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Diffstat (limited to 'contrib/llvm/lib/CodeGen/DwarfEHPrepare.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/DwarfEHPrepare.cpp | 664 |
1 files changed, 664 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/DwarfEHPrepare.cpp b/contrib/llvm/lib/CodeGen/DwarfEHPrepare.cpp new file mode 100644 index 000000000000..550fd3e25fb7 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/DwarfEHPrepare.cpp @@ -0,0 +1,664 @@ +//===-- DwarfEHPrepare - Prepare exception handling for code generation ---===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This pass mulches exception handling code into a form adapted to code +// generation. Required if using dwarf exception handling. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "dwarfehprepare" +#include "llvm/Function.h" +#include "llvm/Instructions.h" +#include "llvm/IntrinsicInst.h" +#include "llvm/Module.h" +#include "llvm/Pass.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Analysis/Dominators.h" +#include "llvm/CodeGen/Passes.h" +#include "llvm/MC/MCAsmInfo.h" +#include "llvm/Support/CallSite.h" +#include "llvm/Target/TargetLowering.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" +#include "llvm/Transforms/Utils/SSAUpdater.h" +using namespace llvm; + +STATISTIC(NumLandingPadsSplit, "Number of landing pads split"); +STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered"); +STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved"); + +namespace { + class DwarfEHPrepare : public FunctionPass { + const TargetMachine *TM; + const TargetLowering *TLI; + + // The eh.exception intrinsic. + Function *ExceptionValueIntrinsic; + + // The eh.selector intrinsic. + Function *SelectorIntrinsic; + + // _Unwind_Resume_or_Rethrow call. + Constant *URoR; + + // The EH language-specific catch-all type. + GlobalVariable *EHCatchAllValue; + + // _Unwind_Resume or the target equivalent. + Constant *RewindFunction; + + // We both use and preserve dominator info. + DominatorTree *DT; + + // The function we are running on. + Function *F; + + // The landing pads for this function. + typedef SmallPtrSet<BasicBlock*, 8> BBSet; + BBSet LandingPads; + + bool NormalizeLandingPads(); + bool LowerUnwinds(); + bool MoveExceptionValueCalls(); + + Instruction *CreateExceptionValueCall(BasicBlock *BB); + + /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still + /// use the "llvm.eh.catch.all.value" call need to convert to using its + /// initializer instead. + bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels); + + bool HasCatchAllInSelector(IntrinsicInst *); + + /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. + void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, + SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels); + + /// FindAllURoRInvokes - Find all URoR invokes in the function. + void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes); + + /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" + /// calls. The "unwind" part of these invokes jump to a landing pad within + /// the current function. This is a candidate to merge the selector + /// associated with the URoR invoke with the one from the URoR's landing + /// pad. + bool HandleURoRInvokes(); + + /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated + /// with the eh.exception call. This recursively looks past instructions + /// which don't change the EH pointer value, like casts or PHI nodes. + bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, + SmallPtrSet<IntrinsicInst*, 8> &SelCalls); + + public: + static char ID; // Pass identification, replacement for typeid. + DwarfEHPrepare(const TargetMachine *tm) : + FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()), + ExceptionValueIntrinsic(0), SelectorIntrinsic(0), + URoR(0), EHCatchAllValue(0), RewindFunction(0) {} + + virtual bool runOnFunction(Function &Fn); + + // getAnalysisUsage - We need the dominator tree for handling URoR. + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + AU.addRequired<DominatorTree>(); + AU.addPreserved<DominatorTree>(); + } + + const char *getPassName() const { + return "Exception handling preparation"; + } + + }; +} // end anonymous namespace + +char DwarfEHPrepare::ID = 0; + +FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) { + return new DwarfEHPrepare(tm); +} + +/// HasCatchAllInSelector - Return true if the intrinsic instruction has a +/// catch-all. +bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) { + if (!EHCatchAllValue) return