lib/CodeGen/LiveDebugVariables.cpp

   1 //===- LiveDebugVariables.cpp - Tracking debug info variables -------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements the LiveDebugVariables analysis.
  10 //
  11 // Remove all DBG_VALUE instructions referencing virtual registers and replace
  12 // them with a data structure tracking where live user variables are kept - in a
  13 // virtual register or in a stack slot.
  14 //
  15 // Allow the data structure to be updated during register allocation when values
  16 // are moved between registers and stack slots. Finally emit new DBG_VALUE
  17 // instructions after register allocation is complete.
  18 //
  19 //===----------------------------------------------------------------------===//
  20
  21 #include "LiveDebugVariables.h"
  22 #include "llvm/ADT/ArrayRef.h"
  23 #include "llvm/ADT/DenseMap.h"
  24 #include "llvm/ADT/IntervalMap.h"
  25 #include "llvm/ADT/MapVector.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 STATISTIC(NumInsertedDebugLabels, "Number of DBG_LABELs inserted");
  75
  76 char LiveDebugVariables::ID = 0;
  77
  78 INITIALIZE_PASS_BEGIN(LiveDebugVariables, DEBUG_TYPE,
  79                 "Debug Variable Analysis", false, false)
  80 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
  81 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
  82 INITIALIZE_PASS_END(LiveDebugVariables, DEBUG_TYPE,
  83                 "Debug Variable Analysis", false, false)
  84
  85 void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
  86   AU.addRequired<MachineDominatorTree>();
  87   AU.addRequiredTransitive<LiveIntervals>();
  88   AU.setPreservesAll();
  89   MachineFunctionPass::getAnalysisUsage(AU);
  90 }
  91
  92 LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID) {
  93   initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
  94 }
  95
  96 enum : unsigned { UndefLocNo = ~0U };
  97
  98 /// Describes a location by number along with some flags about the original
  99 /// usage of the location.
 100 class DbgValueLocation {
 101 public:
 102   DbgValueLocation(unsigned LocNo, bool WasIndirect)
 103       : LocNo(LocNo), WasIndirect(WasIndirect) {
 104     static_assert(sizeof(*this) == sizeof(unsigned), "bad bitfield packing");
 105     assert(locNo() == LocNo && "location truncation");
 106   }
 107
 108   DbgValueLocation() : LocNo(0), WasIndirect(0) {}
 109
 110   unsigned locNo() const {
 111     // Fix up the undef location number, which gets truncated.
 112     return LocNo == INT_MAX ? UndefLocNo : LocNo;
 113   }
 114   bool wasIndirect() const { return WasIndirect; }
 115   bool isUndef() const { return locNo() == UndefLocNo; }
 116
 117   DbgValueLocation changeLocNo(unsigned NewLocNo) const {
 118     return DbgValueLocation(NewLocNo, WasIndirect);
 119   }
 120
 121   friend inline bool operator==(const DbgValueLocation &LHS,
 122                                 const DbgValueLocation &RHS) {
 123     return LHS.LocNo == RHS.LocNo && LHS.WasIndirect == RHS.WasIndirect;
 124   }
 125
 126   friend inline bool operator!=(const DbgValueLocation &LHS,
 127                                 const DbgValueLocation &RHS) {
 128     return !(LHS == RHS);
 129   }
 130
 131 private:
 132   unsigned LocNo : 31;
 133   unsigned WasIndirect : 1;
 134 };
 135
 136 /// Map of where a user value is live, and its location.
 137 using LocMap = IntervalMap<SlotIndex, DbgValueLocation, 4>;
 138
 139 /// Map of stack slot offsets for spilled locations.
 140 /// Non-spilled locations are not added to the map.
 141 using SpillOffsetMap = DenseMap<unsigned, unsigned>;
 142
 143 namespace {
 144
 145 class LDVImpl;
 146
 147 /// A user value is a part of a debug info user variable.
 148 ///
 149 /// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
 150 /// holds part of a user variable. The part is identified by a byte offset.
 151 ///
 152 /// UserValues are grouped into equivalence classes for easier searching. Two
 153 /// user values are related if they refer to the same variable, or if they are
 154 /// held by the same virtual register. The equivalence class is the transitive
 155 /// closure of that relation.
 156 class UserValue {
 157   const DILocalVariable *Variable; ///< The debug info variable we are part of.
 158   const DIExpression *Expression; ///< Any complex address expression.
 159   DebugLoc dl;            ///< The debug location for the variable. This is
 160                           ///< used by dwarf writer to find lexical scope.
 161   UserValue *leader;      ///< Equivalence class leader.
 162   UserValue *next = nullptr; ///< Next value in equivalence class, or null.
 163
 164   /// Numbered locations referenced by locmap.
 165   SmallVector<MachineOperand, 4> locations;
 166
 167   /// Map of slot indices where this value is live.
 168   LocMap locInts;
 169
 170   /// Set of interval start indexes that have been trimmed to the
 171   /// lexical scope.
 172   SmallSet<SlotIndex, 2> trimmedDefs;
 173
 174   /// Insert a DBG_VALUE into MBB at Idx for LocNo.
 175   void insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
 176                         SlotIndex StopIdx, DbgValueLocation Loc, bool Spilled,
 177                         unsigned SpillOffset, LiveIntervals &LIS,
 178                         const TargetInstrInfo &TII,
 179                         const TargetRegisterInfo &TRI);
 180
 181   /// Replace OldLocNo ranges with NewRegs ranges where NewRegs
 182   /// is live. Returns true if any changes were made.
 183   bool splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
 184                      LiveIntervals &LIS);
 185
 186 public:
 187   /// Create a new UserValue.
 188   UserValue(const DILocalVariable *var, const DIExpression *expr, DebugLoc L,
 189             LocMap::Allocator &alloc)
 190       : Variable(var), Expression(expr), dl(std::move(L)), leader(this),
 191         locInts(alloc) {}
 192
 193   /// Get the leader of this value's equivalence class.
 194   UserValue *getLeader() {
 195     UserValue *l = leader;
 196     while (l != l->leader)
 197       l = l->leader;
 198     return leader = l;
 199   }
 200
 201   /// Return the next UserValue in the equivalence class.
 202   UserValue *getNext() const { return next; }
 203
 204   /// Does this UserValue match the parameters?
 205   bool match(const DILocalVariable *Var, const DIExpression *Expr,
 206              const DILocation *IA) const {
 207     // FIXME: The fragment should be part of the equivalence class, but not
 208     // other things in the expression like stack values.
 209     return Var == Variable && Expr == Expression && dl->getInlinedAt() == IA;
 210   }
 211
 212   /// Merge equivalence classes.
 213   static UserValue *merge(UserValue *L1, UserValue *L2) {
 214     L2 = L2->getLeader();
 215     if (!L1)
 216       return L2;
 217     L1 = L1->getLeader();
 218     if (L1 == L2)
 219       return L1;
 220     // Splice L2 before L1's members.
 221     UserValue *End = L2;
 222     while (End->next) {
 223       End->leader = L1;
 224       End = End->next;
 225     }
 226     End->leader = L1;
 227     End->next = L1->next;
 228     L1->next = L2;
 229     return L1;
 230   }
 231
 232   /// Return the location number that matches Loc.
