LiveDebugVariables.cpp revision dce4a407a24b04eebc6a376f8e62b41aaa7b071f 
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) : pass(*ps), EmitDone(false),
333                                    ModifiedMF(false) {}
334  bool runOnMachineFunction(MachineFunction &mf);
335
336  /// clear - Release all memory.
337  void clear() {
338    userValues.clear();
339    virtRegToEqClass.clear();
340    userVarMap.clear();
341    // Make sure we call emitDebugValues if the machine function was modified.
342    assert((!ModifiedMF || EmitDone) &&
343           "Dbg values are not emitted in LDV");
344    EmitDone = false;
345    ModifiedMF = false;
346  }
347
348  /// mapVirtReg - Map virtual register to an equivalence class.
349  void mapVirtReg(unsigned VirtReg, UserValue *EC);
350
351  /// splitRegister -  Replace all references to OldReg with NewRegs.
352  void splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs);
353
354  /// emitDebugValues - Recreate DBG_VALUE instruction from data structures.
355  void emitDebugValues(VirtRegMap *VRM);
356
357  void print(raw_ostream&);
358};
359} // namespace
360
361void UserValue::print(raw_ostream &OS, const TargetMachine *TM) {
362  DIVariable DV(variable);
363  OS << "!\"";
364  DV.printExtendedName(OS);
365  OS << "\"\t";
366  if (offset)
367    OS << '+' << offset;
368  for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
369    OS << " [" << I.start() << ';' << I.stop() << "):";
370    if (I.value() == ~0u)
371      OS << "undef";
372    else
373      OS << I.value();
374  }
375  for (unsigned i = 0, e = locations.size(); i != e; ++i) {
376    OS << " Loc" << i << '=';
377    locations[i].print(OS, TM);
378  }
379  OS << '\n';
380}
381
382void LDVImpl::print(raw_ostream &OS) {
383  OS << "********** DEBUG VARIABLES **********\n";
384  for (unsigned i = 0, e = userValues.size(); i != e; ++i)
385    userValues[i]->print(OS, &MF->getTarget());
386}
387
388void UserValue::coalesceLocation(unsigned LocNo) {
389  unsigned KeepLoc = 0;
390  for (unsigned e = locations.size(); KeepLoc != e; ++KeepLoc) {
391    if (KeepLoc == LocNo)
392      continue;
393    if (locations[KeepLoc].isIdenticalTo(locations[LocNo]))
394      break;
395  }
396  // No matches.
397  if (KeepLoc == locations.size())
398    return;
399
400  // Keep the smaller location, erase the larger one.
401  unsigned EraseLoc = LocNo;
402  if (KeepLoc > EraseLoc)
403    std::swap(KeepLoc, EraseLoc);
404  locations.erase(locations.begin() + EraseLoc);
405
406  // Rewrite values.
407  for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
408    unsigned v = I.value();
409    if (v == EraseLoc)
410      I.setValue(KeepLoc);      // Coalesce when possible.
411    else if (v > EraseLoc)
412      I.setValueUnchecked(v-1); // Avoid coalescing with untransformed values.
413  }
414}
415
416void UserValue::mapVirtRegs(LDVImpl *LDV) {
417  for (unsigned i = 0, e = locations.size(); i != e; ++i)
418    if (locations[i].isReg() &&
419        TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
420      LDV->mapVirtReg(locations[i].getReg(), this);
421}
422
423UserValue *LDVImpl::getUserValue(const MDNode *Var, unsigned Offset,
424                                 bool IsIndirect, DebugLoc DL) {
425  UserValue *&Leader = userVarMap[Var];
426  if (Leader) {
427    UserValue *UV = Leader->getLeader();
428    Leader = UV;
429    for (; UV; UV = UV->getNext())
430      if (UV->match(Var, Offset, IsIndirect))
431        return UV;
432  }
433
434  userValues.push_back(
435      make_unique<UserValue>(Var, Offset, IsIndirect, DL, allocator));
436  UserValue *UV = userValues.back().get();
437  Leader = UserValue::merge(Leader, UV);
438  return UV;
439}
440
441void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
442  assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
443  UserValue *&Leader = virtRegToEqClass[VirtReg];
444  Leader = UserValue::merge(Leader, EC);
445}
446
447UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
448  if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
449    return UV->getLeader();
450  return nullptr;
451}
452
453bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
454  // DBG_VALUE loc, offset, variable
455  if (MI->getNumOperands() != 3 ||
456      !(MI->getOperand(1).isReg() || MI->getOperand(1).isImm()) ||
457      !MI->getOperand(2).isMetadata()) {
458    DEBUG(dbgs() << "Can't handle " << *MI);
459    return false;
460  }
461
462  // Get or create the UserValue for (variable,offset).
