1 //===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
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
7 //===----------------------------------------------------------------------===//
9 /// This pass implements a data flow analysis that propagates debug location
10 /// information by inserting additional DBG_VALUE instructions into the machine
11 /// instruction stream. The pass internally builds debug location liveness
12 /// ranges to determine the points where additional DBG_VALUEs need to be
15 /// This is a separate pass from DbgValueHistoryCalculator to facilitate
16 /// testing and improve modularity.
18 //===----------------------------------------------------------------------===//
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/PostOrderIterator.h"
22 #include "llvm/ADT/SmallPtrSet.h"
23 #include "llvm/ADT/SmallSet.h"
24 #include "llvm/ADT/SmallVector.h"
25 #include "llvm/ADT/SparseBitVector.h"
26 #include "llvm/ADT/Statistic.h"
27 #include "llvm/ADT/UniqueVector.h"
28 #include "llvm/CodeGen/LexicalScopes.h"
29 #include "llvm/CodeGen/MachineBasicBlock.h"
30 #include "llvm/CodeGen/MachineFrameInfo.h"
31 #include "llvm/CodeGen/MachineFunction.h"
32 #include "llvm/CodeGen/MachineFunctionPass.h"
33 #include "llvm/CodeGen/MachineInstr.h"
34 #include "llvm/CodeGen/MachineInstrBuilder.h"
35 #include "llvm/CodeGen/MachineMemOperand.h"
36 #include "llvm/CodeGen/MachineOperand.h"
37 #include "llvm/CodeGen/PseudoSourceValue.h"
38 #include "llvm/CodeGen/RegisterScavenging.h"
39 #include "llvm/CodeGen/TargetFrameLowering.h"
40 #include "llvm/CodeGen/TargetInstrInfo.h"
41 #include "llvm/CodeGen/TargetLowering.h"
42 #include "llvm/CodeGen/TargetPassConfig.h"
43 #include "llvm/CodeGen/TargetRegisterInfo.h"
44 #include "llvm/CodeGen/TargetSubtargetInfo.h"
45 #include "llvm/Config/llvm-config.h"
46 #include "llvm/IR/DIBuilder.h"
47 #include "llvm/IR/DebugInfoMetadata.h"
48 #include "llvm/IR/DebugLoc.h"
49 #include "llvm/IR/Function.h"
50 #include "llvm/IR/Module.h"
51 #include "llvm/MC/MCRegisterInfo.h"
52 #include "llvm/Pass.h"
53 #include "llvm/Support/Casting.h"
54 #include "llvm/Support/Compiler.h"
55 #include "llvm/Support/Debug.h"
56 #include "llvm/Support/raw_ostream.h"
68 #define DEBUG_TYPE "livedebugvalues"
70 STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
72 // If @MI is a DBG_VALUE with debug value described by a defined
73 // register, returns the number of this register. In the other case, returns 0.
74 static Register isDbgValueDescribedByReg(const MachineInstr &MI) {
75 assert(MI.isDebugValue() && "expected a DBG_VALUE");
76 assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
77 // If location of variable is described using a register (directly
78 // or indirectly), this register is always a first operand.
79 return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : Register();
84 class LiveDebugValues : public MachineFunctionPass {
86 const TargetRegisterInfo *TRI;
87 const TargetInstrInfo *TII;
88 const TargetFrameLowering *TFI;
89 BitVector CalleeSavedRegs;
92 enum struct TransferKind { TransferCopy, TransferSpill, TransferRestore };
94 /// Keeps track of lexical scopes associated with a user value's source
96 class UserValueScopes {
99 SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
102 UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(std::move(D)), LS(L) {}
104 /// Return true if current scope dominates at least one machine
105 /// instruction in a given machine basic block.
106 bool dominates(MachineBasicBlock *MBB) {
108 LS.getMachineBasicBlocks(DL, LBlocks);
109 return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB);
113 using FragmentInfo = DIExpression::FragmentInfo;
114 using OptFragmentInfo = Optional<DIExpression::FragmentInfo>;
116 /// Storage for identifying a potentially inlined instance of a variable,
117 /// or a fragment thereof.
118 class DebugVariable {
119 const DILocalVariable *Variable;
120 OptFragmentInfo Fragment;
121 const DILocation *InlinedAt;
123 /// Fragment that will overlap all other fragments. Used as default when
124 /// caller demands a fragment.
125 static const FragmentInfo DefaultFragment;
128 DebugVariable(const DILocalVariable *Var, OptFragmentInfo &&FragmentInfo,
129 const DILocation *InlinedAt)
130 : Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {}
132 DebugVariable(const DILocalVariable *Var, OptFragmentInfo &FragmentInfo,
133 const DILocation *InlinedAt)
134 : Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {}
136 DebugVariable(const DILocalVariable *Var, const DIExpression *DIExpr,
137 const DILocation *InlinedAt)
138 : DebugVariable(Var, DIExpr->getFragmentInfo(), InlinedAt) {}
140 DebugVariable(const MachineInstr &MI)
141 : DebugVariable(MI.getDebugVariable(),
142 MI.getDebugExpression()->getFragmentInfo(),
143 MI.getDebugLoc()->getInlinedAt()) {}
145 const DILocalVariable *getVar() const { return Variable; }
146 const OptFragmentInfo &getFragment() const { return Fragment; }
147 const DILocation *getInlinedAt() const { return InlinedAt; }
149 const FragmentInfo getFragmentDefault() const {
150 return Fragment.getValueOr(DefaultFragment);
153 static bool isFragmentDefault(FragmentInfo &F) {
154 return F == DefaultFragment;
157 bool operator==(const DebugVariable &Other) const {
158 return std::tie(Variable, Fragment, InlinedAt) ==
159 std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
162 bool operator<(const DebugVariable &Other) const {
163 return std::tie(Variable, Fragment, InlinedAt) <
164 std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
168 friend struct llvm::DenseMapInfo<DebugVariable>;
170 /// A pair of debug variable and value location.
172 // The location at which a spilled variable resides. It consists of a
173 // register and an offset.
