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/STLExtras.h"
20 #include "llvm/ADT/SmallSet.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/Support/raw_ostream.h"
33 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
34 #include "llvm/Transforms/Utils/Cloning.h"
35 #include "llvm/Transforms/Utils/Local.h"
39 using namespace llvm::PatternMatch;
41 #define DEBUG_TYPE "winehprepare"
45 // This map is used to model frame variable usage during outlining, to
46 // construct a structure type to hold the frame variables in a frame
47 // allocation block, and to remap the frame variable allocas (including
48 // spill locations as needed) to GEPs that get the variable from the
49 // frame allocation structure.
50 typedef MapVector<Value *, TinyPtrVector<AllocaInst *>> FrameVarInfoMap;
52 typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
54 enum ActionType { Catch, Cleanup };
56 class LandingPadActions;
62 typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
63 typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
65 class WinEHPrepare : public FunctionPass {
67 static char ID; // Pass identification, replacement for typeid.
68 WinEHPrepare(const TargetMachine *TM = nullptr)
71 bool runOnFunction(Function &Fn) override;
73 bool doFinalization(Module &M) override;
75 void getAnalysisUsage(AnalysisUsage &AU) const override;
77 const char *getPassName() const override {
78 return "Windows exception handling preparation";
82 bool prepareExceptionHandlers(Function &F,
83 SmallVectorImpl<LandingPadInst *> &LPads);
84 bool outlineHandler(ActionHandler *Action, Function *SrcFn,
85 LandingPadInst *LPad, BasicBlock *StartBB,
86 FrameVarInfoMap &VarInfo);
88 void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
89 CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
90 VisitedBlockSet &VisitedBlocks);
91 CleanupHandler *findCleanupHandler(BasicBlock *StartBB, BasicBlock *EndBB);
93 void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
95 // All fields are reset by runOnFunction.
96 EHPersonality Personality;
97 CatchHandlerMapTy CatchHandlerMap;
98 CleanupHandlerMapTy CleanupHandlerMap;
99 DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
102 class WinEHFrameVariableMaterializer : public ValueMaterializer {
104 WinEHFrameVariableMaterializer(Function *OutlinedFn,
105 FrameVarInfoMap &FrameVarInfo);
106 ~WinEHFrameVariableMaterializer() {}
108 virtual Value *materializeValueFor(Value *V) override;
111 FrameVarInfoMap &FrameVarInfo;
115 class LandingPadMap {
117 LandingPadMap() : OriginLPad(nullptr) {}
118 void mapLandingPad(const LandingPadInst *LPad);
120 bool isInitialized() { return OriginLPad != nullptr; }
122 bool mapIfEHPtrLoad(const LoadInst *Load) {
123 return mapIfEHLoad(Load, EHPtrStores, EHPtrStoreAddrs);
125 bool mapIfSelectorLoad(const LoadInst *Load) {
126 return mapIfEHLoad(Load, SelectorStores, SelectorStoreAddrs);
129 bool isLandingPadSpecificInst(const Instruction *Inst) const;
131 void remapSelector(ValueToValueMapTy &VMap, Value *MappedValue) const;
134 bool mapIfEHLoad(const LoadInst *Load,
135 SmallVectorImpl<const StoreInst *> &Stores,
136 SmallVectorImpl<const Value *> &StoreAddrs);
138 const LandingPadInst *OriginLPad;
139 // We will normally only see one of each of these instructions, but
140 // if more than one occurs for some reason we can handle that.
141 TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
142 TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
144 // In optimized code, there will typically be at most one instance of
145 // each of the following, but in unoptimized IR it is not uncommon
146 // for the values to be stored, loaded and then stored again. In that
147 // case we will create a second entry for each store and store address.
148 SmallVector<const StoreInst *, 2> EHPtrStores;
149 SmallVector<const StoreInst *, 2> SelectorStores;
150 SmallVector<const Value *, 2> EHPtrStoreAddrs;
151 SmallVector<const Value *, 2> SelectorStoreAddrs;
154 class WinEHCloningDirectorBase : public CloningDirector {
156 WinEHCloningDirectorBase(Function *HandlerFn,
157 FrameVarInfoMap &VarInfo,
158 LandingPadMap &LPadMap)
159 : Materializer(HandlerFn, VarInfo),
160 SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
161 Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
164 CloningAction handleInstruction(ValueToValueMapTy &VMap,
165 const Instruction *Inst,
166 BasicBlock *NewBB) override;
168 virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
169 const Instruction *Inst,
170 BasicBlock *NewBB) = 0;
171 virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
172 const Instruction *Inst,
173 BasicBlock *NewBB) = 0;
174 virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
175 const Instruction *Inst,
176 BasicBlock *NewBB) = 0;
177 virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
178 const InvokeInst *Invoke,
179 BasicBlock *NewBB) = 0;
180 virtual CloningAction handleResume(ValueToValueMapTy &VMap,
181 const ResumeInst *Resume,
182 BasicBlock *NewBB) = 0;
184 ValueMaterializer *getValueMaterializer() override { return &Materializer; }
187 WinEHFrameVariableMaterializer Materializer;
188 Type *SelectorIDType;
190 LandingPadMap &LPadMap;
193 class WinEHCatchDirector : public WinEHCloningDirectorBase {
195 WinEHCatchDirector(Function *CatchFn, Value *Selector,
196 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
197 : WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
198 CurrentSelector(Selector->stripPointerCasts()),
199 ExceptionObjectVar(nullptr) {}
201 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
202 const Instruction *Inst,
203 BasicBlock *NewBB) override;
204 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
205 BasicBlock *NewBB) override;
206 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
207 const Instruction *Inst,
208 BasicBlock *NewBB) override;
209 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
210 BasicBlock *NewBB) override;
211 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
212 BasicBlock *NewBB) override;
214 const Value *getExceptionVar() { return ExceptionObjectVar; }
215 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
218 Value *CurrentSelector;
220 const Value *ExceptionObjectVar;
221 TinyPtrVector<BasicBlock *> ReturnTargets;
224 class WinEHCleanupDirector : public WinEHCloningDirectorBase {
226 WinEHCleanupDirector(Function *CleanupFn,
227 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
228 : WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
230 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
231 const Instruction *Inst,
232 BasicBlock *NewBB) override;
233 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
234 BasicBlock *NewBB) override;
235 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
236 const Instruction *Inst,
237 BasicBlock *NewBB) override;
238 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
239 BasicBlock *NewBB) override;
240 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
241 BasicBlock *NewBB) override;
244 class ActionHandler {
246 ActionHandler(BasicBlock *BB, ActionType Type)
247 : StartBB(BB), Type(Type), HandlerBlockOrFunc(nullptr) {}
249 ActionType getType() const { return Type; }
250 BasicBlock *getStartBlock() const { return StartBB; }
252 bool hasBeenProcessed() { return HandlerBlockOrFunc != nullptr; }
254 void setHandlerBlockOrFunc(Constant *F) { HandlerBlockOrFunc = F; }
255 Constant *getHandlerBlockOrFunc() { return HandlerBlockOrFunc; }
261 // Can be either a BlockAddress or a Function depending on the EH personality.
