| //===---------- AArch64CollectLOH.cpp - AArch64 collect LOH pass --*- C++ -*-=// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains a pass that collect the Linker Optimization Hint (LOH). |
| // This pass should be run at the very end of the compilation flow, just before |
| // assembly printer. |
| // To be useful for the linker, the LOH must be printed into the assembly file. |
| // |
| // A LOH describes a sequence of instructions that may be optimized by the |
| // linker. |
| // This same sequence cannot be optimized by the compiler because some of |
| // the information will be known at link time. |
| // For instance, consider the following sequence: |
| // L1: adrp xA, sym@PAGE |
| // L2: add xB, xA, sym@PAGEOFF |
| // L3: ldr xC, [xB, #imm] |
| // This sequence can be turned into: |
| // A literal load if sym@PAGE + sym@PAGEOFF + #imm - address(L3) is < 1MB: |
| // L3: ldr xC, sym+#imm |
| // It may also be turned into either the following more efficient |
| // code sequences: |
| // - If sym@PAGEOFF + #imm fits the encoding space of L3. |
| // L1: adrp xA, sym@PAGE |
| // L3: ldr xC, [xB, sym@PAGEOFF + #imm] |
| // - If sym@PAGE + sym@PAGEOFF - address(L1) < 1MB: |
| // L1: adr xA, sym |
| // L3: ldr xC, [xB, #imm] |
| // |
| // To be valid a LOH must meet all the requirements needed by all the related |
| // possible linker transformations. |
| // For instance, using the running example, the constraints to emit |
| // ".loh AdrpAddLdr" are: |
| // - L1, L2, and L3 instructions are of the expected type, i.e., |
| // respectively ADRP, ADD (immediate), and LD. |
| // - The result of L1 is used only by L2. |
| // - The register argument (xA) used in the ADD instruction is defined |
| // only by L1. |
| // - The result of L2 is used only by L3. |
| // - The base address (xB) in L3 is defined only L2. |
| // - The ADRP in L1 and the ADD in L2 must reference the same symbol using |
| // @PAGE/@PAGEOFF with no additional constants |
| // |
| // Currently supported LOHs are: |
| // * So called non-ADRP-related: |
| // - .loh AdrpAddLdr L1, L2, L3: |
| // L1: adrp xA, sym@PAGE |
| // L2: add xB, xA, sym@PAGEOFF |
| // L3: ldr xC, [xB, #imm] |
| // - .loh AdrpLdrGotLdr L1, L2, L3: |
| // L1: adrp xA, sym@GOTPAGE |
| // L2: ldr xB, [xA, sym@GOTPAGEOFF] |
| // L3: ldr xC, [xB, #imm] |
| // - .loh AdrpLdr L1, L3: |
| // L1: adrp xA, sym@PAGE |
| // L3: ldr xC, [xA, sym@PAGEOFF] |
| // - .loh AdrpAddStr L1, L2, L3: |
| // L1: adrp xA, sym@PAGE |
| // L2: add xB, xA, sym@PAGEOFF |
| // L3: str xC, [xB, #imm] |
| // - .loh AdrpLdrGotStr L1, L2, L3: |
| // L1: adrp xA, sym@GOTPAGE |
| // L2: ldr xB, [xA, sym@GOTPAGEOFF] |
| // L3: str xC, [xB, #imm] |
| // - .loh AdrpAdd L1, L2: |
| // L1: adrp xA, sym@PAGE |
| // L2: add xB, xA, sym@PAGEOFF |
| // For all these LOHs, L1, L2, L3 form a simple chain: |
| // L1 result is used only by L2 and L2 result by L3. |
| // L3 LOH-related argument is defined only by L2 and L2 LOH-related argument |
| // by L1. |
| // All these LOHs aim at using more efficient load/store patterns by folding |
| // some instructions used to compute the address directly into the load/store. |
| // |
| // * So called ADRP-related: |
| // - .loh AdrpAdrp L2, L1: |
| // L2: ADRP xA, sym1@PAGE |
| // L1: ADRP xA, sym2@PAGE |
| // L2 dominates L1 and xA is not redifined between L2 and L1 |
| // This LOH aims at getting rid of redundant ADRP instructions. |
| // |
| // The overall design for emitting the LOHs is: |
| // 1. AArch64CollectLOH (this pass) records the LOHs in the AArch64FunctionInfo. |
| // 2. AArch64AsmPrinter reads the LOHs from AArch64FunctionInfo and it: |
| // 1. Associates them a label. |
| // 2. Emits them in a MCStreamer (EmitLOHDirective). |
| // - The MCMachOStreamer records them into the MCAssembler. |
| // - The MCAsmStreamer prints them. |
| // - Other MCStreamers ignore them. |
| // 3. Closes the MCStreamer: |
| // - The MachObjectWriter gets them from the MCAssembler and writes |
| // them in the object file. |
| // - Other ObjectWriters ignore them. |
| //===----------------------------------------------------------------------===// |
| |
| #include "AArch64.h" |
| #include "AArch64InstrInfo.h" |
| #include "AArch64MachineFunctionInfo.h" |
| #include "AArch64Subtarget.h" |
| #include "MCTargetDesc/AArch64AddressingModes.h" |
| #include "llvm/ADT/BitVector.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/MapVector.h" |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/CodeGen/MachineBasicBlock.h" |
| #include "llvm/CodeGen/MachineDominators.h" |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Target/TargetRegisterInfo.h" |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "aarch64-collect-loh" |
| |
| static cl::opt<bool> |
| PreCollectRegister("aarch64-collect-loh-pre-collect-register", cl::Hidden, |
| cl::desc("Restrict analysis to registers invovled" |
| " in LOHs"), |
| cl::init(true)); |
| |
| static cl::opt<bool> |
| BasicBlockScopeOnly("aarch64-collect-loh-bb-only", cl::Hidden, |
| cl::desc("Restrict analysis at basic block scope"), |
