lib/CodeGen/LiveDebugVariables.cpp

   1 //===- LiveDebugVariables.cpp - Tracking debug info variables -------------===//
   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 file implements the LiveDebugVariables analysis.
  11 //
  12 // Remove all DBG_VALUE instructions referencing virtual registers and replace
  13 // them with a data structure tracking where live user variables are kept - in a
  14 // virtual register or in a stack slot.
  15 //
  16 // Allow the data structure to be updated during register allocation when values
  17 // are moved between registers and stack slots. Finally emit new DBG_VALUE
  18 // instructions after register allocation is complete.
  19 //
  20 //===----------------------------------------------------------------------===//
  21
  22 #include "LiveDebugVariables.h"
  23 #include "llvm/ADT/ArrayRef.h"
  24 #include "llvm/ADT/DenseMap.h"
  25 #include "llvm/ADT/IntervalMap.h"
  26 #include "llvm/ADT/STLExtras.h"
  27 #include "llvm/ADT/SmallSet.h"
  28 #include "llvm/ADT/SmallVector.h"
  29 #include "llvm/ADT/Statistic.h"
  30 #include "llvm/ADT/StringRef.h"
  31 #include "llvm/CodeGen/LexicalScopes.h"
  32 #include "llvm/CodeGen/LiveInterval.h"
  33 #include "llvm/CodeGen/LiveIntervals.h"
  34 #include "llvm/CodeGen/MachineBasicBlock.h"
  35 #include "llvm/CodeGen/MachineDominators.h"
  36 #include "llvm/CodeGen/MachineFunction.h"
  37 #include "llvm/CodeGen/MachineInstr.h"
  38 #include "llvm/CodeGen/MachineInstrBuilder.h"
  39 #include "llvm/CodeGen/MachineOperand.h"
  40 #include "llvm/CodeGen/MachineRegisterInfo.h"
  41 #include "llvm/CodeGen/SlotIndexes.h"
  42 #include "llvm/CodeGen/TargetInstrInfo.h"
  43 #include "llvm/CodeGen/TargetOpcodes.h"
  44 #include "llvm/CodeGen/TargetRegisterInfo.h"
  45 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  46 #include "llvm/CodeGen/VirtRegMap.h"
  47 #include "llvm/Config/llvm-config.h"
  48 #include "llvm/IR/DebugInfoMetadata.h"
  49 #include "llvm/IR/DebugLoc.h"
  50 #include "llvm/IR/Function.h"
  51 #include "llvm/IR/Metadata.h"
  52 #include "llvm/MC/MCRegisterInfo.h"
  53 #include "llvm/Pass.h"
  54 #include "llvm/Support/Casting.h"
  55 #include "llvm/Support/CommandLine.h"
  56 #include "llvm/Support/Compiler.h"
  57 #include "llvm/Support/Debug.h"
  58 #include "llvm/Support/raw_ostream.h"
  59 #include <algorithm>
  60 #include <cassert>
  61 #include <iterator>
  62 #include <memory>
  63 #include <utility>
  64
  65 using namespace llvm;
  66
  67 #define DEBUG_TYPE "livedebugvars"
  68
  69 static cl::opt<bool>
  70 EnableLDV("live-debug-variables", cl::init(true),
  71           cl::desc("Enable the live debug variables pass"), cl::Hidden);
  72
  73 STATISTIC(NumInsertedDebugValues, "Number of DBG_VALUEs inserted");
  74
  75 char LiveDebugVariables::ID = 0;
  76
  77 INITIALIZE_PASS_BEGIN(LiveDebugVariables, DEBUG_TYPE,
  78                 "Debug Variable Analysis", false, false)
  79 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
  80 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
  81 INITIALIZE_PASS_END(LiveDebugVariables, DEBUG_TYPE,
  82                 "Debug Variable Analysis", false, false)
  83
  84 void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
  85   AU.addRequired<MachineDominatorTree>();
  86   AU.addRequiredTransitive<LiveIntervals>();
  87   AU.setPreservesAll();
  88   MachineFunctionPass::getAnalysisUsage(AU);
  89 }
  90
  91 LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID) {
  92   initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
  93 }
  94
  95 enum : unsigned { UndefLocNo = ~0U };
  96
  97 /// Describes a location by number along with some flags about the original
  98 /// usage of the location.
  99 class DbgValueLocation {
 100 public:
 101   DbgValueLocation(unsigned LocNo, bool WasIndirect)
 102       : LocNo(LocNo), WasIndirect(WasIndirect) {
 103     static_assert(sizeof(*this) == sizeof(unsigned), "bad bitfield packing");
 104     assert(locNo() == LocNo && "location truncation");
 105   }
 106
 107   DbgValueLocation() : LocNo(0), WasIndirect(0) {}
 108
 109   unsigned locNo() const {
 110     // Fix up the undef location number, which gets truncated.
 111     return LocNo == INT_MAX ? UndefLocNo : LocNo;
 112   }
 113   bool wasIndirect() const { return WasIndirect; }
 114   bool isUndef() const { return locNo() == UndefLocNo; }
 115
 116   DbgValueLocation changeLocNo(unsigned NewLocNo) const {
 117     return DbgValueLocation(NewLocNo, WasIndirect);
 118   }
 119
 120   friend inline bool operator==(const DbgValueLocation &LHS,
 121                                 const DbgValueLocation &RHS) {
 122     return LHS.LocNo == RHS.LocNo && LHS.WasIndirect == RHS.WasIndirect;
 123   }
 124
 125   friend inline bool operator!=(const DbgValueLocation &LHS,
 126                                 const DbgValueLocation &RHS) {
 127     return !(LHS == RHS);
 128   }
 129
 130 private:
 131   unsigned LocNo : 31;
 132   unsigned WasIndirect : 1;
 133 };
 134
 135 /// Map of where a user value is live, and its location.
 136 using LocMap = IntervalMap<SlotIndex, DbgValueLocation, 4>;
 137
 138 /// Map of stack slot offsets for spilled locations.
 139 /// Non-spilled locations are not added to the map.
 140 using SpillOffsetMap = DenseMap<unsigned, unsigned>;
 141
 142 namespace {
 143
 144 class LDVImpl;
 145
 146 /// A user value is a part of a debug info user variable.
 147 ///
 148 /// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
 149 /// holds part of a user variable. The part is identified by a byte offset.
 150 ///
 151 /// UserValues are grouped into equivalence classes for easier searching. Two
 152 /// user values are related if they refer to the same variable, or if they are
 153 /// held by the same virtual register. The equivalence class is the transitive
 154 /// closure of that relation.
 155 class UserValue {
 156   const DILocalVariable *Variable; ///< The debug info variable we are part of.
 157   const DIExpression *Expression; ///< Any complex address expression.
 158   DebugLoc dl;            ///< The debug location for the variable. This is
 159                           ///< used by dwarf writer to find lexical scope.