177 bool operator==(const SpillLoc &Other) const {
178 return SpillBase == Other.SpillBase && SpillOffset == Other.SpillOffset;
182 const DebugVariable Var;
183 const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
184 mutable UserValueScopes UVS;
191 } Kind = InvalidKind;
193 /// The value location. Stored separately to avoid repeatedly
194 /// extracting it from MI.
197 SpillLoc SpillLocation;
200 const ConstantFP *FPImm;
201 const ConstantInt *CImm;
204 VarLoc(const MachineInstr &MI, LexicalScopes &LS,
205 VarLocKind K = InvalidKind)
206 : Var(MI), MI(MI), UVS(MI.getDebugLoc(), LS){
207 static_assert((sizeof(Loc) == sizeof(uint64_t)),
208 "hash does not cover all members of Loc");
209 assert(MI.isDebugValue() && "not a DBG_VALUE");
210 assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
211 if (int RegNo = isDbgValueDescribedByReg(MI)) {
212 Kind = MI.isDebugEntryValue() ? EntryValueKind : RegisterKind;
214 } else if (MI.getOperand(0).isImm()) {
215 Kind = ImmediateKind;
216 Loc.Immediate = MI.getOperand(0).getImm();
217 } else if (MI.getOperand(0).isFPImm()) {
218 Kind = ImmediateKind;
219 Loc.FPImm = MI.getOperand(0).getFPImm();
220 } else if (MI.getOperand(0).isCImm()) {
221 Kind = ImmediateKind;
222 Loc.CImm = MI.getOperand(0).getCImm();
224 assert((Kind != ImmediateKind || !MI.isDebugEntryValue()) &&
225 "entry values must be register locations");
228 /// The constructor for spill locations.
229 VarLoc(const MachineInstr &MI, unsigned SpillBase, int SpillOffset,
231 : Var(MI), MI(MI), UVS(MI.getDebugLoc(), LS) {
232 assert(MI.isDebugValue() && "not a DBG_VALUE");
233 assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
235 Loc.SpillLocation = {SpillBase, SpillOffset};
238 // Is the Loc field a constant or constant object?
239 bool isConstant() const { return Kind == ImmediateKind; }
241 /// If this variable is described by a register, return it,
242 /// otherwise return 0.
243 unsigned isDescribedByReg() const {
244 if (Kind == RegisterKind)
249 /// Determine whether the lexical scope of this value's debug location
251 bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); }
253 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
254 LLVM_DUMP_METHOD void dump() const { MI.dump(); }
257 bool operator==(const VarLoc &Other) const {
258 return Kind == Other.Kind && Var == Other.Var &&
259 Loc.Hash == Other.Loc.Hash;
262 /// This operator guarantees that VarLocs are sorted by Variable first.
263 bool operator<(const VarLoc &Other) const {
264 return std::tie(Var, Kind, Loc.Hash) <
265 std::tie(Other.Var, Other.Kind, Other.Loc.Hash);
269 using DebugParamMap = SmallDenseMap<const DILocalVariable *, MachineInstr *>;
270 using VarLocMap = UniqueVector<VarLoc>;
271 using VarLocSet = SparseBitVector<>;
272 using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>;
273 struct TransferDebugPair {
274 MachineInstr *TransferInst;
275 MachineInstr *DebugInst;
277 using TransferMap = SmallVector<TransferDebugPair, 4>;
279 // Types for recording sets of variable fragments that overlap. For a given
280 // local variable, we record all other fragments of that variable that could
281 // overlap it, to reduce search time.
282 using FragmentOfVar =
283 std::pair<const DILocalVariable *, DIExpression::FragmentInfo>;
285 DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>;
287 // Helper while building OverlapMap, a map of all fragments seen for a given
289 using VarToFragments =
290 DenseMap<const DILocalVariable *, SmallSet<FragmentInfo, 4>>;
292 /// This holds the working set of currently open ranges. For fast
293 /// access, this is done both as a set of VarLocIDs, and a map of
294 /// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
295 /// previous open ranges for the same variable.
296 class OpenRangesSet {
298 SmallDenseMap<DebugVariable, unsigned, 8> Vars;
299 OverlapMap &OverlappingFragments;
302 OpenRangesSet(OverlapMap &_OLapMap) : OverlappingFragments(_OLapMap) {}
304 const VarLocSet &getVarLocs() const { return VarLocs; }
306 /// Terminate all open ranges for Var by removing it from the set.
307 void erase(DebugVariable Var);
309 /// Terminate all open ranges listed in \c KillSet by removing
310 /// them from the set.
311 void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) {
312 VarLocs.intersectWithComplement(KillSet);
313 for (unsigned ID : KillSet)
314 Vars.erase(VarLocIDs[ID].Var);
317 /// Insert a new range into the set.
318 void insert(unsigned VarLocID, DebugVariable Var) {
319 VarLocs.set(VarLocID);
320 Vars.insert({Var, VarLocID});
329 /// Return whether the set is empty or not.
331 assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent");
332 return VarLocs.empty();
336 bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
338 /// If a given instruction is identified as a spill, return the spill location
339 /// and set \p Reg to the spilled register.
340 Optional<VarLoc::SpillLoc> isRestoreInstruction(const MachineInstr &MI,
343 /// Given a spill instruction, extract the register and offset used to
344 /// address the spill location in a target independent way.
345 VarLoc::SpillLoc extractSpillBaseRegAndOffset(const MachineInstr &MI);
346 void insertTransferDebugPair(MachineInstr &MI, OpenRangesSet &OpenRanges,
347 TransferMap &Transfers, VarLocMap &VarLocIDs,
348 unsigned OldVarID, TransferKind Kind,
349 unsigned NewReg = 0);
351 void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
352 VarLocMap &VarLocIDs);
353 void transferSpillOrRestoreInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
354 VarLocMap &VarLocIDs, TransferMap &Transfers);
355 void emitEntryValues(MachineInstr &MI, OpenRangesSet &OpenRanges,
356 VarLocMap &VarLocIDs, TransferMap &Transfers,
357 DebugParamMap &DebugEntryVals,
358 SparseBitVector<> &KillSet);
359 void transferRegisterCopy(MachineInstr &MI, OpenRangesSet &OpenRanges,
360 VarLocMap &VarLocIDs, TransferMap &Transfers);
361 void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
362 VarLocMap &VarLocIDs, TransferMap &Transfers,
363 DebugParamMap &DebugEntryVals);
364 bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
365 VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
367 bool process(MachineInstr &MI, OpenRangesSet &OpenRanges,
368 VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
369 TransferMap &Transfers, DebugParamMap &DebugEntryVals,
370 bool transferChanges, OverlapMap &OverlapFragments,
371 VarToFragments &SeenFragments);
373 void accumulateFragmentMap(MachineInstr &MI, VarToFragments &SeenFragments,
374 OverlapMap &OLapMap);
376 bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
377 const VarLocMap &VarLocIDs,
378 SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
379 SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks);
381 bool ExtendRanges(MachineFunction &MF);
386 /// Default construct and initialize the pass.