 233   ///
 234   /// For undef values we always return location number UndefLocNo without
 235   /// inserting anything in locations. Since locations is a vector and the
 236   /// location number is the position in the vector and UndefLocNo is ~0,
 237   /// we would need a very big vector to put the value at the right position.
 238   unsigned getLocationNo(const MachineOperand &LocMO) {
 239     if (LocMO.isReg()) {
 240       if (LocMO.getReg() == 0)
 241         return UndefLocNo;
 242       // For register locations we dont care about use/def and other flags.
 243       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 244         if (locations[i].isReg() &&
 245             locations[i].getReg() == LocMO.getReg() &&
 246             locations[i].getSubReg() == LocMO.getSubReg())
 247           return i;
 248     } else
 249       for (unsigned i = 0, e = locations.size(); i != e; ++i)
 250         if (LocMO.isIdenticalTo(locations[i]))
 251           return i;
 252     locations.push_back(LocMO);
 253     // We are storing a MachineOperand outside a MachineInstr.
 254     locations.back().clearParent();
 255     // Don't store def operands.
 256     if (locations.back().isReg()) {
 257       if (locations.back().isDef())
 258         locations.back().setIsDead(false);
 259       locations.back().setIsUse();
 260     }
 261     return locations.size() - 1;
 262   }
 263
 264   /// Ensure that all virtual register locations are mapped.
 265   void mapVirtRegs(LDVImpl *LDV);
 266
 267   /// Add a definition point to this value.
 268   void addDef(SlotIndex Idx, const MachineOperand &LocMO, bool IsIndirect) {
 269     DbgValueLocation Loc(getLocationNo(LocMO), IsIndirect);
 270     // Add a singular (Idx,Idx) -> Loc mapping.
 271     LocMap::iterator I = locInts.find(Idx);
 272     if (!I.valid() || I.start() != Idx)
 273       I.insert(Idx, Idx.getNextSlot(), Loc);
 274     else
 275       // A later DBG_VALUE at the same SlotIndex overrides the old location.
 276       I.setValue(Loc);
 277   }
 278
 279   /// Extend the current definition as far as possible down.
 280   ///
 281   /// Stop when meeting an existing def or when leaving the live
 282   /// range of VNI. End points where VNI is no longer live are added to Kills.
 283   ///
 284   /// We only propagate DBG_VALUES locally here. LiveDebugValues performs a
 285   /// data-flow analysis to propagate them beyond basic block boundaries.
 286   ///
 287   /// \param Idx Starting point for the definition.
 288   /// \param Loc Location number to propagate.
 289   /// \param LR Restrict liveness to where LR has the value VNI. May be null.
 290   /// \param VNI When LR is not null, this is the value to restrict to.
 291   /// \param [out] Kills Append end points of VNI's live range to Kills.
 292   /// \param LIS Live intervals analysis.
 293   void extendDef(SlotIndex Idx, DbgValueLocation Loc,
 294                  LiveRange *LR, const VNInfo *VNI,
 295                  SmallVectorImpl<SlotIndex> *Kills,
 296                  LiveIntervals &LIS);
 297
 298   /// The value in LI/LocNo may be copies to other registers. Determine if
 299   /// any of the copies are available at the kill points, and add defs if
 300   /// possible.
 301   ///
 302   /// \param LI Scan for copies of the value in LI->reg.
 303   /// \param LocNo Location number of LI->reg.
 304   /// \param WasIndirect Indicates if the original use of LI->reg was indirect
 305   /// \param Kills Points where the range of LocNo could be extended.
 306   /// \param [in,out] NewDefs Append (Idx, LocNo) of inserted defs here.
 307   void addDefsFromCopies(
 308       LiveInterval *LI, unsigned LocNo, bool WasIndirect,
 309       const SmallVectorImpl<SlotIndex> &Kills,
 310       SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
 311       MachineRegisterInfo &MRI, LiveIntervals &LIS);
 312
 313   /// Compute the live intervals of all locations after collecting all their
 314   /// def points.
 315   void computeIntervals(MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
 316                         LiveIntervals &LIS, LexicalScopes &LS);
 317
 318   /// Replace OldReg ranges with NewRegs ranges where NewRegs is
 319   /// live. Returns true if any changes were made.
 320   bool splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
 321                      LiveIntervals &LIS);
 322
 323   /// Rewrite virtual register locations according to the provided virtual
 324   /// register map. Record the stack slot offsets for the locations that
 325   /// were spilled.
 326   void rewriteLocations(VirtRegMap &VRM, const MachineFunction &MF,
 327                         const TargetInstrInfo &TII,
 328                         const TargetRegisterInfo &TRI,
 329                         SpillOffsetMap &SpillOffsets);
 330
 331   /// Recreate DBG_VALUE instruction from data structures.
 332   void emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
 333                        const TargetInstrInfo &TII,
 334                        const TargetRegisterInfo &TRI,
 335                        const SpillOffsetMap &SpillOffsets);
 336
 337   /// Return DebugLoc of this UserValue.
 338   DebugLoc getDebugLoc() { return dl;}
 339
 340   void print(raw_ostream &, const TargetRegisterInfo *);
 341 };
 342
 343 /// A user label is a part of a debug info user label.
 344 class UserLabel {
 345   const DILabel *Label; ///< The debug info label we are part of.
 346   DebugLoc dl;          ///< The debug location for the label. This is
 347                         ///< used by dwarf writer to find lexical scope.
 348   SlotIndex loc;        ///< Slot used by the debug label.
 349
 350   /// Insert a DBG_LABEL into MBB at Idx.
 351   void insertDebugLabel(MachineBasicBlock *MBB, SlotIndex Idx,
 352                         LiveIntervals &LIS, const TargetInstrInfo &TII);
 353
 354 public:
 355   /// Create a new UserLabel.
 356   UserLabel(const DILabel *label, DebugLoc L, SlotIndex Idx)
 357       : Label(label), dl(std::move(L)), loc(Idx) {}
 358
 359   /// Does this UserLabel match the parameters?
 360   bool match(const DILabel *L, const DILocation *IA,
 361              const SlotIndex Index) const {
 362     return Label == L && dl->getInlinedAt() == IA && loc == Index;
 363   }
 364
 365   /// Recreate DBG_LABEL instruction from data structures.
 366   void emitDebugLabel(LiveIntervals &LIS, const TargetInstrInfo &TII);
 367
 368   /// Return DebugLoc of this UserLabel.
 369   DebugLoc getDebugLoc() { return dl; }
 370
 371   void print(raw_ostream &, const TargetRegisterInfo *);
 372 };
 373
 374 /// Implementation of the LiveDebugVariables pass.
 375 class LDVImpl {
 376   LiveDebugVariables &pass;
 377   LocMap::Allocator allocator;
 378   MachineFunction *MF = nullptr;
 379   LiveIntervals *LIS;
 380   const TargetRegisterInfo *TRI;
 381
 382   /// Whether emitDebugValues is called.
 383   bool EmitDone = false;
 384
 385   /// Whether the machine function is modified during the pass.
