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-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains code dealing with the IR generation for cleanups
10// and related information.
11//
12// A "cleanup" is a piece of code which needs to be executed whenever
13// control transfers out of a particular scope. This can be
14// conditionalized to occur only on exceptional control flow, only on
15// 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(value: rv.getScalarVal());
29 if (rv.isAggregate())
30 return DominatingValue<Address>::needsSaving(value: rv.getAggregateAddress());
31 return true;
32}
33
34DominatingValue<RValue>::saved_type
35DominatingValue<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, value: V),
39 DominatingLLVMValue::needsSaving(value: V) ? ScalarAddress
40 : ScalarLiteral);
41 }
42
43 if (rv.isComplex()) {
44 CodeGenFunction::ComplexPairTy V = rv.getComplexVal();
45 return saved_type(DominatingLLVMValue::save(CGF, value: V.first),
46 DominatingLLVMValue::save(CGF, value: V.second));
47 }
48
49 assert(rv.isAggregate());
50 Address V = rv.getAggregateAddress();
51 return saved_type(DominatingValue<Address>::save(CGF, value: V),
52 DominatingValue<Address>::needsSaving(value: V)
53 ? AggregateAddress
54 : AggregateLiteral);
55}
56
57/// Given a saved r-value produced by SaveRValue, perform the code
58/// necessary to restore it to usability at the current insertion
59/// point.
60RValue DominatingValue<RValue>::saved_type::restore(CodeGenFunction &CGF) {
61 switch (K) {
62 case ScalarLiteral:
63 case ScalarAddress:
64 return RValue::get(V: DominatingLLVMValue::restore(CGF, value: Vals.first));
65 case AggregateLiteral:
66 case AggregateAddress:
67 return RValue::getAggregate(
68 addr: DominatingValue<Address>::restore(CGF, value: AggregateAddr));
69 case ComplexAddress: {
70 llvm::Value *real = DominatingLLVMValue::restore(CGF, value: Vals.first);
71 llvm::Value *imag = DominatingLLVMValue::restore(CGF, value: Vals.second);
72 return RValue::getComplex(V1: real, V2: 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(Value: Size, Align: 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(dest: NewStartOfData, src: StartOfData, n: 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(Value: Size, Align: ScopeStackAlignment);
113}
114
115bool EHScopeStack::containsOnlyNoopCleanups(
116 EHScopeStack::stable_iterator Old) const {
117 for (EHScopeStack::iterator it = begin(); stabilize(ir: it) != Old; it++) {
118 EHCleanupScope *cleanup = dyn_cast<EHCleanupScope>(Val: &*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>(Val: &*find(sp: si)))
134 if (cleanup->isLifetimeMarker()) {
135 si = cleanup->getEnclosingEHScope();
136 continue;
137 }
138 return true;
139 }
140
141 return false;
142}
143
144EHScopeStack::stable_iterator
145EHScopeStack::getInnermostActiveNormalCleanup() const {
146 for (stable_iterator si = getInnermostNormalCleanup(), se = stable_end();
147 si != se; ) {
148 EHCleanupScope &cleanup = cast<EHCleanupScope>(Val&: *find(sp: 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(Size: 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, when
165 // terminate is the current EH scope, we may skip adding any EH cleanup
166 // scopes.
167 if (InnermostEHScope != stable_end() &&
168 find(sp: 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 EHCleanup
188 // If exceptions are disabled/ignored and SEH is not in use, then there is no
189 // 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 is
191 // 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>(Val&: *begin());
205 InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup();
206 InnermostEHScope = Cleanup.getEnclosingEHScope();
207 deallocate(Size: 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 are
215 // complete.
216 if (!hasNormalCleanups())
217 BranchFixups.clear();
218
219 // Otherwise we can still trim out unnecessary nulls.
