1384 lines · cpp
1//===--- CGCleanup.cpp - Bookkeeping and code emission for cleanups -------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file contains code dealing with the IR generation for cleanups10// and related information.11//12// A "cleanup" is a piece of code which needs to be executed whenever13// control transfers out of a particular scope. This can be14// conditionalized to occur only on exceptional control flow, only on15// normal control flow, or both.16//17//===----------------------------------------------------------------------===//18 19#include "CGCleanup.h"20#include "CodeGenFunction.h"21#include "llvm/Support/SaveAndRestore.h"22 23using namespace clang;24using namespace CodeGen;25 26bool DominatingValue<RValue>::saved_type::needsSaving(RValue rv) {27 if (rv.isScalar())28 return DominatingLLVMValue::needsSaving(rv.getScalarVal());29 if (rv.isAggregate())30 return DominatingValue<Address>::needsSaving(rv.getAggregateAddress());31 return true;32}33 34DominatingValue<RValue>::saved_type35DominatingValue<RValue>::saved_type::save(CodeGenFunction &CGF, RValue rv) {36 if (rv.isScalar()) {37 llvm::Value *V = rv.getScalarVal();38 return saved_type(DominatingLLVMValue::save(CGF, V),39 DominatingLLVMValue::needsSaving(V) ? ScalarAddress40 : ScalarLiteral);41 }42 43 if (rv.isComplex()) {44 CodeGenFunction::ComplexPairTy V = rv.getComplexVal();45 return saved_type(DominatingLLVMValue::save(CGF, V.first),46 DominatingLLVMValue::save(CGF, V.second));47 }48 49 assert(rv.isAggregate());50 Address V = rv.getAggregateAddress();51 return saved_type(DominatingValue<Address>::save(CGF, V),52 DominatingValue<Address>::needsSaving(V)53 ? AggregateAddress54 : AggregateLiteral);55}56 57/// Given a saved r-value produced by SaveRValue, perform the code58/// necessary to restore it to usability at the current insertion59/// point.60RValue DominatingValue<RValue>::saved_type::restore(CodeGenFunction &CGF) {61 switch (K) {62 case ScalarLiteral:63 case ScalarAddress:64 return RValue::get(DominatingLLVMValue::restore(CGF, Vals.first));65 case AggregateLiteral:66 case AggregateAddress:67 return RValue::getAggregate(68 DominatingValue<Address>::restore(CGF, AggregateAddr));69 case ComplexAddress: {70 llvm::Value *real = DominatingLLVMValue::restore(CGF, Vals.first);71 llvm::Value *imag = DominatingLLVMValue::restore(CGF, Vals.second);72 return RValue::getComplex(real, imag);73 }74 }75 76 llvm_unreachable("bad saved r-value kind");77}78 79/// Push an entry of the given size onto this protected-scope stack.80char *EHScopeStack::allocate(size_t Size) {81 Size = llvm::alignTo(Size, ScopeStackAlignment);82 if (!StartOfBuffer) {83 unsigned Capacity = 1024;84 while (Capacity < Size) Capacity *= 2;85 StartOfBuffer = new char[Capacity];86 StartOfData = EndOfBuffer = StartOfBuffer + Capacity;87 } else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) {88 unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer;89 unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer);90 91 unsigned NewCapacity = CurrentCapacity;92 do {93 NewCapacity *= 2;94 } while (NewCapacity < UsedCapacity + Size);95 96 char *NewStartOfBuffer = new char[NewCapacity];97 char *NewEndOfBuffer = NewStartOfBuffer + NewCapacity;98 char *NewStartOfData = NewEndOfBuffer - UsedCapacity;99 memcpy(NewStartOfData, StartOfData, UsedCapacity);100 delete [] StartOfBuffer;101 StartOfBuffer = NewStartOfBuffer;102 EndOfBuffer = NewEndOfBuffer;103 StartOfData = NewStartOfData;104 }105 106 assert(StartOfBuffer + Size <= StartOfData);107 StartOfData -= Size;108 return StartOfData;109}110 111void EHScopeStack::deallocate(size_t Size) {112 StartOfData += llvm::alignTo(Size, ScopeStackAlignment);113}114 115bool EHScopeStack::containsOnlyNoopCleanups(116 EHScopeStack::stable_iterator Old) const {117 for (EHScopeStack::iterator it = begin(); stabilize(it) != Old; it++) {118 EHCleanupScope *cleanup = dyn_cast<EHCleanupScope>(&*it);119 // If this is anything other than a lifetime marker or fake use cleanup,120 // then the scope stack does not contain only noop cleanups.121 if (!cleanup)122 return false;123 if (!cleanup->isLifetimeMarker() && !cleanup->isFakeUse())124 return false;125 }126 127 return true;128}129 130bool EHScopeStack::requiresLandingPad() const {131 for (stable_iterator si = getInnermostEHScope(); si != stable_end(); ) {132 // Skip lifetime markers.133 if (auto *cleanup = dyn_cast<EHCleanupScope>(&*find(si)))134 if (cleanup->isLifetimeMarker()) {135 si = cleanup->getEnclosingEHScope();136 continue;137 }138 return true;139 }140 141 return false;142}143 144EHScopeStack::stable_iterator145EHScopeStack::getInnermostActiveNormalCleanup() const {146 for (stable_iterator si = getInnermostNormalCleanup(), se = stable_end();147 si != se; ) {148 EHCleanupScope &cleanup = cast<EHCleanupScope>(*find(si));149 if (cleanup.isActive()) return si;150 si = cleanup.getEnclosingNormalCleanup();151 }152 return stable_end();153}154 155 156void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {157 char *Buffer = allocate(EHCleanupScope::getSizeForCleanupSize(Size));158 bool IsNormalCleanup = Kind & NormalCleanup;159 bool IsEHCleanup = Kind & EHCleanup;160 bool IsLifetimeMarker = Kind & LifetimeMarker;161 bool IsFakeUse = Kind & FakeUse;162 163 // Per C++ [except.terminate], it is implementation-defined whether none,164 // some, or all cleanups are called before std::terminate. Thus, when165 // terminate is the current EH scope, we may skip adding any EH cleanup166 // scopes.167 if (InnermostEHScope != stable_end() &&168 find(InnermostEHScope)->getKind() == EHScope::Terminate)169 IsEHCleanup = false;170 171 EHCleanupScope *Scope =172 new (Buffer) EHCleanupScope(IsNormalCleanup,173 IsEHCleanup,174 Size,175 BranchFixups.size(),176 InnermostNormalCleanup,177 InnermostEHScope);178 if (IsNormalCleanup)179 InnermostNormalCleanup = stable_begin();180 if (IsEHCleanup)181 InnermostEHScope = stable_begin();182 if (IsLifetimeMarker)183 Scope->setLifetimeMarker();184 if (IsFakeUse)185 Scope->setFakeUse();186 187 // With Windows -EHa, Invoke llvm.seh.scope.begin() for EHCleanup188 // If exceptions are disabled/ignored and SEH is not in use, then there is no189 // invoke destination. SEH "works" even if exceptions are off. In practice,190 // this means that C++ destructors and other EH cleanups don't run, which is191 // consistent with MSVC's