LiveDebugVariables.cpp revision 223017 
1//===- LiveDebugVariables.cpp - Tracking debug info variables -------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the LiveDebugVariables analysis.
11//
12// Remove all DBG_VALUE instructions referencing virtual registers and replace
13// them with a data structure tracking where live user variables are kept - in a
14// virtual register or in a stack slot.
15//
16// Allow the data structure to be updated during register allocation when values
17// are moved between registers and stack slots. Finally emit new DBG_VALUE
18// instructions after register allocation is complete.
19//
20//===----------------------------------------------------------------------===//
21
22#define DEBUG_TYPE "livedebug"
23#include "LiveDebugVariables.h"
24#include "VirtRegMap.h"
25#include "llvm/Constants.h"
26#include "llvm/Metadata.h"
27#include "llvm/Value.h"
28#include "llvm/ADT/IntervalMap.h"
29#include "llvm/CodeGen/LiveIntervalAnalysis.h"
30#include "llvm/CodeGen/MachineDominators.h"
31#include "llvm/CodeGen/MachineFunction.h"
32#include "llvm/CodeGen/MachineInstrBuilder.h"
33#include "llvm/CodeGen/MachineRegisterInfo.h"
34#include "llvm/CodeGen/Passes.h"
35#include "llvm/Support/CommandLine.h"
36#include "llvm/Support/Debug.h"
37#include "llvm/Target/TargetInstrInfo.h"
38#include "llvm/Target/TargetMachine.h"
39#include "llvm/Target/TargetRegisterInfo.h"
40
41using namespace llvm;
42
43static cl::opt<bool>
44EnableLDV("live-debug-variables", cl::init(true),
45          cl::desc("Enable the live debug variables pass"), cl::Hidden);
46
47char LiveDebugVariables::ID = 0;
48
49INITIALIZE_PASS_BEGIN(LiveDebugVariables, "livedebugvars",
50                "Debug Variable Analysis", false, false)
51INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
52INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
53INITIALIZE_PASS_END(LiveDebugVariables, "livedebugvars",
54                "Debug Variable Analysis", false, false)
55
56void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
57  AU.addRequired<MachineDominatorTree>();
58  AU.addRequiredTransitive<LiveIntervals>();
59  AU.setPreservesAll();
60  MachineFunctionPass::getAnalysisUsage(AU);
61}
62
63LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID), pImpl(0) {
64  initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
65}
66
67/// LocMap - Map of where a user value is live, and its location.
68typedef IntervalMap<SlotIndex, unsigned, 4> LocMap;
69
70/// UserValue - A user value is a part of a debug info user variable.
71///
72/// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
73/// holds part of a user variable. The part is identified by a byte offset.
74///
75/// UserValues are grouped into equivalence classes for easier searching. Two
76/// user values are related if they refer to the same variable, or if they are
77/// held by the same virtual register. The equivalence class is the transitive
78/// closure of that relation.
79namespace {
80class LDVImpl;
81class UserValue {
82  const MDNode *variable; ///< The debug info variable we are part of.
83  unsigned offset;        ///< Byte offset into variable.
84  DebugLoc dl;            ///< The debug location for the variable. This is
85                          ///< used by dwarf writer to find lexical scope.
86  UserValue *leader;      ///< Equivalence class leader.
87  UserValue *next;        ///< Next value in equivalence class, or null.
88
89  /// Numbered locations referenced by locmap.
90  SmallVector<MachineOperand, 4> locations;
91
92  /// Map of slot indices where this value is live.
93  LocMap locInts;
94
95  /// coalesceLocation - After LocNo was changed, check if it has become
96  /// identical to another location, and coalesce them. This may cause LocNo or
97  /// a later location to be erased, but no earlier location will be erased.
98  void coalesceLocation(unsigned LocNo);
99
100  /// insertDebugValue - Insert a DBG_VALUE into MBB at Idx for LocNo.
101  void insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx, unsigned LocNo,
102                        LiveIntervals &LIS, const TargetInstrInfo &TII);
103
104  /// splitLocation - Replace OldLocNo ranges with NewRegs ranges where NewRegs
105  /// is live. Returns true if any changes were made.
106  bool splitLocation(unsigned OldLocNo, ArrayRef<LiveInterval*> NewRegs);
107
108public:
109  /// UserValue - Create a new UserValue.
110  UserValue(const MDNode *var, unsigned o, DebugLoc L,
111            LocMap::Allocator &alloc)
112    : variable(var), offset(o), dl(L), leader(this), next(0), locInts(alloc)
113  {}
114
115  /// getLeader - Get the leader of this value's equivalence class.
