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/Target/TargetLowering.h"
26 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
27 #include "llvm/Transforms/Utils/PromoteMemToReg.h"
30 STATISTIC(NumLandingPadsSplit, "Number of landing pads split");
31 STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered");
32 STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
33 STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced");
36 class DwarfEHPrepare : public FunctionPass {
37 const TargetMachine *TM;
38 const TargetLowering *TLI;
41 // The eh.exception intrinsic.
42 Function *ExceptionValueIntrinsic;
44 // The eh.selector intrinsic.
45 Function *SelectorIntrinsic;
47 // _Unwind_Resume_or_Rethrow call.
50 // The EH language-specific catch-all type.
51 GlobalVariable *EHCatchAllValue;
53 // _Unwind_Resume or the target equivalent.
54 Constant *RewindFunction;
56 // Dominator info is used when turning stack temporaries into registers.
58 DominanceFrontier *DF;
60 // The function we are running on.
63 // The landing pads for this function.
64 typedef SmallPtrSet<BasicBlock*, 8> BBSet;
67 // Stack temporary used to hold eh.exception values.
68 AllocaInst *ExceptionValueVar;
70 bool NormalizeLandingPads();
72 bool MoveExceptionValueCalls();
73 bool FinishStackTemporaries();
74 bool PromoteStackTemporaries();
76 Instruction *CreateExceptionValueCall(BasicBlock *BB);
77 Instruction *CreateValueLoad(BasicBlock *BB);
79 /// CreateReadOfExceptionValue - Return the result of the eh.exception
80 /// intrinsic by calling the intrinsic if in a landing pad, or loading it
81 /// from the exception value variable otherwise.
82 Instruction *CreateReadOfExceptionValue(BasicBlock *BB) {
83 return LandingPads.count(BB) ?
84 CreateExceptionValueCall(BB) : CreateValueLoad(BB);
87 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still
88 /// use the ".llvm.eh.catch.all.value" call need to convert to using its
89 /// initializer instead.
90 bool CleanupSelectors();
92 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
93 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels);
95 /// FindAllURoRInvokes - Find all URoR invokes in the function.
96 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes);
98 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow"
99 /// calls. The "unwind" part of these invokes jump to a landing pad within
100 /// the current function. This is a candidate to merge the selector
101 /// associated with the URoR invoke with the one from the URoR's landing
103 bool HandleURoRInvokes();
105 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated
106 /// with the eh.exception call. This recursively looks past instructions
107 /// which don't change the EH pointer value, like casts or PHI nodes.
108 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
109 SmallPtrSet<IntrinsicInst*, 8> &SelCalls);
111 /// DoMem2RegPromotion - Take an alloca call and promote it from memory to a
113 bool DoMem2RegPromotion(Value *V) {
114 AllocaInst *AI = dyn_cast<AllocaInst>(V);
115 if (!AI || !isAllocaPromotable(AI)) return false;
117 // Turn the alloca into a register.
118 std::vector<AllocaInst*> Allocas(1, AI);
119 PromoteMemToReg(Allocas, *DT, *DF);
123 /// PromoteStoreInst - Perform Mem2Reg on a StoreInst.
124 bool PromoteStoreInst(StoreInst *SI) {
125 if (!SI || !DT || !DF) return false;
126 if (DoMem2RegPromotion(SI->getOperand(1)))
131 /// PromoteEHPtrStore - Promote the storing of an EH pointer into a
132 /// register. This should get rid of the store and subsequent loads.
133 bool PromoteEHPtrStore(IntrinsicInst *II) {
134 if (!DT || !DF) return false;
136 bool Changed = false;
141 for (Value::use_iterator
142 I = II->use_begin(), E = II->use_end(); I != E; ++I) {
143 SI = dyn_cast<StoreInst>(I);
147 if (!PromoteStoreInst(SI))
157 static char ID; // Pass identification, replacement for typeid.
158 DwarfEHPrepare(const TargetMachine *tm, bool fast) :
159 FunctionPass(&ID), TM(tm), TLI(TM->getTargetLowering()),
161 ExceptionValueIntrinsic(0), SelectorIntrinsic(0),
162 URoR(0), EHCatchAllValue(0), RewindFunction(0) {}
164 virtual bool runOnFunction(Function &Fn);
166 // getAnalysisUsage - We need dominance frontiers for memory promotion.