behavior, except in the presence of -EHa.192 // Check getInvokeDest() to generate llvm.seh.scope.begin() as needed.193 if (CGF->getLangOpts().EHAsynch && IsEHCleanup && !IsLifetimeMarker &&194 CGF->getTarget().getCXXABI().isMicrosoft() && CGF->getInvokeDest())195 CGF->EmitSehCppScopeBegin();196 197 return Scope->getCleanupBuffer();198}199 200void EHScopeStack::popCleanup() {201 assert(!empty() && "popping exception stack when not empty");202 203 assert(isa<EHCleanupScope>(*begin()));204 EHCleanupScope &Cleanup = cast<EHCleanupScope>(*begin());205 InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup();206 InnermostEHScope = Cleanup.getEnclosingEHScope();207 deallocate(Cleanup.getAllocatedSize());208 209 // Destroy the cleanup.210 Cleanup.Destroy();211 212 // Check whether we can shrink the branch-fixups stack.213 if (!BranchFixups.empty()) {214 // If we no longer have any normal cleanups, all the fixups are215 // complete.216 if (!hasNormalCleanups())217 BranchFixups.clear();218 219 // Otherwise we can still trim out unnecessary nulls.220 else221 popNullFixups();222 }223}224 225EHFilterScope *EHScopeStack::pushFilter(unsigned numFilters) {226 assert(getInnermostEHScope() == stable_end());227 char *buffer = allocate(EHFilterScope::getSizeForNumFilters(numFilters));228 EHFilterScope *filter = new (buffer) EHFilterScope(numFilters);229 InnermostEHScope = stable_begin();230 return filter;231}232 233void EHScopeStack::popFilter() {234 assert(!empty() && "popping exception stack when not empty");235 236 EHFilterScope &filter = cast<EHFilterScope>(*begin());237 deallocate(EHFilterScope::getSizeForNumFilters(filter.getNumFilters()));238 239 InnermostEHScope = filter.getEnclosingEHScope();240}241 242EHCatchScope *EHScopeStack::pushCatch(unsigned numHandlers) {243 char *buffer = allocate(EHCatchScope::getSizeForNumHandlers(numHandlers));244 EHCatchScope *scope =245 new (buffer) EHCatchScope(numHandlers, InnermostEHScope);246 InnermostEHScope = stable_begin();247 return scope;248}249 250void EHScopeStack::pushTerminate() {251 char *Buffer = allocate(EHTerminateScope::getSize());252 new (Buffer) EHTerminateScope(InnermostEHScope);253 InnermostEHScope = stable_begin();254}255 256/// Remove any 'null' fixups on the stack. However, we can't pop more257/// fixups than the fixup depth on the innermost normal cleanup, or258/// else fixups that we try to add to that cleanup will end up in the259/// wrong place. We *could* try to shrink fixup depths, but that's260/// actually a lot of work for little benefit.261void EHScopeStack::popNullFixups() {262 // We expect this to only be called when there's still an innermost263 // normal cleanup; otherwise there really shouldn't be any fixups.264 assert(hasNormalCleanups());265 266 EHScopeStack::iterator it = find(InnermostNormalCleanup);267 unsigned MinSize = cast<EHCleanupScope>(*it).getFixupDepth();268 assert(BranchFixups.size() >= MinSize && "fixup stack out of order");269 270 while (BranchFixups.size() > MinSize &&271 BranchFixups.back().Destination == nullptr)272 BranchFixups.pop_back();273}274 275RawAddress CodeGenFunction::createCleanupActiveFlag() {276 // Create a variable to decide whether the cleanup needs to be run.277 RawAddress active = CreateTempAllocaWithoutCast(278 Builder.getInt1Ty(), CharUnits::One(), "cleanup.cond");279 280 // Initialize it to false at a site that's guaranteed to be run281 // before each evaluation.282 setBeforeOutermostConditional(Builder.getFalse(), active, *this);283 284 // Initialize it to true at the current location.285 Builder.CreateStore(Builder.getTrue(), active);286 287 return active;288}289 290void CodeGenFunction::initFullExprCleanupWithFlag(RawAddress ActiveFlag) {291 // Set that as the active flag in the cleanup.292 EHCleanupScope &cleanup = cast<EHCleanupScope>(*EHStack.begin());293 assert(!cleanup.hasActiveFlag() && "cleanup already has active flag?");294 cleanup.setActiveFlag(ActiveFlag);295 296 if (cleanup.isNormalCleanup()) cleanup.setTestFlagInNormalCleanup();297 if (cleanup.isEHCleanup()) cleanup.setTestFlagInEHCleanup();298}299 300void EHScopeStack::Cleanup::anchor() {}301 302static void createStoreInstBefore(llvm::Value *value, Address addr,303 llvm::BasicBlock::iterator beforeInst,304 CodeGenFunction &CGF) {305 auto store = new llvm::StoreInst(value, addr.emitRawPointer(CGF), beforeInst);306 store->setAlignment(addr.getAlignment().getAsAlign());307}308 309static llvm::LoadInst *310createLoadInstBefore(Address addr, const Twine &name,311 llvm::BasicBlock::iterator beforeInst,312 CodeGenFunction &CGF) {313 return new llvm::LoadInst(addr.getElementType(), addr.emitRawPointer(CGF),314 name, false, addr.getAlignment().getAsAlign(),315 beforeInst);316}317 318static llvm::LoadInst *createLoadInstBefore(Address addr, const Twine &name,319 CodeGenFunction &CGF) {320 return new llvm::LoadInst(addr.getElementType(), addr.emitRawPointer(CGF),321 name, false, addr.getAlignment().getAsAlign());322}323 324/// All the branch fixups on the EH stack have propagated out past the325/// outermost normal cleanup; resolve them all by adding cases to the326/// given switch instruction.327static void ResolveAllBranchFixups(CodeGenFunction &CGF,328 llvm::SwitchInst *Switch,329 llvm::BasicBlock *CleanupEntry) {330 llvm::SmallPtrSet<llvm::BasicBlock*, 4> CasesAdded;331 332 for (unsigned I = 0, E = CGF.EHStack.getNumBranchFixups(); I != E; ++I) {333 // Skip this fixup if its destination isn't set.334 BranchFixup &Fixup = CGF.EHStack.getBranchFixup(I);335 if (Fixup.Destination == nullptr) continue;336 337 // If there isn't an OptimisticBranchBlock, then InitialBranch is338 // still pointing directly to its destination; forward it to the339 // appropriate cleanup entry. This is required in the specific340 // case of341 // { std::string s; goto lbl; }342 // lbl:343 // i.e. where there's an unresolved fixup inside a single cleanup344 // entry which we're currently popping.345 if (Fixup.OptimisticBranchBlock == nullptr) {346 createStoreInstBefore(CGF.Builder.getInt32(Fixup.DestinationIndex),347 CGF.getNormalCleanupDestSlot(),348 Fixup.InitialBranch->getIterator(), CGF);349 Fixup.InitialBranch->setSuccessor(0, CleanupEntry);350 }351 352 // Don't add this case to the switch statement twice.353 if (!CasesAdded.insert(Fixup.Destination).second)354 continue;355 356 Switch->addCase(CGF.Builder.getInt32(Fixup.DestinationIndex),357 