1 //===- LiveDebugValues.cpp - Tracking Debug Value MIs ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// This pass implements a data flow analysis that propagates debug location
11 /// information by inserting additional DBG_VALUE instructions into the machine
12 /// instruction stream. The pass internally builds debug location liveness
13 /// ranges to determine the points where additional DBG_VALUEs need to be
16 /// This is a separate pass from DbgValueHistoryCalculator to facilitate
17 /// testing and improve modularity.
19 //===----------------------------------------------------------------------===//
21 #include "llvm/ADT/DenseMap.h"
22 #include "llvm/ADT/PostOrderIterator.h"
23 #include "llvm/ADT/SmallPtrSet.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/TargetFrameLowering.h"
39 #include "llvm/CodeGen/TargetInstrInfo.h"
40 #include "llvm/CodeGen/TargetLowering.h"
41 #include "llvm/CodeGen/TargetRegisterInfo.h"
42 #include "llvm/CodeGen/TargetSubtargetInfo.h"
43 #include "llvm/IR/DebugInfoMetadata.h"
44 #include "llvm/IR/DebugLoc.h"
45 #include "llvm/IR/Function.h"
46 #include "llvm/IR/Module.h"
47 #include "llvm/MC/MCRegisterInfo.h"
48 #include "llvm/Pass.h"
49 #include "llvm/Support/Casting.h"
50 #include "llvm/Support/Compiler.h"
51 #include "llvm/Support/Debug.h"
52 #include "llvm/Support/raw_ostream.h"
63 #define DEBUG_TYPE "livedebugvalues"
65 STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted");
67 // \brief If @MI is a DBG_VALUE with debug value described by a defined
68 // register, returns the number of this register. In the other case, returns 0.
69 static unsigned isDbgValueDescribedByReg(const MachineInstr &MI) {
70 assert(MI.isDebugValue() && "expected a DBG_VALUE");
71 assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
72 // If location of variable is described using a register (directly
73 // or indirectly), this register is always a first operand.
74 return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0;
79 class LiveDebugValues : public MachineFunctionPass {
81 const TargetRegisterInfo *TRI;
82 const TargetInstrInfo *TII;
83 const TargetFrameLowering *TFI;
86 /// Keeps track of lexical scopes associated with a user value's source
88 class UserValueScopes {
91 SmallPtrSet<const MachineBasicBlock *, 4> LBlocks;
94 UserValueScopes(DebugLoc D, LexicalScopes &L) : DL(std::move(D)), LS(L) {}
96 /// Return true if current scope dominates at least one machine
97 /// instruction in a given machine basic block.
98 bool dominates(MachineBasicBlock *MBB) {
100 LS.getMachineBasicBlocks(DL, LBlocks);
101 return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB);
105 /// Based on std::pair so it can be used as an index into a DenseMap.
106 using DebugVariableBase =
107 std::pair<const DILocalVariable *, const DILocation *>;
108 /// A potentially inlined instance of a variable.
109 struct DebugVariable : public DebugVariableBase {
110 DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt)
111 : DebugVariableBase(Var, InlinedAt) {}
113 const DILocalVariable *getVar() const { return this->first; }
114 const DILocation *getInlinedAt() const { return this->second; }
116 bool operator<(const DebugVariable &DV) const {
117 if (getVar() == DV.getVar())
118 return getInlinedAt() < DV.getInlinedAt();
119 return getVar() < DV.getVar();
123 /// A pair of debug variable and value location.
125 const DebugVariable Var;
126 const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE.
127 mutable UserValueScopes UVS;
128 enum { InvalidKind = 0, RegisterKind } Kind = InvalidKind;
130 /// The value location. Stored separately to avoid repeatedly
131 /// extracting it from MI.
137 VarLoc(const MachineInstr &MI, LexicalScopes &LS)
138 : Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI),
139 UVS(MI.getDebugLoc(), LS) {
140 static_assert((sizeof(Loc) == sizeof(uint64_t)),
141 "hash does not cover all members of Loc");
142 assert(MI.isDebugValue() && "not a DBG_VALUE");
143 assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
144 if (int RegNo = isDbgValueDescribedByReg(MI)) {
150 /// If this variable is described by a register, return it,
151 /// otherwise return 0.
