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), SEHExceptionCodeSlot(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 findSEHEHReturnPoints(Function &F,
93 SetVector<BasicBlock *> &EHReturnBlocks);
94 void findCXXEHReturnPoints(Function &F,
95 SetVector<BasicBlock *> &EHReturnBlocks);
96 void completeNestedLandingPad(Function *ParentFn,
97 LandingPadInst *OutlinedLPad,
98 const LandingPadInst *OriginalLPad,
99 FrameVarInfoMap &VarInfo);
100 bool outlineHandler(ActionHandler *Action, Function *SrcFn,
101 LandingPadInst *LPad, BasicBlock *StartBB,
102 FrameVarInfoMap &VarInfo);
103 void addStubInvokeToHandlerIfNeeded(Function *Handler, Value *PersonalityFn);
105 void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
106 CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
107 VisitedBlockSet &VisitedBlocks);
108 void findCleanupHandlers(LandingPadActions &Actions, BasicBlock *StartBB,
111 void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
113 // All fields are reset by runOnFunction.
115 EHPersonality Personality;
116 CatchHandlerMapTy CatchHandlerMap;
117 CleanupHandlerMapTy CleanupHandlerMap;
118 DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
120 // This maps landing pad instructions found in outlined handlers to
121 // the landing pad instruction in the parent function from which they
122 // were cloned. The cloned/nested landing pad is used as the key
123 // because the landing pad may be cloned into multiple handlers.
124 // This map will be used to add the llvm.eh.actions call to the nested
125 // landing pads after all handlers have been outlined.
126 DenseMap<LandingPadInst *, const LandingPadInst *> NestedLPtoOriginalLP;
128 // This maps blocks in the parent function which are destinations of
129 // catch handlers to cloned blocks in (other) outlined handlers. This
130 // handles the case where a nested landing pads has a catch handler that
131 // returns to a handler function rather than the parent function.
132 // The original block is used as the key here because there should only
133 // ever be one handler function from which the cloned block is not pruned.
134 // The original block will be pruned from the parent function after all
135 // handlers have been outlined. This map will be used to adjust the
136 // return instructions of handlers which return to the block that was
137 // outlined into a handler. This is done after all handlers have been
138 // outlined but before the outlined code is pruned from the parent function.
139 DenseMap<const BasicBlock *, BasicBlock *> LPadTargetBlocks;
141 AllocaInst *SEHExceptionCodeSlot;
144 class WinEHFrameVariableMaterializer : public ValueMaterializer {
146 WinEHFrameVariableMaterializer(Function *OutlinedFn,
147 FrameVarInfoMap &FrameVarInfo);
148 ~WinEHFrameVariableMaterializer() override {}
150 Value *materializeValueFor(Value *V) override;
152 void escapeCatchObject(Value *V);
155 FrameVarInfoMap &FrameVarInfo;
159 class LandingPadMap {
161 LandingPadMap() : OriginLPad(nullptr) {}
162 void mapLandingPad(const LandingPadInst *LPad);
164 bool isInitialized() { return OriginLPad != nullptr; }
166 bool isOriginLandingPadBlock(const BasicBlock *BB) const;
167 bool isLandingPadSpecificInst(const Instruction *Inst) const;
169 void remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
170 Value *SelectorValue) const;
173 const LandingPadInst *OriginLPad;
174 // We will normally only see one of each of these instructions, but
175 // if more than one occurs for some reason we can handle that.
176 TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
177 TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
180 class WinEHCloningDirectorBase : public CloningDirector {
182 WinEHCloningDirectorBase(Function *HandlerFn, FrameVarInfoMap &VarInfo,
183 LandingPadMap &LPadMap)
184 : Materializer(HandlerFn, VarInfo),
185 SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
186 Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
188 auto AI = HandlerFn->getArgumentList().begin();
190 EstablisherFrame = AI;
193 CloningAction handleInstruction(ValueToValueMapTy &VMap,
194 const Instruction *Inst,
195 BasicBlock *NewBB) override;
197 virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
198 const Instruction *Inst,
199 BasicBlock *NewBB) = 0;
200 virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
201 const Instruction *Inst,
202 BasicBlock *NewBB) = 0;
203 virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
204 const Instruction *Inst,
205 BasicBlock *NewBB) = 0;
206 virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
207 const InvokeInst *Invoke,
208 BasicBlock *NewBB) = 0;
209 virtual CloningAction handleResume(ValueToValueMapTy &VMap,
210 const ResumeInst *Resume,
211 BasicBlock *NewBB) = 0;
212 virtual CloningAction handleCompare(ValueToValueMapTy &VMap,
213 const CmpInst *Compare,
214 BasicBlock *NewBB) = 0;
215 virtual CloningAction handleLandingPad(ValueToValueMapTy &VMap,
216 const LandingPadInst *LPad,
217 BasicBlock *NewBB) = 0;
219 ValueMaterializer *getValueMaterializer() override { return &Materializer; }
222 WinEHFrameVariableMaterializer Materializer;
223 Type *SelectorIDType;
225 LandingPadMap &LPadMap;
227 /// The value representing the parent frame pointer.
228 Value *EstablisherFrame;
231 class WinEHCatchDirector : public WinEHCloningDirectorBase {
234 Function *CatchFn, Value *Selector, FrameVarInfoMap &VarInfo,
235 LandingPadMap &LPadMap,
236 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPads)
237 : WinEHCloningDirectorBase(CatchFn, VarInfo, LPadMap),
238 CurrentSelector(Selector->stripPointerCasts()),
239 ExceptionObjectVar(nullptr), NestedLPtoOriginalLP(NestedLPads) {}
241 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
242 const Instruction *Inst,
243 BasicBlock *NewBB) override;
244 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
245 BasicBlock *NewBB) override;
246 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
247 const Instruction *Inst,
248 BasicBlock *NewBB) override;
249 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
250 BasicBlock *NewBB) override;
251 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
252 BasicBlock *NewBB) override;
253 CloningAction handleCompare(ValueToValueMapTy &VMap, const CmpInst *Compare,
254 BasicBlock *NewBB) override;
255 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
256 const LandingPadInst *LPad,
257 BasicBlock *NewBB) override;
259 Value *getExceptionVar() { return ExceptionObjectVar; }
260 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
263 Value *CurrentSelector;
265 Value *ExceptionObjectVar;
266 TinyPtrVector<BasicBlock *> ReturnTargets;
268 // This will be a reference to the field of the same name in the WinEHPrepare
269 // object which instantiates this WinEHCatchDirector object.
270 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPtoOriginalLP;
273 class WinEHCleanupDirector : public WinEHCloningDirectorBase {
275 WinEHCleanupDirector(Function *CleanupFn, FrameVarInfoMap &VarInfo,
276 LandingPadMap &LPadMap)
277 : WinEHCloningDirectorBase(CleanupFn, VarInfo, LPadMap) {}
279 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
280 const Instruction *Inst,
281 BasicBlock *NewBB) override;
282 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
283 BasicBlock *NewBB) override;
284 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
285 const Instruction *Inst,
286 BasicBlock *NewBB) override;
287 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
288 BasicBlock *NewBB) override;
289 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
290 BasicBlock *NewBB) override;
291 CloningAction handleCompare(ValueToValueMapTy &VMap, const CmpInst *Compare,
292 BasicBlock *NewBB) override;
293 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
294 const LandingPadInst *LPad,
295 BasicBlock *NewBB) override;
298 class LandingPadActions {
300 LandingPadActions() : HasCleanupHandlers(false) {}
302 void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
303 void insertCleanupHandler(CleanupHandler *Action) {
304 Actions.push_back(Action);
305 HasCleanupHandlers = true;
308 bool includesCleanup() const { return HasCleanupHandlers; }
310 SmallVectorImpl<ActionHandler *> &actions() { return Actions; }
311 SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
312 SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
315 // Note that this class does not own the ActionHandler objects in this vector.
316 // The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
317 // in the WinEHPrepare class.
318 SmallVector<ActionHandler *, 4> Actions;
319 bool HasCleanupHandlers;
322 } // end anonymous namespace
324 char WinEHPrepare::ID = 0;
325 INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
328 FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
329 return new WinEHPrepare(TM);
332 bool WinEHPrepare::runOnFunction(Function &Fn) {
333 // No need to prepare outlined handlers.
334 if (Fn.hasFnAttribute("wineh-parent"))
337 SmallVector<LandingPadInst *, 4> LPads;
338 SmallVector<ResumeInst *, 4> Resumes;
339 for (BasicBlock &BB : Fn) {
340 if (auto *LP = BB.getLandingPadInst())
342 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
343 Resumes.push_back(Resume);
346 // No need to prepare functions that lack landing pads.
350 // Classify the personality to see what kind of preparation we need.
351 Personality = classifyEHPersonality(LPads.back()->getPersonalityFn());
353 // Do nothing if this is not an MSVC personality.
354 if (!isMSVCEHPersonality(Personality))
357 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
359 // If there were any landing pads, prepareExceptionHandlers will make changes.
