contrib/llvm/tools/clang/lib/CodeGen/CGCleanup.cpp

   1 //===--- CGCleanup.cpp - Bookkeeping and code emission for cleanups -------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file contains code dealing with the IR generation for cleanups
  11 // and related information.
  12 //
  13 // A "cleanup" is a piece of code which needs to be executed whenever
  14 // control transfers out of a particular scope.  This can be
  15 // conditionalized to occur only on exceptional control flow, only on
  16 // normal control flow, or both.
  17 //
  18 //===----------------------------------------------------------------------===//
  19
  20 #include "CGCleanup.h"
  21 #include "CodeGenFunction.h"
  22 #include "llvm/Support/SaveAndRestore.h"
  23
  24 using namespace clang;
  25 using namespace CodeGen;
  26
  27 bool DominatingValue<RValue>::saved_type::needsSaving(RValue rv) {
  28   if (rv.isScalar())
  29     return DominatingLLVMValue::needsSaving(rv.getScalarVal());
  30   if (rv.isAggregate())
  31     return DominatingLLVMValue::needsSaving(rv.getAggregatePointer());
  32   return true;
  33 }
  34
  35 DominatingValue<RValue>::saved_type
  36 DominatingValue<RValue>::saved_type::save(CodeGenFunction &CGF, RValue rv) {
  37   if (rv.isScalar()) {
  38     llvm::Value *V = rv.getScalarVal();
  39
  40     // These automatically dominate and don't need to be saved.
  41     if (!DominatingLLVMValue::needsSaving(V))
  42       return saved_type(V, ScalarLiteral);
  43
  44     // Everything else needs an alloca.
  45     Address addr =
  46       CGF.CreateDefaultAlignTempAlloca(V->getType(), "saved-rvalue");
  47     CGF.Builder.CreateStore(V, addr);
  48     return saved_type(addr.getPointer(), ScalarAddress);
  49   }
  50
  51   if (rv.isComplex()) {
  52     CodeGenFunction::ComplexPairTy V = rv.getComplexVal();
  53     llvm::Type *ComplexTy =
  54         llvm::StructType::get(V.first->getType(), V.second->getType());
  55     Address addr = CGF.CreateDefaultAlignTempAlloca(ComplexTy, "saved-complex");
  56     CGF.Builder.CreateStore(V.first,
  57                             CGF.Builder.CreateStructGEP(addr, 0, CharUnits()));
  58     CharUnits offset = CharUnits::fromQuantity(
  59                CGF.CGM.getDataLayout().getTypeAllocSize(V.first->getType()));
  60     CGF.Builder.CreateStore(V.second,
  61                             CGF.Builder.CreateStructGEP(addr, 1, offset));
  62     return saved_type(addr.getPointer(), ComplexAddress);
  63   }
  64
  65   assert(rv.isAggregate());
  66   Address V = rv.getAggregateAddress(); // TODO: volatile?
  67   if (!DominatingLLVMValue::needsSaving(V.getPointer()))
  68     return saved_type(V.getPointer(), AggregateLiteral,
  69                       V.getAlignment().getQuantity());
  70
  71   Address addr =
  72     CGF.CreateTempAlloca(V.getType(), CGF.getPointerAlign(), "saved-rvalue");
  73   CGF.Builder.CreateStore(V.getPointer(), addr);
  74   return saved_type(addr.getPointer(), AggregateAddress,
  75                     V.getAlignment().getQuantity());
  76 }
  77
  78 /// Given a saved r-value produced by SaveRValue, perform the code
  79 /// necessary to restore it to usability at the current insertion
  80 /// point.
  81 RValue DominatingValue<RValue>::saved_type::restore(CodeGenFunction &CGF) {
  82   auto getSavingAddress = [&](llvm::Value *value) {
  83     auto alignment = cast<llvm::AllocaInst>(value)->getAlignment();
  84     return Address(value, CharUnits::fromQuantity(alignment));
  85   };
  86   switch (K) {
  87   case ScalarLiteral:
  88     return RValue::get(Value);
  89   case ScalarAddress:
  90     return RValue::get(CGF.Builder.CreateLoad(getSavingAddress(Value)));
  91   case AggregateLiteral:
  92     return RValue::getAggregate(Address(Value, CharUnits::fromQuantity(Align)));
  93   case AggregateAddress: {
  94     auto addr = CGF.Builder.CreateLoad(getSavingAddress(Value));
  95     return RValue::getAggregate(Address(addr, CharUnits::fromQuantity(Align)));
  96   }
  97   case ComplexAddress: {
  98     Address address = getSavingAddress(Value);
  99     llvm::Value *real = CGF.Builder.CreateLoad(
 100                  CGF.Builder.CreateStructGEP(address, 0, CharUnits()));
 101     CharUnits offset = CharUnits::fromQuantity(
 102                  CGF.CGM.getDataLayout().getTypeAllocSize(real->getType()));
 103     llvm::Value *imag = CGF.Builder.CreateLoad(
 104                  CGF.Builder.CreateStructGEP(address, 1, offset));
 105     return RValue::getComplex(real, imag);
 106   }
 107   }
 108
 109   llvm_unreachable("bad saved r-value kind");
 110 }
 111
 112 /// Push an entry of the given size onto this protected-scope stack.
 113 char *EHScopeStack::allocate(size_t Size) {
 114   Size = llvm::alignTo(Size, ScopeStackAlignment);
 115   if (!StartOfBuffer) {
 116     unsigned Capacity = 1024;
 117     while (Capacity < Size) Capacity *= 2;
 118     StartOfBuffer = new char[Capacity];
 119     StartOfData = EndOfBuffer = StartOfBuffer + Capacity;
 120   } else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) {
 121     unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer;
 122     unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer);
 123
 124     unsigned NewCapacity = CurrentCapacity;
 125     do {
 126       NewCapacity *= 2;
 127     } while (NewCapacity < UsedCapacity + Size);
 128
 129     char *NewStartOfBuffer = new char[NewCapacity];
 130     char *NewEndOfBuffer = NewStartOfBuffer + NewCapacity;
 131     char *NewStartOfData = NewEndOfBuffer - UsedCapacity;
 132     memcpy(NewStartOfData, StartOfData, UsedCapacity);
 133     delete [] StartOfBuffer;
 134     StartOfBuffer = NewStartOfBuffer;
 135     EndOfBuffer = NewEndOfBuffer;
 136     StartOfData = NewStartOfData;
 137   }
 138
 139   assert(StartOfBuffer + Size <= StartOfData);
 140   StartOfData -= Size;
 141   return StartOfData;
 142 }
 143
 144 void EHScopeStack::deallocate(size_t Size) {
 145   StartOfData += llvm::alignTo(Size, ScopeStackAlignment);
 146 }
 147
 148 bool EHScopeStack::containsOnlyLifetimeMarkers(
 149     EHScopeStack::stable_iterator Old) const {
 150   for (EHScopeStack::iterator it = begin(); stabilize(it) != Old; it++) {
 151     EHCleanupScope *cleanup = dyn_cast<EHCleanupScope>(&*it);
 152     if (!cleanup || !cleanup->isLifetimeMarker())
 153       return false;
 154   }
 155
 156   return true;
 157 }
 158
 159 bool EHScopeStack::requiresLandingPad() const {
 160   for (stable_iterator si = getInnermostEHScope(); si != stable_end(); ) {
 161     // Skip lifetime markers.
