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Diffstat (limited to 'llvm/lib/CodeGen/LiveDebugValues.cpp')
| -rw-r--r-- | llvm/lib/CodeGen/LiveDebugValues.cpp | 1448 |
1 files changed, 1448 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/LiveDebugValues.cpp b/llvm/lib/CodeGen/LiveDebugValues.cpp new file mode 100644 index 000000000000..f1b237d83e8c --- /dev/null +++ b/llvm/lib/CodeGen/LiveDebugValues.cpp @@ -0,0 +1,1448 @@ +//===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +/// +/// This pass implements a data flow analysis that propagates debug location +/// information by inserting additional DBG_VALUE insts into the machine +/// instruction stream. Before running, each DBG_VALUE inst corresponds to a +/// source assignment of a variable. Afterwards, a DBG_VALUE inst specifies a +/// variable location for the current basic block (see SourceLevelDebugging.rst). +/// +/// This is a separate pass from DbgValueHistoryCalculator to facilitate +/// testing and improve modularity. +/// +/// Each variable location is represented by a VarLoc object that identifies the +/// source variable, its current machine-location, and the DBG_VALUE inst that +/// specifies the location. Each VarLoc is indexed in the (function-scope) +/// VarLocMap, giving each VarLoc a unique index. Rather than operate directly +/// on machine locations, the dataflow analysis in this pass identifies +/// locations by their index in the VarLocMap, meaning all the variable +/// locations in a block can be described by a sparse vector of VarLocMap +/// indexes. +/// +//===----------------------------------------------------------------------===// + +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/PostOrderIterator.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/SparseBitVector.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/ADT/UniqueVector.h" +#include "llvm/CodeGen/LexicalScopes.h" +#include "llvm/CodeGen/MachineBasicBlock.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineFunctionPass.h" +#include "llvm/CodeGen/MachineInstr.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineMemOperand.h" +#include "llvm/CodeGen/MachineOperand.h" +#include "llvm/CodeGen/PseudoSourceValue.h" +#include "llvm/CodeGen/RegisterScavenging.h" +#include "llvm/CodeGen/TargetFrameLowering.h" +#include "llvm/CodeGen/TargetInstrInfo.h" +#include "llvm/CodeGen/TargetLowering.h" +#include "llvm/CodeGen/TargetPassConfig.h" +#include "llvm/CodeGen/TargetRegisterInfo.h" +#include "llvm/CodeGen/TargetSubtargetInfo.h" +#include "llvm/Config/llvm-config.h" +#include "llvm/IR/DIBuilder.h" +#include "llvm/IR/DebugInfoMetadata.h" +#include "llvm/IR/DebugLoc.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/Module.h" +#include "llvm/MC/MCRegisterInfo.h" +#include "llvm/Pass.h" +#include "llvm/Support/Casting.h" +#include "llvm/Support/Compiler.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" +#include <algorithm> +#include <cassert> +#include <cstdint> +#include <functional> +#include <queue> +#include <tuple> +#include <utility> +#include <vector> + +using namespace llvm; + +#define DEBUG_TYPE "livedebugvalues" + +STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted"); +STATISTIC(NumRemoved, "Number of DBG_VALUE instructions removed"); + +// 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 Register 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() : Register(); +} + +namespace { + +class LiveDebugValues : public MachineFunctionPass { +private: + const TargetRegisterInfo *TRI; + const TargetInstrInfo *TII; + const TargetFrameLowering *TFI; + BitVector CalleeSavedRegs; + LexicalScopes LS; + + enum struct TransferKind { TransferCopy, TransferSpill, TransferRestore }; + + /// Keeps track of lexical scopes associated with a user value's source + /// location. + class UserValueScopes { + DebugLoc DL; + LexicalScopes &LS; + SmallPtrSet<const MachineBasicBlock *, 4> LBlocks; + + public: + UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(std::move(D)), LS(L) {} + + /// Return true if current scope dominates at least one machine + /// instruction in a given machine basic block. + bool dominates(MachineBasicBlock *MBB) { + if (LBlocks.empty()) + LS.getMachineBasicBlocks(DL, LBlocks); + return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB); + } + }; + + using FragmentInfo = DIExpression::FragmentInfo; + using OptFragmentInfo = Optional<DIExpression::FragmentInfo>; + + /// Storage for identifying a potentially inlined instance of a variable, + /// or a fragment thereof. + class DebugVariable { + const DILocalVariable *Variable; + OptFragmentInfo Fragment; + const DILocation *InlinedAt; + + /// Fragment that will overlap all other fragments. Used as default when + /// caller demands a fragment. + static const FragmentInfo DefaultFragment; + + public: + DebugVariable(const DILocalVariable *Var, OptFragmentInfo &&FragmentInfo, + const DILocation *InlinedAt) + : Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {} + + DebugVariable(const DILocalVariable *Var, OptFragmentInfo &FragmentInfo, + const DILocation *InlinedAt) + : Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {} + + DebugVariable(const DILocalVariable *Var, const DIExpression *DIExpr, + const DILocation *InlinedAt) + : DebugVariable(Var, DIExpr->getFragmentInfo(), InlinedAt) {} + + DebugVariable(const MachineInstr &MI) + : DebugVariable(MI.getDebugVariable(), + MI.getDebugExpression()->getFragmentInfo(), + MI.getDebugLoc()->getInlinedAt()) {} + + const DILocalVariable *getVar() const { return Variable; } + const OptFragmentInfo &getFragment() const { return Fragment; } + const DILocation *getInlinedAt() const { return InlinedAt; } + + const FragmentInfo getFragmentDefault() const { + return Fragment.getValueOr(DefaultFragment); + } + + static bool isFragmentDefault(FragmentInfo &F) { + return F == DefaultFragment; + } + + bool operator==(const DebugVariable &Other) const { + return std::tie(Variable, Fragment, InlinedAt) == + std::tie(Other.Variable, Other.Fragment, Other.InlinedAt); + } + + bool operator<(const DebugVariable &Other) const { + return std::tie(Variable, Fragment, InlinedAt) < + std::tie(Other.Variable, Other.Fragment, Other.InlinedAt); + } + }; + + friend struct llvm::DenseMapInfo<DebugVariable>; + + /// A pair of debug variable and value location. + struct VarLoc { + // The location at which a spilled variable resides. It consists of a + // register and an offset. + struct SpillLoc { + unsigned SpillBase; + int SpillOffset; + bool operator==(const SpillLoc &Other) const { + return SpillBase == Other.SpillBase && SpillOffset == Other.SpillOffset; + } + }; + + /// Identity of the variable at this location. + const DebugVariable Var; + + /// The expression applied to this location. + const DIExpression *Expr; + + /// DBG_VALUE to clone var/expr information from if this location + /// is moved. + const MachineInstr &MI; + + mutable UserValueScopes UVS; + enum VarLocKind { + InvalidKind = 0, + RegisterKind, + SpillLocKind, + ImmediateKind, + EntryValueKind + } Kind = InvalidKind; + + /// The value location. Stored separately to avoid repeatedly + /// extracting it from MI. + union { + uint64_t RegNo; + SpillLoc SpillLocation; + uint64_t Hash; + int64_t Immediate; + const ConstantFP *FPImm; + const ConstantInt *CImm; + } Loc; + + VarLoc(const MachineInstr &MI, LexicalScopes &LS) + : Var(MI), Expr(MI.getDebugExpression()), MI(MI), + UVS(MI.getDebugLoc(), LS) { + 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 = MI.isDebugEntryValue() ? EntryValueKind : RegisterKind; + Loc.RegNo = RegNo; + } else if (MI.getOperand(0).isImm()) { + Kind = ImmediateKind; + Loc.Immediate = MI.getOperand(0).getImm(); + } else if (MI.getOperand(0).isFPImm()) { + Kind = ImmediateKind; + Loc.FPImm = MI.getOperand(0).getFPImm(); + } else if (MI.getOperand(0).isCImm()) { + Kind = ImmediateKind; + Loc.CImm = MI.getOperand(0).getCImm(); + } + assert((Kind != ImmediateKind || !MI.isDebugEntryValue()) && + "entry values must be register locations"); + } + + /// Take the variable and machine-location in DBG_VALUE MI, and build an + /// entry location using the given expression. + static VarLoc CreateEntryLoc(const MachineInstr &MI, LexicalScopes &LS, + const DIExpression *EntryExpr) { + VarLoc VL(MI, LS); + VL.Kind = EntryValueKind; + VL.Expr = EntryExpr; + return VL; + } + + /// Copy the register location in DBG_VALUE MI, updating the register to + /// be NewReg. + static VarLoc CreateCopyLoc(const MachineInstr &MI, LexicalScopes &LS, + unsigned NewReg) { + VarLoc VL(MI, LS); + assert(VL.Kind == RegisterKind); + VL.Loc.RegNo = NewReg; + return VL; + } + + /// Take the variable described by DBG_VALUE MI, and create a VarLoc + /// locating it in the specified spill location. + static VarLoc CreateSpillLoc(const MachineInstr &MI, unsigned SpillBase, + int SpillOffset, LexicalScopes &LS) { + VarLoc VL(MI, LS); + assert(VL.Kind == RegisterKind); + VL.Kind = SpillLocKind; + VL.Loc.SpillLocation = {SpillBase, SpillOffset}; + return VL; + } + + /// Create a DBG_VALUE representing this VarLoc in the given function. + /// Copies variable-specific information such as DILocalVariable and + /// inlining information from the original DBG_VALUE instruction, which may + /// have been several transfers ago. + MachineInstr *BuildDbgValue(MachineFunction &MF) const { + const DebugLoc &DbgLoc = MI.getDebugLoc(); + bool Indirect = MI.isIndirectDebugValue(); + const auto &IID = MI.getDesc(); + const DILocalVariable *Var = MI.getDebugVariable(); + const DIExpression *DIExpr = MI.getDebugExpression(); + + switch (Kind) { + case EntryValueKind: + // An entry value is a register location -- but with an updated + // expression. + return BuildMI(MF, DbgLoc, IID, Indirect, Loc.RegNo, Var, Expr); + case RegisterKind: + // Register locations are like the source DBG_VALUE, but with the + // register number from this VarLoc. + return BuildMI(MF, DbgLoc, IID, Indirect, Loc.RegNo, Var, DIExpr); + case SpillLocKind: { + // Spills are indirect DBG_VALUEs, with a base register and offset. + // Use the original DBG_VALUEs expression to build the spilt location + // on top of. FIXME: spill locations created before this pass runs + // are not recognized, and not handled here. + auto *SpillExpr = DIExpression::prepend( + DIExpr, DIExpression::ApplyOffset, Loc.SpillLocation.SpillOffset); + unsigned Base = Loc.SpillLocation.SpillBase; + return BuildMI(MF, DbgLoc, IID, true, Base, Var, SpillExpr); + } + case ImmediateKind: { + MachineOperand MO = MI.getOperand(0); + return BuildMI(MF, DbgLoc, IID, Indirect, MO, Var, DIExpr); + } + case InvalidKind: + llvm_unreachable("Tried to produce DBG_VALUE for invalid VarLoc"); + } + llvm_unreachable("Unrecognized LiveDebugValues.VarLoc.Kind enum"); + } + + /// Is the Loc field a constant or constant object? + bool isConstant() const { return Kind == ImmediateKind; } + + /// If this variable is described by a register, return it, + /// otherwise return 0. + unsigned isDescribedByReg() const { + if (Kind == RegisterKind) + return Loc.RegNo; + return 0; + } + + /// Determine whether the lexical scope of this value's debug location + /// dominates MBB. + bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); } + +#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) + // TRI can be null. + void dump(const TargetRegisterInfo *TRI, raw_ostream &Out = dbgs()) const { + dbgs() << "VarLoc("; + switch (Kind) { + case RegisterKind: + case EntryValueKind: + dbgs() << printReg(Loc.RegNo, TRI); + break; + case SpillLocKind: + dbgs() << printReg(Loc.SpillLocation.SpillBase, TRI); + dbgs() << "[" << Loc.SpillLocation.SpillOffset << "]"; + break; + case ImmediateKind: + dbgs() << Loc.Immediate; + break; + case