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 bool WinEHPrepare::runOnFunction(Function &Fn) {
327 // No need to prepare outlined handlers.
328 if (Fn.hasFnAttribute("wineh-parent"))
331 SmallVector<LandingPadInst *, 4> LPads;
332 SmallVector<ResumeInst *, 4> Resumes;
333 for (BasicBlock &BB : Fn) {
334 if (auto *LP = BB.getLandingPadInst())
336 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
337 Resumes.push_back(Resume);
340 // No need to prepare functions that lack landing pads.
344 // Classify the personality to see what kind of preparation we need.
345 Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
347 // Do nothing if this is not an MSVC personality.
348 if (!isMSVCEHPersonality(Personality))
351 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
353 // If there were any landing pads, prepareExceptionHandlers will make changes.
354 prepareExceptionHandlers(Fn, LPads);
358 bool WinEHPrepare::doFinalization(Module &M) { return false; }
360 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
361 AU.addRequired<DominatorTreeWrapperPass>();
364 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
365 Constant *&Selector, BasicBlock *&NextBB);
367 // Finds blocks reachable from the starting set Worklist. Does not follow unwind
368 // edges or blocks listed in StopPoints.
369 static void findReachableBlocks(SmallPtrSetImpl<BasicBlock *> &ReachableBBs,
370 SetVector<BasicBlock *> &Worklist,
371 const SetVector<BasicBlock *> *StopPoints) {
372 while (!Worklist.empty()) {
373 BasicBlock *BB = Worklist.pop_back_val();
375 // Don't cross blocks that we should stop at.
376 if (StopPoints && StopPoints->count(BB))
379 if (!ReachableBBs.insert(BB).second)
380 continue; // Already visited.
382 // Don't follow unwind edges of invokes.
383 if (auto *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
384 Worklist.insert(II->getNormalDest());
388 // Otherwise, follow all successors.
389 Worklist.insert(succ_begin(BB), succ_end(BB));
393 /// Find all points where exceptional control rejoins normal control flow via
394 /// llvm.eh.endcatch. Add them to the normal bb reachability worklist.
395 static void findCXXEHReturnPoints(Function &F,
396 SetVector<BasicBlock *> &EHReturnBlocks) {
397 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
398 BasicBlock *BB = BBI;
399 for (Instruction &I : *BB) {
400 if (match(&I, m_Intrinsic<Intrinsic::eh_endcatch>())) {
401 // Split the block after the call to llvm.eh.endcatch if there is
402 // anything other than an unconditional branch, or if the successor
403 // starts with a phi.
404 auto *Br = dyn_cast<BranchInst>(I.getNextNode());
405 if (!Br || !Br->isUnconditional() ||
406 isa<PHINode>(Br->getSuccessor(0)->begin())) {
407 DEBUG(dbgs() << "splitting block " << BB->getName()
408 << " with llvm.eh.endcatch\n");
409 BBI = BB->splitBasicBlock(I.getNextNode(), "ehreturn");
411 // The next BB is normal control flow.
412 EHReturnBlocks.insert(BB->getTerminator()->getSuccessor(0));
419 static bool isCatchAllLandingPad(const BasicBlock *BB) {
420 const LandingPadInst *LP = BB->getLandingPadInst();
423 unsigned N = LP->getNumClauses();
424 return (N > 0 && LP->isCatch(N - 1) &&
425 isa<ConstantPointerNull>(LP->getClause(N - 1)));
428 /// Find all points where exceptions control rejoins normal control flow via
429 /// selector dispatch.
430 static void findSEHEHReturnPoints(Function &F,
431 SetVector<BasicBlock *> &EHReturnBlocks) {
432 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
433 BasicBlock *BB = BBI;
434 // If the landingpad is a catch-all, treat the whole lpad as if it is
435 // reachable from normal control flow.
436 // FIXME: This is imprecise. We need a better way of identifying where a
437 // catch-all starts and cleanups stop. As far as LLVM is concerned, there
439 if (isCatchAllLandingPad(BB)) {
440 EHReturnBlocks.insert(BB);
444 BasicBlock *CatchHandler;
447 if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
448 // Split the edge if there is a phi node. Returning from EH to a phi node
449 // is just as impossible as having a phi after an indirectbr.
450 if (isa<PHINode>(CatchHandler->begin())) {
451 DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
452 << " to " << CatchHandler->getName() << '\n');
453 BBI = CatchHandler = SplitCriticalEdge(
454 BB, std::find(succ_begin(BB), succ_end(BB), CatchHandler));
456 EHReturnBlocks.insert(CatchHandler);
461 /// Ensure that all values live into and out of exception handlers are stored
463 /// FIXME: This falls down when values are defined in one handler and live into
464 /// another handler. For example, a cleanup defines a value used only by a
466 void WinEHPrepare::demoteValuesLiveAcrossHandlers(
467 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
468 DEBUG(dbgs() << "Demoting values live across exception handlers in function "
469 << F.getName() << '\n');
471 // Build a set of all non-exceptional blocks and exceptional blocks.
472 // - Non-exceptional blocks are blocks reachable from the entry block while
473 // not following invoke unwind edges.
474 // - Exceptional blocks are blocks reachable from landingpads. Analysis does
475 // not follow llvm.eh.endcatch blocks, which mark a transition from
476 // exceptional to normal control.
477 SmallPtrSet<BasicBlock *, 4> NormalBlocks;
478 SmallPtrSet<BasicBlock *, 4> EHBlocks;
479 SetVector<BasicBlock *> EHReturnBlocks;
480 SetVector<BasicBlock *> Worklist;
482 if (Personality == EHPersonality::MSVC_CXX)
483 findCXXEHReturnPoints(F, EHReturnBlocks);
485 findSEHEHReturnPoints(F, EHReturnBlocks);
488 dbgs() << "identified the following blocks as EH return points:\n";
489 for (BasicBlock *BB : EHReturnBlocks)
490 dbgs() << " " << BB->getName() << '\n';
493 // Join points should not have phis at this point, unless they are a
494 // landingpad, in which case we will demote their phis later.
496 for (BasicBlock *BB : EHReturnBlocks)
497 assert((BB->isLandingPad() || !isa<PHINode>(BB->begin())) &&
498 "non-lpad EH return block has phi");
501 // Normal blocks are the blocks reachable from the entry block and all EH
503 Worklist = EHReturnBlocks;
504 Worklist.insert(&F.getEntryBlock());
505 findReachableBlocks(NormalBlocks, Worklist, nullptr);
507 dbgs() << "marked the following blocks as normal:\n";
508 for (BasicBlock *BB : NormalBlocks)
509 dbgs() << " " << BB->getName() << '\n';
512 // Exceptional blocks are the blocks reachable from landingpads that don't
513 // cross EH return points.
515 for (auto *LPI : LPads)
516 Worklist.insert(LPI->getParent());
517 findReachableBlocks(EHBlocks, Worklist, &EHReturnBlocks);
519 dbgs() << "marked the following blocks as exceptional:\n";
520 for (BasicBlock *BB : EHBlocks)
521 dbgs() << " " << BB->getName() << '\n';
524 SetVector<Argument *> ArgsToDemote;
525 SetVector<Instruction *> InstrsToDemote;
526 for (BasicBlock &BB : F) {
527 bool IsNormalBB = NormalBlocks.count(&BB);
528 bool IsEHBB = EHBlocks.count(&BB);
529 if (!IsNormalBB && !IsEHBB)
530 continue; // Blocks that are neither normal nor EH are unreachable.