 162     if (auto *cleanup = dyn_cast<EHCleanupScope>(&*find(si)))
 163       if (cleanup->isLifetimeMarker()) {
 164         si = cleanup->getEnclosingEHScope();
 165         continue;
 166       }
 167     return true;
 168   }
 169
 170   return false;
 171 }
 172
 173 EHScopeStack::stable_iterator
 174 EHScopeStack::getInnermostActiveNormalCleanup() const {
 175   for (stable_iterator si = getInnermostNormalCleanup(), se = stable_end();
 176          si != se; ) {
 177     EHCleanupScope &cleanup = cast<EHCleanupScope>(*find(si));
 178     if (cleanup.isActive()) return si;
 179     si = cleanup.getEnclosingNormalCleanup();
 180   }
 181   return stable_end();
 182 }
 183
 184
 185 void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {
 186   char *Buffer = allocate(EHCleanupScope::getSizeForCleanupSize(Size));
 187   bool IsNormalCleanup = Kind & NormalCleanup;
 188   bool IsEHCleanup = Kind & EHCleanup;
 189   bool IsActive = !(Kind & InactiveCleanup);
 190   bool IsLifetimeMarker = Kind & LifetimeMarker;
 191   EHCleanupScope *Scope =
 192     new (Buffer) EHCleanupScope(IsNormalCleanup,
 193                                 IsEHCleanup,
 194                                 IsActive,
 195                                 Size,
 196                                 BranchFixups.size(),
 197                                 InnermostNormalCleanup,
 198                                 InnermostEHScope);
 199   if (IsNormalCleanup)
 200     InnermostNormalCleanup = stable_begin();
 201   if (IsEHCleanup)
 202     InnermostEHScope = stable_begin();
 203   if (IsLifetimeMarker)
 204     Scope->setLifetimeMarker();
 205
 206   return Scope->getCleanupBuffer();
 207 }
 208
 209 void EHScopeStack::popCleanup() {
 210   assert(!empty() && "popping exception stack when not empty");
 211
 212   assert(isa<EHCleanupScope>(*begin()));
 213   EHCleanupScope &Cleanup = cast<EHCleanupScope>(*begin());
 214   InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup();
 215   InnermostEHScope = Cleanup.getEnclosingEHScope();
 216   deallocate(Cleanup.getAllocatedSize());
 217
 218   // Destroy the cleanup.
 219   Cleanup.Destroy();
 220
 221   // Check whether we can shrink the branch-fixups stack.
 222   if (!BranchFixups.empty()) {
 223     // If we no longer have any normal cleanups, all the fixups are
 224     // complete.
 225     if (!hasNormalCleanups())
 226       BranchFixups.clear();
 227
 228     // Otherwise we can still trim out unnecessary nulls.
 229     else
 230       popNullFixups();
 231   }
 232 }
 233
 234 EHFilterScope *EHScopeStack::pushFilter(unsigned numFilters) {
 235   assert(getInnermostEHScope() == stable_end());
 236   char *buffer = allocate(EHFilterScope::getSizeForNumFilters(numFilters));
 237   EHFilterScope *filter = new (buffer) EHFilterScope(numFilters);
 238   InnermostEHScope = stable_begin();
 239   return filter;
 240 }
 241
 242 void EHScopeStack::popFilter() {
 243   assert(!empty() && "popping exception stack when not empty");
 244
 245   EHFilterScope &filter = cast<EHFilterScope>(*begin());
 246   deallocate(EHFilterScope::getSizeForNumFilters(filter.getNumFilters()));
 247
 248   InnermostEHScope = filter.getEnclosingEHScope();
 249 }
 250
 251 EHCatchScope *EHScopeStack::pushCatch(unsigned numHandlers) {
 252   char *buffer = allocate(EHCatchScope::getSizeForNumHandlers(numHandlers));
 253   EHCatchScope *scope =
 254     new (buffer) EHCatchScope(numHandlers, InnermostEHScope);
 255   InnermostEHScope = stable_begin();
 256   return scope;
 257 }
 258
 259 void EHScopeStack::pushTerminate() {
 260   char *Buffer = allocate(EHTerminateScope::getSize());
 261   new (Buffer) EHTerminateScope(InnermostEHScope);
 262   InnermostEHScope = stable_begin();
 263 }
 264
 265 /// Remove any 'null' fixups on the stack.  However, we can't pop more
 266 /// fixups than the fixup depth on the innermost normal cleanup, or
 267 /// else fixups that we try to add to that cleanup will end up in the
 268 /// wrong place.  We *could* try to shrink fixup depths, but that's
 269 /// actually a lot of work for little benefit.
 270 void EHScopeStack::popNullFixups() {
 271   // We expect this to only be called when there's still an innermost
 272   // normal cleanup;  otherwise there really shouldn't be any fixups.
 273   assert(hasNormalCleanups());
 274
 275   EHScopeStack::iterator it = find(InnermostNormalCleanup);
 276   unsigned MinSize = cast<EHCleanupScope>(*it).getFixupDepth();
 277   assert(BranchFixups.size() >= MinSize && "fixup stack out of order");
 278
 279   while (BranchFixups.size() > MinSize &&
 280          BranchFixups.back().Destination == nullptr)
 281     BranchFixups.pop_back();
 282 }
 283
 284 Address CodeGenFunction::createCleanupActiveFlag() {
 285   // Create a variable to decide whether the cleanup needs to be run.
 286   Address active = CreateTempAllocaWithoutCast(
 287       Builder.getInt1Ty(), CharUnits::One(), "cleanup.cond");
 288
 289   // Initialize it to false at a site that's guaranteed to be run
 290   // before each evaluation.
 291   setBeforeOutermostConditional(Builder.getFalse(), active);
 292
 293   // Initialize it to true at the current location.
 294   Builder.CreateStore(Builder.getTrue(), active);
 295
 296   return active;
 297 }
 298
 299 void CodeGenFunction::initFullExprCleanupWithFlag(Address ActiveFlag) {
 300   // Set that as the active flag in the cleanup.
 301   EHCleanupScope &cleanup = cast<EHCleanupScope>(*EHStack.begin());
 302   assert(!cleanup.hasActiveFlag() && "cleanup already has active flag?");
 303   cleanup.setActiveFlag(ActiveFlag);
 304
 305   if (cleanup.isNormalCleanup()) cleanup.setTestFlagInNormalCleanup();
 306   if (cleanup.isEHCleanup()) cleanup.setTestFlagInEHCleanup();
 307 }
 308
 309 void EHScopeStack::Cleanup::anchor() {}
 310
 311 static void createStoreInstBefore(llvm::Value *value, Address addr,
 312                                   llvm::Instruction *beforeInst) {
 313   auto store = new llvm::StoreInst(value, addr.getPointer(), beforeInst);
 314   store->setAlignment(addr.getAlignment().getQuantity());
 315 }
 316
 317 static llvm::LoadInst *createLoadInstBefore(Address addr, const Twine &name,
 318                                             llvm::Instruction *beforeInst) {
 319   auto load = new llvm::LoadInst(addr.getPointer(), name, beforeInst);
 320   load->setAlignment(addr.getAlignment().getQuantity());
 321   return load;
 322 }
 323
 324 /// All the branch fixups on the EH stack have propagated out past the
 325 /// outermost normal cleanup; resolve them all by adding cases to the
 326 /// given switch instruction.
