| //===--- CGCleanup.cpp - Bookkeeping and code emission for cleanups -------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file contains code dealing with the IR generation for cleanups |
| // and related information. |
| // |
| // A "cleanup" is a piece of code which needs to be executed whenever |
| // control transfers out of a particular scope. This can be |
| // conditionalized to occur only on exceptional control flow, only on |
| // normal control flow, or both. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "CodeGenFunction.h" |
| #include "CGCleanup.h" |
| |
| using namespace clang; |
| using namespace CodeGen; |
| |
| bool DominatingValue<RValue>::saved_type::needsSaving(RValue rv) { |
| if (rv.isScalar()) |
| return DominatingLLVMValue::needsSaving(rv.getScalarVal()); |
| if (rv.isAggregate()) |
| return DominatingLLVMValue::needsSaving(rv.getAggregateAddr()); |
| return true; |
| } |
| |
| DominatingValue<RValue>::saved_type |
| DominatingValue<RValue>::saved_type::save(CodeGenFunction &CGF, RValue rv) { |
| if (rv.isScalar()) { |
| llvm::Value *V = rv.getScalarVal(); |
| |
| // These automatically dominate and don't need to be saved. |
| if (!DominatingLLVMValue::needsSaving(V)) |
| return saved_type(V, ScalarLiteral); |
| |
| // Everything else needs an alloca. |
| llvm::Value *addr = CGF.CreateTempAlloca(V->getType(), "saved-rvalue"); |
| CGF.Builder.CreateStore(V, addr); |
| return saved_type(addr, ScalarAddress); |
| } |
| |
| if (rv.isComplex()) { |
| CodeGenFunction::ComplexPairTy V = rv.getComplexVal(); |
| llvm::Type *ComplexTy = |
| llvm::StructType::get(V.first->getType(), V.second->getType(), |
| (void*) 0); |
| llvm::Value *addr = CGF.CreateTempAlloca(ComplexTy, "saved-complex"); |
| CGF.StoreComplexToAddr(V, addr, /*volatile*/ false); |
| return saved_type(addr, ComplexAddress); |
| } |
| |
| assert(rv.isAggregate()); |
| llvm::Value *V = rv.getAggregateAddr(); // TODO: volatile? |
| if (!DominatingLLVMValue::needsSaving(V)) |
| return saved_type(V, AggregateLiteral); |
| |
| llvm::Value *addr = CGF.CreateTempAlloca(V->getType(), "saved-rvalue"); |
| CGF.Builder.CreateStore(V, addr); |
| return saved_type(addr, AggregateAddress); |
| } |
| |
| /// Given a saved r-value produced by SaveRValue, perform the code |
| /// necessary to restore it to usability at the current insertion |
| /// point. |
| RValue DominatingValue<RValue>::saved_type::restore(CodeGenFunction &CGF) { |
| switch (K) { |
| case ScalarLiteral: |
| return RValue::get(Value); |
| case ScalarAddress: |
| return RValue::get(CGF.Builder.CreateLoad(Value)); |
| case AggregateLiteral: |
| return RValue::getAggregate(Value); |
| case AggregateAddress: |
| return RValue::getAggregate(CGF.Builder.CreateLoad(Value)); |
| case ComplexAddress: |
| return RValue::getComplex(CGF.LoadComplexFromAddr(Value, false)); |
| } |
| |
| llvm_unreachable("bad saved r-value kind"); |
| return RValue(); |
| } |
| |
| /// Push an entry of the given size onto this protected-scope stack. |
| char *EHScopeStack::allocate(size_t Size) { |
| if (!StartOfBuffer) { |
| unsigned Capacity = 1024; |
| while (Capacity < Size) Capacity *= 2; |
| StartOfBuffer = new char[Capacity]; |
| StartOfData = EndOfBuffer = StartOfBuffer + Capacity; |
| } else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) { |
| unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer; |
| unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer); |
| |
| unsigned NewCapacity = CurrentCapacity; |
| do { |
| NewCapacity *= 2; |
| } while (NewCapacity < UsedCapacity + Size); |
| |
| char *NewStartOfBuffer = new char[NewCapacity]; |
| char *NewEndOfBuffer = NewStartOfBuffer + NewCapacity; |
| char *NewStartOfData = NewEndOfBuffer - UsedCapacity; |
| memcpy(NewStartOfData, StartOfData, UsedCapacity); |
| delete [] StartOfBuffer; |
| StartOfBuffer = NewStartOfBuffer; |
| EndOfBuffer = NewEndOfBuffer; |
| StartOfData = NewStartOfData; |
| } |
| |
| assert(StartOfBuffer + Size <= StartOfData); |
| StartOfData -= Size; |
| return StartOfData; |
| } |
| |
| EHScopeStack::stable_iterator |
| EHScopeStack::getInnermostActiveNormalCleanup() const { |
| for (stable_iterator si = getInnermostNormalCleanup(), se = stable_end(); |
| si != se; ) { |
| EHCleanupScope &cleanup = cast<EHCleanupScope>(*find(si)); |
| if (cleanup.isActive()) return si; |
| si = cleanup.getEnclosingNormalCleanup(); |
| } |
| return stable_end(); |
| } |
| |
| EHScopeStack::stable_iterator EHScopeStack::getInnermostActiveEHScope() const { |
| for (stable_iterator si = getInnermostEHScope(), se = stable_end(); |
| si != se; ) { |
| // Skip over inactive cleanups. |
| EHCleanupScope *cleanup = dyn_cast<EHCleanupScope>(&*find(si)); |
| if (cleanup && !cleanup->isActive()) { |
| si = cleanup->getEnclosingEHScope(); |
| continue; |
| } |
| |
| // All other scopes are always active. |
| return si; |
| } |
| |
| return stable_end(); |
| } |
| |
| |
