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