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/CodeGen/WinEHFuncInfo.h"
24 #include "llvm/IR/Dominators.h"
25 #include "llvm/IR/Function.h"
26 #include "llvm/IR/IRBuilder.h"
27 #include "llvm/IR/Instructions.h"
28 #include "llvm/IR/IntrinsicInst.h"
29 #include "llvm/IR/Module.h"
30 #include "llvm/IR/PatternMatch.h"
31 #include "llvm/Pass.h"
32 #include "llvm/Support/CommandLine.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/raw_ostream.h"
35 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
36 #include "llvm/Transforms/Utils/Cloning.h"
37 #include "llvm/Transforms/Utils/Local.h"
38 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
42 using namespace llvm::PatternMatch;
44 #define DEBUG_TYPE "winehprepare"
48 // This map is used to model frame variable usage during outlining, to
49 // construct a structure type to hold the frame variables in a frame
50 // allocation block, and to remap the frame variable allocas (including
51 // spill locations as needed) to GEPs that get the variable from the
52 // frame allocation structure.
53 typedef MapVector<Value *, TinyPtrVector<AllocaInst *>> FrameVarInfoMap;
55 typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
57 class LandingPadActions;
60 typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
61 typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
63 class WinEHPrepare : public FunctionPass {
65 static char ID; // Pass identification, replacement for typeid.
66 WinEHPrepare(const TargetMachine *TM = nullptr)
67 : FunctionPass(ID), DT(nullptr) {}
69 bool runOnFunction(Function &Fn) override;
71 bool doFinalization(Module &M) override;
73 void getAnalysisUsage(AnalysisUsage &AU) const override;
75 const char *getPassName() const override {
76 return "Windows exception handling preparation";
80 bool prepareExceptionHandlers(Function &F,
81 SmallVectorImpl<LandingPadInst *> &LPads);
82 void promoteLandingPadValues(LandingPadInst *LPad);
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.
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 isOriginLandingPadBlock(const BasicBlock *BB) const;
123 bool isLandingPadSpecificInst(const Instruction *Inst) const;
125 void remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
126 Value *SelectorValue) const;
129 const LandingPadInst *OriginLPad;
130 // We will normally only see one of each of these instructions, but
131 // if more than one occurs for some reason we can handle that.
132 TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
133 TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
136 class WinEHCloningDirectorBase : public CloningDirector {
138 WinEHCloningDirectorBase(Function *HandlerFn,
139 FrameVarInfoMap &VarInfo,
140 LandingPadMap &LPadMap)
141 : Materializer(HandlerFn, VarInfo),
142 SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
143 Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
146 CloningAction handleInstruction(ValueToValueMapTy &VMap,
147 const Instruction *Inst,
148 BasicBlock *NewBB) override;
150 virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
151 const Instruction *Inst,
152 BasicBlock *NewBB) = 0;
153 virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
154 const Instruction *Inst,
155 BasicBlock *NewBB) = 0;
156 virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
157 const Instruction *Inst,
158 BasicBlock *NewBB) = 0;
159 virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
160 const InvokeInst *Invoke,
161 BasicBlock *NewBB) = 0;
162 virtual CloningAction handleResume(ValueToValueMapTy &VMap,
163 const ResumeInst *Resume,
164 BasicBlock *NewBB) = 0;
166 ValueMaterializer *getValueMaterializer() override { return &Materializer; }
169 WinEHFrameVariableMaterializer Materializer;
170 Type *SelectorIDType;
172 LandingPadMap &LPadMap;
175 class WinEHCatchDirector : public WinEHCloningDirectorBase {
177 WinEHCatchDirector(Function *CatchFn, Value *Selector,
178 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
179 : WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
180 CurrentSelector(Selector->stripPointerCasts()),
181 ExceptionObjectVar(nullptr) {}
183 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
184 const Instruction *Inst,
185 BasicBlock *NewBB) override;
186 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
187 BasicBlock *NewBB) override;
188 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
189 const Instruction *Inst,
190 BasicBlock *NewBB) override;
191 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
192 BasicBlock *NewBB) override;
193 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
194 BasicBlock *NewBB) override;
196 const Value *getExceptionVar() { return ExceptionObjectVar; }
197 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
200 Value *CurrentSelector;
202 const Value *ExceptionObjectVar;
203 TinyPtrVector<BasicBlock *> ReturnTargets;
206 class WinEHCleanupDirector : public WinEHCloningDirectorBase {
208 WinEHCleanupDirector(Function *CleanupFn,
209 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
210 : WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
212 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
213 const Instruction *Inst,
214 BasicBlock *NewBB) override;
215 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
216 BasicBlock *NewBB) override;
217 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
218 const Instruction *Inst,
219 BasicBlock *NewBB) override;
220 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
221 BasicBlock *NewBB) override;
222 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
223 BasicBlock *NewBB) override;
226 class LandingPadActions {
228 LandingPadActions() : HasCleanupHandlers(false) {}
230 void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
231 void insertCleanupHandler(CleanupHandler *Action) {
232 Actions.push_back(Action);
233 HasCleanupHandlers = true;
236 bool includesCleanup() const { return HasCleanupHandlers; }
238 SmallVectorImpl<ActionHandler *> &actions() { return Actions; }
239 SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
240 SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
243 // Note that this class does not own the ActionHandler objects in this vector.