220 else
221 popNullFixups();
222 }
223}
224
225EHFilterScope *EHScopeStack::pushFilter(unsigned numFilters) {
226 assert(getInnermostEHScope() == stable_end());
227 char *buffer = allocate(Size: 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>(Val&: *begin());
237 deallocate(Size: EHFilterScope::getSizeForNumFilters(numFilters: filter.getNumFilters()));
238
239 InnermostEHScope = filter.getEnclosingEHScope();
240}
241
242EHCatchScope *EHScopeStack::pushCatch(unsigned numHandlers) {
243 char *buffer = allocate(Size: EHCatchScope::getSizeForNumHandlers(N: 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(Size: 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 more
257/// fixups than the fixup depth on the innermost normal cleanup, or
258/// else fixups that we try to add to that cleanup will end up in the
259/// wrong place. We *could* try to shrink fixup depths, but that's
260/// actually a lot of work for little benefit.
261void EHScopeStack::popNullFixups() {
262 // We expect this to only be called when there's still an innermost
263 // normal cleanup; otherwise there really shouldn't be any fixups.
264 assert(hasNormalCleanups());
265
266 EHScopeStack::iterator it = find(sp: InnermostNormalCleanup);
267 unsigned MinSize = cast<EHCleanupScope>(Val&: *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 Ty: Builder.getInt1Ty(), align: CharUnits::One(), Name: "cleanup.cond");
279
280 // Initialize it to false at a site that's guaranteed to be run
281 // before each evaluation.
282 setBeforeOutermostConditional(value: Builder.getFalse(), addr: active, CGF&: *this);
283
284 // Initialize it to true at the current location.
285 Builder.CreateStore(Val: Builder.getTrue(), Addr: 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>(Val&: *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 the
325/// outermost normal cleanup; resolve them all by adding cases to the
326/// 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 is
338 // still pointing directly to its destination; forward it to the
339 // appropriate cleanup entry. This is required in the specific
340 // case of
341 // { std::string s; goto lbl; }
342 // lbl:
343 // i.e. where there's an unresolved fixup inside a single cleanup
344 // entry which we're currently popping.
345 if (Fixup.OptimisticBranchBlock == nullptr) {
346 createStoreInstBefore(value: CGF.Builder.getInt32(C: Fixup.DestinationIndex),
347 addr: CGF.getNormalCleanupDestSlot(),
348 beforeInst: Fixup.InitialBranch->getIterator(), CGF);
349 Fixup.InitialBranch->setSuccessor(idx: 0, NewSucc: CleanupEntry);
350 }
351
352 // Don't add this case to the switch statement twice.
353 if (!CasesAdded.insert(Ptr: Fixup.Destination).second)
354 continue;
355
356 Switch->addCase(OnVal: CGF.Builder.getInt32(C: Fixup.DestinationIndex),
357 Dest: Fixup.Destination);
358 }
359
360 CGF.EHStack.clearFixups();
361}
362
363/// Transitions the terminator of the given exit-block of a cleanup to
364/// 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 default
368 // 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>(Val: Term)) {
373 assert(Br->isUnconditional());
374 auto Load = createLoadInstBefore(addr: CGF.getNormalCleanupDestSlot(),
375 name: "cleanup.dest", beforeInst: Term->getIterator(), CGF);
376 llvm::SwitchInst *Switch =
377 llvm::SwitchInst::Create(Value: Load, Default: Br->getSuccessor(i: 0), NumCases: 4, InsertBefore: Block);
378 Br->eraseFromParent();
379 return Switch;
380 } else {
381 return cast<llvm::SwitchInst>(Val: 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 is
404 // 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(Ptr: BranchBB).second)
411 continue;
412
413 llvm::SwitchInst *Switch = TransitionToCleanupSwitch(CGF&: *this, Block: BranchBB);
414
415 // Add a case to the switch.
416 Switch->addCase(OnVal: Builder.getInt32(C: Fixup.DestinationIndex), Dest: 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>(Val&: *EHStack.begin());
432 HadBranches |= Scope.hasBranches();
433
434 // As long as Old strictly encloses the scope's enclosing normal
435 // cleanup, we're going to emit another normal cleanup which
436 // fallthrough can propagate through.
437 bool FallThroughIsBranchThrough =
438 Old.strictlyEncloses(I: Scope.getEnclosingNormalCleanup());
439
440 PopCleanupBlock(FallThroughIsBranchThrough);
441 }
442
443 // If we didn't have any branches, the insertion point before cleanups must
444 // dominate the current insertion point and we don't need to reload any
445 // values.
