1 //===-- WinEHPrepare - Prepare exception handling for code generation ---===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass lowers LLVM IR exception handling into something closer to what the
11 // backend wants. It snifs the personality function to see which kind of
12 // preparation is necessary. If the personality function uses the Itanium LSDA,
13 // this pass delegates to the DWARF EH preparation pass.
15 //===----------------------------------------------------------------------===//
17 #include "llvm/CodeGen/Passes.h"
18 #include "llvm/ADT/MapVector.h"
19 #include "llvm/ADT/SmallSet.h"
20 #include "llvm/ADT/STLExtras.h"
21 #include "llvm/ADT/TinyPtrVector.h"
22 #include "llvm/Analysis/LibCallSemantics.h"
23 #include "llvm/IR/Function.h"
24 #include "llvm/IR/IRBuilder.h"
25 #include "llvm/IR/Instructions.h"
26 #include "llvm/IR/IntrinsicInst.h"
27 #include "llvm/IR/Module.h"
28 #include "llvm/IR/PatternMatch.h"
29 #include "llvm/Pass.h"
30 #include "llvm/Support/CommandLine.h"
31 #include "llvm/Support/Debug.h"
32 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
33 #include "llvm/Transforms/Utils/Cloning.h"
34 #include "llvm/Transforms/Utils/Local.h"
38 using namespace llvm::PatternMatch;
40 #define DEBUG_TYPE "winehprepare"
44 // This map is used to model frame variable usage during outlining, to
45 // construct a structure type to hold the frame variables in a frame
46 // allocation block, and to remap the frame variable allocas (including
47 // spill locations as needed) to GEPs that get the variable from the
48 // frame allocation structure.
49 typedef MapVector<Value *, TinyPtrVector<AllocaInst *>> FrameVarInfoMap;
51 typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
53 enum ActionType { Catch, Cleanup };
55 class LandingPadActions;
61 typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
62 typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
64 class WinEHPrepare : public FunctionPass {
66 static char ID; // Pass identification, replacement for typeid.
67 WinEHPrepare(const TargetMachine *TM = nullptr)
70 bool runOnFunction(Function &Fn) override;
72 bool doFinalization(Module &M) override;
74 void getAnalysisUsage(AnalysisUsage &AU) const override;
76 const char *getPassName() const override {
77 return "Windows exception handling preparation";
81 bool prepareExceptionHandlers(Function &F,
82 SmallVectorImpl<LandingPadInst *> &LPads);
83 bool outlineHandler(ActionHandler *Action, Function *SrcFn,
84 LandingPadInst *LPad, BasicBlock *StartBB,
85 FrameVarInfoMap &VarInfo);
87 void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
88 CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
89 VisitedBlockSet &VisitedBlocks);
90 CleanupHandler *findCleanupHandler(BasicBlock *StartBB, BasicBlock *EndBB);
92 void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
94 // All fields are reset by runOnFunction.
95 EHPersonality Personality;
96 CatchHandlerMapTy CatchHandlerMap;
97 CleanupHandlerMapTy CleanupHandlerMap;
98 DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
101 class WinEHFrameVariableMaterializer : public ValueMaterializer {
103 WinEHFrameVariableMaterializer(Function *OutlinedFn,
104 FrameVarInfoMap &FrameVarInfo);
105 ~WinEHFrameVariableMaterializer() {}
107 virtual Value *materializeValueFor(Value *V) override;
110 FrameVarInfoMap &FrameVarInfo;
114 class LandingPadMap {
116 LandingPadMap() : OriginLPad(nullptr) {}
117 void mapLandingPad(const LandingPadInst *LPad);
119 bool isInitialized() { return OriginLPad != nullptr; }
121 bool mapIfEHPtrLoad(const LoadInst *Load) {
122 return mapIfEHLoad(Load, EHPtrStores, EHPtrStoreAddrs);
124 bool mapIfSelectorLoad(const LoadInst *Load) {
125 return mapIfEHLoad(Load, SelectorStores, SelectorStoreAddrs);
128 bool isLandingPadSpecificInst(const Instruction *Inst) const;
130 void remapSelector(ValueToValueMapTy &VMap, Value *MappedValue) const;
133 bool mapIfEHLoad(const LoadInst *Load,
134 SmallVectorImpl<const StoreInst *> &Stores,
135 SmallVectorImpl<const Value *> &StoreAddrs);
137 const LandingPadInst *OriginLPad;
138 // We will normally only see one of each of these instructions, but
139 // if more than one occurs for some reason we can handle that.
140 TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
141 TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
143 // In optimized code, there will typically be at most one instance of
144 // each of the following, but in unoptimized IR it is not uncommon
145 // for the values to be stored, loaded and then stored again. In that
146 // case we will create a second entry for each store and store address.
