1 //===- LiveDebugVariables.cpp - Tracking debug info variables -------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the LiveDebugVariables analysis.
10 //
11 // Remove all DBG_VALUE instructions referencing virtual registers and replace
12 // them with a data structure tracking where live user variables are kept - in a
13 // virtual register or in a stack slot.
14 //
15 // Allow the data structure to be updated during register allocation when values
16 // are moved between registers and stack slots. Finally emit new DBG_VALUE
17 // instructions after register allocation is complete.
18 //
19 //===----------------------------------------------------------------------===//
20
21 #include "LiveDebugVariables.h"
22 #include "llvm/ADT/ArrayRef.h"
23 #include "llvm/ADT/DenseMap.h"
24 #include "llvm/ADT/IntervalMap.h"
25 #include "llvm/ADT/MapVector.h"
26 #include "llvm/ADT/STLExtras.h"
27 #include "llvm/ADT/SmallSet.h"
28 #include "llvm/ADT/SmallVector.h"
29 #include "llvm/ADT/Statistic.h"
30 #include "llvm/ADT/StringRef.h"
31 #include "llvm/CodeGen/LexicalScopes.h"
32 #include "llvm/CodeGen/LiveInterval.h"
33 #include "llvm/CodeGen/LiveIntervals.h"
34 #include "llvm/CodeGen/MachineBasicBlock.h"
35 #include "llvm/CodeGen/MachineDominators.h"
36 #include "llvm/CodeGen/MachineFunction.h"
37 #include "llvm/CodeGen/MachineInstr.h"
38 #include "llvm/CodeGen/MachineInstrBuilder.h"
39 #include "llvm/CodeGen/MachineOperand.h"
40 #include "llvm/CodeGen/MachineRegisterInfo.h"
41 #include "llvm/CodeGen/SlotIndexes.h"
42 #include "llvm/CodeGen/TargetInstrInfo.h"
43 #include "llvm/CodeGen/TargetOpcodes.h"
44 #include "llvm/CodeGen/TargetRegisterInfo.h"
45 #include "llvm/CodeGen/TargetSubtargetInfo.h"
46 #include "llvm/CodeGen/VirtRegMap.h"
47 #include "llvm/Config/llvm-config.h"
48 #include "llvm/IR/DebugInfoMetadata.h"
49 #include "llvm/IR/DebugLoc.h"
50 #include "llvm/IR/Function.h"
51 #include "llvm/IR/Metadata.h"
52 #include "llvm/InitializePasses.h"
53 #include "llvm/MC/MCRegisterInfo.h"
54 #include "llvm/Pass.h"
55 #include "llvm/Support/Casting.h"
56 #include "llvm/Support/CommandLine.h"
57 #include "llvm/Support/Debug.h"
58 #include "llvm/Support/raw_ostream.h"
59 #include <algorithm>
60 #include <cassert>
61 #include <iterator>
62 #include <memory>
63 #include <utility>
64
65 using namespace llvm;
66
67 #define DEBUG_TYPE "livedebugvars"
68
69 static cl::opt<bool>
70 EnableLDV("live-debug-variables", cl::init(true),
71 cl::desc("Enable the live debug variables pass"), cl::Hidden);
72
73 STATISTIC(NumInsertedDebugValues, "Number of DBG_VALUEs inserted");
74 STATISTIC(NumInsertedDebugLabels, "Number of DBG_LABELs inserted");
75
76 char LiveDebugVariables::ID = 0;
77
78 INITIALIZE_PASS_BEGIN(LiveDebugVariables, DEBUG_TYPE,
79 "Debug Variable Analysis", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)80 INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
81 INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
82 INITIALIZE_PASS_END(LiveDebugVariables, DEBUG_TYPE,
83 "Debug Variable Analysis", false, false)
84
85 void LiveDebugVariables::getAnalysisUsage(AnalysisUsage &AU) const {
86 AU.addRequired<MachineDominatorTree>();
87 AU.addRequiredTransitive<LiveIntervals>();
88 AU.setPreservesAll();
89 MachineFunctionPass::getAnalysisUsage(AU);
90 }
91
LiveDebugVariables()92 LiveDebugVariables::LiveDebugVariables() : MachineFunctionPass(ID) {
93 initializeLiveDebugVariablesPass(*PassRegistry::getPassRegistry());
94 }
95
96 enum : unsigned { UndefLocNo = ~0U };
97
98 namespace {
99 /// Describes a debug variable value by location number and expression along
100 /// with some flags about the original usage of the location.
101 class DbgVariableValue {
102 public:
DbgVariableValue(unsigned LocNo,bool WasIndirect,const DIExpression & Expression)103 DbgVariableValue(unsigned LocNo, bool WasIndirect,
104 const DIExpression &Expression)
105 : LocNo(LocNo), WasIndirect(WasIndirect), Expression(&Expression) {
106 assert(getLocNo() == LocNo && "location truncation");
107 }
108
DbgVariableValue()109 DbgVariableValue() : LocNo(0), WasIndirect(0) {}
110
getExpression() const111 const DIExpression *getExpression() const { return Expression; }
getLocNo() const112 unsigned getLocNo() const {
113 // Fix up the undef location number, which gets truncated.
114 return LocNo == INT_MAX ? UndefLocNo : LocNo;
115 }
getWasIndirect() const116 bool getWasIndirect() const { return WasIndirect; }
isUndef() const117 bool isUndef() const { return getLocNo() == UndefLocNo; }
118
changeLocNo(unsigned NewLocNo) const119 DbgVariableValue changeLocNo(unsigned NewLocNo) const {
120 return DbgVariableValue(NewLocNo, WasIndirect, *Expression);
121 }
122
operator ==(const DbgVariableValue & LHS,const DbgVariableValue & RHS)123 friend inline bool operator==(const DbgVariableValue &LHS,
124 const DbgVariableValue &RHS) {
125 return LHS.LocNo == RHS.LocNo && LHS.WasIndirect == RHS.WasIndirect &&
126 LHS.Expression == RHS.Expression;
127 }
128
operator !=(const DbgVariableValue & LHS,const DbgVariableValue & RHS)129 friend inline bool operator!=(const DbgVariableValue &LHS,
130 const DbgVariableValue &RHS) {
131 return !(LHS == RHS);
132 }
133
134 private:
135 unsigned LocNo : 31;
136 unsigned WasIndirect : 1;
137 const DIExpression *Expression = nullptr;
138 };
139 } // namespace
140
141 /// Map of where a user value is live to that value.
142 using LocMap = IntervalMap<SlotIndex, DbgVariableValue, 4>;
143
144 /// Map of stack slot offsets for spilled locations.
145 /// Non-spilled locations are not added to the map.
146 using SpillOffsetMap = DenseMap<unsigned, unsigned>;
147
148 namespace {
149
150 class LDVImpl;
151
152 /// A user value is a part of a debug info user variable.
153 ///
154 /// A DBG_VALUE instruction notes that (a sub-register of) a virtual register
155 /// holds part of a user variable. The part is identified by a byte offset.
156 ///
157 /// UserValues are grouped into equivalence classes for easier searching. Two
158 /// user values are related if they are held by the same virtual register. The
159 /// equivalence class is the transitive closure of that relation.
160 class UserValue {
161 const DILocalVariable *Variable; ///< The debug info variable we are part of.
162 /// The part of the variable we describe.
163 const Optional<DIExpression::FragmentInfo> Fragment;
164 DebugLoc dl; ///< The debug location for the variable. This is
165 ///< used by dwarf writer to find lexical scope.
166 UserValue *leader; ///< Equivalence class leader.
167 UserValue *next = nullptr; ///< Next value in equivalence class, or null.
168
169 /// Numbered locations referenced by locmap.
170 SmallVector<MachineOperand, 4> locations;
171
172 /// Map of slot indices where this value is live.
173 LocMap locInts;
174
175 /// Set of interval start indexes that have been trimmed to the
176 /// lexical scope.
177 SmallSet<SlotIndex, 2> trimmedDefs;
178
179 /// Insert a DBG_VALUE into MBB at Idx for DbgValue.
180 void insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
181 SlotIndex StopIdx, DbgVariableValue DbgValue,
182 bool Spilled, unsigned SpillOffset, LiveIntervals &LIS,
183 const TargetInstrInfo &TII,
184 const TargetRegisterInfo &TRI);
185
186 /// Replace OldLocNo ranges with NewRegs ranges where NewRegs
187 /// is live. Returns true if any changes were made.
188 bool splitLocation(unsigned OldLocNo, ArrayRef<Register> NewRegs,
189 LiveIntervals &LIS);
190
191 public:
192 /// Create a new UserValue.