389 /// Tell the pass manager which passes we depend on and what
390 /// information we preserve.
391 void getAnalysisUsage(AnalysisUsage &AU) const override;
393 MachineFunctionProperties getRequiredProperties() const override {
394 return MachineFunctionProperties().set(
395 MachineFunctionProperties::Property::NoVRegs);
398 /// Print to ostream with a message.
399 void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
400 const VarLocMap &VarLocIDs, const char *msg,
401 raw_ostream &Out) const;
403 /// Calculate the liveness information for the given machine function.
404 bool runOnMachineFunction(MachineFunction &MF) override;
407 } // end anonymous namespace
411 template <> struct DenseMapInfo<LiveDebugValues::DebugVariable> {
412 using DV = LiveDebugValues::DebugVariable;
413 using OptFragmentInfo = LiveDebugValues::OptFragmentInfo;
414 using FragmentInfo = LiveDebugValues::FragmentInfo;
416 // Empty key: no key should be generated that has no DILocalVariable.
417 static inline DV getEmptyKey() {
418 return DV(nullptr, OptFragmentInfo(), nullptr);
421 // Difference in tombstone is that the Optional is meaningful
422 static inline DV getTombstoneKey() {
423 return DV(nullptr, OptFragmentInfo({0, 0}), nullptr);
426 static unsigned getHashValue(const DV &D) {
428 const OptFragmentInfo &Fragment = D.getFragment();
430 HV = DenseMapInfo<FragmentInfo>::getHashValue(*Fragment);
432 return hash_combine(D.getVar(), HV, D.getInlinedAt());
435 static bool isEqual(const DV &A, const DV &B) { return A == B; }
440 //===----------------------------------------------------------------------===//
442 //===----------------------------------------------------------------------===//
444 const DIExpression::FragmentInfo
445 LiveDebugValues::DebugVariable::DefaultFragment = {
446 std::numeric_limits<uint64_t>::max(),
447 std::numeric_limits<uint64_t>::min()};
449 char LiveDebugValues::ID = 0;
451 char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
453 INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis",
456 /// Default construct and initialize the pass.
457 LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
458 initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
461 /// Tell the pass manager which passes we depend on and what information we
463 void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
464 AU.setPreservesCFG();
465 MachineFunctionPass::getAnalysisUsage(AU);
468 /// Erase a variable from the set of open ranges, and additionally erase any
469 /// fragments that may overlap it.
470 void LiveDebugValues::OpenRangesSet::erase(DebugVariable Var) {
472 auto DoErase = [this](DebugVariable VarToErase) {
473 auto It = Vars.find(VarToErase);
474 if (It != Vars.end()) {
475 unsigned ID = It->second;
481 // Erase the variable/fragment that ends here.
484 // Extract the fragment. Interpret an empty fragment as one that covers all
486 FragmentInfo ThisFragment = Var.getFragmentDefault();
488 // There may be fragments that overlap the designated fragment. Look them up
489 // in the pre-computed overlap map, and erase them too.
490 auto MapIt = OverlappingFragments.find({Var.getVar(), ThisFragment});
491 if (MapIt != OverlappingFragments.end()) {
492 for (auto Fragment : MapIt->second) {
493 LiveDebugValues::OptFragmentInfo FragmentHolder;
494 if (!DebugVariable::isFragmentDefault(Fragment))
495 FragmentHolder = LiveDebugValues::OptFragmentInfo(Fragment);
496 DoErase({Var.getVar(), FragmentHolder, Var.getInlinedAt()});
501 //===----------------------------------------------------------------------===//
502 // Debug Range Extension Implementation
503 //===----------------------------------------------------------------------===//
506 void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
507 const VarLocInMBB &V,
508 const VarLocMap &VarLocIDs,
510 raw_ostream &Out) const {
511 Out << '\n' << msg << '\n';
512 for (const MachineBasicBlock &BB : MF) {
513 const VarLocSet &L = V.lookup(&BB);
516 Out << "MBB: " << BB.getNumber() << ":\n";
517 for (unsigned VLL : L) {
518 const VarLoc &VL = VarLocIDs[VLL];
519 Out << " Var: " << VL.Var.getVar()->getName();
528 LiveDebugValues::VarLoc::SpillLoc
529 LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI) {
530 assert(MI.hasOneMemOperand() &&
531 "Spill instruction does not have exactly one memory operand?");
532 auto MMOI = MI.memoperands_begin();
533 const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
534 assert(PVal->kind() == PseudoSourceValue::FixedStack &&
535 "Inconsistent memory operand in spill instruction");
536 int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
537 const MachineBasicBlock *MBB = MI.getParent();
539 int Offset = TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
540 return {Reg, Offset};
543 /// End all previous ranges related to @MI and start a new range from @MI
544 /// if it is a DBG_VALUE instr.
545 void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
546 OpenRangesSet &OpenRanges,
547 VarLocMap &VarLocIDs) {
548 if (!MI.isDebugValue())
550 const DILocalVariable *Var = MI.getDebugVariable();
551 const DIExpression *Expr = MI.getDebugExpression();
552 const DILocation *DebugLoc = MI.getDebugLoc();
553 const DILocation *InlinedAt = DebugLoc->getInlinedAt();
554 assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
555 "Expected inlined-at fields to agree");
557 // End all previous ranges of Var.
558 DebugVariable V(Var, Expr, InlinedAt);
561 // Add the VarLoc to OpenRanges from this DBG_VALUE.