| cl::init(true)); |
| |
| STATISTIC(NumADRPSimpleCandidate, |
| "Number of simplifiable ADRP dominate by another"); |
| STATISTIC(NumADRPComplexCandidate2, |
| "Number of simplifiable ADRP reachable by 2 defs"); |
| STATISTIC(NumADRPComplexCandidate3, |
| "Number of simplifiable ADRP reachable by 3 defs"); |
| STATISTIC(NumADRPComplexCandidateOther, |
| "Number of simplifiable ADRP reachable by 4 or more defs"); |
| STATISTIC(NumADDToSTRWithImm, |
| "Number of simplifiable STR with imm reachable by ADD"); |
| STATISTIC(NumLDRToSTRWithImm, |
| "Number of simplifiable STR with imm reachable by LDR"); |
| STATISTIC(NumADDToSTR, "Number of simplifiable STR reachable by ADD"); |
| STATISTIC(NumLDRToSTR, "Number of simplifiable STR reachable by LDR"); |
| STATISTIC(NumADDToLDRWithImm, |
| "Number of simplifiable LDR with imm reachable by ADD"); |
| STATISTIC(NumLDRToLDRWithImm, |
| "Number of simplifiable LDR with imm reachable by LDR"); |
| STATISTIC(NumADDToLDR, "Number of simplifiable LDR reachable by ADD"); |
| STATISTIC(NumLDRToLDR, "Number of simplifiable LDR reachable by LDR"); |
| STATISTIC(NumADRPToLDR, "Number of simplifiable LDR reachable by ADRP"); |
| STATISTIC(NumCplxLvl1, "Number of complex case of level 1"); |
| STATISTIC(NumTooCplxLvl1, "Number of too complex case of level 1"); |
| STATISTIC(NumCplxLvl2, "Number of complex case of level 2"); |
| STATISTIC(NumTooCplxLvl2, "Number of too complex case of level 2"); |
| STATISTIC(NumADRSimpleCandidate, "Number of simplifiable ADRP + ADD"); |
| STATISTIC(NumADRComplexCandidate, "Number of too complex ADRP + ADD"); |
| |
| namespace llvm { |
| void initializeAArch64CollectLOHPass(PassRegistry &); |
| } |
| |
| namespace { |
| struct AArch64CollectLOH : public MachineFunctionPass { |
| static char ID; |
| AArch64CollectLOH() : MachineFunctionPass(ID) { |
| initializeAArch64CollectLOHPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool runOnMachineFunction(MachineFunction &MF) override; |
| |
| const char *getPassName() const override { |
| return "AArch64 Collect Linker Optimization Hint (LOH)"; |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.setPreservesAll(); |
| MachineFunctionPass::getAnalysisUsage(AU); |
| AU.addRequired<MachineDominatorTree>(); |
| } |
| |
| private: |
| }; |
| |
| /// A set of MachineInstruction. |
| typedef SetVector<const MachineInstr *> SetOfMachineInstr; |
| /// Map a basic block to a set of instructions per register. |
| /// This is used to represent the exposed uses of a basic block |
| /// per register. |
| typedef MapVector<const MachineBasicBlock *, |
| std::unique_ptr<SetOfMachineInstr[]>> |
| BlockToSetOfInstrsPerColor; |
| /// Map a basic block to an instruction per register. |
| /// This is used to represent the live-out definitions of a basic block |
| /// per register. |
| typedef MapVector<const MachineBasicBlock *, |
| std::unique_ptr<const MachineInstr *[]>> |
| BlockToInstrPerColor; |
| /// Map an instruction to a set of instructions. Used to represent the |
| /// mapping def to reachable uses or use to definitions. |
| typedef MapVector<const MachineInstr *, SetOfMachineInstr> InstrToInstrs; |
| /// Map a basic block to a BitVector. |
| /// This is used to record the kill registers per basic block. |
| typedef MapVector<const MachineBasicBlock *, BitVector> BlockToRegSet; |
| |
| /// Map a register to a dense id. |
| typedef DenseMap<unsigned, unsigned> MapRegToId; |
| /// Map a dense id to a register. Used for debug purposes. |
| typedef SmallVector<unsigned, 32> MapIdToReg; |
| } // end anonymous namespace. |
| |
| char AArch64CollectLOH::ID = 0; |
| |
| INITIALIZE_PASS_BEGIN(AArch64CollectLOH, "aarch64-collect-loh", |
| "AArch64 Collect Linker Optimization Hint (LOH)", false, |
| false) |
| INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree) |
| INITIALIZE_PASS_END(AArch64CollectLOH, "aarch64-collect-loh", |
| "AArch64 Collect Linker Optimization Hint (LOH)", false, |
| false) |
| |
| /// Given a couple (MBB, reg) get the corresponding set of instruction from |
| /// the given "sets". |
| /// If this couple does not reference any set, an empty set is added to "sets" |
| /// for this couple and returned. |
| /// \param nbRegs is used internally allocate some memory. It must be consistent |
| /// with the way sets is used. |
| static SetOfMachineInstr &getSet(BlockToSetOfInstrsPerColor &sets, |
| const MachineBasicBlock &MBB, unsigned reg, |
| unsigned nbRegs) { |
| SetOfMachineInstr *result; |
| BlockToSetOfInstrsPerColor::iterator it = sets.find(&MBB); |
| if (it != sets.end()) |
| result = it->second.get(); |
| else |
| result = (sets[&MBB] = make_unique<SetOfMachineInstr[]>(nbRegs)).get(); |
| |
| return result[reg]; |
| } |
| |
| /// Given a couple (reg, MI) get the corresponding set of instructions from the |
| /// the given "sets". |
| /// This is used to get the uses record in sets of a definition identified by |
| /// MI and reg, i.e., MI defines reg. |
| /// If the couple does not reference anything, an empty set is added to |
| /// "sets[reg]". |
| /// \pre set[reg] is valid. |
