X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FDwarfEHPrepare.cpp;h=42656fb08db1aaf2e62ac7d3983a31a5fc49a264;hb=354851651c1eae7ff749b71ba840a7d631df1f63;hp=34b1a396bb721e706e5b8c8b68b3f7e8ad55d129;hpb=3ecfc861b4365f341c5c969b40e1afccde676e6f;p=oota-llvm.git diff --git a/lib/CodeGen/DwarfEHPrepare.cpp b/lib/CodeGen/DwarfEHPrepare.cpp index 34b1a396bb7..42656fb08db 100644 --- a/lib/CodeGen/DwarfEHPrepare.cpp +++ b/lib/CodeGen/DwarfEHPrepare.cpp @@ -12,662 +12,258 @@ // //===----------------------------------------------------------------------===// -#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/ADT/BitVector.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/Analysis/CFG.h" +#include "llvm/Analysis/LibCallSemantics.h" +#include "llvm/Analysis/TargetTransformInfo.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/Module.h" +#include "llvm/Pass.h" #include "llvm/Target/TargetLowering.h" -#include "llvm/Transforms/Utils/BasicBlockUtils.h" -#include "llvm/Transforms/Utils/SSAUpdater.h" +#include "llvm/Target/TargetSubtargetInfo.h" +#include "llvm/Transforms/Utils/Local.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"); +#define DEBUG_TYPE "dwarfehprepare" + +STATISTIC(NumResumesLowered, "Number of resume calls lowered"); 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 or _Unwind_SjLj_Resume call. - Constant *URoR; - - // The EH language-specific catch-all type. - GlobalVariable *EHCatchAllValue; - - // _Unwind_Resume or the target equivalent. + // RewindFunction - _Unwind_Resume or the target equivalent. Constant *RewindFunction; - // We both use and preserve dominator info. DominatorTree *DT; + const TargetLowering *TLI; - // The function we are running on. - Function *F; - - // The landing pads for this function. - typedef SmallPtrSet 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 &Sels); - - bool HasCatchAllInSelector(IntrinsicInst *); - - /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. - void FindAllCleanupSelectors(SmallPtrSet &Sels, - SmallPtrSet &CatchAllSels); - - /// FindAllURoRInvokes - Find all URoR invokes in the function. - void FindAllURoRInvokes(SmallPtrSet &URoRInvokes); - - /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or - /// "_Unwind_SjLj_Resume" 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(); + bool InsertUnwindResumeCalls(Function &Fn); + Value *GetExceptionObject(ResumeInst *RI); + size_t + pruneUnreachableResumes(Function &Fn, + SmallVectorImpl &Resumes, + SmallVectorImpl &CleanupLPads); - /// 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 &SelCalls, - SmallPtrSet &SeenPHIs); - 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) { - initializeDominatorTreePass(*PassRegistry::getPassRegistry()); - } - virtual bool runOnFunction(Function &Fn); + // INITIALIZE_TM_PASS requires a default constructor, but it isn't used in + // practice. + DwarfEHPrepare() + : FunctionPass(ID), TM(nullptr), RewindFunction(nullptr), DT(nullptr), + TLI(nullptr) {} - // getAnalysisUsage - We need the dominator tree for handling URoR. - virtual void getAnalysisUsage(AnalysisUsage &AU) const { - AU.addRequired(); - AU.addPreserved(); + DwarfEHPrepare(const TargetMachine *TM) + : FunctionPass(ID), TM(TM), RewindFunction(nullptr), DT(nullptr), + TLI(nullptr) {} + + bool runOnFunction(Function &Fn) override; + + bool doFinalization(Module &M) override { + RewindFunction = nullptr; + return false; } - const char *getPassName() const { + void getAnalysisUsage(AnalysisUsage &AU) const override; + + const char *getPassName() const override { return "Exception handling preparation"; } - }; } // end anonymous namespace char DwarfEHPrepare::ID = 0; - -FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) { - return new DwarfEHPrepare(tm); +INITIALIZE_TM_PASS_BEGIN(DwarfEHPrepare, "dwarfehprepare", + "Prepare DWARF exceptions", false, false) +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) +INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) +INITIALIZE_TM_PASS_END(DwarfEHPrepare, "dwarfehprepare", + "Prepare DWARF exceptions", false, false) + +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(II->getArgOperand(ArgIdx)); - return GV == EHCatchAllValue; +void DwarfEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const { + AU.addRequired(); + AU.addRequired(); } -/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups. -void DwarfEHPrepare:: -FindAllCleanupSelectors(SmallPtrSet &Sels, - SmallPtrSet &CatchAllSels) { - for (Value::use_iterator - I = SelectorIntrinsic->use_begin(), - E = SelectorIntrinsic->use_end(); I != E; ++I) { - IntrinsicInst *II = cast(*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 &URoRInvokes) { - for (Value::use_iterator - I = URoR->use_begin(), - E = URoR->use_end(); I != E; ++I) { - if (InvokeInst *II = dyn_cast(*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 &Sels) { - if (!EHCatchAllValue) return false; - - if (!SelectorIntrinsic) { - SelectorIntrinsic = - Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); - if (!SelectorIntrinsic) return false; - } - - bool Changed = false; - for (SmallPtrSet::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(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 &SelCalls, - SmallPtrSet &SeenPHIs) { - bool Changed = false; - - for (Value::use_iterator - I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) { - Instruction *II = dyn_cast(*I); - if (!II || II->getParent()->getParent() != F) continue; - - if (IntrinsicInst *Sel = dyn_cast(II)) { - if (Sel->getIntrinsicID() == Intrinsic::eh_selector) - SelCalls.insert(Sel); - } else if (InvokeInst *Invoke = dyn_cast(II)) { - if (Invoke->getCalledFunction() == URoR) - URoRInvoke = true; - } else if (CastInst *CI = dyn_cast(II)) { - Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls, SeenPHIs); - } else if (PHINode *PN = dyn_cast(II)) { - if (SeenPHIs.insert(PN)) - // Don't process a PHI node more than once. - Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls, SeenPHIs); +/// GetExceptionObject - Return the exception object from the value passed into +/// the 'resume' instruction (typically an aggregate). Clean up any dead +/// instructions, including the 'resume' instruction. +Value *DwarfEHPrepare::GetExceptionObject(ResumeInst *RI) { + Value *V = RI->getOperand(0); + Value *ExnObj = nullptr; + InsertValueInst *SelIVI = dyn_cast(V); + LoadInst *SelLoad = nullptr; + InsertValueInst *ExcIVI = nullptr; + bool EraseIVIs = false; + + if (SelIVI) { + if (SelIVI->getNumIndices() == 1 && *SelIVI->idx_begin() == 1) { + ExcIVI = dyn_cast(SelIVI->getOperand(0)); + if (ExcIVI && isa(ExcIVI->getOperand(0)) && + ExcIVI->getNumIndices() == 1 && *ExcIVI->idx_begin() == 0) { + ExnObj = ExcIVI->getOperand(1); + SelLoad = dyn_cast(SelIVI->getOperand(1)); + EraseIVIs = true; + } } } - return Changed; -} + if (!ExnObj) + ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI); -/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" or -/// "_Unwind_SjLj_Resume" 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; - } + RI->eraseFromParent(); - if (!SelectorIntrinsic) { - SelectorIntrinsic = - Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector); - if (!SelectorIntrinsic) return false; - } - - SmallPtrSet Sels; - SmallPtrSet CatchAllSels; - FindAllCleanupSelectors(Sels, CatchAllSels); - - if (!URoR) { - URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow"); - if (!URoR) { - URoR = F->getParent()->getFunction("_Unwind_SjLj_Resume"); - if (!URoR) return CleanupSelectors(CatchAllSels); - } + if (EraseIVIs) { + if (SelIVI->use_empty()) + SelIVI->eraseFromParent(); + if (ExcIVI->use_empty()) + ExcIVI->eraseFromParent(); + if (SelLoad && SelLoad->use_empty()) + SelLoad->eraseFromParent(); } - SmallPtrSet URoRInvokes; - FindAllURoRInvokes(URoRInvokes); - - SmallPtrSet SelsToConvert; + return ExnObj; +} - for (SmallPtrSet::iterator - SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) { - const BasicBlock *SelBB = (*SI)->getParent(); - for (SmallPtrSet::iterator - UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) { - const BasicBlock *URoRBB = (*UI)->getParent(); - if (DT->dominates(SelBB, URoRBB)) { - SelsToConvert.insert(*SI); +/// Replace resumes that are not reachable from a cleanup landing pad with +/// unreachable and then simplify those blocks. +size_t DwarfEHPrepare::pruneUnreachableResumes( + Function &Fn, SmallVectorImpl &Resumes, + SmallVectorImpl &CleanupLPads) { + BitVector ResumeReachable(Resumes.size()); + size_t ResumeIndex = 0; + for (auto *RI : Resumes) { + for (auto *LP : CleanupLPads) { + if (isPotentiallyReachable(LP, RI, DT)) { + ResumeReachable.set(ResumeIndex); break; } } + ++ResumeIndex; } - 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(*I); - if (!EHPtr || EHPtr->getParent()->getParent() != F) continue; - - bool URoRInvoke = false; - SmallPtrSet SelCalls; - SmallPtrSet SeenPHIs; - Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls, SeenPHIs); - - 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::iterator - SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) - if (!HasCatchAllInSelector(*SI)) - SelsToConvert.insert(*SI); - } + // If everything is reachable, there is no change. + if (ResumeReachable.all()) + return Resumes.size(); + + const TargetTransformInfo &TTI = + getAnalysis().getTTI(Fn); + LLVMContext &Ctx = Fn.getContext(); + + // Otherwise, insert unreachable instructions and call simplifycfg. + size_t ResumesLeft = 0; + for (size_t I = 0, E = Resumes.size(); I < E; ++I) { + ResumeInst *RI = Resumes[I]; + if (ResumeReachable[I]) { + Resumes[ResumesLeft++] = RI; + } else { + BasicBlock *BB = RI->getParent(); + new UnreachableInst(Ctx, RI); + RI->eraseFromParent(); + SimplifyCFG(BB, TTI, 1); } } - - 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::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(B)) E = B; - - // Add