X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FDwarfEHPrepare.cpp;h=e019dfbc8f7db0a666ae1581f8ac08121d17b8ac;hb=06bd94ca1b397e5a4bf7ebfa46ebd4b52d47f31a;hp=cfaaa70b929409e7300f3680ea0f60f9926f2d2b;hpb=f58898fd41a61d8f02657c3ecddb085c39c0d773;p=oota-llvm.git diff --git a/lib/CodeGen/DwarfEHPrepare.cpp b/lib/CodeGen/DwarfEHPrepare.cpp index cfaaa70b929..e019dfbc8f7 100644 --- a/lib/CodeGen/DwarfEHPrepare.cpp +++ b/lib/CodeGen/DwarfEHPrepare.cpp @@ -8,664 +8,257 @@ //===----------------------------------------------------------------------===// // // This pass mulches exception handling code into a form adapted to code -// generation. Required if using dwarf exception handling. +// generation. Required if using dwarf exception handling. // //===----------------------------------------------------------------------===// -#define DEBUG_TYPE "dwarfehprepare" -#include "llvm/ADT/Statistic.h" -#include "llvm/Analysis/Dominators.h" #include "llvm/CodeGen/Passes.h" -#include "llvm/Function.h" -#include "llvm/Instructions.h" -#include "llvm/IntrinsicInst.h" -#include "llvm/Module.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/Support/Compiler.h" -#include "llvm/Support/IRBuilder.h" #include "llvm/Target/TargetLowering.h" -#include "llvm/Transforms/Utils/BasicBlockUtils.h" -#include "llvm/Transforms/Utils/PromoteMemToReg.h" +#include "llvm/Target/TargetSubtargetInfo.h" +#include "llvm/Transforms/Utils/Local.h" using namespace llvm; -STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved"); -STATISTIC(NumLonelyLandingPads, "Number of landing pads with no selector"); -STATISTIC(NumLonelySelectors, "Number of lonely selectors lowered"); -STATISTIC(NumLandingPadsSplit, "Number of landing pads split"); -STATISTIC(NumSelectorsAdjusted, "Number of selector results adjusted"); -STATISTIC(NumSelectorsSimplified, "Number of selectors truncated"); -STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced"); -STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered"); +#define DEBUG_TYPE "dwarfehprepare" + +STATISTIC(NumResumesLowered, "Number of resume calls lowered"); namespace { class DwarfEHPrepare : public FunctionPass { + const TargetMachine *TM; + + // RewindFunction - _Unwind_Resume or the target equivalent. + Constant *RewindFunction; + + DominatorTree *DT; const TargetLowering *TLI; - // The eh.exception intrinsic. - Function *ExceptionIntrinsic; + bool InsertUnwindResumeCalls(Function &Fn); + Value *GetExceptionObject(ResumeInst *RI); + size_t + pruneUnreachableResumes(Function &Fn, + SmallVectorImpl &Resumes, + SmallVectorImpl &CleanupLPads); - // The eh.selector intrinsic. - Function *SelectorIntrinsic; + public: + static char ID; // Pass identification, replacement for typeid. - // The eh.typeid.for intrinsic. - Function *TypeIdIntrinsic; + // 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) {} - // _Unwind_Resume or the target equivalent. - Constant *RewindFunction; + DwarfEHPrepare(const TargetMachine *TM) + : FunctionPass(ID), TM(TM), RewindFunction(nullptr), DT(nullptr), + TLI(nullptr) {} - // _Unwind_RaiseException. - Constant *UnwindFunction; + bool runOnFunction(Function &Fn) override; - // Dominator info is used when turning stack temporaries into registers. - DominatorTree *DT; - DominanceFrontier *DF; - - // The function we are running on. - Function *F; - - // The current context. - LLVMContext *Context; - - // The personality and catch-all value for this function. - Constant *Personality; - Constant *CatchAll; - - // The landing pads for this function. - typedef SmallPtrSet BBSet; - BBSet LandingPads; - - // Stack temporary used to hold eh.exception values. - AllocaInst *ExceptionValueVar; - - bool NormalizeLandingPads(); - bool LowerUnwinds(); - bool MoveSelectorCalls(); - bool RectifySelectorCalls(); - bool MoveExceptionValueCalls(); - bool AddMissingSelectors(); - bool FinishStackTemporaries(); - bool PromoteStackTemporaries(); - - Instruction *CreateExceptionValueCall(BasicBlock *BB); - Instruction *CreateValueLoad(BasicBlock *BB); - - /// CreateReadOfExceptionValue - Return the result of the eh.exception - /// intrinsic by calling the intrinsic if in a landing pad, or loading - /// it from the exception value