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 for functions using a personality function from a runtime
12 // provided by MSVC. Functions with other personality functions are left alone
13 // and may be prepared by other passes. In particular, all supported MSVC
14 // personality functions require cleanup code to be outlined, and the C++
15 // personality requires catch handler code to be outlined.
17 //===----------------------------------------------------------------------===//
19 #include "llvm/CodeGen/Passes.h"
20 #include "llvm/ADT/MapVector.h"
21 #include "llvm/ADT/STLExtras.h"
22 #include "llvm/ADT/SmallSet.h"
23 #include "llvm/ADT/SetVector.h"
24 #include "llvm/ADT/Triple.h"
25 #include "llvm/ADT/TinyPtrVector.h"
26 #include "llvm/Analysis/LibCallSemantics.h"
27 #include "llvm/Analysis/TargetLibraryInfo.h"
28 #include "llvm/CodeGen/WinEHFuncInfo.h"
29 #include "llvm/IR/Dominators.h"
30 #include "llvm/IR/Function.h"
31 #include "llvm/IR/IRBuilder.h"
32 #include "llvm/IR/Instructions.h"
33 #include "llvm/IR/IntrinsicInst.h"
34 #include "llvm/IR/Module.h"
35 #include "llvm/IR/PatternMatch.h"
36 #include "llvm/Pass.h"
37 #include "llvm/Support/Debug.h"
38 #include "llvm/Support/raw_ostream.h"
39 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
40 #include "llvm/Transforms/Utils/Cloning.h"
41 #include "llvm/Transforms/Utils/Local.h"
42 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
46 using namespace llvm::PatternMatch;
48 #define DEBUG_TYPE "winehprepare"
52 // This map is used to model frame variable usage during outlining, to
53 // construct a structure type to hold the frame variables in a frame
54 // allocation block, and to remap the frame variable allocas (including
55 // spill locations as needed) to GEPs that get the variable from the
56 // frame allocation structure.
57 typedef MapVector<Value *, TinyPtrVector<AllocaInst *>> FrameVarInfoMap;
59 // TinyPtrVector cannot hold nullptr, so we need our own sentinel that isn't
61 AllocaInst *getCatchObjectSentinel() {
62 return static_cast<AllocaInst *>(nullptr) + 1;
65 typedef SmallSet<BasicBlock *, 4> VisitedBlockSet;
67 class LandingPadActions;
70 typedef DenseMap<const BasicBlock *, CatchHandler *> CatchHandlerMapTy;
71 typedef DenseMap<const BasicBlock *, CleanupHandler *> CleanupHandlerMapTy;
73 class WinEHPrepare : public FunctionPass {
75 static char ID; // Pass identification, replacement for typeid.
76 WinEHPrepare(const TargetMachine *TM = nullptr)
79 TheTriple = TM->getTargetTriple();
82 bool runOnFunction(Function &Fn) override;
84 bool doFinalization(Module &M) override;
86 void getAnalysisUsage(AnalysisUsage &AU) const override;
88 const char *getPassName() const override {
89 return "Windows exception handling preparation";
93 bool prepareExceptionHandlers(Function &F,
94 SmallVectorImpl<LandingPadInst *> &LPads);
95 void identifyEHBlocks(Function &F, SmallVectorImpl<LandingPadInst *> &LPads);
96 void promoteLandingPadValues(LandingPadInst *LPad);
97 void demoteValuesLiveAcrossHandlers(Function &F,
98 SmallVectorImpl<LandingPadInst *> &LPads);
99 void findSEHEHReturnPoints(Function &F,
100 SetVector<BasicBlock *> &EHReturnBlocks);
101 void findCXXEHReturnPoints(Function &F,
102 SetVector<BasicBlock *> &EHReturnBlocks);
103 void getPossibleReturnTargets(Function *ParentF, Function *HandlerF,
104 SetVector<BasicBlock*> &Targets);
105 void completeNestedLandingPad(Function *ParentFn,
106 LandingPadInst *OutlinedLPad,
107 const LandingPadInst *OriginalLPad,
108 FrameVarInfoMap &VarInfo);
109 Function *createHandlerFunc(Function *ParentFn, Type *RetTy,
110 const Twine &Name, Module *M, Value *&ParentFP);
111 bool outlineHandler(ActionHandler *Action, Function *SrcFn,
112 LandingPadInst *LPad, BasicBlock *StartBB,
113 FrameVarInfoMap &VarInfo);
114 void addStubInvokeToHandlerIfNeeded(Function *Handler);
116 void mapLandingPadBlocks(LandingPadInst *LPad, LandingPadActions &Actions);
117 CatchHandler *findCatchHandler(BasicBlock *BB, BasicBlock *&NextBB,
118 VisitedBlockSet &VisitedBlocks);
119 void findCleanupHandlers(LandingPadActions &Actions, BasicBlock *StartBB,
122 void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB);
126 // All fields are reset by runOnFunction.
127 DominatorTree *DT = nullptr;
128 const TargetLibraryInfo *LibInfo = nullptr;
129 EHPersonality Personality = EHPersonality::Unknown;
130 CatchHandlerMapTy CatchHandlerMap;
131 CleanupHandlerMapTy CleanupHandlerMap;
132 DenseMap<const LandingPadInst *, LandingPadMap> LPadMaps;
133 SmallPtrSet<BasicBlock *, 4> NormalBlocks;
134 SmallPtrSet<BasicBlock *, 4> EHBlocks;
135 SetVector<BasicBlock *> EHReturnBlocks;
137 // This maps landing pad instructions found in outlined handlers to
138 // the landing pad instruction in the parent function from which they
139 // were cloned. The cloned/nested landing pad is used as the key
140 // because the landing pad may be cloned into multiple handlers.
141 // This map will be used to add the llvm.eh.actions call to the nested
142 // landing pads after all handlers have been outlined.
143 DenseMap<LandingPadInst *, const LandingPadInst *> NestedLPtoOriginalLP;
145 // This maps blocks in the parent function which are destinations of
146 // catch handlers to cloned blocks in (other) outlined handlers. This
147 // handles the case where a nested landing pads has a catch handler that
148 // returns to a handler function rather than the parent function.
149 // The original block is used as the key here because there should only
150 // ever be one handler function from which the cloned block is not pruned.
151 // The original block will be pruned from the parent function after all
152 // handlers have been outlined. This map will be used to adjust the
153 // return instructions of handlers which return to the block that was
154 // outlined into a handler. This is done after all handlers have been
155 // outlined but before the outlined code is pruned from the parent function.
156 DenseMap<const BasicBlock *, BasicBlock *> LPadTargetBlocks;
158 // Map from outlined handler to call to llvm.frameaddress(1). Only used for
160 DenseMap<Function *, Value *> HandlerToParentFP;
162 AllocaInst *SEHExceptionCodeSlot = nullptr;
165 class WinEHFrameVariableMaterializer : public ValueMaterializer {
167 WinEHFrameVariableMaterializer(Function *OutlinedFn, Value *ParentFP,
168 FrameVarInfoMap &FrameVarInfo);
169 ~WinEHFrameVariableMaterializer() override {}
171 Value *materializeValueFor(Value *V) override;
173 void escapeCatchObject(Value *V);
176 FrameVarInfoMap &FrameVarInfo;
180 class LandingPadMap {
182 LandingPadMap() : OriginLPad(nullptr) {}
183 void mapLandingPad(const LandingPadInst *LPad);
185 bool isInitialized() { return OriginLPad != nullptr; }
187 bool isOriginLandingPadBlock(const BasicBlock *BB) const;
188 bool isLandingPadSpecificInst(const Instruction *Inst) const;
190 void remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
191 Value *SelectorValue) const;
194 const LandingPadInst *OriginLPad;
195 // We will normally only see one of each of these instructions, but
196 // if more than one occurs for some reason we can handle that.
197 TinyPtrVector<const ExtractValueInst *> ExtractedEHPtrs;
198 TinyPtrVector<const ExtractValueInst *> ExtractedSelectors;
201 class WinEHCloningDirectorBase : public CloningDirector {
203 WinEHCloningDirectorBase(Function *HandlerFn, Value *ParentFP,
204 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
205 : Materializer(HandlerFn, ParentFP, VarInfo),
206 SelectorIDType(Type::getInt32Ty(HandlerFn->getContext())),
207 Int8PtrType(Type::getInt8PtrTy(HandlerFn->getContext())),
208 LPadMap(LPadMap), ParentFP(ParentFP) {}
210 CloningAction handleInstruction(ValueToValueMapTy &VMap,
211 const Instruction *Inst,
212 BasicBlock *NewBB) override;
214 virtual CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
215 const Instruction *Inst,
216 BasicBlock *NewBB) = 0;
217 virtual CloningAction handleEndCatch(ValueToValueMapTy &VMap,
218 const Instruction *Inst,
219 BasicBlock *NewBB) = 0;
220 virtual CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
221 const Instruction *Inst,
222 BasicBlock *NewBB) = 0;
223 virtual CloningAction handleIndirectBr(ValueToValueMapTy &VMap,
224 const IndirectBrInst *IBr,
225 BasicBlock *NewBB) = 0;
226 virtual CloningAction handleInvoke(ValueToValueMapTy &VMap,
227 const InvokeInst *Invoke,
228 BasicBlock *NewBB) = 0;
229 virtual CloningAction handleResume(ValueToValueMapTy &VMap,
230 const ResumeInst *Resume,
231 BasicBlock *NewBB) = 0;
232 virtual CloningAction handleCompare(ValueToValueMapTy &VMap,
233 const CmpInst *Compare,
234 BasicBlock *NewBB) = 0;
235 virtual CloningAction handleLandingPad(ValueToValueMapTy &VMap,
236 const LandingPadInst *LPad,
237 BasicBlock *NewBB) = 0;
239 ValueMaterializer *getValueMaterializer() override { return &Materializer; }
242 WinEHFrameVariableMaterializer Materializer;
243 Type *SelectorIDType;
245 LandingPadMap &LPadMap;
247 /// The value representing the parent frame pointer.
251 class WinEHCatchDirector : public WinEHCloningDirectorBase {
254 Function *CatchFn, Value *ParentFP, Value *Selector,
255 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap,
256 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPads,
257 DominatorTree *DT, SmallPtrSetImpl<BasicBlock *> &EHBlocks)
258 : WinEHCloningDirectorBase(CatchFn, ParentFP, VarInfo, LPadMap),
259 CurrentSelector(Selector->stripPointerCasts()),
260 ExceptionObjectVar(nullptr), NestedLPtoOriginalLP(NestedLPads),
261 DT(DT), EHBlocks(EHBlocks) {}
263 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
264 const Instruction *Inst,
265 BasicBlock *NewBB) override;
266 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
267 BasicBlock *NewBB) override;
268 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
269 const Instruction *Inst,
270 BasicBlock *NewBB) override;
271 CloningAction handleIndirectBr(ValueToValueMapTy &VMap,
272 const IndirectBrInst *IBr,
273 BasicBlock *NewBB) override;
274 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
275 BasicBlock *NewBB) override;
276 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
277 BasicBlock *NewBB) override;
278 CloningAction handleCompare(ValueToValueMapTy &VMap, const CmpInst *Compare,
279 BasicBlock *NewBB) override;
280 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
281 const LandingPadInst *LPad,
282 BasicBlock *NewBB) override;
284 Value *getExceptionVar() { return ExceptionObjectVar; }
285 TinyPtrVector<BasicBlock *> &getReturnTargets() { return ReturnTargets; }
288 Value *CurrentSelector;
290 Value *ExceptionObjectVar;
291 TinyPtrVector<BasicBlock *> ReturnTargets;
293 // This will be a reference to the field of the same name in the WinEHPrepare
294 // object which instantiates this WinEHCatchDirector object.
295 DenseMap<LandingPadInst *, const LandingPadInst *> &NestedLPtoOriginalLP;
297 SmallPtrSetImpl<BasicBlock *> &EHBlocks;
300 class WinEHCleanupDirector : public WinEHCloningDirectorBase {
302 WinEHCleanupDirector(Function *CleanupFn, Value *ParentFP,
303 FrameVarInfoMap &VarInfo, LandingPadMap &LPadMap)
304 : WinEHCloningDirectorBase(CleanupFn, ParentFP, VarInfo,
307 CloningAction handleBeginCatch(ValueToValueMapTy &VMap,
308 const Instruction *Inst,
309 BasicBlock *NewBB) override;
310 CloningAction handleEndCatch(ValueToValueMapTy &VMap, const Instruction *Inst,
311 BasicBlock *NewBB) override;
312 CloningAction handleTypeIdFor(ValueToValueMapTy &VMap,
313 const Instruction *Inst,
314 BasicBlock *NewBB) override;
315 CloningAction handleIndirectBr(ValueToValueMapTy &VMap,
316 const IndirectBrInst *IBr,
317 BasicBlock *NewBB) override;
318 CloningAction handleInvoke(ValueToValueMapTy &VMap, const InvokeInst *Invoke,
319 BasicBlock *NewBB) override;
320 CloningAction handleResume(ValueToValueMapTy &VMap, const ResumeInst *Resume,
321 BasicBlock *NewBB) override;
322 CloningAction handleCompare(ValueToValueMapTy &VMap, const CmpInst *Compare,
323 BasicBlock *NewBB) override;
324 CloningAction handleLandingPad(ValueToValueMapTy &VMap,
325 const LandingPadInst *LPad,
326 BasicBlock *NewBB) override;
329 class LandingPadActions {
331 LandingPadActions() : HasCleanupHandlers(false) {}
333 void insertCatchHandler(CatchHandler *Action) { Actions.push_back(Action); }
334 void insertCleanupHandler(CleanupHandler *Action) {
335 Actions.push_back(Action);
336 HasCleanupHandlers = true;
339 bool includesCleanup() const { return HasCleanupHandlers; }
341 SmallVectorImpl<ActionHandler *> &actions() { return Actions; }
342 SmallVectorImpl<ActionHandler *>::iterator begin() { return Actions.begin(); }
343 SmallVectorImpl<ActionHandler *>::iterator end() { return Actions.end(); }
346 // Note that this class does not own the ActionHandler objects in this vector.
347 // The ActionHandlers are owned by the CatchHandlerMap and CleanupHandlerMap
348 // in the WinEHPrepare class.
349 SmallVector<ActionHandler *, 4> Actions;
350 bool HasCleanupHandlers;
353 } // end anonymous namespace
355 char WinEHPrepare::ID = 0;
356 INITIALIZE_TM_PASS(WinEHPrepare, "winehprepare", "Prepare Windows exceptions",
359 FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) {
360 return new WinEHPrepare(TM);
363 bool WinEHPrepare::runOnFunction(Function &Fn) {
364 // No need to prepare outlined handlers.
