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
23 using namespace clang;
24 using namespace CodeGen;
25
needsSaving(RValue rv)26 bool DominatingValue<RValue>::saved_type::needsSaving(RValue rv) {
27 if (rv.isScalar())
28 return DominatingLLVMValue::needsSaving(rv.getScalarVal());
29 if (rv.isAggregate())
30 return DominatingLLVMValue::needsSaving(rv.getAggregatePointer());
31 return true;
32 }
33
34 DominatingValue<RValue>::saved_type
save(CodeGenFunction & CGF,RValue rv)35 DominatingValue<RValue>::saved_type::save(CodeGenFunction &CGF, RValue rv) {
36 if (rv.isScalar()) {
37 llvm::Value *V = rv.getScalarVal();
38
39 // These automatically dominate and don't need to be saved.
40 if (!DominatingLLVMValue::needsSaving(V))
41 return saved_type(V, ScalarLiteral);
42
43 // Everything else needs an alloca.
44 Address addr =
45 CGF.CreateDefaultAlignTempAlloca(V->getType(), "saved-rvalue");
46 CGF.Builder.CreateStore(V, addr);
47 return saved_type(addr.getPointer(), ScalarAddress);
48 }
49
50 if (rv.isComplex()) {
51 CodeGenFunction::ComplexPairTy V = rv.getComplexVal();
52 llvm::Type *ComplexTy =
53 llvm::StructType::get(V.first->getType(), V.second->getType());
54 Address addr = CGF.CreateDefaultAlignTempAlloca(ComplexTy, "saved-complex");
55 CGF.Builder.CreateStore(V.first, CGF.Builder.CreateStructGEP(addr, 0));
56 CGF.Builder.CreateStore(V.second, CGF.Builder.CreateStructGEP(addr, 1));
57 return saved_type(addr.getPointer(), ComplexAddress);
58 }
59
60 assert(rv.isAggregate());
61 Address V = rv.getAggregateAddress(); // TODO: volatile?
62 if (!DominatingLLVMValue::needsSaving(V.getPointer()))
63 return saved_type(V.getPointer(), AggregateLiteral,
64 V.getAlignment().getQuantity());
65
66 Address addr =
67 CGF.CreateTempAlloca(V.getType(), CGF.getPointerAlign(), "saved-rvalue");
68 CGF.Builder.CreateStore(V.getPointer(), addr);
69 return saved_type(addr.getPointer(), AggregateAddress,
70 V.getAlignment().getQuantity());
71 }
72
73 /// Given a saved r-value produced by SaveRValue, perform the code
74 /// necessary to restore it to usability at the current insertion
75 /// point.
restore(CodeGenFunction & CGF)76 RValue DominatingValue<RValue>::saved_type::restore(CodeGenFunction &CGF) {
77 auto getSavingAddress = [&](llvm::Value *value) {
78 auto alignment = cast<llvm::AllocaInst>(value)->getAlignment();
79 return Address(value, CharUnits::fromQuantity(alignment));
80 };
81 switch (K) {
82 case ScalarLiteral:
83 return RValue::get(Value);
84 case ScalarAddress:
85 return RValue::get(CGF.Builder.CreateLoad(getSavingAddress(Value)));
86 case AggregateLiteral:
87 return RValue::getAggregate(Address(Value, CharUnits::fromQuantity(Align)));
88 case AggregateAddress: {
89 auto addr = CGF.Builder.CreateLoad(getSavingAddress(Value));
90 return RValue::getAggregate(Address(addr, CharUnits::fromQuantity(Align)));
91 }
92 case ComplexAddress: {
93 Address address = getSavingAddress(Value);
94 llvm::Value *real =
95 CGF.Builder.CreateLoad(CGF.Builder.CreateStructGEP(address, 0));
96 llvm::Value *imag =
97 CGF.Builder.CreateLoad(CGF.Builder.CreateStructGEP(address, 1));
98 return RValue::getComplex(real, imag);
99 }
100 }
101
102 llvm_unreachable("bad saved r-value kind");
103 }
104
105 /// Push an entry of the given size onto this protected-scope stack.
allocate(size_t Size)106 char *EHScopeStack::allocate(size_t Size) {
107 Size = llvm::alignTo(Size, ScopeStackAlignment);
108 if (!StartOfBuffer) {
109 unsigned Capacity = 1024;
110 while (Capacity < Size) Capacity *= 2;
111 StartOfBuffer = new char[Capacity];
112 StartOfData = EndOfBuffer = StartOfBuffer + Capacity;
113 } else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) {
114 unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer;
115 unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer);
116
117 unsigned NewCapacity = CurrentCapacity;
118 do {
119 NewCapacity *= 2;
120 } while (NewCapacity < UsedCapacity + Size);
121
122 char *NewStartOfBuffer = new char[NewCapacity];
123 char *NewEndOfBuffer = NewStartOfBuffer + NewCapacity;
124 char *NewStartOfData = NewEndOfBuffer - UsedCapacity;
125 memcpy(NewStartOfData, StartOfData, UsedCapacity);
126 delete [] StartOfBuffer;
127 StartOfBuffer = NewStartOfBuffer;
128 EndOfBuffer = NewEndOfBuffer;
129 StartOfData = NewStartOfData;
130 }
131
132 assert(StartOfBuffer + Size <= StartOfData);
133 StartOfData -= Size;
134 return StartOfData;
135 }
136
deallocate(size_t Size)137 void EHScopeStack::deallocate(size_t Size) {
138 StartOfData += llvm::alignTo(Size, ScopeStackAlignment);
139 }
140
containsOnlyLifetimeMarkers(EHScopeStack::stable_iterator Old) const141 bool EHScopeStack::containsOnlyLifetimeMarkers(
142 EHScopeStack::stable_iterator Old) const {
143 for (EHScopeStack::iterator it = begin(); stabilize(it) != Old; it++) {
144 EHCleanupScope *cleanup = dyn_cast<EHCleanupScope>(&*it);
145 if (!cleanup || !cleanup->isLifetimeMarker())
146 return false;
147 }
148
149 return true;
150 }
151
requiresLandingPad() const152 bool EHScopeStack::requiresLandingPad() const {
153 for (stable_iterator si = getInnermostEHScope(); si != stable_end(); ) {
154 // Skip lifetime markers.
