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 #define DEBUG_TYPE "livedebug"
  23 #include "LiveDebugVariables.h"
  24 #include "VirtRegMap.h"
  25 #include "llvm/Constants.h"
  26 #include "llvm/Metadata.h"
  27 #include "llvm/Value.h"
  28 #include "llvm/ADT/IntervalMap.h"
  29 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
  30 #include "llvm/CodeGen/MachineDominators.h"
  31 #include "llvm/CodeGen/MachineFunction.h"
  32 #include "llvm/CodeGen/MachineInstrBuilder.h"
  33 #include "llvm/CodeGen/MachineRegisterInfo.h"
  34 #include "llvm/CodeGen/Passes.h"
  35 #include "llvm/Support/CommandLine.h"
  36 #include "llvm/Support/Debug.h"
  37 #include "llvm/Target/TargetInstrInfo.h"
  38 #include "llvm/Target/TargetMachine.h"
  39 #include "llvm/Target/TargetRegisterInfo.h"
  40
  41 using namespace llvm;
  42
  43 static cl::opt<bool>
  44 EnableLDV("live-debug-variables", cl::init(true),
  45           cl::desc("Enable the live debug variables pass"), cl::Hidden);
  46
  47 char LiveDebugVariables::ID = 0;
  48
  49 INITIALIZE_PASS_BEGIN(LiveDebugVariables, "livedebugvars",
  50                 "Debug Variable Analysis", false, false)
  51 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
  52 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
  53 INITIALIZE_PASS_END(LiveDebugVariables, "livedebugvars",
  54                 "Debug Variable Analysis", false, false)
  55
  56 void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
  57   AU.addRequired<MachineDominatorTree>();
  58   AU.addRequiredTransitive<LiveIntervals>();
  59   AU.setPreservesAll();
  60   MachineFunctionPass::getAnalysisUsage(AU);
  61 }
  62
  63 LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID), pImpl(0) {
  64   initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
  65 }
  66
  67 /// LocMap - Map of where a user value is live, and its location.
  68 typedef IntervalMap<SlotIndex, unsigned, 4> LocMap;
  69
  70 /// UserValue - A user value is a part of a debug info user variable.
  71 ///
  72 /// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
  73 /// holds part of a user variable. The part is identified by a byte offset.
  74 ///
  75 /// UserValues are grouped into equivalence classes for easier searching. Two
  76 /// user values are related if they refer to the same variable, or if they are
  77 /// held by the same virtual register. The equivalence class is the transitive
  78 /// closure of that relation.
  79 namespace {
  80 class LDVImpl;
  81 class UserValue {
  82   const MDNode *variable; ///< The debug info variable we are part of.
  83   unsigned offset;        ///< Byte offset into variable.
  84   DebugLoc dl;            ///< The debug location for the variable. This is
  85                           ///< used by dwarf writer to find lexical scope.
  86   UserValue *leader;      ///< Equivalence class leader.
  87   UserValue *next;        ///< Next value in equivalence class, or null.
  88
  89   /// Numbered locations referenced by locmap.
  90   SmallVector<MachineOperand, 4> locations;
  91
  92   /// Map of slot indices where this value is live.
  93   LocMap locInts;
  94
  95   /// coalesceLocation - After LocNo was changed, check if it has become
  96   /// identical to another location, and coalesce them. This may cause LocNo or
  97   /// a later location to be erased, but no earlier location will be erased.
  98   void coalesceLocation(unsigned LocNo);
  99
 100   /// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
 101   void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx, unsigned LocNo,
 102                         LiveIntervals &LIS, const TargetInstrInfo &TII);
 103
 104 public:
 105   /// UserValue - Create a new UserValue.
 106   UserValue(const MDNode *var, unsigned o, DebugLoc L,
 107             LocMap::Allocator &alloc)
 108     : variable(var), offset(o), dl(L), leader(this), next(0), locInts(alloc)
 109   {}
 110
 111   /// getLeader - Get the leader of this value's equivalence class.