| void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) { |
| assert(((Size % sizeof(void*)) == 0) && "cleanup type is misaligned"); |
| char *Buffer = allocate(EHCleanupScope::getSizeForCleanupSize(Size)); |
| bool IsNormalCleanup = Kind & NormalCleanup; |
| bool IsEHCleanup = Kind & EHCleanup; |
| bool IsActive = !(Kind & InactiveCleanup); |
| EHCleanupScope *Scope = |
| new (Buffer) EHCleanupScope(IsNormalCleanup, |
| IsEHCleanup, |
| IsActive, |
| Size, |
| BranchFixups.size(), |
| InnermostNormalCleanup, |
| InnermostEHScope); |
| if (IsNormalCleanup) |
| InnermostNormalCleanup = stable_begin(); |
| if (IsEHCleanup) |
| InnermostEHScope = stable_begin(); |
| |
| return Scope->getCleanupBuffer(); |
| } |
| |
| void EHScopeStack::popCleanup() { |
| assert(!empty() && "popping exception stack when not empty"); |
| |
| assert(isa<EHCleanupScope>(*begin())); |
| EHCleanupScope &Cleanup = cast<EHCleanupScope>(*begin()); |
| InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup(); |
| InnermostEHScope = Cleanup.getEnclosingEHScope(); |
| StartOfData += Cleanup.getAllocatedSize(); |
| |
| // Destroy the cleanup. |
| Cleanup.~EHCleanupScope(); |
| |
| // Check whether we can shrink the branch-fixups stack. |
| if (!BranchFixups.empty()) { |
| // If we no longer have any normal cleanups, all the fixups are |
| // complete. |
| if (!hasNormalCleanups()) |
| BranchFixups.clear(); |
| |
| // Otherwise we can still trim out unnecessary nulls. |
| else |
| popNullFixups(); |
| } |
| } |
| |
| EHFilterScope *EHScopeStack::pushFilter(unsigned numFilters) { |
| assert(getInnermostEHScope() == stable_end()); |
| char *buffer = allocate(EHFilterScope::getSizeForNumFilters(numFilters)); |
| EHFilterScope *filter = new (buffer) EHFilterScope(numFilters); |
| InnermostEHScope = stable_begin(); |
| return filter; |
| } |
| |
| void EHScopeStack::popFilter() { |
| assert(!empty() && "popping exception stack when not empty"); |
| |
| EHFilterScope &filter = cast<EHFilterScope>(*begin()); |
| StartOfData += EHFilterScope::getSizeForNumFilters(filter.getNumFilters()); |
| |
| InnermostEHScope = filter.getEnclosingEHScope(); |
| } |
| |
| EHCatchScope *EHScopeStack::pushCatch(unsigned numHandlers) { |
| char *buffer = allocate(EHCatchScope::getSizeForNumHandlers(numHandlers)); |
| EHCatchScope *scope = |
| new (buffer) EHCatchScope(numHandlers, InnermostEHScope); |
| InnermostEHScope = stable_begin(); |
| return scope; |
| } |
| |
| void EHScopeStack::pushTerminate() { |
| char *Buffer = allocate(EHTerminateScope::getSize()); |
| new (Buffer) EHTerminateScope(InnermostEHScope); |
| InnermostEHScope = stable_begin(); |
| } |
| |
| /// Remove any 'null' fixups on the stack. However, we can't pop more |
| /// fixups than the fixup depth on the innermost normal cleanup, or |
| /// else fixups that we try to add to that cleanup will end up in the |
| /// wrong place. We *could* try to shrink fixup depths, but that's |
| /// actually a lot of work for little benefit. |
| void EHScopeStack::popNullFixups() { |
| // We expect this to only be called when there's still an innermost |
| // normal cleanup; otherwise there really shouldn't be any fixups. |
| assert(hasNormalCleanups()); |
| |
| EHScopeStack::iterator it = find(InnermostNormalCleanup); |
| unsigned MinSize = cast<EHCleanupScope>(*it).getFixupDepth(); |
| assert(BranchFixups.size() >= MinSize && "fixup stack out of order"); |
| |
| while (BranchFixups.size() > MinSize && |
| BranchFixups.back().Destination == 0) |
| BranchFixups.pop_back(); |
| } |
| |
| void CodeGenFunction::initFullExprCleanup() { |
| // Create a variable to decide whether the cleanup needs to be run. |
| llvm::AllocaInst *active |
| = CreateTempAlloca(Builder.getInt1Ty(), "cleanup.cond"); |
| |
| // Initialize it to false at a site that's guaranteed to be run |
| // before each evaluation. |
| llvm::BasicBlock *block = OutermostConditional->getStartingBlock(); |
| new llvm::StoreInst(Builder.getFalse(), active, &block->back()); |
| |
| // Initialize it to true at the current location. |
| Builder.CreateStore(Builder.getTrue(), active); |
| |
| // Set that as the active flag in the cleanup. |
| EHCleanupScope &cleanup = cast<EHCleanupScope>(*EHStack.begin()); |
| assert(cleanup.getActiveFlag() == 0 && "cleanup already has active flag?"); |
| cleanup.setActiveFlag(active); |
| |
| if (cleanup.isNormalCleanup()) cleanup.setTestFlagInNormalCleanup(); |
| if (cleanup.isEHCleanup()) cleanup.setTestFlagInEHCleanup(); |
| } |
| |
| void EHScopeStack::Cleanup::anchor() {} |
| |
| /// All the branch fixups on the EH stack have propagated out past the |
| /// outermost normal cleanup; resolve them all by adding cases to the |
| /// given switch instruction. |
| static void ResolveAllBranchFixups(CodeGenFunction &CGF, |
| llvm::SwitchInst *Switch, |
| llvm::BasicBlock *CleanupEntry) { |
| llvm::SmallPtrSet<llvm::BasicBlock*, 4> CasesAdded; |
| |
| for (unsigned I = 0, E = CGF.EHStack.getNumBranchFixups(); I != E; ++I) { |
