X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FWinEHPrepare.cpp;h=fefb444cea9dca744b9fcf24b38caefefff24d63;hb=66ef931b4346fdd73f82f6d6c24391f2ef923943;hp=0d26ed333ca7134928023f870ce50082299c389f;hpb=ecc0eab4a8ddb12dfd8fca8ab50c45c8a5b931a8;p=oota-llvm.git diff --git a/lib/CodeGen/WinEHPrepare.cpp b/lib/CodeGen/WinEHPrepare.cpp index 0d26ed333ca..fefb444cea9 100644 --- a/lib/CodeGen/WinEHPrepare.cpp +++ b/lib/CodeGen/WinEHPrepare.cpp @@ -23,6 +23,7 @@ #include "llvm/ADT/SetVector.h" #include "llvm/ADT/Triple.h" #include "llvm/ADT/TinyPtrVector.h" +#include "llvm/Analysis/CFG.h" #include "llvm/Analysis/LibCallSemantics.h" #include "llvm/Analysis/TargetLibraryInfo.h" #include "llvm/CodeGen/WinEHFuncInfo.h" @@ -40,6 +41,7 @@ #include "llvm/Transforms/Utils/Cloning.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/Transforms/Utils/PromoteMemToReg.h" +#include "llvm/Transforms/Utils/SSAUpdater.h" #include using namespace llvm; @@ -47,6 +49,17 @@ using namespace llvm::PatternMatch; #define DEBUG_TYPE "winehprepare" +static cl::opt DisableDemotion( + "disable-demotion", cl::Hidden, + cl::desc( + "Clone multicolor basic blocks but do not demote cross funclet values"), + cl::init(false)); + +static cl::opt DisableCleanups( + "disable-cleanups", cl::Hidden, + cl::desc("Do not remove implausible terminators or other similar cleanups"), + cl::init(false)); + namespace { // This map is used to model frame variable usage during outlining, to @@ -120,6 +133,26 @@ private: BasicBlock *EndBB); void processSEHCatchHandler(CatchHandler *Handler, BasicBlock *StartBB); + void insertPHIStores(PHINode *OriginalPHI, AllocaInst *SpillSlot); + void + insertPHIStore(BasicBlock *PredBlock, Value *PredVal, AllocaInst *SpillSlot, + SmallVectorImpl> &Worklist); + AllocaInst *insertPHILoads(PHINode *PN, Function &F); + void replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot, + DenseMap &Loads, Function &F); + void demoteNonlocalUses(Value *V, std::set &ColorsForBB, + Function &F); + bool prepareExplicitEH(Function &F, + SmallVectorImpl &EntryBlocks); + void colorFunclets(Function &F, SmallVectorImpl &EntryBlocks); + void demotePHIsOnFunclets(Function &F); + void demoteUsesBetweenFunclets(Function &F); + void demoteArgumentUses(Function &F); + void cloneCommonBlocks(Function &F, + SmallVectorImpl &EntryBlocks); + void removeImplausibleTerminators(Function &F); + void cleanupPreparedFunclets(Function &F); + void verifyPreparedFunclets(Function &F); Triple TheTriple; @@ -160,6 +193,10 @@ private: DenseMap HandlerToParentFP; AllocaInst *SEHExceptionCodeSlot = nullptr; + + std::map> BlockColors; + std::map> FuncletBlocks; + std::map> FuncletChildren; }; class WinEHFrameVariableMaterializer : public ValueMaterializer { @@ -361,30 +398,46 @@ FunctionPass *llvm::createWinEHPass(const TargetMachine *TM) { } bool WinEHPrepare::runOnFunction(Function &Fn) { + if (!Fn.hasPersonalityFn()) + return false; + // No need to prepare outlined handlers. if (Fn.hasFnAttribute("wineh-parent")) return false; + // Classify the personality to see what kind of preparation we need. + Personality = classifyEHPersonality(Fn.getPersonalityFn()); + + // Do nothing if this is not an MSVC personality. + if (!isMSVCEHPersonality(Personality)) + return false; + SmallVector LPads; SmallVector Resumes; + SmallVector EntryBlocks; + bool ForExplicitEH = false; for (BasicBlock &BB : Fn) { - if (auto *LP = BB.getLandingPadInst()) + Instruction *First = BB.getFirstNonPHI(); + if (auto *LP = dyn_cast(First)) { LPads.push_back(LP); + } else if (First->isEHPad()) { + if (!ForExplicitEH) + EntryBlocks.push_back(&Fn.getEntryBlock()); + if (!isa(First) && !isa(First)) + EntryBlocks.push_back(&BB); + ForExplicitEH = true; + } if (auto *Resume = dyn_cast(BB.getTerminator())) Resumes.push_back(Resume); } + if (ForExplicitEH) + return prepareExplicitEH(Fn, EntryBlocks); + // No need to prepare functions that lack landing pads. if (LPads.empty()) return false; - // Classify the personality to see what kind of preparation we need. - Personality = classifyEHPersonality(Fn.getPersonalityFn()); - - // Do nothing if this is not an MSVC personality. - if (!isMSVCEHPersonality(Personality)) - return false; - DT = &getAnalysis().getDomTree(); LibInfo = &getAnalysis().getTLI(); @@ -2146,7 +2199,7 @@ void WinEHPrepare::mapLandingPadBlocks(LandingPadInst *LPad, // Under some circumstances optimized IR will flow unconditionally into a // handler block without checking the selector. This can only happen if // the landing pad has a catch-all handler and the handler for the - // preceeding catch clause is identical to the catch-call handler + // preceding catch clause is identical to the catch-call handler // (typically