167 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
169 AU.addRequired<DominatorTree>();
170 AU.addPreserved<DominatorTree>();
172 AU.addRequired<DominanceFrontier>();
173 AU.addPreserved<DominanceFrontier>();
176 const char *getPassName() const {
177 return "Exception handling preparation";
181 } // end anonymous namespace
183 char DwarfEHPrepare::ID = 0;
185 FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm, bool fast) {
186 return new DwarfEHPrepare(tm, fast);
189 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
190 void DwarfEHPrepare::
191 FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) {
192 for (Value::use_iterator
193 I = SelectorIntrinsic->use_begin(),
194 E = SelectorIntrinsic->use_end(); I != E; ++I) {
195 IntrinsicInst *SI = cast<IntrinsicInst>(I);
196 if (!SI || SI->getParent()->getParent() != F) continue;
198 unsigned NumOps = SI->getNumOperands();
199 if (NumOps > 4) continue;
200 bool IsCleanUp = (NumOps == 3);
203 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getOperand(3)))
204 IsCleanUp = (CI->getZExtValue() == 0);
211 /// FindAllURoRInvokes - Find all URoR invokes in the function.
212 void DwarfEHPrepare::
213 FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) {
214 for (Value::use_iterator
215 I = URoR->use_begin(),
216 E = URoR->use_end(); I != E; ++I) {
217 if (InvokeInst *II = dyn_cast<InvokeInst>(I))
218 URoRInvokes.insert(II);
222 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use
223 /// the ".llvm.eh.catch.all.value" call need to convert to using its
224 /// initializer instead.
225 bool DwarfEHPrepare::CleanupSelectors() {
226 if (!EHCatchAllValue) return false;
228 if (!SelectorIntrinsic) {
230 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
231 if (!SelectorIntrinsic) return false;
234 bool Changed = false;
235 for (Value::use_iterator
236 I = SelectorIntrinsic->use_begin(),
237 E = SelectorIntrinsic->use_end(); I != E; ++I) {
238 IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(I);
239 if (!Sel || Sel->getParent()->getParent() != F) continue;
241 // Index of the ".llvm.eh.catch.all.value" variable.
242 unsigned OpIdx = Sel->getNumOperands() - 1;
243 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getOperand(OpIdx));
244 if (GV != EHCatchAllValue) continue;
245 Sel->setOperand(OpIdx, EHCatchAllValue->getInitializer());
252 /// FindSelectorAndURoR - Find the eh.selector call associated with the
253 /// eh.exception call. And indicate if there is a URoR "invoke" associated with
254 /// the eh.exception call. This recursively looks past instructions which don't
255 /// change the EH pointer value, like casts or PHI nodes.
257 DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
258 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) {
259 SmallPtrSet<PHINode*, 32> SeenPHIs;
260 bool Changed = false;
263 for (Value::use_iterator
264 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) {
265 Instruction *II = dyn_cast<Instruction>(I);
266 if (!II || II->getParent()->getParent() != F) continue;
268 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) {
269 if (Sel->getIntrinsicID() == Intrinsic::eh_selector)
270 SelCalls.insert(Sel);
271 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) {
272 if (Invoke->getCalledFunction() == URoR)
274 } else if (CastInst *CI = dyn_cast<CastInst>(II)) {
275 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls);
276 } else if (StoreInst *SI = dyn_cast<StoreInst>(II)) {
277 if (!PromoteStoreInst(SI)) continue;
280 goto restart; // Uses may have changed, restart loop.
281 } else if (PHINode *PN = dyn_cast<PHINode>(II)) {
282 if (SeenPHIs.insert(PN))
283 // Don't process a PHI node more than once.
284 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls);
291 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The
292 /// "unwind" part of these invokes jump to a landing pad within the current
293 /// function. This is a candidate to merge the selector associated with the URoR
294 /// invoke with the one from the URoR's landing pad.
295 bool DwarfEHPrepare::HandleURoRInvokes() {
296 if (!DT) return CleanupSelectors(); // We require DominatorTree information.