| static SetOfMachineInstr &getUses(InstrToInstrs *sets, unsigned reg, |
| const MachineInstr &MI) { |
| return sets[reg][&MI]; |
| } |
| |
| /// Same as getUses but does not modify the input map: sets. |
| /// \return NULL if the couple (reg, MI) is not in sets. |
| static const SetOfMachineInstr *getUses(const InstrToInstrs *sets, unsigned reg, |
| const MachineInstr &MI) { |
| InstrToInstrs::const_iterator Res = sets[reg].find(&MI); |
| if (Res != sets[reg].end()) |
| return &(Res->second); |
| return nullptr; |
| } |
| |
| /// Initialize the reaching definition algorithm: |
| /// For each basic block BB in MF, record: |
| /// - its kill set. |
| /// - its reachable uses (uses that are exposed to BB's predecessors). |
| /// - its the generated definitions. |
| /// \param DummyOp if not NULL, specifies a Dummy Operation to be added to |
| /// the list of uses of exposed defintions. |
| /// \param ADRPMode specifies to only consider ADRP instructions for generated |
| /// definition. It also consider definitions of ADRP instructions as uses and |
| /// ignore other uses. The ADRPMode is used to collect the information for LHO |
| /// that involve ADRP operation only. |
| static void initReachingDef(const MachineFunction &MF, |
| InstrToInstrs *ColorOpToReachedUses, |
| BlockToInstrPerColor &Gen, BlockToRegSet &Kill, |
| BlockToSetOfInstrsPerColor &ReachableUses, |
| const MapRegToId &RegToId, |
| const MachineInstr *DummyOp, bool ADRPMode) { |
| const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); |
| unsigned NbReg = RegToId.size(); |
| |
| for (const MachineBasicBlock &MBB : MF) { |
| auto &BBGen = Gen[&MBB]; |
| BBGen = make_unique<const MachineInstr *[]>(NbReg); |
| std::fill(BBGen.get(), BBGen.get() + NbReg, nullptr); |
| |
| BitVector &BBKillSet = Kill[&MBB]; |
| BBKillSet.resize(NbReg); |
| for (const MachineInstr &MI : MBB) { |
| bool IsADRP = MI.getOpcode() == AArch64::ADRP; |
| |
| // Process uses first. |
| if (IsADRP || !ADRPMode) |
| for (const MachineOperand &MO : MI.operands()) { |
| // Treat ADRP def as use, as the goal of the analysis is to find |
| // ADRP defs reached by other ADRP defs. |
| if (!MO.isReg() || (!ADRPMode && !MO.isUse()) || |
| (ADRPMode && (!IsADRP || !MO.isDef()))) |
| continue; |
| unsigned CurReg = MO.getReg(); |
| MapRegToId::const_iterator ItCurRegId = RegToId.find(CurReg); |
| if (ItCurRegId == RegToId.end()) |
| continue; |
| CurReg = ItCurRegId->second; |
| |
| // if CurReg has not been defined, this use is reachable. |
| if (!BBGen[CurReg] && !BBKillSet.test(CurReg)) |
| getSet(ReachableUses, MBB, CurReg, NbReg).insert(&MI); |
| // current basic block definition for this color, if any, is in Gen. |
| if (BBGen[CurReg]) |
| getUses(ColorOpToReachedUses, CurReg, *BBGen[CurReg]).insert(&MI); |
| } |
| |
| // Process clobbers. |
| for (const MachineOperand &MO : MI.operands()) { |
| if (!MO.isRegMask()) |
| continue; |
| // Clobbers kill the related colors. |
| const uint32_t *PreservedRegs = MO.getRegMask(); |
| |
| // Set generated regs. |
| for (const auto &Entry : RegToId) { |
| unsigned Reg = Entry.second; |
| // Use the global register ID when querying APIs external to this |
| // pass. |
| if (MachineOperand::clobbersPhysReg(PreservedRegs, Entry.first)) { |
| // Do not register clobbered definition for no ADRP. |
| // This definition is not used anyway (otherwise register |
| // allocation is wrong). |
| BBGen[Reg] = ADRPMode ? &MI : nullptr; |
| BBKillSet.set(Reg); |
| } |
| } |
| } |
| |
| // Process register defs. |
| for (const MachineOperand &MO : MI.operands()) { |
| if (!MO.isReg() || !MO.isDef()) |
| continue; |
| unsigned CurReg = MO.getReg(); |
| MapRegToId::const_iterator ItCurRegId = RegToId.find(CurReg); |
| if (ItCurRegId == RegToId.end()) |
| continue; |
| |
| for (MCRegAliasIterator AI(CurReg, TRI, true); AI.isValid(); ++AI) { |
| MapRegToId::const_iterator ItRegId = RegToId.find(*AI); |
| assert(ItRegId != RegToId.end() && |
| "Sub-register of an " |
| "involved register, not recorded as involved!"); |
| BBKillSet.set(ItRegId->second); |
| BBGen[ItRegId->second] = &MI; |
| } |
| BBGen[ItCurRegId->second] = &MI; |
| } |
| } |
| |
| // If we restrict our analysis to basic block scope, conservatively add a |
| // dummy |
| // use for each generated value. |
| if (!ADRPMode && DummyOp && !MBB.succ_empty()) |
| for (unsigned CurReg = 0; CurReg < NbReg; ++CurReg) |
| if (BBGen[CurReg]) |
| getUses(ColorOpToReachedUses, CurReg, *BBGen[CurReg]).insert(DummyOp); |
| } |
| } |
| |
| /// Reaching def core algorithm: |
| /// while an Out has changed |
| /// for each bb |
| /// for each color |
| /// In[bb][color] = U Out[bb.predecessors][color] |
| /// insert reachableUses[bb][color] in each in[bb][color] |
| /// op.reachedUses |
| /// |
| /// Out[bb] = Gen[bb] U (In[bb] - Kill[bb]) |
| static void reachingDefAlgorithm(const MachineFunction &MF, |
| InstrToInstrs *ColorOpToReachedUses, |
| BlockToSetOfInstrsPerColor &In, |
| BlockToSetOfInstrsPerColor &Out, |
| BlockToInstrPerColor &Gen, BlockToRegSet &Kill, |
