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/SetVector.h"
22 #include "llvm/ADT/TinyPtrVector.h"
23 #include "llvm/Analysis/LibCallSemantics.h"
24 #include "llvm/CodeGen/WinEHFuncInfo.h"
25 #include "llvm/IR/Dominators.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/IR/IRBuilder.h"
28 #include "llvm/IR/Instructions.h"
29 #include "llvm/IR/IntrinsicInst.h"
30 #include "llvm/IR/Module.h"
31 #include "llvm/IR/PatternMatch.h"
32 #include "llvm/Pass.h"
33 #include "llvm/Support/CommandLine.h"
34 #include "llvm/Support/Debug.h"
35 #include "llvm/Support/raw_ostream.h"
36 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
37 #include "llvm/Transforms/Utils/Cloning.h"
38 #include "llvm/Transforms/Utils/Local.h"
39 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
43 using namespace llvm::PatternMatch;
45 #define DEBUG_TYPE "winehprepare"
49 // This map is used to model frame variable usage during outlining, to
50 // construct a structure type to hold the frame variables in a frame
51 // allocation block, and to remap the frame variable allocas (including
52 // spill locations as needed) to GEPs that get the variable from the
53 // frame allocation structure.
54 typedef MapVector<Value *, TinyPtrVector<AllocaInst *>> FrameVarInfoMap;
56 // TinyPtrVector cannot hold nullptr, so we need our own sentinel that isn't
58 AllocaInst *getCatchObjectSentinel() {
59 return static_cast<AllocaInst *>(nullptr) + 1;
62 typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
64 class LandingPadActions;
67 typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
68 typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
70 class WinEHPrepare : public FunctionPass {
72 static char ID; // Pass identification, replacement for typeid.
73 WinEHPrepare(const TargetMachine *TM = nullptr)
74 : FunctionPass(ID), DT(nullptr) {}
76 bool runOnFunction(Function &Fn) override;
78 bool doFinalization(Module &M) override;
80 void getAnalysisUsage(AnalysisUsage &AU) const override;
82 const char *getPassName() const override {
83 return "Windows exception handling preparation";
87 bool prepareExceptionHandlers(Function &F,
88 SmallVectorImpl<LandingPadInst *> &LPads);
89 void promoteLandingPadValues(LandingPadInst *LPad);
90 void demoteValuesLiveAcrossHandlers(Function &F,
91 SmallVectorImpl<LandingPadInst *> &LPads);
92 void completeNestedLandingPad(Function *ParentFn,
93 LandingPadInst *OutlinedLPad,
94 const LandingPadInst *OriginalLPad,
95 FrameVarInfoMap &VarInfo);
96 bool outlineHandler(ActionHandler *Action, Function *SrcFn,
97 LandingPadInst *LPad, BasicBlock *StartBB,
98 FrameVarInfoMap &VarInfo);
99 void addStubInvokeToHandlerIfNeeded(Function *Handler, Value *PersonalityFn);
101 void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
102 CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
103 VisitedBlockSet &VisitedBlocks);
104 void findCleanupHandlers(LandingPadActions &Actions, BasicBlock *StartBB,
107 void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
109 // All fields are reset by runOnFunction.
111 EHPersonality Personality;
112 CatchHandlerMapTy CatchHandlerMap;
113 CleanupHandlerMapTy CleanupHandlerMap;
114 DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
116 // This maps landing pad instructions found in outlined handlers to
117 // the landing pad instruction in the parent function from which they
118 // were cloned. The cloned/nested landing pad is used as the key
119 // because the landing pad may be cloned into multiple handlers.
120 // This map will be used to add the llvm.eh.actions call to the nested
121 // landing pads after all handlers have been outlined.
122 DenseMap<LandingPadInst *, const LandingPadInst *> NestedLPtoOriginalLP;
124 // This maps blocks in the parent function which are destinations of
125 // catch handlers to cloned blocks in (other) outlined handlers. This
126 // handles the case where a nested landing pads has a catch handler that
127 // returns to a handler function rather than the parent function.
128 // The original block is used as the key here because there should only
129 // ever be one handler function from which the cloned block is not pruned.
130 // The original block will be pruned from the parent function after all
131 // handlers have been outlined. This map will be used to adjust the
132 // return instructions of handlers which return to the block that was
133 // outlined into a handler. This is done after all handlers have been
134 // outlined but before the outlined code is pruned from the parent function.
135 DenseMap<const BasicBlock *, BasicBlock *> LPadTargetBlocks;
138 class WinEHFrameVariableMaterializer : public ValueMaterializer {
140 WinEHFrameVariableMaterializer(Function *OutlinedFn,
141 FrameVarInfoMap &FrameVarInfo);
142 ~WinEHFrameVariableMaterializer() override {}
144 Value *materializeValueFor(Value *V) override;
146 void escapeCatchObject(Value *V);
149 FrameVarInfoMap &FrameVarInfo;
153 class LandingPadMap {
155 LandingPadMap() : OriginLPad(nullptr) {}
156 void mapLandingPad(const LandingPadInst *LPad);
158 bool isInitialized() { return OriginLPad != nullptr; }
160 bool isOriginLandingPadBlock(const BasicBlock *BB) const;
161 bool isLandingPadSpecificInst(const Instruction *Inst) const;
163 void remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
164 Value *SelectorValue) const;
167 const LandingPadInst *OriginLPad;
168 // We will normally only see one of each of these instructions, but
169 // if more than one occurs for some reason we can handle that.
170 TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
171 TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
174 class WinEHCloningDirectorBase : public CloningDirector {
176 WinEHCloningDirectorBase(Function *HandlerFn, FrameVarInfoMap &VarInfo,
177 LandingPadMap &LPadMap)
178 : Materializer(HandlerFn, VarInfo),
179 SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
180 Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
182 auto AI = HandlerFn->getArgumentList().begin();
184 EstablisherFrame = AI;
187 CloningAction handleInstruction(ValueToValueMapTy &VMap,
188 const Instruction *Inst,
189 BasicBlock *NewBB) override;
191 virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
192 const Instruction *Inst,
193 BasicBlock *NewBB) = 0;
194 virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
195 const Instruction *Inst,
196 BasicBlock *NewBB) = 0;
197 virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
198 const Instruction *Inst,
199 BasicBlock *NewBB) = 0;
200 virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
201 const InvokeInst *Invoke,
202 BasicBlock *NewBB) = 0;
203 virtual CloningAction handleResume(ValueToValueMapTy &VMap,
204 const ResumeInst *Resume,
205 BasicBlock *NewBB) = 0;
206 virtual CloningAction handleCompare(ValueToValueMapTy &VMap,
207 const CmpInst *Compare,
208 BasicBlock *NewBB) = 0;
209 virtual CloningAction handleLandingPad(ValueToValueMapTy &VMap,
210 const LandingPadInst *LPad,
211 BasicBlock *NewBB) = 0;
213 ValueMaterializer *getValueMaterializer() override { return &Materializer; }
216 WinEHFrameVariableMaterializer Materializer;
217 Type *SelectorIDType;
219 LandingPadMap &LPadMap;
221 /// The value representing the parent frame pointer.
222 Value *EstablisherFrame;
225 class WinEHCatchDirector : public WinEHCloningDirectorBase {
228 Function *CatchFn, Value *Selector, FrameVarInfoMap &VarInfo,
229 LandingPadMap &LPadMap,
230 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPads)
231 : WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
232 CurrentSelector(Selector->stripPointerCasts()),
233 ExceptionObjectVar(nullptr), NestedLPtoOriginalLP(NestedLPads) {}
235 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
236 const Instruction *Inst,
237 BasicBlock *NewBB) override;
238 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
239 BasicBlock *NewBB) override;
240 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
241 const Instruction *Inst,
242 BasicBlock *NewBB) override;
243 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
244 BasicBlock *NewBB) override;
245 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
246 BasicBlock *NewBB) override;
247 CloningAction handleCompare(ValueToValueMapTy &VMap,
248 const CmpInst *Compare, BasicBlock *NewBB) override;
249 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
250 const LandingPadInst *LPad,
251 BasicBlock *NewBB) override;
253 Value *getExceptionVar() { return ExceptionObjectVar; }
254 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
257 Value *CurrentSelector;
259 Value *ExceptionObjectVar;
260 TinyPtrVector<BasicBlock *> ReturnTargets;
262 // This will be a reference to the field of the same name in the WinEHPrepare
263 // object which instantiates this WinEHCatchDirector object.