false; + + unsigned ArgIdx = II->getNumArgOperands() - 1; + GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx)); + return GV == EHCatchAllValue; +} + +/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. +void DwarfEHPrepare:: +FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels, + SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) { + for (Value::use_iterator + I = SelectorIntrinsic->use_begin(), + E = SelectorIntrinsic->use_end(); I != E; ++I) { + IntrinsicInst *II = cast<IntrinsicInst>(*I); + + if (II->getParent()->getParent() != F) + continue; + + if (!HasCatchAllInSelector(II)) + Sels.insert(II); + else + CatchAllSels.insert(II); + } +} + +/// FindAllURoRInvokes - Find all URoR invokes in the function. +void DwarfEHPrepare:: +FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) { + for (Value::use_iterator + I = URoR->use_begin(), + E = URoR->use_end(); I != E; ++I) { + if (InvokeInst *II = dyn_cast<InvokeInst>(*I)) + URoRInvokes.insert(II); + } +} + +/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use +/// the "llvm.eh.catch.all.value" call need to convert to using its +/// initializer instead. +bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) { + if (!EHCatchAllValue) return false; + + if (!SelectorIntrinsic) { + SelectorIntrinsic = + Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); + if (!SelectorIntrinsic) return false; + } + + bool Changed = false; + for (SmallPtrSet<IntrinsicInst*, 32>::iterator + I = Sels.begin(), E = Sels.end(); I != E; ++I) { + IntrinsicInst *Sel = *I; + + // Index of the "llvm.eh.catch.all.value" variable. + unsigned OpIdx = Sel->getNumArgOperands() - 1; + GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx)); + if (GV != EHCatchAllValue) continue; + Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer()); + Changed = true; + } + + return Changed; +} + +/// FindSelectorAndURoR - Find the eh.selector call associated with the +/// eh.exception call. And indicate if there is a URoR "invoke" associated with +/// the eh.exception call. This recursively looks past instructions which don't +/// change the EH pointer value, like casts or PHI nodes. +bool +DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke, + SmallPtrSet<IntrinsicInst*, 8> &SelCalls) { + SmallPtrSet<PHINode*, 32> SeenPHIs; + bool Changed = false; + + for (Value::use_iterator + I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { + Instruction *II = dyn_cast<Instruction>(*I); + if (!II || II->getParent()->getParent() != F) continue; + + if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) { + if (Sel->getIntrinsicID() == Intrinsic::eh_selector) + SelCalls.insert(Sel); + } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) { + if (Invoke->getCalledFunction() == URoR) + URoRInvoke = true; + } else if (CastInst *CI = dyn_cast<CastInst>(II)) { + Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls); + } else if (PHINode *PN = dyn_cast<PHINode>(II)) { + if (SeenPHIs.insert(PN)) + // Don't process a PHI node more than once. + Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls); + } + } + + return Changed; +} + +/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The +/// "unwind" part of these invokes jump to a landing pad within the current +/// function. This is a candidate to merge the selector associated with the URoR +/// invoke with the one from the URoR's landing pad. +bool DwarfEHPrepare::HandleURoRInvokes() { + if (!EHCatchAllValue) { + EHCatchAllValue = + F->getParent()->getNamedGlobal("llvm.eh.catch.all.value"); + if (!EHCatchAllValue) return false; + } + + if (!SelectorIntrinsic) { + SelectorIntrinsic = + Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); + if (!SelectorIntrinsic) return false; + } + + SmallPtrSet<IntrinsicInst*, 32> Sels; + SmallPtrSet<IntrinsicInst*, 32> CatchAllSels; + FindAllCleanupSelectors(Sels, CatchAllSels); + + if (!URoR) { + URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); + if (!URoR) return CleanupSelectors(CatchAllSels); + } + + SmallPtrSet<InvokeInst*, 32> URoRInvokes; + FindAllURoRInvokes(URoRInvokes); + + SmallPtrSet<IntrinsicInst*, 32> SelsToConvert; + + for (SmallPtrSet<IntrinsicInst*, 32>::iterator + SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) { + const BasicBlock *SelBB = (*SI)->getParent(); + for (SmallPtrSet<InvokeInst*, 32>::iterator + UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) { + const BasicBlock *URoRBB = (*UI)->getParent(); + if (DT->dominates(SelBB, URoRBB)) { + SelsToConvert.insert(*SI); + break; + } + } + } + + bool