1 //===------ LiveDebugValues.cpp - Tracking Debug Value MIs ----------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 /// 10 /// This 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 14 /// inserted. 15 /// 16 /// This is a separate pass from DbgValueHistoryCalculator to facilitate 17 /// testing and improve modularity. 18 /// 19 //===----------------------------------------------------------------------===// 20 21 #include "llvm/ADT/PostOrderIterator.h" 22 #include "llvm/ADT/SmallPtrSet.h" 23 #include "llvm/ADT/SparseBitVector.h" 24 #include "llvm/ADT/Statistic.h" 25 #include "llvm/ADT/UniqueVector.h" 26 #include "llvm/CodeGen/MachineFunction.h" 27 #include "llvm/CodeGen/MachineFunctionPass.h" 28 #include "llvm/CodeGen/MachineInstrBuilder.h" 29 #include "llvm/CodeGen/Passes.h" 30 #include "llvm/IR/DebugInfo.h" 31 #include "llvm/Support/Debug.h" 32 #include "llvm/Support/raw_ostream.h" 33 #include "llvm/Target/TargetInstrInfo.h" 34 #include "llvm/Target/TargetLowering.h" 35 #include "llvm/Target/TargetRegisterInfo.h" 36 #include "llvm/Target/TargetSubtargetInfo.h" 37 #include <list> 38 #include <queue> 39 40 using namespace llvm; 41 42 #define DEBUG_TYPE "live-debug-values" 43 44 STATISTIC(NumInserted, "Number of DBG_VALUE instructions inserted"); 45 46 namespace { 47 48 // \brief If @MI is a DBG_VALUE with debug value described by a defined 49 // register, returns the number of this register. In the other case, returns 0. 50 static unsigned isDbgValueDescribedByReg(const MachineInstr &MI) { 51 assert(MI.isDebugValue() && "expected a DBG_VALUE"); 52 assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE"); 53 // If location of variable is described using a register (directly 54 // or indirectly), this register is always a first operand. 55 return MI.getOperand(0).isReg() ? MI.getOperand(0).getReg() : 0; 56 } 57 58 class LiveDebugValues : public MachineFunctionPass { 59 60 private: 61 const TargetRegisterInfo *TRI; 62 const TargetInstrInfo *TII; 63 64 /// Based on std::pair so it can be used as an index into a DenseMap. 65 typedef std::pair<const DILocalVariable *, const DILocation *> 66 DebugVariableBase; 67 /// A potentially inlined instance of a variable. 68 struct DebugVariable : public DebugVariableBase { 69 DebugVariable(const DILocalVariable *Var, const DILocation *InlinedAt) 70 : DebugVariableBase(Var, InlinedAt) {} 71 72 const DILocalVariable *getVar() const { return this->first; }; 73 const DILocation *getInlinedAt() const { return this->second; }; 74 75 bool operator<(const DebugVariable &DV) const { 76 if (getVar() == DV.getVar()) 77 return getInlinedAt() < DV.getInlinedAt(); 78 return getVar() < DV.getVar(); 79 } 80 }; 81 82 /// A pair of debug variable and value location. 83 struct VarLoc { 84 const DebugVariable Var; 85 const MachineInstr &MI; ///< Only used for cloning a new DBG_VALUE. 86 87 enum { InvalidKind = 0, RegisterKind } Kind; 88 89 /// The value location. Stored separately to avoid repeatedly 90 /// extracting it from MI. 91 union { 92 struct { 93 uint32_t RegNo; 94 uint32_t Offset; 95 } RegisterLoc; 96 uint64_t Hash; 97 } Loc; 98 99 VarLoc(const MachineInstr &MI) 100 : Var(MI.getDebugVariable(), MI.getDebugLoc()->getInlinedAt()), MI(MI), 101 Kind(InvalidKind) { 102 static_assert((sizeof(Loc) == sizeof(uint64_t)), 103 "hash does not cover all members of Loc"); 104 assert(MI.isDebugValue() && "not a DBG_VALUE"); 105 assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE"); 106 if (int RegNo = isDbgValueDescribedByReg(MI)) { 107 Kind = RegisterKind; 108 Loc.RegisterLoc.RegNo = RegNo; 109 uint64_t Offset = 110 MI.isIndirectDebugValue() ? MI.getOperand(1).getImm() : 0; 111 // We don't support offsets larger than 4GiB here. They are 112 // slated to be replaced with DIExpressions anyway. 