264 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPtoOriginalLP;
267 class WinEHCleanupDirector : public WinEHCloningDirectorBase {
269 WinEHCleanupDirector(Function *CleanupFn, FrameVarInfoMap &VarInfo,
270 LandingPadMap &LPadMap)
271 : WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
273 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
274 const Instruction *Inst,
275 BasicBlock *NewBB) override;
276 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
277 BasicBlock *NewBB) override;
278 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
279 const Instruction *Inst,
280 BasicBlock *NewBB) override;
281 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
282 BasicBlock *NewBB) override;
283 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
284 BasicBlock *NewBB) override;
285 CloningAction handleCompare(ValueToValueMapTy &VMap,
286 const CmpInst *Compare, BasicBlock *NewBB) override;
287 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
288 const LandingPadInst *LPad,
289 BasicBlock *NewBB) override;
292 class LandingPadActions {
294 LandingPadActions() : HasCleanupHandlers(false) {}
296 void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
297 void insertCleanupHandler(CleanupHandler *Action) {
298 Actions.push_back(Action);
299 HasCleanupHandlers = true;
302 bool includesCleanup() const { return HasCleanupHandlers; }
304 SmallVectorImpl<ActionHandler *> &actions() { return Actions; }
305 SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
306 SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
309 // Note that this class does not own the ActionHandler objects in this vector.
310 // The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
311 // in the WinEHPrepare class.
312 SmallVector<ActionHandler *, 4> Actions;
313 bool HasCleanupHandlers;
316 } // end anonymous namespace
318 char WinEHPrepare::ID = 0;
319 INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
322 FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
323 return new WinEHPrepare(TM);
326 // FIXME: Remove this once the backend can handle the prepared IR.
328 SEHPrepare("sehprepare", cl::Hidden,
329 cl::desc("Prepare functions with SEH personalities"));
331 bool WinEHPrepare::runOnFunction(Function &Fn) {
332 // No need to prepare outlined handlers.
333 if (Fn.hasFnAttribute("wineh-parent"))
336 SmallVector<LandingPadInst *, 4> LPads;
337 SmallVector<ResumeInst *, 4> Resumes;
338 for (BasicBlock &BB : Fn) {
339 if (auto *LP = BB.getLandingPadInst())
341 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
342 Resumes.push_back(Resume);
345 // No need to prepare functions that lack landing pads.
349 // Classify the personality to see what kind of preparation we need.
350 Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
352 // Do nothing if this is not an MSVC personality.
353 if (!isMSVCEHPersonality(Personality))
356 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
358 if (isAsynchronousEHPersonality(Personality) && !SEHPrepare) {
359 // Replace all resume instructions with unreachable.
360 // FIXME: Remove this once the backend can handle the prepared IR.
361 for (ResumeInst *Resume : Resumes) {
362 IRBuilder<>(Resume).CreateUnreachable();
363 Resume->eraseFromParent();
368 // If there were any landing pads, prepareExceptionHandlers will make changes.
369 prepareExceptionHandlers(Fn, LPads);
373 bool WinEHPrepare::doFinalization(Module &M) { return false; }
375 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
376 AU.addRequired<DominatorTreeWrapperPass>();
379 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
380 Constant *&Selector, BasicBlock *&NextBB);
382 // Finds blocks reachable from the starting set Worklist. Does not follow unwind
383 // edges or blocks listed in StopPoints.
384 static void findReachableBlocks(SmallPtrSetImpl<BasicBlock *> &ReachableBBs,
385 SetVector<BasicBlock *> &Worklist,
386 const SetVector<BasicBlock *> *StopPoints) {
387 while (!Worklist.empty()) {
388 BasicBlock *BB = Worklist.pop_back_val();
390 // Don't cross blocks that we should stop at.
391 if (StopPoints && StopPoints->count(BB))
394 if (!ReachableBBs.insert(BB).second)
395 continue; // Already visited.
397 // Don't follow unwind edges of invokes.
398 if (auto *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
399 Worklist.insert(II->getNormalDest());
403 // Otherwise, follow all successors.
404 Worklist.insert(succ_begin(BB), succ_end(BB));
408 /// Find all points where exceptional control rejoins normal control flow via
409 /// llvm.eh.endcatch. Add them to the normal bb reachability worklist.
410 static void findCXXEHReturnPoints(Function &F,
411 SetVector<BasicBlock *> &EHReturnBlocks) {
412 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
413 BasicBlock *BB = BBI;
414 for (Instruction &I : *BB) {
415 if (match(&I, m_Intrinsic<Intrinsic::eh_endcatch>())) {
416 // Split the block after the call to llvm.eh.endcatch if there is
417 // anything other than an unconditional branch, or if the successor
418 // starts with a phi.
419 auto *Br = dyn_cast<BranchInst>(I.getNextNode());
420 if (!Br || !Br->isUnconditional() ||
421 isa<PHINode>(Br->getSuccessor(0)->begin())) {
422 DEBUG(dbgs() << "splitting block " << BB->getName()
423 << " with llvm.eh.endcatch\n");
424 BBI = BB->splitBasicBlock(I.getNextNode(), "ehreturn");
426 // The next BB is normal control flow.
427 EHReturnBlocks.insert(BB->getTerminator()->getSuccessor(0));
434 static bool isCatchAllLandingPad(const BasicBlock *BB) {
435 const LandingPadInst *LP = BB->getLandingPadInst();
438 unsigned N = LP->getNumClauses();
439 return (N > 0 && LP->isCatch(N - 1) &&
440 isa<ConstantPointerNull>(LP->getClause(N - 1)));
443 /// Find all points where exceptions control rejoins normal control flow via
444 /// selector dispatch.
445 static void findSEHEHReturnPoints(Function &F,
446 SetVector<BasicBlock *> &EHReturnBlocks) {
447 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
448 BasicBlock *BB = BBI;
449 // If the landingpad is a catch-all, treat the whole lpad as if it is
450 // reachable from normal control flow.
451 // FIXME: This is imprecise. We need a better way of identifying where a
452 // catch-all starts and cleanups stop. As far as LLVM is concerned, there
454 if (isCatchAllLandingPad(BB)) {
455 EHReturnBlocks.insert(BB);
459 BasicBlock *CatchHandler;
462 if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
463 // Split the edge if there is a phi node. Returning from EH to a phi node
464 // is just as impossible as having a phi after an indirectbr.
465 if (isa<PHINode>(CatchHandler->begin())) {
466 DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
467 << " to " << CatchHandler->getName() << '\n');
468 BBI = CatchHandler = SplitCriticalEdge(
469 BB, std::find(succ_begin(BB), succ_end(BB), CatchHandler));
471 EHReturnBlocks.insert(CatchHandler);
476 /// Ensure that all values live into and out of exception handlers are stored
478 /// FIXME: This falls down when values are defined in one handler and live into
479 /// another handler. For example, a cleanup defines a value used only by a
481 void WinEHPrepare::demoteValuesLiveAcrossHandlers(
482 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
483 DEBUG(dbgs() << "Demoting values live across exception handlers in function "
484 << F.getName() << '\n');
486 // Build a set of all non-exceptional blocks and exceptional blocks.
487 // - Non-exceptional blocks are blocks reachable from the entry block while
488 // not following invoke unwind edges.
489 // - Exceptional blocks are blocks reachable from landingpads. Analysis does
490 // not follow llvm.eh.endcatch blocks, which mark a transition from
491 // exceptional to normal control.
492 SmallPtrSet<BasicBlock *, 4> NormalBlocks;
493 SmallPtrSet<BasicBlock *, 4> EHBlocks;
494 SetVector<BasicBlock *> EHReturnBlocks;
495 SetVector<BasicBlock *> Worklist;
497 if (Personality == EHPersonality::MSVC_CXX)
498 findCXXEHReturnPoints(F, EHReturnBlocks);
500 findSEHEHReturnPoints(F, EHReturnBlocks);
503 dbgs() << "identified the following blocks as EH return points:\n";
504 for (BasicBlock *BB : EHReturnBlocks)
505 dbgs() << " " << BB->getName() << '\n';
508 // Join points should not have phis at this point, unless they are a
509 // landingpad, in which case we will demote their phis later.
511 for (BasicBlock *BB : EHReturnBlocks)
512 assert((BB->isLandingPad() || !isa<PHINode>(BB->begin())) &&
513 "non-lpad EH return block has phi");
516 // Normal blocks are the blocks reachable from the entry block and all EH
518 Worklist = EHReturnBlocks;
519 Worklist.insert(&F.getEntryBlock());
520 findReachableBlocks(NormalBlocks, Worklist, nullptr);
522 dbgs() << "marked the following blocks as normal:\n";
523 for (BasicBlock *BB : NormalBlocks)
524 dbgs() << " " << BB->getName() << '\n';
527 // Exceptional blocks are the blocks reachable from landingpads that don't
528 // cross EH return points.
530 for (auto *LPI : LPads)
531 Worklist.insert(LPI->getParent());
532 findReachableBlocks(EHBlocks, Worklist, &EHReturnBlocks);
534 dbgs() << "marked the following blocks as exceptional:\n";
535 for (BasicBlock *BB : EHBlocks)
536 dbgs() << " " << BB->getName() << '\n';
539 SetVector<Argument *> ArgsToDemote;
540 SetVector<Instruction *> InstrsToDemote;
541 for (BasicBlock &BB : F) {
542 bool IsNormalBB = NormalBlocks.count(&BB);
543 bool IsEHBB = EHBlocks.count(&BB);
544 if (!IsNormalBB && !IsEHBB)
545 continue; // Blocks that are neither normal nor EH are unreachable.
