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 // TinyPtrVector cannot hold nullptr, so we need our own sentinel that isn't
57 AllocaInst *getCatchObjectSentinel() {
58 return static_cast<AllocaInst *>(nullptr) + 1;
61 typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
63 class LandingPadActions;
66 typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
67 typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
69 class WinEHPrepare : public FunctionPass {
71 static char ID; // Pass identification, replacement for typeid.
72 WinEHPrepare(const TargetMachine *TM = nullptr)
73 : FunctionPass(ID), DT(nullptr) {}
75 bool runOnFunction(Function &Fn) override;
77 bool doFinalization(Module &M) override;
79 void getAnalysisUsage(AnalysisUsage &AU) const override;
81 const char *getPassName() const override {
82 return "Windows exception handling preparation";
86 bool prepareExceptionHandlers(Function &F,
87 SmallVectorImpl<LandingPadInst *> &LPads);
88 void promoteLandingPadValues(LandingPadInst *LPad);
89 void completeNestedLandingPad(Function *ParentFn,
90 LandingPadInst *OutlinedLPad,
91 const LandingPadInst *OriginalLPad,
92 FrameVarInfoMap &VarInfo);
93 bool outlineHandler(ActionHandler *Action, Function *SrcFn,
94 LandingPadInst *LPad, BasicBlock *StartBB,
95 FrameVarInfoMap &VarInfo);
96 void addStubInvokeToHandlerIfNeeded(Function *Handler, Value *PersonalityFn);
98 void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
99 CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
100 VisitedBlockSet &VisitedBlocks);
101 CleanupHandler *findCleanupHandler(BasicBlock *StartBB, BasicBlock *EndBB);
103 void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
105 // All fields are reset by runOnFunction.
107 EHPersonality Personality;
108 CatchHandlerMapTy CatchHandlerMap;
109 CleanupHandlerMapTy CleanupHandlerMap;
110 DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
112 // This maps landing pad instructions found in outlined handlers to
113 // the landing pad instruction in the parent function from which they
114 // were cloned. The cloned/nested landing pad is used as the key
115 // because the landing pad may be cloned into multiple handlers.
116 // This map will be used to add the llvm.eh.actions call to the nested
117 // landing pads after all handlers have been outlined.
118 DenseMap<LandingPadInst *, const LandingPadInst *> NestedLPtoOriginalLP;
120 // This maps blocks in the parent function which are destinations of
121 // catch handlers to cloned blocks in (other) outlined handlers. This
122 // handles the case where a nested landing pads has a catch handler that
123 // returns to a handler function rather than the parent function.
124 // The original block is used as the key here because there should only
125 // ever be one handler function from which the cloned block is not pruned.
126 // The original block will be pruned from the parent function after all
127 // handlers have been outlined. This map will be used to adjust the
128 // return instructions of handlers which return to the block that was
129 // outlined into a handler. This is done after all handlers have been
130 // outlined but before the outlined code is pruned from the parent function.
131 DenseMap<const BasicBlock *, BasicBlock *> LPadTargetBlocks;
134 class WinEHFrameVariableMaterializer : public ValueMaterializer {
136 WinEHFrameVariableMaterializer(Function *OutlinedFn,
137 FrameVarInfoMap &FrameVarInfo);
138 ~WinEHFrameVariableMaterializer() {}
140 virtual Value *materializeValueFor(Value *V) override;
142 void escapeCatchObject(Value *V);
145 FrameVarInfoMap &FrameVarInfo;
149 class LandingPadMap {
151 LandingPadMap() : OriginLPad(nullptr) {}
152 void mapLandingPad(const LandingPadInst *LPad);
154 bool isInitialized() { return OriginLPad != nullptr; }
156 bool isOriginLandingPadBlock(const BasicBlock *BB) const;
157 bool isLandingPadSpecificInst(const Instruction *Inst) const;
159 void remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
160 Value *SelectorValue) const;
163 const LandingPadInst *OriginLPad;
164 // We will normally only see one of each of these instructions, but
165 // if more than one occurs for some reason we can handle that.
166 TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
167 TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
170 class WinEHCloningDirectorBase : public CloningDirector {
172 WinEHCloningDirectorBase(Function *HandlerFn, FrameVarInfoMap &VarInfo,
173 LandingPadMap &LPadMap)
174 : Materializer(HandlerFn, VarInfo),
175 SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
176 Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
179 CloningAction handleInstruction(ValueToValueMapTy &VMap,
180 const Instruction *Inst,
181 BasicBlock *NewBB) override;
183 virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
184 const Instruction *Inst,
185 BasicBlock *NewBB) = 0;
186 virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
187 const Instruction *Inst,
188 BasicBlock *NewBB) = 0;
189 virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
190 const Instruction *Inst,
191 BasicBlock *NewBB) = 0;
192 virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
193 const InvokeInst *Invoke,
194 BasicBlock *NewBB) = 0;
195 virtual CloningAction handleResume(ValueToValueMapTy &VMap,
196 const ResumeInst *Resume,
197 BasicBlock *NewBB) = 0;
198 virtual CloningAction handleLandingPad(ValueToValueMapTy &VMap,
199 const LandingPadInst *LPad,
200 BasicBlock *NewBB) = 0;
202 ValueMaterializer *getValueMaterializer() override { return &Materializer; }
205 WinEHFrameVariableMaterializer Materializer;
206 Type *SelectorIDType;
208 LandingPadMap &LPadMap;
211 class WinEHCatchDirector : public WinEHCloningDirectorBase {
214 Function *CatchFn, Value *Selector, FrameVarInfoMap &VarInfo,
215 LandingPadMap &LPadMap,
216 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPads)
217 : WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
218 CurrentSelector(Selector->stripPointerCasts()),
219 ExceptionObjectVar(nullptr), NestedLPtoOriginalLP(NestedLPads) {}
221 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
222 const Instruction *Inst,
223 BasicBlock *NewBB) override;
224 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
225 BasicBlock *NewBB) override;
226 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
227 const Instruction *Inst,
228 BasicBlock *NewBB) override;
229 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
230 BasicBlock *NewBB) override;
231 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
232 BasicBlock *NewBB) override;
233 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
234 const LandingPadInst *LPad,
235 BasicBlock *NewBB) override;
237 Value *getExceptionVar() { return ExceptionObjectVar; }
238 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
241 Value *CurrentSelector;
243 Value *ExceptionObjectVar;
244 TinyPtrVector<BasicBlock *> ReturnTargets;
246 // This will be a reference to the field of the same name in the WinEHPrepare
247 // object which instantiates this WinEHCatchDirector object.