116  UserValue *getLeader() {
117    UserValue *l = leader;
118    while (l != l->leader)
119      l = l->leader;
120    return leader = l;
121  }
122
123  /// getNext - Return the next UserValue in the equivalence class.
124  UserValue *getNext() const { return next; }
125
126  /// match - Does this UserValue match the aprameters?
127  bool match(const MDNode *Var, unsigned Offset) const {
128    return Var == variable && Offset == offset;
129  }
130
131  /// merge - Merge equivalence classes.
132  static UserValue *merge(UserValue *L1, UserValue *L2) {
133    L2 = L2->getLeader();
134    if (!L1)
135      return L2;
136    L1 = L1->getLeader();
137    if (L1 == L2)
138      return L1;
139    // Splice L2 before L1's members.
140    UserValue *End = L2;
141    while (End->next)
142      End->leader = L1, End = End->next;
143    End->leader = L1;
144    End->next = L1->next;
145    L1->next = L2;
146    return L1;
147  }
148
149  /// getLocationNo - Return the location number that matches Loc.
150  unsigned getLocationNo(const MachineOperand &LocMO) {
151    if (LocMO.isReg()) {
152      if (LocMO.getReg() == 0)
153        return ~0u;
154      // For register locations we dont care about use/def and other flags.
155      for (unsigned i = 0, e = locations.size(); i != e; ++i)
156        if (locations[i].isReg() &&
157            locations[i].getReg() == LocMO.getReg() &&
158            locations[i].getSubReg() == LocMO.getSubReg())
159          return i;
160    } else
161      for (unsigned i = 0, e = locations.size(); i != e; ++i)
162        if (LocMO.isIdenticalTo(locations[i]))
163          return i;
164    locations.push_back(LocMO);
165    // We are storing a MachineOperand outside a MachineInstr.
166    locations.back().clearParent();
167    // Don't store def operands.
168    if (locations.back().isReg())
169      locations.back().setIsUse();
170    return locations.size() - 1;
171  }
172
173  /// mapVirtRegs - Ensure that all virtual register locations are mapped.
174  void mapVirtRegs(LDVImpl *LDV);
175
176  /// addDef - Add a definition point to this value.
177  void addDef(SlotIndex Idx, const MachineOperand &LocMO) {
178    // Add a singular (Idx,Idx) -> Loc mapping.
179    LocMap::iterator I = locInts.find(Idx);
180    if (!I.valid() || I.start() != Idx)
181      I.insert(Idx, Idx.getNextSlot(), getLocationNo(LocMO));
182  }
183
184  /// extendDef - Extend the current definition as far as possible down the
185  /// dominator tree. Stop when meeting an existing def or when leaving the live
186  /// range of VNI.
187  /// End points where VNI is no longer live are added to Kills.
188  /// @param Idx   Starting point for the definition.
189  /// @param LocNo Location number to propagate.
190  /// @param LI    Restrict liveness to where LI has the value VNI. May be null.
191  /// @param VNI   When LI is not null, this is the value to restrict to.
192  /// @param Kills Append end points of VNI's live range to Kills.
193  /// @param LIS   Live intervals analysis.
194  /// @param MDT   Dominator tree.
195  void extendDef(SlotIndex Idx, unsigned LocNo,
196                 LiveInterval *LI, const VNInfo *VNI,
197                 SmallVectorImpl<SlotIndex> *Kills,
198                 LiveIntervals &LIS, MachineDominatorTree &MDT);
199
200  /// addDefsFromCopies - The value in LI/LocNo may be copies to other
201  /// registers. Determine if any of the copies are available at the kill
202  /// points, and add defs if possible.
203  /// @param LI      Scan for copies of the value in LI->reg.
204  /// @param LocNo   Location number of LI->reg.
205  /// @param Kills   Points where the range of LocNo could be extended.
206  /// @param NewDefs Append (Idx, LocNo) of inserted defs here.
207  void addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
208                      const SmallVectorImpl<SlotIndex> &Kills,
209                      SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
210                      MachineRegisterInfo &MRI,
211                      LiveIntervals &LIS);
212
213  /// computeIntervals - Compute the live intervals of all locations after
214  /// collecting all their def points.
215  void computeIntervals(MachineRegisterInfo &MRI,
216                        LiveIntervals &LIS, MachineDominatorTree &MDT);
217
218  /// renameRegister - Update locations to rewrite OldReg as NewReg:SubIdx.
219  void renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx,
220                      const TargetRegisterInfo *TRI);
221
222  /// splitRegister - Replace OldReg ranges with NewRegs ranges where NewRegs is
223  /// live. Returns true if any changes were made.
224  bool splitRegister(unsigned OldLocNo, ArrayRef<LiveInterval*> NewRegs);
225
226  /// rewriteLocations - Rewrite virtual register locations according to the
227  /// provided virtual register map.