 386   bool ModifiedMF = false;
 387
 388   /// All allocated UserValue instances.
 389   SmallVector<std::unique_ptr<UserValue>, 8> userValues;
 390
 391   /// All allocated UserLabel instances.
 392   SmallVector<std::unique_ptr<UserLabel>, 2> userLabels;
 393
 394   /// Map virtual register to eq class leader.
 395   using VRMap = DenseMap<unsigned, UserValue *>;
 396   VRMap virtRegToEqClass;
 397
 398   /// Map user variable to eq class leader.
 399   using UVMap = DenseMap<const DILocalVariable *, UserValue *>;
 400   UVMap userVarMap;
 401
 402   /// Find or create a UserValue.
 403   UserValue *getUserValue(const DILocalVariable *Var, const DIExpression *Expr,
 404                           const DebugLoc &DL);
 405
 406   /// Find the EC leader for VirtReg or null.
 407   UserValue *lookupVirtReg(unsigned VirtReg);
 408
 409   /// Add DBG_VALUE instruction to our maps.
 410   ///
 411   /// \param MI DBG_VALUE instruction
 412   /// \param Idx Last valid SLotIndex before instruction.
 413   ///
 414   /// \returns True if the DBG_VALUE instruction should be deleted.
 415   bool handleDebugValue(MachineInstr &MI, SlotIndex Idx);
 416
 417   /// Add DBG_LABEL instruction to UserLabel.
 418   ///
 419   /// \param MI DBG_LABEL instruction
 420   /// \param Idx Last valid SlotIndex before instruction.
 421   ///
 422   /// \returns True if the DBG_LABEL instruction should be deleted.
 423   bool handleDebugLabel(MachineInstr &MI, SlotIndex Idx);
 424
 425   /// Collect and erase all DBG_VALUE instructions, adding a UserValue def
 426   /// for each instruction.
 427   ///
 428   /// \param mf MachineFunction to be scanned.
 429   ///
 430   /// \returns True if any debug values were found.
 431   bool collectDebugValues(MachineFunction &mf);
 432
 433   /// Compute the live intervals of all user values after collecting all
 434   /// their def points.
 435   void computeIntervals();
 436
 437 public:
 438   LDVImpl(LiveDebugVariables *ps) : pass(*ps) {}
 439
 440   bool runOnMachineFunction(MachineFunction &mf);
 441
 442   /// Release all memory.
 443   void clear() {
 444     MF = nullptr;
 445     userValues.clear();
 446     userLabels.clear();
 447     virtRegToEqClass.clear();
 448     userVarMap.clear();
 449     // Make sure we call emitDebugValues if the machine function was modified.
 450     assert((!ModifiedMF || EmitDone) &&
 451            "Dbg values are not emitted in LDV");
 452     EmitDone = false;
 453     ModifiedMF = false;
 454   }
 455
 456   /// Map virtual register to an equivalence class.
 457   void mapVirtReg(unsigned VirtReg, UserValue *EC);
 458
 459   /// Replace all references to OldReg with NewRegs.
 460   void splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs);
 461
 462   /// Recreate DBG_VALUE instruction from data structures.
 463   void emitDebugValues(VirtRegMap *VRM);
 464
 465   void print(raw_ostream&);
 466 };
 467
 468 } // end anonymous namespace
 469
 470 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 471 static void printDebugLoc(const DebugLoc &DL, raw_ostream &CommentOS,
 472                           const LLVMContext &Ctx) {
 473   if (!DL)
 474     return;
 475
 476   auto *Scope = cast<DIScope>(DL.getScope());
 477   // Omit the directory, because it's likely to be long and uninteresting.
 478   CommentOS << Scope->getFilename();
 479   CommentOS << ':' << DL.getLine();
 480   if (DL.getCol() != 0)
 481     CommentOS << ':' << DL.getCol();
 482
 483   DebugLoc InlinedAtDL = DL.getInlinedAt();
 484   if (!InlinedAtDL)
 485     return;
 486
 487   CommentOS << " @[ ";
 488   printDebugLoc(InlinedAtDL, CommentOS, Ctx);
 489   CommentOS << " ]";
 490 }
 491
 492 static void printExtendedName(raw_ostream &OS, const DINode *Node,
 493                               const DILocation *DL) {
 494   const LLVMContext &Ctx = Node->getContext();
 495   StringRef Res;
 496   unsigned Line;
 497   if (const auto *V = dyn_cast<const DILocalVariable>(Node)) {
 498     Res = V->getName();
 499     Line = V->getLine();
 500   } else if (const auto *L = dyn_cast<const DILabel>(Node)) {
 501     Res = L->getName();
 502     Line = L->getLine();
 503   }
 504
 505   if (!Res.empty())
 506     OS << Res << "," << Line;
 507   auto *InlinedAt = DL ? DL->getInlinedAt() : nullptr;
 508   if (InlinedAt) {
 509     if (DebugLoc InlinedAtDL = InlinedAt) {
 510       OS << " @[";
 511       printDebugLoc(InlinedAtDL, OS, Ctx);
 512       OS << "]";
 513     }
 514   }
 515 }
 516
 517 void UserValue::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
 518   OS << "!\"";
 519   printExtendedName(OS, Variable, dl);
 520
 521   OS << "\"\t";
 522   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
 523     OS << " [" << I.start() << ';' << I.stop() << "):";
 524     if (I.value().isUndef())
 525       OS << "undef";
 526     else {
 527       OS << I.value().locNo();
 528       if (I.value().wasIndirect())
 529         OS << " ind";
 530     }
 531   }
 532   for (unsigned i = 0, e = locations.size(); i != e; ++i) {
 533     OS << " Loc" << i << '=';
 534     locations[i].print(OS, TRI);
 535   }
 536   OS << '\n';
 537 }
 538
 539 void UserLabel::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
 540   OS << "!\"";
 541   printExtendedName(OS, Label, dl);
 542
 543   OS << "\"\t";
 544   OS << loc;
 545   OS << '\n';
 546 }
 547
 548 void LDVImpl::print(raw_ostream &OS) {
 549   OS << "********** DEBUG VARIABLES **********\n";
 550   for (auto &userValue : userValues)
 551     userValue->print(OS, TRI);
 552   OS << "********** DEBUG LABELS **********\n";
 553   for (auto &userLabel : userLabels)
 554     userLabel->print(OS, TRI);
 555 }
 556 #endif
 557
 558 void UserValue::mapVirtRegs(LDVImpl *LDV) {
 559   for (unsigned i = 0, e = locations.size(); i != e; ++i)
 560     if (locations[i].isReg() &&
 561         TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
 562       LDV->mapVirtReg(locations[i].getReg(), this);
 563 }
 564
 565 UserValue *LDVImpl::getUserValue(const DILocalVariable *Var,
 566                                  const DIExpression *Expr, const DebugLoc &DL) {
 567   UserValue *&Leader = userVarMap[Var];
 568   if (Leader) {
 569     UserValue *UV = Leader->getLeader();
 570     Leader = UV;
 571     for (; UV; UV = UV->getNext())
 572       if (UV->match(Var, Expr, DL->getInlinedAt()))
 573         return UV;
 574   }
 575
 576   userValues.push_back(
 577       llvm::make_unique<UserValue>(Var, Expr, DL, allocator));
 578   UserValue *UV = userValues.back().get();
 579   Leader = UserValue::merge(Leader, UV);
 580   return UV;
 581 }
 582
 583 void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
 584   assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
 585   UserValue *&Leader = virtRegToEqClass[VirtReg];
 586   Leader = UserValue::merge(Leader, EC);
 587 }
 588
 589 UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
 590   if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
 591     return UV->getLeader();
 592   return nullptr;
 593 }
 594
 595 bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
 596   // DBG_VALUE loc, offset, variable
 597   if (MI.getNumOperands() != 4 ||
 598       !(MI.getOperand(1).isReg() || MI.getOperand(1).isImm()) ||
 599       !MI.getOperand(2).isMetadata()) {
 600     LLVM_DEBUG(dbgs() << "Can't handle " << MI);
 601     return false;
 602   }
 603
 604   // Detect invalid DBG_VALUE instructions, with a debug-use of a virtual
 605   // register that hasn't been defined yet. If we do not remove those here, then
 606   // the re-insertion of the DBG_VALUE instruction after register allocation
 607   // will be incorrect.