248 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPtoOriginalLP;
251 class WinEHCleanupDirector : public WinEHCloningDirectorBase {
253 WinEHCleanupDirector(Function *CleanupFn, FrameVarInfoMap &VarInfo,
254 LandingPadMap &LPadMap)
255 : WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
257 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
258 const Instruction *Inst,
259 BasicBlock *NewBB) override;
260 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
261 BasicBlock *NewBB) override;
262 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
263 const Instruction *Inst,
264 BasicBlock *NewBB) override;
265 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
266 BasicBlock *NewBB) override;
267 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
268 BasicBlock *NewBB) override;
269 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
270 const LandingPadInst *LPad,
271 BasicBlock *NewBB) override;
274 class LandingPadActions {
276 LandingPadActions() : HasCleanupHandlers(false) {}
278 void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
279 void insertCleanupHandler(CleanupHandler *Action) {
280 Actions.push_back(Action);
281 HasCleanupHandlers = true;
284 bool includesCleanup() const { return HasCleanupHandlers; }
286 SmallVectorImpl<ActionHandler *> &actions() { return Actions; }
287 SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
288 SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
291 // Note that this class does not own the ActionHandler objects in this vector.
292 // The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
293 // in the WinEHPrepare class.
294 SmallVector<ActionHandler *, 4> Actions;
295 bool HasCleanupHandlers;
298 } // end anonymous namespace
300 char WinEHPrepare::ID = 0;
301 INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
304 FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
305 return new WinEHPrepare(TM);
308 // FIXME: Remove this once the backend can handle the prepared IR.
310 SEHPrepare("sehprepare", cl::Hidden,
311 cl::desc("Prepare functions with SEH personalities"));
313 bool WinEHPrepare::runOnFunction(Function &Fn) {
314 SmallVector<LandingPadInst *, 4> LPads;
315 SmallVector<ResumeInst *, 4> Resumes;
316 for (BasicBlock &BB : Fn) {
317 if (auto *LP = BB.getLandingPadInst())
319 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
320 Resumes.push_back(Resume);
323 // No need to prepare functions that lack landing pads.
327 // Classify the personality to see what kind of preparation we need.
328 Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
330 // Do nothing if this is not an MSVC personality.
331 if (!isMSVCEHPersonality(Personality))
334 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
336 if (isAsynchronousEHPersonality(Personality) && !SEHPrepare) {
337 // Replace all resume instructions with unreachable.
338 // FIXME: Remove this once the backend can handle the prepared IR.
339 for (ResumeInst *Resume : Resumes) {
340 IRBuilder<>(Resume).CreateUnreachable();
341 Resume->eraseFromParent();
346 // If there were any landing pads, prepareExceptionHandlers will make changes.
347 prepareExceptionHandlers(Fn, LPads);
351 bool WinEHPrepare::doFinalization(Module &M) { return false; }
353 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
354 AU.addRequired<DominatorTreeWrapperPass>();
357 bool WinEHPrepare::prepareExceptionHandlers(
358 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
359 // These containers are used to re-map frame variables that are used in
360 // outlined catch and cleanup handlers. They will be populated as the
361 // handlers are outlined.
362 FrameVarInfoMap FrameVarInfo;
364 bool HandlersOutlined = false;
366 Module *M = F.getParent();
367 LLVMContext &Context = M->getContext();
369 // Create a new function to receive the handler contents.
370 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
371 Type *Int32Type = Type::getInt32Ty(Context);
372 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
374 for (LandingPadInst *LPad : LPads) {
375 // Look for evidence that this landingpad has already been processed.
376 bool LPadHasActionList = false;
377 BasicBlock *LPadBB = LPad->getParent();
378 for (Instruction &Inst : *LPadBB) {
379 if (auto *IntrinCall = dyn_cast<IntrinsicInst>(&Inst)) {
380 if (IntrinCall->getIntrinsicID() == Intrinsic::eh_actions) {
381 LPadHasActionList = true;
385 // FIXME: This is here to help with the development of nested landing pad
386 // outlining. It should be removed when that is finished.
387 if (isa<UnreachableInst>(Inst)) {
388 LPadHasActionList = true;
393 // If we've already outlined the handlers for this landingpad,
394 // there's nothing more to do here.
395 if (LPadHasActionList)
398 // If either of the values in the aggregate returned by the landing pad is
399 // extracted and stored to memory, promote the stored value to a register.
400 promoteLandingPadValues(LPad);
402 LandingPadActions Actions;
403 mapLandingPadBlocks(LPad, Actions);
405 for (ActionHandler *Action : Actions) {
406 if (Action->hasBeenProcessed())
408 BasicBlock *StartBB = Action->getStartBlock();
410 // SEH doesn't do any outlining for catches. Instead, pass the handler
411 // basic block addr to llvm.eh.actions and list the block as a return
413 if (isAsynchronousEHPersonality(Personality)) {
414 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
415 processSEHCatchHandler(CatchAction, StartBB);
416 HandlersOutlined = true;
421 if (outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo)) {
422 HandlersOutlined = true;
424 } // End for each Action
426 // FIXME: We need a guard against partially outlined functions.
427 if (!HandlersOutlined)
430 // Replace the landing pad with a new llvm.eh.action based landing pad.
431 BasicBlock *NewLPadBB = BasicBlock::Create(Context, "lpad", &F, LPadBB);
432 assert(!isa<PHINode>(LPadBB->begin()));
433 auto *NewLPad = cast<LandingPadInst>(LPad->clone());
434 NewLPadBB->getInstList().push_back(NewLPad);
435 while (!pred_empty(LPadBB)) {
436 auto *pred = *pred_begin(LPadBB);
437 InvokeInst *Invoke = cast<InvokeInst>(pred->getTerminator());
438 Invoke->setUnwindDest(NewLPadBB);
441 // Replace the mapping of any nested landing pad that previously mapped
442 // to this landing pad with a referenced to the cloned version.
443 for (auto &LPadPair : NestedLPtoOriginalLP) {
444 const LandingPadInst *OriginalLPad = LPadPair.second;
445 if (OriginalLPad == LPad) {
446 LPadPair.second = NewLPad;
450 // Replace uses of the old lpad in phis with this block and delete the old
452 LPadBB->replaceSuccessorsPhiUsesWith(NewLPadBB);
453 LPadBB->getTerminator()->eraseFromParent();
454 new UnreachableInst(LPadBB->getContext(), LPadBB);
456 // Add a call to describe the actions for this landing pad.