 327 static void ResolveAllBranchFixups(CodeGenFunction &CGF,
 328                                    llvm::SwitchInst *Switch,
 329                                    llvm::BasicBlock *CleanupEntry) {
 330   llvm::SmallPtrSet<llvm::BasicBlock*, 4> CasesAdded;
 331
 332   for (unsigned I = 0, E = CGF.EHStack.getNumBranchFixups(); I != E; ++I) {
 333     // Skip this fixup if its destination isn't set.
 334     BranchFixup &Fixup = CGF.EHStack.getBranchFixup(I);
 335     if (Fixup.Destination == nullptr) continue;
 336
 337     // If there isn't an OptimisticBranchBlock, then InitialBranch is
 338     // still pointing directly to its destination; forward it to the
 339     // appropriate cleanup entry.  This is required in the specific
 340     // case of
 341     //   { std::string s; goto lbl; }
 342     //   lbl:
 343     // i.e. where there's an unresolved fixup inside a single cleanup
 344     // entry which we're currently popping.
 345     if (Fixup.OptimisticBranchBlock == nullptr) {
 346       createStoreInstBefore(CGF.Builder.getInt32(Fixup.DestinationIndex),
 347                             CGF.getNormalCleanupDestSlot(),
 348                             Fixup.InitialBranch);
 349       Fixup.InitialBranch->setSuccessor(0, CleanupEntry);
 350     }
 351
 352     // Don't add this case to the switch statement twice.
 353     if (!CasesAdded.insert(Fixup.Destination).second)
 354       continue;
 355
 356     Switch->addCase(CGF.Builder.getInt32(Fixup.DestinationIndex),
 357                     Fixup.Destination);
 358   }
 359
 360   CGF.EHStack.clearFixups();
 361 }
 362
 363 /// Transitions the terminator of the given exit-block of a cleanup to
 364 /// be a cleanup switch.
 365 static llvm::SwitchInst *TransitionToCleanupSwitch(CodeGenFunction &CGF,
 366                                                    llvm::BasicBlock *Block) {
 367   // If it's a branch, turn it into a switch whose default
 368   // destination is its original target.
 369   llvm::Instruction *Term = Block->getTerminator();
 370   assert(Term && "can't transition block without terminator");
 371
 372   if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {
 373     assert(Br->isUnconditional());
 374     auto Load = createLoadInstBefore(CGF.getNormalCleanupDestSlot(),
 375                                      "cleanup.dest", Term);
 376     llvm::SwitchInst *Switch =
 377       llvm::SwitchInst::Create(Load, Br->getSuccessor(0), 4, Block);
 378     Br->eraseFromParent();
 379     return Switch;
 380   } else {
 381     return cast<llvm::SwitchInst>(Term);
 382   }
 383 }
 384
 385 void CodeGenFunction::ResolveBranchFixups(llvm::BasicBlock *Block) {
 386   assert(Block && "resolving a null target block");
 387   if (!EHStack.getNumBranchFixups()) return;
 388
 389   assert(EHStack.hasNormalCleanups() &&
 390          "branch fixups exist with no normal cleanups on stack");
 391
 392   llvm::SmallPtrSet<llvm::BasicBlock*, 4> ModifiedOptimisticBlocks;
 393   bool ResolvedAny = false;
 394
 395   for (unsigned I = 0, E = EHStack.getNumBranchFixups(); I != E; ++I) {
 396     // Skip this fixup if its destination doesn't match.
 397     BranchFixup &Fixup = EHStack.getBranchFixup(I);
 398     if (Fixup.Destination != Block) continue;
 399
 400     Fixup.Destination = nullptr;
 401     ResolvedAny = true;
 402
 403     // If it doesn't have an optimistic branch block, LatestBranch is
 404     // already pointing to the right place.
 405     llvm::BasicBlock *BranchBB = Fixup.OptimisticBranchBlock;
 406     if (!BranchBB)
 407       continue;
 408
 409     // Don't process the same optimistic branch block twice.
 410     if (!ModifiedOptimisticBlocks.insert(BranchBB).second)
 411       continue;
 412
 413     llvm::SwitchInst *Switch = TransitionToCleanupSwitch(*this, BranchBB);
 414
 415     // Add a case to the switch.
 416     Switch->addCase(Builder.getInt32(Fixup.DestinationIndex), Block);
 417   }
 418
 419   if (ResolvedAny)
 420     EHStack.popNullFixups();
 421 }
 422
 423 /// Pops cleanup blocks until the given savepoint is reached.
 424 void CodeGenFunction::PopCleanupBlocks(
 425     EHScopeStack::stable_iterator Old,
 426     std::initializer_list<llvm::Value **> ValuesToReload) {
 427   assert(Old.isValid());
 428
 429   bool HadBranches = false;
 430   while (EHStack.stable_begin() != Old) {
 431     EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());
 432     HadBranches |= Scope.hasBranches();
 433
 434     // As long as Old strictly encloses the scope's enclosing normal
 435     // cleanup, we're going to emit another normal cleanup which
 436     // fallthrough can propagate through.
 437     bool FallThroughIsBranchThrough =
 438       Old.strictlyEncloses(Scope.getEnclosingNormalCleanup());
 439
 440     PopCleanupBlock(FallThroughIsBranchThrough);
 441   }
 442
 443   // If we didn't have any branches, the insertion point before cleanups must
 444   // dominate the current insertion point and we don't need to reload any
 445   // values.
 446   if (!HadBranches)
 447     return;
 448
 449   // Spill and reload all values that the caller wants to be live at the current
 450   // insertion point.
 451   for (llvm::Value **ReloadedValue : ValuesToReload) {
 452     auto *Inst = dyn_cast_or_null<llvm::Instruction>(*ReloadedValue);
 453     if (!Inst)
 454       continue;
 455
 456     // Don't spill static allocas, they dominate all cleanups. These are created
 457     // by binding a reference to a local variable or temporary.
 458     auto *AI = dyn_cast<llvm::AllocaInst>(Inst);
 459     if (AI && AI->isStaticAlloca())
 460       continue;
 461
 462     Address Tmp =
 463         CreateDefaultAlignTempAlloca(Inst->getType(), "tmp.exprcleanup");
 464
 465     // Find an insertion point after Inst and spill it to the temporary.
 466     llvm::BasicBlock::iterator InsertBefore;
 467     if (auto *Invoke = dyn_cast<llvm::InvokeInst>(Inst))
 468       InsertBefore = Invoke->getNormalDest()->getFirstInsertionPt();
 469     else
 470       InsertBefore = std::next(Inst->getIterator());
 471     CGBuilderTy(CGM, &*InsertBefore).CreateStore(Inst, Tmp);
 472
 473     // Reload the value at the current insertion point.
 474     *ReloadedValue = Builder.CreateLoad(Tmp);
 475   }
 476 }
 477
 478 /// Pops cleanup blocks until the given savepoint is reached, then add the
 479 /// cleanups from the given savepoint in the lifetime-extended cleanups stack.
