| //===------ CFIInstrInserter.cpp - Insert additional CFI instructions -----===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| /// \file This pass verifies incoming and outgoing CFA information of basic |
| /// blocks. CFA information is information about offset and register set by CFI |
| /// directives, valid at the start and end of a basic block. This pass checks |
| /// that outgoing information of predecessors matches incoming information of |
| /// their successors. Then it checks if blocks have correct CFA calculation rule |
| /// set and inserts additional CFI instruction at their beginnings if they |
| /// don't. CFI instructions are inserted if basic blocks have incorrect offset |
| /// or register set by previous blocks, as a result of a non-linear layout of |
| /// blocks in a function. |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include "llvm/CodeGen/MachineInstrBuilder.h" |
| #include "llvm/CodeGen/MachineModuleInfo.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/CodeGen/TargetFrameLowering.h" |
| #include "llvm/CodeGen/TargetInstrInfo.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/Target/TargetSubtargetInfo.h" |
| using namespace llvm; |
| |
| namespace { |
| class CFIInstrInserter : public MachineFunctionPass { |
| public: |
| static char ID; |
| |
| CFIInstrInserter() : MachineFunctionPass(ID) { |
| initializeCFIInstrInserterPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.setPreservesAll(); |
| MachineFunctionPass::getAnalysisUsage(AU); |
| } |
| |
| bool runOnMachineFunction(MachineFunction &MF) override { |
| |
| if (!MF.getMMI().hasDebugInfo() && |
| !MF.getFunction()->needsUnwindTableEntry()) |
| return false; |
| |
| MBBVector.resize(MF.getNumBlockIDs()); |
| calculateCFAInfo(MF); |
| #ifndef NDEBUG |
| unsigned ErrorNum = verify(MF); |
| if (ErrorNum) |
| report_fatal_error("Found " + Twine(ErrorNum) + |
| " in/out CFI information errors."); |
| #endif |
| bool insertedCFI = insertCFIInstrs(MF); |
| MBBVector.clear(); |
| return insertedCFI; |
| } |
| |
| private: |
| struct MBBCFAInfo { |
| MachineBasicBlock *MBB; |
| /// Value of cfa offset valid at basic block entry. |
| int IncomingCFAOffset = -1; |
| /// Value of cfa offset valid at basic block exit. |
| int OutgoingCFAOffset = -1; |
| /// Value of cfa register valid at basic block entry. |
| unsigned IncomingCFARegister = 0; |
| /// Value of cfa register valid at basic block exit. |
| unsigned OutgoingCFARegister = 0; |
| /// If in/out cfa offset and register values for this block have already |
| /// been set or not. |
| bool Processed = false; |
| }; |
| |
| /// Contains cfa offset and register values valid at entry and exit of basic |
| /// blocks. |
| SmallVector<struct MBBCFAInfo, 4> MBBVector; |
| |
| /// Calculate cfa offset and register values valid at entry and exit for all |
| /// basic blocks in a function. |
| void calculateCFAInfo(MachineFunction &MF); |
| /// Calculate cfa offset and register values valid at basic block exit by |
| /// checking the block for CFI instructions. Block's incoming CFA info remains |
| /// the same. |
| void calculateOutgoingCFAInfo(struct MBBCFAInfo &MBBInfo); |
| /// Update in/out cfa offset and register values for successors of the basic |
| /// block. |
| void updateSuccCFAInfo(struct MBBCFAInfo &MBBInfo); |
| |
| /// Check if incoming CFA information of a basic block matches outgoing CFA |
| /// information of the previous block. If it doesn't, insert CFI instruction |
| /// at the beginning of the block that corrects the CFA calculation rule for |
| /// that block. |
| bool insertCFIInstrs(MachineFunction &MF); |
| /// Return the cfa offset value that should be set at the beginning of a MBB |
| /// if needed. The negated value is needed when creating CFI instructions that |
| /// set absolute offset. |
| int getCorrectCFAOffset(MachineBasicBlock *MBB) { |
| return -MBBVector[MBB->getNumber()].IncomingCFAOffset; |
| } |
| |
| void report(const char *msg, MachineBasicBlock &MBB); |
| /// Go through each MBB in a function and check that outgoing offset and |
| /// register of its predecessors match incoming offset and register of that |
| /// MBB, as well as that incoming offset and register of its successors match |
| /// outgoing offset and register of the MBB. |
