src/llvm/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/IntervalMap.h"
  24 #include "llvm/ADT/Statistic.h"
  25 #include "llvm/CodeGen/LexicalScopes.h"
  26 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
  27 #include "llvm/CodeGen/MachineDominators.h"
  28 #include "llvm/CodeGen/MachineFunction.h"
  29 #include "llvm/CodeGen/MachineInstrBuilder.h"
  30 #include "llvm/CodeGen/MachineRegisterInfo.h"
  31 #include "llvm/CodeGen/Passes.h"
  32 #include "llvm/CodeGen/VirtRegMap.h"
  33 #include "llvm/IR/Constants.h"
  34 #include "llvm/IR/DebugInfo.h"
  35 #include "llvm/IR/Metadata.h"
  36 #include "llvm/IR/Value.h"
  37 #include "llvm/Support/CommandLine.h"
  38 #include "llvm/Support/Debug.h"
  39 #include "llvm/Target/TargetInstrInfo.h"
  40 #include "llvm/Target/TargetMachine.h"
  41 #include "llvm/Target/TargetRegisterInfo.h"
  42 #include "llvm/Target/TargetSubtargetInfo.h"
  43 #include <memory>
  44
  45 using namespace llvm;
  46
  47 #define DEBUG_TYPE "livedebug"
  48
  49 static cl::opt<bool>
  50 EnableLDV("live-debug-variables", cl::init(true),
  51           cl::desc("Enable the live debug variables pass"), cl::Hidden);
  52
  53 STATISTIC(NumInsertedDebugValues, "Number of DBG_VALUEs inserted");
  54 char LiveDebugVariables::ID = 0;
  55
  56 INITIALIZE_PASS_BEGIN(LiveDebugVariables, "livedebugvars",
  57                 "Debug Variable Analysis", false, false)
  58 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
  59 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
  60 INITIALIZE_PASS_END(LiveDebugVariables, "livedebugvars",
  61                 "Debug Variable Analysis", false, false)
  62
  63 void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
  64   AU.addRequired<MachineDominatorTree>();
  65   AU.addRequiredTransitive<LiveIntervals>();
  66   AU.setPreservesAll();
  67   MachineFunctionPass::getAnalysisUsage(AU);
  68 }
  69
  70 LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID), pImpl(nullptr) {
  71   initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
  72 }
  73
  74 /// LocMap - Map of where a user value is live, and its location.
  75 typedef IntervalMap<SlotIndex, unsigned, 4> LocMap;
  76
  77 namespace {
  78 /// UserValueScopes - Keeps track of lexical scopes associated with a
  79 /// user value's source location.
  80 class UserValueScopes {
  81   DebugLoc DL;
  82   LexicalScopes &LS;
  83   SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
  84
  85 public:
  86   UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(D), LS(L) {}
  87
  88   /// dominates - Return true if current scope dominates at least one machine
  89   /// instruction in a given machine basic block.
  90   bool dominates(MachineBasicBlock *MBB) {
  91     if (LBlocks.empty())
  92       LS.getMachineBasicBlocks(DL, LBlocks);
  93     if (LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB))
  94       return true;
  95     return false;
  96   }
  97 };
  98 } // end anonymous namespace
  99
 100 /// UserValue - A user value is a part of a debug info user variable.
 101 ///
 102 /// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
 103 /// holds part of a user variable. The part is identified by a byte offset.
 104 ///
 105 /// UserValues are grouped into equivalence classes for easier searching. Two
 106 /// user values are related if they refer to the same variable, or if they are
 107 /// held by the same virtual register. The equivalence class is the transitive
 108 /// closure of that relation.
 109 namespace {
 110 class LDVImpl;
 111 class UserValue {
 112   const MDNode *Variable;   ///< The debug info variable we are part of.
 113   const MDNode *Expression; ///< Any complex address expression.
 114   unsigned offset;        ///< Byte offset into variable.
 115   bool IsIndirect;        ///< true if this is a register-indirect+offset value.
 116   DebugLoc dl;            ///< The debug location for the variable. This is
 117                           ///< used by dwarf writer to find lexical scope.
 118   UserValue *leader;      ///< Equivalence class leader.
 119   UserValue *next;        ///< Next value in equivalence class, or null.
 120
 121   /// Numbered locations referenced by locmap.
 122   SmallVector<MachineOperand, 4> locations;
 123
 124   /// Map of slot indices where this value is live.
 125   LocMap locInts;
 126
 127   /// coalesceLocation - After LocNo was changed, check if it has become
 128   /// identical to another location, and coalesce them. This may cause LocNo or
 129   /// a later location to be erased, but no earlier location will be erased.
 130   void coalesceLocation(unsigned LocNo);
 131
 132   /// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
 133   void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx, unsigned LocNo,
 134                         LiveIntervals &LIS, const TargetInstrInfo &TII);
 135
 136   /// splitLocation - Replace OldLocNo ranges with NewRegs ranges where NewRegs
 137   /// is live. Returns true if any changes were made.