 160   UserValue *leader;      ///< Equivalence class leader.
 161   UserValue *next = nullptr; ///< Next value in equivalence class, or null.
 162
 163   /// Numbered locations referenced by locmap.
 164   SmallVector<MachineOperand, 4> locations;
 165
 166   /// Map of slot indices where this value is live.
 167   LocMap locInts;
 168
 169   /// Set of interval start indexes that have been trimmed to the
 170   /// lexical scope.
 171   SmallSet<SlotIndex, 2> trimmedDefs;
 172
 173   /// Insert a DBG_VALUE into MBB at Idx for LocNo.
 174   void insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
 175                         SlotIndex StopIdx, DbgValueLocation Loc, bool Spilled,
 176                         unsigned SpillOffset, LiveIntervals &LIS,
 177                         const TargetInstrInfo &TII,
 178                         const TargetRegisterInfo &TRI);
 179
 180   /// Replace OldLocNo ranges with NewRegs ranges where NewRegs
 181   /// is live. Returns true if any changes were made.
 182   bool splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
 183                      LiveIntervals &LIS);
 184
 185 public:
 186   /// Create a new UserValue.
 187   UserValue(const DILocalVariable *var, const DIExpression *expr, DebugLoc L,
 188             LocMap::Allocator &alloc)
 189       : Variable(var), Expression(expr), dl(std::move(L)), leader(this),
 190         locInts(alloc) {}
 191
 192   /// Get the leader of this value's equivalence class.
 193   UserValue *getLeader() {
 194     UserValue *l = leader;
 195     while (l != l->leader)
 196       l = l->leader;
 197     return leader = l;
 198   }
 199
 200   /// Return the next UserValue in the equivalence class.
 201   UserValue *getNext() const { return next; }
 202
 203   /// Does this UserValue match the parameters?
 204   bool match(const DILocalVariable *Var, const DIExpression *Expr,
 205              const DILocation *IA) const {
 206     // FIXME: The fragment should be part of the equivalence class, but not
 207     // other things in the expression like stack values.
 208     return Var == Variable && Expr == Expression && dl->getInlinedAt() == IA;
 209   }
 210
 211   /// Merge equivalence classes.
 212   static UserValue *merge(UserValue *L1, UserValue *L2) {
 213     L2 = L2->getLeader();
 214     if (!L1)
 215       return L2;
 216     L1 = L1->getLeader();
 217     if (L1 == L2)
 218       return L1;
 219     // Splice L2 before L1's members.
 220     UserValue *End = L2;
 221     while (End->next) {
 222       End->leader = L1;
 223       End = End->next;
 224     }
 225     End->leader = L1;
 226     End->next = L1->next;
 227     L1->next = L2;
 228     return L1;
 229   }
 230
 231   /// Return the location number that matches Loc.
 232   ///
 233   /// For undef values we always return location number UndefLocNo without
 234   /// inserting anything in locations. Since locations is a vector and the
 235   /// location number is the position in the vector and UndefLocNo is ~0,
 236   /// we would need a very big vector to put the value at the right position.
 237   unsigned getLocationNo(const MachineOperand &LocMO) {
 238     if (LocMO.isReg()) {
 239       if (LocMO.getReg() == 0)
 240         return UndefLocNo;
 241       // For register locations we dont care about use/def and other flags.
 242       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 243         if (locations[i].isReg() &&
 244             locations[i].getReg() == LocMO.getReg() &&
 245             locations[i].getSubReg() == LocMO.getSubReg())
 246           return i;
 247     } else
 248       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 249         if (LocMO.isIdenticalTo(locations[i]))
 250           return i;
 251     locations.push_back(LocMO);
 252     // We are storing a MachineOperand outside a MachineInstr.
 253     locations.back().clearParent();
 254     // Don't store def operands.
 255     if (locations.back().isReg()) {
 256       if (locations.back().isDef())
 257         locations.back().setIsDead(false);
 258       locations.back().setIsUse();
 259     }
 260     return locations.size() - 1;
 261   }
 262
 263   /// Ensure that all virtual register locations are mapped.
 264   void mapVirtRegs(LDVImpl *LDV);
 265
 266   /// Add a definition point to this value.
 267   void addDef(SlotIndex Idx, const MachineOperand &LocMO, bool IsIndirect) {
 268     DbgValueLocation Loc(getLocationNo(LocMO), IsIndirect);
 269     // Add a singular (Idx,Idx) -> Loc mapping.
 270     LocMap::iterator I = locInts.find(Idx);
 271     if (!I.valid() || I.start() != Idx)
 272       I.insert(Idx, Idx.getNextSlot(), Loc);
 273     else
 274       // A later DBG_VALUE at the same SlotIndex overrides the old location.
 275       I.setValue(Loc);
 276   }
 277
 278   /// Extend the current definition as far as possible down.
 279   ///
 280   /// Stop when meeting an existing def or when leaving the live
 281   /// range of VNI. End points where VNI is no longer live are added to Kills.
 282   ///
 283   /// We only propagate DBG_VALUES locally here. LiveDebugValues performs a
 284   /// data-flow analysis to propagate them beyond basic block boundaries.
 285   ///
 286   /// \param Idx Starting point for the definition.
 287   /// \param Loc Location number to propagate.
 288   /// \param LR Restrict liveness to where LR has the value VNI. May be null.
 289   /// \param VNI When LR is not null, this is the value to restrict to.
 290   /// \param [out] Kills Append end points of VNI's live range to Kills.
 291   /// \param LIS Live intervals analysis.
 292   void extendDef(SlotIndex Idx, DbgValueLocation Loc,
 293                  LiveRange *LR, const VNInfo *VNI,
 294                  SmallVectorImpl<SlotIndex> *Kills,
 295                  LiveIntervals &LIS);
 296
 297   /// The value in LI/LocNo may be copies to other registers. Determine if
 298   /// any of the copies are available at the kill points, and add defs if
 299   /// possible.
 300   ///
 301   /// \param LI Scan for copies of the value in LI->reg.
 302   /// \param LocNo Location number of LI->reg.
 303   /// \param WasIndirect Indicates if the original use of LI->reg was indirect
 304   /// \param Kills Points where the range of LocNo could be extended.
 305   /// \param [in,out] NewDefs Append (Idx, LocNo) of inserted defs here.
 306   void addDefsFromCopies(
 307       LiveInterval *LI, unsigned LocNo, bool WasIndirect,
 308       const SmallVectorImpl<SlotIndex> &Kills,
 309       SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
 310       MachineRegisterInfo &MRI, LiveIntervals &LIS);
 311
 312   /// Compute the live intervals of all locations after collecting all their
 313   /// def points.
 314   void computeIntervals(MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
 315                         LiveIntervals &LIS, LexicalScopes &LS);
 316
 317   /// Replace OldReg ranges with NewRegs ranges where NewRegs is
 318   /// live. Returns true if any changes were made.
