forked from OSchip/llvm-project
471 lines
18 KiB
C++
471 lines
18 KiB
C++
//===-- VPlanTransforms.cpp - Utility VPlan to VPlan transforms -----------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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///
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/// \file
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/// This file implements a set of utility VPlan to VPlan transformations.
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///
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//===----------------------------------------------------------------------===//
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#include "VPlanTransforms.h"
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#include "llvm/ADT/PostOrderIterator.h"
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#include "llvm/ADT/SetVector.h"
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#include "llvm/Analysis/IVDescriptors.h"
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using namespace llvm;
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void VPlanTransforms::VPInstructionsToVPRecipes(
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Loop *OrigLoop, VPlanPtr &Plan,
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function_ref<const InductionDescriptor *(PHINode *)>
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GetIntOrFpInductionDescriptor,
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SmallPtrSetImpl<Instruction *> &DeadInstructions, ScalarEvolution &SE) {
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auto *TopRegion = cast<VPRegionBlock>(Plan->getEntry());
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ReversePostOrderTraversal<VPBlockBase *> RPOT(TopRegion->getEntry());
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for (VPBlockBase *Base : RPOT) {
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// Do not widen instructions in pre-header and exit blocks.
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if (Base->getNumPredecessors() == 0 || Base->getNumSuccessors() == 0)
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continue;
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VPBasicBlock *VPBB = Base->getEntryBasicBlock();
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// Introduce each ingredient into VPlan.
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for (VPRecipeBase &Ingredient : llvm::make_early_inc_range(*VPBB)) {
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VPValue *VPV = Ingredient.getVPSingleValue();
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Instruction *Inst = cast<Instruction>(VPV->getUnderlyingValue());
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if (DeadInstructions.count(Inst)) {
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VPValue DummyValue;
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VPV->replaceAllUsesWith(&DummyValue);
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Ingredient.eraseFromParent();
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continue;
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}
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VPRecipeBase *NewRecipe = nullptr;
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if (auto *VPPhi = dyn_cast<VPWidenPHIRecipe>(&Ingredient)) {
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auto *Phi = cast<PHINode>(VPPhi->getUnderlyingValue());
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if (const auto *II = GetIntOrFpInductionDescriptor(Phi)) {
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VPValue *Start = Plan->getOrAddVPValue(II->getStartValue());
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VPValue *Step =
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vputils::getOrCreateVPValueForSCEVExpr(*Plan, II->getStep(), SE);
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NewRecipe = new VPWidenIntOrFpInductionRecipe(Phi, Start, Step, *II,
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false, true);
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} else {
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Plan->addVPValue(Phi, VPPhi);
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continue;
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}
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} else {
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assert(isa<VPInstruction>(&Ingredient) &&
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"only VPInstructions expected here");
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assert(!isa<PHINode>(Inst) && "phis should be handled above");
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// Create VPWidenMemoryInstructionRecipe for loads and stores.
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if (LoadInst *Load = dyn_cast<LoadInst>(Inst)) {
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NewRecipe = new VPWidenMemoryInstructionRecipe(
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*Load, Plan->getOrAddVPValue(getLoadStorePointerOperand(Inst)),
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nullptr /*Mask*/, false /*Consecutive*/, false /*Reverse*/);
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} else if (StoreInst *Store = dyn_cast<StoreInst>(Inst)) {
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NewRecipe = new VPWidenMemoryInstructionRecipe(
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*Store, Plan->getOrAddVPValue(getLoadStorePointerOperand(Inst)),
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Plan->getOrAddVPValue(Store->getValueOperand()), nullptr /*Mask*/,
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false /*Consecutive*/, false /*Reverse*/);
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} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Inst)) {
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NewRecipe = new VPWidenGEPRecipe(
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GEP, Plan->mapToVPValues(GEP->operands()), OrigLoop);
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} else if (CallInst *CI = dyn_cast<CallInst>(Inst)) {
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NewRecipe =
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new VPWidenCallRecipe(*CI, Plan->mapToVPValues(CI->args()));
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} else if (SelectInst *SI = dyn_cast<SelectInst>(Inst)) {
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bool InvariantCond =
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SE.isLoopInvariant(SE.getSCEV(SI->getOperand(0)), OrigLoop);
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NewRecipe = new VPWidenSelectRecipe(
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*SI, Plan->mapToVPValues(SI->operands()), InvariantCond);
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} else {
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NewRecipe =
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new VPWidenRecipe(*Inst, Plan->mapToVPValues(Inst->operands()));
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}
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}
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NewRecipe->insertBefore(&Ingredient);
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if (NewRecipe->getNumDefinedValues() == 1)
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VPV->replaceAllUsesWith(NewRecipe->getVPSingleValue());
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else
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assert(NewRecipe->getNumDefinedValues() == 0 &&
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"Only recpies with zero or one defined values expected");
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Ingredient.eraseFromParent();
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Plan->removeVPValueFor(Inst);
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for (auto *Def : NewRecipe->definedValues()) {
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Plan->addVPValue(Inst, Def);
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}
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}
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}
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}
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bool VPlanTransforms::sinkScalarOperands(VPlan &Plan) {
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auto Iter = depth_first(
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VPBlockRecursiveTraversalWrapper<VPBlockBase *>(Plan.getEntry()));
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bool Changed = false;
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// First, collect the operands of all predicated replicate recipes as seeds
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// for sinking.