Fixup.Destination);358 }359 360 CGF.EHStack.clearFixups();361}362 363/// Transitions the terminator of the given exit-block of a cleanup to364/// be a cleanup switch.365static llvm::SwitchInst *TransitionToCleanupSwitch(CodeGenFunction &CGF,366 llvm::BasicBlock *Block) {367 // If it's a branch, turn it into a switch whose default368 // destination is its original target.369 llvm::Instruction *Term = Block->getTerminator();370 assert(Term && "can't transition block without terminator");371 372 if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {373 assert(Br->isUnconditional());374 auto Load = createLoadInstBefore(CGF.getNormalCleanupDestSlot(),375 "cleanup.dest", Term->getIterator(), CGF);376 llvm::SwitchInst *Switch =377 llvm::SwitchInst::Create(Load, Br->getSuccessor(0), 4, Block);378 Br->eraseFromParent();379 return Switch;380 } else {381 return cast<llvm::SwitchInst>(Term);382 }383}384 385void CodeGenFunction::ResolveBranchFixups(llvm::BasicBlock *Block) {386 assert(Block && "resolving a null target block");387 if (!EHStack.getNumBranchFixups()) return;388 389 assert(EHStack.hasNormalCleanups() &&390 "branch fixups exist with no normal cleanups on stack");391 392 llvm::SmallPtrSet<llvm::BasicBlock*, 4> ModifiedOptimisticBlocks;393 bool ResolvedAny = false;394 395 for (unsigned I = 0, E = EHStack.getNumBranchFixups(); I != E; ++I) {396 // Skip this fixup if its destination doesn't match.397 BranchFixup &Fixup = EHStack.getBranchFixup(I);398 if (Fixup.Destination != Block) continue;399 400 Fixup.Destination = nullptr;401 ResolvedAny = true;402 403 // If it doesn't have an optimistic branch block, LatestBranch is404 // already pointing to the right place.405 llvm::BasicBlock *BranchBB = Fixup.OptimisticBranchBlock;406 if (!BranchBB)407 continue;408 409 // Don't process the same optimistic branch block twice.410 if (!ModifiedOptimisticBlocks.insert(BranchBB).second)411 continue;412 413 llvm::SwitchInst *Switch = TransitionToCleanupSwitch(*this, BranchBB);414 415 // Add a case to the switch.416 Switch->addCase(Builder.getInt32(Fixup.DestinationIndex), Block);417 }418 419 if (ResolvedAny)420 EHStack.popNullFixups();421}422 423/// Pops cleanup blocks until the given savepoint is reached.424void CodeGenFunction::PopCleanupBlocks(425 EHScopeStack::stable_iterator Old,426 std::initializer_list<llvm::Value **> ValuesToReload) {427 assert(Old.isValid());428 429 bool HadBranches = false;430 while (EHStack.stable_begin() != Old) {431 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());432 HadBranches |= Scope.hasBranches();433 434 // As long as Old strictly encloses the scope's enclosing normal435 // cleanup, we're going to emit another normal cleanup which436 // fallthrough can propagate through.437 bool FallThroughIsBranchThrough =438 Old.strictlyEncloses(Scope.getEnclosingNormalCleanup());439 440 PopCleanupBlock(FallThroughIsBranchThrough);441 }442 443 // If we didn't have any branches, the insertion point before cleanups must444 // dominate the current insertion point and we don't need to reload any445 // values.446 if (!HadBranches)447 return;448 449 // Spill and reload all values that the caller wants to be live at the current450 // insertion point.451 for (llvm::Value **ReloadedValue : ValuesToReload) {452 auto *Inst = dyn_cast_or_null<llvm::Instruction>(*ReloadedValue);453 if (!Inst)454 continue;455 456 // Don't spill static allocas, they dominate all cleanups. These are created457 // by binding a reference to a local variable or temporary.458 auto *AI = dyn_cast<llvm::AllocaInst>(Inst);459 if (AI && AI->isStaticAlloca())460 continue;461 462 Address Tmp =463 CreateDefaultAlignTempAlloca(Inst->getType(), "tmp.exprcleanup");464 465 // Find an insertion point after Inst and spill it to the temporary.466 llvm::BasicBlock::iterator InsertBefore;467 if (auto *Invoke = dyn_cast<llvm::InvokeInst>(Inst))468 InsertBefore = Invoke->getNormalDest()->getFirstInsertionPt();469 else470 InsertBefore = std::next(Inst->getIterator());471 CGBuilderTy(CGM, &*InsertBefore).CreateStore(Inst, Tmp);472 473 // Reload the value at the current insertion point.474 *ReloadedValue = Builder.CreateLoad(Tmp);475 }476}477 478/// Pops cleanup blocks until the given savepoint is reached, then add the479/// cleanups from the given savepoint in the lifetime-extended cleanups stack.480void CodeGenFunction::PopCleanupBlocks(481 EHScopeStack::stable_iterator Old, size_t OldLifetimeExtendedSize,482 std::initializer_list<llvm::Value **> ValuesToReload) {483 PopCleanupBlocks(Old, ValuesToReload);484 485 // Move our deferred cleanups onto the EH stack.486 for (size_t I = OldLifetimeExtendedSize,487 E = LifetimeExtendedCleanupStack.size(); I != E; /**/) {488 // Alignment should be guaranteed by the vptrs in the individual cleanups.489 assert((I % alignof(LifetimeExtendedCleanupHeader) == 0) &&490 "misaligned cleanup stack entry");491 492 LifetimeExtendedCleanupHeader &Header =493 reinterpret_cast<LifetimeExtendedCleanupHeader&>(494 LifetimeExtendedCleanupStack[I]);495 I += sizeof(Header);496 497 EHStack.pushCopyOfCleanup(Header.getKind(),498 &LifetimeExtendedCleanupStack[I],499 Header.getSize());500 I += Header.getSize();501 502 if (Header.isConditional()) {503 RawAddress ActiveFlag =504 reinterpret_cast<RawAddress &>(LifetimeExtendedCleanupStack[I]);505 initFullExprCleanupWithFlag(ActiveFlag);506 I += sizeof(ActiveFlag);507 }508 }509 LifetimeExtendedCleanupStack.resize(OldLifetimeExtendedSize);510}511 512static llvm::BasicBlock *CreateNormalEntry(CodeGenFunction &CGF,513 EHCleanupScope &Scope) {514 assert(Scope.isNormalCleanup());515 llvm::BasicBlock *Entry = Scope.getNormalBlock();516 if (!Entry) {517 Entry = CGF.createBasicBlock("cleanup");518 Scope.setNormalBlock(Entry);519 }520 return Entry;521}522 523/// Attempts to reduce a cleanup's entry block to a fallthrough. This524/// is basically llvm::MergeBlockIntoPredecessor, except525/// simplified/optimized for the tighter constraints on cleanup blocks.526///527/// Returns the new block, whatever it is.528static llvm::BasicBlock *SimplifyCleanupEntry(CodeGenFunction &CGF,529 llvm::BasicBlock *Entry) {530 llvm::BasicBlock *Pred = Entry->getSinglePredecessor();531 if (!Pred) return Entry;532 533 llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Pred->getTerminator());534 if (!Br || Br->isConditional()) return Entry;535 assert(Br->getSuccessor(0) == Entry);536 