1 //===--- CGCleanup.cpp - Bookkeeping and code emission for cleanups -------===//
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
17 //===----------------------------------------------------------------------===//
49   assert(rv.isAggregate());  in save()
57 /// Given a saved r-value produced by SaveRValue, perform the code
76   llvm_unreachable("bad saved r-value kind");  in restore()
79 /// Push an entry of the given size onto this protected-scope stack.
87   } else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) {  in allocate()
88     unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer;  in allocate()
89     unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer);  in allocate()
98     char *NewStartOfData = NewEndOfBuffer - UsedCapacity;  in allocate()
106   assert(StartOfBuffer + Size <= StartOfData);  in allocate()
107   StartOfData -= Size;  in allocate()
119     if (!cleanup || !cleanup->isLifetimeMarker())  in containsOnlyLifetimeMarkers()
130       if (cleanup->isLifetimeMarker()) {  in requiresLandingPad()
131         si = cleanup->getEnclosingEHScope();  in requiresLandingPad()
158   // Per C++ [except.terminate], it is implementation-defined whether none,  in pushCleanup()
163       find(InnermostEHScope)->getKind() == EHScope::Terminate)  in pushCleanup()
178     Scope->setLifetimeMarker();  in pushCleanup()
180   // With Windows -EHa, Invoke llvm.seh.scope.begin() for EHCleanup  in pushCleanup()
184   // consistent with MSVC's behavior, except in the presence of -EHa.  in pushCleanup()
186   if (CGF->getLangOpts().EHAsynch && IsEHCleanup && !IsLifetimeMarker &&  in pushCleanup()
187       CGF->getTarget().getCXXABI().isMicrosoft() && CGF->getInvokeDest())  in pushCleanup()
188     CGF->EmitSehCppScopeBegin();  in pushCleanup()
190   return Scope->getCleanupBuffer();  in pushCleanup()
194   assert(!empty() && "popping exception stack when not empty");  in popCleanup()
196   assert(isa<EHCleanupScope>(*begin()));  in popCleanup()
205   // Check whether we can shrink the branch-fixups stack.  in popCleanup()
219   assert(getInnermostEHScope() == stable_end());  in pushFilter()
227   assert(!empty() && "popping exception stack when not empty");  in popFilter()
257   assert(hasNormalCleanups());  in popNullFixups()
261   assert(BranchFixups.size() >= MinSize && "fixup stack out of order");  in popNullFixups()
286   assert(!cleanup.hasActiveFlag() && "cleanup already has active flag?");  in initFullExprCleanupWithFlag()
299   store->setAlignment(addr.getAlignment().getAsAlign());  in createStoreInstBefore()
335       Fixup.InitialBranch->setSuccessor(0, CleanupEntry);  in ResolveAllBranchFixups()
342     Switch->addCase(CGF.Builder.getInt32(Fixup.DestinationIndex),  in ResolveAllBranchFixups()
349 /// Transitions the terminator of the given exit-block of a cleanup to
355   llvm::Instruction *Term = Block->getTerminator();  in TransitionToCleanupSwitch()
356   assert(Term && "can't transition block without terminator");  in TransitionToCleanupSwitch()
359     assert(Br->isUnconditional());  in TransitionToCleanupSwitch()
363       llvm::SwitchInst::Create(Load, Br->getSuccessor(0), 4, Block);  in TransitionToCleanupSwitch()
364     Br->eraseFromParent();  in TransitionToCleanupSwitch()
372   assert(Block && "resolving a null target block");  in ResolveBranchFixups()
375   assert(EHStack.hasNormalCleanups() &&  in ResolveBranchFixups()
402     Switch->addCase(Builder.getInt32(Fixup.DestinationIndex), Block);  in ResolveBranchFixups()
413   assert(Old.isValid());  in PopCleanupBlocks()
445     if (AI && AI->isStaticAlloca())  in PopCleanupBlocks()
449         CreateDefaultAlignTempAlloca(Inst->getType(), "tmp.exprcleanup");  in PopCleanupBlocks()
454       InsertBefore = Invoke->getNormalDest()->getFirstInsertionPt();  in PopCleanupBlocks()
456       InsertBefore = std::next(Inst->getIterator());  in PopCleanupBlocks()
465 /// cleanups from the given savepoint in the lifetime-extended cleanups stack.