 319   bool splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
 320                      LiveIntervals &LIS);
 321
 322   /// Rewrite virtual register locations according to the provided virtual
 323   /// register map. Record the stack slot offsets for the locations that
 324   /// were spilled.
 325   void rewriteLocations(VirtRegMap &VRM, const MachineFunction &MF,
 326                         const TargetInstrInfo &TII,
 327                         const TargetRegisterInfo &TRI,
 328                         SpillOffsetMap &SpillOffsets);
 329
 330   /// Recreate DBG_VALUE instruction from data structures.
 331   void emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
 332                        const TargetInstrInfo &TII,
 333                        const TargetRegisterInfo &TRI,
 334                        const SpillOffsetMap &SpillOffsets);
 335
 336   /// Return DebugLoc of this UserValue.
 337   DebugLoc getDebugLoc() { return dl;}
 338
 339   void print(raw_ostream &, const TargetRegisterInfo *);
 340 };
 341
 342 /// Implementation of the LiveDebugVariables pass.
 343 class LDVImpl {
 344   LiveDebugVariables &pass;
 345   LocMap::Allocator allocator;
 346   MachineFunction *MF = nullptr;
 347   LiveIntervals *LIS;
 348   const TargetRegisterInfo *TRI;
 349
 350   /// Whether emitDebugValues is called.
 351   bool EmitDone = false;
 352
 353   /// Whether the machine function is modified during the pass.
 354   bool ModifiedMF = false;
 355
 356   /// All allocated UserValue instances.
 357   SmallVector<std::unique_ptr<UserValue>, 8> userValues;
 358
 359   /// Map virtual register to eq class leader.
 360   using VRMap = DenseMap<unsigned, UserValue *>;
 361   VRMap virtRegToEqClass;
 362
 363   /// Map user variable to eq class leader.
 364   using UVMap = DenseMap<const DILocalVariable *, UserValue *>;
 365   UVMap userVarMap;
 366
 367   /// Find or create a UserValue.
 368   UserValue *getUserValue(const DILocalVariable *Var, const DIExpression *Expr,
 369                           const DebugLoc &DL);
 370
 371   /// Find the EC leader for VirtReg or null.
 372   UserValue *lookupVirtReg(unsigned VirtReg);
 373
 374   /// Add DBG_VALUE instruction to our maps.
 375   ///
 376   /// \param MI DBG_VALUE instruction
 377   /// \param Idx Last valid SLotIndex before instruction.
 378   ///
 379   /// \returns True if the DBG_VALUE instruction should be deleted.
 380   bool handleDebugValue(MachineInstr &MI, SlotIndex Idx);
 381
 382   /// Collect and erase all DBG_VALUE instructions, adding a UserValue def
 383   /// for each instruction.
 384   ///
 385   /// \param mf MachineFunction to be scanned.
 386   ///
 387   /// \returns True if any debug values were found.
 388   bool collectDebugValues(MachineFunction &mf);
 389
 390   /// Compute the live intervals of all user values after collecting all
 391   /// their def points.
 392   void computeIntervals();
 393
 394 public:
 395   LDVImpl(LiveDebugVariables *ps) : pass(*ps) {}
 396
 397   bool runOnMachineFunction(MachineFunction &mf);
 398
 399   /// Release all memory.
 400   void clear() {
 401     MF = nullptr;
 402     userValues.clear();
 403     virtRegToEqClass.clear();
 404     userVarMap.clear();
 405     // Make sure we call emitDebugValues if the machine function was modified.
 406     assert((!ModifiedMF || EmitDone) &&
 407            "Dbg values are not emitted in LDV");
 408     EmitDone = false;
 409     ModifiedMF = false;
 410   }
 411
 412   /// Map virtual register to an equivalence class.
 413   void mapVirtReg(unsigned VirtReg, UserValue *EC);
 414
 415   /// Replace all references to OldReg with NewRegs.
 416   void splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs);
 417
 418   /// Recreate DBG_VALUE instruction from data structures.
 419   void emitDebugValues(VirtRegMap *VRM);
 420
 421   void print(raw_ostream&);
 422 };
 423
 424 } // end anonymous namespace
 425
 426 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 427 static void printDebugLoc(const DebugLoc &DL, raw_ostream &CommentOS,
 428                           const LLVMContext &Ctx) {
 429   if (!DL)
 430     return;
 431
 432   auto *Scope = cast<DIScope>(DL.getScope());
 433   // Omit the directory, because it's likely to be long and uninteresting.
 434   CommentOS << Scope->getFilename();
 435   CommentOS << ':' << DL.getLine();
 436   if (DL.getCol() != 0)
 437     CommentOS << ':' << DL.getCol();
 438
 439   DebugLoc InlinedAtDL = DL.getInlinedAt();
 440   if (!InlinedAtDL)
 441     return;
 442
 443   CommentOS << " @[ ";
 444   printDebugLoc(InlinedAtDL, CommentOS, Ctx);
 445   CommentOS << " ]";
 446 }
 447
 448 static void printExtendedName(raw_ostream &OS, const DILocalVariable *V,
 449                               const DILocation *DL) {
 450   const LLVMContext &Ctx = V->getContext();
 451   StringRef Res = V->getName();
 452   if (!Res.empty())
 453     OS << Res << "," << V->getLine();
 454   if (auto *InlinedAt = DL->getInlinedAt()) {
 455     if (DebugLoc InlinedAtDL = InlinedAt) {
 456       OS << " @[";
 457       printDebugLoc(InlinedAtDL, OS, Ctx);
 458       OS << "]";
 459     }
 460   }
 461 }
 462
 463 void UserValue::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
 464   auto *DV = cast<DILocalVariable>(Variable);
 465   OS << "!\"";
 466   printExtendedName(OS, DV, dl);
 467
 468   OS << "\"\t";
 469   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
 470     OS << " [" << I.start() << ';' << I.stop() << "):";
 471     if (I.value().isUndef())
 472       OS << "undef";
 473     else {
 474       OS << I.value().locNo();
 475       if (I.value().wasIndirect())
 476         OS << " ind";
 477     }
 478   }
 479   for (unsigned i = 0, e = locations.size(); i != e; ++i) {
 480     OS << " Loc" << i << '=';
 481     locations[i].print(OS, TRI);
 482   }
 483   OS << '\n';
 484 }
 485
 486 void LDVImpl::print(raw_ostream &OS) {
 487   OS << "********** DEBUG VARIABLES **********\n";
 488   for (unsigned i = 0, e = userValues.size(); i != e; ++i)
 489     userValues[i]->print(OS, TRI);
 490 }
 491 #endif
 492
 493 void UserValue::mapVirtRegs(LDVImpl *LDV) {
 494   for (unsigned i = 0, e = locations.size(); i != e; ++i)
 495     if (locations[i].isReg() &&
 496         TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
 497       LDV->mapVirtReg(locations[i].getReg(), this);
 498 }
 499
 500 UserValue *LDVImpl::getUserValue(const DILocalVariable *Var,
 501                                  const DIExpression *Expr, const DebugLoc &DL) {
 502   UserValue *&Leader = userVarMap[Var];
 503   if (Leader) {
 504     UserValue *UV = Leader->getLeader();
 505     Leader = UV;
 506     for (; UV; UV = UV->getNext())
 507       if (UV->match(Var, Expr, DL->getInlinedAt()))
 508         return UV;
 509   }
 510
 511   userValues.push_back(
 512       llvm::make_unique<UserValue>(Var, Expr, DL, allocator));
 513   UserValue *UV = userValues.back().get();
 514   Leader = UserValue::merge(Leader, UV);
 515   return UV;
 516 }
 517
 518 void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
 519   assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
 520   UserValue *&Leader = virtRegToEqClass[VirtReg];
 521   Leader = UserValue::merge(Leader, EC);
 522 }
 523
 524 UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
 525   if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
 526     return UV->getLeader();
 527   return nullptr;
 528 }
 529
 530 bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
 531   // DBG_VALUE loc, offset, variable
 532   if (MI.getNumOperands() != 4 ||
 533       !(MI.getOperand(1).isReg() || MI.getOperand(1).isImm()) ||
 534       !MI.getOperand(2).isMetadata()) {
 535     LLVM_DEBUG(dbgs() << "Can't handle " << MI);
 536     return false;
 537   }
 538
 539   // Detect invalid DBG_VALUE instructions, with a debug-use of a virtual
 540   // register that hasn't been defined yet. If we do not remove those here, then
 541   // the re-insertion of the DBG_VALUE instruction after register allocation
 542   // will be incorrect.