365 if (Fn.hasFnAttribute("wineh-parent"))
368 SmallVector<LandingPadInst *, 4> LPads;
369 SmallVector<ResumeInst *, 4> Resumes;
370 for (BasicBlock &BB : Fn) {
371 if (auto *LP = BB.getLandingPadInst())
373 if (auto *Resume = dyn_cast<ResumeInst>(BB.getTerminator()))
374 Resumes.push_back(Resume);
377 // No need to prepare functions that lack landing pads.
381 // Classify the personality to see what kind of preparation we need.
382 Personality = classifyEHPersonality(Fn.getPersonalityFn());
384 // Do nothing if this is not an MSVC personality.
385 if (!isMSVCEHPersonality(Personality))
388 DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
389 LibInfo = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
391 // If there were any landing pads, prepareExceptionHandlers will make changes.
392 prepareExceptionHandlers(Fn, LPads);
396 bool WinEHPrepare::doFinalization(Module &M) { return false; }
398 void WinEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const {
399 AU.addRequired<DominatorTreeWrapperPass>();
400 AU.addRequired<TargetLibraryInfoWrapperPass>();
403 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
404 Constant *&Selector, BasicBlock *&NextBB);
406 // Finds blocks reachable from the starting set Worklist. Does not follow unwind
407 // edges or blocks listed in StopPoints.
408 static void findReachableBlocks(SmallPtrSetImpl<BasicBlock *> &ReachableBBs,
409 SetVector<BasicBlock *> &Worklist,
410 const SetVector<BasicBlock *> *StopPoints) {
411 while (!Worklist.empty()) {
412 BasicBlock *BB = Worklist.pop_back_val();
414 // Don't cross blocks that we should stop at.
415 if (StopPoints && StopPoints->count(BB))
418 if (!ReachableBBs.insert(BB).second)
419 continue; // Already visited.
421 // Don't follow unwind edges of invokes.
422 if (auto *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
423 Worklist.insert(II->getNormalDest());
427 // Otherwise, follow all successors.
428 Worklist.insert(succ_begin(BB), succ_end(BB));
432 // Attempt to find an instruction where a block can be split before
433 // a call to llvm.eh.begincatch and its operands. If the block
434 // begins with the begincatch call or one of its adjacent operands
435 // the block will not be split.
436 static Instruction *findBeginCatchSplitPoint(BasicBlock *BB,
438 // If the begincatch call is already the first instruction in the block,
440 Instruction *FirstNonPHI = BB->getFirstNonPHI();
441 if (II == FirstNonPHI)
444 // If either operand is in the same basic block as the instruction and
445 // isn't used by another instruction before the begincatch call, include it
446 // in the split block.
447 auto *Op0 = dyn_cast<Instruction>(II->getOperand(0));
448 auto *Op1 = dyn_cast<Instruction>(II->getOperand(1));
450 Instruction *I = II->getPrevNode();
451 Instruction *LastI = II;
453 while (I == Op0 || I == Op1) {
454 // If the block begins with one of the operands and there are no other
455 // instructions between the operand and the begincatch call, don't split.
456 if (I == FirstNonPHI)
460 I = I->getPrevNode();
463 // If there is at least one instruction in the block before the begincatch
464 // call and its operands, split the block at either the begincatch or
469 /// Find all points where exceptional control rejoins normal control flow via
470 /// llvm.eh.endcatch. Add them to the normal bb reachability worklist.
471 void WinEHPrepare::findCXXEHReturnPoints(
472 Function &F, SetVector<BasicBlock *> &EHReturnBlocks) {
473 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
474 BasicBlock *BB = BBI;
475 for (Instruction &I : *BB) {
476 if (match(&I, m_Intrinsic<Intrinsic::eh_begincatch>())) {
477 Instruction *SplitPt =
478 findBeginCatchSplitPoint(BB, cast<IntrinsicInst>(&I));
480 // Split the block before the llvm.eh.begincatch call to allow
481 // cleanup and catch code to be distinguished later.
482 // Do not update BBI because we still need to process the
483 // portion of the block that we are splitting off.
484 SplitBlock(BB, SplitPt, DT);
488 if (match(&I, m_Intrinsic<Intrinsic::eh_endcatch>())) {
489 // Split the block after the call to llvm.eh.endcatch if there is
490 // anything other than an unconditional branch, or if the successor
491 // starts with a phi.
492 auto *Br = dyn_cast<BranchInst>(I.getNextNode());
493 if (!Br || !Br->isUnconditional() ||
494 isa<PHINode>(Br->getSuccessor(0)->begin())) {
495 DEBUG(dbgs() << "splitting block " << BB->getName()
496 << " with llvm.eh.endcatch\n");
497 BBI = SplitBlock(BB, I.getNextNode(), DT);
499 // The next BB is normal control flow.
500 EHReturnBlocks.insert(BB->getTerminator()->getSuccessor(0));
507 static bool isCatchAllLandingPad(const BasicBlock *BB) {
508 const LandingPadInst *LP = BB->getLandingPadInst();
511 unsigned N = LP->getNumClauses();
512 return (N > 0 && LP->isCatch(N - 1) &&
513 isa<ConstantPointerNull>(LP->getClause(N - 1)));
516 /// Find all points where exceptions control rejoins normal control flow via
517 /// selector dispatch.
518 void WinEHPrepare::findSEHEHReturnPoints(
519 Function &F, SetVector<BasicBlock *> &EHReturnBlocks) {
520 for (auto BBI = F.begin(), BBE = F.end(); BBI != BBE; ++BBI) {
521 BasicBlock *BB = BBI;
522 // If the landingpad is a catch-all, treat the whole lpad as if it is
523 // reachable from normal control flow.
524 // FIXME: This is imprecise. We need a better way of identifying where a
525 // catch-all starts and cleanups stop. As far as LLVM is concerned, there
527 if (isCatchAllLandingPad(BB)) {
528 EHReturnBlocks.insert(BB);
532 BasicBlock *CatchHandler;
535 if (isSelectorDispatch(BB, CatchHandler, Selector, NextBB)) {
536 // Split the edge if there is a phi node. Returning from EH to a phi node
537 // is just as impossible as having a phi after an indirectbr.
538 if (isa<PHINode>(CatchHandler->begin())) {
539 DEBUG(dbgs() << "splitting EH return edge from " << BB->getName()
540 << " to " << CatchHandler->getName() << '\n');
541 BBI = CatchHandler = SplitCriticalEdge(
542 BB, std::find(succ_begin(BB), succ_end(BB), CatchHandler));
544 EHReturnBlocks.insert(CatchHandler);
549 void WinEHPrepare::identifyEHBlocks(Function &F,
550 SmallVectorImpl<LandingPadInst *> &LPads) {
551 DEBUG(dbgs() << "Demoting values live across exception handlers in function "
552 << F.getName() << '\n');
554 // Build a set of all non-exceptional blocks and exceptional blocks.
555 // - Non-exceptional blocks are blocks reachable from the entry block while
556 // not following invoke unwind edges.
557 // - Exceptional blocks are blocks reachable from landingpads. Analysis does
558 // not follow llvm.eh.endcatch blocks, which mark a transition from
559 // exceptional to normal control.
561 if (Personality == EHPersonality::MSVC_CXX)
562 findCXXEHReturnPoints(F, EHReturnBlocks);
564 findSEHEHReturnPoints(F, EHReturnBlocks);
567 dbgs() << "identified the following blocks as EH return points:\n";
568 for (BasicBlock *BB : EHReturnBlocks)
569 dbgs() << " " << BB->getName() << '\n';
572 // Join points should not have phis at this point, unless they are a
573 // landingpad, in which case we will demote their phis later.
575 for (BasicBlock *BB : EHReturnBlocks)
576 assert((BB->isLandingPad() || !isa<PHINode>(BB->begin())) &&
577 "non-lpad EH return block has phi");
580 // Normal blocks are the blocks reachable from the entry block and all EH
582 SetVector<BasicBlock *> Worklist;
583 Worklist = EHReturnBlocks;
584 Worklist.insert(&F.getEntryBlock());
585 findReachableBlocks(NormalBlocks, Worklist, nullptr);
587 dbgs() << "marked the following blocks as normal:\n";
588 for (BasicBlock *BB : NormalBlocks)
589 dbgs() << " " << BB->getName() << '\n';
592 // Exceptional blocks are the blocks reachable from landingpads that don't
593 // cross EH return points.
595 for (auto *LPI : LPads)
596 Worklist.insert(LPI->getParent());
597 findReachableBlocks(EHBlocks, Worklist, &EHReturnBlocks);
599 dbgs() << "marked the following blocks as exceptional:\n";
600 for (BasicBlock *BB : EHBlocks)
601 dbgs() << " " << BB->getName() << '\n';
606 /// Ensure that all values live into and out of exception handlers are stored
608 /// FIXME: This falls down when values are defined in one handler and live into
609 /// another handler. For example, a cleanup defines a value used only by a
611 void WinEHPrepare::demoteValuesLiveAcrossHandlers(
612 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
613 DEBUG(dbgs() << "Demoting values live across exception handlers in function "
614 << F.getName() << '\n');
616 // identifyEHBlocks() should have been called before this function.
617 assert(!NormalBlocks.empty());
619 SetVector<Argument *> ArgsToDemote;
620 SetVector<Instruction *> InstrsToDemote;
621 for (BasicBlock &BB : F) {
622 bool IsNormalBB = NormalBlocks.count(&BB);
623 bool IsEHBB = EHBlocks.count(&BB);
624 if (!IsNormalBB && !IsEHBB)
625 continue; // Blocks that are neither normal nor EH are unreachable.
626 for (Instruction &I : BB) {
627 for (Value *Op : I.operands()) {
628 // Don't demote static allocas, constants, and labels.
629 if (isa<Constant>(Op) || isa<BasicBlock>(Op) || isa<InlineAsm>(Op))
631 auto *AI = dyn_cast<AllocaInst>(Op);
632 if (AI && AI->isStaticAlloca())
635 if (auto *Arg = dyn_cast<Argument>(Op)) {
637 DEBUG(dbgs() << "Demoting argument " << *Arg
638 << " used by EH instr: " << I << "\n");
639 ArgsToDemote.insert(Arg);
644 auto *OpI = cast<Instruction>(Op);
645 BasicBlock *OpBB = OpI->getParent();
646 // If a value is produced and consumed in the same BB, we don't need to
650 bool IsOpNormalBB = NormalBlocks.count(OpBB);
651 bool IsOpEHBB = EHBlocks.count(OpBB);
652 if (IsNormalBB != IsOpNormalBB || IsEHBB != IsOpEHBB) {
654 dbgs() << "Demoting instruction live in-out from EH:\n";
655 dbgs() << "Instr: " << *OpI << '\n';
656 dbgs() << "User: " << I << '\n';
658 InstrsToDemote.insert(OpI);
664 // Demote values live into and out of handlers.
665 // FIXME: This demotion is inefficient. We should insert spills at the point
666 // of definition, insert one reload in each handler that uses the value, and
667 // insert reloads in the BB used to rejoin normal control flow.
668 Instruction *AllocaInsertPt = F.getEntryBlock().getFirstInsertionPt();
669 for (Instruction *I : InstrsToDemote)
670 DemoteRegToStack(*I, false, AllocaInsertPt);
672 // Demote arguments separately, and only for uses in EH blocks.
673 for (Argument *Arg : ArgsToDemote) {
674 auto *Slot = new AllocaInst(Arg->getType(), nullptr,
675 Arg->getName() + ".reg2mem", AllocaInsertPt);
676 SmallVector<User *, 4> Users(Arg->user_begin(), Arg->user_end());
677 for (User *U : Users) {
678 auto *I = dyn_cast<Instruction>(U);
679 if (I && EHBlocks.count(I->getParent())) {
680 auto *Reload = new LoadInst(Slot, Arg->getName() + ".reload", false, I);
681 U->replaceUsesOfWith(Arg, Reload);
684 new StoreInst(Arg, Slot, AllocaInsertPt);
687 // Demote landingpad phis, as the landingpad will be removed from the machine
689 for (LandingPadInst *LPI : LPads) {
690 BasicBlock *BB = LPI->getParent();
691 while (auto *Phi = dyn_cast<PHINode>(BB->begin()))
692 DemotePHIToStack(Phi, AllocaInsertPt);
695 DEBUG(dbgs() << "Demoted " << InstrsToDemote.size() << " instructions and "
696 << ArgsToDemote.size() << " arguments for WinEHPrepare\n\n");
699 bool WinEHPrepare::prepareExceptionHandlers(
700 Function &F, SmallVectorImpl<LandingPadInst *> &LPads) {
701 // Don't run on functions that are already prepared.
702 for (LandingPadInst *LPad : LPads) {
703 BasicBlock *LPadBB = LPad->getParent();
704 for (Instruction &Inst : *LPadBB)
705 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>()))
709 identifyEHBlocks(F, LPads);
710 demoteValuesLiveAcrossHandlers(F, LPads);
712 // These containers are used to re-map frame variables that are used in
713 // outlined catch and cleanup handlers. They will be populated as the
714 // handlers are outlined.
715 FrameVarInfoMap FrameVarInfo;
717 bool HandlersOutlined = false;
719 Module *M = F.getParent();
720 LLVMContext &Context = M->getContext();
722 // Create a new function to receive the handler contents.
723 PointerType *Int8PtrType = Type::getInt8PtrTy(Context);
724 Type *Int32Type = Type::getInt32Ty(Context);
725 Function *ActionIntrin = Intrinsic::getDeclaration(M, Intrinsic::eh_actions);
727 if (isAsynchronousEHPersonality(Personality)) {
728 // FIXME: Switch the ehptr type to i32 and then switch this.
729 SEHExceptionCodeSlot =
730 new AllocaInst(Int8PtrType, nullptr, "seh_exception_code",
731 F.getEntryBlock().getFirstInsertionPt());
734 // In order to handle the case where one outlined catch handler returns
735 // to a block within another outlined catch handler that would otherwise
736 // be unreachable, we need to outline the nested landing pad before we
737 // outline the landing pad which encloses it.
738 if (!isAsynchronousEHPersonality(Personality))
739 std::sort(LPads.begin(), LPads.end(),
740 [this](LandingPadInst *const &L, LandingPadInst *const &R) {
741 return DT->properlyDominates(R->getParent(), L->getParent());
744 // This container stores the llvm.eh.recover and IndirectBr instructions
745 // that make up the body of each landing pad after it has been outlined.
746 // We need to defer the population of the target list for the indirectbr
747 // until all landing pads have been outlined so that we can handle the
748 // case of blocks in the target that are reached only from nested
750 SmallVector<std::pair<CallInst*, IndirectBrInst *>, 4> LPadImpls;
752 for (LandingPadInst *LPad : LPads) {
753 // Look for evidence that this landingpad has already been processed.
754 bool LPadHasActionList = false;
755 BasicBlock *LPadBB = LPad->getParent();
756 for (Instruction &Inst : *LPadBB) {
757 if (match(&Inst, m_Intrinsic<Intrinsic::eh_actions>())) {
758 LPadHasActionList = true;
763 // If we've already outlined the handlers for this landingpad,
764 // there's nothing more to do here.