457 std::vector<Value *> ActionArgs;
458 for (ActionHandler *Action : Actions) {
459 // Action codes from docs are: 0 cleanup, 1 catch.
460 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
461 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
462 ActionArgs.push_back(CatchAction->getSelector());
463 // Find the frame escape index of the exception object alloca in the
465 int FrameEscapeIdx = -1;
466 Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
467 if (EHObj && !isa<ConstantPointerNull>(EHObj)) {
468 auto I = FrameVarInfo.find(EHObj);
469 assert(I != FrameVarInfo.end() &&
470 "failed to map llvm.eh.begincatch var");
471 FrameEscapeIdx = std::distance(FrameVarInfo.begin(), I);
473 ActionArgs.push_back(ConstantInt::get(Int32Type, FrameEscapeIdx));
475 ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
477 ActionArgs.push_back(Action->getHandlerBlockOrFunc());
480 CallInst::Create(ActionIntrin, ActionArgs, "recover", NewLPadBB);
482 // Add an indirect branch listing possible successors of the catch handlers.
483 IndirectBrInst *Branch = IndirectBrInst::Create(Recover, 0, NewLPadBB);
484 for (ActionHandler *Action : Actions) {
485 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
486 for (auto *Target : CatchAction->getReturnTargets()) {
487 Branch->addDestination(Target);
491 } // End for each landingpad
493 // If nothing got outlined, there is no more processing to be done.
494 if (!HandlersOutlined)
497 // Replace any nested landing pad stubs with the correct action handler.
498 // This must be done before we remove unreachable blocks because it
499 // cleans up references to outlined blocks that will be deleted.
500 for (auto &LPadPair : NestedLPtoOriginalLP)
501 completeNestedLandingPad(&F, LPadPair.first, LPadPair.second, FrameVarInfo);
502 NestedLPtoOriginalLP.clear();
504 F.addFnAttr("wineh-parent", F.getName());
506 // Delete any blocks that were only used by handlers that were outlined above.
507 removeUnreachableBlocks(F);
509 BasicBlock *Entry = &F.getEntryBlock();
510 IRBuilder<> Builder(F.getParent()->getContext());
511 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
513 Function *FrameEscapeFn =
514 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
515 Function *RecoverFrameFn =
516 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
518 // Finally, replace all of the temporary allocas for frame variables used in
519 // the outlined handlers with calls to llvm.framerecover.
520 BasicBlock::iterator II = Entry->getFirstInsertionPt();
521 Instruction *AllocaInsertPt = II;
522 SmallVector<Value *, 8> AllocasToEscape;
523 for (auto &VarInfoEntry : FrameVarInfo) {
524 Value *ParentVal = VarInfoEntry.first;
525 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
527 // If the mapped value isn't already an alloca, we need to spill it if it
528 // is a computed value or copy it if it is an argument.
529 AllocaInst *ParentAlloca = dyn_cast<AllocaInst>(ParentVal);
531 if (auto *Arg = dyn_cast<Argument>(ParentVal)) {
532 // Lower this argument to a copy and then demote that to the stack.
533 // We can't just use the argument location because the handler needs
534 // it to be in the frame allocation block.
535 // Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction.
536 Value *TrueValue = ConstantInt::getTrue(Context);
537 Value *UndefValue = UndefValue::get(Arg->getType());
539 SelectInst::Create(TrueValue, Arg, UndefValue,
540 Arg->getName() + ".tmp", AllocaInsertPt);
541 Arg->replaceAllUsesWith(SI);
542 // Reset the select operand, because it was clobbered by the RAUW above.
543 SI->setOperand(1, Arg);
544 ParentAlloca = DemoteRegToStack(*SI, true, SI);
545 } else if (auto *PN = dyn_cast<PHINode>(ParentVal)) {
546 ParentAlloca = DemotePHIToStack(PN, AllocaInsertPt);
548 Instruction *ParentInst = cast<Instruction>(ParentVal);
549 // FIXME: This is a work-around to temporarily handle the case where an
550 // instruction that is only used in handlers is not sunk.
551 // Without uses, DemoteRegToStack would just eliminate the value.
552 // This will fail if ParentInst is an invoke.
553 if (ParentInst->getNumUses() == 0) {
554 BasicBlock::iterator InsertPt = ParentInst;
557 new AllocaInst(ParentInst->getType(), nullptr,
558 ParentInst->getName() + ".reg2mem", AllocaInsertPt);
559 new StoreInst(ParentInst, ParentAlloca, InsertPt);
561 ParentAlloca = DemoteRegToStack(*ParentInst, true, AllocaInsertPt);
566 // FIXME: We should try to sink unescaped allocas from the parent frame into
567 // the child frame. If the alloca is escaped, we have to use the lifetime
568 // markers to ensure that the alloca is only live within the child frame.
570 // Add this alloca to the list of things to escape.
571 AllocasToEscape.push_back(ParentAlloca);
573 // Next replace all outlined allocas that are mapped to it.
574 for (AllocaInst *TempAlloca : Allocas) {
575 if (TempAlloca == getCatchObjectSentinel())
576 continue; // Skip catch parameter sentinels.
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 // Clean up the handler action maps we created for this function
605 DeleteContainerSeconds(CatchHandlerMap);
606 CatchHandlerMap.clear();
607 DeleteContainerSeconds(CleanupHandlerMap);
608 CleanupHandlerMap.clear();
610 return HandlersOutlined;
613 void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
614 // If the return values of the landing pad instruction are extracted and
615 // stored to memory, we want to promote the store locations to reg values.
616 SmallVector<AllocaInst *, 2> EHAllocas;
618 // The landingpad instruction returns an aggregate value. Typically, its
619 // value will be passed to a pair of extract value instructions and the
620 // results of those extracts are often passed to store instructions.
621 // In unoptimized code the stored value will often be loaded and then stored
623 for (auto *U : LPad->users()) {
624 ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
628 for (auto *EU : Extract->users()) {
629 if (auto *Store = dyn_cast<StoreInst>(EU)) {
630 auto *AV = cast<AllocaInst>(Store->getPointerOperand());
631 EHAllocas.push_back(AV);
636 // We can't do this without a dominator tree.
639 if (!EHAllocas.empty()) {
640 PromoteMemToReg(EHAllocas, *DT);
645 void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,
646 LandingPadInst *OutlinedLPad,
647 const LandingPadInst *OriginalLPad,
648 FrameVarInfoMap &FrameVarInfo) {
649 // Get the nested block and erase the unreachable instruction that was
650 // temporarily inserted as its terminator.