147 SmallVector<const StoreInst *, 2> EHPtrStores;
148 SmallVector<const StoreInst *, 2> SelectorStores;
149 SmallVector<const Value *, 2> EHPtrStoreAddrs;
150 SmallVector<const Value *, 2> SelectorStoreAddrs;
153 class WinEHCloningDirectorBase : public CloningDirector {
155 WinEHCloningDirectorBase(Function *HandlerFn,
156 FrameVarInfoMap &VarInfo,
157 LandingPadMap &LPadMap)
158 : Materializer(HandlerFn, VarInfo),
159 SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
160 Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
163 CloningAction handleInstruction(ValueToValueMapTy &VMap,
164 const Instruction *Inst,
165 BasicBlock *NewBB) override;
167 virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
168 const Instruction *Inst,
169 BasicBlock *NewBB) = 0;
170 virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
171 const Instruction *Inst,
172 BasicBlock *NewBB) = 0;
173 virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
174 const Instruction *Inst,
175 BasicBlock *NewBB) = 0;
176 virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
177 const InvokeInst *Invoke,
178 BasicBlock *NewBB) = 0;
179 virtual CloningAction handleResume(ValueToValueMapTy &VMap,
180 const ResumeInst *Resume,
181 BasicBlock *NewBB) = 0;
183 ValueMaterializer *getValueMaterializer() override { return &Materializer; }
186 WinEHFrameVariableMaterializer Materializer;
187 Type *SelectorIDType;
189 LandingPadMap &LPadMap;
192 class WinEHCatchDirector : public WinEHCloningDirectorBase {
194 WinEHCatchDirector(Function *CatchFn, Value *Selector,
195 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
196 : WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
197 CurrentSelector(Selector->stripPointerCasts()),
198 ExceptionObjectVar(nullptr) {}
200 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
201 const Instruction *Inst,
202 BasicBlock *NewBB) override;
203 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
204 BasicBlock *NewBB) override;
205 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
206 const Instruction *Inst,
207 BasicBlock *NewBB) override;
208 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
209 BasicBlock *NewBB) override;
210 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
211 BasicBlock *NewBB) override;
213 const Value *getExceptionVar() { return ExceptionObjectVar; }
214 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
217 Value *CurrentSelector;
219 const Value *ExceptionObjectVar;
220 TinyPtrVector<BasicBlock *> ReturnTargets;
223 class WinEHCleanupDirector : public WinEHCloningDirectorBase {
225 WinEHCleanupDirector(Function *CleanupFn,
226 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
227 : WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
229 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
230 const Instruction *Inst,
231 BasicBlock *NewBB) override;
232 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
233 BasicBlock *NewBB) override;
234 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
235 const Instruction *Inst,
236 BasicBlock *NewBB) override;
237 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
238 BasicBlock *NewBB) override;
239 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
240 BasicBlock *NewBB) override;
243 class ActionHandler {
245 ActionHandler(BasicBlock *BB, ActionType Type)
246 : StartBB(BB), Type(Type), HandlerBlockOrFunc(nullptr) {}
248 ActionType getType() const { return Type; }
249 BasicBlock *getStartBlock() const { return StartBB; }
251 bool hasBeenProcessed() { return HandlerBlockOrFunc != nullptr; }
253 void setHandlerBlockOrFunc(Constant *F) { HandlerBlockOrFunc = F; }
254 Constant *getHandlerBlockOrFunc() { return HandlerBlockOrFunc; }
260 // Can be either a BlockAddress or a Function depending on the EH personality.
261 Constant *HandlerBlockOrFunc;
264 class CatchHandler : public ActionHandler {
266 CatchHandler(BasicBlock *BB, Constant *Selector, BasicBlock *NextBB)
267 : ActionHandler(BB, ActionType::Catch), Selector(Selector),
268 NextBB(NextBB), ExceptionObjectVar(nullptr) {}
270 // Method for support type inquiry through isa, cast, and dyn_cast:
271 static inline bool classof(const ActionHandler *H) {
272 return H->getType() == ActionType::Catch;
275 Constant *getSelector() const { return Selector; }
276 BasicBlock *getNextBB() const { return NextBB; }
278 const Value *getExceptionVar() { return ExceptionObjectVar; }
279 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
281 void setExceptionVar(const Value *Val) { ExceptionObjectVar = Val; }
282 void setReturnTargets(TinyPtrVector<BasicBlock *> &Targets) {
283 ReturnTargets = Targets;
289 const Value *ExceptionObjectVar;
290 TinyPtrVector<BasicBlock *> ReturnTargets;
293 class CleanupHandler : public ActionHandler {
295 CleanupHandler(BasicBlock *BB) : ActionHandler(BB, ActionType::Cleanup) {}
297 // Method for support type inquiry through isa, cast, and dyn_cast:
298 static inline bool classof(const ActionHandler *H) {
299 return H->getType() == ActionType::Cleanup;
303 class LandingPadActions {
305 LandingPadActions() : HasCleanupHandlers(false) {}
307 void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
308 void insertCleanupHandler(CleanupHandler *Action) {
309 Actions.push_back(Action);
310 HasCleanupHandlers = true;
313 bool includesCleanup() const { return HasCleanupHandlers; }
315 SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
316 SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
319 // Note that this class does not own the ActionHandler objects in this vector.
320 // The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
321 // in the WinEHPrepare class.
322 SmallVector<ActionHandler *, 4> Actions;
323 bool HasCleanupHandlers;
326 } // end anonymous namespace
328 char WinEHPrepare::ID = 0;
329 INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
332 FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
333 return new WinEHPrepare(TM);
336 // FIXME: Remove this once the backend can handle the prepared IR.
338 SEHPrepare("sehprepare", cl::Hidden,
339 cl::desc("Prepare functions with SEH personalities"));
341 bool WinEHPrepare::runOnFunction(Function &Fn) {
342 SmallVector<LandingPadInst *, 4> LPads;
343 SmallVector<ResumeInst *, 4> Resumes;
344 for (BasicBlock &BB : Fn) {
345 if (auto *LP = BB.getLandingPadInst())
347 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
348 Resumes.push_back(Resume);
351 // No need to prepare functions that lack landing pads.
355 // Classify the personality to see what kind of preparation we need.
356 Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
358 // Do nothing if this is not an MSVC personality.
359 if (!isMSVCEHPersonality(Personality))
362 if (isAsynchronousEHPersonality(Personality) && !SEHPrepare) {
363 // Replace all resume instructions with unreachable.
364 // FIXME: Remove this once the backend can handle the prepared IR.
365 for (ResumeInst *Resume : Resumes) {
366 IRBuilder<>(Resume).CreateUnreachable();
367 Resume->eraseFromParent();
372 // If there were any landing pads, prepareExceptionHandlers will make changes.