360 prepareExceptionHandlers(Fn, LPads);
364 bool WinEHPrepare::doFinalization(Module &M) { return false; }
366 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
367 AU.addRequired<DominatorTreeWrapperPass>();
370 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
371 Constant *&Selector, BasicBlock *&NextBB);
373 // Finds blocks reachable from the starting set Worklist. Does not follow unwind
374 // edges or blocks listed in StopPoints.
375 static void findReachableBlocks(SmallPtrSetImpl<BasicBlock *> &ReachableBBs,
376 SetVector<BasicBlock *> &Worklist,
377 const SetVector<BasicBlock *> *StopPoints) {
378 while (!Worklist.empty()) {
379 BasicBlock *BB = Worklist.pop_back_val();
381 // Don't cross blocks that we should stop at.
382 if (StopPoints && StopPoints->count(BB))
385 if (!ReachableBBs.insert(BB).second)
386 continue; // Already visited.
388 // Don't follow unwind edges of invokes.
389 if (auto *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
390 Worklist.insert(II->getNormalDest());
394 // Otherwise, follow all successors.
395 Worklist.insert(succ_begin(BB), succ_end(BB));
399 // Attempt to find an instruction where a block can be split before
400 // a call to llvm.eh.begincatch and its operands. If the block
401 // begins with the begincatch call or one of its adjacent operands
402 // the block will not be split.
403 static Instruction *findBeginCatchSplitPoint(BasicBlock *BB,
405 // If the begincatch call is already the first instruction in the block,
407 Instruction *FirstNonPHI = BB->getFirstNonPHI();
408 if (II == FirstNonPHI)
411 // If either operand is in the same basic block as the instruction and
412 // isn't used by another instruction before the begincatch call, include it
413 // in the split block.
414 auto *Op0 = dyn_cast<Instruction>(II->getOperand(0));
415 auto *Op1 = dyn_cast<Instruction>(II->getOperand(1));
417 Instruction *I = II->getPrevNode();
418 Instruction *LastI = II;
420 while (I == Op0 || I == Op1) {
421 // If the block begins with one of the operands and there are no other
422 // instructions between the operand and the begincatch call, don't split.
423 if (I == FirstNonPHI)
427 I = I->getPrevNode();
430 // If there is at least one instruction in the block before the begincatch
431 // call and its operands, split the block at either the begincatch or
436 /// Find all points where exceptional control rejoins normal control flow via
437 /// llvm.eh.endcatch. Add them to the normal bb reachability worklist.
438 void WinEHPrepare::findCXXEHReturnPoints(
439 Function &F, SetVector<BasicBlock *> &EHReturnBlocks) {
440 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
441 BasicBlock *BB = BBI;
442 for (Instruction &I : *BB) {
443 if (match(&I, m_Intrinsic<Intrinsic::eh_begincatch>())) {
444 Instruction *SplitPt =
445 findBeginCatchSplitPoint(BB, cast<IntrinsicInst>(&I));
447 // Split the block before the llvm.eh.begincatch call to allow
448 // cleanup and catch code to be distinguished later.
449 // Do not update BBI because we still need to process the
450 // portion of the block that we are splitting off.
451 SplitBlock(BB, SplitPt, DT);
455 if (match(&I, m_Intrinsic<Intrinsic::eh_endcatch>())) {
456 // Split the block after the call to llvm.eh.endcatch if there is
457 // anything other than an unconditional branch, or if the successor
458 // starts with a phi.
459 auto *Br = dyn_cast<BranchInst>(I.getNextNode());
460 if (!Br || !Br->isUnconditional() ||
461 isa<PHINode>(Br->getSuccessor(0)->begin())) {
462 DEBUG(dbgs() << "splitting block " << BB->getName()
463 << " with llvm.eh.endcatch\n");
464 BBI = SplitBlock(BB, I.getNextNode(), DT);
466 // The next BB is normal control flow.
467 EHReturnBlocks.insert(BB->getTerminator()->getSuccessor(0));
474 static bool isCatchAllLandingPad(const BasicBlock *BB) {
475 const LandingPadInst *LP = BB->getLandingPadInst();
478 unsigned N = LP->getNumClauses();
479 return (N > 0 && LP->isCatch(N - 1) &&
480 isa<ConstantPointerNull>(LP->getClause(N - 1)));
483 /// Find all points where exceptions control rejoins normal control flow via
484 /// selector dispatch.
485 void WinEHPrepare::findSEHEHReturnPoints(
486 Function &F, SetVector<BasicBlock *> &EHReturnBlocks) {
487 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
488 BasicBlock *BB = BBI;
489 // If the landingpad is a catch-all, treat the whole lpad as if it is
490 // reachable from normal control flow.
491 // FIXME: This is imprecise. We need a better way of identifying where a
492 // catch-all starts and cleanups stop. As far as LLVM is concerned, there
494 if (isCatchAllLandingPad(BB)) {
495 EHReturnBlocks.insert(BB);
499 BasicBlock *CatchHandler;
502 if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
503 // Split the edge if there is a phi node. Returning from EH to a phi node
504 // is just as impossible as having a phi after an indirectbr.
505 if (isa<PHINode>(CatchHandler->begin())) {
506 DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
507 << " to " << CatchHandler->getName() << '\n');
508 BBI = CatchHandler = SplitCriticalEdge(
509 BB, std::find(succ_begin(BB), succ_end(BB), CatchHandler));
511 EHReturnBlocks.insert(CatchHandler);
516 /// Ensure that all values live into and out of exception handlers are stored
518 /// FIXME: This falls down when values are defined in one handler and live into
519 /// another handler. For example, a cleanup defines a value used only by a
521 void WinEHPrepare::demoteValuesLiveAcrossHandlers(
522 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
523 DEBUG(dbgs() << "Demoting values live across exception handlers in function "
524 << F.getName() << '\n');
526 // Build a set of all non-exceptional blocks and exceptional blocks.
527 // - Non-exceptional blocks are blocks reachable from the entry block while
528 // not following invoke unwind edges.
529 // - Exceptional blocks are blocks reachable from landingpads. Analysis does
530 // not follow llvm.eh.endcatch blocks, which mark a transition from
531 // exceptional to normal control.
532 SmallPtrSet<BasicBlock *, 4> NormalBlocks;
533 SmallPtrSet<BasicBlock *, 4> EHBlocks;
534 SetVector<BasicBlock *> EHReturnBlocks;
535 SetVector<BasicBlock *> Worklist;
537 if (Personality == EHPersonality::MSVC_CXX)
538 findCXXEHReturnPoints(F, EHReturnBlocks);
540 findSEHEHReturnPoints(F, EHReturnBlocks);
543 dbgs() << "identified the following blocks as EH return points:\n";
544 for (BasicBlock *BB : EHReturnBlocks)
545 dbgs() << " " << BB->getName() << '\n';
548 // Join points should not have phis at this point, unless they are a
549 // landingpad, in which case we will demote their phis later.
551 for (BasicBlock *BB : EHReturnBlocks)
552 assert((BB->isLandingPad() || !isa<PHINode>(BB->begin())) &&
553 "non-lpad EH return block has phi");
556 // Normal blocks are the blocks reachable from the entry block and all EH
558 Worklist = EHReturnBlocks;
559 Worklist.insert(&F.getEntryBlock());
560 findReachableBlocks(NormalBlocks, Worklist, nullptr);
562 dbgs() << "marked the following blocks as normal:\n";
563 for (BasicBlock *BB : NormalBlocks)
564 dbgs() << " " << BB->getName() << '\n';
567 // Exceptional blocks are the blocks reachable from landingpads that don't
568 // cross EH return points.
570 for (auto *LPI : LPads)
571 Worklist.insert(LPI->getParent());
572 findReachableBlocks(EHBlocks, Worklist, &EHReturnBlocks);
574 dbgs() << "marked the following blocks as exceptional:\n";
575 for (BasicBlock *BB : EHBlocks)
576 dbgs() << " " << BB->getName() << '\n';
579 SetVector<Argument *> ArgsToDemote;
580 SetVector<Instruction *> InstrsToDemote;
581 for (BasicBlock &BB : F) {
582 bool IsNormalBB = NormalBlocks.count(&BB);
583 bool IsEHBB = EHBlocks.count(&BB);
584 if (!IsNormalBB && !IsEHBB)
585 continue; // Blocks that are neither normal nor EH are unreachable.
586 for (Instruction &I : BB) {
587 for (Value *Op : I.operands()) {
588 // Don't demote static allocas, constants, and labels.
589 if (isa<Constant>(Op) || isa<BasicBlock>(Op) || isa<InlineAsm>(Op))
591 auto *AI = dyn_cast<AllocaInst>(Op);
592 if (AI && AI->isStaticAlloca())
595 if (auto *Arg = dyn_cast<Argument>(Op)) {
597 DEBUG(dbgs() << "Demoting argument " << *Arg
598 << " used by EH instr: " << I << "\n");
599 ArgsToDemote.insert(Arg);
604 auto *OpI = cast<Instruction>(Op);
605 BasicBlock *OpBB = OpI->getParent();
606 // If a value is produced and consumed in the same BB, we don't need to
610 bool IsOpNormalBB = NormalBlocks.count(OpBB);
611 bool IsOpEHBB = EHBlocks.count(OpBB);
612 if (IsNormalBB != IsOpNormalBB || IsEHBB != IsOpEHBB) {
614 dbgs() << "Demoting instruction live in-out from EH:\n";
615 dbgs() << "Instr: " << *OpI << '\n';
616 dbgs() << "User: " << I << '\n';
618 InstrsToDemote.insert(OpI);
624 // Demote values live into and out of handlers.
