| //===- ParallelDSP.cpp - Parallel DSP Pass --------------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| /// \file |
| /// Armv6 introduced instructions to perform 32-bit SIMD operations. The |
| /// purpose of this pass is do some IR pattern matching to create ACLE |
| /// DSP intrinsics, which map on these 32-bit SIMD operations. |
| /// This pass runs only when unaligned accesses is supported/enabled. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/LoopAccessAnalysis.h" |
| #include "llvm/Analysis/LoopPass.h" |
| #include "llvm/Analysis/LoopInfo.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/NoFolder.h" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/LoopUtils.h" |
| #include "llvm/Pass.h" |
| #include "llvm/PassRegistry.h" |
| #include "llvm/PassSupport.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/IR/PatternMatch.h" |
| #include "llvm/CodeGen/TargetPassConfig.h" |
| #include "ARM.h" |
| #include "ARMSubtarget.h" |
| |
| using namespace llvm; |
| using namespace PatternMatch; |
| |
| #define DEBUG_TYPE "arm-parallel-dsp" |
| |
| STATISTIC(NumSMLAD , "Number of smlad instructions generated"); |
| |
| static cl::opt<bool> |
| DisableParallelDSP("disable-arm-parallel-dsp", cl::Hidden, cl::init(false), |
| cl::desc("Disable the ARM Parallel DSP pass")); |
| |
| namespace { |
| struct OpChain; |
| struct BinOpChain; |
| struct Reduction; |
| |
| using OpChainList = SmallVector<std::unique_ptr<OpChain>, 8>; |
| using ReductionList = SmallVector<Reduction, 8>; |
| using ValueList = SmallVector<Value*, 8>; |
| using MemInstList = SmallVector<Instruction*, 8>; |
| using PMACPair = std::pair<BinOpChain*,BinOpChain*>; |
| using PMACPairList = SmallVector<PMACPair, 8>; |
| using Instructions = SmallVector<Instruction*,16>; |
| using MemLocList = SmallVector<MemoryLocation, 4>; |
| |
| struct OpChain { |
| Instruction *Root; |
| ValueList AllValues; |
| MemInstList VecLd; // List of all load instructions. |
| MemLocList MemLocs; // All memory locations read by this tree. |
| bool ReadOnly = true; |
| |
| OpChain(Instruction *I, ValueList &vl) : Root(I), AllValues(vl) { } |
| virtual ~OpChain() = default; |
| |
| void SetMemoryLocations() { |
| const auto Size = MemoryLocation::UnknownSize; |
| for (auto *V : AllValues) { |
| if (auto *I = dyn_cast<Instruction>(V)) { |
| if (I->mayWriteToMemory()) |
| ReadOnly = false; |
| if (auto *Ld = dyn_cast<LoadInst>(V)) |
| MemLocs.push_back(MemoryLocation(Ld->getPointerOperand(), Size)); |
| } |
| } |
| } |
| |
| unsigned size() const { return AllValues.size(); } |
| }; |
| |
| // 'BinOpChain' and 'Reduction' are just some bookkeeping data structures. |
| // 'Reduction' contains the phi-node and accumulator statement from where we |
| // start pattern matching, and 'BinOpChain' the multiplication |
| // instructions that are candidates for parallel execution. |
| struct BinOpChain : public OpChain { |
| ValueList LHS; // List of all (narrow) left hand operands. |
| ValueList RHS; // List of all (narrow) right hand operands. |
| bool Exchange = false; |
| |
| BinOpChain(Instruction *I, ValueList &lhs, ValueList &rhs) : |