298 if (!EHCatchAllValue) {
300 F->getParent()->getNamedGlobal(".llvm.eh.catch.all.value");
301 if (!EHCatchAllValue) return false;
304 if (!SelectorIntrinsic) {
306 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
307 if (!SelectorIntrinsic) return false;
311 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow");
312 if (!URoR) return CleanupSelectors();
315 SmallPtrSet<IntrinsicInst*, 32> Sels;
316 SmallPtrSet<InvokeInst*, 32> URoRInvokes;
317 FindAllCleanupSelectors(Sels);
318 FindAllURoRInvokes(URoRInvokes);
320 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert;
322 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
323 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) {
324 const BasicBlock *SelBB = (*SI)->getParent();
325 for (SmallPtrSet<InvokeInst*, 32>::iterator
326 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) {
327 const BasicBlock *URoRBB = (*UI)->getParent();
328 if (SelBB == URoRBB || DT->dominates(SelBB, URoRBB)) {
329 SelsToConvert.insert(*SI);
335 bool Changed = false;
337 if (Sels.size() != SelsToConvert.size()) {
338 // If we haven't been able to convert all of the clean-up selectors, then
339 // loop through the slow way to see if they still need to be converted.
340 if (!ExceptionValueIntrinsic) {
341 ExceptionValueIntrinsic =
342 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception);
343 if (!ExceptionValueIntrinsic) return CleanupSelectors();
346 for (Value::use_iterator
347 I = ExceptionValueIntrinsic->use_begin(),
348 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) {
349 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(I);
350 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue;
352 Changed |= PromoteEHPtrStore(EHPtr);
354 bool URoRInvoke = false;
355 SmallPtrSet<IntrinsicInst*, 8> SelCalls;
356 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls);
359 // This EH pointer is being used by an invoke of an URoR instruction and
360 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we
361 // need to convert it to a 'catch-all'.
362 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
363 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) {
364 IntrinsicInst *II = *SI;
365 unsigned NumOps = II->getNumOperands();
368 bool IsCleanUp = (NumOps == 3);
371 if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getOperand(3)))
372 IsCleanUp = (CI->getZExtValue() == 0);
375 SelsToConvert.insert(II);
382 if (!SelsToConvert.empty()) {
383 // Convert all clean-up eh.selectors, which are associated with "invokes" of
384 // URoR calls, into catch-all eh.selectors.
387 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
388 SI = SelsToConvert.begin(), SE = SelsToConvert.end();
390 IntrinsicInst *II = *SI;
391 SmallVector<Value*, 8> Args;
393 // Use the exception object pointer and the personality function
394 // from the original selector.
395 Args.push_back(II->getOperand(1)); // Exception object pointer.
396 Args.push_back(II->getOperand(2)); // Personality function.
397 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator.
399 CallInst *NewSelector =
400 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(),
401 "eh.sel.catch.all", II);
403 NewSelector->setTailCall(II->isTailCall());
404 NewSelector->setAttributes(II->getAttributes());
405 NewSelector->setCallingConv(II->getCallingConv());
407 II->replaceAllUsesWith(NewSelector);
408 II->eraseFromParent();
412 Changed |= CleanupSelectors();
416 /// NormalizeLandingPads - Normalize and discover landing pads, noting them
417 /// in the LandingPads set. A landing pad is normal if the only CFG edges
418 /// that end at it are unwind edges from invoke instructions. If we inlined
419 /// through an invoke we could have a normal branch from the previous
420 /// unwind block through to the landing pad for the original invoke.
421 /// Abnormal landing pads are fixed up by redirecting all unwind edges to
422 /// a new basic block which falls through to the original.
423 bool DwarfEHPrepare::NormalizeLandingPads() {
424 bool Changed = false;
426 const MCAsmInfo *MAI = TM->getMCAsmInfo();
427 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
429 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
430 TerminatorInst *TI = I->getTerminator();
431 if (!isa<InvokeInst>(TI))
433 BasicBlock *LPad = TI->getSuccessor(1);
434 // Skip landing pads that have already been normalized.
435 if (LandingPads.count(LPad))
438 // Check that only invoke unwind edges end at the landing pad.
439 bool OnlyUnwoundTo = true;
440 bool SwitchOK = usingSjLjEH;
441 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
443 TerminatorInst *PT = (*PI)->getTerminator();
444 // The SjLj dispatch block uses a switch instruction. This is effectively
445 // an unwind edge, so we can disregard it here. There will only ever
446 // be one dispatch, however, so if there are multiple switches, one
447 // of them truly is a normal edge, not an unwind edge.
