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",
560 new StoreInst(ParentInst, ParentAlloca, InsertPt);
562 ParentAlloca = DemoteRegToStack(*ParentInst, true, AllocaInsertPt);
567 // FIXME: We should try to sink unescaped allocas from the parent frame into
568 // the child frame. If the alloca is escaped, we have to use the lifetime
569 // markers to ensure that the alloca is only live within the child frame.
571 // Add this alloca to the list of things to escape.
572 AllocasToEscape.push_back(ParentAlloca);
574 // Next replace all outlined allocas that are mapped to it.
575 for (AllocaInst *TempAlloca : Allocas) {
576 if (TempAlloca == getCatchObjectSentinel())
577 continue; // Skip catch parameter sentinels.
578 Function *HandlerFn = TempAlloca->getParent()->getParent();
579 // FIXME: Sink this GEP into the blocks where it is used.
580 Builder.SetInsertPoint(TempAlloca);
581 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
582 Value *RecoverArgs[] = {
583 Builder.CreateBitCast(&F, Int8PtrType, ""),
584 &(HandlerFn->getArgumentList().back()),
585 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
586 Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
587 // Add a pointer bitcast if the alloca wasn't an i8.
588 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
589 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
591 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
593 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
594 TempAlloca->removeFromParent();
595 RecoveredAlloca->takeName(TempAlloca);
598 } // End for each FrameVarInfo entry.
600 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
602 Builder.SetInsertPoint(&F.getEntryBlock().back());
603 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
605 // Clean up the handler action maps we created for this function
606 DeleteContainerSeconds(CatchHandlerMap);
607 CatchHandlerMap.clear();
608 DeleteContainerSeconds(CleanupHandlerMap);
609 CleanupHandlerMap.clear();
611 return HandlersOutlined;
614 void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
615 // If the return values of the landing pad instruction are extracted and
616 // stored to memory, we want to promote the store locations to reg values.
617 SmallVector<AllocaInst *, 2> EHAllocas;
619 // The landingpad instruction returns an aggregate value. Typically, its
620 // value will be passed to a pair of extract value instructions and the
621 // results of those extracts are often passed to store instructions.
622 // In unoptimized code the stored value will often be loaded and then stored
624 for (auto *U : LPad->users()) {
625 ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
629 for (auto *EU : Extract->users()) {
630 if (auto *Store = dyn_cast<StoreInst>(EU)) {
631 auto *AV = cast<AllocaInst>(Store->getPointerOperand());
632 EHAllocas.push_back(AV);
637 // We can't do this without a dominator tree.
640 if (!EHAllocas.empty()) {
641 PromoteMemToReg(EHAllocas, *DT);
646 void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,
647 LandingPadInst *OutlinedLPad,
648 const LandingPadInst *OriginalLPad,
649 FrameVarInfoMap &FrameVarInfo) {
650 // Get the nested block and erase the unreachable instruction that was
651 // temporarily inserted as its terminator.
652 LLVMContext &Context = ParentFn->getContext();
653 BasicBlock *OutlinedBB = OutlinedLPad->getParent();
654 assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
655 OutlinedBB->getTerminator()->eraseFromParent();
656 // That should leave OutlinedLPad as the last instruction in its block.
657 assert(&OutlinedBB->back() == OutlinedLPad);
659 // The original landing pad will have already had its action intrinsic
660 // built by the outlining loop. We need to clone that into the outlined
661 // location. It may also be necessary to add references to the exception
662 // variables to the outlined handler in which this landing pad is nested
663 // and remap return instructions in the nested handlers that should return
664 // to an address in the outlined handler.
665 Function *OutlinedHandlerFn = OutlinedBB->getParent();
666 BasicBlock::const_iterator II = OriginalLPad;
668 // The instruction after the landing pad should now be a call to eh.actions.
669 const Instruction *Recover = II;
670 assert(match(Recover, m_Intrinsic<Intrinsic::eh_actions>()));
671 IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover->clone());
673 // Remap the exception variables into the outlined function.
674 WinEHFrameVariableMaterializer Materializer(OutlinedHandlerFn, FrameVarInfo);
675 SmallVector<BlockAddress *, 4> ActionTargets;
676 SmallVector<ActionHandler *, 4> ActionList;
677 parseEHActions(EHActions, ActionList);
678 for (auto *Action : ActionList) {
679 auto *Catch = dyn_cast<CatchHandler>(Action);
682 // The dyn_cast to function here selects C++ catch handlers and skips
683 // SEH catch handlers.