531 for (Instruction &I : BB) {
532 for (Value *Op : I.operands()) {
533 // Don't demote static allocas, constants, and labels.
534 if (isa<Constant>(Op) || isa<BasicBlock>(Op) || isa<InlineAsm>(Op))
536 auto *AI = dyn_cast<AllocaInst>(Op);
537 if (AI && AI->isStaticAlloca())
540 if (auto *Arg = dyn_cast<Argument>(Op)) {
542 DEBUG(dbgs() << "Demoting argument " << *Arg
543 << " used by EH instr: " << I << "\n");
544 ArgsToDemote.insert(Arg);
549 auto *OpI = cast<Instruction>(Op);
550 BasicBlock *OpBB = OpI->getParent();
551 // If a value is produced and consumed in the same BB, we don't need to
555 bool IsOpNormalBB = NormalBlocks.count(OpBB);
556 bool IsOpEHBB = EHBlocks.count(OpBB);
557 if (IsNormalBB != IsOpNormalBB || IsEHBB != IsOpEHBB) {
559 dbgs() << "Demoting instruction live in-out from EH:\n";
560 dbgs() << "Instr: " << *OpI << '\n';
561 dbgs() << "User: " << I << '\n';
563 InstrsToDemote.insert(OpI);
569 // Demote values live into and out of handlers.
570 // FIXME: This demotion is inefficient. We should insert spills at the point
571 // of definition, insert one reload in each handler that uses the value, and
572 // insert reloads in the BB used to rejoin normal control flow.
573 Instruction *AllocaInsertPt = F.getEntryBlock().getFirstInsertionPt();
574 for (Instruction *I : InstrsToDemote)
575 DemoteRegToStack(*I, false, AllocaInsertPt);
577 // Demote arguments separately, and only for uses in EH blocks.
578 for (Argument *Arg : ArgsToDemote) {
579 auto *Slot = new AllocaInst(Arg->getType(), nullptr,
580 Arg->getName() + ".reg2mem", AllocaInsertPt);
581 SmallVector<User *, 4> Users(Arg->user_begin(), Arg->user_end());
582 for (User *U : Users) {
583 auto *I = dyn_cast<Instruction>(U);
584 if (I && EHBlocks.count(I->getParent())) {
585 auto *Reload = new LoadInst(Slot, Arg->getName() + ".reload", false, I);
586 U->replaceUsesOfWith(Arg, Reload);
589 new StoreInst(Arg, Slot, AllocaInsertPt);
592 // Demote landingpad phis, as the landingpad will be removed from the machine
594 for (LandingPadInst *LPI : LPads) {
595 BasicBlock *BB = LPI->getParent();
596 while (auto *Phi = dyn_cast<PHINode>(BB->begin()))
597 DemotePHIToStack(Phi, AllocaInsertPt);
600 DEBUG(dbgs() << "Demoted " << InstrsToDemote.size() << " instructions and "
601 << ArgsToDemote.size() << " arguments for WinEHPrepare\n\n");
604 bool WinEHPrepare::prepareExceptionHandlers(
605 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
606 // Don't run on functions that are already prepared.
607 for (LandingPadInst *LPad : LPads) {
608 BasicBlock *LPadBB = LPad->getParent();
609 for (Instruction &Inst : *LPadBB)
610 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>()))
614 demoteValuesLiveAcrossHandlers(F, LPads);
616 // These containers are used to re-map frame variables that are used in
617 // outlined catch and cleanup handlers. They will be populated as the
618 // handlers are outlined.
619 FrameVarInfoMap FrameVarInfo;
621 bool HandlersOutlined = false;
623 Module *M = F.getParent();
624 LLVMContext &Context = M->getContext();
626 // Create a new function to receive the handler contents.
627 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
628 Type *Int32Type = Type::getInt32Ty(Context);
629 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
631 for (LandingPadInst *LPad : LPads) {
632 // Look for evidence that this landingpad has already been processed.
633 bool LPadHasActionList = false;
634 BasicBlock *LPadBB = LPad->getParent();
635 for (Instruction &Inst : *LPadBB) {
636 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>())) {
637 LPadHasActionList = true;
642 // If we've already outlined the handlers for this landingpad,
643 // there's nothing more to do here.
644 if (LPadHasActionList)
647 // If either of the values in the aggregate returned by the landing pad is
648 // extracted and stored to memory, promote the stored value to a register.
649 promoteLandingPadValues(LPad);
651 LandingPadActions Actions;
652 mapLandingPadBlocks(LPad, Actions);
654 HandlersOutlined |= !Actions.actions().empty();
655 for (ActionHandler *Action : Actions) {
656 if (Action->hasBeenProcessed())
658 BasicBlock *StartBB = Action->getStartBlock();
660 // SEH doesn't do any outlining for catches. Instead, pass the handler
661 // basic block addr to llvm.eh.actions and list the block as a return
663 if (isAsynchronousEHPersonality(Personality)) {
664 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
665 processSEHCatchHandler(CatchAction, StartBB);
670 outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo);
673 // Split the block after the landingpad instruction so that it is just a
674 // call to llvm.eh.actions followed by indirectbr.
675 assert(!isa<PHINode>(LPadBB->begin()) && "lpad phi not removed");
676 LPadBB->splitBasicBlock(LPad->getNextNode(),
677 LPadBB->getName() + ".prepsplit");
678 // Erase the branch inserted by the split so we can insert indirectbr.
679 LPadBB->getTerminator()->eraseFromParent();
681 // Replace all extracted values with undef and ultimately replace the
682 // landingpad with undef.
683 // FIXME: This doesn't handle SEH GetExceptionCode(). For now, we just give
684 // out undef until we figure out the codegen support.
685 SmallVector<Instruction *, 4> Extracts;
686 for (User *U : LPad->users()) {
687 auto *E = dyn_cast<ExtractValueInst>(U);
690 assert(E->getNumIndices() == 1 &&
691 "Unexpected operation: extracting both landing pad values");
692 Extracts.push_back(E);
694 for (Instruction *E : Extracts) {
695 E->replaceAllUsesWith(UndefValue::get(E->getType()));
696 E->eraseFromParent();
698 LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
700 // Add a call to describe the actions for this landing pad.
701 std::vector<Value *> ActionArgs;
702 for (ActionHandler *Action : Actions) {
703 // Action codes from docs are: 0 cleanup, 1 catch.
704 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
705 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
706 ActionArgs.push_back(CatchAction->getSelector());
707 // Find the frame escape index of the exception object alloca in the
709 int FrameEscapeIdx = -1;
710 Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
711 if (EHObj && !isa<ConstantPointerNull>(EHObj)) {
712 auto I = FrameVarInfo.find(EHObj);
713 assert(I != FrameVarInfo.end() &&
714 "failed to map llvm.eh.begincatch var");
715 FrameEscapeIdx = std::distance(FrameVarInfo.begin(), I);
717 ActionArgs.push_back(ConstantInt::get(Int32Type, FrameEscapeIdx));
719 ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
721 ActionArgs.push_back(Action->getHandlerBlockOrFunc());
724 CallInst::Create(ActionIntrin, ActionArgs, "recover", LPadBB);
726 // Add an indirect branch listing possible successors of the catch handlers.
727 SetVector<BasicBlock *> ReturnTargets;
728 for (ActionHandler *Action : Actions) {
729 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
730 const auto &CatchTargets = CatchAction->getReturnTargets();
731 ReturnTargets.insert(CatchTargets.begin(), CatchTargets.end());
734 IndirectBrInst *Branch =
735 IndirectBrInst::Create(Recover, ReturnTargets.size(), LPadBB);
736 for (BasicBlock *Target : ReturnTargets)
737 Branch->addDestination(Target);
738 } // End for each landingpad
740 // If nothing got outlined, there is no more processing to be done.
