//===------ LiveDebugValues.cpp - Tracking Debug Value MIs ----------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// /// /// This pass implements a data flow analysis that propagates debug location /// information by inserting additional DBG_VALUE instructions into the machine /// instruction stream. The pass internally builds debug location liveness /// ranges to determine the points where additional DBG_VALUEs need to be /// inserted. /// /// This is a separate pass from DbgValueHistoryCalculator to facilitate /// testing and improve modularity. /// //===----------------------------------------------------------------------===// #include "llvm/ADT/PostOrderIterator.h" #include "llvm/ADT/SmallPtrSet.h" #include "llvm/ADT/SparseBitVector.h" #include "llvm/ADT/Statistic.h" #include "llvm/ADT/UniqueVector.h" #include "llvm/CodeGen/MachineFunction.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/Passes.h" #include "llvm/IR/DebugInfo.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" #include "llvm/Target/TargetInstrInfo.h" #include "llvm/Target/TargetLowering.h" #include "llvm/Target/TargetRegisterInfo.h" #include "llvm/Target/TargetSubtargetInfo.h" #include <list> #include <queue> using namespace llvm; #define DEBUG_TYPE "live-debug-values" STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted"); namespace { // \brief If @MI is a DBG_VALUE with debug value described by a defined // register, returns the number of this register. In the other case, returns 0. static unsigned isDbgValueDescribedByReg(const MachineInstr &MI) { assert(MI.isDebugValue() && "expected a DBG_VALUE"); assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE"); // If location of variable is described using a register (directly // or indirectly), this register is always a first operand. return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0; } class LiveDebugValues : public MachineFunctionPass { private: const TargetRegisterInfo *TRI; const TargetInstrInfo *TII; /// Based on std::pair so it can be used as an index into a DenseMap. typedef std::pair<const DILocalVariable *, const DILocation *> DebugVariableBase; /// A potentially inlined instance of a variable. struct DebugVariable : public DebugVariableBase { DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt) : DebugVariableBase(Var, InlinedAt) {} const DILocalVariable *getVar() const { return this->first; }; const DILocation *getInlinedAt() const { return this->second; }; bool operator<(const DebugVariable &DV) const { if (getVar() == DV.getVar()) return getInlinedAt() < DV.getInlinedAt(); return getVar() < DV.getVar(); } }; /// A pair of debug variable and value location. struct VarLoc { const DebugVariable Var; const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE. enum { InvalidKind = 0, RegisterKind } Kind; /// The value location. Stored separately to avoid repeatedly /// extracting it from MI. union { struct { uint32_t RegNo; uint32_t Offset; } RegisterLoc; uint64_t Hash; } Loc; VarLoc(const MachineInstr &MI) : Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI), Kind(InvalidKind) { static_assert((sizeof(Loc) == sizeof(uint64_t)), "hash does not cover all members of Loc"); assert(MI.isDebugValue() && "not a DBG_VALUE"); assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE"); if (int RegNo = isDbgValueDescribedByReg(MI)) { Kind = RegisterKind; Loc.RegisterLoc.RegNo = RegNo; uint64_t Offset = MI.isIndirectDebugValue() ? MI.getOperand(1).getImm() : 0; // We don't support offsets larger than 4GiB here. They are // slated to be replaced with DIExpressions anyway. if (Offset >= (1ULL << 32)) Kind = InvalidKind; else Loc.RegisterLoc.Offset = Offset; } } /// If this variable is described by a register, return it, /// otherwise return 0. unsigned isDescribedByReg() const { if (Kind == RegisterKind) return Loc.RegisterLoc.RegNo; return 0; } void dump() const { MI.dump(); } bool operator==(const VarLoc &Other) const { return Var == Other.Var && Loc.Hash == Other.Loc.Hash; } /// This operator guarantees that VarLocs are sorted by Variable first. bool operator<(const VarLoc &Other) const { if (Var == Other.Var) return Loc.Hash < Other.Loc.Hash; return Var < Other.Var; } }; typedef UniqueVector<VarLoc> VarLocMap; typedef SparseBitVector<> VarLocSet; typedef SmallDenseMap<const MachineBasicBlock *, VarLocSet> VarLocInMBB; /// This holds the working set of currently open ranges. For fast /// access, this is done both as a set of VarLocIDs, and a map of /// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all /// previous open ranges for the same variable. class OpenRangesSet { VarLocSet VarLocs; SmallDenseMap<DebugVariableBase, unsigned, 8> Vars; public: const VarLocSet &getVarLocs() const { return VarLocs; } /// Terminate all open ranges for Var by removing it from the set. void erase(DebugVariable Var) { auto It = Vars.find(Var); if (It != Vars.end()) { unsigned ID = It->second; VarLocs.reset(ID); Vars.erase(It); } } /// Terminate all open ranges listed in \c KillSet by removing /// them from the set. void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) { VarLocs.intersectWithComplement(KillSet); for (unsigned ID : KillSet) Vars.erase(VarLocIDs[ID].Var); } /// Insert a new range into the set. void