| OpChain(I, lhs), LHS(lhs), RHS(rhs) { |
| for (auto *V : RHS) |
| AllValues.push_back(V); |
| } |
| }; |
| |
| struct Reduction { |
| PHINode *Phi; // The Phi-node from where we start |
| // pattern matching. |
| Instruction *AccIntAdd; // The accumulating integer add statement, |
| // i.e, the reduction statement. |
| |
| OpChainList MACCandidates; // The MAC candidates associated with |
| // this reduction statement. |
| Reduction (PHINode *P, Instruction *Acc) : Phi(P), AccIntAdd(Acc) { }; |
| }; |
| |
| class ARMParallelDSP : public LoopPass { |
| ScalarEvolution *SE; |
| AliasAnalysis *AA; |
| TargetLibraryInfo *TLI; |
| DominatorTree *DT; |
| LoopInfo *LI; |
| Loop *L; |
| const DataLayout *DL; |
| Module *M; |
| |
| bool InsertParallelMACs(Reduction &Reduction, PMACPairList &PMACPairs); |
| bool AreSequentialLoads(LoadInst *Ld0, LoadInst *Ld1, MemInstList &VecMem); |
| PMACPairList CreateParallelMACPairs(OpChainList &Candidates); |
| Instruction *CreateSMLADCall(LoadInst *VecLd0, LoadInst *VecLd1, |
| Instruction *Acc, bool Exchange, |
| Instruction *InsertAfter); |
| |
| /// Try to match and generate: SMLAD, SMLADX - Signed Multiply Accumulate |
| /// Dual performs two signed 16x16-bit multiplications. It adds the |
| /// products to a 32-bit accumulate operand. Optionally, the instruction can |
| /// exchange the halfwords of the second operand before performing the |
| /// arithmetic. |
| bool MatchSMLAD(Function &F); |
| |
| public: |
| static char ID; |
| |
| ARMParallelDSP() : LoopPass(ID) { } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| LoopPass::getAnalysisUsage(AU); |
| AU.addRequired<AssumptionCacheTracker>(); |
| AU.addRequired<ScalarEvolutionWrapperPass>(); |
| AU.addRequired<AAResultsWrapperPass>(); |
| AU.addRequired<TargetLibraryInfoWrapperPass>(); |
| AU.addRequired<LoopInfoWrapperPass>(); |
| AU.addRequired<DominatorTreeWrapperPass>(); |
| AU.addRequired<TargetPassConfig>(); |
| AU.addPreserved<LoopInfoWrapperPass>(); |
| AU.setPreservesCFG(); |
| } |
| |
| bool runOnLoop(Loop *TheLoop, LPPassManager &) override { |
| if (DisableParallelDSP) |
| return false; |
| L = TheLoop; |
| SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE(); |
| AA = &getAnalysis<AAResultsWrapperPass>().getAAResults(); |
| TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); |
| DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree(); |
| LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); |
| auto &TPC = getAnalysis<TargetPassConfig>(); |
| |
| BasicBlock *Header = TheLoop->getHeader(); |
| if (!Header) |
| return false; |
| |
| // TODO: We assume the loop header and latch to be the same block. |
| // This is not a fundamental restriction, but lifting this would just |
| // require more work to do the transformation and then patch up the CFG. |
| if (Header != TheLoop->getLoopLatch()) { |
| LLVM_DEBUG(dbgs() << "The loop header is not the loop latch: not " |
| "running pass ARMParallelDSP\n"); |
| return false; |
| } |
| |
| Function &F = *Header->getParent(); |
| M = F.getParent(); |
| DL = &M->getDataLayout(); |
