1 //===-- DwarfEHPrepare - 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 mulches exception handling code into a form adapted to code
11 // generation. Required if using dwarf exception handling.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "dwarfehprepare"
16 #include "llvm/Function.h"
17 #include "llvm/Instructions.h"
18 #include "llvm/IntrinsicInst.h"
19 #include "llvm/Module.h"
20 #include "llvm/Pass.h"
21 #include "llvm/ADT/Statistic.h"
22 #include "llvm/Analysis/Dominators.h"
23 #include "llvm/CodeGen/Passes.h"
24 #include "llvm/MC/MCAsmInfo.h"
25 #include "llvm/Support/CallSite.h"
26 #include "llvm/Target/TargetLowering.h"
27 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
28 #include "llvm/Transforms/Utils/SSAUpdater.h"
31 STATISTIC(NumLandingPadsSplit, "Number of landing pads split");
32 STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered");
33 STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
36 class DwarfEHPrepare : public FunctionPass {
37 const TargetMachine *TM;
38 const TargetLowering *TLI;
40 // The eh.exception intrinsic.
41 Function *ExceptionValueIntrinsic;
43 // The eh.selector intrinsic.
44 Function *SelectorIntrinsic;
46 // _Unwind_Resume_or_Rethrow call.
49 // The EH language-specific catch-all type.
50 GlobalVariable *EHCatchAllValue;
52 // _Unwind_Resume or the target equivalent.
53 Constant *RewindFunction;
55 // We both use and preserve dominator info.
58 // The function we are running on.
61 // The landing pads for this function.
62 typedef SmallPtrSet<BasicBlock*, 8> BBSet;
65 bool NormalizeLandingPads();
67 bool MoveExceptionValueCalls();
69 Instruction *CreateExceptionValueCall(BasicBlock *BB);
71 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still
72 /// use the "llvm.eh.catch.all.value" call need to convert to using its
73 /// initializer instead.
74 bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels);
76 bool HasCatchAllInSelector(IntrinsicInst *);
78 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
79 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
80 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels);
82 /// FindAllURoRInvokes - Find all URoR invokes in the function.
83 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes);
85 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow"
86 /// calls. The "unwind" part of these invokes jump to a landing pad within
87 /// the current function. This is a candidate to merge the selector
88 /// associated with the URoR invoke with the one from the URoR's landing
90 bool HandleURoRInvokes();
92 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated
93 /// with the eh.exception call. This recursively looks past instructions
94 /// which don't change the EH pointer value, like casts or PHI nodes.
95 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
96 SmallPtrSet<IntrinsicInst*, 8> &SelCalls);
99 static char ID; // Pass identification, replacement for typeid.
100 DwarfEHPrepare(const TargetMachine *tm) :
101 FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()),
102 ExceptionValueIntrinsic(0), SelectorIntrinsic(0),
103 URoR(0), EHCatchAllValue(0), RewindFunction(0) {}
105 virtual bool runOnFunction(Function &Fn);
107 // getAnalysisUsage - We need the dominator tree for handling URoR.
108 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
109 AU.addRequired<DominatorTree>();
110 AU.addPreserved<DominatorTree>();
113 const char *getPassName() const {
114 return "Exception handling preparation";
118 } // end anonymous namespace
120 char DwarfEHPrepare::ID = 0;
122 FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
123 return new DwarfEHPrepare(tm);
126 /// HasCatchAllInSelector - Return true if the intrinsic instruction has a
128 bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) {
129 if (!EHCatchAllValue) return false;
131 unsigned ArgIdx = II->getNumArgOperands() - 1;
132 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx));
133 return GV == EHCatchAllValue;
136 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
137 void DwarfEHPrepare::
138 FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
139 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) {
140 for (Value::use_iterator
141 I = SelectorIntrinsic->use_begin(),
142 E = SelectorIntrinsic->use_end(); I != E; ++I) {
143 IntrinsicInst *II = cast<IntrinsicInst>(*I);
145 if (II->getParent()->getParent() != F)
148 if (!HasCatchAllInSelector(II))
151 CatchAllSels.insert(II);
155 /// FindAllURoRInvokes - Find all URoR invokes in the function.
156 void DwarfEHPrepare::
157 FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) {
158 for (Value::use_iterator
159 I = URoR->use_begin(),
160 E = URoR->use_end(); I != E; ++I) {
161 if (InvokeInst *II = dyn_cast<InvokeInst>(*I))
162 URoRInvokes.insert(II);
166 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use
167 /// the "llvm.eh.catch.all.value" call need to convert to using its
168 /// initializer instead.