563 if (isDbgValueDescribedByReg(MI) || MI.getOperand(0).isImm() ||
564 MI.getOperand(0).isFPImm() || MI.getOperand(0).isCImm()) {
565 // Use normal VarLoc constructor for registers and immediates.
567 ID = VarLocIDs.insert(VL);
568 OpenRanges.insert(ID, VL.Var);
569 } else if (MI.hasOneMemOperand()) {
570 // It's a stack spill -- fetch spill base and offset.
571 VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI);
572 VarLoc VL(MI, SpillLocation.SpillBase, SpillLocation.SpillOffset, LS);
573 ID = VarLocIDs.insert(VL);
574 OpenRanges.insert(ID, VL.Var);
576 // This must be an undefined location. We should leave OpenRanges closed.
577 assert(MI.getOperand(0).isReg() && MI.getOperand(0).getReg() == 0 &&
578 "Unexpected non-undef DBG_VALUE encountered");
582 void LiveDebugValues::emitEntryValues(MachineInstr &MI,
583 OpenRangesSet &OpenRanges,
584 VarLocMap &VarLocIDs,
585 TransferMap &Transfers,
586 DebugParamMap &DebugEntryVals,
587 SparseBitVector<> &KillSet) {
588 MachineFunction *MF = MI.getParent()->getParent();
589 for (unsigned ID : KillSet) {
590 if (!VarLocIDs[ID].Var.getVar()->isParameter())
593 const MachineInstr *CurrDebugInstr = &VarLocIDs[ID].MI;
595 // If parameter's DBG_VALUE is not in the map that means we can't
596 // generate parameter's entry value.
597 if (!DebugEntryVals.count(CurrDebugInstr->getDebugVariable()))
600 auto ParamDebugInstr = DebugEntryVals[CurrDebugInstr->getDebugVariable()];
601 DIExpression *NewExpr = DIExpression::prepend(
602 ParamDebugInstr->getDebugExpression(), DIExpression::EntryValue);
603 MachineInstr *EntryValDbgMI =
604 BuildMI(*MF, ParamDebugInstr->getDebugLoc(), ParamDebugInstr->getDesc(),
605 ParamDebugInstr->isIndirectDebugValue(),
606 ParamDebugInstr->getOperand(0).getReg(),
607 ParamDebugInstr->getDebugVariable(), NewExpr);
609 if (ParamDebugInstr->isIndirectDebugValue())
610 EntryValDbgMI->getOperand(1).setImm(
611 ParamDebugInstr->getOperand(1).getImm());
613 Transfers.push_back({&MI, EntryValDbgMI});
614 VarLoc VL(*EntryValDbgMI, LS);
615 unsigned EntryValLocID = VarLocIDs.insert(VL);
616 OpenRanges.insert(EntryValLocID, VL.Var);
620 /// Create new TransferDebugPair and insert it in \p Transfers. The VarLoc
621 /// with \p OldVarID should be deleted form \p OpenRanges and replaced with
622 /// new VarLoc. If \p NewReg is different than default zero value then the
623 /// new location will be register location created by the copy like instruction,
624 /// otherwise it is variable's location on the stack.
625 void LiveDebugValues::insertTransferDebugPair(
626 MachineInstr &MI, OpenRangesSet &OpenRanges, TransferMap &Transfers,
627 VarLocMap &VarLocIDs, unsigned OldVarID, TransferKind Kind,
629 const MachineInstr *DebugInstr = &VarLocIDs[OldVarID].MI;
630 MachineFunction *MF = MI.getParent()->getParent();
631 MachineInstr *NewDebugInstr;
633 auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &DebugInstr,
634 &VarLocIDs](VarLoc &VL, MachineInstr *NewDebugInstr) {
635 unsigned LocId = VarLocIDs.insert(VL);
637 // Close this variable's previous location range.
638 DebugVariable V(*DebugInstr);
641 OpenRanges.insert(LocId, VL.Var);
642 // The newly created DBG_VALUE instruction NewDebugInstr must be inserted
643 // after MI. Keep track of the pairing.
644 TransferDebugPair MIP = {&MI, NewDebugInstr};
645 Transfers.push_back(MIP);
648 // End all previous ranges of Var.
649 OpenRanges.erase(VarLocIDs[OldVarID].Var);
651 case TransferKind::TransferCopy: {
653 "No register supplied when handling a copy of a debug value");
654 // Create a DBG_VALUE instruction to describe the Var in its new
655 // register location.
656 NewDebugInstr = BuildMI(
657 *MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(),
658 DebugInstr->isIndirectDebugValue(), NewReg,
659 DebugInstr->getDebugVariable(), DebugInstr->getDebugExpression());
660 if (DebugInstr->isIndirectDebugValue())
661 NewDebugInstr->getOperand(1).setImm(DebugInstr->getOperand(1).getImm());
662 VarLoc VL(*NewDebugInstr, LS);
663 ProcessVarLoc(VL, NewDebugInstr);
664 LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register copy: ";
665 NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
666 /*SkipOpers*/false, /*SkipDebugLoc*/false,
667 /*AddNewLine*/true, TII));
670 case TransferKind::TransferSpill: {
671 // Create a DBG_VALUE instruction to describe the Var in its spilled
673 VarLoc::SpillLoc SpillLocation = extractSpillBaseRegAndOffset(MI);
674 auto *SpillExpr = DIExpression::prepend(DebugInstr->getDebugExpression(),
675 DIExpression::ApplyOffset,
676 SpillLocation.SpillOffset);
677 NewDebugInstr = BuildMI(
678 *MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), true,
679 SpillLocation.SpillBase, DebugInstr->getDebugVariable(), SpillExpr);
680 VarLoc VL(*NewDebugInstr, SpillLocation.SpillBase,
681 SpillLocation.SpillOffset, LS);
682 ProcessVarLoc(VL, NewDebugInstr);
683 LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
684 NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
685 /*SkipOpers*/false, /*SkipDebugLoc*/false,
686 /*AddNewLine*/true, TII));
689 case TransferKind::TransferRestore: {
691 "No register supplied when handling a restore of a debug value");
692 MachineFunction *MF = MI.getMF();
693 DIBuilder DIB(*const_cast<Function &>(MF->getFunction()).getParent());
695 const DIExpression *NewExpr;
696 if (auto Fragment = DebugInstr->getDebugExpression()->getFragmentInfo())
697 NewExpr = *DIExpression::createFragmentExpression(DIB.createExpression(),
698 Fragment->OffsetInBits, Fragment->SizeInBits);
700 NewExpr = DIB.createExpression();
703 BuildMI(*MF, DebugInstr->getDebugLoc(), DebugInstr->getDesc(), false,
704 NewReg, DebugInstr->getDebugVariable(), NewExpr);
705 VarLoc VL(*NewDebugInstr, LS);
706 ProcessVarLoc(VL, NewDebugInstr);
707 LLVM_DEBUG(dbgs() << "Creating DBG_VALUE inst for register restore: ";
708 NewDebugInstr->print(dbgs(), /*IsStandalone*/false,
709 /*SkipOpers*/false, /*SkipDebugLoc*/false,
710 /*AddNewLine*/true, TII));
714 llvm_unreachable("Invalid transfer kind");
717 /// A definition of a register may mark the end of a range.