262 Constant *HandlerBlockOrFunc;
265 class CatchHandler : public ActionHandler {
267 CatchHandler(BasicBlock *BB, Constant *Selector, BasicBlock *NextBB)
268 : ActionHandler(BB, ActionType::Catch), Selector(Selector),
269 NextBB(NextBB), ExceptionObjectVar(nullptr) {}
271 // Method for support type inquiry through isa, cast, and dyn_cast:
272 static inline bool classof(const ActionHandler *H) {
273 return H->getType() == ActionType::Catch;
276 Constant *getSelector() const { return Selector; }
277 BasicBlock *getNextBB() const { return NextBB; }
279 const Value *getExceptionVar() { return ExceptionObjectVar; }
280 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
282 void setExceptionVar(const Value *Val) { ExceptionObjectVar = Val; }
283 void setReturnTargets(TinyPtrVector<BasicBlock *> &Targets) {
284 ReturnTargets = Targets;
290 const Value *ExceptionObjectVar;
291 TinyPtrVector<BasicBlock *> ReturnTargets;
294 class CleanupHandler : public ActionHandler {
296 CleanupHandler(BasicBlock *BB) : ActionHandler(BB, ActionType::Cleanup) {}
298 // Method for support type inquiry through isa, cast, and dyn_cast:
299 static inline bool classof(const ActionHandler *H) {
300 return H->getType() == ActionType::Cleanup;
304 class LandingPadActions {
306 LandingPadActions() : HasCleanupHandlers(false) {}
308 void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
309 void insertCleanupHandler(CleanupHandler *Action) {
310 Actions.push_back(Action);
311 HasCleanupHandlers = true;
314 bool includesCleanup() const { return HasCleanupHandlers; }
316 SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
317 SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
320 // Note that this class does not own the ActionHandler objects in this vector.
321 // The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
322 // in the WinEHPrepare class.
323 SmallVector<ActionHandler *, 4> Actions;
324 bool HasCleanupHandlers;
327 } // end anonymous namespace
329 char WinEHPrepare::ID = 0;
330 INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
333 FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
334 return new WinEHPrepare(TM);
337 // FIXME: Remove this once the backend can handle the prepared IR.
339 SEHPrepare("sehprepare", cl::Hidden,
340 cl::desc("Prepare functions with SEH personalities"));
342 bool WinEHPrepare::runOnFunction(Function &Fn) {
343 SmallVector<LandingPadInst *, 4> LPads;
344 SmallVector<ResumeInst *, 4> Resumes;
345 for (BasicBlock &BB : Fn) {
346 if (auto *LP = BB.getLandingPadInst())
348 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
349 Resumes.push_back(Resume);
352 // No need to prepare functions that lack landing pads.
356 // Classify the personality to see what kind of preparation we need.
357 Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
359 // Do nothing if this is not an MSVC personality.
360 if (!isMSVCEHPersonality(Personality))
363 if (isAsynchronousEHPersonality(Personality) && !SEHPrepare) {
364 // Replace all resume instructions with unreachable.
365 // FIXME: Remove this once the backend can handle the prepared IR.
366 for (ResumeInst *Resume : Resumes) {
367 IRBuilder<>(Resume).CreateUnreachable();
368 Resume->eraseFromParent();
373 // If there were any landing pads, prepareExceptionHandlers will make changes.
374 prepareExceptionHandlers(Fn, LPads);
378 bool WinEHPrepare::doFinalization(Module &M) {
382 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {}
384 bool WinEHPrepare::prepareExceptionHandlers(
385 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
386 // These containers are used to re-map frame variables that are used in
387 // outlined catch and cleanup handlers. They will be populated as the
388 // handlers are outlined.
389 FrameVarInfoMap FrameVarInfo;
391 bool HandlersOutlined = false;
393 Module *M = F.getParent();
394 LLVMContext &Context = M->getContext();
396 // Create a new function to receive the handler contents.
397 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
398 Type *Int32Type = Type::getInt32Ty(Context);
399 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
401 for (LandingPadInst *LPad : LPads) {
402 // Look for evidence that this landingpad has already been processed.