UserValue(const DILocalVariable * var,Optional<DIExpression::FragmentInfo> Fragment,DebugLoc L,LocMap::Allocator & alloc)193 UserValue(const DILocalVariable *var,
194 Optional<DIExpression::FragmentInfo> Fragment, DebugLoc L,
195 LocMap::Allocator &alloc)
196 : Variable(var), Fragment(Fragment), dl(std::move(L)), leader(this),
197 locInts(alloc) {}
198
199 /// Get the leader of this value's equivalence class.
getLeader()200 UserValue *getLeader() {
201 UserValue *l = leader;
202 while (l != l->leader)
203 l = l->leader;
204 return leader = l;
205 }
206
207 /// Return the next UserValue in the equivalence class.
getNext() const208 UserValue *getNext() const { return next; }
209
210 /// Merge equivalence classes.
merge(UserValue * L1,UserValue * L2)211 static UserValue *merge(UserValue *L1, UserValue *L2) {
212 L2 = L2->getLeader();
213 if (!L1)
214 return L2;
215 L1 = L1->getLeader();
216 if (L1 == L2)
217 return L1;
218 // Splice L2 before L1's members.
219 UserValue *End = L2;
220 while (End->next) {
221 End->leader = L1;
222 End = End->next;
223 }
224 End->leader = L1;
225 End->next = L1->next;
226 L1->next = L2;
227 return L1;
228 }
229
230 /// Return the location number that matches Loc.
231 ///
232 /// For undef values we always return location number UndefLocNo without
233 /// inserting anything in locations. Since locations is a vector and the
234 /// location number is the position in the vector and UndefLocNo is ~0,
235 /// we would need a very big vector to put the value at the right position.
getLocationNo(const MachineOperand & LocMO)236 unsigned getLocationNo(const MachineOperand &LocMO) {
237 if (LocMO.isReg()) {
238 if (LocMO.getReg() == 0)
239 return UndefLocNo;
240 // For register locations we dont care about use/def and other flags.
241 for (unsigned i = 0, e = locations.size(); i != e; ++i)
242 if (locations[i].isReg() &&
243 locations[i].getReg() == LocMO.getReg() &&
244 locations[i].getSubReg() == LocMO.getSubReg())
245 return i;
246 } else
247 for (unsigned i = 0, e = locations.size(); i != e; ++i)
248 if (LocMO.isIdenticalTo(locations[i]))
249 return i;
250 locations.push_back(LocMO);
251 // We are storing a MachineOperand outside a MachineInstr.
252 locations.back().clearParent();
253 // Don't store def operands.
254 if (locations.back().isReg()) {
255 if (locations.back().isDef())
256 locations.back().setIsDead(false);
257 locations.back().setIsUse();
258 }
259 return locations.size() - 1;
260 }
261
262 /// Remove (recycle) a location number. If \p LocNo still is used by the
263 /// locInts nothing is done.
removeLocationIfUnused(unsigned LocNo)264 void removeLocationIfUnused(unsigned LocNo) {
265 // Bail out if LocNo still is used.
266 for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
267 DbgVariableValue DbgValue = I.value();
268 if (DbgValue.getLocNo() == LocNo)
269 return;
270 }
271 // Remove the entry in the locations vector, and adjust all references to
272 // location numbers above the removed entry.
273 locations.erase(locations.begin() + LocNo);
274 for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
275 DbgVariableValue DbgValue = I.value();
276 if (!DbgValue.isUndef() && DbgValue.getLocNo() > LocNo)
277 I.setValueUnchecked(DbgValue.changeLocNo(DbgValue.getLocNo() - 1));
278 }
279 }
280
281 /// Ensure that all virtual register locations are mapped.
282 void mapVirtRegs(LDVImpl *LDV);
283
284 /// Add a definition point to this user value.
addDef(SlotIndex Idx,const MachineOperand & LocMO,bool IsIndirect,const DIExpression & Expr)285 void addDef(SlotIndex Idx, const MachineOperand &LocMO, bool IsIndirect,
286 const DIExpression &Expr) {
287 DbgVariableValue DbgValue(getLocationNo(LocMO), IsIndirect, Expr);
288 // Add a singular (Idx,Idx) -> value mapping.
289 LocMap::iterator I = locInts.find(Idx);
290 if (!I.valid() || I.start() != Idx)
291 I.insert(Idx, Idx.getNextSlot(), DbgValue);
292 else
293 // A later DBG_VALUE at the same SlotIndex overrides the old location.
294 I.setValue(DbgValue);
295 }
296
297 /// Extend the current definition as far as possible down.
298 ///
299 /// Stop when meeting an existing def or when leaving the live
300 /// range of VNI. End points where VNI is no longer live are added to Kills.
301 ///
302 /// We only propagate DBG_VALUES locally here. LiveDebugValues performs a
303 /// data-flow analysis to propagate them beyond basic block boundaries.
304 ///
305 /// \param Idx Starting point for the definition.
306 /// \param DbgValue value to propagate.
307 /// \param LR Restrict liveness to where LR has the value VNI. May be null.
308 /// \param VNI When LR is not null, this is the value to restrict to.
309 /// \param [out] Kills Append end points of VNI's live range to Kills.
310 /// \param LIS Live intervals analysis.
311 void extendDef(SlotIndex Idx, DbgVariableValue DbgValue, LiveRange *LR,
312 const VNInfo *VNI, SmallVectorImpl<SlotIndex> *Kills,
313 LiveIntervals &LIS);
314
315 /// The value in LI may be copies to other registers. Determine if
316 /// any of the copies are available at the kill points, and add defs if
317 /// possible.
318 ///
319 /// \param LI Scan for copies of the value in LI->reg.
320 /// \param DbgValue Location number of LI->reg, and DIExpression.
321 /// \param Kills Points where the range of DbgValue could be extended.
322 /// \param [in,out] NewDefs Append (Idx, DbgValue) of inserted defs here.
323 void addDefsFromCopies(
324 LiveInterval *LI, DbgVariableValue DbgValue,
325 const SmallVectorImpl<SlotIndex> &Kills,
326 SmallVectorImpl<std::pair<SlotIndex, DbgVariableValue>> &NewDefs,
327 MachineRegisterInfo &MRI, LiveIntervals &LIS);
328
329 /// Compute the live intervals of all locations after collecting all their
330 /// def points.
331 void computeIntervals(MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
332 LiveIntervals &LIS, LexicalScopes &LS);
333
334 /// Replace OldReg ranges with NewRegs ranges where NewRegs is
335 /// live. Returns true if any changes were made.
336 bool splitRegister(Register OldReg, ArrayRef<Register> NewRegs,
337 LiveIntervals &LIS);
338
339 /// Rewrite virtual register locations according to the provided virtual
340 /// register map. Record the stack slot offsets for the locations that
341 /// were spilled.
342 void rewriteLocations(VirtRegMap &VRM, const MachineFunction &MF,
343 const TargetInstrInfo &TII,
344 const TargetRegisterInfo &TRI,
345 SpillOffsetMap &SpillOffsets);
346
347 /// Recreate DBG_VALUE instruction from data structures.
348 void emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
349 const TargetInstrInfo &TII,
350 const TargetRegisterInfo &TRI,
351 const SpillOffsetMap &SpillOffsets);
352
353 /// Return DebugLoc of this UserValue.
getDebugLoc()354 DebugLoc getDebugLoc() { return dl;}
355
356 void print(raw_ostream &, const TargetRegisterInfo *);
357 };
358
359 /// A user label is a part of a debug info user label.
360 class UserLabel {
361 const DILabel *Label; ///< The debug info label we are part of.
362 DebugLoc dl; ///< The debug location for the label. This is
363 ///< used by dwarf writer to find lexical scope.
364 SlotIndex loc; ///< Slot used by the debug label.
365
366 /// Insert a DBG_LABEL into MBB at Idx.
367 void insertDebugLabel(MachineBasicBlock *MBB, SlotIndex Idx,
368 LiveIntervals &LIS, const TargetInstrInfo &TII);
369
370 public:
371 /// Create a new UserLabel.
UserLabel(const DILabel * label,DebugLoc L,SlotIndex Idx)372 UserLabel(const DILabel *label, DebugLoc L, SlotIndex Idx)
373 : Label(label), dl(std::move(L)), loc(Idx) {}
374
375 /// Does this UserLabel match the parameters?
matches(const DILabel * L,const DILocation * IA,const SlotIndex Index) const376 bool matches(const DILabel *L, const DILocation *IA,
377 const SlotIndex Index) const {
378 return Label == L && dl->getInlinedAt() == IA && loc == Index;
379 }
380
381 /// Recreate DBG_LABEL instruction from data structures.
382 void emitDebugLabel(LiveIntervals &LIS, const TargetInstrInfo &TII);
383
384 /// Return DebugLoc of this UserLabel.
getDebugLoc()385 DebugLoc getDebugLoc() { return dl; }
386
387 void print(raw_ostream &, const TargetRegisterInfo *);
388 };
389
390 /// Implementation of the LiveDebugVariables pass.
