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
43#include <memory>
44
45using namespace llvm;
46
47#define DEBUG_TYPE "livedebug"
48
49static cl::opt<bool>
50EnableLDV("live-debug-variables", cl::init(true),
51          cl::desc("Enable the live debug variables pass"), cl::Hidden);
52
53STATISTIC(NumInsertedDebugValues, "Number of DBG_VALUEs inserted");
54char LiveDebugVariables::ID = 0;
55
56INITIALIZE_PASS_BEGIN(LiveDebugVariables, "livedebugvars",
57                "Debug Variable Analysis", false, false)
58INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
59INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
60INITIALIZE_PASS_END(LiveDebugVariables, "livedebugvars",
61                "Debug Variable Analysis", false, false)
62
63void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
64  AU.addRequired<MachineDominatorTree>();
65  AU.addRequiredTransitive<LiveIntervals>();
66  AU.setPreservesAll();
67  MachineFunctionPass::getAnalysisUsage(AU);
68}
69
70LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID), pImpl(nullptr) {
71  initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
72}
73
74/// LocMap - Map of where a user value is live, and its location.
75typedef IntervalMap<SlotIndex, unsigned, 4> LocMap;
76
77namespace {
78/// UserValueScopes - Keeps track of lexical scopes associated with a
79/// user value's source location.
80class UserValueScopes {
81  DebugLoc DL;
82  LexicalScopes &LS;
83  SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
84
85public:
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.
109namespace {
110class LDVImpl;
111class UserValue {
112  const MDNode *variable; ///< The debug info variable we are part of.
113  unsigned offset;        ///< Byte offset into variable.
114  bool IsIndirect;        ///< true if this is a register-indirect+offset value.
115  DebugLoc dl;            ///< The debug location for the variable. This is
116                          ///< used by dwarf writer to find lexical scope.
117  UserValue *leader;      ///< Equivalence class leader.
118  UserValue *next;        ///< Next value in equivalence class, or null.
119
120  /// Numbered locations referenced by locmap.
121  SmallVector<MachineOperand, 4> locations;
122
123  /// Map of slot indices where this value is live.
124  LocMap locInts;
125
126  /// coalesceLocation - After LocNo was changed, check if it has become
127  /// identical to another location, and coalesce them. This may cause LocNo or
128  /// a later location to be erased, but no earlier location will be erased.
129  void coalesceLocation(unsigned LocNo);
130
131  /// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
132  void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx, unsigned LocNo,
133                        LiveIntervals &LIS, const TargetInstrInfo &TII);
134
135  /// splitLocation - Replace OldLocNo ranges with NewRegs ranges where NewRegs
136  /// is live. Returns true if any changes were made.
137  bool splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
138                     LiveIntervals &LIS);
139
140public:
141  /// UserValue - Create a new UserValue.
142  UserValue(const MDNode *var, unsigned o, bool i, DebugLoc L,
143            LocMap::Allocator &alloc)
144    : variable(var), offset(o), IsIndirect(i), dl(L), leader(this),
145      next(nullptr), locInts(alloc)
146  {}
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, unsigned Offset, bool indirect) const {
161    return Var == variable && Offset == offset && indirect == IsIndirect;
162  }
163
164  /// merge - Merge equivalence classes.
165  static UserValue *merge(UserValue *L1, UserValue *L2) {
166    L2 = L2->getLeader();
167    if (!L1)
168      return L2;
169    L1 = L1->getLeader();
170    if (L1 == L2)
171      return L1;
172    // Splice L2 before L1's members.
173    UserValue *End = L2;
174    while (End->next)
175      End->leader = L1, End = End->next;
176    End->leader = L1;
177    End->next = L1->next;
178    L1->next = L2;
179    return L1;
180  }
181
182  /// getLocationNo - Return the location number that matches Loc.
183  unsigned getLocationNo(const MachineOperand &LocMO) {
184    if (LocMO.isReg()) {
185      if (LocMO.getReg() == 0)
186        return ~0u;
187      // For register locations we dont care about use/def and other flags.