244 // The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
245 // in the WinEHPrepare class.
246 SmallVector<ActionHandler *, 4> Actions;
247 bool HasCleanupHandlers;
250 } // end anonymous namespace
252 char WinEHPrepare::ID = 0;
253 INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
256 FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
257 return new WinEHPrepare(TM);
260 // FIXME: Remove this once the backend can handle the prepared IR.
262 SEHPrepare("sehprepare", cl::Hidden,
263 cl::desc("Prepare functions with SEH personalities"));
265 bool WinEHPrepare::runOnFunction(Function &Fn) {
266 SmallVector<LandingPadInst *, 4> LPads;
267 SmallVector<ResumeInst *, 4> Resumes;
268 for (BasicBlock &BB : Fn) {
269 if (auto *LP = BB.getLandingPadInst())
271 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
272 Resumes.push_back(Resume);
275 // No need to prepare functions that lack landing pads.
279 // Classify the personality to see what kind of preparation we need.
280 Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
282 // Do nothing if this is not an MSVC personality.
283 if (!isMSVCEHPersonality(Personality))
286 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
288 if (isAsynchronousEHPersonality(Personality) && !SEHPrepare) {
289 // Replace all resume instructions with unreachable.
290 // FIXME: Remove this once the backend can handle the prepared IR.
291 for (ResumeInst *Resume : Resumes) {
292 IRBuilder<>(Resume).CreateUnreachable();
293 Resume->eraseFromParent();
298 // If there were any landing pads, prepareExceptionHandlers will make changes.
299 prepareExceptionHandlers(Fn, LPads);
303 bool WinEHPrepare::doFinalization(Module &M) {
307 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
308 AU.addRequired<DominatorTreeWrapperPass>();
311 bool WinEHPrepare::prepareExceptionHandlers(
312 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
313 // These containers are used to re-map frame variables that are used in
314 // outlined catch and cleanup handlers. They will be populated as the
315 // handlers are outlined.
316 FrameVarInfoMap FrameVarInfo;
318 bool HandlersOutlined = false;
320 Module *M = F.getParent();
321 LLVMContext &Context = M->getContext();
323 // Create a new function to receive the handler contents.
324 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
325 Type *Int32Type = Type::getInt32Ty(Context);
326 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
328 for (LandingPadInst *LPad : LPads) {
329 // Look for evidence that this landingpad has already been processed.
330 bool LPadHasActionList = false;
331 BasicBlock *LPadBB = LPad->getParent();
332 for (Instruction &Inst : *LPadBB) {
333 if (auto *IntrinCall = dyn_cast<IntrinsicInst>(&Inst)) {
334 if (IntrinCall->getIntrinsicID() == Intrinsic::eh_actions) {
335 LPadHasActionList = true;
339 // FIXME: This is here to help with the development of nested landing pad
340 // outlining. It should be removed when that is finished.
341 if (isa<UnreachableInst>(Inst)) {
342 LPadHasActionList = true;
347 // If we've already outlined the handlers for this landingpad,
348 // there's nothing more to do here.
349 if (LPadHasActionList)
352 // If either of the values in the aggregate returned by the landing pad is
353 // extracted and stored to memory, promote the stored value to a register.
354 promoteLandingPadValues(LPad);
356 LandingPadActions Actions;
357 mapLandingPadBlocks(LPad, Actions);
359 for (ActionHandler *Action : Actions) {
360 if (Action->hasBeenProcessed())
362 BasicBlock *StartBB = Action->getStartBlock();
364 // SEH doesn't do any outlining for catches. Instead, pass the handler
365 // basic block addr to llvm.eh.actions and list the block as a return
367 if (isAsynchronousEHPersonality(Personality)) {
368 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
369 processSEHCatchHandler(CatchAction, StartBB);
370 HandlersOutlined = true;
375 if (outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo)) {
376 HandlersOutlined = true;
378 } // End for each Action
380 // FIXME: We need a guard against partially outlined functions.
381 if (!HandlersOutlined)
384 // Replace the landing pad with a new llvm.eh.action based landing pad.
385 BasicBlock *NewLPadBB = BasicBlock::Create(Context, "lpad", &F, LPadBB);
386 assert(!isa<PHINode>(LPadBB->begin()));
387 auto *NewLPad = cast<LandingPadInst>(LPad->clone());
388 NewLPadBB->getInstList().push_back(NewLPad);
389 while (!pred_empty(LPadBB)) {
390 auto *pred = *pred_begin(LPadBB);
391 InvokeInst *Invoke = cast<InvokeInst>(pred->getTerminator());
392 Invoke->setUnwindDest(NewLPadBB);
395 // Replace uses of the old lpad in phis with this block and delete the old
397 LPadBB->replaceSuccessorsPhiUsesWith(NewLPadBB);
398 LPadBB->getTerminator()->eraseFromParent();
399 new UnreachableInst(LPadBB->getContext(), LPadBB);
401 // Add a call to describe the actions for this landing pad.