446 if (!HadBranches)
447 return;
448
449 // Spill and reload all values that the caller wants to be live at the current
450 // insertion point.
451 for (llvm::Value **ReloadedValue : ValuesToReload) {
452 auto *Inst = dyn_cast_or_null<llvm::Instruction>(Val: *ReloadedValue);
453 if (!Inst)
454 continue;
455
456 // Don't spill static allocas, they dominate all cleanups. These are created
457 // by binding a reference to a local variable or temporary.
458 auto *AI = dyn_cast<llvm::AllocaInst>(Val: Inst);
459 if (AI && AI->isStaticAlloca())
460 continue;
461
462 Address Tmp =
463 CreateDefaultAlignTempAlloca(Ty: Inst->getType(), Name: "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>(Val: Inst))
468 InsertBefore = Invoke->getNormalDest()->getFirstInsertionPt();
469 else
470 InsertBefore = std::next(x: Inst->getIterator());
471 CGBuilderTy(CGM, &*InsertBefore).CreateStore(Val: Inst, Addr: Tmp);
472
473 // Reload the value at the current insertion point.
474 *ReloadedValue = Builder.CreateLoad(Addr: Tmp);
475 }
476}
477
478/// Pops cleanup blocks until the given savepoint is reached, then add the
479/// 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(Kind: Header.getKind(),
498 Cleanup: &LifetimeExtendedCleanupStack[I],
499 Size: 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(N: 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(name: "cleanup");
518 Scope.setNormalBlock(Entry);
519 }
520 return Entry;
521}
522
523/// Attempts to reduce a cleanup's entry block to a fallthrough. This
524/// is basically llvm::MergeBlockIntoPredecessor, except
525/// 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>(Val: 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 entry
538 // block, we'll need to continue inserting at the end of the
539 // 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 there
547 // are phis in the cleanup.
548 Entry->replaceAllUsesWith(V: Pred);
549
550 // Merge the blocks.
551 Pred->splice(ToIt: Pred->end(), FromBB: 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's
567 // false.
568 llvm::BasicBlock *ContBB = nullptr;
569 if (ActiveFlag.isValid()) {
570 ContBB = CGF.createBasicBlock(name: "cleanup.done");
571 llvm::BasicBlock *CleanupBB = CGF.createBasicBlock(name: "cleanup.action");
572 llvm::Value *IsActive
573 = CGF.Builder.CreateLoad(Addr: ActiveFlag, Name: "cleanup.is_active");
574 CGF.Builder.CreateCondBr(Cond: IsActive, True: CleanupBB, False: ContBB);
575 CGF.EmitBlock(BB: 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(BB: 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 in
591 // an unconditional branch or a switch.
592 llvm::Instruction *Term = Exit->getTerminator();
593
594 if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Val: Term)) {
595 assert(Br->isUnconditional() && Br->getSuccessor(0) == From);
596 Br->setSuccessor(idx: 0, NewSucc: To);
597 } else {
598 llvm::SwitchInst *Switch = cast<llvm::SwitchInst>(Val: Term);
599 for (unsigned I = 0, E = Switch->getNumSuccessors(); I != E; ++I)
600 if (Switch->getSuccessor(idx: I) == From)
601 Switch->setSuccessor(idx: I, NewSucc: 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 into
607/// existence anyway; if so, destroy it.
608///
609/// The validity of this transformation is very much specific to the
610/// 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_iterator
619 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>(Val: use.getUser());
627 if (si->getNumCases() == 1 && si->getDefaultDest() == unreachableBB) {
628 // Replace the switch with a branch.
629 llvm::BranchInst::Create(IfTrue: si->case_begin()->getCaseSuccessor(),
630 InsertBefore: si->getIterator());
631
632 // The switch operand is a load from the cleanup-dest alloca.