188      for (unsigned i = 0, e = locations.size(); i != e; ++i)
189        if (locations[i].isReg() &&
190            locations[i].getReg() == LocMO.getReg() &&
191            locations[i].getSubReg() == LocMO.getSubReg())
192          return i;
193    } else
194      for (unsigned i = 0, e = locations.size(); i != e; ++i)
195        if (LocMO.isIdenticalTo(locations[i]))
196          return i;
197    locations.push_back(LocMO);
198    // We are storing a MachineOperand outside a MachineInstr.
199    locations.back().clearParent();
200    // Don't store def operands.
201    if (locations.back().isReg())
202      locations.back().setIsUse();
203    return locations.size() - 1;
204  }
205
206  /// mapVirtRegs - Ensure that all virtual register locations are mapped.
207  void mapVirtRegs(LDVImpl *LDV);
208
209  /// addDef - Add a definition point to this value.
210  void addDef(SlotIndex Idx, const MachineOperand &LocMO) {
211    // Add a singular (Idx,Idx) -> Loc mapping.
212    LocMap::iterator I = locInts.find(Idx);
213    if (!I.valid() || I.start() != Idx)
214      I.insert(Idx, Idx.getNextSlot(), getLocationNo(LocMO));
215    else
216      // A later DBG_VALUE at the same SlotIndex overrides the old location.
217      I.setValue(getLocationNo(LocMO));
218  }
219
220  /// extendDef - Extend the current definition as far as possible down the
221  /// dominator tree. Stop when meeting an existing def or when leaving the live
222  /// range of VNI.
223  /// End points where VNI is no longer live are added to Kills.
224  /// @param Idx   Starting point for the definition.
225  /// @param LocNo Location number to propagate.
226  /// @param LR    Restrict liveness to where LR has the value VNI. May be null.
227  /// @param VNI   When LR is not null, this is the value to restrict to.
228  /// @param Kills Append end points of VNI's live range to Kills.
229  /// @param LIS   Live intervals analysis.
230  /// @param MDT   Dominator tree.
231  void extendDef(SlotIndex Idx, unsigned LocNo,
232                 LiveRange *LR, const VNInfo *VNI,
233                 SmallVectorImpl<SlotIndex> *Kills,
234                 LiveIntervals &LIS, MachineDominatorTree &MDT,
235                 UserValueScopes &UVS);
236
237  /// addDefsFromCopies - The value in LI/LocNo may be copies to other
238  /// registers. Determine if any of the copies are available at the kill
239  /// points, and add defs if possible.
240  /// @param LI      Scan for copies of the value in LI->reg.
241  /// @param LocNo   Location number of LI->reg.
242  /// @param Kills   Points where the range of LocNo could be extended.
243  /// @param NewDefs Append (Idx, LocNo) of inserted defs here.
244  void addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
245                      const SmallVectorImpl<SlotIndex> &Kills,
246                      SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
247                      MachineRegisterInfo &MRI,
248                      LiveIntervals &LIS);
249
250  /// computeIntervals - Compute the live intervals of all locations after
251  /// collecting all their def points.
252  void computeIntervals(MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
253                        LiveIntervals &LIS, MachineDominatorTree &MDT,
254                        UserValueScopes &UVS);
255
256  /// splitRegister - Replace OldReg ranges with NewRegs ranges where NewRegs is
257  /// live. Returns true if any changes were made.
258  bool splitRegister(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
259                     LiveIntervals &LIS);
260
261  /// rewriteLocations - Rewrite virtual register locations according to the
262  /// provided virtual register map.
263  void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI);
264
265  /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
266  void emitDebugValues(VirtRegMap *VRM,
267                       LiveIntervals &LIS, const TargetInstrInfo &TRI);
268
269  /// findDebugLoc - Return DebugLoc used for this DBG_VALUE instruction. A
270  /// variable may have more than one corresponding DBG_VALUE instructions.
271  /// Only first one needs DebugLoc to identify variable's lexical scope
272  /// in source file.
273  DebugLoc findDebugLoc();
274
275  /// getDebugLoc - Return DebugLoc of this UserValue.
276  DebugLoc getDebugLoc() { return dl;}
277  void print(raw_ostream&, const TargetMachine*);
278};
279} // namespace
280
281/// LDVImpl - Implementation of the LiveDebugVariables pass.