155 if (auto *cleanup = dyn_cast<EHCleanupScope>(&*find(si)))
156 if (cleanup->isLifetimeMarker()) {
157 si = cleanup->getEnclosingEHScope();
158 continue;
159 }
160 return true;
161 }
162
163 return false;
164 }
165
166 EHScopeStack::stable_iterator
getInnermostActiveNormalCleanup() const167 EHScopeStack::getInnermostActiveNormalCleanup() const {
168 for (stable_iterator si = getInnermostNormalCleanup(), se = stable_end();
169 si != se; ) {
170 EHCleanupScope &cleanup = cast<EHCleanupScope>(*find(si));
171 if (cleanup.isActive()) return si;
172 si = cleanup.getEnclosingNormalCleanup();
173 }
174 return stable_end();
175 }
176
177
pushCleanup(CleanupKind Kind,size_t Size)178 void *EHScopeStack::pushCleanup(CleanupKind Kind, size_t Size) {
179 char *Buffer = allocate(EHCleanupScope::getSizeForCleanupSize(Size));
180 bool IsNormalCleanup = Kind & NormalCleanup;
181 bool IsEHCleanup = Kind & EHCleanup;
182 bool IsActive = !(Kind & InactiveCleanup);
183 bool IsLifetimeMarker = Kind & LifetimeMarker;
184 EHCleanupScope *Scope =
185 new (Buffer) EHCleanupScope(IsNormalCleanup,
186 IsEHCleanup,
187 IsActive,
188 Size,
189 BranchFixups.size(),
190 InnermostNormalCleanup,
191 InnermostEHScope);
192 if (IsNormalCleanup)
193 InnermostNormalCleanup = stable_begin();
194 if (IsEHCleanup)
195 InnermostEHScope = stable_begin();
196 if (IsLifetimeMarker)
197 Scope->setLifetimeMarker();
198
199 return Scope->getCleanupBuffer();
200 }
201
popCleanup()202 void EHScopeStack::popCleanup() {
203 assert(!empty() && "popping exception stack when not empty");
204
205 assert(isa<EHCleanupScope>(*begin()));
206 EHCleanupScope &Cleanup = cast<EHCleanupScope>(*begin());
207 InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup();
208 InnermostEHScope = Cleanup.getEnclosingEHScope();
209 deallocate(Cleanup.getAllocatedSize());
210
211 // Destroy the cleanup.
212 Cleanup.Destroy();
213
214 // Check whether we can shrink the branch-fixups stack.
215 if (!BranchFixups.empty()) {
216 // If we no longer have any normal cleanups, all the fixups are
217 // complete.
218 if (!hasNormalCleanups())
219 BranchFixups.clear();
220
221 // Otherwise we can still trim out unnecessary nulls.
222 else
223 popNullFixups();
224 }
225 }
226
pushFilter(unsigned numFilters)227 EHFilterScope *EHScopeStack::pushFilter(unsigned numFilters) {
228 assert(getInnermostEHScope() == stable_end());
229 char *buffer = allocate(EHFilterScope::getSizeForNumFilters(numFilters));
230 EHFilterScope *filter = new (buffer) EHFilterScope(numFilters);
231 InnermostEHScope = stable_begin();
232 return filter;
233 }
234
popFilter()235 void EHScopeStack::popFilter() {
236 assert(!empty() && "popping exception stack when not empty");
237
238 EHFilterScope &filter = cast<EHFilterScope>(*begin());
239 deallocate(EHFilterScope::getSizeForNumFilters(filter.getNumFilters()));
240
241 InnermostEHScope = filter.getEnclosingEHScope();
242 }
243
pushCatch(unsigned numHandlers)244 EHCatchScope *EHScopeStack::pushCatch(unsigned numHandlers) {
245 char *buffer = allocate(EHCatchScope::getSizeForNumHandlers(numHandlers));
246 EHCatchScope *scope =
247 new (buffer) EHCatchScope(numHandlers, InnermostEHScope);
248 InnermostEHScope = stable_begin();
249 return scope;
250 }
251
pushTerminate()252 void EHScopeStack::pushTerminate() {
253 char *Buffer = allocate(EHTerminateScope::getSize());
254 new (Buffer) EHTerminateScope(InnermostEHScope);
255 InnermostEHScope = stable_begin();
256 }
257
258 /// Remove any 'null' fixups on the stack. However, we can't pop more
259 /// fixups than the fixup depth on the innermost normal cleanup, or
260 /// else fixups that we try to add to that cleanup will end up in the
261 /// wrong place. We *could* try to shrink fixup depths, but that's
262 /// actually a lot of work for little benefit.
popNullFixups()263 void EHScopeStack::popNullFixups() {
264 // We expect this to only be called when there's still an innermost
265 // normal cleanup; otherwise there really shouldn't be any fixups.
266 assert(hasNormalCleanups());
267
268 EHScopeStack::iterator it = find(InnermostNormalCleanup);
269 unsigned MinSize = cast<EHCleanupScope>(*it).getFixupDepth();
270 assert(BranchFixups.size() >= MinSize && "fixup stack out of order");
271
272 while (BranchFixups.size() > MinSize &&
273 BranchFixups.back().Destination == nullptr)
274 BranchFixups.pop_back();
275 }
276
createCleanupActiveFlag()277 Address CodeGenFunction::createCleanupActiveFlag() {
278 // Create a variable to decide whether the cleanup needs to be run.
279 Address active = CreateTempAllocaWithoutCast(
280 Builder.getInt1Ty(), CharUnits::One(), "cleanup.cond");
281
282 // Initialize it to false at a site that's guaranteed to be run
283 // before each evaluation.
284 setBeforeOutermostConditional(Builder.getFalse(), active);
285
286 // Initialize it to true at the current location.
287 Builder.CreateStore(Builder.getTrue(), active);
288
289 return active;
290 }
291
initFullExprCleanupWithFlag(Address ActiveFlag)292 void CodeGenFunction::initFullExprCleanupWithFlag(Address ActiveFlag) {
293 // Set that as the active flag in the cleanup.
294 EHCleanupScope &cleanup = cast<EHCleanupScope>(*EHStack.begin());
295 assert(!cleanup.hasActiveFlag() && "cleanup already has active flag?");
296 cleanup.setActiveFlag(ActiveFlag);
297
298 if (cleanup.isNormalCleanup()) cleanup.setTestFlagInNormalCleanup();
299 if (cleanup.isEHCleanup()) cleanup.setTestFlagInEHCleanup();
300 }
301
anchor()302 void EHScopeStack::Cleanup::anchor() {}
303
createStoreInstBefore(llvm::Value * value,Address addr,llvm::Instruction * beforeInst)304 static void createStoreInstBefore(llvm::Value *value, Address addr,
305 llvm::Instruction *beforeInst) {
306 auto store = new llvm::StoreInst(value, addr.getPointer(), beforeInst);
307 store->setAlignment(addr.getAlignment().getAsAlign());
308 }
309
createLoadInstBefore(Address addr,const Twine & name,llvm::Instruction * beforeInst)310 static llvm::LoadInst *createLoadInstBefore(Address addr, const Twine &name,
311 llvm::Instruction *beforeInst) {
312 auto load = new llvm::LoadInst(addr.getPointer(), name, beforeInst);
313 load->setAlignment(addr.getAlignment().getAsAlign());
314 return load;
315 }
316
317 /// All the branch fixups on the EH stack have propagated out past the
318 /// outermost normal cleanup; resolve them all by adding cases to the
319 /// given switch instruction.
ResolveAllBranchFixups(CodeGenFunction & CGF,llvm::SwitchInst * Switch,llvm::BasicBlock * CleanupEntry)320 static void ResolveAllBranchFixups(CodeGenFunction &CGF,
321 llvm::SwitchInst *Switch,
322 llvm::BasicBlock *CleanupEntry) {
323 llvm::SmallPtrSet<llvm::BasicBlock*, 4> CasesAdded;
324
325 for (unsigned I = 0, E = CGF.EHStack.getNumBranchFixups(); I != E; ++I) {
326 // Skip this fixup if its destination isn't set.