546 for (Instruction &I : BB) {
547 for (Value *Op : I.operands()) {
548 // Don't demote static allocas, constants, and labels.
549 if (isa<Constant>(Op) || isa<BasicBlock>(Op) || isa<InlineAsm>(Op))
551 auto *AI = dyn_cast<AllocaInst>(Op);
552 if (AI && AI->isStaticAlloca())
555 if (auto *Arg = dyn_cast<Argument>(Op)) {
557 DEBUG(dbgs() << "Demoting argument " << *Arg
558 << " used by EH instr: " << I << "\n");
559 ArgsToDemote.insert(Arg);
564 auto *OpI = cast<Instruction>(Op);
565 BasicBlock *OpBB = OpI->getParent();
566 // If a value is produced and consumed in the same BB, we don't need to
570 bool IsOpNormalBB = NormalBlocks.count(OpBB);
571 bool IsOpEHBB = EHBlocks.count(OpBB);
572 if (IsNormalBB != IsOpNormalBB || IsEHBB != IsOpEHBB) {
574 dbgs() << "Demoting instruction live in-out from EH:\n";
575 dbgs() << "Instr: " << *OpI << '\n';
576 dbgs() << "User: " << I << '\n';
578 InstrsToDemote.insert(OpI);
584 // Demote values live into and out of handlers.
585 // FIXME: This demotion is inefficient. We should insert spills at the point
586 // of definition, insert one reload in each handler that uses the value, and
587 // insert reloads in the BB used to rejoin normal control flow.
588 Instruction *AllocaInsertPt = F.getEntryBlock().getFirstInsertionPt();
589 for (Instruction *I : InstrsToDemote)
590 DemoteRegToStack(*I, false, AllocaInsertPt);
592 // Demote arguments separately, and only for uses in EH blocks.
593 for (Argument *Arg : ArgsToDemote) {
594 auto *Slot = new AllocaInst(Arg->getType(), nullptr,
595 Arg->getName() + ".reg2mem", AllocaInsertPt);
596 SmallVector<User *, 4> Users(Arg->user_begin(), Arg->user_end());
597 for (User *U : Users) {
598 auto *I = dyn_cast<Instruction>(U);
599 if (I && EHBlocks.count(I->getParent())) {
600 auto *Reload = new LoadInst(Slot, Arg->getName() + ".reload", false, I);
601 U->replaceUsesOfWith(Arg, Reload);
604 new StoreInst(Arg, Slot, AllocaInsertPt);
607 // Demote landingpad phis, as the landingpad will be removed from the machine
609 for (LandingPadInst *LPI : LPads) {
610 BasicBlock *BB = LPI->getParent();
611 while (auto *Phi = dyn_cast<PHINode>(BB->begin()))
612 DemotePHIToStack(Phi, AllocaInsertPt);
615 DEBUG(dbgs() << "Demoted " << InstrsToDemote.size() << " instructions and "
616 << ArgsToDemote.size() << " arguments for WinEHPrepare\n\n");
619 bool WinEHPrepare::prepareExceptionHandlers(
620 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
621 // Don't run on functions that are already prepared.
622 for (LandingPadInst *LPad : LPads) {
623 BasicBlock *LPadBB = LPad->getParent();
624 for (Instruction &Inst : *LPadBB)
625 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>()))
629 demoteValuesLiveAcrossHandlers(F, LPads);
631 // These containers are used to re-map frame variables that are used in
632 // outlined catch and cleanup handlers. They will be populated as the
633 // handlers are outlined.
634 FrameVarInfoMap FrameVarInfo;
636 bool HandlersOutlined = false;
638 Module *M = F.getParent();
639 LLVMContext &Context = M->getContext();
641 // Create a new function to receive the handler contents.
642 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
643 Type *Int32Type = Type::getInt32Ty(Context);
644 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
646 for (LandingPadInst *LPad : LPads) {
647 // Look for evidence that this landingpad has already been processed.
648 bool LPadHasActionList = false;
649 BasicBlock *LPadBB = LPad->getParent();
650 for (Instruction &Inst : *LPadBB) {
651 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>())) {
652 LPadHasActionList = true;
657 // If we've already outlined the handlers for this landingpad,
658 // there's nothing more to do here.
659 if (LPadHasActionList)
662 // If either of the values in the aggregate returned by the landing pad is
663 // extracted and stored to memory, promote the stored value to a register.
664 promoteLandingPadValues(LPad);
666 LandingPadActions Actions;
667 mapLandingPadBlocks(LPad, Actions);
669 HandlersOutlined |= !Actions.actions().empty();
670 for (ActionHandler *Action : Actions) {
671 if (Action->hasBeenProcessed())
673 BasicBlock *StartBB = Action->getStartBlock();
675 // SEH doesn't do any outlining for catches. Instead, pass the handler
676 // basic block addr to llvm.eh.actions and list the block as a return
678 if (isAsynchronousEHPersonality(Personality)) {
679 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
680 processSEHCatchHandler(CatchAction, StartBB);
685 outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo);
688 // Replace the landing pad with a new llvm.eh.action based landing pad.
689 BasicBlock *NewLPadBB = BasicBlock::Create(Context, "lpad", &F, LPadBB);
690 assert(!isa<PHINode>(LPadBB->begin()));
691 auto *NewLPad = cast<LandingPadInst>(LPad->clone());
692 NewLPadBB->getInstList().push_back(NewLPad);
693 while (!pred_empty(LPadBB)) {
694 auto *pred = *pred_begin(LPadBB);
695 InvokeInst *Invoke = cast<InvokeInst>(pred->getTerminator());
696 Invoke->setUnwindDest(NewLPadBB);
699 // Replace the mapping of any nested landing pad that previously mapped
700 // to this landing pad with a referenced to the cloned version.
701 for (auto &LPadPair : NestedLPtoOriginalLP) {
702 const LandingPadInst *OriginalLPad = LPadPair.second;
703 if (OriginalLPad == LPad) {
704 LPadPair.second = NewLPad;
708 // Replace all extracted values with undef and ultimately replace the
709 // landingpad with undef.
710 // FIXME: This doesn't handle SEH GetExceptionCode(). For now, we just give
711 // out undef until we figure out the codegen support.
712 SmallVector<Instruction *, 4> Extracts;
713 for (User *U : LPad->users()) {
714 auto *E = dyn_cast<ExtractValueInst>(U);
717 assert(E->getNumIndices() == 1 &&
718 "Unexpected operation: extracting both landing pad values");
719 Extracts.push_back(E);
721 for (Instruction *E : Extracts) {
722 E->replaceAllUsesWith(UndefValue::get(E->getType()));
723 E->eraseFromParent();
725 LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
727 // Add a call to describe the actions for this landing pad.
728 std::vector<Value *> ActionArgs;
729 for (ActionHandler *Action : Actions) {
730 // Action codes from docs are: 0 cleanup, 1 catch.
731 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
732 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
733 ActionArgs.push_back(CatchAction->getSelector());
734 // Find the frame escape index of the exception object alloca in the
736 int FrameEscapeIdx = -1;
737 Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
738 if (EHObj && !isa<ConstantPointerNull>(EHObj)) {
739 auto I = FrameVarInfo.find(EHObj);
740 assert(I != FrameVarInfo.end() &&
741 "failed to map llvm.eh.begincatch var");
742 FrameEscapeIdx = std::distance(FrameVarInfo.begin(), I);
744 ActionArgs.push_back(ConstantInt::get(Int32Type, FrameEscapeIdx));
746 ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
748 ActionArgs.push_back(Action->getHandlerBlockOrFunc());
751 CallInst::Create(ActionIntrin, ActionArgs, "recover", NewLPadBB);
753 // Add an indirect branch listing possible successors of the catch handlers.
754 SetVector<BasicBlock *> ReturnTargets;
755 for (ActionHandler *Action : Actions) {
756 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
757 const auto &CatchTargets = CatchAction->getReturnTargets();
758 ReturnTargets.insert(CatchTargets.begin(), CatchTargets.end());
761 IndirectBrInst *Branch =
762 IndirectBrInst::Create(Recover, ReturnTargets.size(), NewLPadBB);
763 for (BasicBlock *Target : ReturnTargets)
764 Branch->addDestination(Target);
765 } // End for each landingpad
767 // If nothing got outlined, there is no more processing to be done.
768 if (!HandlersOutlined)
771 // Replace any nested landing pad stubs with the correct action handler.
772 // This must be done before we remove unreachable blocks because it
773 // cleans up references to outlined blocks that will be deleted.