 138   bool splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
 139                      LiveIntervals &LIS);
 140
 141 public:
 142   /// UserValue - Create a new UserValue.
 143   UserValue(const MDNode *var, const MDNode *expr, unsigned o, bool i,
 144             DebugLoc L, LocMap::Allocator &alloc)
 145       : Variable(var), Expression(expr), offset(o), IsIndirect(i), dl(L),
 146         leader(this), next(nullptr), locInts(alloc) {}
 147
 148   /// getLeader - Get the leader of this value's equivalence class.
 149   UserValue *getLeader() {
 150     UserValue *l = leader;
 151     while (l != l->leader)
 152       l = l->leader;
 153     return leader = l;
 154   }
 155
 156   /// getNext - Return the next UserValue in the equivalence class.
 157   UserValue *getNext() const { return next; }
 158
 159   /// match - Does this UserValue match the parameters?
 160   bool match(const MDNode *Var, const MDNode *Expr, unsigned Offset,
 161              bool indirect) const {
 162     return Var == Variable && Expr == Expression && Offset == offset &&
 163            indirect == IsIndirect;
 164   }
 165
 166   /// merge - Merge equivalence classes.
 167   static UserValue *merge(UserValue *L1, UserValue *L2) {
 168     L2 = L2->getLeader();
 169     if (!L1)
 170       return L2;
 171     L1 = L1->getLeader();
 172     if (L1 == L2)
 173       return L1;
 174     // Splice L2 before L1's members.
 175     UserValue *End = L2;
 176     while (End->next)
 177       End->leader = L1, End = End->next;
 178     End->leader = L1;
 179     End->next = L1->next;
 180     L1->next = L2;
 181     return L1;
 182   }
 183
 184   /// getLocationNo - Return the location number that matches Loc.
 185   unsigned getLocationNo(const MachineOperand &LocMO) {
 186     if (LocMO.isReg()) {
 187       if (LocMO.getReg() == 0)
 188         return ~0u;
 189       // For register locations we dont care about use/def and other flags.
 190       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 191         if (locations[i].isReg() &&
 192             locations[i].getReg() == LocMO.getReg() &&
 193             locations[i].getSubReg() == LocMO.getSubReg())
 194           return i;
 195     } else
 196       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 197         if (LocMO.isIdenticalTo(locations[i]))
 198           return i;
 199     locations.push_back(LocMO);
 200     // We are storing a MachineOperand outside a MachineInstr.
 201     locations.back().clearParent();
 202     // Don't store def operands.
 203     if (locations.back().isReg())
 204       locations.back().setIsUse();
 205     return locations.size() - 1;
 206   }
 207
 208   /// mapVirtRegs - Ensure that all virtual register locations are mapped.
 209   void mapVirtRegs(LDVImpl *LDV);
 210
 211   /// addDef - Add a definition point to this value.
 212   void addDef(SlotIndex Idx, const MachineOperand &LocMO) {
 213     // Add a singular (Idx,Idx) -> Loc mapping.
 214     LocMap::iterator I = locInts.find(Idx);
 215     if (!I.valid() || I.start() != Idx)
 216       I.insert(Idx, Idx.getNextSlot(), getLocationNo(LocMO));
 217     else
 218       // A later DBG_VALUE at the same SlotIndex overrides the old location.
 219       I.setValue(getLocationNo(LocMO));
 220   }
 221
 222   /// extendDef - Extend the current definition as far as possible down the
 223   /// dominator tree. Stop when meeting an existing def or when leaving the live
 224   /// range of VNI.
 225   /// End points where VNI is no longer live are added to Kills.
 226   /// @param Idx   Starting point for the definition.
 227   /// @param LocNo Location number to propagate.
 228   /// @param LR    Restrict liveness to where LR has the value VNI. May be null.
 229   /// @param VNI   When LR is not null, this is the value to restrict to.
 230   /// @param Kills Append end points of VNI's live range to Kills.
 231   /// @param LIS   Live intervals analysis.
 232   /// @param MDT   Dominator tree.
 233   void extendDef(SlotIndex Idx, unsigned LocNo,
 234                  LiveRange *LR, const VNInfo *VNI,
 235                  SmallVectorImpl<SlotIndex> *Kills,
 236                  LiveIntervals &LIS, MachineDominatorTree &MDT,
 237                  UserValueScopes &UVS);
 238
 239   /// addDefsFromCopies - The value in LI/LocNo may be copies to other
 240   /// registers. Determine if any of the copies are available at the kill
 241   /// points, and add defs if possible.
 242   /// @param LI      Scan for copies of the value in LI->reg.
 243   /// @param LocNo   Location number of LI->reg.
 244   /// @param Kills   Points where the range of LocNo could be extended.
 245   /// @param NewDefs Append (Idx, LocNo) of inserted defs here.