684 auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
687 // Visit all the return instructions, looking for places that return
688 // to a location within OutlinedHandlerFn.
689 for (BasicBlock &NestedHandlerBB : *Handler) {
690 auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
694 // Handler functions must always return a block address.
695 BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
696 // The original target will have been in the main parent function,
697 // but if it is the address of a block that has been outlined, it
698 // should be a block that was outlined into OutlinedHandlerFn.
699 assert(BA->getFunction() == ParentFn);
701 // Ignore targets that aren't part of OutlinedHandlerFn.
702 if (!LPadTargetBlocks.count(BA->getBasicBlock()))
705 // If the return value is the address ofF a block that we
706 // previously outlined into the parent handler function, replace
707 // the return instruction and add the mapped target to the list
708 // of possible return addresses.
709 BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
710 assert(MappedBB->getParent() == OutlinedHandlerFn);
711 BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
712 Ret->eraseFromParent();
713 ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
714 ActionTargets.push_back(NewBA);
717 DeleteContainerPointers(ActionList);
719 OutlinedBB->getInstList().push_back(EHActions);
721 // Insert an indirect branch into the outlined landing pad BB.
722 IndirectBrInst *IBr = IndirectBrInst::Create(EHActions, 0, OutlinedBB);
723 // Add the previously collected action targets.
724 for (auto *Target : ActionTargets)
725 IBr->addDestination(Target->getBasicBlock());
728 // This function examines a block to determine whether the block ends with a
729 // conditional branch to a catch handler based on a selector comparison.
730 // This function is used both by the WinEHPrepare::findSelectorComparison() and
731 // WinEHCleanupDirector::handleTypeIdFor().
732 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
733 Constant *&Selector, BasicBlock *&NextBB) {
734 ICmpInst::Predicate Pred;
735 BasicBlock *TBB, *FBB;
738 if (!match(BB->getTerminator(),
739 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
743 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
744 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
747 if (Pred == CmpInst::ICMP_EQ) {
753 if (Pred == CmpInst::ICMP_NE) {
762 static BasicBlock *createStubLandingPad(Function *Handler,
763 Value *PersonalityFn) {
764 // FIXME: Finish this!
765 LLVMContext &Context = Handler->getContext();
766 BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
767 Handler->getBasicBlockList().push_back(StubBB);
768 IRBuilder<> Builder(StubBB);
769 LandingPadInst *LPad = Builder.CreateLandingPad(
770 llvm::StructType::get(Type::getInt8PtrTy(Context),
771 Type::getInt32Ty(Context), nullptr),
773 LPad->setCleanup(true);
774 Builder.CreateUnreachable();
778 // Cycles through the blocks in an outlined handler function looking for an
779 // invoke instruction and inserts an invoke of llvm.donothing with an empty
780 // landing pad if none is found. The code that generates the .xdata tables for
781 // the handler needs at least one landing pad to identify the parent function's
783 void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler,
784 Value *PersonalityFn) {
785 ReturnInst *Ret = nullptr;
786 for (BasicBlock &BB : *Handler) {
787 TerminatorInst *Terminator = BB.getTerminator();
788 // If we find an invoke, there is nothing to be done.
789 auto *II = dyn_cast<InvokeInst>(Terminator);
792 // If we've already recorded a return instruction, keep looking for invokes.
795 // If we haven't recorded a return instruction yet, try this terminator.
796 Ret = dyn_cast<ReturnInst>(Terminator);
799 // If we got this far, the handler contains no invokes. We should have seen
800 // at least one return. We'll insert an invoke of llvm.donothing ahead of
803 BasicBlock *OldRetBB = Ret->getParent();
804 BasicBlock *NewRetBB = SplitBlock(OldRetBB, Ret);
805 // SplitBlock adds an unconditional branch instruction at the end of the
806 // parent block. We want to replace that with an invoke call, so we can
808 OldRetBB->getTerminator()->eraseFromParent();
809 BasicBlock *StubLandingPad = createStubLandingPad(Handler, PersonalityFn);
811 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
812 InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
815 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
816 LandingPadInst *LPad, BasicBlock *StartBB,
817 FrameVarInfoMap &VarInfo) {
818 Module *M = SrcFn->getParent();
819 LLVMContext &Context = M->getContext();
821 // Create a new function to receive the handler contents.
822 Type *Int8PtrType = Type::getInt8PtrTy(Context);
823 std::vector<Type *> ArgTys;
824 ArgTys.push_back(Int8PtrType);
825 ArgTys.push_back(Int8PtrType);
827 if (Action->getType() == Catch) {
828 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
829 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
830 SrcFn->getName() + ".catch", M);
832 FunctionType *FnType =
833 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
834 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
835 SrcFn->getName() + ".cleanup", M);
838 Handler->addFnAttr("wineh-parent", SrcFn->getName());
840 // Generate a standard prolog to setup the frame recovery structure.