an empty catch). In this case, the handler must be shared // by all remaining clauses. if (isa( @@ -2549,14 +2602,47 @@ struct WinEHNumbering { }; } -void WinEHNumbering::createUnwindMapEntry(int ToState, ActionHandler *AH) { +static int addUnwindMapEntry(WinEHFuncInfo &FuncInfo, int ToState, + const Value *V) { WinEHUnwindMapEntry UME; UME.ToState = ToState; - if (auto *CH = dyn_cast_or_null(AH)) - UME.Cleanup = cast(CH->getHandlerBlockOrFunc()); - else - UME.Cleanup = nullptr; + UME.Cleanup = V; FuncInfo.UnwindMap.push_back(UME); + return FuncInfo.getLastStateNumber(); +} + +static void addTryBlockMapEntry(WinEHFuncInfo &FuncInfo, int TryLow, + int TryHigh, int CatchHigh, + ArrayRef Handlers) { + WinEHTryBlockMapEntry TBME; + TBME.TryLow = TryLow; + TBME.TryHigh = TryHigh; + TBME.CatchHigh = CatchHigh; + assert(TBME.TryLow <= TBME.TryHigh); + for (const CatchPadInst *CPI : Handlers) { + WinEHHandlerType HT; + Constant *TypeInfo = cast(CPI->getArgOperand(0)); + if (TypeInfo->isNullValue()) + HT.TypeDescriptor = nullptr; + else + HT.TypeDescriptor = cast(TypeInfo->stripPointerCasts()); + HT.Adjectives = cast(CPI->getArgOperand(1))->getZExtValue(); + HT.Handler = CPI->getNormalDest(); + HT.CatchObjRecoverIdx = -2; + if (isa(CPI->getArgOperand(2))) + HT.CatchObj.Alloca = nullptr; + else + HT.CatchObj.Alloca = cast(CPI->getArgOperand(2)); + TBME.HandlerArray.push_back(HT); + } + FuncInfo.TryBlockMap.push_back(TBME); +} + +void WinEHNumbering::createUnwindMapEntry(int ToState, ActionHandler *AH) { + Value *V = nullptr; + if (auto *CH = dyn_cast_or_null(AH)) + V = cast(CH->getHandlerBlockOrFunc()); + addUnwindMapEntry(FuncInfo, ToState, V); } void WinEHNumbering::createTryBlockMapEntry(int TryLow, int TryHigh, @@ -2573,7 +2659,8 @@ void WinEHNumbering::createTryBlockMapEntry(int TryLow, int TryHigh, continue; int N; for (N = 0; N < NumHandlers; ++N) { - if (Entry.HandlerArray[N].Handler != Handlers[N]->getHandlerBlockOrFunc()) + if (Entry.HandlerArray[N].Handler.get() != + Handlers[N]->getHandlerBlockOrFunc()) break; // breaks out of inner loop } // If all the handlers match, this is what we were looking for. @@ -2621,6 +2708,7 @@ void WinEHNumbering::createTryBlockMapEntry(int TryLow, int TryHigh, } HT.Handler = cast(CH->getHandlerBlockOrFunc()); HT.CatchObjRecoverIdx = CH->getExceptionVarIndex(); + HT.CatchObj.Alloca = nullptr; TBME.HandlerArray.push_back(HT); } FuncInfo.TryBlockMap.push_back(TBME); @@ -2812,7 +2900,7 @@ void WinEHNumbering::calculateStateNumbers(const Function &F) { continue; processCallSite(ActionList, II); ActionList.clear(); - FuncInfo.LandingPadStateMap[LPI] = currentEHNumber(); + FuncInfo.EHPadStateMap[LPI] = currentEHNumber(); DEBUG(dbgs() << "Assigning state " << currentEHNumber() << " to landing pad at " << LPI->getParent()->getName() << '\n'); @@ -2876,10 +2964,233 @@ void WinEHNumbering::findActionRootLPads(const Function &F) { } } +static const CatchPadInst *getSingleCatchPadPredecessor(const BasicBlock *BB) { + for (const BasicBlock *PredBlock : predecessors(BB)) + if (auto *CPI = dyn_cast(PredBlock->getFirstNonPHI())) + return CPI; + return nullptr; +} + +/// Find all the catchpads that feed directly into the catchendpad. Frontends +/// using this personality should ensure that each catchendpad and catchpad has +/// one or zero catchpad predecessors. +/// +/// The following C++ generates the IR after it: +/// try { +/// } catch (A) { +/// } catch (B) { +/// } +/// +/// IR: +/// %catchpad.A +/// catchpad [i8* A typeinfo] +/// to label %catch.A unwind label %catchpad.B +/// %catchpad.B +/// catchpad [i8* B typeinfo] +/// to label %catch.B unwind label %endcatches +/// %endcatches +/// catchendblock unwind to caller +void findCatchPadsForCatchEndPad( + const BasicBlock *CatchEndBB, + SmallVectorImpl &Handlers) { + const CatchPadInst *CPI = getSingleCatchPadPredecessor(CatchEndBB); + while (CPI) { + Handlers.push_back(CPI); + CPI = getSingleCatchPadPredecessor(CPI->getParent()); + } + // We've pushed these back into reverse source order. Reverse them to get + // the list back into source order. + std::reverse(Handlers.begin(), Handlers.end()); +} + +// Given BB which ends in an unwind edge, return the EHPad that this BB belongs +// to. If the unwind edge came from an invoke, return null. +static const BasicBlock *getEHPadFromPredecessor(const BasicBlock *BB) { + const TerminatorInst *TI = BB->getTerminator(); + if (isa(TI)) + return nullptr; + if (TI->isEHPad()) + return BB; + return cast(TI)->getCleanupPad()->getParent(); +} + +static void calculateExplicitCXXStateNumbers(WinEHFuncInfo &FuncInfo, + const BasicBlock &BB, + int ParentState) { + assert(BB.isEHPad()); + const Instruction *FirstNonPHI = BB.getFirstNonPHI(); + // All catchpad instructions will be handled when we process their + // respective catchendpad instruction. + if (isa(FirstNonPHI)) + return; + + if (isa(FirstNonPHI)) { + SmallVector Handlers; + findCatchPadsForCatchEndPad(&BB, Handlers); + const BasicBlock *FirstTryPad = Handlers.front()->getParent(); + int TryLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr); + FuncInfo.EHPadStateMap[Handlers.front()] = TryLow; + for (const BasicBlock *PredBlock : predecessors(FirstTryPad)) + if ((PredBlock = getEHPadFromPredecessor(PredBlock))) + calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, TryLow); + int CatchLow = addUnwindMapEntry(FuncInfo, ParentState, nullptr); + + // catchpads are separate funclets in C++ EH due to the way rethrow works. + // In SEH, they aren't, so no invokes will unwind to the catchendpad. + FuncInfo.EHPadStateMap[FirstNonPHI] = CatchLow; + int TryHigh = CatchLow - 1; + for (const BasicBlock *PredBlock : predecessors(&BB)) + if ((PredBlock = getEHPadFromPredecessor(PredBlock))) + calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, CatchLow); + int CatchHigh = FuncInfo.getLastStateNumber(); + addTryBlockMapEntry(FuncInfo, TryLow, TryHigh, CatchHigh, Handlers); + DEBUG(dbgs() << "TryLow[" << FirstTryPad->getName() << "]: " << TryLow + << '\n'); + DEBUG(dbgs() << "TryHigh[" << FirstTryPad->getName() << "]: " << TryHigh + << '\n'); + DEBUG(dbgs() << "CatchHigh[" << FirstTryPad->getName() << "]: " << CatchHigh + << '\n'); + } else if (isa(FirstNonPHI)) { + int CleanupState = addUnwindMapEntry(FuncInfo, ParentState, &BB); + FuncInfo.EHPadStateMap[FirstNonPHI] = CleanupState; + DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB " + << BB.getName() << '\n'); + for (const BasicBlock *PredBlock : predecessors(&BB)) + if ((PredBlock = getEHPadFromPredecessor(PredBlock))) + calculateExplicitCXXStateNumbers(FuncInfo, *PredBlock, CleanupState); + } else if (isa(FirstNonPHI)) { + report_fatal_error("Not yet implemented!"); + } else { + llvm_unreachable("unexpected EH Pad!"); + } +} + +static int addSEHHandler(WinEHFuncInfo &FuncInfo, int ParentState, + const Function *Filter, const BasicBlock *Handler) { + SEHUnwindMapEntry Entry; + Entry.ToState = ParentState; + Entry.Filter = Filter; + Entry.Handler = Handler; + FuncInfo.SEHUnwindMap.push_back(Entry); + return FuncInfo.SEHUnwindMap.size() - 1; +} + +static void calculateExplicitSEHStateNumbers(WinEHFuncInfo &FuncInfo, + const BasicBlock &BB, + int ParentState) { + assert(BB.isEHPad()); + const Instruction *FirstNonPHI = BB.getFirstNonPHI(); + // All catchpad instructions will be handled when we process their + // respective catchendpad instruction. + if (isa(FirstNonPHI)) + return; + + if (isa(FirstNonPHI)) { + // Extract the filter function and the __except basic block and create a + // state for them. + SmallVector Handlers; + findCatchPadsForCatchEndPad(&BB, Handlers); + assert(Handlers.size() == 1 && + "SEH doesn't have multiple handlers per __try"); + const CatchPadInst *CPI = Handlers.front(); + const BasicBlock *CatchPadBB = CPI->getParent(); + const Function *Filter = + cast(CPI->getArgOperand(0)->stripPointerCasts()); + int TryState = + addSEHHandler(FuncInfo, ParentState, Filter, CPI->getNormalDest()); + + // Everything in the __try block uses TryState as its parent state. + FuncInfo.EHPadStateMap[CPI] = TryState; + DEBUG(dbgs() << "Assigning state #" << TryState << " to BB " + << CatchPadBB->getName() << '\n'); + for (const BasicBlock *PredBlock : predecessors(CatchPadBB)) + if ((PredBlock = getEHPadFromPredecessor(PredBlock))) + calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, TryState); + + // Everything in the __except block unwinds to ParentState, just like code + // outside the __try. + FuncInfo.EHPadStateMap[FirstNonPHI] = ParentState; + DEBUG(dbgs() << "Assigning state #" << ParentState << " to BB " + << BB.getName() << '\n'); + for (const BasicBlock *PredBlock : predecessors(&BB)) + if ((PredBlock = getEHPadFromPredecessor(PredBlock))) + calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, ParentState); + } else if (isa(FirstNonPHI)) { + int CleanupState = + addSEHHandler(FuncInfo, ParentState, /*Filter=*/nullptr, &BB); + FuncInfo.EHPadStateMap[FirstNonPHI] = CleanupState; + DEBUG(dbgs() << "Assigning state #" << CleanupState << " to BB " + << BB.getName() << '\n'); + for (const BasicBlock *PredBlock : predecessors(&BB)) + if ((PredBlock = getEHPadFromPredecessor(PredBlock))) + calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, CleanupState); + } else if (isa(FirstNonPHI)) { + // Anything unwinding through CleanupEndPadInst is in ParentState. + FuncInfo.EHPadStateMap[FirstNonPHI] = ParentState; + DEBUG(dbgs() << "Assigning