 480 void CodeGenFunction::PopCleanupBlocks(
 481     EHScopeStack::stable_iterator Old, size_t OldLifetimeExtendedSize,
 482     std::initializer_list<llvm::Value **> ValuesToReload) {
 483   PopCleanupBlocks(Old, ValuesToReload);
 484
 485   // Move our deferred cleanups onto the EH stack.
 486   for (size_t I = OldLifetimeExtendedSize,
 487               E = LifetimeExtendedCleanupStack.size(); I != E; /**/) {
 488     // Alignment should be guaranteed by the vptrs in the individual cleanups.
 489     assert((I % alignof(LifetimeExtendedCleanupHeader) == 0) &&
 490            "misaligned cleanup stack entry");
 491
 492     LifetimeExtendedCleanupHeader &Header =
 493         reinterpret_cast<LifetimeExtendedCleanupHeader&>(
 494             LifetimeExtendedCleanupStack[I]);
 495     I += sizeof(Header);
 496
 497     EHStack.pushCopyOfCleanup(Header.getKind(),
 498                               &LifetimeExtendedCleanupStack[I],
 499                               Header.getSize());
 500     I += Header.getSize();
 501
 502     if (Header.isConditional()) {
 503       Address ActiveFlag =
 504           reinterpret_cast<Address &>(LifetimeExtendedCleanupStack[I]);
 505       initFullExprCleanupWithFlag(ActiveFlag);
 506       I += sizeof(ActiveFlag);
 507     }
 508   }
 509   LifetimeExtendedCleanupStack.resize(OldLifetimeExtendedSize);
 510 }
 511
 512 static llvm::BasicBlock *CreateNormalEntry(CodeGenFunction &CGF,
 513                                            EHCleanupScope &Scope) {
 514   assert(Scope.isNormalCleanup());
 515   llvm::BasicBlock *Entry = Scope.getNormalBlock();
 516   if (!Entry) {
 517     Entry = CGF.createBasicBlock("cleanup");
 518     Scope.setNormalBlock(Entry);
 519   }
 520   return Entry;
 521 }
 522
 523 /// Attempts to reduce a cleanup's entry block to a fallthrough.  This
 524 /// is basically llvm::MergeBlockIntoPredecessor, except
 525 /// simplified/optimized for the tighter constraints on cleanup blocks.
 526 ///
 527 /// Returns the new block, whatever it is.
 528 static llvm::BasicBlock *SimplifyCleanupEntry(CodeGenFunction &CGF,
 529                                               llvm::BasicBlock *Entry) {
 530   llvm::BasicBlock *Pred = Entry->getSinglePredecessor();
 531   if (!Pred) return Entry;
 532
 533   llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Pred->getTerminator());
 534   if (!Br || Br->isConditional()) return Entry;
 535   assert(Br->getSuccessor(0) == Entry);
 536
 537   // If we were previously inserting at the end of the cleanup entry
 538   // block, we'll need to continue inserting at the end of the
 539   // predecessor.
 540   bool WasInsertBlock = CGF.Builder.GetInsertBlock() == Entry;
 541   assert(!WasInsertBlock || CGF.Builder.GetInsertPoint() == Entry->end());
 542
 543   // Kill the branch.
 544   Br->eraseFromParent();
 545
 546   // Replace all uses of the entry with the predecessor, in case there
 547   // are phis in the cleanup.
 548   Entry->replaceAllUsesWith(Pred);
 549
 550   // Merge the blocks.
 551   Pred->getInstList().splice(Pred->end(), Entry->getInstList());
 552
 553   // Kill the entry block.
 554   Entry->eraseFromParent();
 555
 556   if (WasInsertBlock)
 557     CGF.Builder.SetInsertPoint(Pred);
 558
 559   return Pred;
 560 }
 561
 562 static void EmitCleanup(CodeGenFunction &CGF,
 563                         EHScopeStack::Cleanup *Fn,
 564                         EHScopeStack::Cleanup::Flags flags,
 565                         Address ActiveFlag) {
 566   // If there's an active flag, load it and skip the cleanup if it's
 567   // false.
 568   llvm::BasicBlock *ContBB = nullptr;
 569   if (ActiveFlag.isValid()) {
 570     ContBB = CGF.createBasicBlock("cleanup.done");
 571     llvm::BasicBlock *CleanupBB = CGF.createBasicBlock("cleanup.action");
 572     llvm::Value *IsActive
 573       = CGF.Builder.CreateLoad(ActiveFlag, "cleanup.is_active");
 574     CGF.Builder.CreateCondBr(IsActive, CleanupBB, ContBB);
 575     CGF.EmitBlock(CleanupBB);
 576   }
 577
 578   // Ask the cleanup to emit itself.
 579   Fn->Emit(CGF, flags);
 580   assert(CGF.HaveInsertPoint() && "cleanup ended with no insertion point?");
 581
 582   // Emit the continuation block if there was an active flag.
 583   if (ActiveFlag.isValid())
 584     CGF.EmitBlock(ContBB);
 585 }
 586
 587 static void ForwardPrebranchedFallthrough(llvm::BasicBlock *Exit,
 588                                           llvm::BasicBlock *From,
 589                                           llvm::BasicBlock *To) {
 590   // Exit is the exit block of a cleanup, so it always terminates in
 591   // an unconditional branch or a switch.
 592   llvm::Instruction *Term = Exit->getTerminator();
 593
 594   if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {
 595     assert(Br->isUnconditional() && Br->getSuccessor(0) == From);
 596     Br->setSuccessor(0, To);
 597   } else {
 598     llvm::SwitchInst *Switch = cast<llvm::SwitchInst>(Term);
 599     for (unsigned I = 0, E = Switch->getNumSuccessors(); I != E; ++I)
 600       if (Switch->getSuccessor(I) == From)
 601         Switch->setSuccessor(I, To);
 602   }
 603 }
 604
 605 /// We don't need a normal entry block for the given cleanup.
 606 /// Optimistic fixup branches can cause these blocks to come into
 607 /// existence anyway;  if so, destroy it.
 608 ///
 609 /// The validity of this transformation is very much specific to the
 610 /// exact ways in which we form branches to cleanup entries.
 611 static void destroyOptimisticNormalEntry(CodeGenFunction &CGF,
 612                                          EHCleanupScope &scope) {
 613   llvm::BasicBlock *entry = scope.getNormalBlock();
 614   if (!entry) return;
 615
 616   // Replace all the uses with unreachable.
 617   llvm::BasicBlock *unreachableBB = CGF.getUnreachableBlock();
 618   for (llvm::BasicBlock::use_iterator
 619          i = entry->use_begin(), e = entry->use_end(); i != e; ) {
 620     llvm::Use &use = *i;
 621     ++i;
 622
 623     use.set(unreachableBB);
 624
 625     // The only uses should be fixup switches.
 626     llvm::SwitchInst *si = cast<llvm::SwitchInst>(use.getUser());
 627     if (si->getNumCases() == 1 && si->getDefaultDest() == unreachableBB) {
 628       // Replace the switch with a branch.
 629       llvm::BranchInst::Create(si->case_begin()->getCaseSuccessor(), si);
 630
 631       // The switch operand is a load from the cleanup-dest alloca.
 632       llvm::LoadInst *condition = cast<llvm::LoadInst>(si->getCondition());
 633
 634       // Destroy the switch.
