diff options
Diffstat (limited to 'lib/CodeGen/LiveDebugValues.cpp')
| -rw-r--r-- | lib/CodeGen/LiveDebugValues.cpp | 510 |
1 files changed, 321 insertions, 189 deletions
diff --git a/lib/CodeGen/LiveDebugValues.cpp b/lib/CodeGen/LiveDebugValues.cpp index a669e64692b9..f1b237d83e8c 100644 --- a/lib/CodeGen/LiveDebugValues.cpp +++ b/lib/CodeGen/LiveDebugValues.cpp @@ -7,14 +7,23 @@ //===----------------------------------------------------------------------===// /// /// 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. +/// 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" @@ -68,6 +77,7 @@ 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. @@ -179,8 +189,16 @@ private: } }; + /// Identity of the variable at this location. const DebugVariable Var; - const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE. + + /// 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, @@ -201,9 +219,9 @@ private: const ConstantInt *CImm; } Loc; - VarLoc(const MachineInstr &MI, LexicalScopes &LS, - VarLocKind K = InvalidKind) - : Var(MI), MI(MI), UVS(MI.getDebugLoc(), LS){ + 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"); @@ -225,17 +243,78 @@ private: "entry values must be register locations"); } - /// The constructor for spill locations. - VarLoc(const MachineInstr &MI, unsigned SpillBase, int SpillOffset, - LexicalScopes &LS) - : Var(MI), MI(MI), UVS(MI.getDebugLoc(), LS) { - assert(MI.isDebugValue() && "not a DBG_VALUE"); - assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE"); - Kind = SpillLocKind; - Loc.SpillLocation = {SpillBase, SpillOffset}; + /// 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; } - // Is the Loc field a constant or constant object? + /// 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, @@ -251,18 +330,42 @@ private: bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); } #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) - LLVM_DUMP_METHOD void dump() const { MI.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; + 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) < - std::tie(Other.Var, Other.Kind, Other.Loc.Hash); + return std::tie(Var, Kind, Loc.Hash, Expr) < + std::tie(Other.Var, Other.Kind, Other.Loc.Hash, Other.Expr); } }; @@ -271,8 +374,8 @@ private: using VarLocSet = SparseBitVector<>; using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>; struct TransferDebugPair { - MachineInstr *TransferInst; - MachineInstr *DebugInst; + MachineInstr *TransferInst; /// Instruction where this transfer occurs. + unsigned LocationID; /// Location number for the transfer dest. }; using TransferMap = SmallVector<TransferDebugPair, 4>; @@ -320,6 +423,14 @@ private: 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(); @@ -333,8 +444,18 @@ private: } }; - bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF, - unsigned &Reg); + /// 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, @@ -361,13 +482,13 @@ private: void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocMap &VarLocIDs, TransferMap &Transfers, DebugParamMap &DebugEntryVals); - bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges, - VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs); + bool transferTerminator(MachineBasicBlock *MBB, OpenRangesSet &OpenRanges, + VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs); - bool process(MachineInstr &MI, OpenRangesSet &OpenRanges, + void process(MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocInMBB &OutLocs, VarLocMap &VarLocIDs, TransferMap &Transfers, DebugParamMap &DebugEntryVals, - bool transferChanges, OverlapMap &OverlapFragments, + OverlapMap &OverlapFragments, VarToFragments &SeenFragments); void accumulateFragmentMap(MachineInstr &MI, VarToFragments &SeenFragments, @@ -376,7 +497,12 @@ private: bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs, const VarLocMap &VarLocIDs, SmallPtrSet<const MachineBasicBlock *, 16> &Visited, - SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks); + 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); @@ -518,7 +644,7 @@ void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF, const VarLoc &VL = VarLocIDs[VLL]; Out << " Var: " << VL.Var.getVar()->getName(); Out << " MI: "; - VL.dump(); + VL.dump(TRI, Out); } } Out << "\n"; @@ -567,11 +693,7 @@ void LiveDebugValues::transferDebugValue(const MachineInstr &MI, ID = VarLocIDs.insert(VL); OpenRanges.insert(ID, VL.Var); } else if (MI.hasOneMemOperand()) { - // It's a stack spill -- fetch spill base and