373 prepareExceptionHandlers(Fn, LPads);
377 bool WinEHPrepare::doFinalization(Module &M) {
381 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {}
383 bool WinEHPrepare::prepareExceptionHandlers(
384 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
385 // These containers are used to re-map frame variables that are used in
386 // outlined catch and cleanup handlers. They will be populated as the
387 // handlers are outlined.
388 FrameVarInfoMap FrameVarInfo;
390 bool HandlersOutlined = false;
392 Module *M = F.getParent();
393 LLVMContext &Context = M->getContext();
395 // Create a new function to receive the handler contents.
396 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
397 Type *Int32Type = Type::getInt32Ty(Context);
398 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
400 for (LandingPadInst *LPad : LPads) {
401 // Look for evidence that this landingpad has already been processed.
402 bool LPadHasActionList = false;
403 BasicBlock *LPadBB = LPad->getParent();
404 for (Instruction &Inst : LPadBB->getInstList()) {
405 // FIXME: Make this an intrinsic.
406 if (auto *IntrinCall = dyn_cast<IntrinsicInst>(&Inst)) {
407 if (IntrinCall->getIntrinsicID() == Intrinsic::eh_actions) {
408 LPadHasActionList = true;
412 // FIXME: This is here to help with the development of nested landing pad
413 // outlining. It should be removed when that is finished.
414 if (isa<UnreachableInst>(Inst)) {
415 LPadHasActionList = true;
420 // If we've already outlined the handlers for this landingpad,
421 // there's nothing more to do here.
422 if (LPadHasActionList)
425 LandingPadActions Actions;
426 mapLandingPadBlocks(LPad, Actions);
428 for (ActionHandler *Action : Actions) {
429 if (Action->hasBeenProcessed())
431 BasicBlock *StartBB = Action->getStartBlock();
433 // SEH doesn't do any outlining for catches. Instead, pass the handler
434 // basic block addr to llvm.eh.actions and list the block as a return
436 if (isAsynchronousEHPersonality(Personality)) {
437 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
438 processSEHCatchHandler(CatchAction, StartBB);
439 HandlersOutlined = true;
444 if (outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo)) {
445 HandlersOutlined = true;
447 } // End for each Action
449 // FIXME: We need a guard against partially outlined functions.
450 if (!HandlersOutlined)
453 // Replace the landing pad with a new llvm.eh.action based landing pad.
454 BasicBlock *NewLPadBB = BasicBlock::Create(Context, "lpad", &F, LPadBB);
455 assert(!isa<PHINode>(LPadBB->begin()));
456 Instruction *NewLPad = LPad->clone();
457 NewLPadBB->getInstList().push_back(NewLPad);
458 while (!pred_empty(LPadBB)) {
459 auto *pred = *pred_begin(LPadBB);
460 InvokeInst *Invoke = cast<InvokeInst>(pred->getTerminator());
461 Invoke->setUnwindDest(NewLPadBB);
464 // Replace uses of the old lpad in phis with this block and delete the old
466 LPadBB->replaceSuccessorsPhiUsesWith(NewLPadBB);
467 LPadBB->getTerminator()->eraseFromParent();
468 new UnreachableInst(LPadBB->getContext(), LPadBB);
470 // Add a call to describe the actions for this landing pad.
471 std::vector<Value *> ActionArgs;
472 ActionArgs.push_back(NewLPad);
473 for (ActionHandler *Action : Actions) {
474 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
475 ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
476 ActionArgs.push_back(CatchAction->getSelector());
477 Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
479 ActionArgs.push_back(EHObj);
481 ActionArgs.push_back(ConstantPointerNull::get(Int8PtrType));
483 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
485 Constant *HandlerPtr = ConstantExpr::getBitCast(
486 Action->getHandlerBlockOrFunc(), Int8PtrType);
487 ActionArgs.push_back(HandlerPtr);
490 CallInst::Create(ActionIntrin, ActionArgs, "recover", NewLPadBB);
492 // Add an indirect branch listing possible successors of the catch handlers.
493 IndirectBrInst *Branch = IndirectBrInst::Create(Recover, 0, NewLPadBB);
494 for (ActionHandler *Action : Actions) {
495 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
496 for (auto *Target : CatchAction->getReturnTargets()) {
497 Branch->addDestination(Target);
501 } // End for each landingpad
503 // If nothing got outlined, there is no more processing to be done.
504 if (!HandlersOutlined)
507 // Delete any blocks that were only used by handlers that were outlined above.
508 removeUnreachableBlocks(F);
510 BasicBlock *Entry = &F.getEntryBlock();
511 IRBuilder<> Builder(F.getParent()->getContext());
512 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
514 Function *FrameEscapeFn =
515 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
516 Function *RecoverFrameFn =
517 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
519 // Finally, replace all of the temporary allocas for frame variables used in
520 // the outlined handlers with calls to llvm.framerecover.
521 BasicBlock::iterator II = Entry->getFirstInsertionPt();
522 Instruction *AllocaInsertPt = II;
523 SmallVector<Value *, 8> AllocasToEscape;
524 for (auto &VarInfoEntry : FrameVarInfo) {
525 Value *ParentVal = VarInfoEntry.first;
526 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
528 // If the mapped value isn't already an alloca, we need to spill it if it
529 // is a computed value or copy it if it is an argument.
530 AllocaInst *ParentAlloca = dyn_cast<AllocaInst>(ParentVal);
532 if (auto *Arg = dyn_cast<Argument>(ParentVal)) {
533 // Lower this argument to a copy and then demote that to the stack.
534 // We can't just use the argument location because the handler needs
535 // it to be in the frame allocation block.
536 // Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction.
537 Value *TrueValue = ConstantInt::getTrue(Context);
538 Value *UndefValue = UndefValue::get(Arg->getType());
540 SelectInst::Create(TrueValue, Arg, UndefValue,
541 Arg->getName() + ".tmp", AllocaInsertPt);
542 Arg->replaceAllUsesWith(SI);
543 // Reset the select operand, because it was clobbered by the RAUW above.