| // Skip this fixup if its destination isn't set. |
| BranchFixup &Fixup = CGF.EHStack.getBranchFixup(I); |
| if (Fixup.Destination == 0) continue; |
| |
| // If there isn't an OptimisticBranchBlock, then InitialBranch is |
| // still pointing directly to its destination; forward it to the |
| // appropriate cleanup entry. This is required in the specific |
| // case of |
| // { std::string s; goto lbl; } |
| // lbl: |
| // i.e. where there's an unresolved fixup inside a single cleanup |
| // entry which we're currently popping. |
| if (Fixup.OptimisticBranchBlock == 0) { |
| new llvm::StoreInst(CGF.Builder.getInt32(Fixup.DestinationIndex), |
| CGF.getNormalCleanupDestSlot(), |
| Fixup.InitialBranch); |
| Fixup.InitialBranch->setSuccessor(0, CleanupEntry); |
| } |
| |
| // Don't add this case to the switch statement twice. |
| if (!CasesAdded.insert(Fixup.Destination)) continue; |
| |
| Switch->addCase(CGF.Builder.getInt32(Fixup.DestinationIndex), |
| Fixup.Destination); |
| } |
| |
| CGF.EHStack.clearFixups(); |
| } |
| |
| /// Transitions the terminator of the given exit-block of a cleanup to |
| /// be a cleanup switch. |
| static llvm::SwitchInst *TransitionToCleanupSwitch(CodeGenFunction &CGF, |
| llvm::BasicBlock *Block) { |
| // If it's a branch, turn it into a switch whose default |
| // destination is its original target. |
| llvm::TerminatorInst *Term = Block->getTerminator(); |
| assert(Term && "can't transition block without terminator"); |
| |
| if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) { |
| assert(Br->isUnconditional()); |
| llvm::LoadInst *Load = |
| new llvm::LoadInst(CGF.getNormalCleanupDestSlot(), "cleanup.dest", Term); |
| llvm::SwitchInst *Switch = |
| llvm::SwitchInst::Create(Load, Br->getSuccessor(0), 4, Block); |
| Br->eraseFromParent(); |
| return Switch; |
| } else { |
| return cast<llvm::SwitchInst>(Term); |
| } |
| } |
| |
| void CodeGenFunction::ResolveBranchFixups(llvm::BasicBlock *Block) { |
| assert(Block && "resolving a null target block"); |
| if (!EHStack.getNumBranchFixups()) return; |
| |
| assert(EHStack.hasNormalCleanups() && |
| "branch fixups exist with no normal cleanups on stack"); |
| |
| llvm::SmallPtrSet<llvm::BasicBlock*, 4> ModifiedOptimisticBlocks; |
| bool ResolvedAny = false; |
| |
| for (unsigned I = 0, E = EHStack.getNumBranchFixups(); I != E; ++I) { |
| // Skip this fixup if its destination doesn't match. |
| BranchFixup &Fixup = EHStack.getBranchFixup(I); |
| if (Fixup.Destination != Block) continue; |
| |
| Fixup.Destination = 0; |
| ResolvedAny = true; |
| |
| // If it doesn't have an optimistic branch block, LatestBranch is |
| // already pointing to the right place. |
| llvm::BasicBlock *BranchBB = Fixup.OptimisticBranchBlock; |
| if (!BranchBB) |
| continue; |
| |
| // Don't process the same optimistic branch block twice. |
| if (!ModifiedOptimisticBlocks.insert(BranchBB)) |
| continue; |
| |
| llvm::SwitchInst *Switch = TransitionToCleanupSwitch(*this, BranchBB); |
| |
| // Add a case to the switch. |
| Switch->addCase(Builder.getInt32(Fixup.DestinationIndex), Block); |
| } |
| |
| if (ResolvedAny) |
| EHStack.popNullFixups(); |
| } |
| |
| /// Pops cleanup blocks until the given savepoint is reached. |
| void CodeGenFunction::PopCleanupBlocks(EHScopeStack::stable_iterator Old) { |
| assert(Old.isValid()); |
| |
| while (EHStack.stable_begin() != Old) { |
| EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin()); |
| |
| // As long as Old strictly encloses the scope's enclosing normal |
| // cleanup, we're going to emit another normal cleanup which |
| // fallthrough can propagate through. |
| bool FallThroughIsBranchThrough = |
| Old.strictlyEncloses(Scope.getEnclosingNormalCleanup()); |
| |
| PopCleanupBlock(FallThroughIsBranchThrough); |
| } |
| } |
| |
| static llvm::BasicBlock *CreateNormalEntry(CodeGenFunction &CGF, |
| EHCleanupScope &Scope) { |
| assert(Scope.isNormalCleanup()); |
| llvm::BasicBlock *Entry = Scope.getNormalBlock(); |
| if (!Entry) { |
| Entry = CGF.createBasicBlock("cleanup"); |
| Scope.setNormalBlock(Entry); |
| } |
| return Entry; |
| } |
| |
| /// Attempts to reduce a cleanup's entry block to a fallthrough. This |
| /// is basically llvm::MergeBlockIntoPredecessor, except |
| /// simplified/optimized for the tighter constraints on cleanup blocks. |
| /// |
| /// Returns the new block, whatever it is. |
| static llvm::BasicBlock *SimplifyCleanupEntry(CodeGenFunction &CGF, |
| llvm::BasicBlock *Entry) { |
| llvm::BasicBlock *Pred = Entry->getSinglePredecessor(); |
| if (!Pred) return Entry; |
| |
| llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Pred->getTerminator()); |
| if (!Br || Br->isConditional()) return Entry; |
| assert(Br->getSuccessor(0) == Entry); |
| |
| // If we were previously inserting at the end of the cleanup entry |
| // block, we'll need to continue inserting at the end of the |
| // predecessor. |