 246   void addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
 247                       const SmallVectorImpl<SlotIndex> &Kills,
 248                       SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
 249                       MachineRegisterInfo &MRI,
 250                       LiveIntervals &LIS);
 251
 252   /// computeIntervals - Compute the live intervals of all locations after
 253   /// collecting all their def points.
 254   void computeIntervals(MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
 255                         LiveIntervals &LIS, MachineDominatorTree &MDT,
 256                         UserValueScopes &UVS);
 257
 258   /// splitRegister - Replace OldReg ranges with NewRegs ranges where NewRegs is
 259   /// live. Returns true if any changes were made.
 260   bool splitRegister(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
 261                      LiveIntervals &LIS);
 262
 263   /// rewriteLocations - Rewrite virtual register locations according to the
 264   /// provided virtual register map.
 265   void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI);
 266
 267   /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
 268   void emitDebugValues(VirtRegMap *VRM,
 269                        LiveIntervals &LIS, const TargetInstrInfo &TRI);
 270
 271   /// findDebugLoc - Return DebugLoc used for this DBG_VALUE instruction. A
 272   /// variable may have more than one corresponding DBG_VALUE instructions.
 273   /// Only first one needs DebugLoc to identify variable's lexical scope
 274   /// in source file.
 275   DebugLoc findDebugLoc();
 276
 277   /// getDebugLoc - Return DebugLoc of this UserValue.
 278   DebugLoc getDebugLoc() { return dl;}
 279   void print(raw_ostream&, const TargetMachine*);
 280 };
 281 } // namespace
 282
 283 /// LDVImpl - Implementation of the LiveDebugVariables pass.
 284 namespace {
 285 class LDVImpl {
 286   LiveDebugVariables &pass;
 287   LocMap::Allocator allocator;
 288   MachineFunction *MF;
 289   LiveIntervals *LIS;
 290   LexicalScopes LS;
 291   MachineDominatorTree *MDT;
 292   const TargetRegisterInfo *TRI;
 293
 294   /// Whether emitDebugValues is called.
 295   bool EmitDone;
 296   /// Whether the machine function is modified during the pass.
 297   bool ModifiedMF;
 298
 299   /// userValues - All allocated UserValue instances.
 300   SmallVector<std::unique_ptr<UserValue>, 8> userValues;
 301
 302   /// Map virtual register to eq class leader.
 303   typedef DenseMap<unsigned, UserValue*> VRMap;
 304   VRMap virtRegToEqClass;
 305
 306   /// Map user variable to eq class leader.
 307   typedef DenseMap<const MDNode *, UserValue*> UVMap;
 308   UVMap userVarMap;
 309
 310   /// getUserValue - Find or create a UserValue.
 311   UserValue *getUserValue(const MDNode *Var, const MDNode *Expr,
 312                           unsigned Offset, bool IsIndirect, DebugLoc DL);
 313
 314   /// lookupVirtReg - Find the EC leader for VirtReg or null.
 315   UserValue *lookupVirtReg(unsigned VirtReg);
 316
 317   /// handleDebugValue - Add DBG_VALUE instruction to our maps.
 318   /// @param MI  DBG_VALUE instruction
 319   /// @param Idx Last valid SLotIndex before instruction.
 320   /// @return    True if the DBG_VALUE instruction should be deleted.
 321   bool handleDebugValue(MachineInstr *MI, SlotIndex Idx);
 322
 323   /// collectDebugValues - Collect and erase all DBG_VALUE instructions, adding
 324   /// a UserValue def for each instruction.
 325   /// @param mf MachineFunction to be scanned.
 326   /// @return True if any debug values were found.
 327   bool collectDebugValues(MachineFunction &mf);
 328
 329   /// computeIntervals - Compute the live intervals of all user values after
 330   /// collecting all their def points.
 331   void computeIntervals();
 332
 333 public:
 334   LDVImpl(LiveDebugVariables *ps)
 335       : pass(*ps), MF(nullptr), EmitDone(false), ModifiedMF(false) {}
 336   bool runOnMachineFunction(MachineFunction &mf);
 337
 338   /// clear - Release all memory.
 339   void clear() {
 340     MF = nullptr;
 341     userValues.clear();
 342     virtRegToEqClass.clear();
 343     userVarMap.clear();
 344     // Make sure we call emitDebugValues if the machine function was modified.
 345     assert((!ModifiedMF || EmitDone) &&
 346            "Dbg values are not emitted in LDV");
 347     EmitDone = false;
 348     ModifiedMF = false;
 349     LS.reset();
 350   }
 351
 352   /// mapVirtReg - Map virtual register to an equivalence class.
 353   void mapVirtReg(unsigned VirtReg, UserValue *EC);
 354
 355   /// splitRegister -  Replace all references to OldReg with NewRegs.