 543   // TODO: If earlier passes are corrected to generate sane debug information
 544   // (and if the machine verifier is improved to catch this), then these checks
 545   // could be removed or replaced by asserts.
 546   bool Discard = false;
 547   if (MI.getOperand(0).isReg() &&
 548       TargetRegisterInfo::isVirtualRegister(MI.getOperand(0).getReg())) {
 549     const unsigned Reg = MI.getOperand(0).getReg();
 550     if (!LIS->hasInterval(Reg)) {
 551       // The DBG_VALUE is described by a virtual register that does not have a
 552       // live interval. Discard the DBG_VALUE.
 553       Discard = true;
 554       LLVM_DEBUG(dbgs() << "Discarding debug info (no LIS interval): " << Idx
 555                         << " " << MI);
 556     } else {
 557       // The DBG_VALUE is only valid if either Reg is live out from Idx, or Reg
 558       // is defined dead at Idx (where Idx is the slot index for the instruction
 559       // preceeding the DBG_VALUE).
 560       const LiveInterval &LI = LIS->getInterval(Reg);
 561       LiveQueryResult LRQ = LI.Query(Idx);
 562       if (!LRQ.valueOutOrDead()) {
 563         // We have found a DBG_VALUE with the value in a virtual register that
 564         // is not live. Discard the DBG_VALUE.
 565         Discard = true;
 566         LLVM_DEBUG(dbgs() << "Discarding debug info (reg not live): " << Idx
 567                           << " " << MI);
 568       }
 569     }
 570   }
 571
 572   // Get or create the UserValue for (variable,offset) here.
 573   bool IsIndirect = MI.getOperand(1).isImm();
 574   if (IsIndirect)
 575     assert(MI.getOperand(1).getImm() == 0 && "DBG_VALUE with nonzero offset");
 576   const DILocalVariable *Var = MI.getDebugVariable();
 577   const DIExpression *Expr = MI.getDebugExpression();
 578   UserValue *UV =
 579       getUserValue(Var, Expr, MI.getDebugLoc());
 580   if (!Discard)
 581     UV->addDef(Idx, MI.getOperand(0), IsIndirect);
 582   else {
 583     MachineOperand MO = MachineOperand::CreateReg(0U, false);
 584     MO.setIsDebug();
 585     UV->addDef(Idx, MO, false);
 586   }
 587   return true;
 588 }
 589
 590 bool LDVImpl::collectDebugValues(MachineFunction &mf) {
 591   bool Changed = false;
 592   for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
 593        ++MFI) {
 594     MachineBasicBlock *MBB = &*MFI;
 595     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
 596          MBBI != MBBE;) {
 597       // Use the first debug instruction in the sequence to get a SlotIndex
 598       // for following consecutive debug instructions.
 599       if (!MBBI->isDebugInstr()) {
 600         ++MBBI;
 601         continue;
 602       }
 603       // Debug instructions has no slot index. Use the previous
 604       // non-debug instruction's SlotIndex as its SlotIndex.
 605       SlotIndex Idx =
 606           MBBI == MBB->begin()
 607               ? LIS->getMBBStartIdx(MBB)
 608               : LIS->getInstructionIndex(*std::prev(MBBI)).getRegSlot();
 609       // Handle consecutive debug instructions with the same slot index.
 610       do {
 611         // Only handle DBG_VALUE in handleDebugValue(). Skip all other
 612         // kinds of debug instructions.
 613         if (MBBI->isDebugValue() && handleDebugValue(*MBBI, Idx)) {
 614           MBBI = MBB->erase(MBBI);
 615           Changed = true;
 616         } else
 617           ++MBBI;
 618       } while (MBBI != MBBE && MBBI->isDebugInstr());
 619     }
 620   }
 621   return Changed;
 622 }
 623
 624 void UserValue::extendDef(SlotIndex Idx, DbgValueLocation Loc, LiveRange *LR,
 625                           const VNInfo *VNI, SmallVectorImpl<SlotIndex> *Kills,
 626                           LiveIntervals &LIS) {
 627   SlotIndex Start = Idx;
 628   MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
 629   SlotIndex Stop = LIS.getMBBEndIdx(MBB);
 630   LocMap::iterator I = locInts.find(Start);
 631
 632   // Limit to VNI's live range.
 633   bool ToEnd = true;
 634   if (LR && VNI) {
 635     LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
 636     if (!Segment || Segment->valno != VNI) {
 637       if (Kills)
 638         Kills->push_back(Start);
 639       return;
 640     }
 641     if (Segment->end < Stop) {
 642       Stop = Segment->end;
 643       ToEnd = false;
 644     }
 645   }
 646
 647   // There could already be a short def at Start.
 648   if (I.valid() && I.start() <= Start) {
 649     // Stop when meeting a different location or an already extended interval.
 650     Start = Start.getNextSlot();
 651     if (I.value() != Loc || I.stop() != Start)
 652       return;
 653     // This is a one-slot placeholder. Just skip it.