841 IRBuilder<> Builder(Context);
842 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
843 Handler->getBasicBlockList().push_front(Entry);
844 Builder.SetInsertPoint(Entry);
845 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
847 std::unique_ptr<WinEHCloningDirectorBase> Director;
849 ValueToValueMapTy VMap;
851 LandingPadMap &LPadMap = LPadMaps[LPad];
852 if (!LPadMap.isInitialized())
853 LPadMap.mapLandingPad(LPad);
854 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
855 Constant *Sel = CatchAction->getSelector();
856 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap,
857 NestedLPtoOriginalLP));
858 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
859 ConstantInt::get(Type::getInt32Ty(Context), 1));
861 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
862 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
863 UndefValue::get(Type::getInt32Ty(Context)));
866 SmallVector<ReturnInst *, 8> Returns;
867 ClonedCodeInfo OutlinedFunctionInfo;
869 // If the start block contains PHI nodes, we need to map them.
870 BasicBlock::iterator II = StartBB->begin();
871 while (auto *PN = dyn_cast<PHINode>(II)) {
873 // Look for PHI values that we have already mapped (such as the selector).
874 for (Value *Val : PN->incoming_values()) {
875 if (VMap.count(Val)) {
876 VMap[PN] = VMap[Val];
880 // If we didn't find a match for this value, map it as an undef.
882 VMap[PN] = UndefValue::get(PN->getType());
887 // Skip over PHIs and, if applicable, landingpad instructions.
888 II = StartBB->getFirstInsertionPt();
890 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
891 /*ModuleLevelChanges=*/false, Returns, "",
892 &OutlinedFunctionInfo, Director.get());
894 // Move all the instructions in the first cloned block into our entry block.
895 BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
896 Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
897 FirstClonedBB->eraseFromParent();
899 // Make sure we can identify the handler's personality later.
900 addStubInvokeToHandlerIfNeeded(Handler, LPad->getPersonalityFn());
902 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
903 WinEHCatchDirector *CatchDirector =
904 reinterpret_cast<WinEHCatchDirector *>(Director.get());
905 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
906 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
908 // Look for blocks that are not part of the landing pad that we just
909 // outlined but terminate with a call to llvm.eh.endcatch and a
910 // branch to a block that is in the handler we just outlined.
911 // These blocks will be part of a nested landing pad that intends to
912 // return to an address in this handler. This case is best handled
913 // after both landing pads have been outlined, so for now we'll just
914 // save the association of the blocks in LPadTargetBlocks. The
915 // return instructions which are created from these branches will be
916 // replaced after all landing pads have been outlined.
917 for (const auto &MapEntry : VMap) {
918 // VMap maps all values and blocks that were just cloned, but dead
919 // blocks which were pruned will map to nullptr.
920 if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
922 const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
923 for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
924 auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
925 if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
927 BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
929 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
930 // This would indicate that a nested landing pad wants to return
931 // to a block that is outlined into two different handlers.
932 assert(!LPadTargetBlocks.count(MappedBB));
933 LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
937 } // End if (CatchAction)
939 Action->setHandlerBlockOrFunc(Handler);
944 /// This BB must end in a selector dispatch. All we need to do is pass the
945 /// handler block to llvm.eh.actions and list it as a possible indirectbr
947 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
948 BasicBlock *StartBB) {
949 BasicBlock *HandlerBB;
952 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
954 // If this was EH dispatch, this must be a conditional branch to the handler
956 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
957 // leading to crashes if some optimization hoists stuff here.
958 assert(CatchAction->getSelector() && HandlerBB &&
959 "expected catch EH dispatch");
961 // This must be a catch-all. Split the block after the landingpad.
962 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
964 StartBB->splitBasicBlock(StartBB->getFirstInsertionPt(), "catch.all");
966 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
967 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
968 CatchAction->setReturnTargets(Targets);
971 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
972 // Each instance of this class should only ever be used to map a single
974 assert(OriginLPad == nullptr || OriginLPad == LPad);
976 // If the landing pad has already been mapped, there's nothing more to do.
977 if (OriginLPad == LPad)
982 // The landingpad instruction returns an aggregate value. Typically, its
983 // value will be passed to a pair of extract value instructions and the
984 // results of those extracts will have been promoted to reg values before
985 // this routine is called.