152 unsigned isDescribedByReg() const {
153 if (Kind == RegisterKind)
158 /// Determine whether the lexical scope of this value's debug location
160 bool dominates(MachineBasicBlock &MBB) const { return UVS.dominates(&MBB); }
162 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
163 LLVM_DUMP_METHOD void dump() const { MI.dump(); }
166 bool operator==(const VarLoc &Other) const {
167 return Var == Other.Var && Loc.Hash == Other.Loc.Hash;
170 /// This operator guarantees that VarLocs are sorted by Variable first.
171 bool operator<(const VarLoc &Other) const {
172 if (Var == Other.Var)
173 return Loc.Hash < Other.Loc.Hash;
174 return Var < Other.Var;
178 using VarLocMap = UniqueVector<VarLoc>;
179 using VarLocSet = SparseBitVector<>;
180 using VarLocInMBB = SmallDenseMap<const MachineBasicBlock *, VarLocSet>;
181 struct SpillDebugPair {
182 MachineInstr *SpillInst;
183 MachineInstr *DebugInst;
185 using SpillMap = SmallVector<SpillDebugPair, 4>;
187 /// This holds the working set of currently open ranges. For fast
188 /// access, this is done both as a set of VarLocIDs, and a map of
189 /// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all
190 /// previous open ranges for the same variable.
191 class OpenRangesSet {
193 SmallDenseMap<DebugVariableBase, unsigned, 8> Vars;
196 const VarLocSet &getVarLocs() const { return VarLocs; }
198 /// Terminate all open ranges for Var by removing it from the set.
199 void erase(DebugVariable Var) {
200 auto It = Vars.find(Var);
201 if (It != Vars.end()) {
202 unsigned ID = It->second;
208 /// Terminate all open ranges listed in \c KillSet by removing
209 /// them from the set.
210 void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) {
211 VarLocs.intersectWithComplement(KillSet);
212 for (unsigned ID : KillSet)
213 Vars.erase(VarLocIDs[ID].Var);
216 /// Insert a new range into the set.
217 void insert(unsigned VarLocID, DebugVariableBase Var) {
218 VarLocs.set(VarLocID);
219 Vars.insert({Var, VarLocID});
228 /// Return whether the set is empty or not.
230 assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent");
231 return VarLocs.empty();
235 bool isSpillInstruction(const MachineInstr &MI, MachineFunction *MF,
237 int extractSpillBaseRegAndOffset(const MachineInstr &MI, unsigned &Reg);
239 void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges,
240 VarLocMap &VarLocIDs);
241 void transferSpillInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
242 VarLocMap &VarLocIDs, SpillMap &Spills);
243 void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges,
244 const VarLocMap &VarLocIDs);
245 bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges,
246 VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs);
247 bool transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
248 VarLocInMBB &OutLocs, VarLocMap &VarLocIDs, SpillMap &Spills,
249 bool transferSpills);
251 bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs,
252 const VarLocMap &VarLocIDs,
253 SmallPtrSet<const MachineBasicBlock *, 16> &Visited);
255 bool ExtendRanges(MachineFunction &MF);
260 /// Default construct and initialize the pass.
263 /// Tell the pass manager which passes we depend on and what
264 /// information we preserve.
265 void getAnalysisUsage(AnalysisUsage &AU) const override;
267 MachineFunctionProperties getRequiredProperties() const override {
268 return MachineFunctionProperties().set(
269 MachineFunctionProperties::Property::NoVRegs);
272 /// Print to ostream with a message.
273 void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
274 const VarLocMap &VarLocIDs, const char *msg,
275 raw_ostream &Out) const;
277 /// Calculate the liveness information for the given machine function.
