LCOV - code coverage report
Current view: top level - lib/CodeGen - LiveDebugValues.cpp (source / functions) Hit Total Coverage
Test: llvm-toolchain.info Lines: 147 237 62.0 %
Date: 2018-10-20 13:21:21 Functions: 18 26 69.2 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : //===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
       2             : //
       3             : //                     The LLVM Compiler Infrastructure
       4             : //
       5             : // This file is distributed under the University of Illinois Open Source
       6             : // License. See LICENSE.TXT for details.
       7             : //
       8             : //===----------------------------------------------------------------------===//
       9             : ///
      10             : /// This pass implements a data flow analysis that propagates debug location
      11             : /// information by inserting additional DBG_VALUE instructions into the machine
      12             : /// instruction stream. The pass internally builds debug location liveness
      13             : /// ranges to determine the points where additional DBG_VALUEs need to be
      14             : /// inserted.
      15             : ///
      16             : /// This is a separate pass from DbgValueHistoryCalculator to facilitate
      17             : /// testing and improve modularity.
      18             : ///
      19             : //===----------------------------------------------------------------------===//
      20             : 
      21             : #include "llvm/ADT/DenseMap.h"
      22             : #include "llvm/ADT/PostOrderIterator.h"
      23             : #include "llvm/ADT/SmallPtrSet.h"
      24             : #include "llvm/ADT/SmallVector.h"
      25             : #include "llvm/ADT/SparseBitVector.h"
      26             : #include "llvm/ADT/Statistic.h"
      27             : #include "llvm/ADT/UniqueVector.h"
      28             : #include "llvm/CodeGen/LexicalScopes.h"
      29             : #include "llvm/CodeGen/MachineBasicBlock.h"
      30             : #include "llvm/CodeGen/MachineFrameInfo.h"
      31             : #include "llvm/CodeGen/MachineFunction.h"
      32             : #include "llvm/CodeGen/MachineFunctionPass.h"
      33             : #include "llvm/CodeGen/MachineInstr.h"
      34             : #include "llvm/CodeGen/MachineInstrBuilder.h"
      35             : #include "llvm/CodeGen/MachineMemOperand.h"
      36             : #include "llvm/CodeGen/MachineOperand.h"
      37             : #include "llvm/CodeGen/PseudoSourceValue.h"
      38             : #include "llvm/CodeGen/TargetFrameLowering.h"
      39             : #include "llvm/CodeGen/TargetInstrInfo.h"
      40             : #include "llvm/CodeGen/TargetLowering.h"
      41             : #include "llvm/CodeGen/TargetRegisterInfo.h"
      42             : #include "llvm/CodeGen/TargetSubtargetInfo.h"
      43             : #include "llvm/CodeGen/RegisterScavenging.h"
      44             : #include "llvm/Config/llvm-config.h"
      45             : #include "llvm/IR/DebugInfoMetadata.h"
      46             : #include "llvm/IR/DebugLoc.h"
      47             : #include "llvm/IR/Function.h"
      48             : #include "llvm/IR/Module.h"
      49             : #include "llvm/MC/MCRegisterInfo.h"
      50             : #include "llvm/Pass.h"
      51             : #include "llvm/Support/Casting.h"
      52             : #include "llvm/Support/Compiler.h"
      53             : #include "llvm/Support/Debug.h"
      54             : #include "llvm/Support/raw_ostream.h"
      55             : #include <algorithm>
      56             : #include <cassert>
      57             : #include <cstdint>
      58             : #include <functional>
      59             : #include <queue>
      60             : #include <utility>
      61             : #include <vector>
      62             : 
      63             : using namespace llvm;
      64             : 
      65             : #define DEBUG_TYPE "livedebugvalues"
      66             : 
      67             : STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
      68             : 
      69             : // If @MI is a DBG_VALUE with debug value described by a defined
      70             : // register, returns the number of this register. In the other case, returns 0.
      71             : static unsigned isDbgValueDescribedByReg(const MachineInstr &MI) {
      72             :   assert(MI.isDebugValue() && "expected a DBG_VALUE");
      73             :   assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
      74             :   // If location of variable is described using a register (directly
      75             :   // or indirectly), this register is always a first operand.
      76     1045002 :   return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
      77             : }
      78             : 
      79             : namespace {
      80             : 
      81             : class LiveDebugValues : public MachineFunctionPass {
      82             : private:
      83             :   const TargetRegisterInfo *TRI;
      84             :   const TargetInstrInfo *TII;
      85             :   const TargetFrameLowering *TFI;
      86             :   BitVector CalleeSavedRegs;
      87             :   LexicalScopes LS;
      88             : 
      89             :   /// Keeps track of lexical scopes associated with a user value's source
      90             :   /// location.
      91             :   class UserValueScopes {
      92             :     DebugLoc DL;
      93             :     LexicalScopes &LS;
      94             :     SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
      95             : 
      96             :   public:
      97      635680 :     UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(std::move(D)), LS(L) {}
      98             : 
      99             :     /// Return true if current scope dominates at least one machine
     100             :     /// instruction in a given machine basic block.