 654     ++I;
 655   }
 656
 657   // Limited by the next def.
 658   if (I.valid() && I.start() < Stop) {
 659     Stop = I.start();
 660     ToEnd = false;
 661   }
 662   // Limited by VNI's live range.
 663   else if (!ToEnd && Kills)
 664     Kills->push_back(Stop);
 665
 666   if (Start < Stop)
 667     I.insert(Start, Stop, Loc);
 668 }
 669
 670 void UserValue::addDefsFromCopies(
 671     LiveInterval *LI, unsigned LocNo, bool WasIndirect,
 672     const SmallVectorImpl<SlotIndex> &Kills,
 673     SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
 674     MachineRegisterInfo &MRI, LiveIntervals &LIS) {
 675   if (Kills.empty())
 676     return;
 677   // Don't track copies from physregs, there are too many uses.
 678   if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
 679     return;
 680
 681   // Collect all the (vreg, valno) pairs that are copies of LI.
 682   SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
 683   for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg)) {
 684     MachineInstr *MI = MO.getParent();
 685     // Copies of the full value.
 686     if (MO.getSubReg() || !MI->isCopy())
 687       continue;
 688     unsigned DstReg = MI->getOperand(0).getReg();
 689
 690     // Don't follow copies to physregs. These are usually setting up call
 691     // arguments, and the argument registers are always call clobbered. We are
 692     // better off in the source register which could be a callee-saved register,
 693     // or it could be spilled.
 694     if (!TargetRegisterInfo::isVirtualRegister(DstReg))
 695       continue;
 696
 697     // Is LocNo extended to reach this copy? If not, another def may be blocking
 698     // it, or we are looking at a wrong value of LI.
 699     SlotIndex Idx = LIS.getInstructionIndex(*MI);
 700     LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
 701     if (!I.valid() || I.value().locNo() != LocNo)
 702       continue;
 703
 704     if (!LIS.hasInterval(DstReg))
 705       continue;
 706     LiveInterval *DstLI = &LIS.getInterval(DstReg);
 707     const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
 708     assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
 709     CopyValues.push_back(std::make_pair(DstLI, DstVNI));
 710   }
 711
 712   if (CopyValues.empty())
 713     return;
 714
 715   LLVM_DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI
 716                     << '\n');
 717
 718   // Try to add defs of the copied values for each kill point.
 719   for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
 720     SlotIndex Idx = Kills[i];
 721     for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
 722       LiveInterval *DstLI = CopyValues[j].first;
 723       const VNInfo *DstVNI = CopyValues[j].second;
 724       if (DstLI->getVNInfoAt(Idx) != DstVNI)
 725         continue;
 726       // Check that there isn't already a def at Idx
 727       LocMap::iterator I = locInts.find(Idx);
 728       if (I.valid() && I.start() <= Idx)
 729         continue;
 730       LLVM_DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
 731                         << DstVNI->id << " in " << *DstLI << '\n');
 732       MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
 733       assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
 734       unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
 735       DbgValueLocation NewLoc(LocNo, WasIndirect);
 736       I.insert(Idx, Idx.getNextSlot(), NewLoc);
 737       NewDefs.push_back(std::make_pair(Idx, NewLoc));
 738       break;
 739     }
 740   }
 741 }
 742
 743 void UserValue::computeIntervals(MachineRegisterInfo &MRI,
 744                                  const TargetRegisterInfo &TRI,
 745                                  LiveIntervals &LIS, LexicalScopes &LS) {
 746   SmallVector<std::pair<SlotIndex, DbgValueLocation>, 16> Defs;
 747
 748   // Collect all defs to be extended (Skipping undefs).
 749   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
 750     if (!I.value().isUndef())
 751       Defs.push_back(std::make_pair(I.start(), I.value()));
 752
 753   // Extend all defs, and possibly add new ones along the way.
 754   for (unsigned i = 0; i != Defs.size(); ++i) {
 755     SlotIndex Idx = Defs[i].first;
 756     DbgValueLocation Loc = Defs[i].second;
 757     const MachineOperand &LocMO = locations[Loc.locNo()];
 758
 759     if (!LocMO.isReg()) {
 760       extendDef(Idx, Loc, nullptr, nullptr, nullptr, LIS);
 761       continue;
 762     }
 763
 764     // Register locations are constrained to where the register value is live.
 765     if (TargetRegisterInfo::isVirtualRegister(LocMO.getReg())) {
 766       LiveInterval *LI = nullptr;
 767       const VNInfo *VNI = nullptr;
 768       if (LIS.hasInterval(LocMO.getReg())) {
 769         LI = &LIS.getInterval(LocMO.getReg());
 770         VNI = LI->getVNInfoAt(Idx);
 771       }
 772       SmallVector<SlotIndex, 16> Kills;
 773       extendDef(Idx, Loc, LI, VNI, &Kills, LIS);
 774       // FIXME: Handle sub-registers in addDefsFromCopies. The problem is that
 775       // if the original location for example is %vreg0:sub_hi, and we find a
 776       // full register copy in addDefsFromCopies (at the moment it only handles
 777       // full register copies), then we must add the sub1 sub-register index to
 778       // the new location. However, that is only possible if the new virtual
 779       // register is of the same regclass (or if there is an equivalent
 780       // sub-register in that regclass). For now, simply skip handling copies if
 781       // a sub-register is involved.
 782       if (LI && !LocMO.getSubReg())
 783         addDefsFromCopies(LI, Loc.locNo(), Loc.wasIndirect(), Kills, Defs, MRI,
 784                           LIS);
 785       continue;
 786     }
 787
 788     // For physregs, we only mark the start slot idx. DwarfDebug will see it
 789     // as if the DBG_VALUE is valid up until the end of the basic block, or
 790     // the next def of the physical register. So we do not need to extend the
 791     // range. It might actually happen that the DBG_VALUE is the last use of
 792     // the physical register (e.g. if this is an unused input argument to a
 793     // function).
 794   }
 795
 796   // The computed intervals may extend beyond the range of the debug
 797   // location's lexical scope. In this case, splitting of an interval
 798   // can result in an interval outside of the scope being created,
 799   // causing extra unnecessary DBG_VALUEs to be emitted. To prevent
 800   // this, trim the intervals to the lexical scope.
 801
 802   LexicalScope *Scope = LS.findLexicalScope(dl);
 803   if (!Scope)
 804     return;
 805
 806   SlotIndex PrevEnd;
 807   LocMap::iterator I = locInts.begin();
 808
 809   // Iterate over the lexical scope ranges. Each time round the loop
 810   // we check the intervals for overlap with the end of the previous
 811   // range and the start of the next. The first range is handled as
 812   // a special case where there is no PrevEnd.
