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