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SetVector<std::pair<VPBasicBlock *, VPValue *>> WorkList;
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for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(Iter)) {
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for (auto &Recipe : *VPBB) {
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auto *RepR = dyn_cast<VPReplicateRecipe>(&Recipe);
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if (!RepR || !RepR->isPredicated())
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continue;
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for (VPValue *Op : RepR->operands())
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WorkList.insert(std::make_pair(RepR->getParent(), Op));
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}
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}
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// Try to sink each replicate recipe in the worklist.
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while (!WorkList.empty()) {
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VPBasicBlock *SinkTo;
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VPValue *C;
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std::tie(SinkTo, C) = WorkList.pop_back_val();
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auto *SinkCandidate = dyn_cast_or_null<VPReplicateRecipe>(C->Def);
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if (!SinkCandidate || SinkCandidate->isUniform() ||
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SinkCandidate->getParent() == SinkTo ||
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SinkCandidate->mayHaveSideEffects() ||
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SinkCandidate->mayReadOrWriteMemory())
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continue;
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bool NeedsDuplicating = false;
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// All recipe users of the sink candidate must be in the same block SinkTo
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// or all users outside of SinkTo must be uniform-after-vectorization (
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// i.e., only first lane is used) . In the latter case, we need to duplicate
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// SinkCandidate. At the moment, we identify such UAV's by looking for the
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// address operands of widened memory recipes.
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auto CanSinkWithUser = [SinkTo, &NeedsDuplicating,
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SinkCandidate](VPUser *U) {
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auto *UI = dyn_cast<VPRecipeBase>(U);
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if (!UI)
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return false;
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if (UI->getParent() == SinkTo)
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return true;
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auto *WidenI = dyn_cast<VPWidenMemoryInstructionRecipe>(UI);
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if (WidenI && WidenI->getAddr() == SinkCandidate) {
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NeedsDuplicating = true;
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return true;
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}
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return false;
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};
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if (!all_of(SinkCandidate->users(), CanSinkWithUser))
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continue;
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if (NeedsDuplicating) {
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Instruction *I = cast<Instruction>(SinkCandidate->getUnderlyingValue());
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auto *Clone =
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new VPReplicateRecipe(I, SinkCandidate->operands(), true, false);
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// TODO: add ".cloned" suffix to name of Clone's VPValue.
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Clone->insertBefore(SinkCandidate);
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SmallVector<VPUser *, 4> Users(SinkCandidate->users());
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for (auto *U : Users) {
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auto *UI = cast<VPRecipeBase>(U);
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if (UI->getParent() == SinkTo)
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continue;
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for (unsigned Idx = 0; Idx != UI->getNumOperands(); Idx++) {
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if (UI->getOperand(Idx) != SinkCandidate)
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continue;
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UI->setOperand(Idx, Clone);
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}
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}
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}
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SinkCandidate->moveBefore(*SinkTo, SinkTo->getFirstNonPhi());
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for (VPValue *Op : SinkCandidate->operands())
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WorkList.insert(std::make_pair(SinkTo, Op));
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Changed = true;
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}
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return Changed;
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}
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/// If \p R is a region with a VPBranchOnMaskRecipe in the entry block, return
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/// the mask.