offset. - VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI); - VarLoc VL(MI, SpillLocation.SpillBase, SpillLocation.SpillOffset, LS); - ID = VarLocIDs.insert(VL); - OpenRanges.insert(ID, VL.Var); + 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 && @@ -585,7 +707,6 @@ void LiveDebugValues::emitEntryValues(MachineInstr &MI, TransferMap &Transfers, DebugParamMap &DebugEntryVals, SparseBitVector<> &KillSet) { - MachineFunction *MF = MI.getParent()->getParent(); for (unsigned ID : KillSet) { if (!VarLocIDs[ID].Var.getVar()->isParameter()) continue; @@ -600,20 +721,12 @@ void LiveDebugValues::emitEntryValues(MachineInstr &MI, auto ParamDebugInstr = DebugEntryVals[CurrDebugInstr->getDebugVariable()]; DIExpression *NewExpr = DIExpression::prepend( ParamDebugInstr->getDebugExpression(), DIExpression::EntryValue); - MachineInstr *EntryValDbgMI = - BuildMI(*MF, ParamDebugInstr->getDebugLoc(), ParamDebugInstr->getDesc(), - ParamDebugInstr->isIndirectDebugValue(), - ParamDebugInstr->getOperand(0).getReg(), - ParamDebugInstr->getDebugVariable(), NewExpr); - - if (ParamDebugInstr->isIndirectDebugValue()) - EntryValDbgMI->getOperand(1).setImm( - ParamDebugInstr->getOperand(1).getImm()); - - Transfers.push_back({&MI, EntryValDbgMI}); - VarLoc VL(*EntryValDbgMI, LS); - unsigned EntryValLocID = VarLocIDs.insert(VL); - OpenRanges.insert(EntryValLocID, VL.Var); + + VarLoc EntryLoc = VarLoc::CreateEntryLoc(*ParamDebugInstr, LS, NewExpr); + + unsigned EntryValLocID = VarLocIDs.insert(EntryLoc); + Transfers.push_back({&MI, EntryValLocID}); + OpenRanges.insert(EntryValLocID, EntryLoc.Var); } } @@ -627,21 +740,19 @@ void LiveDebugValues::insertTransferDebugPair( VarLocMap &VarLocIDs, unsigned OldVarID, TransferKind Kind, unsigned NewReg) { const MachineInstr *DebugInstr = &VarLocIDs[OldVarID].MI; - MachineFunction *MF = MI.getParent()->getParent(); - MachineInstr *NewDebugInstr; auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &DebugInstr, - &VarLocIDs](VarLoc &VL, MachineInstr *NewDebugInstr) { + &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); - // The newly created DBG_VALUE instruction NewDebugInstr must be inserted - // after MI. Keep track of the pairing. - TransferDebugPair MIP = {&MI, NewDebugInstr}; + TransferDebugPair MIP = {&MI, LocId}; Transfers.push_back(MIP); }; @@ -653,37 +764,25 @@ void LiveDebugValues::insertTransferDebugPair( "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. - NewDebugInstr = BuildMI( - *MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), - DebugInstr->isIndirectDebugValue(), NewReg, - DebugInstr->getDebugVariable(), DebugInstr->getDebugExpression()); - if (DebugInstr->isIndirectDebugValue()) - NewDebugInstr->getOperand(1).setImm(DebugInstr->getOperand(1).getImm()); - VarLoc VL(*NewDebugInstr, LS); - ProcessVarLoc(VL, NewDebugInstr); - LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register copy: "; - NewDebugInstr->print(dbgs(), /*IsStandalone*/false, - /*SkipOpers*/false, /*SkipDebugLoc*/false, - /*AddNewLine*/true, TII)); + 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); - auto *SpillExpr = DIExpression::prepend(DebugInstr->getDebugExpression(), - DIExpression::ApplyOffset, - SpillLocation.SpillOffset); - NewDebugInstr = BuildMI( - *MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), true, - SpillLocation.SpillBase, DebugInstr->getDebugVariable(), SpillExpr); - VarLoc VL(*NewDebugInstr, SpillLocation.SpillBase, - SpillLocation.SpillOffset, LS); - ProcessVarLoc(VL, NewDebugInstr); - LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: "; - NewDebugInstr->print(dbgs(), /*IsStandalone*/false, - /*SkipOpers*/false, /*SkipDebugLoc*/false, - /*AddNewLine*/true, TII)); + 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: { @@ -691,15 +790,14 @@ void LiveDebugValues::insertTransferDebugPair( "No register supplied when handling a restore of a debug value"); MachineFunction *MF = MI.getMF(); DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent()); - NewDebugInstr = - BuildMI(*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), false, - NewReg, DebugInstr->getDebugVariable(), DIB.createExpression()); - VarLoc VL(*NewDebugInstr, LS); - ProcessVarLoc(VL, NewDebugInstr); - LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register restore: "; - NewDebugInstr->print(dbgs(), /*IsStandalone*/false, - /*SkipOpers*/false, /*SkipDebugLoc*/false, - /*AddNewLine*/true, TII)); + // 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; } } @@ -719,7 +817,7 @@ void LiveDebugValues::transferRegisterDef( // instructions never clobber SP, because some backends (e.g., AArch64) // never list SP in the regmask. if (MO.isReg() && MO.isDef() && MO.getReg() && - TRI->isPhysicalRegister(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) @@ -748,16 +846,8 @@ void LiveDebugValues::transferRegisterDef( } } -/// 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 LiveDebugValues::isSpillInstruction(const MachineInstr &MI, - MachineFunction *MF, unsigned &Reg) { - SmallVector<const MachineMemOperand*, 1> Accesses; - + MachineFunction *MF) { // TODO: Handle multiple stores folded into one. if (!MI.hasOneMemOperand()) return false; @@ -766,6 +856,14 @@ bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI, 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; @@ -834,7 +932,37 @@ void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI, LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump();); - if (isSpillInstruction(MI, MF, Reg)) { + // 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) @@ -854,6 +982,7 @@ void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI, 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"); @@ -885,8 +1014,8 @@ void LiveDebugValues::transferRegisterCopy(MachineInstr &MI, return false; }; - unsigned SrcReg = SrcRegOp->getReg(); - unsigned DestReg = DestRegOp->getReg(); + 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 @@ -906,26 +1035,20 @@ void LiveDebugValues::transferRegisterCopy(MachineInstr &MI, } /// 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 LiveDebugValues::transferTerminator(MachineBasicBlock *CurMBB, + OpenRangesSet &OpenRanges, + VarLocInMBB &OutLocs, + const VarLocMap &VarLocIDs) { bool Changed = false; - const MachineBasicBlock *CurMBB = MI.getParent(); - if (!(MI.isTerminator() || (&MI == &CurMBB->back()))) - return false; - - if (OpenRanges.empty()) - return 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(); + VarLocIDs[ID].dump(TRI); }); VarLocSet &VLS = OutLocs[CurMBB]; - Changed = VLS |= OpenRanges.getVarLocs(); + Changed = VLS != OpenRanges.getVarLocs(); // New OutLocs set may be different due to spill, restore or register // copy instruction processing. if (Changed) @@ -995,26 +1118,17 @@ void LiveDebugValues::accumulateFragmentMap(MachineInstr &MI, } /// This routine creates OpenRanges and OutLocs. -bool LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges, +void LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocInMBB &OutLocs, VarLocMap &VarLocIDs, - TransferMap &Transfers, DebugParamMap &DebugEntryVals, - bool transferChanges, + TransferMap &Transfers, + DebugParamMap &DebugEntryVals, OverlapMap &OverlapFragments, VarToFragments &SeenFragments) { - bool Changed = false; transferDebugValue(MI, OpenRanges, VarLocIDs); transferRegisterDef(MI, OpenRanges, VarLocIDs, Transfers, DebugEntryVals); - if (transferChanges) { - transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers); - transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers); - } else { - // Build up a map of overlapping fragments on the first run through. - if (MI.isDebugValue()) - accumulateFragmentMap(MI, SeenFragments, OverlapFragments); - } - Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs); - return Changed; + transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers); + transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers); } /// This routine joins the analysis results of all incoming edges in @MBB by @@ -1024,7 +1138,8 @@ bool LiveDebugValues::join( MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs, const VarLocMap &VarLocIDs, SmallPtrSet<const MachineBasicBlock *, 16> &Visited, - SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks) { + SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks, + VarLocInMBB &PendingInLocs) { LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n"); bool Changed = false; @@ -1034,9 +1149,11 @@ bool LiveDebugValues::join( // can be joined. int NumVisited = 0; for (auto p : MBB.predecessors()) { - // Ignore unvisited predecessor blocks. As we are processing - // the blocks in reverse post-order any unvisited block can - // be considered to not remove any incoming values. + // 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"); @@ -1086,44 +1203,59 @@ bool LiveDebugValues::join( // is the entry block which has no predecessor. assert((NumVisited || MBB.pred_empty()) && "Should have processed at least one predecessor"); - if (InLocsT.empty()) - return false; VarLocSet &ILS = InLocs[&MBB]; + VarLocSet &Pending = PendingInLocs[&MBB]; - // Insert DBG_VALUE instructions, if not already inserted. + // 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) { - // 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. process() will end this range however appropriate. - const VarLoc &DiffIt = VarLocIDs[ID]; - const MachineInstr *DebugInstr = &DiffIt.MI; - MachineInstr *MI = nullptr; - if (DiffIt.isConstant()) { - MachineOperand MO(DebugInstr->getOperand(0)); - MI = BuildMI(MBB, MBB.instr_begin(), DebugInstr->getDebugLoc(), - DebugInstr->getDesc(), false, MO, - DebugInstr->getDebugVariable(), - DebugInstr->getDebugExpression()); - } else { - MI = BuildMI(MBB, MBB.instr_begin(), DebugInstr->getDebugLoc(), - DebugInstr->getDesc(), DebugInstr->isIndirectDebugValue(), - DebugInstr->getOperand(0).getReg(), - DebugInstr->getDebugVariable(), - DebugInstr->getDebugExpression()); - if (DebugInstr->isIndirectDebugValue()) - MI->getOperand(1).setImm(DebugInstr->getOperand(1).getImm()); - } - LLVM_DEBUG(dbgs() << "Inserted: "; MI->dump();); + 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) { @@ -1140,6 +1272,9 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { 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; @@ -1156,8 +1291,6 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { std::greater<unsigned int>> Pending; - enum : bool { dontTransferChanges = false, transferChanges = true }; - // 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. @@ -1169,7 +1302,7 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { const TargetLowering *TLI = MF.getSubtarget().getTargetLowering(); unsigned SP = TLI->getStackPointerRegisterToSaveRestore(); - unsigned FP = TRI->getFrameRegister(MF); + Register FP = TRI->getFrameRegister(MF); auto IsRegOtherThanSPAndFP = [&](const MachineOperand &Op) -> bool { return Op.isReg() && Op.getReg() != SP && Op.getReg() != FP; }; @@ -1195,23 +1328,14 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { !MI.getDebugExpression()->isFragment()) DebugEntryVals[MI.getDebugVariable()] = &MI; - // Initialize every mbb with OutLocs. - // We are not looking at any spill instructions during the initial pass - // over the BBs. The LiveDebugVariables pass has already created DBG_VALUE - // instructions for spills of registers that are known to be user variables - // within the BB in which the spill occurs. + // Initialize per-block structures and scan for fragment overlaps. for (auto &MBB : MF) { + PendingInLocs[&MBB] = VarLocSet(); + for (auto &MI : MBB) { - process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers, DebugEntryVals, - dontTransferChanges, OverlapFragments, SeenFragments); - } - // Add any entry DBG_VALUE instructions necessitated by parameter - // clobbering. - for (auto &TR : Transfers) { - MBB.insertAfter(MachineBasicBlock::iterator(*TR.TransferInst), - TR.DebugInst); + if (MI.isDebugValue()) + accumulateFragmentMap(MI, SeenFragments, OverlapFragments); } - Transfers.clear(); } auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool { @@ -1248,26 +1372,21 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { while (!Worklist.empty()) { MachineBasicBlock *MBB = OrderToBB[Worklist.top()]; Worklist.pop(); - MBBJoined = - join(*MBB, OutLocs, InLocs, VarLocIDs, Visited, ArtificialBlocks); - Visited.insert(MBB); + 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) - OLChanged |= process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers, - DebugEntryVals, transferChanges, OverlapFragments, - SeenFragments); - - // Add any DBG_VALUE instructions necessitated by spills. - for (auto &TR : Transfers) - MBB->insertAfter(MachineBasicBlock::iterator(*TR.TransferInst), - TR.DebugInst); - Transfers.clear(); + DebugEntryVals, OverlapFragments, SeenFragments); + OLChanged |= transferTerminator(MBB, OpenRanges, OutLocs, VarLocIDs); LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after propagating", dbgs())); @@ -1289,6 +1408,19 @@ bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { 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; @@ -1308,7 +1440,7 @@ bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) { TII = MF.getSubtarget().getInstrInfo(); TFI = MF.getSubtarget().getFrameLowering(); TFI->determineCalleeSaves(MF, CalleeSavedRegs, - make_unique<RegScavenger>().get()); + std::make_unique<RegScavenger>().get()); LS.initialize(MF); bool Changed = ExtendRanges(MF); |