 635       si->eraseFromParent();
 636
 637       // Destroy the load.
 638       assert(condition->getOperand(0) == CGF.NormalCleanupDest.getPointer());
 639       assert(condition->use_empty());
 640       condition->eraseFromParent();
 641     }
 642   }
 643
 644   assert(entry->use_empty());
 645   delete entry;
 646 }
 647
 648 /// Pops a cleanup block.  If the block includes a normal cleanup, the
 649 /// current insertion point is threaded through the cleanup, as are
 650 /// any branch fixups on the cleanup.
 651 void CodeGenFunction::PopCleanupBlock(bool FallthroughIsBranchThrough) {
 652   assert(!EHStack.empty() && "cleanup stack is empty!");
 653   assert(isa<EHCleanupScope>(*EHStack.begin()) && "top not a cleanup!");
 654   EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());
 655   assert(Scope.getFixupDepth() <= EHStack.getNumBranchFixups());
 656
 657   // Remember activation information.
 658   bool IsActive = Scope.isActive();
 659   Address NormalActiveFlag =
 660     Scope.shouldTestFlagInNormalCleanup() ? Scope.getActiveFlag()
 661                                           : Address::invalid();
 662   Address EHActiveFlag =
 663     Scope.shouldTestFlagInEHCleanup() ? Scope.getActiveFlag()
 664                                       : Address::invalid();
 665
 666   // Check whether we need an EH cleanup.  This is only true if we've
 667   // generated a lazy EH cleanup block.
 668   llvm::BasicBlock *EHEntry = Scope.getCachedEHDispatchBlock();
 669   assert(Scope.hasEHBranches() == (EHEntry != nullptr));
 670   bool RequiresEHCleanup = (EHEntry != nullptr);
 671   EHScopeStack::stable_iterator EHParent = Scope.getEnclosingEHScope();
 672
 673   // Check the three conditions which might require a normal cleanup:
 674
 675   // - whether there are branch fix-ups through this cleanup
 676   unsigned FixupDepth = Scope.getFixupDepth();
 677   bool HasFixups = EHStack.getNumBranchFixups() != FixupDepth;
 678
 679   // - whether there are branch-throughs or branch-afters
 680   bool HasExistingBranches = Scope.hasBranches();
 681
 682   // - whether there's a fallthrough
 683   llvm::BasicBlock *FallthroughSource = Builder.GetInsertBlock();
 684   bool HasFallthrough = (FallthroughSource != nullptr && IsActive);
 685
 686   // Branch-through fall-throughs leave the insertion point set to the
 687   // end of the last cleanup, which points to the current scope.  The
 688   // rest of IR gen doesn't need to worry about this; it only happens
 689   // during the execution of PopCleanupBlocks().
 690   bool HasPrebranchedFallthrough =
 691     (FallthroughSource && FallthroughSource->getTerminator());
 692
 693   // If this is a normal cleanup, then having a prebranched
 694   // fallthrough implies that the fallthrough source unconditionally
 695   // jumps here.
 696   assert(!Scope.isNormalCleanup() || !HasPrebranchedFallthrough ||
 697          (Scope.getNormalBlock() &&
 698           FallthroughSource->getTerminator()->getSuccessor(0)
 699             == Scope.getNormalBlock()));
 700
 701   bool RequiresNormalCleanup = false;
 702   if (Scope.isNormalCleanup() &&
 703       (HasFixups || HasExistingBranches || HasFallthrough)) {
 704     RequiresNormalCleanup = true;
 705   }
 706
 707   // If we have a prebranched fallthrough into an inactive normal
 708   // cleanup, rewrite it so that it leads to the appropriate place.
 709   if (Scope.isNormalCleanup() && HasPrebranchedFallthrough && !IsActive) {
 710     llvm::BasicBlock *prebranchDest;
 711
 712     // If the prebranch is semantically branching through the next
 713     // cleanup, just forward it to the next block, leaving the
 714     // insertion point in the prebranched block.
 715     if (FallthroughIsBranchThrough) {
 716       EHScope &enclosing = *EHStack.find(Scope.getEnclosingNormalCleanup());
 717       prebranchDest = CreateNormalEntry(*this, cast<EHCleanupScope>(enclosing));
 718
 719     // Otherwise, we need to make a new block.  If the normal cleanup
 720     // isn't being used at all, we could actually reuse the normal
 721     // entry block, but this is simpler, and it avoids conflicts with
 722     // dead optimistic fixup branches.
 723     } else {
 724       prebranchDest = createBasicBlock("forwarded-prebranch");
 725       EmitBlock(prebranchDest);
 726     }
 727
 728     llvm::BasicBlock *normalEntry = Scope.getNormalBlock();
 729     assert(normalEntry && !normalEntry->use_empty());
 730
 731     ForwardPrebranchedFallthrough(FallthroughSource,
 732                                   normalEntry, prebranchDest);
 733   }
 734
 735   // If we don't need the cleanup at all, we're done.
 736   if (!RequiresNormalCleanup && !RequiresEHCleanup) {
 737     destroyOptimisticNormalEntry(*this, Scope);
 738     EHStack.popCleanup(); // safe because there are no fixups
 739     assert(EHStack.getNumBranchFixups() == 0 ||
 740            EHStack.hasNormalCleanups());
 741     return;
 742   }
 743
 744   // Copy the cleanup emission data out.  This uses either a stack
 745   // array or malloc'd memory, depending on the size, which is
 746   // behavior that SmallVector would provide, if we could use it
 747   // here. Unfortunately, if you ask for a SmallVector<char>, the
 748   // alignment isn't sufficient.
 749   auto *CleanupSource = reinterpret_cast<char *>(Scope.getCleanupBuffer());
 750   llvm::AlignedCharArray<EHScopeStack::ScopeStackAlignment, 8 * sizeof(void *)> CleanupBufferStack;
 751   std::unique_ptr<char[]> CleanupBufferHeap;
 752   size_t CleanupSize = Scope.getCleanupSize();
 753   EHScopeStack::Cleanup *Fn;
 754
 755   if (CleanupSize <= sizeof(CleanupBufferStack)) {
 756     memcpy(CleanupBufferStack.buffer, CleanupSource, CleanupSize);
 757     Fn = reinterpret_cast<EHScopeStack::Cleanup *>(CleanupBufferStack.buffer);
 758   } else {
 759     CleanupBufferHeap.reset(new char[CleanupSize]);
 760     memcpy(CleanupBufferHeap.get(), CleanupSource, CleanupSize);
 761     Fn = reinterpret_cast<EHScopeStack::Cleanup *>(CleanupBufferHeap.get());
 762   }
 763
 764   EHScopeStack::Cleanup::Flags cleanupFlags;
 765   if (Scope.isNormalCleanup())
 766     cleanupFlags.setIsNormalCleanupKind();
 767   if (Scope.isEHCleanup())
 768     cleanupFlags.setIsEHCleanupKind();
 769
 770   if (!RequiresNormalCleanup) {
 771     destroyOptimisticNormalEntry(*this, Scope);
 772     EHStack.popCleanup();
 773   } else {
 774     // If we have a fallthrough and no other need for the cleanup,
 775     // emit it directly.