| |
| auto &TM = TPC.getTM<TargetMachine>(); |
| auto *ST = &TM.getSubtarget<ARMSubtarget>(F); |
| |
| if (!ST->allowsUnalignedMem()) { |
| LLVM_DEBUG(dbgs() << "Unaligned memory access not supported: not " |
| "running pass ARMParallelDSP\n"); |
| return false; |
| } |
| |
| if (!ST->hasDSP()) { |
| LLVM_DEBUG(dbgs() << "DSP extension not enabled: not running pass " |
| "ARMParallelDSP\n"); |
| return false; |
| } |
| |
| LoopAccessInfo LAI(L, SE, TLI, AA, DT, LI); |
| bool Changes = false; |
| |
| LLVM_DEBUG(dbgs() << "\n== Parallel DSP pass ==\n"); |
| LLVM_DEBUG(dbgs() << " - " << F.getName() << "\n\n"); |
| Changes = MatchSMLAD(F); |
| return Changes; |
| } |
| }; |
| } |
| |
| // MaxBitwidth: the maximum supported bitwidth of the elements in the DSP |
| // instructions, which is set to 16. So here we should collect all i8 and i16 |
| // narrow operations. |
| // TODO: we currently only collect i16, and will support i8 later, so that's |
| // why we check that types are equal to MaxBitWidth, and not <= MaxBitWidth. |
| template<unsigned MaxBitWidth> |
| static bool IsNarrowSequence(Value *V, ValueList &VL) { |
| LLVM_DEBUG(dbgs() << "Is narrow sequence? "; V->dump()); |
| ConstantInt *CInt; |
| |
| if (match(V, m_ConstantInt(CInt))) { |
| // TODO: if a constant is used, it needs to fit within the bit width. |
| return false; |
| } |
| |
| auto *I = dyn_cast<Instruction>(V); |
| if (!I) |
| return false; |
| |
| Value *Val, *LHS, *RHS; |
| if (match(V, m_Trunc(m_Value(Val)))) { |
| if (cast<TruncInst>(I)->getDestTy()->getIntegerBitWidth() == MaxBitWidth) |
| return IsNarrowSequence<MaxBitWidth>(Val, VL); |
| } else if (match(V, m_Add(m_Value(LHS), m_Value(RHS)))) { |
| // TODO: we need to implement sadd16/sadd8 for this, which enables to |
| // also do the rewrite for smlad8.ll, but it is unsupported for now. |
| LLVM_DEBUG(dbgs() << "No, unsupported Op:\t"; I->dump()); |
| return false; |
| } else if (match(V, m_ZExtOrSExt(m_Value(Val)))) { |
| if (cast<CastInst>(I)->getSrcTy()->getIntegerBitWidth() != MaxBitWidth) { |
| LLVM_DEBUG(dbgs() << "No, wrong SrcTy size: " << |
| cast<CastInst>(I)->getSrcTy()->getIntegerBitWidth() << "\n"); |
| return false; |
| } |
| |
| if (match(Val, m_Load(m_Value()))) { |
| LLVM_DEBUG(dbgs() << "Yes, found narrow Load:\t"; Val->dump()); |
| VL.push_back(Val); |
| VL.push_back(I); |
| return true; |
| } |
| } |
| LLVM_DEBUG(dbgs() << "No, unsupported Op:\t"; I->dump()); |
| return false; |
| } |
| |
| // Element-by-element comparison of Value lists returning true if they are |
| // instructions with the same opcode or constants with the same value. |
| static bool AreSymmetrical(const ValueList &VL0, |
| const ValueList &VL1) { |
| if (VL0.size() != VL1.size()) { |
| LLVM_DEBUG(dbgs() << "Muls are mismatching operand list lengths: " |
| << VL0.size() << " != " << VL1.size() << "\n"); |
| return false; |
| } |
| |
| const unsigned Pairs = VL0.size(); |
| LLVM_DEBUG(dbgs() << "Number of operand pairs: " << Pairs << "\n"); |
| |
| for (unsigned i = 0; i < Pairs; ++i) { |
| const Value *V0 = VL0[i]; |
| const Value *V1 = VL1[i]; |