403 bool LPadHasActionList = false;
404 BasicBlock *LPadBB = LPad->getParent();
405 for (Instruction &Inst : *LPadBB) {
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 for (ActionHandler *Action : Actions) {
473 // Action codes from docs are: 0 cleanup, 1 catch.
474 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
475 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
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, 0));
485 ActionArgs.push_back(Action->getHandlerBlockOrFunc());
488 CallInst::Create(ActionIntrin, ActionArgs, "recover", NewLPadBB);
490 // Add an indirect branch listing possible successors of the catch handlers.
491 IndirectBrInst *Branch = IndirectBrInst::Create(Recover, 0, NewLPadBB);
492 for (ActionHandler *Action : Actions) {
493 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
494 for (auto *Target : CatchAction->getReturnTargets()) {
495 Branch->addDestination(Target);
499 } // End for each landingpad
501 // If nothing got outlined, there is no more processing to be done.
502 if (!HandlersOutlined)
505 // Delete any blocks that were only used by handlers that were outlined above.
506 removeUnreachableBlocks(F);
508 BasicBlock *Entry = &F.getEntryBlock();
509 IRBuilder<> Builder(F.getParent()->getContext());
510 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
512 Function *FrameEscapeFn =
513 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
514 Function *RecoverFrameFn =
515 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
517 // Finally, replace all of the temporary allocas for frame variables used in
518 // the outlined handlers with calls to llvm.framerecover.
519 BasicBlock::iterator II = Entry->getFirstInsertionPt();
520 Instruction *AllocaInsertPt = II;
521 SmallVector<Value *, 8> AllocasToEscape;
522 for (auto &VarInfoEntry : FrameVarInfo) {
523 Value *ParentVal = VarInfoEntry.first;
524 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
526 // If the mapped value isn't already an alloca, we need to spill it if it
527 // is a computed value or copy it if it is an argument.
528 AllocaInst *ParentAlloca = dyn_cast<AllocaInst>(ParentVal);
530 if (auto *Arg = dyn_cast<Argument>(ParentVal)) {
531 // Lower this argument to a copy and then demote that to the stack.
532 // We can't just use the argument location because the handler needs
533 // it to be in the frame allocation block.
534 // Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction.
535 Value *TrueValue = ConstantInt::getTrue(Context);
536 Value *UndefValue = UndefValue::get(Arg->getType());
538 SelectInst::Create(TrueValue, Arg, UndefValue,
539 Arg->getName() + ".tmp", AllocaInsertPt);
540 Arg->replaceAllUsesWith(SI);
541 // Reset the select operand, because it was clobbered by the RAUW above.
542 SI->setOperand(1, Arg);
543 ParentAlloca = DemoteRegToStack(*SI, true, SI);
544 } else if (auto *PN = dyn_cast<PHINode>(ParentVal)) {
545 ParentAlloca = DemotePHIToStack(PN, AllocaInsertPt);
547 Instruction *ParentInst = cast<Instruction>(ParentVal);
548 // FIXME: This is a work-around to temporarily handle the case where an
549 // instruction that is only used in handlers is not sunk.
550 // Without uses, DemoteRegToStack would just eliminate the value.
551 // This will fail if ParentInst is an invoke.
552 if (ParentInst->getNumUses() == 0) {
553 BasicBlock::iterator InsertPt = ParentInst;
556 new AllocaInst(ParentInst->getType(), nullptr,
557 ParentInst->getName() + ".reg2mem", InsertPt);
558 new StoreInst(ParentInst, ParentAlloca, InsertPt);
560 ParentAlloca = DemoteRegToStack(*ParentInst, true, ParentInst);
565 // If the parent alloca is no longer used and only one of the handlers used
566 // it, erase the parent and leave the copy in the outlined handler.
567 if (ParentAlloca->getNumUses() == 0 && Allocas.size() == 1) {
568 ParentAlloca->eraseFromParent();
572 // Add this alloca to the list of things to escape.
573 AllocasToEscape.push_back(ParentAlloca);
575 // Next replace all outlined allocas that are mapped to it.
576 for (AllocaInst *TempAlloca : Allocas) {
577 Function *HandlerFn = TempAlloca->getParent()->getParent();
578 // FIXME: Sink this GEP into the blocks where it is used.
579 Builder.SetInsertPoint(TempAlloca);
580 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
581 Value *RecoverArgs[] = {
582 Builder.CreateBitCast(&F, Int8PtrType, ""),
583 &(HandlerFn->getArgumentList().back()),
584 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
585 Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
586 // Add a pointer bitcast if the alloca wasn't an i8.
587 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
588 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
590 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
592 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
593 TempAlloca->removeFromParent();
594 RecoveredAlloca->takeName(TempAlloca);
597 } // End for each FrameVarInfo entry.
599 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
601 Builder.SetInsertPoint(&F.getEntryBlock().back());
602 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
604 // Insert an alloca for the EH state in the entry block. On x86, we will also
605 // insert stores to update the EH state, but on other ISAs, the runtime does
607 // FIXME: This record is different on x86.
608 Type *UnwindHelpTy = Type::getInt64Ty(Context);
609 AllocaInst *UnwindHelp =
610 new AllocaInst(UnwindHelpTy, "unwindhelp", &F.getEntryBlock().front());
611 Builder.CreateStore(llvm::ConstantInt::get(UnwindHelpTy, -2), UnwindHelp);
612 Function *UnwindHelpFn =
613 Intrinsic::getDeclaration(M, Intrinsic::eh_unwindhelp);
614 Builder.CreateCall(UnwindHelpFn,
615 Builder.CreateBitCast(UnwindHelp, Int8PtrType));
617 // Clean up the handler action maps we created for this function
618 DeleteContainerSeconds(CatchHandlerMap);
619 CatchHandlerMap.clear();
620 DeleteContainerSeconds(CleanupHandlerMap);
621 CleanupHandlerMap.clear();
623 return HandlersOutlined;
626 // This function examines a block to determine whether the block ends with a
627 // conditional branch to a catch handler based on a selector comparison.