986 for (auto *U : LPad->users()) {
987 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
990 assert(Extract->getNumIndices() == 1 &&
991 "Unexpected operation: extracting both landing pad values");
992 unsigned int Idx = *(Extract->idx_begin());
993 assert((Idx == 0 || Idx == 1) &&
994 "Unexpected operation: extracting an unknown landing pad element");
996 ExtractedEHPtrs.push_back(Extract);
997 } else if (Idx == 1) {
998 ExtractedSelectors.push_back(Extract);
1003 bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
1004 return BB->getLandingPadInst() == OriginLPad;
1007 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
1008 if (Inst == OriginLPad)
1010 for (auto *Extract : ExtractedEHPtrs) {
1011 if (Inst == Extract)
1014 for (auto *Extract : ExtractedSelectors) {
1015 if (Inst == Extract)
1021 void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
1022 Value *SelectorValue) const {
1023 // Remap all landing pad extract instructions to the specified values.
1024 for (auto *Extract : ExtractedEHPtrs)
1025 VMap[Extract] = EHPtrValue;
1026 for (auto *Extract : ExtractedSelectors)
1027 VMap[Extract] = SelectorValue;
1030 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
1031 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1032 // If this is one of the boilerplate landing pad instructions, skip it.
1033 // The instruction will have already been remapped in VMap.
1034 if (LPadMap.isLandingPadSpecificInst(Inst))
1035 return CloningDirector::SkipInstruction;
1037 // Nested landing pads will be cloned as stubs, with just the
1038 // landingpad instruction and an unreachable instruction. When
1039 // all landingpads have been outlined, we'll replace this with the
1040 // llvm.eh.actions call and indirect branch created when the
1041 // landing pad was outlined.
1042 if (auto *LPad = dyn_cast<LandingPadInst>(Inst)) {
1043 return handleLandingPad(VMap, LPad, NewBB);
1046 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
1047 return handleInvoke(VMap, Invoke, NewBB);
1049 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
1050 return handleResume(VMap, Resume, NewBB);
1052 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1053 return handleBeginCatch(VMap, Inst, NewBB);
1054 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1055 return handleEndCatch(VMap, Inst, NewBB);
1056 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1057 return handleTypeIdFor(VMap, Inst, NewBB);
1059 // Continue with the default cloning behavior.
1060 return CloningDirector::CloneInstruction;
1063 CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
1064 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1065 Instruction *NewInst = LPad->clone();
1066 if (LPad->hasName())
1067 NewInst->setName(LPad->getName());
1068 // Save this correlation for later processing.
1069 NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
1070 VMap[LPad] = NewInst;
1071 BasicBlock::InstListType &InstList = NewBB->getInstList();
1072 InstList.push_back(NewInst);
1073 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1074 return CloningDirector::StopCloningBB;
1077 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
1078 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1079 // The argument to the call is some form of the first element of the
1080 // landingpad aggregate value, but that doesn't matter. It isn't used
1082 // The second argument is an outparameter where the exception object will be
1083 // stored. Typically the exception object is a scalar, but it can be an
1084 // aggregate when catching by value.
1085 // FIXME: Leave something behind to indicate where the exception object lives
1086 // for this handler. Should it be part of llvm.eh.actions?
1087 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
1088 "llvm.eh.begincatch found while "
1089 "outlining catch handler.");
1090 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
1091 if (isa<ConstantPointerNull>(ExceptionObjectVar))
1092 return CloningDirector::SkipInstruction;
1093 assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
1094 "catch parameter is not static alloca");
1095 Materializer.escapeCatchObject(ExceptionObjectVar);
1096 return CloningDirector::SkipInstruction;
1099 CloningDirector::CloningAction
1100 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
1101 const Instruction *Inst, BasicBlock *NewBB) {
1102 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1103 // It might be interesting to track whether or not we are inside a catch
1104 // function, but that might make the algorithm more brittle than it needs
1107 // The end catch call can occur in one of two places: either in a
1108 // landingpad block that is part of the catch handlers exception mechanism,
1109 // or at the end of the catch block. However, a catch-all handler may call
1110 // end catch from the original landing pad. If the call occurs in a nested
1111 // landing pad block, we must skip it and continue so that the landing pad
1113 auto *ParentBB = IntrinCall->getParent();
1114 if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
1115 return CloningDirector::SkipInstruction;
1117 // If an end catch occurs anywhere else we want to terminate the handler
1118 // with a return to the code that follows the endcatch call. If the
1119 // next instruction is not an unconditional branch, we need to split the
1120 // block to provide a clear target for the return instruction.