variable otherwise. - Instruction *CreateReadOfExceptionValue(BasicBlock *BB) { - return LandingPads.count(BB) ? - CreateExceptionValueCall(BB) : CreateValueLoad(BB); + bool doFinalization(Module &M) override { + RewindFunction = nullptr; + return false; } - public: - static char ID; // Pass identification, replacement for typeid. - DwarfEHPrepare(const TargetLowering *tli) : - FunctionPass(&ID), TLI(tli), ExceptionIntrinsic(0), - SelectorIntrinsic(0), TypeIdIntrinsic(0), RewindFunction(0), - UnwindFunction(0) {} - - virtual bool runOnFunction(Function &Fn); + void getAnalysisUsage(AnalysisUsage &AU) const override; - const char *getPassName() const { + const char *getPassName() const override { return "Exception handling preparation"; } - }; } // end anonymous namespace char DwarfEHPrepare::ID = 0; +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); +} -FunctionPass *llvm::createDwarfEHPass(const TargetLowering *tli) { - return new DwarfEHPrepare(tli); +void DwarfEHPrepare::getAnalysisUsage(AnalysisUsage &AU) const { + AU.addRequired(); + AU.addRequired(); } -/// 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; - - 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; - for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); - PI != PE; ++PI) { - TerminatorInst *PT = (*PI)->getTerminator(); - if (!isa(PT) || LPad == PT->getSuccessor(0)) { - OnlyUnwoundTo = false; - break; +/// 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; } } - - 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(*Context, - 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; - } - } - - 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 and DominanceFrontier analysis information. - if (DT) - DT->splitBlock(NewBB); - if (DF) - DF->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 UnwindInsts; - - for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { - TerminatorInst *TI = I->getTerminator(); - if (isa(TI)) - UnwindInsts.push_back(TI); } - if (UnwindInsts.empty()) return false; + if (!ExnObj) + ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI); - // Find the rewind function if we didn't already. - if (!RewindFunction) { - std::vector - Params(1, Type::getInt8PtrTy(*Context)); - FunctionType *FTy = FunctionType::get(Type::getVoidTy(*Context), - Params, false); - const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); - RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); - } - - for (SmallVectorImpl::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, - CreateReadOfExceptionValue(TI->getParent()), - "", TI); - CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); - // ...followed by an UnreachableInst. - new UnreachableInst(*Context, TI); + RI->eraseFromParent(); - // Nuke the unwind instruction. - TI->eraseFromParent(); - ++NumUnwindsLowered; + if (EraseIVIs) { + if (SelIVI->use_empty()) + SelIVI->eraseFromParent(); + if (ExcIVI->use_empty()) + ExcIVI->eraseFromParent(); + if (SelLoad && SelLoad->use_empty()) + SelLoad->eraseFromParent(); } - return true; + return ExnObj; } -/// MoveSelectorCalls - Make sure that every call to eh.selector occurs in its -/// own landing pad, the landing pad corresponding to the exception object. -bool DwarfEHPrepare::MoveSelectorCalls() { - // If the eh.selector intrinsic is not declared in the module then there is - // nothing to do. Speed up compilation by checking for this common case. - if (!F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_selector))) - return false; - - // TODO: There is a lot of room for optimization here. - - bool Changed = false; - BasicBlock *UnrBB = 0; - - for (Function::iterator BB = F->begin(); BB != F->end(); ++BB) { - // If this basic block is not a landing pad then synthesize a landing pad - // for every selector in it. - bool SynthesizeLandingPad = !LandingPads.count(BB); - - for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); II != IE; ++II) { - EHSelectorInst *SI = dyn_cast(II); - // Only interested in eh.selector calls. - if (!SI) - continue; - - // Note the personality and catch-all for later use. - Personality = cast(SI->getOperand(2)); - CatchAll = cast(SI->getOperand(SI->getNumOperands() - 1) - ->stripPointerCasts()); - - // The exception