628 // This function is used both by the WinEHPrepare::findSelectorComparison() and
629 // WinEHCleanupDirector::handleTypeIdFor().
630 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
631 Constant *&Selector, BasicBlock *&NextBB) {
632 ICmpInst::Predicate Pred;
633 BasicBlock *TBB, *FBB;
636 if (!match(BB->getTerminator(),
637 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
641 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
642 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
645 if (Pred == CmpInst::ICMP_EQ) {
651 if (Pred == CmpInst::ICMP_NE) {
660 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
661 LandingPadInst *LPad, BasicBlock *StartBB,
662 FrameVarInfoMap &VarInfo) {
663 Module *M = SrcFn->getParent();
664 LLVMContext &Context = M->getContext();
666 // Create a new function to receive the handler contents.
667 Type *Int8PtrType = Type::getInt8PtrTy(Context);
668 std::vector<Type *> ArgTys;
669 ArgTys.push_back(Int8PtrType);
670 ArgTys.push_back(Int8PtrType);
672 if (Action->getType() == Catch) {
673 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
674 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
675 SrcFn->getName() + ".catch", M);
677 FunctionType *FnType =
678 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
679 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
680 SrcFn->getName() + ".cleanup", M);
683 // Generate a standard prolog to setup the frame recovery structure.
684 IRBuilder<> Builder(Context);
685 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
686 Handler->getBasicBlockList().push_front(Entry);
687 Builder.SetInsertPoint(Entry);
688 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
690 std::unique_ptr<WinEHCloningDirectorBase> Director;
692 ValueToValueMapTy VMap;
694 LandingPadMap &LPadMap = LPadMaps[LPad];
695 if (!LPadMap.isInitialized())
696 LPadMap.mapLandingPad(LPad);
697 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
698 // Insert an alloca for the object which holds the address of the parent's
699 // frame pointer. The stack offset of this object needs to be encoded in
701 AllocaInst *ParentFrame = new AllocaInst(Int8PtrType, "parentframe", Entry);
702 Builder.CreateStore(&Handler->getArgumentList().back(), ParentFrame,
704 Function *ParentFrameFn =
705 Intrinsic::getDeclaration(M, Intrinsic::eh_parentframe);
706 Builder.CreateCall(ParentFrameFn, ParentFrame);
708 Constant *Sel = CatchAction->getSelector();
709 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap));
710 LPadMap.remapSelector(VMap, ConstantInt::get(Type::getInt32Ty(Context), 1));
712 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
715 SmallVector<ReturnInst *, 8> Returns;
716 ClonedCodeInfo OutlinedFunctionInfo;
718 // If the start block contains PHI nodes, we need to map them.
719 BasicBlock::iterator II = StartBB->begin();
720 while (auto *PN = dyn_cast<PHINode>(II)) {
722 // Look for PHI values that we have already mapped (such as the selector).
723 for (Value *Val : PN->incoming_values()) {
724 if (VMap.count(Val)) {
725 VMap[PN] = VMap[Val];
729 // If we didn't find a match for this value, map it as an undef.
731 VMap[PN] = UndefValue::get(PN->getType());
736 // Skip over PHIs and, if applicable, landingpad instructions.
737 II = StartBB->getFirstInsertionPt();
739 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
740 /*ModuleLevelChanges=*/false, Returns, "",
741 &OutlinedFunctionInfo, Director.get());
743 // Move all the instructions in the first cloned block into our entry block.
744 BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
745 Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
746 FirstClonedBB->eraseFromParent();
748 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
749 WinEHCatchDirector *CatchDirector =
750 reinterpret_cast<WinEHCatchDirector *>(Director.get());
751 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
752 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
755 Action->setHandlerBlockOrFunc(Handler);
760 /// This BB must end in a selector dispatch. All we need to do is pass the
761 /// handler block to llvm.eh.actions and list it as a possible indirectbr
763 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
764 BasicBlock *StartBB) {
765 BasicBlock *HandlerBB;
768 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
770 // If this was EH dispatch, this must be a conditional branch to the handler
772 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
773 // leading to crashes if some optimization hoists stuff here.
774 assert(CatchAction->getSelector() && HandlerBB &&
775 "expected catch EH dispatch");
777 // This must be a catch-all. Split the block after the landingpad.
778 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
780 StartBB->splitBasicBlock(StartBB->getFirstInsertionPt(), "catch.all");
782 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
783 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
784 CatchAction->setReturnTargets(Targets);
787 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
788 // Each instance of this class should only ever be used to map a single
790 assert(OriginLPad == nullptr || OriginLPad == LPad);
792 // If the landing pad has already been mapped, there's nothing more to do.
793 if (OriginLPad == LPad)
798 // The landingpad instruction returns an aggregate value. Typically, its
799 // value will be passed to a pair of extract value instructions and the
800 // results of those extracts are often passed to store instructions.