544 SI->setOperand(1, Arg);
545 ParentAlloca = DemoteRegToStack(*SI, true, SI);
546 } else if (auto *PN = dyn_cast<PHINode>(ParentVal)) {
547 ParentAlloca = DemotePHIToStack(PN, AllocaInsertPt);
549 Instruction *ParentInst = cast<Instruction>(ParentVal);
550 // FIXME: This is a work-around to temporarily handle the case where an
551 // instruction that is only used in handlers is not sunk.
552 // Without uses, DemoteRegToStack would just eliminate the value.
553 // This will fail if ParentInst is an invoke.
554 if (ParentInst->getNumUses() == 0) {
555 BasicBlock::iterator InsertPt = ParentInst;
558 new AllocaInst(ParentInst->getType(), nullptr,
559 ParentInst->getName() + ".reg2mem", InsertPt);
560 new StoreInst(ParentInst, ParentAlloca, InsertPt);
562 ParentAlloca = DemoteRegToStack(*ParentInst, true, ParentInst);
567 // If the parent alloca is no longer used and only one of the handlers used
568 // it, erase the parent and leave the copy in the outlined handler.
569 if (ParentAlloca->getNumUses() == 0 && Allocas.size() == 1) {
570 ParentAlloca->eraseFromParent();
574 // Add this alloca to the list of things to escape.
575 AllocasToEscape.push_back(ParentAlloca);
577 // Next replace all outlined allocas that are mapped to it.
578 for (AllocaInst *TempAlloca : Allocas) {
579 Function *HandlerFn = TempAlloca->getParent()->getParent();
580 // FIXME: Sink this GEP into the blocks where it is used.
581 Builder.SetInsertPoint(TempAlloca);
582 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
583 Value *RecoverArgs[] = {
584 Builder.CreateBitCast(&F, Int8PtrType, ""),
585 &(HandlerFn->getArgumentList().back()),
586 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
587 Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
588 // Add a pointer bitcast if the alloca wasn't an i8.
589 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
590 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
592 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
594 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
595 TempAlloca->removeFromParent();
596 RecoveredAlloca->takeName(TempAlloca);
599 } // End for each FrameVarInfo entry.
601 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
603 Builder.SetInsertPoint(&F.getEntryBlock().back());
604 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
606 // Clean up the handler action maps we created for this function
607 DeleteContainerSeconds(CatchHandlerMap);
608 CatchHandlerMap.clear();
609 DeleteContainerSeconds(CleanupHandlerMap);
610 CleanupHandlerMap.clear();
612 return HandlersOutlined;
615 // This function examines a block to determine whether the block ends with a
616 // conditional branch to a catch handler based on a selector comparison.
617 // This function is used both by the WinEHPrepare::findSelectorComparison() and
618 // WinEHCleanupDirector::handleTypeIdFor().
619 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
620 Constant *&Selector, BasicBlock *&NextBB) {
621 ICmpInst::Predicate Pred;
622 BasicBlock *TBB, *FBB;
625 if (!match(BB->getTerminator(),
626 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
630 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
631 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
634 if (Pred == CmpInst::ICMP_EQ) {
640 if (Pred == CmpInst::ICMP_NE) {
649 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
650 LandingPadInst *LPad, BasicBlock *StartBB,
651 FrameVarInfoMap &VarInfo) {
652 Module *M = SrcFn->getParent();
653 LLVMContext &Context = M->getContext();
655 // Create a new function to receive the handler contents.
656 Type *Int8PtrType = Type::getInt8PtrTy(Context);
657 std::vector<Type *> ArgTys;
658 ArgTys.push_back(Int8PtrType);
659 ArgTys.push_back(Int8PtrType);
661 if (Action->getType() == Catch) {
662 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
663 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
664 SrcFn->getName() + ".catch", M);
666 FunctionType *FnType =
667 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
668 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
669 SrcFn->getName() + ".cleanup", M);
672 // Generate a standard prolog to setup the frame recovery structure.
673 IRBuilder<> Builder(Context);
674 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
675 Handler->getBasicBlockList().push_front(Entry);
676 Builder.SetInsertPoint(Entry);
677 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
679 std::unique_ptr<WinEHCloningDirectorBase> Director;
681 ValueToValueMapTy VMap;
683 LandingPadMap &LPadMap = LPadMaps[LPad];
684 if (!LPadMap.isInitialized())
685 LPadMap.mapLandingPad(LPad);
686 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
687 Constant *Sel = CatchAction->getSelector();
688 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap));
689 LPadMap.remapSelector(VMap, ConstantInt::get(Type::getInt32Ty(Context), 1));
691 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
694 SmallVector<ReturnInst *, 8> Returns;
695 ClonedCodeInfo OutlinedFunctionInfo;
697 // Skip over PHIs and, if applicable, landingpad instructions.
698 BasicBlock::iterator II = StartBB->getFirstInsertionPt();
700 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
701 /*ModuleLevelChanges=*/false, Returns, "",
702 &OutlinedFunctionInfo, Director.get());
704 // Move all the instructions in the first cloned block into our entry block.
705 BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
706 Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
707 FirstClonedBB->eraseFromParent();
709 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
710 WinEHCatchDirector *CatchDirector =
711 reinterpret_cast<WinEHCatchDirector *>(Director.get());
712 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
713 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
716 Action->setHandlerBlockOrFunc(Handler);
721 /// This BB must end in a selector dispatch. All we need to do is pass the
722 /// handler block to llvm.eh.actions and list it as a possible indirectbr
724 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
725 BasicBlock *StartBB) {
726 BasicBlock *HandlerBB;
729 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
731 // If this was EH dispatch, this must be a conditional branch to the handler
733 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
734 // leading to crashes if some optimization hoists stuff here.