463  bool IsIndirect = MI->isIndirectDebugValue();
464  unsigned Offset = IsIndirect ? MI->getOperand(1).getImm() : 0;
465  const MDNode *Var = MI->getOperand(2).getMetadata();
466  //here.
467  UserValue *UV = getUserValue(Var, Offset, IsIndirect, MI->getDebugLoc());
468  UV->addDef(Idx, MI->getOperand(0));
469  return true;
470}
471
472bool LDVImpl::collectDebugValues(MachineFunction &mf) {
473  bool Changed = false;
474  for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
475       ++MFI) {
476    MachineBasicBlock *MBB = MFI;
477    for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
478         MBBI != MBBE;) {
479      if (!MBBI->isDebugValue()) {
480        ++MBBI;
481        continue;
482      }
483      // DBG_VALUE has no slot index, use the previous instruction instead.
484      SlotIndex Idx = MBBI == MBB->begin() ?
485        LIS->getMBBStartIdx(MBB) :
486        LIS->getInstructionIndex(std::prev(MBBI)).getRegSlot();
487      // Handle consecutive DBG_VALUE instructions with the same slot index.
488      do {
489        if (handleDebugValue(MBBI, Idx)) {
490          MBBI = MBB->erase(MBBI);
491          Changed = true;
492        } else
493          ++MBBI;
494      } while (MBBI != MBBE && MBBI->isDebugValue());
495    }
496  }
497  return Changed;
498}
499
500void UserValue::extendDef(SlotIndex Idx, unsigned LocNo,
501                          LiveRange *LR, const VNInfo *VNI,
502                          SmallVectorImpl<SlotIndex> *Kills,
503                          LiveIntervals &LIS, MachineDominatorTree &MDT,
504                          UserValueScopes &UVS) {
505  SmallVector<SlotIndex, 16> Todo;
506  Todo.push_back(Idx);
507  do {
508    SlotIndex Start = Todo.pop_back_val();
509    MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
510    SlotIndex Stop = LIS.getMBBEndIdx(MBB);
511    LocMap::iterator I = locInts.find(Start);
512
513    // Limit to VNI's live range.
514    bool ToEnd = true;
515    if (LR && VNI) {
516      LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
517      if (!Segment || Segment->valno != VNI) {
518        if (Kills)
519          Kills->push_back(Start);
520        continue;
521      }
522      if (Segment->end < Stop)
523        Stop = Segment->end, ToEnd = false;
524    }
525
526    // There could already be a short def at Start.
527    if (I.valid() && I.start() <= Start) {
528      // Stop when meeting a different location or an already extended interval.
529      Start = Start.getNextSlot();
530      if (I.value() != LocNo || I.stop() != Start)
531        continue;
532      // This is a one-slot placeholder. Just skip it.
533      ++I;
534    }
535
536    // Limited by the next def.
537    if (I.valid() && I.start() < Stop)
538      Stop = I.start(), ToEnd = false;
539    // Limited by VNI's live range.