 112   UserValue *getLeader() {
 113     UserValue *l = leader;
 114     while (l != l->leader)
 115       l = l->leader;
 116     return leader = l;
 117   }
 118
 119   /// getNext - Return the next UserValue in the equivalence class.
 120   UserValue *getNext() const { return next; }
 121
 122   /// match - Does this UserValue match the aprameters?
 123   bool match(const MDNode *Var, unsigned Offset) const {
 124     return Var == variable && Offset == offset;
 125   }
 126
 127   /// merge - Merge equivalence classes.
 128   static UserValue *merge(UserValue *L1, UserValue *L2) {
 129     L2 = L2->getLeader();
 130     if (!L1)
 131       return L2;
 132     L1 = L1->getLeader();
 133     if (L1 == L2)
 134       return L1;
 135     // Splice L2 before L1's members.
 136     UserValue *End = L2;
 137     while (End->next)
 138       End->leader = L1, End = End->next;
 139     End->leader = L1;
 140     End->next = L1->next;
 141     L1->next = L2;
 142     return L1;
 143   }
 144
 145   /// getLocationNo - Return the location number that matches Loc.
 146   unsigned getLocationNo(const MachineOperand &LocMO) {
 147     if (LocMO.isReg()) {
 148       if (LocMO.getReg() == 0)
 149         return ~0u;
 150       // For register locations we dont care about use/def and other flags.
 151       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 152         if (locations[i].isReg() &&
 153             locations[i].getReg() == LocMO.getReg() &&
 154             locations[i].getSubReg() == LocMO.getSubReg())
 155           return i;
 156     } else
 157       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 158         if (LocMO.isIdenticalTo(locations[i]))
 159           return i;
 160     locations.push_back(LocMO);
 161     // We are storing a MachineOperand outside a MachineInstr.
 162     locations.back().clearParent();
 163     // Don't store def operands.
 164     if (locations.back().isReg())
 165       locations.back().setIsUse();
 166     return locations.size() - 1;
 167   }
 168
 169   /// mapVirtRegs - Ensure that all virtual register locations are mapped.
 170   void mapVirtRegs(LDVImpl *LDV);
 171
 172   /// addDef - Add a definition point to this value.
 173   void addDef(SlotIndex Idx, const MachineOperand &LocMO) {
 174     // Add a singular (Idx,Idx) -> Loc mapping.
 175     LocMap::iterator I = locInts.find(Idx);
 176     if (!I.valid() || I.start() != Idx)
 177       I.insert(Idx, Idx.getNextSlot(), getLocationNo(LocMO));
 178   }
 179
 180   /// extendDef - Extend the current definition as far as possible down the
 181   /// dominator tree. Stop when meeting an existing def or when leaving the live
 182   /// range of VNI.
 183   /// End points where VNI is no longer live are added to Kills.
 184   /// @param Idx   Starting point for the definition.
 185   /// @param LocNo Location number to propagate.
 186   /// @param LI    Restrict liveness to where LI has the value VNI. May be null.
 187   /// @param VNI   When LI is not null, this is the value to restrict to.
 188   /// @param Kills Append end points of VNI's live range to Kills.
 189   /// @param LIS   Live intervals analysis.
 190   /// @param MDT   Dominator tree.
 191   void extendDef(SlotIndex Idx, unsigned LocNo,
 192                  LiveInterval *LI, const VNInfo *VNI,
 193                  SmallVectorImpl<SlotIndex> *Kills,
 194                  LiveIntervals &LIS, MachineDominatorTree &MDT);
 195
 196   /// addDefsFromCopies - The value in LI/LocNo may be copies to other
 197   /// registers. Determine if any of the copies are available at the kill
 198   /// points, and add defs if possible.
 199   /// @param LI      Scan for copies of the value in LI->reg.
 200   /// @param LocNo   Location number of LI->reg.
 201   /// @param Kills   Points where the range of LocNo could be extended.
 202   /// @param NewDefs Append (Idx, LocNo) of inserted defs here.