402 std::vector<Value *> ActionArgs;
403 for (ActionHandler *Action : Actions) {
404 // Action codes from docs are: 0 cleanup, 1 catch.
405 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
406 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
407 ActionArgs.push_back(CatchAction->getSelector());
408 Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
410 ActionArgs.push_back(EHObj);
412 ActionArgs.push_back(ConstantPointerNull::get(Int8PtrType));
414 ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
416 ActionArgs.push_back(Action->getHandlerBlockOrFunc());
419 CallInst::Create(ActionIntrin, ActionArgs, "recover", NewLPadBB);
421 // Add an indirect branch listing possible successors of the catch handlers.
422 IndirectBrInst *Branch = IndirectBrInst::Create(Recover, 0, NewLPadBB);
423 for (ActionHandler *Action : Actions) {
424 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
425 for (auto *Target : CatchAction->getReturnTargets()) {
426 Branch->addDestination(Target);
430 } // End for each landingpad
432 // If nothing got outlined, there is no more processing to be done.
433 if (!HandlersOutlined)
436 F.addFnAttr("wineh-parent", F.getName());
438 // Delete any blocks that were only used by handlers that were outlined above.
439 removeUnreachableBlocks(F);
441 BasicBlock *Entry = &F.getEntryBlock();
442 IRBuilder<> Builder(F.getParent()->getContext());
443 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
445 Function *FrameEscapeFn =
446 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
447 Function *RecoverFrameFn =
448 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
450 // Finally, replace all of the temporary allocas for frame variables used in
451 // the outlined handlers with calls to llvm.framerecover.
452 BasicBlock::iterator II = Entry->getFirstInsertionPt();
453 Instruction *AllocaInsertPt = II;
454 SmallVector<Value *, 8> AllocasToEscape;
455 for (auto &VarInfoEntry : FrameVarInfo) {
456 Value *ParentVal = VarInfoEntry.first;
457 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
459 // If the mapped value isn't already an alloca, we need to spill it if it
460 // is a computed value or copy it if it is an argument.
461 AllocaInst *ParentAlloca = dyn_cast<AllocaInst>(ParentVal);
463 if (auto *Arg = dyn_cast<Argument>(ParentVal)) {
464 // Lower this argument to a copy and then demote that to the stack.
465 // We can't just use the argument location because the handler needs
466 // it to be in the frame allocation block.
467 // Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction.
468 Value *TrueValue = ConstantInt::getTrue(Context);
469 Value *UndefValue = UndefValue::get(Arg->getType());
471 SelectInst::Create(TrueValue, Arg, UndefValue,
472 Arg->getName() + ".tmp", AllocaInsertPt);
473 Arg->replaceAllUsesWith(SI);
474 // Reset the select operand, because it was clobbered by the RAUW above.
475 SI->setOperand(1, Arg);
476 ParentAlloca = DemoteRegToStack(*SI, true, SI);
477 } else if (auto *PN = dyn_cast<PHINode>(ParentVal)) {
478 ParentAlloca = DemotePHIToStack(PN, AllocaInsertPt);
480 Instruction *ParentInst = cast<Instruction>(ParentVal);
481 // FIXME: This is a work-around to temporarily handle the case where an
482 // instruction that is only used in handlers is not sunk.
483 // Without uses, DemoteRegToStack would just eliminate the value.
484 // This will fail if ParentInst is an invoke.
485 if (ParentInst->getNumUses() == 0) {
486 BasicBlock::iterator InsertPt = ParentInst;
489 new AllocaInst(ParentInst->getType(), nullptr,
490 ParentInst->getName() + ".reg2mem", InsertPt);
491 new StoreInst(ParentInst, ParentAlloca, InsertPt);
493 ParentAlloca = DemoteRegToStack(*ParentInst, true, ParentInst);
498 // If the parent alloca is no longer used and only one of the handlers used
499 // it, erase the parent and leave the copy in the outlined handler.
500 if (ParentAlloca->getNumUses() == 0 && Allocas.size() == 1) {
501 ParentAlloca->eraseFromParent();
505 // Add this alloca to the list of things to escape.
506 AllocasToEscape.push_back(ParentAlloca);
508 // Next replace all outlined allocas that are mapped to it.
509 for (AllocaInst *TempAlloca : Allocas) {
510 Function *HandlerFn = TempAlloca->getParent()->getParent();
511 // FIXME: Sink this GEP into the blocks where it is used.
512 Builder.SetInsertPoint(TempAlloca);
513 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
514 Value *RecoverArgs[] = {
515 Builder.CreateBitCast(&F, Int8PtrType, ""),
516 &(HandlerFn->getArgumentList().back()),
517 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
518 Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
519 // Add a pointer bitcast if the alloca wasn't an i8.