 356   void splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs);
 357
 358   /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
 359   void emitDebugValues(VirtRegMap *VRM);
 360
 361   void print(raw_ostream&);
 362 };
 363 } // namespace
 364
 365 void UserValue::print(raw_ostream &OS, const TargetMachine *TM) {
 366   DIVariable DV(Variable);
 367   OS << "!\"";
 368   DV.printExtendedName(OS);
 369   OS << "\"\t";
 370   if (offset)
 371     OS << '+' << offset;
 372   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
 373     OS << " [" << I.start() << ';' << I.stop() << "):";
 374     if (I.value() == ~0u)
 375       OS << "undef";
 376     else
 377       OS << I.value();
 378   }
 379   for (unsigned i = 0, e = locations.size(); i != e; ++i) {
 380     OS << " Loc" << i << '=';
 381     locations[i].print(OS, TM);
 382   }
 383   OS << '\n';
 384 }
 385
 386 void LDVImpl::print(raw_ostream &OS) {
 387   OS << "********** DEBUG VARIABLES **********\n";
 388   for (unsigned i = 0, e = userValues.size(); i != e; ++i)
 389     userValues[i]->print(OS, &MF->getTarget());
 390 }
 391
 392 void UserValue::coalesceLocation(unsigned LocNo) {
 393   unsigned KeepLoc = 0;
 394   for (unsigned e = locations.size(); KeepLoc != e; ++KeepLoc) {
 395     if (KeepLoc == LocNo)
 396       continue;
 397     if (locations[KeepLoc].isIdenticalTo(locations[LocNo]))
 398       break;
 399   }
 400   // No matches.
 401   if (KeepLoc == locations.size())
 402     return;
 403
 404   // Keep the smaller location, erase the larger one.
 405   unsigned EraseLoc = LocNo;
 406   if (KeepLoc > EraseLoc)
 407     std::swap(KeepLoc, EraseLoc);
 408   locations.erase(locations.begin() + EraseLoc);
 409
 410   // Rewrite values.
 411   for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
 412     unsigned v = I.value();
 413     if (v == EraseLoc)
 414       I.setValue(KeepLoc);      // Coalesce when possible.
 415     else if (v > EraseLoc)
 416       I.setValueUnchecked(v-1); // Avoid coalescing with untransformed values.
 417   }
 418 }
 419
 420 void UserValue::mapVirtRegs(LDVImpl *LDV) {
 421   for (unsigned i = 0, e = locations.size(); i != e; ++i)
 422     if (locations[i].isReg() &&
 423         TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
 424       LDV->mapVirtReg(locations[i].getReg(), this);
 425 }
 426
 427 UserValue *LDVImpl::getUserValue(const MDNode *Var, const MDNode *Expr,
 428                                  unsigned Offset, bool IsIndirect,
 429                                  DebugLoc DL) {
 430   UserValue *&Leader = userVarMap[Var];
 431   if (Leader) {
 432     UserValue *UV = Leader->getLeader();
 433     Leader = UV;
 434     for (; UV; UV = UV->getNext())
 435       if (UV->match(Var, Expr, Offset, IsIndirect))
 436         return UV;
 437   }
 438
 439   userValues.push_back(
 440       make_unique<UserValue>(Var, Expr, Offset, IsIndirect, DL, allocator));
 441   UserValue *UV = userValues.back().get();
 442   Leader = UserValue::merge(Leader, UV);
 443   return UV;
 444 }
 445
 446 void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
 447   assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
 448   UserValue *&Leader = virtRegToEqClass[VirtReg];
 449   Leader = UserValue::merge(Leader, EC);
 450 }
 451
 452 UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
 453   if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
 454     return UV->getLeader();
 455   return nullptr;
 456 }
 457
 458 bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
 459   // DBG_VALUE loc, offset, variable
 460   if (MI->getNumOperands() != 4 ||
 461       !(MI->getOperand(1).isReg() || MI->getOperand(1).isImm()) ||
 462       !MI->getOperand(2).isMetadata()) {
 463     DEBUG(dbgs() << "Can't handle " << *MI);
 464     return false;
 465   }
 466
 467   // Get or create the UserValue for (variable,offset).
 468   bool IsIndirect = MI->isIndirectDebugValue();
 469   unsigned Offset = IsIndirect ? MI->getOperand(1).getImm() : 0;
 470   const MDNode *Var = MI->getDebugVariable();
 471   const MDNode *Expr = MI->getDebugExpression();
 472   //here.
 473   UserValue *UV =
 474       getUserValue(Var, Expr, Offset, IsIndirect, MI->getDebugLoc());
 475   UV->addDef(Idx, MI->getOperand(0));
 476   return true;
 477 }
 478
 479 bool LDVImpl::collectDebugValues(MachineFunction &mf) {
 480   bool Changed = false;
 481   for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
 482        ++MFI) {
 483     MachineBasicBlock *MBB = MFI;
 484     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
 485          MBBI != MBBE;) {
 486       if (!MBBI->isDebugValue()) {
 487         ++MBBI;
 488         continue;
 489       }
 490       // DBG_VALUE has no slot index, use the previous instruction instead.