     101      367630 :     bool dominates(MachineBasicBlock *MBB) {
     102      367630 :       if (LBlocks.empty())
     103       52431 :         LS.getMachineBasicBlocks(DL, LBlocks);
     104      367630 :       return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB);
     105             :     }
     106             :   };
     107             : 
     108             :   /// Based on std::pair so it can be used as an index into a DenseMap.
     109             :   using DebugVariableBase =
     110             :       std::pair<const DILocalVariable *, const DILocation *>;
     111             :   /// A potentially inlined instance of a variable.
     112             :   struct DebugVariable : public DebugVariableBase {
     113             :     DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt)
     114             :         : DebugVariableBase(Var, InlinedAt) {}
     115             : 
     116           0 :     const DILocalVariable *getVar() const { return this->first; }
     117           0 :     const DILocation *getInlinedAt() const { return this->second; }
     118             : 
     119             :     bool operator<(const DebugVariable &DV) const {
     120      213393 :       if (getVar() == DV.getVar())
     121       63216 :         return getInlinedAt() < DV.getInlinedAt();
     122      150177 :       return getVar() < DV.getVar();
     123             :     }
     124             :   };
     125             : 
     126             :   /// A pair of debug variable and value location.
     127      770971 :   struct VarLoc {
     128             :     const DebugVariable Var;
     129             :     const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
     130             :     mutable UserValueScopes UVS;
     131             :     enum { InvalidKind = 0, RegisterKind } Kind = InvalidKind;
     132             : 
     133             :     /// The value location. Stored separately to avoid repeatedly
     134             :     /// extracting it from MI.
     135             :     union {
     136             :       uint64_t RegNo;
     137             :       uint64_t Hash;
     138             :     } Loc;
     139             : 
     140      317840 :     VarLoc(const MachineInstr &MI, LexicalScopes &LS)
     141      317840 :         : Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
     142      635680 :           UVS(MI.getDebugLoc(), LS) {
     143             :       static_assert((sizeof(Loc) == sizeof(uint64_t)),
     144             :                     "hash does not cover all members of Loc");
     145             :       assert(MI.isDebugValue() && "not a DBG_VALUE");
     146             :       assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
     147      317840 :       if (int RegNo = isDbgValueDescribedByReg(MI)) {
     148      317840 :         Kind = RegisterKind;
     149      317840 :         Loc.RegNo = RegNo;
     150             :       }
     151      317840 :     }
     152             : 
     153             :     /// If this variable is described by a register, return it,
     154             :     /// otherwise return 0.
     155           0 :     unsigned isDescribedByReg() const {
     156           0 :       if (Kind == RegisterKind)
     157        6940 :         return Loc.RegNo;
     158             :       return 0;
     159             :     }
     160             : 
     161             :     /// Determine whether the lexical scope of this value's debug location
     162             :     /// dominates MBB.
     163           0 :     bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); }
     164             : 
     165             : #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
     166             :     LLVM_DUMP_METHOD void dump() const { MI.dump(); }
     167             : #endif
     168             : 
     169             :     bool operator==(const VarLoc &Other) const {
     170             :       return Var == Other.Var && Loc.Hash == Other.Loc.Hash;
     171             :     }
     172             : 
     173             :     /// This operator guarantees that VarLocs are sorted by Variable first.
     174             :     bool operator<(const VarLoc &Other) const {
     175      484594 :       if (Var == Other.Var)
     176      271201 :         return Loc.Hash < Other.Loc.Hash;
     177             :       return Var < Other.Var;
     178             :     }
     179             :   };
     180             : 
     181             :   using VarLocMap = UniqueVector<VarLoc>;
     182             :   using VarLocSet = SparseBitVector<>;
     183             :   using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>;
     184             :   struct TransferDebugPair {
     185             :     MachineInstr *TransferInst;
     186             :     MachineInstr *DebugInst;
     187             :   };
     188             :   using TransferMap = SmallVector<TransferDebugPair, 4>;
     189             : 
     190             :   /// This holds the working set of currently open ranges. For fast
     191             :   /// access, this is done both as a set of VarLocIDs, and a map of
     192             :   /// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
     193             :   /// previous open ranges for the same variable.
     194             :   class OpenRangesSet {
     195             :     VarLocSet VarLocs;
     196             :     SmallDenseMap<DebugVariableBase, unsigned, 8> Vars;
     197             : 
     198             :   public:
     199        1438 :     const VarLocSet &getVarLocs() const { return VarLocs; }
     200             : 
     201             :     /// Terminate all open ranges for Var by removing it from the set.
     202      364312 :     void erase(DebugVariable Var) {
     203      364312 :       auto It = Vars.find(Var);
     204      364312 :       if (It != Vars.end()) {
     205       32617 :         unsigned ID = It->second;
     206       32617 :         VarLocs.reset(ID);
     207             :         Vars.erase(It);
     208             :       }
     209      364312 :     }
     210             : 
     211             :     /// Terminate all open ranges listed in \c KillSet by removing
     212             :     /// them from the set.
     213     2220777 :     void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) {
     214     2220777 :       VarLocs.intersectWithComplement(KillSet);
     215       35049 :       for (unsigned ID : KillSet)
     216       70098 :         Vars.erase(VarLocIDs[ID].Var);
     217     2220777 :     }
     218             : 
     219             :     /// Insert a new range into the set.