| const auto *Inst0 = dyn_cast<Instruction>(V0); |
| const auto *Inst1 = dyn_cast<Instruction>(V1); |
| |
| LLVM_DEBUG(dbgs() << "Pair " << i << ":\n"; |
| dbgs() << "mul1: "; V0->dump(); |
| dbgs() << "mul2: "; V1->dump()); |
| |
| if (!Inst0 || !Inst1) |
| return false; |
| |
| if (Inst0->isSameOperationAs(Inst1)) { |
| LLVM_DEBUG(dbgs() << "OK: same operation found!\n"); |
| continue; |
| } |
| |
| const APInt *C0, *C1; |
| if (!(match(V0, m_APInt(C0)) && match(V1, m_APInt(C1)) && C0 == C1)) |
| return false; |
| } |
| |
| LLVM_DEBUG(dbgs() << "OK: found symmetrical operand lists.\n"); |
| return true; |
| } |
| |
| template<typename MemInst> |
| static bool AreSequentialAccesses(MemInst *MemOp0, MemInst *MemOp1, |
| MemInstList &VecMem, const DataLayout &DL, |
| ScalarEvolution &SE) { |
| if (!MemOp0->isSimple() || !MemOp1->isSimple()) { |
| LLVM_DEBUG(dbgs() << "No, not touching volatile access\n"); |
| return false; |
| } |
| if (isConsecutiveAccess(MemOp0, MemOp1, DL, SE)) { |
| VecMem.clear(); |
| VecMem.push_back(MemOp0); |
| VecMem.push_back(MemOp1); |
| LLVM_DEBUG(dbgs() << "OK: accesses are consecutive.\n"); |
| return true; |
| } |
| LLVM_DEBUG(dbgs() << "No, accesses aren't consecutive.\n"); |
| return false; |
| } |
| |
| bool ARMParallelDSP::AreSequentialLoads(LoadInst *Ld0, LoadInst *Ld1, |
| MemInstList &VecMem) { |
| if (!Ld0 || !Ld1) |
| return false; |
| |
| LLVM_DEBUG(dbgs() << "Are consecutive loads:\n"; |
| dbgs() << "Ld0:"; Ld0->dump(); |
| dbgs() << "Ld1:"; Ld1->dump(); |
| ); |
| |
| if (!Ld0->hasOneUse() || !Ld1->hasOneUse()) { |
| LLVM_DEBUG(dbgs() << "No, load has more than one use.\n"); |
| return false; |
| } |
| |
| return AreSequentialAccesses<LoadInst>(Ld0, Ld1, VecMem, *DL, *SE); |
| } |
| |
| PMACPairList |
| ARMParallelDSP::CreateParallelMACPairs(OpChainList &Candidates) { |
| const unsigned Elems = Candidates.size(); |
| PMACPairList PMACPairs; |
| |
| if (Elems < 2) |
| return PMACPairs; |
| |
| SmallPtrSet<const Instruction*, 4> Paired; |
| for (unsigned i = 0; i < Elems; ++i) { |
| BinOpChain *PMul0 = static_cast<BinOpChain*>(Candidates[i].get()); |
| if (Paired.count(PMul0->Root)) |
| continue; |
| |
| for (unsigned j = 0; j < Elems; ++j) { |
| if (i == j) |
| continue; |
| |
| BinOpChain *PMul1 = static_cast<BinOpChain*>(Candidates[j].get()); |
| if (Paired.count(PMul1->Root)) |
| continue; |
| |
| const Instruction *Mul0 = PMul0->Root; |
| const Instruction *Mul1 = PMul1->Root; |
| if (Mul0 == Mul1) |
| continue; |
| |
| assert(PMul0 != PMul1 && "expected different chains"); |
| |
| LLVM_DEBUG(dbgs() << "\nCheck parallel muls:\n"; |
| dbgs() << "- "; Mul0->dump(); |
| dbgs() << "- "; Mul1->dump()); |
| |
| const ValueList &Mul0_LHS = PMul0->LHS; |
| const ValueList &Mul0_RHS = PMul0->RHS; |
| const ValueList &Mul1_LHS = PMul1->LHS; |
| const ValueList &Mul1_RHS = PMul1->RHS; |
| |
| if (!AreSymmetrical(Mul0_LHS, Mul1_LHS) || |
| !AreSymmetrical(Mul0_RHS, Mul1_RHS)) |
| continue; |
| |
| LLVM_DEBUG(dbgs() << "OK: mul operands list match:\n"); |
| // The first elements of each vector should be loads with sexts. If we |