327 BranchFixup &Fixup = CGF.EHStack.getBranchFixup(I);
328 if (Fixup.Destination == nullptr) continue;
329
330 // If there isn't an OptimisticBranchBlock, then InitialBranch is
331 // still pointing directly to its destination; forward it to the
332 // appropriate cleanup entry. This is required in the specific
333 // case of
334 // { std::string s; goto lbl; }
335 // lbl:
336 // i.e. where there's an unresolved fixup inside a single cleanup
337 // entry which we're currently popping.
338 if (Fixup.OptimisticBranchBlock == nullptr) {
339 createStoreInstBefore(CGF.Builder.getInt32(Fixup.DestinationIndex),
340 CGF.getNormalCleanupDestSlot(),
341 Fixup.InitialBranch);
342 Fixup.InitialBranch->setSuccessor(0, CleanupEntry);
343 }
344
345 // Don't add this case to the switch statement twice.
346 if (!CasesAdded.insert(Fixup.Destination).second)
347 continue;
348
349 Switch->addCase(CGF.Builder.getInt32(Fixup.DestinationIndex),
350 Fixup.Destination);
351 }
352
353 CGF.EHStack.clearFixups();
354 }
355
356 /// Transitions the terminator of the given exit-block of a cleanup to
357 /// be a cleanup switch.
TransitionToCleanupSwitch(CodeGenFunction & CGF,llvm::BasicBlock * Block)358 static llvm::SwitchInst *TransitionToCleanupSwitch(CodeGenFunction &CGF,
359 llvm::BasicBlock *Block) {
360 // If it's a branch, turn it into a switch whose default
361 // destination is its original target.
362 llvm::Instruction *Term = Block->getTerminator();
363 assert(Term && "can't transition block without terminator");
364
365 if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {
366 assert(Br->isUnconditional());
367 auto Load = createLoadInstBefore(CGF.getNormalCleanupDestSlot(),
368 "cleanup.dest", Term);
369 llvm::SwitchInst *Switch =
370 llvm::SwitchInst::Create(Load, Br->getSuccessor(0), 4, Block);
371 Br->eraseFromParent();
372 return Switch;
373 } else {
374 return cast<llvm::SwitchInst>(Term);
375 }
376 }
377
ResolveBranchFixups(llvm::BasicBlock * Block)378 void CodeGenFunction::ResolveBranchFixups(llvm::BasicBlock *Block) {
379 assert(Block && "resolving a null target block");
380 if (!EHStack.getNumBranchFixups()) return;
381
382 assert(EHStack.hasNormalCleanups() &&
383 "branch fixups exist with no normal cleanups on stack");
384
385 llvm::SmallPtrSet<llvm::BasicBlock*, 4> ModifiedOptimisticBlocks;
386 bool ResolvedAny = false;
387
388 for (unsigned I = 0, E = EHStack.getNumBranchFixups(); I != E; ++I) {
389 // Skip this fixup if its destination doesn't match.
390 BranchFixup &Fixup = EHStack.getBranchFixup(I);
391 if (Fixup.Destination != Block) continue;
392
393 Fixup.Destination = nullptr;
394 ResolvedAny = true;
395
396 // If it doesn't have an optimistic branch block, LatestBranch is
397 // already pointing to the right place.
398 llvm::BasicBlock *BranchBB = Fixup.OptimisticBranchBlock;
399 if (!BranchBB)
400 continue;
401
402 // Don't process the same optimistic branch block twice.
403 if (!ModifiedOptimisticBlocks.insert(BranchBB).second)
404 continue;
405
406 llvm::SwitchInst *Switch = TransitionToCleanupSwitch(*this, BranchBB);
407
408 // Add a case to the switch.
409 Switch->addCase(Builder.getInt32(Fixup.DestinationIndex), Block);
410 }
411
412 if (ResolvedAny)
413 EHStack.popNullFixups();
414 }
415
416 /// Pops cleanup blocks until the given savepoint is reached.
PopCleanupBlocks(EHScopeStack::stable_iterator Old,std::initializer_list<llvm::Value ** > ValuesToReload)417 void CodeGenFunction::PopCleanupBlocks(
418 EHScopeStack::stable_iterator Old,
419 std::initializer_list<llvm::Value **> ValuesToReload) {
420 assert(Old.isValid());
421
422 bool HadBranches = false;
423 while (EHStack.stable_begin() != Old) {
424 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());
425 HadBranches |= Scope.hasBranches();
426
427 // As long as Old strictly encloses the scope's enclosing normal
428 // cleanup, we're going to emit another normal cleanup which
429 // fallthrough can propagate through.
430 bool FallThroughIsBranchThrough =
431 Old.strictlyEncloses(Scope.getEnclosingNormalCleanup());
432
433 PopCleanupBlock(FallThroughIsBranchThrough);
434 }
435
436 // If we didn't have any branches, the insertion point before cleanups must
437 // dominate the current insertion point and we don't need to reload any
438 // values.
439 if (!HadBranches)
440 return;
441
442 // Spill and reload all values that the caller wants to be live at the current
443 // insertion point.
444 for (llvm::Value **ReloadedValue : ValuesToReload) {
445 auto *Inst = dyn_cast_or_null<llvm::Instruction>(*ReloadedValue);
446 if (!Inst)
447 continue;
448
449 // Don't spill static allocas, they dominate all cleanups. These are created
450 // by binding a reference to a local variable or temporary.
451 auto *AI = dyn_cast<llvm::AllocaInst>(Inst);
452 if (AI && AI->isStaticAlloca())
453 continue;
454
455 Address Tmp =
456 CreateDefaultAlignTempAlloca(Inst->getType(), "tmp.exprcleanup");
457
458 // Find an insertion point after Inst and spill it to the temporary.
459 llvm::BasicBlock::iterator InsertBefore;
460 if (auto *Invoke = dyn_cast<llvm::InvokeInst>(Inst))
461 InsertBefore = Invoke->getNormalDest()->getFirstInsertionPt();
462 else
463 InsertBefore = std::next(Inst->getIterator());
464 CGBuilderTy(CGM, &*InsertBefore).CreateStore(Inst, Tmp);
465
466 // Reload the value at the current insertion point.
467 *ReloadedValue = Builder.CreateLoad(Tmp);
468 }
469 }
470
471 /// Pops cleanup blocks until the given savepoint is reached, then add the
472 /// cleanups from the given savepoint in the lifetime-extended cleanups stack.
PopCleanupBlocks(EHScopeStack::stable_iterator Old,size_t OldLifetimeExtendedSize,std::initializer_list<llvm::Value ** > ValuesToReload)473 void CodeGenFunction::PopCleanupBlocks(
474 EHScopeStack::stable_iterator Old, size_t OldLifetimeExtendedSize,
475 std::initializer_list<llvm::Value **> ValuesToReload) {
476 PopCleanupBlocks(Old, ValuesToReload);
477
478 // Move our deferred cleanups onto the EH stack.
479 for (size_t I = OldLifetimeExtendedSize,
480 E = LifetimeExtendedCleanupStack.size(); I != E; /**/) {
481 // Alignment should be guaranteed by the vptrs in the individual cleanups.