475     assert((I % alignof(LifetimeExtendedCleanupHeader) == 0) &&  in PopCleanupBlocks()
500   assert(Scope.isNormalCleanup());  in CreateNormalEntry()
516   llvm::BasicBlock *Pred = Entry->getSinglePredecessor();  in SimplifyCleanupEntry()
519   llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Pred->getTerminator());  in SimplifyCleanupEntry()
520   if (!Br || Br->isConditional()) return Entry;  in SimplifyCleanupEntry()
521   assert(Br->getSuccessor(0) == Entry);  in SimplifyCleanupEntry()
527   assert(!WasInsertBlock || CGF.Builder.GetInsertPoint() == Entry->end());  in SimplifyCleanupEntry()
530   Br->eraseFromParent();  in SimplifyCleanupEntry()
534   Entry->replaceAllUsesWith(Pred);  in SimplifyCleanupEntry()
537   Pred->splice(Pred->end(), Entry);  in SimplifyCleanupEntry()
540   Entry->eraseFromParent();  in SimplifyCleanupEntry()
565   Fn->Emit(CGF, flags);  in EmitCleanup()
566   assert(CGF.HaveInsertPoint() && "cleanup ended with no insertion point?");  in EmitCleanup()
578   llvm::Instruction *Term = Exit->getTerminator();  in ForwardPrebranchedFallthrough()
581     assert(Br->isUnconditional() && Br->getSuccessor(0) == From);  in ForwardPrebranchedFallthrough()
582     Br->setSuccessor(0, To);  in ForwardPrebranchedFallthrough()
585     for (unsigned I = 0, E = Switch->getNumSuccessors(); I != E; ++I)  in ForwardPrebranchedFallthrough()
586       if (Switch->getSuccessor(I) == From)  in ForwardPrebranchedFallthrough()
587         Switch->setSuccessor(I, To);  in ForwardPrebranchedFallthrough()
605          i = entry->use_begin(), e = entry->use_end(); i != e; ) {  in destroyOptimisticNormalEntry()
613     if (si->getNumCases() == 1 && si->getDefaultDest() == unreachableBB) {  in destroyOptimisticNormalEntry()
615       llvm::BranchInst::Create(si->case_begin()->getCaseSuccessor(), si);  in destroyOptimisticNormalEntry()
617       // The switch operand is a load from the cleanup-dest alloca.  in destroyOptimisticNormalEntry()
618       llvm::LoadInst *condition = cast<llvm::LoadInst>(si->getCondition());  in destroyOptimisticNormalEntry()
621       si->eraseFromParent();  in destroyOptimisticNormalEntry()
624       assert(condition->getOperand(0) == CGF.NormalCleanupDest.getPointer());  in destroyOptimisticNormalEntry()
625       assert(condition->use_empty());  in destroyOptimisticNormalEntry()
626       condition->eraseFromParent();  in destroyOptimisticNormalEntry()
630   assert(entry->use_empty());  in destroyOptimisticNormalEntry()
639   assert(!EHStack.empty() && "cleanup stack is empty!");  in PopCleanupBlock()
640   assert(isa<EHCleanupScope>(*EHStack.begin()) && "top not a cleanup!");  in PopCleanupBlock()
642   assert(Scope.getFixupDepth() <= EHStack.getNumBranchFixups());  in PopCleanupBlock()
662   assert(Scope.hasEHBranches() == (EHEntry != nullptr));  in PopCleanupBlock()
668   // - whether there are branch fix-ups through this cleanup  in PopCleanupBlock()
672   // - whether there are branch-throughs or branch-afters  in PopCleanupBlock()
675   // - whether there's a fallthrough  in PopCleanupBlock()
680   // Branch-through fall-throughs leave the insertion point set to the  in PopCleanupBlock()
685     (FallthroughSource && FallthroughSource->getTerminator());  in PopCleanupBlock()
690   assert(!Scope.isNormalCleanup() || !HasPrebranchedFallthrough ||  in PopCleanupBlock()
692           FallthroughSource->getTerminator()->getSuccessor(0)  in PopCleanupBlock()
706     // fallthrough and add tests. Otherwise delete this and assert against it.  in PopCleanupBlock()
707     assert(!IsActive);  in PopCleanupBlock()
722       prebranchDest = createBasicBlock("forwarded-prebranch");  in PopCleanupBlock()
727     assert(normalEntry && !normalEntry->use_empty());  in PopCleanupBlock()
737     assert(EHStack.getNumBranchFixups() == 0 ||  in PopCleanupBlock()
771   // Under -EHa, invoke seh.scope.end() to mark scope end before dtor  in PopCleanupBlock()
775     // Mark CPP scope end for passed-by-value Arg temp  in PopCleanupBlock()
797       // mark SEH scope end for fall-through flow  in PopCleanupBlock()
817       // I.  Set up the fallthrough edge in.  in PopCleanupBlock()
822       // destination index.  For fall-throughs this is always zero.  in PopCleanupBlock()
830         assert(!IsActive && "source without fallthrough for active cleanup");  in PopCleanupBlock()
853       // Compute the branch-through dest if we need it:  in PopCleanupBlock()
854       //   - if there are branch-throughs threaded through the scope  in PopCleanupBlock()