625 // FIXME: This demotion is inefficient. We should insert spills at the point
626 // of definition, insert one reload in each handler that uses the value, and
627 // insert reloads in the BB used to rejoin normal control flow.
628 Instruction *AllocaInsertPt = F.getEntryBlock().getFirstInsertionPt();
629 for (Instruction *I : InstrsToDemote)
630 DemoteRegToStack(*I, false, AllocaInsertPt);
632 // Demote arguments separately, and only for uses in EH blocks.
633 for (Argument *Arg : ArgsToDemote) {
634 auto *Slot = new AllocaInst(Arg->getType(), nullptr,
635 Arg->getName() + ".reg2mem", AllocaInsertPt);
636 SmallVector<User *, 4> Users(Arg->user_begin(), Arg->user_end());
637 for (User *U : Users) {
638 auto *I = dyn_cast<Instruction>(U);
639 if (I && EHBlocks.count(I->getParent())) {
640 auto *Reload = new LoadInst(Slot, Arg->getName() + ".reload", false, I);
641 U->replaceUsesOfWith(Arg, Reload);
644 new StoreInst(Arg, Slot, AllocaInsertPt);
647 // Demote landingpad phis, as the landingpad will be removed from the machine
649 for (LandingPadInst *LPI : LPads) {
650 BasicBlock *BB = LPI->getParent();
651 while (auto *Phi = dyn_cast<PHINode>(BB->begin()))
652 DemotePHIToStack(Phi, AllocaInsertPt);
655 DEBUG(dbgs() << "Demoted " << InstrsToDemote.size() << " instructions and "
656 << ArgsToDemote.size() << " arguments for WinEHPrepare\n\n");
659 bool WinEHPrepare::prepareExceptionHandlers(
660 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
661 // Don't run on functions that are already prepared.
662 for (LandingPadInst *LPad : LPads) {
663 BasicBlock *LPadBB = LPad->getParent();
664 for (Instruction &Inst : *LPadBB)
665 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>()))
669 demoteValuesLiveAcrossHandlers(F, LPads);
671 // These containers are used to re-map frame variables that are used in
672 // outlined catch and cleanup handlers. They will be populated as the
673 // handlers are outlined.
674 FrameVarInfoMap FrameVarInfo;
676 bool HandlersOutlined = false;
678 Module *M = F.getParent();
679 LLVMContext &Context = M->getContext();
681 // Create a new function to receive the handler contents.
682 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
683 Type *Int32Type = Type::getInt32Ty(Context);
684 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
686 if (isAsynchronousEHPersonality(Personality)) {
687 // FIXME: Switch the ehptr type to i32 and then switch this.
688 SEHExceptionCodeSlot =
689 new AllocaInst(Int8PtrType, nullptr, "seh_exception_code",
690 F.getEntryBlock().getFirstInsertionPt());
693 for (LandingPadInst *LPad : LPads) {
694 // Look for evidence that this landingpad has already been processed.
695 bool LPadHasActionList = false;
696 BasicBlock *LPadBB = LPad->getParent();
697 for (Instruction &Inst : *LPadBB) {
698 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>())) {
699 LPadHasActionList = true;
704 // If we've already outlined the handlers for this landingpad,
705 // there's nothing more to do here.
706 if (LPadHasActionList)
709 // If either of the values in the aggregate returned by the landing pad is
710 // extracted and stored to memory, promote the stored value to a register.
711 promoteLandingPadValues(LPad);
713 LandingPadActions Actions;
714 mapLandingPadBlocks(LPad, Actions);
716 HandlersOutlined |= !Actions.actions().empty();
717 for (ActionHandler *Action : Actions) {
718 if (Action->hasBeenProcessed())
720 BasicBlock *StartBB = Action->getStartBlock();
722 // SEH doesn't do any outlining for catches. Instead, pass the handler
723 // basic block addr to llvm.eh.actions and list the block as a return
725 if (isAsynchronousEHPersonality(Personality)) {
726 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
727 processSEHCatchHandler(CatchAction, StartBB);
732 outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo);
735 // Split the block after the landingpad instruction so that it is just a
736 // call to llvm.eh.actions followed by indirectbr.
737 assert(!isa<PHINode>(LPadBB->begin()) && "lpad phi not removed");
738 SplitBlock(LPadBB, LPad->getNextNode(), DT);
739 // Erase the branch inserted by the split so we can insert indirectbr.
740 LPadBB->getTerminator()->eraseFromParent();
742 // Replace all extracted values with undef and ultimately replace the
743 // landingpad with undef.
744 SmallVector<Instruction *, 4> SEHCodeUses;
745 SmallVector<Instruction *, 4> EHUndefs;
746 for (User *U : LPad->users()) {
747 auto *E = dyn_cast<ExtractValueInst>(U);
750 assert(E->getNumIndices() == 1 &&
751 "Unexpected operation: extracting both landing pad values");
752 unsigned Idx = *E->idx_begin();
753 assert((Idx == 0 || Idx == 1) && "unexpected index");
754 if (Idx == 0 && isAsynchronousEHPersonality(Personality))
755 SEHCodeUses.push_back(E);
757 EHUndefs.push_back(E);
759 for (Instruction *E : EHUndefs) {
760 E->replaceAllUsesWith(UndefValue::get(E->getType()));
761 E->eraseFromParent();
763 LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
765 // Rewrite uses of the exception pointer to loads of an alloca.
766 for (Instruction *E : SEHCodeUses) {
767 SmallVector<Use *, 4> Uses;
768 for (Use &U : E->uses())
770 for (Use *U : Uses) {
771 auto *I = cast<Instruction>(U->getUser());
772 if (isa<ResumeInst>(I))
775 if (auto *Phi = dyn_cast<PHINode>(I))
776 LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false,
777 Phi->getIncomingBlock(*U));
779 LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I);
782 E->replaceAllUsesWith(UndefValue::get(E->getType()));
783 E->eraseFromParent();
786 // Add a call to describe the actions for this landing pad.
787 std::vector<Value *> ActionArgs;
788 for (ActionHandler *Action : Actions) {
789 // Action codes from docs are: 0 cleanup, 1 catch.
790 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
791 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
792 ActionArgs.push_back(CatchAction->getSelector());
793 // Find the frame escape index of the exception object alloca in the
795 int FrameEscapeIdx = -1;
796 Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
797 if (EHObj && !isa<ConstantPointerNull>(EHObj)) {
798 auto I = FrameVarInfo.find(EHObj);
799 assert(I != FrameVarInfo.end() &&
800 "failed to map llvm.eh.begincatch var");
801 FrameEscapeIdx = std::distance(FrameVarInfo.begin(), I);
803 ActionArgs.push_back(ConstantInt::get(Int32Type, FrameEscapeIdx));
805 ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
807 ActionArgs.push_back(Action->getHandlerBlockOrFunc());
810 CallInst::Create(ActionIntrin, ActionArgs, "recover", LPadBB);
812 // Add an indirect branch listing possible successors of the catch handlers.
813 SetVector<BasicBlock *> ReturnTargets;
814 for (ActionHandler *Action : Actions) {
815 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
816 const auto &CatchTargets = CatchAction->getReturnTargets();
817 ReturnTargets.insert(CatchTargets.begin(), CatchTargets.end());
820 IndirectBrInst *Branch =
821 IndirectBrInst::Create(Recover, ReturnTargets.size(), LPadBB);
822 for (BasicBlock *Target : ReturnTargets)
823 Branch->addDestination(Target);
824 } // End for each landingpad
826 // If nothing got outlined, there is no more processing to be done.
827 if (!HandlersOutlined)
830 // Replace any nested landing pad stubs with the correct action handler.
831 // This must be done before we remove unreachable blocks because it
832 // cleans up references to outlined blocks that will be deleted.
833 for (auto &LPadPair : NestedLPtoOriginalLP)
834 completeNestedLandingPad(&F, LPadPair.first, LPadPair.second, FrameVarInfo);
835 NestedLPtoOriginalLP.clear();
837 F.addFnAttr("wineh-parent", F.getName());
839 // Delete any blocks that were only used by handlers that were outlined above.
840 removeUnreachableBlocks(F);
842 BasicBlock *Entry = &F.getEntryBlock();
843 IRBuilder<> Builder(F.getParent()->getContext());
844 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
846 Function *FrameEscapeFn =
847 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
848 Function *RecoverFrameFn =
849 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
850 SmallVector<Value *, 8> AllocasToEscape;
852 // Scan the entry block for an existing call to llvm.frameescape. We need to
853 // keep escaping those objects.
854 for (Instruction &I : F.front()) {
855 auto *II = dyn_cast<IntrinsicInst>(&I);
856 if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
857 auto Args = II->arg_operands();
858 AllocasToEscape.append(Args.begin(), Args.end());
859 II->eraseFromParent();
864 // Finally, replace all of the temporary allocas for frame variables used in
865 // the outlined handlers with calls to llvm.framerecover.