     220      317840 :     void insert(unsigned VarLocID, DebugVariableBase Var) {
     221      317840 :       VarLocs.set(VarLocID);
     222      317840 :       Vars.insert({Var, VarLocID});
     223      317840 :     }
     224             : 
     225             :     /// Empty the set.
     226       49239 :     void clear() {
     227             :       VarLocs.clear();
     228       49239 :       Vars.clear();
     229       49239 :     }
     230             : 
     231             :     /// Return whether the set is empty or not.
     232             :     bool empty() const {
     233             :       assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent");
     234             :       return VarLocs.empty();
     235             :     }
     236             :   };
     237             : 
     238             :   bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
     239             :                           unsigned &Reg);
     240             :   int extractSpillBaseRegAndOffset(const MachineInstr &MI, unsigned &Reg);
     241             :   void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges,
     242             :                                TransferMap &Transfers, VarLocMap &VarLocIDs,
     243             :                                unsigned OldVarID, unsigned NewReg = 0);
     244             : 
     245             :   void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
     246             :                           VarLocMap &VarLocIDs);
     247             :   void transferSpillInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
     248             :                          VarLocMap &VarLocIDs, TransferMap &Transfers);
     249             :   void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges,
     250             :                             VarLocMap &VarLocIDs, TransferMap &Transfers);
     251             :   void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
     252             :                            const VarLocMap &VarLocIDs);
     253             :   bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
     254             :                               VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
     255             :   bool process(MachineInstr &MI, OpenRangesSet &OpenRanges,
     256             :                VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
     257             :                TransferMap &Transfers, bool transferChanges);
     258             : 
     259             :   bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
     260             :             const VarLocMap &VarLocIDs,
     261             :             SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
     262             :             SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks);
     263             : 
     264             :   bool ExtendRanges(MachineFunction &MF);
     265             : 
     266             : public:
     267             :   static char ID;
     268             : 
     269             :   /// Default construct and initialize the pass.
     270             :   LiveDebugValues();
     271             : 
     272             :   /// Tell the pass manager which passes we depend on and what
     273             :   /// information we preserve.
     274             :   void getAnalysisUsage(AnalysisUsage &AU) const override;
     275             : 
     276       26737 :   MachineFunctionProperties getRequiredProperties() const override {
     277       26737 :     return MachineFunctionProperties().set(
     278       26737 :         MachineFunctionProperties::Property::NoVRegs);
     279             :   }
     280             : 
     281             :   /// Print to ostream with a message.
     282             :   void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
     283             :                         const VarLocMap &VarLocIDs, const char *msg,
     284             :                         raw_ostream &Out) const;
     285             : 
     286             :   /// Calculate the liveness information for the given machine function.
     287             :   bool runOnMachineFunction(MachineFunction &MF) override;
     288             : };
     289             : 
     290             : } // end anonymous namespace
     291             : 
     292             : //===----------------------------------------------------------------------===//
     293             : //            Implementation
     294             : //===----------------------------------------------------------------------===//
     295             : 
     296             : char LiveDebugValues::ID = 0;
     297             : 
     298             : char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
     299             : 
     300      112060 : INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis",
     301             :                 false, false)
     302             : 
     303             : /// Default construct and initialize the pass.
     304       26913 : LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
     305       26913 :   initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
     306       26913 : }
     307             : 
     308             : /// Tell the pass manager which passes we depend on and what information we
     309             : /// preserve.
     310       26734 : void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
     311       26734 :   AU.setPreservesCFG();
     312       26734 :   MachineFunctionPass::getAnalysisUsage(AU);
     313       26734 : }
     314             : 
     315             : //===----------------------------------------------------------------------===//
     316             : //            Debug Range Extension Implementation
     317             : //===----------------------------------------------------------------------===//
     318             : 
     319             : #ifndef NDEBUG
     320             : void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
     321             :                                        const VarLocInMBB &V,
     322             :                                        const VarLocMap &VarLocIDs,
     323             :                                        const char *msg,
     324             :                                        raw_ostream &Out) const {
     325             :   Out << '\n' << msg << '\n';
     326             :   for (const MachineBasicBlock &BB : MF) {
     327             :     const VarLocSet &L = V.lookup(&BB);
     328             :     if (L.empty())
     329             :       continue;
     330             :     Out << "MBB: " << BB.getNumber() << ":\n";
     331             :     for (unsigned VLL : L) {
     332             :       const VarLoc &VL = VarLocIDs[VLL];
     333             :       Out << " Var: " << VL.Var.getVar()->getName();
     334             :       Out << " MI: ";
     335             :       VL.dump();
     336             :     }
     337             :   }
     338             :   Out << "\n";
     339             : }
     340             : #endif
     341             : 
     342             : /// Given a spill instruction, extract the register and offset used to
     343             : /// address the spill location in a target independent way.