278 bool runOnMachineFunction(MachineFunction &MF) override;
281 } // end anonymous namespace
283 //===----------------------------------------------------------------------===//
285 //===----------------------------------------------------------------------===//
287 char LiveDebugValues::ID = 0;
289 char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
291 INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis",
294 /// Default construct and initialize the pass.
295 LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
296 initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry());
299 /// Tell the pass manager which passes we depend on and what information we
301 void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const {
302 AU.setPreservesCFG();
303 MachineFunctionPass::getAnalysisUsage(AU);
306 //===----------------------------------------------------------------------===//
307 // Debug Range Extension Implementation
308 //===----------------------------------------------------------------------===//
311 void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
312 const VarLocInMBB &V,
313 const VarLocMap &VarLocIDs,
315 raw_ostream &Out) const {
316 Out << '\n' << msg << '\n';
317 for (const MachineBasicBlock &BB : MF) {
318 const auto &L = V.lookup(&BB);
319 Out << "MBB: " << BB.getName() << ":\n";
320 for (unsigned VLL : L) {
321 const VarLoc &VL = VarLocIDs[VLL];
322 Out << " Var: " << VL.Var.getVar()->getName();
331 /// Given a spill instruction, extract the register and offset used to
332 /// address the spill location in a target independent way.
333 int LiveDebugValues::extractSpillBaseRegAndOffset(const MachineInstr &MI,
335 assert(MI.hasOneMemOperand() &&
336 "Spill instruction does not have exactly one memory operand?");
337 auto MMOI = MI.memoperands_begin();
338 const PseudoSourceValue *PVal = (*MMOI)->getPseudoValue();
339 assert(PVal->kind() == PseudoSourceValue::FixedStack &&
340 "Inconsistent memory operand in spill instruction");
341 int FI = cast<FixedStackPseudoSourceValue>(PVal)->getFrameIndex();
342 const MachineBasicBlock *MBB = MI.getParent();
343 return TFI->getFrameIndexReference(*MBB->getParent(), FI, Reg);
346 /// End all previous ranges related to @MI and start a new range from @MI
347 /// if it is a DBG_VALUE instr.
348 void LiveDebugValues::transferDebugValue(const MachineInstr &MI,
349 OpenRangesSet &OpenRanges,
350 VarLocMap &VarLocIDs) {
351 if (!MI.isDebugValue())
353 const DILocalVariable *Var = MI.getDebugVariable();
354 const DILocation *DebugLoc = MI.getDebugLoc();
355 const DILocation *InlinedAt = DebugLoc->getInlinedAt();
356 assert(Var->isValidLocationForIntrinsic(DebugLoc) &&
357 "Expected inlined-at fields to agree");
359 // End all previous ranges of Var.
360 DebugVariable V(Var, InlinedAt);
363 // Add the VarLoc to OpenRanges from this DBG_VALUE.
364 // TODO: Currently handles DBG_VALUE which has only reg as location.
365 if (isDbgValueDescribedByReg(MI)) {
367 unsigned ID = VarLocIDs.insert(VL);
368 OpenRanges.insert(ID, VL.Var);
372 /// A definition of a register may mark the end of a range.
373 void LiveDebugValues::transferRegisterDef(MachineInstr &MI,
374 OpenRangesSet &OpenRanges,
375 const VarLocMap &VarLocIDs) {
376 MachineFunction *MF = MI.getMF();
377 const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
378 unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
379 SparseBitVector<> KillSet;
380 for (const MachineOperand &MO : MI.operands()) {
381 // Determine whether the operand is a register def. Assume that call
382 // instructions never clobber SP, because some backends (e.g., AArch64)
383 // never list SP in the regmask.
384 if (MO.isReg() && MO.isDef() && MO.getReg() &&
385 TRI->isPhysicalRegister(MO.getReg()) &&
386 !(MI.isCall() && MO.getReg() == SP)) {
387 // Remove ranges of all aliased registers.