765 if (LPadHasActionList)
768 // If either of the values in the aggregate returned by the landing pad is
769 // extracted and stored to memory, promote the stored value to a register.
770 promoteLandingPadValues(LPad);
772 LandingPadActions Actions;
773 mapLandingPadBlocks(LPad, Actions);
775 HandlersOutlined |= !Actions.actions().empty();
776 for (ActionHandler *Action : Actions) {
777 if (Action->hasBeenProcessed())
779 BasicBlock *StartBB = Action->getStartBlock();
781 // SEH doesn't do any outlining for catches. Instead, pass the handler
782 // basic block addr to llvm.eh.actions and list the block as a return
784 if (isAsynchronousEHPersonality(Personality)) {
785 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
786 processSEHCatchHandler(CatchAction, StartBB);
791 outlineHandler(Action, &F, LPad, StartBB, FrameVarInfo);
794 // Split the block after the landingpad instruction so that it is just a
795 // call to llvm.eh.actions followed by indirectbr.
796 assert(!isa<PHINode>(LPadBB->begin()) && "lpad phi not removed");
797 SplitBlock(LPadBB, LPad->getNextNode(), DT);
798 // Erase the branch inserted by the split so we can insert indirectbr.
799 LPadBB->getTerminator()->eraseFromParent();
801 // Replace all extracted values with undef and ultimately replace the
802 // landingpad with undef.
803 SmallVector<Instruction *, 4> SEHCodeUses;
804 SmallVector<Instruction *, 4> EHUndefs;
805 for (User *U : LPad->users()) {
806 auto *E = dyn_cast<ExtractValueInst>(U);
809 assert(E->getNumIndices() == 1 &&
810 "Unexpected operation: extracting both landing pad values");
811 unsigned Idx = *E->idx_begin();
812 assert((Idx == 0 || Idx == 1) && "unexpected index");
813 if (Idx == 0 && isAsynchronousEHPersonality(Personality))
814 SEHCodeUses.push_back(E);
816 EHUndefs.push_back(E);
818 for (Instruction *E : EHUndefs) {
819 E->replaceAllUsesWith(UndefValue::get(E->getType()));
820 E->eraseFromParent();
822 LPad->replaceAllUsesWith(UndefValue::get(LPad->getType()));
824 // Rewrite uses of the exception pointer to loads of an alloca.
825 for (Instruction *E : SEHCodeUses) {
826 SmallVector<Use *, 4> Uses;
827 for (Use &U : E->uses())
829 for (Use *U : Uses) {
830 auto *I = cast<Instruction>(U->getUser());
831 if (isa<ResumeInst>(I))
834 if (auto *Phi = dyn_cast<PHINode>(I))
835 LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false,
836 Phi->getIncomingBlock(*U));
838 LI = new LoadInst(SEHExceptionCodeSlot, "sehcode", false, I);
841 E->replaceAllUsesWith(UndefValue::get(E->getType()));
842 E->eraseFromParent();
845 // Add a call to describe the actions for this landing pad.
846 std::vector<Value *> ActionArgs;
847 for (ActionHandler *Action : Actions) {
848 // Action codes from docs are: 0 cleanup, 1 catch.
849 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
850 ActionArgs.push_back(ConstantInt::get(Int32Type, 1));
851 ActionArgs.push_back(CatchAction->getSelector());
852 // Find the frame escape index of the exception object alloca in the
854 int FrameEscapeIdx = -1;
855 Value *EHObj = const_cast<Value *>(CatchAction->getExceptionVar());
856 if (EHObj && !isa<ConstantPointerNull>(EHObj)) {
857 auto I = FrameVarInfo.find(EHObj);
858 assert(I != FrameVarInfo.end() &&
859 "failed to map llvm.eh.begincatch var");
860 FrameEscapeIdx = std::distance(FrameVarInfo.begin(), I);
862 ActionArgs.push_back(ConstantInt::get(Int32Type, FrameEscapeIdx));
864 ActionArgs.push_back(ConstantInt::get(Int32Type, 0));
866 ActionArgs.push_back(Action->getHandlerBlockOrFunc());
869 CallInst::Create(ActionIntrin, ActionArgs, "recover", LPadBB);
871 SetVector<BasicBlock *> ReturnTargets;
872 for (ActionHandler *Action : Actions) {
873 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
874 const auto &CatchTargets = CatchAction->getReturnTargets();
875 ReturnTargets.insert(CatchTargets.begin(), CatchTargets.end());
878 IndirectBrInst *Branch =
879 IndirectBrInst::Create(Recover, ReturnTargets.size(), LPadBB);
880 for (BasicBlock *Target : ReturnTargets)
881 Branch->addDestination(Target);
883 if (!isAsynchronousEHPersonality(Personality)) {
884 // C++ EH must repopulate the targets later to handle the case of
885 // targets that are reached indirectly through nested landing pads.
886 LPadImpls.push_back(std::make_pair(Recover, Branch));
889 } // End for each landingpad
891 // If nothing got outlined, there is no more processing to be done.
892 if (!HandlersOutlined)
895 // Replace any nested landing pad stubs with the correct action handler.
896 // This must be done before we remove unreachable blocks because it
897 // cleans up references to outlined blocks that will be deleted.
898 for (auto &LPadPair : NestedLPtoOriginalLP)
899 completeNestedLandingPad(&F, LPadPair.first, LPadPair.second, FrameVarInfo);
900 NestedLPtoOriginalLP.clear();
902 // Update the indirectbr instructions' target lists if necessary.
903 SetVector<BasicBlock*> CheckedTargets;
904 SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
905 for (auto &LPadImplPair : LPadImpls) {
906 IntrinsicInst *Recover = cast<IntrinsicInst>(LPadImplPair.first);
907 IndirectBrInst *Branch = LPadImplPair.second;
909 // Get a list of handlers called by
910 parseEHActions(Recover, ActionList);
912 // Add an indirect branch listing possible successors of the catch handlers.
913 SetVector<BasicBlock *> ReturnTargets;
914 for (const auto &Action : ActionList) {
915 if (auto *CA = dyn_cast<CatchHandler>(Action.get())) {
916 Function *Handler = cast<Function>(CA->getHandlerBlockOrFunc());
917 getPossibleReturnTargets(&F, Handler, ReturnTargets);
921 // Clear any targets we already knew about.
922 for (unsigned int I = 0, E = Branch->getNumDestinations(); I < E; ++I) {
923 BasicBlock *KnownTarget = Branch->getDestination(I);
924 if (ReturnTargets.count(KnownTarget))
925 ReturnTargets.remove(KnownTarget);
927 for (BasicBlock *Target : ReturnTargets) {
928 Branch->addDestination(Target);
929 // The target may be a block that we excepted to get pruned.
930 // If it is, it may contain a call to llvm.eh.endcatch.
931 if (CheckedTargets.insert(Target)) {
932 // Earlier preparations guarantee that all calls to llvm.eh.endcatch
933 // will be followed by an unconditional branch.
934 auto *Br = dyn_cast<BranchInst>(Target->getTerminator());
935 if (Br && Br->isUnconditional() &&
936 Br != Target->getFirstNonPHIOrDbgOrLifetime()) {
937 Instruction *Prev = Br->getPrevNode();
938 if (match(cast<Value>(Prev), m_Intrinsic<Intrinsic::eh_endcatch>()))
939 Prev->eraseFromParent();
946 F.addFnAttr("wineh-parent", F.getName());
948 // Delete any blocks that were only used by handlers that were outlined above.
949 removeUnreachableBlocks(F);
951 BasicBlock *Entry = &F.getEntryBlock();
952 IRBuilder<> Builder(F.getParent()->getContext());
953 Builder.SetInsertPoint(Entry->getFirstInsertionPt());
955 Function *FrameEscapeFn =
956 Intrinsic::getDeclaration(M, Intrinsic::frameescape);
957 Function *RecoverFrameFn =
958 Intrinsic::getDeclaration(M, Intrinsic::framerecover);
959 SmallVector<Value *, 8> AllocasToEscape;
961 // Scan the entry block for an existing call to llvm.frameescape. We need to
962 // keep escaping those objects.
963 for (Instruction &I : F.front()) {
964 auto *II = dyn_cast<IntrinsicInst>(&I);
965 if (II && II->getIntrinsicID() == Intrinsic::frameescape) {
966 auto Args = II->arg_operands();
967 AllocasToEscape.append(Args.begin(), Args.end());
968 II->eraseFromParent();
973 // Finally, replace all of the temporary allocas for frame variables used in
974 // the outlined handlers with calls to llvm.framerecover.
975 for (auto &VarInfoEntry : FrameVarInfo) {
976 Value *ParentVal = VarInfoEntry.first;
977 TinyPtrVector<AllocaInst *> &Allocas = VarInfoEntry.second;
978 AllocaInst *ParentAlloca = cast<AllocaInst>(ParentVal);
980 // FIXME: We should try to sink unescaped allocas from the parent frame into
981 // the child frame. If the alloca is escaped, we have to use the lifetime
982 // markers to ensure that the alloca is only live within the child frame.
984 // Add this alloca to the list of things to escape.
985 AllocasToEscape.push_back(ParentAlloca);
987 // Next replace all outlined allocas that are mapped to it.
988 for (AllocaInst *TempAlloca : Allocas) {
989 if (TempAlloca == getCatchObjectSentinel())
990 continue; // Skip catch parameter sentinels.
991 Function *HandlerFn = TempAlloca->getParent()->getParent();
992 llvm::Value *FP = HandlerToParentFP[HandlerFn];
995 // FIXME: Sink this framerecover into the blocks where it is used.
996 Builder.SetInsertPoint(TempAlloca);
997 Builder.SetCurrentDebugLocation(TempAlloca->getDebugLoc());
998 Value *RecoverArgs[] = {
999 Builder.CreateBitCast(&F, Int8PtrType, ""), FP,
1000 llvm::ConstantInt::get(Int32Type, AllocasToEscape.size() - 1)};
1001 Instruction *RecoveredAlloca =
1002 Builder.CreateCall(RecoverFrameFn, RecoverArgs);
1004 // Add a pointer bitcast if the alloca wasn't an i8.
1005 if (RecoveredAlloca->getType() != TempAlloca->getType()) {
1006 RecoveredAlloca->setName(Twine(TempAlloca->getName()) + ".i8");
1007 RecoveredAlloca = cast<Instruction>(
1008 Builder.CreateBitCast(RecoveredAlloca, TempAlloca->getType()));
1010 TempAlloca->replaceAllUsesWith(RecoveredAlloca);
1011 TempAlloca->removeFromParent();
1012 RecoveredAlloca->takeName(TempAlloca);
1015 } // End for each FrameVarInfo entry.
1017 // Insert 'call void (...)* @llvm.frameescape(...)' at the end of the entry
1019 Builder.SetInsertPoint(&F.getEntryBlock().back());
1020 Builder.CreateCall(FrameEscapeFn, AllocasToEscape);
1022 if (SEHExceptionCodeSlot) {
1023 if (isAllocaPromotable(SEHExceptionCodeSlot)) {
1024 SmallPtrSet<BasicBlock *, 4> UserBlocks;
1025 for (User *U : SEHExceptionCodeSlot->users()) {
1026 if (auto *Inst = dyn_cast<Instruction>(U))
1027 UserBlocks.insert(Inst->getParent());
1029 PromoteMemToReg(SEHExceptionCodeSlot, *DT);
1030 // After the promotion, kill off dead instructions.
1031 for (BasicBlock *BB : UserBlocks)
1032 SimplifyInstructionsInBlock(BB, LibInfo);
1036 // Clean up the handler action maps we created for this function
1037 DeleteContainerSeconds(CatchHandlerMap);
1038 CatchHandlerMap.clear();
1039 DeleteContainerSeconds(CleanupHandlerMap);
1040 CleanupHandlerMap.clear();
1041 HandlerToParentFP.clear();
1044 SEHExceptionCodeSlot = nullptr;
1046 NormalBlocks.clear();
1047 EHReturnBlocks.clear();
1049 return HandlersOutlined;
1052 void WinEHPrepare::promoteLandingPadValues(LandingPadInst *LPad) {
1053 // If the return values of the landing pad instruction are extracted and
1054 // stored to memory, we want to promote the store locations to reg values.
1055 SmallVector<AllocaInst *, 2> EHAllocas;
1057 // The landingpad instruction returns an aggregate value. Typically, its
1058 // value will be passed to a pair of extract value instructions and the
1059 // results of those extracts are often passed to store instructions.
1060 // In unoptimized code the stored value will often be loaded and then stored
1062 for (auto *U : LPad->users()) {
1063 ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
1067 for (auto *EU : Extract->users()) {
1068 if (auto *Store = dyn_cast<StoreInst>(EU)) {
1069 auto *AV = cast<AllocaInst>(Store->getPointerOperand());
1070 EHAllocas.push_back(AV);
1075 // We can't do this without a dominator tree.
1078 if (!EHAllocas.empty()) {
1079 PromoteMemToReg(EHAllocas, *DT);
1083 // After promotion, some extracts may be trivially dead. Remove them.
1084 SmallVector<Value *, 4> Users(LPad->user_begin(), LPad->user_end());
1085 for (auto *U : Users)
1086 RecursivelyDeleteTriviallyDeadInstructions(U);
1089 void WinEHPrepare::getPossibleReturnTargets(Function *ParentF,
1091 SetVector<BasicBlock*> &Targets) {
1092 for (BasicBlock &BB : *HandlerF) {
1093 // If the handler contains landing pads, check for any
1094 // handlers that may return directly to a block in the
1096 if (auto *LPI = BB.getLandingPadInst()) {
1097 IntrinsicInst *Recover = cast<IntrinsicInst>(LPI->getNextNode());
1098 SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
1099 parseEHActions(Recover, ActionList);
1100 for (const auto &Action : ActionList) {
1101 if (auto *CH = dyn_cast<CatchHandler>(Action.get())) {
1102 Function *NestedF = cast<Function>(CH->getHandlerBlockOrFunc());
1103 getPossibleReturnTargets(ParentF, NestedF, Targets);
1108 auto *Ret = dyn_cast<ReturnInst>(BB.getTerminator());
1112 // Handler functions must always return a block address.
1113 BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
1115 // If this is the handler for a nested landing pad, the
1116 // return address may have been remapped to a block in the
1117 // parent handler. We're not interested in those.
1118 if (BA->getFunction() != ParentF)
1121 Targets.insert(BA->getBasicBlock());
1125 void WinEHPrepare::completeNestedLandingPad(Function *ParentFn,
1126 LandingPadInst *OutlinedLPad,
1127 const LandingPadInst *OriginalLPad,
1128 FrameVarInfoMap &FrameVarInfo) {
1129 // Get the nested block and erase the unreachable instruction that was
1130 // temporarily inserted as its terminator.