| BlockToSetOfInstrsPerColor &ReachableUses, |
| unsigned NbReg) { |
| bool HasChanged; |
| do { |
| HasChanged = false; |
| for (const MachineBasicBlock &MBB : MF) { |
| unsigned CurReg; |
| for (CurReg = 0; CurReg < NbReg; ++CurReg) { |
| SetOfMachineInstr &BBInSet = getSet(In, MBB, CurReg, NbReg); |
| SetOfMachineInstr &BBReachableUses = |
| getSet(ReachableUses, MBB, CurReg, NbReg); |
| SetOfMachineInstr &BBOutSet = getSet(Out, MBB, CurReg, NbReg); |
| unsigned Size = BBOutSet.size(); |
| // In[bb][color] = U Out[bb.predecessors][color] |
| for (const MachineBasicBlock *PredMBB : MBB.predecessors()) { |
| SetOfMachineInstr &PredOutSet = getSet(Out, *PredMBB, CurReg, NbReg); |
| BBInSet.insert(PredOutSet.begin(), PredOutSet.end()); |
| } |
| // insert reachableUses[bb][color] in each in[bb][color] op.reachedses |
| for (const MachineInstr *MI : BBInSet) { |
| SetOfMachineInstr &OpReachedUses = |
| getUses(ColorOpToReachedUses, CurReg, *MI); |
| OpReachedUses.insert(BBReachableUses.begin(), BBReachableUses.end()); |
| } |
| // Out[bb] = Gen[bb] U (In[bb] - Kill[bb]) |
| if (!Kill[&MBB].test(CurReg)) |
| BBOutSet.insert(BBInSet.begin(), BBInSet.end()); |
| if (Gen[&MBB][CurReg]) |
| BBOutSet.insert(Gen[&MBB][CurReg]); |
| HasChanged |= BBOutSet.size() != Size; |
| } |
| } |
| } while (HasChanged); |
| } |
| |
| /// Reaching definition algorithm. |
| /// \param MF function on which the algorithm will operate. |
| /// \param[out] ColorOpToReachedUses will contain the result of the reaching |
| /// def algorithm. |
| /// \param ADRPMode specify whether the reaching def algorithm should be tuned |
| /// for ADRP optimization. \see initReachingDef for more details. |
| /// \param DummyOp if not NULL, the algorithm will work at |
| /// basic block scope and will set for every exposed definition a use to |
| /// @p DummyOp. |
| /// \pre ColorOpToReachedUses is an array of at least number of registers of |
| /// InstrToInstrs. |
| static void reachingDef(const MachineFunction &MF, |
| InstrToInstrs *ColorOpToReachedUses, |
| const MapRegToId &RegToId, bool ADRPMode = false, |
| const MachineInstr *DummyOp = nullptr) { |
| // structures: |
| // For each basic block. |
| // Out: a set per color of definitions that reach the |
| // out boundary of this block. |
| // In: Same as Out but for in boundary. |
| // Gen: generated color in this block (one operation per color). |
| // Kill: register set of killed color in this block. |
| // ReachableUses: a set per color of uses (operation) reachable |
| // for "In" definitions. |
| BlockToSetOfInstrsPerColor Out, In, ReachableUses; |
| BlockToInstrPerColor Gen; |
| BlockToRegSet Kill; |
| |
| // Initialize Gen, kill and reachableUses. |
| initReachingDef(MF, ColorOpToReachedUses, Gen, Kill, ReachableUses, RegToId, |
| DummyOp, ADRPMode); |
| |
| // Algo. |
| if (!DummyOp) |
| reachingDefAlgorithm(MF, ColorOpToReachedUses, In, Out, Gen, Kill, |
| ReachableUses, RegToId.size()); |
| } |
| |
| #ifndef NDEBUG |
| /// print the result of the reaching definition algorithm. |
| static void printReachingDef(const InstrToInstrs *ColorOpToReachedUses, |
| unsigned NbReg, const TargetRegisterInfo *TRI, |
| const MapIdToReg &IdToReg) { |
| unsigned CurReg; |
| for (CurReg = 0; CurReg < NbReg; ++CurReg) { |
| if (ColorOpToReachedUses[CurReg].empty()) |
| continue; |
| DEBUG(dbgs() << "*** Reg " << PrintReg(IdToReg[CurReg], TRI) << " ***\n"); |
| |
| for (const auto &DefsIt : ColorOpToReachedUses[CurReg]) { |
| DEBUG(dbgs() << "Def:\n"); |
| DEBUG(DefsIt.first->print(dbgs())); |
| DEBUG(dbgs() << "Reachable uses:\n"); |
| for (const MachineInstr *MI : DefsIt.second) { |
| DEBUG(MI->print(dbgs())); |
| } |
| } |
| } |
| } |
| #endif // NDEBUG |
| |
| /// Answer the following question: Can Def be one of the definition |
| /// involved in a part of a LOH? |
| static bool canDefBePartOfLOH(const MachineInstr *Def) { |
| unsigned Opc = Def->getOpcode(); |
| // Accept ADRP, ADDLow and LOADGot. |
| switch (Opc) { |
| default: |
| return false; |
| case AArch64::ADRP: |
| return true; |
| case AArch64::ADDXri: |
| // Check immediate to see if the immediate is an address. |
| switch (Def->getOperand(2).getType()) { |
| default: |
| return false; |
| case MachineOperand::MO_GlobalAddress: |
| case MachineOperand::MO_JumpTableIndex: |
| case MachineOperand::MO_ConstantPoolIndex: |
| case MachineOperand::MO_BlockAddress: |
| return true; |
| } |
| case AArch64::LDRXui: |
| // Check immediate to see if the immediate is an address. |
| switch (Def->getOperand(2).getType()) { |
| default: |
| return false; |
| case MachineOperand::MO_GlobalAddress: |
| return true; |
| } |
| } |
| // Unreachable. |
| return false; |
| } |
| |
| /// Check whether the given instruction can the end of a LOH chain involving a |
| /// store. |
| static bool isCandidateStore(const MachineInstr *Instr) { |
| switch (Instr->getOpcode()) { |
| default: |
| return false; |
| case AArch64::STRBui: |
| case AArch64::STRHui: |
| case AArch64::STRWui: |
| case AArch64::STRXui: |
| case AArch64::STRSui: |
| case AArch64::STRDui: |