228  void rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI);
229
230  /// emitDebugVariables - Recreate DBG_VALUE instruction from data structures.
231  void emitDebugValues(VirtRegMap *VRM,
232                       LiveIntervals &LIS, const TargetInstrInfo &TRI);
233
234  /// findDebugLoc - Return DebugLoc used for this DBG_VALUE instruction. A
235  /// variable may have more than one corresponding DBG_VALUE instructions.
236  /// Only first one needs DebugLoc to identify variable's lexical scope
237  /// in source file.
238  DebugLoc findDebugLoc();
239  void print(raw_ostream&, const TargetMachine*);
240};
241} // namespace
242
243/// LDVImpl - Implementation of the LiveDebugVariables pass.
244namespace {
245class LDVImpl {
246  LiveDebugVariables &pass;
247  LocMap::Allocator allocator;
248  MachineFunction *MF;
249  LiveIntervals *LIS;
250  MachineDominatorTree *MDT;
251  const TargetRegisterInfo *TRI;
252
253  /// userValues - All allocated UserValue instances.
254  SmallVector<UserValue*, 8> userValues;
255
256  /// Map virtual register to eq class leader.
257  typedef DenseMap<unsigned, UserValue*> VRMap;
258  VRMap virtRegToEqClass;
259
260  /// Map user variable to eq class leader.
261  typedef DenseMap<const MDNode *, UserValue*> UVMap;
262  UVMap userVarMap;
263
264  /// getUserValue - Find or create a UserValue.
265  UserValue *getUserValue(const MDNode *Var, unsigned Offset, DebugLoc DL);
266
267  /// lookupVirtReg - Find the EC leader for VirtReg or null.
268  UserValue *lookupVirtReg(unsigned VirtReg);
269
270  /// handleDebugValue - Add DBG_VALUE instruction to our maps.
271  /// @param MI  DBG_VALUE instruction
272  /// @param Idx Last valid SLotIndex before instruction.
273  /// @return    True if the DBG_VALUE instruction should be deleted.
274  bool handleDebugValue(MachineInstr *MI, SlotIndex Idx);
275
276  /// collectDebugValues - Collect and erase all DBG_VALUE instructions, adding
277  /// a UserValue def for each instruction.
278  /// @param mf MachineFunction to be scanned.
279  /// @return True if any debug values were found.
280  bool collectDebugValues(MachineFunction &mf);
281
282  /// computeIntervals - Compute the live intervals of all user values after
283  /// collecting all their def points.
284  void computeIntervals();
285
286public:
287  LDVImpl(LiveDebugVariables *ps) : pass(*ps) {}
288  bool runOnMachineFunction(MachineFunction &mf);
289
290  /// clear - Relase all memory.
291  void clear() {
292    DeleteContainerPointers(userValues);
293    userValues.clear();
294    virtRegToEqClass.clear();
295    userVarMap.clear();
296  }
297
298  /// mapVirtReg - Map virtual register to an equivalence class.
299  void mapVirtReg(unsigned VirtReg, UserValue *EC);
300
301  /// renameRegister - Replace all references to OldReg with NewReg:SubIdx.
302  void renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx);
303
304  /// splitRegister -  Replace all references to OldReg with NewRegs.
305  void splitRegister(unsigned OldReg, ArrayRef<LiveInterval*> NewRegs);
306
307  /// emitDebugVariables - Recreate DBG_VALUE instruction from data structures.
308  void emitDebugValues(VirtRegMap *VRM);
309
310  void print(raw_ostream&);
311};
312} // namespace
313
314void UserValue::print(raw_ostream &OS, const TargetMachine *TM) {
315  if (const MDString *MDS = dyn_cast<MDString>(variable->getOperand(2)))
316    OS << "!\"" << MDS->getString() << "\"\t";
317  if (offset)
318    OS << '+' << offset;
319  for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
320    OS << " [" << I.start() << ';' << I.stop() << "):";
321    if (I.value() == ~0u)
322      OS << "undef";
323    else
324      OS << I.value();
325  }
326  for (unsigned i = 0, e = locations.size(); i != e; ++i) {
327    OS << " Loc" << i << '=';
328    locations[i].print(OS, TM);
329  }
330  OS << '\n';
331}
332
333void LDVImpl::print(raw_ostream &OS) {
334  OS << "********** DEBUG VARIABLES **********\n";
335  for (unsigned i = 0, e = userValues.size(); i != e; ++i)
336    userValues[i]->print(OS, &MF->getTarget());
337}
338
339void UserValue::coalesceLocation(unsigned LocNo) {
340  unsigned KeepLoc = 0;
341  for (unsigned e = locations.size(); KeepLoc != e; ++KeepLoc) {
342    if (KeepLoc == LocNo)
343      continue;
344    if (locations[KeepLoc].isIdenticalTo(locations[LocNo]))
345      break;
346  }
347  // No matches.