540    else if (!ToEnd && Kills)
541      Kills->push_back(Stop);
542
543    if (Start >= Stop)
544      continue;
545
546    I.insert(Start, Stop, LocNo);
547
548    // If we extended to the MBB end, propagate down the dominator tree.
549    if (!ToEnd)
550      continue;
551    const std::vector<MachineDomTreeNode*> &Children =
552      MDT.getNode(MBB)->getChildren();
553    for (unsigned i = 0, e = Children.size(); i != e; ++i) {
554      MachineBasicBlock *MBB = Children[i]->getBlock();
555      if (UVS.dominates(MBB))
556        Todo.push_back(LIS.getMBBStartIdx(MBB));
557    }
558  } while (!Todo.empty());
559}
560
561void
562UserValue::addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
563                      const SmallVectorImpl<SlotIndex> &Kills,
564                      SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
565                      MachineRegisterInfo &MRI, LiveIntervals &LIS) {
566  if (Kills.empty())
567    return;
568  // Don't track copies from physregs, there are too many uses.
569  if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
570    return;
571
572  // Collect all the (vreg, valno) pairs that are copies of LI.
573  SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
574  for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg)) {
575    MachineInstr *MI = MO.getParent();
576    // Copies of the full value.
577    if (MO.getSubReg() || !MI->isCopy())
578      continue;
579    unsigned DstReg = MI->getOperand(0).getReg();
580
581    // Don't follow copies to physregs. These are usually setting up call
582    // arguments, and the argument registers are always call clobbered. We are
583    // better off in the source register which could be a callee-saved register,
584    // or it could be spilled.
585    if (!TargetRegisterInfo::isVirtualRegister(DstReg))
586      continue;
587
588    // Is LocNo extended to reach this copy? If not, another def may be blocking
589    // it, or we are looking at a wrong value of LI.
590    SlotIndex Idx = LIS.getInstructionIndex(MI);
591    LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
592    if (!I.valid() || I.value() != LocNo)
593      continue;
594
595    if (!LIS.hasInterval(DstReg))
596      continue;
597    LiveInterval *DstLI = &LIS.getInterval(DstReg);
598    const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
599    assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
600    CopyValues.push_back(std::make_pair(DstLI, DstVNI));
601  }
602
603  if (CopyValues.empty())
604    return;
605
606  DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI << '\n');
607
608  // Try to add defs of the copied values for each kill point.
609  for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
610    SlotIndex Idx = Kills[i];
611    for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
612      LiveInterval *DstLI = CopyValues[j].first;
613      const VNInfo *DstVNI = CopyValues[j].second;
614      if (DstLI->getVNInfoAt(Idx) != DstVNI)
615        continue;
616      // Check that there isn't already a def at Idx
617      LocMap::iterator I = locInts.find(Idx);
618      if (I.valid() && I.start() <= Idx)
619        continue;
620      DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
621                   << DstVNI->id << " in " << *DstLI << '\n');
622      MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
623      assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
624      unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
625      I.insert(Idx, Idx.getNextSlot(), LocNo);
626      NewDefs.push_back(std::make_pair(Idx, LocNo));
627      break;
628    }
629  }
630}
631
632void
633UserValue::computeIntervals(MachineRegisterInfo &MRI,
634                            const TargetRegisterInfo &TRI,
635                            LiveIntervals &LIS,
636                            MachineDominatorTree &MDT,
637                            UserValueScopes &UVS) {
638  SmallVector<std::pair<SlotIndex, unsigned>, 16> Defs;
639
640  // Collect all defs to be extended (Skipping undefs).
641  for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
642    if (I.value() != ~0u)
643      Defs.push_back(std::make_pair(I.start(), I.value()));
644
645  // Extend all defs, and possibly add new ones along the way.
646  for (unsigned i = 0; i != Defs.size(); ++i) {
647    SlotIndex Idx = Defs[i].first;
648    unsigned LocNo = Defs[i].second;
649    const MachineOperand &Loc = locations[LocNo];
650
651    if (!Loc.isReg()) {
652      extendDef(Idx, LocNo, nullptr, nullptr, nullptr, LIS, MDT, UVS);
653      continue;
654    }
655
656    // Register locations are constrained to where the register value is live.