 203   void addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
 204                       const SmallVectorImpl<SlotIndex> &Kills,
 205                       SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
 206                       MachineRegisterInfo &MRI,
 207                       LiveIntervals &LIS);
 208
 209   /// computeIntervals - Compute the live intervals of all locations after
 210   /// collecting all their def points.
 211   void computeIntervals(MachineRegisterInfo &MRI,
 212                         LiveIntervals &LIS, MachineDominatorTree &MDT);
 213
 214   /// renameRegister - Update locations to rewrite OldReg as NewReg:SubIdx.
 215   void renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx,
 216                       const TargetRegisterInfo *TRI);
 217
 218   /// rewriteLocations - Rewrite virtual register locations according to the
 219   /// provided virtual register map.
 220   void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI);
 221
 222   /// emitDebugVariables - Recreate DBG_VALUE instruction from data structures.
 223   void emitDebugValues(VirtRegMap *VRM,
 224                        LiveIntervals &LIS, const TargetInstrInfo &TRI);
 225
 226   /// findDebugLoc - Return DebugLoc used for this DBG_VALUE instruction. A
 227   /// variable may have more than one corresponding DBG_VALUE instructions.
 228   /// Only first one needs DebugLoc to identify variable's lexical scope
 229   /// in source file.
 230   DebugLoc findDebugLoc();
 231   void print(raw_ostream&, const TargetRegisterInfo*);
 232 };
 233 } // namespace
 234
 235 /// LDVImpl - Implementation of the LiveDebugVariables pass.
 236 namespace {
 237 class LDVImpl {
 238   LiveDebugVariables &pass;
 239   LocMap::Allocator allocator;
 240   MachineFunction *MF;
 241   LiveIntervals *LIS;
 242   MachineDominatorTree *MDT;
 243   const TargetRegisterInfo *TRI;
 244
 245   /// userValues - All allocated UserValue instances.
 246   SmallVector<UserValue*, 8> userValues;
 247
 248   /// Map virtual register to eq class leader.
 249   typedef DenseMap<unsigned, UserValue*> VRMap;
 250   VRMap virtRegToEqClass;
 251
 252   /// Map user variable to eq class leader.
 253   typedef DenseMap<const MDNode *, UserValue*> UVMap;
 254   UVMap userVarMap;
 255
 256   /// getUserValue - Find or create a UserValue.
 257   UserValue *getUserValue(const MDNode *Var, unsigned Offset, DebugLoc DL);
 258
 259   /// lookupVirtReg - Find the EC leader for VirtReg or null.
 260   UserValue *lookupVirtReg(unsigned VirtReg);
 261
 262   /// handleDebugValue - Add DBG_VALUE instruction to our maps.
 263   /// @param MI  DBG_VALUE instruction
 264   /// @param Idx Last valid SLotIndex before instruction.
 265   /// @return    True if the DBG_VALUE instruction should be deleted.
 266   bool handleDebugValue(MachineInstr *MI, SlotIndex Idx);
 267
 268   /// collectDebugValues - Collect and erase all DBG_VALUE instructions, adding
 269   /// a UserValue def for each instruction.
 270   /// @param mf MachineFunction to be scanned.
 271   /// @return True if any debug values were found.
 272   bool collectDebugValues(MachineFunction &mf);
 273
 274   /// computeIntervals - Compute the live intervals of all user values after
 275   /// collecting all their def points.
 276   void computeIntervals();
 277
 278 public:
 279   LDVImpl(LiveDebugVariables *ps) : pass(*ps) {}
 280   bool runOnMachineFunction(MachineFunction &mf);
 281
 282   /// clear - Relase all memory.
 283   void clear() {
 284     DeleteContainerPointers(userValues);
 285     userValues.clear();
 286     virtRegToEqClass.clear();
 287     userVarMap.clear();
 288   }
 289
 290   /// mapVirtReg - Map virtual register to an equivalence class.
