |
| Ingredient.eraseFromParent(); |
| Plan->removeVPValueFor(Inst); |
| for (auto *Def : NewRecipe->definedValues()) { |
| Plan->addVPValue(Inst, Def); |
| } |
| } |
| } |
| } |
| |
| bool VPlanTransforms::sinkScalarOperands(VPlan &Plan) { |
| auto Iter = depth_first( |
| VPBlockRecursiveTraversalWrapper<VPBlockBase *>(Plan.getEntry())); |
| bool Changed = false; |
| // First, collect the operands of all predicated replicate recipes as seeds |
| // for sinking. |
| SetVector<std::pair<VPBasicBlock *, VPValue *>> WorkList; |
| for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(Iter)) { |
| for (auto &Recipe : *VPBB) { |
| auto *RepR = dyn_cast<VPReplicateRecipe>(&Recipe); |
| if (!RepR || !RepR->isPredicated()) |
| continue; |
| for (VPValue *Op : RepR->operands()) |
| WorkList.insert(std::make_pair(RepR->getParent(), Op)); |
| } |
| } |
| |
| // Try to sink each replicate recipe in the worklist. |
| while (!WorkList.empty()) { |
| VPBasicBlock *SinkTo; |
| VPValue *C; |
| std::tie(SinkTo, C) = WorkList.pop_back_val(); |
| auto *SinkCandidate = dyn_cast_or_null<VPReplicateRecipe>(C->Def); |
| if (!SinkCandidate || SinkCandidate->isUniform() || |
| SinkCandidate->getParent() == SinkTo || |
| SinkCandidate->mayHaveSideEffects() || |
| SinkCandidate->mayReadOrWriteMemory()) |
| continue; |
| |
| bool NeedsDuplicating = false; |
| // All recipe users of the sink candidate must be in the same block SinkTo |
| // or all users outside of SinkTo must be uniform-after-vectorization ( |
| // i.e., only first lane is used) . In the latter case, we need to duplicate |
| // SinkCandidate. At the moment, we identify such UAV's by looking for the |
| // address operands of widened memory recipes. |
| auto CanSinkWithUser = [SinkTo, &NeedsDuplicating, |
| SinkCandidate](VPUser *U) { |
| auto *UI = dyn_cast<VPRecipeBase>(U); |
| if (!UI) |
| return false; |
| if (UI->getParent() == SinkTo) |
| return true; |
| auto *WidenI = dyn_cast<VPWidenMemoryInstructionRecipe>(UI); |
| if (WidenI && WidenI->getAddr() == SinkCandidate) { |
| NeedsDuplicating = true; |
| return true; |
| } |
| return false; |
| }; |
| if (!all_of(SinkCandidate->users(), CanSinkWithUser)) |
| continue; |
| |
| if (NeedsDuplicating) { |
| Instruction *I = cast<Instruction>(SinkCandidate->getUnderlyingValue()); |
| auto *Clone = |
| new VPReplicateRecipe(I, SinkCandidate->operands(), true, false); |
| // TODO: add ".cloned" suffix to name of Clone's VPValue. |
| |
| Clone->insertBefore(SinkCandidate); |
| SmallVector<VPUser *, 4> Users(SinkCandidate->user_begin(), |
| SinkCandidate->user_end()); |
| for (auto *U : Users) { |
| auto *UI = cast<VPRecipeBase>(U); |
| if (UI->getParent() == SinkTo) |
| continue; |
| |
| for (unsigned Idx = 0; Idx != UI->getNumOperands(); Idx++) { |
| if (UI->getOperand(Idx) != SinkCandidate) |
| continue; |
| UI->setOperand(Idx, Clone); |
| } |
| } |
| } |
| SinkCandidate->moveBefore(*SinkTo, SinkTo->getFirstNonPhi()); |
| for (VPValue *Op : SinkCandidate->operands()) |
| WorkList.insert(std::make_pair(SinkTo, Op)); |
| Changed = true; |
| } |
| return Changed; |
| } |
| |
| /// If \p R is a region with a VPBranchOnMaskRecipe in the entry block, return |
| /// the mask. |
| VPValue *getPredicatedMask(VPRegionBlock *R) { |
| auto *EntryBB = dyn_cast<VPBasicBlock>(R->getEntry()); |
| if (!EntryBB || EntryBB->size() != 1 || |
| !isa<VPBranchOnMaskRecipe>(EntryBB->begin())) |
| return nullptr; |
| |
| return cast<VPBranchOnMaskRecipe>(&*EntryBB->begin())->getOperand(0); |
| } |
| |
| /// If \p R is a triangle region, return the 'then' block of the triangle. |
| static VPBasicBlock *getPredicatedThenBlock(VPRegionBlock *R) { |
| auto *EntryBB = cast<VPBasicBlock>(R->getEntry()); |
| if (EntryBB->getNumSuccessors() != 2) |