855       //   - if fall-through is a branch-through  in PopCleanupBlock()
856       //   - if there are fixups that will be optimistically forwarded  in PopCleanupBlock()
862         assert(HasEnclosingCleanups);  in PopCleanupBlock()
870       // If there's exactly one branch-after and no other threads,  in PopCleanupBlock()
873       // abnormal termination. (SEH: Except _leave and fall-through at  in PopCleanupBlock()
879         assert(!BranchThroughDest || !IsActive);  in PopCleanupBlock()
884         if (NormalCleanupDestSlot->hasOneUse()) {  in PopCleanupBlock()
885           NormalCleanupDestSlot->user_back()->eraseFromParent();  in PopCleanupBlock()
886           NormalCleanupDestSlot->eraseFromParent();  in PopCleanupBlock()
893       // Build a switch-out if we need it:  in PopCleanupBlock()
894       //   - if there are branch-afters threaded through the scope  in PopCleanupBlock()
895       //   - if fall-through is a branch-after  in PopCleanupBlock()
896       //   - if there are fixups that have nowhere left to go and  in PopCleanupBlock()
905         // TODO: base this on the number of branch-afters and fixups  in PopCleanupBlock()
919         // Branch-after fallthrough.  in PopCleanupBlock()
923             Switch->addCase(Builder.getInt32(0), FallthroughDest);  in PopCleanupBlock()
927           Switch->addCase(Scope.getBranchAfterIndex(I),  in PopCleanupBlock()
936         // We should always have a branch-through destination in this case.  in PopCleanupBlock()
937         assert(BranchThroughDest);  in PopCleanupBlock()
944       assert(EHStack.hasNormalCleanups() == HasEnclosingCleanups);  in PopCleanupBlock()
951         InstsToAppend[I]->insertInto(NormalExit, NormalExit->end());  in PopCleanupBlock()
953       // Optimistically hope that any fixups will continue falling through.  in PopCleanupBlock()
962           Fixup.InitialBranch->setSuccessor(0, NormalEntry);  in PopCleanupBlock()
967       // V.  Set up the fallthrough edge out.  in PopCleanupBlock()
973         // Non-prebranched fallthrough doesn't need to be forwarded.  in PopCleanupBlock()
975         assert(!IsActive);  in PopCleanupBlock()
982         assert(!FallthroughIsBranchThrough);  in PopCleanupBlock()
998       // This might invalidate (non-IR) pointers to NormalEntry.  in PopCleanupBlock()
1013   assert(EHStack.hasNormalCleanups() || EHStack.getNumBranchFixups() == 0);  in PopCleanupBlock()
1038     // Non-MSVC personalities need to terminate when an EH cleanup throws.  in PopCleanupBlock()
1068 /// isObviouslyBranchWithoutCleanups - Return true if a branch to the
1072   assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())  in isObviouslyBranchWithoutCleanups()
1092 /// the current cleanup-protected scope.  The target scope may not yet
1095 /// As a side-effect, this method clears the insertion point.
1097   assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())  in EmitBranchThroughCleanup()
1142     BI->setSuccessor(0, CreateNormalEntry(*this, Scope));  in EmitBranchThroughCleanup()
1151       assert(Scope.isNormalCleanup());  in EmitBranchThroughCleanup()
1175   if (EHStack.find(cleanup)->hasEHBranches())  in IsUsedAsEHCleanup()
1181     assert(cleanup.strictlyEncloses(i));  in IsUsedAsEHCleanup()
1202 /// extra uses *after* the change-over point.
1219   //   - as a normal cleanup  in SetupCleanupBlockActivation()
1225   //  - as an EH cleanup  in SetupCleanupBlockActivation()
1244     assert(dominatingIP && "no existing variable and no dominating IP!");  in SetupCleanupBlockActivation()
1265   assert(C != EHStack.stable_end() && "activating bottom of stack?");  in ActivateCleanupBlock()
1267   assert(!Scope.isActive() && "double activation");  in ActivateCleanupBlock()
1277   assert(C != EHStack.stable_end() && "deactivating bottom of stack?");  in DeactivateCleanupBlock()
1279   assert(Scope.isActive() && "double deactivation");  in DeactivateCleanupBlock()
1316   assert(CGF.Builder.GetInsertBlock() && InvokeDest);  in EmitSehScope()
1327 // Invoke a llvm.seh.scope.begin at the beginning of a CPP scope for -EHa
1329   assert(getLangOpts().EHAsynch);  in EmitSehCppScopeBegin()
1337 // Invoke a llvm.seh.scope.end at the end of a CPP scope for -EHa
1340   assert(getLangOpts().EHAsynch);  in EmitSehCppScopeEnd()
1348 // Invoke a llvm.seh.try.begin at the beginning of a SEH scope for -EHa
1350   assert(getLangOpts().EHAsynch);  in EmitSehTryScopeBegin()
1358 // Invoke a llvm.seh.try.end at the end of a SEH scope for -EHa
1360   assert(getLangOpts().EHAsynch);  in EmitSehTryScopeEnd()