 291   void mapVirtReg(unsigned VirtReg, UserValue *EC);
 292
 293   /// renameRegister - Replace all references to OldReg with NewReg:SubIdx.
 294   void renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx);
 295
 296   /// emitDebugVariables - Recreate DBG_VALUE instruction from data structures.
 297   void emitDebugValues(VirtRegMap *VRM);
 298
 299   void print(raw_ostream&);
 300 };
 301 } // namespace
 302
 303 void UserValue::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
 304   if (const MDString *MDS = dyn_cast<MDString>(variable->getOperand(2)))
 305     OS << "!\"" << MDS->getString() << "\"\t";
 306   if (offset)
 307     OS << '+' << offset;
 308   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
 309     OS << " [" << I.start() << ';' << I.stop() << "):";
 310     if (I.value() == ~0u)
 311       OS << "undef";
 312     else
 313       OS << I.value();
 314   }
 315   for (unsigned i = 0, e = locations.size(); i != e; ++i)
 316     OS << " Loc" << i << '=' << locations[i];
 317   OS << '\n';
 318 }
 319
 320 void LDVImpl::print(raw_ostream &OS) {
 321   OS << "********** DEBUG VARIABLES **********\n";
 322   for (unsigned i = 0, e = userValues.size(); i != e; ++i)
 323     userValues[i]->print(OS, TRI);
 324 }
 325
 326 void UserValue::coalesceLocation(unsigned LocNo) {
 327   unsigned KeepLoc = 0;
 328   for (unsigned e = locations.size(); KeepLoc != e; ++KeepLoc) {
 329     if (KeepLoc == LocNo)
 330       continue;
 331     if (locations[KeepLoc].isIdenticalTo(locations[LocNo]))
 332       break;
 333   }
 334   // No matches.
 335   if (KeepLoc == locations.size())
 336     return;
 337
 338   // Keep the smaller location, erase the larger one.
 339   unsigned EraseLoc = LocNo;
 340   if (KeepLoc > EraseLoc)
 341     std::swap(KeepLoc, EraseLoc);
 342   locations.erase(locations.begin() + EraseLoc);
 343
 344   // Rewrite values.
 345   for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
 346     unsigned v = I.value();
 347     if (v == EraseLoc)
 348       I.setValue(KeepLoc);      // Coalesce when possible.
 349     else if (v > EraseLoc)
 350       I.setValueUnchecked(v-1); // Avoid coalescing with untransformed values.
 351   }
 352 }
 353
 354 void UserValue::mapVirtRegs(LDVImpl *LDV) {
 355   for (unsigned i = 0, e = locations.size(); i != e; ++i)
 356     if (locations[i].isReg() &&
 357         TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
 358       LDV->mapVirtReg(locations[i].getReg(), this);
 359 }
 360
 361 UserValue *LDVImpl::getUserValue(const MDNode *Var, unsigned Offset,
 362                                  DebugLoc DL) {
 363   UserValue *&Leader = userVarMap[Var];
 364   if (Leader) {
 365     UserValue *UV = Leader->getLeader();
 366     Leader = UV;
 367     for (; UV; UV = UV->getNext())
 368       if (UV->match(Var, Offset))
 369         return UV;
 370   }
 371
 372   UserValue *UV = new UserValue(Var, Offset, DL, allocator);
 373   userValues.push_back(UV);
 374   Leader = UserValue::merge(Leader, UV);
 375   return UV;
 376 }
 377
 378 void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
 379   assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
 380   UserValue *&Leader = virtRegToEqClass[VirtReg];
 381   Leader = UserValue::merge(Leader, EC);
 382 }
 383
 384 UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
 385   if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
 386     return UV->getLeader();
 387   return 0;
 388 }
 389
 390 bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
 391   // DBG_VALUE loc, offset, variable
 392   if (MI->getNumOperands() != 3 ||
 393       !MI->getOperand(1).isImm() || !MI->getOperand(2).isMetadata()) {
 394     DEBUG(dbgs() << "Can't handle " << *MI);
 395     return false;
 396   }
 397
 398   // Get or create the UserValue for (variable,offset).