insert(unsigned VarLocID, DebugVariableBase Var) { VarLocs.set(VarLocID); Vars.insert({Var, VarLocID}); } /// Empty the set. void clear() { VarLocs.clear(); Vars.clear(); } /// Return whether the set is empty or not. bool empty() const { assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent"); return VarLocs.empty(); } }; void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocMap &VarLocIDs); void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges, const VarLocMap &VarLocIDs); bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs); bool transfer(MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocInMBB &OutLocs, VarLocMap &VarLocIDs); bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs, const VarLocMap &VarLocIDs); bool ExtendRanges(MachineFunction &MF); public: static char ID; /// Default construct and initialize the pass. LiveDebugValues(); /// Tell the pass manager which passes we depend on and what /// information we preserve. void getAnalysisUsage(AnalysisUsage &AU) const override; MachineFunctionProperties getRequiredProperties() const override { return MachineFunctionProperties().set( MachineFunctionProperties::Property::AllVRegsAllocated); } /// Print to ostream with a message. void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V, const VarLocMap &VarLocIDs, const char *msg, raw_ostream &Out) const; /// Calculate the liveness information for the given machine function. bool runOnMachineFunction(MachineFunction &MF) override; }; } // namespace //===----------------------------------------------------------------------===// // Implementation //===----------------------------------------------------------------------===// char LiveDebugValues::ID = 0; char &llvm::LiveDebugValuesID = LiveDebugValues::ID; INITIALIZE_PASS(LiveDebugValues, "livedebugvalues", "Live DEBUG_VALUE analysis", false, false) /// Default construct and initialize the pass. LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) { initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry()); } /// Tell the pass manager which passes we depend on and what information we /// preserve. void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesCFG(); MachineFunctionPass::getAnalysisUsage(AU); } //===----------------------------------------------------------------------===// // Debug Range Extension Implementation //===----------------------------------------------------------------------===// void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V, const VarLocMap &VarLocIDs, const char *msg, raw_ostream &Out) const { for (const MachineBasicBlock &BB : MF) { const auto &L = V.lookup(&BB); Out << "MBB: " << BB.getName() << ":\n"; for (unsigned VLL : L) { const VarLoc &VL = VarLocIDs[VLL]; Out << " Var: " << VL.Var.getVar()->getName(); Out << " MI: "; VL.dump(); Out << "\n"; } } Out << "\n"; } /// End all previous ranges related to @MI and start a new range from @MI /// if it is a DBG_VALUE instr. void LiveDebugValues::transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocMap &VarLocIDs) { if (!MI.isDebugValue()) return; const DILocalVariable *Var = MI.getDebugVariable(); const DILocation *DebugLoc = MI.getDebugLoc(); const DILocation *InlinedAt = DebugLoc->getInlinedAt(); assert(Var->isValidLocationForIntrinsic(DebugLoc) && "Expected inlined-at fields to agree"); // End all previous ranges of Var. DebugVariable V(Var, InlinedAt); OpenRanges.erase(V); // Add the VarLoc to OpenRanges from this DBG_VALUE. // TODO: Currently handles DBG_VALUE which has only reg as location. if (isDbgValueDescribedByReg(MI)) { VarLoc VL(MI); unsigned ID = VarLocIDs.insert(VL); OpenRanges.insert(ID, VL.Var); } } /// A definition of a register may mark the end of a range. void LiveDebugValues::transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges, const VarLocMap &VarLocIDs) { MachineFunction *MF = MI.getParent()->getParent(); const TargetLowering *TLI = MF->getSubtarget().getTargetLowering(); unsigned SP = TLI->getStackPointerRegisterToSaveRestore(); SparseBitVector<> KillSet; for (const MachineOperand &MO : MI.operands()) { if (MO.isReg() && MO.isDef() && MO.getReg() && TRI->isPhysicalRegister(MO.getReg())) { // Remove ranges of all aliased registers. for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI) for (unsigned ID : OpenRanges.getVarLocs()) if (VarLocIDs[ID].isDescribedByReg() == *RAI) KillSet.set(ID); } else if (MO.isRegMask()) { // Remove ranges of all clobbered registers. Register masks don't usually // list SP as preserved. While the debug info may be off for an // instruction or two around callee-cleanup calls, transferring the // DEBUG_VALUE across the call is still a better user experience. for (unsigned ID : OpenRanges.getVarLocs()) { unsigned Reg = VarLocIDs[ID].isDescribedByReg(); if (Reg && Reg != SP && MO.clobbersPhysReg(Reg)) KillSet.set(ID); } } } OpenRanges.erase(KillSet, VarLocIDs); } /// Terminate all open ranges at the end of the current basic block. bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs) { bool Changed = false; const MachineBasicBlock *CurMBB = MI.getParent(); if (!