482 assert((I % alignof(LifetimeExtendedCleanupHeader) == 0) &&
483 "misaligned cleanup stack entry");
484
485 LifetimeExtendedCleanupHeader &Header =
486 reinterpret_cast<LifetimeExtendedCleanupHeader&>(
487 LifetimeExtendedCleanupStack[I]);
488 I += sizeof(Header);
489
490 EHStack.pushCopyOfCleanup(Header.getKind(),
491 &LifetimeExtendedCleanupStack[I],
492 Header.getSize());
493 I += Header.getSize();
494
495 if (Header.isConditional()) {
496 Address ActiveFlag =
497 reinterpret_cast<Address &>(LifetimeExtendedCleanupStack[I]);
498 initFullExprCleanupWithFlag(ActiveFlag);
499 I += sizeof(ActiveFlag);
500 }
501 }
502 LifetimeExtendedCleanupStack.resize(OldLifetimeExtendedSize);
503 }
504
CreateNormalEntry(CodeGenFunction & CGF,EHCleanupScope & Scope)505 static llvm::BasicBlock *CreateNormalEntry(CodeGenFunction &CGF,
506 EHCleanupScope &Scope) {
507 assert(Scope.isNormalCleanup());
508 llvm::BasicBlock *Entry = Scope.getNormalBlock();
509 if (!Entry) {
510 Entry = CGF.createBasicBlock("cleanup");
511 Scope.setNormalBlock(Entry);
512 }
513 return Entry;
514 }
515
516 /// Attempts to reduce a cleanup's entry block to a fallthrough. This
517 /// is basically llvm::MergeBlockIntoPredecessor, except
518 /// simplified/optimized for the tighter constraints on cleanup blocks.
519 ///
520 /// Returns the new block, whatever it is.
SimplifyCleanupEntry(CodeGenFunction & CGF,llvm::BasicBlock * Entry)521 static llvm::BasicBlock *SimplifyCleanupEntry(CodeGenFunction &CGF,
522 llvm::BasicBlock *Entry) {
523 llvm::BasicBlock *Pred = Entry->getSinglePredecessor();
524 if (!Pred) return Entry;
525
526 llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Pred->getTerminator());
527 if (!Br || Br->isConditional()) return Entry;
528 assert(Br->getSuccessor(0) == Entry);
529
530 // If we were previously inserting at the end of the cleanup entry
531 // block, we'll need to continue inserting at the end of the
532 // predecessor.
533 bool WasInsertBlock = CGF.Builder.GetInsertBlock() == Entry;
534 assert(!WasInsertBlock || CGF.Builder.GetInsertPoint() == Entry->end());
535
536 // Kill the branch.
537 Br->eraseFromParent();
538
539 // Replace all uses of the entry with the predecessor, in case there
540 // are phis in the cleanup.
541 Entry->replaceAllUsesWith(Pred);
542
543 // Merge the blocks.
544 Pred->getInstList().splice(Pred->end(), Entry->getInstList());
545
546 // Kill the entry block.
547 Entry->eraseFromParent();
548
549 if (WasInsertBlock)
550 CGF.Builder.SetInsertPoint(Pred);
551
552 return Pred;
553 }
554
EmitCleanup(CodeGenFunction & CGF,EHScopeStack::Cleanup * Fn,EHScopeStack::Cleanup::Flags flags,Address ActiveFlag)555 static void EmitCleanup(CodeGenFunction &CGF,
556 EHScopeStack::Cleanup *Fn,
557 EHScopeStack::Cleanup::Flags flags,
558 Address ActiveFlag) {
559 // If there's an active flag, load it and skip the cleanup if it's
560 // false.
561 llvm::BasicBlock *ContBB = nullptr;
562 if (ActiveFlag.isValid()) {
563 ContBB = CGF.createBasicBlock("cleanup.done");
564 llvm::BasicBlock *CleanupBB = CGF.createBasicBlock("cleanup.action");
565 llvm::Value *IsActive
566 = CGF.Builder.CreateLoad(ActiveFlag, "cleanup.is_active");
567 CGF.Builder.CreateCondBr(IsActive, CleanupBB, ContBB);
568 CGF.EmitBlock(CleanupBB);
569 }
570
571 // Ask the cleanup to emit itself.
572 Fn->Emit(CGF, flags);
573 assert(CGF.HaveInsertPoint() && "cleanup ended with no insertion point?");
574
575 // Emit the continuation block if there was an active flag.
576 if (ActiveFlag.isValid())
577 CGF.EmitBlock(ContBB);
578 }
579
ForwardPrebranchedFallthrough(llvm::BasicBlock * Exit,llvm::BasicBlock * From,llvm::BasicBlock * To)580 static void ForwardPrebranchedFallthrough(llvm::BasicBlock *Exit,
581 llvm::BasicBlock *From,
582 llvm::BasicBlock *To) {
583 // Exit is the exit block of a cleanup, so it always terminates in
584 // an unconditional branch or a switch.
585 llvm::Instruction *Term = Exit->getTerminator();
586
587 if (llvm::BranchInst *Br = dyn_cast<llvm::BranchInst>(Term)) {
588 assert(Br->isUnconditional() && Br->getSuccessor(0) == From);
589 Br->setSuccessor(0, To);
590 } else {
591 llvm::SwitchInst *Switch = cast<llvm::SwitchInst>(Term);
592 for (unsigned I = 0, E = Switch->getNumSuccessors(); I != E; ++I)
593 if (Switch->getSuccessor(I) == From)
594 Switch->setSuccessor(I, To);
595 }
596 }
597
598 /// We don't need a normal entry block for the given cleanup.
599 /// Optimistic fixup branches can cause these blocks to come into
600 /// existence anyway; if so, destroy it.
601 ///
602 /// The validity of this transformation is very much specific to the
603 /// exact ways in which we form branches to cleanup entries.
destroyOptimisticNormalEntry(CodeGenFunction & CGF,EHCleanupScope & scope)604 static void destroyOptimisticNormalEntry(CodeGenFunction &CGF,
605 EHCleanupScope &scope) {
606 llvm::BasicBlock *entry = scope.getNormalBlock();
607 if (!entry) return;
608
609 // Replace all the uses with unreachable.
610 llvm::BasicBlock *unreachableBB = CGF.getUnreachableBlock();
611 for (llvm::BasicBlock::use_iterator
612 i = entry->use_begin(), e = entry->use_end(); i != e; ) {
613 llvm::Use &use = *i;
614 ++i;
615
616 use.set(unreachableBB);
617
618 // The only uses should be fixup switches.
619 llvm::SwitchInst *si = cast<llvm::SwitchInst>(use.getUser());
620 if (si->getNumCases() == 1 && si->getDefaultDest() == unreachableBB) {
621 // Replace the switch with a branch.
622 llvm::BranchInst::Create(si->case_begin()->getCaseSuccessor(), si);
623
624 // The switch operand is a load from the cleanup-dest alloca.
625 llvm::LoadInst *condition = cast<llvm::LoadInst>(si->getCondition());
626
627 // Destroy the switch.
628 si->eraseFromParent();
629
630 // Destroy the load.
631 assert(condition->getOperand(0) == CGF.NormalCleanupDest.getPointer());
632 assert(condition->use_empty());
633 condition->eraseFromParent();
634 }
635 }
636
637 assert(entry->use_empty());
638 delete entry;
639 }
640
641 /// Pops a cleanup block. If the block includes a normal cleanup, the
642 /// current insertion point is threaded through the cleanup, as are
643 /// any branch fixups on the cleanup.