520 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
521 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
523 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
525 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
526 TempAlloca->removeFromParent();
527 RecoveredAlloca->takeName(TempAlloca);
530 } // End for each FrameVarInfo entry.
532 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
534 Builder.SetInsertPoint(&F.getEntryBlock().back());
535 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
537 // Insert an alloca for the EH state in the entry block. On x86, we will also
538 // insert stores to update the EH state, but on other ISAs, the runtime does
540 // FIXME: This record is different on x86.
541 Type *UnwindHelpTy = Type::getInt64Ty(Context);
542 AllocaInst *UnwindHelp =
543 new AllocaInst(UnwindHelpTy, "unwindhelp", &F.getEntryBlock().front());
544 Builder.CreateStore(llvm::ConstantInt::get(UnwindHelpTy, -2), UnwindHelp,
545 /*isVolatile=*/true);
546 Function *UnwindHelpFn =
547 Intrinsic::getDeclaration(M, Intrinsic::eh_unwindhelp);
548 Builder.CreateCall(UnwindHelpFn,
549 Builder.CreateBitCast(UnwindHelp, Int8PtrType));
551 // Clean up the handler action maps we created for this function
552 DeleteContainerSeconds(CatchHandlerMap);
553 CatchHandlerMap.clear();
554 DeleteContainerSeconds(CleanupHandlerMap);
555 CleanupHandlerMap.clear();
557 return HandlersOutlined;
560 void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
561 // If the return values of the landing pad instruction are extracted and
562 // stored to memory, we want to promote the store locations to reg values.
563 SmallVector<AllocaInst *, 2> EHAllocas;
565 // The landingpad instruction returns an aggregate value. Typically, its
566 // value will be passed to a pair of extract value instructions and the
567 // results of those extracts are often passed to store instructions.
568 // In unoptimized code the stored value will often be loaded and then stored
570 for (auto *U : LPad->users()) {
571 ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
575 for (auto *EU : Extract->users()) {
576 if (auto *Store = dyn_cast<StoreInst>(EU)) {
577 auto *AV = cast<AllocaInst>(Store->getPointerOperand());
578 EHAllocas.push_back(AV);
583 // We can't do this without a dominator tree.
586 if (!EHAllocas.empty()) {
587 PromoteMemToReg(EHAllocas, *DT);
592 // This function examines a block to determine whether the block ends with a
593 // conditional branch to a catch handler based on a selector comparison.
594 // This function is used both by the WinEHPrepare::findSelectorComparison() and
595 // WinEHCleanupDirector::handleTypeIdFor().
596 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
597 Constant *&Selector, BasicBlock *&NextBB) {
598 ICmpInst::Predicate Pred;
599 BasicBlock *TBB, *FBB;
602 if (!match(BB->getTerminator(),
603 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
607 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
608 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
611 if (Pred == CmpInst::ICMP_EQ) {
617 if (Pred == CmpInst::ICMP_NE) {
626 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
627 LandingPadInst *LPad, BasicBlock *StartBB,
628 FrameVarInfoMap &VarInfo) {
629 Module *M = SrcFn->getParent();
630 LLVMContext &Context = M->getContext();
632 // Create a new function to receive the handler contents.
633 Type *Int8PtrType = Type::getInt8PtrTy(Context);
634 std::vector<Type *> ArgTys;
635 ArgTys.push_back(Int8PtrType);
636 ArgTys.push_back(Int8PtrType);
638 if (Action->getType() == Catch) {
639 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
640 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
641 SrcFn->getName() + ".catch", M);
643 FunctionType *FnType =
644 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
645 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
646 SrcFn->getName() + ".cleanup", M);
649 Handler->addFnAttr("wineh-parent", SrcFn->getName());
651 // Generate a standard prolog to setup the frame recovery structure.
652 IRBuilder<> Builder(Context);
653 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
654 Handler->getBasicBlockList().push_front(Entry);
655 Builder.SetInsertPoint(Entry);
656 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
658 std::unique_ptr<WinEHCloningDirectorBase> Director;
660 ValueToValueMapTy VMap;
662 LandingPadMap &LPadMap = LPadMaps[LPad];
663 if (!LPadMap.isInitialized())
664 LPadMap.mapLandingPad(LPad);
665 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
666 Constant *Sel = CatchAction->getSelector();
667 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap));
668 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
669 ConstantInt::get(Type::getInt32Ty(Context), 1));
671 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
672 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
673 UndefValue::get(Type::getInt32Ty(Context)));
676 SmallVector<ReturnInst *, 8> Returns;
677 ClonedCodeInfo OutlinedFunctionInfo;
679 // If the start block contains PHI nodes, we need to map them.
680 BasicBlock::iterator II = StartBB->begin();
681 while (auto *PN = dyn_cast<PHINode>(II)) {
683 // Look for PHI values that we have already mapped (such as the selector).
684 for (Value *Val : PN->incoming_values()) {
685 if (VMap.count(Val)) {
686 VMap[PN] = VMap[Val];
690 // If we didn't find a match for this value, map it as an undef.