1131 LLVMContext &Context = ParentFn->getContext();
1132 BasicBlock *OutlinedBB = OutlinedLPad->getParent();
1133 // If the nested landing pad was outlined before the landing pad that enclosed
1134 // it, it will already be in outlined form. In that case, we just need to see
1135 // if the returns and the enclosing branch instruction need to be updated.
1136 IndirectBrInst *Branch =
1137 dyn_cast<IndirectBrInst>(OutlinedBB->getTerminator());
1139 // If the landing pad wasn't in outlined form, it should be a stub with
1140 // an unreachable terminator.
1141 assert(isa<UnreachableInst>(OutlinedBB->getTerminator()));
1142 OutlinedBB->getTerminator()->eraseFromParent();
1143 // That should leave OutlinedLPad as the last instruction in its block.
1144 assert(&OutlinedBB->back() == OutlinedLPad);
1147 // The original landing pad will have already had its action intrinsic
1148 // built by the outlining loop. We need to clone that into the outlined
1149 // location. It may also be necessary to add references to the exception
1150 // variables to the outlined handler in which this landing pad is nested
1151 // and remap return instructions in the nested handlers that should return
1152 // to an address in the outlined handler.
1153 Function *OutlinedHandlerFn = OutlinedBB->getParent();
1154 BasicBlock::const_iterator II = OriginalLPad;
1156 // The instruction after the landing pad should now be a call to eh.actions.
1157 const Instruction *Recover = II;
1158 const IntrinsicInst *EHActions = cast<IntrinsicInst>(Recover);
1160 // Remap the return target in the nested handler.
1161 SmallVector<BlockAddress *, 4> ActionTargets;
1162 SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
1163 parseEHActions(EHActions, ActionList);
1164 for (const auto &Action : ActionList) {
1165 auto *Catch = dyn_cast<CatchHandler>(Action.get());
1168 // The dyn_cast to function here selects C++ catch handlers and skips
1169 // SEH catch handlers.
1170 auto *Handler = dyn_cast<Function>(Catch->getHandlerBlockOrFunc());
1173 // Visit all the return instructions, looking for places that return
1174 // to a location within OutlinedHandlerFn.
1175 for (BasicBlock &NestedHandlerBB : *Handler) {
1176 auto *Ret = dyn_cast<ReturnInst>(NestedHandlerBB.getTerminator());
1180 // Handler functions must always return a block address.
1181 BlockAddress *BA = cast<BlockAddress>(Ret->getReturnValue());
1182 // The original target will have been in the main parent function,
1183 // but if it is the address of a block that has been outlined, it
1184 // should be a block that was outlined into OutlinedHandlerFn.
1185 assert(BA->getFunction() == ParentFn);
1187 // Ignore targets that aren't part of an outlined handler function.
1188 if (!LPadTargetBlocks.count(BA->getBasicBlock()))
1191 // If the return value is the address ofF a block that we
1192 // previously outlined into the parent handler function, replace
1193 // the return instruction and add the mapped target to the list
1194 // of possible return addresses.
1195 BasicBlock *MappedBB = LPadTargetBlocks[BA->getBasicBlock()];
1196 assert(MappedBB->getParent() == OutlinedHandlerFn);
1197 BlockAddress *NewBA = BlockAddress::get(OutlinedHandlerFn, MappedBB);
1198 Ret->eraseFromParent();
1199 ReturnInst::Create(Context, NewBA, &NestedHandlerBB);
1200 ActionTargets.push_back(NewBA);
1206 // If the landing pad was already in outlined form, just update its targets.
1207 for (unsigned int I = Branch->getNumDestinations(); I > 0; --I)
1208 Branch->removeDestination(I);
1209 // Add the previously collected action targets.
1210 for (auto *Target : ActionTargets)
1211 Branch->addDestination(Target->getBasicBlock());
1213 // If the landing pad was previously stubbed out, fill in its outlined form.
1214 IntrinsicInst *NewEHActions = cast<IntrinsicInst>(EHActions->clone());
1215 OutlinedBB->getInstList().push_back(NewEHActions);
1217 // Insert an indirect branch into the outlined landing pad BB.
1218 IndirectBrInst *IBr = IndirectBrInst::Create(NewEHActions, 0, OutlinedBB);
1219 // Add the previously collected action targets.
1220 for (auto *Target : ActionTargets)
1221 IBr->addDestination(Target->getBasicBlock());
1225 // This function examines a block to determine whether the block ends with a
1226 // conditional branch to a catch handler based on a selector comparison.
1227 // This function is used both by the WinEHPrepare::findSelectorComparison() and
1228 // WinEHCleanupDirector::handleTypeIdFor().
1229 static bool isSelectorDispatch(BasicBlock *BB, BasicBlock *&CatchHandler,
1230 Constant *&Selector, BasicBlock *&NextBB) {
1231 ICmpInst::Predicate Pred;
1232 BasicBlock *TBB, *FBB;
1235 if (!match(BB->getTerminator(),
1236 m_Br(m_ICmp(Pred, m_Value(LHS), m_Value(RHS)), TBB, FBB)))
1240 m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))) &&
1241 !match(RHS, m_Intrinsic<Intrinsic::eh_typeid_for>(m_Constant(Selector))))
1244 if (Pred == CmpInst::ICMP_EQ) {
1250 if (Pred == CmpInst::ICMP_NE) {
1259 static bool isCatchBlock(BasicBlock *BB) {
1260 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
1262 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_begincatch>()))
1268 static BasicBlock *createStubLandingPad(Function *Handler) {
1269 // FIXME: Finish this!
1270 LLVMContext &Context = Handler->getContext();
1271 BasicBlock *StubBB = BasicBlock::Create(Context, "stub");
1272 Handler->getBasicBlockList().push_back(StubBB);
1273 IRBuilder<> Builder(StubBB);
1274 LandingPadInst *LPad = Builder.CreateLandingPad(
1275 llvm::StructType::get(Type::getInt8PtrTy(Context),
1276 Type::getInt32Ty(Context), nullptr),
1278 // Insert a call to llvm.eh.actions so that we don't try to outline this lpad.
1279 Function *ActionIntrin =
1280 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::eh_actions);
1281 Builder.CreateCall(ActionIntrin, {}, "recover");
1282 LPad->setCleanup(true);
1283 Builder.CreateUnreachable();
1287 // Cycles through the blocks in an outlined handler function looking for an
1288 // invoke instruction and inserts an invoke of llvm.donothing with an empty
1289 // landing pad if none is found. The code that generates the .xdata tables for
1290 // the handler needs at least one landing pad to identify the parent function's
1292 void WinEHPrepare::addStubInvokeToHandlerIfNeeded(Function *Handler) {
1293 ReturnInst *Ret = nullptr;
1294 UnreachableInst *Unreached = nullptr;
1295 for (BasicBlock &BB : *Handler) {
1296 TerminatorInst *Terminator = BB.getTerminator();
1297 // If we find an invoke, there is nothing to be done.
1298 auto *II = dyn_cast<InvokeInst>(Terminator);
1301 // If we've already recorded a return instruction, keep looking for invokes.
1303 Ret = dyn_cast<ReturnInst>(Terminator);
1304 // If we haven't recorded an unreachable instruction, try this terminator.
1306 Unreached = dyn_cast<UnreachableInst>(Terminator);
1309 // If we got this far, the handler contains no invokes. We should have seen
1310 // at least one return or unreachable instruction. We'll insert an invoke of
1311 // llvm.donothing ahead of that instruction.
1312 assert(Ret || Unreached);
1313 TerminatorInst *Term;
1318 BasicBlock *OldRetBB = Term->getParent();
1319 BasicBlock *NewRetBB = SplitBlock(OldRetBB, Term, DT);
1320 // SplitBlock adds an unconditional branch instruction at the end of the
1321 // parent block. We want to replace that with an invoke call, so we can
1323 OldRetBB->getTerminator()->eraseFromParent();
1324 BasicBlock *StubLandingPad = createStubLandingPad(Handler);
1326 Intrinsic::getDeclaration(Handler->getParent(), Intrinsic::donothing);
1327 InvokeInst::Create(F, NewRetBB, StubLandingPad, None, "", OldRetBB);
1330 // FIXME: Consider sinking this into lib/Target/X86 somehow. TargetLowering
1331 // usually doesn't build LLVM IR, so that's probably the wrong place.
1332 Function *WinEHPrepare::createHandlerFunc(Function *ParentFn, Type *RetTy,
1333 const Twine &Name, Module *M,
1335 // x64 uses a two-argument prototype where the parent FP is the second
1336 // argument. x86 uses no arguments, just the incoming EBP value.
1337 LLVMContext &Context = M->getContext();
1338 Type *Int8PtrType = Type::getInt8PtrTy(Context);
1339 FunctionType *FnType;
1340 if (TheTriple.getArch() == Triple::x86_64) {
1341 Type *ArgTys[2] = {Int8PtrType, Int8PtrType};
1342 FnType = FunctionType::get(RetTy, ArgTys, false);
1344 FnType = FunctionType::get(RetTy, None, false);
1348 Function::Create(FnType, GlobalVariable::InternalLinkage, Name, M);
1349 BasicBlock *Entry = BasicBlock::Create(Context, "entry");
1350 Handler->getBasicBlockList().push_front(Entry);
1351 if (TheTriple.getArch() == Triple::x86_64) {
1352 ParentFP = &(Handler->getArgumentList().back());
1355 Function *FrameAddressFn =
1356 Intrinsic::getDeclaration(M, Intrinsic::frameaddress);
1357 Function *RecoverFPFn =
1358 Intrinsic::getDeclaration(M, Intrinsic::x86_seh_recoverfp);
1359 IRBuilder<> Builder(&Handler->getEntryBlock());
1361 Builder.CreateCall(FrameAddressFn, {Builder.getInt32(1)}, "ebp");
1362 Value *ParentI8Fn = Builder.CreateBitCast(ParentFn, Int8PtrType);
1363 ParentFP = Builder.CreateCall(RecoverFPFn, {ParentI8Fn, EBP});
1368 bool WinEHPrepare::outlineHandler(ActionHandler *Action, Function *SrcFn,
1369 LandingPadInst *LPad, BasicBlock *StartBB,
1370 FrameVarInfoMap &VarInfo) {
1371 Module *M = SrcFn->getParent();
1372 LLVMContext &Context = M->getContext();
1373 Type *Int8PtrType = Type::getInt8PtrTy(Context);
1375 // Create a new function to receive the handler contents.
1378 if (Action->getType() == Catch) {
1379 Handler = createHandlerFunc(SrcFn, Int8PtrType, SrcFn->getName() + ".catch", M,
1382 Handler = createHandlerFunc(SrcFn, Type::getVoidTy(Context),
1383 SrcFn->getName() + ".cleanup", M, ParentFP);
1385 Handler->setPersonalityFn(SrcFn->getPersonalityFn());
1386 HandlerToParentFP[Handler] = ParentFP;
1387 Handler->addFnAttr("wineh-parent", SrcFn->getName());
1388 BasicBlock *Entry = &Handler->getEntryBlock();
1390 // Generate a standard prolog to setup the frame recovery structure.
1391 IRBuilder<> Builder(Context);
1392 Builder.SetInsertPoint(Entry);
1393 Builder.SetCurrentDebugLocation(LPad->getDebugLoc());
1395 std::unique_ptr<WinEHCloningDirectorBase> Director;
1397 ValueToValueMapTy VMap;
1399 LandingPadMap &LPadMap = LPadMaps[LPad];
1400 if (!LPadMap.isInitialized())
1401 LPadMap.mapLandingPad(LPad);
1402 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1403 Constant *Sel = CatchAction->getSelector();
1404 Director.reset(new WinEHCatchDirector(Handler, ParentFP, Sel, VarInfo,
1405 LPadMap, NestedLPtoOriginalLP, DT,
1407 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1408 ConstantInt::get(Type::getInt32Ty(Context), 1));
1411 new WinEHCleanupDirector(Handler, ParentFP, VarInfo, LPadMap));
1412 LPadMap.remapEHValues(VMap, UndefValue::get(Int8PtrType),
1413 UndefValue::get(Type::getInt32Ty(Context)));
1416 SmallVector<ReturnInst *, 8> Returns;
1417 ClonedCodeInfo OutlinedFunctionInfo;
1419 // If the start block contains PHI nodes, we need to map them.
1420 BasicBlock::iterator II = StartBB->begin();
1421 while (auto *PN = dyn_cast<PHINode>(II)) {
1422 bool Mapped = false;
1423 // Look for PHI values that we have already mapped (such as the selector).
1424 for (Value *Val : PN->incoming_values()) {
1425 if (VMap.count(Val)) {
1426 VMap[PN] = VMap[Val];
1430 // If we didn't find a match for this value, map it as an undef.
1432 VMap[PN] = UndefValue::get(PN->getType());
1437 // The landing pad value may be used by PHI nodes. It will ultimately be
1438 // eliminated, but we need it in the map for intermediate handling.
1439 VMap[LPad] = UndefValue::get(LPad->getType());
1441 // Skip over PHIs and, if applicable, landingpad instructions.
1442 II = StartBB->getFirstInsertionPt();
1444 CloneAndPruneIntoFromInst(Handler, SrcFn, II, VMap,
1445 /*ModuleLevelChanges=*/false, Returns, "",
1446 &OutlinedFunctionInfo, Director.get());
1448 // Move all the instructions in the cloned "entry" block into our entry block.
1449 // Depending on how the parent function was laid out, the block that will
1450 // correspond to the outlined entry block may not be the first block in the
1451 // list. We can recognize it, however, as the cloned block which has no
1452 // predecessors. Any other block wouldn't have been cloned if it didn't
1453 // have a predecessor which was also cloned.
1454 Function::iterator ClonedIt = std::next(Function::iterator(Entry));
1455 while (!pred_empty(ClonedIt))
1457 BasicBlock *ClonedEntryBB = ClonedIt;
1458 assert(ClonedEntryBB);
1459 Entry->getInstList().splice(Entry->end(), ClonedEntryBB->getInstList());
1460 ClonedEntryBB->eraseFromParent();
1462 // Make sure we can identify the handler's personality later.
1463 addStubInvokeToHandlerIfNeeded(Handler);
1465 if (auto *CatchAction = dyn_cast<CatchHandler>(Action)) {
1466 WinEHCatchDirector *CatchDirector =
1467 reinterpret_cast<WinEHCatchDirector *>(Director.get());
1468 CatchAction->setExceptionVar(CatchDirector->getExceptionVar());
1469 CatchAction->setReturnTargets(CatchDirector->getReturnTargets());
1471 // Look for blocks that are not part of the landing pad that we just
1472 // outlined but terminate with a call to llvm.eh.endcatch and a
1473 // branch to a block that is in the handler we just outlined.
1474 // These blocks will be part of a nested landing pad that intends to
1475 // return to an address in this handler. This case is best handled
1476 // after both landing pads have been outlined, so for now we'll just
1477 // save the association of the blocks in LPadTargetBlocks. The
1478 // return instructions which are created from these branches will be
1479 // replaced after all landing pads have been outlined.