651 LLVMContext &Context = ParentFn->getContext();
652 BasicBlock *OutlinedBB = OutlinedLPad->getParent();
653 assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
654 OutlinedBB->getTerminator()->eraseFromParent();
655 // That should leave OutlinedLPad as the last instruction in its block.
656 assert(&OutlinedBB->back() == OutlinedLPad);
658 // The original landing pad will have already had its action intrinsic
659 // built by the outlining loop. We need to clone that into the outlined
660 // location. It may also be necessary to add references to the exception
661 // variables to the outlined handler in which this landing pad is nested
662 // and remap return instructions in the nested handlers that should return
663 // to an address in the outlined handler.
664 Function *OutlinedHandlerFn = OutlinedBB->getParent();
665 BasicBlock::const_iterator II = OriginalLPad;
667 // The instruction after the landing pad should now be a call to eh.actions.
668 const Instruction *Recover = II;
669 assert(match(Recover, m_Intrinsic<Intrinsic::eh_actions>()));
670 IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover->clone());
672 // Remap the exception variables into the outlined function.
673 WinEHFrameVariableMaterializer Materializer(OutlinedHandlerFn, FrameVarInfo);
674 SmallVector<BlockAddress *, 4> ActionTargets;
675 SmallVector<ActionHandler *, 4> ActionList;
676 parseEHActions(EHActions, ActionList);
677 for (auto *Action : ActionList) {
678 auto *Catch = dyn_cast<CatchHandler>(Action);
681 // The dyn_cast to function here selects C++ catch handlers and skips
682 // SEH catch handlers.
683 auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
686 // Visit all the return instructions, looking for places that return
687 // to a location within OutlinedHandlerFn.
688 for (BasicBlock &NestedHandlerBB : *Handler) {
689 auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
693 // Handler functions must always return a block address.
694 BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
695 // The original target will have been in the main parent function,
696 // but if it is the address of a block that has been outlined, it
697 // should be a block that was outlined into OutlinedHandlerFn.
698 assert(BA->getFunction() == ParentFn);
700 // Ignore targets that aren't part of OutlinedHandlerFn.
701 if (!LPadTargetBlocks.count(BA->getBasicBlock()))
704 // If the return value is the address ofF a block that we
705 // previously outlined into the parent handler function, replace
706 // the return instruction and add the mapped target to the list
707 // of possible return addresses.
708 BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
709 assert(MappedBB->getParent() == OutlinedHandlerFn);
710 BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
711 Ret->eraseFromParent();
712 ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
713 ActionTargets.push_back(NewBA);
716 DeleteContainerPointers(ActionList);
718 OutlinedBB->getInstList().push_back(EHActions);
720 // Insert an indirect branch into the outlined landing pad BB.
721 IndirectBrInst *IBr = IndirectBrInst::Create(EHActions, 0, OutlinedBB);
722 // Add the previously collected action targets.
723 for (auto *Target : ActionTargets)
724 IBr->addDestination(Target->getBasicBlock());
727 // This function examines a block to determine whether the block ends with a
728 // conditional branch to a catch handler based on a selector comparison.
729 // This function is used both by the WinEHPrepare::findSelectorComparison() and
730 // WinEHCleanupDirector::handleTypeIdFor().
731 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
732 Constant *&Selector, BasicBlock *&NextBB) {
733 ICmpInst::Predicate Pred;
734 BasicBlock *TBB, *FBB;
737 if (!match(BB->getTerminator(),
738 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
742 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
743 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
746 if (Pred == CmpInst::ICMP_EQ) {
752 if (Pred == CmpInst::ICMP_NE) {
761 static BasicBlock *createStubLandingPad(Function *Handler,
762 Value *PersonalityFn) {
763 // FIXME: Finish this!
764 LLVMContext &Context = Handler->getContext();
765 BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
766 Handler->getBasicBlockList().push_back(StubBB);
767 IRBuilder<> Builder(StubBB);
768 LandingPadInst *LPad = Builder.CreateLandingPad(
769 llvm::StructType::get(Type::getInt8PtrTy(Context),
770 Type::getInt32Ty(Context), nullptr),
772 LPad->setCleanup(true);
773 Builder.CreateUnreachable();
777 // Cycles through the blocks in an outlined handler function looking for an
778 // invoke instruction and inserts an invoke of llvm.donothing with an empty
779 // landing pad if none is found. The code that generates the .xdata tables for
780 // the handler needs at least one landing pad to identify the parent function's
782 void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler,
783 Value *PersonalityFn) {
784 ReturnInst *Ret = nullptr;
785 for (BasicBlock &BB : *Handler) {
786 TerminatorInst *Terminator = BB.getTerminator();
787 // If we find an invoke, there is nothing to be done.
788 auto *II = dyn_cast<InvokeInst>(Terminator);
791 // If we've already recorded a return instruction, keep looking for invokes.
794 // If we haven't recorded a return instruction yet, try this terminator.
795 Ret = dyn_cast<ReturnInst>(Terminator);
798 // If we got this far, the handler contains no invokes. We should have seen
799 // at least one return. We'll insert an invoke of llvm.donothing ahead of
802 BasicBlock *OldRetBB = Ret->getParent();
803 BasicBlock *NewRetBB = SplitBlock(OldRetBB, Ret);
804 // SplitBlock adds an unconditional branch instruction at the end of the
805 // parent block. We want to replace that with an invoke call, so we can
807 OldRetBB->getTerminator()->eraseFromParent();
808 BasicBlock *StubLandingPad = createStubLandingPad(Handler, PersonalityFn);
810 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
811 InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
814 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
815 LandingPadInst *LPad, BasicBlock *StartBB,
816 FrameVarInfoMap &VarInfo) {
817 Module *M = SrcFn->getParent();
818 LLVMContext &Context = M->getContext();
820 // Create a new function to receive the handler contents.
821 Type *Int8PtrType = Type::getInt8PtrTy(Context);
822 std::vector<Type *> ArgTys;
823 ArgTys.push_back(Int8PtrType);
824 ArgTys.push_back(Int8PtrType);
826 if (Action->getType() == Catch) {
827 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
828 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
829 SrcFn->getName() + ".catch", M);
831 FunctionType *FnType =
832 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
833 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
834 SrcFn->getName() + ".cleanup", M);
837 Handler->addFnAttr("wineh-parent", SrcFn->getName());
839 // Generate a standard prolog to setup the frame recovery structure.