801 // In unoptimized code the stored value will often be loaded and then stored
803 for (auto *U : LPad->users()) {
804 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
807 assert(Extract->getNumIndices() == 1 &&
808 "Unexpected operation: extracting both landing pad values");
809 unsigned int Idx = *(Extract->idx_begin());
810 assert((Idx == 0 || Idx == 1) &&
811 "Unexpected operation: extracting an unknown landing pad element");
813 // Element 0 doesn't directly corresponds to anything in the WinEH
815 // It will be stored to a memory location, then later loaded and finally
816 // the loaded value will be used as the argument to an
817 // llvm.eh.begincatch
818 // call. We're tracking it here so that we can skip the store and load.
819 ExtractedEHPtrs.push_back(Extract);
820 } else if (Idx == 1) {
821 // Element 1 corresponds to the filter selector. We'll map it to 1 for
822 // matching purposes, but it will also probably be stored to memory and
823 // reloaded, so we need to track the instuction so that we can map the
825 ExtractedSelectors.push_back(Extract);
828 // Look for stores of the extracted values.
829 for (auto *EU : Extract->users()) {
830 if (auto *Store = dyn_cast<StoreInst>(EU)) {
832 SelectorStores.push_back(Store);
833 SelectorStoreAddrs.push_back(Store->getPointerOperand());
835 EHPtrStores.push_back(Store);
836 EHPtrStoreAddrs.push_back(Store->getPointerOperand());
843 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
844 if (Inst == OriginLPad)
846 for (auto *Extract : ExtractedEHPtrs) {
850 for (auto *Extract : ExtractedSelectors) {
854 for (auto *Store : EHPtrStores) {
858 for (auto *Store : SelectorStores) {
866 void LandingPadMap::remapSelector(ValueToValueMapTy &VMap,
867 Value *MappedValue) const {
868 // Remap all selector extract instructions to the specified value.
869 for (auto *Extract : ExtractedSelectors)
870 VMap[Extract] = MappedValue;
873 bool LandingPadMap::mapIfEHLoad(const LoadInst *Load,
874 SmallVectorImpl<const StoreInst *> &Stores,
875 SmallVectorImpl<const Value *> &StoreAddrs) {
876 // This makes the assumption that a store we've previously seen dominates
877 // this load instruction. That might seem like a rather huge assumption,
878 // but given the way that landingpads are constructed its fairly safe.
879 // FIXME: Add debug/assert code that verifies this.
880 const Value *LoadAddr = Load->getPointerOperand();
881 for (auto *StoreAddr : StoreAddrs) {
882 if (LoadAddr == StoreAddr) {
883 // Handle the common debug scenario where this loaded value is stored
884 // to a different location.
885 for (auto *U : Load->users()) {
886 if (auto *Store = dyn_cast<StoreInst>(U)) {
887 Stores.push_back(Store);
888 StoreAddrs.push_back(Store->getPointerOperand());
897 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
898 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
899 // If this is one of the boilerplate landing pad instructions, skip it.
900 // The instruction will have already been remapped in VMap.
901 if (LPadMap.isLandingPadSpecificInst(Inst))
902 return CloningDirector::SkipInstruction;
904 if (auto *Load = dyn_cast<LoadInst>(Inst)) {
905 // Look for loads of (previously suppressed) landingpad values.
906 // The EHPtr load can be mapped to an undef value as it should only be used
907 // as an argument to llvm.eh.begincatch, but the selector value needs to be
908 // mapped to a constant value of 1. This value will be used to simplify the
909 // branching to always flow to the current handler.
910 if (LPadMap.mapIfSelectorLoad(Load)) {
911 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
912 return CloningDirector::SkipInstruction;
914 if (LPadMap.mapIfEHPtrLoad(Load)) {
915 VMap[Inst] = UndefValue::get(Int8PtrType);
916 return CloningDirector::SkipInstruction;
919 // Any other loads just get cloned.
920 return CloningDirector::CloneInstruction;
923 // Nested landing pads will be cloned as stubs, with just the
924 // landingpad instruction and an unreachable instruction. When
925 // all landingpads have been outlined, we'll replace this with the
926 // llvm.eh.actions call and indirect branch created when the
927 // landing pad was outlined.
928 if (auto *NestedLPad = dyn_cast<LandingPadInst>(Inst)) {
929 Instruction *NewInst = NestedLPad->clone();
930 if (NestedLPad->hasName())
931 NewInst->setName(NestedLPad->getName());
932 // FIXME: Store this mapping somewhere else also.
933 VMap[NestedLPad] = NewInst;
934 BasicBlock::InstListType &InstList = NewBB->getInstList();
935 InstList.push_back(NewInst);
936 InstList.push_back(new UnreachableInst(NewBB->getContext()));
937 return CloningDirector::StopCloningBB;
940 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
941 return handleInvoke(VMap, Invoke, NewBB);
943 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
944 return handleResume(VMap, Resume, NewBB);
946 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
947 return handleBeginCatch(VMap, Inst, NewBB);
948 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
949 return handleEndCatch(VMap, Inst, NewBB);
950 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
951 return handleTypeIdFor(VMap, Inst, NewBB);
953 // Continue with the default cloning behavior.
954 return CloningDirector::CloneInstruction;
957 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
958 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
959 // The argument to the call is some form of the first element of the
960 // landingpad aggregate value, but that doesn't matter. It isn't used
962 // The second argument is an outparameter where the exception object will be
963 // stored. Typically the exception object is a scalar, but it can be an
964 // aggregate when catching by value.
965 // FIXME: Leave something behind to indicate where the exception object lives
966 // for this handler. Should it be part of llvm.eh.actions?