741 if (!HandlersOutlined)
744 // Replace any nested landing pad stubs with the correct action handler.
745 // This must be done before we remove unreachable blocks because it
746 // cleans up references to outlined blocks that will be deleted.
747 for (auto &LPadPair : NestedLPtoOriginalLP)
748 completeNestedLandingPad(&F, LPadPair.first, LPadPair.second, FrameVarInfo);
749 NestedLPtoOriginalLP.clear();
751 F.addFnAttr("wineh-parent", F.getName());
753 // Delete any blocks that were only used by handlers that were outlined above.
754 removeUnreachableBlocks(F);
756 BasicBlock *Entry = &F.getEntryBlock();
757 IRBuilder<> Builder(F.getParent()->getContext());
758 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
760 Function *FrameEscapeFn =
761 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
762 Function *RecoverFrameFn =
763 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
764 SmallVector<Value *, 8> AllocasToEscape;
766 // Scan the entry block for an existing call to llvm.frameescape. We need to
767 // keep escaping those objects.
768 for (Instruction &I : F.front()) {
769 auto *II = dyn_cast<IntrinsicInst>(&I);
770 if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
771 auto Args = II->arg_operands();
772 AllocasToEscape.append(Args.begin(), Args.end());
773 II->eraseFromParent();
778 // Finally, replace all of the temporary allocas for frame variables used in
779 // the outlined handlers with calls to llvm.framerecover.
780 for (auto &VarInfoEntry : FrameVarInfo) {
781 Value *ParentVal = VarInfoEntry.first;
782 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
783 AllocaInst *ParentAlloca = cast<AllocaInst>(ParentVal);
785 // FIXME: We should try to sink unescaped allocas from the parent frame into
786 // the child frame. If the alloca is escaped, we have to use the lifetime
787 // markers to ensure that the alloca is only live within the child frame.
789 // Add this alloca to the list of things to escape.
790 AllocasToEscape.push_back(ParentAlloca);
792 // Next replace all outlined allocas that are mapped to it.
793 for (AllocaInst *TempAlloca : Allocas) {
794 if (TempAlloca == getCatchObjectSentinel())
795 continue; // Skip catch parameter sentinels.
796 Function *HandlerFn = TempAlloca->getParent()->getParent();
797 // FIXME: Sink this GEP into the blocks where it is used.
798 Builder.SetInsertPoint(TempAlloca);
799 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
800 Value *RecoverArgs[] = {
801 Builder.CreateBitCast(&F, Int8PtrType, ""),
802 &(HandlerFn->getArgumentList().back()),
803 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
804 Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
805 // Add a pointer bitcast if the alloca wasn't an i8.
806 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
807 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
809 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
811 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
812 TempAlloca->removeFromParent();
813 RecoveredAlloca->takeName(TempAlloca);
816 } // End for each FrameVarInfo entry.
818 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
820 Builder.SetInsertPoint(&F.getEntryBlock().back());
821 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
823 // Clean up the handler action maps we created for this function
824 DeleteContainerSeconds(CatchHandlerMap);
825 CatchHandlerMap.clear();
826 DeleteContainerSeconds(CleanupHandlerMap);
827 CleanupHandlerMap.clear();
829 return HandlersOutlined;
832 void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
833 // If the return values of the landing pad instruction are extracted and
834 // stored to memory, we want to promote the store locations to reg values.
835 SmallVector<AllocaInst *, 2> EHAllocas;
837 // The landingpad instruction returns an aggregate value. Typically, its
838 // value will be passed to a pair of extract value instructions and the
839 // results of those extracts are often passed to store instructions.
840 // In unoptimized code the stored value will often be loaded and then stored
842 for (auto *U : LPad->users()) {
843 ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
847 for (auto *EU : Extract->users()) {
848 if (auto *Store = dyn_cast<StoreInst>(EU)) {
849 auto *AV = cast<AllocaInst>(Store->getPointerOperand());
850 EHAllocas.push_back(AV);
855 // We can't do this without a dominator tree.
858 if (!EHAllocas.empty()) {
859 PromoteMemToReg(EHAllocas, *DT);
863 // After promotion, some extracts may be trivially dead. Remove them.
864 SmallVector<Value *, 4> Users(LPad->user_begin(), LPad->user_end());
865 for (auto *U : Users)
866 RecursivelyDeleteTriviallyDeadInstructions(U);
869 void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,
870 LandingPadInst *OutlinedLPad,
871 const LandingPadInst *OriginalLPad,
872 FrameVarInfoMap &FrameVarInfo) {
873 // Get the nested block and erase the unreachable instruction that was
874 // temporarily inserted as its terminator.
875 LLVMContext &Context = ParentFn->getContext();
876 BasicBlock *OutlinedBB = OutlinedLPad->getParent();
877 assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
878 OutlinedBB->getTerminator()->eraseFromParent();
879 // That should leave OutlinedLPad as the last instruction in its block.
880 assert(&OutlinedBB->back() == OutlinedLPad);
882 // The original landing pad will have already had its action intrinsic
883 // built by the outlining loop. We need to clone that into the outlined
884 // location. It may also be necessary to add references to the exception
885 // variables to the outlined handler in which this landing pad is nested
886 // and remap return instructions in the nested handlers that should return
887 // to an address in the outlined handler.
888 Function *OutlinedHandlerFn = OutlinedBB->getParent();
889 BasicBlock::const_iterator II = OriginalLPad;
891 // The instruction after the landing pad should now be a call to eh.actions.
892 const Instruction *Recover = II;
893 assert(match(Recover, m_Intrinsic<Intrinsic::eh_actions>()));
894 IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover->clone());
896 // Remap the exception variables into the outlined function.
897 WinEHFrameVariableMaterializer Materializer(OutlinedHandlerFn, FrameVarInfo);
898 SmallVector<BlockAddress *, 4> ActionTargets;
899 SmallVector<ActionHandler *, 4> ActionList;
900 parseEHActions(EHActions, ActionList);
901 for (auto *Action : ActionList) {
902 auto *Catch = dyn_cast<CatchHandler>(Action);
905 // The dyn_cast to function here selects C++ catch handlers and skips
906 // SEH catch handlers.
907 auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
910 // Visit all the return instructions, looking for places that return
911 // to a location within OutlinedHandlerFn.
912 for (BasicBlock &NestedHandlerBB : *Handler) {
913 auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
917 // Handler functions must always return a block address.
918 BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
919 // The original target will have been in the main parent function,
920 // but if it is the address of a block that has been outlined, it
921 // should be a block that was outlined into OutlinedHandlerFn.
922 assert(BA->getFunction() == ParentFn);
924 // Ignore targets that aren't part of OutlinedHandlerFn.
925 if (!LPadTargetBlocks.count(BA->getBasicBlock()))
928 // If the return value is the address ofF a block that we
929 // previously outlined into the parent handler function, replace
930 // the return instruction and add the mapped target to the list
931 // of possible return addresses.
932 BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
933 assert(MappedBB->getParent() == OutlinedHandlerFn);
934 BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
935 Ret->eraseFromParent();
936 ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
937 ActionTargets.push_back(NewBA);
940 DeleteContainerPointers(ActionList);
942 OutlinedBB->getInstList().push_back(EHActions);
944 // Insert an indirect branch into the outlined landing pad BB.
945 IndirectBrInst *IBr = IndirectBrInst::Create(EHActions, 0, OutlinedBB);
946 // Add the previously collected action targets.
