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/PromoteMemToReg.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");
34 STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced");
37 class DwarfEHPrepare : public FunctionPass {
38 const TargetMachine *TM;
39 const TargetLowering *TLI;
42 // The eh.exception intrinsic.
43 Function *ExceptionValueIntrinsic;
45 // The eh.selector intrinsic.
46 Function *SelectorIntrinsic;
48 // _Unwind_Resume_or_Rethrow call.
51 // The EH language-specific catch-all type.
52 GlobalVariable *EHCatchAllValue;
54 // _Unwind_Resume or the target equivalent.
55 Constant *RewindFunction;
57 // Dominator info is used when turning stack temporaries into registers.
59 DominanceFrontier *DF;
61 // The function we are running on.
64 // The landing pads for this function.
65 typedef SmallPtrSet<BasicBlock*, 8> BBSet;
68 // Stack temporary used to hold eh.exception values.
69 AllocaInst *ExceptionValueVar;
71 bool NormalizeLandingPads();
73 bool MoveExceptionValueCalls();
74 bool FinishStackTemporaries();
75 bool PromoteStackTemporaries();
77 Instruction *CreateExceptionValueCall(BasicBlock *BB);
78 Instruction *CreateValueLoad(BasicBlock *BB);
80 /// CreateReadOfExceptionValue - Return the result of the eh.exception
81 /// intrinsic by calling the intrinsic if in a landing pad, or loading it
82 /// from the exception value variable otherwise.
83 Instruction *CreateReadOfExceptionValue(BasicBlock *BB) {
84 return LandingPads.count(BB) ?
85 CreateExceptionValueCall(BB) : CreateValueLoad(BB);
88 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still
89 /// use the ".llvm.eh.catch.all.value" call need to convert to using its
90 /// initializer instead.
91 bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels);
93 bool HasCatchAllInSelector(IntrinsicInst *);
95 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
96 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
97 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels);
99 /// FindAllURoRInvokes - Find all URoR invokes in the function.
100 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes);
102 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow"
103 /// calls. The "unwind" part of these invokes jump to a landing pad within
104 /// the current function. This is a candidate to merge the selector
105 /// associated with the URoR invoke with the one from the URoR's landing
107 bool HandleURoRInvokes();
109 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated
110 /// with the eh.exception call. This recursively looks past instructions
111 /// which don't change the EH pointer value, like casts or PHI nodes.
112 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
113 SmallPtrSet<IntrinsicInst*, 8> &SelCalls);
115 /// DoMem2RegPromotion - Take an alloca call and promote it from memory to a
117 bool DoMem2RegPromotion(Value *V) {
118 AllocaInst *AI = dyn_cast<AllocaInst>(V);
119 if (!AI || !isAllocaPromotable(AI)) return false;
121 // Turn the alloca into a register.
122 std::vector<AllocaInst*> Allocas(1, AI);
123 PromoteMemToReg(Allocas, *DT, *DF);
127 /// PromoteStoreInst - Perform Mem2Reg on a StoreInst.
128 bool PromoteStoreInst(StoreInst *SI) {
129 if (!SI || !DT || !DF) return false;
130 if (DoMem2RegPromotion(SI->getOperand(1)))
135 /// PromoteEHPtrStore - Promote the storing of an EH pointer into a
136 /// register. This should get rid of the store and subsequent loads.
137 bool PromoteEHPtrStore(IntrinsicInst *II) {
138 if (!DT || !DF) return false;
140 bool Changed = false;
145 for (Value::use_iterator
146 I = II->use_begin(), E = II->use_end(); I != E; ++I) {
147 SI = dyn_cast<StoreInst>(I);
151 if (!PromoteStoreInst(SI))
161 static char ID; // Pass identification, replacement for typeid.
162 DwarfEHPrepare(const TargetMachine *tm, bool fast) :
163 FunctionPass(&ID), TM(tm), TLI(TM->getTargetLowering()),
165 ExceptionValueIntrinsic(0), SelectorIntrinsic(0),
166 URoR(0), EHCatchAllValue(0), RewindFunction(0) {}
168 virtual bool runOnFunction(Function &Fn);
170 // getAnalysisUsage - We need dominance frontiers for memory promotion.