object. - Value *Exception = SI->getOperand(1); - - if (!SynthesizeLandingPad) { - // Did the exception come from unwinding to this landing pad or another? - // If it comes from a different landing pad then we need to synthesize a - // new landing pad for the selector. - EHExceptionInst *EI = dyn_cast(Exception); - SynthesizeLandingPad = !EI || EI->getParent() != BB; - } - - if (!SynthesizeLandingPad) { - // This is the first selector in this landing pad, and it is the landing - // pad corresponding to the exception object. No need to do anything to - // this selector, but any subsequent selectors in this landing pad will - // need their own invoke in order to make them independent of this one. - SynthesizeLandingPad = true; - continue; - } - - // Rethrow the exception and catch it again, generating a landing pad for - // this selector to live in. - - // Find _Unwind_RaiseException if we didn't already. - if (!UnwindFunction) { - std::vector ArgTys(1, Type::getInt8PtrTy(*Context)); - const FunctionType *FTy = - FunctionType::get(Type::getInt32Ty(*Context), ArgTys, true); - - const char *Name = "_Unwind_RaiseException"; - UnwindFunction = F->getParent()->getOrInsertFunction(Name, FTy); - } - - // Create a basic block containing only an unreachable instruction if we - // didn't already. - if (!UnrBB) { - UnrBB = BasicBlock::Create(*Context, "unreachable", F); - new UnreachableInst(*Context, UnrBB); +/// 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; } - - // Split the basic block before the selector. - BasicBlock *NewBB = SplitBlock(BB, SI, this); - - // Replace the terminator with an invoke of _Unwind_RaiseException. - BB->getTerminator()->eraseFromParent(); - InvokeInst::Create(UnwindFunction, UnrBB, NewBB, &Exception, - 1 + &Exception, "", BB); - - // The split off basic block is now a landing pad. - LandingPads.insert(NewBB); - - // Replace the exception argument in the selector call with a call to - // eh.exception. This is not really necessary but it makes things more - // regular. - Exception = CreateExceptionValueCall(NewBB); - SI->setOperand(1, Exception); - - ++NumLonelySelectors; - Changed = true; - - // All instructions still in the original basic block have been scanned. - // Move on to the next basic block. - break; } + ++ResumeIndex; } - return Changed; + // 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); + } + } + Resumes.resize(ResumesLeft); + return ResumesLeft; } -/// RectifySelectorCalls - Remove useless catch-all clauses from the ends of -/// selectors, or correct the selector result for the presence of the catch-all -/// if it is really needed. -bool DwarfEHPrepare::RectifySelectorCalls() { - // If the eh.selector intrinsic is not declared in the module then there is - // nothing to do. Speed up compilation by checking for this common case. - if (!F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_selector))) - return false; - - bool Changed = false; - - for (BBSet::iterator I = LandingPads.begin(), E = LandingPads.end(); I != E; - ++I) - for (BasicBlock::iterator II = (*I)->begin(), IE = (*I)->end(); II != IE; ) - if (EHSelectorInst *SI = dyn_cast(II++)) { - // Found a call to eh.selector. Check whether it has a catch-all in the - // middle. - unsigned LastIndex = 0; - for (unsigned i = 3, e = SI->getNumOperands() - 1; i < e; ++i) { - Value *V = SI->getOperand(i); - if (V->stripPointerCasts() == CatchAll) { - // A catch-all. The catch-all at the end was not needed. - LastIndex = i; - break; - } else if (ConstantInt *FilterLength = dyn_cast(V)) { - // A cleanup or a filter. - unsigned Length = FilterLength->getZExtValue(); - if (Length == 0) - // A cleanup - skip it. - continue; - if (Length == 1) { - // A catch-all filter. Drop everything that follows. - LastIndex = i; - break; - } - // A filter, skip over the typeinfos. - i += Length - 1; - } - } - - if (LastIndex) { - // Drop the pointless catch-all from the end. In fact drop everything - // after LastIndex as an optimization. - SmallVector Args; - Args.reserve(LastIndex); - for (unsigned i = 1; i <= LastIndex; ++i) - Args.push_back(SI->getOperand(i)); - CallInst *CI = CallInst::Create(SI->getOperand(0), Args.begin(), - Args.end(), "", SI); - CI->takeName(SI); - SI->replaceAllUsesWith(CI); - SI->eraseFromParent(); - ++NumSelectorsSimplified; - } else if (!isa(CatchAll) && // Not a cleanup. - !SI->use_empty()) { - // Correct the selector value to return zero if the catch-all matches. - Constant *Zero = ConstantInt::getNullValue(Type::getInt32Ty(*Context)); - - // Create the new selector value, with placeholders instead of the - // real operands and make everyone use it. The reason for this round - // about approach is that the computation of the new value makes use - // of the old value, so we can't just compute it then do RAUW. - SelectInst *S = SelectInst::Create(ConstantInt::getFalse(*Context), - Zero, Zero, "", II); - SI->replaceAllUsesWith(S); - - // Now calculate the operands of the select. - IRBuilder<> Builder(*I, S); - - // Find the eh.typeid.for intrinsic if we didn't already. - if (!TypeIdIntrinsic) - TypeIdIntrinsic = Intrinsic::getDeclaration(F->getParent(), - Intrinsic::eh_typeid_for); - - // Obtain the id of the catch-all. - Value *CatchAllId = Builder.CreateCall(TypeIdIntrinsic, - ConstantExpr::getBitCast(CatchAll, Type::getInt8PtrTy(*Context))); - - // Compare it with the original selector result. If it matched then - // the selector result is zero, otherwise it is the original selector. - Value *MatchesCatchAll = Builder.CreateICmpEQ(SI, CatchAllId); - S->setOperand(0, MatchesCatchAll); - S->setOperand(2, SI); - ++NumSelectorsAdjusted; - } - - Changed = true; - break; - } - - return Changed; -} +/// 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; + 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); + } -/// Make sure every landing pad has a selector in it. -bool DwarfEHPrepare::AddMissingSelectors() { - if (!Personality) - // We only know how to codegen invokes if there is a personality. - // FIXME: This results in wrong code. + if (Resumes.empty()) return false; - bool Changed = false; - - for (BBSet::iterator I = LandingPads.begin(), E = LandingPads.end(); I != E; - ++I) { - bool FoundSelector = false; - - // Check whether the landing pad already contains a call to eh.selector. - for (BasicBlock::iterator II = (*I)->begin(), IE = (*I)->end(); II != IE; - ++II) - if (isa(II)) { - FoundSelector = true; - break; - } - - if (FoundSelector) - continue; - - // Find the eh.selector intrinsic if we didn't already. - if (!SelectorIntrinsic) - SelectorIntrinsic = Intrinsic::getDeclaration(F->getParent(), - Intrinsic::eh_selector); + // Check the personality, don't do anything if it's for MSVC. + EHPersonality Pers = classifyEHPersonality(Fn.getPersonalityFn()); + if (isMSVCEHPersonality(Pers)) + return false; - // Get the exception object. - Instruction *Exception = CreateExceptionValueCall(*I); + LLVMContext &Ctx = Fn.getContext(); - Value *Args[3] = { Exception, Personality, CatchAll }; - CallInst *Selector = CallInst::Create(SelectorIntrinsic, Args, Args + 3); - Selector->insertAfter(Exception); + size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads); + if (ResumesLeft == 0) + return true; // We pruned them all. - ++NumLonelyLandingPads; - Changed = true; + // Find the rewind function if we didn't already. + if (!RewindFunction) { + FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx), + Type::getInt8PtrTy(Ctx), false); + const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); + RewindFunction = Fn.getParent()->getOrInsertFunction(RewindName, FTy); } - return Changed; -} + // 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); -/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from -/// landing pads by replacing calls outside of landing pads with loads from a -/// stack temporary. 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 (!ExceptionIntrinsic && - !