947 for (auto *Target : ActionTargets)
948 IBr->addDestination(Target->getBasicBlock());
951 // This function examines a block to determine whether the block ends with a
952 // conditional branch to a catch handler based on a selector comparison.
953 // This function is used both by the WinEHPrepare::findSelectorComparison() and
954 // WinEHCleanupDirector::handleTypeIdFor().
955 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
956 Constant *&Selector, BasicBlock *&NextBB) {
957 ICmpInst::Predicate Pred;
958 BasicBlock *TBB, *FBB;
961 if (!match(BB->getTerminator(),
962 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
966 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
967 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
970 if (Pred == CmpInst::ICMP_EQ) {
976 if (Pred == CmpInst::ICMP_NE) {
985 static bool isCatchBlock(BasicBlock *BB) {
986 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
988 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_begincatch>()))
994 static BasicBlock *createStubLandingPad(Function *Handler,
995 Value *PersonalityFn) {
996 // FIXME: Finish this!
997 LLVMContext &Context = Handler->getContext();
998 BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
999 Handler->getBasicBlockList().push_back(StubBB);
1000 IRBuilder<> Builder(StubBB);
1001 LandingPadInst *LPad = Builder.CreateLandingPad(
1002 llvm::StructType::get(Type::getInt8PtrTy(Context),
1003 Type::getInt32Ty(Context), nullptr),
1005 // Insert a call to llvm.eh.actions so that we don't try to outline this lpad.
1006 Function *ActionIntrin = Intrinsic::getDeclaration(Handler->getParent(),
1007 Intrinsic::eh_actions);
1008 Builder.CreateCall(ActionIntrin, "recover");
1009 LPad->setCleanup(true);
1010 Builder.CreateUnreachable();
1014 // Cycles through the blocks in an outlined handler function looking for an
1015 // invoke instruction and inserts an invoke of llvm.donothing with an empty
1016 // landing pad if none is found. The code that generates the .xdata tables for
1017 // the handler needs at least one landing pad to identify the parent function's
1019 void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler,
1020 Value *PersonalityFn) {
1021 ReturnInst *Ret = nullptr;
1022 UnreachableInst *Unreached = nullptr;
1023 for (BasicBlock &BB : *Handler) {
1024 TerminatorInst *Terminator = BB.getTerminator();
1025 // If we find an invoke, there is nothing to be done.
1026 auto *II = dyn_cast<InvokeInst>(Terminator);
1029 // If we've already recorded a return instruction, keep looking for invokes.
1031 Ret = dyn_cast<ReturnInst>(Terminator);
1032 // If we haven't recorded an unreachable instruction, try this terminator.
1034 Unreached = dyn_cast<UnreachableInst>(Terminator);
1037 // If we got this far, the handler contains no invokes. We should have seen
1038 // at least one return or unreachable instruction. We'll insert an invoke of
1039 // llvm.donothing ahead of that instruction.
1040 assert(Ret || Unreached);
1041 TerminatorInst *Term;
1046 BasicBlock *OldRetBB = Term->getParent();
1047 BasicBlock *NewRetBB = SplitBlock(OldRetBB, Term);
1048 // SplitBlock adds an unconditional branch instruction at the end of the
1049 // parent block. We want to replace that with an invoke call, so we can
1051 OldRetBB->getTerminator()->eraseFromParent();
1052 BasicBlock *StubLandingPad = createStubLandingPad(Handler, PersonalityFn);
1054 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
1055 InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
1058 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
1059 LandingPadInst *LPad, BasicBlock *StartBB,
1060 FrameVarInfoMap &VarInfo) {
1061 Module *M = SrcFn->getParent();
1062 LLVMContext &Context = M->getContext();
1064 // Create a new function to receive the handler contents.
1065 Type *Int8PtrType = Type::getInt8PtrTy(Context);
1066 std::vector<Type *> ArgTys;
1067 ArgTys.push_back(Int8PtrType);
1068 ArgTys.push_back(Int8PtrType);
1070 if (Action->getType() == Catch) {
1071 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
1072 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
1073 SrcFn->getName() + ".catch", M);
1075 FunctionType *FnType =
1076 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
1077 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
1078 SrcFn->getName() + ".cleanup", M);
1081 Handler->addFnAttr("wineh-parent", SrcFn->getName());
1083 // Generate a standard prolog to setup the frame recovery structure.
1084 IRBuilder<> Builder(Context);
1085 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
1086 Handler->getBasicBlockList().push_front(Entry);
1087 Builder.SetInsertPoint(Entry);
1088 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
1090 std::unique_ptr<WinEHCloningDirectorBase> Director;
1092 ValueToValueMapTy VMap;
1094 LandingPadMap &LPadMap = LPadMaps[LPad];
1095 if (!LPadMap.isInitialized())
1096 LPadMap.mapLandingPad(LPad);
1097 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1098 Constant *Sel = CatchAction->getSelector();
1099 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap,
1100 NestedLPtoOriginalLP));
1101 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1102 ConstantInt::get(Type::getInt32Ty(Context), 1));
1104 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
1105 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1106 UndefValue::get(Type::getInt32Ty(Context)));
1109 SmallVector<ReturnInst *, 8> Returns;
1110 ClonedCodeInfo OutlinedFunctionInfo;
1112 // If the start block contains PHI nodes, we need to map them.
1113 BasicBlock::iterator II = StartBB->begin();
1114 while (auto *PN = dyn_cast<PHINode>(II)) {
1115 bool Mapped = false;
1116 // Look for PHI values that we have already mapped (such as the selector).
1117 for (Value *Val : PN->incoming_values()) {
1118 if (VMap.count(Val)) {
1119 VMap[PN] = VMap[Val];
1123 // If we didn't find a match for this value, map it as an undef.
1125 VMap[PN] = UndefValue::get(PN->getType());
1130 // The landing pad value may be used by PHI nodes. It will ultimately be
1131 // eliminated, but we need it in the map for intermediate handling.
1132 VMap[LPad] = UndefValue::get(LPad->getType());
1134 // Skip over PHIs and, if applicable, landingpad instructions.
1135 II = StartBB->getFirstInsertionPt();
1137 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
1138 /*ModuleLevelChanges=*/false, Returns, "",
1139 &OutlinedFunctionInfo, Director.get());
1141 // Move all the instructions in the first cloned block into our entry block.
1142 BasicBlock *FirstClonedBB = std::next(Function::iterator(Entry));
1143 Entry->getInstList().splice(Entry->end(), FirstClonedBB->getInstList());
1144 FirstClonedBB->eraseFromParent();
1146 // Make sure we can identify the handler's personality later.
1147 addStubInvokeToHandlerIfNeeded(Handler, LPad->getPersonalityFn());
1149 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1150 WinEHCatchDirector *CatchDirector =
1151 reinterpret_cast<WinEHCatchDirector *>(Director.get());
1152 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
1153 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
1155 // Look for blocks that are not part of the landing pad that we just
1156 // outlined but terminate with a call to llvm.eh.endcatch and a
1157 // branch to a block that is in the handler we just outlined.
1158 // These blocks will be part of a nested landing pad that intends to
1159 // return to an address in this handler. This case is best handled
1160 // after both landing pads have been outlined, so for now we'll just
1161 // save the association of the blocks in LPadTargetBlocks. The
1162 // return instructions which are created from these branches will be
1163 // replaced after all landing pads have been outlined.
1164 for (const auto MapEntry : VMap) {
1165 // VMap maps all values and blocks that were just cloned, but dead
1166 // blocks which were pruned will map to nullptr.