866 for (auto &VarInfoEntry : FrameVarInfo) {
867 Value *ParentVal = VarInfoEntry.first;
868 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
869 AllocaInst *ParentAlloca = cast<AllocaInst>(ParentVal);
871 // FIXME: We should try to sink unescaped allocas from the parent frame into
872 // the child frame. If the alloca is escaped, we have to use the lifetime
873 // markers to ensure that the alloca is only live within the child frame.
875 // Add this alloca to the list of things to escape.
876 AllocasToEscape.push_back(ParentAlloca);
878 // Next replace all outlined allocas that are mapped to it.
879 for (AllocaInst *TempAlloca : Allocas) {
880 if (TempAlloca == getCatchObjectSentinel())
881 continue; // Skip catch parameter sentinels.
882 Function *HandlerFn = TempAlloca->getParent()->getParent();
883 // FIXME: Sink this GEP into the blocks where it is used.
884 Builder.SetInsertPoint(TempAlloca);
885 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
886 Value *RecoverArgs[] = {
887 Builder.CreateBitCast(&F, Int8PtrType, ""),
888 &(HandlerFn->getArgumentList().back()),
889 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
890 Value *RecoveredAlloca = Builder.CreateCall(RecoverFrameFn, RecoverArgs);
891 // Add a pointer bitcast if the alloca wasn't an i8.
892 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
893 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
895 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType());
897 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
898 TempAlloca->removeFromParent();
899 RecoveredAlloca->takeName(TempAlloca);
902 } // End for each FrameVarInfo entry.
904 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
906 Builder.SetInsertPoint(&F.getEntryBlock().back());
907 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
909 if (SEHExceptionCodeSlot) {
910 if (SEHExceptionCodeSlot->hasNUses(0))
911 SEHExceptionCodeSlot->eraseFromParent();
913 PromoteMemToReg(SEHExceptionCodeSlot, *DT);
916 // Clean up the handler action maps we created for this function
917 DeleteContainerSeconds(CatchHandlerMap);
918 CatchHandlerMap.clear();
919 DeleteContainerSeconds(CleanupHandlerMap);
920 CleanupHandlerMap.clear();
922 return HandlersOutlined;
925 void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
926 // If the return values of the landing pad instruction are extracted and
927 // stored to memory, we want to promote the store locations to reg values.
928 SmallVector<AllocaInst *, 2> EHAllocas;
930 // The landingpad instruction returns an aggregate value. Typically, its
931 // value will be passed to a pair of extract value instructions and the
932 // results of those extracts are often passed to store instructions.
933 // In unoptimized code the stored value will often be loaded and then stored
935 for (auto *U : LPad->users()) {
936 ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
940 for (auto *EU : Extract->users()) {
941 if (auto *Store = dyn_cast<StoreInst>(EU)) {
942 auto *AV = cast<AllocaInst>(Store->getPointerOperand());
943 EHAllocas.push_back(AV);
948 // We can't do this without a dominator tree.
951 if (!EHAllocas.empty()) {
952 PromoteMemToReg(EHAllocas, *DT);
956 // After promotion, some extracts may be trivially dead. Remove them.
957 SmallVector<Value *, 4> Users(LPad->user_begin(), LPad->user_end());
958 for (auto *U : Users)
959 RecursivelyDeleteTriviallyDeadInstructions(U);
962 void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,
963 LandingPadInst *OutlinedLPad,
964 const LandingPadInst *OriginalLPad,
965 FrameVarInfoMap &FrameVarInfo) {
966 // Get the nested block and erase the unreachable instruction that was
967 // temporarily inserted as its terminator.
968 LLVMContext &Context = ParentFn->getContext();
969 BasicBlock *OutlinedBB = OutlinedLPad->getParent();
970 assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
971 OutlinedBB->getTerminator()->eraseFromParent();
972 // That should leave OutlinedLPad as the last instruction in its block.
973 assert(&OutlinedBB->back() == OutlinedLPad);
975 // The original landing pad will have already had its action intrinsic
976 // built by the outlining loop. We need to clone that into the outlined
977 // location. It may also be necessary to add references to the exception
978 // variables to the outlined handler in which this landing pad is nested
979 // and remap return instructions in the nested handlers that should return
980 // to an address in the outlined handler.
981 Function *OutlinedHandlerFn = OutlinedBB->getParent();
982 BasicBlock::const_iterator II = OriginalLPad;
984 // The instruction after the landing pad should now be a call to eh.actions.
985 const Instruction *Recover = II;
986 assert(match(Recover, m_Intrinsic<Intrinsic::eh_actions>()));
987 IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover->clone());
989 // Remap the exception variables into the outlined function.
990 WinEHFrameVariableMaterializer Materializer(OutlinedHandlerFn, FrameVarInfo);
991 SmallVector<BlockAddress *, 4> ActionTargets;
992 SmallVector<ActionHandler *, 4> ActionList;
993 parseEHActions(EHActions, ActionList);
994 for (auto *Action : ActionList) {
995 auto *Catch = dyn_cast<CatchHandler>(Action);
998 // The dyn_cast to function here selects C++ catch handlers and skips
999 // SEH catch handlers.
1000 auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
1003 // Visit all the return instructions, looking for places that return
1004 // to a location within OutlinedHandlerFn.
1005 for (BasicBlock &NestedHandlerBB : *Handler) {
1006 auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
1010 // Handler functions must always return a block address.
1011 BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
1012 // The original target will have been in the main parent function,
1013 // but if it is the address of a block that has been outlined, it
1014 // should be a block that was outlined into OutlinedHandlerFn.
1015 assert(BA->getFunction() == ParentFn);
1017 // Ignore targets that aren't part of OutlinedHandlerFn.
1018 if (!LPadTargetBlocks.count(BA->getBasicBlock()))
1021 // If the return value is the address ofF a block that we
1022 // previously outlined into the parent handler function, replace
1023 // the return instruction and add the mapped target to the list
1024 // of possible return addresses.
1025 BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
1026 assert(MappedBB->getParent() == OutlinedHandlerFn);
1027 BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
1028 Ret->eraseFromParent();
1029 ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
1030 ActionTargets.push_back(NewBA);
1033 DeleteContainerPointers(ActionList);
1035 OutlinedBB->getInstList().push_back(EHActions);
1037 // Insert an indirect branch into the outlined landing pad BB.
1038 IndirectBrInst *IBr = IndirectBrInst::Create(EHActions, 0, OutlinedBB);
1039 // Add the previously collected action targets.
1040 for (auto *Target : ActionTargets)
1041 IBr->addDestination(Target->getBasicBlock());
1044 // This function examines a block to determine whether the block ends with a
1045 // conditional branch to a catch handler based on a selector comparison.
1046 // This function is used both by the WinEHPrepare::findSelectorComparison() and
1047 // WinEHCleanupDirector::handleTypeIdFor().
1048 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
1049 Constant *&Selector, BasicBlock *&NextBB) {
1050 ICmpInst::Predicate Pred;
1051 BasicBlock *TBB, *FBB;
1054 if (!match(BB->getTerminator(),
1055 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
1059 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
1060 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
1063 if (Pred == CmpInst::ICMP_EQ) {
1069 if (Pred == CmpInst::ICMP_NE) {
1078 static bool isCatchBlock(BasicBlock *BB) {
1079 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1081 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_begincatch>()))
1087 static BasicBlock *createStubLandingPad(Function *Handler,
1088 Value *PersonalityFn) {
1089 // FIXME: Finish this!
1090 LLVMContext &Context = Handler->getContext();
1091 BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
1092 Handler->getBasicBlockList().push_back(StubBB);
1093 IRBuilder<> Builder(StubBB);
1094 LandingPadInst *LPad = Builder.CreateLandingPad(
1095 llvm::StructType::get(Type::getInt8PtrTy(Context),
1096 Type::getInt32Ty(Context), nullptr),
1098 // Insert a call to llvm.eh.actions so that we don't try to outline this lpad.
1099 Function *ActionIntrin =
1100 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::eh_actions);
1101 Builder.CreateCall(ActionIntrin, "recover");
1102 LPad->setCleanup(true);
1103 Builder.CreateUnreachable();
1107 // Cycles through the blocks in an outlined handler function looking for an
1108 // invoke instruction and inserts an invoke of llvm.donothing with an empty
1109 // landing pad if none is found. The code that generates the .xdata tables for
1110 // the handler needs at least one landing pad to identify the parent function's
1112 void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler,
1113 Value *PersonalityFn) {
1114 ReturnInst *Ret = nullptr;
1115 UnreachableInst *Unreached = nullptr;
1116 for (BasicBlock &BB : *Handler) {
1117 TerminatorInst *Terminator = BB.getTerminator();
1118 // If we find an invoke, there is nothing to be done.
1119 auto *II = dyn_cast<InvokeInst>(Terminator);
1122 // If we've already recorded a return instruction, keep looking for invokes.
1124 Ret = dyn_cast<ReturnInst>(Terminator);
1125 // If we haven't recorded an unreachable instruction, try this terminator.
1127 Unreached = dyn_cast<UnreachableInst>(Terminator);
1130 // If we got this far, the handler contains no invokes. We should have seen
1131 // at least one return or unreachable instruction. We'll insert an invoke of
1132 // llvm.donothing ahead of that instruction.