     344           0 : int LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI,
     345             :                                                   unsigned &Reg) {
     346             :   assert(MI.hasOneMemOperand() &&
     347             :          "Spill instruction does not have exactly one memory operand?");
     348             :   auto MMOI = MI.memoperands_begin();
     349           0 :   const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
     350             :   assert(PVal->kind() == PseudoSourceValue::FixedStack &&
     351             :          "Inconsistent memory operand in spill instruction");
     352           0 :   int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
     353           0 :   const MachineBasicBlock *MBB = MI.getParent();
     354           0 :   return TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
     355             : }
     356             : 
     357             : /// End all previous ranges related to @MI and start a new range from @MI
     358             : /// if it is a DBG_VALUE instr.
     359     2220777 : void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
     360             :                                          OpenRangesSet &OpenRanges,
     361             :                                          VarLocMap &VarLocIDs) {
     362     2220777 :   if (!MI.isDebugValue())
     363     1857196 :     return;
     364      363581 :   const DILocalVariable *Var = MI.getDebugVariable();
     365             :   const DILocation *DebugLoc = MI.getDebugLoc();
     366             :   const DILocation *InlinedAt = DebugLoc->getInlinedAt();
     367             :   assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
     368             :          "Expected inlined-at fields to agree");
     369             : 
     370             :   // End all previous ranges of Var.
     371             :   DebugVariable V(Var, InlinedAt);
     372      363581 :   OpenRanges.erase(V);
     373             : 
     374             :   // Add the VarLoc to OpenRanges from this DBG_VALUE.
     375             :   // TODO: Currently handles DBG_VALUE which has only reg as location.
     376      348699 :   if (isDbgValueDescribedByReg(MI)) {
     377      317109 :     VarLoc VL(MI, LS);
     378      317109 :     unsigned ID = VarLocIDs.insert(VL);
     379      317109 :     OpenRanges.insert(ID, VL.Var);
     380             :   }
     381             : }
     382             : 
     383             : /// Create new TransferDebugPair and insert it in \p Transfers. The VarLoc
     384             : /// with \p OldVarID should be deleted form \p OpenRanges and replaced with
     385             : /// new VarLoc. If \p NewReg is different than default zero value then the
     386             : /// new location will be register location created by the copy like instruction,
     387             : /// otherwise it is variable's location on the stack.
     388         731 : void LiveDebugValues::insertTransferDebugPair(
     389             :     MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers,
     390             :     VarLocMap &VarLocIDs, unsigned OldVarID, unsigned NewReg) {
     391         731 :   const MachineInstr *DMI = &VarLocIDs[OldVarID].MI;
     392         731 :   MachineFunction *MF = MI.getParent()->getParent();
     393             :   MachineInstr *NewDMI;
     394         731 :   if (NewReg) {
     395             :     // Create a DBG_VALUE instruction to describe the Var in its new
     396             :     // register location.
     397         461 :     NewDMI = BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(),
     398             :                      DMI->isIndirectDebugValue(), NewReg,
     399        1383 :                      DMI->getDebugVariable(), DMI->getDebugExpression());
     400             :     if (DMI->isIndirectDebugValue())
     401           0 :       NewDMI->getOperand(1).setImm(DMI->getOperand(1).getImm());
     402             :     LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register copy: ";
     403             :                NewDMI->print(dbgs(), false, false, false, TII));
     404             :   } else {
     405             :     // Create a DBG_VALUE instruction to describe the Var in its spilled
     406             :     // location.
     407             :     unsigned SpillBase;
     408         270 :     int SpillOffset = extractSpillBaseRegAndOffset(MI, SpillBase);
     409         270 :     auto *SpillExpr = DIExpression::prepend(DMI->getDebugExpression(),
     410             :                                             DIExpression::NoDeref, SpillOffset);
     411         270 :     NewDMI = BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(), true, SpillBase,
     412         270 :                      DMI->getDebugVariable(), SpillExpr);
     413             :     LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
     414             :                NewDMI->print(dbgs(), false, false, false, TII));
     415             :   }
     416             : 
     417             :   // The newly created DBG_VALUE instruction NewDMI must be inserted after
     418             :   // MI. Keep track of the pairing.
     419         731 :   TransferDebugPair MIP = {&MI, NewDMI};
     420         731 :   Transfers.push_back(MIP);
     421             : 
     422             :   // End all previous ranges of Var.
     423         731 :   OpenRanges.erase(VarLocIDs[OldVarID].Var);
     424             : 
     425             :   // Add the VarLoc to OpenRanges.
     426         731 :   VarLoc VL(*NewDMI, LS);
     427         731 :   unsigned LocID = VarLocIDs.insert(VL);
     428         731 :   OpenRanges.insert(LocID, VL.Var);
     429         731 : }
     430             : 
     431             : /// A definition of a register may mark the end of a range.
     432           0 : void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
     433             :                                           OpenRangesSet &OpenRanges,
     434             :                                           const VarLocMap &VarLocIDs) {
     435             :   MachineFunction *MF = MI.getMF();
     436           0 :   const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
     437           0 :   unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
     438             :   SparseBitVector<> KillSet;
     439           0 :   for (const MachineOperand &MO : MI.operands()) {
     440             :     // Determine whether the operand is a register def.  Assume that call
     441             :     // instructions never clobber SP, because some backends (e.g., AArch64)
     442             :     // never list SP in the regmask.