718 void LiveDebugValues::transferRegisterDef(
719 MachineInstr &MI, OpenRangesSet &OpenRanges, VarLocMap &VarLocIDs,
720 TransferMap &Transfers, DebugParamMap &DebugEntryVals) {
721 MachineFunction *MF = MI.getMF();
722 const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
723 unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
724 SparseBitVector<> KillSet;
725 for (const MachineOperand &MO : MI.operands()) {
726 // Determine whether the operand is a register def. Assume that call
727 // instructions never clobber SP, because some backends (e.g., AArch64)
728 // never list SP in the regmask.
729 if (MO.isReg() && MO.isDef() && MO.getReg() &&
730 TRI->isPhysicalRegister(MO.getReg()) &&
731 !(MI.isCall() && MO.getReg() == SP)) {
732 // Remove ranges of all aliased registers.
733 for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
734 for (unsigned ID : OpenRanges.getVarLocs())
735 if (VarLocIDs[ID].isDescribedByReg() == *RAI)
737 } else if (MO.isRegMask()) {
738 // Remove ranges of all clobbered registers. Register masks don't usually
739 // list SP as preserved. While the debug info may be off for an
740 // instruction or two around callee-cleanup calls, transferring the
741 // DEBUG_VALUE across the call is still a better user experience.
742 for (unsigned ID : OpenRanges.getVarLocs()) {
743 unsigned Reg = VarLocIDs[ID].isDescribedByReg();
744 if (Reg && Reg != SP && MO.clobbersPhysReg(Reg))
749 OpenRanges.erase(KillSet, VarLocIDs);
751 if (auto *TPC = getAnalysisIfAvailable<TargetPassConfig>()) {
752 auto &TM = TPC->getTM<TargetMachine>();
753 if (TM.Options.EnableDebugEntryValues)
754 emitEntryValues(MI, OpenRanges, VarLocIDs, Transfers, DebugEntryVals,
759 /// Decide if @MI is a spill instruction and return true if it is. We use 2
760 /// criteria to make this decision:
761 /// - Is this instruction a store to a spill slot?
762 /// - Is there a register operand that is both used and killed?
763 /// TODO: Store optimization can fold spills into other stores (including
764 /// other spills). We do not handle this yet (more than one memory operand).
765 bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
766 MachineFunction *MF, unsigned &Reg) {
767 SmallVector<const MachineMemOperand*, 1> Accesses;
769 // TODO: Handle multiple stores folded into one.
770 if (!MI.hasOneMemOperand())
773 if (!MI.getSpillSize(TII) && !MI.getFoldedSpillSize(TII))
774 return false; // This is not a spill instruction, since no valid size was
775 // returned from either function.
777 auto isKilledReg = [&](const MachineOperand MO, unsigned &Reg) {
778 if (!MO.isReg() || !MO.isUse()) {
786 for (const MachineOperand &MO : MI.operands()) {
787 // In a spill instruction generated by the InlineSpiller the spilled
788 // register has its kill flag set.
789 if (isKilledReg(MO, Reg))
792 // Check whether next instruction kills the spilled register.
793 // FIXME: Current solution does not cover search for killed register in
794 // bundles and instructions further down the chain.
795 auto NextI = std::next(MI.getIterator());
796 // Skip next instruction that points to basic block end iterator.
797 if (MI.getParent()->end() == NextI)
800 for (const MachineOperand &MONext : NextI->operands()) {
801 // Return true if we came across the register from the
802 // previous spill instruction that is killed in NextI.
803 if (isKilledReg(MONext, RegNext) && RegNext == Reg)
808 // Return false if we didn't find spilled register.
812 Optional<LiveDebugValues::VarLoc::SpillLoc>
813 LiveDebugValues::isRestoreInstruction(const MachineInstr &MI,
814 MachineFunction *MF, unsigned &Reg) {
815 if (!MI.hasOneMemOperand())
818 // FIXME: Handle folded restore instructions with more than one memory
820 if (MI.getRestoreSize(TII)) {
821 Reg = MI.getOperand(0).getReg();
822 return extractSpillBaseRegAndOffset(MI);
827 /// A spilled register may indicate that we have to end the current range of
828 /// a variable and create a new one for the spill location.
829 /// A restored register may indicate the reverse situation.
830 /// We don't want to insert any instructions in process(), so we just create
831 /// the DBG_VALUE without inserting it and keep track of it in \p Transfers.
832 /// It will be inserted into the BB when we're done iterating over the
834 void LiveDebugValues::transferSpillOrRestoreInst(MachineInstr &MI,
835 OpenRangesSet &OpenRanges,
836 VarLocMap &VarLocIDs,
837 TransferMap &Transfers) {
838 MachineFunction *MF = MI.getMF();
841 Optional<VarLoc::SpillLoc> Loc;
843 LLVM_DEBUG(dbgs() << "Examining instruction: "; MI.dump(););
845 if (isSpillInstruction(MI, MF, Reg)) {
846 TKind = TransferKind::TransferSpill;
847 LLVM_DEBUG(dbgs() << "Recognized as spill: "; MI.dump(););
848 LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
851 if (!(Loc = isRestoreInstruction(MI, MF, Reg)))
853 TKind = TransferKind::TransferRestore;
854 LLVM_DEBUG(dbgs() << "Recognized as restore: "; MI.dump(););
855 LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
858 // Check if the register or spill location is the location of a debug value.