171 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
173 AU.addRequired<DominatorTree>();
174 AU.addPreserved<DominatorTree>();
176 AU.addRequired<DominanceFrontier>();
177 AU.addPreserved<DominanceFrontier>();
180 const char *getPassName() const {
181 return "Exception handling preparation";
185 } // end anonymous namespace
187 char DwarfEHPrepare::ID = 0;
189 FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm, bool fast) {
190 return new DwarfEHPrepare(tm, fast);
193 /// HasCatchAllInSelector - Return true if the intrinsic instruction has a
195 bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) {
196 if (!EHCatchAllValue) return false;
198 unsigned ArgIdx = II->getNumArgOperands() - 1;
199 GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx));
200 return GV == EHCatchAllValue;
203 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
204 void DwarfEHPrepare::
205 FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
206 SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) {
207 for (Value::use_iterator
208 I = SelectorIntrinsic->use_begin(),
209 E = SelectorIntrinsic->use_end(); I != E; ++I) {
210 IntrinsicInst *II = cast<IntrinsicInst>(I);
212 if (II->getParent()->getParent() != F)
215 if (!HasCatchAllInSelector(II))
218 CatchAllSels.insert(II);
222 /// FindAllURoRInvokes - Find all URoR invokes in the function.
223 void DwarfEHPrepare::
224 FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) {
225 for (Value::use_iterator
226 I = URoR->use_begin(),
227 E = URoR->use_end(); I != E; ++I) {
228 if (InvokeInst *II = dyn_cast<InvokeInst>(I))
229 URoRInvokes.insert(II);
233 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use
234 /// the ".llvm.eh.catch.all.value" call need to convert to using its
235 /// initializer instead.
236 bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) {
237 if (!EHCatchAllValue) return false;
239 if (!SelectorIntrinsic) {
241 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
242 if (!SelectorIntrinsic) return false;
245 bool Changed = false;
246 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
247 I = Sels.begin(), E = Sels.end(); I != E; ++I) {
248 IntrinsicInst *Sel = *I;
250 // Index of the ".llvm.eh.catch.all.value" variable.
251 unsigned OpIdx = Sel->getNumArgOperands() - 1;
252 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx));
253 if (GV != EHCatchAllValue) continue;
254 Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer());
261 /// FindSelectorAndURoR - Find the eh.selector call associated with the
262 /// eh.exception call. And indicate if there is a URoR "invoke" associated with
263 /// the eh.exception call. This recursively looks past instructions which don't
264 /// change the EH pointer value, like casts or PHI nodes.
266 DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
267 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) {
268 SmallPtrSet<PHINode*, 32> SeenPHIs;
269 bool Changed = false;
272 for (Value::use_iterator
273 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) {
274 Instruction *II = dyn_cast<Instruction>(I);
275 if (!II || II->getParent()->getParent() != F) continue;
277 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) {
278 if (Sel->getIntrinsicID() == Intrinsic::eh_selector)
279 SelCalls.insert(Sel);
280 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) {
281 if (Invoke->getCalledFunction() == URoR)
283 } else if (CastInst *CI = dyn_cast<CastInst>(II)) {
284 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls);
285 } else if (StoreInst *SI = dyn_cast<StoreInst>(II)) {
286 if (!PromoteStoreInst(SI)) continue;
289 goto restart; // Uses may have changed, restart loop.
290 } else if (PHINode *PN = dyn_cast<PHINode>(II)) {
291 if (SeenPHIs.insert(PN))
292 // Don't process a PHI node more than once.
293 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls);
300 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The
301 /// "unwind" part of these invokes jump to a landing pad within the current
302 /// function. This is a candidate to merge the selector associated with the URoR
303 /// invoke with the one from the URoR's landing pad.
304 bool DwarfEHPrepare::HandleURoRInvokes() {
305 if (!EHCatchAllValue) {
307 F->getParent()->getNamedGlobal(".llvm.eh.catch.all.value");
308 if (!EHCatchAllValue) return false;
311 if (!SelectorIntrinsic) {
313 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
314 if (!SelectorIntrinsic) return false;
317 SmallPtrSet<IntrinsicInst*, 32> Sels;
318 SmallPtrSet<IntrinsicInst*, 32> CatchAllSels;
319 FindAllCleanupSelectors(Sels, CatchAllSels);
322 // We require DominatorTree information.