391 class LDVImpl {
392 LiveDebugVariables &pass;
393 LocMap::Allocator allocator;
394 MachineFunction *MF = nullptr;
395 LiveIntervals *LIS;
396 const TargetRegisterInfo *TRI;
397
398 using StashedInstrRef =
399 std::tuple<unsigned, unsigned, const DILocalVariable *,
400 const DIExpression *, DebugLoc>;
401 std::map<SlotIndex, std::vector<StashedInstrRef>> StashedInstrReferences;
402
403 /// Whether emitDebugValues is called.
404 bool EmitDone = false;
405
406 /// Whether the machine function is modified during the pass.
407 bool ModifiedMF = false;
408
409 /// All allocated UserValue instances.
410 SmallVector<std::unique_ptr<UserValue>, 8> userValues;
411
412 /// All allocated UserLabel instances.
413 SmallVector<std::unique_ptr<UserLabel>, 2> userLabels;
414
415 /// Map virtual register to eq class leader.
416 using VRMap = DenseMap<unsigned, UserValue *>;
417 VRMap virtRegToEqClass;
418
419 /// Map to find existing UserValue instances.
420 using UVMap = DenseMap<DebugVariable, UserValue *>;
421 UVMap userVarMap;
422
423 /// Find or create a UserValue.
424 UserValue *getUserValue(const DILocalVariable *Var,
425 Optional<DIExpression::FragmentInfo> Fragment,
426 const DebugLoc &DL);
427
428 /// Find the EC leader for VirtReg or null.
429 UserValue *lookupVirtReg(Register VirtReg);
430
431 /// Add DBG_VALUE instruction to our maps.
432 ///
433 /// \param MI DBG_VALUE instruction
434 /// \param Idx Last valid SLotIndex before instruction.
435 ///
436 /// \returns True if the DBG_VALUE instruction should be deleted.
437 bool handleDebugValue(MachineInstr &MI, SlotIndex Idx);
438
439 /// Track a DBG_INSTR_REF. This needs to be removed from the MachineFunction
440 /// during regalloc -- but there's no need to maintain live ranges, as we
441 /// refer to a value rather than a location.
442 ///
443 /// \param MI DBG_INSTR_REF instruction
444 /// \param Idx Last valid SlotIndex before instruction
445 ///
446 /// \returns True if the DBG_VALUE instruction should be deleted.
447 bool handleDebugInstrRef(MachineInstr &MI, SlotIndex Idx);
448
449 /// Add DBG_LABEL instruction to UserLabel.
450 ///
451 /// \param MI DBG_LABEL instruction
452 /// \param Idx Last valid SlotIndex before instruction.
453 ///
454 /// \returns True if the DBG_LABEL instruction should be deleted.
455 bool handleDebugLabel(MachineInstr &MI, SlotIndex Idx);
456
457 /// Collect and erase all DBG_VALUE instructions, adding a UserValue def
458 /// for each instruction.
459 ///
460 /// \param mf MachineFunction to be scanned.
461 ///
462 /// \returns True if any debug values were found.
463 bool collectDebugValues(MachineFunction &mf);
464
465 /// Compute the live intervals of all user values after collecting all
466 /// their def points.
467 void computeIntervals();
468
469 public:
LDVImpl(LiveDebugVariables * ps)470 LDVImpl(LiveDebugVariables *ps) : pass(*ps) {}
471
472 bool runOnMachineFunction(MachineFunction &mf);
473
474 /// Release all memory.
clear()475 void clear() {
476 MF = nullptr;
477 StashedInstrReferences.clear();
478 userValues.clear();
479 userLabels.clear();
480 virtRegToEqClass.clear();
481 userVarMap.clear();
482 // Make sure we call emitDebugValues if the machine function was modified.
483 assert((!ModifiedMF || EmitDone) &&
484 "Dbg values are not emitted in LDV");
485 EmitDone = false;
486 ModifiedMF = false;
487 }
488
489 /// Map virtual register to an equivalence class.
490 void mapVirtReg(Register VirtReg, UserValue *EC);
491
492 /// Replace all references to OldReg with NewRegs.
493 void splitRegister(Register OldReg, ArrayRef<Register> NewRegs);
494
495 /// Recreate DBG_VALUE instruction from data structures.
496 void emitDebugValues(VirtRegMap *VRM);
497
498 void print(raw_ostream&);
499 };
500
501 } // end anonymous namespace
502
503 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
printDebugLoc(const DebugLoc & DL,raw_ostream & CommentOS,const LLVMContext & Ctx)504 static void printDebugLoc(const DebugLoc &DL, raw_ostream &CommentOS,
505 const LLVMContext &Ctx) {
506 if (!DL)
507 return;
508
509 auto *Scope = cast<DIScope>(DL.getScope());
510 // Omit the directory, because it's likely to be long and uninteresting.
511 CommentOS << Scope->getFilename();
512 CommentOS << ':' << DL.getLine();
513 if (DL.getCol() != 0)
514 CommentOS << ':' << DL.getCol();
515
516 DebugLoc InlinedAtDL = DL.getInlinedAt();
517 if (!InlinedAtDL)
518 return;
519
520 CommentOS << " @[ ";
521 printDebugLoc(InlinedAtDL, CommentOS, Ctx);
522 CommentOS << " ]";
523 }
524
printExtendedName(raw_ostream & OS,const DINode * Node,const DILocation * DL)525 static void printExtendedName(raw_ostream &OS, const DINode *Node,
526 const DILocation *DL) {
527 const LLVMContext &Ctx = Node->getContext();
528 StringRef Res;
529 unsigned Line = 0;
530 if (const auto *V = dyn_cast<const DILocalVariable>(Node)) {
531 Res = V->getName();
532 Line = V->getLine();
533 } else if (const auto *L = dyn_cast<const DILabel>(Node)) {
534 Res = L->getName();
535 Line = L->getLine();
536 }
537
538 if (!Res.empty())
539 OS << Res << "," << Line;
540 auto *InlinedAt = DL ? DL->getInlinedAt() : nullptr;
541 if (InlinedAt) {
542 if (DebugLoc InlinedAtDL = InlinedAt) {
543 OS << " @[";
544 printDebugLoc(InlinedAtDL, OS, Ctx);
545 OS << "]";
546 }
547 }
548 }
549
print(raw_ostream & OS,const TargetRegisterInfo * TRI)550 void UserValue::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
551 OS << "!\"";
552 printExtendedName(OS, Variable, dl);
553
554 OS << "\"\t";
555 for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I) {
556 OS << " [" << I.start() << ';' << I.stop() << "):";
557 if (I.value().isUndef())
558 OS << "undef";
559 else {
560 OS << I.value().getLocNo();
561 if (I.value().getWasIndirect())
562 OS << " ind";
563 }
564 }
565 for (unsigned i = 0, e = locations.size(); i != e; ++i) {
566 OS << " Loc" << i << '=';
567 locations[i].print(OS, TRI);
568 }
569 OS << '\n';
570 }
571
print(raw_ostream & OS,const TargetRegisterInfo * TRI)572 void UserLabel::print(raw_ostream &OS, const TargetRegisterInfo *TRI) {
573 OS << "!\"";
574 printExtendedName(OS, Label, dl);
575
576 OS << "\"\t";
577 OS << loc;
578 OS << '\n';
579 }
580
print(raw_ostream & OS)581 void LDVImpl::print(raw_ostream &OS) {
582 OS << "********** DEBUG VARIABLES **********\n";
583 for (auto &userValue : userValues)
584 userValue->print(OS, TRI);
585 OS << "********** DEBUG LABELS **********\n";
586 for (auto &userLabel : userLabels)
587 userLabel->print(OS, TRI);
588 }
589 #endif
590
mapVirtRegs(LDVImpl * LDV)591 void UserValue::mapVirtRegs(LDVImpl *LDV) {
592 for (unsigned i = 0, e = locations.size(); i != e; ++i)
593 if (locations[i].isReg() &&
594 Register::isVirtualRegister(locations[i].getReg()))
595 LDV->mapVirtReg(locations[i].getReg(), this);
596 }
597
getUserValue(const DILocalVariable * Var,Optional<DIExpression::FragmentInfo> Fragment,const DebugLoc & DL)598 UserValue *LDVImpl::getUserValue(const DILocalVariable *Var,
599 Optional<DIExpression::FragmentInfo> Fragment,
600 const DebugLoc &DL) {
601 // FIXME: Handle partially overlapping fragments. See
602 // https://reviews.llvm.org/D70121#1849741.