967 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
968 "llvm.eh.begincatch found while "
969 "outlining catch handler.");
970 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
971 return CloningDirector::SkipInstruction;
974 CloningDirector::CloningAction
975 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
976 const Instruction *Inst, BasicBlock *NewBB) {
977 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
978 // It might be interesting to track whether or not we are inside a catch
979 // function, but that might make the algorithm more brittle than it needs
982 // The end catch call can occur in one of two places: either in a
983 // landingpad block that is part of the catch handlers exception mechanism,
984 // or at the end of the catch block. If it occurs in a landing pad, we must
985 // skip it and continue so that the landing pad gets cloned.
986 // FIXME: This case isn't fully supported yet and shouldn't turn up in any
987 // of the test cases until it is.
988 if (IntrinCall->getParent()->isLandingPad())
989 return CloningDirector::SkipInstruction;
991 // If an end catch occurs anywhere else the next instruction should be an
992 // unconditional branch instruction that we want to replace with a return
993 // to the the address of the branch target.
994 const BasicBlock *EndCatchBB = IntrinCall->getParent();
995 const TerminatorInst *Terminator = EndCatchBB->getTerminator();
996 const BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
997 assert(Branch && Branch->isUnconditional());
998 assert(std::next(BasicBlock::const_iterator(IntrinCall)) ==
999 BasicBlock::const_iterator(Branch));
1001 BasicBlock *ContinueLabel = Branch->getSuccessor(0);
1002 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueLabel),
1004 ReturnTargets.push_back(ContinueLabel);
1006 // We just added a terminator to the cloned block.
1007 // Tell the caller to stop processing the current basic block so that
1008 // the branch instruction will be skipped.
1009 return CloningDirector::StopCloningBB;
1012 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
1013 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1014 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1015 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1016 // This causes a replacement that will collapse the landing pad CFG based
1017 // on the filter function we intend to match.
1018 if (Selector == CurrentSelector)
1019 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
1021 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1022 // Tell the caller not to clone this instruction.
1023 return CloningDirector::SkipInstruction;
1026 CloningDirector::CloningAction
1027 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
1028 const InvokeInst *Invoke, BasicBlock *NewBB) {
1029 return CloningDirector::CloneInstruction;
1032 CloningDirector::CloningAction
1033 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
1034 const ResumeInst *Resume, BasicBlock *NewBB) {
1035 // Resume instructions shouldn't be reachable from catch handlers.
1036 // We still need to handle it, but it will be pruned.
1037 BasicBlock::InstListType &InstList = NewBB->getInstList();
1038 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1039 return CloningDirector::StopCloningBB;
1042 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1043 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1044 // Catch blocks within cleanup handlers will always be unreachable.
1045 // We'll insert an unreachable instruction now, but it will be pruned
1046 // before the cloning process is complete.
1047 BasicBlock::InstListType &InstList = NewBB->getInstList();
1048 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1049 return CloningDirector::StopCloningBB;
1052 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1053 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1054 // Catch blocks within cleanup handlers will always be unreachable.
1055 // We'll insert an unreachable instruction now, but it will be pruned
1056 // before the cloning process is complete.
1057 BasicBlock::InstListType &InstList = NewBB->getInstList();
1058 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1059 return CloningDirector::StopCloningBB;
1062 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1063 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1064 // If we encounter a selector comparison while cloning a cleanup handler,
1065 // we want to stop cloning immediately. Anything after the dispatch
1066 // will be outlined into a different handler.
1067 BasicBlock *CatchHandler;
1070 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1071 CatchHandler, Selector, NextBB)) {
1072 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1073 return CloningDirector::StopCloningBB;
1075 // If eg.typeid.for is called for any other reason, it can be ignored.
1076 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1077 return CloningDirector::SkipInstruction;
1080 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1081 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1082 // All invokes in cleanup handlers can be replaced with calls.
1083 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1084 // Insert a normal call instruction...
1086 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1087 Invoke->getName(), NewBB);
1088 NewCall->setCallingConv(Invoke->getCallingConv());
1089 NewCall->setAttributes(Invoke->getAttributes());
1090 NewCall->setDebugLoc(Invoke->getDebugLoc());
1091 VMap[Invoke] = NewCall;
1093 // Insert an unconditional branch to the normal destination.
1094 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1096 // The unwind destination won't be cloned into the new function, so
1097 // we don't need to clean up its phi nodes.
1099 // We just added a terminator to the cloned block.
1100 // Tell the caller to stop processing the current basic block.
1101 return CloningDirector::StopCloningBB;
1104 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1105 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1106 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1108 // We just added a terminator to the cloned block.
1109 // Tell the caller to stop processing the current basic block so that
1110 // the branch instruction will be skipped.
1111 return CloningDirector::StopCloningBB;
1114 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1115 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1116 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1117 Builder.SetInsertPoint(&OutlinedFn->getEntryBlock());
1120 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1121 // If we're asked to materialize a value that is an instruction, we
1122 // temporarily create an alloca in the outlined function and add this
1123 // to the FrameVarInfo map. When all the outlining is complete, we'll
1124 // collect these into a structure, spilling non-alloca values in the
1125 // parent frame as necessary, and replace these temporary allocas with
1126 // GEPs referencing the frame allocation block.
1128 // If the value is an alloca, the mapping is direct.
1129 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1130 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1131 Builder.Insert(NewAlloca, AV->getName());
1132 FrameVarInfo[AV].push_back(NewAlloca);
1136 // For other types of instructions or arguments, we need an alloca based on
1137 // the value's type and a load of the alloca. The alloca will be replaced
1138 // by a GEP, but the load will stay. In the parent function, the value will
1139 // be spilled to a location in the frame allocation block.