| case AArch64::STRQui: |
| // In case we have str xA, [xA, #imm], this is two different uses |
| // of xA and we cannot fold, otherwise the xA stored may be wrong, |
| // even if #imm == 0. |
| if (Instr->getOperand(0).getReg() != Instr->getOperand(1).getReg()) |
| return true; |
| } |
| return false; |
| } |
| |
| /// Given the result of a reaching definition algorithm in ColorOpToReachedUses, |
| /// Build the Use to Defs information and filter out obvious non-LOH candidates. |
| /// In ADRPMode, non-LOH candidates are "uses" with non-ADRP definitions. |
| /// In non-ADRPMode, non-LOH candidates are "uses" with several definition, |
| /// i.e., no simple chain. |
| /// \param ADRPMode -- \see initReachingDef. |
| static void reachedUsesToDefs(InstrToInstrs &UseToReachingDefs, |
| const InstrToInstrs *ColorOpToReachedUses, |
| const MapRegToId &RegToId, |
| bool ADRPMode = false) { |
| |
| SetOfMachineInstr NotCandidate; |
| unsigned NbReg = RegToId.size(); |
| MapRegToId::const_iterator EndIt = RegToId.end(); |
| for (unsigned CurReg = 0; CurReg < NbReg; ++CurReg) { |
| // If this color is never defined, continue. |
| if (ColorOpToReachedUses[CurReg].empty()) |
| continue; |
| |
| for (const auto &DefsIt : ColorOpToReachedUses[CurReg]) { |
| for (const MachineInstr *MI : DefsIt.second) { |
| const MachineInstr *Def = DefsIt.first; |
| MapRegToId::const_iterator It; |
| // if all the reaching defs are not adrp, this use will not be |
| // simplifiable. |
| if ((ADRPMode && Def->getOpcode() != AArch64::ADRP) || |
| (!ADRPMode && !canDefBePartOfLOH(Def)) || |
| (!ADRPMode && isCandidateStore(MI) && |
| // store are LOH candidate iff the end of the chain is used as |
| // base. |
| ((It = RegToId.find((MI)->getOperand(1).getReg())) == EndIt || |
| It->second != CurReg))) { |
| NotCandidate.insert(MI); |
| continue; |
| } |
| // Do not consider self reaching as a simplifiable case for ADRP. |
| if (!ADRPMode || MI != DefsIt.first) { |
| UseToReachingDefs[MI].insert(DefsIt.first); |
| // If UsesIt has several reaching definitions, it is not |
| // candidate for simplificaton in non-ADRPMode. |
| if (!ADRPMode && UseToReachingDefs[MI].size() > 1) |
| NotCandidate.insert(MI); |
| } |
| } |
| } |
| } |
| for (const MachineInstr *Elem : NotCandidate) { |
| DEBUG(dbgs() << "Too many reaching defs: " << *Elem << "\n"); |
| // It would have been better if we could just remove the entry |
| // from the map. Because of that, we have to filter the garbage |
| // (second.empty) in the subsequence analysis. |
| UseToReachingDefs[Elem].clear(); |
| } |
| } |
| |
| /// Based on the use to defs information (in ADRPMode), compute the |
| /// opportunities of LOH ADRP-related. |
| static void computeADRP(const InstrToInstrs &UseToDefs, |
| AArch64FunctionInfo &AArch64FI, |
| const MachineDominatorTree *MDT) { |
| DEBUG(dbgs() << "*** Compute LOH for ADRP\n"); |
| for (const auto &Entry : UseToDefs) { |
| unsigned Size = Entry.second.size(); |
| if (Size == 0) |
| continue; |
| if (Size == 1) { |
| const MachineInstr *L2 = *Entry.second.begin(); |
| const MachineInstr *L1 = Entry.first; |
| if (!MDT->dominates(L2, L1)) { |
| DEBUG(dbgs() << "Dominance check failed:\n" << *L2 << '\n' << *L1 |
| << '\n'); |
| continue; |
| } |
| DEBUG(dbgs() << "Record AdrpAdrp:\n" << *L2 << '\n' << *L1 << '\n'); |
| SmallVector<const MachineInstr *, 2> Args; |
| Args.push_back(L2); |
| Args.push_back(L1); |
| AArch64FI.addLOHDirective(MCLOH_AdrpAdrp, Args); |
| ++NumADRPSimpleCandidate; |
| } |
| #ifdef DEBUG |
| else if (Size == 2) |
| ++NumADRPComplexCandidate2; |
| else if (Size == 3) |
| ++NumADRPComplexCandidate3; |
| else |
| ++NumADRPComplexCandidateOther; |
| #endif |
| // if Size < 1, the use should have been removed from the candidates |
| assert(Size >= 1 && "No reaching defs for that use!"); |
| } |
| } |
| |
| /// Check whether the given instruction can be the end of a LOH chain |
| /// involving a load. |
| static bool isCandidateLoad(const MachineInstr *Instr) { |
| switch (Instr->getOpcode()) { |
| default: |
| return false; |
| case AArch64::LDRSBWui: |
| case AArch64::LDRSBXui: |
| case AArch64::LDRSHWui: |
| case AArch64::LDRSHXui: |
| case AArch64::LDRSWui: |
| case AArch64::LDRBui: |
| case AArch64::LDRHui: |
| case AArch64::LDRWui: |
| case AArch64::LDRXui: |
| case AArch64::LDRSui: |
| case AArch64::LDRDui: |
| case AArch64::LDRQui: |
| if (Instr->getOperand(2).getTargetFlags() & AArch64II::MO_GOT) |
| return false; |
| return true; |
| } |
| // Unreachable. |
| return false; |
| } |
| |
| /// Check whether the given instruction can load a litteral. |
| static bool supportLoadFromLiteral(const MachineInstr *Instr) { |
| switch (Instr->getOpcode()) { |
| default: |
| return false; |
| case AArch64::LDRSWui: |
| case AArch64::LDRWui: |
| case AArch64::LDRXui: |
| case AArch64::LDRSui: |
| case AArch64::LDRDui: |
| case AArch64::LDRQui: |
| return true; |
| } |
| // Unreachable. |
| return false; |
| } |
| |
| /// Check whether the given instruction is a LOH candidate. |