633 llvm::LoadInst *condition = cast<llvm::LoadInst>(Val: 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, the
650/// current insertion point is threaded through the cleanup, as are
651/// 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>(Val&: *EHStack.begin());
657 assert(Scope.getFixupDepth() <= EHStack.getNumBranchFixups());
658
659 // If we are deactivating a normal cleanup, we need to pretend that the
660 // 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've
675 // 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 cleanup
684 unsigned FixupDepth = Scope.getFixupDepth();
685 bool HasFixups = EHStack.getNumBranchFixups() != FixupDepth;
686
687 // - whether there are branch-throughs or branch-afters
688 bool HasExistingBranches = Scope.hasBranches();
689
690 // - whether there's a fallthrough
691 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 the
696 // end of the last cleanup, which points to the current scope. The
697 // rest of IR gen doesn't need to worry about this; it only happens
698 // during the execution of PopCleanupBlocks().
699 bool HasPrebranchedFallthrough =
700 (FallthroughSource && FallthroughSource->getTerminator());
701
702 // If this is a normal cleanup, then having a prebranched
703 // fallthrough implies that the fallthrough source unconditionally
704 // 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 normal
717 // 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 prebranched
721 // 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 next
726 // cleanup, just forward it to the next block, leaving the
727 // insertion point in the prebranched block.
728 if (FallthroughIsBranchThrough) {
729 EHScope &enclosing = *EHStack.find(sp: Scope.getEnclosingNormalCleanup());
730 prebranchDest = CreateNormalEntry(CGF&: *this, Scope&: cast<EHCleanupScope>(Val&: enclosing));
731
732 // Otherwise, we need to make a new block. If the normal cleanup
733 // isn't being used at all, we could actually reuse the normal
734 // entry block, but this is simpler, and it avoids conflicts with
735 // dead optimistic fixup branches.
736 } else {
737 prebranchDest = createBasicBlock(name: "forwarded-prebranch");
738 EmitBlock(BB: prebranchDest);
739 }
740
741 llvm::BasicBlock *normalEntry = Scope.getNormalBlock();
742 assert(normalEntry && !normalEntry->use_empty());
743
744 ForwardPrebranchedFallthrough(Exit: FallthroughSource,
745 From: normalEntry, To: prebranchDest);
746 }
747
748 // If we don't need the cleanup at all, we're done.
749 if (!RequiresNormalCleanup && !RequiresEHCleanup) {
750 destroyOptimisticNormalEntry(CGF&: *this, scope&: Scope);
751 EHStack.popCleanup(); // safe because there are no fixups
752 assert(EHStack.getNumBranchFixups() == 0 ||
753 EHStack.hasNormalCleanups());
754 if (NormalDeactivateOrigIP.isSet())
755 Builder.restoreIP(IP: NormalDeactivateOrigIP);
756 return;
757 }
758
759 // Copy the cleanup emission data out. This uses either a stack
760 // array or malloc'd memory, depending on the size, which is
761 // behavior that SmallVector would provide, if we could use it
762 // here. Unfortunately, if you ask for a SmallVector<char>, the
763 // alignment isn't sufficient.
764 auto *CleanupSource = reinterpret_cast<char *>(Scope.getCleanupBuffer());
765 alignas(EHScopeStack::ScopeStackAlignment) char
766 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(dest: CleanupBufferStack, src: CleanupSource, n: CleanupSize);
773 Fn = reinterpret_cast<EHScopeStack::Cleanup *>(CleanupBufferStack);
774 } else {
775 CleanupBufferHeap.reset(p: new char[CleanupSize]);
776 memcpy(dest: CleanupBufferHeap.get(), src: CleanupSource, n: 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 dtor
787 bool IsEHa = getLangOpts().EHAsynch && !Scope.isLifetimeMarker();
788 const EHPersonality &Personality = EHPersonality::get(CGF&: *this);
789 if (!RequiresNormalCleanup) {
790 // Mark CPP scope end for passed-by-value Arg temp
791 // per Windows ABI which is "normally" Cleanup in callee
792 if (IsEHa && getInvokeDest()) {
793 // If we are deactivating a normal cleanup then we don't have a
794 // fallthrough. Restore original IP to emit CPP scope ends in the correct
795 // block.