537 // If we were previously inserting at the end of the cleanup entry538 // block, we'll need to continue inserting at the end of the539 // predecessor.540 bool WasInsertBlock = CGF.Builder.GetInsertBlock() == Entry;541 assert(!WasInsertBlock || CGF.Builder.GetInsertPoint() == Entry->end());542 543 // Kill the branch.544 Br->eraseFromParent();545 546 // Replace all uses of the entry with the predecessor, in case there547 // are phis in the cleanup.548 Entry->replaceAllUsesWith(Pred);549 550 // Merge the blocks.551 Pred->splice(Pred->end(), Entry);552 553 // Kill the entry block.554 Entry->eraseFromParent();555 556 if (WasInsertBlock)557 CGF.Builder.SetInsertPoint(Pred);558 559 return Pred;560}561 562static void EmitCleanup(CodeGenFunction &CGF,563 EHScopeStack::Cleanup *Fn,564 EHScopeStack::Cleanup::Flags flags,565 Address ActiveFlag) {566 // If there's an active flag, load it and skip the cleanup if it's567 // false.568 llvm::BasicBlock *ContBB = nullptr;569 if (ActiveFlag.isValid()) {570 ContBB = CGF.createBasicBlock("cleanup.done");571 llvm::BasicBlock *CleanupBB = CGF.createBasicBlock("cleanup.action");572 llvm::Value *IsActive573 = CGF.Builder.CreateLoad(ActiveFlag, "cleanup.is_active");574 CGF.Builder.CreateCondBr(IsActive, CleanupBB, ContBB);575 CGF.EmitBlock(CleanupBB);576 }577 578 // Ask the cleanup to emit itself.579 Fn->Emit(CGF, flags);580 assert(CGF.HaveInsertPoint() && "cleanup ended with no insertion point?");581 582 // Emit the continuation block if there was an active flag.583 if (ActiveFlag.isValid())584 CGF.EmitBlock(ContBB);585}586 587static void ForwardPrebranchedFallthrough(llvm::BasicBlock *Exit,588 llvm::BasicBlock *From,589 llvm::BasicBlock *To) {590 // Exit is the exit block of a cleanup, so it always terminates in591 // an unconditional branch or a switch.592 llvm::Instruction *Term = Exit->getTerminator();593 594 if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {595 assert(Br->isUnconditional() && Br->getSuccessor(0) == From);596 Br->setSuccessor(0, To);597 } else {598 llvm::SwitchInst *Switch = cast<llvm::SwitchInst>(Term);599 for (unsigned I = 0, E = Switch->getNumSuccessors(); I != E; ++I)600 if (Switch->getSuccessor(I) == From)601 Switch->setSuccessor(I, To);602 }603}604 605/// We don't need a normal entry block for the given cleanup.606/// Optimistic fixup branches can cause these blocks to come into607/// existence anyway; if so, destroy it.608///609/// The validity of this transformation is very much specific to the610/// exact ways in which we form branches to cleanup entries.611static void destroyOptimisticNormalEntry(CodeGenFunction &CGF,612 EHCleanupScope &scope) {613 llvm::BasicBlock *entry = scope.getNormalBlock();614 if (!entry) return;615 616 // Replace all the uses with unreachable.617 llvm::BasicBlock *unreachableBB = CGF.getUnreachableBlock();618 for (llvm::BasicBlock::use_iterator619 i = entry->use_begin(), e = entry->use_end(); i != e; ) {620 llvm::Use &use = *i;621 ++i;622 623 use.set(unreachableBB);624 625 // The only uses should be fixup switches.626 llvm::SwitchInst *si = cast<llvm::SwitchInst>(use.getUser());627 if (si->getNumCases() == 1 && si->getDefaultDest() == unreachableBB) {628 // Replace the switch with a branch.629 llvm::BranchInst::Create(si->case_begin()->getCaseSuccessor(),630 si->getIterator());631 632 // The switch operand is a load from the cleanup-dest alloca.633 llvm::LoadInst *condition = cast<llvm::LoadInst>(si->getCondition());634 635 // Destroy the switch.636 si->eraseFromParent();637 638 // Destroy the load.639 assert(condition->getOperand(0) == CGF.NormalCleanupDest.getPointer());640 assert(condition->use_empty());641 condition->eraseFromParent();642 }643 }644 645 assert(entry->use_empty());646 delete entry;647}648 649/// Pops a cleanup block. If the block includes a normal cleanup, the650/// current insertion point is threaded through the cleanup, as are651/// any branch fixups on the cleanup.652void CodeGenFunction::PopCleanupBlock(bool FallthroughIsBranchThrough,653 bool ForDeactivation) {654 assert(!EHStack.empty() && "cleanup stack is empty!");655 assert(isa<EHCleanupScope>(*EHStack.begin()) && "top not a cleanup!");656 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());657 assert(Scope.getFixupDepth() <= EHStack.getNumBranchFixups());658 659 // If we are deactivating a normal cleanup, we need to pretend that the660 // fallthrough is unreachable. We restore this IP before returning.661 CGBuilderTy::InsertPoint NormalDeactivateOrigIP;662 if (ForDeactivation && (Scope.isNormalCleanup() || !getLangOpts().EHAsynch)) {663 NormalDeactivateOrigIP = Builder.saveAndClearIP();664 }665 // Remember activation information.666 bool IsActive = Scope.isActive();667 Address NormalActiveFlag =668 Scope.shouldTestFlagInNormalCleanup() ? Scope.getActiveFlag()669 : Address::invalid();670 Address EHActiveFlag =671 Scope.shouldTestFlagInEHCleanup() ? Scope.getActiveFlag()672 : Address::invalid();673 674 // Check whether we need an EH cleanup. This is only true if we've675 // generated a lazy EH cleanup block.676 llvm::BasicBlock *EHEntry = Scope.getCachedEHDispatchBlock();677 assert(Scope.hasEHBranches() == (EHEntry != nullptr));678 bool RequiresEHCleanup = (EHEntry != nullptr);679 EHScopeStack::stable_iterator EHParent = Scope.getEnclosingEHScope();680 681 // Check the three conditions which might require a normal cleanup:682 683 // - whether there are branch fix-ups through this cleanup684 unsigned FixupDepth = Scope.getFixupDepth();685 bool HasFixups = EHStack.getNumBranchFixups() != FixupDepth;686 687 // - whether there are branch-throughs or branch-afters688 bool HasExistingBranches = Scope.hasBranches();689 690 // - whether there's a fallthrough691 llvm::BasicBlock *FallthroughSource = Builder.GetInsertBlock();692 bool HasFallthrough =693 FallthroughSource != nullptr && (IsActive || HasExistingBranches);694 695 // Branch-through fall-throughs leave the insertion point set to the696 // end of the last cleanup, which points to the current scope. The697 // rest of IR gen doesn't need to worry about this; it only happens698 // during the execution of PopCleanupBlocks().699 bool HasPrebranchedFallthrough =700 (FallthroughSource && FallthroughSource->getTerminator());701 702 // If this is a normal cleanup, then having a prebranched703 // fallthrough implies that the fallthrough source