692 VMap[PN] = UndefValue::get(PN->getType());
697 // Skip over PHIs and, if applicable, landingpad instructions.
698 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 will have been promoted to reg values before
762 // this routine is called.
763 for (auto *U : LPad->users()) {
764 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
767 assert(Extract->getNumIndices() == 1 &&
768 "Unexpected operation: extracting both landing pad values");
769 unsigned int Idx = *(Extract->idx_begin());
770 assert((Idx == 0 || Idx == 1) &&
771 "Unexpected operation: extracting an unknown landing pad element");
773 ExtractedEHPtrs.push_back(Extract);
774 } else if (Idx == 1) {
775 ExtractedSelectors.push_back(Extract);
780 bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
781 return BB->getLandingPadInst() == OriginLPad;
784 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
785 if (Inst == OriginLPad)
787 for (auto *Extract : ExtractedEHPtrs) {
791 for (auto *Extract : ExtractedSelectors) {
798 void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
799 Value *SelectorValue) const {
800 // Remap all landing pad extract instructions to the specified values.
801 for (auto *Extract : ExtractedEHPtrs)
802 VMap[Extract] = EHPtrValue;
803 for (auto *Extract : ExtractedSelectors)
804 VMap[Extract] = SelectorValue;
807 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
808 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
809 // If this is one of the boilerplate landing pad instructions, skip it.
810 // The instruction will have already been remapped in VMap.
811 if (LPadMap.isLandingPadSpecificInst(Inst))
812 return CloningDirector::SkipInstruction;
814 // Nested landing pads will be cloned as stubs, with just the
815 // landingpad instruction and an unreachable instruction. When
816 // all landingpads have been outlined, we'll replace this with the
817 // llvm.eh.actions call and indirect branch created when the
818 // landing pad was outlined.
819 if (auto *NestedLPad = dyn_cast<LandingPadInst>(Inst)) {
820 Instruction *NewInst = NestedLPad->clone();
821 if (NestedLPad->hasName())
822 NewInst->setName(NestedLPad->getName());
823 // FIXME: Store this mapping somewhere else also.
824 VMap[NestedLPad] = NewInst;
825 BasicBlock::InstListType &InstList = NewBB->getInstList();
826 InstList.push_back(NewInst);
827 InstList.push_back(new UnreachableInst(NewBB->getContext()));
828 return CloningDirector::StopCloningBB;
831 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
832 return handleInvoke(VMap, Invoke, NewBB);
834 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
835 return handleResume(VMap, Resume, NewBB);
837 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
838 return handleBeginCatch(VMap, Inst, NewBB);
839 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
840 return handleEndCatch(VMap, Inst, NewBB);
841 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
842 return handleTypeIdFor(VMap, Inst, NewBB);
844 // Continue with the default cloning behavior.
845 return CloningDirector::CloneInstruction;
848 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
849 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
850 // The argument to the call is some form of the first element of the
851 // landingpad aggregate value, but that doesn't matter. It isn't used
853 // The second argument is an outparameter where the exception object will be
854 // stored. Typically the exception object is a scalar, but it can be an
855 // aggregate when catching by value.
856 // FIXME: Leave something behind to indicate where the exception object lives
857 // for this handler. Should it be part of llvm.eh.actions?
858 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
859 "llvm.eh.begincatch found while "
860 "outlining catch handler.");
861 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
862 return CloningDirector::SkipInstruction;
865 CloningDirector::CloningAction
866 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
867 const Instruction *Inst, BasicBlock *NewBB) {
868 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
869 // It might be interesting to track whether or not we are inside a catch
870 // function, but that might make the algorithm more brittle than it needs
873 // The end catch call can occur in one of two places: either in a
874 // landingpad block that is part of the catch handlers exception mechanism,
875 // or at the end of the catch block. However, a catch-all handler may call
876 // end catch from the original landing pad. If the call occurs in a nested
877 // landing pad block, we must skip it and continue so that the landing pad
879 auto *ParentBB = IntrinCall->getParent();
880 if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
881 return CloningDirector::SkipInstruction;
883 // If an end catch occurs anywhere else we want to terminate the handler
884 // with a return to the code that follows the endcatch call. If the
885 // next instruction is not an unconditional branch, we need to split the
886 // block to provide a clear target for the return instruction.
887 BasicBlock *ContinueBB;
888 auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
889 const BranchInst *Branch = dyn_cast<BranchInst>(Next);
890 if (!Branch || !Branch->isUnconditional()) {
891 // We're interrupting the cloning process at this location, so the
892 // const_cast we're doing here will not cause a problem.
893 ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
894 const_cast<Instruction *>(cast<Instruction>(Next)));
896 ContinueBB = Branch->getSuccessor(0);
899 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
900 ReturnTargets.push_back(ContinueBB);
902 // We just added a terminator to the cloned block.
903 // Tell the caller to stop processing the current basic block so that
904 // the branch instruction will be skipped.
905 return CloningDirector::StopCloningBB;
908 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
909 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
910 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
911 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
912 // This causes a replacement that will collapse the landing pad CFG based
913 // on the filter function we intend to match.