388 for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI)
389 for (unsigned ID : OpenRanges.getVarLocs())
390 if (VarLocIDs[ID].isDescribedByReg() == *RAI)
392 } else if (MO.isRegMask()) {
393 // Remove ranges of all clobbered registers. Register masks don't usually
394 // list SP as preserved. While the debug info may be off for an
395 // instruction or two around callee-cleanup calls, transferring the
396 // DEBUG_VALUE across the call is still a better user experience.
397 for (unsigned ID : OpenRanges.getVarLocs()) {
398 unsigned Reg = VarLocIDs[ID].isDescribedByReg();
399 if (Reg && Reg != SP && MO.clobbersPhysReg(Reg))
404 OpenRanges.erase(KillSet, VarLocIDs);
407 /// Decide if @MI is a spill instruction and return true if it is. We use 2
408 /// criteria to make this decision:
409 /// - Is this instruction a store to a spill slot?
410 /// - Is there a register operand that is both used and killed?
411 /// TODO: Store optimization can fold spills into other stores (including
412 /// other spills). We do not handle this yet (more than one memory operand).
413 bool LiveDebugValues::isSpillInstruction(const MachineInstr &MI,
414 MachineFunction *MF, unsigned &Reg) {
415 const MachineFrameInfo &FrameInfo = MF->getFrameInfo();
417 const MachineMemOperand *MMO;
419 // TODO: Handle multiple stores folded into one.
420 if (!MI.hasOneMemOperand())
423 // To identify a spill instruction, use the same criteria as in AsmPrinter.
424 if (!((TII->isStoreToStackSlotPostFE(MI, FI) ||
425 TII->hasStoreToStackSlot(MI, MMO, FI)) &&
426 FrameInfo.isSpillSlotObjectIndex(FI)))
429 // In a spill instruction generated by the InlineSpiller the spilled register
430 // has its kill flag set. Return false if we don't find such a register.
432 for (const MachineOperand &MO : MI.operands()) {
433 if (MO.isReg() && MO.isUse() && MO.isKill()) {
441 /// A spilled register may indicate that we have to end the current range of
442 /// a variable and create a new one for the spill location.
443 /// We don't want to insert any instructions in transfer(), so we just create
444 /// the DBG_VALUE witout inserting it and keep track of it in @Spills.
445 /// It will be inserted into the BB when we're done iterating over the
447 void LiveDebugValues::transferSpillInst(MachineInstr &MI,
448 OpenRangesSet &OpenRanges,
449 VarLocMap &VarLocIDs,
452 MachineFunction *MF = MI.getMF();
453 if (!isSpillInstruction(MI, MF, Reg))
456 // Check if the register is the location of a debug value.
457 for (unsigned ID : OpenRanges.getVarLocs()) {
458 if (VarLocIDs[ID].isDescribedByReg() == Reg) {
459 DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
460 << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
462 // Create a DBG_VALUE instruction to describe the Var in its spilled
463 // location, but don't insert it yet to avoid invalidating the
464 // iterator in our caller.
466 int SpillOffset = extractSpillBaseRegAndOffset(MI, SpillBase);
467 const MachineInstr *DMI = &VarLocIDs[ID].MI;
468 auto *SpillExpr = DIExpression::prepend(
469 DMI->getDebugExpression(), DIExpression::NoDeref, SpillOffset);
470 MachineInstr *SpDMI =
471 BuildMI(*MF, DMI->getDebugLoc(), DMI->getDesc(), true, SpillBase,
472 DMI->getDebugVariable(), SpillExpr);
473 DEBUG(dbgs() << "Creating DBG_VALUE inst for spill: ";
474 SpDMI->print(dbgs(), false, TII));
476 // The newly created DBG_VALUE instruction SpDMI must be inserted after
477 // MI. Keep track of the pairing.
478 SpillDebugPair MIP = {&MI, SpDMI};
479 Spills.push_back(MIP);
481 // End all previous ranges of Var.
482 OpenRanges.erase(VarLocIDs[ID].Var);
484 // Add the VarLoc to OpenRanges.
485 VarLoc VL(*SpDMI, LS);
486 unsigned SpillLocID = VarLocIDs.insert(VL);
487 OpenRanges.insert(SpillLocID, VL.Var);
493 /// Terminate all open ranges at the end of the current basic block.