282namespace {
283class LDVImpl {
284  LiveDebugVariables &pass;
285  LocMap::Allocator allocator;
286  MachineFunction *MF;
287  LiveIntervals *LIS;
288  LexicalScopes LS;
289  MachineDominatorTree *MDT;
290  const TargetRegisterInfo *TRI;
291
292  /// Whether emitDebugValues is called.
293  bool EmitDone;
294  /// Whether the machine function is modified during the pass.
295  bool ModifiedMF;
296
297  /// userValues - All allocated UserValue instances.
298  SmallVector<std::unique_ptr<UserValue>, 8> userValues;
299
300  /// Map virtual register to eq class leader.
301  typedef DenseMap<unsigned, UserValue*> VRMap;
302  VRMap virtRegToEqClass;
303
304  /// Map user variable to eq class leader.
305  typedef DenseMap<const MDNode *, UserValue*> UVMap;
306  UVMap userVarMap;
307
308  /// getUserValue - Find or create a UserValue.
309  UserValue *getUserValue(const MDNode *Var, unsigned Offset,
310                          bool IsIndirect, DebugLoc DL);
311
312  /// lookupVirtReg - Find the EC leader for VirtReg or null.
313  UserValue *lookupVirtReg(unsigned VirtReg);
314
315  /// handleDebugValue - Add DBG_VALUE instruction to our maps.
316  /// @param MI  DBG_VALUE instruction
317  /// @param Idx Last valid SLotIndex before instruction.
318  /// @return    True if the DBG_VALUE instruction should be deleted.
319  bool handleDebugValue(MachineInstr *MI, SlotIndex Idx);
320
321  /// collectDebugValues - Collect and erase all DBG_VALUE instructions, adding
322  /// a UserValue def for each instruction.
323  /// @param mf MachineFunction to be scanned.
324  /// @return True if any debug values were found.
325  bool collectDebugValues(MachineFunction &mf);
326
327  /// computeIntervals - Compute the live intervals of all user values after
328  /// collecting all their def points.
329  void computeIntervals();
330
331public:
332  LDVImpl(LiveDebugVariables *ps)
333      : pass(*ps), MF(nullptr), EmitDone(false), ModifiedMF(false) {}
334  bool runOnMachineFunction(MachineFunction &mf);
335
336  /// clear - Release all memory.
337  void clear() {
338    MF = nullptr;
339    userValues.clear();
340    virtRegToEqClass.clear();
341    userVarMap.clear();
342    // Make sure we call emitDebugValues if the machine function was modified.
343    assert((!ModifiedMF || EmitDone) &&
344           "Dbg values are not emitted in LDV");
345    EmitDone = false;
346    ModifiedMF = false;
347  }
348
349  /// mapVirtReg - Map virtual register to an equivalence class.
350  void mapVirtReg(unsigned VirtReg, UserValue *EC);
351
352  /// splitRegister -  Replace all references to OldReg with NewRegs.
353  void splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs);
354
355  /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
356  void emitDebugValues(VirtRegMap *VRM);
357
358  void print(raw_ostream&);
359};
360} // namespace
361
362void UserValue::print(raw_ostream &OS, const TargetMachine *TM) {
363  DIVariable DV(variable);
364  OS << "!\"";
365  DV.printExtendedName(OS);
366  OS << "\"\t";
367  if (offset)
368    OS << '+' << offset;
369  for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
370    OS << " [" << I.start() << ';' << I.stop() << "):";
371    if (I.value() == ~0u)
372      OS << "undef";
373    else
374      OS << I.value();
375  }
376  for (unsigned i = 0, e = locations.size(); i != e; ++i) {
377    OS << " Loc" << i << '=';
378    locations[i].print(OS, TM);
379  }
380  OS << '\n';
381}
382
383void LDVImpl::print(raw_ostream &OS) {
384  OS << "********** DEBUG VARIABLES **********\n";
385  for (unsigned i = 0, e = userValues.size(); i != e; ++i)
386    userValues[i]->print(OS, &MF->getTarget());
387}
388
389void UserValue::coalesceLocation(unsigned LocNo) {
390  unsigned KeepLoc = 0;
391  for (unsigned e = locations.size(); KeepLoc != e; ++KeepLoc) {
392    if (KeepLoc == LocNo)
393      continue;
394    if (locations[KeepLoc].isIdenticalTo(locations[LocNo]))
395      break;
396  }
397  // No matches.