774 for (auto &LPadPair : NestedLPtoOriginalLP)
775 completeNestedLandingPad(&F, LPadPair.first, LPadPair.second, FrameVarInfo);
776 NestedLPtoOriginalLP.clear();
778 F.addFnAttr("wineh-parent", F.getName());
780 // Delete any blocks that were only used by handlers that were outlined above.
781 removeUnreachableBlocks(F);
783 BasicBlock *Entry = &F.getEntryBlock();
784 IRBuilder<> Builder(F.getParent()->getContext());
785 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
787 Function *FrameEscapeFn =
788 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
789 Function *RecoverFrameFn =
790 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
791 SmallVector<Value *, 8> AllocasToEscape;
793 // Scan the entry block for an existing call to llvm.frameescape. We need to
794 // keep escaping those objects.
795 for (Instruction &I : F.front()) {
796 auto *II = dyn_cast<IntrinsicInst>(&I);
797 if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
798 auto Args = II->arg_operands();
799 AllocasToEscape.append(Args.begin(), Args.end());
800 II->eraseFromParent();
805 // Finally, replace all of the temporary allocas for frame variables used in
806 // the outlined handlers with calls to llvm.framerecover.
807 for (auto &VarInfoEntry : FrameVarInfo) {
808 Value *ParentVal = VarInfoEntry.first;
809 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
810 AllocaInst *ParentAlloca = cast<AllocaInst>(ParentVal);
812 // FIXME: We should try to sink unescaped allocas from the parent frame into
813 // the child frame. If the alloca is escaped, we have to use the lifetime
814 // markers to ensure that the alloca is only live within the child frame.
816 // Add this alloca to the list of things to escape.
817 AllocasToEscape.push_back(ParentAlloca);
819 // Next replace all outlined allocas that are mapped to it.
820 for (AllocaInst *TempAlloca : Allocas) {
821 if (TempAlloca == getCatchObjectSentinel())
822 continue; // Skip catch parameter sentinels.
823 Function *HandlerFn = TempAlloca->getParent()->getParent();
824 // FIXME: Sink this GEP into the blocks where it is used.
825 Builder.SetInsertPoint(TempAlloca);
826 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
827 Value *RecoverArgs[] = {
828 Builder.CreateBitCast(&F, Int8PtrType, ""),
829 &(HandlerFn->getArgumentList().back()),
830 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
831 Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
832 // Add a pointer bitcast if the alloca wasn't an i8.
833 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
834 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
836 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
838 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
839 TempAlloca->removeFromParent();
840 RecoveredAlloca->takeName(TempAlloca);
843 } // End for each FrameVarInfo entry.
845 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
847 Builder.SetInsertPoint(&F.getEntryBlock().back());
848 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
850 // Clean up the handler action maps we created for this function
851 DeleteContainerSeconds(CatchHandlerMap);
852 CatchHandlerMap.clear();
853 DeleteContainerSeconds(CleanupHandlerMap);
854 CleanupHandlerMap.clear();
856 return HandlersOutlined;
859 void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
860 // If the return values of the landing pad instruction are extracted and
861 // stored to memory, we want to promote the store locations to reg values.
862 SmallVector<AllocaInst *, 2> EHAllocas;
864 // The landingpad instruction returns an aggregate value. Typically, its
865 // value will be passed to a pair of extract value instructions and the
866 // results of those extracts are often passed to store instructions.
867 // In unoptimized code the stored value will often be loaded and then stored
869 for (auto *U : LPad->users()) {
870 ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
874 for (auto *EU : Extract->users()) {
875 if (auto *Store = dyn_cast<StoreInst>(EU)) {
876 auto *AV = cast<AllocaInst>(Store->getPointerOperand());
877 EHAllocas.push_back(AV);
882 // We can't do this without a dominator tree.
885 if (!EHAllocas.empty()) {
886 PromoteMemToReg(EHAllocas, *DT);
890 // After promotion, some extracts may be trivially dead. Remove them.
891 SmallVector<Value *, 4> Users(LPad->user_begin(), LPad->user_end());
892 for (auto *U : Users)
893 RecursivelyDeleteTriviallyDeadInstructions(U);
896 void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,
897 LandingPadInst *OutlinedLPad,
898 const LandingPadInst *OriginalLPad,
899 FrameVarInfoMap &FrameVarInfo) {
900 // Get the nested block and erase the unreachable instruction that was
901 // temporarily inserted as its terminator.
902 LLVMContext &Context = ParentFn->getContext();
903 BasicBlock *OutlinedBB = OutlinedLPad->getParent();
904 assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
905 OutlinedBB->getTerminator()->eraseFromParent();
906 // That should leave OutlinedLPad as the last instruction in its block.
907 assert(&OutlinedBB->back() == OutlinedLPad);
909 // The original landing pad will have already had its action intrinsic
910 // built by the outlining loop. We need to clone that into the outlined
911 // location. It may also be necessary to add references to the exception
912 // variables to the outlined handler in which this landing pad is nested
913 // and remap return instructions in the nested handlers that should return
914 // to an address in the outlined handler.
915 Function *OutlinedHandlerFn = OutlinedBB->getParent();
916 BasicBlock::const_iterator II = OriginalLPad;
918 // The instruction after the landing pad should now be a call to eh.actions.
919 const Instruction *Recover = II;
920 assert(match(Recover, m_Intrinsic<Intrinsic::eh_actions>()));
921 IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover->clone());
923 // Remap the exception variables into the outlined function.
924 WinEHFrameVariableMaterializer Materializer(OutlinedHandlerFn, FrameVarInfo);
925 SmallVector<BlockAddress *, 4> ActionTargets;
926 SmallVector<ActionHandler *, 4> ActionList;
927 parseEHActions(EHActions, ActionList);
928 for (auto *Action : ActionList) {
929 auto *Catch = dyn_cast<CatchHandler>(Action);
932 // The dyn_cast to function here selects C++ catch handlers and skips
933 // SEH catch handlers.
934 auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
937 // Visit all the return instructions, looking for places that return
938 // to a location within OutlinedHandlerFn.
939 for (BasicBlock &NestedHandlerBB : *Handler) {
940 auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
944 // Handler functions must always return a block address.
945 BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
946 // The original target will have been in the main parent function,
947 // but if it is the address of a block that has been outlined, it
948 // should be a block that was outlined into OutlinedHandlerFn.
949 assert(BA->getFunction() == ParentFn);
951 // Ignore targets that aren't part of OutlinedHandlerFn.
952 if (!LPadTargetBlocks.count(BA->getBasicBlock()))
955 // If the return value is the address ofF a block that we
956 // previously outlined into the parent handler function, replace
957 // the return instruction and add the mapped target to the list
958 // of possible return addresses.
959 BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
960 assert(MappedBB->getParent() == OutlinedHandlerFn);
961 BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
962 Ret->eraseFromParent();
963 ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
964 ActionTargets.push_back(NewBA);
967 DeleteContainerPointers(ActionList);
969 OutlinedBB->getInstList().push_back(EHActions);
971 // Insert an indirect branch into the outlined landing pad BB.
972 IndirectBrInst *IBr = IndirectBrInst::Create(EHActions, 0, OutlinedBB);
973 // Add the previously collected action targets.
974 for (auto *Target : ActionTargets)
975 IBr->addDestination(Target->getBasicBlock());
978 // This function examines a block to determine whether the block ends with a
979 // conditional branch to a catch handler based on a selector comparison.
980 // This function is used both by the WinEHPrepare::findSelectorComparison() and
981 // WinEHCleanupDirector::handleTypeIdFor().
982 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
983 Constant *&Selector, BasicBlock *&NextBB) {
984 ICmpInst::Predicate Pred;
985 BasicBlock *TBB, *FBB;
988 if (!match(BB->getTerminator(),
989 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
993 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
994 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
997 if (Pred == CmpInst::ICMP_EQ) {
1003 if (Pred == CmpInst::ICMP_NE) {
1012 static bool isCatchBlock(BasicBlock *BB) {
1013 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1015 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_begincatch>()))
1021 static BasicBlock *createStubLandingPad(Function *Handler,
1022 Value *PersonalityFn) {
1023 // FIXME: Finish this!
1024 LLVMContext &Context = Handler->getContext();
1025 BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
1026 Handler->getBasicBlockList().push_back(StubBB);
1027 IRBuilder<> Builder(StubBB);
1028 LandingPadInst *LPad = Builder.CreateLandingPad(
1029 llvm::StructType::get(Type::getInt8PtrTy(Context),
1030 Type::getInt32Ty(Context), nullptr),
1032 // Insert a call to llvm.eh.actions so that we don't try to outline this lpad.