Changed = false; + + if (Sels.size() != SelsToConvert.size()) { + // If we haven't been able to convert all of the clean-up selectors, then + // loop through the slow way to see if they still need to be converted. + if (!ExceptionValueIntrinsic) { + ExceptionValueIntrinsic = + Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception); + if (!ExceptionValueIntrinsic) + return CleanupSelectors(CatchAllSels); + } + + for (Value::use_iterator + I = ExceptionValueIntrinsic->use_begin(), + E = ExceptionValueIntrinsic->use_end(); I != E; ++I) { + IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I); + if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; + + bool URoRInvoke = false; + SmallPtrSet<IntrinsicInst*, 8> SelCalls; + Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls); + + if (URoRInvoke) { + // This EH pointer is being used by an invoke of an URoR instruction and + // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we + // need to convert it to a 'catch-all'. + for (SmallPtrSet<IntrinsicInst*, 8>::iterator + SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) + if (!HasCatchAllInSelector(*SI)) + SelsToConvert.insert(*SI); + } + } + } + + if (!SelsToConvert.empty()) { + // Convert all clean-up eh.selectors, which are associated with "invokes" of + // URoR calls, into catch-all eh.selectors. + Changed = true; + + for (SmallPtrSet<IntrinsicInst*, 8>::iterator + SI = SelsToConvert.begin(), SE = SelsToConvert.end(); + SI != SE; ++SI) { + IntrinsicInst *II = *SI; + + // Use the exception object pointer and the personality function + // from the original selector. + CallSite CS(II); + IntrinsicInst::op_iterator I = CS.arg_begin(); + IntrinsicInst::op_iterator E = CS.arg_end(); + IntrinsicInst::op_iterator B = prior(E); + + // Exclude last argument if it is an integer. + if (isa<ConstantInt>(B)) E = B; + + // Add exception object pointer (front). + // Add personality function (next). + // Add in any filter IDs (rest). + SmallVector<Value*, 8> Args(I, E); + + Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator. + + CallInst *NewSelector = + CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(), + "eh.sel.catch.all", II); + + NewSelector->setTailCall(II->isTailCall()); + NewSelector->setAttributes(II->getAttributes()); + NewSelector->setCallingConv(II->getCallingConv()); + + II->replaceAllUsesWith(NewSelector); + II->eraseFromParent(); + } + } + + Changed |= CleanupSelectors(CatchAllSels); + return Changed; +} + +/// NormalizeLandingPads - Normalize and discover landing pads, noting them +/// in the LandingPads set. A landing pad is normal if the only CFG edges +/// that end at it are unwind edges from invoke instructions. If we inlined +/// through an invoke we could have a normal branch from the previous +/// unwind block through to the landing pad for the original invoke. +/// Abnormal landing pads are fixed up by redirecting all unwind edges to +/// a new basic block which falls through to the original. +bool DwarfEHPrepare::NormalizeLandingPads() { + bool Changed = false; + + const MCAsmInfo *MAI = TM->getMCAsmInfo(); + bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj; + + for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { + TerminatorInst *TI = I->getTerminator(); + if (!isa<InvokeInst>(TI)) + continue; + BasicBlock *LPad = TI->getSuccessor(1); + // Skip landing pads that have already been normalized. + if (LandingPads.count(LPad)) + continue; + + // Check that only invoke unwind edges end at the landing pad. + bool OnlyUnwoundTo = true; + bool SwitchOK = usingSjLjEH; + for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); + PI != PE; ++PI) { + TerminatorInst *PT = (*PI)->getTerminator(); + // The SjLj dispatch block uses a switch instruction. This is effectively + // an unwind edge, so we can disregard it here. There will only ever + // be one dispatch, however, so if there are multiple switches, one + // of them truly is a normal edge, not an unwind edge. + if (SwitchOK && isa<SwitchInst>(PT)) { + SwitchOK = false; + continue; + } + if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) { + OnlyUnwoundTo = false; + break; + } + } + + if (OnlyUnwoundTo) { + // Only unwind edges lead to the landing pad. Remember the landing pad. + LandingPads.insert(LPad); + continue; + } + + // At least one normal edge ends at the landing pad. Redirect the unwind + // edges to a new basic block which falls through into this one. + + // Create the new basic block. + BasicBlock *NewBB = BasicBlock::Create(F->getContext(), + LPad->getName() + "_unwind_edge"); + + // Insert it into the function right before the original landing pad. + LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); + + // Redirect unwind edges from the original landing pad to NewBB. + for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) { + TerminatorInst *PT = (*PI++)->getTerminator(); + if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad) + // Unwind to the new block. + PT->setSuccessor(1, NewBB); + } + + // If there are any PHI nodes in LPad, we need to update them so that they + // merge incoming values from NewBB instead. + for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) { + PHINode *PN = cast<PHINode>(II); + pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB); + + // Check to see if all of the values coming in via unwind edges are the + // same. If so, we don't need to create a new PHI node. + Value *InVal = PN->getIncomingValueForBlock(*PB); + for (pred_iterator PI = PB; PI != PE; ++PI) { + if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) { + InVal = 0; + break; + } + } + + if (InVal == 0) { + // Different unwind edges have different values. Create a new PHI node + // in NewBB. + PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind", + NewBB); + // Add an entry for each unwind edge, using the value from the old PHI. + for (pred_iterator PI = PB; PI != PE; ++PI) + NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI); + + // Now use this new PHI as the common incoming value for NewBB in PN. + InVal = NewPN; + } + + // Revector exactly one entry in the PHI node to come from NewBB + // and delete all other entries that come from unwind edges. If + // there are both normal and unwind edges from the same predecessor, + // this leaves an entry for the normal edge. + for (pred_iterator PI = PB; PI != PE; ++PI) + PN->removeIncomingValue(*PI); + PN->addIncoming(InVal, NewBB); + } + + // Add a fallthrough from NewBB to the original landing pad. + BranchInst::Create(LPad, NewBB); + + // Now update DominatorTree analysis information. + DT->splitBlock(NewBB); + + // Remember the newly constructed landing pad. The original landing pad + // LPad is no longer a landing pad now that all unwind edges have been + // revectored to NewBB. + LandingPads.insert(NewBB); + ++NumLandingPadsSplit; + Changed = true; + } + + return Changed; +} + +/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume, +/// rethrowing any previously caught exception. This will crash horribly +/// at runtime if there is no such exception: using unwind to throw a new +/// exception is currently not supported. +bool DwarfEHPrepare::LowerUnwinds() { + SmallVector<TerminatorInst*, 16> UnwindInsts; + + for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { + TerminatorInst *TI = I->getTerminator(); + if (isa<UnwindInst>(TI)) + UnwindInsts.push_back(TI); + } + + if (UnwindInsts.empty()) return false; + + // Find the rewind function if we didn't already. + if (!RewindFunction) { + LLVMContext &Ctx = UnwindInsts[0]->getContext(); + std::vector<const Type*> + Params(1, Type::getInt8PtrTy(Ctx)); + FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), + Params, false); + const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); + RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); + } + + bool Changed = false; + + for (SmallVectorImpl<TerminatorInst*>::iterator + I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) { + TerminatorInst *TI = *I; + + // Replace the unwind instruction with a call to _Unwind_Resume (or the + // appropriate target equivalent) followed by an UnreachableInst. + + // Create the call... + CallInst *CI = CallInst::Create(RewindFunction, + CreateExceptionValueCall(TI->getParent()), + "", TI); + CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); + // ...followed by an UnreachableInst. + new UnreachableInst(TI->getContext(), TI); + + // Nuke the unwind instruction. + TI->eraseFromParent(); + ++NumUnwindsLowered; + Changed = true; + } + + return Changed; +} + +/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from +/// landing pads by replacing calls outside of landing pads with direct use of +/// a register holding the appropriate value; this requires adding calls inside +/// all landing pads to initialize the register. Also, move eh.exception calls +/// inside landing pads to the start of the landing pad (optional, but may make +/// things simpler for later passes). +bool DwarfEHPrepare::MoveExceptionValueCalls() { + // If the eh.exception intrinsic is not declared in the module then there is + // nothing to do. Speed up compilation by checking for this common case. + if (!ExceptionValueIntrinsic && + !