 491       SlotIndex Idx = MBBI == MBB->begin() ?
 492         LIS->getMBBStartIdx(MBB) :
 493         LIS->getInstructionIndex(std::prev(MBBI)).getRegSlot();
 494       // Handle consecutive DBG_VALUE instructions with the same slot index.
 495       do {
 496         if (handleDebugValue(MBBI, Idx)) {
 497           MBBI = MBB->erase(MBBI);
 498           Changed = true;
 499         } else
 500           ++MBBI;
 501       } while (MBBI != MBBE && MBBI->isDebugValue());
 502     }
 503   }
 504   return Changed;
 505 }
 506
 507 void UserValue::extendDef(SlotIndex Idx, unsigned LocNo,
 508                           LiveRange *LR, const VNInfo *VNI,
 509                           SmallVectorImpl<SlotIndex> *Kills,
 510                           LiveIntervals &LIS, MachineDominatorTree &MDT,
 511                           UserValueScopes &UVS) {
 512   SmallVector<SlotIndex, 16> Todo;
 513   Todo.push_back(Idx);
 514   do {
 515     SlotIndex Start = Todo.pop_back_val();
 516     MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
 517     SlotIndex Stop = LIS.getMBBEndIdx(MBB);
 518     LocMap::iterator I = locInts.find(Start);
 519
 520     // Limit to VNI's live range.
 521     bool ToEnd = true;
 522     if (LR && VNI) {
 523       LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
 524       if (!Segment || Segment->valno != VNI) {
 525         if (Kills)
 526           Kills->push_back(Start);
 527         continue;
 528       }
 529       if (Segment->end < Stop)
 530         Stop = Segment->end, ToEnd = false;
 531     }
 532
 533     // There could already be a short def at Start.
 534     if (I.valid() && I.start() <= Start) {
 535       // Stop when meeting a different location or an already extended interval.
 536       Start = Start.getNextSlot();
 537       if (I.value() != LocNo || I.stop() != Start)
 538         continue;
 539       // This is a one-slot placeholder. Just skip it.
 540       ++I;
 541     }
 542
 543     // Limited by the next def.
 544     if (I.valid() && I.start() < Stop)
 545       Stop = I.start(), ToEnd = false;
 546     // Limited by VNI's live range.
 547     else if (!ToEnd && Kills)
 548       Kills->push_back(Stop);
 549
 550     if (Start >= Stop)
 551       continue;
 552
 553     I.insert(Start, Stop, LocNo);
 554
 555     // If we extended to the MBB end, propagate down the dominator tree.
 556     if (!ToEnd)
 557       continue;
 558     const std::vector<MachineDomTreeNode*> &Children =
 559       MDT.getNode(MBB)->getChildren();
 560     for (unsigned i = 0, e = Children.size(); i != e; ++i) {
 561       MachineBasicBlock *MBB = Children[i]->getBlock();
 562       if (UVS.dominates(MBB))
 563         Todo.push_back(LIS.getMBBStartIdx(MBB));
 564     }
 565   } while (!Todo.empty());
 566 }
 567
 568 void
 569 UserValue::addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
 570                       const SmallVectorImpl<SlotIndex> &Kills,
 571                       SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
 572                       MachineRegisterInfo &MRI, LiveIntervals &LIS) {
 573   if (Kills.empty())
 574     return;
 575   // Don't track copies from physregs, there are too many uses.
 576   if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
 577     return;
 578
 579   // Collect all the (vreg, valno) pairs that are copies of LI.
 580   SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
 581   for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg)) {
 582     MachineInstr *MI = MO.getParent();
 583     // Copies of the full value.
 584     if (MO.getSubReg() || !MI->isCopy())
 585       continue;
 586     unsigned DstReg = MI->getOperand(0).getReg();
 587
 588     // Don't follow copies to physregs. These are usually setting up call
 589     // arguments, and the argument registers are always call clobbered. We are
 590     // better off in the source register which could be a callee-saved register,
 591     // or it could be spilled.
 592     if (!TargetRegisterInfo::isVirtualRegister(DstReg))
 593       continue;
 594
 595     // Is LocNo extended to reach this copy? If not, another def may be blocking
 596     // it, or we are looking at a wrong value of LI.
 597     SlotIndex Idx = LIS.getInstructionIndex(MI);
 598     LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
 599     if (!I.valid() || I.value() != LocNo)
 600       continue;
 601
 602     if (!LIS.hasInterval(DstReg))
 603       continue;
 604     LiveInterval *DstLI = &LIS.getInterval(DstReg);
 605     const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
 606     assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
 607     CopyValues.push_back(std::make_pair(DstLI, DstVNI));
 608   }
 609
 610   if (CopyValues.empty())
 611     return;
 612
 613   DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI << '\n');
 614
 615   // Try to add defs of the copied values for each kill point.