| bool WasInsertBlock = CGF.Builder.GetInsertBlock() == Entry; |
| assert(!WasInsertBlock || CGF.Builder.GetInsertPoint() == Entry->end()); |
| |
| // Kill the branch. |
| Br->eraseFromParent(); |
| |
| // Replace all uses of the entry with the predecessor, in case there |
| // are phis in the cleanup. |
| Entry->replaceAllUsesWith(Pred); |
| |
| // Merge the blocks. |
| Pred->getInstList().splice(Pred->end(), Entry->getInstList()); |
| |
| // Kill the entry block. |
| Entry->eraseFromParent(); |
| |
| if (WasInsertBlock) |
| CGF.Builder.SetInsertPoint(Pred); |
| |
| return Pred; |
| } |
| |
| static void EmitCleanup(CodeGenFunction &CGF, |
| EHScopeStack::Cleanup *Fn, |
| EHScopeStack::Cleanup::Flags flags, |
| llvm::Value *ActiveFlag) { |
| // EH cleanups always occur within a terminate scope. |
| if (flags.isForEHCleanup()) CGF.EHStack.pushTerminate(); |
| |
| // If there's an active flag, load it and skip the cleanup if it's |
| // false. |
| llvm::BasicBlock *ContBB = 0; |
| if (ActiveFlag) { |
| ContBB = CGF.createBasicBlock("cleanup.done"); |
| llvm::BasicBlock *CleanupBB = CGF.createBasicBlock("cleanup.action"); |
| llvm::Value *IsActive |
| = CGF.Builder.CreateLoad(ActiveFlag, "cleanup.is_active"); |
| CGF.Builder.CreateCondBr(IsActive, CleanupBB, ContBB); |
| CGF.EmitBlock(CleanupBB); |
| } |
| |
| // Ask the cleanup to emit itself. |
| Fn->Emit(CGF, flags); |
| assert(CGF.HaveInsertPoint() && "cleanup ended with no insertion point?"); |
| |
| // Emit the continuation block if there was an active flag. |
| if (ActiveFlag) |
| CGF.EmitBlock(ContBB); |
| |
| // Leave the terminate scope. |
| if (flags.isForEHCleanup()) CGF.EHStack.popTerminate(); |
| } |
| |
| static void ForwardPrebranchedFallthrough(llvm::BasicBlock *Exit, |
| llvm::BasicBlock *From, |
| llvm::BasicBlock *To) { |
| // Exit is the exit block of a cleanup, so it always terminates in |
| // an unconditional branch or a switch. |
| llvm::TerminatorInst *Term = Exit->getTerminator(); |
| |
| if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) { |
| assert(Br->isUnconditional() && Br->getSuccessor(0) == From); |
| Br->setSuccessor(0, To); |
| } else { |
| llvm::SwitchInst *Switch = cast<llvm::SwitchInst>(Term); |
| for (unsigned I = 0, E = Switch->getNumSuccessors(); I != E; ++I) |
| if (Switch->getSuccessor(I) == From) |
| Switch->setSuccessor(I, To); |
| } |
| } |
| |
| /// We don't need a normal entry block for the given cleanup. |
| /// Optimistic fixup branches can cause these blocks to come into |
| /// existence anyway; if so, destroy it. |
| /// |
| /// The validity of this transformation is very much specific to the |
| /// exact ways in which we form branches to cleanup entries. |
| static void destroyOptimisticNormalEntry(CodeGenFunction &CGF, |
| EHCleanupScope &scope) { |
| llvm::BasicBlock *entry = scope.getNormalBlock(); |
| if (!entry) return; |
| |
| // Replace all the uses with unreachable. |
| llvm::BasicBlock *unreachableBB = CGF.getUnreachableBlock(); |
| for (llvm::BasicBlock::use_iterator |
| i = entry->use_begin(), e = entry->use_end(); i != e; ) { |
| llvm::Use &use = i.getUse(); |
| ++i; |
| |
| use.set(unreachableBB); |
| |
| // The only uses should be fixup switches. |
| llvm::SwitchInst *si = cast<llvm::SwitchInst>(use.getUser()); |
| if (si->getNumCases() == 2 && si->getDefaultDest() == unreachableBB) { |
| // Replace the switch with a branch. |
| llvm::BranchInst::Create(si->getSuccessor(1), si); |
| |
| // The switch operand is a load from the cleanup-dest alloca. |
| llvm::LoadInst *condition = cast<llvm::LoadInst>(si->getCondition()); |
| |
| // Destroy the switch. |
| si->eraseFromParent(); |
| |
| // Destroy the load. |
| assert(condition->getOperand(0) == CGF.NormalCleanupDest); |
| assert(condition->use_empty()); |
| condition->eraseFromParent(); |
| } |
| } |
| |
| assert(entry->use_empty()); |
| delete entry; |
| } |
| |
| /// Pops a cleanup block. If the block includes a normal cleanup, the |
| /// current insertion point is threaded through the cleanup, as are |
| /// any branch fixups on the cleanup. |
| void CodeGenFunction::PopCleanupBlock(bool FallthroughIsBranchThrough) { |
| assert(!EHStack.empty() && "cleanup stack is empty!"); |
| assert(isa<EHCleanupScope>(*EHStack.begin()) && "top not a cleanup!"); |
| EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin()); |
| assert(Scope.getFixupDepth() <= EHStack.getNumBranchFixups()); |
| |
| // Remember activation information. |
| bool IsActive = Scope.isActive(); |
| llvm::Value *NormalActiveFlag = |
| Scope.shouldTestFlagInNormalCleanup() ? Scope.getActiveFlag() : 0; |
| llvm::Value *EHActiveFlag = |
| Scope.shouldTestFlagInEHCleanup() ? Scope.getActiveFlag() : 0; |
| |
| // Check whether we need an EH cleanup. This is only true if we've |
| // generated a lazy EH cleanup block. |
| llvm::BasicBlock *EHEntry = Scope.getCachedEHDispatchBlock(); |
| assert(Scope.hasEHBranches() == (EHEntry != 0)); |