348  if (KeepLoc == locations.size())
349    return;
350
351  // Keep the smaller location, erase the larger one.
352  unsigned EraseLoc = LocNo;
353  if (KeepLoc > EraseLoc)
354    std::swap(KeepLoc, EraseLoc);
355  locations.erase(locations.begin() + EraseLoc);
356
357  // Rewrite values.
358  for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
359    unsigned v = I.value();
360    if (v == EraseLoc)
361      I.setValue(KeepLoc);      // Coalesce when possible.
362    else if (v > EraseLoc)
363      I.setValueUnchecked(v-1); // Avoid coalescing with untransformed values.
364  }
365}
366
367void UserValue::mapVirtRegs(LDVImpl *LDV) {
368  for (unsigned i = 0, e = locations.size(); i != e; ++i)
369    if (locations[i].isReg() &&
370        TargetRegisterInfo::isVirtualRegister(locations[i].getReg()))
371      LDV->mapVirtReg(locations[i].getReg(), this);
372}
373
374UserValue *LDVImpl::getUserValue(const MDNode *Var, unsigned Offset,
375                                 DebugLoc DL) {
376  UserValue *&Leader = userVarMap[Var];
377  if (Leader) {
378    UserValue *UV = Leader->getLeader();
379    Leader = UV;
380    for (; UV; UV = UV->getNext())
381      if (UV->match(Var, Offset))
382        return UV;
383  }
384
385  UserValue *UV = new UserValue(Var, Offset, DL, allocator);
386  userValues.push_back(UV);
387  Leader = UserValue::merge(Leader, UV);
388  return UV;
389}
390
391void LDVImpl::mapVirtReg(unsigned VirtReg, UserValue *EC) {
392  assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && "Only map VirtRegs");
393  UserValue *&Leader = virtRegToEqClass[VirtReg];
394  Leader = UserValue::merge(Leader, EC);
395}
396
397UserValue *LDVImpl::lookupVirtReg(unsigned VirtReg) {
398  if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
399    return UV->getLeader();
400  return 0;
401}
402
403bool LDVImpl::handleDebugValue(MachineInstr *MI, SlotIndex Idx) {
404  // DBG_VALUE loc, offset, variable
405  if (MI->getNumOperands() != 3 ||
406      !MI->getOperand(1).isImm() || !MI->getOperand(2).isMetadata()) {
407    DEBUG(dbgs() << "Can't handle " << *MI);
408    return false;
409  }
410
411  // Get or create the UserValue for (variable,offset).
412  unsigned Offset = MI->getOperand(1).getImm();
413  const MDNode *Var = MI->getOperand(2).getMetadata();
414  UserValue *UV = getUserValue(Var, Offset, MI->getDebugLoc());
415  UV->addDef(Idx, MI->getOperand(0));
416  return true;
417}
418
419bool LDVImpl::collectDebugValues(MachineFunction &mf) {
420  bool Changed = false;
421  for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
422       ++MFI) {
423    MachineBasicBlock *MBB = MFI;
424    for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
425         MBBI != MBBE;) {
426      if (!MBBI->isDebugValue()) {
427        ++MBBI;
428        continue;
429      }
430      // DBG_VALUE has no slot index, use the previous instruction instead.
431      SlotIndex Idx = MBBI == MBB->begin() ?
432        LIS->getMBBStartIdx(MBB) :
433        LIS->getInstructionIndex(llvm::prior(MBBI)).getDefIndex();
434      // Handle consecutive DBG_VALUE instructions with the same slot index.
435      do {
436        if (handleDebugValue(MBBI, Idx)) {
437          MBBI = MBB->erase(MBBI);
438          Changed = true;
439        } else
440          ++MBBI;
441      } while (MBBI != MBBE && MBBI->isDebugValue());
442    }
443  }
444  return Changed;
445}
446
447void UserValue::extendDef(SlotIndex Idx, unsigned LocNo,
448                          LiveInterval *LI, const VNInfo *VNI,
449                          SmallVectorImpl<SlotIndex> *Kills,
450                          LiveIntervals &LIS, MachineDominatorTree &MDT) {
451  SmallVector<SlotIndex, 16> Todo;
452  Todo.push_back(Idx);
453
454  do {
455    SlotIndex Start = Todo.pop_back_val();
456    MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
457    SlotIndex Stop = LIS.getMBBEndIdx(MBB);
458    LocMap::iterator I = locInts.find(Start);
459
460    // Limit to VNI's live range.