     443           0 :     if (MO.isReg() && MO.isDef() && MO.getReg() &&
     444           0 :         TRI->isPhysicalRegister(MO.getReg()) &&
     445           0 :         !(MI.isCall() && MO.getReg() == SP)) {
     446             :       // Remove ranges of all aliased registers.
     447           0 :       for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
     448           0 :         for (unsigned ID : OpenRanges.getVarLocs())
     449           0 :           if (VarLocIDs[ID].isDescribedByReg() == *RAI)
     450           0 :             KillSet.set(ID);
     451           0 :     } else if (MO.isRegMask()) {
     452             :       // Remove ranges of all clobbered registers. Register masks don't usually
     453             :       // list SP as preserved.  While the debug info may be off for an
     454             :       // instruction or two around callee-cleanup calls, transferring the
     455             :       // DEBUG_VALUE across the call is still a better user experience.
     456           0 :       for (unsigned ID : OpenRanges.getVarLocs()) {
     457           0 :         unsigned Reg = VarLocIDs[ID].isDescribedByReg();
     458           0 :         if (Reg && Reg != SP && MO.clobbersPhysReg(Reg))
     459           0 :           KillSet.set(ID);
     460             :       }
     461             :     }
     462             :   }
     463           0 :   OpenRanges.erase(KillSet, VarLocIDs);
     464           0 : }
     465             : 
     466             : /// Decide if @MI is a spill instruction and return true if it is. We use 2
     467             : /// criteria to make this decision:
     468             : /// - Is this instruction a store to a spill slot?
     469             : /// - Is there a register operand that is both used and killed?
     470             : /// TODO: Store optimization can fold spills into other stores (including
     471             : /// other spills). We do not handle this yet (more than one memory operand).
     472           0 : bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
     473             :                                          MachineFunction *MF, unsigned &Reg) {
     474           0 :   const MachineFrameInfo &FrameInfo = MF->getFrameInfo();
     475             :   int FI;
     476             :   SmallVector<const MachineMemOperand*, 1> Accesses;
     477             : 
     478             :   // TODO: Handle multiple stores folded into one.
     479           0 :   if (!MI.hasOneMemOperand())
     480           0 :     return false;
     481             : 
     482             :   // To identify a spill instruction, use the same criteria as in AsmPrinter.
     483           0 :   if (!((TII->isStoreToStackSlotPostFE(MI, FI) &&
     484           0 :          FrameInfo.isSpillSlotObjectIndex(FI)) ||
     485           0 :         (TII->hasStoreToStackSlot(MI, Accesses) &&
     486             :          llvm::any_of(Accesses, [&FrameInfo](const MachineMemOperand *MMO) {
     487           0 :            return FrameInfo.isSpillSlotObjectIndex(
     488             :                cast<FixedStackPseudoSourceValue>(MMO->getPseudoValue())
     489             :                    ->getFrameIndex());
     490             :          }))))
     491           0 :     return false;
     492             : 
     493             :   auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) {
     494           0 :     if (!MO.isReg() || !MO.isUse()) {
     495           0 :       Reg = 0;
     496             :       return false;
     497             :     }
     498           0 :     Reg = MO.getReg();
     499             :     return MO.isKill();
     500             :   };
     501             : 
     502           0 :   for (const MachineOperand &MO : MI.operands()) {
     503             :     // In a spill instruction generated by the InlineSpiller the spilled
     504             :     // register has its kill flag set.
     505           0 :     if (isKilledReg(MO, Reg))
     506           0 :       return true;
     507           0 :     if (Reg != 0) {
     508             :       // Check whether next instruction kills the spilled register.
     509             :       // FIXME: Current solution does not cover search for killed register in
     510             :       // bundles and instructions further down the chain.
     511           0 :       auto NextI = std::next(MI.getIterator());
     512             :       // Skip next instruction that points to basic block end iterator.
     513           0 :       if (MI.getParent()->end() == NextI)
     514             :         continue;
     515             :       unsigned RegNext;
     516           0 :       for (const MachineOperand &MONext : NextI->operands()) {
     517             :         // Return true if we came across the register from the
     518             :         // previous spill instruction that is killed in NextI.
     519           0 :         if (isKilledReg(MONext, RegNext) && RegNext == Reg)
     520           0 :           return true;
     521             :       }
     522             :     }
     523             :   }
     524             :   // Return false if we didn't find spilled register.
     525             :   return false;
     526             : }
     527             : 
     528             : /// A spilled register may indicate that we have to end the current range of
     529             : /// a variable and create a new one for the spill location.
     530             : /// We don't want to insert any instructions in process(), so we just create
     531             : /// the DBG_VALUE without inserting it and keep track of it in \p Transfers.
     532             : /// It will be inserted into the BB when we're done iterating over the
     533             : /// instructions.
     534      410030 : void LiveDebugValues::transferSpillInst(MachineInstr &MI,
     535             :                                         OpenRangesSet &OpenRanges,
     536             :                                         VarLocMap &VarLocIDs,
     537             :                                         TransferMap &Transfers) {
     538             :   unsigned Reg;
     539             :   MachineFunction *MF = MI.getMF();
     540      410030 :   if (!isSpillInstruction(MI, MF, Reg))
     541      409669 :     return;
     542             : 
     543             :   // Check if the register is the location of a debug value.