unconditionally704 // jumps here.705 assert(!Scope.isNormalCleanup() || !HasPrebranchedFallthrough ||706 (Scope.getNormalBlock() &&707 FallthroughSource->getTerminator()->getSuccessor(0)708 == Scope.getNormalBlock()));709 710 bool RequiresNormalCleanup = false;711 if (Scope.isNormalCleanup() &&712 (HasFixups || HasExistingBranches || HasFallthrough)) {713 RequiresNormalCleanup = true;714 }715 716 // If we have a prebranched fallthrough into an inactive normal717 // cleanup, rewrite it so that it leads to the appropriate place.718 if (Scope.isNormalCleanup() && HasPrebranchedFallthrough &&719 !RequiresNormalCleanup) {720 // FIXME: Come up with a program which would need forwarding prebranched721 // fallthrough and add tests. Otherwise delete this and assert against it.722 assert(!IsActive);723 llvm::BasicBlock *prebranchDest;724 725 // If the prebranch is semantically branching through the next726 // cleanup, just forward it to the next block, leaving the727 // insertion point in the prebranched block.728 if (FallthroughIsBranchThrough) {729 EHScope &enclosing = *EHStack.find(Scope.getEnclosingNormalCleanup());730 prebranchDest = CreateNormalEntry(*this, cast<EHCleanupScope>(enclosing));731 732 // Otherwise, we need to make a new block. If the normal cleanup733 // isn't being used at all, we could actually reuse the normal734 // entry block, but this is simpler, and it avoids conflicts with735 // dead optimistic fixup branches.736 } else {737 prebranchDest = createBasicBlock("forwarded-prebranch");738 EmitBlock(prebranchDest);739 }740 741 llvm::BasicBlock *normalEntry = Scope.getNormalBlock();742 assert(normalEntry && !normalEntry->use_empty());743 744 ForwardPrebranchedFallthrough(FallthroughSource,745 normalEntry, prebranchDest);746 }747 748 // If we don't need the cleanup at all, we're done.749 if (!RequiresNormalCleanup && !RequiresEHCleanup) {750 destroyOptimisticNormalEntry(*this, Scope);751 EHStack.popCleanup(); // safe because there are no fixups752 assert(EHStack.getNumBranchFixups() == 0 ||753 EHStack.hasNormalCleanups());754 if (NormalDeactivateOrigIP.isSet())755 Builder.restoreIP(NormalDeactivateOrigIP);756 return;757 }758 759 // Copy the cleanup emission data out. This uses either a stack760 // array or malloc'd memory, depending on the size, which is761 // behavior that SmallVector would provide, if we could use it762 // here. Unfortunately, if you ask for a SmallVector<char>, the763 // alignment isn't sufficient.764 auto *CleanupSource = reinterpret_cast<char *>(Scope.getCleanupBuffer());765 alignas(EHScopeStack::ScopeStackAlignment) char766 CleanupBufferStack[8 * sizeof(void *)];767 std::unique_ptr<char[]> CleanupBufferHeap;768 size_t CleanupSize = Scope.getCleanupSize();769 EHScopeStack::Cleanup *Fn;770 771 if (CleanupSize <= sizeof(CleanupBufferStack)) {772 memcpy(CleanupBufferStack, CleanupSource, CleanupSize);773 Fn = reinterpret_cast<EHScopeStack::Cleanup *>(CleanupBufferStack);774 } else {775 CleanupBufferHeap.reset(new char[CleanupSize]);776 memcpy(CleanupBufferHeap.get(), CleanupSource, CleanupSize);777 Fn = reinterpret_cast<EHScopeStack::Cleanup *>(CleanupBufferHeap.get());778 }779 780 EHScopeStack::Cleanup::Flags cleanupFlags;781 if (Scope.isNormalCleanup())782 cleanupFlags.setIsNormalCleanupKind();783 if (Scope.isEHCleanup())784 cleanupFlags.setIsEHCleanupKind();785 786 // Under -EHa, invoke seh.scope.end() to mark scope end before dtor787 bool IsEHa = getLangOpts().EHAsynch && !Scope.isLifetimeMarker();788 const EHPersonality &Personality = EHPersonality::get(*this);789 if (!RequiresNormalCleanup) {790 // Mark CPP scope end for passed-by-value Arg temp791 // per Windows ABI which is "normally" Cleanup in callee792 if (IsEHa && getInvokeDest()) {793 // If we are deactivating a normal cleanup then we don't have a794 // fallthrough. Restore original IP to emit CPP scope ends in the correct795 // block.796 if (NormalDeactivateOrigIP.isSet())797 Builder.restoreIP(NormalDeactivateOrigIP);798 if (Personality.isMSVCXXPersonality() && Builder.GetInsertBlock())799 EmitSehCppScopeEnd();800 if (NormalDeactivateOrigIP.isSet())801 NormalDeactivateOrigIP = Builder.saveAndClearIP();802 }803 destroyOptimisticNormalEntry(*this, Scope);804 Scope.MarkEmitted();805 EHStack.popCleanup();806 } else {807 // If we have a fallthrough and no other need for the cleanup,808 // emit it directly.809 if (HasFallthrough && !HasPrebranchedFallthrough && !HasFixups &&810 !HasExistingBranches) {811 812 // mark SEH scope end for fall-through flow813 if (IsEHa && getInvokeDest()) {814 if (Personality.isMSVCXXPersonality())815 EmitSehCppScopeEnd();816 else817 EmitSehTryScopeEnd();818 }819 820 destroyOptimisticNormalEntry(*this, Scope);821 Scope.MarkEmitted();822 EHStack.popCleanup();823 824 EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);825 826 // Otherwise, the best approach is to thread everything through827 // the cleanup block and then try to clean up after ourselves.828 } else {829 // Force the entry block to exist.830 llvm::BasicBlock *NormalEntry = CreateNormalEntry(*this, Scope);831 832 // I. Set up the fallthrough edge in.833 834 CGBuilderTy::InsertPoint savedInactiveFallthroughIP;835 836 // If there's a fallthrough, we need to store the cleanup837 // destination index. For fall-throughs this is always zero.838 if (HasFallthrough) {839 if (!HasPrebranchedFallthrough)840 Builder.CreateStore(Builder.getInt32(0), getNormalCleanupDestSlot());841 842 // Otherwise, save and clear the IP if we don't have fallthrough843 // because the cleanup is inactive.844 } else if (FallthroughSource) {845 assert(!IsActive && "source without fallthrough for active cleanup");846 savedInactiveFallthroughIP = Builder.saveAndClearIP();847 }848 849 // II. Emit the entry block. This implicitly branches to it if850 // we have fallthrough. All the fixups and existing branches851 // should already be branched to it.852 EmitBlock(NormalEntry);853 854 // intercept normal cleanup to mark SEH scope end855 if (IsEHa && getInvokeDest()) {856 if (Personality.isMSVCXXPersonality())857 EmitSehCppScopeEnd();858 else859 EmitSehTryScopeEnd();860 }861 862 // III. Figure out where we're going and build the cleanup863 // epilogue.864 865 bool HasEnclosingCleanups =866 (Scope.getEnclosingNormalCleanup() != EHStack.stable_end());867 868 // Compute the branch-through dest if we need it:869 // - if there are