323 return CleanupSelectors(CatchAllSels);
326 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow");
327 if (!URoR) return CleanupSelectors(CatchAllSels);
330 SmallPtrSet<InvokeInst*, 32> URoRInvokes;
331 FindAllURoRInvokes(URoRInvokes);
333 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert;
335 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
336 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) {
337 const BasicBlock *SelBB = (*SI)->getParent();
338 for (SmallPtrSet<InvokeInst*, 32>::iterator
339 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) {
340 const BasicBlock *URoRBB = (*UI)->getParent();
341 if (SelBB == URoRBB || DT->dominates(SelBB, URoRBB)) {
342 SelsToConvert.insert(*SI);
348 bool Changed = false;
350 if (Sels.size() != SelsToConvert.size()) {
351 // If we haven't been able to convert all of the clean-up selectors, then
352 // loop through the slow way to see if they still need to be converted.
353 if (!ExceptionValueIntrinsic) {
354 ExceptionValueIntrinsic =
355 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception);
356 if (!ExceptionValueIntrinsic)
357 return CleanupSelectors(CatchAllSels);
360 for (Value::use_iterator
361 I = ExceptionValueIntrinsic->use_begin(),
362 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) {
363 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(I);
364 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue;
366 Changed |= PromoteEHPtrStore(EHPtr);
368 bool URoRInvoke = false;
369 SmallPtrSet<IntrinsicInst*, 8> SelCalls;
370 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls);
373 // This EH pointer is being used by an invoke of an URoR instruction and
374 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we
375 // need to convert it to a 'catch-all'.
376 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
377 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI)
378 if (!HasCatchAllInSelector(*SI))
379 SelsToConvert.insert(*SI);
384 if (!SelsToConvert.empty()) {
385 // Convert all clean-up eh.selectors, which are associated with "invokes" of
386 // URoR calls, into catch-all eh.selectors.
389 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
390 SI = SelsToConvert.begin(), SE = SelsToConvert.end();
392 IntrinsicInst *II = *SI;
394 // Use the exception object pointer and the personality function
395 // from the original selector.
397 IntrinsicInst::op_iterator I = CS.arg_begin();
398 IntrinsicInst::op_iterator E = CS.arg_end();
399 IntrinsicInst::op_iterator B = prior(E);
401 // Exclude last argument if it is an integer.
402 if (isa<ConstantInt>(B)) E = B;
404 // Add exception object pointer (front).
405 // Add personality function (next).
406 // Add in any filter IDs (rest).
407 SmallVector<Value*, 8> Args(I, E);
409 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator.
411 CallInst *NewSelector =
412 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(),
413 "eh.sel.catch.all", II);
415 NewSelector->setTailCall(II->isTailCall());
416 NewSelector->setAttributes(II->getAttributes());
417 NewSelector->setCallingConv(II->getCallingConv());
419 II->replaceAllUsesWith(NewSelector);
420 II->eraseFromParent();
424 Changed |= CleanupSelectors(CatchAllSels);
428 /// NormalizeLandingPads - Normalize and discover landing pads, noting them
429 /// in the LandingPads set. A landing pad is normal if the only CFG edges
430 /// that end at it are unwind edges from invoke instructions. If we inlined
431 /// through an invoke we could have a normal branch from the previous
432 /// unwind block through to the landing pad for the original invoke.
433 /// Abnormal landing pads are fixed up by redirecting all unwind edges to
434 /// a new basic block which falls through to the original.
435 bool DwarfEHPrepare::NormalizeLandingPads() {
436 bool Changed = false;
438 const MCAsmInfo *MAI = TM->getMCAsmInfo();
439 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
441 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
442 TerminatorInst *TI = I->getTerminator();
443 if (!isa<InvokeInst>(TI))
445 BasicBlock *LPad = TI->getSuccessor(1);
446 // Skip landing pads that have already been normalized.
447 if (LandingPads.count(LPad))
450 // Check that only invoke unwind edges end at the landing pad.
451 bool OnlyUnwoundTo = true;
452 bool SwitchOK = usingSjLjEH;
453 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
455 TerminatorInst *PT = (*PI)->getTerminator();
456 // The SjLj dispatch block uses a switch instruction. This is effectively
457 // an unwind edge, so we can disregard it here. There will only ever
458 // be one dispatch, however, so if there are multiple switches, one
459 // of them truly is a normal edge, not an unwind edge.