1033 Function *ActionIntrin = Intrinsic::getDeclaration(Handler->getParent(),
1034 Intrinsic::eh_actions);
1035 Builder.CreateCall(ActionIntrin, "recover");
1036 LPad->setCleanup(true);
1037 Builder.CreateUnreachable();
1041 // Cycles through the blocks in an outlined handler function looking for an
1042 // invoke instruction and inserts an invoke of llvm.donothing with an empty
1043 // landing pad if none is found. The code that generates the .xdata tables for
1044 // the handler needs at least one landing pad to identify the parent function's
1046 void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler,
1047 Value *PersonalityFn) {
1048 ReturnInst *Ret = nullptr;
1049 UnreachableInst *Unreached = nullptr;
1050 for (BasicBlock &BB : *Handler) {
1051 TerminatorInst *Terminator = BB.getTerminator();
1052 // If we find an invoke, there is nothing to be done.
1053 auto *II = dyn_cast<InvokeInst>(Terminator);
1056 // If we've already recorded a return instruction, keep looking for invokes.
1058 Ret = dyn_cast<ReturnInst>(Terminator);
1059 // If we haven't recorded an unreachable instruction, try this terminator.
1061 Unreached = dyn_cast<UnreachableInst>(Terminator);
1064 // If we got this far, the handler contains no invokes. We should have seen
1065 // at least one return or unreachable instruction. We'll insert an invoke of
1066 // llvm.donothing ahead of that instruction.
1067 assert(Ret || Unreached);
1068 TerminatorInst *Term;
1073 BasicBlock *OldRetBB = Term->getParent();
1074 BasicBlock *NewRetBB = SplitBlock(OldRetBB, Term);
1075 // SplitBlock adds an unconditional branch instruction at the end of the
1076 // parent block. We want to replace that with an invoke call, so we can
1078 OldRetBB->getTerminator()->eraseFromParent();
1079 BasicBlock *StubLandingPad = createStubLandingPad(Handler, PersonalityFn);
1081 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
1082 InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
1085 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
1086 LandingPadInst *LPad, BasicBlock *StartBB,
1087 FrameVarInfoMap &VarInfo) {
1088 Module *M = SrcFn->getParent();
1089 LLVMContext &Context = M->getContext();
1091 // Create a new function to receive the handler contents.
1092 Type *Int8PtrType = Type::getInt8PtrTy(Context);
1093 std::vector<Type *> ArgTys;
1094 ArgTys.push_back(Int8PtrType);
1095 ArgTys.push_back(Int8PtrType);
1097 if (Action->getType() == Catch) {
1098 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
1099 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
1100 SrcFn->getName() + ".catch", M);
1102 FunctionType *FnType =
1103 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
1104 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
1105 SrcFn->getName() + ".cleanup", M);
1108 Handler->addFnAttr("wineh-parent", SrcFn->getName());
1110 // Generate a standard prolog to setup the frame recovery structure.
1111 IRBuilder<> Builder(Context);
1112 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
1113 Handler->getBasicBlockList().push_front(Entry);
1114 Builder.SetInsertPoint(Entry);
1115 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
1117 std::unique_ptr<WinEHCloningDirectorBase> Director;
1119 ValueToValueMapTy VMap;
1121 LandingPadMap &LPadMap = LPadMaps[LPad];
1122 if (!LPadMap.isInitialized())
1123 LPadMap.mapLandingPad(LPad);
1124 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1125 Constant *Sel = CatchAction->getSelector();
1126 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap,
1127 NestedLPtoOriginalLP));
1128 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1129 ConstantInt::get(Type::getInt32Ty(Context), 1));
1131 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
1132 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1133 UndefValue::get(Type::getInt32Ty(Context)));
1136 SmallVector<ReturnInst *, 8> Returns;
1137 ClonedCodeInfo OutlinedFunctionInfo;
1139 // If the start block contains PHI nodes, we need to map them.
1140 BasicBlock::iterator II = StartBB->begin();
1141 while (auto *PN = dyn_cast<PHINode>(II)) {
1142 bool Mapped = false;
1143 // Look for PHI values that we have already mapped (such as the selector).
1144 for (Value *Val : PN->incoming_values()) {
1145 if (VMap.count(Val)) {
1146 VMap[PN] = VMap[Val];
1150 // If we didn't find a match for this value, map it as an undef.
1152 VMap[PN] = UndefValue::get(PN->getType());
1157 // The landing pad value may be used by PHI nodes. It will ultimately be
1158 // eliminated, but we need it in the map for intermediate handling.
1159 VMap[LPad] = UndefValue::get(LPad->getType());
1161 // Skip over PHIs and, if applicable, landingpad instructions.
1162 II = StartBB->getFirstInsertionPt();
1164 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
1165 /*ModuleLevelChanges=*/false, Returns, "",
1166 &OutlinedFunctionInfo, Director.get());
1168 // Move all the instructions in the first cloned block into our entry block.
1169 BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
1170 Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
1171 FirstClonedBB->eraseFromParent();
1173 // Make sure we can identify the handler's personality later.
1174 addStubInvokeToHandlerIfNeeded(Handler, LPad->getPersonalityFn());
1176 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1177 WinEHCatchDirector *CatchDirector =
1178 reinterpret_cast<WinEHCatchDirector *>(Director.get());
1179 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
1180 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
1182 // Look for blocks that are not part of the landing pad that we just
1183 // outlined but terminate with a call to llvm.eh.endcatch and a
1184 // branch to a block that is in the handler we just outlined.
1185 // These blocks will be part of a nested landing pad that intends to
1186 // return to an address in this handler. This case is best handled
1187 // after both landing pads have been outlined, so for now we'll just
1188 // save the association of the blocks in LPadTargetBlocks. The
1189 // return instructions which are created from these branches will be
1190 // replaced after all landing pads have been outlined.
1191 for (const auto MapEntry : VMap) {
1192 // VMap maps all values and blocks that were just cloned, but dead
1193 // blocks which were pruned will map to nullptr.
1194 if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
1196 const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
1197 for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
1198 auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
1199 if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
1201 BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
1203 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
1204 // This would indicate that a nested landing pad wants to return
1205 // to a block that is outlined into two different handlers.
1206 assert(!LPadTargetBlocks.count(MappedBB));
1207 LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
1211 } // End if (CatchAction)
1213 Action->setHandlerBlockOrFunc(Handler);
1218 /// This BB must end in a selector dispatch. All we need to do is pass the
1219 /// handler block to llvm.eh.actions and list it as a possible indirectbr
1221 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
1222 BasicBlock *StartBB) {
1223 BasicBlock *HandlerBB;
1226 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
1228 // If this was EH dispatch, this must be a conditional branch to the handler
1230 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
1231 // leading to crashes if some optimization hoists stuff here.
1232 assert(CatchAction->getSelector() && HandlerBB &&
1233 "expected catch EH dispatch");
1235 // This must be a catch-all. Split the block after the landingpad.
1236 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
1238 StartBB->splitBasicBlock(StartBB->getFirstInsertionPt(), "catch.all");
1240 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
1241 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
1242 CatchAction->setReturnTargets(Targets);
1245 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
1246 // Each instance of this class should only ever be used to map a single
1248 assert(OriginLPad == nullptr || OriginLPad == LPad);
1250 // If the landing pad has already been mapped, there's nothing more to do.
1251 if (OriginLPad == LPad)
1256 // The landingpad instruction returns an aggregate value. Typically, its
1257 // value will be passed to a pair of extract value instructions and the
1258 // results of those extracts will have been promoted to reg values before
1259 // this routine is called.
1260 for (auto *U : LPad->users()) {
1261 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
1264 assert(Extract->getNumIndices() == 1 &&
1265 "Unexpected operation: extracting both landing pad values");
1266 unsigned int Idx = *(Extract->idx_begin());
1267 assert((Idx == 0 || Idx == 1) &&
1268 "Unexpected operation: extracting an unknown landing pad element");
1270 ExtractedEHPtrs.push_back(Extract);
1271 } else if (Idx == 1) {
1272 ExtractedSelectors.push_back(Extract);
1277 bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
1278 return BB->getLandingPadInst() == OriginLPad;
1281 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
1282 if (Inst == OriginLPad)
1284 for (auto *Extract : ExtractedEHPtrs) {
1285 if (Inst == Extract)
1288 for (auto *Extract : ExtractedSelectors) {
1289 if (Inst == Extract)
1295 void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
1296 Value *SelectorValue) const {
1297 // Remap all landing pad extract instructions to the specified values.
1298 for (auto *Extract : ExtractedEHPtrs)
1299 VMap[Extract] = EHPtrValue;
1300 for (auto *Extract : ExtractedSelectors)
1301 VMap[Extract] = SelectorValue;
1304 static bool isFrameAddressCall(const Value *V) {
1305 return match(const_cast<Value *>(V),
1306 m_Intrinsic<Intrinsic::frameaddress>(m_SpecificInt(0)));
1309 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
1310 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1311 // If this is one of the boilerplate landing pad instructions, skip it.
1312 // The instruction will have already been remapped in VMap.
1313 if (LPadMap.isLandingPadSpecificInst(Inst))
1314 return CloningDirector::SkipInstruction;
1316 // Nested landing pads will be cloned as stubs, with just the
1317 // landingpad instruction and an unreachable instruction. When
1318 // all landingpads have been outlined, we'll replace this with the
1319 // llvm.eh.actions call and indirect branch created when the
1320 // landing pad was outlined.