 776     if (HasFallthrough && !HasPrebranchedFallthrough &&
 777         !HasFixups && !HasExistingBranches) {
 778
 779       destroyOptimisticNormalEntry(*this, Scope);
 780       EHStack.popCleanup();
 781
 782       EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);
 783
 784     // Otherwise, the best approach is to thread everything through
 785     // the cleanup block and then try to clean up after ourselves.
 786     } else {
 787       // Force the entry block to exist.
 788       llvm::BasicBlock *NormalEntry = CreateNormalEntry(*this, Scope);
 789
 790       // I.  Set up the fallthrough edge in.
 791
 792       CGBuilderTy::InsertPoint savedInactiveFallthroughIP;
 793
 794       // If there's a fallthrough, we need to store the cleanup
 795       // destination index.  For fall-throughs this is always zero.
 796       if (HasFallthrough) {
 797         if (!HasPrebranchedFallthrough)
 798           Builder.CreateStore(Builder.getInt32(0), getNormalCleanupDestSlot());
 799
 800       // Otherwise, save and clear the IP if we don't have fallthrough
 801       // because the cleanup is inactive.
 802       } else if (FallthroughSource) {
 803         assert(!IsActive && "source without fallthrough for active cleanup");
 804         savedInactiveFallthroughIP = Builder.saveAndClearIP();
 805       }
 806
 807       // II.  Emit the entry block.  This implicitly branches to it if
 808       // we have fallthrough.  All the fixups and existing branches
 809       // should already be branched to it.
 810       EmitBlock(NormalEntry);
 811
 812       // III.  Figure out where we're going and build the cleanup
 813       // epilogue.
 814
 815       bool HasEnclosingCleanups =
 816         (Scope.getEnclosingNormalCleanup() != EHStack.stable_end());
 817
 818       // Compute the branch-through dest if we need it:
 819       //   - if there are branch-throughs threaded through the scope
 820       //   - if fall-through is a branch-through
 821       //   - if there are fixups that will be optimistically forwarded
 822       //     to the enclosing cleanup
 823       llvm::BasicBlock *BranchThroughDest = nullptr;
 824       if (Scope.hasBranchThroughs() ||
 825           (FallthroughSource && FallthroughIsBranchThrough) ||
 826           (HasFixups && HasEnclosingCleanups)) {
 827         assert(HasEnclosingCleanups);
 828         EHScope &S = *EHStack.find(Scope.getEnclosingNormalCleanup());
 829         BranchThroughDest = CreateNormalEntry(*this, cast<EHCleanupScope>(S));
 830       }
 831
 832       llvm::BasicBlock *FallthroughDest = nullptr;
 833       SmallVector<llvm::Instruction*, 2> InstsToAppend;
 834
 835       // If there's exactly one branch-after and no other threads,
 836       // we can route it without a switch.
 837       if (!Scope.hasBranchThroughs() && !HasFixups && !HasFallthrough &&
 838           Scope.getNumBranchAfters() == 1) {
 839         assert(!BranchThroughDest || !IsActive);
 840
 841         // Clean up the possibly dead store to the cleanup dest slot.
 842         llvm::Instruction *NormalCleanupDestSlot =
 843             cast<llvm::Instruction>(getNormalCleanupDestSlot().getPointer());
 844         if (NormalCleanupDestSlot->hasOneUse()) {
 845           NormalCleanupDestSlot->user_back()->eraseFromParent();
 846           NormalCleanupDestSlot->eraseFromParent();
 847           NormalCleanupDest = Address::invalid();
 848         }
 849
 850         llvm::BasicBlock *BranchAfter = Scope.getBranchAfterBlock(0);
 851         InstsToAppend.push_back(llvm::BranchInst::Create(BranchAfter));
 852
 853       // Build a switch-out if we need it:
 854       //   - if there are branch-afters threaded through the scope
 855       //   - if fall-through is a branch-after
 856       //   - if there are fixups that have nowhere left to go and
 857       //     so must be immediately resolved
 858       } else if (Scope.getNumBranchAfters() ||
 859                  (HasFallthrough && !FallthroughIsBranchThrough) ||
 860                  (HasFixups && !HasEnclosingCleanups)) {
 861
 862         llvm::BasicBlock *Default =
 863           (BranchThroughDest ? BranchThroughDest : getUnreachableBlock());
 864
 865         // TODO: base this on the number of branch-afters and fixups
 866         const unsigned SwitchCapacity = 10;
 867
 868         llvm::LoadInst *Load =
 869           createLoadInstBefore(getNormalCleanupDestSlot(), "cleanup.dest",
 870                                nullptr);
 871         llvm::SwitchInst *Switch =
 872           llvm::SwitchInst::Create(Load, Default, SwitchCapacity);
 873
 874         InstsToAppend.push_back(Load);
 875         InstsToAppend.push_back(Switch);
 876
 877         // Branch-after fallthrough.
 878         if (FallthroughSource && !FallthroughIsBranchThrough) {
 879           FallthroughDest = createBasicBlock("cleanup.cont");
 880           if (HasFallthrough)
 881             Switch->addCase(Builder.getInt32(0), FallthroughDest);
 882         }
 883
 884         for (unsigned I = 0, E = Scope.getNumBranchAfters(); I != E; ++I) {
 885           Switch->addCase(Scope.getBranchAfterIndex(I),
 886                           Scope.getBranchAfterBlock(I));
 887         }
 888
 889         // If there aren't any enclosing cleanups, we can resolve all
 890         // the fixups now.
 891         if (HasFixups && !HasEnclosingCleanups)
 892           ResolveAllBranchFixups(*this, Switch, NormalEntry);
 893       } else {
 894         // We should always have a branch-through destination in this case.
 895         assert(BranchThroughDest);
 896         InstsToAppend.push_back(llvm::BranchInst::Create(BranchThroughDest));
 897       }
 898
 899       // IV.  Pop the cleanup and emit it.
 900       EHStack.popCleanup();
 901       assert(EHStack.hasNormalCleanups() == HasEnclosingCleanups);
 902
 903       EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);
 904
 905       // Append the prepared cleanup prologue from above.
 906       llvm::BasicBlock *NormalExit = Builder.GetInsertBlock();
 907       for (unsigned I = 0, E = InstsToAppend.size(); I != E; ++I)
 908         NormalExit->getInstList().push_back(InstsToAppend[I]);
 909
 910       // Optimistically hope that any fixups will continue falling through.
 911       for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();
 912            I < E; ++I) {
 913         BranchFixup &Fixup = EHStack.getBranchFixup(I);
 914         if (!Fixup.Destination) continue;
 915         if (!Fixup.OptimisticBranchBlock) {
 916           createStoreInstBefore(Builder.getInt32(Fixup.DestinationIndex),
 917                                 getNormalCleanupDestSlot(),
 918                                 Fixup.InitialBranch);
 919           Fixup.InitialBranch->setSuccessor(0, NormalEntry);
 920         }
 921         Fixup.OptimisticBranchBlock = NormalExit;
 922       }
 923
 924       // V.  Set up the fallthrough edge out.
 925
 926       // Case 1: a fallthrough source exists but doesn't branch to the
 927       // cleanup because the cleanup is inactive.
 928       if (!HasFallthrough && FallthroughSource) {
 929         // Prebranched fallthrough was forwarded earlier.
 930         // Non-prebranched fallthrough doesn't need to be forwarded.