InvalidKind: + llvm_unreachable("Invalid VarLoc in dump method"); + } + + dbgs() << ", \"" << Var.getVar()->getName() << "\", " << *Expr << ", "; + if (Var.getInlinedAt()) + dbgs() << "!" << Var.getInlinedAt()->getMetadataID() << ")\n"; + else + dbgs() << "(null))\n"; + } +#endif + + bool operator==(const VarLoc &Other) const { + return Kind == Other.Kind && Var == Other.Var && + Loc.Hash == Other.Loc.Hash && Expr == Other.Expr; + } + + /// This operator guarantees that VarLocs are sorted by Variable first. + bool operator<(const VarLoc &Other) const { + return std::tie(Var, Kind, Loc.Hash, Expr) < + std::tie(Other.Var, Other.Kind, Other.Loc.Hash, Other.Expr); + } + }; + + using DebugParamMap = SmallDenseMap<const DILocalVariable *, MachineInstr *>; + using VarLocMap = UniqueVector<VarLoc>; + using VarLocSet = SparseBitVector<>; + using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>; + struct TransferDebugPair { + MachineInstr *TransferInst; /// Instruction where this transfer occurs. + unsigned LocationID; /// Location number for the transfer dest. + }; + using TransferMap = SmallVector<TransferDebugPair, 4>; + + // Types for recording sets of variable fragments that overlap. For a given + // local variable, we record all other fragments of that variable that could + // overlap it, to reduce search time. + using FragmentOfVar = + std::pair<const DILocalVariable *, DIExpression::FragmentInfo>; + using OverlapMap = + DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>; + + // Helper while building OverlapMap, a map of all fragments seen for a given + // DILocalVariable. + using VarToFragments = + DenseMap<const DILocalVariable *, SmallSet<FragmentInfo, 4>>; + + /// 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<DebugVariable, unsigned, 8> Vars; + OverlapMap &OverlappingFragments; + + public: + OpenRangesSet(OverlapMap &_OLapMap) : OverlappingFragments(_OLapMap) {} + + const VarLocSet &getVarLocs() const { return VarLocs; } + + /// Terminate all open ranges for Var by removing it from the set. + void erase(DebugVariable Var); + + /// 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, DebugVariable Var) { + VarLocs.set(VarLocID); + Vars.insert({Var, VarLocID}); + } + + /// Insert a set of ranges. + void insertFromLocSet(const VarLocSet &ToLoad, const VarLocMap &Map) { + for (unsigned Id : ToLoad) { + const VarLoc &Var = Map[Id]; + insert(Id, Var.Var); + } + } + + /// 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(); + } + }; + + /// Tests whether this instruction is a spill to a stack location. + bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF); + + /// Decide if @MI is a spill instruction and return true if it is. We use 2 + /// criteria to make this decision: + /// - Is this instruction a store to a spill slot? + /// - Is there a register operand that is both used and killed? + /// TODO: Store optimization can fold spills into other stores (including + /// other spills). We do not handle this yet (more than one memory operand). + bool isLocationSpill(const MachineInstr &MI, MachineFunction *MF, + unsigned &Reg); + + /// If a given instruction is identified as a spill, return the spill location + /// and set \p Reg to the spilled register. + Optional<VarLoc::SpillLoc> isRestoreInstruction(const MachineInstr &MI, + MachineFunction *MF, + unsigned &Reg); + /// Given a spill instruction, extract the register and offset used to + /// address the spill location in a target independent way. + VarLoc::SpillLoc extractSpillBaseRegAndOffset(const MachineInstr &MI); + void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges, + TransferMap &Transfers, VarLocMap &VarLocIDs, + unsigned OldVarID, TransferKind Kind, + unsigned NewReg = 0); + + void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs); + void transferSpillOrRestoreInst(MachineInstr &MI, OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs, TransferMap &Transfers); + void emitEntryValues(MachineInstr &MI, OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs, TransferMap &Transfers, + DebugParamMap &DebugEntryVals, + SparseBitVector<> &KillSet); + void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs, TransferMap &Transfers); + void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs, TransferMap &Transfers, + DebugParamMap &DebugEntryVals); + bool transferTerminator(MachineBasicBlock *MBB, OpenRangesSet &OpenRanges, + VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs); + + void process(MachineInstr &MI, OpenRangesSet &OpenRanges, + VarLocInMBB &OutLocs, VarLocMap &VarLocIDs, + TransferMap &Transfers, DebugParamMap &DebugEntryVals, + OverlapMap &OverlapFragments, + VarToFragments &SeenFragments); + + void accumulateFragmentMap(MachineInstr &MI, VarToFragments &SeenFragments, + OverlapMap &OLapMap); + + bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs, + const VarLocMap &VarLocIDs, + SmallPtrSet<const MachineBasicBlock *, 16> &Visited, + SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks, + VarLocInMBB &PendingInLocs); + + /// Create DBG_VALUE insts for inlocs that have been propagated but + /// had their instruction creation deferred. + void flushPendingLocs(VarLocInMBB &PendingInLocs, 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::NoVRegs); + } + + /// 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; +}; + +} // end anonymous namespace + +namespace llvm { + +template <> struct DenseMapInfo<LiveDebugValues::DebugVariable> { + using DV = LiveDebugValues::DebugVariable; + using OptFragmentInfo = LiveDebugValues::OptFragmentInfo; + using FragmentInfo = LiveDebugValues::FragmentInfo; + + // Empty key: no key should be generated that has no DILocalVariable. + static inline DV getEmptyKey() { + return DV(nullptr, OptFragmentInfo(), nullptr); + } + + // Difference in tombstone is that the Optional is meaningful + static inline DV