1140 if (isa<Instruction>(V) || isa<Argument>(V)) {
1141 AllocaInst *NewAlloca =
1142 Builder.CreateAlloca(V->getType(), nullptr, "eh.temp.alloca");
1143 FrameVarInfo[V].push_back(NewAlloca);
1144 LoadInst *NewLoad = Builder.CreateLoad(NewAlloca, V->getName() + ".reload");
1148 // Don't materialize other values.
1152 // This function maps the catch and cleanup handlers that are reachable from the
1153 // specified landing pad. The landing pad sequence will have this basic shape:
1155 // <cleanup handler>
1156 // <selector comparison>
1158 // <cleanup handler>
1159 // <selector comparison>
1161 // <cleanup handler>
1164 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1165 // any arbitrary control flow, but all paths through the cleanup code must
1166 // eventually reach the next selector comparison and no path can skip to a
1167 // different selector comparisons, though some paths may terminate abnormally.
1168 // Therefore, we will use a depth first search from the start of any given
1169 // cleanup block and stop searching when we find the next selector comparison.
1171 // If the landingpad instruction does not have a catch clause, we will assume
1172 // that any instructions other than selector comparisons and catch handlers can
1173 // be ignored. In practice, these will only be the boilerplate instructions.
1175 // The catch handlers may also have any control structure, but we are only
1176 // interested in the start of the catch handlers, so we don't need to actually
1177 // follow the flow of the catch handlers. The start of the catch handlers can
1178 // be located from the compare instructions, but they can be skipped in the
1179 // flow by following the contrary branch.
1180 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1181 LandingPadActions &Actions) {
1182 unsigned int NumClauses = LPad->getNumClauses();
1183 unsigned int HandlersFound = 0;
1184 BasicBlock *BB = LPad->getParent();
1186 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1188 if (NumClauses == 0) {
1189 // This landing pad contains only cleanup code.
1190 CleanupHandler *Action = new CleanupHandler(BB);
1191 CleanupHandlerMap[BB] = Action;
1192 Actions.insertCleanupHandler(Action);
1193 DEBUG(dbgs() << " Assuming cleanup code in block " << BB->getName()
1195 assert(LPad->isCleanup());
1199 VisitedBlockSet VisitedBlocks;
1201 while (HandlersFound != NumClauses) {
1202 BasicBlock *NextBB = nullptr;
1204 // See if the clause we're looking for is a catch-all.
1205 // If so, the catch begins immediately.
1206 if (isa<ConstantPointerNull>(LPad->getClause(HandlersFound))) {
1207 // The catch all must occur last.
1208 assert(HandlersFound == NumClauses - 1);
1210 // For C++ EH, check if there is any interesting cleanup code before we
1211 // begin the catch. This is important because cleanups cannot rethrow
1212 // exceptions but code called from catches can. For SEH, it isn't
1213 // important if some finally code before a catch-all is executed out of
1214 // line or after recovering from the exception.
1215 if (Personality == EHPersonality::MSVC_CXX) {
1216 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1217 // Add a cleanup entry to the list
1218 Actions.insertCleanupHandler(CleanupAction);
1219 DEBUG(dbgs() << " Found cleanup code in block "
1220 << CleanupAction->getStartBlock()->getName() << "\n");
1224 // Add the catch handler to the action list.
1225 CatchHandler *Action =
1226 new CatchHandler(BB, LPad->getClause(HandlersFound), nullptr);
1227 CatchHandlerMap[BB] = Action;
1228 Actions.insertCatchHandler(Action);
1229 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1232 // Once we reach a catch-all, don't expect to hit a resume instruction.
1237 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1238 // See if there is any interesting code executed before the dispatch.
1239 if (auto *CleanupAction =
1240 findCleanupHandler(BB, CatchAction->getStartBlock())) {
1241 // Add a cleanup entry to the list
1242 Actions.insertCleanupHandler(CleanupAction);
1243 DEBUG(dbgs() << " Found cleanup code in block "
1244 << CleanupAction->getStartBlock()->getName() << "\n");
1247 assert(CatchAction);
1250 // Add the catch handler to the action list.
1251 Actions.insertCatchHandler(CatchAction);
1252 DEBUG(dbgs() << " Found catch dispatch in block "
1253 << CatchAction->getStartBlock()->getName() << "\n");
1255 // Move on to the block after the catch handler.
1259 // If we didn't wind up in a catch-all, see if there is any interesting code
1260 // executed before the resume.
1261 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1262 // Add a cleanup entry to the list
1263 Actions.insertCleanupHandler(CleanupAction);
1264 DEBUG(dbgs() << " Found cleanup code in block "
1265 << CleanupAction->getStartBlock()->getName() << "\n");
1268 // It's possible that some optimization moved code into a landingpad that
1270 // previously being used for cleanup. If that happens, we need to execute
1272 // extra code from a cleanup handler.
1273 if (Actions.includesCleanup() && !LPad->isCleanup())
1274 LPad->setCleanup(true);
1277 // This function searches starting with the input block for the next
1278 // block that terminates with a branch whose condition is based on a selector
1279 // comparison. This may be the input block. See the mapLandingPadBlocks
1280 // comments for a discussion of control flow assumptions.
1282 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1283 BasicBlock *&NextBB,
1284 VisitedBlockSet &VisitedBlocks) {
1285 // See if we've already found a catch handler use it.
1286 // Call count() first to avoid creating a null entry for blocks
1287 // we haven't seen before.
1288 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1289 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1290 NextBB = Action->getNextBB();
1294 // VisitedBlocks applies only to the current search. We still
1295 // need to consider blocks that we've visited while mapping other
1297 VisitedBlocks.insert(BB);
1299 BasicBlock *CatchBlock = nullptr;
1300 Constant *Selector = nullptr;
1302 // If this is the first time we've visited this block from any landing pad
1303 // look to see if it is a selector dispatch block.