840 IRBuilder<> Builder(Context);
841 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
842 Handler->getBasicBlockList().push_front(Entry);
843 Builder.SetInsertPoint(Entry);
844 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
846 std::unique_ptr<WinEHCloningDirectorBase> Director;
848 ValueToValueMapTy VMap;
850 LandingPadMap &LPadMap = LPadMaps[LPad];
851 if (!LPadMap.isInitialized())
852 LPadMap.mapLandingPad(LPad);
853 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
854 Constant *Sel = CatchAction->getSelector();
855 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap,
856 NestedLPtoOriginalLP));
857 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
858 ConstantInt::get(Type::getInt32Ty(Context), 1));
860 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
861 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
862 UndefValue::get(Type::getInt32Ty(Context)));
865 SmallVector<ReturnInst *, 8> Returns;
866 ClonedCodeInfo OutlinedFunctionInfo;
868 // If the start block contains PHI nodes, we need to map them.
869 BasicBlock::iterator II = StartBB->begin();
870 while (auto *PN = dyn_cast<PHINode>(II)) {
872 // Look for PHI values that we have already mapped (such as the selector).
873 for (Value *Val : PN->incoming_values()) {
874 if (VMap.count(Val)) {
875 VMap[PN] = VMap[Val];
879 // If we didn't find a match for this value, map it as an undef.
881 VMap[PN] = UndefValue::get(PN->getType());
886 // Skip over PHIs and, if applicable, landingpad instructions.
887 II = StartBB->getFirstInsertionPt();
889 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
890 /*ModuleLevelChanges=*/false, Returns, "",
891 &OutlinedFunctionInfo, Director.get());
893 // Move all the instructions in the first cloned block into our entry block.
894 BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
895 Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
896 FirstClonedBB->eraseFromParent();
898 // Make sure we can identify the handler's personality later.
899 addStubInvokeToHandlerIfNeeded(Handler, LPad->getPersonalityFn());
901 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
902 WinEHCatchDirector *CatchDirector =
903 reinterpret_cast<WinEHCatchDirector *>(Director.get());
904 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
905 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
907 // Look for blocks that are not part of the landing pad that we just
908 // outlined but terminate with a call to llvm.eh.endcatch and a
909 // branch to a block that is in the handler we just outlined.
910 // These blocks will be part of a nested landing pad that intends to
911 // return to an address in this handler. This case is best handled
912 // after both landing pads have been outlined, so for now we'll just
913 // save the association of the blocks in LPadTargetBlocks. The
914 // return instructions which are created from these branches will be
915 // replaced after all landing pads have been outlined.
916 for (const auto &MapEntry : VMap) {
917 // VMap maps all values and blocks that were just cloned, but dead
918 // blocks which were pruned will map to nullptr.
919 if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
921 const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
922 for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
923 auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
924 if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
926 BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
928 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
929 // This would indicate that a nested landing pad wants to return
930 // to a block that is outlined into two different handlers.
931 assert(!LPadTargetBlocks.count(MappedBB));
932 LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
936 } // End if (CatchAction)
938 Action->setHandlerBlockOrFunc(Handler);
943 /// This BB must end in a selector dispatch. All we need to do is pass the
944 /// handler block to llvm.eh.actions and list it as a possible indirectbr
946 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
947 BasicBlock *StartBB) {
948 BasicBlock *HandlerBB;
951 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
953 // If this was EH dispatch, this must be a conditional branch to the handler
955 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
956 // leading to crashes if some optimization hoists stuff here.
957 assert(CatchAction->getSelector() && HandlerBB &&
958 "expected catch EH dispatch");
960 // This must be a catch-all. Split the block after the landingpad.
961 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
963 StartBB->splitBasicBlock(StartBB->getFirstInsertionPt(), "catch.all");
965 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
966 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
967 CatchAction->setReturnTargets(Targets);
970 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
971 // Each instance of this class should only ever be used to map a single
973 assert(OriginLPad == nullptr || OriginLPad == LPad);
975 // If the landing pad has already been mapped, there's nothing more to do.
976 if (OriginLPad == LPad)
981 // The landingpad instruction returns an aggregate value. Typically, its
982 // value will be passed to a pair of extract value instructions and the
983 // results of those extracts will have been promoted to reg values before
984 // this routine is called.
985 for (auto *U : LPad->users()) {
986 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
989 assert(Extract->getNumIndices() == 1 &&
990 "Unexpected operation: extracting both landing pad values");
991 unsigned int Idx = *(Extract->idx_begin());
992 assert((Idx == 0 || Idx == 1) &&
993 "Unexpected operation: extracting an unknown landing pad element");
995 ExtractedEHPtrs.push_back(Extract);
996 } else if (Idx == 1) {
997 ExtractedSelectors.push_back(Extract);
1002 bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
1003 return BB->getLandingPadInst() == OriginLPad;
1006 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
1007 if (Inst == OriginLPad)
1009 for (auto *Extract : ExtractedEHPtrs) {
1010 if (Inst == Extract)
1013 for (auto *Extract : ExtractedSelectors) {
1014 if (Inst == Extract)
1020 void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
1021 Value *SelectorValue) const {
1022 // Remap all landing pad extract instructions to the specified values.
1023 for (auto *Extract : ExtractedEHPtrs)
1024 VMap[Extract] = EHPtrValue;
1025 for (auto *Extract : ExtractedSelectors)
1026 VMap[Extract] = SelectorValue;
1029 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
1030 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1031 // If this is one of the boilerplate landing pad instructions, skip it.
1032 // The instruction will have already been remapped in VMap.
1033 if (LPadMap.isLandingPadSpecificInst(Inst))
1034 return CloningDirector::SkipInstruction;
1036 // Nested landing pads will be cloned as stubs, with just the
1037 // landingpad instruction and an unreachable instruction. When
1038 // all landingpads have been outlined, we'll replace this with the
1039 // llvm.eh.actions call and indirect branch created when the
1040 // landing pad was outlined.
1041 if (auto *LPad = dyn_cast<LandingPadInst>(Inst)) {
1042 return handleLandingPad(VMap, LPad, NewBB);
1045 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
1046 return handleInvoke(VMap, Invoke, NewBB);
1048 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
1049 return handleResume(VMap, Resume, NewBB);
1051 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1052 return handleBeginCatch(VMap, Inst, NewBB);
1053 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1054 return handleEndCatch(VMap, Inst, NewBB);
1055 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1056 return handleTypeIdFor(VMap, Inst, NewBB);
1058 // Continue with the default cloning behavior.
1059 return CloningDirector::CloneInstruction;
1062 CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
1063 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1064 Instruction *NewInst = LPad->clone();
1065 if (LPad->hasName())
1066 NewInst->setName(LPad->getName());
1067 // Save this correlation for later processing.