PopCleanupBlock(bool FallthroughIsBranchThrough)644 void CodeGenFunction::PopCleanupBlock(bool FallthroughIsBranchThrough) {
645 assert(!EHStack.empty() && "cleanup stack is empty!");
646 assert(isa<EHCleanupScope>(*EHStack.begin()) && "top not a cleanup!");
647 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.begin());
648 assert(Scope.getFixupDepth() <= EHStack.getNumBranchFixups());
649
650 // Remember activation information.
651 bool IsActive = Scope.isActive();
652 Address NormalActiveFlag =
653 Scope.shouldTestFlagInNormalCleanup() ? Scope.getActiveFlag()
654 : Address::invalid();
655 Address EHActiveFlag =
656 Scope.shouldTestFlagInEHCleanup() ? Scope.getActiveFlag()
657 : Address::invalid();
658
659 // Check whether we need an EH cleanup. This is only true if we've
660 // generated a lazy EH cleanup block.
661 llvm::BasicBlock *EHEntry = Scope.getCachedEHDispatchBlock();
662 assert(Scope.hasEHBranches() == (EHEntry != nullptr));
663 bool RequiresEHCleanup = (EHEntry != nullptr);
664 EHScopeStack::stable_iterator EHParent = Scope.getEnclosingEHScope();
665
666 // Check the three conditions which might require a normal cleanup:
667
668 // - whether there are branch fix-ups through this cleanup
669 unsigned FixupDepth = Scope.getFixupDepth();
670 bool HasFixups = EHStack.getNumBranchFixups() != FixupDepth;
671
672 // - whether there are branch-throughs or branch-afters
673 bool HasExistingBranches = Scope.hasBranches();
674
675 // - whether there's a fallthrough
676 llvm::BasicBlock *FallthroughSource = Builder.GetInsertBlock();
677 bool HasFallthrough = (FallthroughSource != nullptr && IsActive);
678
679 // Branch-through fall-throughs leave the insertion point set to the
680 // end of the last cleanup, which points to the current scope. The
681 // rest of IR gen doesn't need to worry about this; it only happens
682 // during the execution of PopCleanupBlocks().
683 bool HasPrebranchedFallthrough =
684 (FallthroughSource && FallthroughSource->getTerminator());
685
686 // If this is a normal cleanup, then having a prebranched
687 // fallthrough implies that the fallthrough source unconditionally
688 // jumps here.
689 assert(!Scope.isNormalCleanup() || !HasPrebranchedFallthrough ||
690 (Scope.getNormalBlock() &&
691 FallthroughSource->getTerminator()->getSuccessor(0)
692 == Scope.getNormalBlock()));
693
694 bool RequiresNormalCleanup = false;
695 if (Scope.isNormalCleanup() &&
696 (HasFixups || HasExistingBranches || HasFallthrough)) {
697 RequiresNormalCleanup = true;
698 }
699
700 // If we have a prebranched fallthrough into an inactive normal
701 // cleanup, rewrite it so that it leads to the appropriate place.
702 if (Scope.isNormalCleanup() && HasPrebranchedFallthrough && !IsActive) {
703 llvm::BasicBlock *prebranchDest;
704
705 // If the prebranch is semantically branching through the next
706 // cleanup, just forward it to the next block, leaving the
707 // insertion point in the prebranched block.
708 if (FallthroughIsBranchThrough) {
709 EHScope &enclosing = *EHStack.find(Scope.getEnclosingNormalCleanup());
710 prebranchDest = CreateNormalEntry(*this, cast<EHCleanupScope>(enclosing));
711
712 // Otherwise, we need to make a new block. If the normal cleanup
713 // isn't being used at all, we could actually reuse the normal
714 // entry block, but this is simpler, and it avoids conflicts with
715 // dead optimistic fixup branches.
716 } else {
717 prebranchDest = createBasicBlock("forwarded-prebranch");
718 EmitBlock(prebranchDest);
719 }
720
721 llvm::BasicBlock *normalEntry = Scope.getNormalBlock();
722 assert(normalEntry && !normalEntry->use_empty());
723
724 ForwardPrebranchedFallthrough(FallthroughSource,
725 normalEntry, prebranchDest);
726 }
727
728 // If we don't need the cleanup at all, we're done.
729 if (!RequiresNormalCleanup && !RequiresEHCleanup) {
730 destroyOptimisticNormalEntry(*this, Scope);
731 EHStack.popCleanup(); // safe because there are no fixups
732 assert(EHStack.getNumBranchFixups() == 0 ||
733 EHStack.hasNormalCleanups());
734 return;
735 }
736
737 // Copy the cleanup emission data out. This uses either a stack
738 // array or malloc'd memory, depending on the size, which is
739 // behavior that SmallVector would provide, if we could use it
740 // here. Unfortunately, if you ask for a SmallVector<char>, the
741 // alignment isn't sufficient.
742 auto *CleanupSource = reinterpret_cast<char *>(Scope.getCleanupBuffer());
743 alignas(EHScopeStack::ScopeStackAlignment) char
744 CleanupBufferStack[8 * sizeof(void *)];
745 std::unique_ptr<char[]> CleanupBufferHeap;
746 size_t CleanupSize = Scope.getCleanupSize();
747 EHScopeStack::Cleanup *Fn;
748
749 if (CleanupSize <= sizeof(CleanupBufferStack)) {
750 memcpy(CleanupBufferStack, CleanupSource, CleanupSize);
751 Fn = reinterpret_cast<EHScopeStack::Cleanup *>(CleanupBufferStack);
752 } else {
753 CleanupBufferHeap.reset(new char[CleanupSize]);
754 memcpy(CleanupBufferHeap.get(), CleanupSource, CleanupSize);
755 Fn = reinterpret_cast<EHScopeStack::Cleanup *>(CleanupBufferHeap.get());
756 }
757
758 EHScopeStack::Cleanup::Flags cleanupFlags;
759 if (Scope.isNormalCleanup())
760 cleanupFlags.setIsNormalCleanupKind();
761 if (Scope.isEHCleanup())
762 cleanupFlags.setIsEHCleanupKind();
763
764 if (!RequiresNormalCleanup) {
765 destroyOptimisticNormalEntry(*this, Scope);
766 EHStack.popCleanup();
767 } else {
768 // If we have a fallthrough and no other need for the cleanup,
769 // emit it directly.
770 if (HasFallthrough && !HasPrebranchedFallthrough &&
771 !HasFixups && !HasExistingBranches) {
772
773 destroyOptimisticNormalEntry(*this, Scope);
774 EHStack.popCleanup();
775
776 EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);
777
778 // Otherwise, the best approach is to thread everything through
779 // the cleanup block and then try to clean up after ourselves.
780 } else {
781 // Force the entry block to exist.
782 llvm::BasicBlock *NormalEntry = CreateNormalEntry(*this, Scope);
783
784 // I. Set up the fallthrough edge in.
785
786 CGBuilderTy::InsertPoint savedInactiveFallthroughIP;
787
788 // If there's a fallthrough, we need to store the cleanup
789 // destination index. For fall-throughs this is always zero.