branch-throughs threaded through the scope870 // - if fall-through is a branch-through871 // - if there are fixups that will be optimistically forwarded872 // to the enclosing cleanup873 llvm::BasicBlock *BranchThroughDest = nullptr;874 if (Scope.hasBranchThroughs() ||875 (FallthroughSource && FallthroughIsBranchThrough) ||876 (HasFixups && HasEnclosingCleanups)) {877 assert(HasEnclosingCleanups);878 EHScope &S = *EHStack.find(Scope.getEnclosingNormalCleanup());879 BranchThroughDest = CreateNormalEntry(*this, cast<EHCleanupScope>(S));880 }881 882 llvm::BasicBlock *FallthroughDest = nullptr;883 SmallVector<llvm::Instruction*, 2> InstsToAppend;884 885 // If there's exactly one branch-after and no other threads,886 // we can route it without a switch.887 // Skip for SEH, since ExitSwitch is used to generate code to indicate888 // abnormal termination. (SEH: Except _leave and fall-through at889 // the end, all other exits in a _try (return/goto/continue/break)890 // are considered as abnormal terminations, using NormalCleanupDestSlot891 // to indicate abnormal termination)892 if (!Scope.hasBranchThroughs() && !HasFixups && !HasFallthrough &&893 !currentFunctionUsesSEHTry() && Scope.getNumBranchAfters() == 1) {894 assert(!BranchThroughDest || !IsActive);895 896 // Clean up the possibly dead store to the cleanup dest slot.897 llvm::Instruction *NormalCleanupDestSlot =898 cast<llvm::Instruction>(getNormalCleanupDestSlot().getPointer());899 if (NormalCleanupDestSlot->hasOneUse()) {900 NormalCleanupDestSlot->user_back()->eraseFromParent();901 NormalCleanupDestSlot->eraseFromParent();902 NormalCleanupDest = RawAddress::invalid();903 }904 905 llvm::BasicBlock *BranchAfter = Scope.getBranchAfterBlock(0);906 InstsToAppend.push_back(llvm::BranchInst::Create(BranchAfter));907 908 // Build a switch-out if we need it:909 // - if there are branch-afters threaded through the scope910 // - if fall-through is a branch-after911 // - if there are fixups that have nowhere left to go and912 // so must be immediately resolved913 } else if (Scope.getNumBranchAfters() ||914 (HasFallthrough && !FallthroughIsBranchThrough) ||915 (HasFixups && !HasEnclosingCleanups)) {916 917 llvm::BasicBlock *Default =918 (BranchThroughDest ? BranchThroughDest : getUnreachableBlock());919 920 // TODO: base this on the number of branch-afters and fixups921 const unsigned SwitchCapacity = 10;922 923 // pass the abnormal exit flag to Fn (SEH cleanup)924 cleanupFlags.setHasExitSwitch();925 926 llvm::LoadInst *Load = createLoadInstBefore(getNormalCleanupDestSlot(),927 "cleanup.dest", *this);928 llvm::SwitchInst *Switch =929 llvm::SwitchInst::Create(Load, Default, SwitchCapacity);930 931 InstsToAppend.push_back(Load);932 InstsToAppend.push_back(Switch);933 934 // Branch-after fallthrough.935 if (FallthroughSource && !FallthroughIsBranchThrough) {936 FallthroughDest = createBasicBlock("cleanup.cont");937 if (HasFallthrough)938 Switch->addCase(Builder.getInt32(0), FallthroughDest);939 }940 941 for (unsigned I = 0, E = Scope.getNumBranchAfters(); I != E; ++I) {942 Switch->addCase(Scope.getBranchAfterIndex(I),943 Scope.getBranchAfterBlock(I));944 }945 946 // If there aren't any enclosing cleanups, we can resolve all947 // the fixups now.948 if (HasFixups && !HasEnclosingCleanups)949 ResolveAllBranchFixups(*this, Switch, NormalEntry);950 } else {951 // We should always have a branch-through destination in this case.952 assert(BranchThroughDest);953 InstsToAppend.push_back(llvm::BranchInst::Create(BranchThroughDest));954 }955 956 // IV. Pop the cleanup and emit it.957 Scope.MarkEmitted();958 EHStack.popCleanup();959 assert(EHStack.hasNormalCleanups() == HasEnclosingCleanups);960 961 EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);962 963 // Append the prepared cleanup prologue from above.964 llvm::BasicBlock *NormalExit = Builder.GetInsertBlock();965 for (llvm::Instruction *Inst : InstsToAppend)966 Inst->insertInto(NormalExit, NormalExit->end());967 968 // Optimistically hope that any fixups will continue falling through.969 for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();970 I < E; ++I) {971 BranchFixup &Fixup = EHStack.getBranchFixup(I);972 if (!Fixup.Destination)973 continue;974 if (!Fixup.OptimisticBranchBlock) {975 createStoreInstBefore(Builder.getInt32(Fixup.DestinationIndex),976 getNormalCleanupDestSlot(),977 Fixup.InitialBranch->getIterator(), *this);978 Fixup.InitialBranch->setSuccessor(0, NormalEntry);979 }980 Fixup.OptimisticBranchBlock = NormalExit;981 }982 983 // V. Set up the fallthrough edge out.984 985 // Case 1: a fallthrough source exists but doesn't branch to the986 // cleanup because the cleanup is inactive.987 if (!HasFallthrough && FallthroughSource) {988 // Prebranched fallthrough was forwarded earlier.989 // Non-prebranched fallthrough doesn't need to be forwarded.990 // Either way, all we need to do is restore the IP we cleared before.991 assert(!IsActive);992 Builder.restoreIP(savedInactiveFallthroughIP);993 994 // Case 2: a fallthrough source exists and should branch to the995 // cleanup, but we're not supposed to branch through to the next996 // cleanup.997 } else if (HasFallthrough && FallthroughDest) {998 assert(!FallthroughIsBranchThrough);999 EmitBlock(FallthroughDest);1000 1001 // Case 3: a fallthrough source exists and should branch to the1002 // cleanup and then through to the next.1003 } else if (HasFallthrough) {1004 // Everything is already set up for this.1005 1006 // Case 4: no fallthrough source exists.1007 } else {1008 Builder.ClearInsertionPoint();1009 }1010 1011 // VI. Assorted cleaning.1012 1013 // Check whether we can merge NormalEntry into a single predecessor.1014 // This might invalidate (non-IR) pointers to NormalEntry.1015 llvm::BasicBlock *NewNormalEntry =1016 SimplifyCleanupEntry(*this, NormalEntry);1017 1018 // If it did invalidate those pointers, and NormalEntry was the same1019 // as NormalExit, go back and patch up the fixups.1020 if (NewNormalEntry != NormalEntry && NormalEntry == NormalExit)1021 for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();1022 I < E; ++I)1023 EHStack.getBranchFixup(I).OptimisticBranchBlock = NewNormalEntry;1024 }1025 }1026 1027 if (NormalDeactivateOrigIP.isSet())1028 Builder.restoreIP(NormalDeactivateOrigIP);1029 assert(EHStack.hasNormalCleanups() || EHStack.getNumBranchFixups() == 0);1030 1031 // Emit the EH cleanup