735 assert(CatchAction->getSelector() && HandlerBB &&
736 "expected catch EH dispatch");
738 // This must be a catch-all. Split the block after the landingpad.
739 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
741 StartBB->splitBasicBlock(StartBB->getFirstInsertionPt(), "catch.all");
743 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
744 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
745 CatchAction->setReturnTargets(Targets);
748 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
749 // Each instance of this class should only ever be used to map a single
751 assert(OriginLPad == nullptr || OriginLPad == LPad);
753 // If the landing pad has already been mapped, there's nothing more to do.
754 if (OriginLPad == LPad)
759 // The landingpad instruction returns an aggregate value. Typically, its
760 // value will be passed to a pair of extract value instructions and the
761 // results of those extracts are often passed to store instructions.
762 // In unoptimized code the stored value will often be loaded and then stored
764 for (auto *U : LPad->users()) {
765 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
768 assert(Extract->getNumIndices() == 1 &&
769 "Unexpected operation: extracting both landing pad values");
770 unsigned int Idx = *(Extract->idx_begin());
771 assert((Idx == 0 || Idx == 1) &&
772 "Unexpected operation: extracting an unknown landing pad element");
774 // Element 0 doesn't directly corresponds to anything in the WinEH
776 // It will be stored to a memory location, then later loaded and finally
777 // the loaded value will be used as the argument to an
778 // llvm.eh.begincatch
779 // call. We're tracking it here so that we can skip the store and load.
780 ExtractedEHPtrs.push_back(Extract);
781 } else if (Idx == 1) {
782 // Element 1 corresponds to the filter selector. We'll map it to 1 for
783 // matching purposes, but it will also probably be stored to memory and
784 // reloaded, so we need to track the instuction so that we can map the
786 ExtractedSelectors.push_back(Extract);
789 // Look for stores of the extracted values.
790 for (auto *EU : Extract->users()) {
791 if (auto *Store = dyn_cast<StoreInst>(EU)) {
793 SelectorStores.push_back(Store);
794 SelectorStoreAddrs.push_back(Store->getPointerOperand());
796 EHPtrStores.push_back(Store);
797 EHPtrStoreAddrs.push_back(Store->getPointerOperand());
804 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
805 if (Inst == OriginLPad)
807 for (auto *Extract : ExtractedEHPtrs) {
811 for (auto *Extract : ExtractedSelectors) {
815 for (auto *Store : EHPtrStores) {
819 for (auto *Store : SelectorStores) {
827 void LandingPadMap::remapSelector(ValueToValueMapTy &VMap,
828 Value *MappedValue) const {
829 // Remap all selector extract instructions to the specified value.
830 for (auto *Extract : ExtractedSelectors)
831 VMap[Extract] = MappedValue;
834 bool LandingPadMap::mapIfEHLoad(const LoadInst *Load,
835 SmallVectorImpl<const StoreInst *> &Stores,
836 SmallVectorImpl<const Value *> &StoreAddrs) {
837 // This makes the assumption that a store we've previously seen dominates
838 // this load instruction. That might seem like a rather huge assumption,
839 // but given the way that landingpads are constructed its fairly safe.
840 // FIXME: Add debug/assert code that verifies this.
841 const Value *LoadAddr = Load->getPointerOperand();
842 for (auto *StoreAddr : StoreAddrs) {
843 if (LoadAddr == StoreAddr) {
844 // Handle the common debug scenario where this loaded value is stored
845 // to a different location.
846 for (auto *U : Load->users()) {
847 if (auto *Store = dyn_cast<StoreInst>(U)) {
848 Stores.push_back(Store);
849 StoreAddrs.push_back(Store->getPointerOperand());
858 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
859 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
860 // If this is one of the boilerplate landing pad instructions, skip it.
861 // The instruction will have already been remapped in VMap.
862 if (LPadMap.isLandingPadSpecificInst(Inst))
863 return CloningDirector::SkipInstruction;
865 if (auto *Load = dyn_cast<LoadInst>(Inst)) {
866 // Look for loads of (previously suppressed) landingpad values.
867 // The EHPtr load can be mapped to an undef value as it should only be used
868 // as an argument to llvm.eh.begincatch, but the selector value needs to be
869 // mapped to a constant value of 1. This value will be used to simplify the
870 // branching to always flow to the current handler.
871 if (LPadMap.mapIfSelectorLoad(Load)) {
872 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
873 return CloningDirector::SkipInstruction;
875 if (LPadMap.mapIfEHPtrLoad(Load)) {
876 VMap[Inst] = UndefValue::get(Int8PtrType);
877 return CloningDirector::SkipInstruction;
880 // Any other loads just get cloned.
881 return CloningDirector::CloneInstruction;
884 // Nested landing pads will be cloned as stubs, with just the
885 // landingpad instruction and an unreachable instruction. When
886 // all landingpads have been outlined, we'll replace this with the
887 // llvm.eh.actions call and indirect branch created when the
888 // landing pad was outlined.
889 if (auto *NestedLPad = dyn_cast<LandingPadInst>(Inst)) {
890 Instruction *NewInst = NestedLPad->clone();
891 if (NestedLPad->hasName())
892 NewInst->setName(NestedLPad->getName());
893 // FIXME: Store this mapping somewhere else also.
894 VMap[NestedLPad] = NewInst;
895 BasicBlock::InstListType &InstList = NewBB->getInstList();
896 InstList.push_back(NewInst);
897 InstList.push_back(new UnreachableInst(NewBB->getContext()));
898 return CloningDirector::StopCloningBB;
901 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
902 return handleInvoke(VMap, Invoke, NewBB);
904 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
905 return handleResume(VMap, Resume, NewBB);
907 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
908 return handleBeginCatch(VMap, Inst, NewBB);
909 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
910 return handleEndCatch(VMap, Inst, NewBB);
911 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
912 return handleTypeIdFor(VMap, Inst, NewBB);
914 // Continue with the default cloning behavior.