| return nullptr; |
| |
| auto *Succ0 = dyn_cast<VPBasicBlock>(EntryBB->getSuccessors()[0]); |
| auto *Succ1 = dyn_cast<VPBasicBlock>(EntryBB->getSuccessors()[1]); |
| if (!Succ0 || !Succ1) |
| return nullptr; |
| |
| if (Succ0->getNumSuccessors() + Succ1->getNumSuccessors() != 1) |
| return nullptr; |
| if (Succ0->getSingleSuccessor() == Succ1) |
| return Succ0; |
| if (Succ1->getSingleSuccessor() == Succ0) |
| return Succ1; |
| return nullptr; |
| } |
| |
| bool VPlanTransforms::mergeReplicateRegions(VPlan &Plan) { |
| SetVector<VPRegionBlock *> DeletedRegions; |
| bool Changed = false; |
| |
| // Collect region blocks to process up-front, to avoid iterator invalidation |
| // issues while merging regions. |
| SmallVector<VPRegionBlock *, 8> CandidateRegions( |
| VPBlockUtils::blocksOnly<VPRegionBlock>(depth_first( |
| VPBlockRecursiveTraversalWrapper<VPBlockBase *>(Plan.getEntry())))); |
| |
| // Check if Base is a predicated triangle, followed by an empty block, |
| // followed by another predicate triangle. If that's the case, move the |
| // recipes from the first to the second triangle. |
| for (VPRegionBlock *Region1 : CandidateRegions) { |
| if (DeletedRegions.contains(Region1)) |
| continue; |
| auto *MiddleBasicBlock = |
| dyn_cast_or_null<VPBasicBlock>(Region1->getSingleSuccessor()); |
| if (!MiddleBasicBlock || !MiddleBasicBlock->empty()) |
| continue; |
| |
| auto *Region2 = |
| dyn_cast_or_null<VPRegionBlock>(MiddleBasicBlock->getSingleSuccessor()); |
| if (!Region2) |
| continue; |
| |
| VPValue *Mask1 = getPredicatedMask(Region1); |
| VPValue *Mask2 = getPredicatedMask(Region2); |
| if (!Mask1 || Mask1 != Mask2) |
| continue; |
| VPBasicBlock *Then1 = getPredicatedThenBlock(Region1); |
| VPBasicBlock *Then2 = getPredicatedThenBlock(Region2); |
| if (!Then1 || !Then2) |
| continue; |
| |
| assert(Mask1 && Mask2 && "both region must have conditions"); |
| |
| // Note: No fusion-preventing memory dependencies are expected in either |
| // region. Such dependencies should be rejected during earlier dependence |
| // checks, which guarantee accesses can be re-ordered for vectorization. |
| // |
| // Move recipes to the successor region. |
| for (VPRecipeBase &ToMove : make_early_inc_range(reverse(*Then1))) |
| ToMove.moveBefore(*Then2, Then2->getFirstNonPhi()); |
| |
| auto *Merge1 = cast<VPBasicBlock>(Then1->getSingleSuccessor()); |
| auto *Merge2 = cast<VPBasicBlock>(Then2->getSingleSuccessor()); |
| |
| // Move VPPredInstPHIRecipes from the merge block to the successor region's |
| // merge block. Update all users inside the successor region to use the |
| // original values. |
| for (VPRecipeBase &Phi1ToMove : make_early_inc_range(reverse(*Merge1))) { |
| VPValue *PredInst1 = |
| cast<VPPredInstPHIRecipe>(&Phi1ToMove)->getOperand(0); |
| VPValue *Phi1ToMoveV = Phi1ToMove.getVPSingleValue(); |
| SmallVector<VPUser *> Users(Phi1ToMoveV->user_begin(), |
| Phi1ToMoveV->user_end()); |
| for (VPUser *U : Users) { |
| auto *UI = dyn_cast<VPRecipeBase>(U); |
| if (!UI || UI->getParent() != Then2) |
| continue; |
| for (unsigned I = 0, E = U->getNumOperands(); I != E; ++I) { |
| if (Phi1ToMoveV != U->getOperand(I)) |
| continue; |
| U->setOperand(I, PredInst1); |
| } |
| } |
| |
| Phi1ToMove.moveBefore(*Merge2, Merge2->begin()); |
| } |
| |
| // Finally, remove the first region. |
| for (VPBlockBase *Pred : make_early_inc_range(Region1->getPredecessors())) { |
| VPBlockUtils::disconnectBlocks(Pred, Region1); |
| VPBlockUtils::connectBlocks(Pred, MiddleBasicBlock); |
| } |
| VPBlockUtils::disconnectBlocks(Region1, MiddleBasicBlock); |
| DeletedRegions.insert(Region1); |
| } |
| |
| for (VPRegionBlock *ToDelete : DeletedRegions) |
| delete ToDelete; |
| return Changed; |
| } |