exception object pointer (front). - // Add personality function (next). - // Add in any filter IDs (rest). - SmallVector 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; + Resumes.resize(ResumesLeft); + return ResumesLeft; } -/// 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(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(PT)) { - SwitchOK = false; - continue; - } - if (!isa(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(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(II); ++II) { - PHINode *PN = cast(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; - } +/// InsertUnwindResumeCalls - Convert the ResumeInsts that are still present +/// into calls to the appropriate _Unwind_Resume function. +bool DwarfEHPrepare::InsertUnwindResumeCalls(Function &Fn) { + SmallVector Resumes; + SmallVector CleanupLPads; + bool FoundLP = false; + for (BasicBlock &BB : Fn) { + if (auto *RI = dyn_cast(BB.getTerminator())) + Resumes.push_back(RI); + if (auto *LP = BB.getLandingPadInst()) { + if (LP->isCleanup()) + CleanupLPads.push_back(LP); + // Check the personality on the first landingpad. Don't do anything if + // it's for MSVC. + if (!FoundLP) { + FoundLP = true; + EHPersonality Pers = classifyEHPersonality(LP->getPersonalityFn()); + if (isMSVCEHPersonality(Pers)) + return false; } - - if (InVal == 0) { - // Different unwind edges have different values. Create a new PHI node - // in NewBB. - PHINode *NewPN = PHINode::Create(PN->getType(), - PN->getNumIncomingValues(), - 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; -} + if (Resumes.empty()) + return false; -/// 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 UnwindInsts; - - for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { - TerminatorInst *TI = I->getTerminator(); - if (isa(TI)) - UnwindInsts.push_back(TI); - } + LLVMContext &Ctx = Fn.getContext(); - if (UnwindInsts.empty()) return false; + size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads); + if (ResumesLeft == 0) + return true; // We pruned them all. // Find the rewind function if we didn't already. if (!RewindFunction) { - LLVMContext &Ctx = UnwindInsts[0]->getContext(); - std::vector - Params(1, Type::getInt8PtrTy(Ctx)); FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), - Params, false); + Type::getInt8PtrTy(Ctx), false); const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); - RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); + RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy); } - bool Changed = false; - - for (SmallVectorImpl::iterator - I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) { - TerminatorInst *TI = *I; + // Create the basic block where the _Unwind_Resume call will live. + if (ResumesLeft == 1) { + // Instead of creating a new BB and PHI node, just append the call to + // _Unwind_Resume to the end of the single resume block. + ResumeInst *RI = Resumes.front(); + BasicBlock *UnwindBB = RI->getParent(); + Value *ExnObj = GetExceptionObject(RI); - // 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); + // Call the _Unwind_Resume function. + CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB); 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; + // We never expect _Unwind_Resume to return. + new UnreachableInst(Ctx, UnwindBB); + return true; } - return Changed; -} + BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn); + PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesLeft, + "exn.obj", UnwindBB); -/// 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(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; - } - } + // Extract the exception object from the ResumeInst and add it to the PHI node + // that feeds the _Unwind_Resume call. + for (ResumeInst *RI : Resumes) { + BasicBlock *Parent = RI->getParent(); + BranchInst::Create(UnwindBB, Parent); - // 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(II)) { - SSA.Initialize(II->getType(), II->getName()); - FoundCallOutsideLandingPad = true; - break; - } + Value *ExnObj = GetExceptionObject(RI); + PN->addIncoming(ExnObj, Parent); - if (FoundCallOutsideLandingPad) - break; + ++NumResumesLowered; } - // 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(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; - } - } + // Call the function. + CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB); + CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); + // We never expect _Unwind_Resume to return. + new UnreachableInst(Ctx, UnwindBB); 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(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(); - 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(); - + assert(TM && "DWARF EH preparation requires a target machine"); + DT = &getAnalysis().getDomTree(); + TLI = TM->getSubtargetImpl(Fn)->getTargetLowering(); + bool Changed = InsertUnwindResumeCalls(Fn); + DT = nullptr; + TLI = nullptr; return Changed; }