113 if (Offset >= (1ULL << 32)) 114 Kind = InvalidKind; 115 else 116 Loc.RegisterLoc.Offset = Offset; 117 } 118 } 119 120 /// If this variable is described by a register, return it, 121 /// otherwise return 0. 122 unsigned isDescribedByReg() const { 123 if (Kind == RegisterKind) 124 return Loc.RegisterLoc.RegNo; 125 return 0; 126 } 127 128 void dump() const { MI.dump(); } 129 130 bool operator==(const VarLoc &Other) const { 131 return Var == Other.Var && Loc.Hash == Other.Loc.Hash; 132 } 133 134 /// This operator guarantees that VarLocs are sorted by Variable first. 135 bool operator<(const VarLoc &Other) const { 136 if (Var == Other.Var) 137 return Loc.Hash < Other.Loc.Hash; 138 return Var < Other.Var; 139 } 140 }; 141 142 typedef UniqueVector<VarLoc> VarLocMap; 143 typedef SparseBitVector<> VarLocSet; 144 typedef SmallDenseMap<const MachineBasicBlock *, VarLocSet> VarLocInMBB; 145 146 /// This holds the working set of currently open ranges. For fast 147 /// access, this is done both as a set of VarLocIDs, and a map of 148 /// DebugVariable to recent VarLocID. Note that a DBG_VALUE ends all 149 /// previous open ranges for the same variable. 150 class OpenRangesSet { 151 VarLocSet VarLocs; 152 SmallDenseMap<DebugVariableBase, unsigned, 8> Vars; 153 154 public: 155 const VarLocSet &getVarLocs() const { return VarLocs; } 156 157 /// Terminate all open ranges for Var by removing it from the set. 158 void erase(DebugVariable Var) { 159 auto It = Vars.find(Var); 160 if (It != Vars.end()) { 161 unsigned ID = It->second; 162 VarLocs.reset(ID); 163 Vars.erase(It); 164 } 165 } 166 167 /// Terminate all open ranges listed in \c KillSet by removing 168 /// them from the set. 169 void erase(const VarLocSet &KillSet, const VarLocMap &VarLocIDs) { 170 VarLocs.intersectWithComplement(KillSet); 171 for (unsigned ID : KillSet) 172 Vars.erase(VarLocIDs[ID].Var); 173 } 174 175 /// Insert a new range into the set. 176 void insert(unsigned VarLocID, DebugVariableBase Var) { 177 VarLocs.set(VarLocID); 178 Vars.insert({Var, VarLocID}); 179 } 180 181 /// Empty the set. 182 void clear() { 183 VarLocs.clear(); 184 Vars.clear(); 185 } 186 187 /// Return whether the set is empty or not. 188 bool empty() const { 189 assert(Vars.empty() == VarLocs.empty() && "open ranges are inconsistent"); 190 return VarLocs.empty(); 191 } 192 }; 193 194 void transferDebugValue(const MachineInstr &MI, OpenRangesSet &OpenRanges, 195 VarLocMap &VarLocIDs); 196 void transferRegisterDef(MachineInstr &MI, OpenRangesSet &OpenRanges, 197 const VarLocMap &VarLocIDs); 198 bool transferTerminatorInst(MachineInstr &MI, OpenRangesSet &OpenRanges, 199 VarLocInMBB &OutLocs, const VarLocMap &VarLocIDs); 200 bool transfer(MachineInstr &MI, OpenRangesSet &OpenRanges, 201 VarLocInMBB &OutLocs, VarLocMap &VarLocIDs); 202 203 bool join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, VarLocInMBB &InLocs, 204 const VarLocMap &VarLocIDs); 205 206 bool ExtendRanges(MachineFunction &MF); 207 208 public: 209 static char ID; 210 211 /// Default construct and initialize the pass. 212 LiveDebugValues(); 213 214 /// Tell the pass manager which passes we depend on and what 215 /// information we preserve. 216 void getAnalysisUsage(AnalysisUsage &AU) const override; 217 218 MachineFunctionProperties getRequiredProperties() const override { 219 return MachineFunctionProperties().set( 220 MachineFunctionProperties::Property::AllVRegsAllocated); 221 } 222 223 /// Print to ostream with a message. 