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VPValue *getPredicatedMask(VPRegionBlock *R) {
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auto *EntryBB = dyn_cast<VPBasicBlock>(R->getEntry());
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if (!EntryBB || EntryBB->size() != 1 ||
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!isa<VPBranchOnMaskRecipe>(EntryBB->begin()))
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return nullptr;
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return cast<VPBranchOnMaskRecipe>(&*EntryBB->begin())->getOperand(0);
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}
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/// If \p R is a triangle region, return the 'then' block of the triangle.
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static VPBasicBlock *getPredicatedThenBlock(VPRegionBlock *R) {
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auto *EntryBB = cast<VPBasicBlock>(R->getEntry());
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if (EntryBB->getNumSuccessors() != 2)
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return nullptr;
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auto *Succ0 = dyn_cast<VPBasicBlock>(EntryBB->getSuccessors()[0]);
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auto *Succ1 = dyn_cast<VPBasicBlock>(EntryBB->getSuccessors()[1]);
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if (!Succ0 || !Succ1)
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return nullptr;
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if (Succ0->getNumSuccessors() + Succ1->getNumSuccessors() != 1)
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return nullptr;
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if (Succ0->getSingleSuccessor() == Succ1)
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return Succ0;
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if (Succ1->getSingleSuccessor() == Succ0)
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return Succ1;
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return nullptr;
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}
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bool VPlanTransforms::mergeReplicateRegions(VPlan &Plan) {
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SetVector<VPRegionBlock *> DeletedRegions;
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bool Changed = false;
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// Collect region blocks to process up-front, to avoid iterator invalidation
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// issues while merging regions.
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SmallVector<VPRegionBlock *, 8> CandidateRegions(
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VPBlockUtils::blocksOnly<VPRegionBlock>(depth_first(
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VPBlockRecursiveTraversalWrapper<VPBlockBase *>(Plan.getEntry()))));
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// Check if Base is a predicated triangle, followed by an empty block,
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// followed by another predicate triangle. If that's the case, move the
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// recipes from the first to the second triangle.
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for (VPRegionBlock *Region1 : CandidateRegions) {
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if (DeletedRegions.contains(Region1))
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continue;
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auto *MiddleBasicBlock =
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dyn_cast_or_null<VPBasicBlock>(Region1->getSingleSuccessor());
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if (!MiddleBasicBlock || !MiddleBasicBlock->empty())
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continue;
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auto *Region2 =
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dyn_cast_or_null<VPRegionBlock>(MiddleBasicBlock->getSingleSuccessor());
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if (!Region2)
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continue;
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VPValue *Mask1 = getPredicatedMask(Region1);
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VPValue *Mask2 = getPredicatedMask(Region2);
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if (!Mask1 || Mask1 != Mask2)
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continue;
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VPBasicBlock *Then1 = getPredicatedThenBlock(Region1);
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VPBasicBlock *Then2 = getPredicatedThenBlock(Region2);
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if (!Then1 || !Then2)
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continue;
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assert(Mask1 && Mask2 && "both region must have conditions");
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// Note: No fusion-preventing memory dependencies are expected in either
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// region. Such dependencies should be rejected during earlier dependence
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// checks, which guarantee accesses can be re-ordered for vectorization.
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//
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// Move recipes to the successor region.
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for (VPRecipeBase &ToMove : make_early_inc_range(reverse(*Then1)))
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ToMove.moveBefore(*Then2, Then2->getFirstNonPhi());
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auto *Merge1 = cast<VPBasicBlock>(Then1->getSingleSuccessor());
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auto *Merge2 = cast<VPBasicBlock>(Then2->getSingleSuccessor());
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// Move VPPredInstPHIRecipes from the merge block to the successor region's
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// merge block. Update all users inside the successor region to use the
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// original values.