398  if (KeepLoc == locations.size())
399    return;
400
401  // Keep the smaller location, erase the larger one.
402  unsigned EraseLoc = LocNo;
403  if (KeepLoc > EraseLoc)
404    std::swap(KeepLoc, EraseLoc);
405  locations.erase(locations.begin() + EraseLoc);
406
407  // Rewrite values.
408  for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
409    unsigned v = I.value();
410    if (v == EraseLoc)
411      I.setValue(KeepLoc);      // Coalesce when possible.
412    else if (v > EraseLoc)
413      I.setValueUnchecked(v-1); // Avoid coalescing with untransformed values.
414  }
415}
416
417void UserValue::mapVirtRegs(LDVImpl *LDV) {
418  for (unsigned i = 0, e = locations.size(); i != e; ++i)
419    if (locations[i].isReg() &&
420        TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
421      LDV->mapVirtReg(locations[i].getReg(), this);
422}
423
424UserValue *LDVImpl::getUserValue(const MDNode *Var, unsigned Offset,
425                                 bool IsIndirect, DebugLoc DL) {
426  UserValue *&Leader = userVarMap[Var];
427  if (Leader) {
428    UserValue *UV = Leader->getLeader();
429    Leader = UV;
430    for (; UV; UV = UV->getNext())
431      if (UV->match(Var, Offset, IsIndirect))
432        return UV;
433  }
434
435  userValues.push_back(
436      make_unique<UserValue>(Var, Offset, IsIndirect, DL, allocator));
437  UserValue *UV = userValues.back().get();
438  Leader = UserValue::merge(Leader, UV);
439  return UV;
440}
441
442void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
443  assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
444  UserValue *&Leader = virtRegToEqClass[VirtReg];
445  Leader = UserValue::merge(Leader, EC);
446}
447
448UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
449  if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
450    return UV->getLeader();
451  return nullptr;
452}
453
454bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
455  // DBG_VALUE loc, offset, variable
456  if (MI->getNumOperands() != 3 ||
457      !(MI->getOperand(1).isReg() || MI->getOperand(1).isImm()) ||
458      !MI->getOperand(2).isMetadata()) {
459    DEBUG(dbgs() << "Can't handle " << *MI);
460    return false;
461  }
462
463  // Get or create the UserValue for (variable,offset).
464  bool IsIndirect = MI->isIndirectDebugValue();
465  unsigned Offset = IsIndirect ? MI->getOperand(1).getImm() : 0;
466  const MDNode *Var = MI->getOperand(2).getMetadata();
467  //here.
468  UserValue *UV = getUserValue(Var, Offset, IsIndirect, MI->getDebugLoc());
469  UV->addDef(Idx, MI->getOperand(0));
470  return true;
471}
472
473bool LDVImpl::collectDebugValues(MachineFunction &mf) {
474  bool Changed = false;
475  for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
476       ++MFI) {
477    MachineBasicBlock *MBB = MFI;
478    for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
479         MBBI != MBBE;) {
480      if (!MBBI->isDebugValue()) {
481        ++MBBI;
482        continue;
483      }
484      // DBG_VALUE has no slot index, use the previous instruction instead.
485      SlotIndex Idx = MBBI == MBB->begin() ?
486        LIS->getMBBStartIdx(MBB) :
487        LIS->getInstructionIndex(std::prev(MBBI)).getRegSlot();
488      // Handle consecutive DBG_VALUE instructions with the same slot index.
489      do {
490        if (handleDebugValue(MBBI, Idx)) {
491          MBBI = MBB->erase(MBBI);
492          Changed = true;
493        } else
494          ++MBBI;
495      } while (MBBI != MBBE && MBBI->isDebugValue());
496    }
497  }
498  return Changed;
499}
500
501void UserValue::extendDef(SlotIndex Idx, unsigned LocNo,
502                          LiveRange *LR, const VNInfo *VNI,
503                          SmallVectorImpl<SlotIndex> *Kills,
504                          LiveIntervals &LIS, MachineDominatorTree &MDT,
505                          UserValueScopes &UVS) {
506  SmallVector<SlotIndex, 16> Todo;
507  Todo.push_back(Idx);
508  do {
509    SlotIndex Start = Todo.pop_back_val();
510    MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
511    SlotIndex Stop = LIS.getMBBEndIdx(MBB);
512    LocMap::iterator I = locInts.find(Start);
513
514    // Limit to VNI's live range.