1321 if (auto *LPad = dyn_cast<LandingPadInst>(Inst)) {
1322 return handleLandingPad(VMap, LPad, NewBB);
1325 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
1326 return handleInvoke(VMap, Invoke, NewBB);
1328 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
1329 return handleResume(VMap, Resume, NewBB);
1331 if (auto *Cmp = dyn_cast<CmpInst>(Inst))
1332 return handleCompare(VMap, Cmp, NewBB);
1334 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1335 return handleBeginCatch(VMap, Inst, NewBB);
1336 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1337 return handleEndCatch(VMap, Inst, NewBB);
1338 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1339 return handleTypeIdFor(VMap, Inst, NewBB);
1341 // When outlining llvm.frameaddress(i32 0), remap that to the second argument,
1342 // which is the FP of the parent.
1343 if (isFrameAddressCall(Inst)) {
1344 VMap[Inst] = EstablisherFrame;
1345 return CloningDirector::SkipInstruction;
1348 // Continue with the default cloning behavior.
1349 return CloningDirector::CloneInstruction;
1352 CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
1353 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1354 Instruction *NewInst = LPad->clone();
1355 if (LPad->hasName())
1356 NewInst->setName(LPad->getName());
1357 // Save this correlation for later processing.
1358 NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
1359 VMap[LPad] = NewInst;
1360 BasicBlock::InstListType &InstList = NewBB->getInstList();
1361 InstList.push_back(NewInst);
1362 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1363 return CloningDirector::StopCloningBB;
1366 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
1367 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1368 // The argument to the call is some form of the first element of the
1369 // landingpad aggregate value, but that doesn't matter. It isn't used
1371 // The second argument is an outparameter where the exception object will be
1372 // stored. Typically the exception object is a scalar, but it can be an
1373 // aggregate when catching by value.
1374 // FIXME: Leave something behind to indicate where the exception object lives
1375 // for this handler. Should it be part of llvm.eh.actions?
1376 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
1377 "llvm.eh.begincatch found while "
1378 "outlining catch handler.");
1379 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
1380 if (isa<ConstantPointerNull>(ExceptionObjectVar))
1381 return CloningDirector::SkipInstruction;
1382 assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
1383 "catch parameter is not static alloca");
1384 Materializer.escapeCatchObject(ExceptionObjectVar);
1385 return CloningDirector::SkipInstruction;
1388 CloningDirector::CloningAction
1389 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
1390 const Instruction *Inst, BasicBlock *NewBB) {
1391 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1392 // It might be interesting to track whether or not we are inside a catch
1393 // function, but that might make the algorithm more brittle than it needs
1396 // The end catch call can occur in one of two places: either in a
1397 // landingpad block that is part of the catch handlers exception mechanism,
1398 // or at the end of the catch block. However, a catch-all handler may call
1399 // end catch from the original landing pad. If the call occurs in a nested
1400 // landing pad block, we must skip it and continue so that the landing pad
1402 auto *ParentBB = IntrinCall->getParent();
1403 if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
1404 return CloningDirector::SkipInstruction;
1406 // If an end catch occurs anywhere else we want to terminate the handler
1407 // with a return to the code that follows the endcatch call. If the
1408 // next instruction is not an unconditional branch, we need to split the
1409 // block to provide a clear target for the return instruction.
1410 BasicBlock *ContinueBB;
1411 auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
1412 const BranchInst *Branch = dyn_cast<BranchInst>(Next);
1413 if (!Branch || !Branch->isUnconditional()) {
1414 // We're interrupting the cloning process at this location, so the
1415 // const_cast we're doing here will not cause a problem.
1416 ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
1417 const_cast<Instruction *>(cast<Instruction>(Next)));
1419 ContinueBB = Branch->getSuccessor(0);
1422 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
1423 ReturnTargets.push_back(ContinueBB);
1425 // We just added a terminator to the cloned block.
1426 // Tell the caller to stop processing the current basic block so that
1427 // the branch instruction will be skipped.
1428 return CloningDirector::StopCloningBB;
1431 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
1432 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1433 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1434 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1435 // This causes a replacement that will collapse the landing pad CFG based
1436 // on the filter function we intend to match.
1437 if (Selector == CurrentSelector)
1438 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
1440 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1441 // Tell the caller not to clone this instruction.
1442 return CloningDirector::SkipInstruction;
1445 CloningDirector::CloningAction
1446 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
1447 const InvokeInst *Invoke, BasicBlock *NewBB) {
1448 return CloningDirector::CloneInstruction;
1451 CloningDirector::CloningAction
1452 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
1453 const ResumeInst *Resume, BasicBlock *NewBB) {
1454 // Resume instructions shouldn't be reachable from catch handlers.
1455 // We still need to handle it, but it will be pruned.
1456 BasicBlock::InstListType &InstList = NewBB->getInstList();
1457 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1458 return CloningDirector::StopCloningBB;
1461 CloningDirector::CloningAction
1462 WinEHCatchDirector::handleCompare(ValueToValueMapTy &VMap,
1463 const CmpInst *Compare, BasicBlock *NewBB) {
1464 const IntrinsicInst *IntrinCall = nullptr;
1465 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1466 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(0));
1467 } else if (match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1468 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(1));
1471 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1472 // This causes a replacement that will collapse the landing pad CFG based
1473 // on the filter function we intend to match.
1474 if (Selector == CurrentSelector->stripPointerCasts()) {
1475 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1478 VMap[Compare] = ConstantInt::get(SelectorIDType, 0);
1480 return CloningDirector::SkipInstruction;
1482 return CloningDirector::CloneInstruction;
1485 CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
1486 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1487 // The MS runtime will terminate the process if an exception occurs in a
1488 // cleanup handler, so we shouldn't encounter landing pads in the actual
1489 // cleanup code, but they may appear in catch blocks. Depending on where
1490 // we started cloning we may see one, but it will get dropped during dead
1492 Instruction *NewInst = new UnreachableInst(NewBB->getContext());
1493 VMap[LPad] = NewInst;
1494 BasicBlock::InstListType &InstList = NewBB->getInstList();
1495 InstList.push_back(NewInst);
1496 return CloningDirector::StopCloningBB;
1499 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1500 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1501 // Cleanup code may flow into catch blocks or the catch block may be part
1502 // of a branch that will be optimized away. We'll insert a return
1503 // instruction now, but it may be pruned before the cloning process is
1505 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1506 return CloningDirector::StopCloningBB;
1509 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1510 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1511 // Cleanup handlers nested within catch handlers may begin with a call to
1512 // eh.endcatch. We can just ignore that instruction.
1513 return CloningDirector::SkipInstruction;
1516 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1517 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1518 // If we encounter a selector comparison while cloning a cleanup handler,
1519 // we want to stop cloning immediately. Anything after the dispatch
1520 // will be outlined into a different handler.
1521 BasicBlock *CatchHandler;
1524 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1525 CatchHandler, Selector, NextBB)) {
1526 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1527 return CloningDirector::StopCloningBB;
1529 // If eg.typeid.for is called for any other reason, it can be ignored.
1530 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1531 return CloningDirector::SkipInstruction;
1534 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1535 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1536 // All invokes in cleanup handlers can be replaced with calls.
1537 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1538 // Insert a normal call instruction...
1540 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1541 Invoke->getName(), NewBB);
1542 NewCall->setCallingConv(Invoke->getCallingConv());
1543 NewCall->setAttributes(Invoke->getAttributes());
1544 NewCall->setDebugLoc(Invoke->getDebugLoc());
1545 VMap[Invoke] = NewCall;
1547 // Remap the operands.
1548 llvm::RemapInstruction(NewCall, VMap, RF_None, nullptr, &Materializer);
1550 // Insert an unconditional branch to the normal destination.
1551 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1553 // The unwind destination won't be cloned into the new function, so
1554 // we don't need to clean up its phi nodes.
1556 // We just added a terminator to the cloned block.
1557 // Tell the caller to stop processing the current basic block.
1558 return CloningDirector::CloneSuccessors;
1561 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1562 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1563 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1565 // We just added a terminator to the cloned block.
1566 // Tell the caller to stop processing the current basic block so that
1567 // the branch instruction will be skipped.
1568 return CloningDirector::StopCloningBB;
1571 CloningDirector::CloningAction
1572 WinEHCleanupDirector::handleCompare(ValueToValueMapTy &VMap,
1573 const CmpInst *Compare, BasicBlock *NewBB) {
1574 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>()) ||
1575 match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1576 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1577 return CloningDirector::SkipInstruction;
1579 return CloningDirector::CloneInstruction;
1583 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1584 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1585 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1586 BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
1587 Builder.SetInsertPoint(EntryBB, EntryBB->getFirstInsertionPt());
1590 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1591 // If we're asked to materialize a static alloca, we temporarily create an
1592 // alloca in the outlined function and add this to the FrameVarInfo map. When
1593 // all the outlining is complete, we'll replace these temporary allocas with
1594 // calls to llvm.framerecover.