1121 BasicBlock *ContinueBB;
1122 auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
1123 const BranchInst *Branch = dyn_cast<BranchInst>(Next);
1124 if (!Branch || !Branch->isUnconditional()) {
1125 // We're interrupting the cloning process at this location, so the
1126 // const_cast we're doing here will not cause a problem.
1127 ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
1128 const_cast<Instruction *>(cast<Instruction>(Next)));
1130 ContinueBB = Branch->getSuccessor(0);
1133 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
1134 ReturnTargets.push_back(ContinueBB);
1136 // We just added a terminator to the cloned block.
1137 // Tell the caller to stop processing the current basic block so that
1138 // the branch instruction will be skipped.
1139 return CloningDirector::StopCloningBB;
1142 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
1143 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1144 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1145 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1146 // This causes a replacement that will collapse the landing pad CFG based
1147 // on the filter function we intend to match.
1148 if (Selector == CurrentSelector)
1149 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
1151 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1152 // Tell the caller not to clone this instruction.
1153 return CloningDirector::SkipInstruction;
1156 CloningDirector::CloningAction
1157 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
1158 const InvokeInst *Invoke, BasicBlock *NewBB) {
1159 return CloningDirector::CloneInstruction;
1162 CloningDirector::CloningAction
1163 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
1164 const ResumeInst *Resume, BasicBlock *NewBB) {
1165 // Resume instructions shouldn't be reachable from catch handlers.
1166 // We still need to handle it, but it will be pruned.
1167 BasicBlock::InstListType &InstList = NewBB->getInstList();
1168 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1169 return CloningDirector::StopCloningBB;
1172 CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
1173 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1174 // The MS runtime will terminate the process if an exception occurs in a
1175 // cleanup handler, so we shouldn't encounter landing pads in the actual
1176 // cleanup code, but they may appear in catch blocks. Depending on where
1177 // we started cloning we may see one, but it will get dropped during dead
1179 Instruction *NewInst = new UnreachableInst(NewBB->getContext());
1180 VMap[LPad] = NewInst;
1181 BasicBlock::InstListType &InstList = NewBB->getInstList();
1182 InstList.push_back(NewInst);
1183 return CloningDirector::StopCloningBB;
1186 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1187 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1188 // Catch blocks within cleanup handlers will always be unreachable.
1189 // We'll insert an unreachable instruction now, but it will be pruned
1190 // before the cloning process is complete.
1191 BasicBlock::InstListType &InstList = NewBB->getInstList();
1192 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1193 return CloningDirector::StopCloningBB;
1196 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1197 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1198 // Cleanup handlers nested within catch handlers may begin with a call to
1199 // eh.endcatch. We can just ignore that instruction.
1200 return CloningDirector::SkipInstruction;
1203 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1204 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1205 // If we encounter a selector comparison while cloning a cleanup handler,
1206 // we want to stop cloning immediately. Anything after the dispatch
1207 // will be outlined into a different handler.
1208 BasicBlock *CatchHandler;
1211 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1212 CatchHandler, Selector, NextBB)) {
1213 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1214 return CloningDirector::StopCloningBB;
1216 // If eg.typeid.for is called for any other reason, it can be ignored.
1217 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1218 return CloningDirector::SkipInstruction;
1221 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1222 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1223 // All invokes in cleanup handlers can be replaced with calls.
1224 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1225 // Insert a normal call instruction...
1227 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1228 Invoke->getName(), NewBB);
1229 NewCall->setCallingConv(Invoke->getCallingConv());
1230 NewCall->setAttributes(Invoke->getAttributes());
1231 NewCall->setDebugLoc(Invoke->getDebugLoc());
1232 VMap[Invoke] = NewCall;
1234 // Insert an unconditional branch to the normal destination.
1235 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1237 // The unwind destination won't be cloned into the new function, so
1238 // we don't need to clean up its phi nodes.
1240 // We just added a terminator to the cloned block.
1241 // Tell the caller to stop processing the current basic block.
1242 return CloningDirector::StopCloningBB;
1245 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1246 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1247 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1249 // We just added a terminator to the cloned block.
1250 // Tell the caller to stop processing the current basic block so that
1251 // the branch instruction will be skipped.
1252 return CloningDirector::StopCloningBB;
1255 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1256 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1257 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1258 BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
1259 Builder.SetInsertPoint(EntryBB, EntryBB->getFirstInsertionPt());
1262 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1263 // If we're asked to materialize a value that is an instruction, we
1264 // temporarily create an alloca in the outlined function and add this
1265 // to the FrameVarInfo map. When all the outlining is complete, we'll
1266 // collect these into a structure, spilling non-alloca values in the
1267 // parent frame as necessary, and replace these temporary allocas with
1268 // GEPs referencing the frame allocation block.