657    if (TargetRegisterInfo::isVirtualRegister(Loc.getReg())) {
658      LiveInterval *LI = nullptr;
659      const VNInfo *VNI = nullptr;
660      if (LIS.hasInterval(Loc.getReg())) {
661        LI = &LIS.getInterval(Loc.getReg());
662        VNI = LI->getVNInfoAt(Idx);
663      }
664      SmallVector<SlotIndex, 16> Kills;
665      extendDef(Idx, LocNo, LI, VNI, &Kills, LIS, MDT, UVS);
666      if (LI)
667        addDefsFromCopies(LI, LocNo, Kills, Defs, MRI, LIS);
668      continue;
669    }
670
671    // For physregs, use the live range of the first regunit as a guide.
672    unsigned Unit = *MCRegUnitIterator(Loc.getReg(), &TRI);
673    LiveRange *LR = &LIS.getRegUnit(Unit);
674    const VNInfo *VNI = LR->getVNInfoAt(Idx);
675    // Don't track copies from physregs, it is too expensive.
676    extendDef(Idx, LocNo, LR, VNI, nullptr, LIS, MDT, UVS);
677  }
678
679  // Finally, erase all the undefs.
680  for (LocMap::iterator I = locInts.begin(); I.valid();)
681    if (I.value() == ~0u)
682      I.erase();
683    else
684      ++I;
685}
686
687void LDVImpl::computeIntervals() {
688  for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
689    UserValueScopes UVS(userValues[i]->getDebugLoc(), LS);
690    userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, *MDT, UVS);
691    userValues[i]->mapVirtRegs(this);
692  }
693}
694
695bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
696  MF = &mf;
697  LIS = &pass.getAnalysis<LiveIntervals>();
698  MDT = &pass.getAnalysis<MachineDominatorTree>();
699  TRI = mf.getTarget().getRegisterInfo();
700  clear();
701  LS.initialize(mf);
702  DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
703               << mf.getName() << " **********\n");
704
705  bool Changed = collectDebugValues(mf);
706  computeIntervals();
707  DEBUG(print(dbgs()));
708  ModifiedMF = Changed;
709  return Changed;
710}
711
712bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
713  if (!EnableLDV)
714    return false;
715  if (!pImpl)
716    pImpl = new LDVImpl(this);
717  return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
718}
719
720void LiveDebugVariables::releaseMemory() {
721  if (pImpl)
722    static_cast<LDVImpl*>(pImpl)->clear();
723}
724
725LiveDebugVariables::~LiveDebugVariables() {
726  if (pImpl)
727    delete static_cast<LDVImpl*>(pImpl);
728}
729
730//===----------------------------------------------------------------------===//
731//                           Live Range Splitting
732//===----------------------------------------------------------------------===//
733
734bool
735UserValue::splitLocation(unsigned OldLocNo, ArrayRef<unsigned> NewRegs,
736                         LiveIntervals& LIS) {
737  DEBUG({
738    dbgs() << "Splitting Loc" << OldLocNo << '\t';
739    print(dbgs(), nullptr);
740  });
741  bool DidChange = false;
742  LocMap::iterator LocMapI;
743  LocMapI.setMap(locInts);
744  for (unsigned i = 0; i != NewRegs.size(); ++i) {
745    LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
746    if (LI->empty())
747      continue;
748
749    // Don't allocate the new LocNo until it is needed.
750    unsigned NewLocNo = ~0u;
751
752    // Iterate over the overlaps between locInts and LI.
753    LocMapI.find(LI->beginIndex());
754    if (!LocMapI.valid())
755      continue;
756    LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
757    LiveInterval::iterator LIE = LI->end();
758    while (LocMapI.valid() && LII != LIE) {
759      // At this point, we know that LocMapI.stop() > LII->start.