| // find that its two pairs of consecutive loads, then these can be |
| // transformed into two wider loads and the users can be replaced with |
| // DSP intrinsics. |
| bool Found = false; |
| for (unsigned x = 0; x < Mul0_LHS.size(); x += 2) { |
| auto *Ld0 = dyn_cast<LoadInst>(Mul0_LHS[x]); |
| auto *Ld1 = dyn_cast<LoadInst>(Mul1_LHS[x]); |
| auto *Ld2 = dyn_cast<LoadInst>(Mul0_RHS[x]); |
| auto *Ld3 = dyn_cast<LoadInst>(Mul1_RHS[x]); |
| |
| if (!Ld0 || !Ld1 || !Ld2 || !Ld3) |
| continue; |
| |
| LLVM_DEBUG(dbgs() << "Looking at operands " << x << ":\n" |
| << "\t Ld0: " << *Ld0 << "\n" |
| << "\t Ld1: " << *Ld1 << "\n" |
| << "and operands " << x + 2 << ":\n" |
| << "\t Ld2: " << *Ld2 << "\n" |
| << "\t Ld3: " << *Ld3 << "\n"); |
| |
| if (AreSequentialLoads(Ld0, Ld1, PMul0->VecLd)) { |
| if (AreSequentialLoads(Ld2, Ld3, PMul1->VecLd)) { |
| LLVM_DEBUG(dbgs() << "OK: found two pairs of parallel loads!\n"); |
| PMACPairs.push_back(std::make_pair(PMul0, PMul1)); |
| Found = true; |
| } else if (AreSequentialLoads(Ld3, Ld2, PMul1->VecLd)) { |
| LLVM_DEBUG(dbgs() << "OK: found two pairs of parallel loads!\n"); |
| LLVM_DEBUG(dbgs() << " exchanging Ld2 and Ld3\n"); |
| PMul1->Exchange = true; |
| PMACPairs.push_back(std::make_pair(PMul0, PMul1)); |
| Found = true; |
| } |
| } else if (AreSequentialLoads(Ld1, Ld0, PMul0->VecLd)) { |
| if (AreSequentialLoads(Ld2, Ld3, PMul1->VecLd)) { |
| LLVM_DEBUG(dbgs() << "OK: found two pairs of parallel loads!\n"); |
| LLVM_DEBUG(dbgs() << " exchanging Ld0 and Ld1\n"); |
| LLVM_DEBUG(dbgs() << " and swapping muls\n"); |
| PMul0->Exchange = true; |
| // Only the second operand can be exchanged, so swap the muls. |
| PMACPairs.push_back(std::make_pair(PMul1, PMul0)); |
| Found = true; |
| } |
| } |
| } |
| if (Found) { |
| Paired.insert(Mul0); |
| Paired.insert(Mul1); |
| break; |
| } |
| } |
| } |
| return PMACPairs; |
| } |
| |
| bool ARMParallelDSP::InsertParallelMACs(Reduction &Reduction, |
| PMACPairList &PMACPairs) { |
| Instruction *Acc = Reduction.Phi; |
| Instruction *InsertAfter = Reduction.AccIntAdd; |
| |
| for (auto &Pair : PMACPairs) { |
| BinOpChain *PMul0 = Pair.first; |
| BinOpChain *PMul1 = Pair.second; |
| LLVM_DEBUG(dbgs() << "Found parallel MACs!!\n"; |
| dbgs() << "- "; PMul0->Root->dump(); |
| dbgs() << "- "; PMul1->Root->dump()); |
| |
| auto *VecLd0 = cast<LoadInst>(PMul0->VecLd[0]); |
| auto *VecLd1 = cast<LoadInst>(PMul1->VecLd[0]); |
| Acc = CreateSMLADCall(VecLd0, VecLd1, Acc, PMul1->Exchange, InsertAfter); |
| InsertAfter = Acc; |
| } |
| |
| if (Acc != Reduction.Phi) { |
| LLVM_DEBUG(dbgs() << "Replace Accumulate: "; Acc->dump()); |
| Reduction.AccIntAdd->replaceAllUsesWith(Acc); |
| return true; |
| } |
| return false; |
| } |
| |
| static void MatchReductions(Function &F, Loop *TheLoop, BasicBlock *Header, |
| ReductionList &Reductions) { |
| RecurrenceDescriptor RecDesc; |
| const bool HasFnNoNaNAttr = |
| F.getFnAttribute("no-nans-fp-math").getValueAsString() == "true"; |
| const BasicBlock *Latch = TheLoop->getLoopLatch(); |
| |
| // We need a preheader as getIncomingValueForBlock assumes there is one. |