1068 NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
1069 VMap[LPad] = NewInst;
1070 BasicBlock::InstListType &InstList = NewBB->getInstList();
1071 InstList.push_back(NewInst);
1072 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1073 return CloningDirector::StopCloningBB;
1076 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
1077 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1078 // The argument to the call is some form of the first element of the
1079 // landingpad aggregate value, but that doesn't matter. It isn't used
1081 // The second argument is an outparameter where the exception object will be
1082 // stored. Typically the exception object is a scalar, but it can be an
1083 // aggregate when catching by value.
1084 // FIXME: Leave something behind to indicate where the exception object lives
1085 // for this handler. Should it be part of llvm.eh.actions?
1086 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
1087 "llvm.eh.begincatch found while "
1088 "outlining catch handler.");
1089 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
1090 if (isa<ConstantPointerNull>(ExceptionObjectVar))
1091 return CloningDirector::SkipInstruction;
1092 assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
1093 "catch parameter is not static alloca");
1094 Materializer.escapeCatchObject(ExceptionObjectVar);
1095 return CloningDirector::SkipInstruction;
1098 CloningDirector::CloningAction
1099 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
1100 const Instruction *Inst, BasicBlock *NewBB) {
1101 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1102 // It might be interesting to track whether or not we are inside a catch
1103 // function, but that might make the algorithm more brittle than it needs
1106 // The end catch call can occur in one of two places: either in a
1107 // landingpad block that is part of the catch handlers exception mechanism,
1108 // or at the end of the catch block. However, a catch-all handler may call
1109 // end catch from the original landing pad. If the call occurs in a nested
1110 // landing pad block, we must skip it and continue so that the landing pad
1112 auto *ParentBB = IntrinCall->getParent();
1113 if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
1114 return CloningDirector::SkipInstruction;
1116 // If an end catch occurs anywhere else we want to terminate the handler
1117 // with a return to the code that follows the endcatch call. If the
1118 // next instruction is not an unconditional branch, we need to split the
1119 // block to provide a clear target for the return instruction.
1120 BasicBlock *ContinueBB;
1121 auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
1122 const BranchInst *Branch = dyn_cast<BranchInst>(Next);
1123 if (!Branch || !Branch->isUnconditional()) {
1124 // We're interrupting the cloning process at this location, so the
1125 // const_cast we're doing here will not cause a problem.
1126 ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
1127 const_cast<Instruction *>(cast<Instruction>(Next)));
1129 ContinueBB = Branch->getSuccessor(0);
1132 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
1133 ReturnTargets.push_back(ContinueBB);
1135 // We just added a terminator to the cloned block.
1136 // Tell the caller to stop processing the current basic block so that
1137 // the branch instruction will be skipped.
1138 return CloningDirector::StopCloningBB;
1141 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
1142 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1143 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1144 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1145 // This causes a replacement that will collapse the landing pad CFG based
1146 // on the filter function we intend to match.
1147 if (Selector == CurrentSelector)
1148 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
1150 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1151 // Tell the caller not to clone this instruction.
1152 return CloningDirector::SkipInstruction;
1155 CloningDirector::CloningAction
1156 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
1157 const InvokeInst *Invoke, BasicBlock *NewBB) {
1158 return CloningDirector::CloneInstruction;
1161 CloningDirector::CloningAction
1162 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
1163 const ResumeInst *Resume, BasicBlock *NewBB) {
1164 // Resume instructions shouldn't be reachable from catch handlers.
1165 // We still need to handle it, but it will be pruned.
1166 BasicBlock::InstListType &InstList = NewBB->getInstList();
1167 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1168 return CloningDirector::StopCloningBB;
1171 CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
1172 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1173 // The MS runtime will terminate the process if an exception occurs in a
1174 // cleanup handler, so we shouldn't encounter landing pads in the actual
1175 // cleanup code, but they may appear in catch blocks. Depending on where
1176 // we started cloning we may see one, but it will get dropped during dead
1178 Instruction *NewInst = new UnreachableInst(NewBB->getContext());
1179 VMap[LPad] = NewInst;
1180 BasicBlock::InstListType &InstList = NewBB->getInstList();
1181 InstList.push_back(NewInst);
1182 return CloningDirector::StopCloningBB;
1185 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1186 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1187 // Catch blocks within cleanup handlers will always be unreachable.
1188 // We'll insert an unreachable instruction now, but it will be pruned
1189 // before the cloning process is complete.
1190 BasicBlock::InstListType &InstList = NewBB->getInstList();
1191 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1192 return CloningDirector::StopCloningBB;
1195 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1196 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1197 // Cleanup handlers nested within catch handlers may begin with a call to
1198 // eh.endcatch. We can just ignore that instruction.
1199 return CloningDirector::SkipInstruction;
1202 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1203 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1204 // If we encounter a selector comparison while cloning a cleanup handler,
1205 // we want to stop cloning immediately. Anything after the dispatch
1206 // will be outlined into a different handler.
1207 BasicBlock *CatchHandler;
1210 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1211 CatchHandler, Selector, NextBB)) {
1212 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1213 return CloningDirector::StopCloningBB;
1215 // If eg.typeid.for is called for any other reason, it can be ignored.
1216 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1217 return CloningDirector::SkipInstruction;
1220 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1221 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1222 // All invokes in cleanup handlers can be replaced with calls.
1223 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1224 // Insert a normal call instruction...
1226 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1227 Invoke->getName(), NewBB);
1228 NewCall->setCallingConv(Invoke->getCallingConv());
1229 NewCall->setAttributes(Invoke->getAttributes());
1230 NewCall->setDebugLoc(Invoke->getDebugLoc());
1231 VMap[Invoke] = NewCall;
1233 // Insert an unconditional branch to the normal destination.
1234 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1236 // The unwind destination won't be cloned into the new function, so
1237 // we don't need to clean up its phi nodes.
1239 // We just added a terminator to the cloned block.
1240 // Tell the caller to stop processing the current basic block.
1241 return CloningDirector::StopCloningBB;
1244 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1245 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1246 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1248 // We just added a terminator to the cloned block.
1249 // Tell the caller to stop processing the current basic block so that
1250 // the branch instruction will be skipped.
1251 return CloningDirector::StopCloningBB;
1254 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1255 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1256 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1257 BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
1258 Builder.SetInsertPoint(EntryBB, EntryBB->getFirstInsertionPt());
1261 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1262 // If we're asked to materialize a value that is an instruction, we
1263 // temporarily create an alloca in the outlined function and add this
1264 // to the FrameVarInfo map. When all the outlining is complete, we'll
1265 // collect these into a structure, spilling non-alloca values in the
1266 // parent frame as necessary, and replace these temporary allocas with
1267 // GEPs referencing the frame allocation block.