448 if (SwitchOK && isa<SwitchInst>(PT)) {
452 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
453 OnlyUnwoundTo = false;
459 // Only unwind edges lead to the landing pad. Remember the landing pad.
460 LandingPads.insert(LPad);
464 // At least one normal edge ends at the landing pad. Redirect the unwind
465 // edges to a new basic block which falls through into this one.
467 // Create the new basic block.
468 BasicBlock *NewBB = BasicBlock::Create(F->getContext(),
469 LPad->getName() + "_unwind_edge");
471 // Insert it into the function right before the original landing pad.
472 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);
474 // Redirect unwind edges from the original landing pad to NewBB.
475 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
476 TerminatorInst *PT = (*PI++)->getTerminator();
477 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
478 // Unwind to the new block.
479 PT->setSuccessor(1, NewBB);
482 // If there are any PHI nodes in LPad, we need to update them so that they
483 // merge incoming values from NewBB instead.
484 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
485 PHINode *PN = cast<PHINode>(II);
486 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);
488 // Check to see if all of the values coming in via unwind edges are the
489 // same. If so, we don't need to create a new PHI node.
490 Value *InVal = PN->getIncomingValueForBlock(*PB);
491 for (pred_iterator PI = PB; PI != PE; ++PI) {
492 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
499 // Different unwind edges have different values. Create a new PHI node
501 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind",
503 // Add an entry for each unwind edge, using the value from the old PHI.
504 for (pred_iterator PI = PB; PI != PE; ++PI)
505 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);
507 // Now use this new PHI as the common incoming value for NewBB in PN.
511 // Revector exactly one entry in the PHI node to come from NewBB
512 // and delete all other entries that come from unwind edges. If
513 // there are both normal and unwind edges from the same predecessor,
514 // this leaves an entry for the normal edge.
515 for (pred_iterator PI = PB; PI != PE; ++PI)
516 PN->removeIncomingValue(*PI);
517 PN->addIncoming(InVal, NewBB);
520 // Add a fallthrough from NewBB to the original landing pad.
521 BranchInst::Create(LPad, NewBB);
523 // Now update DominatorTree and DominanceFrontier analysis information.
525 DT->splitBlock(NewBB);
527 DF->splitBlock(NewBB);
529 // Remember the newly constructed landing pad. The original landing pad
530 // LPad is no longer a landing pad now that all unwind edges have been
531 // revectored to NewBB.
532 LandingPads.insert(NewBB);
533 ++NumLandingPadsSplit;
540 /// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
541 /// rethrowing any previously caught exception. This will crash horribly
542 /// at runtime if there is no such exception: using unwind to throw a new
543 /// exception is currently not supported.
544 bool DwarfEHPrepare::LowerUnwinds() {
545 SmallVector<TerminatorInst*, 16> UnwindInsts;
547 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
548 TerminatorInst *TI = I->getTerminator();
549 if (isa<UnwindInst>(TI))
550 UnwindInsts.push_back(TI);
553 if (UnwindInsts.empty()) return false;
555 // Find the rewind function if we didn't already.
556 if (!RewindFunction) {
557 LLVMContext &Ctx = UnwindInsts[0]->getContext();
558 std::vector<const Type*>
559 Params(1, Type::getInt8PtrTy(Ctx));
560 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
562 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
563 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
566 bool Changed = false;
568 for (SmallVectorImpl<TerminatorInst*>::iterator
569 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) {
570 TerminatorInst *TI = *I;
572 // Replace the unwind instruction with a call to _Unwind_Resume (or the
573 // appropriate target equivalent) followed by an UnreachableInst.
575 // Create the call...
576 CallInst *CI = CallInst::Create(RewindFunction,
577 CreateReadOfExceptionValue(TI->getParent()),
579 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
580 // ...followed by an UnreachableInst.
581 new UnreachableInst(TI->getContext(), TI);
583 // Nuke the unwind instruction.
584 TI->eraseFromParent();
592 /// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
593 /// landing pads by replacing calls outside of landing pads with loads from a
594 /// stack temporary. Move eh.exception calls inside landing pads to the start
595 /// of the landing pad (optional, but may make things simpler for later passes).