| if (!TheLoop->getLoopPreheader()) { |
| LLVM_DEBUG(dbgs() << "No preheader found, bailing out\n"); |
| return; |
| } |
| |
| for (PHINode &Phi : Header->phis()) { |
| const auto *Ty = Phi.getType(); |
| if (!Ty->isIntegerTy(32) && !Ty->isIntegerTy(64)) |
| continue; |
| |
| const bool IsReduction = |
| RecurrenceDescriptor::AddReductionVar(&Phi, |
| RecurrenceDescriptor::RK_IntegerAdd, |
| TheLoop, HasFnNoNaNAttr, RecDesc); |
| if (!IsReduction) |
| continue; |
| |
| Instruction *Acc = dyn_cast<Instruction>(Phi.getIncomingValueForBlock(Latch)); |
| if (!Acc) |
| continue; |
| |
| Reductions.push_back(Reduction(&Phi, Acc)); |
| } |
| |
| LLVM_DEBUG( |
| dbgs() << "\nAccumulating integer additions (reductions) found:\n"; |
| for (auto &R : Reductions) { |
| dbgs() << "- "; R.Phi->dump(); |
| dbgs() << "-> "; R.AccIntAdd->dump(); |
| } |
| ); |
| } |
| |
| static void AddMACCandidate(OpChainList &Candidates, |
| Instruction *Mul, |
| Value *MulOp0, Value *MulOp1) { |
| LLVM_DEBUG(dbgs() << "OK, found acc mul:\t"; Mul->dump()); |
| assert(Mul->getOpcode() == Instruction::Mul && |
| "expected mul instruction"); |
| ValueList LHS; |
| ValueList RHS; |
| if (IsNarrowSequence<16>(MulOp0, LHS) && |
| IsNarrowSequence<16>(MulOp1, RHS)) { |
| LLVM_DEBUG(dbgs() << "OK, found narrow mul: "; Mul->dump()); |
| Candidates.push_back(make_unique<BinOpChain>(Mul, LHS, RHS)); |
| } |
| } |
| |
| static void MatchParallelMACSequences(Reduction &R, |
| OpChainList &Candidates) { |
| Instruction *Acc = R.AccIntAdd; |
| LLVM_DEBUG(dbgs() << "\n- Analysing:\t" << *Acc); |
| |
| // Returns false to signal the search should be stopped. |
| std::function<bool(Value*)> Match = |
| [&Candidates, &Match](Value *V) -> bool { |
| |
| auto *I = dyn_cast<Instruction>(V); |
| if (!I) |
| return false; |
| |
| Value *MulOp0, *MulOp1; |
| |
| switch (I->getOpcode()) { |
| case Instruction::Add: |
| if (Match(I->getOperand(0)) || (Match(I->getOperand(1)))) |
| return true; |
| break; |
| case Instruction::Mul: |
| if (match (I, (m_Mul(m_Value(MulOp0), m_Value(MulOp1))))) { |
| AddMACCandidate(Candidates, I, MulOp0, MulOp1); |
| return false; |
| } |
| break; |
| case Instruction::SExt: |
| if (match (I, (m_SExt(m_Mul(m_Value(MulOp0), m_Value(MulOp1)))))) { |
| Instruction *Mul = cast<Instruction>(I->getOperand(0)); |
| AddMACCandidate(Candidates, Mul, MulOp0, MulOp1); |
| return false; |
| } |
| break; |
| } |
| return false; |
| }; |
| |
| while (Match (Acc)); |
| LLVM_DEBUG(dbgs() << "Finished matching MAC sequences, found " |
| << Candidates.size() << " candidates.\n"); |
| } |
| |
| // Collects all instructions that are not part of the MAC chains, which is the |
| // set of instructions that can potentially alias with the MAC operands. |
| static void AliasCandidates(BasicBlock *Header, Instructions &Reads, |
| Instructions &Writes) { |
| for (auto &I : *Header) { |
| if (I.mayReadFromMemory()) |
| Reads.push_back(&I); |
| if (I.mayWriteToMemory()) |
| Writes.push_back(&I); |
| } |
| } |
| |
| // Check whether statements in the basic block that write to memory alias with |