790 if (HasFallthrough) {
791 if (!HasPrebranchedFallthrough)
792 Builder.CreateStore(Builder.getInt32(0), getNormalCleanupDestSlot());
793
794 // Otherwise, save and clear the IP if we don't have fallthrough
795 // because the cleanup is inactive.
796 } else if (FallthroughSource) {
797 assert(!IsActive && "source without fallthrough for active cleanup");
798 savedInactiveFallthroughIP = Builder.saveAndClearIP();
799 }
800
801 // II. Emit the entry block. This implicitly branches to it if
802 // we have fallthrough. All the fixups and existing branches
803 // should already be branched to it.
804 EmitBlock(NormalEntry);
805
806 // III. Figure out where we're going and build the cleanup
807 // epilogue.
808
809 bool HasEnclosingCleanups =
810 (Scope.getEnclosingNormalCleanup() != EHStack.stable_end());
811
812 // Compute the branch-through dest if we need it:
813 // - if there are branch-throughs threaded through the scope
814 // - if fall-through is a branch-through
815 // - if there are fixups that will be optimistically forwarded
816 // to the enclosing cleanup
817 llvm::BasicBlock *BranchThroughDest = nullptr;
818 if (Scope.hasBranchThroughs() ||
819 (FallthroughSource && FallthroughIsBranchThrough) ||
820 (HasFixups && HasEnclosingCleanups)) {
821 assert(HasEnclosingCleanups);
822 EHScope &S = *EHStack.find(Scope.getEnclosingNormalCleanup());
823 BranchThroughDest = CreateNormalEntry(*this, cast<EHCleanupScope>(S));
824 }
825
826 llvm::BasicBlock *FallthroughDest = nullptr;
827 SmallVector<llvm::Instruction*, 2> InstsToAppend;
828
829 // If there's exactly one branch-after and no other threads,
830 // we can route it without a switch.
831 if (!Scope.hasBranchThroughs() && !HasFixups && !HasFallthrough &&
832 Scope.getNumBranchAfters() == 1) {
833 assert(!BranchThroughDest || !IsActive);
834
835 // Clean up the possibly dead store to the cleanup dest slot.
836 llvm::Instruction *NormalCleanupDestSlot =
837 cast<llvm::Instruction>(getNormalCleanupDestSlot().getPointer());
838 if (NormalCleanupDestSlot->hasOneUse()) {
839 NormalCleanupDestSlot->user_back()->eraseFromParent();
840 NormalCleanupDestSlot->eraseFromParent();
841 NormalCleanupDest = Address::invalid();
842 }
843
844 llvm::BasicBlock *BranchAfter = Scope.getBranchAfterBlock(0);
845 InstsToAppend.push_back(llvm::BranchInst::Create(BranchAfter));
846
847 // Build a switch-out if we need it:
848 // - if there are branch-afters threaded through the scope
849 // - if fall-through is a branch-after
850 // - if there are fixups that have nowhere left to go and
851 // so must be immediately resolved
852 } else if (Scope.getNumBranchAfters() ||
853 (HasFallthrough && !FallthroughIsBranchThrough) ||
854 (HasFixups && !HasEnclosingCleanups)) {
855
856 llvm::BasicBlock *Default =
857 (BranchThroughDest ? BranchThroughDest : getUnreachableBlock());
858
859 // TODO: base this on the number of branch-afters and fixups
860 const unsigned SwitchCapacity = 10;
861
862 llvm::LoadInst *Load =
863 createLoadInstBefore(getNormalCleanupDestSlot(), "cleanup.dest",
864 nullptr);
865 llvm::SwitchInst *Switch =
866 llvm::SwitchInst::Create(Load, Default, SwitchCapacity);
867
868 InstsToAppend.push_back(Load);
869 InstsToAppend.push_back(Switch);
870
871 // Branch-after fallthrough.
872 if (FallthroughSource && !FallthroughIsBranchThrough) {
873 FallthroughDest = createBasicBlock("cleanup.cont");
874 if (HasFallthrough)
875 Switch->addCase(Builder.getInt32(0), FallthroughDest);
876 }
877
878 for (unsigned I = 0, E = Scope.getNumBranchAfters(); I != E; ++I) {
879 Switch->addCase(Scope.getBranchAfterIndex(I),
880 Scope.getBranchAfterBlock(I));
881 }
882
883 // If there aren't any enclosing cleanups, we can resolve all
884 // the fixups now.
885 if (HasFixups && !HasEnclosingCleanups)
886 ResolveAllBranchFixups(*this, Switch, NormalEntry);
887 } else {
888 // We should always have a branch-through destination in this case.
889 assert(BranchThroughDest);
890 InstsToAppend.push_back(llvm::BranchInst::Create(BranchThroughDest));
891 }
892
893 // IV. Pop the cleanup and emit it.
894 EHStack.popCleanup();
895 assert(EHStack.hasNormalCleanups() == HasEnclosingCleanups);
896
897 EmitCleanup(*this, Fn, cleanupFlags, NormalActiveFlag);
898
899 // Append the prepared cleanup prologue from above.
900 llvm::BasicBlock *NormalExit = Builder.GetInsertBlock();
901 for (unsigned I = 0, E = InstsToAppend.size(); I != E; ++I)
902 NormalExit->getInstList().push_back(InstsToAppend[I]);
903
904 // Optimistically hope that any fixups will continue falling through.
905 for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();
906 I < E; ++I) {
907 BranchFixup &Fixup = EHStack.getBranchFixup(I);
908 if (!Fixup.Destination) continue;
909 if (!Fixup.OptimisticBranchBlock) {
910 createStoreInstBefore(Builder.getInt32(Fixup.DestinationIndex),
911 getNormalCleanupDestSlot(),
912 Fixup.InitialBranch);
913 Fixup.InitialBranch->setSuccessor(0, NormalEntry);
914 }
915 Fixup.OptimisticBranchBlock = NormalExit;
916 }
917
918 // V. Set up the fallthrough edge out.
919
920 // Case 1: a fallthrough source exists but doesn't branch to the
921 // cleanup because the cleanup is inactive.
922 if (!HasFallthrough && FallthroughSource) {
923 // Prebranched fallthrough was forwarded earlier.
924 // Non-prebranched fallthrough doesn't need to be forwarded.
925 // Either way, all we need to do is restore the IP we cleared before.
926 assert(!IsActive);
927 Builder.restoreIP(savedInactiveFallthroughIP);
928
929 // Case 2: a fallthrough source exists and should branch to the
930 // cleanup, but we're not supposed to branch through to the next
931 // cleanup.
932 } else if (HasFallthrough && FallthroughDest) {
933 assert(!FallthroughIsBranchThrough);
934 EmitBlock(FallthroughDest);
935
936 // Case 3: a fallthrough source exists and should branch to the
937 // cleanup and then through to the next.
938 } else if (HasFallthrough) {
939 // Everything is already set up for this.
940
941 // Case 4: no fallthrough source exists.
942 } else {
943 Builder.ClearInsertionPoint();
944 }
945
946 // VI. Assorted cleaning.
947
948 // Check whether we can merge NormalEntry into a single predecessor.
949 // This might invalidate (non-IR) pointers to NormalEntry.