(MI.isTerminator() || (&MI == &CurMBB->instr_back()))) return false; if (OpenRanges.empty()) return false; DEBUG(for (unsigned ID : OpenRanges.getVarLocs()) { // Copy OpenRanges to OutLocs, if not already present. dbgs() << "Add to OutLocs: "; VarLocIDs[ID].dump(); }); VarLocSet &VLS = OutLocs[CurMBB]; Changed = VLS |= OpenRanges.getVarLocs(); OpenRanges.clear(); return Changed; } /// This routine creates OpenRanges and OutLocs. bool LiveDebugValues::transfer(MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocInMBB &OutLocs, VarLocMap &VarLocIDs) { bool Changed = false; transferDebugValue(MI, OpenRanges, VarLocIDs); transferRegisterDef(MI, OpenRanges, VarLocIDs); Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs); return Changed; } /// This routine joins the analysis results of all incoming edges in @MBB by /// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same /// source variable in all the predecessors of @MBB reside in the same location. bool LiveDebugValues::join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs, const VarLocMap &VarLocIDs) { DEBUG(dbgs() << "join MBB: " << MBB.getName() << "\n"); bool Changed = false; VarLocSet InLocsT; // Temporary incoming locations. // For all predecessors of this MBB, find the set of VarLocs that // can be joined. for (auto p : MBB.predecessors()) { auto OL = OutLocs.find(p); // Join is null in case of empty OutLocs from any of the pred. if (OL == OutLocs.end()) return false; // Just copy over the Out locs to incoming locs for the first predecessor. if (p == *MBB.pred_begin()) { InLocsT = OL->second; continue; } // Join with this predecessor. InLocsT &= OL->second; } if (InLocsT.empty()) return false; VarLocSet &ILS = InLocs[&MBB]; // Insert DBG_VALUE instructions, if not already inserted. VarLocSet Diff = InLocsT; Diff.intersectWithComplement(ILS); for (auto ID : Diff) { // This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a // new range is started for the var from the mbb's beginning by inserting // a new DBG_VALUE. transfer() will end this range however appropriate. const VarLoc &DiffIt = VarLocIDs[ID]; const MachineInstr *DMI = &DiffIt.MI; MachineInstr *MI = BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(), DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(), 0, DMI->getDebugVariable(), DMI->getDebugExpression()); if (DMI->isIndirectDebugValue()) MI->getOperand(1).setImm(DMI->getOperand(1).getImm()); DEBUG(dbgs() << "Inserted: "; MI->dump();); ILS.set(ID); ++NumInserted; Changed = true; } return Changed; } /// Calculate the liveness information for the given machine function and /// extend ranges across basic blocks. bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { DEBUG(dbgs() << "\nDebug Range Extension\n"); bool Changed = false; bool OLChanged = false; bool MBBJoined = false; VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors. OpenRangesSet OpenRanges; // Ranges that are open until end of bb. VarLocInMBB OutLocs; // Ranges that exist beyond bb. VarLocInMBB InLocs; // Ranges that are incoming after joining. DenseMap<unsigned int, MachineBasicBlock *> OrderToBB; DenseMap<MachineBasicBlock *, unsigned int> BBToOrder; std::priority_queue<unsigned int, std::vector<unsigned int>, std::greater<unsigned int>> Worklist; std::priority_queue<unsigned int, std::vector<unsigned int>, std::greater<unsigned int>> Pending; // Initialize every mbb with OutLocs. for (auto &MBB : MF) for (auto &MI : MBB) transfer(MI, OpenRanges, OutLocs, VarLocIDs); DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after initialization", dbgs())); ReversePostOrderTraversal<MachineFunction *> RPOT(&MF); unsigned int RPONumber = 0; for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) { OrderToBB[RPONumber] = *RI; BBToOrder[*RI] = RPONumber; Worklist.push(RPONumber); ++RPONumber; } // This is a standard "union of predecessor outs" dataflow problem. // To solve it, we perform join() and transfer() using the two worklist method // until the ranges converge. // Ranges have converged when both worklists are empty. while (!Worklist.empty() || !Pending.empty()) { // We track what is on the pending worklist to avoid inserting the same // thing twice. We could avoid this with a custom priority queue, but this // is probably not worth it. SmallPtrSet<MachineBasicBlock *, 16> OnPending; while (!Worklist.empty()) { MachineBasicBlock *MBB = OrderToBB[Worklist.top()]; Worklist.pop(); MBBJoined = join(*MBB, OutLocs, InLocs, VarLocIDs); if (MBBJoined) { MBBJoined = false; Changed = true; for (auto &MI : *MBB) OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs); DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after propagating", dbgs())); DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "InLocs after propagating", dbgs())); if (OLChanged) { OLChanged = false; for (auto s : MBB->successors()) if (OnPending.insert(s).second) { Pending.push(BBToOrder[s]); } } } } Worklist.swap(Pending); // At this point, pending must be empty, since it was just the empty // worklist assert(Pending.empty() && "Pending should be empty"); } DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs())); DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs())); return Changed; } bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) { TRI = MF.getSubtarget().getRegisterInfo(); TII = MF.getSubtarget().getInstrInfo(); bool Changed = false; Changed |= ExtendRanges(MF); return Changed; }