461    bool ToEnd = true;
462    if (LI && VNI) {
463      LiveRange *Range = LI->getLiveRangeContaining(Start);
464      if (!Range || Range->valno != VNI) {
465        if (Kills)
466          Kills->push_back(Start);
467        continue;
468      }
469      if (Range->end < Stop)
470        Stop = Range->end, ToEnd = false;
471    }
472
473    // There could already be a short def at Start.
474    if (I.valid() && I.start() <= Start) {
475      // Stop when meeting a different location or an already extended interval.
476      Start = Start.getNextSlot();
477      if (I.value() != LocNo || I.stop() != Start)
478        continue;
479      // This is a one-slot placeholder. Just skip it.
480      ++I;
481    }
482
483    // Limited by the next def.
484    if (I.valid() && I.start() < Stop)
485      Stop = I.start(), ToEnd = false;
486    // Limited by VNI's live range.
487    else if (!ToEnd && Kills)
488      Kills->push_back(Stop);
489
490    if (Start >= Stop)
491      continue;
492
493    I.insert(Start, Stop, LocNo);
494
495    // If we extended to the MBB end, propagate down the dominator tree.
496    if (!ToEnd)
497      continue;
498    const std::vector<MachineDomTreeNode*> &Children =
499      MDT.getNode(MBB)->getChildren();
500    for (unsigned i = 0, e = Children.size(); i != e; ++i)
501      Todo.push_back(LIS.getMBBStartIdx(Children[i]->getBlock()));
502  } while (!Todo.empty());
503}
504
505void
506UserValue::addDefsFromCopies(LiveInterval *LI, unsigned LocNo,
507                      const SmallVectorImpl<SlotIndex> &Kills,
508                      SmallVectorImpl<std::pair<SlotIndex, unsigned> > &NewDefs,
509                      MachineRegisterInfo &MRI, LiveIntervals &LIS) {
510  if (Kills.empty())
511    return;
512  // Don't track copies from physregs, there are too many uses.
513  if (!TargetRegisterInfo::isVirtualRegister(LI->reg))
514    return;
515
516  // Collect all the (vreg, valno) pairs that are copies of LI.
517  SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
518  for (MachineRegisterInfo::use_nodbg_iterator
519         UI = MRI.use_nodbg_begin(LI->reg),
520         UE = MRI.use_nodbg_end(); UI != UE; ++UI) {
521    // Copies of the full value.
522    if (UI.getOperand().getSubReg() || !UI->isCopy())
523      continue;
524    MachineInstr *MI = &*UI;
525    unsigned DstReg = MI->getOperand(0).getReg();
526
527    // Don't follow copies to physregs. These are usually setting up call
528    // arguments, and the argument registers are always call clobbered. We are
529    // better off in the source register which could be a callee-saved register,
530    // or it could be spilled.
531    if (!TargetRegisterInfo::isVirtualRegister(DstReg))
532      continue;
533
534    // Is LocNo extended to reach this copy? If not, another def may be blocking
535    // it, or we are looking at a wrong value of LI.
536    SlotIndex Idx = LIS.getInstructionIndex(MI);
537    LocMap::iterator I = locInts.find(Idx.getUseIndex());
538    if (!I.valid() || I.value() != LocNo)
539      continue;
540
541    if (!LIS.hasInterval(DstReg))
542      continue;
543    LiveInterval *DstLI = &LIS.getInterval(DstReg);
544    const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getDefIndex());
545    assert(DstVNI && DstVNI->def == Idx.getDefIndex() && "Bad copy value");
546    CopyValues.push_back(std::make_pair(DstLI, DstVNI));
547  }
548
549  if (CopyValues.empty())
550    return;
551
552  DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI << '\n');
553
554  // Try to add defs of the copied values for each kill point.
555  for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
556    SlotIndex Idx = Kills[i];
557    for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
558      LiveInterval *DstLI = CopyValues[j].first;
559      const VNInfo *DstVNI = CopyValues[j].second;
560      if (DstLI->getVNInfoAt(Idx) != DstVNI)
561        continue;
562      // Check that there isn't already a def at Idx
563      LocMap::iterator I = locInts.find(Idx);
564      if (I.valid() && I.start() <= Idx)
565        continue;
566      DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
567                   << DstVNI->id << " in " << *DstLI << '\n');
568      MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
569      assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
570      unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
571      I.insert(Idx, Idx.getNextSlot(), LocNo);
572      NewDefs.push_back(std::make_pair(Idx, LocNo));
573      break;
574    }
575  }
576}
577
578void
579UserValue::computeIntervals(MachineRegisterInfo &MRI,
580                            LiveIntervals &LIS,
581                            MachineDominatorTree &MDT) {
582  SmallVector<std::pair<SlotIndex, unsigned>, 16> Defs;
583
584  // Collect all defs to be extended (Skipping undefs).