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for (VPRecipeBase &Phi1ToMove : make_early_inc_range(reverse(*Merge1))) {
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VPValue *PredInst1 =
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cast<VPPredInstPHIRecipe>(&Phi1ToMove)->getOperand(0);
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VPValue *Phi1ToMoveV = Phi1ToMove.getVPSingleValue();
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SmallVector<VPUser *> Users(Phi1ToMoveV->users());
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for (VPUser *U : Users) {
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auto *UI = dyn_cast<VPRecipeBase>(U);
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if (!UI || UI->getParent() != Then2)
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continue;
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for (unsigned I = 0, E = U->getNumOperands(); I != E; ++I) {
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if (Phi1ToMoveV != U->getOperand(I))
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continue;
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U->setOperand(I, PredInst1);
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}
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}
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Phi1ToMove.moveBefore(*Merge2, Merge2->begin());
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}
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// Finally, remove the first region.
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for (VPBlockBase *Pred : make_early_inc_range(Region1->getPredecessors())) {
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VPBlockUtils::disconnectBlocks(Pred, Region1);
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VPBlockUtils::connectBlocks(Pred, MiddleBasicBlock);
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}
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VPBlockUtils::disconnectBlocks(Region1, MiddleBasicBlock);
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DeletedRegions.insert(Region1);
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}
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for (VPRegionBlock *ToDelete : DeletedRegions)
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delete ToDelete;
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return Changed;
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}
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void VPlanTransforms::removeRedundantInductionCasts(VPlan &Plan) {
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for (auto &Phi : Plan.getVectorLoopRegion()->getEntryBasicBlock()->phis()) {
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auto *IV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi);
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if (!IV || IV->getTruncInst())
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continue;
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// A sequence of IR Casts has potentially been recorded for IV, which
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// *must be bypassed* when the IV is vectorized, because the vectorized IV
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// will produce the desired casted value. This sequence forms a def-use
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// chain and is provided in reverse order, ending with the cast that uses
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// the IV phi. Search for the recipe of the last cast in the chain and
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// replace it with the original IV. Note that only the final cast is
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// expected to have users outside the cast-chain and the dead casts left
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// over will be cleaned up later.
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auto &Casts = IV->getInductionDescriptor().getCastInsts();
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VPValue *FindMyCast = IV;
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for (Instruction *IRCast : reverse(Casts)) {
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VPRecipeBase *FoundUserCast = nullptr;
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for (auto *U : FindMyCast->users()) {
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auto *UserCast = cast<VPRecipeBase>(U);
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if (UserCast->getNumDefinedValues() == 1 &&
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UserCast->getVPSingleValue()->getUnderlyingValue() == IRCast) {
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FoundUserCast = UserCast;
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break;
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}
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}
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FindMyCast = FoundUserCast->getVPSingleValue();
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}
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FindMyCast->replaceAllUsesWith(IV);
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}
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}
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void VPlanTransforms::removeRedundantCanonicalIVs(VPlan &Plan) {
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VPCanonicalIVPHIRecipe *CanonicalIV = Plan.getCanonicalIV();
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VPWidenCanonicalIVRecipe *WidenNewIV = nullptr;
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for (VPUser *U : CanonicalIV->users()) {
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WidenNewIV = dyn_cast<VPWidenCanonicalIVRecipe>(U);
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if (WidenNewIV)
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break;
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}
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if (!WidenNewIV)
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return;
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VPBasicBlock *HeaderVPBB = Plan.getVectorLoopRegion()->getEntryBasicBlock();
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for (VPRecipeBase &Phi : HeaderVPBB->phis()) {
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auto *WidenOriginalIV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi);
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if (!WidenOriginalIV || !WidenOriginalIV->isCanonical() ||
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WidenOriginalIV->getScalarType() != WidenNewIV->getScalarType())
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continue;
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// Replace WidenNewIV with WidenOriginalIV if WidenOriginalIV provides
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// everything WidenNewIV's users need. That is, WidenOriginalIV will
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// generate a vector phi or all users of WidenNewIV demand the first lane
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// only.
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if (WidenOriginalIV->needsVectorIV() ||
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vputils::onlyFirstLaneUsed(WidenNewIV)) {
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WidenNewIV->replaceAllUsesWith(WidenOriginalIV);
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WidenNewIV->eraseFromParent();
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return;
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}
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}
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}
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// Check for live-out users currently not modeled in VPlan.