1269 // If the value is an alloca, the mapping is direct.
1270 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1271 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1272 Builder.Insert(NewAlloca, AV->getName());
1273 FrameVarInfo[AV].push_back(NewAlloca);
1277 // For other types of instructions or arguments, we need an alloca based on
1278 // the value's type and a load of the alloca. The alloca will be replaced
1279 // by a GEP, but the load will stay. In the parent function, the value will
1280 // be spilled to a location in the frame allocation block.
1281 if (isa<Instruction>(V) || isa<Argument>(V)) {
1282 AllocaInst *NewAlloca =
1283 Builder.CreateAlloca(V->getType(), nullptr, "eh.temp.alloca");
1284 FrameVarInfo[V].push_back(NewAlloca);
1285 LoadInst *NewLoad = Builder.CreateLoad(NewAlloca, V->getName() + ".reload");
1289 // Don't materialize other values.
1293 void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
1294 // Catch parameter objects have to live in the parent frame. When we see a use
1295 // of a catch parameter, add a sentinel to the multimap to indicate that it's
1296 // used from another handler. This will prevent us from trying to sink the
1297 // alloca into the handler and ensure that the catch parameter is present in
1298 // the call to llvm.frameescape.
1299 FrameVarInfo[V].push_back(getCatchObjectSentinel());
1302 // This function maps the catch and cleanup handlers that are reachable from the
1303 // specified landing pad. The landing pad sequence will have this basic shape:
1305 // <cleanup handler>
1306 // <selector comparison>
1308 // <cleanup handler>
1309 // <selector comparison>
1311 // <cleanup handler>
1314 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1315 // any arbitrary control flow, but all paths through the cleanup code must
1316 // eventually reach the next selector comparison and no path can skip to a
1317 // different selector comparisons, though some paths may terminate abnormally.
1318 // Therefore, we will use a depth first search from the start of any given
1319 // cleanup block and stop searching when we find the next selector comparison.
1321 // If the landingpad instruction does not have a catch clause, we will assume
1322 // that any instructions other than selector comparisons and catch handlers can
1323 // be ignored. In practice, these will only be the boilerplate instructions.
1325 // The catch handlers may also have any control structure, but we are only
1326 // interested in the start of the catch handlers, so we don't need to actually
1327 // follow the flow of the catch handlers. The start of the catch handlers can
1328 // be located from the compare instructions, but they can be skipped in the
1329 // flow by following the contrary branch.
1330 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1331 LandingPadActions &Actions) {
1332 unsigned int NumClauses = LPad->getNumClauses();
1333 unsigned int HandlersFound = 0;
1334 BasicBlock *BB = LPad->getParent();
1336 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1338 if (NumClauses == 0) {
1339 // This landing pad contains only cleanup code.
1340 CleanupHandler *Action = new CleanupHandler(BB);
1341 CleanupHandlerMap[BB] = Action;
1342 Actions.insertCleanupHandler(Action);
1343 DEBUG(dbgs() << " Assuming cleanup code in block " << BB->getName()
1345 assert(LPad->isCleanup());
1349 VisitedBlockSet VisitedBlocks;
1351 while (HandlersFound != NumClauses) {
1352 BasicBlock *NextBB = nullptr;
1354 // See if the clause we're looking for is a catch-all.
1355 // If so, the catch begins immediately.
1356 if (isa<ConstantPointerNull>(LPad->getClause(HandlersFound))) {
1357 // The catch all must occur last.
1358 assert(HandlersFound == NumClauses - 1);
1360 // For C++ EH, check if there is any interesting cleanup code before we
1361 // begin the catch. This is important because cleanups cannot rethrow
1362 // exceptions but code called from catches can. For SEH, it isn't
1363 // important if some finally code before a catch-all is executed out of
1364 // line or after recovering from the exception.
1365 if (Personality == EHPersonality::MSVC_CXX) {
1366 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1367 // Add a cleanup entry to the list
1368 Actions.insertCleanupHandler(CleanupAction);
1369 DEBUG(dbgs() << " Found cleanup code in block "
1370 << CleanupAction->getStartBlock()->getName() << "\n");
1374 // Add the catch handler to the action list.
1375 CatchHandler *Action =
1376 new CatchHandler(BB, LPad->getClause(HandlersFound), nullptr);
1377 CatchHandlerMap[BB] = Action;
1378 Actions.insertCatchHandler(Action);
1379 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1382 // Once we reach a catch-all, don't expect to hit a resume instruction.
1387 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1388 // See if there is any interesting code executed before the dispatch.
1389 if (auto *CleanupAction =
1390 findCleanupHandler(BB, CatchAction->getStartBlock())) {
1391 // Add a cleanup entry to the list
1392 Actions.insertCleanupHandler(CleanupAction);
1393 DEBUG(dbgs() << " Found cleanup code in block "
1394 << CleanupAction->getStartBlock()->getName() << "\n");
1397 assert(CatchAction);
1400 // Add the catch handler to the action list.
1401 Actions.insertCatchHandler(CatchAction);
1402 DEBUG(dbgs() << " Found catch dispatch in block "
1403 << CatchAction->getStartBlock()->getName() << "\n");
1405 // Move on to the block after the catch handler.
1409 // If we didn't wind up in a catch-all, see if there is any interesting code
1410 // executed before the resume.
1411 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1412 // Add a cleanup entry to the list
1413 Actions.insertCleanupHandler(CleanupAction);
1414 DEBUG(dbgs() << " Found cleanup code in block "
1415 << CleanupAction->getStartBlock()->getName() << "\n");
1418 // It's possible that some optimization moved code into a landingpad that
1420 // previously being used for cleanup. If that happens, we need to execute
1422 // extra code from a cleanup handler.
1423 if (Actions.includesCleanup() && !LPad->isCleanup())
1424 LPad->setCleanup(true);
1427 // This function searches starting with the input block for the next
1428 // block that terminates with a branch whose condition is based on a selector
1429 // comparison. This may be the input block. See the mapLandingPadBlocks
1430 // comments for a discussion of control flow assumptions.
1432 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1433 BasicBlock *&NextBB,
1434 VisitedBlockSet &VisitedBlocks) {
1435 // See if we've already found a catch handler use it.
1436 // Call count() first to avoid creating a null entry for blocks
1437 // we haven't seen before.
1438 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1439 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1440 NextBB = Action->getNextBB();
1444 // VisitedBlocks applies only to the current search. We still
1445 // need to consider blocks that we've visited while mapping other
1447 VisitedBlocks.insert(BB);
1449 BasicBlock *CatchBlock = nullptr;
1450 Constant *Selector = nullptr;
1452 // If this is the first time we've visited this block from any landing pad
1453 // look to see if it is a selector dispatch block.