 616   for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
 617     SlotIndex Idx = Kills[i];
 618     for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
 619       LiveInterval *DstLI = CopyValues[j].first;
 620       const VNInfo *DstVNI = CopyValues[j].second;
 621       if (DstLI->getVNInfoAt(Idx) != DstVNI)
 622         continue;
 623       // Check that there isn't already a def at Idx
 624       LocMap::iterator I = locInts.find(Idx);
 625       if (I.valid() && I.start() <= Idx)
 626         continue;
 627       DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
 628                    << DstVNI->id << " in " << *DstLI << '\n');
 629       MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
 630       assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
 631       unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
 632       I.insert(Idx, Idx.getNextSlot(), LocNo);
 633       NewDefs.push_back(std::make_pair(Idx, LocNo));
 634       break;
 635     }
 636   }
 637 }
 638
 639 void
 640 UserValue::computeIntervals(MachineRegisterInfo &MRI,
 641                             const TargetRegisterInfo &TRI,
 642                             LiveIntervals &LIS,
 643                             MachineDominatorTree &MDT,
 644                             UserValueScopes &UVS) {
 645   SmallVector<std::pair<SlotIndex, unsigned>, 16> Defs;
 646
 647   // Collect all defs to be extended (Skipping undefs).
 648   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
 649     if (I.value() != ~0u)
 650       Defs.push_back(std::make_pair(I.start(), I.value()));
 651
 652   // Extend all defs, and possibly add new ones along the way.
 653   for (unsigned i = 0; i != Defs.size(); ++i) {
 654     SlotIndex Idx = Defs[i].first;
 655     unsigned LocNo = Defs[i].second;
 656     const MachineOperand &Loc = locations[LocNo];
 657
 658     if (!Loc.isReg()) {
 659       extendDef(Idx, LocNo, nullptr, nullptr, nullptr, LIS, MDT, UVS);
 660       continue;
 661     }
 662
 663     // Register locations are constrained to where the register value is live.
 664     if (TargetRegisterInfo::isVirtualRegister(Loc.getReg())) {
 665       LiveInterval *LI = nullptr;
 666       const VNInfo *VNI = nullptr;
 667       if (LIS.hasInterval(Loc.getReg())) {
 668         LI = &LIS.getInterval(Loc.getReg());
 669         VNI = LI->getVNInfoAt(Idx);
 670       }
 671       SmallVector<SlotIndex, 16> Kills;
 672       extendDef(Idx, LocNo, LI, VNI, &Kills, LIS, MDT, UVS);
 673       if (LI)
 674         addDefsFromCopies(LI, LocNo, Kills, Defs, MRI, LIS);
 675       continue;
 676     }
 677
 678     // For physregs, use the live range of the first regunit as a guide.
 679     unsigned Unit = *MCRegUnitIterator(Loc.getReg(), &TRI);
 680     LiveRange *LR = &LIS.getRegUnit(Unit);
 681     const VNInfo *VNI = LR->getVNInfoAt(Idx);
 682     // Don't track copies from physregs, it is too expensive.
 683     extendDef(Idx, LocNo, LR, VNI, nullptr, LIS, MDT, UVS);
 684   }
 685
 686   // Finally, erase all the undefs.
 687   for (LocMap::iterator I = locInts.begin(); I.valid();)
 688     if (I.value() == ~0u)
 689       I.erase();
 690     else
 691       ++I;
 692 }
 693
 694 void LDVImpl::computeIntervals() {
 695   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
 696     UserValueScopes UVS(userValues[i]->getDebugLoc(), LS);
 697     userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, *MDT, UVS);
 698     userValues[i]->mapVirtRegs(this);
 699   }
 700 }
 701
 702 bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
 703   clear();
 704   MF = &mf;
 705   LIS = &pass.getAnalysis<LiveIntervals>();
 706   MDT = &pass.getAnalysis<MachineDominatorTree>();
 707   TRI = mf.getSubtarget().getRegisterInfo();
 708   LS.initialize(mf);
 709   DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
 710                << mf.getName() << " **********\n");
 711
 712   bool Changed = collectDebugValues(mf);
 713   computeIntervals();
 714   DEBUG(print(dbgs()));
 715   ModifiedMF = Changed;
 716   return Changed;
 717 }
 718
 719 static void removeDebugValues(MachineFunction &mf) {
 720   for (MachineBasicBlock &MBB : mf) {
 721     for (auto MBBI = MBB.begin(), MBBE = MBB.end(); MBBI != MBBE; ) {
 722       if (!MBBI->isDebugValue()) {
 723         ++MBBI;
 724         continue;
 725       }
 726       MBBI = MBB.erase(MBBI);
 727     }
 728   }
 729 }
 730
 731 bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
 732   if (!EnableLDV)
 733     return false;
 734   if (!FunctionDIs.count(mf.getFunction())) {
 735     removeDebugValues(mf);
 736     return false;
 737   }
 738   if (!pImpl)
 739     pImpl = new LDVImpl(this);
 740   return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
 741 }
 742
 743 void LiveDebugVariables::releaseMemory() {
 744   if (pImpl)
 745     static_cast<LDVImpl*>(pImpl)->clear();
 746 }
 747
 748 LiveDebugVariables::~LiveDebugVariables() {
 749   if (pImpl)
 750     delete static_cast<LDVImpl*>(pImpl);
 751 }
 752
 753 //===----------------------------------------------------------------------===//
 754 //                           Live Range Splitting
 755 //===----------------------------------------------------------------------===//
 756
 757 bool
 758 UserValue::splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
 759                          LiveIntervals& LIS) {
 760   DEBUG({
 761     dbgs() << "Splitting Loc" << OldLocNo << '\t';
 762     print(dbgs(), nullptr);
 763   });
 764   bool DidChange = false;
 765   LocMap::iterator LocMapI;
 766   LocMapI.setMap(locInts);
 767   for (unsigned i = 0; i != NewRegs.size(); ++i) {
 768     LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
 769     if (LI->empty())
 770       continue;
 771
 772     // Don't allocate the new LocNo until it is needed.