 608   // TODO: If earlier passes are corrected to generate sane debug information
 609   // (and if the machine verifier is improved to catch this), then these checks
 610   // could be removed or replaced by asserts.
 611   bool Discard = false;
 612   if (MI.getOperand(0).isReg() &&
 613       TargetRegisterInfo::isVirtualRegister(MI.getOperand(0).getReg())) {
 614     const unsigned Reg = MI.getOperand(0).getReg();
 615     if (!LIS->hasInterval(Reg)) {
 616       // The DBG_VALUE is described by a virtual register that does not have a
 617       // live interval. Discard the DBG_VALUE.
 618       Discard = true;
 619       LLVM_DEBUG(dbgs() << "Discarding debug info (no LIS interval): " << Idx
 620                         << " " << MI);
 621     } else {
 622       // The DBG_VALUE is only valid if either Reg is live out from Idx, or Reg
 623       // is defined dead at Idx (where Idx is the slot index for the instruction
 624       // preceding the DBG_VALUE).
 625       const LiveInterval &LI = LIS->getInterval(Reg);
 626       LiveQueryResult LRQ = LI.Query(Idx);
 627       if (!LRQ.valueOutOrDead()) {
 628         // We have found a DBG_VALUE with the value in a virtual register that
 629         // is not live. Discard the DBG_VALUE.
 630         Discard = true;
 631         LLVM_DEBUG(dbgs() << "Discarding debug info (reg not live): " << Idx
 632                           << " " << MI);
 633       }
 634     }
 635   }
 636
 637   // Get or create the UserValue for (variable,offset) here.
 638   bool IsIndirect = MI.getOperand(1).isImm();
 639   if (IsIndirect)
 640     assert(MI.getOperand(1).getImm() == 0 && "DBG_VALUE with nonzero offset");
 641   const DILocalVariable *Var = MI.getDebugVariable();
 642   const DIExpression *Expr = MI.getDebugExpression();
 643   UserValue *UV =
 644       getUserValue(Var, Expr, MI.getDebugLoc());
 645   if (!Discard)
 646     UV->addDef(Idx, MI.getOperand(0), IsIndirect);
 647   else {
 648     MachineOperand MO = MachineOperand::CreateReg(0U, false);
 649     MO.setIsDebug();
 650     UV->addDef(Idx, MO, false);
 651   }
 652   return true;
 653 }
 654
 655 bool LDVImpl::handleDebugLabel(MachineInstr &MI, SlotIndex Idx) {
 656   // DBG_LABEL label
 657   if (MI.getNumOperands() != 1 || !MI.getOperand(0).isMetadata()) {
 658     LLVM_DEBUG(dbgs() << "Can't handle " << MI);
 659     return false;
 660   }
 661
 662   // Get or create the UserLabel for label here.
 663   const DILabel *Label = MI.getDebugLabel();
 664   const DebugLoc &DL = MI.getDebugLoc();
 665   bool Found = false;
 666   for (auto const &L : userLabels) {
 667     if (L->match(Label, DL->getInlinedAt(), Idx)) {
 668       Found = true;
 669       break;
 670     }
 671   }
 672   if (!Found)
 673     userLabels.push_back(llvm::make_unique<UserLabel>(Label, DL, Idx));
 674
 675   return true;
 676 }
 677
 678 bool LDVImpl::collectDebugValues(MachineFunction &mf) {
 679   bool Changed = false;
 680   for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
 681        ++MFI) {
 682     MachineBasicBlock *MBB = &*MFI;
 683     for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
 684          MBBI != MBBE;) {
 685       // Use the first debug instruction in the sequence to get a SlotIndex
 686       // for following consecutive debug instructions.
 687       if (!MBBI->isDebugInstr()) {
 688         ++MBBI;
 689         continue;
 690       }
 691       // Debug instructions has no slot index. Use the previous
 692       // non-debug instruction's SlotIndex as its SlotIndex.
 693       SlotIndex Idx =
 694           MBBI == MBB->begin()
 695               ? LIS->getMBBStartIdx(MBB)
 696               : LIS->getInstructionIndex(*std::prev(MBBI)).getRegSlot();
 697       // Handle consecutive debug instructions with the same slot index.
 698       do {
 699         // Only handle DBG_VALUE in handleDebugValue(). Skip all other
 700         // kinds of debug instructions.
 701         if ((MBBI->isDebugValue() && handleDebugValue(*MBBI, Idx)) ||
 702             (MBBI->isDebugLabel() && handleDebugLabel(*MBBI, Idx))) {
 703           MBBI = MBB->erase(MBBI);
 704           Changed = true;
 705         } else
 706           ++MBBI;
 707       } while (MBBI != MBBE && MBBI->isDebugInstr());
 708     }
 709   }
 710   return Changed;
 711 }
 712
 713 void UserValue::extendDef(SlotIndex Idx, DbgValueLocation Loc, LiveRange *LR,
 714                           const VNInfo *VNI, SmallVectorImpl<SlotIndex> *Kills,
 715                           LiveIntervals &LIS) {
 716   SlotIndex Start = Idx;
 717   MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
 718   SlotIndex Stop = LIS.getMBBEndIdx(MBB);
 719   LocMap::iterator I = locInts.find(Start);
 720
 721   // Limit to VNI's live range.
 722   bool ToEnd = true;
 723   if (LR && VNI) {
 724     LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
 725     if (!Segment || Segment->valno != VNI) {
 726       if (Kills)
 727         Kills->push_back(Start);
 728       return;
 729     }
 730     if (Segment->end < Stop) {
 731       Stop = Segment->end;
 732       ToEnd = false;
 733     }
 734   }
 735
 736   // There could already be a short def at Start.
 737   if (I.valid() && I.start() <= Start) {
 738     // Stop when meeting a different location or an already extended interval.
 739     Start = Start.getNextSlot();
 740     if (I.value() != Loc || I.stop() != Start)
 741       return;
 742     // This is a one-slot placeholder. Just skip it.