515    bool ToEnd = true;
516    if (LR && VNI) {
517      LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
518      if (!Segment || Segment->valno != VNI) {
519        if (Kills)
520          Kills->push_back(Start);
521        continue;
522      }
523      if (Segment->end < Stop)
524        Stop = Segment->end, ToEnd = false;
525    }
526
527    // There could already be a short def at Start.
528    if (I.valid() && I.start() <= Start) {
529      // Stop when meeting a different location or an already extended interval.
530      Start = Start.getNextSlot();
531      if (I.value() != LocNo || I.stop() != Start)
532        continue;
533      // This is a one-slot placeholder. Just skip it.
534      ++I;
535    }
536
537    // Limited by the next def.
538    if (I.valid() && I.start() < Stop)
539      Stop = I.start(), ToEnd = false;
540    // Limited by VNI's live range.
541    else if (!ToEnd && Kills)
542      Kills->push_back(Stop);
543
544    if (Start >= Stop)
545      continue;
546
547    I.insert(Start, Stop, LocNo);
548
549    // If we extended to the MBB end, propagate down the dominator tree.
550    if (!ToEnd)
551      continue;
552    const std::vector<MachineDomTreeNode*> &Children =
553      MDT.getNode(MBB)->getChildren();
554    for (unsigned i = 0, e = Children.size(); i != e; ++i) {
555      MachineBasicBlock *MBB = Children[i]->getBlock();
556      if (UVS.dominates(MBB))
557        Todo.push_back(LIS.getMBBStartIdx(MBB));
558    }
559  } while (!Todo.empty());
560}
561
562void
563UserValue::addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
564                      const SmallVectorImpl<SlotIndex> &Kills,
565                      SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
566                      MachineRegisterInfo &MRI, LiveIntervals &LIS) {
567  if (Kills.empty())
568    return;
569  // Don't track copies from physregs, there are too many uses.
570  if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
571    return;
572
573  // Collect all the (vreg, valno) pairs that are copies of LI.
574  SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
575  for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg)) {
576    MachineInstr *MI = MO.getParent();
577    // Copies of the full value.
578    if (MO.getSubReg() || !MI->isCopy())
579      continue;
580    unsigned DstReg = MI->getOperand(0).getReg();
581
582    // Don't follow copies to physregs. These are usually setting up call
583    // arguments, and the argument registers are always call clobbered. We are
584    // better off in the source register which could be a callee-saved register,
585    // or it could be spilled.
586    if (!TargetRegisterInfo::isVirtualRegister(DstReg))
587      continue;
588
589    // Is LocNo extended to reach this copy? If not, another def may be blocking
590    // it, or we are looking at a wrong value of LI.
591    SlotIndex Idx = LIS.getInstructionIndex(MI);
592    LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
593    if (!I.valid() || I.value() != LocNo)
594      continue;
595
596    if (!LIS.hasInterval(DstReg))
597      continue;
598    LiveInterval *DstLI = &LIS.getInterval(DstReg);
599    const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
600    assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
601    CopyValues.push_back(std::make_pair(DstLI, DstVNI));
602  }
603
604  if (CopyValues.empty())
605    return;
606
607  DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI << '\n');
608
609  // Try to add defs of the copied values for each kill point.
610  for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
611    SlotIndex Idx = Kills[i];
612    for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
613      LiveInterval *DstLI = CopyValues[j].first;
614      const VNInfo *DstVNI = CopyValues[j].second;
615      if (DstLI->getVNInfoAt(Idx) != DstVNI)
616        continue;
617      // Check that there isn't already a def at Idx
618      LocMap::iterator I = locInts.find(Idx);
619      if (I.valid() && I.start() <= Idx)
620        continue;
621      DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
622                   << DstVNI->id << " in " << *DstLI << '\n');
623      MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
624      assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
625      unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
626      I.insert(Idx, Idx.getNextSlot(), LocNo);
627      NewDefs.push_back(std::make_pair(Idx, LocNo));
628      break;
629    }
630  }
631}
632
633void
634UserValue::computeIntervals(MachineRegisterInfo &MRI,
635                            const TargetRegisterInfo &TRI,
636                            LiveIntervals &LIS,
637                            MachineDominatorTree &MDT,
638                            UserValueScopes &UVS) {
639  SmallVector<std::pair<SlotIndex, unsigned>, 16> Defs;
640
641  // Collect all defs to be extended (Skipping undefs).