915 return CloningDirector::CloneInstruction;
918 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
919 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
920 // The argument to the call is some form of the first element of the
921 // landingpad aggregate value, but that doesn't matter. It isn't used
923 // The second argument is an outparameter where the exception object will be
924 // stored. Typically the exception object is a scalar, but it can be an
925 // aggregate when catching by value.
926 // FIXME: Leave something behind to indicate where the exception object lives
927 // for this handler. Should it be part of llvm.eh.actions?
928 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
929 "llvm.eh.begincatch found while "
930 "outlining catch handler.");
931 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
932 return CloningDirector::SkipInstruction;
935 CloningDirector::CloningAction
936 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
937 const Instruction *Inst, BasicBlock *NewBB) {
938 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
939 // It might be interesting to track whether or not we are inside a catch
940 // function, but that might make the algorithm more brittle than it needs
943 // The end catch call can occur in one of two places: either in a
944 // landingpad block that is part of the catch handlers exception mechanism,
945 // or at the end of the catch block. If it occurs in a landing pad, we must
946 // skip it and continue so that the landing pad gets cloned.
947 // FIXME: This case isn't fully supported yet and shouldn't turn up in any
948 // of the test cases until it is.
949 if (IntrinCall->getParent()->isLandingPad())
950 return CloningDirector::SkipInstruction;
952 // If an end catch occurs anywhere else the next instruction should be an
953 // unconditional branch instruction that we want to replace with a return
954 // to the the address of the branch target.
955 const BasicBlock *EndCatchBB = IntrinCall->getParent();
956 const TerminatorInst *Terminator = EndCatchBB->getTerminator();
957 const BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
958 assert(Branch && Branch->isUnconditional());
959 assert(std::next(BasicBlock::const_iterator(IntrinCall)) ==
960 BasicBlock::const_iterator(Branch));
962 BasicBlock *ContinueLabel = Branch->getSuccessor(0);
963 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueLabel),
965 ReturnTargets.push_back(ContinueLabel);
967 // We just added a terminator to the cloned block.
968 // Tell the caller to stop processing the current basic block so that
969 // the branch instruction will be skipped.
970 return CloningDirector::StopCloningBB;
973 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
974 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
975 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
976 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
977 // This causes a replacement that will collapse the landing pad CFG based
978 // on the filter function we intend to match.
979 if (Selector == CurrentSelector)
980 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
982 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
983 // Tell the caller not to clone this instruction.
984 return CloningDirector::SkipInstruction;
987 CloningDirector::CloningAction
988 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
989 const InvokeInst *Invoke, BasicBlock *NewBB) {
990 return CloningDirector::CloneInstruction;
993 CloningDirector::CloningAction
994 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
995 const ResumeInst *Resume, BasicBlock *NewBB) {
996 // Resume instructions shouldn't be reachable from catch handlers.
997 // We still need to handle it, but it will be pruned.
998 BasicBlock::InstListType &InstList = NewBB->getInstList();
999 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1000 return CloningDirector::StopCloningBB;
1003 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1004 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1005 // Catch blocks within cleanup handlers will always be unreachable.
1006 // We'll insert an unreachable instruction now, but it will be pruned
1007 // before the cloning process is complete.
1008 BasicBlock::InstListType &InstList = NewBB->getInstList();
1009 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1010 return CloningDirector::StopCloningBB;
1013 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1014 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1015 // Catch blocks within cleanup handlers will always be unreachable.
1016 // We'll insert an unreachable instruction now, but it will be pruned
1017 // before the cloning process is complete.
1018 BasicBlock::InstListType &InstList = NewBB->getInstList();
1019 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1020 return CloningDirector::StopCloningBB;
1023 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1024 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1025 // If we encounter a selector comparison while cloning a cleanup handler,
1026 // we want to stop cloning immediately. Anything after the dispatch
1027 // will be outlined into a different handler.
1028 BasicBlock *CatchHandler;
1031 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1032 CatchHandler, Selector, NextBB)) {
1033 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1034 return CloningDirector::StopCloningBB;
1036 // If eg.typeid.for is called for any other reason, it can be ignored.
1037 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1038 return CloningDirector::SkipInstruction;
1041 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1042 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1043 // All invokes in cleanup handlers can be replaced with calls.
1044 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1045 // Insert a normal call instruction...
1047 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1048 Invoke->getName(), NewBB);
1049 NewCall->setCallingConv(Invoke->getCallingConv());
1050 NewCall->setAttributes(Invoke->getAttributes());
1051 NewCall->setDebugLoc(Invoke->getDebugLoc());
1052 VMap[Invoke] = NewCall;
1054 // Insert an unconditional branch to the normal destination.
1055 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1057 // The unwind destination won't be cloned into the new function, so
1058 // we don't need to clean up its phi nodes.
1060 // We just added a terminator to the cloned block.
1061 // Tell the caller to stop processing the current basic block.
1062 return CloningDirector::StopCloningBB;
1065 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1066 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1067 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1069 // We just added a terminator to the cloned block.
1070 // Tell the caller to stop processing the current basic block so that
1071 // the branch instruction will be skipped.
1072 return CloningDirector::StopCloningBB;
1075 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1076 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1077 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1078 Builder.SetInsertPoint(&OutlinedFn->getEntryBlock());
1081 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1082 // If we're asked to materialize a value that is an instruction, we
1083 // temporarily create an alloca in the outlined function and add this
1084 // to the FrameVarInfo map. When all the outlining is complete, we'll
1085 // collect these into a structure, spilling non-alloca values in the
1086 // parent frame as necessary, and replace these temporary allocas with
1087 // GEPs referencing the frame allocation block.
1089 // If the value is an alloca, the mapping is direct.