| /// \param UseToDefs is used to check that Instr is at the end of LOH supported |
| /// chain. |
| /// \pre UseToDefs contains only on def per use, i.e., obvious non candidate are |
| /// already been filtered out. |
| static bool isCandidate(const MachineInstr *Instr, |
| const InstrToInstrs &UseToDefs, |
| const MachineDominatorTree *MDT) { |
| if (!isCandidateLoad(Instr) && !isCandidateStore(Instr)) |
| return false; |
| |
| const MachineInstr *Def = *UseToDefs.find(Instr)->second.begin(); |
| if (Def->getOpcode() != AArch64::ADRP) { |
| // At this point, Def is ADDXri or LDRXui of the right type of |
| // symbol, because we filtered out the uses that were not defined |
| // by these kind of instructions (+ ADRP). |
| |
| // Check if this forms a simple chain: each intermediate node must |
| // dominates the next one. |
| if (!MDT->dominates(Def, Instr)) |
| return false; |
| // Move one node up in the simple chain. |
| if (UseToDefs.find(Def) == |
| UseToDefs.end() |
| // The map may contain garbage we have to ignore. |
| || |
| UseToDefs.find(Def)->second.empty()) |
| return false; |
| Instr = Def; |
| Def = *UseToDefs.find(Def)->second.begin(); |
| } |
| // Check if we reached the top of the simple chain: |
| // - top is ADRP. |
| // - check the simple chain property: each intermediate node must |
| // dominates the next one. |
| if (Def->getOpcode() == AArch64::ADRP) |
| return MDT->dominates(Def, Instr); |
| return false; |
| } |
| |
| static bool registerADRCandidate(const MachineInstr &Use, |
| const InstrToInstrs &UseToDefs, |
| const InstrToInstrs *DefsPerColorToUses, |
| AArch64FunctionInfo &AArch64FI, |
| SetOfMachineInstr *InvolvedInLOHs, |
| const MapRegToId &RegToId) { |
| // Look for opportunities to turn ADRP -> ADD or |
| // ADRP -> LDR GOTPAGEOFF into ADR. |
| // If ADRP has more than one use. Give up. |
| if (Use.getOpcode() != AArch64::ADDXri && |
| (Use.getOpcode() != AArch64::LDRXui || |
| !(Use.getOperand(2).getTargetFlags() & AArch64II::MO_GOT))) |
| return false; |
| InstrToInstrs::const_iterator It = UseToDefs.find(&Use); |
| // The map may contain garbage that we need to ignore. |
| if (It == UseToDefs.end() || It->second.empty()) |
| return false; |
| const MachineInstr &Def = **It->second.begin(); |
| if (Def.getOpcode() != AArch64::ADRP) |
| return false; |
| // Check the number of users of ADRP. |
| const SetOfMachineInstr *Users = |
| getUses(DefsPerColorToUses, |
| RegToId.find(Def.getOperand(0).getReg())->second, Def); |
| if (Users->size() > 1) { |
| ++NumADRComplexCandidate; |
| return false; |
| } |
| ++NumADRSimpleCandidate; |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(&Def)) && |
| "ADRP already involved in LOH."); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(&Use)) && |
| "ADD already involved in LOH."); |
| DEBUG(dbgs() << "Record AdrpAdd\n" << Def << '\n' << Use << '\n'); |
| |
| SmallVector<const MachineInstr *, 2> Args; |
| Args.push_back(&Def); |
| Args.push_back(&Use); |
| |
| AArch64FI.addLOHDirective(Use.getOpcode() == AArch64::ADDXri ? MCLOH_AdrpAdd |
| : MCLOH_AdrpLdrGot, |
| Args); |
| return true; |
| } |
| |
| /// Based on the use to defs information (in non-ADRPMode), compute the |
| /// opportunities of LOH non-ADRP-related |
| static void computeOthers(const InstrToInstrs &UseToDefs, |
| const InstrToInstrs *DefsPerColorToUses, |
| AArch64FunctionInfo &AArch64FI, const MapRegToId &RegToId, |
| const MachineDominatorTree *MDT) { |
| SetOfMachineInstr *InvolvedInLOHs = nullptr; |
| #ifdef DEBUG |
| SetOfMachineInstr InvolvedInLOHsStorage; |
| InvolvedInLOHs = &InvolvedInLOHsStorage; |
| #endif // DEBUG |
| DEBUG(dbgs() << "*** Compute LOH for Others\n"); |
| // ADRP -> ADD/LDR -> LDR/STR pattern. |
| // Fall back to ADRP -> ADD pattern if we fail to catch the bigger pattern. |
| |
| // FIXME: When the statistics are not important, |
| // This initial filtering loop can be merged into the next loop. |
| // Currently, we didn't do it to have the same code for both DEBUG and |
| // NDEBUG builds. Indeed, the iterator of the second loop would need |
| // to be changed. |
| SetOfMachineInstr PotentialCandidates; |
| SetOfMachineInstr PotentialADROpportunities; |
| for (auto &Use : UseToDefs) { |
| // If no definition is available, this is a non candidate. |
| if (Use.second.empty()) |
| continue; |
| // Keep only instructions that are load or store and at the end of |
| // a ADRP -> ADD/LDR/Nothing chain. |
| // We already filtered out the no-chain cases. |
| if (!isCandidate(Use.first, UseToDefs, MDT)) { |
| PotentialADROpportunities.insert(Use.first); |
| continue; |
| } |
| PotentialCandidates.insert(Use.first); |
| } |
| |
| // Make the following distinctions for statistics as the linker does |
| // know how to decode instructions: |
| // - ADD/LDR/Nothing make there different patterns. |
| // - LDR/STR make two different patterns. |
| // Hence, 6 - 1 base patterns. |
| // (because ADRP-> Nothing -> STR is not simplifiable) |
| |
| // The linker is only able to have a simple semantic, i.e., if pattern A |
| // do B. |
| // However, we want to see the opportunity we may miss if we were able to |