642  for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
643    if (I.value() != ~0u)
644      Defs.push_back(std::make_pair(I.start(), I.value()));
645
646  // Extend all defs, and possibly add new ones along the way.
647  for (unsigned i = 0; i != Defs.size(); ++i) {
648    SlotIndex Idx = Defs[i].first;
649    unsigned LocNo = Defs[i].second;
650    const MachineOperand &Loc = locations[LocNo];
651
652    if (!Loc.isReg()) {
653      extendDef(Idx, LocNo, nullptr, nullptr, nullptr, LIS, MDT, UVS);
654      continue;
655    }
656
657    // Register locations are constrained to where the register value is live.
658    if (TargetRegisterInfo::isVirtualRegister(Loc.getReg())) {
659      LiveInterval *LI = nullptr;
660      const VNInfo *VNI = nullptr;
661      if (LIS.hasInterval(Loc.getReg())) {
662        LI = &LIS.getInterval(Loc.getReg());
663        VNI = LI->getVNInfoAt(Idx);
664      }
665      SmallVector<SlotIndex, 16> Kills;
666      extendDef(Idx, LocNo, LI, VNI, &Kills, LIS, MDT, UVS);
667      if (LI)
668        addDefsFromCopies(LI, LocNo, Kills, Defs, MRI, LIS);
669      continue;
670    }
671
672    // For physregs, use the live range of the first regunit as a guide.
673    unsigned Unit = *MCRegUnitIterator(Loc.getReg(), &TRI);
674    LiveRange *LR = &LIS.getRegUnit(Unit);
675    const VNInfo *VNI = LR->getVNInfoAt(Idx);
676    // Don't track copies from physregs, it is too expensive.
677    extendDef(Idx, LocNo, LR, VNI, nullptr, LIS, MDT, UVS);
678  }
679
680  // Finally, erase all the undefs.
681  for (LocMap::iterator I = locInts.begin(); I.valid();)
682    if (I.value() == ~0u)
683      I.erase();
684    else
685      ++I;
686}
687
688void LDVImpl::computeIntervals() {
689  for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
690    UserValueScopes UVS(userValues[i]->getDebugLoc(), LS);
691    userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, *MDT, UVS);
692    userValues[i]->mapVirtRegs(this);
693  }
694}
695
696bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
697  clear();
698  MF = &mf;
699  LIS = &pass.getAnalysis<LiveIntervals>();
700  MDT = &pass.getAnalysis<MachineDominatorTree>();
701  TRI = mf.getTarget().getRegisterInfo();
702  LS.initialize(mf);
703  DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
704               << mf.getName() << " **********\n");
705
706  bool Changed = collectDebugValues(mf);
707  computeIntervals();
708  DEBUG(print(dbgs()));
709  ModifiedMF = Changed;
710  return Changed;
711}
712
713bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
714  if (!EnableLDV)
715    return false;
716  if (!FunctionDIs.count(mf.getFunction()))
717    return false;
718  if (!pImpl)
719    pImpl = new LDVImpl(this);
720  return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
721}
722
723void LiveDebugVariables::releaseMemory() {
724  if (pImpl)
725    static_cast<LDVImpl*>(pImpl)->clear();
726}
727
728LiveDebugVariables::~LiveDebugVariables() {
729  if (pImpl)
730    delete static_cast<LDVImpl*>(pImpl);
731}
732
733//===----------------------------------------------------------------------===//
734//                           Live Range Splitting
735//===----------------------------------------------------------------------===//
736
737bool
738UserValue::splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
739                         LiveIntervals& LIS) {
740  DEBUG({
741    dbgs() << "Splitting Loc" << OldLocNo << '\t';
742    print(dbgs(), nullptr);
743  });
744  bool DidChange = false;
745  LocMap::iterator LocMapI;
746  LocMapI.setMap(locInts);
747  for (unsigned i = 0; i != NewRegs.size(); ++i) {
748    LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
749    if (LI->empty())
750      continue;
751
752    // Don't allocate the new LocNo until it is needed.