 743     ++I;
 744   }
 745
 746   // Limited by the next def.
 747   if (I.valid() && I.start() < Stop) {
 748     Stop = I.start();
 749     ToEnd = false;
 750   }
 751   // Limited by VNI's live range.
 752   else if (!ToEnd && Kills)
 753     Kills->push_back(Stop);
 754
 755   if (Start < Stop)
 756     I.insert(Start, Stop, Loc);
 757 }
 758
 759 void UserValue::addDefsFromCopies(
 760     LiveInterval *LI, unsigned LocNo, bool WasIndirect,
 761     const SmallVectorImpl<SlotIndex> &Kills,
 762     SmallVectorImpl<std::pair<SlotIndex, DbgValueLocation>> &NewDefs,
 763     MachineRegisterInfo &MRI, LiveIntervals &LIS) {
 764   if (Kills.empty())
 765     return;
 766   // Don't track copies from physregs, there are too many uses.
 767   if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
 768     return;
 769
 770   // Collect all the (vreg, valno) pairs that are copies of LI.
 771   SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
 772   for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg)) {
 773     MachineInstr *MI = MO.getParent();
 774     // Copies of the full value.
 775     if (MO.getSubReg() || !MI->isCopy())
 776       continue;
 777     unsigned DstReg = MI->getOperand(0).getReg();
 778
 779     // Don't follow copies to physregs. These are usually setting up call
 780     // arguments, and the argument registers are always call clobbered. We are
 781     // better off in the source register which could be a callee-saved register,
 782     // or it could be spilled.
 783     if (!TargetRegisterInfo::isVirtualRegister(DstReg))
 784       continue;
 785
 786     // Is LocNo extended to reach this copy? If not, another def may be blocking
 787     // it, or we are looking at a wrong value of LI.
 788     SlotIndex Idx = LIS.getInstructionIndex(*MI);
 789     LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
 790     if (!I.valid() || I.value().locNo() != LocNo)
 791       continue;
 792
 793     if (!LIS.hasInterval(DstReg))
 794       continue;
 795     LiveInterval *DstLI = &LIS.getInterval(DstReg);
 796     const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
 797     assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
 798     CopyValues.push_back(std::make_pair(DstLI, DstVNI));
 799   }
 800
 801   if (CopyValues.empty())
 802     return;
 803
 804   LLVM_DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI
 805                     << '\n');
 806
 807   // Try to add defs of the copied values for each kill point.
 808   for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
 809     SlotIndex Idx = Kills[i];
 810     for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
 811       LiveInterval *DstLI = CopyValues[j].first;
 812       const VNInfo *DstVNI = CopyValues[j].second;
 813       if (DstLI->getVNInfoAt(Idx) != DstVNI)
 814         continue;
 815       // Check that there isn't already a def at Idx
 816       LocMap::iterator I = locInts.find(Idx);
 817       if (I.valid() && I.start() <= Idx)
 818         continue;
 819       LLVM_DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
 820                         << DstVNI->id << " in " << *DstLI << '\n');
 821       MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
 822       assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
 823       unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
 824       DbgValueLocation NewLoc(LocNo, WasIndirect);
 825       I.insert(Idx, Idx.getNextSlot(), NewLoc);
 826       NewDefs.push_back(std::make_pair(Idx, NewLoc));
 827       break;
 828     }
 829   }
 830 }
 831
 832 void UserValue::computeIntervals(MachineRegisterInfo &MRI,
 833                                  const TargetRegisterInfo &TRI,
 834                                  LiveIntervals &LIS, LexicalScopes &LS) {
 835   SmallVector<std::pair<SlotIndex, DbgValueLocation>, 16> Defs;
 836
 837   // Collect all defs to be extended (Skipping undefs).
 838   for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
 839     if (!I.value().isUndef())
 840       Defs.push_back(std::make_pair(I.start(), I.value()));
 841
 842   // Extend all defs, and possibly add new ones along the way.
 843   for (unsigned i = 0; i != Defs.size(); ++i) {
 844     SlotIndex Idx = Defs[i].first;
 845     DbgValueLocation Loc = Defs[i].second;
 846     const MachineOperand &LocMO = locations[Loc.locNo()];
 847
 848     if (!LocMO.isReg()) {
 849       extendDef(Idx, Loc, nullptr, nullptr, nullptr, LIS);
 850       continue;
 851     }
 852
 853     // Register locations are constrained to where the register value is live.
 854     if (TargetRegisterInfo::isVirtualRegister(LocMO.getReg())) {
 855       LiveInterval *LI = nullptr;
 856       const VNInfo *VNI = nullptr;
 857       if (LIS.hasInterval(LocMO.getReg())) {
 858         LI = &LIS.getInterval(LocMO.getReg());
 859         VNI = LI->getVNInfoAt(Idx);
 860       }
 861       SmallVector<SlotIndex, 16> Kills;
 862       extendDef(Idx, Loc, LI, VNI, &Kills, LIS);
 863       // FIXME: Handle sub-registers in addDefsFromCopies. The problem is that
 864       // if the original location for example is %vreg0:sub_hi, and we find a
 865       // full register copy in addDefsFromCopies (at the moment it only handles
 866       // full register copies), then we must add the sub1 sub-register index to
 867       // the new location. However, that is only possible if the new virtual
 868       // register is of the same regclass (or if there is an equivalent
 869       // sub-register in that regclass). For now, simply skip handling copies if
 870       // a sub-register is involved.
 871       if (LI && !LocMO.getSubReg())
 872         addDefsFromCopies(LI, Loc.locNo(), Loc.wasIndirect(), Kills, Defs, MRI,
 873                           LIS);
 874       continue;
 875     }
 876
 877     // For physregs, we only mark the start slot idx. DwarfDebug will see it
 878     // as if the DBG_VALUE is valid up until the end of the basic block, or
 879     // the next def of the physical register. So we do not need to extend the
 880     // range. It might actually happen that the DBG_VALUE is the last use of
 881     // the physical register (e.g. if this is an unused input argument to a
 882     // function).
 883   }
 884
 885   // The computed intervals may extend beyond the range of the debug
 886   // location's lexical scope. In this case, splitting of an interval
 887   // can result in an interval outside of the scope being created,
 888   // causing extra unnecessary DBG_VALUEs to be emitted. To prevent
 889   // this, trim the intervals to the lexical scope.
 890
 891   LexicalScope *Scope = LS.findLexicalScope(dl);
 892   if (!Scope)
 893     return;
 894
 895   SlotIndex PrevEnd;
 896   LocMap::iterator I = locInts.begin();
 897
 898   // Iterate over the lexical scope ranges. Each time round the loop
 899   // we check the intervals for overlap with the end of the previous
 900   // range and the start of the next. The first range is handled as
 901   // a special case where there is no PrevEnd.
 902   for (const InsnRange &Range : Scope->getRanges()) {
 903     SlotIndex RStart = LIS.getInstructionIndex(*Range.first);
 904     SlotIndex REnd = LIS.getInstructionIndex(*Range.second);
 905
 906     // At the start of each iteration I has been advanced so that
 907     // I.stop() >= PrevEnd. Check for overlap.