1454 if (!CatchHandlerMap.count(BB)) {
1455 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1456 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1457 CatchHandlerMap[BB] = Action;
1462 // Visit each successor, looking for the dispatch.
1463 // FIXME: We expect to find the dispatch quickly, so this will probably
1464 // work better as a breadth first search.
1465 for (BasicBlock *Succ : successors(BB)) {
1466 if (VisitedBlocks.count(Succ))
1469 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1476 // These are helper functions to combine repeated code from findCleanupHandler.
1477 static CleanupHandler *
1478 createCleanupHandler(CleanupHandlerMapTy &CleanupHandlerMap, BasicBlock *BB) {
1479 CleanupHandler *Action = new CleanupHandler(BB);
1480 CleanupHandlerMap[BB] = Action;
1484 // This function searches starting with the input block for the next block that
1485 // contains code that is not part of a catch handler and would not be eliminated
1486 // during handler outlining.
1488 CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
1489 BasicBlock *EndBB) {
1490 // Here we will skip over the following:
1492 // landing pad prolog:
1494 // Unconditional branches
1496 // Selector dispatch
1500 // Anything else marks the start of an interesting block
1502 BasicBlock *BB = StartBB;
1503 // Anything other than an unconditional branch will kick us out of this loop
1504 // one way or another.
1506 // If we've already scanned this block, don't scan it again. If it is
1507 // a cleanup block, there will be an action in the CleanupHandlerMap.
1508 // If we've scanned it and it is not a cleanup block, there will be a
1509 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1510 // be no entry in the CleanupHandlerMap. We must call count() first to
1511 // avoid creating a null entry for blocks we haven't scanned.
1512 if (CleanupHandlerMap.count(BB)) {
1513 if (auto *Action = CleanupHandlerMap[BB]) {
1514 return cast<CleanupHandler>(Action);
1516 // Here we handle the case where the cleanup handler map contains a
1517 // value for this block but the value is a nullptr. This means that
1518 // we have previously analyzed the block and determined that it did
1519 // not contain any cleanup code. Based on the earlier analysis, we
1520 // know the the block must end in either an unconditional branch, a
1521 // resume or a conditional branch that is predicated on a comparison
1522 // with a selector. Either the resume or the selector dispatch
1523 // would terminate the search for cleanup code, so the unconditional
1524 // branch is the only case for which we might need to continue
1529 if (!match(BB->getTerminator(), m_UnconditionalBr(SuccBB)))
1536 // Create an entry in the cleanup handler map for this block. Initially
1537 // we create an entry that says this isn't a cleanup block. If we find
1538 // cleanup code, the caller will replace this entry.
1539 CleanupHandlerMap[BB] = nullptr;
1541 TerminatorInst *Terminator = BB->getTerminator();
1543 // Landing pad blocks have extra instructions we need to accept.
1544 LandingPadMap *LPadMap = nullptr;
1545 if (BB->isLandingPad()) {
1546 LandingPadInst *LPad = BB->getLandingPadInst();
1547 LPadMap = &LPadMaps[LPad];
1548 if (!LPadMap->isInitialized())
1549 LPadMap->mapLandingPad(LPad);
1552 // Look for the bare resume pattern:
1553 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
1554 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
1555 // resume { i8*, i32 } %lpad.val2
1556 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
1557 InsertValueInst *Insert1 = nullptr;
1558 InsertValueInst *Insert2 = nullptr;
1559 Value *ResumeVal = Resume->getOperand(0);
1560 // If there is only one landingpad, we may use the lpad directly with no
1562 if (isa<LandingPadInst>(ResumeVal))
1564 if (!isa<PHINode>(ResumeVal)) {
1565 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
1567 return createCleanupHandler(CleanupHandlerMap, BB);
1568 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
1570 return createCleanupHandler(CleanupHandlerMap, BB);
1572 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1574 Instruction *Inst = II;
1575 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1577 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
1579 if (!Inst->hasOneUse() ||
1580 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
1581 return createCleanupHandler(CleanupHandlerMap, BB);
1587 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
1588 if (Branch && Branch->isConditional()) {
1589 // Look for the selector dispatch.
1590 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
1591 // %matches = icmp eq i32 %sel, %2
1592 // br i1 %matches, label %catch14, label %eh.resume
1593 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
1594 if (!Compare || !Compare->isEquality())
1595 return createCleanupHandler(CleanupHandlerMap, BB);
1596 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1598 Instruction *Inst = II;
1599 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1601 if (Inst == Compare || Inst == Branch)
1603 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1605 return createCleanupHandler(CleanupHandlerMap, BB);
1607 // The selector dispatch block should always terminate our search.
1608 assert(BB == EndBB);
1612 // Anything else is either a catch block or interesting cleanup code.
1613 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1615 Instruction *Inst = II;
1616 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1618 // Unconditional branches fall through to this loop.
1621 // If this is a catch block, there is no cleanup code to be found.
1622 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1624 // If this a nested landing pad, it may contain an endcatch call.
1625 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1627 // Anything else makes this interesting cleanup code.
1628 return createCleanupHandler(CleanupHandlerMap, BB);
1631 // Only unconditional branches in empty blocks should get this far.
1632 assert(Branch && Branch->isUnconditional());
1635 BB = Branch->getSuccessor(0);
1640 // This is a public function, declared in WinEHFuncInfo.h and is also
1641 // referenced by WinEHNumbering in FunctionLoweringInfo.cpp.
1642 void llvm::parseEHActions(const IntrinsicInst *II,
1643 SmallVectorImpl<ActionHandler *> &Actions) {
1644 for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
1645 uint64_t ActionKind =
1646 cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
1647 if (ActionKind == /*catch=*/1) {
1648 auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
1649 ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
1650 int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
1651 Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
1653 auto *CH = new CatchHandler(/*BB=*/nullptr, Selector, /*NextBB=*/nullptr);
1654 CH->setHandlerBlockOrFunc(Handler);
1655 CH->setExceptionVarIndex(EHObjIndexVal);
1656 Actions.push_back(CH);
1657 } else if (ActionKind == 0) {
1658 Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
1660 auto *CH = new CleanupHandler(/*BB=*/nullptr);
1661 CH->setHandlerBlockOrFunc(Handler);
1662 Actions.push_back(CH);
1664 llvm_unreachable("Expected either a catch or cleanup handler!");
1667 std::reverse(Actions.begin(), Actions.end());