| bool RequiresEHCleanup = (EHEntry != 0); |
| EHScopeStack::stable_iterator EHParent = Scope.getEnclosingEHScope(); |
| |
| // Check the three conditions which might require a normal cleanup: |
| |
| // - whether there are branch fix-ups through this cleanup |
| unsigned FixupDepth = Scope.getFixupDepth(); |
| bool HasFixups = EHStack.getNumBranchFixups() != FixupDepth; |
| |
| // - whether there are branch-throughs or branch-afters |
| bool HasExistingBranches = Scope.hasBranches(); |
| |
| // - whether there's a fallthrough |
| llvm::BasicBlock *FallthroughSource = Builder.GetInsertBlock(); |
| bool HasFallthrough = (FallthroughSource != 0 && IsActive); |
| |
| // Branch-through fall-throughs leave the insertion point set to the |
| // end of the last cleanup, which points to the current scope. The |
| // rest of IR gen doesn't need to worry about this; it only happens |
| // during the execution of PopCleanupBlocks(). |
| bool HasPrebranchedFallthrough = |
| (FallthroughSource && FallthroughSource->getTerminator()); |
| |
| // If this is a normal cleanup, then having a prebranched |
| // fallthrough implies that the fallthrough source unconditionally |
| // jumps here. |
| assert(!Scope.isNormalCleanup() || !HasPrebranchedFallthrough || |
| (Scope.getNormalBlock() && |
| FallthroughSource->getTerminator()->getSuccessor(0) |
| == Scope.getNormalBlock())); |
| |
| bool RequiresNormalCleanup = false; |
| if (Scope.isNormalCleanup() && |
| (HasFixups || HasExistingBranches || HasFallthrough)) { |
| RequiresNormalCleanup = true; |
| } |
| |
| // If we have a prebranched fallthrough into an inactive normal |
| // cleanup, rewrite it so that it leads to the appropriate place. |
| if (Scope.isNormalCleanup() && HasPrebranchedFallthrough && !IsActive) { |
| llvm::BasicBlock *prebranchDest; |
| |
| // If the prebranch is semantically branching through the next |
| // cleanup, just forward it to the next block, leaving the |
| // insertion point in the prebranched block. |
| if (FallthroughIsBranchThrough) { |
| EHScope &enclosing = *EHStack.find(Scope.getEnclosingNormalCleanup()); |
| prebranchDest = CreateNormalEntry(*this, cast<EHCleanupScope>(enclosing)); |
| |
| // Otherwise, we need to make a new block. If the normal cleanup |
| // isn't being used at all, we could actually reuse the normal |
| // entry block, but this is simpler, and it avoids conflicts with |
| // dead optimistic fixup branches. |
| } else { |
| prebranchDest = createBasicBlock("forwarded-prebranch"); |
| EmitBlock(prebranchDest); |
| } |
| |
| llvm::BasicBlock *normalEntry = Scope.getNormalBlock(); |
| assert(normalEntry && !normalEntry->use_empty()); |
| |
| ForwardPrebranchedFallthrough(FallthroughSource, |
| normalEntry, prebranchDest); |
| } |
| |
| // If we don't need the cleanup at all, we're done. |
| if (!RequiresNormalCleanup && !RequiresEHCleanup) { |
| destroyOptimisticNormalEntry(*this, Scope); |
| EHStack.popCleanup(); // safe because there are no fixups |
| assert(EHStack.getNumBranchFixups() == 0 || |
| EHStack.hasNormalCleanups()); |
| return; |
| } |
| |
| // Copy the cleanup emission data out. Note that SmallVector |
| // guarantees maximal alignment for its buffer regardless of its |
| // type parameter. |
| SmallVector<char, 8*sizeof(void*)> CleanupBuffer; |
| CleanupBuffer.reserve(Scope.getCleanupSize()); |
| memcpy(CleanupBuffer.data(), |
| Scope.getCleanupBuffer(), Scope.getCleanupSize()); |
| CleanupBuffer.set_size(Scope.getCleanupSize()); |
| EHScopeStack::Cleanup *Fn = |
| reinterpret_cast<EHScopeStack::Cleanup*>(CleanupBuffer.data()); |
| |
| EHScopeStack::Cleanup::Flags cleanupFlags; |
| if (Scope.isNormalCleanup()) |
| cleanupFlags.setIsNormalCleanupKind(); |
| if (Scope.isEHCleanup()) |
| cleanupFlags.setIsEHCleanupKind(); |
| |
| if (!RequiresNormalCleanup) { |
| destroyOptimisticNormalEntry(*this, Scope); |
| EHStack.popCleanup(); |
| } else { |
| // If we have a fallthrough and no other need for the cleanup, |
| // emit it directly. |
| if (HasFallthrough && !HasPrebranchedFallthrough && |
| !HasFixups && !HasExistingBranches) { |
| |
| destroyOptimisticNormalEntry(*this, Scope); |
| EHStack.popCleanup(); |
| |
| EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag); |
| |
| // Otherwise, the best approach is to thread everything through |
| // the cleanup block and then try to clean up after ourselves. |
| } else { |
| // Force the entry block to exist. |
| llvm::BasicBlock *NormalEntry = CreateNormalEntry(*this, Scope); |
| |
| // I. Set up the fallthrough edge in. |
| |
| CGBuilderTy::InsertPoint savedInactiveFallthroughIP; |
| |
| // If there's a fallthrough, we need to store the cleanup |
| // destination index. For fall-throughs this is always zero. |
| if (HasFallthrough) { |
| if (!HasPrebranchedFallthrough) |
| Builder.CreateStore(Builder.getInt32(0), getNormalCleanupDestSlot()); |
| |
| // Otherwise, save and clear the IP if we don't have fallthrough |