 399   unsigned Offset = MI->getOperand(1).getImm();
 400   const MDNode *Var = MI->getOperand(2).getMetadata();
 401   UserValue *UV = getUserValue(Var, Offset, MI->getDebugLoc());
 402   UV->addDef(Idx, MI->getOperand(0));
 403   return true;
 404 }
 405
 406 bool LDVImpl::collectDebugValues(MachineFunction &mf) {
 407   bool Changed = false;
 408   for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
 409        ++MFI) {
 410     MachineBasicBlock *MBB = MFI;
 411     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
 412          MBBI != MBBE;) {
 413       if (!MBBI->isDebugValue()) {
 414         ++MBBI;
 415         continue;
 416       }
 417       // DBG_VALUE has no slot index, use the previous instruction instead.
 418       SlotIndex Idx = MBBI == MBB->begin() ?
 419         LIS->getMBBStartIdx(MBB) :
 420         LIS->getInstructionIndex(llvm::prior(MBBI)).getDefIndex();
 421       // Handle consecutive DBG_VALUE instructions with the same slot index.
 422       do {
 423         if (handleDebugValue(MBBI, Idx)) {
 424           MBBI = MBB->erase(MBBI);
 425           Changed = true;
 426         } else
 427           ++MBBI;
 428       } while (MBBI != MBBE && MBBI->isDebugValue());
 429     }
 430   }
 431   return Changed;
 432 }
 433
 434 void UserValue::extendDef(SlotIndex Idx, unsigned LocNo,
 435                           LiveInterval *LI, const VNInfo *VNI,
 436                           SmallVectorImpl<SlotIndex> *Kills,
 437                           LiveIntervals &LIS, MachineDominatorTree &MDT) {
 438   SmallVector<SlotIndex, 16> Todo;
 439   Todo.push_back(Idx);
 440
 441   do {
 442     SlotIndex Start = Todo.pop_back_val();
 443     MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
 444     SlotIndex Stop = LIS.getMBBEndIdx(MBB);
 445     LocMap::iterator I = locInts.find(Start);
 446
 447     // Limit to VNI's live range.
 448     bool ToEnd = true;
 449     if (LI && VNI) {
 450       LiveRange *Range = LI->getLiveRangeContaining(Start);
 451       if (!Range || Range->valno != VNI) {
 452         if (Kills)
 453           Kills->push_back(Start);
 454         continue;
 455       }
 456       if (Range->end < Stop)
 457         Stop = Range->end, ToEnd = false;
 458     }
 459
 460     // There could already be a short def at Start.
 461     if (I.valid() && I.start() <= Start) {
 462       // Stop when meeting a different location or an already extended interval.
 463       Start = Start.getNextSlot();
 464       if (I.value() != LocNo || I.stop() != Start)
 465         continue;
 466       // This is a one-slot placeholder. Just skip it.
 467       ++I;
 468     }
 469
 470     // Limited by the next def.
 471     if (I.valid() && I.start() < Stop)
 472       Stop = I.start(), ToEnd = false;
 473     // Limited by VNI's live range.
 474     else if (!ToEnd && Kills)
 475       Kills->push_back(Stop);
 476
 477     if (Start >= Stop)
 478       continue;
 479
 480     I.insert(Start, Stop, LocNo);
 481
 482     // If we extended to the MBB end, propagate down the dominator tree.
 483     if (!ToEnd)
 484       continue;
 485     const std::vector<MachineDomTreeNode*> &Children =
 486       MDT.getNode(MBB)->getChildren();
 487     for (unsigned i = 0, e = Children.size(); i != e; ++i)
 488       Todo.push_back(LIS.getMBBStartIdx(Children[i]->getBlock()));
 489   } while (!Todo.empty());
 490 }
 491
 492 void
 493 UserValue::addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
 494                       const SmallVectorImpl<SlotIndex> &Kills,
 495                       SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
 496                       MachineRegisterInfo &MRI, LiveIntervals &LIS) {
 497   if (Kills.empty())
 498     return;
 499   // Don't track copies from physregs, there are too many uses.
