X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FDwarfEHPrepare.cpp;h=42656fb08db1aaf2e62ac7d3983a31a5fc49a264;hb=db573736fdcd5cb377c2e585039beaf665bcf64b;hp=5fa8dcea3467992f9563e54bb9cb12328a2e464f;hpb=9adc0abad3c3ed40a268ccbcee0c74cb9e1359fe;p=oota-llvm.git diff --git a/lib/CodeGen/DwarfEHPrepare.cpp b/lib/CodeGen/DwarfEHPrepare.cpp index 5fa8dcea346..42656fb08db 100644 --- a/lib/CodeGen/DwarfEHPrepare.cpp +++ b/lib/CodeGen/DwarfEHPrepare.cpp @@ -8,391 +8,262 @@ //===----------------------------------------------------------------------===// // // 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/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(NumLandingPadsSplit, "Number of landing pads split"); -STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered"); -STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved"); -STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced"); +#define DEBUG_TYPE "dwarfehprepare" + +STATISTIC(NumResumesLowered, "Number of resume calls lowered"); namespace { - class VISIBILITY_HIDDEN DwarfEHPrepare : public FunctionPass { - const TargetLowering *TLI; - bool CompileFast; + class DwarfEHPrepare : public FunctionPass { + const TargetMachine *TM; - // The eh.exception intrinsic. - Function *ExceptionValueIntrinsic; - - // _Unwind_Resume or the target equivalent. + // RewindFunction - _Unwind_Resume or the target equivalent. Constant *RewindFunction; - // Dominator info is used when turning stack temporaries into registers. DominatorTree *DT; - DominanceFrontier *DF; + const TargetLowering *TLI; - // The function we are running on. - Function *F; + bool InsertUnwindResumeCalls(Function &Fn); + Value *GetExceptionObject(ResumeInst *RI); + size_t + pruneUnreachableResumes(Function &Fn, + SmallVectorImpl &Resumes, + SmallVectorImpl &CleanupLPads); - // The landing pads for this function. - typedef SmallPtrSet BBSet; - BBSet LandingPads; + public: + static char ID; // Pass identification, replacement for typeid. - // Stack temporary used to hold eh.exception values. - AllocaInst *ExceptionValueVar; + // 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) {} - bool NormalizeLandingPads(); - bool LowerUnwinds(); - bool MoveExceptionValueCalls(); - bool FinishStackTemporaries(); - bool PromoteStackTemporaries(); + DwarfEHPrepare(const TargetMachine *TM) + : FunctionPass(ID), TM(TM), RewindFunction(nullptr), DT(nullptr), + TLI(nullptr) {} - Instruction *CreateExceptionValueCall(BasicBlock *BB); - Instruction *CreateValueLoad(BasicBlock *BB); + bool runOnFunction(Function &Fn) override; - /// 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, bool fast) : - FunctionPass(&ID), TLI(tli), CompileFast(fast), - ExceptionValueIntrinsic(0), RewindFunction(0) {} - - virtual bool runOnFunction(Function &Fn); - - // getAnalysisUsage - We need dominance frontiers for memory promotion. - virtual void getAnalysisUsage(AnalysisUsage &AU) const { - if (!CompileFast) - AU.addRequired(); - AU.addPreserved(); - if (!CompileFast) - AU.addRequired(); - AU.addPreserved(); - } + 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, bool fast) { - return new DwarfEHPrepare(tli, fast); +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. -/// 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(LPad->getName() + "_unwind_edge"); + if (!ExnObj) + ExnObj = ExtractValueInst::Create(RI->getOperand(0), 0, "exn.obj", RI); - // Insert it into the function right before the original landing pad. - LPad->getParent()->getBasicBlockList().insert(LPad, NewBB); + RI->eraseFromParent(); - // 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 (EraseIVIs) { + if (SelIVI->use_empty()) + SelIVI->eraseFromParent(); + if (ExcIVI->use_empty()) + ExcIVI->eraseFromParent(); + if (SelLoad && SelLoad->use_empty()) + SelLoad->eraseFromParent(); + } - // 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; - } - } + return ExnObj; +} - 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; +/// 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; } - - // 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; + ++ResumeIndex; } - 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() { - bool Changed = false; - - for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) { - TerminatorInst *TI = I->getTerminator(); - if (!isa(TI)) - continue; - - // Replace the unwind instruction with a call to _Unwind_Resume (or the - // appropriate target equivalent) followed by an UnreachableInst. - - // Find the rewind function if we didn't already. - if (!RewindFunction) { - std::vector Params(1, PointerType::getUnqual(Type::Int8Ty)); - FunctionType *FTy = FunctionType::get(Type::VoidTy, Params, false); - const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME); - RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy); + // 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); } - - // Create the call... - CallInst::Create(RewindFunction, CreateReadOfExceptionValue(I), "", TI); - // ...followed by an UnreachableInst. - new UnreachableInst(TI); - - // Nuke the unwind instruction. - TI->eraseFromParent(); - ++NumUnwindsLowered; - Changed = true; } - - return Changed; + Resumes.resize(ResumesLeft); + return ResumesLeft; } -/// 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 (!ExceptionValueIntrinsic && - !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception))) - return false; - - 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; - } +/// 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; + } + } } - return Changed; -} - -/// 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. + if (Resumes.empty()) return false; - bool Changed = false; + LLVMContext &Ctx = Fn.getContext(); - // 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; - } - - return Changed; -} + size_t ResumesLeft = pruneUnreachableResumes(Fn, Resumes, CleanupLPads); + if (ResumesLeft == 0) + return true; // We pruned them all. -/// 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; + // 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 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 (!ExceptionValueIntrinsic) - ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(), - Intrinsic::eh_exception); - - // Create the call. - return CallInst::Create(ExceptionValueIntrinsic, "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(*Context, - PointerType::getUnqual(Type::Int8Ty), - "eh.value", F->begin()->begin()); - ++NumStackTempsIntroduced; - } - - // Load the value. - return new LoadInst(ExceptionValueVar, "eh.value.load", Start); -} -bool DwarfEHPrepare::runOnFunction(Function &Fn) { - bool Changed = false; + // 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); - // Initialize internal state. - DT = getAnalysisIfAvailable(); - DF = getAnalysisIfAvailable(); - ExceptionValueVar = 0; - F = &Fn; + // Call the _Unwind_Resume function. + CallInst *CI = CallInst::Create(RewindFunction, ExnObj, "", UnwindBB); + CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); - // Ensure that only unwind edges end at landing pads (a landing pad is a - // basic block where an invoke unwind edge ends). - Changed |= NormalizeLandingPads(); + // We never expect _Unwind_Resume to return. + new UnreachableInst(Ctx, UnwindBB); + return true; + } - // Turn unwind instructions into libcalls. - Changed |= LowerUnwinds(); + BasicBlock *UnwindBB = BasicBlock::Create(Ctx, "unwind_resume", &Fn); + PHINode *PN = PHINode::Create(Type::getInt8PtrTy(Ctx), ResumesLeft, + "exn.obj", UnwindBB); - // TODO: Move eh.selector calls to landing pads and combine them. + // 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); - // Move eh.exception calls to landing pads. - Changed |= MoveExceptionValueCalls(); + Value *ExnObj = GetExceptionObject(RI); + PN->addIncoming(ExnObj, Parent); - // Initialize any stack temporaries we introduced. - Changed |= FinishStackTemporaries(); + ++NumResumesLowered; + } - // Turn any stack temporaries into registers if possible. - if (!CompileFast) - Changed |= PromoteStackTemporaries(); + // Call the function. + CallInst *CI = CallInst::Create(RewindFunction, PN, "", UnwindBB); + CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME)); - LandingPads.clear(); + // We never expect _Unwind_Resume to return. + new UnreachableInst(Ctx, UnwindBB); + return true; +} +bool DwarfEHPrepare::runOnFunction(Function &Fn) { + 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; }