760      LII = LI->advanceTo(LII, LocMapI.start());
761      if (LII == LIE)
762        break;
763
764      // Now LII->end > LocMapI.start(). Do we have an overlap?
765      if (LocMapI.value() == OldLocNo && LII->start < LocMapI.stop()) {
766        // Overlapping correct location. Allocate NewLocNo now.
767        if (NewLocNo == ~0u) {
768          MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
769          MO.setSubReg(locations[OldLocNo].getSubReg());
770          NewLocNo = getLocationNo(MO);
771          DidChange = true;
772        }
773
774        SlotIndex LStart = LocMapI.start();
775        SlotIndex LStop  = LocMapI.stop();
776
777        // Trim LocMapI down to the LII overlap.
778        if (LStart < LII->start)
779          LocMapI.setStartUnchecked(LII->start);
780        if (LStop > LII->end)
781          LocMapI.setStopUnchecked(LII->end);
782
783        // Change the value in the overlap. This may trigger coalescing.
784        LocMapI.setValue(NewLocNo);
785
786        // Re-insert any removed OldLocNo ranges.
787        if (LStart < LocMapI.start()) {
788          LocMapI.insert(LStart, LocMapI.start(), OldLocNo);
789          ++LocMapI;
790          assert(LocMapI.valid() && "Unexpected coalescing");
791        }
792        if (LStop > LocMapI.stop()) {
793          ++LocMapI;
794          LocMapI.insert(LII->end, LStop, OldLocNo);
795          --LocMapI;
796        }
797      }
798
799      // Advance to the next overlap.
800      if (LII->end < LocMapI.stop()) {
801        if (++LII == LIE)
802          break;
803        LocMapI.advanceTo(LII->start);
804      } else {
805        ++LocMapI;
806        if (!LocMapI.valid())
807          break;
808        LII = LI->advanceTo(LII, LocMapI.start());
809      }
810    }
811  }
812
813  // Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
814  locations.erase(locations.begin() + OldLocNo);
815  LocMapI.goToBegin();
816  while (LocMapI.valid()) {
817    unsigned v = LocMapI.value();
818    if (v == OldLocNo) {
819      DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
820                   << LocMapI.stop() << ")\n");
821      LocMapI.erase();
822    } else {
823      if (v > OldLocNo)
824        LocMapI.setValueUnchecked(v-1);
825      ++LocMapI;
826    }
827  }
828
829  DEBUG({dbgs() << "Split result: \t"; print(dbgs(), nullptr);});
830  return DidChange;
831}
832
833bool
834UserValue::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs,
835                         LiveIntervals &LIS) {
836  bool DidChange = false;
837  // Split locations referring to OldReg. Iterate backwards so splitLocation can
838  // safely erase unused locations.
839  for (unsigned i = locations.size(); i ; --i) {
840    unsigned LocNo = i-1;
841    const MachineOperand *Loc = &locations[LocNo];
842    if (!Loc->isReg() || Loc->getReg() != OldReg)
843      continue;
844    DidChange |= splitLocation(LocNo, NewRegs, LIS);
845  }
846  return DidChange;
847}
848
849void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs) {
850  bool DidChange = false;
851  for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
852    DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
853
854  if (!DidChange)
855    return;
856
857  // Map all of the new virtual registers.
858  UserValue *UV = lookupVirtReg(OldReg);
859  for (unsigned i = 0; i != NewRegs.size(); ++i)
860    mapVirtReg(NewRegs[i], UV);
861}
862
863void LiveDebugVariables::
864splitRegister(unsigned OldReg, ArrayRef<unsigned> NewRegs, LiveIntervals &LIS) {
865  if (pImpl)
866    static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
867}
868
869void
870UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI) {
871  // Iterate over locations in reverse makes it easier to handle coalescing.
872  for (unsigned i = locations.size(); i ; --i) {
873    unsigned LocNo = i-1;
874    MachineOperand &Loc = locations[LocNo];
875    // Only virtual registers are rewritten.