914 if (Selector == CurrentSelector)
915 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
917 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
918 // Tell the caller not to clone this instruction.
919 return CloningDirector::SkipInstruction;
922 CloningDirector::CloningAction
923 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
924 const InvokeInst *Invoke, BasicBlock *NewBB) {
925 return CloningDirector::CloneInstruction;
928 CloningDirector::CloningAction
929 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
930 const ResumeInst *Resume, BasicBlock *NewBB) {
931 // Resume instructions shouldn't be reachable from catch handlers.
932 // We still need to handle it, but it will be pruned.
933 BasicBlock::InstListType &InstList = NewBB->getInstList();
934 InstList.push_back(new UnreachableInst(NewBB->getContext()));
935 return CloningDirector::StopCloningBB;
938 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
939 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
940 // Catch blocks within cleanup handlers will always be unreachable.
941 // We'll insert an unreachable instruction now, but it will be pruned
942 // before the cloning process is complete.
943 BasicBlock::InstListType &InstList = NewBB->getInstList();
944 InstList.push_back(new UnreachableInst(NewBB->getContext()));
945 return CloningDirector::StopCloningBB;
948 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
949 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
950 // Catch blocks within cleanup handlers will always be unreachable.
951 // We'll insert an unreachable instruction now, but it will be pruned
952 // before the cloning process is complete.
953 BasicBlock::InstListType &InstList = NewBB->getInstList();
954 InstList.push_back(new UnreachableInst(NewBB->getContext()));
955 return CloningDirector::StopCloningBB;
958 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
959 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
960 // If we encounter a selector comparison while cloning a cleanup handler,
961 // we want to stop cloning immediately. Anything after the dispatch
962 // will be outlined into a different handler.
963 BasicBlock *CatchHandler;
966 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
967 CatchHandler, Selector, NextBB)) {
968 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
969 return CloningDirector::StopCloningBB;
971 // If eg.typeid.for is called for any other reason, it can be ignored.
972 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
973 return CloningDirector::SkipInstruction;
976 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
977 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
978 // All invokes in cleanup handlers can be replaced with calls.
979 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
980 // Insert a normal call instruction...
982 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
983 Invoke->getName(), NewBB);
984 NewCall->setCallingConv(Invoke->getCallingConv());
985 NewCall->setAttributes(Invoke->getAttributes());
986 NewCall->setDebugLoc(Invoke->getDebugLoc());
987 VMap[Invoke] = NewCall;
989 // Insert an unconditional branch to the normal destination.
990 BranchInst::Create(Invoke->getNormalDest(), NewBB);
992 // The unwind destination won't be cloned into the new function, so
993 // we don't need to clean up its phi nodes.
995 // We just added a terminator to the cloned block.
996 // Tell the caller to stop processing the current basic block.
997 return CloningDirector::StopCloningBB;
1000 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1001 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1002 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1004 // We just added a terminator to the cloned block.
1005 // Tell the caller to stop processing the current basic block so that
1006 // the branch instruction will be skipped.
1007 return CloningDirector::StopCloningBB;
1010 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1011 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1012 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1013 Builder.SetInsertPoint(&OutlinedFn->getEntryBlock());
1016 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1017 // If we're asked to materialize a value that is an instruction, we
1018 // temporarily create an alloca in the outlined function and add this
1019 // to the FrameVarInfo map. When all the outlining is complete, we'll
1020 // collect these into a structure, spilling non-alloca values in the
1021 // parent frame as necessary, and replace these temporary allocas with
1022 // GEPs referencing the frame allocation block.
1024 // If the value is an alloca, the mapping is direct.
1025 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1026 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1027 Builder.Insert(NewAlloca, AV->getName());
1028 FrameVarInfo[AV].push_back(NewAlloca);
1032 // For other types of instructions or arguments, we need an alloca based on
1033 // the value's type and a load of the alloca. The alloca will be replaced
1034 // by a GEP, but the load will stay. In the parent function, the value will
1035 // be spilled to a location in the frame allocation block.
1036 if (isa<Instruction>(V) || isa<Argument>(V)) {
1037 AllocaInst *NewAlloca =
1038 Builder.CreateAlloca(V->getType(), nullptr, "eh.temp.alloca");
1039 FrameVarInfo[V].push_back(NewAlloca);
1040 LoadInst *NewLoad = Builder.CreateLoad(NewAlloca, V->getName() + ".reload");
1044 // Don't materialize other values.
1048 // This function maps the catch and cleanup handlers that are reachable from the
1049 // specified landing pad. The landing pad sequence will have this basic shape:
1051 // <cleanup handler>
1052 // <selector comparison>
1054 // <cleanup handler>
1055 // <selector comparison>
1057 // <cleanup handler>
1060 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1061 // any arbitrary control flow, but all paths through the cleanup code must
1062 // eventually reach the next selector comparison and no path can skip to a
1063 // different selector comparisons, though some paths may terminate abnormally.
1064 // Therefore, we will use a depth first search from the start of any given
1065 // cleanup block and stop searching when we find the next selector comparison.