585  for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
586    if (I.value() != ~0u)
587      Defs.push_back(std::make_pair(I.start(), I.value()));
588
589  // Extend all defs, and possibly add new ones along the way.
590  for (unsigned i = 0; i != Defs.size(); ++i) {
591    SlotIndex Idx = Defs[i].first;
592    unsigned LocNo = Defs[i].second;
593    const MachineOperand &Loc = locations[LocNo];
594
595    // Register locations are constrained to where the register value is live.
596    if (Loc.isReg() && LIS.hasInterval(Loc.getReg())) {
597      LiveInterval *LI = &LIS.getInterval(Loc.getReg());
598      const VNInfo *VNI = LI->getVNInfoAt(Idx);
599      SmallVector<SlotIndex, 16> Kills;
600      extendDef(Idx, LocNo, LI, VNI, &Kills, LIS, MDT);
601      addDefsFromCopies(LI, LocNo, Kills, Defs, MRI, LIS);
602    } else
603      extendDef(Idx, LocNo, 0, 0, 0, LIS, MDT);
604  }
605
606  // Finally, erase all the undefs.
607  for (LocMap::iterator I = locInts.begin(); I.valid();)
608    if (I.value() == ~0u)
609      I.erase();
610    else
611      ++I;
612}
613
614void LDVImpl::computeIntervals() {
615  for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
616    userValues[i]->computeIntervals(MF->getRegInfo(), *LIS, *MDT);
617    userValues[i]->mapVirtRegs(this);
618  }
619}
620
621bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
622  MF = &mf;
623  LIS = &pass.getAnalysis<LiveIntervals>();
624  MDT = &pass.getAnalysis<MachineDominatorTree>();
625  TRI = mf.getTarget().getRegisterInfo();
626  clear();
627  DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
628               << ((Value*)mf.getFunction())->getName()
629               << " **********\n");
630
631  bool Changed = collectDebugValues(mf);
632  computeIntervals();
633  DEBUG(print(dbgs()));
634  return Changed;
635}
636
637bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
638  if (!EnableLDV)
639    return false;
640  if (!pImpl)
641    pImpl = new LDVImpl(this);
642  return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
643}
644
645void LiveDebugVariables::releaseMemory() {
646  if (pImpl)
647    static_cast<LDVImpl*>(pImpl)->clear();
648}
649
650LiveDebugVariables::~LiveDebugVariables() {
651  if (pImpl)
652    delete static_cast<LDVImpl*>(pImpl);
653}
654
655void UserValue::
656renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx,
657               const TargetRegisterInfo *TRI) {
658  for (unsigned i = locations.size(); i; --i) {
659    unsigned LocNo = i - 1;
660    MachineOperand &Loc = locations[LocNo];
661    if (!Loc.isReg() || Loc.getReg() != OldReg)
662      continue;
663    if (TargetRegisterInfo::isPhysicalRegister(NewReg))
664      Loc.substPhysReg(NewReg, *TRI);
665    else
666      Loc.substVirtReg(NewReg, SubIdx, *TRI);
667    coalesceLocation(LocNo);
668  }
669}
670
671void LDVImpl::
672renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx) {
673  UserValue *UV = lookupVirtReg(OldReg);
674  if (!UV)
675    return;
676
677  if (TargetRegisterInfo::isVirtualRegister(NewReg))
678    mapVirtReg(NewReg, UV);
679  virtRegToEqClass.erase(OldReg);
680
681  do {
682    UV->renameRegister(OldReg, NewReg, SubIdx, TRI);
683    UV = UV->getNext();
684  } while (UV);
685}
686
687void LiveDebugVariables::
688renameRegister(unsigned OldReg, unsigned NewReg, unsigned SubIdx) {
689  if (pImpl)
690    static_cast<LDVImpl*>(pImpl)->renameRegister(OldReg, NewReg, SubIdx);
691}
692
693//===----------------------------------------------------------------------===//
694//                           Live Range Splitting
695//===----------------------------------------------------------------------===//
696
697bool
698UserValue::splitLocation(unsigned OldLocNo, ArrayRef<LiveInterval*> NewRegs) {
699  DEBUG({
700    dbgs() << "Splitting Loc" << OldLocNo << '\t';
701    print(dbgs(), 0);
702  });
703  bool DidChange = false;
704  LocMap::iterator LocMapI;
705  LocMapI.setMap(locInts);
706  for (unsigned i = 0; i != NewRegs.size(); ++i) {
707    LiveInterval *LI = NewRegs[i];
708    if (LI->empty())
709      continue;
710
711    // Don't allocate the new LocNo until it is needed.
712    unsigned NewLocNo = ~0u;
713
714    // Iterate over the overlaps between locInts and LI.