859 // FIXME: Don't create a spill transfer if there is a complex expression,
860 // because we currently cannot recover the original expression on restore.
861 for (unsigned ID : OpenRanges.getVarLocs()) {
862 const MachineInstr *DebugInstr = &VarLocIDs[ID].MI;
864 if (TKind == TransferKind::TransferSpill &&
865 VarLocIDs[ID].isDescribedByReg() == Reg &&
866 !DebugInstr->getDebugExpression()->isComplex()) {
867 LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
868 << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
869 } else if (TKind == TransferKind::TransferRestore &&
870 VarLocIDs[ID].Loc.SpillLocation == *Loc) {
871 LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '('
872 << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
875 insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID, TKind,
881 /// If \p MI is a register copy instruction, that copies a previously tracked
882 /// value from one register to another register that is callee saved, we
883 /// create new DBG_VALUE instruction described with copy destination register.
884 void LiveDebugValues::transferRegisterCopy(MachineInstr &MI,
885 OpenRangesSet &OpenRanges,
886 VarLocMap &VarLocIDs,
887 TransferMap &Transfers) {
888 const MachineOperand *SrcRegOp, *DestRegOp;
890 if (!TII->isCopyInstr(MI, SrcRegOp, DestRegOp) || !SrcRegOp->isKill() ||
894 auto isCalleSavedReg = [&](unsigned Reg) {
895 for (MCRegAliasIterator RAI(Reg, TRI, true); RAI.isValid(); ++RAI)
896 if (CalleeSavedRegs.test(*RAI))
901 unsigned SrcReg = SrcRegOp->getReg();
902 unsigned DestReg = DestRegOp->getReg();
904 // We want to recognize instructions where destination register is callee
905 // saved register. If register that could be clobbered by the call is
906 // included, there would be a great chance that it is going to be clobbered
907 // soon. It is more likely that previous register location, which is callee
908 // saved, is going to stay unclobbered longer, even if it is killed.
909 if (!isCalleSavedReg(DestReg))
912 for (unsigned ID : OpenRanges.getVarLocs()) {
913 if (VarLocIDs[ID].isDescribedByReg() == SrcReg) {
914 insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID,
915 TransferKind::TransferCopy, DestReg);
921 /// Terminate all open ranges at the end of the current basic block.
922 bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
923 OpenRangesSet &OpenRanges,
924 VarLocInMBB &OutLocs,
925 const VarLocMap &VarLocIDs) {
926 bool Changed = false;
927 const MachineBasicBlock *CurMBB = MI.getParent();
928 if (!(MI.isTerminator() || (&MI == &CurMBB->back())))
931 if (OpenRanges.empty())
934 LLVM_DEBUG(for (unsigned ID
935 : OpenRanges.getVarLocs()) {
936 // Copy OpenRanges to OutLocs, if not already present.
937 dbgs() << "Add to OutLocs in MBB #" << CurMBB->getNumber() << ": ";
938 VarLocIDs[ID].dump();
940 VarLocSet &VLS = OutLocs[CurMBB];
941 Changed = VLS |= OpenRanges.getVarLocs();
942 // New OutLocs set may be different due to spill, restore or register
943 // copy instruction processing.
945 VLS = OpenRanges.getVarLocs();
950 /// Accumulate a mapping between each DILocalVariable fragment and other
951 /// fragments of that DILocalVariable which overlap. This reduces work during
952 /// the data-flow stage from "Find any overlapping fragments" to "Check if the
953 /// known-to-overlap fragments are present".
954 /// \param MI A previously unprocessed DEBUG_VALUE instruction to analyze for
956 /// \param SeenFragments Map from DILocalVariable to all fragments of that
957 /// Variable which are known to exist.
958 /// \param OverlappingFragments The overlap map being constructed, from one
959 /// Var/Fragment pair to a vector of fragments known to overlap.
960 void LiveDebugValues::accumulateFragmentMap(MachineInstr &MI,
961 VarToFragments &SeenFragments,
962 OverlapMap &OverlappingFragments) {
963 DebugVariable MIVar(MI);
964 FragmentInfo ThisFragment = MIVar.getFragmentDefault();
966 // If this is the first sighting of this variable, then we are guaranteed
967 // there are currently no overlapping fragments either. Initialize the set
968 // of seen fragments, record no overlaps for the current one, and return.
969 auto SeenIt = SeenFragments.find(MIVar.getVar());
970 if (SeenIt == SeenFragments.end()) {
971 SmallSet<FragmentInfo, 4> OneFragment;
972 OneFragment.insert(ThisFragment);
973 SeenFragments.insert({MIVar.getVar(), OneFragment});
975 OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}});
979 // If this particular Variable/Fragment pair already exists in the overlap
980 // map, it has already been accounted for.
982 OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}});
983 if (!IsInOLapMap.second)
986 auto &ThisFragmentsOverlaps = IsInOLapMap.first->second;
987 auto &AllSeenFragments = SeenIt->second;
989 // Otherwise, examine all other seen fragments for this variable, with "this"
990 // fragment being a previously unseen fragment. Record any pair of
991 // overlapping fragments.
992 for (auto &ASeenFragment : AllSeenFragments) {
993 // Does this previously seen fragment overlap?
994 if (DIExpression::fragmentsOverlap(ThisFragment, ASeenFragment)) {
995 // Yes: Mark the current fragment as being overlapped.
996 ThisFragmentsOverlaps.push_back(ASeenFragment);
997 // Mark the previously seen fragment as being overlapped by the current
999 auto ASeenFragmentsOverlaps =
1000 OverlappingFragments.find({MIVar.getVar(), ASeenFragment});
1001 assert(ASeenFragmentsOverlaps != OverlappingFragments.end() &&
1002 "Previously seen var fragment has no vector of overlaps");
1003 ASeenFragmentsOverlaps->second.push_back(ThisFragment);
1007 AllSeenFragments.insert(ThisFragment);
1010 /// This routine creates OpenRanges and OutLocs.