169 bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) {
170 if (!EHCatchAllValue) return false;
172 if (!SelectorIntrinsic) {
174 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
175 if (!SelectorIntrinsic) return false;
178 bool Changed = false;
179 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
180 I = Sels.begin(), E = Sels.end(); I != E; ++I) {
181 IntrinsicInst *Sel = *I;
183 // Index of the "llvm.eh.catch.all.value" variable.
184 unsigned OpIdx = Sel->getNumArgOperands() - 1;
185 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx));
186 if (GV != EHCatchAllValue) continue;
187 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer());
194 /// FindSelectorAndURoR - Find the eh.selector call associated with the
195 /// eh.exception call. And indicate if there is a URoR "invoke" associated with
196 /// the eh.exception call. This recursively looks past instructions which don't
197 /// change the EH pointer value, like casts or PHI nodes.
199 DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
200 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) {
201 SmallPtrSet<PHINode*, 32> SeenPHIs;
202 bool Changed = false;
204 for (Value::use_iterator
205 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) {
206 Instruction *II = dyn_cast<Instruction>(*I);
207 if (!II || II->getParent()->getParent() != F) continue;
209 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) {
210 if (Sel->getIntrinsicID() == Intrinsic::eh_selector)
211 SelCalls.insert(Sel);
212 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) {
213 if (Invoke->getCalledFunction() == URoR)
215 } else if (CastInst *CI = dyn_cast<CastInst>(II)) {
216 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls);
217 } else if (PHINode *PN = dyn_cast<PHINode>(II)) {
218 if (SeenPHIs.insert(PN))
219 // Don't process a PHI node more than once.
220 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls);
227 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The
228 /// "unwind" part of these invokes jump to a landing pad within the current
229 /// function. This is a candidate to merge the selector associated with the URoR
230 /// invoke with the one from the URoR's landing pad.
231 bool DwarfEHPrepare::HandleURoRInvokes() {
232 if (!EHCatchAllValue) {
234 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value");
235 if (!EHCatchAllValue) return false;
238 if (!SelectorIntrinsic) {
240 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
241 if (!SelectorIntrinsic) return false;
244 SmallPtrSet<IntrinsicInst*, 32> Sels;
245 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels;
246 FindAllCleanupSelectors(Sels, CatchAllSels);
249 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow");
250 if (!URoR) return CleanupSelectors(CatchAllSels);
253 SmallPtrSet<InvokeInst*, 32> URoRInvokes;
254 FindAllURoRInvokes(URoRInvokes);
256 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert;
258 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
259 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) {
260 const BasicBlock *SelBB = (*SI)->getParent();
261 for (SmallPtrSet<InvokeInst*, 32>::iterator
262 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) {
263 const BasicBlock *URoRBB = (*UI)->getParent();
264 if (DT->dominates(SelBB, URoRBB)) {
265 SelsToConvert.insert(*SI);
271 bool Changed = false;
273 if (Sels.size() != SelsToConvert.size()) {
274 // If we haven't been able to convert all of the clean-up selectors, then
275 // loop through the slow way to see if they still need to be converted.
276 if (!ExceptionValueIntrinsic) {
277 ExceptionValueIntrinsic =
278 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception);
279 if (!ExceptionValueIntrinsic)
280 return CleanupSelectors(CatchAllSels);
283 for (Value::use_iterator
284 I = ExceptionValueIntrinsic->use_begin(),
285 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) {
286 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I);
287 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue;
289 bool URoRInvoke = false;
290 SmallPtrSet<IntrinsicInst*, 8> SelCalls;
291 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls);
294 // This EH pointer is being used by an invoke of an URoR instruction and
295 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we
296 // need to convert it to a 'catch-all'.
297 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
298 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI)
299 if (!HasCatchAllInSelector(*SI))
300 SelsToConvert.insert(*SI);
305 if (!SelsToConvert.empty()) {
306 // Convert all clean-up eh.selectors, which are associated with "invokes" of
307 // URoR calls, into catch-all eh.selectors.
310 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
311 SI = SelsToConvert.begin(), SE = SelsToConvert.end();
313 IntrinsicInst *II = *SI;
315 // Use the exception object pointer and the personality function
316 // from the original selector.
318 IntrinsicInst::op_iterator I = CS.arg_begin();
319 IntrinsicInst::op_iterator E = CS.arg_end();
320 IntrinsicInst::op_iterator B = prior(E);
322 // Exclude last argument if it is an integer.
323 if (isa<ConstantInt>(B)) E = B;
325 // Add exception object pointer (front).
326 // Add personality function (next).
327 // Add in any filter IDs (rest).
328 SmallVector<Value*, 8> Args(I, E);
330 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator.