1067 // If the landingpad instruction does not have a catch clause, we will assume
1068 // that any instructions other than selector comparisons and catch handlers can
1069 // be ignored. In practice, these will only be the boilerplate instructions.
1071 // The catch handlers may also have any control structure, but we are only
1072 // interested in the start of the catch handlers, so we don't need to actually
1073 // follow the flow of the catch handlers. The start of the catch handlers can
1074 // be located from the compare instructions, but they can be skipped in the
1075 // flow by following the contrary branch.
1076 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1077 LandingPadActions &Actions) {
1078 unsigned int NumClauses = LPad->getNumClauses();
1079 unsigned int HandlersFound = 0;
1080 BasicBlock *BB = LPad->getParent();
1082 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1084 if (NumClauses == 0) {
1085 // This landing pad contains only cleanup code.
1086 CleanupHandler *Action = new CleanupHandler(BB);
1087 CleanupHandlerMap[BB] = Action;
1088 Actions.insertCleanupHandler(Action);
1089 DEBUG(dbgs() << " Assuming cleanup code in block " << BB->getName()
1091 assert(LPad->isCleanup());
1095 VisitedBlockSet VisitedBlocks;
1097 while (HandlersFound != NumClauses) {
1098 BasicBlock *NextBB = nullptr;
1100 // See if the clause we're looking for is a catch-all.
1101 // If so, the catch begins immediately.
1102 if (isa<ConstantPointerNull>(LPad->getClause(HandlersFound))) {
1103 // The catch all must occur last.
1104 assert(HandlersFound == NumClauses - 1);
1106 // For C++ EH, check if there is any interesting cleanup code before we
1107 // begin the catch. This is important because cleanups cannot rethrow
1108 // exceptions but code called from catches can. For SEH, it isn't
1109 // important if some finally code before a catch-all is executed out of
1110 // line or after recovering from the exception.
1111 if (Personality == EHPersonality::MSVC_CXX) {
1112 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1113 // Add a cleanup entry to the list
1114 Actions.insertCleanupHandler(CleanupAction);
1115 DEBUG(dbgs() << " Found cleanup code in block "
1116 << CleanupAction->getStartBlock()->getName() << "\n");
1120 // Add the catch handler to the action list.
1121 CatchHandler *Action =
1122 new CatchHandler(BB, LPad->getClause(HandlersFound), nullptr);
1123 CatchHandlerMap[BB] = Action;
1124 Actions.insertCatchHandler(Action);
1125 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1128 // Once we reach a catch-all, don't expect to hit a resume instruction.
1133 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1134 // See if there is any interesting code executed before the dispatch.
1135 if (auto *CleanupAction =
1136 findCleanupHandler(BB, CatchAction->getStartBlock())) {
1137 // Add a cleanup entry to the list
1138 Actions.insertCleanupHandler(CleanupAction);
1139 DEBUG(dbgs() << " Found cleanup code in block "
1140 << CleanupAction->getStartBlock()->getName() << "\n");
1143 assert(CatchAction);
1146 // Add the catch handler to the action list.
1147 Actions.insertCatchHandler(CatchAction);
1148 DEBUG(dbgs() << " Found catch dispatch in block "
1149 << CatchAction->getStartBlock()->getName() << "\n");
1151 // Move on to the block after the catch handler.
1155 // If we didn't wind up in a catch-all, see if there is any interesting code
1156 // executed before the resume.
1157 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1158 // Add a cleanup entry to the list
1159 Actions.insertCleanupHandler(CleanupAction);
1160 DEBUG(dbgs() << " Found cleanup code in block "
1161 << CleanupAction->getStartBlock()->getName() << "\n");
1164 // It's possible that some optimization moved code into a landingpad that
1166 // previously being used for cleanup. If that happens, we need to execute
1168 // extra code from a cleanup handler.
1169 if (Actions.includesCleanup() && !LPad->isCleanup())
1170 LPad->setCleanup(true);
1173 // This function searches starting with the input block for the next
1174 // block that terminates with a branch whose condition is based on a selector
1175 // comparison. This may be the input block. See the mapLandingPadBlocks
1176 // comments for a discussion of control flow assumptions.
1178 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1179 BasicBlock *&NextBB,
1180 VisitedBlockSet &VisitedBlocks) {
1181 // See if we've already found a catch handler use it.
1182 // Call count() first to avoid creating a null entry for blocks
1183 // we haven't seen before.
1184 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1185 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1186 NextBB = Action->getNextBB();
1190 // VisitedBlocks applies only to the current search. We still
1191 // need to consider blocks that we've visited while mapping other
1193 VisitedBlocks.insert(BB);
1195 BasicBlock *CatchBlock = nullptr;
1196 Constant *Selector = nullptr;
1198 // If this is the first time we've visited this block from any landing pad
1199 // look to see if it is a selector dispatch block.
1200 if (!CatchHandlerMap.count(BB)) {
1201 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1202 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1203 CatchHandlerMap[BB] = Action;
1208 // Visit each successor, looking for the dispatch.