 908     if (PrevEnd && I.start() < PrevEnd) {
 909       SlotIndex IStop = I.stop();
 910       DbgValueLocation Loc = I.value();
 911
 912       // Stop overlaps previous end - trim the end of the interval to
 913       // the scope range.
 914       I.setStopUnchecked(PrevEnd);
 915       ++I;
 916
 917       // If the interval also overlaps the start of the "next" (i.e.
 918       // current) range create a new interval for the remainder (which
 919       // may be further trimmed).
 920       if (RStart < IStop)
 921         I.insert(RStart, IStop, Loc);
 922     }
 923
 924     // Advance I so that I.stop() >= RStart, and check for overlap.
 925     I.advanceTo(RStart);
 926     if (!I.valid())
 927       return;
 928
 929     if (I.start() < RStart) {
 930       // Interval start overlaps range - trim to the scope range.
 931       I.setStartUnchecked(RStart);
 932       // Remember that this interval was trimmed.
 933       trimmedDefs.insert(RStart);
 934     }
 935
 936     // The end of a lexical scope range is the last instruction in the
 937     // range. To convert to an interval we need the index of the
 938     // instruction after it.
 939     REnd = REnd.getNextIndex();
 940
 941     // Advance I to first interval outside current range.
 942     I.advanceTo(REnd);
 943     if (!I.valid())
 944       return;
 945
 946     PrevEnd = REnd;
 947   }
 948
 949   // Check for overlap with end of final range.
 950   if (PrevEnd && I.start() < PrevEnd)
 951     I.setStopUnchecked(PrevEnd);
 952 }
 953
 954 void LDVImpl::computeIntervals() {
 955   LexicalScopes LS;
 956   LS.initialize(*MF);
 957
 958   for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
 959     userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, LS);
 960     userValues[i]->mapVirtRegs(this);
 961   }
 962 }
 963
 964 bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
 965   clear();
 966   MF = &mf;
 967   LIS = &pass.getAnalysis<LiveIntervals>();
 968   TRI = mf.getSubtarget().getRegisterInfo();
 969   LLVM_DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
 970                     << mf.getName() << " **********\n");
 971
 972   bool Changed = collectDebugValues(mf);
 973   computeIntervals();
 974   LLVM_DEBUG(print(dbgs()));
 975   ModifiedMF = Changed;
 976   return Changed;
 977 }
 978
 979 static void removeDebugValues(MachineFunction &mf) {
 980   for (MachineBasicBlock &MBB : mf) {
 981     for (auto MBBI = MBB.begin(), MBBE = MBB.end(); MBBI != MBBE; ) {
 982       if (!MBBI->isDebugValue()) {
 983         ++MBBI;
 984         continue;
 985       }
 986       MBBI = MBB.erase(MBBI);
 987     }
 988   }
 989 }
 990
 991 bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
 992   if (!EnableLDV)
 993     return false;
 994   if (!mf.getFunction().getSubprogram()) {
 995     removeDebugValues(mf);
 996     return false;
 997   }
 998   if (!pImpl)
 999     pImpl = new LDVImpl(this);
1000   return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
1001 }
1002
1003 void LiveDebugVariables::releaseMemory() {
1004   if (pImpl)
1005     static_cast<LDVImpl*>(pImpl)->clear();
1006 }
1007
1008 LiveDebugVariables::~LiveDebugVariables() {
1009   if (pImpl)
1010     delete static_cast<LDVImpl*>(pImpl);
1011 }
1012
1013 //===----------------------------------------------------------------------===//
1014 //                           Live Range Splitting
1015 //===----------------------------------------------------------------------===//
1016
1017 bool
1018 UserValue::splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
1019                          LiveIntervals& LIS) {
1020   LLVM_DEBUG({
1021     dbgs() << "Splitting Loc" << OldLocNo << '\t';
1022     print(dbgs(), nullptr);
1023   });
1024   bool DidChange = false;
1025   LocMap::iterator LocMapI;
1026   LocMapI.setMap(locInts);
1027   for (unsigned i = 0; i != NewRegs.size(); ++i) {
1028     LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
1029     if (LI->empty())
1030       continue;
1031
1032     // Don't allocate the new LocNo until it is needed.
1033     unsigned NewLocNo = UndefLocNo;
1034
1035     // Iterate over the overlaps between locInts and LI.
1036     LocMapI.find(LI->beginIndex());
1037     if (!LocMapI.valid())
1038       continue;
1039     LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
1040     LiveInterval::iterator LIE = LI->end();
1041     while (LocMapI.valid() && LII != LIE) {
1042       // At this point, we know that LocMapI.stop() > LII->start.
1043       LII = LI->advanceTo(LII, LocMapI.start());
1044       if (LII == LIE)
1045         break;
1046
1047       // Now LII->end > LocMapI.start(). Do we have an overlap?
1048       if (LocMapI.value().locNo() == OldLocNo && LII->start < LocMapI.stop()) {
1049         // Overlapping correct location. Allocate NewLocNo now.
1050         if (NewLocNo == UndefLocNo) {
1051           MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
1052           MO.setSubReg(locations[OldLocNo].getSubReg());
1053           NewLocNo = getLocationNo(MO);
1054           DidChange = true;
1055         }
1056
1057         SlotIndex LStart = LocMapI.start();
1058         SlotIndex LStop  = LocMapI.stop();
1059         DbgValueLocation OldLoc = LocMapI.value();
1060
1061         // Trim LocMapI down to the LII overlap.
1062         if (LStart < LII->start)
1063           LocMapI.setStartUnchecked(LII->start);
1064         if (LStop > LII->end)
1065           LocMapI.setStopUnchecked(LII->end);
1066
1067         // Change the value in the overlap. This may trigger coalescing.
1068         LocMapI.setValue(OldLoc.changeLocNo(NewLocNo));
1069
1070         // Re-insert any removed OldLocNo ranges.
1071         if (LStart < LocMapI.start()) {
1072           LocMapI.insert(LStart, LocMapI.start(), OldLoc);
1073           ++LocMapI;
1074           assert(LocMapI.valid() && "Unexpected coalescing");
1075         }
1076         if (LStop > LocMapI.stop()) {
1077           ++LocMapI;
1078           LocMapI.insert(LII->end, LStop, OldLoc);
1079           --LocMapI;
1080         }
1081       }
1082
1083       // Advance to the next overlap.
1084       if (LII->end < LocMapI.stop()) {
1085         if (++LII == LIE)
1086           break;
1087         LocMapI.advanceTo(LII->start);
1088       } else {
1089         ++LocMapI;
1090         if (!LocMapI.valid())
1091           break;
1092         LII = LI->advanceTo(LII, LocMapI.start());
1093       }
1094     }
1095   }
1096
1097   // Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
1098   locations.erase(locations.begin() + OldLocNo);
1099   LocMapI.goToBegin();
1100   while (LocMapI.valid()) {
1101     DbgValueLocation v = LocMapI.value();
1102     if (v.locNo() == OldLocNo) {
1103       LLVM_DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
1104                         << LocMapI.stop() << ")\n");
1105       LocMapI.erase();
1106     } else {
1107       // Undef values always have location number UndefLocNo, so don't change
1108       // locNo in that case. See getLocationNo().