 773     unsigned NewLocNo = ~0u;
 774
 775     // Iterate over the overlaps between locInts and LI.
 776     LocMapI.find(LI->beginIndex());
 777     if (!LocMapI.valid())
 778       continue;
 779     LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
 780     LiveInterval::iterator LIE = LI->end();
 781     while (LocMapI.valid() && LII != LIE) {
 782       // At this point, we know that LocMapI.stop() > LII->start.
 783       LII = LI->advanceTo(LII, LocMapI.start());
 784       if (LII == LIE)
 785         break;
 786
 787       // Now LII->end > LocMapI.start(). Do we have an overlap?
 788       if (LocMapI.value() == OldLocNo && LII->start < LocMapI.stop()) {
 789         // Overlapping correct location. Allocate NewLocNo now.
 790         if (NewLocNo == ~0u) {
 791           MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
 792           MO.setSubReg(locations[OldLocNo].getSubReg());
 793           NewLocNo = getLocationNo(MO);
 794           DidChange = true;
 795         }
 796
 797         SlotIndex LStart = LocMapI.start();
 798         SlotIndex LStop  = LocMapI.stop();
 799
 800         // Trim LocMapI down to the LII overlap.
 801         if (LStart < LII->start)
 802           LocMapI.setStartUnchecked(LII->start);
 803         if (LStop > LII->end)
 804           LocMapI.setStopUnchecked(LII->end);
 805
 806         // Change the value in the overlap. This may trigger coalescing.
 807         LocMapI.setValue(NewLocNo);
 808
 809         // Re-insert any removed OldLocNo ranges.
 810         if (LStart < LocMapI.start()) {
 811           LocMapI.insert(LStart, LocMapI.start(), OldLocNo);
 812           ++LocMapI;
 813           assert(LocMapI.valid() && "Unexpected coalescing");
 814         }
 815         if (LStop > LocMapI.stop()) {
 816           ++LocMapI;
 817           LocMapI.insert(LII->end, LStop, OldLocNo);
 818           --LocMapI;
 819         }
 820       }
 821
 822       // Advance to the next overlap.
 823       if (LII->end < LocMapI.stop()) {
 824         if (++LII == LIE)
 825           break;
 826         LocMapI.advanceTo(LII->start);
 827       } else {
 828         ++LocMapI;
 829         if (!LocMapI.valid())
 830           break;
 831         LII = LI->advanceTo(LII, LocMapI.start());
 832       }
 833     }
 834   }
 835
 836   // Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
 837   locations.erase(locations.begin() + OldLocNo);
 838   LocMapI.goToBegin();
 839   while (LocMapI.valid()) {
 840     unsigned v = LocMapI.value();
 841     if (v == OldLocNo) {
 842       DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
 843                    << LocMapI.stop() << ")\n");
 844       LocMapI.erase();
 845     } else {
 846       if (v > OldLocNo)
 847         LocMapI.setValueUnchecked(v-1);
 848       ++LocMapI;
 849     }
 850   }
 851
 852   DEBUG({dbgs() << "Split result: \t"; print(dbgs(), nullptr);});
 853   return DidChange;
 854 }
 855
 856 bool
 857 UserValue::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
 858                          LiveIntervals &LIS) {
 859   bool DidChange = false;
 860   // Split locations referring to OldReg. Iterate backwards so splitLocation can
 861   // safely erase unused locations.
 862   for (unsigned i = locations.size(); i ; --i) {
 863     unsigned LocNo = i-1;
 864     const MachineOperand *Loc = &locations[LocNo];
 865     if (!Loc->isReg() || Loc->getReg() != OldReg)
 866       continue;
 867     DidChange |= splitLocation(LocNo, NewRegs, LIS);
 868   }
 869   return DidChange;
 870 }
 871
 872 void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs) {
 873   bool DidChange = false;
 874   for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
 875     DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
 876
 877   if (!DidChange)
 878     return;
 879
 880   // Map all of the new virtual registers.