332 CallInst *NewSelector =
333 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(),
334 "eh.sel.catch.all", II);
336 NewSelector->setTailCall(II->isTailCall());
337 NewSelector->setAttributes(II->getAttributes());
338 NewSelector->setCallingConv(II->getCallingConv());
340 II->replaceAllUsesWith(NewSelector);
341 II->eraseFromParent();
345 Changed |= CleanupSelectors(CatchAllSels);
349 /// NormalizeLandingPads - Normalize and discover landing pads, noting them
350 /// in the LandingPads set. A landing pad is normal if the only CFG edges
351 /// that end at it are unwind edges from invoke instructions. If we inlined
352 /// through an invoke we could have a normal branch from the previous
353 /// unwind block through to the landing pad for the original invoke.
354 /// Abnormal landing pads are fixed up by redirecting all unwind edges to
355 /// a new basic block which falls through to the original.
356 bool DwarfEHPrepare::NormalizeLandingPads() {
357 bool Changed = false;
359 const MCAsmInfo *MAI = TM->getMCAsmInfo();
360 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
362 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
363 TerminatorInst *TI = I->getTerminator();
364 if (!isa<InvokeInst>(TI))
366 BasicBlock *LPad = TI->getSuccessor(1);
367 // Skip landing pads that have already been normalized.
368 if (LandingPads.count(LPad))
371 // Check that only invoke unwind edges end at the landing pad.
372 bool OnlyUnwoundTo = true;
373 bool SwitchOK = usingSjLjEH;
374 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
376 TerminatorInst *PT = (*PI)->getTerminator();
377 // The SjLj dispatch block uses a switch instruction. This is effectively
378 // an unwind edge, so we can disregard it here. There will only ever
379 // be one dispatch, however, so if there are multiple switches, one
380 // of them truly is a normal edge, not an unwind edge.
381 if (SwitchOK && isa<SwitchInst>(PT)) {
385 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
386 OnlyUnwoundTo = false;
392 // Only unwind edges lead to the landing pad. Remember the landing pad.
393 LandingPads.insert(LPad);
397 // At least one normal edge ends at the landing pad. Redirect the unwind
398 // edges to a new basic block which falls through into this one.
400 // Create the new basic block.
401 BasicBlock *NewBB = BasicBlock::Create(F->getContext(),
402 LPad->getName() + "_unwind_edge");
404 // Insert it into the function right before the original landing pad.
405 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);
407 // Redirect unwind edges from the original landing pad to NewBB.
408 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
409 TerminatorInst *PT = (*PI++)->getTerminator();
410 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
411 // Unwind to the new block.
412 PT->setSuccessor(1, NewBB);
415 // If there are any PHI nodes in LPad, we need to update them so that they
416 // merge incoming values from NewBB instead.
417 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
418 PHINode *PN = cast<PHINode>(II);
419 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);
421 // Check to see if all of the values coming in via unwind edges are the
422 // same. If so, we don't need to create a new PHI node.
423 Value *InVal = PN->getIncomingValueForBlock(*PB);
424 for (pred_iterator PI = PB; PI != PE; ++PI) {
425 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
432 // Different unwind edges have different values. Create a new PHI node
434 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind",
436 // Add an entry for each unwind edge, using the value from the old PHI.
437 for (pred_iterator PI = PB; PI != PE; ++PI)
438 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);
440 // Now use this new PHI as the common incoming value for NewBB in PN.
444 // Revector exactly one entry in the PHI node to come from NewBB
445 // and delete all other entries that come from unwind edges. If
446 // there are both normal and unwind edges from the same predecessor,
447 // this leaves an entry for the normal edge.
448 for (pred_iterator PI = PB; PI != PE; ++PI)
449 PN->removeIncomingValue(*PI);
450 PN->addIncoming(InVal, NewBB);
453 // Add a fallthrough from NewBB to the original landing pad.
454 BranchInst::Create(LPad, NewBB);
456 // Now update DominatorTree analysis information.
457 DT->splitBlock(NewBB);
459 // Remember the newly constructed landing pad. The original landing pad
460 // LPad is no longer a landing pad now that all unwind edges have been
461 // revectored to NewBB.
462 LandingPads.insert(NewBB);
463 ++NumLandingPadsSplit;
470 /// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
471 /// rethrowing any previously caught exception. This will crash horribly
472 /// at runtime if there is no such exception: using unwind to throw a new
473 /// exception is currently not supported.
474 bool DwarfEHPrepare::LowerUnwinds() {
475 SmallVector<TerminatorInst*, 16> UnwindInsts;
477 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
478 TerminatorInst *TI = I->getTerminator();
479 if (isa<UnwindInst>(TI))
480 UnwindInsts.push_back(TI);
483 if (UnwindInsts.empty()) return false;
485 // Find the rewind function if we didn't already.