1133 assert(Ret || Unreached);
1134 TerminatorInst *Term;
1139 BasicBlock *OldRetBB = Term->getParent();
1140 BasicBlock *NewRetBB = SplitBlock(OldRetBB, Term, DT);
1141 // SplitBlock adds an unconditional branch instruction at the end of the
1142 // parent block. We want to replace that with an invoke call, so we can
1144 OldRetBB->getTerminator()->eraseFromParent();
1145 BasicBlock *StubLandingPad = createStubLandingPad(Handler, PersonalityFn);
1147 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
1148 InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
1151 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
1152 LandingPadInst *LPad, BasicBlock *StartBB,
1153 FrameVarInfoMap &VarInfo) {
1154 Module *M = SrcFn->getParent();
1155 LLVMContext &Context = M->getContext();
1157 // Create a new function to receive the handler contents.
1158 Type *Int8PtrType = Type::getInt8PtrTy(Context);
1159 std::vector<Type *> ArgTys;
1160 ArgTys.push_back(Int8PtrType);
1161 ArgTys.push_back(Int8PtrType);
1163 if (Action->getType() == Catch) {
1164 FunctionType *FnType = FunctionType::get(Int8PtrType, ArgTys, false);
1165 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
1166 SrcFn->getName() + ".catch", M);
1168 FunctionType *FnType =
1169 FunctionType::get(Type::getVoidTy(Context), ArgTys, false);
1170 Handler = Function::Create(FnType, GlobalVariable::InternalLinkage,
1171 SrcFn->getName() + ".cleanup", M);
1174 Handler->addFnAttr("wineh-parent", SrcFn->getName());
1176 // Generate a standard prolog to setup the frame recovery structure.
1177 IRBuilder<> Builder(Context);
1178 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
1179 Handler->getBasicBlockList().push_front(Entry);
1180 Builder.SetInsertPoint(Entry);
1181 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
1183 std::unique_ptr<WinEHCloningDirectorBase> Director;
1185 ValueToValueMapTy VMap;
1187 LandingPadMap &LPadMap = LPadMaps[LPad];
1188 if (!LPadMap.isInitialized())
1189 LPadMap.mapLandingPad(LPad);
1190 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1191 Constant *Sel = CatchAction->getSelector();
1192 Director.reset(new WinEHCatchDirector(Handler, Sel, VarInfo, LPadMap,
1193 NestedLPtoOriginalLP));
1194 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1195 ConstantInt::get(Type::getInt32Ty(Context), 1));
1197 Director.reset(new WinEHCleanupDirector(Handler, VarInfo, LPadMap));
1198 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1199 UndefValue::get(Type::getInt32Ty(Context)));
1202 SmallVector<ReturnInst *, 8> Returns;
1203 ClonedCodeInfo OutlinedFunctionInfo;
1205 // If the start block contains PHI nodes, we need to map them.
1206 BasicBlock::iterator II = StartBB->begin();
1207 while (auto *PN = dyn_cast<PHINode>(II)) {
1208 bool Mapped = false;
1209 // Look for PHI values that we have already mapped (such as the selector).
1210 for (Value *Val : PN->incoming_values()) {
1211 if (VMap.count(Val)) {
1212 VMap[PN] = VMap[Val];
1216 // If we didn't find a match for this value, map it as an undef.
1218 VMap[PN] = UndefValue::get(PN->getType());
1223 // The landing pad value may be used by PHI nodes. It will ultimately be
1224 // eliminated, but we need it in the map for intermediate handling.
1225 VMap[LPad] = UndefValue::get(LPad->getType());
1227 // Skip over PHIs and, if applicable, landingpad instructions.
1228 II = StartBB->getFirstInsertionPt();
1230 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
1231 /*ModuleLevelChanges=*/false, Returns, "",
1232 &OutlinedFunctionInfo, Director.get());
1234 // Move all the instructions in the cloned "entry" block into our entry block.
1235 // Depending on how the parent function was laid out, the block that will
1236 // correspond to the outlined entry block may not be the first block in the
1237 // list. We can recognize it, however, as the cloned block which has no
1238 // predecessors. Any other block wouldn't have been cloned if it didn't
1239 // have a predecessor which was also cloned.
1240 Function::iterator ClonedIt = std::next(Function::iterator(Entry));
1241 while (!pred_empty(ClonedIt))
1243 BasicBlock *ClonedEntryBB = ClonedIt;
1244 assert(ClonedEntryBB);
1245 Entry->getInstList().splice(Entry->end(), ClonedEntryBB->getInstList());
1246 ClonedEntryBB->eraseFromParent();
1248 // Make sure we can identify the handler's personality later.
1249 addStubInvokeToHandlerIfNeeded(Handler, LPad->getPersonalityFn());
1251 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1252 WinEHCatchDirector *CatchDirector =
1253 reinterpret_cast<WinEHCatchDirector *>(Director.get());
1254 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
1255 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
1257 // Look for blocks that are not part of the landing pad that we just
1258 // outlined but terminate with a call to llvm.eh.endcatch and a
1259 // branch to a block that is in the handler we just outlined.
1260 // These blocks will be part of a nested landing pad that intends to
1261 // return to an address in this handler. This case is best handled
1262 // after both landing pads have been outlined, so for now we'll just
1263 // save the association of the blocks in LPadTargetBlocks. The
1264 // return instructions which are created from these branches will be
1265 // replaced after all landing pads have been outlined.
1266 for (const auto MapEntry : VMap) {
1267 // VMap maps all values and blocks that were just cloned, but dead
1268 // blocks which were pruned will map to nullptr.
1269 if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
1271 const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
1272 for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
1273 auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
1274 if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
1276 BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
1278 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
1279 // This would indicate that a nested landing pad wants to return
1280 // to a block that is outlined into two different handlers.
1281 assert(!LPadTargetBlocks.count(MappedBB));
1282 LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
1286 } // End if (CatchAction)
1288 Action->setHandlerBlockOrFunc(Handler);
1293 /// This BB must end in a selector dispatch. All we need to do is pass the
1294 /// handler block to llvm.eh.actions and list it as a possible indirectbr
1296 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
1297 BasicBlock *StartBB) {
1298 BasicBlock *HandlerBB;
1301 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
1303 // If this was EH dispatch, this must be a conditional branch to the handler
1305 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
1306 // leading to crashes if some optimization hoists stuff here.
1307 assert(CatchAction->getSelector() && HandlerBB &&
1308 "expected catch EH dispatch");
1310 // This must be a catch-all. Split the block after the landingpad.
1311 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
1312 HandlerBB = SplitBlock(StartBB, StartBB->getFirstInsertionPt(), DT);
1314 IRBuilder<> Builder(HandlerBB->getFirstInsertionPt());
1315 Function *EHCodeFn = Intrinsic::getDeclaration(
1316 StartBB->getParent()->getParent(), Intrinsic::eh_exceptioncode);
1317 Value *Code = Builder.CreateCall(EHCodeFn, "sehcode");
1318 Code = Builder.CreateIntToPtr(Code, SEHExceptionCodeSlot->getAllocatedType());
1319 Builder.CreateStore(Code, SEHExceptionCodeSlot);
1320 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
1321 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
1322 CatchAction->setReturnTargets(Targets);
1325 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
1326 // Each instance of this class should only ever be used to map a single
1328 assert(OriginLPad == nullptr || OriginLPad == LPad);
1330 // If the landing pad has already been mapped, there's nothing more to do.
1331 if (OriginLPad == LPad)
1336 // The landingpad instruction returns an aggregate value. Typically, its
1337 // value will be passed to a pair of extract value instructions and the
1338 // results of those extracts will have been promoted to reg values before
1339 // this routine is called.
1340 for (auto *U : LPad->users()) {
1341 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
1344 assert(Extract->getNumIndices() == 1 &&
1345 "Unexpected operation: extracting both landing pad values");
1346 unsigned int Idx = *(Extract->idx_begin());
1347 assert((Idx == 0 || Idx == 1) &&
1348 "Unexpected operation: extracting an unknown landing pad element");
1350 ExtractedEHPtrs.push_back(Extract);
1351 } else if (Idx == 1) {
1352 ExtractedSelectors.push_back(Extract);
1357 bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
1358 return BB->getLandingPadInst() == OriginLPad;
1361 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
1362 if (Inst == OriginLPad)
1364 for (auto *Extract : ExtractedEHPtrs) {
1365 if (Inst == Extract)
1368 for (auto *Extract : ExtractedSelectors) {
1369 if (Inst == Extract)
1375 void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
1376 Value *SelectorValue) const {
1377 // Remap all landing pad extract instructions to the specified values.
1378 for (auto *Extract : ExtractedEHPtrs)
1379 VMap[Extract] = EHPtrValue;
1380 for (auto *Extract : ExtractedSelectors)
1381 VMap[Extract] = SelectorValue;
1384 static bool isFrameAddressCall(const Value *V) {
1385 return match(const_cast<Value *>(V),
1386 m_Intrinsic<Intrinsic::frameaddress>(m_SpecificInt(0)));
1389 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
1390 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1391 // If this is one of the boilerplate landing pad instructions, skip it.