1480 for (const auto MapEntry : VMap) {
1481 // VMap maps all values and blocks that were just cloned, but dead
1482 // blocks which were pruned will map to nullptr.
1483 if (!isa<BasicBlock>(MapEntry.first) || MapEntry.second == nullptr)
1485 const BasicBlock *MappedBB = cast<BasicBlock>(MapEntry.first);
1486 for (auto *Pred : predecessors(const_cast<BasicBlock *>(MappedBB))) {
1487 auto *Branch = dyn_cast<BranchInst>(Pred->getTerminator());
1488 if (!Branch || !Branch->isUnconditional() || Pred->size() <= 1)
1490 BasicBlock::iterator II = const_cast<BranchInst *>(Branch);
1492 if (match(cast<Value>(II), m_Intrinsic<Intrinsic::eh_endcatch>())) {
1493 // This would indicate that a nested landing pad wants to return
1494 // to a block that is outlined into two different handlers.
1495 assert(!LPadTargetBlocks.count(MappedBB));
1496 LPadTargetBlocks[MappedBB] = cast<BasicBlock>(MapEntry.second);
1500 } // End if (CatchAction)
1502 Action->setHandlerBlockOrFunc(Handler);
1507 /// This BB must end in a selector dispatch. All we need to do is pass the
1508 /// handler block to llvm.eh.actions and list it as a possible indirectbr
1510 void WinEHPrepare::processSEHCatchHandler(CatchHandler *CatchAction,
1511 BasicBlock *StartBB) {
1512 BasicBlock *HandlerBB;
1515 bool Res = isSelectorDispatch(StartBB, HandlerBB, Selector, NextBB);
1517 // If this was EH dispatch, this must be a conditional branch to the handler
1519 // FIXME: Handle instructions in the dispatch block. Currently we drop them,
1520 // leading to crashes if some optimization hoists stuff here.
1521 assert(CatchAction->getSelector() && HandlerBB &&
1522 "expected catch EH dispatch");
1524 // This must be a catch-all. Split the block after the landingpad.
1525 assert(CatchAction->getSelector()->isNullValue() && "expected catch-all");
1526 HandlerBB = SplitBlock(StartBB, StartBB->getFirstInsertionPt(), DT);
1528 IRBuilder<> Builder(HandlerBB->getFirstInsertionPt());
1529 Function *EHCodeFn = Intrinsic::getDeclaration(
1530 StartBB->getParent()->getParent(), Intrinsic::eh_exceptioncode);
1531 Value *Code = Builder.CreateCall(EHCodeFn, {}, "sehcode");
1532 Code = Builder.CreateIntToPtr(Code, SEHExceptionCodeSlot->getAllocatedType());
1533 Builder.CreateStore(Code, SEHExceptionCodeSlot);
1534 CatchAction->setHandlerBlockOrFunc(BlockAddress::get(HandlerBB));
1535 TinyPtrVector<BasicBlock *> Targets(HandlerBB);
1536 CatchAction->setReturnTargets(Targets);
1539 void LandingPadMap::mapLandingPad(const LandingPadInst *LPad) {
1540 // Each instance of this class should only ever be used to map a single
1542 assert(OriginLPad == nullptr || OriginLPad == LPad);
1544 // If the landing pad has already been mapped, there's nothing more to do.
1545 if (OriginLPad == LPad)
1550 // The landingpad instruction returns an aggregate value. Typically, its
1551 // value will be passed to a pair of extract value instructions and the
1552 // results of those extracts will have been promoted to reg values before
1553 // this routine is called.
1554 for (auto *U : LPad->users()) {
1555 const ExtractValueInst *Extract = dyn_cast<ExtractValueInst>(U);
1558 assert(Extract->getNumIndices() == 1 &&
1559 "Unexpected operation: extracting both landing pad values");
1560 unsigned int Idx = *(Extract->idx_begin());
1561 assert((Idx == 0 || Idx == 1) &&
1562 "Unexpected operation: extracting an unknown landing pad element");
1564 ExtractedEHPtrs.push_back(Extract);
1565 } else if (Idx == 1) {
1566 ExtractedSelectors.push_back(Extract);
1571 bool LandingPadMap::isOriginLandingPadBlock(const BasicBlock *BB) const {
1572 return BB->getLandingPadInst() == OriginLPad;
1575 bool LandingPadMap::isLandingPadSpecificInst(const Instruction *Inst) const {
1576 if (Inst == OriginLPad)
1578 for (auto *Extract : ExtractedEHPtrs) {
1579 if (Inst == Extract)
1582 for (auto *Extract : ExtractedSelectors) {
1583 if (Inst == Extract)
1589 void LandingPadMap::remapEHValues(ValueToValueMapTy &VMap, Value *EHPtrValue,
1590 Value *SelectorValue) const {
1591 // Remap all landing pad extract instructions to the specified values.
1592 for (auto *Extract : ExtractedEHPtrs)
1593 VMap[Extract] = EHPtrValue;
1594 for (auto *Extract : ExtractedSelectors)
1595 VMap[Extract] = SelectorValue;
1598 static bool isFrameAddressCall(const Value *V) {
1599 return match(const_cast<Value *>(V),
1600 m_Intrinsic<Intrinsic::frameaddress>(m_SpecificInt(0)));
1603 CloningDirector::CloningAction WinEHCloningDirectorBase::handleInstruction(
1604 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1605 // If this is one of the boilerplate landing pad instructions, skip it.
1606 // The instruction will have already been remapped in VMap.
1607 if (LPadMap.isLandingPadSpecificInst(Inst))
1608 return CloningDirector::SkipInstruction;
1610 // Nested landing pads that have not already been outlined will be cloned as
1611 // stubs, with just the landingpad instruction and an unreachable instruction.
1612 // When all landingpads have been outlined, we'll replace this with the
1613 // llvm.eh.actions call and indirect branch created when the landing pad was
1615 if (auto *LPad = dyn_cast<LandingPadInst>(Inst)) {
1616 return handleLandingPad(VMap, LPad, NewBB);
1619 // Nested landing pads that have already been outlined will be cloned in their
1620 // outlined form, but we need to intercept the ibr instruction to filter out
1621 // targets that do not return to the handler we are outlining.
1622 if (auto *IBr = dyn_cast<IndirectBrInst>(Inst)) {
1623 return handleIndirectBr(VMap, IBr, NewBB);
1626 if (auto *Invoke = dyn_cast<InvokeInst>(Inst))
1627 return handleInvoke(VMap, Invoke, NewBB);
1629 if (auto *Resume = dyn_cast<ResumeInst>(Inst))
1630 return handleResume(VMap, Resume, NewBB);
1632 if (auto *Cmp = dyn_cast<CmpInst>(Inst))
1633 return handleCompare(VMap, Cmp, NewBB);
1635 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
1636 return handleBeginCatch(VMap, Inst, NewBB);
1637 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
1638 return handleEndCatch(VMap, Inst, NewBB);
1639 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
1640 return handleTypeIdFor(VMap, Inst, NewBB);
1642 // When outlining llvm.frameaddress(i32 0), remap that to the second argument,
1643 // which is the FP of the parent.
1644 if (isFrameAddressCall(Inst)) {
1645 VMap[Inst] = ParentFP;
1646 return CloningDirector::SkipInstruction;
1649 // Continue with the default cloning behavior.
1650 return CloningDirector::CloneInstruction;
1653 CloningDirector::CloningAction WinEHCatchDirector::handleLandingPad(
1654 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1655 // If the instruction after the landing pad is a call to llvm.eh.actions
1656 // the landing pad has already been outlined. In this case, we should
1657 // clone it because it may return to a block in the handler we are
1658 // outlining now that would otherwise be unreachable. The landing pads
1659 // are sorted before outlining begins to enable this case to work
1661 const Instruction *NextI = LPad->getNextNode();
1662 if (match(NextI, m_Intrinsic<Intrinsic::eh_actions>()))
1663 return CloningDirector::CloneInstruction;
1665 // If the landing pad hasn't been outlined yet, the landing pad we are
1666 // outlining now does not dominate it and so it cannot return to a block
1667 // in this handler. In that case, we can just insert a stub landing
1668 // pad now and patch it up later.
1669 Instruction *NewInst = LPad->clone();
1670 if (LPad->hasName())
1671 NewInst->setName(LPad->getName());
1672 // Save this correlation for later processing.
1673 NestedLPtoOriginalLP[cast<LandingPadInst>(NewInst)] = LPad;
1674 VMap[LPad] = NewInst;
1675 BasicBlock::InstListType &InstList = NewBB->getInstList();
1676 InstList.push_back(NewInst);
1677 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1678 return CloningDirector::StopCloningBB;
1681 CloningDirector::CloningAction WinEHCatchDirector::handleBeginCatch(
1682 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1683 // The argument to the call is some form of the first element of the
1684 // landingpad aggregate value, but that doesn't matter. It isn't used
1686 // The second argument is an outparameter where the exception object will be
1687 // stored. Typically the exception object is a scalar, but it can be an
1688 // aggregate when catching by value.
1689 // FIXME: Leave something behind to indicate where the exception object lives
1690 // for this handler. Should it be part of llvm.eh.actions?
1691 assert(ExceptionObjectVar == nullptr && "Multiple calls to "
1692 "llvm.eh.begincatch found while "
1693 "outlining catch handler.");
1694 ExceptionObjectVar = Inst->getOperand(1)->stripPointerCasts();
1695 if (isa<ConstantPointerNull>(ExceptionObjectVar))
1696 return CloningDirector::SkipInstruction;
1697 assert(cast<AllocaInst>(ExceptionObjectVar)->isStaticAlloca() &&
1698 "catch parameter is not static alloca");
1699 Materializer.escapeCatchObject(ExceptionObjectVar);
1700 return CloningDirector::SkipInstruction;
1703 CloningDirector::CloningAction
1704 WinEHCatchDirector::handleEndCatch(ValueToValueMapTy &VMap,
1705 const Instruction *Inst, BasicBlock *NewBB) {
1706 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1707 // It might be interesting to track whether or not we are inside a catch
1708 // function, but that might make the algorithm more brittle than it needs
1711 // The end catch call can occur in one of two places: either in a
1712 // landingpad block that is part of the catch handlers exception mechanism,
1713 // or at the end of the catch block. However, a catch-all handler may call
1714 // end catch from the original landing pad. If the call occurs in a nested
1715 // landing pad block, we must skip it and continue so that the landing pad
1717 auto *ParentBB = IntrinCall->getParent();
1718 if (ParentBB->isLandingPad() && !LPadMap.isOriginLandingPadBlock(ParentBB))
1719 return CloningDirector::SkipInstruction;
1721 // If an end catch occurs anywhere else we want to terminate the handler
1722 // with a return to the code that follows the endcatch call. If the
1723 // next instruction is not an unconditional branch, we need to split the
1724 // block to provide a clear target for the return instruction.
1725 BasicBlock *ContinueBB;
1726 auto Next = std::next(BasicBlock::const_iterator(IntrinCall));
1727 const BranchInst *Branch = dyn_cast<BranchInst>(Next);
1728 if (!Branch || !Branch->isUnconditional()) {
1729 // We're interrupting the cloning process at this location, so the
1730 // const_cast we're doing here will not cause a problem.
1731 ContinueBB = SplitBlock(const_cast<BasicBlock *>(ParentBB),
1732 const_cast<Instruction *>(cast<Instruction>(Next)));
1734 ContinueBB = Branch->getSuccessor(0);
1737 ReturnInst::Create(NewBB->getContext(), BlockAddress::get(ContinueBB), NewBB);
1738 ReturnTargets.push_back(ContinueBB);
1740 // We just added a terminator to the cloned block.
1741 // Tell the caller to stop processing the current basic block so that
1742 // the branch instruction will be skipped.
1743 return CloningDirector::StopCloningBB;
1746 CloningDirector::CloningAction WinEHCatchDirector::handleTypeIdFor(
1747 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1748 auto *IntrinCall = dyn_cast<IntrinsicInst>(Inst);
1749 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1750 // This causes a replacement that will collapse the landing pad CFG based
1751 // on the filter function we intend to match.
1752 if (Selector == CurrentSelector)
1753 VMap[Inst] = ConstantInt::get(SelectorIDType, 1);
1755 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1756 // Tell the caller not to clone this instruction.
1757 return CloningDirector::SkipInstruction;
1760 CloningDirector::CloningAction WinEHCatchDirector::handleIndirectBr(
1761 ValueToValueMapTy &VMap,
1762 const IndirectBrInst *IBr,
1763 BasicBlock *NewBB) {
1764 // If this indirect branch is not part of a landing pad block, just clone it.
1765 const BasicBlock *ParentBB = IBr->getParent();
1766 if (!ParentBB->isLandingPad())
1767 return CloningDirector::CloneInstruction;
1769 // If it is part of a landing pad, we want to filter out target blocks
1770 // that are not part of the handler we are outlining.
1771 const LandingPadInst *LPad = ParentBB->getLandingPadInst();
1773 // Save this correlation for later processing.
1774 NestedLPtoOriginalLP[cast<LandingPadInst>(VMap[LPad])] = LPad;
1776 // We should only get here for landing pads that have already been outlined.
1777 assert(match(LPad->getNextNode(), m_Intrinsic<Intrinsic::eh_actions>()));
1779 // Copy the indirectbr, but only include targets that were previously
1780 // identified as EH blocks and are dominated by the nested landing pad.
1781 SetVector<const BasicBlock *> ReturnTargets;
1782 for (int I = 0, E = IBr->getNumDestinations(); I < E; ++I) {
1783 auto *TargetBB = IBr->getDestination(I);
1784 if (EHBlocks.count(const_cast<BasicBlock*>(TargetBB)) &&
1785 DT->dominates(ParentBB, TargetBB)) {
1786 DEBUG(dbgs() << " Adding destination " << TargetBB->getName() << "\n");
1787 ReturnTargets.insert(TargetBB);
1790 IndirectBrInst *NewBranch =
1791 IndirectBrInst::Create(const_cast<Value *>(IBr->getAddress()),
1792 ReturnTargets.size(), NewBB);
1793 for (auto *Target : ReturnTargets)
1794 NewBranch->addDestination(const_cast<BasicBlock*>(Target));
1796 // The operands and targets of the branch instruction are remapped later
1797 // because it is a terminator. Tell the cloning code to clone the
1798 // blocks we just added to the target list.
1799 return CloningDirector::CloneSuccessors;
1802 CloningDirector::CloningAction
1803 WinEHCatchDirector::handleInvoke(ValueToValueMapTy &VMap,
1804 const InvokeInst *Invoke, BasicBlock *NewBB) {
1805 return CloningDirector::CloneInstruction;
1808 CloningDirector::CloningAction
1809 WinEHCatchDirector::handleResume(ValueToValueMapTy &VMap,
1810 const ResumeInst *Resume, BasicBlock *NewBB) {
1811 // Resume instructions shouldn't be reachable from catch handlers.