1011 bool LiveDebugValues::process(MachineInstr &MI, OpenRangesSet &OpenRanges,
1012 VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
1013 TransferMap &Transfers, DebugParamMap &DebugEntryVals,
1014 bool transferChanges,
1015 OverlapMap &OverlapFragments,
1016 VarToFragments &SeenFragments) {
1017 bool Changed = false;
1018 transferDebugValue(MI, OpenRanges, VarLocIDs);
1019 transferRegisterDef(MI, OpenRanges, VarLocIDs, Transfers,
1021 if (transferChanges) {
1022 transferRegisterCopy(MI, OpenRanges, VarLocIDs, Transfers);
1023 transferSpillOrRestoreInst(MI, OpenRanges, VarLocIDs, Transfers);
1025 // Build up a map of overlapping fragments on the first run through.
1026 if (MI.isDebugValue())
1027 accumulateFragmentMap(MI, SeenFragments, OverlapFragments);
1029 Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
1033 /// This routine joins the analysis results of all incoming edges in @MBB by
1034 /// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
1035 /// source variable in all the predecessors of @MBB reside in the same location.
1036 bool LiveDebugValues::join(
1037 MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
1038 const VarLocMap &VarLocIDs,
1039 SmallPtrSet<const MachineBasicBlock *, 16> &Visited,
1040 SmallPtrSetImpl<const MachineBasicBlock *> &ArtificialBlocks) {
1041 LLVM_DEBUG(dbgs() << "join MBB: " << MBB.getNumber() << "\n");
1042 bool Changed = false;
1044 VarLocSet InLocsT; // Temporary incoming locations.
1046 // For all predecessors of this MBB, find the set of VarLocs that
1049 for (auto p : MBB.predecessors()) {
1050 // Ignore unvisited predecessor blocks. As we are processing
1051 // the blocks in reverse post-order any unvisited block can
1052 // be considered to not remove any incoming values.
1053 if (!Visited.count(p)) {
1054 LLVM_DEBUG(dbgs() << " ignoring unvisited pred MBB: " << p->getNumber()
1058 auto OL = OutLocs.find(p);
1059 // Join is null in case of empty OutLocs from any of the pred.
1060 if (OL == OutLocs.end())
1063 // Just copy over the Out locs to incoming locs for the first visited
1064 // predecessor, and for all other predecessors join the Out locs.
1066 InLocsT = OL->second;
1068 InLocsT &= OL->second;
1071 if (!InLocsT.empty()) {
1072 for (auto ID : InLocsT)
1073 dbgs() << " gathered candidate incoming var: "
1074 << VarLocIDs[ID].Var.getVar()->getName() << "\n";
1081 // Filter out DBG_VALUES that are out of scope.
1083 bool IsArtificial = ArtificialBlocks.count(&MBB);
1084 if (!IsArtificial) {
1085 for (auto ID : InLocsT) {
1086 if (!VarLocIDs[ID].dominates(MBB)) {
1089 auto Name = VarLocIDs[ID].Var.getVar()->getName();
1090 dbgs() << " killing " << Name << ", it doesn't dominate MBB\n";
1095 InLocsT.intersectWithComplement(KillSet);
1097 // As we are processing blocks in reverse post-order we
1098 // should have processed at least one predecessor, unless it
1099 // is the entry block which has no predecessor.
1100 assert((NumVisited || MBB.pred_empty()) &&
1101 "Should have processed at least one predecessor");
1102 if (InLocsT.empty())
1105 VarLocSet &ILS = InLocs[&MBB];
1107 // Insert DBG_VALUE instructions, if not already inserted.
1108 VarLocSet Diff = InLocsT;
1109 Diff.intersectWithComplement(ILS);
1110 for (auto ID : Diff) {
1111 // This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
1112 // new range is started for the var from the mbb's beginning by inserting
1113 // a new DBG_VALUE. process() will end this range however appropriate.
1114 const VarLoc &DiffIt = VarLocIDs[ID];
1115 const MachineInstr *DebugInstr = &DiffIt.MI;
1116 MachineInstr *MI = nullptr;
1117 if (DiffIt.isConstant()) {
1118 MachineOperand MO(DebugInstr->getOperand(0));
1119 MI = BuildMI(MBB, MBB.instr_begin(), DebugInstr->getDebugLoc(),
1120 DebugInstr->getDesc(), false, MO,
1121 DebugInstr->getDebugVariable(),
1122 DebugInstr->getDebugExpression());
1124 MI = BuildMI(MBB, MBB.instr_begin(), DebugInstr->getDebugLoc(),
1125 DebugInstr->getDesc(), DebugInstr->isIndirectDebugValue(),
1126 DebugInstr->getOperand(0).getReg(),
1127 DebugInstr->getDebugVariable(),
1128 DebugInstr->getDebugExpression());
1129 if (DebugInstr->isIndirectDebugValue())
1130 MI->getOperand(1).setImm(DebugInstr->getOperand(1).getImm());
1132 LLVM_DEBUG(dbgs() << "Inserted: "; MI->dump(););
1140 /// Calculate the liveness information for the given machine function and
1141 /// extend ranges across basic blocks.
1142 bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
1143 LLVM_DEBUG(dbgs() << "\nDebug Range Extension\n");
1145 bool Changed = false;
1146 bool OLChanged = false;
1147 bool MBBJoined = false;
1149 VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors.
1150 OverlapMap OverlapFragments; // Map of overlapping variable fragments
1151 OpenRangesSet OpenRanges(OverlapFragments);
1152 // Ranges that are open until end of bb.
1153 VarLocInMBB OutLocs; // Ranges that exist beyond bb.
1154 VarLocInMBB InLocs; // Ranges that are incoming after joining.
1155 TransferMap Transfers; // DBG_VALUEs associated with spills.
1157 VarToFragments SeenFragments;
1159 // Blocks which are artificial, i.e. blocks which exclusively contain
1160 // instructions without locations, or with line 0 locations.