| unsigned verify(MachineFunction &MF); |
| }; |
| } |
| |
| char CFIInstrInserter::ID = 0; |
| INITIALIZE_PASS(CFIInstrInserter, "cfi-instr-inserter", |
| "Check CFA info and insert CFI instructions if needed", false, |
| false) |
| FunctionPass *llvm::createCFIInstrInserter() { return new CFIInstrInserter(); } |
| |
| void CFIInstrInserter::calculateCFAInfo(MachineFunction &MF) { |
| // Initial CFA offset value i.e. the one valid at the beginning of the |
| // function. |
| int InitialOffset = |
| MF.getSubtarget().getFrameLowering()->getInitialCFAOffset(MF); |
| // Initial CFA register value i.e. the one valid at the beginning of the |
| // function. |
| unsigned InitialRegister = |
| MF.getSubtarget().getFrameLowering()->getInitialCFARegister(MF); |
| |
| // Initialize MBBMap. |
| for (MachineBasicBlock &MBB : MF) { |
| struct MBBCFAInfo MBBInfo; |
| MBBInfo.MBB = &MBB; |
| MBBInfo.IncomingCFAOffset = InitialOffset; |
| MBBInfo.OutgoingCFAOffset = InitialOffset; |
| MBBInfo.IncomingCFARegister = InitialRegister; |
| MBBInfo.OutgoingCFARegister = InitialRegister; |
| MBBVector[MBB.getNumber()] = MBBInfo; |
| } |
| |
| // Set in/out cfa info for all blocks in the function. This traversal is based |
| // on the assumption that the first block in the function is the entry block |
| // i.e. that it has initial cfa offset and register values as incoming CFA |
| // information. |
| for (MachineBasicBlock &MBB : MF) { |
| if (MBBVector[MBB.getNumber()].Processed) continue; |
| calculateOutgoingCFAInfo(MBBVector[MBB.getNumber()]); |
| updateSuccCFAInfo(MBBVector[MBB.getNumber()]); |
| } |
| } |
| |
| void CFIInstrInserter::calculateOutgoingCFAInfo(struct MBBCFAInfo &MBBInfo) { |
| // Outgoing cfa offset set by the block. |
| int SetOffset = MBBInfo.IncomingCFAOffset; |
| // Outgoing cfa register set by the block. |
| unsigned SetRegister = MBBInfo.IncomingCFARegister; |
| const std::vector<MCCFIInstruction> &Instrs = |
| MBBInfo.MBB->getParent()->getFrameInstructions(); |
| |
| // Determine cfa offset and register set by the block. |
| for (MachineInstr &MI : |
| make_range(MBBInfo.MBB->instr_begin(), MBBInfo.MBB->instr_end())) { |
| if (MI.isCFIInstruction()) { |
| unsigned CFIIndex = MI.getOperand(0).getCFIIndex(); |
| const MCCFIInstruction &CFI = Instrs[CFIIndex]; |
| if (CFI.getOperation() == MCCFIInstruction::OpDefCfaRegister) { |
| SetRegister = CFI.getRegister(); |
| } else if (CFI.getOperation() == MCCFIInstruction::OpDefCfaOffset) { |
| SetOffset = CFI.getOffset(); |
| } else if (CFI.getOperation() == MCCFIInstruction::OpAdjustCfaOffset) { |
| SetOffset += CFI.getOffset(); |
| } else if (CFI.getOperation() == MCCFIInstruction::OpDefCfa) { |
| SetRegister = CFI.getRegister(); |
| SetOffset = CFI.getOffset(); |
| } |
| } |
| } |
| |
| MBBInfo.Processed = true; |
| |
| // Update outgoing CFA info. |
| MBBInfo.OutgoingCFAOffset = SetOffset; |
| MBBInfo.OutgoingCFARegister = SetRegister; |
| } |
| |
| void CFIInstrInserter::updateSuccCFAInfo(struct MBBCFAInfo &MBBInfo) { |
| |
| for (MachineBasicBlock *Succ : MBBInfo.MBB->successors()) { |
| struct MBBCFAInfo &SuccInfo = MBBVector[Succ->getNumber()]; |
| if (SuccInfo.Processed) continue; |
| SuccInfo.IncomingCFAOffset = MBBInfo.OutgoingCFAOffset; |
| SuccInfo.IncomingCFARegister = MBBInfo.OutgoingCFARegister; |
| calculateOutgoingCFAInfo(SuccInfo); |
| updateSuccCFAInfo(SuccInfo); |
| } |
| } |
| |
| bool CFIInstrInserter::insertCFIInstrs(MachineFunction &MF) { |
| |
| const struct MBBCFAInfo *PrevMBBInfo = &MBBVector[MF.front().getNumber()]; |
| const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo(); |
| bool InsertedCFIInstr = false; |
| |
| for (MachineBasicBlock &MBB : MF) { |
| // Skip the first MBB in a function |
| if (MBB.getNumber() == MF.front().getNumber()) continue; |
| |
| const struct MBBCFAInfo& MBBInfo = MBBVector[MBB.getNumber()]; |
| auto MBBI = MBBInfo.MBB->begin(); |
| DebugLoc DL = MBBInfo.MBB->findDebugLoc(MBBI); |
| |
| if (PrevMBBInfo->OutgoingCFAOffset != MBBInfo.IncomingCFAOffset) { |
| // If both outgoing offset and register of a previous block don't match |
| // incoming offset and register of this block, add a def_cfa instruction |
| // with the correct offset and register for this block. |
| if (PrevMBBInfo->OutgoingCFARegister != MBBInfo.IncomingCFARegister) { |