796 if (NormalDeactivateOrigIP.isSet())
797 Builder.restoreIP(IP: NormalDeactivateOrigIP);
798 if (Personality.isMSVCXXPersonality() && Builder.GetInsertBlock())
799 EmitSehCppScopeEnd();
800 if (NormalDeactivateOrigIP.isSet())
801 NormalDeactivateOrigIP = Builder.saveAndClearIP();
802 }
803 destroyOptimisticNormalEntry(CGF&: *this, scope&: 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 flow
813 if (IsEHa && getInvokeDest()) {
814 if (Personality.isMSVCXXPersonality())
815 EmitSehCppScopeEnd();
816 else
817 EmitSehTryScopeEnd();
818 }
819
820 destroyOptimisticNormalEntry(CGF&: *this, scope&: Scope);
821 Scope.MarkEmitted();
822 EHStack.popCleanup();
823
824 EmitCleanup(CGF&: *this, Fn, flags: cleanupFlags, ActiveFlag: NormalActiveFlag);
825
826 // Otherwise, the best approach is to thread everything through
827 // 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(CGF&: *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 cleanup
837 // destination index. For fall-throughs this is always zero.
838 if (HasFallthrough) {
839 if (!HasPrebranchedFallthrough)
840 Builder.CreateStore(Val: Builder.getInt32(C: 0), Addr: getNormalCleanupDestSlot());
841
842 // Otherwise, save and clear the IP if we don't have fallthrough
843 // 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 if
850 // we have fallthrough. All the fixups and existing branches
851 // should already be branched to it.
852 EmitBlock(BB: NormalEntry);
853
854 // intercept normal cleanup to mark SEH scope end
855 if (IsEHa && getInvokeDest()) {
856 if (Personality.isMSVCXXPersonality())
857 EmitSehCppScopeEnd();
858 else
859 EmitSehTryScopeEnd();
860 }
861
862 // III. Figure out where we're going and build the cleanup
863 // 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 scope
870 // - if fall-through is a branch-through
871 // - if there are fixups that will be optimistically forwarded
872 // to the enclosing cleanup
873 llvm::BasicBlock *BranchThroughDest = nullptr;
874 if (Scope.hasBranchThroughs() ||
875 (FallthroughSource && FallthroughIsBranchThrough) ||
876 (HasFixups && HasEnclosingCleanups)) {
877 assert(HasEnclosingCleanups);
878 EHScope &S = *EHStack.find(sp: Scope.getEnclosingNormalCleanup());
879 BranchThroughDest = CreateNormalEntry(CGF&: *this, Scope&: cast<EHCleanupScope>(Val&: 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 indicate
888 // abnormal termination. (SEH: Except _leave and fall-through at
889 // the end, all other exits in a _try (return/goto/continue/break)
890 // are considered as abnormal terminations, using NormalCleanupDestSlot
891 // 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>(Val: 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(I: 0);
906 InstsToAppend.push_back(Elt: llvm::BranchInst::Create(IfTrue: BranchAfter));
907
908 // Build a switch-out if we need it:
909 // - if there are branch-afters threaded through the scope
910 // - if fall-through is a branch-after
911 // - if there are fixups that have nowhere left to go and
912 // so must be immediately resolved
913 } 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 fixups
921 const unsigned SwitchCapacity = 10;
922
923 // pass the abnormal exit flag to Fn (SEH cleanup)
924 cleanupFlags.setHasExitSwitch();
925
926 llvm::LoadInst *Load = createLoadInstBefore(addr: getNormalCleanupDestSlot(),
927 name: "cleanup.dest", CGF&: *this);
928 llvm::SwitchInst *Switch =
929 llvm::SwitchInst::Create(Value: Load, Default, NumCases: SwitchCapacity);
930
931 InstsToAppend.push_back(Elt: Load);
932 InstsToAppend.push_back(Elt: Switch);
933
934 // Branch-after fallthrough.