460 if (SwitchOK && isa<SwitchInst>(PT)) {
464 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
465 OnlyUnwoundTo = false;
471 // Only unwind edges lead to the landing pad. Remember the landing pad.
472 LandingPads.insert(LPad);
476 // At least one normal edge ends at the landing pad. Redirect the unwind
477 // edges to a new basic block which falls through into this one.
479 // Create the new basic block.
480 BasicBlock *NewBB = BasicBlock::Create(F->getContext(),
481 LPad->getName() + "_unwind_edge");
483 // Insert it into the function right before the original landing pad.
484 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);
486 // Redirect unwind edges from the original landing pad to NewBB.
487 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
488 TerminatorInst *PT = (*PI++)->getTerminator();
489 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
490 // Unwind to the new block.
491 PT->setSuccessor(1, NewBB);
494 // If there are any PHI nodes in LPad, we need to update them so that they
495 // merge incoming values from NewBB instead.
496 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
497 PHINode *PN = cast<PHINode>(II);
498 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);
500 // Check to see if all of the values coming in via unwind edges are the
501 // same. If so, we don't need to create a new PHI node.
502 Value *InVal = PN->getIncomingValueForBlock(*PB);
503 for (pred_iterator PI = PB; PI != PE; ++PI) {
504 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
511 // Different unwind edges have different values. Create a new PHI node
513 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind",
515 // Add an entry for each unwind edge, using the value from the old PHI.
516 for (pred_iterator PI = PB; PI != PE; ++PI)
517 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);
519 // Now use this new PHI as the common incoming value for NewBB in PN.
523 // Revector exactly one entry in the PHI node to come from NewBB
524 // and delete all other entries that come from unwind edges. If
525 // there are both normal and unwind edges from the same predecessor,
526 // this leaves an entry for the normal edge.
527 for (pred_iterator PI = PB; PI != PE; ++PI)
528 PN->removeIncomingValue(*PI);
529 PN->addIncoming(InVal, NewBB);
532 // Add a fallthrough from NewBB to the original landing pad.
533 BranchInst::Create(LPad, NewBB);
535 // Now update DominatorTree and DominanceFrontier analysis information.
537 DT->splitBlock(NewBB);
539 DF->splitBlock(NewBB);
541 // Remember the newly constructed landing pad. The original landing pad
542 // LPad is no longer a landing pad now that all unwind edges have been
543 // revectored to NewBB.
544 LandingPads.insert(NewBB);
545 ++NumLandingPadsSplit;
552 /// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
553 /// rethrowing any previously caught exception. This will crash horribly
554 /// at runtime if there is no such exception: using unwind to throw a new
555 /// exception is currently not supported.
556 bool DwarfEHPrepare::LowerUnwinds() {
557 SmallVector<TerminatorInst*, 16> UnwindInsts;
559 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
560 TerminatorInst *TI = I->getTerminator();
561 if (isa<UnwindInst>(TI))
562 UnwindInsts.push_back(TI);
565 if (UnwindInsts.empty()) return false;
567 // Find the rewind function if we didn't already.
568 if (!RewindFunction) {
569 LLVMContext &Ctx = UnwindInsts[0]->getContext();
570 std::vector<const Type*>
571 Params(1, Type::getInt8PtrTy(Ctx));
572 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
574 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
575 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
578 bool Changed = false;
580 for (SmallVectorImpl<TerminatorInst*>::iterator
581 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) {
582 TerminatorInst *TI = *I;
584 // Replace the unwind instruction with a call to _Unwind_Resume (or the
585 // appropriate target equivalent) followed by an UnreachableInst.
587 // Create the call...
588 CallInst *CI = CallInst::Create(RewindFunction,
589 CreateReadOfExceptionValue(TI->getParent()),
591 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
592 // ...followed by an UnreachableInst.
593 new UnreachableInst(TI->getContext(), TI);
595 // Nuke the unwind instruction.
596 TI->eraseFromParent();
604 /// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
605 /// landing pads by replacing calls outside of landing pads with loads from a
606 /// stack temporary. Move eh.exception calls inside landing pads to the start
607 /// of the landing pad (optional, but may make things simpler for later passes).