| // the memory locations accessed by the MAC-chains. |
| // TODO: we need the read statements when we accept more complicated chains. |
| static bool AreAliased(AliasAnalysis *AA, Instructions &Reads, |
| Instructions &Writes, OpChainList &MACCandidates) { |
| LLVM_DEBUG(dbgs() << "Alias checks:\n"); |
| for (auto &MAC : MACCandidates) { |
| LLVM_DEBUG(dbgs() << "mul: "; MAC->Root->dump()); |
| |
| // At the moment, we allow only simple chains that only consist of reads, |
| // accumulate their result with an integer add, and thus that don't write |
| // memory, and simply bail if they do. |
| if (!MAC->ReadOnly) |
| return true; |
| |
| // Now for all writes in the basic block, check that they don't alias with |
| // the memory locations accessed by our MAC-chain: |
| for (auto *I : Writes) { |
| LLVM_DEBUG(dbgs() << "- "; I->dump()); |
| assert(MAC->MemLocs.size() >= 2 && "expecting at least 2 memlocs"); |
| for (auto &MemLoc : MAC->MemLocs) { |
| if (isModOrRefSet(intersectModRef(AA->getModRefInfo(I, MemLoc), |
| ModRefInfo::ModRef))) { |
| LLVM_DEBUG(dbgs() << "Yes, aliases found\n"); |
| return true; |
| } |
| } |
| } |
| } |
| |
| LLVM_DEBUG(dbgs() << "OK: no aliases found!\n"); |
| return false; |
| } |
| |
| static bool CheckMACMemory(OpChainList &Candidates) { |
| for (auto &C : Candidates) { |
| // A mul has 2 operands, and a narrow op consist of sext and a load; thus |
| // we expect at least 4 items in this operand value list. |
| if (C->size() < 4) { |
| LLVM_DEBUG(dbgs() << "Operand list too short.\n"); |
| return false; |
| } |
| C->SetMemoryLocations(); |
| ValueList &LHS = static_cast<BinOpChain*>(C.get())->LHS; |
| ValueList &RHS = static_cast<BinOpChain*>(C.get())->RHS; |
| |
| // Use +=2 to skip over the expected extend instructions. |
| for (unsigned i = 0, e = LHS.size(); i < e; i += 2) { |
| if (!isa<LoadInst>(LHS[i]) || !isa<LoadInst>(RHS[i])) |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| // Loop Pass that needs to identify integer add/sub reductions of 16-bit vector |
| // multiplications. |
| // To use SMLAD: |
| // 1) we first need to find integer add reduction PHIs, |
| // 2) then from the PHI, look for this pattern: |
| // |
| // acc0 = phi i32 [0, %entry], [%acc1, %loop.body] |
| // ld0 = load i16 |
| // sext0 = sext i16 %ld0 to i32 |
| // ld1 = load i16 |
| // sext1 = sext i16 %ld1 to i32 |
| // mul0 = mul %sext0, %sext1 |
| // ld2 = load i16 |
| // sext2 = sext i16 %ld2 to i32 |
| // ld3 = load i16 |
| // sext3 = sext i16 %ld3 to i32 |
| // mul1 = mul i32 %sext2, %sext3 |
| // add0 = add i32 %mul0, %acc0 |
| // acc1 = add i32 %add0, %mul1 |
| // |
| // Which can be selected to: |
| // |
| // ldr.h r0 |
| // ldr.h r1 |
| // smlad r2, r0, r1, r2 |
| // |
| // If constants are used instead of loads, these will need to be hoisted |
| // out and into a register. |
| // |
| // If loop invariants are used instead of loads, these need to be packed |
| // before the loop begins. |
| // |
| bool ARMParallelDSP::MatchSMLAD(Function &F) { |
| BasicBlock *Header = L->getHeader(); |
| LLVM_DEBUG(dbgs() << "= Matching SMLAD =\n"; |