1812 // We still need to handle it, but it will be pruned.
1813 BasicBlock::InstListType &InstList = NewBB->getInstList();
1814 InstList.push_back(new UnreachableInst(NewBB->getContext()));
1815 return CloningDirector::StopCloningBB;
1818 CloningDirector::CloningAction
1819 WinEHCatchDirector::handleCompare(ValueToValueMapTy &VMap,
1820 const CmpInst *Compare, BasicBlock *NewBB) {
1821 const IntrinsicInst *IntrinCall = nullptr;
1822 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1823 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(0));
1824 } else if (match(Compare->getOperand(1),
1825 m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1826 IntrinCall = dyn_cast<IntrinsicInst>(Compare->getOperand(1));
1829 Value *Selector = IntrinCall->getArgOperand(0)->stripPointerCasts();
1830 // This causes a replacement that will collapse the landing pad CFG based
1831 // on the filter function we intend to match.
1832 if (Selector == CurrentSelector->stripPointerCasts()) {
1833 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1835 VMap[Compare] = ConstantInt::get(SelectorIDType, 0);
1837 return CloningDirector::SkipInstruction;
1839 return CloningDirector::CloneInstruction;
1842 CloningDirector::CloningAction WinEHCleanupDirector::handleLandingPad(
1843 ValueToValueMapTy &VMap, const LandingPadInst *LPad, BasicBlock *NewBB) {
1844 // The MS runtime will terminate the process if an exception occurs in a
1845 // cleanup handler, so we shouldn't encounter landing pads in the actual
1846 // cleanup code, but they may appear in catch blocks. Depending on where
1847 // we started cloning we may see one, but it will get dropped during dead
1849 Instruction *NewInst = new UnreachableInst(NewBB->getContext());
1850 VMap[LPad] = NewInst;
1851 BasicBlock::InstListType &InstList = NewBB->getInstList();
1852 InstList.push_back(NewInst);
1853 return CloningDirector::StopCloningBB;
1856 CloningDirector::CloningAction WinEHCleanupDirector::handleBeginCatch(
1857 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1858 // Cleanup code may flow into catch blocks or the catch block may be part
1859 // of a branch that will be optimized away. We'll insert a return
1860 // instruction now, but it may be pruned before the cloning process is
1862 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1863 return CloningDirector::StopCloningBB;
1866 CloningDirector::CloningAction WinEHCleanupDirector::handleEndCatch(
1867 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1868 // Cleanup handlers nested within catch handlers may begin with a call to
1869 // eh.endcatch. We can just ignore that instruction.
1870 return CloningDirector::SkipInstruction;
1873 CloningDirector::CloningAction WinEHCleanupDirector::handleTypeIdFor(
1874 ValueToValueMapTy &VMap, const Instruction *Inst, BasicBlock *NewBB) {
1875 // If we encounter a selector comparison while cloning a cleanup handler,
1876 // we want to stop cloning immediately. Anything after the dispatch
1877 // will be outlined into a different handler.
1878 BasicBlock *CatchHandler;
1881 if (isSelectorDispatch(const_cast<BasicBlock *>(Inst->getParent()),
1882 CatchHandler, Selector, NextBB)) {
1883 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1884 return CloningDirector::StopCloningBB;
1886 // If eg.typeid.for is called for any other reason, it can be ignored.
1887 VMap[Inst] = ConstantInt::get(SelectorIDType, 0);
1888 return CloningDirector::SkipInstruction;
1891 CloningDirector::CloningAction WinEHCleanupDirector::handleIndirectBr(
1892 ValueToValueMapTy &VMap,
1893 const IndirectBrInst *IBr,
1894 BasicBlock *NewBB) {
1895 // No special handling is required for cleanup cloning.
1896 return CloningDirector::CloneInstruction;
1899 CloningDirector::CloningAction WinEHCleanupDirector::handleInvoke(
1900 ValueToValueMapTy &VMap, const InvokeInst *Invoke, BasicBlock *NewBB) {
1901 // All invokes in cleanup handlers can be replaced with calls.
1902 SmallVector<Value *, 16> CallArgs(Invoke->op_begin(), Invoke->op_end() - 3);
1903 // Insert a normal call instruction...
1905 CallInst::Create(const_cast<Value *>(Invoke->getCalledValue()), CallArgs,
1906 Invoke->getName(), NewBB);
1907 NewCall->setCallingConv(Invoke->getCallingConv());
1908 NewCall->setAttributes(Invoke->getAttributes());
1909 NewCall->setDebugLoc(Invoke->getDebugLoc());
1910 VMap[Invoke] = NewCall;
1912 // Remap the operands.
1913 llvm::RemapInstruction(NewCall, VMap, RF_None, nullptr, &Materializer);
1915 // Insert an unconditional branch to the normal destination.
1916 BranchInst::Create(Invoke->getNormalDest(), NewBB);
1918 // The unwind destination won't be cloned into the new function, so
1919 // we don't need to clean up its phi nodes.
1921 // We just added a terminator to the cloned block.
1922 // Tell the caller to stop processing the current basic block.
1923 return CloningDirector::CloneSuccessors;
1926 CloningDirector::CloningAction WinEHCleanupDirector::handleResume(
1927 ValueToValueMapTy &VMap, const ResumeInst *Resume, BasicBlock *NewBB) {
1928 ReturnInst::Create(NewBB->getContext(), nullptr, NewBB);
1930 // We just added a terminator to the cloned block.
1931 // Tell the caller to stop processing the current basic block so that
1932 // the branch instruction will be skipped.
1933 return CloningDirector::StopCloningBB;
1936 CloningDirector::CloningAction
1937 WinEHCleanupDirector::handleCompare(ValueToValueMapTy &VMap,
1938 const CmpInst *Compare, BasicBlock *NewBB) {
1939 if (match(Compare->getOperand(0), m_Intrinsic<Intrinsic::eh_typeid_for>()) ||
1940 match(Compare->getOperand(1), m_Intrinsic<Intrinsic::eh_typeid_for>())) {
1941 VMap[Compare] = ConstantInt::get(SelectorIDType, 1);
1942 return CloningDirector::SkipInstruction;
1944 return CloningDirector::CloneInstruction;
1947 WinEHFrameVariableMaterializer::WinEHFrameVariableMaterializer(
1948 Function *OutlinedFn, Value *ParentFP, FrameVarInfoMap &FrameVarInfo)
1949 : FrameVarInfo(FrameVarInfo), Builder(OutlinedFn->getContext()) {
1950 BasicBlock *EntryBB = &OutlinedFn->getEntryBlock();
1952 // New allocas should be inserted in the entry block, but after the parent FP
1953 // is established if it is an instruction.
1954 Instruction *InsertPoint = EntryBB->getFirstInsertionPt();
1955 if (auto *FPInst = dyn_cast<Instruction>(ParentFP))
1956 InsertPoint = FPInst->getNextNode();
1957 Builder.SetInsertPoint(EntryBB, InsertPoint);
1960 Value *WinEHFrameVariableMaterializer::materializeValueFor(Value *V) {
1961 // If we're asked to materialize a static alloca, we temporarily create an
1962 // alloca in the outlined function and add this to the FrameVarInfo map. When
1963 // all the outlining is complete, we'll replace these temporary allocas with
1964 // calls to llvm.framerecover.
1965 if (auto *AV = dyn_cast<AllocaInst>(V)) {
1966 assert(AV->isStaticAlloca() &&
1967 "cannot materialize un-demoted dynamic alloca");
1968 AllocaInst *NewAlloca = dyn_cast<AllocaInst>(AV->clone());
1969 Builder.Insert(NewAlloca, AV->getName());
1970 FrameVarInfo[AV].push_back(NewAlloca);
1974 if (isa<Instruction>(V) || isa<Argument>(V)) {
1975 Function *Parent = isa<Instruction>(V)
1976 ? cast<Instruction>(V)->getParent()->getParent()
1977 : cast<Argument>(V)->getParent();
1979 << "Failed to demote instruction used in exception handler of function "
1980 << GlobalValue::getRealLinkageName(Parent->getName()) << ":\n";
1981 errs() << " " << *V << '\n';
1982 report_fatal_error("WinEHPrepare failed to demote instruction");
1985 // Don't materialize other values.
1989 void WinEHFrameVariableMaterializer::escapeCatchObject(Value *V) {
1990 // Catch parameter objects have to live in the parent frame. When we see a use
1991 // of a catch parameter, add a sentinel to the multimap to indicate that it's
1992 // used from another handler. This will prevent us from trying to sink the
1993 // alloca into the handler and ensure that the catch parameter is present in
1994 // the call to llvm.frameescape.
1995 FrameVarInfo[V].push_back(getCatchObjectSentinel());
1998 // This function maps the catch and cleanup handlers that are reachable from the
1999 // specified landing pad. The landing pad sequence will have this basic shape:
2001 // <cleanup handler>
2002 // <selector comparison>
2004 // <cleanup handler>
2005 // <selector comparison>
2007 // <cleanup handler>
2010 // Any of the cleanup slots may be absent. The cleanup slots may be occupied by
2011 // any arbitrary control flow, but all paths through the cleanup code must
2012 // eventually reach the next selector comparison and no path can skip to a
2013 // different selector comparisons, though some paths may terminate abnormally.
2014 // Therefore, we will use a depth first search from the start of any given
2015 // cleanup block and stop searching when we find the next selector comparison.
2017 // If the landingpad instruction does not have a catch clause, we will assume
2018 // that any instructions other than selector comparisons and catch handlers can
2019 // be ignored. In practice, these will only be the boilerplate instructions.
2021 // The catch handlers may also have any control structure, but we are only
2022 // interested in the start of the catch handlers, so we don't need to actually
2023 // follow the flow of the catch handlers. The start of the catch handlers can
2024 // be located from the compare instructions, but they can be skipped in the
2025 // flow by following the contrary branch.
2026 void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad,
2027 LandingPadActions &Actions) {
2028 unsigned int NumClauses = LPad->getNumClauses();
2029 unsigned int HandlersFound = 0;
2030 BasicBlock *BB = LPad->getParent();
2032 DEBUG(dbgs() << "Mapping landing pad: " << BB->getName() << "\n");
2034 if (NumClauses == 0) {
2035 findCleanupHandlers(Actions, BB, nullptr);
2039 VisitedBlockSet VisitedBlocks;
2041 while (HandlersFound != NumClauses) {
2042 BasicBlock *NextBB = nullptr;
2044 // Skip over filter clauses.
2045 if (LPad->isFilter(HandlersFound)) {
2050 // See if the clause we're looking for is a catch-all.
2051 // If so, the catch begins immediately.
2052 Constant *ExpectedSelector =
2053 LPad->getClause(HandlersFound)->stripPointerCasts();
2054 if (isa<ConstantPointerNull>(ExpectedSelector)) {
2055 // The catch all must occur last.
2056 assert(HandlersFound == NumClauses - 1);
2058 // There can be additional selector dispatches in the call chain that we
2060 BasicBlock *CatchBlock = nullptr;
2062 while (BB && isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
2063 DEBUG(dbgs() << " Found extra catch dispatch in block "
2064 << CatchBlock->getName() << "\n");
2068 // Add the catch handler to the action list.
2069 CatchHandler *Action = nullptr;
2070 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
2071 // If the CatchHandlerMap already has an entry for this BB, re-use it.
2072 Action = CatchHandlerMap[BB];
2073 assert(Action->getSelector() == ExpectedSelector);
2075 // We don't expect a selector dispatch, but there may be a call to
2076 // llvm.eh.begincatch, which separates catch handling code from
2077 // cleanup code in the same control flow. This call looks for the
2078 // begincatch intrinsic.
2079 Action = findCatchHandler(BB, NextBB, VisitedBlocks);
2081 // For C++ EH, check if there is any interesting cleanup code before
2082 // we begin the catch. This is important because cleanups cannot
2083 // rethrow exceptions but code called from catches can. For SEH, it
2084 // isn't important if some finally code before a catch-all is executed
2085 // out of line or after recovering from the exception.
2086 if (Personality == EHPersonality::MSVC_CXX)
2087 findCleanupHandlers(Actions, BB, BB);
2089 // If an action was not found, it means that the control flows
2090 // directly into the catch-all handler and there is no cleanup code.
2091 // That's an expected situation and we must create a catch action.
2092 // Since this is a catch-all handler, the selector won't actually
2093 // appear in the code anywhere. ExpectedSelector here is the constant
2094 // null ptr that we got from the landing pad instruction.
2095 Action = new CatchHandler(BB, ExpectedSelector, nullptr);
2096 CatchHandlerMap[BB] = Action;
2099 Actions.insertCatchHandler(Action);
2100 DEBUG(dbgs() << " Catch all handler at block " << BB->getName() << "\n");
2103 // Once we reach a catch-all, don't expect to hit a resume instruction.
2108 CatchHandler *CatchAction = findCatchHandler(BB, NextBB, VisitedBlocks);
2109 assert(CatchAction);
2111 // See if there is any interesting code executed before the dispatch.
2112 findCleanupHandlers(Actions, BB, CatchAction->getStartBlock());
2114 // When the source program contains multiple nested try blocks the catch
2115 // handlers can get strung together in such a way that we can encounter
2116 // a dispatch for a selector that we've already had a handler for.
2117 if (CatchAction->getSelector()->stripPointerCasts() == ExpectedSelector) {
2120 // Add the catch handler to the action list.
2121 DEBUG(dbgs() << " Found catch dispatch in block "
2122 << CatchAction->getStartBlock()->getName() << "\n");
2123 Actions.insertCatchHandler(CatchAction);
2125 // Under some circumstances optimized IR will flow unconditionally into a
2126 // handler block without checking the selector. This can only happen if
2127 // the landing pad has a catch-all handler and the handler for the
2128 // preceeding catch clause is identical to the catch-call handler
2129 // (typically an empty catch). In this case, the handler must be shared
2130 // by all remaining clauses.
2131 if (isa<ConstantPointerNull>(
2132 CatchAction->getSelector()->stripPointerCasts())) {
2133 DEBUG(dbgs() << " Applying early catch-all handler in block "
2134 << CatchAction->getStartBlock()->getName()
2135 << " to all remaining clauses.\n");
2136 Actions.insertCatchHandler(CatchAction);
2140 DEBUG(dbgs() << " Found extra catch dispatch in block "
2141 << CatchAction->getStartBlock()->getName() << "\n");
2144 // Move on to the block after the catch handler.
2148 // If we didn't wind up in a catch-all, see if there is any interesting code
2149 // executed before the resume.
2150 findCleanupHandlers(Actions, BB, BB);
2152 // It's possible that some optimization moved code into a landingpad that
2154 // previously being used for cleanup. If that happens, we need to execute
2156 // extra code from a cleanup handler.