1270 // If the value is an alloca, the mapping is direct.
1271 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1272 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1273 Builder.Insert(NewAlloca, AV->getName());
1274 FrameVarInfo[AV].push_back(NewAlloca);
1278 // For other types of instructions or arguments, we need an alloca based on
1279 // the value's type and a load of the alloca. The alloca will be replaced
1280 // by a GEP, but the load will stay. In the parent function, the value will
1281 // be spilled to a location in the frame allocation block.
1282 if (isa<Instruction>(V) || isa<Argument>(V)) {
1283 AllocaInst *NewAlloca =
1284 Builder.CreateAlloca(V->getType(), nullptr, "eh.temp.alloca");
1285 FrameVarInfo[V].push_back(NewAlloca);
1286 LoadInst *NewLoad = Builder.CreateLoad(NewAlloca, V->getName() + ".reload");
1290 // Don't materialize other values.
1294 void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
1295 // Catch parameter objects have to live in the parent frame. When we see a use
1296 // of a catch parameter, add a sentinel to the multimap to indicate that it's
1297 // used from another handler. This will prevent us from trying to sink the
1298 // alloca into the handler and ensure that the catch parameter is present in
1299 // the call to llvm.frameescape.
1300 FrameVarInfo[V].push_back(getCatchObjectSentinel());
1303 // This function maps the catch and cleanup handlers that are reachable from the
1304 // specified landing pad. The landing pad sequence will have this basic shape:
1306 // <cleanup handler>
1307 // <selector comparison>
1309 // <cleanup handler>
1310 // <selector comparison>
1312 // <cleanup handler>
1315 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1316 // any arbitrary control flow, but all paths through the cleanup code must
1317 // eventually reach the next selector comparison and no path can skip to a
1318 // different selector comparisons, though some paths may terminate abnormally.
1319 // Therefore, we will use a depth first search from the start of any given
1320 // cleanup block and stop searching when we find the next selector comparison.
1322 // If the landingpad instruction does not have a catch clause, we will assume
1323 // that any instructions other than selector comparisons and catch handlers can
1324 // be ignored. In practice, these will only be the boilerplate instructions.
1326 // The catch handlers may also have any control structure, but we are only
1327 // interested in the start of the catch handlers, so we don't need to actually
1328 // follow the flow of the catch handlers. The start of the catch handlers can
1329 // be located from the compare instructions, but they can be skipped in the
1330 // flow by following the contrary branch.
1331 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1332 LandingPadActions &Actions) {
1333 unsigned int NumClauses = LPad->getNumClauses();
1334 unsigned int HandlersFound = 0;
1335 BasicBlock *BB = LPad->getParent();
1337 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1339 if (NumClauses == 0) {
1340 // This landing pad contains only cleanup code.
1341 CleanupHandler *Action = new CleanupHandler(BB);
1342 CleanupHandlerMap[BB] = Action;
1343 Actions.insertCleanupHandler(Action);
1344 DEBUG(dbgs() << " Assuming cleanup code in block " << BB->getName()
1346 assert(LPad->isCleanup());
1350 VisitedBlockSet VisitedBlocks;
1352 while (HandlersFound != NumClauses) {
1353 BasicBlock *NextBB = nullptr;
1355 // See if the clause we're looking for is a catch-all.
1356 // If so, the catch begins immediately.
1357 if (isa<ConstantPointerNull>(LPad->getClause(HandlersFound))) {
1358 // The catch all must occur last.
1359 assert(HandlersFound == NumClauses - 1);
1361 // For C++ EH, check if there is any interesting cleanup code before we
1362 // begin the catch. This is important because cleanups cannot rethrow
1363 // exceptions but code called from catches can. For SEH, it isn't
1364 // important if some finally code before a catch-all is executed out of
1365 // line or after recovering from the exception.
1366 if (Personality == EHPersonality::MSVC_CXX) {
1367 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1368 // Add a cleanup entry to the list
1369 Actions.insertCleanupHandler(CleanupAction);
1370 DEBUG(dbgs() << " Found cleanup code in block "
1371 << CleanupAction->getStartBlock()->getName() << "\n");
1375 // Add the catch handler to the action list.