603 DebugVariable ID(Var, Fragment, DL->getInlinedAt());
604 UserValue *&UV = userVarMap[ID];
605 if (!UV) {
606 userValues.push_back(
607 std::make_unique<UserValue>(Var, Fragment, DL, allocator));
608 UV = userValues.back().get();
609 }
610 return UV;
611 }
612
mapVirtReg(Register VirtReg,UserValue * EC)613 void LDVImpl::mapVirtReg(Register VirtReg, UserValue *EC) {
614 assert(Register::isVirtualRegister(VirtReg) && "Only map VirtRegs");
615 UserValue *&Leader = virtRegToEqClass[VirtReg];
616 Leader = UserValue::merge(Leader, EC);
617 }
618
lookupVirtReg(Register VirtReg)619 UserValue *LDVImpl::lookupVirtReg(Register VirtReg) {
620 if (UserValue *UV = virtRegToEqClass.lookup(VirtReg))
621 return UV->getLeader();
622 return nullptr;
623 }
624
handleDebugValue(MachineInstr & MI,SlotIndex Idx)625 bool LDVImpl::handleDebugValue(MachineInstr &MI, SlotIndex Idx) {
626 // DBG_VALUE loc, offset, variable
627 if (MI.getNumOperands() != 4 ||
628 !(MI.getDebugOffset().isReg() || MI.getDebugOffset().isImm()) ||
629 !MI.getDebugVariableOp().isMetadata()) {
630 LLVM_DEBUG(dbgs() << "Can't handle " << MI);
631 return false;
632 }
633
634 // Detect invalid DBG_VALUE instructions, with a debug-use of a virtual
635 // register that hasn't been defined yet. If we do not remove those here, then
636 // the re-insertion of the DBG_VALUE instruction after register allocation
637 // will be incorrect.
638 // TODO: If earlier passes are corrected to generate sane debug information
639 // (and if the machine verifier is improved to catch this), then these checks
640 // could be removed or replaced by asserts.
641 bool Discard = false;
642 if (MI.getDebugOperand(0).isReg() &&
643 Register::isVirtualRegister(MI.getDebugOperand(0).getReg())) {
644 const Register Reg = MI.getDebugOperand(0).getReg();
645 if (!LIS->hasInterval(Reg)) {
646 // The DBG_VALUE is described by a virtual register that does not have a
647 // live interval. Discard the DBG_VALUE.
648 Discard = true;
649 LLVM_DEBUG(dbgs() << "Discarding debug info (no LIS interval): " << Idx
650 << " " << MI);
651 } else {
652 // The DBG_VALUE is only valid if either Reg is live out from Idx, or Reg
653 // is defined dead at Idx (where Idx is the slot index for the instruction
654 // preceding the DBG_VALUE).
655 const LiveInterval &LI = LIS->getInterval(Reg);
656 LiveQueryResult LRQ = LI.Query(Idx);
657 if (!LRQ.valueOutOrDead()) {
658 // We have found a DBG_VALUE with the value in a virtual register that
659 // is not live. Discard the DBG_VALUE.
660 Discard = true;
661 LLVM_DEBUG(dbgs() << "Discarding debug info (reg not live): " << Idx
662 << " " << MI);
663 }
664 }
665 }
666
667 // Get or create the UserValue for (variable,offset) here.
668 bool IsIndirect = MI.isDebugOffsetImm();
669 if (IsIndirect)
670 assert(MI.getDebugOffset().getImm() == 0 &&
671 "DBG_VALUE with nonzero offset");
672 const DILocalVariable *Var = MI.getDebugVariable();
673 const DIExpression *Expr = MI.getDebugExpression();
674 UserValue *UV = getUserValue(Var, Expr->getFragmentInfo(), MI.getDebugLoc());
675 if (!Discard)
676 UV->addDef(Idx, MI.getDebugOperand(0), IsIndirect, *Expr);
677 else {
678 MachineOperand MO = MachineOperand::CreateReg(0U, false);
679 MO.setIsDebug();
680 UV->addDef(Idx, MO, false, *Expr);
681 }
682 return true;
683 }
684
handleDebugInstrRef(MachineInstr & MI,SlotIndex Idx)685 bool LDVImpl::handleDebugInstrRef(MachineInstr &MI, SlotIndex Idx) {
686 assert(MI.isDebugRef());
687 unsigned InstrNum = MI.getOperand(0).getImm();
688 unsigned OperandNum = MI.getOperand(1).getImm();
689 auto *Var = MI.getDebugVariable();
690 auto *Expr = MI.getDebugExpression();
691 auto &DL = MI.getDebugLoc();
692 StashedInstrRef Stashed =
693 std::make_tuple(InstrNum, OperandNum, Var, Expr, DL);
694 StashedInstrReferences[Idx].push_back(Stashed);
695 return true;
696 }
697
handleDebugLabel(MachineInstr & MI,SlotIndex Idx)698 bool LDVImpl::handleDebugLabel(MachineInstr &MI, SlotIndex Idx) {
699 // DBG_LABEL label
700 if (MI.getNumOperands() != 1 || !MI.getOperand(0).isMetadata()) {
701 LLVM_DEBUG(dbgs() << "Can't handle " << MI);
702 return false;
703 }
704
705 // Get or create the UserLabel for label here.
706 const DILabel *Label = MI.getDebugLabel();
707 const DebugLoc &DL = MI.getDebugLoc();
708 bool Found = false;
709 for (auto const &L : userLabels) {
710 if (L->matches(Label, DL->getInlinedAt(), Idx)) {
711 Found = true;
712 break;
713 }
714 }
715 if (!Found)
716 userLabels.push_back(std::make_unique<UserLabel>(Label, DL, Idx));
717
718 return true;
719 }
720
collectDebugValues(MachineFunction & mf)721 bool LDVImpl::collectDebugValues(MachineFunction &mf) {
722 bool Changed = false;
723 for (MachineFunction::iterator MFI = mf.begin(), MFE = mf.end(); MFI != MFE;
724 ++MFI) {
725 MachineBasicBlock *MBB = &*MFI;
726 for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
727 MBBI != MBBE;) {
728 // Use the first debug instruction in the sequence to get a SlotIndex
729 // for following consecutive debug instructions.
730 if (!MBBI->isDebugInstr()) {
731 ++MBBI;
732 continue;
733 }
734 // Debug instructions has no slot index. Use the previous
735 // non-debug instruction's SlotIndex as its SlotIndex.
736 SlotIndex Idx =
737 MBBI == MBB->begin()
738 ? LIS->getMBBStartIdx(MBB)
739 : LIS->getInstructionIndex(*std::prev(MBBI)).getRegSlot();
740 // Handle consecutive debug instructions with the same slot index.
741 do {
742 // Only handle DBG_VALUE in handleDebugValue(). Skip all other
743 // kinds of debug instructions.
744 if ((MBBI->isDebugValue() && handleDebugValue(*MBBI, Idx)) ||
745 (MBBI->isDebugRef() && handleDebugInstrRef(*MBBI, Idx)) ||
746 (MBBI->isDebugLabel() && handleDebugLabel(*MBBI, Idx))) {
747 MBBI = MBB->erase(MBBI);
748 Changed = true;
749 } else
750 ++MBBI;
751 } while (MBBI != MBBE && MBBI->isDebugInstr());
752 }
753 }
754 return Changed;
755 }
756
extendDef(SlotIndex Idx,DbgVariableValue DbgValue,LiveRange * LR,const VNInfo * VNI,SmallVectorImpl<SlotIndex> * Kills,LiveIntervals & LIS)757 void UserValue::extendDef(SlotIndex Idx, DbgVariableValue DbgValue, LiveRange *LR,
758 const VNInfo *VNI, SmallVectorImpl<SlotIndex> *Kills,
759 LiveIntervals &LIS) {
760 SlotIndex Start = Idx;
761 MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
762 SlotIndex Stop = LIS.getMBBEndIdx(MBB);
763 LocMap::iterator I = locInts.find(Start);
764
765 // Limit to VNI's live range.
766 bool ToEnd = true;
767 if (LR && VNI) {
768 LiveInterval::Segment *Segment = LR->getSegmentContaining(Start);
769 if (!Segment || Segment->valno != VNI) {
770 if (Kills)
771 Kills->push_back(Start);
772 return;
773 }
774 if (Segment->end < Stop) {
775 Stop = Segment->end;
776 ToEnd = false;
777 }
778 }
779
780 // There could already be a short def at Start.
781 if (I.valid() && I.start() <= Start) {
782 // Stop when meeting a different location or an already extended interval.
783 Start = Start.getNextSlot();
784 if (I.value() != DbgValue || I.stop() != Start)
785 return;
786 // This is a one-slot placeholder. Just skip it.
787 ++I;
788 }
789
790 // Limited by the next def.
791 if (I.valid() && I.start() < Stop)
792 Stop = I.start();
793 // Limited by VNI's live range.
