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(NumResumesLowered, "Number of eh.resume calls lowered");
34 STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
37 class DwarfEHPrepare : public FunctionPass {
38 const TargetMachine *TM;
39 const TargetLowering *TLI;
41 // The eh.exception intrinsic.
42 Function *ExceptionValueIntrinsic;
44 // The eh.selector intrinsic.
45 Function *SelectorIntrinsic;
47 // _Unwind_Resume_or_Rethrow or _Unwind_SjLj_Resume call.
50 // The EH language-specific catch-all type.
51 GlobalVariable *EHCatchAllValue;
53 // _Unwind_Resume or the target equivalent.
54 Constant *RewindFunction;
56 // We both use and preserve dominator info.
59 // The function we are running on.
62 // The landing pads for this function.
63 typedef SmallPtrSet<BasicBlock*, 8> BBSet;
66 bool NormalizeLandingPads();
67 bool LowerUnwindsAndResumes();
68 bool MoveExceptionValueCalls();
70 Instruction *CreateExceptionValueCall(BasicBlock *BB);
72 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still
73 /// use the "llvm.eh.catch.all.value" call need to convert to using its
74 /// initializer instead.
75 bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels);
77 bool HasCatchAllInSelector(IntrinsicInst *);
79 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
80 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
81 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels);
83 /// FindAllURoRInvokes - Find all URoR invokes in the function.
84 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes);
86 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or
87 /// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to
88 /// a landing pad within the current function. This is a candidate to merge
89 /// the selector associated with the URoR invoke with the one from the
90 /// URoR's landing pad.
91 bool HandleURoRInvokes();
93 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated
94 /// with the eh.exception call. This recursively looks past instructions
95 /// which don't change the EH pointer value, like casts or PHI nodes.
96 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
97 SmallPtrSet<IntrinsicInst*, 8> &SelCalls,
98 SmallPtrSet<PHINode*, 32> &SeenPHIs);
101 static char ID; // Pass identification, replacement for typeid.
102 DwarfEHPrepare(const TargetMachine *tm) :
103 FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()),
104 ExceptionValueIntrinsic(0), SelectorIntrinsic(0),
105 URoR(0), EHCatchAllValue(0), RewindFunction(0) {
106 initializeDominatorTreePass(*PassRegistry::getPassRegistry());
109 virtual bool runOnFunction(Function &Fn);
111 // getAnalysisUsage - We need the dominator tree for handling URoR.
112 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
113 AU.addRequired<DominatorTree>();
114 AU.addPreserved<DominatorTree>();
117 const char *getPassName() const {
118 return "Exception handling preparation";
122 } // end anonymous namespace
124 char DwarfEHPrepare::ID = 0;
126 FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
127 return new DwarfEHPrepare(tm);
130 /// HasCatchAllInSelector - Return true if the intrinsic instruction has a
132 bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) {
133 if (!EHCatchAllValue) return false;
135 unsigned ArgIdx = II->getNumArgOperands() - 1;
136 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx));
137 return GV == EHCatchAllValue;
140 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
141 void DwarfEHPrepare::
142 FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
143 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) {
144 for (Value::use_iterator
145 I = SelectorIntrinsic->use_begin(),
146 E = SelectorIntrinsic->use_end(); I != E; ++I) {
147 IntrinsicInst *II = cast<IntrinsicInst>(*I);
149 if (II->getParent()->getParent() != F)
152 if (!HasCatchAllInSelector(II))
155 CatchAllSels.insert(II);
159 /// FindAllURoRInvokes - Find all URoR invokes in the function.
160 void DwarfEHPrepare::
161 FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) {
162 for (Value::use_iterator
163 I = URoR->use_begin(),
164 E = URoR->use_end(); I != E; ++I) {
165 if (InvokeInst *II = dyn_cast<InvokeInst>(*I))
166 URoRInvokes.insert(II);
170 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use
171 /// the "llvm.eh.catch.all.value" call need to convert to using its
172 /// initializer instead.