2157 if (Actions.includesCleanup() && !LPad->isCleanup())
2158 LPad->setCleanup(true);
2161 // This function searches starting with the input block for the next
2162 // block that terminates with a branch whose condition is based on a selector
2163 // comparison. This may be the input block. See the mapLandingPadBlocks
2164 // comments for a discussion of control flow assumptions.
2166 CatchHandler *WinEHPrepare::findCatchHandler(BasicBlock *BB,
2167 BasicBlock *&NextBB,
2168 VisitedBlockSet &VisitedBlocks) {
2169 // See if we've already found a catch handler use it.
2170 // Call count() first to avoid creating a null entry for blocks
2171 // we haven't seen before.
2172 if (CatchHandlerMap.count(BB) && CatchHandlerMap[BB] != nullptr) {
2173 CatchHandler *Action = cast<CatchHandler>(CatchHandlerMap[BB]);
2174 NextBB = Action->getNextBB();
2178 // VisitedBlocks applies only to the current search. We still
2179 // need to consider blocks that we've visited while mapping other
2181 VisitedBlocks.insert(BB);
2183 BasicBlock *CatchBlock = nullptr;
2184 Constant *Selector = nullptr;
2186 // If this is the first time we've visited this block from any landing pad
2187 // look to see if it is a selector dispatch block.
2188 if (!CatchHandlerMap.count(BB)) {
2189 if (isSelectorDispatch(BB, CatchBlock, Selector, NextBB)) {
2190 CatchHandler *Action = new CatchHandler(BB, Selector, NextBB);
2191 CatchHandlerMap[BB] = Action;
2194 // If we encounter a block containing an llvm.eh.begincatch before we
2195 // find a selector dispatch block, the handler is assumed to be
2196 // reached unconditionally. This happens for catch-all blocks, but
2197 // it can also happen for other catch handlers that have been combined
2198 // with the catch-all handler during optimization.
2199 if (isCatchBlock(BB)) {
2200 PointerType *Int8PtrTy = Type::getInt8PtrTy(BB->getContext());
2201 Constant *NullSelector = ConstantPointerNull::get(Int8PtrTy);
2202 CatchHandler *Action = new CatchHandler(BB, NullSelector, nullptr);
2203 CatchHandlerMap[BB] = Action;
2208 // Visit each successor, looking for the dispatch.
2209 // FIXME: We expect to find the dispatch quickly, so this will probably
2210 // work better as a breadth first search.
2211 for (BasicBlock *Succ : successors(BB)) {
2212 if (VisitedBlocks.count(Succ))
2215 CatchHandler *Action = findCatchHandler(Succ, NextBB, VisitedBlocks);
2222 // These are helper functions to combine repeated code from findCleanupHandlers.
2223 static void createCleanupHandler(LandingPadActions &Actions,
2224 CleanupHandlerMapTy &CleanupHandlerMap,
2226 CleanupHandler *Action = new CleanupHandler(BB);
2227 CleanupHandlerMap[BB] = Action;
2228 Actions.insertCleanupHandler(Action);
2229 DEBUG(dbgs() << " Found cleanup code in block "
2230 << Action->getStartBlock()->getName() << "\n");
2233 static CallSite matchOutlinedFinallyCall(BasicBlock *BB,
2234 Instruction *MaybeCall) {
2235 // Look for finally blocks that Clang has already outlined for us.
2236 // %fp = call i8* @llvm.frameaddress(i32 0)
2237 // call void @"fin$parent"(iN 1, i8* %fp)
2238 if (isFrameAddressCall(MaybeCall) && MaybeCall != BB->getTerminator())
2239 MaybeCall = MaybeCall->getNextNode();
2240 CallSite FinallyCall(MaybeCall);
2241 if (!FinallyCall || FinallyCall.arg_size() != 2)
2243 if (!match(FinallyCall.getArgument(0), m_SpecificInt(1)))
2245 if (!isFrameAddressCall(FinallyCall.getArgument(1)))
2250 static BasicBlock *followSingleUnconditionalBranches(BasicBlock *BB) {
2251 // Skip single ubr blocks.
2252 while (BB->getFirstNonPHIOrDbg() == BB->getTerminator()) {
2253 auto *Br = dyn_cast<BranchInst>(BB->getTerminator());
2254 if (Br && Br->isUnconditional())
2255 BB = Br->getSuccessor(0);
2262 // This function searches starting with the input block for the next block that
2263 // contains code that is not part of a catch handler and would not be eliminated
2264 // during handler outlining.
2266 void WinEHPrepare::findCleanupHandlers(LandingPadActions &Actions,
2267 BasicBlock *StartBB, BasicBlock *EndBB) {
2268 // Here we will skip over the following:
2270 // landing pad prolog:
2272 // Unconditional branches
2274 // Selector dispatch
2278 // Anything else marks the start of an interesting block
2280 BasicBlock *BB = StartBB;
2281 // Anything other than an unconditional branch will kick us out of this loop
2282 // one way or another.
2284 BB = followSingleUnconditionalBranches(BB);
2285 // If we've already scanned this block, don't scan it again. If it is
2286 // a cleanup block, there will be an action in the CleanupHandlerMap.
2287 // If we've scanned it and it is not a cleanup block, there will be a
2288 // nullptr in the CleanupHandlerMap. If we have not scanned it, there will
2289 // be no entry in the CleanupHandlerMap. We must call count() first to
2290 // avoid creating a null entry for blocks we haven't scanned.
2291 if (CleanupHandlerMap.count(BB)) {
2292 if (auto *Action = CleanupHandlerMap[BB]) {
2293 Actions.insertCleanupHandler(Action);
2294 DEBUG(dbgs() << " Found cleanup code in block "
2295 << Action->getStartBlock()->getName() << "\n");
2296 // FIXME: This cleanup might chain into another, and we need to discover
2300 // Here we handle the case where the cleanup handler map contains a
2301 // value for this block but the value is a nullptr. This means that
2302 // we have previously analyzed the block and determined that it did
2303 // not contain any cleanup code. Based on the earlier analysis, we
2304 // know the block must end in either an unconditional branch, a
2305 // resume or a conditional branch that is predicated on a comparison
2306 // with a selector. Either the resume or the selector dispatch
2307 // would terminate the search for cleanup code, so the unconditional
2308 // branch is the only case for which we might need to continue
2310 BasicBlock *SuccBB = followSingleUnconditionalBranches(BB);
2311 if (SuccBB == BB || SuccBB == EndBB)
2318 // Create an entry in the cleanup handler map for this block. Initially
2319 // we create an entry that says this isn't a cleanup block. If we find
2320 // cleanup code, the caller will replace this entry.
2321 CleanupHandlerMap[BB] = nullptr;
2323 TerminatorInst *Terminator = BB->getTerminator();
2325 // Landing pad blocks have extra instructions we need to accept.
2326 LandingPadMap *LPadMap = nullptr;
2327 if (BB->isLandingPad()) {
2328 LandingPadInst *LPad = BB->getLandingPadInst();
2329 LPadMap = &LPadMaps[LPad];
2330 if (!LPadMap->isInitialized())
2331 LPadMap->mapLandingPad(LPad);
2334 // Look for the bare resume pattern:
2335 // %lpad.val1 = insertvalue { i8*, i32 } undef, i8* %exn, 0
2336 // %lpad.val2 = insertvalue { i8*, i32 } %lpad.val1, i32 %sel, 1
2337 // resume { i8*, i32 } %lpad.val2
2338 if (auto *Resume = dyn_cast<ResumeInst>(Terminator)) {
2339 InsertValueInst *Insert1 = nullptr;
2340 InsertValueInst *Insert2 = nullptr;
2341 Value *ResumeVal = Resume->getOperand(0);
2342 // If the resume value isn't a phi or landingpad value, it should be a
2343 // series of insertions. Identify them so we can avoid them when scanning
2345 if (!isa<PHINode>(ResumeVal) && !isa<LandingPadInst>(ResumeVal)) {
2346 Insert2 = dyn_cast<InsertValueInst>(ResumeVal);
2348 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2349 Insert1 = dyn_cast<InsertValueInst>(Insert2->getAggregateOperand());
2351 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2353 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2355 Instruction *Inst = II;
2356 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2358 if (Inst == Insert1 || Inst == Insert2 || Inst == Resume)
2360 if (!Inst->hasOneUse() ||
2361 (Inst->user_back() != Insert1 && Inst->user_back() != Insert2)) {
2362 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2368 BranchInst *Branch = dyn_cast<BranchInst>(Terminator);
2369 if (Branch && Branch->isConditional()) {
2370 // Look for the selector dispatch.
2371 // %2 = call i32 @llvm.eh.typeid.for(i8* bitcast (i8** @_ZTIf to i8*))
2372 // %matches = icmp eq i32 %sel, %2
2373 // br i1 %matches, label %catch14, label %eh.resume
2374 CmpInst *Compare = dyn_cast<CmpInst>(Branch->getCondition());
2375 if (!Compare || !Compare->isEquality())
2376 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2377 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2379 Instruction *Inst = II;
2380 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2382 if (Inst == Compare || Inst == Branch)
2384 if (match(Inst, m_Intrinsic<Intrinsic::eh_typeid_for>()))
2386 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2388 // The selector dispatch block should always terminate our search.
2389 assert(BB == EndBB);
2393 if (isAsynchronousEHPersonality(Personality)) {
2394 // If this is a landingpad block, split the block at the first non-landing
2396 Instruction *MaybeCall = BB->getFirstNonPHIOrDbg();
2398 while (MaybeCall != BB->getTerminator() &&
2399 LPadMap->isLandingPadSpecificInst(MaybeCall))
2400 MaybeCall = MaybeCall->getNextNode();
2403 // Look for outlined finally calls on x64, since those happen to match the
2404 // prototype provided by the runtime.
2405 if (TheTriple.getArch() == Triple::x86_64) {
2406 if (CallSite FinallyCall = matchOutlinedFinallyCall(BB, MaybeCall)) {
2407 Function *Fin = FinallyCall.getCalledFunction();
2408 assert(Fin && "outlined finally call should be direct");
2409 auto *Action = new CleanupHandler(BB);
2410 Action->setHandlerBlockOrFunc(Fin);
2411 Actions.insertCleanupHandler(Action);
2412 CleanupHandlerMap[BB] = Action;
2413 DEBUG(dbgs() << " Found frontend-outlined finally call to "
2414 << Fin->getName() << " in block "
2415 << Action->getStartBlock()->getName() << "\n");
2417 // Split the block if there were more interesting instructions and
2418 // look for finally calls in the normal successor block.
2419 BasicBlock *SuccBB = BB;
2420 if (FinallyCall.getInstruction() != BB->getTerminator() &&
2421 FinallyCall.getInstruction()->getNextNode() !=
2422 BB->getTerminator()) {
2424 SplitBlock(BB, FinallyCall.getInstruction()->getNextNode(), DT);
2426 if (FinallyCall.isInvoke()) {
2427 SuccBB = cast<InvokeInst>(FinallyCall.getInstruction())
2430 SuccBB = BB->getUniqueSuccessor();
2432 "splitOutlinedFinallyCalls didn't insert a branch");
2443 // Anything else is either a catch block or interesting cleanup code.
2444 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
2446 Instruction *Inst = II;
2447 if (LPadMap && LPadMap->isLandingPadSpecificInst(Inst))
2449 // Unconditional branches fall through to this loop.
2452 // If this is a catch block, there is no cleanup code to be found.
2453 if (match(Inst, m_Intrinsic<Intrinsic::eh_begincatch>()))
2455 // If this a nested landing pad, it may contain an endcatch call.
2456 if (match(Inst, m_Intrinsic<Intrinsic::eh_endcatch>()))
2458 // Anything else makes this interesting cleanup code.
2459 return createCleanupHandler(Actions, CleanupHandlerMap, BB);
2462 // Only unconditional branches in empty blocks should get this far.
2463 assert(Branch && Branch->isUnconditional());
2466 BB = Branch->getSuccessor(0);
2470 // This is a public function, declared in WinEHFuncInfo.h and is also
2471 // referenced by WinEHNumbering in FunctionLoweringInfo.cpp.
2472 void llvm::parseEHActions(
2473 const IntrinsicInst *II,
2474 SmallVectorImpl<std::unique_ptr<ActionHandler>> &Actions) {
2475 assert(II->getIntrinsicID() == Intrinsic::eh_actions &&
2476 "attempted to parse non eh.actions intrinsic");
2477 for (unsigned I = 0, E = II->getNumArgOperands(); I != E;) {
2478 uint64_t ActionKind =
2479 cast<ConstantInt>(II->getArgOperand(I))->getZExtValue();
2480 if (ActionKind == /*catch=*/1) {
2481 auto *Selector = cast<Constant>(II->getArgOperand(I + 1));
2482 ConstantInt *EHObjIndex = cast<ConstantInt>(II->getArgOperand(I + 2));
2483 int64_t EHObjIndexVal = EHObjIndex->getSExtValue();
2484 Constant *Handler = cast<Constant>(II->getArgOperand(I + 3));
2486 auto CH = make_unique<CatchHandler>(/*BB=*/nullptr, Selector,
2487 /*NextBB=*/nullptr);
2488 CH->setHandlerBlockOrFunc(Handler);
2489 CH->setExceptionVarIndex(EHObjIndexVal);
2490 Actions.push_back(std::move(CH));
2491 } else if (ActionKind == 0) {
2492 Constant *Handler = cast<Constant>(II->getArgOperand(I + 1));
2494 auto CH = make_unique<CleanupHandler>(/*BB=*/nullptr);
2495 CH->setHandlerBlockOrFunc(Handler);
2496 Actions.push_back(std::move(CH));
2498 llvm_unreachable("Expected either a catch or cleanup handler!");
2501 std::reverse(Actions.begin(), Actions.end());
2505 struct WinEHNumbering {
2506 WinEHNumbering(WinEHFuncInfo &FuncInfo) : FuncInfo(FuncInfo),
2507 CurrentBaseState(-1), NextState(0) {}
2509 WinEHFuncInfo &FuncInfo;
2510 int CurrentBaseState;
2513 SmallVector<std::unique_ptr<ActionHandler>, 4> HandlerStack;
2514 SmallPtrSet<const Function *, 4> VisitedHandlers;
2516 int currentEHNumber() const {
2517 return HandlerStack.empty() ? CurrentBaseState : HandlerStack.back()->getEHState();
2520 void createUnwindMapEntry(int ToState, ActionHandler *AH);
2521 void createTryBlockMapEntry(int TryLow, int TryHigh,
2522 ArrayRef<CatchHandler *> Handlers);
2523 void processCallSite(MutableArrayRef<std::unique_ptr<ActionHandler>> Actions,
2524 ImmutableCallSite CS);
2525 void popUnmatchedActions(int FirstMismatch);
2526 void calculateStateNumbers(const Function &F);
2527 void findActionRootLPads(const Function &F);
2531 void WinEHNumbering::createUnwindMapEntry(int ToState, ActionHandler *AH) {
2532 WinEHUnwindMapEntry UME;
2533 UME.ToState = ToState;
2534 if (auto *CH = dyn_cast_or_null<CleanupHandler>(AH))
2535 UME.Cleanup = cast<Function>(CH->getHandlerBlockOrFunc());
2537 UME.Cleanup = nullptr;
2538 FuncInfo.UnwindMap.push_back(UME);
2541 void WinEHNumbering::createTryBlockMapEntry(int TryLow, int TryHigh,
2542 ArrayRef<CatchHandler *> Handlers) {
2543 // See if we already have an entry for this set of handlers.