 931         // Either way, all we need to do is restore the IP we cleared before.
 932         assert(!IsActive);
 933         Builder.restoreIP(savedInactiveFallthroughIP);
 934
 935       // Case 2: a fallthrough source exists and should branch to the
 936       // cleanup, but we're not supposed to branch through to the next
 937       // cleanup.
 938       } else if (HasFallthrough && FallthroughDest) {
 939         assert(!FallthroughIsBranchThrough);
 940         EmitBlock(FallthroughDest);
 941
 942       // Case 3: a fallthrough source exists and should branch to the
 943       // cleanup and then through to the next.
 944       } else if (HasFallthrough) {
 945         // Everything is already set up for this.
 946
 947       // Case 4: no fallthrough source exists.
 948       } else {
 949         Builder.ClearInsertionPoint();
 950       }
 951
 952       // VI.  Assorted cleaning.
 953
 954       // Check whether we can merge NormalEntry into a single predecessor.
 955       // This might invalidate (non-IR) pointers to NormalEntry.
 956       llvm::BasicBlock *NewNormalEntry =
 957         SimplifyCleanupEntry(*this, NormalEntry);
 958
 959       // If it did invalidate those pointers, and NormalEntry was the same
 960       // as NormalExit, go back and patch up the fixups.
 961       if (NewNormalEntry != NormalEntry && NormalEntry == NormalExit)
 962         for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();
 963                I < E; ++I)
 964           EHStack.getBranchFixup(I).OptimisticBranchBlock = NewNormalEntry;
 965     }
 966   }
 967
 968   assert(EHStack.hasNormalCleanups() || EHStack.getNumBranchFixups() == 0);
 969
 970   // Emit the EH cleanup if required.
 971   if (RequiresEHCleanup) {
 972     CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
 973
 974     EmitBlock(EHEntry);
 975
 976     llvm::BasicBlock *NextAction = getEHDispatchBlock(EHParent);
 977
 978     // Push a terminate scope or cleanupendpad scope around the potentially
 979     // throwing cleanups. For funclet EH personalities, the cleanupendpad models
 980     // program termination when cleanups throw.
 981     bool PushedTerminate = false;
 982     SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(
 983         CurrentFuncletPad);
 984     llvm::CleanupPadInst *CPI = nullptr;
 985
 986     const EHPersonality &Personality = EHPersonality::get(*this);
 987     if (Personality.usesFuncletPads()) {
 988       llvm::Value *ParentPad = CurrentFuncletPad;
 989       if (!ParentPad)
 990         ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext());
 991       CurrentFuncletPad = CPI = Builder.CreateCleanupPad(ParentPad);
 992     }
 993
 994     // Non-MSVC personalities need to terminate when an EH cleanup throws.
 995     if (!Personality.isMSVCPersonality()) {
 996       EHStack.pushTerminate();
 997       PushedTerminate = true;
 998     }
 999
1000     // We only actually emit the cleanup code if the cleanup is either
1001     // active or was used before it was deactivated.
1002     if (EHActiveFlag.isValid() || IsActive) {
1003       cleanupFlags.setIsForEHCleanup();
1004       EmitCleanup(*this, Fn, cleanupFlags, EHActiveFlag);
1005     }
1006
1007     if (CPI)
1008       Builder.CreateCleanupRet(CPI, NextAction);
1009     else
1010       Builder.CreateBr(NextAction);
1011
1012     // Leave the terminate scope.
1013     if (PushedTerminate)
1014       EHStack.popTerminate();
1015
1016     Builder.restoreIP(SavedIP);
1017
1018     SimplifyCleanupEntry(*this, EHEntry);
1019   }
1020 }
1021
1022 /// isObviouslyBranchWithoutCleanups - Return true if a branch to the
1023 /// specified destination obviously has no cleanups to run.  'false' is always
1024 /// a conservatively correct answer for this method.
1025 bool CodeGenFunction::isObviouslyBranchWithoutCleanups(JumpDest Dest) const {
1026   assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())
1027          && "stale jump destination");
1028
1029   // Calculate the innermost active normal cleanup.
1030   EHScopeStack::stable_iterator TopCleanup =
1031     EHStack.getInnermostActiveNormalCleanup();
1032
1033   // If we're not in an active normal cleanup scope, or if the
1034   // destination scope is within the innermost active normal cleanup
1035   // scope, we don't need to worry about fixups.
1036   if (TopCleanup == EHStack.stable_end() ||
1037       TopCleanup.encloses(Dest.getScopeDepth())) // works for invalid
1038     return true;
1039
1040   // Otherwise, we might need some cleanups.
1041   return false;
1042 }
1043
1044
1045 /// Terminate the current block by emitting a branch which might leave
1046 /// the current cleanup-protected scope.  The target scope may not yet
1047 /// be known, in which case this will require a fixup.
1048 ///
1049 /// As a side-effect, this method clears the insertion point.
1050 void CodeGenFunction::EmitBranchThroughCleanup(JumpDest Dest) {
1051   assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())
1052          && "stale jump destination");
1053
1054   if (!HaveInsertPoint())
1055     return;
1056
1057   // Create the branch.
1058   llvm::BranchInst *BI = Builder.CreateBr(Dest.getBlock());
1059
1060   // Calculate the innermost active normal cleanup.
1061   EHScopeStack::stable_iterator
1062     TopCleanup = EHStack.getInnermostActiveNormalCleanup();
1063
1064   // If we're not in an active normal cleanup scope, or if the
1065   // destination scope is within the innermost active normal cleanup
1066   // scope, we don't need to worry about fixups.
1067   if (TopCleanup == EHStack.stable_end() ||
1068       TopCleanup.encloses(Dest.getScopeDepth())) { // works for invalid
1069     Builder.ClearInsertionPoint();
1070     return;
1071   }
1072
1073   // If we can't resolve the destination cleanup scope, just add this
1074   // to the current cleanup scope as a branch fixup.
1075   if (!Dest.getScopeDepth().isValid()) {
1076     BranchFixup &Fixup = EHStack.addBranchFixup();
1077     Fixup.Destination = Dest.getBlock();
1078     Fixup.DestinationIndex = Dest.getDestIndex();
1079     Fixup.InitialBranch = BI;
1080     Fixup.OptimisticBranchBlock = nullptr;
1081
1082     Builder.ClearInsertionPoint();
1083     return;
1084   }
1085
1086   // Otherwise, thread through all the normal cleanups in scope.
1087
1088   // Store the index at the start.
1089   llvm::ConstantInt *Index = Builder.getInt32(Dest.getDestIndex());
1090   createStoreInstBefore(Index, getNormalCleanupDestSlot(), BI);
1091
1092   // Adjust BI to point to the first cleanup block.
1093   {
1094     EHCleanupScope &Scope =
1095       cast<EHCleanupScope>(*EHStack.find(TopCleanup));
1096     BI->setSuccessor(0, CreateNormalEntry(*this, Scope));
1097   }
1098
1099   // Add this destination to all the scopes involved.
1100   EHScopeStack::stable_iterator I = TopCleanup;
1101   EHScopeStack::stable_iterator E = Dest.getScopeDepth();
1102   if (E.strictlyEncloses(I)) {
1103     while (true) {
1104       EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(I));
1105       assert(Scope.isNormalCleanup());
1106       I = Scope.getEnclosingNormalCleanup();
1107
1108       // If this is the last cleanup we're propagating through, tell it
1109       // that there's a resolved jump moving through it.