608 bool DwarfEHPrepare::MoveExceptionValueCalls() {
609 // If the eh.exception intrinsic is not declared in the module then there is
610 // nothing to do. Speed up compilation by checking for this common case.
611 if (!ExceptionValueIntrinsic &&
612 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception)))
615 bool Changed = false;
617 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
618 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
619 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
620 if (CI->getIntrinsicID() == Intrinsic::eh_exception) {
621 if (!CI->use_empty()) {
622 Value *ExceptionValue = CreateReadOfExceptionValue(BB);
623 if (CI == ExceptionValue) {
624 // The call was at the start of a landing pad - leave it alone.
625 assert(LandingPads.count(BB) &&
626 "Created eh.exception call outside landing pad!");
629 CI->replaceAllUsesWith(ExceptionValue);
631 CI->eraseFromParent();
632 ++NumExceptionValuesMoved;
640 /// FinishStackTemporaries - If we introduced a stack variable to hold the
641 /// exception value then initialize it in each landing pad.
642 bool DwarfEHPrepare::FinishStackTemporaries() {
643 if (!ExceptionValueVar)
647 bool Changed = false;
649 // Make sure that there is a store of the exception value at the start of
651 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
653 Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI);
654 Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar);
655 Store->insertAfter(ExceptionValue);
662 /// PromoteStackTemporaries - Turn any stack temporaries we introduced into
663 /// registers if possible.
664 bool DwarfEHPrepare::PromoteStackTemporaries() {
665 if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) {
666 // Turn the exception temporary into registers and phi nodes if possible.
667 std::vector<AllocaInst*> Allocas(1, ExceptionValueVar);
668 PromoteMemToReg(Allocas, *DT, *DF);
674 /// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
675 /// the start of the basic block (unless there already is one, in which case
676 /// the existing call is returned).
677 Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
678 Instruction *Start = BB->getFirstNonPHIOrDbg();
679 // Is this a call to eh.exception?
680 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start))
681 if (CI->getIntrinsicID() == Intrinsic::eh_exception)
682 // Reuse the existing call.
685 // Find the eh.exception intrinsic if we didn't already.
686 if (!ExceptionValueIntrinsic)
687 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(),
688 Intrinsic::eh_exception);
691 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start);
694 /// CreateValueLoad - Insert a load of the exception value stack variable
695 /// (creating it if necessary) at the start of the basic block (unless
696 /// there already is a load, in which case the existing load is returned).
697 Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) {
698 Instruction *Start = BB->getFirstNonPHIOrDbg();
699 // Is this a load of the exception temporary?
700 if (ExceptionValueVar)
701 if (LoadInst* LI = dyn_cast<LoadInst>(Start))
702 if (LI->getPointerOperand() == ExceptionValueVar)
703 // Reuse the existing load.
706 // Create the temporary if we didn't already.
707 if (!ExceptionValueVar) {
708 ExceptionValueVar = new AllocaInst(PointerType::getUnqual(
709 Type::getInt8Ty(BB->getContext())), "eh.value", F->begin()->begin());
710 ++NumStackTempsIntroduced;
714 return new LoadInst(ExceptionValueVar, "eh.value.load", Start);
717 bool DwarfEHPrepare::runOnFunction(Function &Fn) {
718 bool Changed = false;
720 // Initialize internal state.
721 DT = getAnalysisIfAvailable<DominatorTree>();
722 DF = getAnalysisIfAvailable<DominanceFrontier>();
723 ExceptionValueVar = 0;
726 // Ensure that only unwind edges end at landing pads (a landing pad is a
727 // basic block where an invoke unwind edge ends).
728 Changed |= NormalizeLandingPads();
730 // Turn unwind instructions into libcalls.
731 Changed |= LowerUnwinds();
733 // TODO: Move eh.selector calls to landing pads and combine them.
735 // Move eh.exception calls to landing pads.
736 Changed |= MoveExceptionValueCalls();
738 // Initialize any stack temporaries we introduced.
739 Changed |= FinishStackTemporaries();
741 // Turn any stack temporaries into registers if possible.
743 Changed |= PromoteStackTemporaries();
745 Changed |= HandleURoRInvokes();