1595 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1596 assert(AV->isStaticAlloca() &&
1597 "cannot materialize un-demoted dynamic alloca");
1598 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1599 Builder.Insert(NewAlloca, AV->getName());
1600 FrameVarInfo[AV].push_back(NewAlloca);
1604 if (isa<Instruction>(V) || isa<Argument>(V)) {
1605 errs() << "Failed to demote instruction used in exception handler:\n";
1606 errs() << " " << *V << '\n';
1607 report_fatal_error("WinEHPrepare failed to demote instruction");
1610 // Don't materialize other values.
1614 void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
1615 // Catch parameter objects have to live in the parent frame. When we see a use
1616 // of a catch parameter, add a sentinel to the multimap to indicate that it's
1617 // used from another handler. This will prevent us from trying to sink the
1618 // alloca into the handler and ensure that the catch parameter is present in
1619 // the call to llvm.frameescape.
1620 FrameVarInfo[V].push_back(getCatchObjectSentinel());
1623 // This function maps the catch and cleanup handlers that are reachable from the
1624 // specified landing pad. The landing pad sequence will have this basic shape:
1626 // <cleanup handler>
1627 // <selector comparison>
1629 // <cleanup handler>
1630 // <selector comparison>
1632 // <cleanup handler>
1635 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1636 // any arbitrary control flow, but all paths through the cleanup code must
1637 // eventually reach the next selector comparison and no path can skip to a
1638 // different selector comparisons, though some paths may terminate abnormally.
1639 // Therefore, we will use a depth first search from the start of any given
1640 // cleanup block and stop searching when we find the next selector comparison.
1642 // If the landingpad instruction does not have a catch clause, we will assume
1643 // that any instructions other than selector comparisons and catch handlers can
1644 // be ignored. In practice, these will only be the boilerplate instructions.
1646 // The catch handlers may also have any control structure, but we are only
1647 // interested in the start of the catch handlers, so we don't need to actually
1648 // follow the flow of the catch handlers. The start of the catch handlers can
1649 // be located from the compare instructions, but they can be skipped in the
1650 // flow by following the contrary branch.
1651 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1652 LandingPadActions &Actions) {
1653 unsigned int NumClauses = LPad->getNumClauses();
1654 unsigned int HandlersFound = 0;
1655 BasicBlock *BB = LPad->getParent();
1657 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1659 if (NumClauses == 0) {
1660 findCleanupHandlers(Actions, BB, nullptr);
1664 VisitedBlockSet VisitedBlocks;
1666 while (HandlersFound != NumClauses) {
1667 BasicBlock *NextBB = nullptr;
1669 // Skip over filter clauses.
1670 if (LPad->isFilter(HandlersFound)) {
1675 // See if the clause we're looking for is a catch-all.
1676 // If so, the catch begins immediately.
1677 Constant *ExpectedSelector = LPad->getClause(HandlersFound)->stripPointerCasts();
1678 if (isa<ConstantPointerNull>(ExpectedSelector)) {
1679 // The catch all must occur last.
1680 assert(HandlersFound == NumClauses - 1);
1682 // There can be additional selector dispatches in the call chain that we
1684 BasicBlock *CatchBlock = nullptr;
1686 while (BB && isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1687 DEBUG(dbgs() << " Found extra catch dispatch in block "
1688 << CatchBlock->getName() << "\n");
1692 // For C++ EH, check if there is any interesting cleanup code before we
1693 // begin the catch. This is important because cleanups cannot rethrow
1694 // exceptions but code called from catches can. For SEH, it isn't
1695 // important if some finally code before a catch-all is executed out of
1696 // line or after recovering from the exception.
1697 if (Personality == EHPersonality::MSVC_CXX)
1698 findCleanupHandlers(Actions, BB, BB);
1700 // Add the catch handler to the action list.
1701 CatchHandler *Action = nullptr;
1702 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1703 // If the CatchHandlerMap already has an entry for this BB, re-use it.
1704 Action = CatchHandlerMap[BB];
1705 assert(Action->getSelector() == ExpectedSelector);
1707 // Since this is a catch-all handler, the selector won't actually appear
1708 // in the code anywhere. ExpectedSelector here is the constant null ptr
1709 // that we got from the landing pad instruction.
1710 Action = new CatchHandler(BB, ExpectedSelector, nullptr);
1711 CatchHandlerMap[BB] = Action;
1713 Actions.insertCatchHandler(Action);
1714 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1717 // Once we reach a catch-all, don't expect to hit a resume instruction.
1722 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1723 assert(CatchAction);
1725 // See if there is any interesting code executed before the dispatch.
1726 findCleanupHandlers(Actions, BB, CatchAction->getStartBlock());
1728 // When the source program contains multiple nested try blocks the catch
1729 // handlers can get strung together in such a way that we can encounter
1730 // a dispatch for a selector that we've already had a handler for.
1731 if (CatchAction->getSelector()->stripPointerCasts() == ExpectedSelector) {
1734 // Add the catch handler to the action list.
1735 DEBUG(dbgs() << " Found catch dispatch in block "
1736 << CatchAction->getStartBlock()->getName() << "\n");
1737 Actions.insertCatchHandler(CatchAction);
1739 // Under some circumstances optimized IR will flow unconditionally into a
1740 // handler block without checking the selector. This can only happen if
1741 // the landing pad has a catch-all handler and the handler for the
1742 // preceeding catch clause is identical to the catch-call handler
1743 // (typically an empty catch). In this case, the handler must be shared
1744 // by all remaining clauses.
1745 if (isa<ConstantPointerNull>(
1746 CatchAction->getSelector()->stripPointerCasts())) {
1747 DEBUG(dbgs() << " Applying early catch-all handler in block "
1748 << CatchAction->getStartBlock()->getName()
1749 << " to all remaining clauses.\n");
1750 Actions.insertCatchHandler(CatchAction);
1754 DEBUG(dbgs() << " Found extra catch dispatch in block "
1755 << CatchAction->getStartBlock()->getName() << "\n");
1758 // Move on to the block after the catch handler.
1762 // If we didn't wind up in a catch-all, see if there is any interesting code
1763 // executed before the resume.
1764 findCleanupHandlers(Actions, BB, BB);
1766 // It's possible that some optimization moved code into a landingpad that
1768 // previously being used for cleanup. If that happens, we need to execute
1770 // extra code from a cleanup handler.
1771 if (Actions.includesCleanup() && !LPad->isCleanup())
1772 LPad->setCleanup(true);
1775 // This function searches starting with the input block for the next
1776 // block that terminates with a branch whose condition is based on a selector
1777 // comparison. This may be the input block. See the mapLandingPadBlocks
1778 // comments for a discussion of control flow assumptions.
1780 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1781 BasicBlock *&NextBB,
1782 VisitedBlockSet &VisitedBlocks) {
1783 // See if we've already found a catch handler use it.
1784 // Call count() first to avoid creating a null entry for blocks
1785 // we haven't seen before.
1786 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1787 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1788 NextBB = Action->getNextBB();
1792 // VisitedBlocks applies only to the current search. We still
1793 // need to consider blocks that we've visited while mapping other
1795 VisitedBlocks.insert(BB);
1797 BasicBlock *CatchBlock = nullptr;
1798 Constant *Selector = nullptr;
1800 // If this is the first time we've visited this block from any landing pad
1801 // look to see if it is a selector dispatch block.
1802 if (!CatchHandlerMap.count(BB)) {
1803 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1804 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1805 CatchHandlerMap[BB] = Action;
1808 // If we encounter a block containing an llvm.eh.begincatch before we
1809 // find a selector dispatch block, the handler is assumed to be
1810 // reached unconditionally. This happens for catch-all blocks, but
1811 // it can also happen for other catch handlers that have been combined
1812 // with the catch-all handler during optimization.
1813 if (isCatchBlock(BB)) {
1814 PointerType *Int8PtrTy = Type::getInt8PtrTy(BB->getContext());
1815 Constant *NullSelector = ConstantPointerNull::get(Int8PtrTy);
1816 CatchHandler *Action = new CatchHandler(BB, NullSelector, nullptr);
1817 CatchHandlerMap[BB] = Action;
1822 // Visit each successor, looking for the dispatch.
1823 // FIXME: We expect to find the dispatch quickly, so this will probably
1824 // work better as a breadth first search.
1825 for (BasicBlock *Succ : successors(BB)) {
1826 if (VisitedBlocks.count(Succ))
1829 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1836 // These are helper functions to combine repeated code from findCleanupHandlers.
