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

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