1392 // The instruction will have already been remapped in VMap.
1393 if (LPadMap.isLandingPadSpecificInst(Inst))
1394 return CloningDirector::SkipInstruction;
1396 // Nested landing pads will be cloned as stubs, with just the
1397 // landingpad instruction and an unreachable instruction. When
1398 // all landingpads have been outlined, we'll replace this with the
1399 // llvm.eh.actions call and indirect branch created when the
1400 // landing pad was outlined.
1401 if (auto *LPad = dyn_cast<LandingPadInst>(Inst)) {
1402 return handleLandingPad(VMap, LPad, NewBB);
1405 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
1406 return handleInvoke(VMap, Invoke, NewBB);
1408 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
1409 return handleResume(VMap, Resume, NewBB);
1411 if (auto *Cmp = dyn_cast<CmpInst>(Inst))
1412 return handleCompare(VMap, Cmp, NewBB);
1414 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1415 return handleBeginCatch(VMap, Inst, NewBB);
1416 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1417 return handleEndCatch(VMap, Inst, NewBB);
1418 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1419 return handleTypeIdFor(VMap, Inst, NewBB);
1421 // When outlining llvm.frameaddress(i32 0), remap that to the second argument,
1422 // which is the FP of the parent.
1423 if (isFrameAddressCall(Inst)) {
1424 VMap[Inst] = EstablisherFrame;
1425 return CloningDirector::SkipInstruction;
1428 // Continue with the default cloning behavior.
1429 return CloningDirector::CloneInstruction;
1432 CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
1433 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1434 Instruction *NewInst = LPad->clone();
1435 if (LPad->hasName())
1436 NewInst->setName(LPad->getName());
1437 // Save this correlation for later processing.
1438 NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
1439 VMap[LPad] = NewInst;
1440 BasicBlock::InstListType &InstList = NewBB->getInstList();
1441 InstList.push_back(NewInst);
1442 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1443 return CloningDirector::StopCloningBB;
1446 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
1447 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1448 // The argument to the call is some form of the first element of the
1449 // landingpad aggregate value, but that doesn't matter. It isn't used
1451 // The second argument is an outparameter where the exception object will be
1452 // stored. Typically the exception object is a scalar, but it can be an
1453 // aggregate when catching by value.
1454 // FIXME: Leave something behind to indicate where the exception object lives
1455 // for this handler. Should it be part of llvm.eh.actions?
1456 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
1457 "llvm.eh.begincatch found while "
1458 "outlining catch handler.");
1459 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
1460 if (isa<ConstantPointerNull>(ExceptionObjectVar))
1461 return CloningDirector::SkipInstruction;
1462 assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
1463 "catch parameter is not static alloca");
1464 Materializer.escapeCatchObject(ExceptionObjectVar);
1465 return CloningDirector::SkipInstruction;
1468 CloningDirector::CloningAction
1469 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
1470 const Instruction *Inst, BasicBlock *NewBB) {
1471 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1472 // It might be interesting to track whether or not we are inside a catch
1473 // function, but that might make the algorithm more brittle than it needs
1476 // The end catch call can occur in one of two places: either in a
1477 // landingpad block that is part of the catch handlers exception mechanism,
1478 // or at the end of the catch block. However, a catch-all handler may call
1479 // end catch from the original landing pad. If the call occurs in a nested
1480 // landing pad block, we must skip it and continue so that the landing pad
1482 auto *ParentBB = IntrinCall->getParent();
1483 if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
1484 return CloningDirector::SkipInstruction;
1486 // If an end catch occurs anywhere else we want to terminate the handler
1487 // with a return to the code that follows the endcatch call. If the
1488 // next instruction is not an unconditional branch, we need to split the
1489 // block to provide a clear target for the return instruction.
1490 BasicBlock *ContinueBB;
1491 auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
1492 const BranchInst *Branch = dyn_cast<BranchInst>(Next);
1493 if (!Branch || !Branch->isUnconditional()) {
1494 // We're interrupting the cloning process at this location, so the
1495 // const_cast we're doing here will not cause a problem.
1496 ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
1497 const_cast<Instruction *>(cast<Instruction>(Next)));
1499 ContinueBB = Branch->getSuccessor(0);
1502 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
1503 ReturnTargets.push_back(ContinueBB);
1505 // We just added a terminator to the cloned block.
1506 // Tell the caller to stop processing the current basic block so that
1507 // the branch instruction will be skipped.
1508 return CloningDirector::StopCloningBB;
1511 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
1512 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1513 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1514 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1515 // This causes a replacement that will collapse the landing pad CFG based
1516 // on the filter function we intend to match.
1517 if (Selector == CurrentSelector)
1518 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
1520 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1521 // Tell the caller not to clone this instruction.
1522 return CloningDirector::SkipInstruction;
1525 CloningDirector::CloningAction
1526 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
1527 const InvokeInst *Invoke, BasicBlock *NewBB) {
1528 return CloningDirector::CloneInstruction;
1531 CloningDirector::CloningAction
1532 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
1533 const ResumeInst *Resume, BasicBlock *NewBB) {
1534 // Resume instructions shouldn't be reachable from catch handlers.
1535 // We still need to handle it, but it will be pruned.
1536 BasicBlock::InstListType &InstList = NewBB->getInstList();
1537 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1538 return CloningDirector::StopCloningBB;
1541 CloningDirector::CloningAction
1542 WinEHCatchDirector::handleCompare(ValueToValueMapTy &VMap,
1543 const CmpInst *Compare, BasicBlock *NewBB) {
1544 const IntrinsicInst *IntrinCall = nullptr;
1545 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1546 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(0));
1547 } else if (match(Compare->getOperand(1),
1548 m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1549 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(1));
1552 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1553 // This causes a replacement that will collapse the landing pad CFG based
1554 // on the filter function we intend to match.
1555 if (Selector == CurrentSelector->stripPointerCasts()) {
1556 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1558 VMap[Compare] = ConstantInt::get(SelectorIDType, 0);
1560 return CloningDirector::SkipInstruction;
1562 return CloningDirector::CloneInstruction;
1565 CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
1566 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1567 // The MS runtime will terminate the process if an exception occurs in a
1568 // cleanup handler, so we shouldn't encounter landing pads in the actual
1569 // cleanup code, but they may appear in catch blocks. Depending on where
1570 // we started cloning we may see one, but it will get dropped during dead
1572 Instruction *NewInst = new UnreachableInst(NewBB->getContext());
1573 VMap[LPad] = NewInst;
1574 BasicBlock::InstListType &InstList = NewBB->getInstList();
1575 InstList.push_back(NewInst);
1576 return CloningDirector::StopCloningBB;
1579 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1580 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1581 // Cleanup code may flow into catch blocks or the catch block may be part
1582 // of a branch that will be optimized away. We'll insert a return
1583 // instruction now, but it may be pruned before the cloning process is
1585 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1586 return CloningDirector::StopCloningBB;
1589 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1590 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1591 // Cleanup handlers nested within catch handlers may begin with a call to
1592 // eh.endcatch. We can just ignore that instruction.
1593 return CloningDirector::SkipInstruction;
1596 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1597 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1598 // If we encounter a selector comparison while cloning a cleanup handler,
1599 // we want to stop cloning immediately. Anything after the dispatch
1600 // will be outlined into a different handler.
1601 BasicBlock *CatchHandler;
1604 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1605 CatchHandler, Selector, NextBB)) {
1606 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1607 return CloningDirector::StopCloningBB;
1609 // If eg.typeid.for is called for any other reason, it can be ignored.
1610 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1611 return CloningDirector::SkipInstruction;
1614 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1615 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1616 // All invokes in cleanup handlers can be replaced with calls.
1617 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1618 // Insert a normal call instruction...
1620 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1621 Invoke->getName(), NewBB);
1622 NewCall->setCallingConv(Invoke->getCallingConv());
1623 NewCall->setAttributes(Invoke->getAttributes());
1624 NewCall->setDebugLoc(Invoke->getDebugLoc());
1625 VMap[Invoke] = NewCall;
1627 // Remap the operands.
1628 llvm::RemapInstruction(NewCall, VMap, RF_None, nullptr, &Materializer);
1630 // Insert an unconditional branch to the normal destination.
1631 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1633 // The unwind destination won't be cloned into the new function, so
1634 // we don't need to clean up its phi nodes.
1636 // We just added a terminator to the cloned block.
1637 // Tell the caller to stop processing the current basic block.
1638 return CloningDirector::CloneSuccessors;
1641 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1642 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1643 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1645 // We just added a terminator to the cloned block.
1646 // Tell the caller to stop processing the current basic block so that
1647 // the branch instruction will be skipped.
1648 return CloningDirector::StopCloningBB;
1651 CloningDirector::CloningAction
1652 WinEHCleanupDirector::handleCompare(ValueToValueMapTy &VMap,
1653 const CmpInst *Compare, BasicBlock *NewBB) {
1654 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>()) ||
1655 match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1656 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1657 return CloningDirector::SkipInstruction;
1659 return CloningDirector::CloneInstruction;
1662 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1663 Function *OutlinedFn, FrameVarInfoMap &FrameVarInfo)
1664 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1665 BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
1666 Builder.SetInsertPoint(EntryBB, EntryBB->getFirstInsertionPt());
1669 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1670 // If we're asked to materialize a static alloca, we temporarily create an
1671 // alloca in the outlined function and add this to the FrameVarInfo map. When
1672 // all the outlining is complete, we'll replace these temporary allocas with
1673 // calls to llvm.framerecover.