1167 if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
1169 const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
1170 for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
1171 auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
1172 if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
1174 BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
1176 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
1177 // This would indicate that a nested landing pad wants to return
1178 // to a block that is outlined into two different handlers.
1179 assert(!LPadTargetBlocks.count(MappedBB));
1180 LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
1184 } // End if (CatchAction)
1186 Action->setHandlerBlockOrFunc(Handler);
1191 /// This BB must end in a selector dispatch. All we need to do is pass the
1192 /// handler block to llvm.eh.actions and list it as a possible indirectbr
1194 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
1195 BasicBlock *StartBB) {
1196 BasicBlock *HandlerBB;
1199 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
1201 // If this was EH dispatch, this must be a conditional branch to the handler
1203 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
1204 // leading to crashes if some optimization hoists stuff here.
1205 assert(CatchAction->getSelector() && HandlerBB &&
1206 "expected catch EH dispatch");
1208 // This must be a catch-all. Split the block after the landingpad.
1209 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
1211 StartBB->splitBasicBlock(StartBB->getFirstInsertionPt(), "catch.all");
1213 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
1214 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
1215 CatchAction->setReturnTargets(Targets);
1218 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
1219 // Each instance of this class should only ever be used to map a single
1221 assert(OriginLPad == nullptr || OriginLPad == LPad);
1223 // If the landing pad has already been mapped, there's nothing more to do.
1224 if (OriginLPad == LPad)
1229 // The landingpad instruction returns an aggregate value. Typically, its
1230 // value will be passed to a pair of extract value instructions and the
1231 // results of those extracts will have been promoted to reg values before
1232 // this routine is called.
1233 for (auto *U : LPad->users()) {
1234 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
1237 assert(Extract->getNumIndices() == 1 &&
1238 "Unexpected operation: extracting both landing pad values");
1239 unsigned int Idx = *(Extract->idx_begin());
1240 assert((Idx == 0 || Idx == 1) &&
1241 "Unexpected operation: extracting an unknown landing pad element");
1243 ExtractedEHPtrs.push_back(Extract);
1244 } else if (Idx == 1) {
1245 ExtractedSelectors.push_back(Extract);
1250 bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
1251 return BB->getLandingPadInst() == OriginLPad;
1254 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
1255 if (Inst == OriginLPad)
1257 for (auto *Extract : ExtractedEHPtrs) {
1258 if (Inst == Extract)
1261 for (auto *Extract : ExtractedSelectors) {
1262 if (Inst == Extract)
1268 void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
1269 Value *SelectorValue) const {
1270 // Remap all landing pad extract instructions to the specified values.
1271 for (auto *Extract : ExtractedEHPtrs)
1272 VMap[Extract] = EHPtrValue;
1273 for (auto *Extract : ExtractedSelectors)
1274 VMap[Extract] = SelectorValue;
1277 static bool isFrameAddressCall(const Value *V) {
1278 return match(const_cast<Value *>(V),
1279 m_Intrinsic<Intrinsic::frameaddress>(m_SpecificInt(0)));
1282 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
1283 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1284 // If this is one of the boilerplate landing pad instructions, skip it.
1285 // The instruction will have already been remapped in VMap.
1286 if (LPadMap.isLandingPadSpecificInst(Inst))
1287 return CloningDirector::SkipInstruction;
1289 // Nested landing pads will be cloned as stubs, with just the
1290 // landingpad instruction and an unreachable instruction. When
1291 // all landingpads have been outlined, we'll replace this with the
1292 // llvm.eh.actions call and indirect branch created when the
1293 // landing pad was outlined.
1294 if (auto *LPad = dyn_cast<LandingPadInst>(Inst)) {
1295 return handleLandingPad(VMap, LPad, NewBB);
1298 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
1299 return handleInvoke(VMap, Invoke, NewBB);
1301 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
1302 return handleResume(VMap, Resume, NewBB);
1304 if (auto *Cmp = dyn_cast<CmpInst>(Inst))
1305 return handleCompare(VMap, Cmp, NewBB);
1307 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1308 return handleBeginCatch(VMap, Inst, NewBB);
1309 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1310 return handleEndCatch(VMap, Inst, NewBB);
1311 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1312 return handleTypeIdFor(VMap, Inst, NewBB);
1314 // When outlining llvm.frameaddress(i32 0), remap that to the second argument,
1315 // which is the FP of the parent.
1316 if (isFrameAddressCall(Inst)) {
1317 VMap[Inst] = EstablisherFrame;
1318 return CloningDirector::SkipInstruction;
1321 // Continue with the default cloning behavior.
1322 return CloningDirector::CloneInstruction;
1325 CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
1326 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1327 Instruction *NewInst = LPad->clone();
1328 if (LPad->hasName())
1329 NewInst->setName(LPad->getName());
1330 // Save this correlation for later processing.
1331 NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
1332 VMap[LPad] = NewInst;
1333 BasicBlock::InstListType &InstList = NewBB->getInstList();
1334 InstList.push_back(NewInst);
1335 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1336 return CloningDirector::StopCloningBB;
1339 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
1340 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1341 // The argument to the call is some form of the first element of the
1342 // landingpad aggregate value, but that doesn't matter. It isn't used
1344 // The second argument is an outparameter where the exception object will be
1345 // stored. Typically the exception object is a scalar, but it can be an
1346 // aggregate when catching by value.
1347 // FIXME: Leave something behind to indicate where the exception object lives
1348 // for this handler. Should it be part of llvm.eh.actions?
1349 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
1350 "llvm.eh.begincatch found while "
1351 "outlining catch handler.");
1352 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
1353 if (isa<ConstantPointerNull>(ExceptionObjectVar))
1354 return CloningDirector::SkipInstruction;
1355 assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
1356 "catch parameter is not static alloca");
1357 Materializer.escapeCatchObject(ExceptionObjectVar);
1358 return CloningDirector::SkipInstruction;
1361 CloningDirector::CloningAction
1362 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
1363 const Instruction *Inst, BasicBlock *NewBB) {
1364 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1365 // It might be interesting to track whether or not we are inside a catch
1366 // function, but that might make the algorithm more brittle than it needs
1369 // The end catch call can occur in one of two places: either in a
1370 // landingpad block that is part of the catch handlers exception mechanism,
1371 // or at the end of the catch block. However, a catch-all handler may call
1372 // end catch from the original landing pad. If the call occurs in a nested
1373 // landing pad block, we must skip it and continue so that the landing pad
1375 auto *ParentBB = IntrinCall->getParent();
1376 if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
1377 return CloningDirector::SkipInstruction;
1379 // If an end catch occurs anywhere else we want to terminate the handler
1380 // with a return to the code that follows the endcatch call. If the
1381 // next instruction is not an unconditional branch, we need to split the
1382 // block to provide a clear target for the return instruction.
1383 BasicBlock *ContinueBB;
1384 auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
1385 const BranchInst *Branch = dyn_cast<BranchInst>(Next);
1386 if (!Branch || !Branch->isUnconditional()) {
1387 // We're interrupting the cloning process at this location, so the
1388 // const_cast we're doing here will not cause a problem.
1389 ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
1390 const_cast<Instruction *>(cast<Instruction>(Next)));
1392 ContinueBB = Branch->getSuccessor(0);
1395 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
1396 ReturnTargets.push_back(ContinueBB);
1398 // We just added a terminator to the cloned block.
1399 // Tell the caller to stop processing the current basic block so that
1400 // the branch instruction will be skipped.