596 bool DwarfEHPrepare::MoveExceptionValueCalls() {
597 // If the eh.exception intrinsic is not declared in the module then there is
598 // nothing to do. Speed up compilation by checking for this common case.
599 if (!ExceptionValueIntrinsic &&
600 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception)))
603 bool Changed = false;
605 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
606 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
607 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
608 if (CI->getIntrinsicID() == Intrinsic::eh_exception) {
609 if (!CI->use_empty()) {
610 Value *ExceptionValue = CreateReadOfExceptionValue(BB);
611 if (CI == ExceptionValue) {
612 // The call was at the start of a landing pad - leave it alone.
613 assert(LandingPads.count(BB) &&
614 "Created eh.exception call outside landing pad!");
617 CI->replaceAllUsesWith(ExceptionValue);
619 CI->eraseFromParent();
620 ++NumExceptionValuesMoved;
628 /// FinishStackTemporaries - If we introduced a stack variable to hold the
629 /// exception value then initialize it in each landing pad.
630 bool DwarfEHPrepare::FinishStackTemporaries() {
631 if (!ExceptionValueVar)
635 bool Changed = false;
637 // Make sure that there is a store of the exception value at the start of
639 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
641 Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI);
642 Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar);
643 Store->insertAfter(ExceptionValue);
650 /// PromoteStackTemporaries - Turn any stack temporaries we introduced into
651 /// registers if possible.
652 bool DwarfEHPrepare::PromoteStackTemporaries() {
653 if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) {
654 // Turn the exception temporary into registers and phi nodes if possible.
655 std::vector<AllocaInst*> Allocas(1, ExceptionValueVar);
656 PromoteMemToReg(Allocas, *DT, *DF);
662 /// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
663 /// the start of the basic block (unless there already is one, in which case
664 /// the existing call is returned).
665 Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
666 Instruction *Start = BB->getFirstNonPHIOrDbg();
667 // Is this a call to eh.exception?
668 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start))
669 if (CI->getIntrinsicID() == Intrinsic::eh_exception)
670 // Reuse the existing call.
673 // Find the eh.exception intrinsic if we didn't already.
674 if (!ExceptionValueIntrinsic)
675 ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(),
676 Intrinsic::eh_exception);
679 return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start);
682 /// CreateValueLoad - Insert a load of the exception value stack variable
683 /// (creating it if necessary) at the start of the basic block (unless
684 /// there already is a load, in which case the existing load is returned).
685 Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) {
686 Instruction *Start = BB->getFirstNonPHIOrDbg();
687 // Is this a load of the exception temporary?
688 if (ExceptionValueVar)
689 if (LoadInst* LI = dyn_cast<LoadInst>(Start))
690 if (LI->getPointerOperand() == ExceptionValueVar)
691 // Reuse the existing load.
694 // Create the temporary if we didn't already.
695 if (!ExceptionValueVar) {
696 ExceptionValueVar = new AllocaInst(PointerType::getUnqual(
697 Type::getInt8Ty(BB->getContext())), "eh.value", F->begin()->begin());
698 ++NumStackTempsIntroduced;
702 return new LoadInst(ExceptionValueVar, "eh.value.load", Start);
705 bool DwarfEHPrepare::runOnFunction(Function &Fn) {
706 bool Changed = false;
708 // Initialize internal state.
709 DT = getAnalysisIfAvailable<DominatorTree>();
710 DF = getAnalysisIfAvailable<DominanceFrontier>();
711 ExceptionValueVar = 0;
714 // Ensure that only unwind edges end at landing pads (a landing pad is a
715 // basic block where an invoke unwind edge ends).
716 Changed |= NormalizeLandingPads();
718 // Turn unwind instructions into libcalls.
719 Changed |= LowerUnwinds();
721 // TODO: Move eh.selector calls to landing pads and combine them.
723 // Move eh.exception calls to landing pads.
724 Changed |= MoveExceptionValueCalls();
726 // Initialize any stack temporaries we introduced.
727 Changed |= FinishStackTemporaries();
729 // Turn any stack temporaries into registers if possible.
731 Changed |= PromoteStackTemporaries();
733 Changed |= HandleURoRInvokes();