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) - return false; + // Call the _Unwind_Resume function. + CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB); + CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); - bool Changed = false; - - for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) { - for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;) - if (IntrinsicInst *CI = dyn_cast(II++)) - if (CI->getIntrinsicID() == Intrinsic::eh_exception) { - if (!CI->use_empty()) { - Value *ExceptionValue = CreateReadOfExceptionValue(BB); - if (CI == ExceptionValue) { - // The call was at the start of a landing pad - leave it alone. - assert(LandingPads.count(BB) && - "Created eh.exception call outside landing pad!"); - continue; - } - CI->replaceAllUsesWith(ExceptionValue); - } - CI->eraseFromParent(); - ++NumExceptionValuesMoved; - 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); -/// FinishStackTemporaries - If we introduced a stack variable to hold the -/// exception value then initialize it in each landing pad. -bool DwarfEHPrepare::FinishStackTemporaries() { - if (!ExceptionValueVar) - // Nothing to do. - return false; + // 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); - bool Changed = false; + Value *ExnObj = GetExceptionObject(RI); + PN->addIncoming(ExnObj, Parent); - // Make sure that there is a store of the exception value at the start of - // each landing pad. - for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end(); - LI != LE; ++LI) { - Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI); - Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar); - Store->insertAfter(ExceptionValue); - Changed = true; + ++NumResumesLowered; } - return Changed; -} - -/// PromoteStackTemporaries - Turn any stack temporaries we introduced into -/// registers if possible. -bool DwarfEHPrepare::PromoteStackTemporaries() { - if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) { - // Turn the exception temporary into registers and phi nodes if possible. - std::vector Allocas(1, ExceptionValueVar); - PromoteMemToReg(Allocas, *DT, *DF, *Context); - return true; - } - return false; -} - -/// 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->getFirstNonPHI(); - // 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 (!ExceptionIntrinsic) - ExceptionIntrinsic = Intrinsic::getDeclaration(F->getParent(), - Intrinsic::eh_exception); - - // Create the call. - return CallInst::Create(ExceptionIntrinsic, "eh.value.call", Start); -} - -/// CreateValueLoad - Insert a load of the exception value stack variable -/// (creating it if necessary) at the start of the basic block (unless -/// there already is a load, in which case the existing load is returned). -Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) { - Instruction *Start = BB->getFirstNonPHI(); - // Is this a load of the exception temporary? - if (ExceptionValueVar) - if (LoadInst* LI = dyn_cast(Start)) - if (LI->getPointerOperand() == ExceptionValueVar) - // Reuse the existing load. - return Start; - - // Create the temporary if we didn't already. - if (!ExceptionValueVar) { - ExceptionValueVar = new AllocaInst(PointerType::getUnqual( - Type::getInt8Ty(*Context)), "eh.value", F->begin()->begin()); - ++NumStackTempsIntroduced; - } + // Call the function. + CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB); + CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); - // Load the value. - return new LoadInst(ExceptionValueVar, "eh.value.load", Start); + // We never expect _Unwind_Resume to return. + new UnreachableInst(Ctx, UnwindBB); + return true; } bool DwarfEHPrepare::runOnFunction(Function &Fn) { - bool Changed = false; - - // Initialize internal state. - DT = getAnalysisIfAvailable(); - DF = getAnalysisIfAvailable(); - ExceptionValueVar = 0; - Personality = 0; - CatchAll = 0; - Context = &Fn.getContext(); - 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(); - - // Make sure that every call to eh.selector occurs in its own landing pad. - Changed |= MoveSelectorCalls(); - - // Remove useless catch-all clauses from the ends of selectors, or correct the - // selector result for the presence of the catch-all if it is really needed. - Changed |= RectifySelectorCalls(); - - // Make sure every landing pad has a selector in it. - Changed |= AddMissingSelectors(); - - // Move eh.exception calls to landing pads. - Changed |= MoveExceptionValueCalls(); - - // Initialize any stack temporaries we introduced. - Changed |= FinishStackTemporaries(); - - // Turn any stack temporaries into registers if possible. -//TODO if (!CompileFast) -//TODO Changed |= PromoteStackTemporaries(); - - 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; }