173 bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) {
174 if (!EHCatchAllValue) return false;
176 if (!SelectorIntrinsic) {
178 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
179 if (!SelectorIntrinsic) return false;
182 bool Changed = false;
183 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
184 I = Sels.begin(), E = Sels.end(); I != E; ++I) {
185 IntrinsicInst *Sel = *I;
187 // Index of the "llvm.eh.catch.all.value" variable.
188 unsigned OpIdx = Sel->getNumArgOperands() - 1;
189 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx));
190 if (GV != EHCatchAllValue) continue;
191 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer());
198 /// FindSelectorAndURoR - Find the eh.selector call associated with the
199 /// eh.exception call. And indicate if there is a URoR "invoke" associated with
200 /// the eh.exception call. This recursively looks past instructions which don't
201 /// change the EH pointer value, like casts or PHI nodes.
203 DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
204 SmallPtrSet<IntrinsicInst*, 8> &SelCalls,
205 SmallPtrSet<PHINode*, 32> &SeenPHIs) {
206 bool Changed = false;
208 for (Value::use_iterator
209 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) {
210 Instruction *II = dyn_cast<Instruction>(*I);
211 if (!II || II->getParent()->getParent() != F) continue;
213 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) {
214 if (Sel->getIntrinsicID() == Intrinsic::eh_selector)
215 SelCalls.insert(Sel);
216 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) {
217 if (Invoke->getCalledFunction() == URoR)
219 } else if (CastInst *CI = dyn_cast<CastInst>(II)) {
220 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls, SeenPHIs);
221 } else if (PHINode *PN = dyn_cast<PHINode>(II)) {
222 if (SeenPHIs.insert(PN))
223 // Don't process a PHI node more than once.
224 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls, SeenPHIs);
231 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or
232 /// "_Unwind_SjLj_Resume" calls. The "unwind" part of these invokes jump to a
233 /// landing pad within the current function. This is a candidate to merge the
234 /// selector associated with the URoR invoke with the one from the URoR's
236 bool DwarfEHPrepare::HandleURoRInvokes() {
237 if (!EHCatchAllValue) {
239 F->getParent()->getNamedGlobal("llvm.eh.catch.all.value");
240 if (!EHCatchAllValue) return false;
243 if (!SelectorIntrinsic) {
245 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
246 if (!SelectorIntrinsic) return false;
249 SmallPtrSet<IntrinsicInst*, 32> Sels;
250 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels;
251 FindAllCleanupSelectors(Sels, CatchAllSels);
254 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow");
256 URoR = F->getParent()->getFunction("_Unwind_SjLj_Resume");
257 if (!URoR) return CleanupSelectors(CatchAllSels);
261 SmallPtrSet<InvokeInst*, 32> URoRInvokes;
262 FindAllURoRInvokes(URoRInvokes);
264 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert;
266 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
267 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) {
268 const BasicBlock *SelBB = (*SI)->getParent();
269 for (SmallPtrSet<InvokeInst*, 32>::iterator
270 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) {
271 const BasicBlock *URoRBB = (*UI)->getParent();
272 if (DT->dominates(SelBB, URoRBB)) {
273 SelsToConvert.insert(*SI);
279 bool Changed = false;
281 if (Sels.size() != SelsToConvert.size()) {
282 // If we haven't been able to convert all of the clean-up selectors, then
283 // loop through the slow way to see if they still need to be converted.
284 if (!ExceptionValueIntrinsic) {
285 ExceptionValueIntrinsic =
286 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception);
287 if (!ExceptionValueIntrinsic)
288 return CleanupSelectors(CatchAllSels);
291 for (Value::use_iterator
292 I = ExceptionValueIntrinsic->use_begin(),
293 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) {
294 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I);
295 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue;
297 bool URoRInvoke = false;
298 SmallPtrSet<IntrinsicInst*, 8> SelCalls;
299 SmallPtrSet<PHINode*, 32> SeenPHIs;
300 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls, SeenPHIs);
303 // This EH pointer is being used by an invoke of an URoR instruction and
304 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we
305 // need to convert it to a 'catch-all'.