1837 static void createCleanupHandler(LandingPadActions &Actions,
1838 CleanupHandlerMapTy &CleanupHandlerMap,
1840 CleanupHandler *Action = new CleanupHandler(BB);
1841 CleanupHandlerMap[BB] = Action;
1842 Actions.insertCleanupHandler(Action);
1843 DEBUG(dbgs() << " Found cleanup code in block "
1844 << Action->getStartBlock()->getName() << "\n");
1847 static CallSite matchOutlinedFinallyCall(BasicBlock *BB,
1848 Instruction *MaybeCall) {
1849 // Look for finally blocks that Clang has already outlined for us.
1850 // %fp = call i8* @llvm.frameaddress(i32 0)
1851 // call void @"fin$parent"(iN 1, i8* %fp)
1852 if (isFrameAddressCall(MaybeCall) && MaybeCall != BB->getTerminator())
1853 MaybeCall = MaybeCall->getNextNode();
1854 CallSite FinallyCall(MaybeCall);
1855 if (!FinallyCall || FinallyCall.arg_size() != 2)
1857 if (!match(FinallyCall.getArgument(0), m_SpecificInt(1)))
1859 if (!isFrameAddressCall(FinallyCall.getArgument(1)))
1864 static BasicBlock *followSingleUnconditionalBranches(BasicBlock *BB) {
1865 // Skip single ubr blocks.
1866 while (BB->getFirstNonPHIOrDbg() == BB->getTerminator()) {
1867 auto *Br = dyn_cast<BranchInst>(BB->getTerminator());
1868 if (Br && Br->isUnconditional())
1869 BB = Br->getSuccessor(0);
1876 // This function searches starting with the input block for the next block that
1877 // contains code that is not part of a catch handler and would not be eliminated
1878 // during handler outlining.
1880 void WinEHPrepare::findCleanupHandlers(LandingPadActions &Actions,
1881 BasicBlock *StartBB, BasicBlock *EndBB) {
1882 // Here we will skip over the following:
1884 // landing pad prolog:
1886 // Unconditional branches
1888 // Selector dispatch
1892 // Anything else marks the start of an interesting block
1894 BasicBlock *BB = StartBB;
1895 // Anything other than an unconditional branch will kick us out of this loop
1896 // one way or another.
1898 BB = followSingleUnconditionalBranches(BB);
1899 // If we've already scanned this block, don't scan it again. If it is
1900 // a cleanup block, there will be an action in the CleanupHandlerMap.
1901 // If we've scanned it and it is not a cleanup block, there will be a
1902 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1903 // be no entry in the CleanupHandlerMap. We must call count() first to
1904 // avoid creating a null entry for blocks we haven't scanned.
1905 if (CleanupHandlerMap.count(BB)) {
1906 if (auto *Action = CleanupHandlerMap[BB]) {
1907 Actions.insertCleanupHandler(Action);
1908 DEBUG(dbgs() << " Found cleanup code in block "
1909 << Action->getStartBlock()->getName() << "\n");
1910 // FIXME: This cleanup might chain into another, and we need to discover
1914 // Here we handle the case where the cleanup handler map contains a
1915 // value for this block but the value is a nullptr. This means that
1916 // we have previously analyzed the block and determined that it did
1917 // not contain any cleanup code. Based on the earlier analysis, we
1918 // know the the block must end in either an unconditional branch, a
1919 // resume or a conditional branch that is predicated on a comparison
1920 // with a selector. Either the resume or the selector dispatch
1921 // would terminate the search for cleanup code, so the unconditional
1922 // branch is the only case for which we might need to continue
1924 BasicBlock *SuccBB = followSingleUnconditionalBranches(BB);
1925 if (SuccBB == BB || SuccBB == EndBB)
1932 // Create an entry in the cleanup handler map for this block. Initially
1933 // we create an entry that says this isn't a cleanup block. If we find
1934 // cleanup code, the caller will replace this entry.
1935 CleanupHandlerMap[BB] = nullptr;
1937 TerminatorInst *Terminator = BB->getTerminator();
1939 // Landing pad blocks have extra instructions we need to accept.
1940 LandingPadMap *LPadMap = nullptr;
1941 if (BB->isLandingPad()) {
1942 LandingPadInst *LPad = BB->getLandingPadInst();
1943 LPadMap = &LPadMaps[LPad];
1944 if (!LPadMap->isInitialized())
1945 LPadMap->mapLandingPad(LPad);
1948 // Look for the bare resume pattern:
1949 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
1950 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
1951 // resume { i8*, i32 } %lpad.val2
1952 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
1953 InsertValueInst *Insert1 = nullptr;
1954 InsertValueInst *Insert2 = nullptr;
1955 Value *ResumeVal = Resume->getOperand(0);
1956 // If the resume value isn't a phi or landingpad value, it should be a
1957 // series of insertions. Identify them so we can avoid them when scanning
1959 if (!isa<PHINode>(ResumeVal) && !isa<LandingPadInst>(ResumeVal)) {
1960 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
1962 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1963 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
1965 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1967 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1969 Instruction *Inst = II;
1970 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1972 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
1974 if (!Inst->hasOneUse() ||
1975 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
1976 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1982 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
1983 if (Branch && Branch->isConditional()) {
1984 // Look for the selector dispatch.
1985 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
1986 // %matches = icmp eq i32 %sel, %2
1987 // br i1 %matches, label %catch14, label %eh.resume
1988 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
1989 if (!Compare || !Compare->isEquality())
1990 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1991 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1993 Instruction *Inst = II;
1994 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1996 if (Inst == Compare || Inst == Branch)
1998 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
2000 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2002 // The selector dispatch block should always terminate our search.
2003 assert(BB == EndBB);
2007 if (isAsynchronousEHPersonality(Personality)) {
2008 // If this is a landingpad block, split the block at the first non-landing
2010 Instruction *MaybeCall = BB->getFirstNonPHIOrDbg();
2012 while (MaybeCall != BB->getTerminator() &&
2013 LPadMap->isLandingPadSpecificInst(MaybeCall))
2014 MaybeCall = MaybeCall->getNextNode();
2017 // Look for outlined finally calls.
2018 if (CallSite FinallyCall = matchOutlinedFinallyCall(BB, MaybeCall)) {
2019 Function *Fin = FinallyCall.getCalledFunction();
2020 assert(Fin && "outlined finally call should be direct");
2021 auto *Action = new CleanupHandler(BB);
2022 Action->setHandlerBlockOrFunc(Fin);
2023 Actions.insertCleanupHandler(Action);
2024 CleanupHandlerMap[BB] = Action;
2025 DEBUG(dbgs() << " Found frontend-outlined finally call to "
2026 << Fin->getName() << " in block "
2027 << Action->getStartBlock()->getName() << "\n");
2029 // Split the block if there were more interesting instructions and look
2030 // for finally calls in the normal successor block.
2031 BasicBlock *SuccBB = BB;
2032 if (FinallyCall.getInstruction() != BB->getTerminator() &&
2033 FinallyCall.getInstruction()->getNextNode() != BB->getTerminator()) {
2034 SuccBB = BB->splitBasicBlock(FinallyCall.getInstruction()->getNextNode());
2036 if (FinallyCall.isInvoke()) {
2037 SuccBB = cast<InvokeInst>(FinallyCall.getInstruction())->getNormalDest();
2039 SuccBB = BB->getUniqueSuccessor();
2040 assert(SuccBB && "splitOutlinedFinallyCalls didn't insert a branch");
2050 // Anything else is either a catch block or interesting cleanup code.
2051 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2053 Instruction *Inst = II;
2054 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2056 // Unconditional branches fall through to this loop.
2059 // If this is a catch block, there is no cleanup code to be found.
2060 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
2062 // If this a nested landing pad, it may contain an endcatch call.
2063 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
2065 // Anything else makes this interesting cleanup code.
2066 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2069 // Only unconditional branches in empty blocks should get this far.
2070 assert(Branch && Branch->isUnconditional());
2073 BB = Branch->getSuccessor(0);
2077 // This is a public function, declared in WinEHFuncInfo.h and is also
2078 // referenced by WinEHNumbering in FunctionLoweringInfo.cpp.
2079 void llvm::parseEHActions(const IntrinsicInst *II,
2080 SmallVectorImpl<ActionHandler *> &Actions) {
2081 for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
2082 uint64_t ActionKind =
2083 cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
2084 if (ActionKind == /*catch=*/1) {
2085 auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
2086 ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
2087 int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
2088 Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
2090 auto *CH = new CatchHandler(/*BB=*/nullptr, Selector, /*NextBB=*/nullptr);
2091 CH->setHandlerBlockOrFunc(Handler);
2092 CH->setExceptionVarIndex(EHObjIndexVal);
2093 Actions.push_back(CH);
2094 } else if (ActionKind == 0) {
2095 Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
2097 auto *CH = new CleanupHandler(/*BB=*/nullptr);
2098 CH->setHandlerBlockOrFunc(Handler);
2099 Actions.push_back(CH);
2101 llvm_unreachable("Expected either a catch or cleanup handler!");
2104 std::reverse(Actions.begin(), Actions.end());