935 if (FallthroughSource && !FallthroughIsBranchThrough) {
936 FallthroughDest = createBasicBlock(name: "cleanup.cont");
937 if (HasFallthrough)
938 Switch->addCase(OnVal: Builder.getInt32(C: 0), Dest: FallthroughDest);
939 }
940
941 for (unsigned I = 0, E = Scope.getNumBranchAfters(); I != E; ++I) {
942 Switch->addCase(OnVal: Scope.getBranchAfterIndex(I),
943 Dest: Scope.getBranchAfterBlock(I));
944 }
945
946 // If there aren't any enclosing cleanups, we can resolve all
947 // the fixups now.
948 if (HasFixups && !HasEnclosingCleanups)
949 ResolveAllBranchFixups(CGF&: *this, Switch, CleanupEntry: NormalEntry);
950 } else {
951 // We should always have a branch-through destination in this case.
952 assert(BranchThroughDest);
953 InstsToAppend.push_back(Elt: llvm::BranchInst::Create(IfTrue: 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(CGF&: *this, Fn, flags: cleanupFlags, ActiveFlag: 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(ParentBB: NormalExit, It: 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(value: Builder.getInt32(C: Fixup.DestinationIndex),
976 addr: getNormalCleanupDestSlot(),
977 beforeInst: Fixup.InitialBranch->getIterator(), CGF&: *this);
978 Fixup.InitialBranch->setSuccessor(idx: 0, NewSucc: 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 the
986 // 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(IP: savedInactiveFallthroughIP);
993
994 // Case 2: a fallthrough source exists and should branch to the
995 // cleanup, but we're not supposed to branch through to the next
996 // cleanup.
997 } else if (HasFallthrough && FallthroughDest) {
998 assert(!FallthroughIsBranchThrough);
999 EmitBlock(BB: FallthroughDest);
1000
1001 // Case 3: a fallthrough source exists and should branch to the
1002 // 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(CGF&: *this, Entry: NormalEntry);
1017
1018 // If it did invalidate those pointers, and NormalEntry was the same
1019 // 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(IP: 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(BB: EHEntry);
1036
1037 llvm::BasicBlock *NextAction = getEHDispatchBlock(scope: EHParent);
1038
1039 // Push a terminate scope or cleanupendpad scope around the potentially
1040 // throwing cleanups. For funclet EH personalities, the cleanupendpad models
1041 // 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(CGF&: *this);
1047 if (Personality.usesFuncletPads()) {
1048 llvm::Value *ParentPad = CurrentFuncletPad;
1049 if (!ParentPad)
1050 ParentPad = llvm::ConstantTokenNone::get(Context&: 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 either
1063 // active or was used before it was deactivated.
1064 if (EHActiveFlag.isValid() || IsActive) {
1065 cleanupFlags.setIsForEHCleanup();
1066 EmitCleanup(CGF&: *this, Fn, flags: cleanupFlags, ActiveFlag: EHActiveFlag);
1067 }
1068
1069 if (CPI)
1070 Builder.CreateCleanupRet(CleanupPad: CPI, UnwindBB: NextAction);
1071 else
1072 Builder.CreateBr(Dest: NextAction);
1073
1074 // Leave the terminate scope.
1075 if (PushedTerminate)
1076 EHStack.popTerminate();
1077
1078 Builder.restoreIP(IP: SavedIP);
1079
1080 SimplifyCleanupEntry(CGF&: *this, Entry: EHEntry);
1081 }
1082}
1083
1084/// isObviouslyBranchWithoutCleanups - Return true if a branch to the
1085/// specified destination obviously has no cleanups to run. 'false' is always
1086/// 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 the
1096 // destination scope is within the innermost active normal cleanup
1097 // scope, we don't need to worry about fixups.
1098 if (TopCleanup == EHStack.stable_end() ||
1099 TopCleanup.encloses(I: Dest.getScopeDepth())) // works for invalid
1100 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 leave
1108/// the current cleanup-protected scope. The target scope may not yet
1109/// 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: Dest.getBlock());
1121 addInstToCurrentSourceAtom(KeyInstruction: BI, Backup: nullptr);
1122
1123 // Calculate the innermost active normal cleanup.