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) + return false; + + bool Changed = false; + + // Move calls to eh.exception that are inside a landing pad to the start of + // the landing pad. + for (BBSet::const_iterator LI = LandingPads.begin(), LE = LandingPads.end(); + LI != LE; ++LI) { + BasicBlock *LP = *LI; + for (BasicBlock::iterator II = LP->getFirstNonPHIOrDbg(), IE = LP->end(); + II != IE;) + if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { + // Found a call to eh.exception. + if (!EI->use_empty()) { + // If there is already a call to eh.exception at the start of the + // landing pad, then get hold of it; otherwise create such a call. + Value *CallAtStart = CreateExceptionValueCall(LP); + + // If the call was at the start of a landing pad then leave it alone. + if (EI == CallAtStart) + continue; + EI->replaceAllUsesWith(CallAtStart); + } + EI->eraseFromParent(); + ++NumExceptionValuesMoved; + Changed = true; + } + } + + // Look for calls to eh.exception that are not in a landing pad. If one is + // found, then a register that holds the exception value will be created in + // each landing pad, and the SSAUpdater will be used to compute the values + // returned by eh.exception calls outside of landing pads. + SSAUpdater SSA; + + // Remember where we found the eh.exception call, to avoid rescanning earlier + // basic blocks which we already know contain no eh.exception calls. + bool FoundCallOutsideLandingPad = false; + Function::iterator BB = F->begin(); + for (Function::iterator BE = F->end(); BB != BE; ++BB) { + // Skip over landing pads. + if (LandingPads.count(BB)) + continue; + + for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); + II != IE; ++II) + if (isa<EHExceptionInst>(II)) { + SSA.Initialize(II->getType(), II->getName()); + FoundCallOutsideLandingPad = true; + break; + } + + if (FoundCallOutsideLandingPad) + break; + } + + // If all calls to eh.exception are in landing pads then we are done. + if (!FoundCallOutsideLandingPad) + return Changed; + + // Add a call to eh.exception at the start of each landing pad, and tell the + // SSAUpdater that this is the value produced by the landing pad. + for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); + LI != LE; ++LI) + SSA.AddAvailableValue(*LI, CreateExceptionValueCall(*LI)); + + // Now turn all calls to eh.exception that are not in a landing pad into a use + // of the appropriate register. + for (Function::iterator BE = F->end(); BB != BE; ++BB) { + // Skip over landing pads. + if (LandingPads.count(BB)) + continue; + + for (BasicBlock::iterator II = BB->getFirstNonPHIOrDbg(), IE = BB->end(); + II != IE;) + if (EHExceptionInst *EI = dyn_cast<EHExceptionInst>(II++)) { + // Found a call to eh.exception, replace it with the value from any + // upstream landing pad(s). + EI->replaceAllUsesWith(SSA.GetValueAtEndOfBlock(BB)); + EI->eraseFromParent(); + ++NumExceptionValuesMoved; + } + } + + return true; +} + +/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at +/// the start of the basic block (unless there already is one, in which case +/// the existing call is returned). +Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) { + Instruction *Start = BB->getFirstNonPHIOrDbg(); + // Is this a call to eh.exception? + if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start)) + if (CI->getIntrinsicID() == Intrinsic::eh_exception) + // Reuse the existing call. + return Start; + + // Find the eh.exception intrinsic if we didn't already. + if (!ExceptionValueIntrinsic) + ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), + Intrinsic::eh_exception); + + // Create the call. + return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start); +} + +bool DwarfEHPrepare::runOnFunction(Function &Fn) { + bool Changed = false; + + // Initialize internal state. + DT = &getAnalysis<DominatorTree>(); + F = &Fn; + + // Ensure that only unwind edges end at landing pads (a landing pad is a + // basic block where an invoke unwind edge ends). + Changed |= NormalizeLandingPads(); + + // Turn unwind instructions into libcalls. + Changed |= LowerUnwinds(); + + // TODO: Move eh.selector calls to landing pads and combine them. + + // Move eh.exception calls to landing pads. + Changed |= MoveExceptionValueCalls(); + + Changed |= HandleURoRInvokes(); + + LandingPads.clear(); + + return Changed; +} |