1109       if (!v.isUndef() && v.locNo() > OldLocNo)
1110         LocMapI.setValueUnchecked(v.changeLocNo(v.locNo() - 1));
1111       ++LocMapI;
1112     }
1113   }
1114
1115   LLVM_DEBUG({
1116     dbgs() << "Split result: \t";
1117     print(dbgs(), nullptr);
1118   });
1119   return DidChange;
1120 }
1121
1122 bool
1123 UserValue::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
1124                          LiveIntervals &LIS) {
1125   bool DidChange = false;
1126   // Split locations referring to OldReg. Iterate backwards so splitLocation can
1127   // safely erase unused locations.
1128   for (unsigned i = locations.size(); i ; --i) {
1129     unsigned LocNo = i-1;
1130     const MachineOperand *Loc = &locations[LocNo];
1131     if (!Loc->isReg() || Loc->getReg() != OldReg)
1132       continue;
1133     DidChange |= splitLocation(LocNo, NewRegs, LIS);
1134   }
1135   return DidChange;
1136 }
1137
1138 void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs) {
1139   bool DidChange = false;
1140   for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
1141     DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
1142
1143   if (!DidChange)
1144     return;
1145
1146   // Map all of the new virtual registers.
1147   UserValue *UV = lookupVirtReg(OldReg);
1148   for (unsigned i = 0; i != NewRegs.size(); ++i)
1149     mapVirtReg(NewRegs[i], UV);
1150 }
1151
1152 void LiveDebugVariables::
1153 splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
1154   if (pImpl)
1155     static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
1156 }
1157
1158 void UserValue::rewriteLocations(VirtRegMap &VRM, const MachineFunction &MF,
1159                                  const TargetInstrInfo &TII,
1160                                  const TargetRegisterInfo &TRI,
1161                                  SpillOffsetMap &SpillOffsets) {
1162   // Build a set of new locations with new numbers so we can coalesce our
1163   // IntervalMap if two vreg intervals collapse to the same physical location.
1164   // Use MapVector instead of SetVector because MapVector::insert returns the
1165   // position of the previously or newly inserted element. The boolean value
1166   // tracks if the location was produced by a spill.
1167   // FIXME: This will be problematic if we ever support direct and indirect
1168   // frame index locations, i.e. expressing both variables in memory and
1169   // 'int x, *px = &x'. The "spilled" bit must become part of the location.
1170   MapVector<MachineOperand, std::pair<bool, unsigned>> NewLocations;
1171   SmallVector<unsigned, 4> LocNoMap(locations.size());
1172   for (unsigned I = 0, E = locations.size(); I != E; ++I) {
1173     bool Spilled = false;
1174     unsigned SpillOffset = 0;
1175     MachineOperand Loc = locations[I];
1176     // Only virtual registers are rewritten.
1177     if (Loc.isReg() && Loc.getReg() &&
1178         TargetRegisterInfo::isVirtualRegister(Loc.getReg())) {
1179       unsigned VirtReg = Loc.getReg();
1180       if (VRM.isAssignedReg(VirtReg) &&
1181           TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
1182         // This can create a %noreg operand in rare cases when the sub-register
1183         // index is no longer available. That means the user value is in a
1184         // non-existent sub-register, and %noreg is exactly what we want.
1185         Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
1186       } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
1187         // Retrieve the stack slot offset.
1188         unsigned SpillSize;
1189         const MachineRegisterInfo &MRI = MF.getRegInfo();
1190         const TargetRegisterClass *TRC = MRI.getRegClass(VirtReg);
1191         bool Success = TII.getStackSlotRange(TRC, Loc.getSubReg(), SpillSize,
1192                                              SpillOffset, MF);
1193
1194         // FIXME: Invalidate the location if the offset couldn't be calculated.
1195         (void)Success;
1196
1197         Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
1198         Spilled = true;
1199       } else {
1200         Loc.setReg(0);
1201         Loc.setSubReg(0);
1202       }
1203     }
1204
1205     // Insert this location if it doesn't already exist and record a mapping
1206     // from the old number to the new number.
1207     auto InsertResult = NewLocations.insert({Loc, {Spilled, SpillOffset}});
1208     unsigned NewLocNo = std::distance(NewLocations.begin(), InsertResult.first);
1209     LocNoMap[I] = NewLocNo;
1210   }
1211
1212   // Rewrite the locations and record the stack slot offsets for spills.
1213   locations.clear();
1214   SpillOffsets.clear();
1215   for (auto &Pair : NewLocations) {
1216     bool Spilled;
1217     unsigned SpillOffset;
1218     std::tie(Spilled, SpillOffset) = Pair.second;
1219     locations.push_back(Pair.first);
1220     if (Spilled) {
1221       unsigned NewLocNo = std::distance(&*NewLocations.begin(), &Pair);
1222       SpillOffsets[NewLocNo] = SpillOffset;
1223     }
1224   }
1225
1226   // Update the interval map, but only coalesce left, since intervals to the
1227   // right use the old location numbers. This should merge two contiguous
1228   // DBG_VALUE intervals with different vregs that were allocated to the same
1229   // physical register.
1230   for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
1231     DbgValueLocation Loc = I.value();
1232     // Undef values don't exist in locations (and thus not in LocNoMap either)
1233     // so skip over them. See getLocationNo().
1234     if (Loc.isUndef())
1235       continue;
1236     unsigned NewLocNo = LocNoMap[Loc.locNo()];
1237     I.setValueUnchecked(Loc.changeLocNo(NewLocNo));
1238     I.setStart(I.start());
1239   }
1240 }
1241
1242 /// Find an iterator for inserting a DBG_VALUE instruction.
1243 static MachineBasicBlock::iterator
1244 findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
1245                    LiveIntervals &LIS) {
1246   SlotIndex Start = LIS.getMBBStartIdx(MBB);
1247   Idx = Idx.getBaseIndex();
1248
1249   // Try to find an insert location by going backwards from Idx.
1250   MachineInstr *MI;
1251   while (!(MI = LIS.getInstructionFromIndex(Idx))) {
1252     // We've reached the beginning of MBB.
1253     if (Idx == Start) {
1254       MachineBasicBlock::iterator I = MBB->SkipPHIsLabelsAndDebug(MBB->begin());
1255       return I;
1256     }
1257     Idx = Idx.getPrevIndex();
1258   }
1259
1260   // Don't insert anything after the first terminator, though.
1261   return MI->isTerminator() ? MBB->getFirstTerminator() :
1262                               std::next(MachineBasicBlock::iterator(MI));
1263 }
1264
1265 /// Find an iterator for inserting the next DBG_VALUE instruction
1266 /// (or end if no more insert locations found).
1267 static MachineBasicBlock::iterator
1268 findNextInsertLocation(MachineBasicBlock *MBB,
1269                        MachineBasicBlock::iterator I,
1270                        SlotIndex StopIdx, MachineOperand &LocMO,
1271                        LiveIntervals &LIS,
1272                        const TargetRegisterInfo &TRI) {
1273   if (!LocMO.isReg())
1274     return MBB->instr_end();
1275   unsigned Reg = LocMO.getReg();
1276
1277   // Find the next instruction in the MBB that define the register Reg.