getTombstoneKey() { + return DV(nullptr, OptFragmentInfo({0, 0}), nullptr); + } + + static unsigned getHashValue(const DV &D) { + unsigned HV = 0; + const OptFragmentInfo &Fragment = D.getFragment(); + if (Fragment) + HV = DenseMapInfo<FragmentInfo>::getHashValue(*Fragment); + + return hash_combine(D.getVar(), HV, D.getInlinedAt()); + } + + static bool isEqual(const DV &A, const DV &B) { return A == B; } +}; + +} // namespace llvm + +//===----------------------------------------------------------------------===// +// Implementation +//===----------------------------------------------------------------------===// + +const DIExpression::FragmentInfo + LiveDebugValues::DebugVariable::DefaultFragment = { + std::numeric_limits<uint64_t>::max(), + std::numeric_limits<uint64_t>::min()}; + +char LiveDebugValues::ID = 0; + +char &llvm::LiveDebugValuesID = LiveDebugValues::ID; + +INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "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); +} + +/// Erase a variable from the set of open ranges, and additionally erase any +/// fragments that may overlap it. +void LiveDebugValues::OpenRangesSet::erase(DebugVariable Var) { + // Erasure helper. + auto DoErase = [this](DebugVariable VarToErase) { + auto It = Vars.find(VarToErase); + if (It != Vars.end()) { + unsigned ID = It->second; + VarLocs.reset(ID); + Vars.erase(It); + } + }; + + // Erase the variable/fragment that ends here. + DoErase(Var); + + // Extract the fragment. Interpret an empty fragment as one that covers all + // possible bits. + FragmentInfo ThisFragment = Var.getFragmentDefault(); + + // There may be fragments that overlap the designated fragment. Look them up + // in the pre-computed overlap map, and erase them too. + auto MapIt = OverlappingFragments.find({Var.getVar(), ThisFragment}); + if (MapIt != OverlappingFragments.end()) { + for (auto Fragment : MapIt->second) { + LiveDebugValues::OptFragmentInfo FragmentHolder; + if (!DebugVariable::isFragmentDefault(Fragment)) + FragmentHolder = LiveDebugValues::OptFragmentInfo(Fragment); + DoErase({Var.getVar(), FragmentHolder, Var.getInlinedAt()}); + } + } +} + +//===----------------------------------------------------------------------===// +// Debug Range Extension Implementation +//===----------------------------------------------------------------------===// + +#ifndef NDEBUG +void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF, + const VarLocInMBB &V, + const VarLocMap &VarLocIDs, + const char *msg, + raw_ostream &Out) const { + Out << '\n' << msg << '\n'; + for (const MachineBasicBlock &BB : MF) { + const VarLocSet &L = V.lookup(&BB); + if (L.empty()) + continue; + Out << "MBB: " << BB.getNumber() << ":\n"; + for (unsigned VLL : L) { + const VarLoc &VL = VarLocIDs[VLL]; + Out << " Var: " << VL.Var.getVar()->getName(); + Out << " MI: "; + VL.dump(TRI, Out); + } + } + Out << "\n"; +} +#endif + +LiveDebugValues::VarLoc::SpillLoc +LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI) { + assert(MI.hasOneMemOperand() && + "Spill instruction does not have exactly one memory operand?"); + auto MMOI = MI.memoperands_begin(); + const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue(); + assert(PVal->kind() == PseudoSourceValue::FixedStack && + "Inconsistent memory operand in spill instruction"); + int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex(); + const MachineBasicBlock *MBB = MI.getParent(); + unsigned Reg; + int Offset = TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg); + return {Reg, Offset}; +} + +/// 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 DIExpression *Expr = MI.getDebugExpression(); + 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, Expr, InlinedAt); + OpenRanges.erase(V); + + // Add the VarLoc to OpenRanges from this DBG_VALUE. + unsigned ID; + if (isDbgValueDescribedByReg(MI) || MI.getOperand(0).isImm() || + MI.getOperand(0).isFPImm() || MI.getOperand(0).isCImm()) { + // Use normal VarLoc constructor for registers and immediates. + VarLoc VL(MI, LS); + ID = VarLocIDs.insert(VL); + OpenRanges.insert(ID, VL.Var); + } else if (MI.hasOneMemOperand()) { + llvm_unreachable("DBG_VALUE with mem operand encountered after regalloc?"); + } else { + // This must be an undefined location. We should leave OpenRanges closed. + assert(MI.getOperand(0).isReg() && MI.getOperand(0).getReg() == 0 && + "Unexpected non-undef DBG_VALUE encountered"); + } +} + +void LiveDebugValues::emitEntryValues(MachineInstr &MI, + OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs, + TransferMap &Transfers, + DebugParamMap &DebugEntryVals, + SparseBitVector<> &KillSet) { + for (unsigned ID : KillSet) { + if (!VarLocIDs[ID].Var.getVar()->isParameter()) + continue; + + const MachineInstr *CurrDebugInstr = &VarLocIDs[ID].MI; + + // If parameter's DBG_VALUE is not in the map that means we can't + // generate parameter's entry value. + if (!DebugEntryVals.count(CurrDebugInstr->getDebugVariable())) + continue; + + auto ParamDebugInstr = DebugEntryVals[CurrDebugInstr->getDebugVariable()]; + DIExpression *NewExpr = DIExpression::prepend( + ParamDebugInstr->getDebugExpression(), DIExpression::EntryValue); + + VarLoc EntryLoc = VarLoc::CreateEntryLoc(*ParamDebugInstr, LS, NewExpr); + + unsigned EntryValLocID = VarLocIDs.insert(EntryLoc); + Transfers.push_back({&MI, EntryValLocID}); + OpenRanges.insert(EntryValLocID, EntryLoc.Var); + } +} + +/// Create new TransferDebugPair and insert it in \p Transfers. The VarLoc +/// with \p OldVarID should be deleted form \p OpenRanges and replaced with +/// new VarLoc. If \p NewReg is different than default zero value then the +/// new location will be register location created by the copy like instruction, +/// otherwise it is variable's location on the stack. +void LiveDebugValues::insertTransferDebugPair( + MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers, + VarLocMap &VarLocIDs, unsigned OldVarID, TransferKind Kind, + unsigned NewReg) { + const MachineInstr *DebugInstr = &VarLocIDs[OldVarID].MI; + + auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &DebugInstr, + &VarLocIDs](VarLoc &VL) { + unsigned LocId = VarLocIDs.insert(VL); + + // Close this variable's previous location range. + DebugVariable V(*DebugInstr); + OpenRanges.erase(V); + + // Record the new location as an open range, and a postponed transfer + // inserting a DBG_VALUE for this location. + OpenRanges.insert(LocId, VL.Var); + TransferDebugPair MIP = {&MI, LocId}; + Transfers.push_back(MIP); + }; + + // End all previous ranges of Var. + OpenRanges.erase(VarLocIDs[OldVarID].Var); + switch (Kind) { + case TransferKind::TransferCopy: { + assert(NewReg && + "No register supplied when handling a copy of a debug value"); + // Create a DBG_VALUE instruction to describe the Var in its new + // register location. + VarLoc VL = VarLoc::CreateCopyLoc(*DebugInstr, LS, NewReg); + ProcessVarLoc(VL); + LLVM_DEBUG({ + dbgs() << "Creating VarLoc for register copy:"; + VL.dump(TRI); + }); + return; + } + case TransferKind::TransferSpill: { + // Create a DBG_VALUE instruction to describe the Var in its spilled + // location. + VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI); + VarLoc VL = VarLoc::CreateSpillLoc(*DebugInstr, SpillLocation.SpillBase, + SpillLocation.SpillOffset, LS); + ProcessVarLoc(VL); + LLVM_DEBUG({ + dbgs() << "Creating VarLoc for spill:"; + VL.dump(TRI); + }); + return; + } + case TransferKind::TransferRestore: { + assert(NewReg && + "No register supplied when handling a restore of a debug value"); + MachineFunction *MF = MI.getMF(); + DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent()); + // DebugInstr refers to the pre-spill location, therefore we can reuse + // its expression. + VarLoc VL = VarLoc::CreateCopyLoc(*DebugInstr, LS, NewReg); + ProcessVarLoc(VL); + LLVM_DEBUG({ + dbgs() << "Creating VarLoc for restore:"; + VL.dump(TRI); + }); + return; + } + } + llvm_unreachable("Invalid transfer kind"); +} + +/// A definition of a register may mark the end of a range. +void LiveDebugValues::transferRegisterDef( + MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocMap &VarLocIDs, + TransferMap &Transfers, DebugParamMap &DebugEntryVals) { + MachineFunction *MF = MI.getMF(); + const TargetLowering *TLI = MF->getSubtarget().getTargetLowering(); + unsigned SP = TLI->getStackPointerRegisterToSaveRestore(); + SparseBitVector<> KillSet; + for (const MachineOperand &MO : MI.operands()) { + // Determine whether the operand is a register def. Assume that call + // instructions never clobber SP, because some backends (e.g., AArch64) + // never list SP in the regmask. + if (MO.isReg() && MO.isDef() && MO.getReg() && + Register::isPhysicalRegister(MO.getReg()) && + !(MI.isCall() && MO.getReg() == SP)) { + // 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); + + if (auto *TPC = getAnalysisIfAvailable<TargetPassConfig>()) { + auto &TM = TPC->getTM<TargetMachine>(); + if (TM.Options.EnableDebugEntryValues) + emitEntryValues(MI, OpenRanges, VarLocIDs, Transfers, DebugEntryVals, + KillSet); + } +} + +bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI, + MachineFunction *MF) { + // TODO: Handle multiple stores folded into one. + if (!MI.hasOneMemOperand()) + return false; + + if (!MI.getSpillSize(TII) && !MI.getFoldedSpillSize(TII)) + return false; // This is not a spill instruction, since no valid size was + // returned from either function. + + return true; +} + +bool LiveDebugValues::isLocationSpill(const MachineInstr &MI, + MachineFunction *MF, unsigned &Reg) { + if (!isSpillInstruction(MI, MF)) + return false; + + auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) { + if (!MO.isReg() || !MO.isUse()) { + Reg = 0; + return false; + } + Reg = MO.getReg(); + return MO.isKill(); + }; + + for (const MachineOperand &MO : MI.operands()) { + // In a spill instruction generated by the InlineSpiller the spilled + // register has its kill flag set. + if (isKilledReg(MO, Reg)) + return true; + if (Reg != 0) { + // Check whether next instruction kills the spilled register. + // FIXME: Current solution does not cover search for killed register in + // bundles and instructions further down the chain. + auto NextI = std::next(MI.getIterator()); + // Skip next instruction that points to basic block end iterator. + if (MI.getParent()->end() == NextI) + continue; + unsigned RegNext; + for (const MachineOperand &MONext : NextI->operands()) { + // Return true if we came across the register from the + // previous spill instruction that is killed in NextI. + if (isKilledReg(MONext, RegNext) && RegNext == Reg) + return true; + } + } + } + // Return false if we didn't find spilled register. + return false; +} + +Optional<LiveDebugValues::VarLoc::SpillLoc> +LiveDebugValues::isRestoreInstruction(const MachineInstr &MI, + MachineFunction *MF, unsigned &Reg) { + if (!MI.hasOneMemOperand()) + return None; + + // FIXME: Handle folded restore instructions with more than one memory + // operand. + if (MI.getRestoreSize(TII)) { + Reg = MI.getOperand(0).getReg(); + return extractSpillBaseRegAndOffset(MI); + } + return None; +} + +/// A spilled register may indicate that we have to end the current range of +/// a variable and create a new one for the spill location. +/// A restored register may indicate the reverse situation. +/// We don't want to insert any instructions in process(), so we just create +/// the DBG_VALUE without inserting it and keep track of it in \p Transfers. +/// It will be inserted into the BB when we're done iterating over the +/// instructions. +void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI, + OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs, + TransferMap &Transfers) { + MachineFunction *MF = MI.getMF(); + TransferKind