794 else if (!ToEnd && Kills)
795 Kills->push_back(Stop);
796
797 if (Start < Stop)
798 I.insert(Start, Stop, DbgValue);
799 }
800
addDefsFromCopies(LiveInterval * LI,DbgVariableValue DbgValue,const SmallVectorImpl<SlotIndex> & Kills,SmallVectorImpl<std::pair<SlotIndex,DbgVariableValue>> & NewDefs,MachineRegisterInfo & MRI,LiveIntervals & LIS)801 void UserValue::addDefsFromCopies(
802 LiveInterval *LI, DbgVariableValue DbgValue,
803 const SmallVectorImpl<SlotIndex> &Kills,
804 SmallVectorImpl<std::pair<SlotIndex, DbgVariableValue>> &NewDefs,
805 MachineRegisterInfo &MRI, LiveIntervals &LIS) {
806 if (Kills.empty())
807 return;
808 // Don't track copies from physregs, there are too many uses.
809 if (!Register::isVirtualRegister(LI->reg()))
810 return;
811
812 // Collect all the (vreg, valno) pairs that are copies of LI.
813 SmallVector<std::pair<LiveInterval*, const VNInfo*>, 8> CopyValues;
814 for (MachineOperand &MO : MRI.use_nodbg_operands(LI->reg())) {
815 MachineInstr *MI = MO.getParent();
816 // Copies of the full value.
817 if (MO.getSubReg() || !MI->isCopy())
818 continue;
819 Register DstReg = MI->getOperand(0).getReg();
820
821 // Don't follow copies to physregs. These are usually setting up call
822 // arguments, and the argument registers are always call clobbered. We are
823 // better off in the source register which could be a callee-saved register,
824 // or it could be spilled.
825 if (!Register::isVirtualRegister(DstReg))
826 continue;
827
828 // Is the value extended to reach this copy? If not, another def may be
829 // blocking it, or we are looking at a wrong value of LI.
830 SlotIndex Idx = LIS.getInstructionIndex(*MI);
831 LocMap::iterator I = locInts.find(Idx.getRegSlot(true));
832 if (!I.valid() || I.value() != DbgValue)
833 continue;
834
835 if (!LIS.hasInterval(DstReg))
836 continue;
837 LiveInterval *DstLI = &LIS.getInterval(DstReg);
838 const VNInfo *DstVNI = DstLI->getVNInfoAt(Idx.getRegSlot());
839 assert(DstVNI && DstVNI->def == Idx.getRegSlot() && "Bad copy value");
840 CopyValues.push_back(std::make_pair(DstLI, DstVNI));
841 }
842
843 if (CopyValues.empty())
844 return;
845
846 LLVM_DEBUG(dbgs() << "Got " << CopyValues.size() << " copies of " << *LI
847 << '\n');
848
849 // Try to add defs of the copied values for each kill point.
850 for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
851 SlotIndex Idx = Kills[i];
852 for (unsigned j = 0, e = CopyValues.size(); j != e; ++j) {
853 LiveInterval *DstLI = CopyValues[j].first;
854 const VNInfo *DstVNI = CopyValues[j].second;
855 if (DstLI->getVNInfoAt(Idx) != DstVNI)
856 continue;
857 // Check that there isn't already a def at Idx
858 LocMap::iterator I = locInts.find(Idx);
859 if (I.valid() && I.start() <= Idx)
860 continue;
861 LLVM_DEBUG(dbgs() << "Kill at " << Idx << " covered by valno #"
862 << DstVNI->id << " in " << *DstLI << '\n');
863 MachineInstr *CopyMI = LIS.getInstructionFromIndex(DstVNI->def);
864 assert(CopyMI && CopyMI->isCopy() && "Bad copy value");
865 unsigned LocNo = getLocationNo(CopyMI->getOperand(0));
866 DbgVariableValue NewValue = DbgValue.changeLocNo(LocNo);
867 I.insert(Idx, Idx.getNextSlot(), NewValue);
868 NewDefs.push_back(std::make_pair(Idx, NewValue));
869 break;
870 }
871 }
872 }
873
computeIntervals(MachineRegisterInfo & MRI,const TargetRegisterInfo & TRI,LiveIntervals & LIS,LexicalScopes & LS)874 void UserValue::computeIntervals(MachineRegisterInfo &MRI,
875 const TargetRegisterInfo &TRI,
876 LiveIntervals &LIS, LexicalScopes &LS) {
877 SmallVector<std::pair<SlotIndex, DbgVariableValue>, 16> Defs;
878
879 // Collect all defs to be extended (Skipping undefs).
880 for (LocMap::const_iterator I = locInts.begin(); I.valid(); ++I)
881 if (!I.value().isUndef())
882 Defs.push_back(std::make_pair(I.start(), I.value()));
883
884 // Extend all defs, and possibly add new ones along the way.
885 for (unsigned i = 0; i != Defs.size(); ++i) {
886 SlotIndex Idx = Defs[i].first;
887 DbgVariableValue DbgValue = Defs[i].second;
888 const MachineOperand &LocMO = locations[DbgValue.getLocNo()];
889
890 if (!LocMO.isReg()) {
891 extendDef(Idx, DbgValue, nullptr, nullptr, nullptr, LIS);
892 continue;
893 }
894
895 // Register locations are constrained to where the register value is live.
896 if (Register::isVirtualRegister(LocMO.getReg())) {
897 LiveInterval *LI = nullptr;
898 const VNInfo *VNI = nullptr;
899 if (LIS.hasInterval(LocMO.getReg())) {
900 LI = &LIS.getInterval(LocMO.getReg());
901 VNI = LI->getVNInfoAt(Idx);
902 }
903 SmallVector<SlotIndex, 16> Kills;
904 extendDef(Idx, DbgValue, LI, VNI, &Kills, LIS);
905 // FIXME: Handle sub-registers in addDefsFromCopies. The problem is that
906 // if the original location for example is %vreg0:sub_hi, and we find a
907 // full register copy in addDefsFromCopies (at the moment it only handles
908 // full register copies), then we must add the sub1 sub-register index to
909 // the new location. However, that is only possible if the new virtual
910 // register is of the same regclass (or if there is an equivalent
911 // sub-register in that regclass). For now, simply skip handling copies if
912 // a sub-register is involved.
913 if (LI && !LocMO.getSubReg())
914 addDefsFromCopies(LI, DbgValue, Kills, Defs, MRI, LIS);
915 continue;
916 }
917
918 // For physregs, we only mark the start slot idx. DwarfDebug will see it
919 // as if the DBG_VALUE is valid up until the end of the basic block, or
920 // the next def of the physical register. So we do not need to extend the
921 // range. It might actually happen that the DBG_VALUE is the last use of
922 // the physical register (e.g. if this is an unused input argument to a
923 // function).
924 }
925
926 // The computed intervals may extend beyond the range of the debug
927 // location's lexical scope. In this case, splitting of an interval
928 // can result in an interval outside of the scope being created,
929 // causing extra unnecessary DBG_VALUEs to be emitted. To prevent
930 // this, trim the intervals to the lexical scope.
931
932 LexicalScope *Scope = LS.findLexicalScope(dl);
933 if (!Scope)
934 return;
935
936 SlotIndex PrevEnd;
937 LocMap::iterator I = locInts.begin();
938
939 // Iterate over the lexical scope ranges. Each time round the loop
940 // we check the intervals for overlap with the end of the previous
941 // range and the start of the next. The first range is handled as
942 // a special case where there is no PrevEnd.
943 for (const InsnRange &Range : Scope->getRanges()) {
944 SlotIndex RStart = LIS.getInstructionIndex(*Range.first);
945 SlotIndex REnd = LIS.getInstructionIndex(*Range.second);
946
947 // Variable locations at the first instruction of a block should be
948 // based on the block's SlotIndex, not the first instruction's index.
949 if (Range.first == Range.first->getParent()->begin())
950 RStart = LIS.getSlotIndexes()->getIndexBefore(*Range.first);
951
952 // At the start of each iteration I has been advanced so that
953 // I.stop() >= PrevEnd. Check for overlap.
954 if (PrevEnd && I.start() < PrevEnd) {
955 SlotIndex IStop = I.stop();
956 DbgVariableValue DbgValue = I.value();
957
958 // Stop overlaps previous end - trim the end of the interval to
959 // the scope range.
960 I.setStopUnchecked(PrevEnd);
961 ++I;
962
963 // If the interval also overlaps the start of the "next" (i.e.
964 // current) range create a new interval for the remainder (which
965 // may be further trimmed).
966 if (RStart < IStop)
967 I.insert(RStart, IStop, DbgValue);
968 }
969
970 // Advance I so that I.stop() >= RStart, and check for overlap.
971 I.advanceTo(RStart);
972 if (!I.valid())
973 return;
974
975 if (I.start() < RStart) {
976 // Interval start overlaps range - trim to the scope range.