1376 CatchHandler *Action =
1377 new CatchHandler(BB, LPad->getClause(HandlersFound), nullptr);
1378 CatchHandlerMap[BB] = Action;
1379 Actions.insertCatchHandler(Action);
1380 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1383 // Once we reach a catch-all, don't expect to hit a resume instruction.
1388 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1389 // See if there is any interesting code executed before the dispatch.
1390 if (auto *CleanupAction =
1391 findCleanupHandler(BB, CatchAction->getStartBlock())) {
1392 // Add a cleanup entry to the list
1393 Actions.insertCleanupHandler(CleanupAction);
1394 DEBUG(dbgs() << " Found cleanup code in block "
1395 << CleanupAction->getStartBlock()->getName() << "\n");
1398 assert(CatchAction);
1401 // Add the catch handler to the action list.
1402 Actions.insertCatchHandler(CatchAction);
1403 DEBUG(dbgs() << " Found catch dispatch in block "
1404 << CatchAction->getStartBlock()->getName() << "\n");
1406 // Move on to the block after the catch handler.
1410 // If we didn't wind up in a catch-all, see if there is any interesting code
1411 // executed before the resume.
1412 if (auto *CleanupAction = findCleanupHandler(BB, BB)) {
1413 // Add a cleanup entry to the list
1414 Actions.insertCleanupHandler(CleanupAction);
1415 DEBUG(dbgs() << " Found cleanup code in block "
1416 << CleanupAction->getStartBlock()->getName() << "\n");
1419 // It's possible that some optimization moved code into a landingpad that
1421 // previously being used for cleanup. If that happens, we need to execute
1423 // extra code from a cleanup handler.
1424 if (Actions.includesCleanup() && !LPad->isCleanup())
1425 LPad->setCleanup(true);
1428 // This function searches starting with the input block for the next
1429 // block that terminates with a branch whose condition is based on a selector
1430 // comparison. This may be the input block. See the mapLandingPadBlocks
1431 // comments for a discussion of control flow assumptions.
1433 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1434 BasicBlock *&NextBB,
1435 VisitedBlockSet &VisitedBlocks) {
1436 // See if we've already found a catch handler use it.
1437 // Call count() first to avoid creating a null entry for blocks
1438 // we haven't seen before.
1439 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1440 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1441 NextBB = Action->getNextBB();
1445 // VisitedBlocks applies only to the current search. We still
1446 // need to consider blocks that we've visited while mapping other
1448 VisitedBlocks.insert(BB);
1450 BasicBlock *CatchBlock = nullptr;
1451 Constant *Selector = nullptr;
1453 // If this is the first time we've visited this block from any landing pad
1454 // look to see if it is a selector dispatch block.
1455 if (!CatchHandlerMap.count(BB)) {
1456 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1457 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1458 CatchHandlerMap[BB] = Action;
1463 // Visit each successor, looking for the dispatch.
1464 // FIXME: We expect to find the dispatch quickly, so this will probably
1465 // work better as a breadth first search.
1466 for (BasicBlock *Succ : successors(BB)) {
1467 if (VisitedBlocks.count(Succ))
1470 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1477 // These are helper functions to combine repeated code from findCleanupHandler.
1478 static CleanupHandler *
1479 createCleanupHandler(CleanupHandlerMapTy &CleanupHandlerMap, BasicBlock *BB) {
1480 CleanupHandler *Action = new CleanupHandler(BB);
1481 CleanupHandlerMap[BB] = Action;
1485 // This function searches starting with the input block for the next block that
1486 // contains code that is not part of a catch handler and would not be eliminated
1487 // during handler outlining.
1489 CleanupHandler *WinEHPrepare::findCleanupHandler(BasicBlock *StartBB,
1490 BasicBlock *EndBB) {
1491 // Here we will skip over the following:
1493 // landing pad prolog:
1495 // Unconditional branches
1497 // Selector dispatch
1501 // Anything else marks the start of an interesting block
1503 BasicBlock *BB = StartBB;
1504 // Anything other than an unconditional branch will kick us out of this loop
1505 // one way or another.
1507 // If we've already scanned this block, don't scan it again. If it is
1508 // a cleanup block, there will be an action in the CleanupHandlerMap.
1509 // If we've scanned it and it is not a cleanup block, there will be a
1510 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1511 // be no entry in the CleanupHandlerMap. We must call count() first to
1512 // avoid creating a null entry for blocks we haven't scanned.