715    LocMapI.find(LI->beginIndex());
716    if (!LocMapI.valid())
717      continue;
718    LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
719    LiveInterval::iterator LIE = LI->end();
720    while (LocMapI.valid() && LII != LIE) {
721      // At this point, we know that LocMapI.stop() > LII->start.
722      LII = LI->advanceTo(LII, LocMapI.start());
723      if (LII == LIE)
724        break;
725
726      // Now LII->end > LocMapI.start(). Do we have an overlap?
727      if (LocMapI.value() == OldLocNo && LII->start < LocMapI.stop()) {
728        // Overlapping correct location. Allocate NewLocNo now.
729        if (NewLocNo == ~0u) {
730          MachineOperand MO = MachineOperand::CreateReg(LI->reg, false);
731          MO.setSubReg(locations[OldLocNo].getSubReg());
732          NewLocNo = getLocationNo(MO);
733          DidChange = true;
734        }
735
736        SlotIndex LStart = LocMapI.start();
737        SlotIndex LStop  = LocMapI.stop();
738
739        // Trim LocMapI down to the LII overlap.
740        if (LStart < LII->start)
741          LocMapI.setStartUnchecked(LII->start);
742        if (LStop > LII->end)
743          LocMapI.setStopUnchecked(LII->end);
744
745        // Change the value in the overlap. This may trigger coalescing.
746        LocMapI.setValue(NewLocNo);
747
748        // Re-insert any removed OldLocNo ranges.
749        if (LStart < LocMapI.start()) {
750          LocMapI.insert(LStart, LocMapI.start(), OldLocNo);
751          ++LocMapI;
752          assert(LocMapI.valid() && "Unexpected coalescing");
753        }
754        if (LStop > LocMapI.stop()) {
755          ++LocMapI;
756          LocMapI.insert(LII->end, LStop, OldLocNo);
757          --LocMapI;
758        }
759      }
760
761      // Advance to the next overlap.
762      if (LII->end < LocMapI.stop()) {
763        if (++LII == LIE)
764          break;
765        LocMapI.advanceTo(LII->start);
766      } else {
767        ++LocMapI;
768        if (!LocMapI.valid())
769          break;
770        LII = LI->advanceTo(LII, LocMapI.start());
771      }
772    }
773  }
774
775  // Finally, remove any remaining OldLocNo intervals and OldLocNo itself.
776  locations.erase(locations.begin() + OldLocNo);
777  LocMapI.goToBegin();
778  while (LocMapI.valid()) {
779    unsigned v = LocMapI.value();
780    if (v == OldLocNo) {
781      DEBUG(dbgs() << "Erasing [" << LocMapI.start() << ';'
782                   << LocMapI.stop() << ")\n");
783      LocMapI.erase();
784    } else {
785      if (v > OldLocNo)
786        LocMapI.setValueUnchecked(v-1);
787      ++LocMapI;
788    }
789  }
790
791  DEBUG({dbgs() << "Split result: \t"; print(dbgs(), 0);});
792  return DidChange;
793}
794
795bool
796UserValue::splitRegister(unsigned OldReg, ArrayRef<LiveInterval*> NewRegs) {
797  bool DidChange = false;
798  // Split locations referring to OldReg. Iterate backwards so splitLocation can
799  // safely erase unuused locations.
800  for (unsigned i = locations.size(); i ; --i) {
801    unsigned LocNo = i-1;
802    const MachineOperand *Loc = &locations[LocNo];
803    if (!Loc->isReg() || Loc->getReg() != OldReg)
804      continue;
805    DidChange |= splitLocation(LocNo, NewRegs);
806  }
807  return DidChange;
808}
809
810void LDVImpl::splitRegister(unsigned OldReg, ArrayRef<LiveInterval*> NewRegs) {
811  bool DidChange = false;
812  for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
813    DidChange |= UV->splitRegister(OldReg, NewRegs);
814
815  if (!DidChange)
816    return;
817
818  // Map all of the new virtual registers.
819  UserValue *UV = lookupVirtReg(OldReg);
820  for (unsigned i = 0; i != NewRegs.size(); ++i)
821    mapVirtReg(NewRegs[i]->reg, UV);
822}
823
824void LiveDebugVariables::
825splitRegister(unsigned OldReg, ArrayRef<LiveInterval*> NewRegs) {
826  if (pImpl)
827    static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
828}
829
830void
831UserValue::rewriteLocations(VirtRegMap &VRM, const TargetRegisterInfo &TRI) {
832  // Iterate over locations in reverse makes it easier to handle coalescing.
833  for (unsigned i = locations.size(); i ; --i) {
834    unsigned LocNo = i-1;
835    MachineOperand &Loc = locations[LocNo];
836    // Only virtual registers are rewritten.