1401 return CloningDirector::StopCloningBB;
1404 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
1405 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1406 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1407 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1408 // This causes a replacement that will collapse the landing pad CFG based
1409 // on the filter function we intend to match.
1410 if (Selector == CurrentSelector)
1411 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
1413 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1414 // Tell the caller not to clone this instruction.
1415 return CloningDirector::SkipInstruction;
1418 CloningDirector::CloningAction
1419 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
1420 const InvokeInst *Invoke, BasicBlock *NewBB) {
1421 return CloningDirector::CloneInstruction;
1424 CloningDirector::CloningAction
1425 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
1426 const ResumeInst *Resume, BasicBlock *NewBB) {
1427 // Resume instructions shouldn't be reachable from catch handlers.
1428 // We still need to handle it, but it will be pruned.
1429 BasicBlock::InstListType &InstList = NewBB->getInstList();
1430 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1431 return CloningDirector::StopCloningBB;
1434 CloningDirector::CloningAction
1435 WinEHCatchDirector::handleCompare(ValueToValueMapTy &VMap,
1436 const CmpInst *Compare, BasicBlock *NewBB) {
1437 const IntrinsicInst *IntrinCall = nullptr;
1438 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1439 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(0));
1440 } else if (match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1441 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(1));
1444 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1445 // This causes a replacement that will collapse the landing pad CFG based
1446 // on the filter function we intend to match.
1447 if (Selector == CurrentSelector->stripPointerCasts()) {
1448 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1451 VMap[Compare] = ConstantInt::get(SelectorIDType, 0);
1453 return CloningDirector::SkipInstruction;
1455 return CloningDirector::CloneInstruction;
1458 CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
1459 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1460 // The MS runtime will terminate the process if an exception occurs in a
1461 // cleanup handler, so we shouldn't encounter landing pads in the actual
1462 // cleanup code, but they may appear in catch blocks. Depending on where
1463 // we started cloning we may see one, but it will get dropped during dead
1465 Instruction *NewInst = new UnreachableInst(NewBB->getContext());
1466 VMap[LPad] = NewInst;
1467 BasicBlock::InstListType &InstList = NewBB->getInstList();
1468 InstList.push_back(NewInst);
1469 return CloningDirector::StopCloningBB;
1472 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1473 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1474 // Cleanup code may flow into catch blocks or the catch block may be part
1475 // of a branch that will be optimized away. We'll insert a return
1476 // instruction now, but it may be pruned before the cloning process is
1478 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1479 return CloningDirector::StopCloningBB;
1482 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1483 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1484 // Cleanup handlers nested within catch handlers may begin with a call to
1485 // eh.endcatch. We can just ignore that instruction.
1486 return CloningDirector::SkipInstruction;
1489 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1490 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1491 // If we encounter a selector comparison while cloning a cleanup handler,
1492 // we want to stop cloning immediately. Anything after the dispatch
1493 // will be outlined into a different handler.
1494 BasicBlock *CatchHandler;
1497 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1498 CatchHandler, Selector, NextBB)) {
1499 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1500 return CloningDirector::StopCloningBB;
1502 // If eg.typeid.for is called for any other reason, it can be ignored.
1503 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1504 return CloningDirector::SkipInstruction;
1507 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1508 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1509 // All invokes in cleanup handlers can be replaced with calls.
1510 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1511 // Insert a normal call instruction...
1513 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1514 Invoke->getName(), NewBB);
1515 NewCall->setCallingConv(Invoke->getCallingConv());
1516 NewCall->setAttributes(Invoke->getAttributes());
1517 NewCall->setDebugLoc(Invoke->getDebugLoc());
1518 VMap[Invoke] = NewCall;
1520 // Remap the operands.
1521 llvm::RemapInstruction(NewCall, VMap, RF_None, nullptr, &Materializer);
1523 // Insert an unconditional branch to the normal destination.
1524 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1526 // The unwind destination won't be cloned into the new function, so
1527 // we don't need to clean up its phi nodes.
1529 // We just added a terminator to the cloned block.
1530 // Tell the caller to stop processing the current basic block.
1531 return CloningDirector::CloneSuccessors;
1534 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1535 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1536 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1538 // We just added a terminator to the cloned block.
1539 // Tell the caller to stop processing the current basic block so that
1540 // the branch instruction will be skipped.
1541 return CloningDirector::StopCloningBB;
1544 CloningDirector::CloningAction
1545 WinEHCleanupDirector::handleCompare(ValueToValueMapTy &VMap,
1546 const CmpInst *Compare, BasicBlock *NewBB) {
1547 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>()) ||
1548 match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1549 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1550 return CloningDirector::SkipInstruction;
1552 return CloningDirector::CloneInstruction;
1556 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1557 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1558 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1559 BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
1560 Builder.SetInsertPoint(EntryBB, EntryBB->getFirstInsertionPt());
1563 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1564 // If we're asked to materialize a static alloca, we temporarily create an
1565 // alloca in the outlined function and add this to the FrameVarInfo map. When
1566 // all the outlining is complete, we'll replace these temporary allocas with
1567 // calls to llvm.framerecover.
1568 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1569 assert(AV->isStaticAlloca() &&
1570 "cannot materialize un-demoted dynamic alloca");
1571 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1572 Builder.Insert(NewAlloca, AV->getName());
1573 FrameVarInfo[AV].push_back(NewAlloca);
1577 if (isa<Instruction>(V) || isa<Argument>(V)) {
1578 errs() << "Failed to demote instruction used in exception handler:\n";
1579 errs() << " " << *V << '\n';
1580 report_fatal_error("WinEHPrepare failed to demote instruction");
1583 // Don't materialize other values.
1587 void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
1588 // Catch parameter objects have to live in the parent frame. When we see a use
1589 // of a catch parameter, add a sentinel to the multimap to indicate that it's
1590 // used from another handler. This will prevent us from trying to sink the
1591 // alloca into the handler and ensure that the catch parameter is present in
1592 // the call to llvm.frameescape.
1593 FrameVarInfo[V].push_back(getCatchObjectSentinel());
1596 // This function maps the catch and cleanup handlers that are reachable from the
1597 // specified landing pad. The landing pad sequence will have this basic shape:
1599 // <cleanup handler>
1600 // <selector comparison>
1602 // <cleanup handler>
1603 // <selector comparison>
1605 // <cleanup handler>
1608 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1609 // any arbitrary control flow, but all paths through the cleanup code must
1610 // eventually reach the next selector comparison and no path can skip to a
1611 // different selector comparisons, though some paths may terminate abnormally.
1612 // Therefore, we will use a depth first search from the start of any given
1613 // cleanup block and stop searching when we find the next selector comparison.
1615 // If the landingpad instruction does not have a catch clause, we will assume
1616 // that any instructions other than selector comparisons and catch handlers can
1617 // be ignored. In practice, these will only be the boilerplate instructions.
1619 // The catch handlers may also have any control structure, but we are only
1620 // interested in the start of the catch handlers, so we don't need to actually
1621 // follow the flow of the catch handlers. The start of the catch handlers can
1622 // be located from the compare instructions, but they can be skipped in the
1623 // flow by following the contrary branch.
1624 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1625 LandingPadActions &Actions) {
1626 unsigned int NumClauses = LPad->getNumClauses();
1627 unsigned int HandlersFound = 0;
1628 BasicBlock *BB = LPad->getParent();
1630 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1632 if (NumClauses == 0) {
1633 findCleanupHandlers(Actions, BB, nullptr);
1637 VisitedBlockSet VisitedBlocks;
1639 while (HandlersFound != NumClauses) {
1640 BasicBlock *NextBB = nullptr;
1642 // Skip over filter clauses.