1674 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1675 assert(AV->isStaticAlloca() &&
1676 "cannot materialize un-demoted dynamic alloca");
1677 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1678 Builder.Insert(NewAlloca, AV->getName());
1679 FrameVarInfo[AV].push_back(NewAlloca);
1683 if (isa<Instruction>(V) || isa<Argument>(V)) {
1684 errs() << "Failed to demote instruction used in exception handler:\n";
1685 errs() << " " << *V << '\n';
1686 report_fatal_error("WinEHPrepare failed to demote instruction");
1689 // Don't materialize other values.
1693 void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
1694 // Catch parameter objects have to live in the parent frame. When we see a use
1695 // of a catch parameter, add a sentinel to the multimap to indicate that it's
1696 // used from another handler. This will prevent us from trying to sink the
1697 // alloca into the handler and ensure that the catch parameter is present in
1698 // the call to llvm.frameescape.
1699 FrameVarInfo[V].push_back(getCatchObjectSentinel());
1702 // This function maps the catch and cleanup handlers that are reachable from the
1703 // specified landing pad. The landing pad sequence will have this basic shape:
1705 // <cleanup handler>
1706 // <selector comparison>
1708 // <cleanup handler>
1709 // <selector comparison>
1711 // <cleanup handler>
1714 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
1715 // any arbitrary control flow, but all paths through the cleanup code must
1716 // eventually reach the next selector comparison and no path can skip to a
1717 // different selector comparisons, though some paths may terminate abnormally.
1718 // Therefore, we will use a depth first search from the start of any given
1719 // cleanup block and stop searching when we find the next selector comparison.
1721 // If the landingpad instruction does not have a catch clause, we will assume
1722 // that any instructions other than selector comparisons and catch handlers can
1723 // be ignored. In practice, these will only be the boilerplate instructions.
1725 // The catch handlers may also have any control structure, but we are only
1726 // interested in the start of the catch handlers, so we don't need to actually
1727 // follow the flow of the catch handlers. The start of the catch handlers can
1728 // be located from the compare instructions, but they can be skipped in the
1729 // flow by following the contrary branch.
1730 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
1731 LandingPadActions &Actions) {
1732 unsigned int NumClauses = LPad->getNumClauses();
1733 unsigned int HandlersFound = 0;
1734 BasicBlock *BB = LPad->getParent();
1736 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
1738 if (NumClauses == 0) {
1739 findCleanupHandlers(Actions, BB, nullptr);
1743 VisitedBlockSet VisitedBlocks;
1745 while (HandlersFound != NumClauses) {
1746 BasicBlock *NextBB = nullptr;
1748 // Skip over filter clauses.
1749 if (LPad->isFilter(HandlersFound)) {
1754 // See if the clause we're looking for is a catch-all.
1755 // If so, the catch begins immediately.
1756 Constant *ExpectedSelector =
1757 LPad->getClause(HandlersFound)->stripPointerCasts();
1758 if (isa<ConstantPointerNull>(ExpectedSelector)) {
1759 // The catch all must occur last.
1760 assert(HandlersFound == NumClauses - 1);
1762 // There can be additional selector dispatches in the call chain that we
1764 BasicBlock *CatchBlock = nullptr;
1766 while (BB && isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1767 DEBUG(dbgs() << " Found extra catch dispatch in block "
1768 << CatchBlock->getName() << "\n");
1772 // Add the catch handler to the action list.
1773 CatchHandler *Action = nullptr;
1774 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1775 // If the CatchHandlerMap already has an entry for this BB, re-use it.
1776 Action = CatchHandlerMap[BB];
1777 assert(Action->getSelector() == ExpectedSelector);
1779 // We don't expect a selector dispatch, but there may be a call to
1780 // llvm.eh.begincatch, which separates catch handling code from
1781 // cleanup code in the same control flow. This call looks for the
1782 // begincatch intrinsic.
1783 Action = findCatchHandler(BB, NextBB, VisitedBlocks);
1785 // For C++ EH, check if there is any interesting cleanup code before
1786 // we begin the catch. This is important because cleanups cannot
1787 // rethrow exceptions but code called from catches can. For SEH, it
1788 // isn't important if some finally code before a catch-all is executed
1789 // out of line or after recovering from the exception.
1790 if (Personality == EHPersonality::MSVC_CXX)
1791 findCleanupHandlers(Actions, BB, BB);
1793 // If an action was not found, it means that the control flows
1794 // directly into the catch-all handler and there is no cleanup code.
1795 // That's an expected situation and we must create a catch action.
1796 // Since this is a catch-all handler, the selector won't actually
1797 // appear in the code anywhere. ExpectedSelector here is the constant
1798 // null ptr that we got from the landing pad instruction.
1799 Action = new CatchHandler(BB, ExpectedSelector, nullptr);
1800 CatchHandlerMap[BB] = Action;
1803 Actions.insertCatchHandler(Action);
1804 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
1807 // Once we reach a catch-all, don't expect to hit a resume instruction.
1812 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
1813 assert(CatchAction);
1815 // See if there is any interesting code executed before the dispatch.
1816 findCleanupHandlers(Actions, BB, CatchAction->getStartBlock());
1818 // When the source program contains multiple nested try blocks the catch
1819 // handlers can get strung together in such a way that we can encounter
1820 // a dispatch for a selector that we've already had a handler for.
1821 if (CatchAction->getSelector()->stripPointerCasts() == ExpectedSelector) {
1824 // Add the catch handler to the action list.
1825 DEBUG(dbgs() << " Found catch dispatch in block "
1826 << CatchAction->getStartBlock()->getName() << "\n");
1827 Actions.insertCatchHandler(CatchAction);
1829 // Under some circumstances optimized IR will flow unconditionally into a
1830 // handler block without checking the selector. This can only happen if
1831 // the landing pad has a catch-all handler and the handler for the
1832 // preceeding catch clause is identical to the catch-call handler
1833 // (typically an empty catch). In this case, the handler must be shared
1834 // by all remaining clauses.
1835 if (isa<ConstantPointerNull>(
1836 CatchAction->getSelector()->stripPointerCasts())) {
1837 DEBUG(dbgs() << " Applying early catch-all handler in block "
1838 << CatchAction->getStartBlock()->getName()
1839 << " to all remaining clauses.\n");
1840 Actions.insertCatchHandler(CatchAction);
1844 DEBUG(dbgs() << " Found extra catch dispatch in block "
1845 << CatchAction->getStartBlock()->getName() << "\n");
1848 // Move on to the block after the catch handler.
1852 // If we didn't wind up in a catch-all, see if there is any interesting code
1853 // executed before the resume.
1854 findCleanupHandlers(Actions, BB, BB);
1856 // It's possible that some optimization moved code into a landingpad that
1858 // previously being used for cleanup. If that happens, we need to execute
1860 // extra code from a cleanup handler.
1861 if (Actions.includesCleanup() && !LPad->isCleanup())
1862 LPad->setCleanup(true);
1865 // This function searches starting with the input block for the next
1866 // block that terminates with a branch whose condition is based on a selector
1867 // comparison. This may be the input block. See the mapLandingPadBlocks
1868 // comments for a discussion of control flow assumptions.
1870 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
1871 BasicBlock *&NextBB,
1872 VisitedBlockSet &VisitedBlocks) {
1873 // See if we've already found a catch handler use it.
1874 // Call count() first to avoid creating a null entry for blocks
1875 // we haven't seen before.
1876 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
1877 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
1878 NextBB = Action->getNextBB();
1882 // VisitedBlocks applies only to the current search. We still
1883 // need to consider blocks that we've visited while mapping other
1885 VisitedBlocks.insert(BB);
1887 BasicBlock *CatchBlock = nullptr;
1888 Constant *Selector = nullptr;
1890 // If this is the first time we've visited this block from any landing pad
1891 // look to see if it is a selector dispatch block.
1892 if (!CatchHandlerMap.count(BB)) {
1893 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
1894 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
1895 CatchHandlerMap[BB] = Action;
1898 // If we encounter a block containing an llvm.eh.begincatch before we
1899 // find a selector dispatch block, the handler is assumed to be
1900 // reached unconditionally. This happens for catch-all blocks, but
1901 // it can also happen for other catch handlers that have been combined
1902 // with the catch-all handler during optimization.
1903 if (isCatchBlock(BB)) {
1904 PointerType *Int8PtrTy = Type::getInt8PtrTy(BB->getContext());
1905 Constant *NullSelector = ConstantPointerNull::get(Int8PtrTy);
1906 CatchHandler *Action = new CatchHandler(BB, NullSelector, nullptr);
1907 CatchHandlerMap[BB] = Action;
1912 // Visit each successor, looking for the dispatch.
1913 // FIXME: We expect to find the dispatch quickly, so this will probably
1914 // work better as a breadth first search.