876    if (!Loc.isReg() || !Loc.getReg() ||
877        !TargetRegisterInfo::isVirtualRegister(Loc.getReg()))
878      continue;
879    unsigned VirtReg = Loc.getReg();
880    if (VRM.isAssignedReg(VirtReg) &&
881        TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
882      // This can create a %noreg operand in rare cases when the sub-register
883      // index is no longer available. That means the user value is in a
884      // non-existent sub-register, and %noreg is exactly what we want.
885      Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
886    } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
887      // FIXME: Translate SubIdx to a stackslot offset.
888      Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
889    } else {
890      Loc.setReg(0);
891      Loc.setSubReg(0);
892    }
893    coalesceLocation(LocNo);
894  }
895}
896
897/// findInsertLocation - Find an iterator for inserting a DBG_VALUE
898/// instruction.
899static MachineBasicBlock::iterator
900findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
901                   LiveIntervals &LIS) {
902  SlotIndex Start = LIS.getMBBStartIdx(MBB);
903  Idx = Idx.getBaseIndex();
904
905  // Try to find an insert location by going backwards from Idx.
906  MachineInstr *MI;
907  while (!(MI = LIS.getInstructionFromIndex(Idx))) {
908    // We've reached the beginning of MBB.
909    if (Idx == Start) {
910      MachineBasicBlock::iterator I = MBB->SkipPHIsAndLabels(MBB->begin());
911      return I;
912    }
913    Idx = Idx.getPrevIndex();
914  }
915
916  // Don't insert anything after the first terminator, though.
917  return MI->isTerminator() ? MBB->getFirstTerminator() :
918                              std::next(MachineBasicBlock::iterator(MI));
919}
920
921DebugLoc UserValue::findDebugLoc() {
922  DebugLoc D = dl;
923  dl = DebugLoc();
924  return D;
925}
926void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
927                                 unsigned LocNo,
928                                 LiveIntervals &LIS,
929                                 const TargetInstrInfo &TII) {
930  MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
931  MachineOperand &Loc = locations[LocNo];
932  ++NumInsertedDebugValues;
933
934  if (Loc.isReg())
935    BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
936            IsIndirect, Loc.getReg(), offset, variable);
937  else
938    BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
939      .addOperand(Loc).addImm(offset).addMetadata(variable);
940}
941
942void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
943                                const TargetInstrInfo &TII) {
944  MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
945
946  for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
947    SlotIndex Start = I.start();
948    SlotIndex Stop = I.stop();
949    unsigned LocNo = I.value();
950    DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << LocNo);
951    MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start);
952    SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);
953
954    DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
955    insertDebugValue(MBB, Start, LocNo, LIS, TII);
956    // This interval may span multiple basic blocks.
957    // Insert a DBG_VALUE into each one.
958    while(Stop > MBBEnd) {
959      // Move to the next block.
960      Start = MBBEnd;
961      if (++MBB == MFEnd)
962        break;
963      MBBEnd = LIS.getMBBEndIdx(MBB);
964      DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
965      insertDebugValue(MBB, Start, LocNo, LIS, TII);
966    }
967    DEBUG(dbgs() << '\n');
968    if (MBB == MFEnd)
969      break;
970
971    ++I;
972  }
973}
974
975void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
976  DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
977  const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
978  for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
979    DEBUG(userValues[i]->print(dbgs(), &MF->getTarget()));
980    userValues[i]->rewriteLocations(*VRM, *TRI);
981    userValues[i]->emitDebugValues(VRM, *LIS, *TII);
982  }
983  EmitDone = true;
984}
985
986void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
987  if (pImpl)
988    static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
989}
990
991
992#ifndef NDEBUG
993void LiveDebugVariables::dump() {
994  if (pImpl)
995    static_cast<LDVImpl*>(pImpl)->print(dbgs());
996}
997#endif
998