977 I.setStartUnchecked(RStart);
978 // Remember that this interval was trimmed.
979 trimmedDefs.insert(RStart);
980 }
981
982 // The end of a lexical scope range is the last instruction in the
983 // range. To convert to an interval we need the index of the
984 // instruction after it.
985 REnd = REnd.getNextIndex();
986
987 // Advance I to first interval outside current range.
988 I.advanceTo(REnd);
989 if (!I.valid())
990 return;
991
992 PrevEnd = REnd;
993 }
994
995 // Check for overlap with end of final range.
996 if (PrevEnd && I.start() < PrevEnd)
997 I.setStopUnchecked(PrevEnd);
998 }
999
computeIntervals()1000 void LDVImpl::computeIntervals() {
1001 LexicalScopes LS;
1002 LS.initialize(*MF);
1003
1004 for (unsigned i = 0, e = userValues.size(); i != e; ++i) {
1005 userValues[i]->computeIntervals(MF->getRegInfo(), *TRI, *LIS, LS);
1006 userValues[i]->mapVirtRegs(this);
1007 }
1008 }
1009
runOnMachineFunction(MachineFunction & mf)1010 bool LDVImpl::runOnMachineFunction(MachineFunction &mf) {
1011 clear();
1012 MF = &mf;
1013 LIS = &pass.getAnalysis<LiveIntervals>();
1014 TRI = mf.getSubtarget().getRegisterInfo();
1015 LLVM_DEBUG(dbgs() << "********** COMPUTING LIVE DEBUG VARIABLES: "
1016 << mf.getName() << " **********\n");
1017
1018 bool Changed = collectDebugValues(mf);
1019 computeIntervals();
1020 LLVM_DEBUG(print(dbgs()));
1021 ModifiedMF = Changed;
1022 return Changed;
1023 }
1024
removeDebugInstrs(MachineFunction & mf)1025 static void removeDebugInstrs(MachineFunction &mf) {
1026 for (MachineBasicBlock &MBB : mf) {
1027 for (auto MBBI = MBB.begin(), MBBE = MBB.end(); MBBI != MBBE; ) {
1028 if (!MBBI->isDebugInstr()) {
1029 ++MBBI;
1030 continue;
1031 }
1032 MBBI = MBB.erase(MBBI);
1033 }
1034 }
1035 }
1036
runOnMachineFunction(MachineFunction & mf)1037 bool LiveDebugVariables::runOnMachineFunction(MachineFunction &mf) {
1038 if (!EnableLDV)
1039 return false;
1040 if (!mf.getFunction().getSubprogram()) {
1041 removeDebugInstrs(mf);
1042 return false;
1043 }
1044 if (!pImpl)
1045 pImpl = new LDVImpl(this);
1046 return static_cast<LDVImpl*>(pImpl)->runOnMachineFunction(mf);
1047 }
1048
releaseMemory()1049 void LiveDebugVariables::releaseMemory() {
1050 if (pImpl)
1051 static_cast<LDVImpl*>(pImpl)->clear();
1052 }
1053
~LiveDebugVariables()1054 LiveDebugVariables::~LiveDebugVariables() {
1055 if (pImpl)
1056 delete static_cast<LDVImpl*>(pImpl);
1057 }
1058
1059 //===----------------------------------------------------------------------===//
1060 // Live Range Splitting
1061 //===----------------------------------------------------------------------===//
1062
1063 bool
splitLocation(unsigned OldLocNo,ArrayRef<Register> NewRegs,LiveIntervals & LIS)1064 UserValue::splitLocation(unsigned OldLocNo, ArrayRef<Register> NewRegs,
1065 LiveIntervals& LIS) {
1066 LLVM_DEBUG({
1067 dbgs() << "Splitting Loc" << OldLocNo << '\t';
1068 print(dbgs(), nullptr);
1069 });
1070 bool DidChange = false;
1071 LocMap::iterator LocMapI;
1072 LocMapI.setMap(locInts);
1073 for (unsigned i = 0; i != NewRegs.size(); ++i) {
1074 LiveInterval *LI = &LIS.getInterval(NewRegs[i]);
1075 if (LI->empty())
1076 continue;
1077
1078 // Don't allocate the new LocNo until it is needed.
1079 unsigned NewLocNo = UndefLocNo;
1080
1081 // Iterate over the overlaps between locInts and LI.
1082 LocMapI.find(LI->beginIndex());
1083 if (!LocMapI.valid())
1084 continue;
1085 LiveInterval::iterator LII = LI->advanceTo(LI->begin(), LocMapI.start());
1086 LiveInterval::iterator LIE = LI->end();
1087 while (LocMapI.valid() && LII != LIE) {
1088 // At this point, we know that LocMapI.stop() > LII->start.
1089 LII = LI->advanceTo(LII, LocMapI.start());
1090 if (LII == LIE)
1091 break;
1092
1093 // Now LII->end > LocMapI.start(). Do we have an overlap?
1094 if (LocMapI.value().getLocNo() == OldLocNo &&
1095 LII->start < LocMapI.stop()) {
1096 // Overlapping correct location. Allocate NewLocNo now.
1097 if (NewLocNo == UndefLocNo) {
1098 MachineOperand MO = MachineOperand::CreateReg(LI->reg(), false);
1099 MO.setSubReg(locations[OldLocNo].getSubReg());
1100 NewLocNo = getLocationNo(MO);
1101 DidChange = true;
1102 }
1103
1104 SlotIndex LStart = LocMapI.start();
1105 SlotIndex LStop = LocMapI.stop();
1106 DbgVariableValue OldDbgValue = LocMapI.value();
1107
1108 // Trim LocMapI down to the LII overlap.
1109 if (LStart < LII->start)
1110 LocMapI.setStartUnchecked(LII->start);
1111 if (LStop > LII->end)
1112 LocMapI.setStopUnchecked(LII->end);
1113
1114 // Change the value in the overlap. This may trigger coalescing.
1115 LocMapI.setValue(OldDbgValue.changeLocNo(NewLocNo));
1116
1117 // Re-insert any removed OldDbgValue ranges.
1118 if (LStart < LocMapI.start()) {
1119 LocMapI.insert(LStart, LocMapI.start(), OldDbgValue);
1120 ++LocMapI;
1121 assert(LocMapI.valid() && "Unexpected coalescing");
1122 }
1123 if (LStop > LocMapI.stop()) {
1124 ++LocMapI;
1125 LocMapI.insert(LII->end, LStop, OldDbgValue);
1126 --LocMapI;
1127 }
1128 }
1129
1130 // Advance to the next overlap.
1131 if (LII->end < LocMapI.stop()) {
1132 if (++LII == LIE)
1133 break;
1134 LocMapI.advanceTo(LII->start);
1135 } else {
1136 ++LocMapI;
1137 if (!LocMapI.valid())
1138 break;
1139 LII = LI->advanceTo(LII, LocMapI.start());
1140 }
1141 }
1142 }
1143
1144 // Finally, remove OldLocNo unless it is still used by some interval in the
1145 // locInts map. One case when OldLocNo still is in use is when the register
1146 // has been spilled. In such situations the spilled register is kept as a
1147 // location until rewriteLocations is called (VirtRegMap is mapping the old
1148 // register to the spill slot). So for a while we can have locations that map
1149 // to virtual registers that have been removed from both the MachineFunction
1150 // and from LiveIntervals.
1151 //
1152 // We may also just be using the location for a value with a different
1153 // expression.
1154 removeLocationIfUnused(OldLocNo);
1155
1156 LLVM_DEBUG({
1157 dbgs() << "Split result: \t";
1158 print(dbgs(), nullptr);
1159 });
1160 return DidChange;
1161 }
1162
1163 bool
splitRegister(Register OldReg,ArrayRef<Register> NewRegs,LiveIntervals & LIS)1164 UserValue::splitRegister(Register OldReg, ArrayRef<Register> NewRegs,
1165 LiveIntervals &LIS) {
1166 bool DidChange = false;
1167 // Split locations referring to OldReg. Iterate backwards so splitLocation can
1168 // safely erase unused locations.
1169 for (unsigned i = locations.size(); i ; --i) {
1170 unsigned LocNo = i-1;
1171 const MachineOperand *Loc = &locations[LocNo];
1172 if (!Loc->isReg() || Loc->getReg() != OldReg)
1173 continue;
1174 DidChange |= splitLocation(LocNo, NewRegs, LIS);
1175 }
1176 return DidChange;
1177 }
1178
splitRegister(Register OldReg,ArrayRef<Register> NewRegs)1179 void LDVImpl::splitRegister(Register OldReg, ArrayRef<Register> NewRegs) {
1180 bool DidChange = false;
1181 for (UserValue *UV = lookupVirtReg(OldReg); UV; UV = UV->getNext())
1182 DidChange |= UV->splitRegister(OldReg, NewRegs, *LIS);
1183
1184 if (!DidChange)
1185 return;
1186
1187 // Map all of the new virtual registers.