494 bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI,
495 OpenRangesSet &OpenRanges,
496 VarLocInMBB &OutLocs,
497 const VarLocMap &VarLocIDs) {
498 bool Changed = false;
499 const MachineBasicBlock *CurMBB = MI.getParent();
500 if (!(MI.isTerminator() || (&MI == &CurMBB->instr_back())))
503 if (OpenRanges.empty())
506 DEBUG(for (unsigned ID : OpenRanges.getVarLocs()) {
507 // Copy OpenRanges to OutLocs, if not already present.
508 dbgs() << "Add to OutLocs: "; VarLocIDs[ID].dump();
510 VarLocSet &VLS = OutLocs[CurMBB];
511 Changed = VLS |= OpenRanges.getVarLocs();
516 /// This routine creates OpenRanges and OutLocs.
517 bool LiveDebugValues::transfer(MachineInstr &MI, OpenRangesSet &OpenRanges,
518 VarLocInMBB &OutLocs, VarLocMap &VarLocIDs,
519 SpillMap &Spills, bool transferSpills) {
520 bool Changed = false;
521 transferDebugValue(MI, OpenRanges, VarLocIDs);
522 transferRegisterDef(MI, OpenRanges, VarLocIDs);
524 transferSpillInst(MI, OpenRanges, VarLocIDs, Spills);
525 Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs);
529 /// This routine joins the analysis results of all incoming edges in @MBB by
530 /// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same
531 /// source variable in all the predecessors of @MBB reside in the same location.
532 bool LiveDebugValues::join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs,
533 VarLocInMBB &InLocs, const VarLocMap &VarLocIDs,
534 SmallPtrSet<const MachineBasicBlock *, 16> &Visited) {
535 DEBUG(dbgs() << "join MBB: " << MBB.getName() << "\n");
536 bool Changed = false;
538 VarLocSet InLocsT; // Temporary incoming locations.
540 // For all predecessors of this MBB, find the set of VarLocs that
543 for (auto p : MBB.predecessors()) {
544 // Ignore unvisited predecessor blocks. As we are processing
545 // the blocks in reverse post-order any unvisited block can
546 // be considered to not remove any incoming values.
547 if (!Visited.count(p))
549 auto OL = OutLocs.find(p);
550 // Join is null in case of empty OutLocs from any of the pred.
551 if (OL == OutLocs.end())
554 // Just copy over the Out locs to incoming locs for the first visited
555 // predecessor, and for all other predecessors join the Out locs.
557 InLocsT = OL->second;
559 InLocsT &= OL->second;
563 // Filter out DBG_VALUES that are out of scope.
565 for (auto ID : InLocsT)
566 if (!VarLocIDs[ID].dominates(MBB))
568 InLocsT.intersectWithComplement(KillSet);
570 // As we are processing blocks in reverse post-order we
571 // should have processed at least one predecessor, unless it
572 // is the entry block which has no predecessor.
573 assert((NumVisited || MBB.pred_empty()) &&
574 "Should have processed at least one predecessor");
578 VarLocSet &ILS = InLocs[&MBB];
580 // Insert DBG_VALUE instructions, if not already inserted.
581 VarLocSet Diff = InLocsT;
582 Diff.intersectWithComplement(ILS);
583 for (auto ID : Diff) {
584 // This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a
585 // new range is started for the var from the mbb's beginning by inserting
586 // a new DBG_VALUE. transfer() will end this range however appropriate.
587 const VarLoc &DiffIt = VarLocIDs[ID];
588 const MachineInstr *DMI = &DiffIt.MI;
590 BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(),
591 DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(),
592 DMI->getDebugVariable(), DMI->getDebugExpression());
593 if (DMI->isIndirectDebugValue())
594 MI->getOperand(1).setImm(DMI->getOperand(1).getImm());
595 DEBUG(dbgs() << "Inserted: "; MI->dump(););
603 /// Calculate the liveness information for the given machine function and
604 /// extend ranges across basic blocks.