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// Note that exit values of inductions are generated independent of
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// the recipe. This means VPWidenIntOrFpInductionRecipe &
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// VPScalarIVStepsRecipe can be removed, independent of uses outside
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// the loop.
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// TODO: Remove once live-outs are modeled in VPlan.
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static bool hasOutsideUser(Instruction &I, Loop &OrigLoop) {
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return any_of(I.users(), [&OrigLoop](User *U) {
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if (!OrigLoop.contains(cast<Instruction>(U)))
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return true;
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// Look through single-value phis in the loop, as they won't be modeled in
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// VPlan and may be used outside the loop.
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if (auto *PN = dyn_cast<PHINode>(U))
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if (PN->getNumIncomingValues() == 1)
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return hasOutsideUser(*PN, OrigLoop);
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return false;
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});
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}
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void VPlanTransforms::removeDeadRecipes(VPlan &Plan, Loop &OrigLoop) {
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VPBasicBlock *Header = Plan.getVectorLoopRegion()->getEntryBasicBlock();
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// Check if \p R is used outside the loop, if required.
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// TODO: Remove once live-outs are modeled in VPlan.
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auto HasUsersOutsideLoop = [&OrigLoop](VPRecipeBase &R) {
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// Exit values for induction recipes are generated independent of the
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// recipes, expect for truncated inductions. Hence there is no need to check
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// for users outside the loop for them.
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if (isa<VPScalarIVStepsRecipe>(&R) ||
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(isa<VPWidenIntOrFpInductionRecipe>(&R) &&
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!isa<TruncInst>(R.getUnderlyingInstr())))
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return false;
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return R.getUnderlyingInstr() &&
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hasOutsideUser(*R.getUnderlyingInstr(), OrigLoop);
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};
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// Remove dead recipes in header block. The recipes in the block are processed
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// in reverse order, to catch chains of dead recipes.
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// TODO: Remove dead recipes across whole plan.
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for (VPRecipeBase &R : make_early_inc_range(reverse(*Header))) {
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if (R.mayHaveSideEffects() ||
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any_of(R.definedValues(),
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[](VPValue *V) { return V->getNumUsers() > 0; }) ||
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HasUsersOutsideLoop(R))
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continue;
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R.eraseFromParent();
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}
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}
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void VPlanTransforms::optimizeInductions(VPlan &Plan, ScalarEvolution &SE) {
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SmallVector<VPRecipeBase *> ToRemove;
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VPBasicBlock *HeaderVPBB = Plan.getVectorLoopRegion()->getEntryBasicBlock();
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for (VPRecipeBase &Phi : HeaderVPBB->phis()) {
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auto *IV = dyn_cast<VPWidenIntOrFpInductionRecipe>(&Phi);
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if (!IV || !IV->needsScalarIV())
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continue;
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const InductionDescriptor &ID = IV->getInductionDescriptor();
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VPValue *Step =
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vputils::getOrCreateVPValueForSCEVExpr(Plan, ID.getStep(), SE);
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Instruction *TruncI = IV->getTruncInst();
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VPScalarIVStepsRecipe *Steps = new VPScalarIVStepsRecipe(
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IV->getPHINode()->getType(), ID, Plan.getCanonicalIV(),
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IV->getStartValue(), Step, TruncI ? TruncI->getType() : nullptr);
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HeaderVPBB->insert(Steps, HeaderVPBB->getFirstNonPhi());
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// If there are no vector users of IV, simply update all users to use Step
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// instead.
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if (!IV->needsVectorIV()) {
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IV->replaceAllUsesWith(Steps);
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continue;
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}
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// Otherwise only update scalar users of IV to use Step instead. Use
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// SetVector to ensure the list of users doesn't contain duplicates.
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SetVector<VPUser *> Users(IV->user_begin(), IV->user_end());
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for (VPUser *U : Users) {
|
|
VPRecipeBase *R = cast<VPRecipeBase>(U);
|
|
if (!R->usesScalars(IV))
|
|
continue;
|
|
for (unsigned I = 0, E = R->getNumOperands(); I != E; I++) {
|
|
if (R->getOperand(I) != IV)
|
|
continue;
|
|
R->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();
|
|
}
|
|
}
|