224 void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V, 225 const VarLocMap &VarLocIDs, const char *msg, 226 raw_ostream &Out) const; 227 228 /// Calculate the liveness information for the given machine function. 229 bool runOnMachineFunction(MachineFunction &MF) override; 230 }; 231 } // namespace 232 233 //===----------------------------------------------------------------------===// 234 // Implementation 235 //===----------------------------------------------------------------------===// 236 237 char LiveDebugValues::ID = 0; 238 char &llvm::LiveDebugValuesID = LiveDebugValues::ID; 239 INITIALIZE_PASS(LiveDebugValues, "livedebugvalues", "Live DEBUG_VALUE analysis", 240 false, false) 241 242 /// Default construct and initialize the pass. 243 LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) { 244 initializeLiveDebugValuesPass(*PassRegistry::getPassRegistry()); 245 } 246 247 /// Tell the pass manager which passes we depend on and what information we 248 /// preserve. 249 void LiveDebugValues::getAnalysisUsage(AnalysisUsage &AU) const { 250 AU.setPreservesCFG(); 251 MachineFunctionPass::getAnalysisUsage(AU); 252 } 253 254 //===----------------------------------------------------------------------===// 255 // Debug Range Extension Implementation 256 //===----------------------------------------------------------------------===// 257 258 void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF, 259 const VarLocInMBB &V, 260 const VarLocMap &VarLocIDs, 261 const char *msg, 262 raw_ostream &Out) const { 263 for (const MachineBasicBlock &BB : MF) { 264 const auto &L = V.lookup(&BB); 265 Out << "MBB: " << BB.getName() << ":\n"; 266 for (unsigned VLL : L) { 267 const VarLoc &VL = VarLocIDs[VLL]; 268 Out << " Var: " << VL.Var.getVar()->getName(); 269 Out << " MI: "; 270 VL.dump(); 271 Out << "\n"; 272 } 273 } 274 Out << "\n"; 275 } 276 277 /// End all previous ranges related to @MI and start a new range from @MI 278 /// if it is a DBG_VALUE instr. 279 void LiveDebugValues::transferDebugValue(const MachineInstr &MI, 280 OpenRangesSet &OpenRanges, 281 VarLocMap &VarLocIDs) { 282 if (!MI.isDebugValue()) 283 return; 284 const DILocalVariable *Var = MI.getDebugVariable(); 285 const DILocation *DebugLoc = MI.getDebugLoc(); 286 const DILocation *InlinedAt = DebugLoc->getInlinedAt(); 287 assert(Var->isValidLocationForIntrinsic(DebugLoc) && 288 "Expected inlined-at fields to agree"); 289 290 // End all previous ranges of Var. 291 DebugVariable V(Var, InlinedAt); 292 OpenRanges.erase(V); 293 294 // Add the VarLoc to OpenRanges from this DBG_VALUE. 295 // TODO: Currently handles DBG_VALUE which has only reg as location. 296 if (isDbgValueDescribedByReg(MI)) { 297 VarLoc VL(MI); 298 unsigned ID = VarLocIDs.insert(VL); 299 OpenRanges.insert(ID, VL.Var); 300 } 301 } 302 303 /// A definition of a register may mark the end of a range. 304 void LiveDebugValues::transferRegisterDef(MachineInstr &MI, 305 OpenRangesSet &OpenRanges, 306 const VarLocMap &VarLocIDs) { 307 MachineFunction *MF = MI.getParent()->getParent(); 308 const TargetLowering *TLI = MF->getSubtarget().getTargetLowering(); 309 unsigned SP = TLI->getStackPointerRegisterToSaveRestore(); 310 SparseBitVector<> KillSet; 311 for (const MachineOperand &MO : MI.operands()) { 312 if (MO.isReg() && MO.isDef() && MO.getReg() && 313 TRI->isPhysicalRegister(MO.getReg())) { 314 // Remove ranges of all aliased registers. 