state #" << ParentState << " to BB " + << BB.getName() << '\n'); + for (const BasicBlock *PredBlock : predecessors(&BB)) + if ((PredBlock = getEHPadFromPredecessor(PredBlock))) + calculateExplicitSEHStateNumbers(FuncInfo, *PredBlock, ParentState); + } else if (isa(FirstNonPHI)) { + report_fatal_error("Not yet implemented!"); + } else { + llvm_unreachable("unexpected EH Pad!"); + } +} + +/// Check if the EH Pad unwinds to caller. Cleanups are a little bit of a +/// special case because we have to look at the cleanupret instruction that uses +/// the cleanuppad. +static bool doesEHPadUnwindToCaller(const Instruction *EHPad) { + auto *CPI = dyn_cast(EHPad); + if (!CPI) + return EHPad->mayThrow(); + + // This cleanup does not return or unwind, so we say it unwinds to caller. + if (CPI->use_empty()) + return true; + + const Instruction *User = CPI->user_back(); + if (auto *CRI = dyn_cast(User)) + return CRI->unwindsToCaller(); + return cast(User)->unwindsToCaller(); +} + +void llvm::calculateSEHStateNumbers(const Function *ParentFn, + WinEHFuncInfo &FuncInfo) { + // Don't compute state numbers twice. + if (!FuncInfo.SEHUnwindMap.empty()) + return; + + for (const BasicBlock &BB : *ParentFn) { + if (!BB.isEHPad() || !doesEHPadUnwindToCaller(BB.getFirstNonPHI())) + continue; + calculateExplicitSEHStateNumbers(FuncInfo, BB, -1); + } +} + void llvm::calculateWinCXXEHStateNumbers(const Function *ParentFn, WinEHFuncInfo &FuncInfo) { // Return if it's already been done. - if (!FuncInfo.LandingPadStateMap.empty()) + if (!FuncInfo.EHPadStateMap.empty()) + return; + + bool IsExplicit = false; + for (const BasicBlock &BB : *ParentFn) { + if (!BB.isEHPad()) + continue; + const Instruction *FirstNonPHI = BB.getFirstNonPHI(); + // Skip cleanupendpads; they are exits, not entries. + if (isa(FirstNonPHI)) + continue; + if (!doesEHPadUnwindToCaller(FirstNonPHI)) + continue; + calculateExplicitCXXStateNumbers(FuncInfo, BB, -1); + IsExplicit = true; + } + + if (IsExplicit) return; WinEHNumbering Num(FuncInfo); @@ -2894,3 +3205,610 @@ void llvm::calculateWinCXXEHStateNumbers(const Function *ParentFn, while (!Num.HandlerStack.empty()) Num.processCallSite(None, ImmutableCallSite()); } + +void WinEHPrepare::colorFunclets(Function &F, + SmallVectorImpl &EntryBlocks) { + SmallVector, 16> Worklist; + BasicBlock *EntryBlock = &F.getEntryBlock(); + + // Build up the color map, which maps each block to its set of 'colors'. + // For any block B, the "colors" of B are the set of funclets F (possibly + // including a root "funclet" representing the main function), such that + // F will need to directly contain B or a copy of B (where the term "directly + // contain" is used to distinguish from being "transitively contained" in + // a nested funclet). + // Use a CFG walk driven by a worklist of (block, color) pairs. The "color" + // sets attached during this processing to a block which is the entry of some + // funclet F is actually the set of F's parents -- i.e. the union of colors + // of all predecessors of F's entry. For all other blocks, the color sets + // are as defined above. A post-pass fixes up the block color map to reflect + // the same sense of "color" for funclet entries as for other blocks. + + Worklist.push_back({EntryBlock, EntryBlock}); + + while (!Worklist.empty()) { + BasicBlock *Visiting; + BasicBlock *Color; + std::tie(Visiting, Color) = Worklist.pop_back_val(); + Instruction *VisitingHead = Visiting->getFirstNonPHI(); + if (VisitingHead->isEHPad() && !isa(VisitingHead) && + !isa(VisitingHead)) { + // Mark this as a funclet head as a member of itself. + FuncletBlocks[Visiting].insert(Visiting); + // Queue exits with the parent color. + for (User *Exit : VisitingHead->users()) { + for (BasicBlock *Succ : + successors(cast(Exit)->getParent())) { + if (BlockColors[Succ].insert(Color).second) { + Worklist.push_back({Succ, Color}); + } + } + } + // Handle CatchPad specially since its successors need different colors. + if (CatchPadInst *CatchPad = dyn_cast(VisitingHead)) { + // Visit the normal successor with the color of the new EH pad, and + // visit the unwind successor with the color of the parent. + BasicBlock *NormalSucc = CatchPad->getNormalDest(); + if (BlockColors[NormalSucc].insert(Visiting).second) { + Worklist.push_back({NormalSucc, Visiting}); + } + BasicBlock *UnwindSucc = CatchPad->getUnwindDest(); + if (BlockColors[UnwindSucc].insert(Color).second) { + Worklist.push_back({UnwindSucc, Color}); + } + continue; + } + // Switch color to the current node, except for terminate pads which + // have no bodies and only unwind successors and so need their successors + // visited with the color of the parent. + if (!isa(VisitingHead)) + Color = Visiting; + } else { + // Note that this is a member of the given color. + FuncletBlocks[Color].insert(Visiting); + } + + TerminatorInst *Terminator = Visiting->getTerminator(); + if (isa(Terminator) || + isa(Terminator) || + isa(Terminator)) { + // These blocks' successors have already been queued with the parent + // color. + continue; + } + for (BasicBlock *Succ : successors(Visiting)) { + if (isa(Succ->getFirstNonPHI())) { + // The catchendpad needs to be visited with the parent's color, not + // the current color. This will happen in the code above that visits + // any catchpad unwind successor with the parent color, so we can + // safely skip this successor here. + continue; + } + if (BlockColors[Succ].insert(Color).second) { + Worklist.push_back({Succ, Color}); + } + } + } + + // The processing above actually accumulated the parent set for this + // funclet into the color set for its entry; use the parent set to + // populate the children map, and reset the color set to include just + // the funclet itself (no instruction can target a funclet entry except on + // that transitions to the child funclet). + for (BasicBlock *FuncletEntry : EntryBlocks) { + std::set &ColorMapItem = BlockColors[FuncletEntry]; + for (BasicBlock *Parent : ColorMapItem) + FuncletChildren[Parent].insert(FuncletEntry); + ColorMapItem.clear(); + ColorMapItem.insert(FuncletEntry); + } +} + +void WinEHPrepare::demotePHIsOnFunclets(Function &F) { + // Strip PHI nodes off of EH pads. + SmallVector PHINodes; + for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) { + BasicBlock *BB = FI++; + if (!BB->isEHPad()) + continue; + for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) { + Instruction *I = BI++; + auto *PN = dyn_cast(I); + // Stop at the first non-PHI. + if (!PN) + break; + + AllocaInst *SpillSlot = insertPHILoads(PN, F); + if (SpillSlot) + insertPHIStores(PN, SpillSlot); + + PHINodes.push_back(PN); + } + } + + for (auto *PN : PHINodes) { + // There may be lingering uses on other EH PHIs being removed + PN->replaceAllUsesWith(UndefValue::get(PN->getType())); + PN->eraseFromParent(); + } +} + +void WinEHPrepare::demoteUsesBetweenFunclets(Function &F) { + // Turn all inter-funclet uses of a Value into loads and stores. + for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) { + BasicBlock *BB = FI++; + std::set &ColorsForBB = BlockColors[BB]; + for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) { + Instruction *I = BI++; + // Funclets are permitted to use static allocas. + if (auto *AI = dyn_cast(I)) + if (AI->isStaticAlloca()) + continue; + + demoteNonlocalUses(I, ColorsForBB, F); + } + } +} + +void WinEHPrepare::demoteArgumentUses(Function &F) { + // Also demote function parameters used in funclets. + std::set &ColorsForEntry = BlockColors[&F.getEntryBlock()]; + for (Argument &Arg : F.args()) + demoteNonlocalUses(&Arg, ColorsForEntry, F); +} + +void WinEHPrepare::cloneCommonBlocks( + Function &F, SmallVectorImpl &EntryBlocks) { + // We need to clone all blocks which belong to multiple funclets. Values are + // remapped throughout the funclet to propogate both the new instructions + // *and* the new basic blocks themselves. + for (BasicBlock *FuncletPadBB : EntryBlocks) { + std::set &BlocksInFunclet = FuncletBlocks[FuncletPadBB]; + + std::map Orig2Clone; + ValueToValueMapTy VMap; + for (BasicBlock *BB : BlocksInFunclet) { + std::set &ColorsForBB = BlockColors[BB]; + // We don't need to do anything if the block is monochromatic. + size_t NumColorsForBB = ColorsForBB.size(); + if (NumColorsForBB == 1) + continue; + + // Create a new basic block and copy instructions into it! + BasicBlock *CBB = + CloneBasicBlock(BB, VMap, Twine(".for.", FuncletPadBB->getName())); + // Insert the clone immediately after the original to ensure determinism + // and to keep the same relative ordering of any funclet's blocks. + CBB->insertInto(&F, BB->getNextNode()); + + // Add basic block mapping. + VMap[BB] = CBB; + + // Record delta operations that we need to perform to our color mappings. + Orig2Clone[BB] = CBB; + } + + // Update our color mappings to reflect that one block has lost a color and + // another has gained a color. + for (auto &BBMapping : Orig2Clone) { + BasicBlock *OldBlock = BBMapping.first; + BasicBlock *NewBlock = BBMapping.second; + + BlocksInFunclet.insert(NewBlock); + BlockColors[NewBlock].insert(FuncletPadBB); + + BlocksInFunclet.erase(OldBlock); + BlockColors[OldBlock].erase(FuncletPadBB); + } + + // Loop over all of the instructions in the function, fixing up operand + // references as we go. This uses VMap to do all the hard work. + for (BasicBlock *BB : BlocksInFunclet) + // Loop over all instructions, fixing each one as we