486 if (!RewindFunction) {
487 LLVMContext &Ctx = UnwindInsts[0]->getContext();
488 std::vector<const Type*>
489 Params(1, Type::getInt8PtrTy(Ctx));
490 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
492 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
493 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
496 bool Changed = false;
498 for (SmallVectorImpl<TerminatorInst*>::iterator
499 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) {
500 TerminatorInst *TI = *I;
502 // Replace the unwind instruction with a call to _Unwind_Resume (or the
503 // appropriate target equivalent) followed by an UnreachableInst.
505 // Create the call...
506 CallInst *CI = CallInst::Create(RewindFunction,
507 CreateExceptionValueCall(TI->getParent()),
509 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
510 // ...followed by an UnreachableInst.
511 new UnreachableInst(TI->getContext(), TI);
513 // Nuke the unwind instruction.
514 TI->eraseFromParent();
522 /// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
523 /// landing pads by replacing calls outside of landing pads with direct use of
524 /// a register holding the appropriate value; this requires adding calls inside
525 /// all landing pads to initialize the register. Also, move eh.exception calls
526 /// inside landing pads to the start of the landing pad (optional, but may make
527 /// things simpler for later passes).
528 bool DwarfEHPrepare::MoveExceptionValueCalls() {
529 // If the eh.exception intrinsic is not declared in the module then there is
530 // nothing to do. Speed up compilation by checking for this common case.
531 if (!ExceptionValueIntrinsic &&
532 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception)))
535 bool Changed = false;
537 // Move calls to eh.exception that are inside a landing pad to the start of
539 for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end();
541 BasicBlock *LP = *LI;
542 for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end();
544 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) {
545 // Found a call to eh.exception.
546 if (!EI->use_empty()) {
547 // If there is already a call to eh.exception at the start of the
548 // landing pad, then get hold of it; otherwise create such a call.
549 Value *CallAtStart = CreateExceptionValueCall(LP);
551 // If the call was at the start of a landing pad then leave it alone.
552 if (EI == CallAtStart)
554 EI->replaceAllUsesWith(CallAtStart);
556 EI->eraseFromParent();
557 ++NumExceptionValuesMoved;
562 // Look for calls to eh.exception that are not in a landing pad. If one is
563 // found, then a register that holds the exception value will be created in
564 // each landing pad, and the SSAUpdater will be used to compute the values
565 // returned by eh.exception calls outside of landing pads.
568 // Remember where we found the eh.exception call, to avoid rescanning earlier
569 // basic blocks which we already know contain no eh.exception calls.
570 bool FoundCallOutsideLandingPad = false;
571 Function::iterator BB = F->begin();
572 for (Function::iterator BE = F->end(); BB != BE; ++BB) {
573 // Skip over landing pads.
574 if (LandingPads.count(BB))
577 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
579 if (isa<EHExceptionInst>(II)) {
580 SSA.Initialize(II->getType(), II->getName());
581 FoundCallOutsideLandingPad = true;
585 if (FoundCallOutsideLandingPad)
589 // If all calls to eh.exception are in landing pads then we are done.
590 if (!FoundCallOutsideLandingPad)
593 // Add a call to eh.exception at the start of each landing pad, and tell the
594 // SSAUpdater that this is the value produced by the landing pad.
595 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
597 SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI));
599 // Now turn all calls to eh.exception that are not in a landing pad into a use
600 // of the appropriate register.
601 for (Function::iterator BE = F->end(); BB != BE; ++BB) {
602 // Skip over landing pads.
603 if (LandingPads.count(BB))
606 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
608 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) {
609 // Found a call to eh.exception, replace it with the value from any
610 // upstream landing pad(s).
611 EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB));
612 EI->eraseFromParent();
613 ++NumExceptionValuesMoved;
620 /// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
621 /// the start of the basic block (unless there already is one, in which case
622 /// the existing call is returned).
623 Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
624 Instruction *Start = BB->getFirstNonPHIOrDbg();
625 // Is this a call to eh.exception?
626 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start))
627 if (CI->getIntrinsicID() == Intrinsic::eh_exception)
628 // Reuse the existing call.
631 // Find the eh.exception intrinsic if we didn't already.
632 if (!ExceptionValueIntrinsic)
633 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(),
634 Intrinsic::eh_exception);
637 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start);
640 bool DwarfEHPrepare::runOnFunction(Function &Fn) {
641 bool Changed = false;
643 // Initialize internal state.
644 DT = &getAnalysis<DominatorTree>();
647 // Ensure that only unwind edges end at landing pads (a landing pad is a
648 // basic block where an invoke unwind edge ends).
649 Changed |= NormalizeLandingPads();
651 // Turn unwind instructions into libcalls.
652 Changed |= LowerUnwinds();
654 // TODO: Move eh.selector calls to landing pads and combine them.
656 // Move eh.exception calls to landing pads.
657 Changed |= MoveExceptionValueCalls();
659 Changed |= HandleURoRInvokes();