1915 for (BasicBlock *Succ : successors(BB)) {
1916 if (VisitedBlocks.count(Succ))
1919 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
1926 // These are helper functions to combine repeated code from findCleanupHandlers.
1927 static void createCleanupHandler(LandingPadActions &Actions,
1928 CleanupHandlerMapTy &CleanupHandlerMap,
1930 CleanupHandler *Action = new CleanupHandler(BB);
1931 CleanupHandlerMap[BB] = Action;
1932 Actions.insertCleanupHandler(Action);
1933 DEBUG(dbgs() << " Found cleanup code in block "
1934 << Action->getStartBlock()->getName() << "\n");
1937 static CallSite matchOutlinedFinallyCall(BasicBlock *BB,
1938 Instruction *MaybeCall) {
1939 // Look for finally blocks that Clang has already outlined for us.
1940 // %fp = call i8* @llvm.frameaddress(i32 0)
1941 // call void @"fin$parent"(iN 1, i8* %fp)
1942 if (isFrameAddressCall(MaybeCall) && MaybeCall != BB->getTerminator())
1943 MaybeCall = MaybeCall->getNextNode();
1944 CallSite FinallyCall(MaybeCall);
1945 if (!FinallyCall || FinallyCall.arg_size() != 2)
1947 if (!match(FinallyCall.getArgument(0), m_SpecificInt(1)))
1949 if (!isFrameAddressCall(FinallyCall.getArgument(1)))
1954 static BasicBlock *followSingleUnconditionalBranches(BasicBlock *BB) {
1955 // Skip single ubr blocks.
1956 while (BB->getFirstNonPHIOrDbg() == BB->getTerminator()) {
1957 auto *Br = dyn_cast<BranchInst>(BB->getTerminator());
1958 if (Br && Br->isUnconditional())
1959 BB = Br->getSuccessor(0);
1966 // This function searches starting with the input block for the next block that
1967 // contains code that is not part of a catch handler and would not be eliminated
1968 // during handler outlining.
1970 void WinEHPrepare::findCleanupHandlers(LandingPadActions &Actions,
1971 BasicBlock *StartBB, BasicBlock *EndBB) {
1972 // Here we will skip over the following:
1974 // landing pad prolog:
1976 // Unconditional branches
1978 // Selector dispatch
1982 // Anything else marks the start of an interesting block
1984 BasicBlock *BB = StartBB;
1985 // Anything other than an unconditional branch will kick us out of this loop
1986 // one way or another.
1988 BB = followSingleUnconditionalBranches(BB);
1989 // If we've already scanned this block, don't scan it again. If it is
1990 // a cleanup block, there will be an action in the CleanupHandlerMap.
1991 // If we've scanned it and it is not a cleanup block, there will be a
1992 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
1993 // be no entry in the CleanupHandlerMap. We must call count() first to
1994 // avoid creating a null entry for blocks we haven't scanned.
1995 if (CleanupHandlerMap.count(BB)) {
1996 if (auto *Action = CleanupHandlerMap[BB]) {
1997 Actions.insertCleanupHandler(Action);
1998 DEBUG(dbgs() << " Found cleanup code in block "
1999 << Action->getStartBlock()->getName() << "\n");
2000 // FIXME: This cleanup might chain into another, and we need to discover
2004 // Here we handle the case where the cleanup handler map contains a
2005 // value for this block but the value is a nullptr. This means that
2006 // we have previously analyzed the block and determined that it did
2007 // not contain any cleanup code. Based on the earlier analysis, we
2008 // know the the block must end in either an unconditional branch, a
2009 // resume or a conditional branch that is predicated on a comparison
2010 // with a selector. Either the resume or the selector dispatch
2011 // would terminate the search for cleanup code, so the unconditional
2012 // branch is the only case for which we might need to continue
2014 BasicBlock *SuccBB = followSingleUnconditionalBranches(BB);
2015 if (SuccBB == BB || SuccBB == EndBB)
2022 // Create an entry in the cleanup handler map for this block. Initially
2023 // we create an entry that says this isn't a cleanup block. If we find
2024 // cleanup code, the caller will replace this entry.
2025 CleanupHandlerMap[BB] = nullptr;
2027 TerminatorInst *Terminator = BB->getTerminator();
2029 // Landing pad blocks have extra instructions we need to accept.
2030 LandingPadMap *LPadMap = nullptr;
2031 if (BB->isLandingPad()) {
2032 LandingPadInst *LPad = BB->getLandingPadInst();
2033 LPadMap = &LPadMaps[LPad];
2034 if (!LPadMap->isInitialized())
2035 LPadMap->mapLandingPad(LPad);
2038 // Look for the bare resume pattern:
2039 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
2040 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
2041 // resume { i8*, i32 } %lpad.val2
2042 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
2043 InsertValueInst *Insert1 = nullptr;
2044 InsertValueInst *Insert2 = nullptr;
2045 Value *ResumeVal = Resume->getOperand(0);
2046 // If the resume value isn't a phi or landingpad value, it should be a
2047 // series of insertions. Identify them so we can avoid them when scanning
2049 if (!isa<PHINode>(ResumeVal) && !isa<LandingPadInst>(ResumeVal)) {
2050 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
2052 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2053 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
2055 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2057 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2059 Instruction *Inst = II;
2060 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2062 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
2064 if (!Inst->hasOneUse() ||
2065 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
2066 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2072 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
2073 if (Branch && Branch->isConditional()) {
2074 // Look for the selector dispatch.
2075 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
2076 // %matches = icmp eq i32 %sel, %2
2077 // br i1 %matches, label %catch14, label %eh.resume
2078 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
2079 if (!Compare || !Compare->isEquality())
2080 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2081 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2083 Instruction *Inst = II;
2084 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2086 if (Inst == Compare || Inst == Branch)
2088 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
2090 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2092 // The selector dispatch block should always terminate our search.
2093 assert(BB == EndBB);
2097 if (isAsynchronousEHPersonality(Personality)) {
2098 // If this is a landingpad block, split the block at the first non-landing
2100 Instruction *MaybeCall = BB->getFirstNonPHIOrDbg();
2102 while (MaybeCall != BB->getTerminator() &&
2103 LPadMap->isLandingPadSpecificInst(MaybeCall))
2104 MaybeCall = MaybeCall->getNextNode();
2107 // Look for outlined finally calls.
2108 if (CallSite FinallyCall = matchOutlinedFinallyCall(BB, MaybeCall)) {
2109 Function *Fin = FinallyCall.getCalledFunction();
2110 assert(Fin && "outlined finally call should be direct");
2111 auto *Action = new CleanupHandler(BB);
2112 Action->setHandlerBlockOrFunc(Fin);
2113 Actions.insertCleanupHandler(Action);
2114 CleanupHandlerMap[BB] = Action;
2115 DEBUG(dbgs() << " Found frontend-outlined finally call to "
2116 << Fin->getName() << " in block "
2117 << Action->getStartBlock()->getName() << "\n");
2119 // Split the block if there were more interesting instructions and look
2120 // for finally calls in the normal successor block.
2121 BasicBlock *SuccBB = BB;
2122 if (FinallyCall.getInstruction() != BB->getTerminator() &&
2123 FinallyCall.getInstruction()->getNextNode() !=
2124 BB->getTerminator()) {
2126 SplitBlock(BB, FinallyCall.getInstruction()->getNextNode(), DT);
2128 if (FinallyCall.isInvoke()) {
2130 cast<InvokeInst>(FinallyCall.getInstruction())->getNormalDest();
2132 SuccBB = BB->getUniqueSuccessor();
2134 "splitOutlinedFinallyCalls didn't insert a branch");
2144 // Anything else is either a catch block or interesting cleanup code.
2145 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2147 Instruction *Inst = II;
2148 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2150 // Unconditional branches fall through to this loop.
2153 // If this is a catch block, there is no cleanup code to be found.
2154 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
2156 // If this a nested landing pad, it may contain an endcatch call.
2157 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
2159 // Anything else makes this interesting cleanup code.
2160 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2163 // Only unconditional branches in empty blocks should get this far.
2164 assert(Branch && Branch->isUnconditional());
2167 BB = Branch->getSuccessor(0);
2171 // This is a public function, declared in WinEHFuncInfo.h and is also
2172 // referenced by WinEHNumbering in FunctionLoweringInfo.cpp.
2173 void llvm::parseEHActions(const IntrinsicInst *II,
2174 SmallVectorImpl<ActionHandler *> &Actions) {
2175 for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
2176 uint64_t ActionKind =
2177 cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
2178 if (ActionKind == /*catch=*/1) {
2179 auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
2180 ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
2181 int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
2182 Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
2184 auto *CH = new CatchHandler(/*BB=*/nullptr, Selector, /*NextBB=*/nullptr);
2185 CH->setHandlerBlockOrFunc(Handler);
2186 CH->setExceptionVarIndex(EHObjIndexVal);
2187 Actions.push_back(CH);
2188 } else if (ActionKind == 0) {
2189 Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
2191 auto *CH = new CleanupHandler(/*BB=*/nullptr);
2192 CH->setHandlerBlockOrFunc(Handler);
2193 Actions.push_back(CH);
2195 llvm_unreachable("Expected either a catch or cleanup handler!");
2198 std::reverse(Actions.begin(), Actions.end());