 500   if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
 501     return;
 502
 503   // Collect all the (vreg, valno) pairs that are copies of LI.
 504   SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
 505   for (MachineRegisterInfo::use_nodbg_iterator
 506          UI = MRI.use_nodbg_begin(LI->reg),
 507          UE = MRI.use_nodbg_end(); UI != UE; ++UI) {
 508     // Copies of the full value.
 509     if (UI.getOperand().getSubReg() || !UI->isCopy())
 510       continue;
 511     MachineInstr *MI = &*UI;
 512     unsigned DstReg = MI->getOperand(0).getReg();
 513
 514     // Don't follow copies to physregs. These are usually setting up call
 515     // arguments, and the argument registers are always call clobbered. We are
 516     // better off in the source register which could be a callee-saved register,
 517     // or it could be spilled.
 518     if (!TargetRegisterInfo::isVirtualRegister(DstReg))
 519       continue;
 520
 521     // Is LocNo extended to reach this copy? If not, another def may be blocking
 522     // it, or we are looking at a wrong value of LI.
 523     SlotIndex Idx = LIS.getInstructionIndex(MI);
 524     LocMap::iterator I = locInts.find(Idx.getUseIndex());
 525     if (!I.valid() || I.value() != LocNo)
 526       continue;
 527
 528     if (!LIS.hasInterval(DstReg))
 529       continue;
 530     LiveInterval *DstLI = &LIS.getInterval(DstReg);
 531     const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getDefIndex());
 532     assert(DstVNI && DstVNI->def == Idx.getDefIndex() && "Bad copy value");
 533     CopyValues.push_back(std::make_pair(DstLI, DstVNI));
 534   }
 535
 536   if (CopyValues.empty())
 537     return;
 538
 539   DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI << '\n');
 540
 541   // Try to add defs of the copied values for each kill point.
 542   for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
 543     SlotIndex Idx = Kills[i];
 544     for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
 545       LiveInterval *DstLI = CopyValues[j].first;
 546       const VNInfo *DstVNI = CopyValues[j].second;
 547       if (DstLI->getVNInfoAt(Idx) != DstVNI)
 548         continue;
 549       // Check that there isn't already a def at Idx
 550       LocMap::iterator I = locInts.find(Idx);
 551       if (I.valid() && I.start() <= Idx)
 552         continue;
 553       DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
 554                    << DstVNI->id << " in " << *DstLI << '\n');
 555       MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
 556       assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
 557       unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
 558       I.insert(Idx, Idx.getNextSlot(), LocNo);
 559       NewDefs.push_back(std::make_pair(Idx, LocNo));
 560       break;
 561     }
 562   }
 563 }
 564
 565 void
 566 UserValue::computeIntervals(MachineRegisterInfo &MRI,
 567                             LiveIntervals &LIS,
 568                             MachineDominatorTree &MDT) {
 569   SmallVector<std::pair<SlotIndex, unsigned>, 16> Defs;
 570
 571   // Collect all defs to be extended (Skipping undefs).
 572   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
 573     if (I.value() != ~0u)
 574       Defs.push_back(std::make_pair(I.start(), I.value()));
 575
 576   // Extend all defs, and possibly add new ones along the way.
 577   for (unsigned i = 0; i != Defs.size(); ++i) {
 578     SlotIndex Idx = Defs[i].first;
 579     unsigned LocNo = Defs[i].second;
 580     const MachineOperand &Loc = locations[LocNo];
 581
 582     // Register locations are constrained to where the register value is live.
 583     if (Loc.isReg() && LIS.hasInterval(Loc.getReg())) {
 584       LiveInterval *LI = &LIS.getInterval(Loc.getReg());
 585       const VNInfo *VNI = LI->getVNInfoAt(Idx);
 586       SmallVector<SlotIndex, 16> Kills;
 587       extendDef(Idx, LocNo, LI, VNI, &Kills, LIS, MDT);
 588       addDefsFromCopies(LI, LocNo, Kills, Defs, MRI, LIS);
 589     } else
 590       extendDef(Idx, LocNo, 0, 0, 0, LIS, MDT);
 591   }
 592
 593   // Finally, erase all the undefs.