950 llvm::BasicBlock *NewNormalEntry =
951 SimplifyCleanupEntry(*this, NormalEntry);
952
953 // If it did invalidate those pointers, and NormalEntry was the same
954 // as NormalExit, go back and patch up the fixups.
955 if (NewNormalEntry != NormalEntry && NormalEntry == NormalExit)
956 for (unsigned I = FixupDepth, E = EHStack.getNumBranchFixups();
957 I < E; ++I)
958 EHStack.getBranchFixup(I).OptimisticBranchBlock = NewNormalEntry;
959 }
960 }
961
962 assert(EHStack.hasNormalCleanups() || EHStack.getNumBranchFixups() == 0);
963
964 // Emit the EH cleanup if required.
965 if (RequiresEHCleanup) {
966 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
967
968 EmitBlock(EHEntry);
969
970 llvm::BasicBlock *NextAction = getEHDispatchBlock(EHParent);
971
972 // Push a terminate scope or cleanupendpad scope around the potentially
973 // throwing cleanups. For funclet EH personalities, the cleanupendpad models
974 // program termination when cleanups throw.
975 bool PushedTerminate = false;
976 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad(
977 CurrentFuncletPad);
978 llvm::CleanupPadInst *CPI = nullptr;
979
980 const EHPersonality &Personality = EHPersonality::get(*this);
981 if (Personality.usesFuncletPads()) {
982 llvm::Value *ParentPad = CurrentFuncletPad;
983 if (!ParentPad)
984 ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext());
985 CurrentFuncletPad = CPI = Builder.CreateCleanupPad(ParentPad);
986 }
987
988 // Non-MSVC personalities need to terminate when an EH cleanup throws.
989 if (!Personality.isMSVCPersonality()) {
990 EHStack.pushTerminate();
991 PushedTerminate = true;
992 }
993
994 // We only actually emit the cleanup code if the cleanup is either
995 // active or was used before it was deactivated.
996 if (EHActiveFlag.isValid() || IsActive) {
997 cleanupFlags.setIsForEHCleanup();
998 EmitCleanup(*this, Fn, cleanupFlags, EHActiveFlag);
999 }
1000
1001 if (CPI)
1002 Builder.CreateCleanupRet(CPI, NextAction);
1003 else
1004 Builder.CreateBr(NextAction);
1005
1006 // Leave the terminate scope.
1007 if (PushedTerminate)
1008 EHStack.popTerminate();
1009
1010 Builder.restoreIP(SavedIP);
1011
1012 SimplifyCleanupEntry(*this, EHEntry);
1013 }
1014 }
1015
1016 /// isObviouslyBranchWithoutCleanups - Return true if a branch to the
1017 /// specified destination obviously has no cleanups to run. 'false' is always
1018 /// a conservatively correct answer for this method.
isObviouslyBranchWithoutCleanups(JumpDest Dest) const1019 bool CodeGenFunction::isObviouslyBranchWithoutCleanups(JumpDest Dest) const {
1020 assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())
1021 && "stale jump destination");
1022
1023 // Calculate the innermost active normal cleanup.
1024 EHScopeStack::stable_iterator TopCleanup =
1025 EHStack.getInnermostActiveNormalCleanup();
1026
1027 // If we're not in an active normal cleanup scope, or if the
1028 // destination scope is within the innermost active normal cleanup
1029 // scope, we don't need to worry about fixups.
1030 if (TopCleanup == EHStack.stable_end() ||
1031 TopCleanup.encloses(Dest.getScopeDepth())) // works for invalid
1032 return true;
1033
1034 // Otherwise, we might need some cleanups.
1035 return false;
1036 }
1037
1038
1039 /// Terminate the current block by emitting a branch which might leave
1040 /// the current cleanup-protected scope. The target scope may not yet
1041 /// be known, in which case this will require a fixup.
1042 ///
1043 /// As a side-effect, this method clears the insertion point.
EmitBranchThroughCleanup(JumpDest Dest)1044 void CodeGenFunction::EmitBranchThroughCleanup(JumpDest Dest) {
1045 assert(Dest.getScopeDepth().encloses(EHStack.stable_begin())
1046 && "stale jump destination");
1047
1048 if (!HaveInsertPoint())
1049 return;
1050
1051 // Create the branch.
1052 llvm::BranchInst *BI = Builder.CreateBr(Dest.getBlock());
1053
1054 // Calculate the innermost active normal cleanup.
1055 EHScopeStack::stable_iterator
1056 TopCleanup = EHStack.getInnermostActiveNormalCleanup();
1057
1058 // If we're not in an active normal cleanup scope, or if the
1059 // destination scope is within the innermost active normal cleanup
1060 // scope, we don't need to worry about fixups.
1061 if (TopCleanup == EHStack.stable_end() ||
1062 TopCleanup.encloses(Dest.getScopeDepth())) { // works for invalid
1063 Builder.ClearInsertionPoint();
1064 return;
1065 }
1066
1067 // If we can't resolve the destination cleanup scope, just add this
1068 // to the current cleanup scope as a branch fixup.
1069 if (!Dest.getScopeDepth().isValid()) {
1070 BranchFixup &Fixup = EHStack.addBranchFixup();
1071 Fixup.Destination = Dest.getBlock();
1072 Fixup.DestinationIndex = Dest.getDestIndex();
1073 Fixup.InitialBranch = BI;
1074 Fixup.OptimisticBranchBlock = nullptr;
1075
1076 Builder.ClearInsertionPoint();
1077 return;
1078 }
1079
1080 // Otherwise, thread through all the normal cleanups in scope.
1081
1082 // Store the index at the start.
1083 llvm::ConstantInt *Index = Builder.getInt32(Dest.getDestIndex());
1084 createStoreInstBefore(Index, getNormalCleanupDestSlot(), BI);
1085
1086 // Adjust BI to point to the first cleanup block.
1087 {
1088 EHCleanupScope &Scope =
1089 cast<EHCleanupScope>(*EHStack.find(TopCleanup));
1090 BI->setSuccessor(0, CreateNormalEntry(*this, Scope));
1091 }
1092
1093 // Add this destination to all the scopes involved.
1094 EHScopeStack::stable_iterator I = TopCleanup;
1095 EHScopeStack::stable_iterator E = Dest.getScopeDepth();
1096 if (E.strictlyEncloses(I)) {
1097 while (true) {
1098 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(I));
1099 assert(Scope.isNormalCleanup());
1100 I = Scope.getEnclosingNormalCleanup();
1101
1102 // If this is the last cleanup we're propagating through, tell it
1103 // that there's a resolved jump moving through it.
1104 if (!E.strictlyEncloses(I)) {
1105 Scope.addBranchAfter(Index, Dest.getBlock());
1106 break;
1107 }
1108
1109 // Otherwise, tell the scope that there's a jump propagating
1110 // through it. If this isn't new information, all the rest of
1111 // the work has been done before.
1112 if (!Scope.addBranchThrough(Dest.getBlock()))
1113 break;
1114 }
1115 }
1116
1117 Builder.ClearInsertionPoint();
1118 }
1119
IsUsedAsNormalCleanup(EHScopeStack & EHStack,EHScopeStack::stable_iterator C)1120 static bool IsUsedAsNormalCleanup(EHScopeStack &EHStack,
1121 EHScopeStack::stable_iterator C) {
1122 // If we needed a normal block for any reason, that counts.