315 for (MCRegAliasIterator RAI(MO.getReg(), TRI, true); RAI.isValid(); ++RAI) 316 for (unsigned ID : OpenRanges.getVarLocs()) 317 if (VarLocIDs[ID].isDescribedByReg() == *RAI) 318 KillSet.set(ID); 319 } else if (MO.isRegMask()) { 320 // Remove ranges of all clobbered registers. Register masks don't usually 321 // list SP as preserved. While the debug info may be off for an 322 // instruction or two around callee-cleanup calls, transferring the 323 // DEBUG_VALUE across the call is still a better user experience. 324 for (unsigned ID : OpenRanges.getVarLocs()) { 325 unsigned Reg = VarLocIDs[ID].isDescribedByReg(); 326 if (Reg && Reg != SP && MO.clobbersPhysReg(Reg)) 327 KillSet.set(ID); 328 } 329 } 330 } 331 OpenRanges.erase(KillSet, VarLocIDs); 332 } 333 334 /// Terminate all open ranges at the end of the current basic block. 335 bool LiveDebugValues::transferTerminatorInst(MachineInstr &MI, 336 OpenRangesSet &OpenRanges, 337 VarLocInMBB &OutLocs, 338 const VarLocMap &VarLocIDs) { 339 bool Changed = false; 340 const MachineBasicBlock *CurMBB = MI.getParent(); 341 if (!(MI.isTerminator() || (&MI == &CurMBB->instr_back()))) 342 return false; 343 344 if (OpenRanges.empty()) 345 return false; 346 347 DEBUG(for (unsigned ID : OpenRanges.getVarLocs()) { 348 // Copy OpenRanges to OutLocs, if not already present. 349 dbgs() << "Add to OutLocs: "; VarLocIDs[ID].dump(); 350 }); 351 VarLocSet &VLS = OutLocs[CurMBB]; 352 Changed = VLS |= OpenRanges.getVarLocs(); 353 OpenRanges.clear(); 354 return Changed; 355 } 356 357 /// This routine creates OpenRanges and OutLocs. 358 bool LiveDebugValues::transfer(MachineInstr &MI, OpenRangesSet &OpenRanges, 359 VarLocInMBB &OutLocs, VarLocMap &VarLocIDs) { 360 bool Changed = false; 361 transferDebugValue(MI, OpenRanges, VarLocIDs); 362 transferRegisterDef(MI, OpenRanges, VarLocIDs); 363 Changed = transferTerminatorInst(MI, OpenRanges, OutLocs, VarLocIDs); 364 return Changed; 365 } 366 367 /// This routine joins the analysis results of all incoming edges in @MBB by 368 /// inserting a new DBG_VALUE instruction at the start of the @MBB - if the same 369 /// source variable in all the predecessors of @MBB reside in the same location. 370 bool LiveDebugValues::join(MachineBasicBlock &MBB, VarLocInMBB &OutLocs, 371 VarLocInMBB &InLocs, const VarLocMap &VarLocIDs) { 372 DEBUG(dbgs() << "join MBB: " << MBB.getName() << "\n"); 373 bool Changed = false; 374 375 VarLocSet InLocsT; // Temporary incoming locations. 376 377 // For all predecessors of this MBB, find the set of VarLocs that 378 // can be joined. 379 for (auto p : MBB.predecessors()) { 380 auto OL = OutLocs.find(p); 381 // Join is null in case of empty OutLocs from any of the pred. 382 if (OL == OutLocs.end()) 383 return false; 384 385 // Just copy over the Out locs to incoming locs for the first predecessor. 386 if (p == *MBB.pred_begin()) { 387 InLocsT = OL->second; 388 continue; 389 } 390 // Join with this predecessor. 391 InLocsT &= OL->second; 392 } 393 394 if (InLocsT.empty()) 395 return false; 396 397 VarLocSet &ILS = InLocs[&MBB]; 398 399 // Insert DBG_VALUE instructions, if not already inserted. 400 VarLocSet Diff = InLocsT; 401 Diff.intersectWithComplement(ILS); 402 for (auto ID : Diff) { 403 // This VarLoc is not found in InLocs i.e. it is not yet inserted. So, a 404 // new range is started for the var from the mbb's beginning by inserting 405 // a new DBG_VALUE. transfer() will end this range however appropriate. 