| // catch more complex cases. |
| |
| // PotentialCandidates are result of a chain ADRP -> ADD/LDR -> |
| // A potential candidate becomes a candidate, if its current immediate |
| // operand is zero and all nodes of the chain have respectively only one user |
| #ifdef DEBUG |
| SetOfMachineInstr DefsOfPotentialCandidates; |
| #endif |
| for (const MachineInstr *Candidate : PotentialCandidates) { |
| // Get the definition of the candidate i.e., ADD or LDR. |
| const MachineInstr *Def = *UseToDefs.find(Candidate)->second.begin(); |
| // Record the elements of the chain. |
| const MachineInstr *L1 = Def; |
| const MachineInstr *L2 = nullptr; |
| unsigned ImmediateDefOpc = Def->getOpcode(); |
| if (Def->getOpcode() != AArch64::ADRP) { |
| // Check the number of users of this node. |
| const SetOfMachineInstr *Users = |
| getUses(DefsPerColorToUses, |
| RegToId.find(Def->getOperand(0).getReg())->second, *Def); |
| if (Users->size() > 1) { |
| #ifdef DEBUG |
| // if all the uses of this def are in potential candidate, this is |
| // a complex candidate of level 2. |
| bool IsLevel2 = true; |
| for (const MachineInstr *MI : *Users) { |
| if (!PotentialCandidates.count(MI)) { |
| ++NumTooCplxLvl2; |
| IsLevel2 = false; |
| break; |
| } |
| } |
| if (IsLevel2) |
| ++NumCplxLvl2; |
| #endif // DEBUG |
| PotentialADROpportunities.insert(Def); |
| continue; |
| } |
| L2 = Def; |
| Def = *UseToDefs.find(Def)->second.begin(); |
| L1 = Def; |
| } // else the element in the middle of the chain is nothing, thus |
| // Def already contains the first element of the chain. |
| |
| // Check the number of users of the first node in the chain, i.e., ADRP |
| const SetOfMachineInstr *Users = |
| getUses(DefsPerColorToUses, |
| RegToId.find(Def->getOperand(0).getReg())->second, *Def); |
| if (Users->size() > 1) { |
| #ifdef DEBUG |
| // if all the uses of this def are in the defs of the potential candidate, |
| // this is a complex candidate of level 1 |
| if (DefsOfPotentialCandidates.empty()) { |
| // lazy init |
| DefsOfPotentialCandidates = PotentialCandidates; |
| for (const MachineInstr *Candidate : PotentialCandidates) { |
| if (!UseToDefs.find(Candidate)->second.empty()) |
| DefsOfPotentialCandidates.insert( |
| *UseToDefs.find(Candidate)->second.begin()); |
| } |
| } |
| bool Found = false; |
| for (auto &Use : *Users) { |
| if (!DefsOfPotentialCandidates.count(Use)) { |
| ++NumTooCplxLvl1; |
| Found = true; |
| break; |
| } |
| } |
| if (!Found) |
| ++NumCplxLvl1; |
| #endif // DEBUG |
| continue; |
| } |
| |
| bool IsL2Add = (ImmediateDefOpc == AArch64::ADDXri); |
| // If the chain is three instructions long and ldr is the second element, |
| // then this ldr must load form GOT, otherwise this is not a correct chain. |
| if (L2 && !IsL2Add && L2->getOperand(2).getTargetFlags() != AArch64II::MO_GOT) |
| continue; |
| SmallVector<const MachineInstr *, 3> Args; |
| MCLOHType Kind; |
| if (isCandidateLoad(Candidate)) { |
| if (!L2) { |
| // At this point, the candidate LOH indicates that the ldr instruction |
| // may use a direct access to the symbol. There is not such encoding |
| // for loads of byte and half. |
| if (!supportLoadFromLiteral(Candidate)) |
| continue; |
| |
| DEBUG(dbgs() << "Record AdrpLdr:\n" << *L1 << '\n' << *Candidate |
| << '\n'); |
| Kind = MCLOH_AdrpLdr; |
| Args.push_back(L1); |
| Args.push_back(Candidate); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L1)) && |
| "L1 already involved in LOH."); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(Candidate)) && |
| "Candidate already involved in LOH."); |
| ++NumADRPToLDR; |
| } else { |
| DEBUG(dbgs() << "Record Adrp" << (IsL2Add ? "Add" : "LdrGot") |
| << "Ldr:\n" << *L1 << '\n' << *L2 << '\n' << *Candidate |
| << '\n'); |
| |
| Kind = IsL2Add ? MCLOH_AdrpAddLdr : MCLOH_AdrpLdrGotLdr; |
| Args.push_back(L1); |
| Args.push_back(L2); |
| Args.push_back(Candidate); |
| |
| PotentialADROpportunities.remove(L2); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L1)) && |
| "L1 already involved in LOH."); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L2)) && |
| "L2 already involved in LOH."); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(Candidate)) && |
| "Candidate already involved in LOH."); |
| #ifdef DEBUG |
| // get the immediate of the load |
| if (Candidate->getOperand(2).getImm() == 0) |
| if (ImmediateDefOpc == AArch64::ADDXri) |
| ++NumADDToLDR; |
| else |
| ++NumLDRToLDR; |
| else if (ImmediateDefOpc == AArch64::ADDXri) |
| ++NumADDToLDRWithImm; |
| else |
| ++NumLDRToLDRWithImm; |
| #endif // DEBUG |
| } |
| } else { |
| if (ImmediateDefOpc == AArch64::ADRP) |
| continue; |
| else { |
| |
| DEBUG(dbgs() << "Record Adrp" << (IsL2Add ? "Add" : "LdrGot") |
| << "Str:\n" << *L1 << '\n' << *L2 << '\n' << *Candidate |
| << '\n'); |
| |
| Kind = IsL2Add ? MCLOH_AdrpAddStr : MCLOH_AdrpLdrGotStr; |
| Args.push_back(L1); |
| Args.push_back(L2); |
| Args.push_back(Candidate); |
| |
| PotentialADROpportunities.remove(L2); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L1)) && |