1643 if (LPad->isFilter(HandlersFound)) {
1648 // See if the clause we're looking for is a catch-all.
1649 // If so, the catch begins immediately.
1650 Constant *ExpectedSelector = LPad->getClause(HandlersFound)->stripPointerCasts();
1651 if (isa<ConstantPointerNull>(ExpectedSelector)) {
1652 // The catch all must occur last.
1653 assert(HandlersFound == NumClauses - 1);
1655 // There can be additional selector dispatches in the call chain that we
1657 BasicBlock *CatchBlock = nullptr;
1659 while (BB && isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1660 DEBUG(dbgs() << " Found extra catch dispatch in block "
1661 << CatchBlock->getName() << "\n");
1665 // For C++ EH, check if there is any interesting cleanup code before we
1666 // begin the catch. This is important because cleanups cannot rethrow
1667 // exceptions but code called from catches can. For SEH, it isn't
1668 // important if some finally code before a catch-all is executed out of
1669 // line or after recovering from the exception.
1670 if (Personality == EHPersonality::MSVC_CXX)
1671 findCleanupHandlers(Actions, BB, BB);
1673 // Add the catch handler to the action list.
1674 CatchHandler *Action = nullptr;
1675 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1676 // If the CatchHandlerMap already has an entry for this BB, re-use it.
1677 Action = CatchHandlerMap[BB];
1678 assert(Action->getSelector() == ExpectedSelector);
1680 // Since this is a catch-all handler, the selector won't actually appear
1681 // in the code anywhere. ExpectedSelector here is the constant null ptr
1682 // that we got from the landing pad instruction.
1683 Action = new CatchHandler(BB, ExpectedSelector, nullptr);
1684 CatchHandlerMap[BB] = Action;
1686 Actions.insertCatchHandler(Action);
1687 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1690 // Once we reach a catch-all, don't expect to hit a resume instruction.
1695 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1696 assert(CatchAction);
1698 // See if there is any interesting code executed before the dispatch.
1699 findCleanupHandlers(Actions, BB, CatchAction->getStartBlock());
1701 // When the source program contains multiple nested try blocks the catch
1702 // handlers can get strung together in such a way that we can encounter
1703 // a dispatch for a selector that we've already had a handler for.
1704 if (CatchAction->getSelector()->stripPointerCasts() == ExpectedSelector) {
1707 // Add the catch handler to the action list.
1708 DEBUG(dbgs() << " Found catch dispatch in block "
1709 << CatchAction->getStartBlock()->getName() << "\n");
1710 Actions.insertCatchHandler(CatchAction);
1712 // Under some circumstances optimized IR will flow unconditionally into a
1713 // handler block without checking the selector. This can only happen if
1714 // the landing pad has a catch-all handler and the handler for the
1715 // preceeding catch clause is identical to the catch-call handler
1716 // (typically an empty catch). In this case, the handler must be shared
1717 // by all remaining clauses.
1718 if (isa<ConstantPointerNull>(
1719 CatchAction->getSelector()->stripPointerCasts())) {
1720 DEBUG(dbgs() << " Applying early catch-all handler in block "
1721 << CatchAction->getStartBlock()->getName()
1722 << " to all remaining clauses.\n");
1723 Actions.insertCatchHandler(CatchAction);
1727 DEBUG(dbgs() << " Found extra catch dispatch in block "
1728 << CatchAction->getStartBlock()->getName() << "\n");
1731 // Move on to the block after the catch handler.
1735 // If we didn't wind up in a catch-all, see if there is any interesting code
1736 // executed before the resume.
1737 findCleanupHandlers(Actions, BB, BB);
1739 // It's possible that some optimization moved code into a landingpad that
1741 // previously being used for cleanup. If that happens, we need to execute
1743 // extra code from a cleanup handler.
1744 if (Actions.includesCleanup() && !LPad->isCleanup())
1745 LPad->setCleanup(true);
1748 // This function searches starting with the input block for the next
1749 // block that terminates with a branch whose condition is based on a selector
1750 // comparison. This may be the input block. See the mapLandingPadBlocks
1751 // comments for a discussion of control flow assumptions.
1753 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1754 BasicBlock *&NextBB,
1755 VisitedBlockSet &VisitedBlocks) {
1756 // See if we've already found a catch handler use it.
1757 // Call count() first to avoid creating a null entry for blocks
1758 // we haven't seen before.
1759 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1760 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1761 NextBB = Action->getNextBB();
1765 // VisitedBlocks applies only to the current search. We still
1766 // need to consider blocks that we've visited while mapping other
1768 VisitedBlocks.insert(BB);
1770 BasicBlock *CatchBlock = nullptr;
1771 Constant *Selector = nullptr;
1773 // If this is the first time we've visited this block from any landing pad
1774 // look to see if it is a selector dispatch block.
1775 if (!CatchHandlerMap.count(BB)) {
1776 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1777 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1778 CatchHandlerMap[BB] = Action;
1781 // If we encounter a block containing an llvm.eh.begincatch before we
1782 // find a selector dispatch block, the handler is assumed to be
1783 // reached unconditionally. This happens for catch-all blocks, but
1784 // it can also happen for other catch handlers that have been combined
1785 // with the catch-all handler during optimization.
1786 if (isCatchBlock(BB)) {
1787 PointerType *Int8PtrTy = Type::getInt8PtrTy(BB->getContext());
1788 Constant *NullSelector = ConstantPointerNull::get(Int8PtrTy);
1789 CatchHandler *Action = new CatchHandler(BB, NullSelector, nullptr);
1790 CatchHandlerMap[BB] = Action;
1795 // Visit each successor, looking for the dispatch.
1796 // FIXME: We expect to find the dispatch quickly, so this will probably
1797 // work better as a breadth first search.
1798 for (BasicBlock *Succ : successors(BB)) {
1799 if (VisitedBlocks.count(Succ))
1802 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1809 // These are helper functions to combine repeated code from findCleanupHandlers.
1810 static void createCleanupHandler(LandingPadActions &Actions,
1811 CleanupHandlerMapTy &CleanupHandlerMap,
1813 CleanupHandler *Action = new CleanupHandler(BB);
1814 CleanupHandlerMap[BB] = Action;
1815 Actions.insertCleanupHandler(Action);
1816 DEBUG(dbgs() << " Found cleanup code in block "
1817 << Action->getStartBlock()->getName() << "\n");
1820 static CallSite matchOutlinedFinallyCall(BasicBlock *BB,
1821 Instruction *MaybeCall) {
1822 // Look for finally blocks that Clang has already outlined for us.
1823 // %fp = call i8* @llvm.frameaddress(i32 0)
1824 // call void @"fin$parent"(iN 1, i8* %fp)
1825 if (isFrameAddressCall(MaybeCall) && MaybeCall != BB->getTerminator())
1826 MaybeCall = MaybeCall->getNextNode();
1827 CallSite FinallyCall(MaybeCall);
1828 if (!FinallyCall || FinallyCall.arg_size() != 2)
1830 if (!match(FinallyCall.getArgument(0), m_SpecificInt(1)))
1832 if (!isFrameAddressCall(FinallyCall.getArgument(1)))
1837 static BasicBlock *followSingleUnconditionalBranches(BasicBlock *BB) {
1838 // Skip single ubr blocks.
1839 while (BB->getFirstNonPHIOrDbg() == BB->getTerminator()) {
1840 auto *Br = dyn_cast<BranchInst>(BB->getTerminator());
1841 if (Br && Br->isUnconditional())
1842 BB = Br->getSuccessor(0);
1849 // This function searches starting with the input block for the next block that
1850 // contains code that is not part of a catch handler and would not be eliminated
1851 // during handler outlining.