1161 SmallPtrSet<const MachineBasicBlock *, 16> ArtificialBlocks;
1163 DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
1164 DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
1165 std::priority_queue<unsigned int, std::vector<unsigned int>,
1166 std::greater<unsigned int>>
1168 std::priority_queue<unsigned int, std::vector<unsigned int>,
1169 std::greater<unsigned int>>
1172 enum : bool { dontTransferChanges = false, transferChanges = true };
1174 // Besides parameter's modification, check whether a DBG_VALUE is inlined
1175 // in order to deduce whether the variable that it tracks comes from
1176 // a different function. If that is the case we can't track its entry value.
1177 auto IsUnmodifiedFuncParam = [&](const MachineInstr &MI) {
1178 auto *DIVar = MI.getDebugVariable();
1179 return DIVar->isParameter() && DIVar->isNotModified() &&
1180 !MI.getDebugLoc()->getInlinedAt();
1183 const TargetLowering *TLI = MF.getSubtarget().getTargetLowering();
1184 unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
1185 unsigned FP = TRI->getFrameRegister(MF);
1186 auto IsRegOtherThanSPAndFP = [&](const MachineOperand &Op) -> bool {
1187 return Op.isReg() && Op.getReg() != SP && Op.getReg() != FP;
1190 // Working set of currently collected debug variables mapped to DBG_VALUEs
1191 // representing candidates for production of debug entry values.
1192 DebugParamMap DebugEntryVals;
1194 MachineBasicBlock &First_MBB = *(MF.begin());
1195 // Only in the case of entry MBB collect DBG_VALUEs representing
1196 // function parameters in order to generate debug entry values for them.
1197 // Currently, we generate debug entry values only for parameters that are
1198 // unmodified throughout the function and located in a register.
1199 // TODO: Add support for parameters that are described as fragments.
1200 // TODO: Add support for modified arguments that can be expressed
1201 // by using its entry value.
1202 // TODO: Add support for local variables that are expressed in terms of
1203 // parameters entry values.
1204 for (auto &MI : First_MBB)
1205 if (MI.isDebugValue() && IsUnmodifiedFuncParam(MI) &&
1206 !MI.isIndirectDebugValue() && IsRegOtherThanSPAndFP(MI.getOperand(0)) &&
1207 !DebugEntryVals.count(MI.getDebugVariable()) &&
1208 !MI.getDebugExpression()->isFragment())
1209 DebugEntryVals[MI.getDebugVariable()] = &MI;
1211 // Initialize every mbb with OutLocs.
1212 // We are not looking at any spill instructions during the initial pass
1213 // over the BBs. The LiveDebugVariables pass has already created DBG_VALUE
1214 // instructions for spills of registers that are known to be user variables
1215 // within the BB in which the spill occurs.
1216 for (auto &MBB : MF) {
1217 for (auto &MI : MBB) {
1218 process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers, DebugEntryVals,
1219 dontTransferChanges, OverlapFragments, SeenFragments);
1221 // Add any entry DBG_VALUE instructions necessitated by parameter
1223 for (auto &TR : Transfers) {
1224 MBB.insertAfter(MachineBasicBlock::iterator(*TR.TransferInst),
1230 auto hasNonArtificialLocation = [](const MachineInstr &MI) -> bool {
1231 if (const DebugLoc &DL = MI.getDebugLoc())
1232 return DL.getLine() != 0;
1235 for (auto &MBB : MF)
1236 if (none_of(MBB.instrs(), hasNonArtificialLocation))
1237 ArtificialBlocks.insert(&MBB);
1239 LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
1240 "OutLocs after initialization", dbgs()));
1242 ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
1243 unsigned int RPONumber = 0;
1244 for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) {
1245 OrderToBB[RPONumber] = *RI;
1246 BBToOrder[*RI] = RPONumber;
1247 Worklist.push(RPONumber);
1250 // This is a standard "union of predecessor outs" dataflow problem.
1251 // To solve it, we perform join() and process() using the two worklist method
1252 // until the ranges converge.
1253 // Ranges have converged when both worklists are empty.
1254 SmallPtrSet<const MachineBasicBlock *, 16> Visited;
1255 while (!Worklist.empty() || !Pending.empty()) {
1256 // We track what is on the pending worklist to avoid inserting the same
1257 // thing twice. We could avoid this with a custom priority queue, but this
1258 // is probably not worth it.
1259 SmallPtrSet<MachineBasicBlock *, 16> OnPending;
1260 LLVM_DEBUG(dbgs() << "Processing Worklist\n");
1261 while (!Worklist.empty()) {
1262 MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
1265 join(*MBB, OutLocs, InLocs, VarLocIDs, Visited, ArtificialBlocks);
1266 Visited.insert(MBB);
1270 // Now that we have started to extend ranges across BBs we need to
1271 // examine spill instructions to see whether they spill registers that
1272 // correspond to user variables.
1273 for (auto &MI : *MBB)
1275 process(MI, OpenRanges, OutLocs, VarLocIDs, Transfers,
1276 DebugEntryVals, transferChanges, OverlapFragments,
1279 // Add any DBG_VALUE instructions necessitated by spills.
1280 for (auto &TR : Transfers)
1281 MBB->insertAfter(MachineBasicBlock::iterator(*TR.TransferInst),
1285 LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
1286 "OutLocs after propagating", dbgs()));
1287 LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
1288 "InLocs after propagating", dbgs()));
1292 for (auto s : MBB->successors())
1293 if (OnPending.insert(s).second) {
1294 Pending.push(BBToOrder[s]);
1299 Worklist.swap(Pending);
1300 // At this point, pending must be empty, since it was just the empty
1302 assert(Pending.empty() && "Pending should be empty");
1305 LLVM_DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
1306 LLVM_DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
1310 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
1311 if (!MF.getFunction().getSubprogram())
1312 // LiveDebugValues will already have removed all DBG_VALUEs.
1315 // Skip functions from NoDebug compilation units.
1316 if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
1317 DICompileUnit::NoDebug)
1320 TRI = MF.getSubtarget().getRegisterInfo();
1321 TII = MF.getSubtarget().getInstrInfo();
1322 TFI = MF.getSubtarget().getFrameLowering();
1323 TFI->determineCalleeSaves(MF, CalleeSavedRegs,
1324 make_unique<RegScavenger>().get());
1327 bool Changed = ExtendRanges(MF);