| //===-- 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" |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/Analysis/IVDescriptors.h" |
| |
| using namespace llvm; |
| |
| void VPlanTransforms::VPInstructionsToVPRecipes( |
| Loop *OrigLoop, VPlanPtr &Plan, |
| function_ref<const InductionDescriptor *(PHINode *)> |
| GetIntOrFpInductionDescriptor, |
| SmallPtrSetImpl<Instruction *> &DeadInstructions, ScalarEvolution &SE) { |
| |
| ReversePostOrderTraversal<VPBlockRecursiveTraversalWrapper<VPBlockBase *>> |
| RPOT(Plan->getEntry()); |
| for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(RPOT)) { |
| VPRecipeBase *Term = VPBB->getTerminator(); |
| auto EndIter = Term ? Term->getIterator() : VPBB->end(); |
| // Introduce each ingredient into VPlan. |
| for (VPRecipeBase &Ingredient : |
| make_early_inc_range(make_range(VPBB->begin(), EndIter))) { |
| |
| 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()); |
| if (const auto *II = GetIntOrFpInductionDescriptor(Phi)) { |
| VPValue *Start = Plan->getOrAddVPValue(II->getStartValue()); |
| VPValue *Step = |
| vputils::getOrCreateVPValueForSCEVExpr(*Plan, II->getStep(), SE); |
| NewRecipe = |
| new VPWidenIntOrFpInductionRecipe(Phi, Start, Step, *II, true); |
| } 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->users()); |
| 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->users()); |
| 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; |
| } |
| |
| void VPlanTransforms::removeRedundantInductionCasts(VPlan &Plan) { |
| for (auto &Phi : Plan.getVectorLoopRegion()->getEntryBasicBlock()->phis()) { |
| auto *IV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi); |
| if (!IV || IV->getTruncInst()) |
| continue; |
| |
| // A sequence of IR Casts has potentially been recorded for IV, which |
| // *must be bypassed* when the IV is vectorized, because the vectorized IV |
| // will produce the desired casted value. This sequence forms a def-use |
| // chain and is provided in reverse order, ending with the cast that uses |
| // the IV phi. Search for the recipe of the last cast in the chain and |
| // replace it with the original IV. Note that only the final cast is |
| // expected to have users outside the cast-chain and the dead casts left |
| // over will be cleaned up later. |
| auto &Casts = IV->getInductionDescriptor().getCastInsts(); |
| VPValue *FindMyCast = IV; |
| for (Instruction *IRCast : reverse(Casts)) { |
| VPRecipeBase *FoundUserCast = nullptr; |
| for (auto *U : FindMyCast->users()) { |
| auto *UserCast = cast<VPRecipeBase>(U); |
| if (UserCast->getNumDefinedValues() == 1 && |
| UserCast->getVPSingleValue()->getUnderlyingValue() == IRCast) { |
| FoundUserCast = UserCast; |
| break; |
| } |
| } |
| FindMyCast = FoundUserCast->getVPSingleValue(); |
| } |
| FindMyCast->replaceAllUsesWith(IV); |
| } |
| } |
| |
| void VPlanTransforms::removeRedundantCanonicalIVs(VPlan &Plan) { |
| VPCanonicalIVPHIRecipe *CanonicalIV = Plan.getCanonicalIV(); |
| VPWidenCanonicalIVRecipe *WidenNewIV = nullptr; |
| for (VPUser *U : CanonicalIV->users()) { |
| WidenNewIV = dyn_cast<VPWidenCanonicalIVRecipe>(U); |
| if (WidenNewIV) |
| break; |
| } |
| |
| if (!WidenNewIV) |
| return; |
| |
| VPBasicBlock *HeaderVPBB = Plan.getVectorLoopRegion()->getEntryBasicBlock(); |