1090 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1091 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1092 Builder.Insert(NewAlloca, AV->getName());
1093 FrameVarInfo[AV].push_back(NewAlloca);
1097 // For other types of instructions or arguments, we need an alloca based on
1098 // the value's type and a load of the alloca. The alloca will be replaced
1099 // by a GEP, but the load will stay. In the parent function, the value will
1100 // be spilled to a location in the frame allocation block.
1101 if (isa<Instruction>(V) || isa<Argument>(V)) {
1102 AllocaInst *NewAlloca =
1103 Builder.CreateAlloca(V->getType(), nullptr, "eh.temp.alloca");
1104 FrameVarInfo[V].push_back(NewAlloca);
1105 LoadInst *NewLoad = Builder.CreateLoad(NewAlloca, V->getName() + ".reload");
1109 // Don't materialize other values.
1113 // This function maps the catch and cleanup handlers that are reachable from the
1114 // specified landing pad. The landing pad sequence will have this basic shape:
1116 // <cleanup handler>
1117 // <selector comparison>
1119 // <cleanup handler>
1120 // <selector comparison>
1122 // <cleanup handler>
1125 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1126 // any arbitrary control flow, but all paths through the cleanup code must
1127 // eventually reach the next selector comparison and no path can skip to a
1128 // different selector comparisons, though some paths may terminate abnormally.
1129 // Therefore, we will use a depth first search from the start of any given
1130 // cleanup block and stop searching when we find the next selector comparison.
1132 // If the landingpad instruction does not have a catch clause, we will assume
1133 // that any instructions other than selector comparisons and catch handlers can
1134 // be ignored. In practice, these will only be the boilerplate instructions.
1136 // The catch handlers may also have any control structure, but we are only
1137 // interested in the start of the catch handlers, so we don't need to actually
1138 // follow the flow of the catch handlers. The start of the catch handlers can
1139 // be located from the compare instructions, but they can be skipped in the
1140 // flow by following the contrary branch.
1141 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1142 LandingPadActions &Actions) {
1143 unsigned int NumClauses = LPad->getNumClauses();
1144 unsigned int HandlersFound = 0;
1145 BasicBlock *BB = LPad->getParent();
1147 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1149 if (NumClauses == 0) {
1150 // This landing pad contains only cleanup code.
1151 CleanupHandler *Action = new CleanupHandler(BB);
1152 CleanupHandlerMap[BB] = Action;
1153 Actions.insertCleanupHandler(Action);
1154 DEBUG(dbgs() << " Assuming cleanup code in block " << BB->getName()
1156 assert(LPad->isCleanup());
1160 VisitedBlockSet VisitedBlocks;
1162 while (HandlersFound != NumClauses) {
1163 BasicBlock *NextBB = nullptr;
1165 // See if the clause we're looking for is a catch-all.
1166 // If so, the catch begins immediately.
1167 if (isa<ConstantPointerNull>(LPad->getClause(HandlersFound))) {
1168 // The catch all must occur last.
1169 assert(HandlersFound == NumClauses - 1);
1171 // For C++ EH, check if there is any interesting cleanup code before we
1172 // begin the catch. This is important because cleanups cannot rethrow
1173 // exceptions but code called from catches can. For SEH, it isn't
1174 // important if some finally code before a catch-all is executed out of
1175 // line or after recovering from the exception.
1176 if (Personality == EHPersonality::MSVC_CXX) {
1177 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1178 // Add a cleanup entry to the list
1179 Actions.insertCleanupHandler(CleanupAction);
1180 DEBUG(dbgs() << " Found cleanup code in block "
1181 << CleanupAction->getStartBlock()->getName() << "\n");
1185 // Add the catch handler to the action list.
1186 CatchHandler *Action =
1187 new CatchHandler(BB, LPad->getClause(HandlersFound), nullptr);
1188 CatchHandlerMap[BB] = Action;
1189 Actions.insertCatchHandler(Action);
1190 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1193 // Once we reach a catch-all, don't expect to hit a resume instruction.
1198 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1199 // See if there is any interesting code executed before the dispatch.
1200 if (auto *CleanupAction =
1201 findCleanupHandler(BB, CatchAction->getStartBlock())) {
1202 // Add a cleanup entry to the list
1203 Actions.insertCleanupHandler(CleanupAction);
1204 DEBUG(dbgs() << " Found cleanup code in block "
1205 << CleanupAction->getStartBlock()->getName() << "\n");
1208 assert(CatchAction);
1211 // Add the catch handler to the action list.
1212 Actions.insertCatchHandler(CatchAction);
1213 DEBUG(dbgs() << " Found catch dispatch in block "
1214 << CatchAction->getStartBlock()->getName() << "\n");
1216 // Move on to the block after the catch handler.
1220 // If we didn't wind up in a catch-all, see if there is any interesting code
1221 // executed before the resume.
1222 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1223 // Add a cleanup entry to the list
1224 Actions.insertCleanupHandler(CleanupAction);
1225 DEBUG(dbgs() << " Found cleanup code in block "
1226 << CleanupAction->getStartBlock()->getName() << "\n");
1229 // It's possible that some optimization moved code into a landingpad that
1231 // previously being used for cleanup. If that happens, we need to execute
1233 // extra code from a cleanup handler.
1234 if (Actions.includesCleanup() && !LPad->isCleanup())
1235 LPad->setCleanup(true);
1238 // This function searches starting with the input block for the next
1239 // block that terminates with a branch whose condition is based on a selector
1240 // comparison. This may be the input block. See the mapLandingPadBlocks
1241 // comments for a discussion of control flow assumptions.
1243 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1244 BasicBlock *&NextBB,
1245 VisitedBlockSet &VisitedBlocks) {
1246 // See if we've already found a catch handler use it.
1247 // Call count() first to avoid creating a null entry for blocks
1248 // we haven't seen before.