 813   for (const InsnRange &Range : Scope->getRanges()) {
 814     SlotIndex RStart = LIS.getInstructionIndex(*Range.first);
 815     SlotIndex REnd = LIS.getInstructionIndex(*Range.second);
 816
 817     // At the start of each iteration I has been advanced so that
 818     // I.stop() >= PrevEnd. Check for overlap.
 819     if (PrevEnd && I.start() < PrevEnd) {
 820       SlotIndex IStop = I.stop();
 821       DbgValueLocation Loc = I.value();
 822
 823       // Stop overlaps previous end - trim the end of the interval to
 824       // the scope range.
 825       I.setStopUnchecked(PrevEnd);
 826       ++I;
 827
 828       // If the interval also overlaps the start of the "next" (i.e.
 829       // current) range create a new interval for the remainder (which
 830       // may be further trimmed).
 831       if (RStart < IStop)
 832         I.insert(RStart, IStop, Loc);
 833     }
 834
 835     // Advance I so that I.stop() >= RStart, and check for overlap.
 836     I.advanceTo(RStart);
 837     if (!I.valid())
 838       return;
 839
 840     if (I.start() < RStart) {
 841       // Interval start overlaps range - trim to the scope range.
 842       I.setStartUnchecked(RStart);
 843       // Remember that this interval was trimmed.
 844       trimmedDefs.insert(RStart);
 845     }
 846
 847     // The end of a lexical scope range is the last instruction in the
 848     // range. To convert to an interval we need the index of the
 849     // instruction after it.
 850     REnd = REnd.getNextIndex();
 851
 852     // Advance I to first interval outside current range.
 853     I.advanceTo(REnd);
 854     if (!I.valid())
 855       return;
 856
 857     PrevEnd = REnd;
 858   }
 859
 860   // Check for overlap with end of final range.
 861   if (PrevEnd && I.start() < PrevEnd)
 862     I.setStopUnchecked(PrevEnd);
 863 }
 864
 865 void LDVImpl::computeIntervals() {
 866   LexicalScopes LS;
 867   LS.initialize(*MF);
 868
 869   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
 870     userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, LS);
 871     userValues[i]->mapVirtRegs(this);
 872   }
 873 }
 874
 875 bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
 876   clear();
 877   MF = &mf;
 878   LIS = &pass.getAnalysis<LiveIntervals>();
 879   TRI = mf.getSubtarget().getRegisterInfo();
 880   LLVM_DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
 881                     << mf.getName() << " **********\n");
 882
 883   bool Changed = collectDebugValues(mf);
 884   computeIntervals();
 885   LLVM_DEBUG(print(dbgs()));
 886   ModifiedMF = Changed;
 887   return Changed;
 888 }
 889
 890 static void removeDebugValues(MachineFunction &mf) {
 891   for (MachineBasicBlock &MBB : mf) {
 892     for (auto MBBI = MBB.begin(), MBBE = MBB.end(); MBBI != MBBE; ) {
 893       if (!MBBI->isDebugValue()) {
 894         ++MBBI;
 895         continue;
 896       }
 897       MBBI = MBB.erase(MBBI);
 898     }
 899   }
 900 }
 901
 902 bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
 903   if (!EnableLDV)
 904     return false;
 905   if (!mf.getFunction().getSubprogram()) {
 906     removeDebugValues(mf);
 907     return false;
 908   }
 909   if (!pImpl)
 910     pImpl = new LDVImpl(this);
 911   return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
 912 }
 913
 914 void LiveDebugVariables::releaseMemory() {
 915   if (pImpl)
 916     static_cast<LDVImpl*>(pImpl)->clear();
 917 }
 918
 919 LiveDebugVariables::~LiveDebugVariables() {
 920   if (pImpl)
 921     delete static_cast<LDVImpl*>(pImpl);
 922 }
 923
 924 //===----------------------------------------------------------------------===//
 925 //                           Live Range Splitting
 926 //===----------------------------------------------------------------------===//
 927
 928 bool
 929 UserValue::splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
 930                          LiveIntervals& LIS) {
 931   LLVM_DEBUG({
 932     dbgs() << "Splitting Loc" << OldLocNo << '\t';
 933     print(dbgs(), nullptr);
 934   });
 935   bool DidChange = false;
 936   LocMap::iterator LocMapI;
 937   LocMapI.setMap(locInts);
 938   for (unsigned i = 0; i != NewRegs.size(); ++i) {
 939     LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
 940     if (LI->empty())
 941       continue;
 942
 943     // Don't allocate the new LocNo until it is needed.
 944     unsigned NewLocNo = UndefLocNo;
 945
 946     // Iterate over the overlaps between locInts and LI.
 947     LocMapI.find(LI->beginIndex());
 948     if (!LocMapI.valid())
 949       continue;
 950     LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
 951     LiveInterval::iterator LIE = LI->end();
 952     while (LocMapI.valid() && LII != LIE) {
 953       // At this point, we know that LocMapI.stop() > LII->start.
 954       LII = LI->advanceTo(LII, LocMapI.start());
 955       if (LII == LIE)
 956         break;
 957
 958       // Now LII->end > LocMapI.start(). Do we have an overlap?
 959       if (LocMapI.value().locNo() == OldLocNo && LII->start < LocMapI.stop()) {
 960         // Overlapping correct location. Allocate NewLocNo now.
 961         if (NewLocNo == UndefLocNo) {
 962           MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
 963           MO.setSubReg(locations[OldLocNo].getSubReg());
 964           NewLocNo = getLocationNo(MO);
 965           DidChange = true;
 966         }
 967
 968         SlotIndex LStart = LocMapI.start();
 969         SlotIndex LStop  = LocMapI.stop();
 970         DbgValueLocation OldLoc = LocMapI.value();
 971
 972         // Trim LocMapI down to the LII overlap.
 973         if (LStart < LII->start)
 974           LocMapI.setStartUnchecked(LII->start);
 975         if (LStop > LII->end)
 976           LocMapI.setStopUnchecked(LII->end);
 977
 978         // Change the value in the overlap. This may trigger coalescing.
 979         LocMapI.setValue(OldLoc.changeLocNo(NewLocNo));
 980
 981         // Re-insert any removed OldLocNo ranges.
 982         if (LStart < LocMapI.start()) {
 983           LocMapI.insert(LStart, LocMapI.start(), OldLoc);
 984           ++LocMapI;
 985           assert(LocMapI.valid() && "Unexpected coalescing");
 986         }
 987         if (LStop > LocMapI.stop()) {
 988           ++LocMapI;
 989           LocMapI.insert(LII->end, LStop, OldLoc);
 990           --LocMapI;
 991         }
 992       }
 993
 994       // Advance to the next overlap.