| for (VPRecipeBase &Phi : HeaderVPBB->phis()) { |
| auto *WidenOriginalIV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi); |
| |
| if (!WidenOriginalIV || !WidenOriginalIV->isCanonical() || |
| WidenOriginalIV->getScalarType() != WidenNewIV->getScalarType()) |
| continue; |
| |
| // Replace WidenNewIV with WidenOriginalIV if WidenOriginalIV provides |
| // everything WidenNewIV's users need. That is, WidenOriginalIV will |
| // generate a vector phi or all users of WidenNewIV demand the first lane |
| // only. |
| if (WidenOriginalIV->needsVectorIV() || |
| vputils::onlyFirstLaneUsed(WidenNewIV)) { |
| WidenNewIV->replaceAllUsesWith(WidenOriginalIV); |
| WidenNewIV->eraseFromParent(); |
| return; |
| } |
| } |
| } |
| |
| void VPlanTransforms::removeDeadRecipes(VPlan &Plan) { |
| ReversePostOrderTraversal<VPBlockRecursiveTraversalWrapper<VPBlockBase *>> |
| RPOT(Plan.getEntry()); |
| |
| for (VPBasicBlock *VPBB : reverse(VPBlockUtils::blocksOnly<VPBasicBlock>(RPOT))) { |
| // The recipes in the block are processed in reverse order, to catch chains |
| // of dead recipes. |
| for (VPRecipeBase &R : make_early_inc_range(reverse(*VPBB))) { |
| if (R.mayHaveSideEffects() || any_of(R.definedValues(), [](VPValue *V) { |
| return V->getNumUsers() > 0; |
| })) |
| continue; |
| R.eraseFromParent(); |
| } |
| } |
| } |
| |
| void VPlanTransforms::optimizeInductions(VPlan &Plan, ScalarEvolution &SE) { |
| SmallVector<VPRecipeBase *> ToRemove; |
| VPBasicBlock *HeaderVPBB = Plan.getVectorLoopRegion()->getEntryBasicBlock(); |
| bool HasOnlyVectorVFs = !Plan.hasVF(ElementCount::getFixed(1)); |
| for (VPRecipeBase &Phi : HeaderVPBB->phis()) { |
| auto *IV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi); |
| if (!IV) |
| continue; |
| if (HasOnlyVectorVFs && |
| none_of(IV->users(), [IV](VPUser *U) { return U->usesScalars(IV); })) |
| continue; |
| |
| const InductionDescriptor &ID = IV->getInductionDescriptor(); |
| VPValue *Step = |
| vputils::getOrCreateVPValueForSCEVExpr(Plan, ID.getStep(), SE); |
| Instruction *TruncI = IV->getTruncInst(); |
| VPScalarIVStepsRecipe *Steps = new VPScalarIVStepsRecipe( |
| IV->getPHINode()->getType(), ID, Plan.getCanonicalIV(), |
| IV->getStartValue(), Step, TruncI ? TruncI->getType() : nullptr); |
| HeaderVPBB->insert(Steps, HeaderVPBB->getFirstNonPhi()); |
| |
| // Update scalar users of IV to use Step instead. Use SetVector to ensure |
| // the list of users doesn't contain duplicates. |
| SetVector<VPUser *> Users(IV->user_begin(), IV->user_end()); |
| for (VPUser *U : Users) { |
| if (HasOnlyVectorVFs && !U->usesScalars(IV)) |
| continue; |
| for (unsigned I = 0, E = U->getNumOperands(); I != E; I++) { |
| if (U->getOperand(I) != IV) |
| continue; |
| U->setOperand(I, Steps); |
| } |
| } |
| } |
| } |
| |
| void VPlanTransforms::removeRedundantExpandSCEVRecipes(VPlan &Plan) { |
| DenseMap<const SCEV *, VPValue *> SCEV2VPV; |
| |
| for (VPRecipeBase &R : |
| make_early_inc_range(*Plan.getEntry()->getEntryBasicBlock())) { |
| auto *ExpR = dyn_cast<VPExpandSCEVRecipe>(&R); |
| if (!ExpR) |
| continue; |
| |
| auto I = SCEV2VPV.insert({ExpR->getSCEV(), ExpR}); |
| if (I.second) |
| continue; |
| ExpR->replaceAllUsesWith(I.first->second); |
| ExpR->eraseFromParent(); |
| } |
| } |