1123 if (cast<EHCleanupScope>(*EHStack.find(C)).getNormalBlock())
1124 return true;
1125
1126 // Check whether any enclosed cleanups were needed.
1127 for (EHScopeStack::stable_iterator
1128 I = EHStack.getInnermostNormalCleanup();
1129 I != C; ) {
1130 assert(C.strictlyEncloses(I));
1131 EHCleanupScope &S = cast<EHCleanupScope>(*EHStack.find(I));
1132 if (S.getNormalBlock()) return true;
1133 I = S.getEnclosingNormalCleanup();
1134 }
1135
1136 return false;
1137 }
1138
IsUsedAsEHCleanup(EHScopeStack & EHStack,EHScopeStack::stable_iterator cleanup)1139 static bool IsUsedAsEHCleanup(EHScopeStack &EHStack,
1140 EHScopeStack::stable_iterator cleanup) {
1141 // If we needed an EH block for any reason, that counts.
1142 if (EHStack.find(cleanup)->hasEHBranches())
1143 return true;
1144
1145 // Check whether any enclosed cleanups were needed.
1146 for (EHScopeStack::stable_iterator
1147 i = EHStack.getInnermostEHScope(); i != cleanup; ) {
1148 assert(cleanup.strictlyEncloses(i));
1149
1150 EHScope &scope = *EHStack.find(i);
1151 if (scope.hasEHBranches())
1152 return true;
1153
1154 i = scope.getEnclosingEHScope();
1155 }
1156
1157 return false;
1158 }
1159
1160 enum ForActivation_t {
1161 ForActivation,
1162 ForDeactivation
1163 };
1164
1165 /// The given cleanup block is changing activation state. Configure a
1166 /// cleanup variable if necessary.
1167 ///
1168 /// It would be good if we had some way of determining if there were
1169 /// extra uses *after* the change-over point.
SetupCleanupBlockActivation(CodeGenFunction & CGF,EHScopeStack::stable_iterator C,ForActivation_t kind,llvm::Instruction * dominatingIP)1170 static void SetupCleanupBlockActivation(CodeGenFunction &CGF,
1171 EHScopeStack::stable_iterator C,
1172 ForActivation_t kind,
1173 llvm::Instruction *dominatingIP) {
1174 EHCleanupScope &Scope = cast<EHCleanupScope>(*CGF.EHStack.find(C));
1175
1176 // We always need the flag if we're activating the cleanup in a
1177 // conditional context, because we have to assume that the current
1178 // location doesn't necessarily dominate the cleanup's code.
1179 bool isActivatedInConditional =
1180 (kind == ForActivation && CGF.isInConditionalBranch());
1181
1182 bool needFlag = false;
1183
1184 // Calculate whether the cleanup was used:
1185
1186 // - as a normal cleanup
1187 if (Scope.isNormalCleanup() &&
1188 (isActivatedInConditional || IsUsedAsNormalCleanup(CGF.EHStack, C))) {
1189 Scope.setTestFlagInNormalCleanup();
1190 needFlag = true;
1191 }
1192
1193 // - as an EH cleanup
1194 if (Scope.isEHCleanup() &&
1195 (isActivatedInConditional || IsUsedAsEHCleanup(CGF.EHStack, C))) {
1196 Scope.setTestFlagInEHCleanup();
1197 needFlag = true;
1198 }
1199
1200 // If it hasn't yet been used as either, we're done.
1201 if (!needFlag) return;
1202
1203 Address var = Scope.getActiveFlag();
1204 if (!var.isValid()) {
1205 var = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), CharUnits::One(),
1206 "cleanup.isactive");
1207 Scope.setActiveFlag(var);
1208
1209 assert(dominatingIP && "no existing variable and no dominating IP!");
1210
1211 // Initialize to true or false depending on whether it was
1212 // active up to this point.
1213 llvm::Constant *value = CGF.Builder.getInt1(kind == ForDeactivation);
1214
1215 // If we're in a conditional block, ignore the dominating IP and
1216 // use the outermost conditional branch.
1217 if (CGF.isInConditionalBranch()) {
1218 CGF.setBeforeOutermostConditional(value, var);
1219 } else {
1220 createStoreInstBefore(value, var, dominatingIP);
1221 }
1222 }
1223
1224 CGF.Builder.CreateStore(CGF.Builder.getInt1(kind == ForActivation), var);
1225 }
1226
1227 /// Activate a cleanup that was created in an inactivated state.
ActivateCleanupBlock(EHScopeStack::stable_iterator C,llvm::Instruction * dominatingIP)1228 void CodeGenFunction::ActivateCleanupBlock(EHScopeStack::stable_iterator C,
1229 llvm::Instruction *dominatingIP) {
1230 assert(C != EHStack.stable_end() && "activating bottom of stack?");
1231 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));
1232 assert(!Scope.isActive() && "double activation");
1233
1234 SetupCleanupBlockActivation(*this, C, ForActivation, dominatingIP);
1235
1236 Scope.setActive(true);
1237 }
1238
1239 /// Deactive a cleanup that was created in an active state.
DeactivateCleanupBlock(EHScopeStack::stable_iterator C,llvm::Instruction * dominatingIP)1240 void CodeGenFunction::DeactivateCleanupBlock(EHScopeStack::stable_iterator C,
1241 llvm::Instruction *dominatingIP) {
1242 assert(C != EHStack.stable_end() && "deactivating bottom of stack?");
1243 EHCleanupScope &Scope = cast<EHCleanupScope>(*EHStack.find(C));
1244 assert(Scope.isActive() && "double deactivation");
1245
1246 // If it's the top of the stack, just pop it, but do so only if it belongs
1247 // to the current RunCleanupsScope.
1248 if (C == EHStack.stable_begin() &&
1249 CurrentCleanupScopeDepth.strictlyEncloses(C)) {
1250 // If it's a normal cleanup, we need to pretend that the
1251 // fallthrough is unreachable.
1252 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP();
1253 PopCleanupBlock();
1254 Builder.restoreIP(SavedIP);
1255 return;
1256 }
1257
1258 // Otherwise, follow the general case.
1259 SetupCleanupBlockActivation(*this, C, ForDeactivation, dominatingIP);
1260
1261 Scope.setActive(false);
1262 }
1263
getNormalCleanupDestSlot()1264 Address CodeGenFunction::getNormalCleanupDestSlot() {
1265 if (!NormalCleanupDest.isValid())
1266 NormalCleanupDest =
1267 CreateDefaultAlignTempAlloca(Builder.getInt32Ty(), "cleanup.dest.slot");
1268 return NormalCleanupDest;
1269 }
1270
1271 /// Emits all the code to cause the given temporary to be cleaned up.
EmitCXXTemporary(const CXXTemporary * Temporary,QualType TempType,Address Ptr)1272 void CodeGenFunction::EmitCXXTemporary(const CXXTemporary *Temporary,
1273 QualType TempType,
1274 Address Ptr) {
1275 pushDestroy(NormalAndEHCleanup, Ptr, TempType, destroyCXXObject,
1276 /*useEHCleanup*/ true);
1277 }
1278