 995       if (LII->end < LocMapI.stop()) {
 996         if (++LII == LIE)
 997           break;
 998         LocMapI.advanceTo(LII->start);
 999       } else {
1000         ++LocMapI;
1001         if (!LocMapI.valid())
1002           break;
1003         LII = LI->advanceTo(LII, LocMapI.start());
1004       }
1005     }
1006   }
1007
1008   // Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
1009   locations.erase(locations.begin() + OldLocNo);
1010   LocMapI.goToBegin();
1011   while (LocMapI.valid()) {
1012     DbgValueLocation v = LocMapI.value();
1013     if (v.locNo() == OldLocNo) {
1014       LLVM_DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
1015                         << LocMapI.stop() << ")\n");
1016       LocMapI.erase();
1017     } else {
1018       // Undef values always have location number UndefLocNo, so don't change
1019       // locNo in that case. See getLocationNo().
1020       if (!v.isUndef() && v.locNo() > OldLocNo)
1021         LocMapI.setValueUnchecked(v.changeLocNo(v.locNo() - 1));
1022       ++LocMapI;
1023     }
1024   }
1025
1026   LLVM_DEBUG({
1027     dbgs() << "Split result: \t";
1028     print(dbgs(), nullptr);
1029   });
1030   return DidChange;
1031 }
1032
1033 bool
1034 UserValue::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
1035                          LiveIntervals &LIS) {
1036   bool DidChange = false;
1037   // Split locations referring to OldReg. Iterate backwards so splitLocation can
1038   // safely erase unused locations.
1039   for (unsigned i = locations.size(); i ; --i) {
1040     unsigned LocNo = i-1;
1041     const MachineOperand *Loc = &locations[LocNo];
1042     if (!Loc->isReg() || Loc->getReg() != OldReg)
1043       continue;
1044     DidChange |= splitLocation(LocNo, NewRegs, LIS);
1045   }
1046   return DidChange;
1047 }
1048
1049 void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs) {
1050   bool DidChange = false;
1051   for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
1052     DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
1053
1054   if (!DidChange)
1055     return;
1056
1057   // Map all of the new virtual registers.
1058   UserValue *UV = lookupVirtReg(OldReg);
1059   for (unsigned i = 0; i != NewRegs.size(); ++i)
1060     mapVirtReg(NewRegs[i], UV);
1061 }
1062
1063 void LiveDebugVariables::
1064 splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
1065   if (pImpl)
1066     static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
1067 }
1068
1069 void UserValue::rewriteLocations(VirtRegMap &VRM, const MachineFunction &MF,
1070                                  const TargetInstrInfo &TII,
1071                                  const TargetRegisterInfo &TRI,
1072                                  SpillOffsetMap &SpillOffsets) {
1073   // Build a set of new locations with new numbers so we can coalesce our
1074   // IntervalMap if two vreg intervals collapse to the same physical location.
1075   // Use MapVector instead of SetVector because MapVector::insert returns the
1076   // position of the previously or newly inserted element. The boolean value
1077   // tracks if the location was produced by a spill.
1078   // FIXME: This will be problematic if we ever support direct and indirect
1079   // frame index locations, i.e. expressing both variables in memory and
1080   // 'int x, *px = &x'. The "spilled" bit must become part of the location.
1081   MapVector<MachineOperand, std::pair<bool, unsigned>> NewLocations;
1082   SmallVector<unsigned, 4> LocNoMap(locations.size());
1083   for (unsigned I = 0, E = locations.size(); I != E; ++I) {
1084     bool Spilled = false;
1085     unsigned SpillOffset = 0;
1086     MachineOperand Loc = locations[I];
1087     // Only virtual registers are rewritten.
1088     if (Loc.isReg() && Loc.getReg() &&
1089         TargetRegisterInfo::isVirtualRegister(Loc.getReg())) {
1090       unsigned VirtReg = Loc.getReg();
1091       if (VRM.isAssignedReg(VirtReg) &&
1092           TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
1093         // This can create a %noreg operand in rare cases when the sub-register
1094         // index is no longer available. That means the user value is in a
1095         // non-existent sub-register, and %noreg is exactly what we want.
1096         Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
1097       } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
1098         // Retrieve the stack slot offset.
1099         unsigned SpillSize;
1100         const MachineRegisterInfo &MRI = MF.getRegInfo();
1101         const TargetRegisterClass *TRC = MRI.getRegClass(VirtReg);
1102         bool Success = TII.getStackSlotRange(TRC, Loc.getSubReg(), SpillSize,
1103                                              SpillOffset, MF);
1104
1105         // FIXME: Invalidate the location if the offset couldn't be calculated.
1106         (void)Success;
1107
1108         Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
1109         Spilled = true;
1110       } else {
1111         Loc.setReg(0);
1112         Loc.setSubReg(0);
1113       }
1114     }
1115
1116     // Insert this location if it doesn't already exist and record a mapping
1117     // from the old number to the new number.
1118     auto InsertResult = NewLocations.insert({Loc, {Spilled, SpillOffset}});
1119     unsigned NewLocNo = std::distance(NewLocations.begin(), InsertResult.first);
1120     LocNoMap[I] = NewLocNo;
1121   }
1122
1123   // Rewrite the locations and record the stack slot offsets for spills.
1124   locations.clear();
1125   SpillOffsets.clear();
1126   for (auto &Pair : NewLocations) {
1127     bool Spilled;
1128     unsigned SpillOffset;
1129     std::tie(Spilled, SpillOffset) = Pair.second;
1130     locations.push_back(Pair.first);
1131     if (Spilled) {
1132       unsigned NewLocNo = std::distance(&*NewLocations.begin(), &Pair);
1133       SpillOffsets[NewLocNo] = SpillOffset;
1134     }
1135   }
1136
1137   // Update the interval map, but only coalesce left, since intervals to the
1138   // right use the old location numbers. This should merge two contiguous
1139   // DBG_VALUE intervals with different vregs that were allocated to the same
1140   // physical register.
1141   for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
1142     DbgValueLocation Loc = I.value();
1143     // Undef values don't exist in locations (and thus not in LocNoMap either)
1144     // so skip over them. See getLocationNo().
1145     if (Loc.isUndef())
1146       continue;
1147     unsigned NewLocNo = LocNoMap[Loc.locNo()];
1148     I.setValueUnchecked(Loc.changeLocNo(NewLocNo));
1149     I.setStart(I.start());
1150   }
1151 }
1152
1153 /// Find an iterator for inserting a DBG_VALUE instruction.
1154 static MachineBasicBlock::iterator
1155 findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
1156                    LiveIntervals &LIS) {
1157   SlotIndex Start = LIS.getMBBStartIdx(MBB);
1158   Idx = Idx.getBaseIndex();
1159
1160   // Try to find an insert location by going backwards from Idx.
1161   MachineInstr *MI;
1162   while (!(MI = LIS.getInstructionFromIndex(Idx))) {
1163     // We've reached the beginning of MBB.
1164     if (Idx == Start) {
1165       MachineBasicBlock::iterator I = MBB->SkipPHIsLabelsAndDebug(MBB->begin());
1166       return I;
1167     }
1168     Idx = Idx.getPrevIndex();
1169   }
1170
1171   // Don't insert anything after the first terminator, though.