TKind; + unsigned Reg; + Optional<VarLoc::SpillLoc> Loc; + + LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump();); + + // First, if there are any DBG_VALUEs pointing at a spill slot that is + // written to, then close the variable location. The value in memory + // will have changed. + VarLocSet KillSet; + if (isSpillInstruction(MI, MF)) { + Loc = extractSpillBaseRegAndOffset(MI); + for (unsigned ID : OpenRanges.getVarLocs()) { + const VarLoc &VL = VarLocIDs[ID]; + if (VL.Kind == VarLoc::SpillLocKind && VL.Loc.SpillLocation == *Loc) { + // This location is overwritten by the current instruction -- terminate + // the open range, and insert an explicit DBG_VALUE $noreg. + // + // Doing this at a later stage would require re-interpreting all + // DBG_VALUes and DIExpressions to identify whether they point at + // memory, and then analysing all memory writes to see if they + // overwrite that memory, which is expensive. + // + // At this stage, we already know which DBG_VALUEs are for spills and + // where they are located; it's best to fix handle overwrites now. + KillSet.set(ID); + VarLoc UndefVL = VarLoc::CreateCopyLoc(VL.MI, LS, 0); + unsigned UndefLocID = VarLocIDs.insert(UndefVL); + Transfers.push_back({&MI, UndefLocID}); + } + } + OpenRanges.erase(KillSet, VarLocIDs); + } + + // Try to recognise spill and restore instructions that may create a new + // variable location. + if (isLocationSpill(MI, MF, Reg)) { + TKind = TransferKind::TransferSpill; + LLVM_DEBUG(dbgs() << "Recognized as spill: "; MI.dump();); + LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI) + << "\n"); + } else { + if (!(Loc = isRestoreInstruction(MI, MF, Reg))) + return; + TKind = TransferKind::TransferRestore; + LLVM_DEBUG(dbgs() << "Recognized as restore: "; MI.dump();); + LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI) + << "\n"); + } + // Check if the register or spill location is the location of a debug value. + for (unsigned ID : OpenRanges.getVarLocs()) { + if (TKind == TransferKind::TransferSpill && + VarLocIDs[ID].isDescribedByReg() == Reg) { + LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '(' + << VarLocIDs[ID].Var.getVar()->getName() << ")\n"); + } else if (TKind == TransferKind::TransferRestore && + VarLocIDs[ID].Kind == VarLoc::SpillLocKind && + VarLocIDs[ID].Loc.SpillLocation == *Loc) { + LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '(' + << VarLocIDs[ID].Var.getVar()->getName() << ")\n"); + } else + continue; + insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID, TKind, + Reg); + return; + } +} + +/// If \p MI is a register copy instruction, that copies a previously tracked +/// value from one register to another register that is callee saved, we +/// create new DBG_VALUE instruction described with copy destination register. +void LiveDebugValues::transferRegisterCopy(MachineInstr &MI, + OpenRangesSet &OpenRanges, + VarLocMap &VarLocIDs, + TransferMap &Transfers) { + const MachineOperand *SrcRegOp, *DestRegOp; + + if (!TII->isCopyInstr(MI, SrcRegOp, DestRegOp) || !SrcRegOp->isKill() || + !DestRegOp->isDef()) + return; + + auto isCalleSavedReg = [&](unsigned Reg) { + for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI) + if (CalleeSavedRegs.test(*RAI)) + return true; + return false; + }; + + Register SrcReg = SrcRegOp->getReg(); + Register DestReg = DestRegOp->getReg(); + + // We want to recognize instructions where destination register is callee + // saved register. If register that could be clobbered by the call is + // included, there would be a great chance that it is going to be clobbered + // soon. It is more likely that previous register location, which is callee + // saved, is going to stay unclobbered longer, even if it is killed. + if (!isCalleSavedReg(DestReg)) + return; + + for (unsigned ID : OpenRanges.getVarLocs()) { + if (VarLocIDs[ID].isDescribedByReg() == SrcReg) { + insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID, + TransferKind::TransferCopy, DestReg); + return; + } + } +} + +/// Terminate all open ranges at the end of the current basic block. +bool LiveDebugValues::transferTerminator(MachineBasicBlock *CurMBB, + OpenRangesSet &OpenRanges, + VarLocInMBB &OutLocs, + const VarLocMap &VarLocIDs) { + bool Changed = false; + + LLVM_DEBUG(for (unsigned ID + : OpenRanges.getVarLocs()) { + // Copy OpenRanges to OutLocs, if not already present. + dbgs() << "Add to OutLocs in MBB #" << CurMBB->getNumber() << ": "; + VarLocIDs[ID].dump(TRI); + }); + VarLocSet &VLS = OutLocs[CurMBB]; + Changed = VLS != OpenRanges.getVarLocs(); + // New OutLocs set may be different due to spill, restore or register + // copy instruction processing. + if (Changed) + VLS = OpenRanges.getVarLocs(); + OpenRanges.clear(); + return Changed; +} + +/// Accumulate a mapping between each DILocalVariable fragment and other +/// fragments of that DILocalVariable which overlap. This reduces work during +/// the data-flow stage from "Find any overlapping fragments" to "Check if the +/// known-to-overlap fragments are present". +/// \param MI A previously unprocessed DEBUG_VALUE instruction to analyze for +/// fragment usage. +/// \param SeenFragments Map from DILocalVariable to all fragments of that +/// Variable which are known to exist. +/// \param OverlappingFragments The overlap map being constructed, from one +/// Var/Fragment pair to a vector of fragments known to overlap. +void LiveDebugValues::accumulateFragmentMap(MachineInstr &MI, + VarToFragments &SeenFragments, + OverlapMap &OverlappingFragments) { + DebugVariable MIVar(MI); + FragmentInfo ThisFragment = MIVar.getFragmentDefault(); + + // If this is the first sighting of this variable, then we are guaranteed + // there are currently no overlapping fragments either. Initialize the set + // of seen fragments, record no overlaps for the current one, and return. + auto SeenIt = SeenFragments.find(MIVar.getVar()); + if (SeenIt == SeenFragments.end()) { + SmallSet<FragmentInfo, 4> OneFragment; + OneFragment.insert(ThisFragment); + SeenFragments.insert({MIVar.getVar(), OneFragment}); + + OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}}); + return; + } + + // If this particular Variable/Fragment pair already exists in the overlap + // map, it has already been accounted for. + auto IsInOLapMap = + OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}}); + if (!IsInOLapMap.second) + return; + + auto &ThisFragmentsOverlaps = IsInOLapMap.first->second; + auto &AllSeenFragments = SeenIt->second; + + // Otherwise, examine all other seen fragments for this variable, with "this" + // fragment being a previously unseen fragment. Record any pair of + // overlapping fragments. + for (auto &ASeenFragment : AllSeenFragments) { + // Does this previously seen fragment overlap? + if (DIExpression::fragmentsOverlap(ThisFragment, ASeenFragment)) { + // Yes: Mark the current fragment as being overlapped. + ThisFragmentsOverlaps.push_back(ASeenFragment); + // Mark the previously seen fragment as being overlapped by the current + // one. + auto ASeenFragmentsOverlaps = + OverlappingFragments.find({MIVar.getVar(), ASeenFragment}); + assert(ASeenFragmentsOverlaps != OverlappingFragments.end() && + "Previously seen var fragment has no vector of overlaps"); + ASeenFragmentsOverlaps->second.push_back(ThisFragment); + } + } + + AllSeenFragments.insert(ThisFragment); +} + +/// This routine creates OpenRanges and OutLocs. +void LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges, + VarLocInMBB &OutLocs, VarLocMap &VarLocIDs, + TransferMap &Transfers, + DebugParamMap &DebugEntryVals, + OverlapMap &OverlapFragments, + VarToFragments &SeenFragments) { + transferDebugValue(MI, OpenRanges, VarLocIDs); + transferRegisterDef(MI, OpenRanges, VarLocIDs, Transfers, + DebugEntryVals); + transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers); + transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers); +} + +/// 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, + SmallPtrSet<const MachineBasicBlock *, 16> &Visited, + SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks, + VarLocInMBB &PendingInLocs) { + LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n"); + bool Changed = false; + + VarLocSet InLocsT; // Temporary incoming locations. + + // For all predecessors of this MBB, find the set of VarLocs that + // can be joined. + int NumVisited = 0; + for (auto p : MBB.predecessors()) { + // Ignore backedges if we have not visited the predecessor yet. As the + // predecessor hasn't yet had locations propagated into it, most locations + // will not yet be valid, so treat them as all being uninitialized and + // potentially valid. If a location guessed to be correct here is + // invalidated later, we will remove it when we revisit this block. + if (!Visited.count(p)) { + LLVM_DEBUG(dbgs() << " ignoring unvisited pred MBB: " << p->getNumber() + << "\n"); + continue; + } + 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 visited + // predecessor, and for all other predecessors join the Out locs. + if (!NumVisited) + InLocsT = OL->second; + else + InLocsT &= OL->second; + + LLVM_DEBUG({ + if (!InLocsT.empty()) { + for (auto ID : InLocsT) + dbgs() << " gathered candidate incoming var: " + << VarLocIDs[ID].Var.getVar()->getName() << "\n"; + } + }); + + NumVisited++; + } + + // Filter out DBG_VALUES that are out of scope. + VarLocSet KillSet; + bool IsArtificial = ArtificialBlocks.count(&MBB); + if (!IsArtificial) { + for (auto ID : InLocsT) { + if (!VarLocIDs[ID].dominates(MBB)) { + KillSet.set(ID); + LLVM_DEBUG({ + auto Name = VarLocIDs[ID].Var.getVar()->getName(); + dbgs() << " killing " << Name << ", it doesn't dominate MBB\n"; + }); + } + } + } + InLocsT.intersectWithComplement(KillSet); + + // As we are processing blocks in reverse post-order we + // should have processed at least one predecessor, unless it + // is the entry block which has no predecessor. + assert((NumVisited || MBB.pred_empty()) && + "Should have processed at least one predecessor"); + + VarLocSet &ILS = InLocs[&MBB]; + VarLocSet &Pending = PendingInLocs[&MBB]; + + // New locations will have DBG_VALUE insts inserted at the start of the + // block, after location propagation has finished. Record the insertions + // that we need to perform in the Pending set. + VarLocSet Diff = InLocsT; + Diff.intersectWithComplement(ILS); + for (auto ID : Diff) { + Pending.set(ID); + ILS.set(ID); + ++NumInserted; + Changed = true; + } + + // We may have lost locations by learning about a predecessor that either + // loses or moves a variable. Find any locations in ILS that are not in the + // new in-locations, and delete those. + VarLocSet Removed = ILS; + Removed.intersectWithComplement(InLocsT); + for (auto ID : Removed) { + Pending.reset(ID); + ILS.reset(ID); + ++NumRemoved; + Changed = true; + } + + return Changed; +} + +void LiveDebugValues::flushPendingLocs(VarLocInMBB &PendingInLocs, + VarLocMap &VarLocIDs) { + // PendingInLocs records all locations propagated into blocks, which have + // not had DBG_VALUE insts created. Go through and create those insts now. + for (auto &Iter : PendingInLocs) { + // Map is keyed on a constant pointer, unwrap it so we can insert insts. + auto &MBB = const_cast<MachineBasicBlock &>(*Iter.first); + VarLocSet &Pending = Iter.second; + + for (unsigned ID : Pending) { + // The ID location is live-in to MBB -- work out what kind of machine + // location it is and create a DBG_VALUE. + const VarLoc &DiffIt = VarLocIDs[ID]; + MachineInstr *MI = DiffIt.BuildDbgValue(*MBB.getParent()); + MBB.insert(MBB.instr_begin(), MI); + + (void)MI; + LLVM_DEBUG(dbgs() << "Inserted: "; MI->dump();); + } + } +} + +/// Calculate the liveness information for the given machine function