306 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
307 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI)
308 if (!HasCatchAllInSelector(*SI))
309 SelsToConvert.insert(*SI);
314 if (!SelsToConvert.empty()) {
315 // Convert all clean-up eh.selectors, which are associated with "invokes" of
316 // URoR calls, into catch-all eh.selectors.
319 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
320 SI = SelsToConvert.begin(), SE = SelsToConvert.end();
322 IntrinsicInst *II = *SI;
324 // Use the exception object pointer and the personality function
325 // from the original selector.
327 IntrinsicInst::op_iterator I = CS.arg_begin();
328 IntrinsicInst::op_iterator E = CS.arg_end();
329 IntrinsicInst::op_iterator B = prior(E);
331 // Exclude last argument if it is an integer.
332 if (isa<ConstantInt>(B)) E = B;
334 // Add exception object pointer (front).
335 // Add personality function (next).
336 // Add in any filter IDs (rest).
337 SmallVector<Value*, 8> Args(I, E);
339 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator.
341 CallInst *NewSelector =
342 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(),
343 "eh.sel.catch.all", II);
345 NewSelector->setTailCall(II->isTailCall());
346 NewSelector->setAttributes(II->getAttributes());
347 NewSelector->setCallingConv(II->getCallingConv());
349 II->replaceAllUsesWith(NewSelector);
350 II->eraseFromParent();
354 Changed |= CleanupSelectors(CatchAllSels);
358 /// NormalizeLandingPads - Normalize and discover landing pads, noting them
359 /// in the LandingPads set. A landing pad is normal if the only CFG edges
360 /// that end at it are unwind edges from invoke instructions. If we inlined
361 /// through an invoke we could have a normal branch from the previous
362 /// unwind block through to the landing pad for the original invoke.
363 /// Abnormal landing pads are fixed up by redirecting all unwind edges to
364 /// a new basic block which falls through to the original.
365 bool DwarfEHPrepare::NormalizeLandingPads() {
366 bool Changed = false;
368 const MCAsmInfo *MAI = TM->getMCAsmInfo();
369 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
371 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
372 TerminatorInst *TI = I->getTerminator();
373 if (!isa<InvokeInst>(TI))
375 BasicBlock *LPad = TI->getSuccessor(1);
376 // Skip landing pads that have already been normalized.
377 if (LandingPads.count(LPad))
380 // Check that only invoke unwind edges end at the landing pad.
381 bool OnlyUnwoundTo = true;
382 bool SwitchOK = usingSjLjEH;
383 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
385 TerminatorInst *PT = (*PI)->getTerminator();
386 // The SjLj dispatch block uses a switch instruction. This is effectively
387 // an unwind edge, so we can disregard it here. There will only ever
388 // be one dispatch, however, so if there are multiple switches, one
389 // of them truly is a normal edge, not an unwind edge.
390 if (SwitchOK && isa<SwitchInst>(PT)) {
394 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
395 OnlyUnwoundTo = false;
401 // Only unwind edges lead to the landing pad. Remember the landing pad.
402 LandingPads.insert(LPad);
406 // At least one normal edge ends at the landing pad. Redirect the unwind
407 // edges to a new basic block which falls through into this one.
409 // Create the new basic block.
410 BasicBlock *NewBB = BasicBlock::Create(F->getContext(),
411 LPad->getName() + "_unwind_edge");
413 // Insert it into the function right before the original landing pad.
414 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);
416 // Redirect unwind edges from the original landing pad to NewBB.
417 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
418 TerminatorInst *PT = (*PI++)->getTerminator();
419 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
420 // Unwind to the new block.
421 PT->setSuccessor(1, NewBB);
424 // If there are any PHI nodes in LPad, we need to update them so that they
425 // merge incoming values from NewBB instead.