1172   return MI->isTerminator() ? MBB->getFirstTerminator() :
1173                               std::next(MachineBasicBlock::iterator(MI));
1174 }
1175
1176 /// Find an iterator for inserting the next DBG_VALUE instruction
1177 /// (or end if no more insert locations found).
1178 static MachineBasicBlock::iterator
1179 findNextInsertLocation(MachineBasicBlock *MBB,
1180                        MachineBasicBlock::iterator I,
1181                        SlotIndex StopIdx, MachineOperand &LocMO,
1182                        LiveIntervals &LIS,
1183                        const TargetRegisterInfo &TRI) {
1184   if (!LocMO.isReg())
1185     return MBB->instr_end();
1186   unsigned Reg = LocMO.getReg();
1187
1188   // Find the next instruction in the MBB that define the register Reg.
1189   while (I != MBB->end() && !I->isTerminator()) {
1190     if (!LIS.isNotInMIMap(*I) &&
1191         SlotIndex::isEarlierEqualInstr(StopIdx, LIS.getInstructionIndex(*I)))
1192       break;
1193     if (I->definesRegister(Reg, &TRI))
1194       // The insert location is directly after the instruction/bundle.
1195       return std::next(I);
1196     ++I;
1197   }
1198   return MBB->end();
1199 }
1200
1201 void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
1202                                  SlotIndex StopIdx, DbgValueLocation Loc,
1203                                  bool Spilled, unsigned SpillOffset,
1204                                  LiveIntervals &LIS, const TargetInstrInfo &TII,
1205                                  const TargetRegisterInfo &TRI) {
1206   SlotIndex MBBEndIdx = LIS.getMBBEndIdx(&*MBB);
1207   // Only search within the current MBB.
1208   StopIdx = (MBBEndIdx < StopIdx) ? MBBEndIdx : StopIdx;
1209   MachineBasicBlock::iterator I = findInsertLocation(MBB, StartIdx, LIS);
1210   // Undef values don't exist in locations so create new "noreg" register MOs
1211   // for them. See getLocationNo().
1212   MachineOperand MO = !Loc.isUndef() ?
1213     locations[Loc.locNo()] :
1214     MachineOperand::CreateReg(/* Reg */ 0, /* isDef */ false, /* isImp */ false,
1215                               /* isKill */ false, /* isDead */ false,
1216                               /* isUndef */ false, /* isEarlyClobber */ false,
1217                               /* SubReg */ 0, /* isDebug */ true);
1218
1219   ++NumInsertedDebugValues;
1220
1221   assert(cast<DILocalVariable>(Variable)
1222              ->isValidLocationForIntrinsic(getDebugLoc()) &&
1223          "Expected inlined-at fields to agree");
1224
1225   // If the location was spilled, the new DBG_VALUE will be indirect. If the
1226   // original DBG_VALUE was indirect, we need to add DW_OP_deref to indicate
1227   // that the original virtual register was a pointer. Also, add the stack slot
1228   // offset for the spilled register to the expression.
1229   const DIExpression *Expr = Expression;
1230   bool IsIndirect = Loc.wasIndirect();
1231   if (Spilled) {
1232     auto Deref = IsIndirect ? DIExpression::WithDeref : DIExpression::NoDeref;
1233     Expr =
1234         DIExpression::prepend(Expr, DIExpression::NoDeref, SpillOffset, Deref);
1235     IsIndirect = true;
1236   }
1237
1238   assert((!Spilled || MO.isFI()) && "a spilled location must be a frame index");
1239
1240   do {
1241     BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
1242             IsIndirect, MO, Variable, Expr);
1243
1244     // Continue and insert DBG_VALUES after every redefinition of register
1245     // associated with the debug value within the range
1246     I = findNextInsertLocation(MBB, I, StopIdx, MO, LIS, TRI);
1247   } while (I != MBB->end());
1248 }
1249
1250 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
1251                                 const TargetInstrInfo &TII,
1252                                 const TargetRegisterInfo &TRI,
1253                                 const SpillOffsetMap &SpillOffsets) {
1254   MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
1255
1256   for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
1257     SlotIndex Start = I.start();
1258     SlotIndex Stop = I.stop();
1259     DbgValueLocation Loc = I.value();
1260     auto SpillIt =
1261         !Loc.isUndef() ? SpillOffsets.find(Loc.locNo()) : SpillOffsets.end();
1262     bool Spilled = SpillIt != SpillOffsets.end();
1263     unsigned SpillOffset = Spilled ? SpillIt->second : 0;
1264
1265     // If the interval start was trimmed to the lexical scope insert the
1266     // DBG_VALUE at the previous index (otherwise it appears after the
1267     // first instruction in the range).
1268     if (trimmedDefs.count(Start))
1269       Start = Start.getPrevIndex();
1270
1271     LLVM_DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << Loc.locNo());
1272     MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start)->getIterator();
1273     SlotIndex MBBEnd = LIS.getMBBEndIdx(&*MBB);
1274
1275     LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB) << '-' << MBBEnd);
1276     insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, SpillOffset, LIS, TII,
1277                      TRI);
1278     // This interval may span multiple basic blocks.
1279     // Insert a DBG_VALUE into each one.
1280     while (Stop > MBBEnd) {
1281       // Move to the next block.
1282       Start = MBBEnd;
1283       if (++MBB == MFEnd)
1284         break;
1285       MBBEnd = LIS.getMBBEndIdx(&*MBB);
1286       LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB) << '-' << MBBEnd);
1287       insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, SpillOffset, LIS, TII,
1288                        TRI);
1289     }
1290     LLVM_DEBUG(dbgs() << '\n');
1291     if (MBB == MFEnd)
1292       break;
1293
1294     ++I;
1295   }
1296 }
1297
1298 void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
1299   LLVM_DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
1300   if (!MF)
1301     return;
1302   const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
1303   SpillOffsetMap SpillOffsets;
1304   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
1305     LLVM_DEBUG(userValues[i]->print(dbgs(), TRI));
1306     userValues[i]->rewriteLocations(*VRM, *MF, *TII, *TRI, SpillOffsets);
1307     userValues[i]->emitDebugValues(VRM, *LIS, *TII, *TRI, SpillOffsets);
1308   }
1309   EmitDone = true;
1310 }
1311
1312 void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
1313   if (pImpl)
1314     static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
1315 }
1316
1317 bool LiveDebugVariables::doInitialization(Module &M) {
1318   return Pass::doInitialization(M);
1319 }
1320
1321 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1322 LLVM_DUMP_METHOD void LiveDebugVariables::dump() const {
1323   if (pImpl)
1324     static_cast<LDVImpl*>(pImpl)->print(dbgs());
1325 }
1326 #endif