and +/// extend ranges across basic blocks. +bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { + LLVM_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. + OverlapMap OverlapFragments; // Map of overlapping variable fragments + OpenRangesSet OpenRanges(OverlapFragments); + // Ranges that are open until end of bb. + VarLocInMBB OutLocs; // Ranges that exist beyond bb. + VarLocInMBB InLocs; // Ranges that are incoming after joining. + TransferMap Transfers; // DBG_VALUEs associated with spills. + VarLocInMBB PendingInLocs; // Ranges that are incoming after joining, but + // that we have deferred creating DBG_VALUE insts + // for immediately. + + VarToFragments SeenFragments; + + // Blocks which are artificial, i.e. blocks which exclusively contain + // instructions without locations, or with line 0 locations. + SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks; + + 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; + + // Besides parameter's modification, check whether a DBG_VALUE is inlined + // in order to deduce whether the variable that it tracks comes from + // a different function. If that is the case we can't track its entry value. + auto IsUnmodifiedFuncParam = [&](const MachineInstr &MI) { + auto *DIVar = MI.getDebugVariable(); + return DIVar->isParameter() && DIVar->isNotModified() && + !MI.getDebugLoc()->getInlinedAt(); + }; + + const TargetLowering *TLI = MF.getSubtarget().getTargetLowering(); + unsigned SP = TLI->getStackPointerRegisterToSaveRestore(); + Register FP = TRI->getFrameRegister(MF); + auto IsRegOtherThanSPAndFP = [&](const MachineOperand &Op) -> bool { + return Op.isReg() && Op.getReg() != SP && Op.getReg() != FP; + }; + + // Working set of currently collected debug variables mapped to DBG_VALUEs + // representing candidates for production of debug entry values. + DebugParamMap DebugEntryVals; + + MachineBasicBlock &First_MBB = *(MF.begin()); + // Only in the case of entry MBB collect DBG_VALUEs representing + // function parameters in order to generate debug entry values for them. + // Currently, we generate debug entry values only for parameters that are + // unmodified throughout the function and located in a register. + // TODO: Add support for parameters that are described as fragments. + // TODO: Add support for modified arguments that can be expressed + // by using its entry value. + // TODO: Add support for local variables that are expressed in terms of + // parameters entry values. + for (auto &MI : First_MBB) + if (MI.isDebugValue() && IsUnmodifiedFuncParam(MI) && + !MI.isIndirectDebugValue() && IsRegOtherThanSPAndFP(MI.getOperand(0)) && + !DebugEntryVals.count(MI.getDebugVariable()) && + !MI.getDebugExpression()->isFragment()) + DebugEntryVals[MI.getDebugVariable()] = &MI; + + // Initialize per-block structures and scan for fragment overlaps. + for (auto &MBB : MF) { + PendingInLocs[&MBB] = VarLocSet(); + + for (auto &MI : MBB) { + if (MI.isDebugValue()) + accumulateFragmentMap(MI, SeenFragments, OverlapFragments); + } + } + + auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool { + if (const DebugLoc &DL = MI.getDebugLoc()) + return DL.getLine() != 0; + return false; + }; + for (auto &MBB : MF) + if (none_of(MBB.instrs(), hasNonArtificialLocation)) + ArtificialBlocks.insert(&MBB); + + LLVM_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 process() using the two worklist method + // until the ranges converge. + // Ranges have converged when both worklists are empty. + SmallPtrSet<const MachineBasicBlock *, 16> Visited; + 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; + LLVM_DEBUG(dbgs() << "Processing Worklist\n"); + while (!Worklist.empty()) { + MachineBasicBlock *MBB = OrderToBB[Worklist.top()]; + Worklist.pop(); + MBBJoined = join(*MBB, OutLocs, InLocs, VarLocIDs, Visited, + ArtificialBlocks, PendingInLocs); + MBBJoined |= Visited.insert(MBB).second; + if (MBBJoined) { + MBBJoined = false; + Changed = true; + // Now that we have started to extend ranges across BBs we need to + // examine spill instructions to see whether they spill registers that + // correspond to user variables. + // First load any pending inlocs. + OpenRanges.insertFromLocSet(PendingInLocs[MBB], VarLocIDs); + for (auto &MI : *MBB) + process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers, + DebugEntryVals, OverlapFragments, SeenFragments); + OLChanged |= transferTerminator(MBB, OpenRanges, OutLocs, VarLocIDs); + + LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, + "OutLocs after propagating", dbgs())); + LLVM_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"); + } + + // Add any DBG_VALUE instructions created by location transfers. + for (auto &TR : Transfers) { + MachineBasicBlock *MBB = TR.TransferInst->getParent(); + const VarLoc &VL = VarLocIDs[TR.LocationID]; + MachineInstr *MI = VL.BuildDbgValue(MF); + MBB->insertAfterBundle(TR.TransferInst->getIterator(), MI); + } + Transfers.clear(); + + // Deferred inlocs will not have had any DBG_VALUE insts created; do + // that now. + flushPendingLocs(PendingInLocs, VarLocIDs); + + LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs())); + LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs())); + return Changed; +} + +bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) { + if (!MF.getFunction().getSubprogram()) + // LiveDebugValues will already have removed all DBG_VALUEs. + return false; + + // Skip functions from NoDebug compilation units. + if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() == + DICompileUnit::NoDebug) + return false; + + TRI = MF.getSubtarget().getRegisterInfo(); + TII = MF.getSubtarget().getInstrInfo(); + TFI = MF.getSubtarget().getFrameLowering(); + TFI->determineCalleeSaves(MF, CalleeSavedRegs, + std::make_unique<RegScavenger>().get()); + LS.initialize(MF); + + bool Changed = ExtendRanges(MF); + return Changed; +} |