find it... + for (Instruction &I : *BB) + RemapInstruction(&I, VMap, RF_IgnoreMissingEntries); + + // Check to see if SuccBB has PHI nodes. If so, we need to add entries to + // the PHI nodes for NewBB now. + for (auto &BBMapping : Orig2Clone) { + BasicBlock *OldBlock = BBMapping.first; + BasicBlock *NewBlock = BBMapping.second; + for (BasicBlock *SuccBB : successors(NewBlock)) { + for (Instruction &SuccI : *SuccBB) { + auto *SuccPN = dyn_cast(&SuccI); + if (!SuccPN) + break; + + // Ok, we have a PHI node. Figure out what the incoming value was for + // the OldBlock. + int OldBlockIdx = SuccPN->getBasicBlockIndex(OldBlock); + if (OldBlockIdx == -1) + break; + Value *IV = SuccPN->getIncomingValue(OldBlockIdx); + + // Remap the value if necessary. + if (auto *Inst = dyn_cast(IV)) { + ValueToValueMapTy::iterator I = VMap.find(Inst); + if (I != VMap.end()) + IV = I->second; + } + + SuccPN->addIncoming(IV, NewBlock); + } + } + } + + for (ValueToValueMapTy::value_type VT : VMap) { + // If there were values defined in BB that are used outside the funclet, + // then we now have to update all uses of the value to use either the + // original value, the cloned value, or some PHI derived value. This can + // require arbitrary PHI insertion, of which we are prepared to do, clean + // these up now. + SmallVector UsesToRename; + + auto *OldI = dyn_cast(const_cast(VT.first)); + if (!OldI) + continue; + auto *NewI = cast(VT.second); + // Scan all uses of this instruction to see if it is used outside of its + // funclet, and if so, record them in UsesToRename. + for (Use &U : OldI->uses()) { + Instruction *UserI = cast(U.getUser()); + BasicBlock *UserBB = UserI->getParent(); + std::set &ColorsForUserBB = BlockColors[UserBB]; + assert(!ColorsForUserBB.empty()); + if (ColorsForUserBB.size() > 1 || + *ColorsForUserBB.begin() != FuncletPadBB) + UsesToRename.push_back(&U); + } + + // If there are no uses outside the block, we're done with this + // instruction. + if (UsesToRename.empty()) + continue; + + // We found a use of OldI outside of the funclet. Rename all uses of OldI + // that are outside its funclet to be uses of the appropriate PHI node + // etc. + SSAUpdater SSAUpdate; + SSAUpdate.Initialize(OldI->getType(), OldI->getName()); + SSAUpdate.AddAvailableValue(OldI->getParent(), OldI); + SSAUpdate.AddAvailableValue(NewI->getParent(), NewI); + + while (!UsesToRename.empty()) + SSAUpdate.RewriteUseAfterInsertions(*UsesToRename.pop_back_val()); + } + } +} + +void WinEHPrepare::removeImplausibleTerminators(Function &F) { + // Remove implausible terminators and replace them with UnreachableInst. + for (auto &Funclet : FuncletBlocks) { + BasicBlock *FuncletPadBB = Funclet.first; + std::set &BlocksInFunclet = Funclet.second; + Instruction *FirstNonPHI = FuncletPadBB->getFirstNonPHI(); + auto *CatchPad = dyn_cast(FirstNonPHI); + auto *CleanupPad = dyn_cast(FirstNonPHI); + + for (BasicBlock *BB : BlocksInFunclet) { + TerminatorInst *TI = BB->getTerminator(); + // CatchPadInst and CleanupPadInst can't transfer control to a ReturnInst. + bool IsUnreachableRet = isa(TI) && (CatchPad || CleanupPad); + // The token consumed by a CatchReturnInst must match the funclet token. + bool IsUnreachableCatchret = false; + if (auto *CRI = dyn_cast(TI)) + IsUnreachableCatchret = CRI->getCatchPad() != CatchPad; + // The token consumed by a CleanupReturnInst must match the funclet token. + bool IsUnreachableCleanupret = false; + if (auto *CRI = dyn_cast(TI)) + IsUnreachableCleanupret = CRI->getCleanupPad() != CleanupPad; + // The token consumed by a CleanupEndPadInst must match the funclet token. + bool IsUnreachableCleanupendpad = false; + if (auto *CEPI = dyn_cast(TI)) + IsUnreachableCleanupendpad = CEPI->getCleanupPad() != CleanupPad; + if (IsUnreachableRet || IsUnreachableCatchret || + IsUnreachableCleanupret || IsUnreachableCleanupendpad) { + // Loop through all of our successors and make sure they know that one + // of their predecessors is going away. + for (BasicBlock *SuccBB : TI->successors()) + SuccBB->removePredecessor(BB); + + new UnreachableInst(BB->getContext(), TI); + TI->eraseFromParent(); + } + } + } +} + +void WinEHPrepare::cleanupPreparedFunclets(Function &F) { + // Clean-up some of the mess we made by removing useles PHI nodes, trivial + // branches, etc. + for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) { + BasicBlock *BB = FI++; + SimplifyInstructionsInBlock(BB); + ConstantFoldTerminator(BB, /*DeleteDeadConditions=*/true); + MergeBlockIntoPredecessor(BB); + } + + // We might have some unreachable blocks after cleaning up some impossible + // control flow. + removeUnreachableBlocks(F); +} + +void WinEHPrepare::verifyPreparedFunclets(Function &F) { + // Recolor the CFG to verify that all is well. + for (BasicBlock &BB : F) { + size_t NumColors = BlockColors[&BB].size(); + assert(NumColors == 1 && "Expected monochromatic BB!"); + if (NumColors == 0) + report_fatal_error("Uncolored BB!"); + if (NumColors > 1) + report_fatal_error("Multicolor BB!"); + if (!DisableDemotion) { + bool EHPadHasPHI = BB.isEHPad() && isa(BB.begin()); + assert(!EHPadHasPHI && "EH Pad still has a PHI!"); + if (EHPadHasPHI) + report_fatal_error("EH Pad still has a PHI!"); + } + } +} + +bool WinEHPrepare::prepareExplicitEH( + Function &F, SmallVectorImpl &EntryBlocks) { + // Remove unreachable blocks. It is not valuable to assign them a color and + // their existence can trick us into thinking values are alive when they are + // not. + removeUnreachableBlocks(F); + + // Determine which blocks are reachable from which funclet entries. + colorFunclets(F, EntryBlocks); + + if (!DisableDemotion) { + demotePHIsOnFunclets(F); + + demoteUsesBetweenFunclets(F); + + demoteArgumentUses(F); + } + + cloneCommonBlocks(F, EntryBlocks); + + if (!DisableCleanups) { + removeImplausibleTerminators(F); + + cleanupPreparedFunclets(F); + } + + verifyPreparedFunclets(F); + + BlockColors.clear(); + FuncletBlocks.clear(); + FuncletChildren.clear(); + + return true; +} + +// TODO: Share loads when one use dominates another, or when a catchpad exit +// dominates uses (needs dominators). +AllocaInst *WinEHPrepare::insertPHILoads(PHINode *PN, Function &F) { + BasicBlock *PHIBlock = PN->getParent(); + AllocaInst *SpillSlot = nullptr; + + if (isa(PHIBlock->getFirstNonPHI())) { + // Insert a load in place of the PHI and replace all uses. + SpillSlot = new AllocaInst(PN->getType(), nullptr, + Twine(PN->getName(), ".wineh.spillslot"), + F.getEntryBlock().begin()); + Value *V = new LoadInst(SpillSlot, Twine(PN->getName(), ".wineh.reload"), + PHIBlock->getFirstInsertionPt()); + PN->replaceAllUsesWith(V); + return SpillSlot; + } + + DenseMap Loads; + for (Value::use_iterator UI = PN->use_begin(), UE = PN->use_end(); + UI != UE;) { + Use &U = *UI++; + auto *UsingInst = cast(U.getUser()); + BasicBlock *UsingBB = UsingInst->getParent(); + if (UsingBB->isEHPad()) { + // Use is on an EH pad phi. Leave it alone; we'll insert loads and + // stores for it separately. + assert(isa(UsingInst)); + continue; + } + replaceUseWithLoad(PN, U, SpillSlot, Loads, F); + } + return SpillSlot; +} + +// TODO: improve store placement. Inserting at def is probably good, but need +// to be careful not to introduce interfering stores (needs liveness analysis). +// TODO: identify related phi nodes that can share spill slots, and share them +// (also needs liveness). +void WinEHPrepare::insertPHIStores(PHINode *OriginalPHI, + AllocaInst *SpillSlot) { + // Use a worklist of (Block, Value) pairs -- the given Value needs to be + // stored to the spill slot by the end of the given Block. + SmallVector, 4> Worklist; + + Worklist.push_back({OriginalPHI->getParent(), OriginalPHI}); + + while (!Worklist.empty()) { + BasicBlock *EHBlock; + Value *InVal; + std::tie(EHBlock, InVal) = Worklist.pop_back_val(); + + PHINode *PN = dyn_cast(InVal); + if (PN && PN->getParent() == EHBlock) { + // The value is defined by another PHI we need to remove, with no room to + // insert a store after the PHI, so each predecessor needs to store its + // incoming value. + for (unsigned i = 0, e = PN->getNumIncomingValues(); i < e; ++i) { + Value *PredVal = PN->getIncomingValue(i); + + // Undef can safely be skipped. + if (isa(PredVal)) + continue; + + insertPHIStore(PN->getIncomingBlock(i), PredVal, SpillSlot, Worklist); + } + } else { + // We need to store InVal, which dominates EHBlock, but can't put a store + // in EHBlock, so need to put stores in each predecessor. + for (BasicBlock *PredBlock : predecessors(EHBlock)) { + insertPHIStore(PredBlock, InVal, SpillSlot, Worklist); + } + } + } +} + +void WinEHPrepare::insertPHIStore( + BasicBlock *PredBlock, Value *PredVal, AllocaInst *SpillSlot, + SmallVectorImpl> &Worklist) { + + if (PredBlock->isEHPad() && + !isa(PredBlock->getFirstNonPHI())) { + // Pred is unsplittable, so we need to queue it on the worklist. + Worklist.push_back({PredBlock, PredVal}); + return; + } + + // Otherwise, insert the store at the end of the basic block. + new StoreInst(PredVal, SpillSlot, PredBlock->getTerminator()); +} + +// TODO: Share loads for same-funclet uses (requires dominators if funclets +// aren't properly nested). +void WinEHPrepare::demoteNonlocalUses(Value *V, + std::set &ColorsForBB, + Function &F) { + // Tokens can only be used non-locally due to control flow involving + // unreachable edges. Don't try to demote the token usage, we'll simply + // delete the