2544 // This is using iterators rather than a range-based for loop because
2545 // if we find the entry we're looking for we'll need the iterator to erase it.
2546 int NumHandlers = Handlers.size();
2547 auto I = FuncInfo.TryBlockMap.begin();
2548 auto E = FuncInfo.TryBlockMap.end();
2549 for ( ; I != E; ++I) {
2551 if (Entry.HandlerArray.size() != (size_t)NumHandlers)
2554 for (N = 0; N < NumHandlers; ++N) {
2555 if (Entry.HandlerArray[N].Handler != Handlers[N]->getHandlerBlockOrFunc())
2556 break; // breaks out of inner loop
2558 // If all the handlers match, this is what we were looking for.
2559 if (N == NumHandlers) {
2564 // If we found an existing entry for this set of handlers, extend the range
2565 // but move the entry to the end of the map vector. The order of entries
2566 // in the map is critical to the way that the runtime finds handlers.
2567 // FIXME: Depending on what has happened with block ordering, this may
2568 // incorrectly combine entries that should remain separate.
2570 // Copy the existing entry.
2571 WinEHTryBlockMapEntry Entry = *I;
2572 Entry.TryLow = std::min(TryLow, Entry.TryLow);
2573 Entry.TryHigh = std::max(TryHigh, Entry.TryHigh);
2574 assert(Entry.TryLow <= Entry.TryHigh);
2575 // Erase the old entry and add this one to the back.
2576 FuncInfo.TryBlockMap.erase(I);
2577 FuncInfo.TryBlockMap.push_back(Entry);
2581 // If we didn't find an entry, create a new one.
2582 WinEHTryBlockMapEntry TBME;
2583 TBME.TryLow = TryLow;
2584 TBME.TryHigh = TryHigh;
2585 assert(TBME.TryLow <= TBME.TryHigh);
2586 for (CatchHandler *CH : Handlers) {
2587 WinEHHandlerType HT;
2588 if (CH->getSelector()->isNullValue()) {
2589 HT.Adjectives = 0x40;
2590 HT.TypeDescriptor = nullptr;
2592 auto *GV = cast<GlobalVariable>(CH->getSelector()->stripPointerCasts());
2593 // Selectors are always pointers to GlobalVariables with 'struct' type.
2594 // The struct has two fields, adjectives and a type descriptor.
2595 auto *CS = cast<ConstantStruct>(GV->getInitializer());
2597 cast<ConstantInt>(CS->getAggregateElement(0U))->getZExtValue();
2599 cast<GlobalVariable>(CS->getAggregateElement(1)->stripPointerCasts());
2601 HT.Handler = cast<Function>(CH->getHandlerBlockOrFunc());
2602 HT.CatchObjRecoverIdx = CH->getExceptionVarIndex();
2603 TBME.HandlerArray.push_back(HT);
2605 FuncInfo.TryBlockMap.push_back(TBME);
2608 static void print_name(const Value *V) {
2611 DEBUG(dbgs() << "null");
2615 if (const auto *F = dyn_cast<Function>(V))
2616 DEBUG(dbgs() << F->getName());
2622 void WinEHNumbering::processCallSite(
2623 MutableArrayRef<std::unique_ptr<ActionHandler>> Actions,
2624 ImmutableCallSite CS) {
2625 DEBUG(dbgs() << "processCallSite (EH state = " << currentEHNumber()
2627 print_name(CS ? CS.getCalledValue() : nullptr);
2628 DEBUG(dbgs() << '\n');
2630 DEBUG(dbgs() << "HandlerStack: \n");
2631 for (int I = 0, E = HandlerStack.size(); I < E; ++I) {
2632 DEBUG(dbgs() << " ");
2633 print_name(HandlerStack[I]->getHandlerBlockOrFunc());
2634 DEBUG(dbgs() << '\n');
2636 DEBUG(dbgs() << "Actions: \n");
2637 for (int I = 0, E = Actions.size(); I < E; ++I) {
2638 DEBUG(dbgs() << " ");
2639 print_name(Actions[I]->getHandlerBlockOrFunc());
2640 DEBUG(dbgs() << '\n');
2642 int FirstMismatch = 0;
2643 for (int E = std::min(HandlerStack.size(), Actions.size()); FirstMismatch < E;
2645 if (HandlerStack[FirstMismatch]->getHandlerBlockOrFunc() !=
2646 Actions[FirstMismatch]->getHandlerBlockOrFunc())
2650 // Remove unmatched actions from the stack and process their EH states.
2651 popUnmatchedActions(FirstMismatch);
2653 DEBUG(dbgs() << "Pushing actions for CallSite: ");
2654 print_name(CS ? CS.getCalledValue() : nullptr);
2655 DEBUG(dbgs() << '\n');
2657 bool LastActionWasCatch = false;
2658 const LandingPadInst *LastRootLPad = nullptr;
2659 for (size_t I = FirstMismatch; I != Actions.size(); ++I) {
2660 // We can reuse eh states when pushing two catches for the same invoke.
2661 bool CurrActionIsCatch = isa<CatchHandler>(Actions[I].get());
2662 auto *Handler = cast<Function>(Actions[I]->getHandlerBlockOrFunc());
2663 // Various conditions can lead to a handler being popped from the
2664 // stack and re-pushed later. That shouldn't create a new state.
2665 // FIXME: Can code optimization lead to re-used handlers?
2666 if (FuncInfo.HandlerEnclosedState.count(Handler)) {
2667 // If we already assigned the state enclosed by this handler re-use it.
2668 Actions[I]->setEHState(FuncInfo.HandlerEnclosedState[Handler]);
2671 const LandingPadInst* RootLPad = FuncInfo.RootLPad[Handler];
2672 if (CurrActionIsCatch && LastActionWasCatch && RootLPad == LastRootLPad) {
2673 DEBUG(dbgs() << "setEHState for handler to " << currentEHNumber() << "\n");
2674 Actions[I]->setEHState(currentEHNumber());
2676 DEBUG(dbgs() << "createUnwindMapEntry(" << currentEHNumber() << ", ");
2677 print_name(Actions[I]->getHandlerBlockOrFunc());
2678 DEBUG(dbgs() << ") with EH state " << NextState << "\n");
2679 createUnwindMapEntry(currentEHNumber(), Actions[I].get());
2680 DEBUG(dbgs() << "setEHState for handler to " << NextState << "\n");
2681 Actions[I]->setEHState(NextState);
2684 HandlerStack.push_back(std::move(Actions[I]));
2685 LastActionWasCatch = CurrActionIsCatch;
2686 LastRootLPad = RootLPad;
2689 // This is used to defer numbering states for a handler until after the
2690 // last time it appears in an invoke action list.
2691 if (CS.isInvoke()) {
2692 for (int I = 0, E = HandlerStack.size(); I < E; ++I) {
2693 auto *Handler = cast<Function>(HandlerStack[I]->getHandlerBlockOrFunc());
2694 if (FuncInfo.LastInvoke[Handler] != cast<InvokeInst>(CS.getInstruction()))
2696 FuncInfo.LastInvokeVisited[Handler] = true;
2697 DEBUG(dbgs() << "Last invoke of ");
2698 print_name(Handler);
2699 DEBUG(dbgs() << " has been visited.\n");
2703 DEBUG(dbgs() << "In EHState " << currentEHNumber() << " for CallSite: ");
2704 print_name(CS ? CS.getCalledValue() : nullptr);
2705 DEBUG(dbgs() << '\n');
2708 void WinEHNumbering::popUnmatchedActions(int FirstMismatch) {
2709 // Don't recurse while we are looping over the handler stack. Instead, defer
2710 // the numbering of the catch handlers until we are done popping.
2711 SmallVector<CatchHandler *, 4> PoppedCatches;
2712 for (int I = HandlerStack.size() - 1; I >= FirstMismatch; --I) {
2713 std::unique_ptr<ActionHandler> Handler = HandlerStack.pop_back_val();
2714 if (isa<CatchHandler>(Handler.get()))
2715 PoppedCatches.push_back(cast<CatchHandler>(Handler.release()));
2718 int TryHigh = NextState - 1;
2719 int LastTryLowIdx = 0;
2720 for (int I = 0, E = PoppedCatches.size(); I != E; ++I) {
2721 CatchHandler *CH = PoppedCatches[I];
2722 DEBUG(dbgs() << "Popped handler with state " << CH->getEHState() << "\n");
2723 if (I + 1 == E || CH->getEHState() != PoppedCatches[I + 1]->getEHState()) {
2724 int TryLow = CH->getEHState();
2726 makeArrayRef(&PoppedCatches[LastTryLowIdx], I - LastTryLowIdx + 1);
2727 DEBUG(dbgs() << "createTryBlockMapEntry(" << TryLow << ", " << TryHigh);
2728 for (size_t J = 0; J < Handlers.size(); ++J) {
2729 DEBUG(dbgs() << ", ");
2730 print_name(Handlers[J]->getHandlerBlockOrFunc());
2732 DEBUG(dbgs() << ")\n");
2733 createTryBlockMapEntry(TryLow, TryHigh, Handlers);
2734 LastTryLowIdx = I + 1;
2738 for (CatchHandler *CH : PoppedCatches) {
2739 if (auto *F = dyn_cast<Function>(CH->getHandlerBlockOrFunc())) {
2740 if (FuncInfo.LastInvokeVisited[F]) {
2741 DEBUG(dbgs() << "Assigning base state " << NextState << " to ");
2743 DEBUG(dbgs() << '\n');
2744 FuncInfo.HandlerBaseState[F] = NextState;
2745 DEBUG(dbgs() << "createUnwindMapEntry(" << currentEHNumber()
2747 createUnwindMapEntry(currentEHNumber(), nullptr);
2749 calculateStateNumbers(*F);
2752 DEBUG(dbgs() << "Deferring handling of ");
2754 DEBUG(dbgs() << " until last invoke visited.\n");
2761 void WinEHNumbering::calculateStateNumbers(const Function &F) {
2762 auto I = VisitedHandlers.insert(&F);
2764 return; // We've already visited this handler, don't renumber it.
2766 int OldBaseState = CurrentBaseState;
2767 if (FuncInfo.HandlerBaseState.count(&F)) {
2768 CurrentBaseState = FuncInfo.HandlerBaseState[&F];
2771 size_t SavedHandlerStackSize = HandlerStack.size();
2773 DEBUG(dbgs() << "Calculating state numbers for: " << F.getName() << '\n');
2774 SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
2775 for (const BasicBlock &BB : F) {
2776 for (const Instruction &I : BB) {
2777 const auto *CI = dyn_cast<CallInst>(&I);
2778 if (!CI || CI->doesNotThrow())
2780 processCallSite(None, CI);
2782 const auto *II = dyn_cast<InvokeInst>(BB.getTerminator());
2785 const LandingPadInst *LPI = II->getLandingPadInst();
2786 auto *ActionsCall = dyn_cast<IntrinsicInst>(LPI->getNextNode());
2789 parseEHActions(ActionsCall, ActionList);
2790 if (ActionList.empty())
2792 processCallSite(ActionList, II);
2794 FuncInfo.LandingPadStateMap[LPI] = currentEHNumber();
2795 DEBUG(dbgs() << "Assigning state " << currentEHNumber()
2796 << " to landing pad at " << LPI->getParent()->getName()
2800 // Pop any actions that were pushed on the stack for this function.
2801 popUnmatchedActions(SavedHandlerStackSize);
2803 DEBUG(dbgs() << "Assigning max state " << NextState - 1
2804 << " to " << F.getName() << '\n');
2805 FuncInfo.CatchHandlerMaxState[&F] = NextState - 1;
2807 CurrentBaseState = OldBaseState;
2810 // This function follows the same basic traversal as calculateStateNumbers
2811 // but it is necessary to identify the root landing pad associated
2812 // with each action before we start assigning state numbers.
2813 void WinEHNumbering::findActionRootLPads(const Function &F) {
2814 auto I = VisitedHandlers.insert(&F);
2816 return; // We've already visited this handler, don't revisit it.
2818 SmallVector<std::unique_ptr<ActionHandler>, 4> ActionList;
2819 for (const BasicBlock &BB : F) {
2820 const auto *II = dyn_cast<InvokeInst>(BB.getTerminator());
2823 const LandingPadInst *LPI = II->getLandingPadInst();
2824 auto *ActionsCall = dyn_cast<IntrinsicInst>(LPI->getNextNode());
2828 assert(ActionsCall->getIntrinsicID() == Intrinsic::eh_actions);
2829 parseEHActions(ActionsCall, ActionList);
2830 if (ActionList.empty())
2832 for (int I = 0, E = ActionList.size(); I < E; ++I) {
2834 = dyn_cast<Function>(ActionList[I]->getHandlerBlockOrFunc())) {
2835 FuncInfo.LastInvoke[Handler] = II;
2836 // Don't replace the root landing pad if we previously saw this
2837 // handler in a different function.
2838 if (FuncInfo.RootLPad.count(Handler) &&
2839 FuncInfo.RootLPad[Handler]->getParent()->getParent() != &F)
2841 DEBUG(dbgs() << "Setting root lpad for ");
2842 print_name(Handler);
2843 DEBUG(dbgs() << " to " << LPI->getParent()->getName() << '\n');
2844 FuncInfo.RootLPad[Handler] = LPI;
2847 // Walk the actions again and look for nested handlers. This has to
2848 // happen after all of the actions have been processed in the current
2850 for (int I = 0, E = ActionList.size(); I < E; ++I)
2852 = dyn_cast<Function>(ActionList[I]->getHandlerBlockOrFunc()))
2853 findActionRootLPads(*Handler);
2858 void llvm::calculateWinCXXEHStateNumbers(const Function *ParentFn,
2859 WinEHFuncInfo &FuncInfo) {
2860 // Return if it's already been done.
2861 if (!FuncInfo.LandingPadStateMap.empty())
2864 WinEHNumbering Num(FuncInfo);
2865 Num.findActionRootLPads(*ParentFn);
2866 // The VisitedHandlers list is used by both findActionRootLPads and
2867 // calculateStateNumbers, but both functions need to visit all handlers.
2868 Num.VisitedHandlers.clear();
2869 Num.calculateStateNumbers(*ParentFn);
2870 // Pop everything on the handler stack.
2871 // It may be necessary to call this more than once because a handler can
2872 // be pushed on the stack as a result of clearing the stack.
2873 while (!Num.HandlerStack.empty())
2874 Num.processCallSite(None, ImmutableCallSite());