1513 if (CleanupHandlerMap.count(BB)) {
1514 if (auto *Action = CleanupHandlerMap[BB]) {
1515 return cast<CleanupHandler>(Action);
1517 // Here we handle the case where the cleanup handler map contains a
1518 // value for this block but the value is a nullptr. This means that
1519 // we have previously analyzed the block and determined that it did
1520 // not contain any cleanup code. Based on the earlier analysis, we
1521 // know the the block must end in either an unconditional branch, a
1522 // resume or a conditional branch that is predicated on a comparison
1523 // with a selector. Either the resume or the selector dispatch
1524 // would terminate the search for cleanup code, so the unconditional
1525 // branch is the only case for which we might need to continue
1530 if (!match(BB->getTerminator(), m_UnconditionalBr(SuccBB)))
1537 // Create an entry in the cleanup handler map for this block. Initially
1538 // we create an entry that says this isn't a cleanup block. If we find
1539 // cleanup code, the caller will replace this entry.
1540 CleanupHandlerMap[BB] = nullptr;
1542 TerminatorInst *Terminator = BB->getTerminator();
1544 // Landing pad blocks have extra instructions we need to accept.
1545 LandingPadMap *LPadMap = nullptr;
1546 if (BB->isLandingPad()) {
1547 LandingPadInst *LPad = BB->getLandingPadInst();
1548 LPadMap = &LPadMaps[LPad];
1549 if (!LPadMap->isInitialized())
1550 LPadMap->mapLandingPad(LPad);
1553 // Look for the bare resume pattern:
1554 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
1555 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
1556 // resume { i8*, i32 } %lpad.val2
1557 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
1558 InsertValueInst *Insert1 = nullptr;
1559 InsertValueInst *Insert2 = nullptr;
1560 Value *ResumeVal = Resume->getOperand(0);
1561 // If there is only one landingpad, we may use the lpad directly with no
1563 if (isa<LandingPadInst>(ResumeVal))
1565 if (!isa<PHINode>(ResumeVal)) {
1566 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
1568 return createCleanupHandler(CleanupHandlerMap, BB);
1569 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
1571 return createCleanupHandler(CleanupHandlerMap, BB);
1573 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1575 Instruction *Inst = II;
1576 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1578 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
1580 if (!Inst->hasOneUse() ||
1581 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
1582 return createCleanupHandler(CleanupHandlerMap, BB);
1588 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
1589 if (Branch && Branch->isConditional()) {
1590 // Look for the selector dispatch.
1591 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
1592 // %matches = icmp eq i32 %sel, %2
1593 // br i1 %matches, label %catch14, label %eh.resume
1594 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
1595 if (!Compare || !Compare->isEquality())
1596 return createCleanupHandler(CleanupHandlerMap, BB);
1597 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1599 Instruction *Inst = II;
1600 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1602 if (Inst == Compare || Inst == Branch)
1604 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1606 return createCleanupHandler(CleanupHandlerMap, BB);
1608 // The selector dispatch block should always terminate our search.
1609 assert(BB == EndBB);
1613 // Anything else is either a catch block or interesting cleanup code.
1614 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1616 Instruction *Inst = II;
1617 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1619 // Unconditional branches fall through to this loop.
1622 // If this is a catch block, there is no cleanup code to be found.
1623 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1625 // If this a nested landing pad, it may contain an endcatch call.
1626 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1628 // Anything else makes this interesting cleanup code.
1629 return createCleanupHandler(CleanupHandlerMap, BB);
1632 // Only unconditional branches in empty blocks should get this far.
1633 assert(Branch && Branch->isUnconditional());
1636 BB = Branch->getSuccessor(0);
1641 // This is a public function, declared in WinEHFuncInfo.h and is also
1642 // referenced by WinEHNumbering in FunctionLoweringInfo.cpp.
1643 void llvm::parseEHActions(const IntrinsicInst *II,
1644 SmallVectorImpl<ActionHandler *> &Actions) {
1645 for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
1646 uint64_t ActionKind =
1647 cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
1648 if (ActionKind == /*catch=*/1) {
1649 auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
1650 ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
1651 int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
1652 Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
1654 auto *CH = new CatchHandler(/*BB=*/nullptr, Selector, /*NextBB=*/nullptr);
1655 CH->setHandlerBlockOrFunc(Handler);
1656 CH->setExceptionVarIndex(EHObjIndexVal);
1657 Actions.push_back(CH);
1658 } else if (ActionKind == 0) {
1659 Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
1661 auto *CH = new CleanupHandler(/*BB=*/nullptr);
1662 CH->setHandlerBlockOrFunc(Handler);
1663 Actions.push_back(CH);
1665 llvm_unreachable("Expected either a catch or cleanup handler!");
1668 std::reverse(Actions.begin(), Actions.end());