605 bool LiveDebugValues::ExtendRanges(MachineFunction &MF) {
606 DEBUG(dbgs() << "\nDebug Range Extension\n");
608 bool Changed = false;
609 bool OLChanged = false;
610 bool MBBJoined = false;
612 VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors.
613 OpenRangesSet OpenRanges; // Ranges that are open until end of bb.
614 VarLocInMBB OutLocs; // Ranges that exist beyond bb.
615 VarLocInMBB InLocs; // Ranges that are incoming after joining.
616 SpillMap Spills; // DBG_VALUEs associated with spills.
618 DenseMap<unsigned int, MachineBasicBlock *> OrderToBB;
619 DenseMap<MachineBasicBlock *, unsigned int> BBToOrder;
620 std::priority_queue<unsigned int, std::vector<unsigned int>,
621 std::greater<unsigned int>>
623 std::priority_queue<unsigned int, std::vector<unsigned int>,
624 std::greater<unsigned int>>
627 // Initialize every mbb with OutLocs.
628 // We are not looking at any spill instructions during the initial pass
629 // over the BBs. The LiveDebugVariables pass has already created DBG_VALUE
630 // instructions for spills of registers that are known to be user variables
631 // within the BB in which the spill occurs.
634 transfer(MI, OpenRanges, OutLocs, VarLocIDs, Spills,
635 /*transferSpills=*/false);
637 DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after initialization",
640 ReversePostOrderTraversal<MachineFunction *> RPOT(&MF);
641 unsigned int RPONumber = 0;
642 for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) {
643 OrderToBB[RPONumber] = *RI;
644 BBToOrder[*RI] = RPONumber;
645 Worklist.push(RPONumber);
648 // This is a standard "union of predecessor outs" dataflow problem.
649 // To solve it, we perform join() and transfer() using the two worklist method
650 // until the ranges converge.
651 // Ranges have converged when both worklists are empty.
652 SmallPtrSet<const MachineBasicBlock *, 16> Visited;
653 while (!Worklist.empty() || !Pending.empty()) {
654 // We track what is on the pending worklist to avoid inserting the same
655 // thing twice. We could avoid this with a custom priority queue, but this
656 // is probably not worth it.
657 SmallPtrSet<MachineBasicBlock *, 16> OnPending;
658 DEBUG(dbgs() << "Processing Worklist\n");
659 while (!Worklist.empty()) {
660 MachineBasicBlock *MBB = OrderToBB[Worklist.top()];
662 MBBJoined = join(*MBB, OutLocs, InLocs, VarLocIDs, Visited);
667 // Now that we have started to extend ranges across BBs we need to
668 // examine spill instructions to see whether they spill registers that
669 // correspond to user variables.
670 for (auto &MI : *MBB)
671 OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs, Spills,
672 /*transferSpills=*/true);
674 // Add any DBG_VALUE instructions necessitated by spills.
675 for (auto &SP : Spills)
676 MBB->insertAfter(MachineBasicBlock::iterator(*SP.SpillInst),
680 DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs,
681 "OutLocs after propagating", dbgs()));
682 DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs,
683 "InLocs after propagating", dbgs()));
687 for (auto s : MBB->successors())
688 if (OnPending.insert(s).second) {
689 Pending.push(BBToOrder[s]);
694 Worklist.swap(Pending);
695 // At this point, pending must be empty, since it was just the empty
697 assert(Pending.empty() && "Pending should be empty");
700 DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs()));
701 DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs()));
705 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
706 if (!MF.getFunction().getSubprogram())
707 // LiveDebugValues will already have removed all DBG_VALUEs.
710 // Skip functions from NoDebug compilation units.
711 if (MF.getFunction().getSubprogram()->getUnit()->getEmissionKind() ==
712 DICompileUnit::NoDebug)
715 TRI = MF.getSubtarget().getRegisterInfo();
716 TII = MF.getSubtarget().getInstrInfo();
717 TFI = MF.getSubtarget().getFrameLowering();
720 bool Changed = ExtendRanges(MF);