406 const VarLoc &DiffIt = VarLocIDs[ID]; 407 const MachineInstr *DMI = &DiffIt.MI; 408 MachineInstr *MI = 409 BuildMI(MBB, MBB.instr_begin(), DMI->getDebugLoc(), DMI->getDesc(), 410 DMI->isIndirectDebugValue(), DMI->getOperand(0).getReg(), 0, 411 DMI->getDebugVariable(), DMI->getDebugExpression()); 412 if (DMI->isIndirectDebugValue()) 413 MI->getOperand(1).setImm(DMI->getOperand(1).getImm()); 414 DEBUG(dbgs() << "Inserted: "; MI->dump();); 415 ILS.set(ID); 416 ++NumInserted; 417 Changed = true; 418 } 419 return Changed; 420 } 421 422 /// Calculate the liveness information for the given machine function and 423 /// extend ranges across basic blocks. 424 bool LiveDebugValues::ExtendRanges(MachineFunction &MF) { 425 426 DEBUG(dbgs() << "\nDebug Range Extension\n"); 427 428 bool Changed = false; 429 bool OLChanged = false; 430 bool MBBJoined = false; 431 432 VarLocMap VarLocIDs; // Map VarLoc<>unique ID for use in bitvectors. 433 OpenRangesSet OpenRanges; // Ranges that are open until end of bb. 434 VarLocInMBB OutLocs; // Ranges that exist beyond bb. 435 VarLocInMBB InLocs; // Ranges that are incoming after joining. 436 437 DenseMap<unsigned int, MachineBasicBlock *> OrderToBB; 438 DenseMap<MachineBasicBlock *, unsigned int> BBToOrder; 439 std::priority_queue<unsigned int, std::vector<unsigned int>, 440 std::greater<unsigned int>> 441 Worklist; 442 std::priority_queue<unsigned int, std::vector<unsigned int>, 443 std::greater<unsigned int>> 444 Pending; 445 446 // Initialize every mbb with OutLocs. 447 for (auto &MBB : MF) 448 for (auto &MI : MBB) 449 transfer(MI, OpenRanges, OutLocs, VarLocIDs); 450 451 DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "OutLocs after initialization", 452 dbgs())); 453 454 ReversePostOrderTraversal<MachineFunction *> RPOT(&MF); 455 unsigned int RPONumber = 0; 456 for (auto RI = RPOT.begin(), RE = RPOT.end(); RI != RE; ++RI) { 457 OrderToBB[RPONumber] = *RI; 458 BBToOrder[*RI] = RPONumber; 459 Worklist.push(RPONumber); 460 ++RPONumber; 461 } 462 // This is a standard "union of predecessor outs" dataflow problem. 463 // To solve it, we perform join() and transfer() using the two worklist method 464 // until the ranges converge. 465 // Ranges have converged when both worklists are empty. 466 while (!Worklist.empty() || !Pending.empty()) { 467 // We track what is on the pending worklist to avoid inserting the same 468 // thing twice. We could avoid this with a custom priority queue, but this 469 // is probably not worth it. 470 SmallPtrSet<MachineBasicBlock *, 16> OnPending; 471 while (!Worklist.empty()) { 472 MachineBasicBlock *MBB = OrderToBB[Worklist.top()]; 473 Worklist.pop(); 474 MBBJoined = join(*MBB, OutLocs, InLocs, VarLocIDs); 475 476 if (MBBJoined) { 477 MBBJoined = false; 478 Changed = true; 479 for (auto &MI : *MBB) 480 OLChanged |= transfer(MI, OpenRanges, OutLocs, VarLocIDs); 481 482 DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, 483 "OutLocs after propagating", dbgs())); 484 DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, 485 "InLocs after propagating", dbgs())); 486 487 if (OLChanged) { 488 OLChanged = false; 489 for (auto s : MBB->successors()) 490 if (OnPending.insert(s).second) { 491 Pending.push(BBToOrder[s]); 492 } 493 } 494 } 495 } 496 Worklist.swap(Pending); 497 // At this point, pending must be empty, since it was just the empty 498 // worklist 499 assert(Pending.empty() && "Pending should be empty"); 500 } 501 502 DEBUG(printVarLocInMBB(MF, OutLocs, VarLocIDs, "Final OutLocs", dbgs())); 503 DEBUG(printVarLocInMBB(MF, InLocs, VarLocIDs, "Final InLocs", dbgs())); 504 return Changed; 505 } 506 507 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) { 508 TRI = MF.getSubtarget().getRegisterInfo(); 509 TII = MF.getSubtarget().getInstrInfo(); 510 511 bool Changed = false; 512 513 Changed |= ExtendRanges(MF); 514 515 return Changed; 516 } 517