426 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
427 PHINode *PN = cast<PHINode>(II);
428 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);
430 // Check to see if all of the values coming in via unwind edges are the
431 // same. If so, we don't need to create a new PHI node.
432 Value *InVal = PN->getIncomingValueForBlock(*PB);
433 for (pred_iterator PI = PB; PI != PE; ++PI) {
434 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
441 // Different unwind edges have different values. Create a new PHI node
443 PHINode *NewPN = PHINode::Create(PN->getType(),
444 PN->getNumIncomingValues(),
445 PN->getName()+".unwind", NewBB);
446 // Add an entry for each unwind edge, using the value from the old PHI.
447 for (pred_iterator PI = PB; PI != PE; ++PI)
448 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);
450 // Now use this new PHI as the common incoming value for NewBB in PN.
454 // Revector exactly one entry in the PHI node to come from NewBB
455 // and delete all other entries that come from unwind edges. If
456 // there are both normal and unwind edges from the same predecessor,
457 // this leaves an entry for the normal edge.
458 for (pred_iterator PI = PB; PI != PE; ++PI)
459 PN->removeIncomingValue(*PI);
460 PN->addIncoming(InVal, NewBB);
463 // Add a fallthrough from NewBB to the original landing pad.
464 BranchInst::Create(LPad, NewBB);
466 // Now update DominatorTree analysis information.
467 DT->splitBlock(NewBB);
469 // Remember the newly constructed landing pad. The original landing pad
470 // LPad is no longer a landing pad now that all unwind edges have been
471 // revectored to NewBB.
472 LandingPads.insert(NewBB);
473 ++NumLandingPadsSplit;
480 /// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
481 /// rethrowing any previously caught exception. This will crash horribly
482 /// at runtime if there is no such exception: using unwind to throw a new
483 /// exception is currently not supported.
484 bool DwarfEHPrepare::LowerUnwindsAndResumes() {
485 SmallVector<Instruction*, 16> ResumeInsts;
487 for (Function::iterator fi = F->begin(), fe = F->end(); fi != fe; ++fi) {
488 for (BasicBlock::iterator bi = fi->begin(), be = fi->end(); bi != be; ++bi){
489 if (isa<UnwindInst>(bi))
490 ResumeInsts.push_back(bi);
491 else if (CallInst *call = dyn_cast<CallInst>(bi))
492 if (Function *fn = dyn_cast<Function>(call->getCalledValue()))
493 if (fn->getName() == "llvm.eh.resume")
494 ResumeInsts.push_back(bi);
498 if (ResumeInsts.empty()) return false;
500 // Find the rewind function if we didn't already.
501 if (!RewindFunction) {
502 LLVMContext &Ctx = ResumeInsts[0]->getContext();
503 std::vector<const Type*>
504 Params(1, Type::getInt8PtrTy(Ctx));
505 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
507 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
508 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
511 bool Changed = false;
513 for (SmallVectorImpl<Instruction*>::iterator
514 I = ResumeInsts.begin(), E = ResumeInsts.end(); I != E; ++I) {
515 Instruction *RI = *I;
517 // Replace the resuming instruction with a call to _Unwind_Resume (or the
518 // appropriate target equivalent).
520 llvm::Value *ExnValue;
521 if (isa<UnwindInst>(RI))
522 ExnValue = CreateExceptionValueCall(RI->getParent());
524 ExnValue = cast<CallInst>(RI)->getArgOperand(0);
526 // Create the call...
527 CallInst *CI = CallInst::Create(RewindFunction, ExnValue, "", RI);
528 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
530 // ...followed by an UnreachableInst, if it was an unwind.
531 // Calls to llvm.eh.resume are typically already followed by this.
532 if (isa<UnwindInst>(RI))
533 new UnreachableInst(RI->getContext(), RI);
535 // Nuke the resume instruction.
536 RI->eraseFromParent();
538 if (isa<UnwindInst>(RI))
548 /// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
549 /// landing pads by replacing calls outside of landing pads with direct use of
550 /// a register holding the appropriate value; this requires adding calls inside
551 /// all landing pads to initialize the register. Also, move eh.exception calls
552 /// inside landing pads to the start of the landing pad (optional, but may make
553 /// things simpler for later passes).