| "L1 already involved in LOH."); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(L2)) && |
| "L2 already involved in LOH."); |
| assert((!InvolvedInLOHs || InvolvedInLOHs->insert(Candidate)) && |
| "Candidate already involved in LOH."); |
| #ifdef DEBUG |
| // get the immediate of the store |
| if (Candidate->getOperand(2).getImm() == 0) |
| if (ImmediateDefOpc == AArch64::ADDXri) |
| ++NumADDToSTR; |
| else |
| ++NumLDRToSTR; |
| else if (ImmediateDefOpc == AArch64::ADDXri) |
| ++NumADDToSTRWithImm; |
| else |
| ++NumLDRToSTRWithImm; |
| #endif // DEBUG |
| } |
| } |
| AArch64FI.addLOHDirective(Kind, Args); |
| } |
| |
| // Now, we grabbed all the big patterns, check ADR opportunities. |
| for (const MachineInstr *Candidate : PotentialADROpportunities) |
| registerADRCandidate(*Candidate, UseToDefs, DefsPerColorToUses, AArch64FI, |
| InvolvedInLOHs, RegToId); |
| } |
| |
| /// Look for every register defined by potential LOHs candidates. |
| /// Map these registers with dense id in @p RegToId and vice-versa in |
| /// @p IdToReg. @p IdToReg is populated only in DEBUG mode. |
| static void collectInvolvedReg(const MachineFunction &MF, MapRegToId &RegToId, |
| MapIdToReg &IdToReg, |
| const TargetRegisterInfo *TRI) { |
| unsigned CurRegId = 0; |
| if (!PreCollectRegister) { |
| unsigned NbReg = TRI->getNumRegs(); |
| for (; CurRegId < NbReg; ++CurRegId) { |
| RegToId[CurRegId] = CurRegId; |
| DEBUG(IdToReg.push_back(CurRegId)); |
| DEBUG(assert(IdToReg[CurRegId] == CurRegId && "Reg index mismatches")); |
| } |
| return; |
| } |
| |
| DEBUG(dbgs() << "** Collect Involved Register\n"); |
| for (const auto &MBB : MF) { |
| for (const MachineInstr &MI : MBB) { |
| if (!canDefBePartOfLOH(&MI)) |
| continue; |
| |
| // Process defs |
| for (MachineInstr::const_mop_iterator IO = MI.operands_begin(), |
| IOEnd = MI.operands_end(); |
| IO != IOEnd; ++IO) { |
| if (!IO->isReg() || !IO->isDef()) |
| continue; |
| unsigned CurReg = IO->getReg(); |
| for (MCRegAliasIterator AI(CurReg, TRI, true); AI.isValid(); ++AI) |
| if (RegToId.find(*AI) == RegToId.end()) { |
| DEBUG(IdToReg.push_back(*AI); |
| assert(IdToReg[CurRegId] == *AI && |
| "Reg index mismatches insertion index.")); |
| RegToId[*AI] = CurRegId++; |
| DEBUG(dbgs() << "Register: " << PrintReg(*AI, TRI) << '\n'); |
| } |
| } |
| } |
| } |
| } |
| |
| bool AArch64CollectLOH::runOnMachineFunction(MachineFunction &MF) { |
| const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo(); |
| const MachineDominatorTree *MDT = &getAnalysis<MachineDominatorTree>(); |
| |
| MapRegToId RegToId; |
| MapIdToReg IdToReg; |
| AArch64FunctionInfo *AArch64FI = MF.getInfo<AArch64FunctionInfo>(); |
| assert(AArch64FI && "No MachineFunctionInfo for this function!"); |
| |
| DEBUG(dbgs() << "Looking for LOH in " << MF.getName() << '\n'); |
| |
| collectInvolvedReg(MF, RegToId, IdToReg, TRI); |
| if (RegToId.empty()) |
| return false; |
| |
| MachineInstr *DummyOp = nullptr; |
| if (BasicBlockScopeOnly) { |
| const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); |
| // For local analysis, create a dummy operation to record uses that are not |
| // local. |
| DummyOp = MF.CreateMachineInstr(TII->get(AArch64::COPY), DebugLoc()); |
| } |
| |
| unsigned NbReg = RegToId.size(); |
| bool Modified = false; |
| |
| // Start with ADRP. |
| InstrToInstrs *ColorOpToReachedUses = new InstrToInstrs[NbReg]; |
| |
| // Compute the reaching def in ADRP mode, meaning ADRP definitions |
| // are first considered as uses. |
| reachingDef(MF, ColorOpToReachedUses, RegToId, true, DummyOp); |
| DEBUG(dbgs() << "ADRP reaching defs\n"); |
| DEBUG(printReachingDef(ColorOpToReachedUses, NbReg, TRI, IdToReg)); |
| |
| // Translate the definition to uses map into a use to definitions map to ease |
| // statistic computation. |
| InstrToInstrs ADRPToReachingDefs; |
| reachedUsesToDefs(ADRPToReachingDefs, ColorOpToReachedUses, RegToId, true); |
| |
| // Compute LOH for ADRP. |
| computeADRP(ADRPToReachingDefs, *AArch64FI, MDT); |
| delete[] ColorOpToReachedUses; |
| |
| // Continue with general ADRP -> ADD/LDR -> LDR/STR pattern. |
| ColorOpToReachedUses = new InstrToInstrs[NbReg]; |
| |
| // first perform a regular reaching def analysis. |
| reachingDef(MF, ColorOpToReachedUses, RegToId, false, DummyOp); |
| DEBUG(dbgs() << "All reaching defs\n"); |
| DEBUG(printReachingDef(ColorOpToReachedUses, NbReg, TRI, IdToReg)); |
| |
| // Turn that into a use to defs to ease statistic computation. |
| InstrToInstrs UsesToReachingDefs; |
| reachedUsesToDefs(UsesToReachingDefs, ColorOpToReachedUses, RegToId, false); |
| |
| // Compute other than AdrpAdrp LOH. |
| computeOthers(UsesToReachingDefs, ColorOpToReachedUses, *AArch64FI, RegToId, |
| MDT); |
| delete[] ColorOpToReachedUses; |
| |
| if (BasicBlockScopeOnly) |
| MF.DeleteMachineInstr(DummyOp); |
| |
| return Modified; |
| } |
| |
| /// createAArch64CollectLOHPass - returns an instance of the Statistic for |
| /// linker optimization pass. |
| FunctionPass *llvm::createAArch64CollectLOHPass() { |
| return new AArch64CollectLOH(); |
| } |