1188 UserValue *UV = lookupVirtReg(OldReg);
1189 for (unsigned i = 0; i != NewRegs.size(); ++i)
1190 mapVirtReg(NewRegs[i], UV);
1191 }
1192
1193 void LiveDebugVariables::
splitRegister(Register OldReg,ArrayRef<Register> NewRegs,LiveIntervals & LIS)1194 splitRegister(Register OldReg, ArrayRef<Register> NewRegs, LiveIntervals &LIS) {
1195 if (pImpl)
1196 static_cast<LDVImpl*>(pImpl)->splitRegister(OldReg, NewRegs);
1197 }
1198
rewriteLocations(VirtRegMap & VRM,const MachineFunction & MF,const TargetInstrInfo & TII,const TargetRegisterInfo & TRI,SpillOffsetMap & SpillOffsets)1199 void UserValue::rewriteLocations(VirtRegMap &VRM, const MachineFunction &MF,
1200 const TargetInstrInfo &TII,
1201 const TargetRegisterInfo &TRI,
1202 SpillOffsetMap &SpillOffsets) {
1203 // Build a set of new locations with new numbers so we can coalesce our
1204 // IntervalMap if two vreg intervals collapse to the same physical location.
1205 // Use MapVector instead of SetVector because MapVector::insert returns the
1206 // position of the previously or newly inserted element. The boolean value
1207 // tracks if the location was produced by a spill.
1208 // FIXME: This will be problematic if we ever support direct and indirect
1209 // frame index locations, i.e. expressing both variables in memory and
1210 // 'int x, *px = &x'. The "spilled" bit must become part of the location.
1211 MapVector<MachineOperand, std::pair<bool, unsigned>> NewLocations;
1212 SmallVector<unsigned, 4> LocNoMap(locations.size());
1213 for (unsigned I = 0, E = locations.size(); I != E; ++I) {
1214 bool Spilled = false;
1215 unsigned SpillOffset = 0;
1216 MachineOperand Loc = locations[I];
1217 // Only virtual registers are rewritten.
1218 if (Loc.isReg() && Loc.getReg() &&
1219 Register::isVirtualRegister(Loc.getReg())) {
1220 Register VirtReg = Loc.getReg();
1221 if (VRM.isAssignedReg(VirtReg) &&
1222 Register::isPhysicalRegister(VRM.getPhys(VirtReg))) {
1223 // This can create a %noreg operand in rare cases when the sub-register
1224 // index is no longer available. That means the user value is in a
1225 // non-existent sub-register, and %noreg is exactly what we want.
1226 Loc.substPhysReg(VRM.getPhys(VirtReg), TRI);
1227 } else if (VRM.getStackSlot(VirtReg) != VirtRegMap::NO_STACK_SLOT) {
1228 // Retrieve the stack slot offset.
1229 unsigned SpillSize;
1230 const MachineRegisterInfo &MRI = MF.getRegInfo();
1231 const TargetRegisterClass *TRC = MRI.getRegClass(VirtReg);
1232 bool Success = TII.getStackSlotRange(TRC, Loc.getSubReg(), SpillSize,
1233 SpillOffset, MF);
1234
1235 // FIXME: Invalidate the location if the offset couldn't be calculated.
1236 (void)Success;
1237
1238 Loc = MachineOperand::CreateFI(VRM.getStackSlot(VirtReg));
1239 Spilled = true;
1240 } else {
1241 Loc.setReg(0);
1242 Loc.setSubReg(0);
1243 }
1244 }
1245
1246 // Insert this location if it doesn't already exist and record a mapping
1247 // from the old number to the new number.
1248 auto InsertResult = NewLocations.insert({Loc, {Spilled, SpillOffset}});
1249 unsigned NewLocNo = std::distance(NewLocations.begin(), InsertResult.first);
1250 LocNoMap[I] = NewLocNo;
1251 }
1252
1253 // Rewrite the locations and record the stack slot offsets for spills.
1254 locations.clear();
1255 SpillOffsets.clear();
1256 for (auto &Pair : NewLocations) {
1257 bool Spilled;
1258 unsigned SpillOffset;
1259 std::tie(Spilled, SpillOffset) = Pair.second;
1260 locations.push_back(Pair.first);
1261 if (Spilled) {
1262 unsigned NewLocNo = std::distance(&*NewLocations.begin(), &Pair);
1263 SpillOffsets[NewLocNo] = SpillOffset;
1264 }
1265 }
1266
1267 // Update the interval map, but only coalesce left, since intervals to the
1268 // right use the old location numbers. This should merge two contiguous
1269 // DBG_VALUE intervals with different vregs that were allocated to the same
1270 // physical register.
1271 for (LocMap::iterator I = locInts.begin(); I.valid(); ++I) {
1272 DbgVariableValue DbgValue = I.value();
1273 // Undef values don't exist in locations (and thus not in LocNoMap either)
1274 // so skip over them. See getLocationNo().
1275 if (DbgValue.isUndef())
1276 continue;
1277 unsigned NewLocNo = LocNoMap[DbgValue.getLocNo()];
1278 I.setValueUnchecked(DbgValue.changeLocNo(NewLocNo));
1279 I.setStart(I.start());
1280 }
1281 }
1282
1283 /// Find an iterator for inserting a DBG_VALUE instruction.
1284 static MachineBasicBlock::iterator
findInsertLocation(MachineBasicBlock * MBB,SlotIndex Idx,LiveIntervals & LIS)1285 findInsertLocation(MachineBasicBlock *MBB, SlotIndex Idx,
1286 LiveIntervals &LIS) {
1287 SlotIndex Start = LIS.getMBBStartIdx(MBB);
1288 Idx = Idx.getBaseIndex();
1289
1290 // Try to find an insert location by going backwards from Idx.
1291 MachineInstr *MI;
1292 while (!(MI = LIS.getInstructionFromIndex(Idx))) {
1293 // We've reached the beginning of MBB.
1294 if (Idx == Start) {
1295 MachineBasicBlock::iterator I = MBB->SkipPHIsLabelsAndDebug(MBB->begin());
1296 return I;
1297 }
1298 Idx = Idx.getPrevIndex();
1299 }
1300
1301 // Don't insert anything after the first terminator, though.
1302 return MI->isTerminator() ? MBB->getFirstTerminator() :
1303 std::next(MachineBasicBlock::iterator(MI));
1304 }
1305
1306 /// Find an iterator for inserting the next DBG_VALUE instruction
1307 /// (or end if no more insert locations found).
1308 static MachineBasicBlock::iterator
findNextInsertLocation(MachineBasicBlock * MBB,MachineBasicBlock::iterator I,SlotIndex StopIdx,MachineOperand & LocMO,LiveIntervals & LIS,const TargetRegisterInfo & TRI)1309 findNextInsertLocation(MachineBasicBlock *MBB,
1310 MachineBasicBlock::iterator I,
1311 SlotIndex StopIdx, MachineOperand &LocMO,
1312 LiveIntervals &LIS,
1313 const TargetRegisterInfo &TRI) {
1314 if (!LocMO.isReg())
1315 return MBB->instr_end();
1316 Register Reg = LocMO.getReg();
1317
1318 // Find the next instruction in the MBB that define the register Reg.
1319 while (I != MBB->end() && !I->isTerminator()) {
1320 if (!LIS.isNotInMIMap(*I) &&
1321 SlotIndex::isEarlierEqualInstr(StopIdx, LIS.getInstructionIndex(*I)))
1322 break;
1323 if (I->definesRegister(Reg, &TRI))
1324 // The insert location is directly after the instruction/bundle.
1325 return std::next(I);
1326 ++I;
1327 }
1328 return MBB->end();
1329 }
1330
insertDebugValue(MachineBasicBlock * MBB,SlotIndex StartIdx,SlotIndex StopIdx,DbgVariableValue DbgValue,bool Spilled,unsigned SpillOffset,LiveIntervals & LIS,const TargetInstrInfo & TII,const TargetRegisterInfo & TRI)1331 void UserValue::insertDebugValue(MachineBasicBlock *MBB, SlotIndex StartIdx,
1332 SlotIndex StopIdx, DbgVariableValue DbgValue,
1333 bool Spilled, unsigned SpillOffset,
1334 LiveIntervals &LIS, const TargetInstrInfo &TII,
1335 const TargetRegisterInfo &TRI) {
1336 SlotIndex MBBEndIdx = LIS.getMBBEndIdx(&*MBB);
1337 // Only search within the current MBB.