if required.1032 if (RequiresEHCleanup) {1033 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();1034 1035 EmitBlock(EHEntry);1036 1037 llvm::BasicBlock *NextAction = getEHDispatchBlock(EHParent);1038 1039 // Push a terminate scope or cleanupendpad scope around the potentially1040 // throwing cleanups. For funclet EH personalities, the cleanupendpad models1041 // program termination when cleanups throw.1042 bool PushedTerminate = false;1043 SaveAndRestore RestoreCurrentFuncletPad(CurrentFuncletPad);1044 llvm::CleanupPadInst *CPI = nullptr;1045 1046 const EHPersonality &Personality = EHPersonality::get(*this);1047 if (Personality.usesFuncletPads()) {1048 llvm::Value *ParentPad = CurrentFuncletPad;1049 if (!ParentPad)1050 ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext());1051 CurrentFuncletPad = CPI = Builder.CreateCleanupPad(ParentPad);1052 }1053 1054 // Non-MSVC personalities need to terminate when an EH cleanup throws.1055 if (!Personality.isMSVCPersonality()) {1056 EHStack.pushTerminate();1057 PushedTerminate = true;1058 } else if (IsEHa && getInvokeDest()) {1059 EmitSehCppScopeEnd();1060 }1061 1062 // We only actually emit the cleanup code if the cleanup is either1063 // active or was used before it was deactivated.1064 if (EHActiveFlag.isValid() || IsActive) {1065 cleanupFlags.setIsForEHCleanup();1066 EmitCleanup(*this, Fn, cleanupFlags, EHActiveFlag);1067 }1068 1069 if (CPI)1070 Builder.CreateCleanupRet(CPI, NextAction);1071 else1072 Builder.CreateBr(NextAction);1073 1074 // Leave the terminate scope.1075 if (PushedTerminate)1076 EHStack.popTerminate();1077 1078 Builder.restoreIP(SavedIP);1079 1080 SimplifyCleanupEntry(*this, EHEntry);1081 }1082}1083 1084/// isObviouslyBranchWithoutCleanups - Return true if a branch to the1085/// specified destination obviously has no cleanups to run. 'false' is always1086/// a conservatively correct answer for this method.1087bool CodeGenFunction::isObviouslyBranchWithoutCleanups(JumpDest Dest) const {1088 assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())1089 && "stale jump destination");1090 1091 // Calculate the innermost active normal cleanup.1092 EHScopeStack::stable_iterator TopCleanup =1093 EHStack.getInnermostActiveNormalCleanup();1094 1095 // If we're not in an active normal cleanup scope, or if the1096 // destination scope is within the innermost active normal cleanup1097 // scope, we don't need to worry about fixups.1098 if (TopCleanup == EHStack.stable_end() ||1099 TopCleanup.encloses(Dest.getScopeDepth())) // works for invalid1100 return true;1101 1102 // Otherwise, we might need some cleanups.1103 return false;1104}1105 1106 1107/// Terminate the current block by emitting a branch which might leave1108/// the current cleanup-protected scope. The target scope may not yet1109/// be known, in which case this will require a fixup.1110///1111/// As a side-effect, this method clears the insertion point.1112void CodeGenFunction::EmitBranchThroughCleanup(JumpDest Dest) {1113 assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())1114 && "stale jump destination");1115 1116 if (!HaveInsertPoint())1117 return;1118 1119 // Create the branch.1120 llvm::BranchInst *BI = Builder.CreateBr(Dest.getBlock());1121 addInstToCurrentSourceAtom(BI, nullptr);1122 1123 // Calculate the innermost active normal cleanup.1124 EHScopeStack::stable_iterator1125 TopCleanup = EHStack.getInnermostActiveNormalCleanup();1126 1127 // If we're not in an active normal cleanup scope, or if the1128 // destination scope is within the innermost active normal cleanup1129 // scope, we don't need to worry about fixups.1130 if (TopCleanup == EHStack.stable_end() ||1131 TopCleanup.encloses(Dest.getScopeDepth())) { // works for invalid1132 Builder.ClearInsertionPoint();1133 return;1134 }1135 1136 // If we can't resolve the destination cleanup scope, just add this1137 // to the current cleanup scope as a branch fixup.1138 if (!Dest.getScopeDepth().isValid()) {1139 BranchFixup &Fixup = EHStack.addBranchFixup();1140 Fixup.Destination = Dest.getBlock();1141 Fixup.DestinationIndex = Dest.getDestIndex();1142 Fixup.InitialBranch = BI;1143 Fixup.OptimisticBranchBlock = nullptr;1144 1145 Builder.ClearInsertionPoint();1146 return;1147 }1148 1149 // Otherwise, thread through all the normal cleanups in scope.1150 1151 // Store the index at the start.1152 llvm::ConstantInt *Index = Builder.getInt32(Dest.getDestIndex());1153 createStoreInstBefore(Index, getNormalCleanupDestSlot(), BI->getIterator(),1154 *this);1155 1156 // Adjust BI to point to the first cleanup block.1157 {1158 EHCleanupScope &Scope =1159 cast<EHCleanupScope>(*EHStack.find(TopCleanup));1160 BI->setSuccessor(0, CreateNormalEntry(*this, Scope));1161 }1162 1163 // Add this destination to all the scopes involved.1164 EHScopeStack::stable_iterator I = TopCleanup;1165 EHScopeStack::stable_iterator E = Dest.getScopeDepth();1166 if (E.strictlyEncloses(I)) {1167 while (true) {1168 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(I));1169 assert(Scope.isNormalCleanup());1170 I = Scope.getEnclosingNormalCleanup();1171 1172 // If this is the last cleanup we're propagating through, tell it1173 // that there's a resolved jump moving through it.1174 if (!E.strictlyEncloses(I)) {1175 Scope.addBranchAfter(Index, Dest.getBlock());1176 break;1177 }1178 1179 // Otherwise, tell the scope that there's a jump propagating1180 // through it. If this isn't new information, all the rest of1181 // the work has been done before.1182 if (!Scope.addBranchThrough(Dest.getBlock()))1183 break;1184 }1185 }1186 1187 Builder.ClearInsertionPoint();1188}1189 1190static bool IsUsedAsEHCleanup(EHScopeStack &EHStack,1191 EHScopeStack::stable_iterator cleanup) {1192 // If we needed an EH block for any reason, that counts.1193 if (EHStack.find(cleanup)->hasEHBranches())1194 return true;1195 1196 // Check whether any enclosed cleanups were needed.1197 for (EHScopeStack::stable_iterator1198 i = EHStack.getInnermostEHScope(); i != cleanup; ) {1199 assert(cleanup.strictlyEncloses(i));1200 1201 EHScope &scope = *EHStack.find(i);1202 if (scope.hasEHBranches())1203 return true;1204 1205 i = scope.getEnclosingEHScope();1206 }1207 1208 return false;1209}1210 1211enum ForActivation_t {1212 ForActivation,1213 ForDeactivation1214};1215 1216/// The given cleanup block is changing activation state. Configure a1217/// cleanup variable