1853 void WinEHPrepare::findCleanupHandlers(LandingPadActions &Actions,
1854 BasicBlock *StartBB, BasicBlock *EndBB) {
1855 // Here we will skip over the following:
1857 // landing pad prolog:
1859 // Unconditional branches
1861 // Selector dispatch
1865 // Anything else marks the start of an interesting block
1867 BasicBlock *BB = StartBB;
1868 // Anything other than an unconditional branch will kick us out of this loop
1869 // one way or another.
1871 BB = followSingleUnconditionalBranches(BB);
1872 // If we've already scanned this block, don't scan it again. If it is
1873 // a cleanup block, there will be an action in the CleanupHandlerMap.
1874 // If we've scanned it and it is not a cleanup block, there will be a
1875 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1876 // be no entry in the CleanupHandlerMap. We must call count() first to
1877 // avoid creating a null entry for blocks we haven't scanned.
1878 if (CleanupHandlerMap.count(BB)) {
1879 if (auto *Action = CleanupHandlerMap[BB]) {
1880 Actions.insertCleanupHandler(Action);
1881 DEBUG(dbgs() << " Found cleanup code in block "
1882 << Action->getStartBlock()->getName() << "\n");
1883 // FIXME: This cleanup might chain into another, and we need to discover
1887 // Here we handle the case where the cleanup handler map contains a
1888 // value for this block but the value is a nullptr. This means that
1889 // we have previously analyzed the block and determined that it did
1890 // not contain any cleanup code. Based on the earlier analysis, we
1891 // know the the block must end in either an unconditional branch, a
1892 // resume or a conditional branch that is predicated on a comparison
1893 // with a selector. Either the resume or the selector dispatch
1894 // would terminate the search for cleanup code, so the unconditional
1895 // branch is the only case for which we might need to continue
1897 BasicBlock *SuccBB = followSingleUnconditionalBranches(BB);
1898 if (SuccBB == BB || SuccBB == EndBB)
1905 // Create an entry in the cleanup handler map for this block. Initially
1906 // we create an entry that says this isn't a cleanup block. If we find
1907 // cleanup code, the caller will replace this entry.
1908 CleanupHandlerMap[BB] = nullptr;
1910 TerminatorInst *Terminator = BB->getTerminator();
1912 // Landing pad blocks have extra instructions we need to accept.
1913 LandingPadMap *LPadMap = nullptr;
1914 if (BB->isLandingPad()) {
1915 LandingPadInst *LPad = BB->getLandingPadInst();
1916 LPadMap = &LPadMaps[LPad];
1917 if (!LPadMap->isInitialized())
1918 LPadMap->mapLandingPad(LPad);
1921 // Look for the bare resume pattern:
1922 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
1923 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
1924 // resume { i8*, i32 } %lpad.val2
1925 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
1926 InsertValueInst *Insert1 = nullptr;
1927 InsertValueInst *Insert2 = nullptr;
1928 Value *ResumeVal = Resume->getOperand(0);
1929 // If the resume value isn't a phi or landingpad value, it should be a
1930 // series of insertions. Identify them so we can avoid them when scanning
1932 if (!isa<PHINode>(ResumeVal) && !isa<LandingPadInst>(ResumeVal)) {
1933 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
1935 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1936 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
1938 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1940 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1942 Instruction *Inst = II;
1943 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1945 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
1947 if (!Inst->hasOneUse() ||
1948 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
1949 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1955 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
1956 if (Branch && Branch->isConditional()) {
1957 // Look for the selector dispatch.
1958 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
1959 // %matches = icmp eq i32 %sel, %2
1960 // br i1 %matches, label %catch14, label %eh.resume
1961 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
1962 if (!Compare || !Compare->isEquality())
1963 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1964 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1966 Instruction *Inst = II;
1967 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
1969 if (Inst == Compare || Inst == Branch)
1971 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1973 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
1975 // The selector dispatch block should always terminate our search.
1976 assert(BB == EndBB);
1980 if (isAsynchronousEHPersonality(Personality)) {
1981 // If this is a landingpad block, split the block at the first non-landing
1983 Instruction *MaybeCall = BB->getFirstNonPHIOrDbg();
1985 while (MaybeCall != BB->getTerminator() &&
1986 LPadMap->isLandingPadSpecificInst(MaybeCall))
1987 MaybeCall = MaybeCall->getNextNode();
1990 // Look for outlined finally calls.
1991 if (CallSite FinallyCall = matchOutlinedFinallyCall(BB, MaybeCall)) {
1992 Function *Fin = FinallyCall.getCalledFunction();
1993 assert(Fin && "outlined finally call should be direct");
1994 auto *Action = new CleanupHandler(BB);
1995 Action->setHandlerBlockOrFunc(Fin);
1996 Actions.insertCleanupHandler(Action);
1997 CleanupHandlerMap[BB] = Action;
1998 DEBUG(dbgs() << " Found frontend-outlined finally call to "
1999 << Fin->getName() << " in block "
2000 << Action->getStartBlock()->getName() << "\n");
2002 // Split the block if there were more interesting instructions and look
2003 // for finally calls in the normal successor block.
2004 BasicBlock *SuccBB = BB;
2005 if (FinallyCall.getInstruction() != BB->getTerminator() &&
2006 FinallyCall.getInstruction()->getNextNode() != BB->getTerminator()) {
2007 SuccBB = BB->splitBasicBlock(FinallyCall.getInstruction()->getNextNode());
2009 if (FinallyCall.isInvoke()) {
2010 SuccBB = cast<InvokeInst>(FinallyCall.getInstruction())->getNormalDest();
2012 SuccBB = BB->getUniqueSuccessor();
2013 assert(SuccBB && "splitOutlinedFinallyCalls didn't insert a branch");
2023 // Anything else is either a catch block or interesting cleanup code.
2024 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2026 Instruction *Inst = II;
2027 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2029 // Unconditional branches fall through to this loop.
2032 // If this is a catch block, there is no cleanup code to be found.
2033 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
2035 // If this a nested landing pad, it may contain an endcatch call.
2036 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
2038 // Anything else makes this interesting cleanup code.
2039 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2042 // Only unconditional branches in empty blocks should get this far.
2043 assert(Branch && Branch->isUnconditional());
2046 BB = Branch->getSuccessor(0);
2050 // This is a public function, declared in WinEHFuncInfo.h and is also
2051 // referenced by WinEHNumbering in FunctionLoweringInfo.cpp.
2052 void llvm::parseEHActions(const IntrinsicInst *II,
2053 SmallVectorImpl<ActionHandler *> &Actions) {
2054 for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
2055 uint64_t ActionKind =
2056 cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
2057 if (ActionKind == /*catch=*/1) {
2058 auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
2059 ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
2060 int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
2061 Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
2063 auto *CH = new CatchHandler(/*BB=*/nullptr, Selector, /*NextBB=*/nullptr);
2064 CH->setHandlerBlockOrFunc(Handler);
2065 CH->setExceptionVarIndex(EHObjIndexVal);
2066 Actions.push_back(CH);
2067 } else if (ActionKind == 0) {
2068 Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
2070 auto *CH = new CleanupHandler(/*BB=*/nullptr);
2071 CH->setHandlerBlockOrFunc(Handler);
2072 Actions.push_back(CH);
2074 llvm_unreachable("Expected either a catch or cleanup handler!");
2077 std::reverse(Actions.begin(), Actions.end());