 594   for (LocMap::iterator I = locInts.begin(); I.valid();)
 595     if (I.value() == ~0u)
 596       I.erase();
 597     else
 598       ++I;
 599 }
 600
 601 void LDVImpl::computeIntervals() {
 602   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
 603     userValues[i]->computeIntervals(MF->getRegInfo(), *LIS, *MDT);
 604     userValues[i]->mapVirtRegs(this);
 605   }
 606 }
 607
 608 bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
 609   MF = &mf;
 610   LIS = &pass.getAnalysis<LiveIntervals>();
 611   MDT = &pass.getAnalysis<MachineDominatorTree>();
 612   TRI = mf.getTarget().getRegisterInfo();
 613   clear();
 614   DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
 615                << ((Value*)mf.getFunction())->getName()
 616                << " **********\n");
 617
 618   bool Changed = collectDebugValues(mf);
 619   computeIntervals();
 620   DEBUG(print(dbgs()));
 621   return Changed;
 622 }
 623
 624 bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
 625   if (!EnableLDV)
 626     return false;
 627   if (!pImpl)
 628     pImpl = new LDVImpl(this);
 629   return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
 630 }
 631
 632 void LiveDebugVariables::releaseMemory() {
 633   if (pImpl)
 634     static_cast<LDVImpl*>(pImpl)->clear();
 635 }
 636
 637 LiveDebugVariables::~LiveDebugVariables() {
 638   if (pImpl)
 639     delete static_cast<LDVImpl*>(pImpl);
 640 }
 641
 642 void UserValue::
 643 renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx,
 644                const TargetRegisterInfo *TRI) {
 645   for (unsigned i = locations.size(); i; --i) {
 646     unsigned LocNo = i - 1;
 647     MachineOperand &Loc = locations[LocNo];
 648     if (!Loc.isReg() || Loc.getReg() != OldReg)
 649       continue;
 650     if (TargetRegisterInfo::isPhysicalRegister(NewReg))
 651       Loc.substPhysReg(NewReg, *TRI);
 652     else
 653       Loc.substVirtReg(NewReg, SubIdx, *TRI);
 654     coalesceLocation(LocNo);
 655   }
 656 }
 657
 658 void LDVImpl::
 659 renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx) {
 660   UserValue *UV = lookupVirtReg(OldReg);
 661   if (!UV)
 662     return;
 663
 664   if (TargetRegisterInfo::isVirtualRegister(NewReg))
 665     mapVirtReg(NewReg, UV);
 666   virtRegToEqClass.erase(OldReg);
 667
 668   do {
 669     UV->renameRegister(OldReg, NewReg, SubIdx, TRI);
 670     UV = UV->getNext();
 671   } while (UV);
 672 }
 673
 674 void LiveDebugVariables::
 675 renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx) {
 676   if (pImpl)
 677     static_cast<LDVImpl*>(pImpl)->renameRegister(OldReg, NewReg, SubIdx);
 678 }
 679
 680 void
 681 UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI) {
 682   // Iterate over locations in reverse makes it easier to handle coalescing.
 683   for (unsigned i = locations.size(); i ; --i) {
 684     unsigned LocNo = i-1;
 685     MachineOperand &Loc = locations[LocNo];
 686     // Only virtual registers are rewritten.
 687     if (!Loc.isReg() || !Loc.getReg() ||
 688         !TargetRegisterInfo::isVirtualRegister(Loc.getReg()))
 689       continue;
 690     unsigned VirtReg = Loc.getReg();
 691     if (VRM.isAssignedReg(VirtReg) &&
 692         TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
 693       Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
 694     } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT &&
 695                VRM.isSpillSlotUsed(VRM.getStackSlot(VirtReg))) {
 696       // FIXME: Translate SubIdx to a stackslot offset.
