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

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