554 bool DwarfEHPrepare::MoveExceptionValueCalls() {
555 // If the eh.exception intrinsic is not declared in the module then there is
556 // nothing to do. Speed up compilation by checking for this common case.
557 if (!ExceptionValueIntrinsic &&
558 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception)))
561 bool Changed = false;
563 // Move calls to eh.exception that are inside a landing pad to the start of
565 for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end();
567 BasicBlock *LP = *LI;
568 for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end();
570 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) {
571 // Found a call to eh.exception.
572 if (!EI->use_empty()) {
573 // If there is already a call to eh.exception at the start of the
574 // landing pad, then get hold of it; otherwise create such a call.
575 Value *CallAtStart = CreateExceptionValueCall(LP);
577 // If the call was at the start of a landing pad then leave it alone.
578 if (EI == CallAtStart)
580 EI->replaceAllUsesWith(CallAtStart);
582 EI->eraseFromParent();
583 ++NumExceptionValuesMoved;
588 // Look for calls to eh.exception that are not in a landing pad. If one is
589 // found, then a register that holds the exception value will be created in
590 // each landing pad, and the SSAUpdater will be used to compute the values
591 // returned by eh.exception calls outside of landing pads.
594 // Remember where we found the eh.exception call, to avoid rescanning earlier
595 // basic blocks which we already know contain no eh.exception calls.
596 bool FoundCallOutsideLandingPad = false;
597 Function::iterator BB = F->begin();
598 for (Function::iterator BE = F->end(); BB != BE; ++BB) {
599 // Skip over landing pads.
600 if (LandingPads.count(BB))
603 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
605 if (isa<EHExceptionInst>(II)) {
606 SSA.Initialize(II->getType(), II->getName());
607 FoundCallOutsideLandingPad = true;
611 if (FoundCallOutsideLandingPad)
615 // If all calls to eh.exception are in landing pads then we are done.
616 if (!FoundCallOutsideLandingPad)
619 // Add a call to eh.exception at the start of each landing pad, and tell the
620 // SSAUpdater that this is the value produced by the landing pad.
621 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
623 SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI));
625 // Now turn all calls to eh.exception that are not in a landing pad into a use
626 // of the appropriate register.
627 for (Function::iterator BE = F->end(); BB != BE; ++BB) {
628 // Skip over landing pads.
629 if (LandingPads.count(BB))
632 for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end();
634 if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) {
635 // Found a call to eh.exception, replace it with the value from any
636 // upstream landing pad(s).
637 EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB));
638 EI->eraseFromParent();
639 ++NumExceptionValuesMoved;
646 /// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
647 /// the start of the basic block (unless there already is one, in which case
648 /// the existing call is returned).
649 Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
650 Instruction *Start = BB->getFirstNonPHIOrDbg();
651 // Is this a call to eh.exception?
652 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start))
653 if (CI->getIntrinsicID() == Intrinsic::eh_exception)
654 // Reuse the existing call.
657 // Find the eh.exception intrinsic if we didn't already.
658 if (!ExceptionValueIntrinsic)
659 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(),
660 Intrinsic::eh_exception);
663 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start);
666 bool DwarfEHPrepare::runOnFunction(Function &Fn) {
667 bool Changed = false;
669 // Initialize internal state.
670 DT = &getAnalysis<DominatorTree>();
673 // Ensure that only unwind edges end at landing pads (a landing pad is a
674 // basic block where an invoke unwind edge ends).
675 Changed |= NormalizeLandingPads();
677 // Turn unwind instructions and eh.resume calls into libcalls.
678 Changed |= LowerUnwindsAndResumes();
680 // TODO: Move eh.selector calls to landing pads and combine them.
682 // Move eh.exception calls to landing pads.
683 Changed |= MoveExceptionValueCalls();
685 Changed |= HandleURoRInvokes();