1278   while (I != MBB->end() && !I->isTerminator()) {
1279     if (!LIS.isNotInMIMap(*I) &&
1280         SlotIndex::isEarlierEqualInstr(StopIdx, LIS.getInstructionIndex(*I)))
1281       break;
1282     if (I->definesRegister(Reg, &TRI))
1283       // The insert location is directly after the instruction/bundle.
1284       return std::next(I);
1285     ++I;
1286   }
1287   return MBB->end();
1288 }
1289
1290 void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
1291                                  SlotIndex StopIdx, DbgValueLocation Loc,
1292                                  bool Spilled, unsigned SpillOffset,
1293                                  LiveIntervals &LIS, const TargetInstrInfo &TII,
1294                                  const TargetRegisterInfo &TRI) {
1295   SlotIndex MBBEndIdx = LIS.getMBBEndIdx(&*MBB);
1296   // Only search within the current MBB.
1297   StopIdx = (MBBEndIdx < StopIdx) ? MBBEndIdx : StopIdx;
1298   MachineBasicBlock::iterator I = findInsertLocation(MBB, StartIdx, LIS);
1299   // Undef values don't exist in locations so create new "noreg" register MOs
1300   // for them. See getLocationNo().
1301   MachineOperand MO = !Loc.isUndef() ?
1302     locations[Loc.locNo()] :
1303     MachineOperand::CreateReg(/* Reg */ 0, /* isDef */ false, /* isImp */ false,
1304                               /* isKill */ false, /* isDead */ false,
1305                               /* isUndef */ false, /* isEarlyClobber */ false,
1306                               /* SubReg */ 0, /* isDebug */ true);
1307
1308   ++NumInsertedDebugValues;
1309
1310   assert(cast<DILocalVariable>(Variable)
1311              ->isValidLocationForIntrinsic(getDebugLoc()) &&
1312          "Expected inlined-at fields to agree");
1313
1314   // If the location was spilled, the new DBG_VALUE will be indirect. If the
1315   // original DBG_VALUE was indirect, we need to add DW_OP_deref to indicate
1316   // that the original virtual register was a pointer. Also, add the stack slot
1317   // offset for the spilled register to the expression.
1318   const DIExpression *Expr = Expression;
1319   bool IsIndirect = Loc.wasIndirect();
1320   if (Spilled) {
1321     auto Deref = IsIndirect ? DIExpression::WithDeref : DIExpression::NoDeref;
1322     Expr =
1323         DIExpression::prepend(Expr, DIExpression::NoDeref, SpillOffset, Deref);
1324     IsIndirect = true;
1325   }
1326
1327   assert((!Spilled || MO.isFI()) && "a spilled location must be a frame index");
1328
1329   do {
1330     BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
1331             IsIndirect, MO, Variable, Expr);
1332
1333     // Continue and insert DBG_VALUES after every redefinition of register
1334     // associated with the debug value within the range
1335     I = findNextInsertLocation(MBB, I, StopIdx, MO, LIS, TRI);
1336   } while (I != MBB->end());
1337 }
1338
1339 void UserLabel::insertDebugLabel(MachineBasicBlock *MBB, SlotIndex Idx,
1340                                  LiveIntervals &LIS,
1341                                  const TargetInstrInfo &TII) {
1342   MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
1343   ++NumInsertedDebugLabels;
1344   BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_LABEL))
1345       .addMetadata(Label);
1346 }
1347
1348 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
1349                                 const TargetInstrInfo &TII,
1350                                 const TargetRegisterInfo &TRI,
1351                                 const SpillOffsetMap &SpillOffsets) {
1352   MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
1353
1354   for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
1355     SlotIndex Start = I.start();
1356     SlotIndex Stop = I.stop();
1357     DbgValueLocation Loc = I.value();
1358     auto SpillIt =
1359         !Loc.isUndef() ? SpillOffsets.find(Loc.locNo()) : SpillOffsets.end();
1360     bool Spilled = SpillIt != SpillOffsets.end();
1361     unsigned SpillOffset = Spilled ? SpillIt->second : 0;
1362
1363     // If the interval start was trimmed to the lexical scope insert the
1364     // DBG_VALUE at the previous index (otherwise it appears after the
1365     // first instruction in the range).
1366     if (trimmedDefs.count(Start))
1367       Start = Start.getPrevIndex();
1368
1369     LLVM_DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << Loc.locNo());
1370     MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start)->getIterator();
1371     SlotIndex MBBEnd = LIS.getMBBEndIdx(&*MBB);
1372
1373     LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB) << '-' << MBBEnd);
1374     insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, SpillOffset, LIS, TII,
1375                      TRI);
1376     // This interval may span multiple basic blocks.
1377     // Insert a DBG_VALUE into each one.
1378     while (Stop > MBBEnd) {
1379       // Move to the next block.
1380       Start = MBBEnd;
1381       if (++MBB == MFEnd)
1382         break;
1383       MBBEnd = LIS.getMBBEndIdx(&*MBB);
1384       LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB) << '-' << MBBEnd);
1385       insertDebugValue(&*MBB, Start, Stop, Loc, Spilled, SpillOffset, LIS, TII,
1386                        TRI);
1387     }
1388     LLVM_DEBUG(dbgs() << '\n');
1389     if (MBB == MFEnd)
1390       break;
1391
1392     ++I;
1393   }
1394 }
1395
1396 void UserLabel::emitDebugLabel(LiveIntervals &LIS, const TargetInstrInfo &TII) {
1397   LLVM_DEBUG(dbgs() << "\t" << loc);
1398   MachineFunction::iterator MBB = LIS.getMBBFromIndex(loc)->getIterator();
1399
1400   LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB));
1401   insertDebugLabel(&*MBB, loc, LIS, TII);
1402
1403   LLVM_DEBUG(dbgs() << '\n');
1404 }
1405
1406 void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
1407   LLVM_DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
1408   if (!MF)
1409     return;
1410   const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
1411   SpillOffsetMap SpillOffsets;
1412   for (auto &userValue : userValues) {
1413     LLVM_DEBUG(userValue->print(dbgs(), TRI));
1414     userValue->rewriteLocations(*VRM, *MF, *TII, *TRI, SpillOffsets);
1415     userValue->emitDebugValues(VRM, *LIS, *TII, *TRI, SpillOffsets);
1416   }
1417   LLVM_DEBUG(dbgs() << "********** EMITTING LIVE DEBUG LABELS **********\n");
1418   for (auto &userLabel : userLabels) {
1419     LLVM_DEBUG(userLabel->print(dbgs(), TRI));
1420     userLabel->emitDebugLabel(*LIS, *TII);
1421   }
1422   EmitDone = true;
1423 }
1424
1425 void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
1426   if (pImpl)
1427     static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
1428 }
1429
1430 bool LiveDebugVariables::doInitialization(Module &M) {
1431   return Pass::doInitialization(M);
1432 }
1433
1434 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1435 LLVM_DUMP_METHOD void LiveDebugVariables::dump() const {
1436   if (pImpl)
1437     static_cast<LDVImpl*>(pImpl)->print(dbgs());
1438 }
1439 #endif