| // because the cleanup is inactive. |
| } else if (FallthroughSource) { |
| assert(!IsActive && "source without fallthrough for active cleanup"); |
| savedInactiveFallthroughIP = Builder.saveAndClearIP(); |
| } |
| |
| // II. Emit the entry block. This implicitly branches to it if |
| // we have fallthrough. All the fixups and existing branches |
| // should already be branched to it. |
| EmitBlock(NormalEntry); |
| |
| // III. Figure out where we're going and build the cleanup |
| // epilogue. |
| |
| bool HasEnclosingCleanups = |
| (Scope.getEnclosingNormalCleanup() != EHStack.stable_end()); |
| |
| // Compute the branch-through dest if we need it: |
| // - if there are branch-throughs threaded through the scope |
| // - if fall-through is a branch-through |
| // - if there are fixups that will be optimistically forwarded |
| // to the enclosing cleanup |
| llvm::BasicBlock *BranchThroughDest = 0; |
| if (Scope.hasBranchThroughs() || |
| (FallthroughSource && FallthroughIsBranchThrough) || |
| (HasFixups && HasEnclosingCleanups)) { |
| assert(HasEnclosingCleanups); |
| EHScope &S = *EHStack.find(Scope.getEnclosingNormalCleanup()); |
| BranchThroughDest = CreateNormalEntry(*this, cast<EHCleanupScope>(S)); |
| } |
| |
| llvm::BasicBlock *FallthroughDest = 0; |
| SmallVector<llvm::Instruction*, 2> InstsToAppend; |
| |
| // If there's exactly one branch-after and no other threads, |
| // we can route it without a switch. |
| if (!Scope.hasBranchThroughs() && !HasFixups && !HasFallthrough && |
| Scope.getNumBranchAfters() == 1) { |
| assert(!BranchThroughDest || !IsActive); |
| |
| // TODO: clean up the possibly dead stores to the cleanup dest slot. |
| llvm::BasicBlock *BranchAfter = Scope.getBranchAfterBlock(0); |
| InstsToAppend.push_back(llvm::BranchInst::Create(BranchAfter)); |
| |
| // Build a switch-out if we need it: |
| // - if there are branch-afters threaded through the scope |
| // - if fall-through is a branch-after |
| // - if there are fixups that have nowhere left to go and |
| // so must be immediately resolved |
| } else if (Scope.getNumBranchAfters() || |
| (HasFallthrough && !FallthroughIsBranchThrough) || |
| (HasFixups && !HasEnclosingCleanups)) { |
| |
| llvm::BasicBlock *Default = |
| (BranchThroughDest ? BranchThroughDest : getUnreachableBlock()); |
| |
| // TODO: base this on the number of branch-afters and fixups |
| const unsigned SwitchCapacity = 10; |
| |
| llvm::LoadInst *Load = |
| new llvm::LoadInst(getNormalCleanupDestSlot(), "cleanup.dest"); |
| llvm::SwitchInst *Switch = |
| llvm::SwitchInst::Create(Load, Default, SwitchCapacity); |
| |
| InstsToAppend.push_back(Load); |
| InstsToAppend.push_back(Switch); |
| |
| // Branch-after fallthrough. |
| if (FallthroughSource && !FallthroughIsBranchThrough) { |
| FallthroughDest = createBasicBlock("cleanup.cont"); |
| if (HasFallthrough) |
| Switch->addCase(Builder.getInt32(0), FallthroughDest); |
| } |
| |
| for (unsigned I = 0, E = Scope.getNumBranchAfters(); I != E; ++I) { |
| Switch->addCase(Scope.getBranchAfterIndex(I), |
| Scope.getBranchAfterBlock(I)); |
| } |
| |
| // If there aren't any enclosing cleanups, we can resolve all |
| // the fixups now. |
| if (HasFixups && !HasEnclosingCleanups) |
| ResolveAllBranchFixups(*this, Switch, NormalEntry); |
| } else { |
| // We should always have a branch-through destination in this case. |
| assert(BranchThroughDest); |
| InstsToAppend.push_back(llvm::BranchInst::Create(BranchThroughDest)); |
| } |
| |
| // IV. Pop the cleanup and emit it. |
| EHStack.popCleanup(); |
| assert(EHStack.hasNormalCleanups() == HasEnclosingCleanups); |
| |
| EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag); |
| |
| // Append the prepared cleanup prologue from above. |
| llvm::BasicBlock *NormalExit = Builder.GetInsertBlock(); |
| for (unsigned I = 0, E = InstsToAppend.size(); I != E; ++I) |
| NormalExit->getInstList().push_back(InstsToAppend[I]); |
| |
| // Optimistically hope that any fixups will continue falling through. |
| for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups(); |
| I < E; ++I) { |
| BranchFixup &Fixup = EHStack.getBranchFixup(I); |
| if (!Fixup.Destination) continue; |
| if (!Fixup.OptimisticBranchBlock) { |
| new llvm::StoreInst(Builder.getInt32(Fixup.DestinationIndex), |
| getNormalCleanupDestSlot(), |
| Fixup.InitialBranch); |
| Fixup.InitialBranch->setSuccessor(0, NormalEntry); |
| } |
| Fixup.OptimisticBranchBlock = NormalExit; |
| } |
| |
| // V. Set up the fallthrough edge out. |
| |
| // Case 1: a fallthrough source exists but doesn't branch to the |
| // cleanup because the cleanup is inactive. |
| if (!HasFallthrough && FallthroughSource) { |
| // Prebranched fallthrough was forwarded earlier. |
| // Non-prebranched fallthrough doesn't need to be forwarded. |
| // Either way, all we need to do is restore the IP we cleared before. |
| assert(!IsActive); |
| Builder.restoreIP(savedInactiveFallthroughIP); |
| |