     544        3728 :   for (unsigned ID : OpenRanges.getVarLocs()) {
     545        7456 :     if (VarLocIDs[ID].isDescribedByReg() == Reg) {
     546             :       LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
     547             :                         << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
     548         270 :       insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID);
     549         270 :       return;
     550             :     }
     551             :   }
     552             : }
     553             : 
     554             : /// If \p MI is a register copy instruction, that copies a previously tracked
     555             : /// value from one register to another register that is callee saved, we
     556             : /// create new DBG_VALUE instruction  described with copy destination register.
     557      410030 : void LiveDebugValues::transferRegisterCopy(MachineInstr &MI,
     558             :                                            OpenRangesSet &OpenRanges,
     559             :                                            VarLocMap &VarLocIDs,
     560             :                                            TransferMap &Transfers) {
     561             :   const MachineOperand *SrcRegOp, *DestRegOp;
     562             : 
     563      820060 :   if (!TII->isCopyInstr(MI, SrcRegOp, DestRegOp) || !SrcRegOp->isKill() ||
     564        5724 :       !DestRegOp->isDef())
     565      409684 :     return;
     566             : 
     567             :   auto isCalleSavedReg = [&](unsigned Reg) {
     568             :     for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
     569             :       if (CalleeSavedRegs.test(*RAI))
     570             :         return true;
     571             :     return false;
     572        5724 :   };
     573             : 
     574        5724 :   unsigned SrcReg = SrcRegOp->getReg();
     575        5724 :   unsigned DestReg = DestRegOp->getReg();
     576             : 
     577             :   // We want to recognize instructions where destination register is callee
     578             :   // saved register. If register that could be clobbered by the call is
     579             :   // included, there would be a great chance that it is going to be clobbered
     580             :   // soon. It is more likely that previous register location, which is callee
     581             :   // saved, is going to stay unclobbered longer, even if it is killed.
     582        5724 :   if (!isCalleSavedReg(DestReg))
     583             :     return;
     584             : 
     585        3212 :   for (unsigned ID : OpenRanges.getVarLocs()) {
     586        6424 :     if (VarLocIDs[ID].isDescribedByReg() == SrcReg) {
     587         461 :       insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID,
     588             :                               DestReg);
     589         461 :       return;
     590             :     }
     591             :   }
     592             : }
     593             : 
     594             : /// Terminate all open ranges at the end of the current basic block.
     595           0 : bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
     596             :                                              OpenRangesSet &OpenRanges,
     597             :                                              VarLocInMBB &OutLocs,
     598             :                                              const VarLocMap &VarLocIDs) {
     599             :   bool Changed = false;
     600           0 :   const MachineBasicBlock *CurMBB = MI.getParent();
     601           0 :   if (!(MI.isTerminator() || (&MI == &CurMBB->back())))
     602           0 :     return false;
     603             : 
     604           0 :   if (OpenRanges.empty())
     605           0 :     return false;
     606             : 
     607             :   LLVM_DEBUG(for (unsigned ID
     608             :                   : OpenRanges.getVarLocs()) {
     609             :     // Copy OpenRanges to OutLocs, if not already present.
     610             :     dbgs() << "Add to OutLocs in MBB #" << CurMBB->getNumber() << ":  ";
     611             :     VarLocIDs[ID].dump();
     612             :   });
     613             :   VarLocSet &VLS = OutLocs[CurMBB];
     614           0 :   Changed = VLS |= OpenRanges.getVarLocs();
     615           0 :   OpenRanges.clear();
     616           0 :   return Changed;
     617             : }
     618             : 
     619             : /// This routine creates OpenRanges and OutLocs.
     620     2220777 : bool LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges,
     621             :                               VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
     622             :                               TransferMap &Transfers, bool transferChanges) {
     623             :   bool Changed = false;
     624     2220777 :   transferDebugValue(MI, OpenRanges, VarLocIDs);
     625     2220777 :   transferRegisterDef(MI, OpenRanges, VarLocIDs);
     626     2220777 :   if (transferChanges) {
     627      410030 :     transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers);
     628      410030 :     transferSpillInst(MI, OpenRanges, VarLocIDs, Transfers);
     629             :   }
     630     2220777 :   Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
     631     2220777 :   return Changed;
     632             : }
     633             : 
     634             : /// This routine joins the analysis results of all incoming edges in @MBB by
     635             : /// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
     636             : /// source variable in all the predecessors of @MBB reside in the same location.
     637           0 : bool LiveDebugValues::join(
     638             :     MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
     639             :     const VarLocMap &VarLocIDs,
     640             :     SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
     641             :     SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks) {
     642             :   LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
     643             :   bool Changed = false;
     644             : 
     645             :   VarLocSet InLocsT; // Temporary incoming locations.
     646             : 
     647             :   // For all predecessors of this MBB, find the set of VarLocs that
     648             :   // can be joined.