cloned user later. + if (isa(V) || isa(V)) + return; + + DenseMap Loads; + AllocaInst *SpillSlot = nullptr; + for (Value::use_iterator UI = V->use_begin(), UE = V->use_end(); UI != UE;) { + Use &U = *UI++; + auto *UsingInst = cast(U.getUser()); + BasicBlock *UsingBB = UsingInst->getParent(); + + // Is the Use inside a block which is colored the same as the Def? + // If so, we don't need to escape the Def because we will clone + // ourselves our own private copy. + std::set &ColorsForUsingBB = BlockColors[UsingBB]; + if (ColorsForUsingBB == ColorsForBB) + continue; + + replaceUseWithLoad(V, U, SpillSlot, Loads, F); + } + if (SpillSlot) { + // Insert stores of the computed value into the stack slot. + // We have to be careful if I is an invoke instruction, + // because we can't insert the store AFTER the terminator instruction. + BasicBlock::iterator InsertPt; + if (isa(V)) { + InsertPt = F.getEntryBlock().getTerminator(); + } else if (isa(V)) { + auto *II = cast(V); + // We cannot demote invoke instructions to the stack if their normal + // edge is critical. Therefore, split the critical edge and create a + // basic block into which the store can be inserted. + if (!II->getNormalDest()->getSinglePredecessor()) { + unsigned SuccNum = + GetSuccessorNumber(II->getParent(), II->getNormalDest()); + assert(isCriticalEdge(II, SuccNum) && "Expected a critical edge!"); + BasicBlock *NewBlock = SplitCriticalEdge(II, SuccNum); + assert(NewBlock && "Unable to split critical edge."); + // Update the color mapping for the newly split edge. + std::set &ColorsForUsingBB = BlockColors[II->getParent()]; + BlockColors[NewBlock] = ColorsForUsingBB; + for (BasicBlock *FuncletPad : ColorsForUsingBB) + FuncletBlocks[FuncletPad].insert(NewBlock); + } + InsertPt = II->getNormalDest()->getFirstInsertionPt(); + } else { + InsertPt = cast(V); + ++InsertPt; + // Don't insert before PHI nodes or EH pad instrs. + for (; isa(InsertPt) || InsertPt->isEHPad(); ++InsertPt) + ; + } + new StoreInst(V, SpillSlot, InsertPt); + } +} + +void WinEHPrepare::replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot, + DenseMap &Loads, + Function &F) { + // Lazilly create the spill slot. + if (!SpillSlot) + SpillSlot = new AllocaInst(V->getType(), nullptr, + Twine(V->getName(), ".wineh.spillslot"), + F.getEntryBlock().begin()); + + auto *UsingInst = cast(U.getUser()); + if (auto *UsingPHI = dyn_cast(UsingInst)) { + // If this is a PHI node, we can't insert a load of the value before + // the use. Instead insert the load in the predecessor block + // corresponding to the incoming value. + // + // Note that if there are multiple edges from a basic block to this + // PHI node that we cannot have multiple loads. The problem is that + // the resulting PHI node will have multiple values (from each load) + // coming in from the same block, which is illegal SSA form. + // For this reason, we keep track of and reuse loads we insert. + BasicBlock *IncomingBlock = UsingPHI->getIncomingBlock(U); + if (auto *CatchRet = + dyn_cast(IncomingBlock->getTerminator())) { + // Putting a load above a catchret and use on the phi would still leave + // a cross-funclet def/use. We need to split the edge, change the + // catchret to target the new block, and put the load there. + BasicBlock *PHIBlock = UsingInst->getParent(); + BasicBlock *NewBlock = SplitEdge(IncomingBlock, PHIBlock); + // SplitEdge gives us: + // IncomingBlock: + // ... + // br label %NewBlock + // NewBlock: + // catchret label %PHIBlock + // But we need: + // IncomingBlock: + // ... + // catchret label %NewBlock + // NewBlock: + // br label %PHIBlock + // So move the terminators to each others' blocks and swap their + // successors. + BranchInst *Goto = cast(IncomingBlock->getTerminator()); + Goto->removeFromParent(); + CatchRet->removeFromParent(); + IncomingBlock->getInstList().push_back(CatchRet); + NewBlock->getInstList().push_back(Goto); + Goto->setSuccessor(0, PHIBlock); + CatchRet->setSuccessor(NewBlock); + // Update the color mapping for the newly split edge. + std::set &ColorsForPHIBlock = BlockColors[PHIBlock]; + BlockColors[NewBlock] = ColorsForPHIBlock; + for (BasicBlock *FuncletPad : ColorsForPHIBlock) + FuncletBlocks[FuncletPad].insert(NewBlock); + // Treat the new block as incoming for load insertion. + IncomingBlock = NewBlock; + } + Value *&Load = Loads[IncomingBlock]; + // Insert the load into the predecessor block + if (!Load) + Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"), + /*Volatile=*/false, IncomingBlock->getTerminator()); + + U.set(Load); + } else { + // Reload right before the old use. + auto *Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"), + /*Volatile=*/false, UsingInst); + U.set(Load); + } +}