1338 StopIdx = (MBBEndIdx < StopIdx) ? MBBEndIdx : StopIdx;
1339 MachineBasicBlock::iterator I = findInsertLocation(MBB, StartIdx, LIS);
1340 // Undef values don't exist in locations so create new "noreg" register MOs
1341 // for them. See getLocationNo().
1342 MachineOperand MO =
1343 !DbgValue.isUndef()
1344 ? locations[DbgValue.getLocNo()]
1345 : MachineOperand::CreateReg(
1346 /* Reg */ 0, /* isDef */ false, /* isImp */ false,
1347 /* isKill */ false, /* isDead */ false,
1348 /* isUndef */ false, /* isEarlyClobber */ false,
1349 /* SubReg */ 0, /* isDebug */ true);
1350
1351 ++NumInsertedDebugValues;
1352
1353 assert(cast<DILocalVariable>(Variable)
1354 ->isValidLocationForIntrinsic(getDebugLoc()) &&
1355 "Expected inlined-at fields to agree");
1356
1357 // If the location was spilled, the new DBG_VALUE will be indirect. If the
1358 // original DBG_VALUE was indirect, we need to add DW_OP_deref to indicate
1359 // that the original virtual register was a pointer. Also, add the stack slot
1360 // offset for the spilled register to the expression.
1361 const DIExpression *Expr = DbgValue.getExpression();
1362 uint8_t DIExprFlags = DIExpression::ApplyOffset;
1363 bool IsIndirect = DbgValue.getWasIndirect();
1364 if (Spilled) {
1365 if (IsIndirect)
1366 DIExprFlags |= DIExpression::DerefAfter;
1367 Expr =
1368 DIExpression::prepend(Expr, DIExprFlags, SpillOffset);
1369 IsIndirect = true;
1370 }
1371
1372 assert((!Spilled || MO.isFI()) && "a spilled location must be a frame index");
1373
1374 do {
1375 BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_VALUE),
1376 IsIndirect, MO, Variable, Expr);
1377
1378 // Continue and insert DBG_VALUES after every redefinition of register
1379 // associated with the debug value within the range
1380 I = findNextInsertLocation(MBB, I, StopIdx, MO, LIS, TRI);
1381 } while (I != MBB->end());
1382 }
1383
insertDebugLabel(MachineBasicBlock * MBB,SlotIndex Idx,LiveIntervals & LIS,const TargetInstrInfo & TII)1384 void UserLabel::insertDebugLabel(MachineBasicBlock *MBB, SlotIndex Idx,
1385 LiveIntervals &LIS,
1386 const TargetInstrInfo &TII) {
1387 MachineBasicBlock::iterator I = findInsertLocation(MBB, Idx, LIS);
1388 ++NumInsertedDebugLabels;
1389 BuildMI(*MBB, I, getDebugLoc(), TII.get(TargetOpcode::DBG_LABEL))
1390 .addMetadata(Label);
1391 }
1392
emitDebugValues(VirtRegMap * VRM,LiveIntervals & LIS,const TargetInstrInfo & TII,const TargetRegisterInfo & TRI,const SpillOffsetMap & SpillOffsets)1393 void UserValue::emitDebugValues(VirtRegMap *VRM, LiveIntervals &LIS,
1394 const TargetInstrInfo &TII,
1395 const TargetRegisterInfo &TRI,
1396 const SpillOffsetMap &SpillOffsets) {
1397 MachineFunction::iterator MFEnd = VRM->getMachineFunction().end();
1398
1399 for (LocMap::const_iterator I = locInts.begin(); I.valid();) {
1400 SlotIndex Start = I.start();
1401 SlotIndex Stop = I.stop();
1402 DbgVariableValue DbgValue = I.value();
1403 auto SpillIt = !DbgValue.isUndef() ? SpillOffsets.find(DbgValue.getLocNo())
1404 : SpillOffsets.end();
1405 bool Spilled = SpillIt != SpillOffsets.end();
1406 unsigned SpillOffset = Spilled ? SpillIt->second : 0;
1407
1408 // If the interval start was trimmed to the lexical scope insert the
1409 // DBG_VALUE at the previous index (otherwise it appears after the
1410 // first instruction in the range).
1411 if (trimmedDefs.count(Start))
1412 Start = Start.getPrevIndex();
1413
1414 LLVM_DEBUG(dbgs() << "\t[" << Start << ';' << Stop
1415 << "):" << DbgValue.getLocNo());
1416 MachineFunction::iterator MBB = LIS.getMBBFromIndex(Start)->getIterator();
1417 SlotIndex MBBEnd = LIS.getMBBEndIdx(&*MBB);
1418
1419 LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB) << '-' << MBBEnd);
1420 insertDebugValue(&*MBB, Start, Stop, DbgValue, Spilled, SpillOffset, LIS,
1421 TII, TRI);
1422 // This interval may span multiple basic blocks.
1423 // Insert a DBG_VALUE into each one.
1424 while (Stop > MBBEnd) {
1425 // Move to the next block.
1426 Start = MBBEnd;
1427 if (++MBB == MFEnd)
1428 break;
1429 MBBEnd = LIS.getMBBEndIdx(&*MBB);
1430 LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB) << '-' << MBBEnd);
1431 insertDebugValue(&*MBB, Start, Stop, DbgValue, Spilled, SpillOffset, LIS,
1432 TII, TRI);
1433 }
1434 LLVM_DEBUG(dbgs() << '\n');
1435 if (MBB == MFEnd)
1436 break;
1437
1438 ++I;
1439 }
1440 }
1441
emitDebugLabel(LiveIntervals & LIS,const TargetInstrInfo & TII)1442 void UserLabel::emitDebugLabel(LiveIntervals &LIS, const TargetInstrInfo &TII) {
1443 LLVM_DEBUG(dbgs() << "\t" << loc);
1444 MachineFunction::iterator MBB = LIS.getMBBFromIndex(loc)->getIterator();
1445
1446 LLVM_DEBUG(dbgs() << ' ' << printMBBReference(*MBB));
1447 insertDebugLabel(&*MBB, loc, LIS, TII);
1448
1449 LLVM_DEBUG(dbgs() << '\n');
1450 }
1451
emitDebugValues(VirtRegMap * VRM)1452 void LDVImpl::emitDebugValues(VirtRegMap *VRM) {
1453 LLVM_DEBUG(dbgs() << "********** EMITTING LIVE DEBUG VARIABLES **********\n");
1454 if (!MF)
1455 return;
1456 const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
1457 SpillOffsetMap SpillOffsets;
1458 for (auto &userValue : userValues) {
1459 LLVM_DEBUG(userValue->print(dbgs(), TRI));
1460 userValue->rewriteLocations(*VRM, *MF, *TII, *TRI, SpillOffsets);
1461 userValue->emitDebugValues(VRM, *LIS, *TII, *TRI, SpillOffsets);
1462 }
1463 LLVM_DEBUG(dbgs() << "********** EMITTING LIVE DEBUG LABELS **********\n");
1464 for (auto &userLabel : userLabels) {
1465 LLVM_DEBUG(userLabel->print(dbgs(), TRI));
1466 userLabel->emitDebugLabel(*LIS, *TII);
1467 }
1468
1469 LLVM_DEBUG(dbgs() << "********** EMITTING INSTR REFERENCES **********\n");
1470
1471 // Re-insert any DBG_INSTR_REFs back in the position they were. Ordering
1472 // is preserved by vector.
1473 auto Slots = LIS->getSlotIndexes();
1474 const MCInstrDesc &RefII = TII->get(TargetOpcode::DBG_INSTR_REF);
1475 for (auto &P : StashedInstrReferences) {
1476 const SlotIndex &Idx = P.first;
1477 auto *MBB = Slots->getMBBFromIndex(Idx);
1478 MachineBasicBlock::iterator insertPos = findInsertLocation(MBB, Idx, *LIS);
1479 for (auto &Stashed : P.second) {
1480 auto MIB = BuildMI(*MF, std::get<4>(Stashed), RefII);
1481 MIB.addImm(std::get<0>(Stashed));
1482 MIB.addImm(std::get<1>(Stashed));
1483 MIB.addMetadata(std::get<2>(Stashed));
1484 MIB.addMetadata(std::get<3>(Stashed));
1485 MachineInstr *New = MIB;
1486 MBB->insert(insertPos, New);
1487 }
1488 }
1489
1490 EmitDone = true;
1491 }
1492
emitDebugValues(VirtRegMap * VRM)1493 void LiveDebugVariables::emitDebugValues(VirtRegMap *VRM) {
1494 if (pImpl)
1495 static_cast<LDVImpl*>(pImpl)->emitDebugValues(VRM);
1496 }
1497
1498 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
dump() const1499 LLVM_DUMP_METHOD void LiveDebugVariables::dump() const {
1500 if (pImpl)
1501 static_cast<LDVImpl*>(pImpl)->print(dbgs());
1502 }
1503 #endif
1504