| // Case 2: a fallthrough source exists and should branch to the |
| // cleanup, but we're not supposed to branch through to the next |
| // cleanup. |
| } else if (HasFallthrough && FallthroughDest) { |
| assert(!FallthroughIsBranchThrough); |
| EmitBlock(FallthroughDest); |
| |
| // Case 3: a fallthrough source exists and should branch to the |
| // cleanup and then through to the next. |
| } else if (HasFallthrough) { |
| // Everything is already set up for this. |
| |
| // Case 4: no fallthrough source exists. |
| } else { |
| Builder.ClearInsertionPoint(); |
| } |
| |
| // VI. Assorted cleaning. |
| |
| // Check whether we can merge NormalEntry into a single predecessor. |
| // This might invalidate (non-IR) pointers to NormalEntry. |
| llvm::BasicBlock *NewNormalEntry = |
| SimplifyCleanupEntry(*this, NormalEntry); |
| |
| // If it did invalidate those pointers, and NormalEntry was the same |
| // as NormalExit, go back and patch up the fixups. |
| if (NewNormalEntry != NormalEntry && NormalEntry == NormalExit) |
| for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups(); |
| I < E; ++I) |
| EHStack.getBranchFixup(I).OptimisticBranchBlock = NewNormalEntry; |
| } |
| } |
| |
| assert(EHStack.hasNormalCleanups() || EHStack.getNumBranchFixups() == 0); |
| |
| // Emit the EH cleanup if required. |
| if (RequiresEHCleanup) { |
| CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); |
| |
| EmitBlock(EHEntry); |
| |
| cleanupFlags.setIsForEHCleanup(); |
| EmitCleanup(*this, Fn, cleanupFlags, EHActiveFlag); |
| |
| Builder.CreateBr(getEHDispatchBlock(EHParent)); |
| |
| Builder.restoreIP(SavedIP); |
| |
| SimplifyCleanupEntry(*this, EHEntry); |
| } |
| } |
| |
| /// isObviouslyBranchWithoutCleanups - Return true if a branch to the |
| /// specified destination obviously has no cleanups to run. 'false' is always |
| /// a conservatively correct answer for this method. |
| bool CodeGenFunction::isObviouslyBranchWithoutCleanups(JumpDest Dest) const { |
| assert(Dest.getScopeDepth().encloses(EHStack.stable_begin()) |
| && "stale jump destination"); |
| |
| // Calculate the innermost active normal cleanup. |
| EHScopeStack::stable_iterator TopCleanup = |
| EHStack.getInnermostActiveNormalCleanup(); |
| |
| // If we're not in an active normal cleanup scope, or if the |
| // destination scope is within the innermost active normal cleanup |
| // scope, we don't need to worry about fixups. |
| if (TopCleanup == EHStack.stable_end() || |
| TopCleanup.encloses(Dest.getScopeDepth())) // works for invalid |
| return true; |
| |
| // Otherwise, we might need some cleanups. |
| return false; |
| } |
| |
| |
| /// Terminate the current block by emitting a branch which might leave |
| /// the current cleanup-protected scope. The target scope may not yet |
| /// be known, in which case this will require a fixup. |
| /// |
| /// As a side-effect, this method clears the insertion point. |
| void CodeGenFunction::EmitBranchThroughCleanup(JumpDest Dest) { |
| assert(Dest.getScopeDepth().encloses(EHStack.stable_begin()) |
| && "stale jump destination"); |
| |
| if (!HaveInsertPoint()) |
| return; |
| |
| // Create the branch. |
| llvm::BranchInst *BI = Builder.CreateBr(Dest.getBlock()); |
| |
| // Calculate the innermost active normal cleanup. |
| EHScopeStack::stable_iterator |
| TopCleanup = EHStack.getInnermostActiveNormalCleanup(); |
| |
| // If we're not in an active normal cleanup scope, or if the |
| // destination scope is within the innermost active normal cleanup |
| // scope, we don't need to worry about fixups. |
| if (TopCleanup == EHStack.stable_end() || |
| TopCleanup.encloses(Dest.getScopeDepth())) { // works for invalid |
| Builder.ClearInsertionPoint(); |
| return; |
| } |
| |
| // If we can't resolve the destination cleanup scope, just add this |
| // to the current cleanup scope as a branch fixup. |
| if (!Dest.getScopeDepth().isValid()) { |
| BranchFixup &Fixup = EHStack.addBranchFixup(); |
| Fixup.Destination = Dest.getBlock(); |
| Fixup.DestinationIndex = Dest.getDestIndex(); |
| Fixup.InitialBranch = BI; |
| Fixup.OptimisticBranchBlock = 0; |
| |
| Builder.ClearInsertionPoint(); |
| return; |
| } |
| |
| // Otherwise, thread through all the normal cleanups in scope. |
| |
| // Store the index at the start. |
| llvm::ConstantInt *Index = Builder.getInt32(Dest.getDestIndex()); |
| new llvm::StoreInst(Index, getNormalCleanupDestSlot(), BI); |
| |
| // Adjust BI to point to the first cleanup block. |
| { |
| EHCleanupScope &Scope = |
| cast<EHCleanupScope>(*EHStack.find(TopCleanup)); |
| BI->setSuccessor(0, CreateNormalEntry(*this, Scope)); |
| } |
| |
| // Add this destination to all the scopes involved. |
| EHScopeStack::stable_iterator I = TopCleanup; |
| EHScopeStack::stable_iterator E = Dest.getScopeDepth(); |
| if (E.strictlyEncloses(I)) { |
| while (true) { |
| EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(I)); |
| assert(Scope.isNormalCleanup()); |