753    unsigned NewLocNo = ~0u;
754
755    // Iterate over the overlaps between locInts and LI.
756    LocMapI.find(LI->beginIndex());
757    if (!LocMapI.valid())
758      continue;
759    LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
760    LiveInterval::iterator LIE = LI->end();
761    while (LocMapI.valid() && LII != LIE) {
762      // At this point, we know that LocMapI.stop() > LII->start.
763      LII = LI->advanceTo(LII, LocMapI.start());
764      if (LII == LIE)
765        break;
766
767      // Now LII->end > LocMapI.start(). Do we have an overlap?
768      if (LocMapI.value() == OldLocNo && LII->start < LocMapI.stop()) {
769        // Overlapping correct location. Allocate NewLocNo now.
770        if (NewLocNo == ~0u) {
771          MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
772          MO.setSubReg(locations[OldLocNo].getSubReg());
773          NewLocNo = getLocationNo(MO);
774          DidChange = true;
775        }
776
777        SlotIndex LStart = LocMapI.start();
778        SlotIndex LStop  = LocMapI.stop();
779
780        // Trim LocMapI down to the LII overlap.
781        if (LStart < LII->start)
782          LocMapI.setStartUnchecked(LII->start);
783        if (LStop > LII->end)
784          LocMapI.setStopUnchecked(LII->end);
785
786        // Change the value in the overlap. This may trigger coalescing.
787        LocMapI.setValue(NewLocNo);
788
789        // Re-insert any removed OldLocNo ranges.
790        if (LStart < LocMapI.start()) {
791          LocMapI.insert(LStart, LocMapI.start(), OldLocNo);
792          ++LocMapI;
793          assert(LocMapI.valid() && "Unexpected coalescing");
794        }
795        if (LStop > LocMapI.stop()) {
796          ++LocMapI;
797          LocMapI.insert(LII->end, LStop, OldLocNo);
798          --LocMapI;
799        }
800      }
801
802      // Advance to the next overlap.
803      if (LII->end < LocMapI.stop()) {
804        if (++LII == LIE)
805          break;
806        LocMapI.advanceTo(LII->start);
807      } else {
808        ++LocMapI;
809        if (!LocMapI.valid())
810          break;
811        LII = LI->advanceTo(LII, LocMapI.start());
812      }
813    }
814  }
815
816  // Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
817  locations.erase(locations.begin() + OldLocNo);
818  LocMapI.goToBegin();
819  while (LocMapI.valid()) {
820    unsigned v = LocMapI.value();
821    if (v == OldLocNo) {
822      DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
823                   << LocMapI.stop() << ")\n");
824      LocMapI.erase();
825    } else {
826      if (v > OldLocNo)
827        LocMapI.setValueUnchecked(v-1);
828      ++LocMapI;
829    }
830  }
831
832  DEBUG({dbgs() << "Split result: \t"; print(dbgs(), nullptr);});
833  return DidChange;
834}
835
836bool
837UserValue::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
838                         LiveIntervals &LIS) {
839  bool DidChange = false;
840  // Split locations referring to OldReg. Iterate backwards so splitLocation can
841  // safely erase unused locations.
842  for (unsigned i = locations.size(); i ; --i) {
843    unsigned LocNo = i-1;
844    const MachineOperand *Loc = &locations[LocNo];
845    if (!Loc->isReg() || Loc->getReg() != OldReg)
846      continue;
847    DidChange |= splitLocation(LocNo, NewRegs, LIS);
848  }
849  return DidChange;
850}
851
852void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs) {
853  bool DidChange = false;
854  for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
855    DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
856
857  if (!DidChange)
858    return;
859
860  // Map all of the new virtual registers.
861  UserValue *UV = lookupVirtReg(OldReg);
862  for (unsigned i = 0; i != NewRegs.size(); ++i)
863    mapVirtReg(NewRegs[i], UV);
864}
865
866void LiveDebugVariables::
867splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
868  if (pImpl)
869    static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
870}
871
872void
873UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI) {
874  // Iterate over locations in reverse makes it easier to handle coalescing.