 881   UserValue *UV = lookupVirtReg(OldReg);
 882   for (unsigned i = 0; i != NewRegs.size(); ++i)
 883     mapVirtReg(NewRegs[i], UV);
 884 }
 885
 886 void LiveDebugVariables::
 887 splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
 888   if (pImpl)
 889     static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
 890 }
 891
 892 void
 893 UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI) {
 894   // Iterate over locations in reverse makes it easier to handle coalescing.
 895   for (unsigned i = locations.size(); i ; --i) {
 896     unsigned LocNo = i-1;
 897     MachineOperand &Loc = locations[LocNo];
 898     // Only virtual registers are rewritten.
 899     if (!Loc.isReg() || !Loc.getReg() ||
 900         !TargetRegisterInfo::isVirtualRegister(Loc.getReg()))
 901       continue;
 902     unsigned VirtReg = Loc.getReg();
 903     if (VRM.isAssignedReg(VirtReg) &&
 904         TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
 905       // This can create a %noreg operand in rare cases when the sub-register
 906       // index is no longer available. That means the user value is in a
 907       // non-existent sub-register, and %noreg is exactly what we want.
 908       Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
 909     } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
 910       // FIXME: Translate SubIdx to a stackslot offset.
 911       Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
 912     } else {
 913       Loc.setReg(0);
 914       Loc.setSubReg(0);
 915     }
 916     coalesceLocation(LocNo);
 917   }
 918 }
 919
 920 /// findInsertLocation - Find an iterator for inserting a DBG_VALUE
 921 /// instruction.
 922 static MachineBasicBlock::iterator
 923 findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
 924                    LiveIntervals &LIS) {
 925   SlotIndex Start = LIS.getMBBStartIdx(MBB);
 926   Idx = Idx.getBaseIndex();
 927
 928   // Try to find an insert location by going backwards from Idx.
 929   MachineInstr *MI;
 930   while (!(MI = LIS.getInstructionFromIndex(Idx))) {
 931     // We've reached the beginning of MBB.
 932     if (Idx == Start) {
 933       MachineBasicBlock::iterator I = MBB->SkipPHIsAndLabels(MBB->begin());
 934       return I;
 935     }
 936     Idx = Idx.getPrevIndex();
 937   }
 938
 939   // Don't insert anything after the first terminator, though.
 940   return MI->isTerminator() ? MBB->getFirstTerminator() :
 941                               std::next(MachineBasicBlock::iterator(MI));
 942 }
 943
 944 DebugLoc UserValue::findDebugLoc() {
 945   DebugLoc D = dl;
 946   dl = DebugLoc();
 947   return D;
 948 }
 949 void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
 950                                  unsigned LocNo,
 951                                  LiveIntervals &LIS,
 952                                  const TargetInstrInfo &TII) {
 953   MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
 954   MachineOperand &Loc = locations[LocNo];
 955   ++NumInsertedDebugValues;
 956
 957   if (Loc.isReg())
 958     BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
 959             IsIndirect, Loc.getReg(), offset, Variable, Expression);
 960   else
 961     BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
 962         .addOperand(Loc)
 963         .addImm(offset)
 964         .addMetadata(Variable)
 965         .addMetadata(Expression);
 966 }
 967
 968 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
 969                                 const TargetInstrInfo &TII) {
 970   MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
 971
 972   for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
 973     SlotIndex Start = I.start();
 974     SlotIndex Stop = I.stop();
 975     unsigned LocNo = I.value();
 976     DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << LocNo);
 977     MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start);
 978     SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);
 979
 980     DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
 981     insertDebugValue(MBB, Start, LocNo, LIS, TII);
 982     // This interval may span multiple basic blocks.
 983     // Insert a DBG_VALUE into each one.
 984     while(Stop > MBBEnd) {
 985       // Move to the next block.
 986       Start = MBBEnd;
 987       if (++MBB == MFEnd)
 988         break;
 989       MBBEnd = LIS.getMBBEndIdx(MBB);
 990       DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
 991       insertDebugValue(MBB, Start, LocNo, LIS, TII);
 992     }
 993     DEBUG(dbgs() << '\n');
 994     if (MBB == MFEnd)
 995       break;
 996
 997     ++I;
 998   }
 999 }
1000
1001 void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
1002   DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
1003   if (!MF)
1004     return;
1005   const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
1006   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
1007     DEBUG(userValues[i]->print(dbgs(), &MF->getTarget()));
1008     userValues[i]->rewriteLocations(*VRM, *TRI);
1009     userValues[i]->emitDebugValues(VRM, *LIS, *TII);
1010   }
1011   EmitDone = true;
1012 }
1013
1014 void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
1015   if (pImpl)
1016     static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
1017 }
1018
1019 bool LiveDebugVariables::doInitialization(Module &M) {
1020   FunctionDIs = makeSubprogramMap(M);
1021   return Pass::doInitialization(M);
1022 }
1023
1024 #ifndef NDEBUG
1025 void LiveDebugVariables::dump() {
1026   if (pImpl)
1027     static_cast<LDVImpl*>(pImpl)->print(dbgs());
1028 }
1029 #endif