| dbgs() << "Header block:\n"; Header->dump(); |
| dbgs() << "Loop info:\n\n"; L->dump()); |
| |
| bool Changed = false; |
| ReductionList Reductions; |
| MatchReductions(F, L, Header, Reductions); |
| |
| for (auto &R : Reductions) { |
| OpChainList MACCandidates; |
| MatchParallelMACSequences(R, MACCandidates); |
| if (!CheckMACMemory(MACCandidates)) |
| continue; |
| |
| R.MACCandidates = std::move(MACCandidates); |
| |
| LLVM_DEBUG(dbgs() << "MAC candidates:\n"; |
| for (auto &M : R.MACCandidates) |
| M->Root->dump(); |
| dbgs() << "\n";); |
| } |
| |
| // Collect all instructions that may read or write memory. Our alias |
| // analysis checks bail out if any of these instructions aliases with an |
| // instruction from the MAC-chain. |
| Instructions Reads, Writes; |
| AliasCandidates(Header, Reads, Writes); |
| |
| for (auto &R : Reductions) { |
| if (AreAliased(AA, Reads, Writes, R.MACCandidates)) |
| return false; |
| PMACPairList PMACPairs = CreateParallelMACPairs(R.MACCandidates); |
| Changed |= InsertParallelMACs(R, PMACPairs); |
| } |
| |
| LLVM_DEBUG(if (Changed) dbgs() << "Header block:\n"; Header->dump();); |
| return Changed; |
| } |
| |
| static LoadInst *CreateLoadIns(IRBuilder<NoFolder> &IRB, LoadInst &BaseLoad, |
| const Type *LoadTy) { |
| const unsigned AddrSpace = BaseLoad.getPointerAddressSpace(); |
| |
| Value *VecPtr = IRB.CreateBitCast(BaseLoad.getPointerOperand(), |
| LoadTy->getPointerTo(AddrSpace)); |
| return IRB.CreateAlignedLoad(VecPtr, BaseLoad.getAlignment()); |
| } |
| |
| Instruction *ARMParallelDSP::CreateSMLADCall(LoadInst *VecLd0, LoadInst *VecLd1, |
| Instruction *Acc, bool Exchange, |
| Instruction *InsertAfter) { |
| LLVM_DEBUG(dbgs() << "Create SMLAD intrinsic using:\n" |
| << "- " << *VecLd0 << "\n" |
| << "- " << *VecLd1 << "\n" |
| << "- " << *Acc << "\n" |
| << "Exchange: " << Exchange << "\n"); |
| |
| IRBuilder<NoFolder> Builder(InsertAfter->getParent(), |
| ++BasicBlock::iterator(InsertAfter)); |
| |
| // Replace the reduction chain with an intrinsic call |
| const Type *Ty = IntegerType::get(M->getContext(), 32); |
| LoadInst *NewLd0 = CreateLoadIns(Builder, VecLd0[0], Ty); |
| LoadInst *NewLd1 = CreateLoadIns(Builder, VecLd1[0], Ty); |
| Value* Args[] = { NewLd0, NewLd1, Acc }; |
| Function *SMLAD = nullptr; |
| if (Exchange) |
| SMLAD = Acc->getType()->isIntegerTy(32) ? |
| Intrinsic::getDeclaration(M, Intrinsic::arm_smladx) : |
| Intrinsic::getDeclaration(M, Intrinsic::arm_smlaldx); |
| else |
| SMLAD = Acc->getType()->isIntegerTy(32) ? |
| Intrinsic::getDeclaration(M, Intrinsic::arm_smlad) : |
| Intrinsic::getDeclaration(M, Intrinsic::arm_smlald); |
| CallInst *Call = Builder.CreateCall(SMLAD, Args); |
| NumSMLAD++; |
| return Call; |
| } |
| |
| Pass *llvm::createARMParallelDSPPass() { |
| return new ARMParallelDSP(); |
| } |
| |
| char ARMParallelDSP::ID = 0; |
| |
| INITIALIZE_PASS_BEGIN(ARMParallelDSP, "arm-parallel-dsp", |
| "Transform loops to use DSP intrinsics", false, false) |
| INITIALIZE_PASS_END(ARMParallelDSP, "arm-parallel-dsp", |
| "Transform loops to use DSP intrinsics", false, false) |