1124 EHScopeStack::stable_iterator
1125 TopCleanup = EHStack.getInnermostActiveNormalCleanup();
1126
1127 // If we're not in an active normal cleanup scope, or if the
1128 // destination scope is within the innermost active normal cleanup
1129 // scope, we don't need to worry about fixups.
1130 if (TopCleanup == EHStack.stable_end() ||
1131 TopCleanup.encloses(I: Dest.getScopeDepth())) { // works for invalid
1132 Builder.ClearInsertionPoint();
1133 return;
1134 }
1135
1136 // If we can't resolve the destination cleanup scope, just add this
1137 // 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(C: Dest.getDestIndex());
1153 createStoreInstBefore(value: Index, addr: getNormalCleanupDestSlot(), beforeInst: BI->getIterator(),
1154 CGF&: *this);
1155
1156 // Adjust BI to point to the first cleanup block.
1157 {
1158 EHCleanupScope &Scope =
1159 cast<EHCleanupScope>(Val&: *EHStack.find(sp: TopCleanup));
1160 BI->setSuccessor(idx: 0, NewSucc: CreateNormalEntry(CGF&: *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>(Val&: *EHStack.find(sp: I));
1169 assert(Scope.isNormalCleanup());
1170 I = Scope.getEnclosingNormalCleanup();
1171
1172 // If this is the last cleanup we're propagating through, tell it
1173 // that there's a resolved jump moving through it.
1174 if (!E.strictlyEncloses(I)) {
1175 Scope.addBranchAfter(Index, Block: Dest.getBlock());
1176 break;
1177 }
1178
1179 // Otherwise, tell the scope that there's a jump propagating
1180 // through it. If this isn't new information, all the rest of
1181 // the work has been done before.
1182 if (!Scope.addBranchThrough(Block: 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(sp: cleanup)->hasEHBranches())
1194 return true;
1195
1196 // Check whether any enclosed cleanups were needed.
1197 for (EHScopeStack::stable_iterator
1198 i = EHStack.getInnermostEHScope(); i != cleanup; ) {
1199 assert(cleanup.strictlyEncloses(i));
1200
1201 EHScope &scope = *EHStack.find(sp: 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 ForDeactivation
1214};
1215
1216/// The given cleanup block is changing activation state. Configure a
1217/// cleanup variable if necessary.
1218///
1219/// It would be good if we had some way of determining if there were
1220/// 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>(Val&: *CGF.EHStack.find(sp: C));
1226
1227 // We always need the flag if we're activating the cleanup in a
1228 // conditional context, because we have to assume that the current
1229 // 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 cleanup
1238 if (Scope.isNormalCleanup()) {
1239 Scope.setTestFlagInNormalCleanup();
1240 needFlag = true;
1241 }
1242
1243 // - as an EH cleanup
1244 if (Scope.isEHCleanup() &&
1245 (isActivatedInConditional || IsUsedAsEHCleanup(EHStack&: CGF.EHStack, cleanup: 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(Ty: CGF.Builder.getInt1Ty(), align: CharUnits::One(),
1258 Name: "cleanup.isactive");
1259 Scope.setActiveFlag(var);
1260 Scope.AddAuxAllocas(Allocas: AllocaTracker.Take());
1261
1262 assert(dominatingIP && "no existing variable and no dominating IP!");
1263
1264 // Initialize to true or false depending on whether it was
1265 // active up to this point.
1266 llvm::Constant *value = CGF.Builder.getInt1(V: kind == ForDeactivation);
1267
1268 // If we're in a conditional block, ignore the dominating IP and
1269 // use the outermost conditional branch.
1270 if (CGF.isInConditionalBranch()) {
1271 CGF.setBeforeOutermostConditional(value, addr: var, CGF);
1272 } else {
1273 createStoreInstBefore(value, addr: var, beforeInst: dominatingIP->getIterator(), CGF);
1274 }
1275 }
1276
1277 CGF.Builder.CreateStore(Val: CGF.Builder.getInt1(V: kind == ForActivation), Addr: 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>(Val&: *EHStack.find(sp: C));
1285 assert(!Scope.isActive() && "double activation");
1286
1287 SetupCleanupBlockActivation(CGF&: *this, C, kind: 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>(Val&: *EHStack.find(sp: 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 belongs
1300 // to the current RunCleanupsScope.