| I = Scope.getEnclosingNormalCleanup(); |
| |
| // If this is the last cleanup we're propagating through, tell it |
| // that there's a resolved jump moving through it. |
| if (!E.strictlyEncloses(I)) { |
| Scope.addBranchAfter(Index, Dest.getBlock()); |
| break; |
| } |
| |
| // Otherwise, tell the scope that there's a jump propoagating |
| // through it. If this isn't new information, all the rest of |
| // the work has been done before. |
| if (!Scope.addBranchThrough(Dest.getBlock())) |
| break; |
| } |
| } |
| |
| Builder.ClearInsertionPoint(); |
| } |
| |
| static bool IsUsedAsNormalCleanup(EHScopeStack &EHStack, |
| EHScopeStack::stable_iterator C) { |
| // If we needed a normal block for any reason, that counts. |
| if (cast<EHCleanupScope>(*EHStack.find(C)).getNormalBlock()) |
| return true; |
| |
| // Check whether any enclosed cleanups were needed. |
| for (EHScopeStack::stable_iterator |
| I = EHStack.getInnermostNormalCleanup(); |
| I != C; ) { |
| assert(C.strictlyEncloses(I)); |
| EHCleanupScope &S = cast<EHCleanupScope>(*EHStack.find(I)); |
| if (S.getNormalBlock()) return true; |
| I = S.getEnclosingNormalCleanup(); |
| } |
| |
| return false; |
| } |
| |
| static bool IsUsedAsEHCleanup(EHScopeStack &EHStack, |
| EHScopeStack::stable_iterator cleanup) { |
| // If we needed an EH block for any reason, that counts. |
| if (EHStack.find(cleanup)->hasEHBranches()) |
| return true; |
| |
| // Check whether any enclosed cleanups were needed. |
| for (EHScopeStack::stable_iterator |
| i = EHStack.getInnermostEHScope(); i != cleanup; ) { |
| assert(cleanup.strictlyEncloses(i)); |
| |
| EHScope &scope = *EHStack.find(i); |
| if (scope.hasEHBranches()) |
| return true; |
| |
| i = scope.getEnclosingEHScope(); |
| } |
| |
| return false; |
| } |
| |
| enum ForActivation_t { |
| ForActivation, |
| ForDeactivation |
| }; |
| |
| /// The given cleanup block is changing activation state. Configure a |
| /// cleanup variable if necessary. |
| /// |
| /// It would be good if we had some way of determining if there were |
| /// extra uses *after* the change-over point. |
| static void SetupCleanupBlockActivation(CodeGenFunction &CGF, |
| EHScopeStack::stable_iterator C, |
| ForActivation_t Kind) { |
| EHCleanupScope &Scope = cast<EHCleanupScope>(*CGF.EHStack.find(C)); |
| |
| // We always need the flag if we're activating the cleanup, because |
| // we have to assume that the current location doesn't necessarily |
| // dominate all future uses of the cleanup. |
| bool NeedFlag = (Kind == ForActivation); |
| |
| // Calculate whether the cleanup was used: |
| |
| // - as a normal cleanup |
| if (Scope.isNormalCleanup() && IsUsedAsNormalCleanup(CGF.EHStack, C)) { |
| Scope.setTestFlagInNormalCleanup(); |
| NeedFlag = true; |
| } |
| |
| // - as an EH cleanup |
| if (Scope.isEHCleanup() && IsUsedAsEHCleanup(CGF.EHStack, C)) { |
| Scope.setTestFlagInEHCleanup(); |
| NeedFlag = true; |
| } |
| |
| // If it hasn't yet been used as either, we're done. |
| if (!NeedFlag) return; |
| |
| llvm::AllocaInst *Var = Scope.getActiveFlag(); |
| if (!Var) { |
| Var = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "cleanup.isactive"); |
| Scope.setActiveFlag(Var); |
| |
| // Initialize to true or false depending on whether it was |
| // active up to this point. |
| CGF.InitTempAlloca(Var, CGF.Builder.getInt1(Kind == ForDeactivation)); |
| } |
| |
| CGF.Builder.CreateStore(CGF.Builder.getInt1(Kind == ForActivation), Var); |
| } |
| |
| /// Activate a cleanup that was created in an inactivated state. |
| void CodeGenFunction::ActivateCleanupBlock(EHScopeStack::stable_iterator C) { |
| assert(C != EHStack.stable_end() && "activating bottom of stack?"); |
| EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C)); |
| assert(!Scope.isActive() && "double activation"); |
| |
| SetupCleanupBlockActivation(*this, C, ForActivation); |
| |
| Scope.setActive(true); |
| } |
| |
| /// Deactive a cleanup that was created in an active state. |
| void CodeGenFunction::DeactivateCleanupBlock(EHScopeStack::stable_iterator C) { |
| assert(C != EHStack.stable_end() && "deactivating bottom of stack?"); |
| EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C)); |
| assert(Scope.isActive() && "double deactivation"); |
| |
| // If it's the top of the stack, just pop it. |
| if (C == EHStack.stable_begin()) { |
| // If it's a normal cleanup, we need to pretend that the |
| // fallthrough is unreachable. |
| CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); |
| PopCleanupBlock(); |
| Builder.restoreIP(SavedIP); |
| return; |
| } |
| |
| // Otherwise, follow the general case. |
| SetupCleanupBlockActivation(*this, C, ForDeactivation); |
| |
| Scope.setActive(false); |
| } |
| |
| llvm::Value *CodeGenFunction::getNormalCleanupDestSlot() { |
| if (!NormalCleanupDest) |
| NormalCleanupDest = |
| CreateTempAlloca(Builder.getInt32Ty(), "cleanup.dest.slot"); |
| return NormalCleanupDest; |
| } |