     649             :   int NumVisited = 0;
     650           0 :   for (auto p : MBB.predecessors()) {
     651             :     // Ignore unvisited predecessor blocks.  As we are processing
     652             :     // the blocks in reverse post-order any unvisited block can
     653             :     // be considered to not remove any incoming values.
     654           0 :     if (!Visited.count(p)) {
     655             :       LLVM_DEBUG(dbgs() << "  ignoring unvisited pred MBB: " << p->getNumber()
     656             :                         << "\n");
     657           0 :       continue;
     658             :     }
     659           0 :     auto OL = OutLocs.find(p);
     660             :     // Join is null in case of empty OutLocs from any of the pred.
     661           0 :     if (OL == OutLocs.end())
     662           0 :       return false;
     663             : 
     664             :     // Just copy over the Out locs to incoming locs for the first visited
     665             :     // predecessor, and for all other predecessors join the Out locs.
     666           0 :     if (!NumVisited)
     667           0 :       InLocsT = OL->second;
     668             :     else
     669           0 :       InLocsT &= OL->second;
     670             : 
     671             :     LLVM_DEBUG({
     672             :       if (!InLocsT.empty()) {
     673             :         for (auto ID : InLocsT)
     674             :           dbgs() << "  gathered candidate incoming var: "
     675             :                  << VarLocIDs[ID].Var.getVar()->getName() << "\n";
     676             :       }
     677             :     });
     678             : 
     679           0 :     NumVisited++;
     680             :   }
     681             : 
     682             :   // Filter out DBG_VALUES that are out of scope.
     683             :   VarLocSet KillSet;
     684           0 :   bool IsArtificial = ArtificialBlocks.count(&MBB);
     685           0 :   if (!IsArtificial) {
     686           0 :     for (auto ID : InLocsT) {
     687           0 :       if (!VarLocIDs[ID].dominates(MBB)) {
     688           0 :         KillSet.set(ID);
     689             :         LLVM_DEBUG({
     690             :           auto Name = VarLocIDs[ID].Var.getVar()->getName();
     691             :           dbgs() << "  killing " << Name << ", it doesn't dominate MBB\n";
     692             :         });
     693             :       }
     694             :     }
     695             :   }
     696           0 :   InLocsT.intersectWithComplement(KillSet);
     697             : 
     698             :   // As we are processing blocks in reverse post-order we
     699             :   // should have processed at least one predecessor, unless it
     700             :   // is the entry block which has no predecessor.
     701             :   assert((NumVisited || MBB.pred_empty()) &&
     702             :          "Should have processed at least one predecessor");
     703           0 :   if (InLocsT.empty())
     704           0 :     return false;
     705             : 
     706           0 :   VarLocSet &ILS = InLocs[&MBB];
     707             : 
     708             :   // Insert DBG_VALUE instructions, if not already inserted.
     709           0 :   VarLocSet Diff = InLocsT;
     710           0 :   Diff.intersectWithComplement(ILS);
     711           0 :   for (auto ID : Diff) {
     712             :     // This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
     713             :     // new range is started for the var from the mbb's beginning by inserting
     714             :     // a new DBG_VALUE. process() will end this range however appropriate.
     715             :     const VarLoc &DiffIt = VarLocIDs[ID];
     716           0 :     const MachineInstr *DMI = &DiffIt.MI;
     717             :     MachineInstr *MI =
     718           0 :         BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(),
     719           0 :                 DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(),
     720           0 :                 DMI->getDebugVariable(), DMI->getDebugExpression());
     721             :     if (DMI->isIndirectDebugValue())
     722           0 :       MI->getOperand(1).setImm(DMI->getOperand(1).getImm());
     723             :     LLVM_DEBUG(dbgs() << "Inserted: "; MI->dump(););
     724           0 :     ILS.set(ID);
     725             :     ++NumInserted;
     726             :     Changed = true;
     727             :   }
     728             :   return Changed;
     729             : }
     730             : 
     731             : /// Calculate the liveness information for the given machine function and
     732             : /// extend ranges across basic blocks.
     733        9672 : bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
     734             :   LLVM_DEBUG(dbgs() << "\nDebug Range Extension\n");
     735             : 
     736             :   bool Changed = false;
     737             :   bool OLChanged = false;
     738             :   bool MBBJoined = false;
     739             : 
     740             :   VarLocMap VarLocIDs;      // Map VarLoc<>unique ID for use in bitvectors.
     741        9672 :   OpenRangesSet OpenRanges; // Ranges that are open until end of bb.
     742        9672 :   VarLocInMBB OutLocs;      // Ranges that exist beyond bb.
     743        9671 :   VarLocInMBB InLocs;       // Ranges that are incoming after joining.
     744        9672 :   TransferMap Transfers;    // DBG_VALUEs associated with spills.
     745             : 
     746             :   // Blocks which are artificial, i.e. blocks which exclusively contain
     747             :   // instructions without locations, or with line 0 locations.
     748             :   SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks;
     749             : 
     750             :   DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
     751             :   DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
     752             :   std::priority_queue<unsigned int, std::vector<unsigned int>,
     753             :                       std::greater<unsigned int>>
     754             :       Worklist;
     755             :   std::priority_queue<unsigned int, std::vector<unsigned int>,
     756             :                       std::greater<unsigned int>>
     757             :       Pending;
     758             : 
     759             :   enum : bool { dontTransferChanges = false, transferChanges = true };
     760             : 
     761             :   // Initialize every mbb with OutLocs.