| unsigned CFIIndex = MF.addFrameInst(MCCFIInstruction::createDefCfa( |
| nullptr, MBBInfo.IncomingCFARegister, getCorrectCFAOffset(&MBB))); |
| BuildMI(*MBBInfo.MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION)) |
| .addCFIIndex(CFIIndex); |
| // If outgoing offset of a previous block doesn't match incoming offset |
| // of this block, add a def_cfa_offset instruction with the correct |
| // offset for this block. |
| } else { |
| unsigned CFIIndex = |
| MF.addFrameInst(MCCFIInstruction::createDefCfaOffset( |
| nullptr, getCorrectCFAOffset(&MBB))); |
| BuildMI(*MBBInfo.MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION)) |
| .addCFIIndex(CFIIndex); |
| } |
| InsertedCFIInstr = true; |
| // If outgoing register of a previous block doesn't match incoming |
| // register of this block, add a def_cfa_register instruction with the |
| // correct register for this block. |
| } else if (PrevMBBInfo->OutgoingCFARegister != MBBInfo.IncomingCFARegister) { |
| unsigned CFIIndex = |
| MF.addFrameInst(MCCFIInstruction::createDefCfaRegister( |
| nullptr, MBBInfo.IncomingCFARegister)); |
| BuildMI(*MBBInfo.MBB, MBBI, DL, TII->get(TargetOpcode::CFI_INSTRUCTION)) |
| .addCFIIndex(CFIIndex); |
| InsertedCFIInstr = true; |
| } |
| PrevMBBInfo = &MBBInfo; |
| } |
| return InsertedCFIInstr; |
| } |
| |
| void CFIInstrInserter::report(const char *msg, MachineBasicBlock &MBB) { |
| errs() << '\n'; |
| errs() << "*** " << msg << " ***\n" |
| << "- function: " << MBB.getParent()->getName() << "\n"; |
| errs() << "- basic block: BB#" << MBB.getNumber() << ' ' << MBB.getName() |
| << " (" << (const void *)&MBB << ')'; |
| errs() << '\n'; |
| } |
| |
| unsigned CFIInstrInserter::verify(MachineFunction &MF) { |
| unsigned ErrorNum = 0; |
| for (MachineBasicBlock &CurrMBB : MF) { |
| const struct MBBCFAInfo& CurrMBBInfo = MBBVector[CurrMBB.getNumber()]; |
| for (MachineBasicBlock *Pred : CurrMBB.predecessors()) { |
| const struct MBBCFAInfo& PredMBBInfo = MBBVector[Pred->getNumber()]; |
| // Check that outgoing offset values of predecessors match the incoming |
| // offset value of CurrMBB |
| if (PredMBBInfo.OutgoingCFAOffset != CurrMBBInfo.IncomingCFAOffset) { |
| report("The outgoing offset of a predecessor is inconsistent.", |
| CurrMBB); |
| errs() << "Predecessor BB#" << Pred->getNumber() |
| << " has outgoing offset (" << PredMBBInfo.OutgoingCFAOffset |
| << "), while BB#" << CurrMBB.getNumber() |
| << " has incoming offset (" << CurrMBBInfo.IncomingCFAOffset |
| << ").\n"; |
| ErrorNum++; |
| } |
| // Check that outgoing register values of predecessors match the incoming |
| // register value of CurrMBB |
| if (PredMBBInfo.OutgoingCFARegister != CurrMBBInfo.IncomingCFARegister) { |
| report("The outgoing register of a predecessor is inconsistent.", |
| CurrMBB); |
| errs() << "Predecessor BB#" << Pred->getNumber() |
| << " has outgoing register (" << PredMBBInfo.OutgoingCFARegister |
| << "), while BB#" << CurrMBB.getNumber() |
| << " has incoming register (" << CurrMBBInfo.IncomingCFARegister |
| << ").\n"; |
| ErrorNum++; |
| } |
| } |
| |
| for (MachineBasicBlock *Succ : CurrMBB.successors()) { |
| const struct MBBCFAInfo& SuccMBBInfo = MBBVector[Succ->getNumber()]; |
| // Check that incoming offset values of successors match the outgoing |
| // offset value of CurrMBB |
| if (SuccMBBInfo.IncomingCFAOffset != CurrMBBInfo.OutgoingCFAOffset) { |
| report("The incoming offset of a successor is inconsistent.", CurrMBB); |
| errs() << "Successor BB#" << Succ->getNumber() |
| << " has incoming offset (" << SuccMBBInfo.IncomingCFAOffset |
| << "), while BB#" << CurrMBB.getNumber() |
| << " has outgoing offset (" << CurrMBBInfo.OutgoingCFAOffset |
| << ").\n"; |
| ErrorNum++; |
| } |
| // Check that incoming register values of successors match the outgoing |
| // register value of CurrMBB |
| if (SuccMBBInfo.IncomingCFARegister != CurrMBBInfo.OutgoingCFARegister) { |
| report("The incoming register of a successor is inconsistent.", |
| CurrMBB); |
| errs() << "Successor BB#" << Succ->getNumber() |
| << " has incoming register (" << SuccMBBInfo.IncomingCFARegister |
| << "), while BB#" << CurrMBB.getNumber() |
| << " has outgoing register (" << CurrMBBInfo.OutgoingCFARegister |
| << ").\n"; |
| ErrorNum++; |
| } |
| } |
| } |
| return ErrorNum; |
| } |