837    if (!Loc.isReg() || !Loc.getReg() ||
838        !TargetRegisterInfo::isVirtualRegister(Loc.getReg()))
839      continue;
840    unsigned VirtReg = Loc.getReg();
841    if (VRM.isAssignedReg(VirtReg) &&
842        TargetRegisterInfo::isPhysicalRegister(VRM.getPhys(VirtReg))) {
843      // This can create a %noreg operand in rare cases when the sub-register
844      // index is no longer available. That means the user value is in a
845      // non-existent sub-register, and %noreg is exactly what we want.
846      Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
847    } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT &&
848               VRM.isSpillSlotUsed(VRM.getStackSlot(VirtReg))) {
849      // FIXME: Translate SubIdx to a stackslot offset.
850      Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
851    } else {
852      Loc.setReg(0);
853      Loc.setSubReg(0);
854    }
855    coalesceLocation(LocNo);
856  }
857}
858
859/// findInsertLocation - Find an iterator for inserting a DBG_VALUE
860/// instruction.
861static MachineBasicBlock::iterator
862findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
863                   LiveIntervals &LIS) {
864  SlotIndex Start = LIS.getMBBStartIdx(MBB);
865  Idx = Idx.getBaseIndex();
866
867  // Try to find an insert location by going backwards from Idx.
868  MachineInstr *MI;
869  while (!(MI = LIS.getInstructionFromIndex(Idx))) {
870    // We've reached the beginning of MBB.
871    if (Idx == Start) {
872      MachineBasicBlock::iterator I = MBB->SkipPHIsAndLabels(MBB->begin());
873      return I;
874    }
875    Idx = Idx.getPrevIndex();
876  }
877
878  // Don't insert anything after the first terminator, though.
879  return MI->getDesc().isTerminator() ? MBB->getFirstTerminator() :
880                                    llvm::next(MachineBasicBlock::iterator(MI));
881}
882
883DebugLoc UserValue::findDebugLoc() {
884  DebugLoc D = dl;
885  dl = DebugLoc();
886  return D;
887}
888void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex Idx,
889                                 unsigned LocNo,
890                                 LiveIntervals &LIS,
891                                 const TargetInstrInfo &TII) {
892  MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
893  MachineOperand &Loc = locations[LocNo];
894
895  // Frame index locations may require a target callback.
896  if (Loc.isFI()) {
897    MachineInstr *MI = TII.emitFrameIndexDebugValue(*MBB->getParent(),
898                                          Loc.getIndex(), offset, variable,
899                                                    findDebugLoc());
900    if (MI) {
901      MBB->insert(I, MI);
902      return;
903    }
904  }
905  // This is not a frame index, or the target is happy with a standard FI.
906  BuildMI(*MBB, I, findDebugLoc(), TII.get(TargetOpcode::DBG_VALUE))
907    .addOperand(Loc).addImm(offset).addMetadata(variable);
908}
909
910void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
911                                const TargetInstrInfo &TII) {
912  MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
913
914  for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
915    SlotIndex Start = I.start();
916    SlotIndex Stop = I.stop();
917    unsigned LocNo = I.value();
918    DEBUG(dbgs() << "\t[" << Start << ';' << Stop << "):" << LocNo);
919    MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start);
920    SlotIndex MBBEnd = LIS.getMBBEndIdx(MBB);
921
922    DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
923    insertDebugValue(MBB, Start, LocNo, LIS, TII);
924
925    // This interval may span multiple basic blocks.
926    // Insert a DBG_VALUE into each one.
927    while(Stop > MBBEnd) {
928      // Move to the next block.
929      Start = MBBEnd;
930      if (++MBB == MFEnd)
931        break;
932      MBBEnd = LIS.getMBBEndIdx(MBB);
933      DEBUG(dbgs() << " BB#" << MBB->getNumber() << '-' << MBBEnd);
934      insertDebugValue(MBB, Start, LocNo, LIS, TII);
935    }
936    DEBUG(dbgs() << '\n');
937    if (MBB == MFEnd)
938      break;
939
940    ++I;
941  }
942}
943
944void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
945  DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
946  const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
947  for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
948    DEBUG(userValues[i]->print(dbgs(), &MF->getTarget()));
949    userValues[i]->rewriteLocations(*VRM, *TRI);
950    userValues[i]->emitDebugValues(VRM, *LIS, *TII);
951  }
952}
953
954void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
955  if (pImpl)
956    static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
957}
958
959
960#ifndef NDEBUG
961void LiveDebugVariables::dump() {
962  if (pImpl)
963    static_cast<LDVImpl*>(pImpl)->print(dbgs());
964}
965#endif
966
967