     762             :   // We are not looking at any spill instructions during the initial pass
     763             :   // over the BBs. The LiveDebugVariables pass has already created DBG_VALUE
     764             :   // instructions for spills of registers that are known to be user variables
     765             :   // within the BB in which the spill occurs.
     766      240960 :   for (auto &MBB : MF)
     767     2042035 :     for (auto &MI : MBB)
     768     1810747 :       process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
     769             :               dontTransferChanges);
     770             : 
     771             :   auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool {
     772           0 :     if (const DebugLoc &DL = MI.getDebugLoc())
     773           0 :       return DL.getLine() != 0;
     774             :     return false;
     775             :   };
     776      240960 :   for (auto &MBB : MF)
     777      231287 :     if (none_of(MBB.instrs(), hasNonArtificialLocation))
     778       54629 :       ArtificialBlocks.insert(&MBB);
     779             : 
     780             :   LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
     781             :                               "OutLocs after initialization", dbgs()));
     782             : 
     783             :   ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
     784       19344 :   unsigned int RPONumber = 0;
     785      240953 :   for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) {
     786      231280 :     OrderToBB[RPONumber] = *RI;
     787      231280 :     BBToOrder[*RI] = RPONumber;
     788      231280 :     Worklist.push(RPONumber);
     789      231281 :     ++RPONumber;
     790             :   }
     791             :   // This is a standard "union of predecessor outs" dataflow problem.
     792             :   // To solve it, we perform join() and process() using the two worklist method
     793             :   // until the ranges converge.
     794             :   // Ranges have converged when both worklists are empty.
     795             :   SmallPtrSet<const MachineBasicBlock *, 16> Visited;
     796       20947 :   while (!Worklist.empty() || !Pending.empty()) {
     797             :     // We track what is on the pending worklist to avoid inserting the same
     798             :     // thing twice.  We could avoid this with a custom priority queue, but this
     799             :     // is probably not worth it.
     800             :     SmallPtrSet<MachineBasicBlock *, 16> OnPending;
     801             :     LLVM_DEBUG(dbgs() << "Processing Worklist\n");
     802      278074 :     while (!Worklist.empty()) {
     803      266798 :       MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
     804             :       Worklist.pop();
     805             :       MBBJoined =
     806      266799 :           join(*MBB, OutLocs, InLocs, VarLocIDs, Visited, ArtificialBlocks);
     807      266799 :       Visited.insert(MBB);
     808      266799 :       if (MBBJoined) {
     809             :         MBBJoined = false;
     810             :         Changed = true;
     811             :         // Now that we have started to extend ranges across BBs we need to
     812             :         // examine spill instructions to see whether they spill registers that
     813             :         // correspond to user variables.
     814      448201 :         for (auto &MI : *MBB)
     815      410030 :           OLChanged |= process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
     816             :                                transferChanges);
     817             : 
     818             :         // Add any DBG_VALUE instructions necessitated by spills.
     819       38902 :         for (auto &TR : Transfers)
     820         731 :           MBB->insertAfter(MachineBasicBlock::iterator(*TR.TransferInst),
     821         731 :                            TR.DebugInst);
     822             :         Transfers.clear();
     823             : 
     824             :         LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
     825             :                                     "OutLocs after propagating", dbgs()));
     826             :         LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
     827             :                                     "InLocs after propagating", dbgs()));
     828             : 
     829       38171 :         if (OLChanged) {
     830             :           OLChanged = false;
     831       90494 :           for (auto s : MBB->successors())
     832       54462 :             if (OnPending.insert(s).second) {
     833       35518 :               Pending.push(BBToOrder[s]);
     834             :             }
     835             :         }
     836             :       }
     837             :     }
     838             :     Worklist.swap(Pending);
     839             :     // At this point, pending must be empty, since it was just the empty
     840             :     // worklist
     841             :     assert(Pending.empty() && "Pending should be empty");
     842             :   }
     843             : 
     844             :   LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
     845             :   LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
     846        9672 :   return Changed;
     847             : }
     848             : 
     849      401378 : bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
     850      401378 :   if (!MF.getFunction().getSubprogram())
     851             :     // LiveDebugValues will already have removed all DBG_VALUEs.
     852             :     return false;
     853             : 
     854             :   // Skip functions from NoDebug compilation units.
     855       19376 :   if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
     856             :       DICompileUnit::NoDebug)
     857             :     return false;
     858             : 
     859        9672 :   TRI = MF.getSubtarget().getRegisterInfo();
     860        9672 :   TII = MF.getSubtarget().getInstrInfo();
     861        9672 :   TFI = MF.getSubtarget().getFrameLowering();
     862        9671 :   TFI->determineCalleeSaves(MF, CalleeSavedRegs,
     863       19344 :                             make_unique<RegScavenger>().get());
     864        9672 :   LS.initialize(MF);
     865             : 
     866        9672 :   bool Changed = ExtendRanges(MF);
     867        9672 :   return Changed;
     868             : }

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