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