1209 // FIXME: We expect to find the dispatch quickly, so this will probably
1210 // work better as a breadth first search.
1211 for (BasicBlock *Succ : successors(BB)) {
1212 if (VisitedBlocks.count(Succ))
1215 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1222 // These are helper functions to combine repeated code from findCleanupHandler.
1223 static CleanupHandler *createCleanupHandler(CleanupHandlerMapTy &CleanupHandlerMap,
1225 CleanupHandler *Action = new CleanupHandler(BB);
1226 CleanupHandlerMap[BB] = Action;
1230 // This function searches starting with the input block for the next block that
1231 // contains code that is not part of a catch handler and would not be eliminated
1232 // during handler outlining.
1234 CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
1235 BasicBlock *EndBB) {
1236 // Here we will skip over the following:
1238 // landing pad prolog:
1240 // Unconditional branches
1242 // Selector dispatch
1246 // Anything else marks the start of an interesting block
1248 BasicBlock *BB = StartBB;
1249 // Anything other than an unconditional branch will kick us out of this loop
1250 // one way or another.
1252 // If we've already scanned this block, don't scan it again. If it is
1253 // a cleanup block, there will be an action in the CleanupHandlerMap.
1254 // If we've scanned it and it is not a cleanup block, there will be a
1255 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1256 // be no entry in the CleanupHandlerMap. We must call count() first to
1257 // avoid creating a null entry for blocks we haven't scanned.
1258 if (CleanupHandlerMap.count(BB)) {
1259 if (auto *Action = CleanupHandlerMap[BB]) {
1260 return cast<CleanupHandler>(Action);
1262 // Here we handle the case where the cleanup handler map contains a
1263 // value for this block but the value is a nullptr. This means that
1264 // we have previously analyzed the block and determined that it did
1265 // not contain any cleanup code. Based on the earlier analysis, we
1266 // know the the block must end in either an unconditional branch, a
1267 // resume or a conditional branch that is predicated on a comparison
1268 // with a selector. Either the resume or the selector dispatch
1269 // would terminate the search for cleanup code, so the unconditional
1270 // branch is the only case for which we might need to continue
1275 if (!match(BB->getTerminator(), m_UnconditionalBr(SuccBB)))
1282 // Create an entry in the cleanup handler map for this block. Initially
1283 // we create an entry that says this isn't a cleanup block. If we find
1284 // cleanup code, the caller will replace this entry.
1285 CleanupHandlerMap[BB] = nullptr;
1287 TerminatorInst *Terminator = BB->getTerminator();
1289 // Landing pad blocks have extra instructions we need to accept.
1290 LandingPadMap *LPadMap = nullptr;
1291 if (BB->isLandingPad()) {
1292 LandingPadInst *LPad = BB->getLandingPadInst();
1293 LPadMap = &LPadMaps[LPad];
1294 if (!LPadMap->isInitialized())
1295 LPadMap->mapLandingPad(LPad);
1298 // Look for the bare resume pattern:
1299 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
1300 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
1301 // resume { i8*, i32 } %lpad.val2
1302 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
1303 InsertValueInst *Insert1 = nullptr;
1304 InsertValueInst *Insert2 = nullptr;
1305 Value *ResumeVal = Resume->getOperand(0);
1306 // If there is only one landingpad, we may use the lpad directly with no
1308 if (isa<LandingPadInst>(ResumeVal))
1310 if (!isa<PHINode>(ResumeVal)) {
1311 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
1313 return createCleanupHandler(CleanupHandlerMap, BB);
1314 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
1316 return createCleanupHandler(CleanupHandlerMap, BB);
1318 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1320 Instruction *Inst = II;
1321 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1323 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
1325 if (!Inst->hasOneUse() ||
1326 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
1327 return createCleanupHandler(CleanupHandlerMap, BB);
1333 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
1334 if (Branch && Branch->isConditional()) {
1335 // Look for the selector dispatch.
1336 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
1337 // %matches = icmp eq i32 %sel, %2
1338 // br i1 %matches, label %catch14, label %eh.resume
1339 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
1340 if (!Compare || !Compare->isEquality())
1341 return createCleanupHandler(CleanupHandlerMap, BB);
1342 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
1345 Instruction *Inst = II;
1346 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1348 if (Inst == Compare || Inst == Branch)
1350 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1352 return createCleanupHandler(CleanupHandlerMap, BB);
1354 // The selector dispatch block should always terminate our search.
1355 assert(BB == EndBB);
1359 // Anything else is either a catch block or interesting cleanup code.
1360 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(),
1363 Instruction *Inst = II;
1364 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1366 // Unconditional branches fall through to this loop.
1369 // If this is a catch block, there is no cleanup code to be found.
1370 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1372 // Anything else makes this interesting cleanup code.
1373 return createCleanupHandler(CleanupHandlerMap, BB);
1376 // Only unconditional branches in empty blocks should get this far.
1377 assert(Branch && Branch->isUnconditional());
1380 BB = Branch->getSuccessor(0);