1304 if (!CatchHandlerMap.count(BB)) {
1305 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1306 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1307 CatchHandlerMap[BB] = Action;
1312 // Visit each successor, looking for the dispatch.
1313 // FIXME: We expect to find the dispatch quickly, so this will probably
1314 // work better as a breadth first search.
1315 for (BasicBlock *Succ : successors(BB)) {
1316 if (VisitedBlocks.count(Succ))
1319 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1326 // These are helper functions to combine repeated code from findCleanupHandler.
1327 static CleanupHandler *createCleanupHandler(CleanupHandlerMapTy &CleanupHandlerMap,
1329 CleanupHandler *Action = new CleanupHandler(BB);
1330 CleanupHandlerMap[BB] = Action;
1334 // This function searches starting with the input block for the next block that
1335 // contains code that is not part of a catch handler and would not be eliminated
1336 // during handler outlining.
1338 CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
1339 BasicBlock *EndBB) {
1340 // Here we will skip over the following:
1342 // landing pad prolog:
1344 // Unconditional branches
1346 // Selector dispatch
1350 // Anything else marks the start of an interesting block
1352 BasicBlock *BB = StartBB;
1353 // Anything other than an unconditional branch will kick us out of this loop
1354 // one way or another.
1356 // If we've already scanned this block, don't scan it again. If it is
1357 // a cleanup block, there will be an action in the CleanupHandlerMap.
1358 // If we've scanned it and it is not a cleanup block, there will be a
1359 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1360 // be no entry in the CleanupHandlerMap. We must call count() first to
1361 // avoid creating a null entry for blocks we haven't scanned.
1362 if (CleanupHandlerMap.count(BB)) {
1363 if (auto *Action = CleanupHandlerMap[BB]) {
1364 return cast<CleanupHandler>(Action);
1366 // Here we handle the case where the cleanup handler map contains a
1367 // value for this block but the value is a nullptr. This means that
1368 // we have previously analyzed the block and determined that it did
1369 // not contain any cleanup code. Based on the earlier analysis, we
1370 // know the the block must end in either an unconditional branch, a
1371 // resume or a conditional branch that is predicated on a comparison
1372 // with a selector. Either the resume or the selector dispatch
1373 // would terminate the search for cleanup code, so the unconditional
1374 // branch is the only case for which we might need to continue
1379 if (!match(BB->getTerminator(), m_UnconditionalBr(SuccBB)))
1386 // Create an entry in the cleanup handler map for this block. Initially
1387 // we create an entry that says this isn't a cleanup block. If we find
1388 // cleanup code, the caller will replace this entry.
1389 CleanupHandlerMap[BB] = nullptr;
1391 TerminatorInst *Terminator = BB->getTerminator();
1393 // Landing pad blocks have extra instructions we need to accept.
1394 LandingPadMap *LPadMap = nullptr;
1395 if (BB->isLandingPad()) {
1396 LandingPadInst *LPad = BB->getLandingPadInst();
1397 LPadMap = &LPadMaps[LPad];
1398 if (!LPadMap->isInitialized())
1399 LPadMap->mapLandingPad(LPad);
1402 // Look for the bare resume pattern:
1403 // %exn2 = load i8** %exn.slot
1404 // %sel2 = load i32* %ehselector.slot
1405 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn2, 0
1406 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel2, 1
1407 // resume { i8*, i32 } %lpad.val2
1408 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
1409 InsertValueInst *Insert1 = nullptr;
1410 InsertValueInst *Insert2 = nullptr;
1411 Value *ResumeVal = Resume->getOperand(0);
1412 // If there is only one landingpad, we may use the lpad directly with no
1414 if (isa<LandingPadInst>(ResumeVal))
1416 if (!isa<PHINode>(ResumeVal)) {
1417 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
1419 return createCleanupHandler(CleanupHandlerMap, BB);
1420 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
1422 return createCleanupHandler(CleanupHandlerMap, BB);
1424 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1426 Instruction *Inst = II;
1427 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1429 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
1431 if (!Inst->hasOneUse() ||
1432 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
1433 return createCleanupHandler(CleanupHandlerMap, BB);
1439 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
1441 if (Branch->isConditional()) {
1442 // Look for the selector dispatch.
1443 // %sel = load i32* %ehselector.slot
1444 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
1445 // %matches = icmp eq i32 %sel12, %2
1446 // br i1 %matches, label %catch14, label %eh.resume
1447 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
1448 if (!Compare || !Compare->isEquality())
1449 return createCleanupHandler(CleanupHandlerMap, BB);
1450 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
1453 Instruction *Inst = II;
1454 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1456 if (Inst == Compare || Inst == Branch)
1458 if (!Inst->hasOneUse() || (Inst->user_back() != Compare))
1459 return createCleanupHandler(CleanupHandlerMap, BB);
1460 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1462 if (!isa<LoadInst>(Inst))
1463 return createCleanupHandler(CleanupHandlerMap, BB);
1465 // The selector dispatch block should always terminate our search.
1466 assert(BB == EndBB);
1469 // Look for empty blocks with unconditional branches.
1470 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
1473 Instruction *Inst = II;
1474 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1478 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1480 // Anything else makes this interesting cleanup code.
1481 return createCleanupHandler(CleanupHandlerMap, BB);
1485 // The branch was unconditional.
1486 BB = Branch->getSuccessor(0);
1488 } // End else of if branch was conditional
1491 // Anything else makes this interesting cleanup code.
1492 return createCleanupHandler(CleanupHandlerMap, BB);