1301 if (C == EHStack.stable_begin() &&
1302 CurrentCleanupScopeDepth.strictlyEncloses(I: C)) {
1303 PopCleanupBlock(/*FallthroughIsBranchThrough=*/false,
1304 /*ForDeactivation=*/true);
1305 return;
1306 }
1307
1308 // Otherwise, follow the general case.
1309 SetupCleanupBlockActivation(CGF&: *this, C, kind: ForDeactivation, dominatingIP);
1310
1311 Scope.setActive(false);
1312}
1313
1314RawAddress CodeGenFunction::getNormalCleanupDestSlot() {
1315 if (!NormalCleanupDest.isValid())
1316 NormalCleanupDest =
1317 CreateDefaultAlignTempAlloca(Ty: Builder.getInt32Ty(), Name: "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(kind: NormalAndEHCleanup, addr: Ptr, type: TempType, destroyer: destroyCXXObject,
1326 /*useEHCleanup*/ useEHCleanupForArray: true);
1327}
1328
1329// Need to set "funclet" in OperandBundle properly for noThrow
1330// 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(name: "invoke.cont");
1336 SmallVector<llvm::OperandBundleDef, 1> BundleList =
1337 CGF.getBundlesForFunclet(Callee: SehCppScope.getCallee());
1338 if (CGF.CurrentFuncletPad)
1339 BundleList.emplace_back(Args: "funclet", Args&: CGF.CurrentFuncletPad);
1340 CGF.Builder.CreateInvoke(Callee: SehCppScope, NormalDest: Cont, UnwindDest: InvokeDest, Args: {}, OpBundles: BundleList);
1341 CGF.EmitBlock(BB: Cont);
1342}
1343
1344// Invoke a llvm.seh.scope.begin at the beginning of a CPP scope for -EHa
1345void CodeGenFunction::EmitSehCppScopeBegin() {
1346 assert(getLangOpts().EHAsynch);
1347 llvm::FunctionType *FTy =
1348 llvm::FunctionType::get(Result: CGM.VoidTy, /*isVarArg=*/false);
1349 llvm::FunctionCallee SehCppScope =
1350 CGM.CreateRuntimeFunction(Ty: FTy, Name: "llvm.seh.scope.begin");
1351 EmitSehScope(CGF&: *this, SehCppScope);
1352}
1353
1354// Invoke a llvm.seh.scope.end at the end of a CPP scope for -EHa
1355// 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(Result: CGM.VoidTy, /*isVarArg=*/false);
1360 llvm::FunctionCallee SehCppScope =
1361 CGM.CreateRuntimeFunction(Ty: FTy, Name: "llvm.seh.scope.end");
1362 EmitSehScope(CGF&: *this, SehCppScope);
1363}
1364
1365// Invoke a llvm.seh.try.begin at the beginning of a SEH scope for -EHa
1366void CodeGenFunction::EmitSehTryScopeBegin() {
1367 assert(getLangOpts().EHAsynch);
1368 llvm::FunctionType *FTy =
1369 llvm::FunctionType::get(Result: CGM.VoidTy, /*isVarArg=*/false);
1370 llvm::FunctionCallee SehCppScope =
1371 CGM.CreateRuntimeFunction(Ty: FTy, Name: "llvm.seh.try.begin");
1372 EmitSehScope(CGF&: *this, SehCppScope);
1373}
1374
1375// Invoke a llvm.seh.try.end at the end of a SEH scope for -EHa
1376void CodeGenFunction::EmitSehTryScopeEnd() {
1377 assert(getLangOpts().EHAsynch);
1378 llvm::FunctionType *FTy =
1379 llvm::FunctionType::get(Result: CGM.VoidTy, /*isVarArg=*/false);
1380 llvm::FunctionCallee SehCppScope =
1381 CGM.CreateRuntimeFunction(Ty: FTy, Name: "llvm.seh.try.end");
1382 EmitSehScope(CGF&: *this, SehCppScope);
1383}
1384