1110       if (!E.strictlyEncloses(I)) {
1111         Scope.addBranchAfter(Index, Dest.getBlock());
1112         break;
1113       }
1114
1115       // Otherwise, tell the scope that there's a jump propagating
1116       // through it.  If this isn't new information, all the rest of
1117       // the work has been done before.
1118       if (!Scope.addBranchThrough(Dest.getBlock()))
1119         break;
1120     }
1121   }
1122
1123   Builder.ClearInsertionPoint();
1124 }
1125
1126 static bool IsUsedAsNormalCleanup(EHScopeStack &EHStack,
1127                                   EHScopeStack::stable_iterator C) {
1128   // If we needed a normal block for any reason, that counts.
1129   if (cast<EHCleanupScope>(*EHStack.find(C)).getNormalBlock())
1130     return true;
1131
1132   // Check whether any enclosed cleanups were needed.
1133   for (EHScopeStack::stable_iterator
1134          I = EHStack.getInnermostNormalCleanup();
1135          I != C; ) {
1136     assert(C.strictlyEncloses(I));
1137     EHCleanupScope &S = cast<EHCleanupScope>(*EHStack.find(I));
1138     if (S.getNormalBlock()) return true;
1139     I = S.getEnclosingNormalCleanup();
1140   }
1141
1142   return false;
1143 }
1144
1145 static bool IsUsedAsEHCleanup(EHScopeStack &EHStack,
1146                               EHScopeStack::stable_iterator cleanup) {
1147   // If we needed an EH block for any reason, that counts.
1148   if (EHStack.find(cleanup)->hasEHBranches())
1149     return true;
1150
1151   // Check whether any enclosed cleanups were needed.
1152   for (EHScopeStack::stable_iterator
1153          i = EHStack.getInnermostEHScope(); i != cleanup; ) {
1154     assert(cleanup.strictlyEncloses(i));
1155
1156     EHScope &scope = *EHStack.find(i);
1157     if (scope.hasEHBranches())
1158       return true;
1159
1160     i = scope.getEnclosingEHScope();
1161   }
1162
1163   return false;
1164 }
1165
1166 enum ForActivation_t {
1167   ForActivation,
1168   ForDeactivation
1169 };
1170
1171 /// The given cleanup block is changing activation state.  Configure a
1172 /// cleanup variable if necessary.
1173 ///
1174 /// It would be good if we had some way of determining if there were
1175 /// extra uses *after* the change-over point.
1176 static void SetupCleanupBlockActivation(CodeGenFunction &CGF,
1177                                         EHScopeStack::stable_iterator C,
1178                                         ForActivation_t kind,
1179                                         llvm::Instruction *dominatingIP) {
1180   EHCleanupScope &Scope = cast<EHCleanupScope>(*CGF.EHStack.find(C));
1181
1182   // We always need the flag if we're activating the cleanup in a
1183   // conditional context, because we have to assume that the current
1184   // location doesn't necessarily dominate the cleanup's code.
1185   bool isActivatedInConditional =
1186     (kind == ForActivation && CGF.isInConditionalBranch());
1187
1188   bool needFlag = false;
1189
1190   // Calculate whether the cleanup was used:
1191
1192   //   - as a normal cleanup
1193   if (Scope.isNormalCleanup() &&
1194       (isActivatedInConditional || IsUsedAsNormalCleanup(CGF.EHStack, C))) {
1195     Scope.setTestFlagInNormalCleanup();
1196     needFlag = true;
1197   }
1198
1199   //  - as an EH cleanup
1200   if (Scope.isEHCleanup() &&
1201       (isActivatedInConditional || IsUsedAsEHCleanup(CGF.EHStack, C))) {
1202     Scope.setTestFlagInEHCleanup();
1203     needFlag = true;
1204   }
1205
1206   // If it hasn't yet been used as either, we're done.
1207   if (!needFlag) return;
1208
1209   Address var = Scope.getActiveFlag();
1210   if (!var.isValid()) {
1211     var = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), CharUnits::One(),
1212                                "cleanup.isactive");
1213     Scope.setActiveFlag(var);
1214
1215     assert(dominatingIP && "no existing variable and no dominating IP!");
1216
1217     // Initialize to true or false depending on whether it was
1218     // active up to this point.
1219     llvm::Constant *value = CGF.Builder.getInt1(kind == ForDeactivation);
1220
1221     // If we're in a conditional block, ignore the dominating IP and
1222     // use the outermost conditional branch.
1223     if (CGF.isInConditionalBranch()) {
1224       CGF.setBeforeOutermostConditional(value, var);
1225     } else {
1226       createStoreInstBefore(value, var, dominatingIP);
1227     }
1228   }
1229
1230   CGF.Builder.CreateStore(CGF.Builder.getInt1(kind == ForActivation), var);
1231 }
1232
1233 /// Activate a cleanup that was created in an inactivated state.
1234 void CodeGenFunction::ActivateCleanupBlock(EHScopeStack::stable_iterator C,
1235                                            llvm::Instruction *dominatingIP) {
1236   assert(C != EHStack.stable_end() && "activating bottom of stack?");
1237   EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));
1238   assert(!Scope.isActive() && "double activation");
1239
1240   SetupCleanupBlockActivation(*this, C, ForActivation, dominatingIP);
1241
1242   Scope.setActive(true);
1243 }
1244
1245 /// Deactive a cleanup that was created in an active state.
1246 void CodeGenFunction::DeactivateCleanupBlock(EHScopeStack::stable_iterator C,
1247                                              llvm::Instruction *dominatingIP) {
1248   assert(C != EHStack.stable_end() && "deactivating bottom of stack?");
1249   EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));
1250   assert(Scope.isActive() && "double deactivation");
1251
1252   // If it's the top of the stack, just pop it, but do so only if it belongs
1253   // to the current RunCleanupsScope.
1254   if (C == EHStack.stable_begin() &&
1255       CurrentCleanupScopeDepth.strictlyEncloses(C)) {
1256     // If it's a normal cleanup, we need to pretend that the
1257     // fallthrough is unreachable.
1258     CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1259     PopCleanupBlock();
1260     Builder.restoreIP(SavedIP);
1261     return;
1262   }
1263
1264   // Otherwise, follow the general case.
1265   SetupCleanupBlockActivation(*this, C, ForDeactivation, dominatingIP);
1266
1267   Scope.setActive(false);
1268 }
1269
1270 Address CodeGenFunction::getNormalCleanupDestSlot() {
1271   if (!NormalCleanupDest.isValid())
1272     NormalCleanupDest =
1273       CreateDefaultAlignTempAlloca(Builder.getInt32Ty(), "cleanup.dest.slot");
1274   return NormalCleanupDest;
1275 }
1276
1277 /// Emits all the code to cause the given temporary to be cleaned up.
1278 void CodeGenFunction::EmitCXXTemporary(const CXXTemporary *Temporary,
1279                                        QualType TempType,
1280                                        Address Ptr) {
1281   pushDestroy(NormalAndEHCleanup, Ptr, TempType, destroyCXXObject,
1282               /*useEHCleanup*/ true);
1283 }