1249 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1250 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1251 NextBB = Action->getNextBB();
1255 // VisitedBlocks applies only to the current search. We still
1256 // need to consider blocks that we've visited while mapping other
1258 VisitedBlocks.insert(BB);
1260 BasicBlock *CatchBlock = nullptr;
1261 Constant *Selector = nullptr;
1263 // If this is the first time we've visited this block from any landing pad
1264 // look to see if it is a selector dispatch block.
1265 if (!CatchHandlerMap.count(BB)) {
1266 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1267 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1268 CatchHandlerMap[BB] = Action;
1273 // Visit each successor, looking for the dispatch.
1274 // FIXME: We expect to find the dispatch quickly, so this will probably
1275 // work better as a breadth first search.
1276 for (BasicBlock *Succ : successors(BB)) {
1277 if (VisitedBlocks.count(Succ))
1280 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1287 // These are helper functions to combine repeated code from findCleanupHandler.
1288 static CleanupHandler *createCleanupHandler(CleanupHandlerMapTy &CleanupHandlerMap,
1290 CleanupHandler *Action = new CleanupHandler(BB);
1291 CleanupHandlerMap[BB] = Action;
1295 // This function searches starting with the input block for the next block that
1296 // contains code that is not part of a catch handler and would not be eliminated
1297 // during handler outlining.
1299 CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
1300 BasicBlock *EndBB) {
1301 // Here we will skip over the following:
1303 // landing pad prolog:
1305 // Unconditional branches
1307 // Selector dispatch
1311 // Anything else marks the start of an interesting block
1313 BasicBlock *BB = StartBB;
1314 // Anything other than an unconditional branch will kick us out of this loop
1315 // one way or another.
1317 // If we've already scanned this block, don't scan it again. If it is
1318 // a cleanup block, there will be an action in the CleanupHandlerMap.
1319 // If we've scanned it and it is not a cleanup block, there will be a
1320 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1321 // be no entry in the CleanupHandlerMap. We must call count() first to
1322 // avoid creating a null entry for blocks we haven't scanned.
1323 if (CleanupHandlerMap.count(BB)) {
1324 if (auto *Action = CleanupHandlerMap[BB]) {
1325 return cast<CleanupHandler>(Action);
1327 // Here we handle the case where the cleanup handler map contains a
1328 // value for this block but the value is a nullptr. This means that
1329 // we have previously analyzed the block and determined that it did
1330 // not contain any cleanup code. Based on the earlier analysis, we
1331 // know the the block must end in either an unconditional branch, a
1332 // resume or a conditional branch that is predicated on a comparison
1333 // with a selector. Either the resume or the selector dispatch
1334 // would terminate the search for cleanup code, so the unconditional
1335 // branch is the only case for which we might need to continue
1340 if (!match(BB->getTerminator(), m_UnconditionalBr(SuccBB)))
1347 // Create an entry in the cleanup handler map for this block. Initially
1348 // we create an entry that says this isn't a cleanup block. If we find
1349 // cleanup code, the caller will replace this entry.
1350 CleanupHandlerMap[BB] = nullptr;
1352 TerminatorInst *Terminator = BB->getTerminator();
1354 // Landing pad blocks have extra instructions we need to accept.
1355 LandingPadMap *LPadMap = nullptr;
1356 if (BB->isLandingPad()) {
1357 LandingPadInst *LPad = BB->getLandingPadInst();
1358 LPadMap = &LPadMaps[LPad];
1359 if (!LPadMap->isInitialized())
1360 LPadMap->mapLandingPad(LPad);
1363 // Look for the bare resume pattern:
1364 // %exn2 = load i8** %exn.slot
1365 // %sel2 = load i32* %ehselector.slot
1366 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn2, 0
1367 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel2, 1
1368 // resume { i8*, i32 } %lpad.val2
1369 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
1370 InsertValueInst *Insert1 = nullptr;
1371 InsertValueInst *Insert2 = nullptr;
1372 Value *ResumeVal = Resume->getOperand(0);
1373 // If there is only one landingpad, we may use the lpad directly with no
1375 if (isa<LandingPadInst>(ResumeVal))
1377 if (!isa<PHINode>(ResumeVal)) {
1378 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
1380 return createCleanupHandler(CleanupHandlerMap, BB);
1381 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
1383 return createCleanupHandler(CleanupHandlerMap, BB);
1385 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1387 Instruction *Inst = II;
1388 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1390 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
1392 if (!Inst->hasOneUse() ||
1393 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
1394 return createCleanupHandler(CleanupHandlerMap, BB);
1400 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
1402 if (Branch->isConditional()) {
1403 // Look for the selector dispatch.
1404 // %sel = load i32* %ehselector.slot
1405 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
1406 // %matches = icmp eq i32 %sel12, %2
1407 // br i1 %matches, label %catch14, label %eh.resume
1408 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
1409 if (!Compare || !Compare->isEquality())
1410 return createCleanupHandler(CleanupHandlerMap, BB);
1411 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
1414 Instruction *Inst = II;
1415 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1417 if (Inst == Compare || Inst == Branch)
1419 if (!Inst->hasOneUse() || (Inst->user_back() != Compare))
1420 return createCleanupHandler(CleanupHandlerMap, BB);
1421 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1423 if (!isa<LoadInst>(Inst))
1424 return createCleanupHandler(CleanupHandlerMap, BB);
1426 // The selector dispatch block should always terminate our search.
1427 assert(BB == EndBB);
1430 // Look for empty blocks with unconditional branches.
1431 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
1434 Instruction *Inst = II;
1435 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1439 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1441 // Anything else makes this interesting cleanup code.
1442 return createCleanupHandler(CleanupHandlerMap, BB);
1446 // The branch was unconditional.
1447 BB = Branch->getSuccessor(0);
1449 } // End else of if branch was conditional
1452 // Anything else makes this interesting cleanup code.
1453 return createCleanupHandler(CleanupHandlerMap, BB);