875  for (unsigned i = locations.size(); i ; --i) {
876    unsigned LocNo = i-1;
877    MachineOperand &Loc = locations[LocNo];
878    // Only virtual registers are rewritten.
879    if (!Loc.isReg() || !Loc.getReg() ||
880        !TargetRegisterInfo::isVirtualRegister(Loc.getReg()))
881      continue;
882    unsigned VirtReg = Loc.getReg();
883    if (VRM.isAssignedReg(VirtReg) &&
884        TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
885      // This can create a %noreg operand in rare cases when the sub-register
886      // index is no longer available. That means the user value is in a
887      // non-existent sub-register, and %noreg is exactly what we want.
888      Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
889    } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
890      // FIXME: Translate SubIdx to a stackslot offset.
891      Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
892    } else {
893      Loc.setReg(0);
894      Loc.setSubReg(0);
895    }
896    coalesceLocation(LocNo);
897  }
898}
899
900/// findInsertLocation - Find an iterator for inserting a DBG_VALUE
901/// instruction.
902static MachineBasicBlock::iterator
903findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
904                   LiveIntervals &LIS) {
905  SlotIndex Start = LIS.getMBBStartIdx(MBB);
906  Idx = Idx.getBaseIndex();
907
908  // Try to find an insert location by going backwards from Idx.
909  MachineInstr *MI;
910  while (!(MI = LIS.getInstructionFromIndex(Idx))) {
911    // We've reached the beginning of MBB.
912    if (Idx == Start) {
913      MachineBasicBlock::iterator I = MBB->SkipPHIsAndLabels(MBB->begin());
914      return I;
915    }
916    Idx = Idx.getPrevIndex();
917  }
918
919  // Don't insert anything after the first terminator, though.
920  return MI->isTerminator() ? MBB->getFirstTerminator() :
921                              std::next(MachineBasicBlock::iterator(MI));
922}
923
924DebugLoc UserValue::findDebugLoc() {
925  DebugLoc D = dl;
926  dl = DebugLoc();
927  return D;
928}
929void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
930                                 unsigned LocNo,
931                                 LiveIntervals &LIS,
932                                 const TargetInstrInfo &TII) {
933  MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
934  MachineOperand &Loc = locations[LocNo];
935  ++NumInsertedDebugValues;
936
937  if (Loc.isReg())
938    BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
939            IsIndirect, Loc.getReg(), offset, variable);
940  else
941    BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
942      .addOperand(Loc).addImm(offset).addMetadata(variable);
943}
944
945void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
946                                const TargetInstrInfo &TII) {
947  MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
948
949  for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
950    SlotIndex Start = I.start();
951    SlotIndex Stop = I.stop();
952    unsigned LocNo = I.value();
953    DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << LocNo);
954    MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start);
955    SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);
956
957    DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
958    insertDebugValue(MBB, Start, LocNo, LIS, TII);
959    // This interval may span multiple basic blocks.
960    // Insert a DBG_VALUE into each one.
961    while(Stop > MBBEnd) {
962      // Move to the next block.
963      Start = MBBEnd;
964      if (++MBB == MFEnd)
965        break;
966      MBBEnd = LIS.getMBBEndIdx(MBB);
967      DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
968      insertDebugValue(MBB, Start, LocNo, LIS, TII);
969    }
970    DEBUG(dbgs() << '\n');
971    if (MBB == MFEnd)
972      break;
973
974    ++I;
975  }
976}
977
978void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
979  DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
980  if (!MF)
981    return;
982  const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
983  for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
984    DEBUG(userValues[i]->print(dbgs(), &MF->getTarget()));
985    userValues[i]->rewriteLocations(*VRM, *TRI);
986    userValues[i]->emitDebugValues(VRM, *LIS, *TII);
987  }
988  EmitDone = true;
989}
990
991void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
992  if (pImpl)
993    static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
994}
995
996bool LiveDebugVariables::doInitialization(Module &M) {
997  FunctionDIs = makeSubprogramMap(M);
998  return Pass::doInitialization(M);
999}
1000
1001#ifndef NDEBUG
1002void LiveDebugVariables::dump() {
1003  if (pImpl)
1004    static_cast<LDVImpl*>(pImpl)->print(dbgs());
1005}
1006#endif
1007