 697       Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
 698     } else {
 699       Loc.setReg(0);
 700       Loc.setSubReg(0);
 701     }
 702     coalesceLocation(LocNo);
 703   }
 704   DEBUG(print(dbgs(), &TRI));
 705 }
 706
 707 /// findInsertLocation - Find an iterator for inserting a DBG_VALUE
 708 /// instruction.
 709 static MachineBasicBlock::iterator
 710 findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
 711                    LiveIntervals &LIS) {
 712   SlotIndex Start = LIS.getMBBStartIdx(MBB);
 713   Idx = Idx.getBaseIndex();
 714
 715   // Try to find an insert location by going backwards from Idx.
 716   MachineInstr *MI;
 717   while (!(MI = LIS.getInstructionFromIndex(Idx))) {
 718     // We've reached the beginning of MBB.
 719     if (Idx == Start) {
 720       MachineBasicBlock::iterator I = MBB->SkipPHIsAndLabels(MBB->begin());
 721       return I;
 722     }
 723     Idx = Idx.getPrevIndex();
 724   }
 725
 726   // Don't insert anything after the first terminator, though.
 727   return MI->getDesc().isTerminator() ? MBB->getFirstTerminator() :
 728                                     llvm::next(MachineBasicBlock::iterator(MI));
 729 }
 730
 731 DebugLoc UserValue::findDebugLoc() {
 732   DebugLoc D = dl;
 733   dl = DebugLoc();
 734   return D;
 735 }
 736 void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
 737                                  unsigned LocNo,
 738                                  LiveIntervals &LIS,
 739                                  const TargetInstrInfo &TII) {
 740   MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
 741   MachineOperand &Loc = locations[LocNo];
 742
 743   // Frame index locations may require a target callback.
 744   if (Loc.isFI()) {
 745     MachineInstr *MI = TII.emitFrameIndexDebugValue(*MBB->getParent(),
 746                                           Loc.getIndex(), offset, variable,
 747                                                     findDebugLoc());
 748     if (MI) {
 749       MBB->insert(I, MI);
 750       return;
 751     }
 752   }
 753   // This is not a frame index, or the target is happy with a standard FI.
 754   BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
 755     .addOperand(Loc).addImm(offset).addMetadata(variable);
 756 }
 757
 758 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
 759                                 const TargetInstrInfo &TII) {
 760   MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
 761
 762   for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
 763     SlotIndex Start = I.start();
 764     SlotIndex Stop = I.stop();
 765     unsigned LocNo = I.value();
 766     DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << LocNo);
 767     MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start);
 768     SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);
 769
 770     DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
 771     insertDebugValue(MBB, Start, LocNo, LIS, TII);
 772
 773     // This interval may span multiple basic blocks.
 774     // Insert a DBG_VALUE into each one.
 775     while(Stop > MBBEnd) {
 776       // Move to the next block.
 777       Start = MBBEnd;
 778       if (++MBB == MFEnd)
 779         break;
 780       MBBEnd = LIS.getMBBEndIdx(MBB);
 781       DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
 782       insertDebugValue(MBB, Start, LocNo, LIS, TII);
 783     }
 784     DEBUG(dbgs() << '\n');
 785     if (MBB == MFEnd)
 786       break;
 787
 788     ++I;
 789   }
 790 }
 791
 792 void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
 793   DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
 794   const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
 795   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
 796     userValues[i]->rewriteLocations(*VRM, *TRI);
 797     userValues[i]->emitDebugValues(VRM, *LIS, *TII);
 798   }
 799 }
 800
 801 void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
 802   if (pImpl)
 803     static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
 804 }
 805
 806
 807 #ifndef NDEBUG
 808 void LiveDebugVariables::dump() {
 809   if (pImpl)
 810     static_cast<LDVImpl*>(pImpl)->print(dbgs());
 811 }
 812 #endif
 813