if necessary.1218///1219/// It would be good if we had some way of determining if there were1220/// extra uses *after* the change-over point.1221static void SetupCleanupBlockActivation(CodeGenFunction &CGF,1222 EHScopeStack::stable_iterator C,1223 ForActivation_t kind,1224 llvm::Instruction *dominatingIP) {1225 EHCleanupScope &Scope = cast<EHCleanupScope>(*CGF.EHStack.find(C));1226 1227 // We always need the flag if we're activating the cleanup in a1228 // conditional context, because we have to assume that the current1229 // location doesn't necessarily dominate the cleanup's code.1230 bool isActivatedInConditional =1231 (kind == ForActivation && CGF.isInConditionalBranch());1232 1233 bool needFlag = false;1234 1235 // Calculate whether the cleanup was used:1236 1237 // - as a normal cleanup1238 if (Scope.isNormalCleanup()) {1239 Scope.setTestFlagInNormalCleanup();1240 needFlag = true;1241 }1242 1243 // - as an EH cleanup1244 if (Scope.isEHCleanup() &&1245 (isActivatedInConditional || IsUsedAsEHCleanup(CGF.EHStack, C))) {1246 Scope.setTestFlagInEHCleanup();1247 needFlag = true;1248 }1249 1250 // If it hasn't yet been used as either, we're done.1251 if (!needFlag)1252 return;1253 1254 Address var = Scope.getActiveFlag();1255 if (!var.isValid()) {1256 CodeGenFunction::AllocaTrackerRAII AllocaTracker(CGF);1257 var = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), CharUnits::One(),1258 "cleanup.isactive");1259 Scope.setActiveFlag(var);1260 Scope.AddAuxAllocas(AllocaTracker.Take());1261 1262 assert(dominatingIP && "no existing variable and no dominating IP!");1263 1264 // Initialize to true or false depending on whether it was1265 // active up to this point.1266 llvm::Constant *value = CGF.Builder.getInt1(kind == ForDeactivation);1267 1268 // If we're in a conditional block, ignore the dominating IP and1269 // use the outermost conditional branch.1270 if (CGF.isInConditionalBranch()) {1271 CGF.setBeforeOutermostConditional(value, var, CGF);1272 } else {1273 createStoreInstBefore(value, var, dominatingIP->getIterator(), CGF);1274 }1275 }1276 1277 CGF.Builder.CreateStore(CGF.Builder.getInt1(kind == ForActivation), var);1278}1279 1280/// Activate a cleanup that was created in an inactivated state.1281void CodeGenFunction::ActivateCleanupBlock(EHScopeStack::stable_iterator C,1282 llvm::Instruction *dominatingIP) {1283 assert(C != EHStack.stable_end() && "activating bottom of stack?");1284 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));1285 assert(!Scope.isActive() && "double activation");1286 1287 SetupCleanupBlockActivation(*this, C, ForActivation, dominatingIP);1288 1289 Scope.setActive(true);1290}1291 1292/// Deactive a cleanup that was created in an active state.1293void CodeGenFunction::DeactivateCleanupBlock(EHScopeStack::stable_iterator C,1294 llvm::Instruction *dominatingIP) {1295 assert(C != EHStack.stable_end() && "deactivating bottom of stack?");1296 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));1297 assert(Scope.isActive() && "double deactivation");1298 1299 // If it's the top of the stack, just pop it, but do so only if it belongs1300 // to the current RunCleanupsScope.1301 if (C == EHStack.stable_begin() &&1302 CurrentCleanupScopeDepth.strictlyEncloses(C)) {1303 PopCleanupBlock(/*FallthroughIsBranchThrough=*/false,1304 /*ForDeactivation=*/true);1305 return;1306 }1307 1308 // Otherwise, follow the general case.1309 SetupCleanupBlockActivation(*this, C, ForDeactivation, dominatingIP);1310 1311 Scope.setActive(false);1312}1313 1314RawAddress CodeGenFunction::getNormalCleanupDestSlot() {1315 if (!NormalCleanupDest.isValid())1316 NormalCleanupDest =1317 CreateDefaultAlignTempAlloca(Builder.getInt32Ty(), "cleanup.dest.slot");1318 return NormalCleanupDest;1319}1320 1321/// Emits all the code to cause the given temporary to be cleaned up.1322void CodeGenFunction::EmitCXXTemporary(const CXXTemporary *Temporary,1323 QualType TempType,1324 Address Ptr) {1325 pushDestroy(NormalAndEHCleanup, Ptr, TempType, destroyCXXObject,1326 /*useEHCleanup*/ true);1327}1328 1329// Need to set "funclet" in OperandBundle properly for noThrow1330// intrinsic (see CGCall.cpp)1331static void EmitSehScope(CodeGenFunction &CGF,1332 llvm::FunctionCallee &SehCppScope) {1333 llvm::BasicBlock *InvokeDest = CGF.getInvokeDest();1334 assert(CGF.Builder.GetInsertBlock() && InvokeDest);1335 llvm::BasicBlock *Cont = CGF.createBasicBlock("invoke.cont");1336 SmallVector<llvm::OperandBundleDef, 1> BundleList =1337 CGF.getBundlesForFunclet(SehCppScope.getCallee());1338 if (CGF.CurrentFuncletPad)1339 BundleList.emplace_back("funclet", CGF.CurrentFuncletPad);1340 CGF.Builder.CreateInvoke(SehCppScope, Cont, InvokeDest, {}, BundleList);1341 CGF.EmitBlock(Cont);1342}1343 1344// Invoke a llvm.seh.scope.begin at the beginning of a CPP scope for -EHa1345void CodeGenFunction::EmitSehCppScopeBegin() {1346 assert(getLangOpts().EHAsynch);1347 llvm::FunctionType *FTy =1348 llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);1349 llvm::FunctionCallee SehCppScope =1350 CGM.CreateRuntimeFunction(FTy, "llvm.seh.scope.begin");1351 EmitSehScope(*this, SehCppScope);1352}1353 1354// Invoke a llvm.seh.scope.end at the end of a CPP scope for -EHa1355// llvm.seh.scope.end is emitted before popCleanup, so it's "invoked"1356void CodeGenFunction::EmitSehCppScopeEnd() {1357 assert(getLangOpts().EHAsynch);1358 llvm::FunctionType *FTy =1359 llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);1360 llvm::FunctionCallee SehCppScope =1361 CGM.CreateRuntimeFunction(FTy, "llvm.seh.scope.end");1362 EmitSehScope(*this, SehCppScope);1363}1364 1365// Invoke a llvm.seh.try.begin at the beginning of a SEH scope for -EHa1366void CodeGenFunction::EmitSehTryScopeBegin() {1367 assert(getLangOpts().EHAsynch);1368 llvm::FunctionType *FTy =1369 llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);1370 llvm::FunctionCallee SehCppScope =1371 CGM.CreateRuntimeFunction(FTy, "llvm.seh.try.begin");1372 EmitSehScope(*this, SehCppScope);1373}1374 1375// Invoke a llvm.seh.try.end at the end of a SEH scope for -EHa1376void CodeGenFunction::EmitSehTryScopeEnd() {1377 assert(getLangOpts().EHAsynch);1378 llvm::FunctionType *FTy =1379 llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);1380 llvm::FunctionCallee SehCppScope =1381 CGM.CreateRuntimeFunction(FTy, "llvm.seh.try.end");1382 EmitSehScope(*this, SehCppScope);1383}1384