| //===- SjLjEHPrepare.cpp - Eliminate Invoke & Unwind instructions ---------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This transformation is designed for use by code generators which use SjLj |
| // based exception handling. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/IRBuilder.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/Intrinsics.h" |
| #include "llvm/IR/LLVMContext.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetLowering.h" |
| #include "llvm/Target/TargetSubtargetInfo.h" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include <set> |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "sjljehprepare" |
| |
| STATISTIC(NumInvokes, "Number of invokes replaced"); |
| STATISTIC(NumSpilled, "Number of registers live across unwind edges"); |
| |
| namespace { |
| class SjLjEHPrepare : public FunctionPass { |
| Type *doubleUnderDataTy; |
| Type *doubleUnderJBufTy; |
| Type *FunctionContextTy; |
| Constant *RegisterFn; |
| Constant *UnregisterFn; |
| Constant *BuiltinSetjmpFn; |
| Constant *FrameAddrFn; |
| Constant *StackAddrFn; |
| Constant *StackRestoreFn; |
| Constant *LSDAAddrFn; |
| Value *PersonalityFn; |
| Constant *CallSiteFn; |
| Constant *FuncCtxFn; |
| AllocaInst *FuncCtx; |
| |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| explicit SjLjEHPrepare() : FunctionPass(ID) {} |
| bool doInitialization(Module &M) override; |
| bool runOnFunction(Function &F) override; |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override {} |
| const char *getPassName() const override { |
| return "SJLJ Exception Handling preparation"; |
| } |
| |
| private: |
| bool setupEntryBlockAndCallSites(Function &F); |
| void substituteLPadValues(LandingPadInst *LPI, Value *ExnVal, Value *SelVal); |
| Value *setupFunctionContext(Function &F, ArrayRef<LandingPadInst *> LPads); |
| void lowerIncomingArguments(Function &F); |
| void lowerAcrossUnwindEdges(Function &F, ArrayRef<InvokeInst *> Invokes); |
| void insertCallSiteStore(Instruction *I, int Number); |
| }; |
| } // end anonymous namespace |
| |
| char SjLjEHPrepare::ID = 0; |
| INITIALIZE_PASS(SjLjEHPrepare, "sjljehprepare", "Prepare SjLj exceptions", |
| false, false) |
| |
| // Public Interface To the SjLjEHPrepare pass. |
| FunctionPass *llvm::createSjLjEHPreparePass() { return new SjLjEHPrepare(); } |
| // doInitialization - Set up decalarations and types needed to process |
| // exceptions. |
| bool SjLjEHPrepare::doInitialization(Module &M) { |
| // Build the function context structure. |
| // builtin_setjmp uses a five word jbuf |
| Type *VoidPtrTy = Type::getInt8PtrTy(M.getContext()); |
| Type *Int32Ty = Type::getInt32Ty(M.getContext()); |
| doubleUnderDataTy = ArrayType::get(Int32Ty, 4); |
| doubleUnderJBufTy = ArrayType::get(VoidPtrTy, 5); |
| FunctionContextTy = StructType::get(VoidPtrTy, // __prev |
| Int32Ty, // call_site |
| doubleUnderDataTy, // __data |
| VoidPtrTy, // __personality |
| VoidPtrTy, // __lsda |
| doubleUnderJBufTy, // __jbuf |
| nullptr); |
| RegisterFn = M.getOrInsertFunction( |
| "_Unwind_SjLj_Register", Type::getVoidTy(M.getContext()), |
| PointerType::getUnqual(FunctionContextTy), (Type *)nullptr); |
| UnregisterFn = M.getOrInsertFunction( |
| "_Unwind_SjLj_Unregister", Type::getVoidTy(M.getContext()), |
| PointerType::getUnqual(FunctionContextTy), (Type *)nullptr); |
| FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress); |
| StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave); |
| StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore); |
| BuiltinSetjmpFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setjmp); |
| LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda); |
| CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite); |
| FuncCtxFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_functioncontext); |
| PersonalityFn = nullptr; |
| |
| return true; |
| } |
| |
| /// insertCallSiteStore - Insert a store of the call-site value to the |
| /// function context |
| void SjLjEHPrepare::insertCallSiteStore(Instruction *I, int Number) { |
| IRBuilder<> Builder(I); |
| |
| // Get a reference to the call_site field. |
| Type *Int32Ty = Type::getInt32Ty(I->getContext()); |
| Value *Zero = ConstantInt::get(Int32Ty, 0); |
| Value *One = ConstantInt::get(Int32Ty, 1); |
| Value *Idxs[2] = { Zero, One }; |
| Value *CallSite = |
| Builder.CreateGEP(FunctionContextTy, FuncCtx, Idxs, "call_site"); |
| |
| // Insert a store of the call-site number |
| ConstantInt *CallSiteNoC = |
| ConstantInt::get(Type::getInt32Ty(I->getContext()), Number); |
| Builder.CreateStore(CallSiteNoC, CallSite, true /*volatile*/); |
| } |
| |
| /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until |
| /// we reach blocks we've already seen. |
| static void MarkBlocksLiveIn(BasicBlock *BB, |
| SmallPtrSetImpl<BasicBlock *> &LiveBBs) { |
| if (!LiveBBs.insert(BB).second) |
| return; // already been here. |
| |
| for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) |
| MarkBlocksLiveIn(*PI, LiveBBs); |
| } |
| |
| /// substituteLPadValues - Substitute the values returned by the landingpad |
| /// instruction with those returned by the personality function. |
| void SjLjEHPrepare::substituteLPadValues(LandingPadInst *LPI, Value *ExnVal, |
| Value *SelVal) { |
| SmallVector<Value *, 8> UseWorkList(LPI->user_begin(), LPI->user_end()); |
| while (!UseWorkList.empty()) { |
| Value *Val = UseWorkList.pop_back_val(); |
| ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Val); |
| if (!EVI) |
| continue; |
| if (EVI->getNumIndices() != 1) |
| continue; |
| if (*EVI->idx_begin() == 0) |
| EVI->replaceAllUsesWith(ExnVal); |
| else if (*EVI->idx_begin() == 1) |
| EVI->replaceAllUsesWith(SelVal); |
| if (EVI->getNumUses() == 0) |
| EVI->eraseFromParent(); |
| } |
| |
| if (LPI->getNumUses() == 0) |
| return; |
| |
| // There are still some uses of LPI. Construct an aggregate with the exception |
| // values and replace the LPI with that aggregate. |
| Type *LPadType = LPI->getType(); |
| Value *LPadVal = UndefValue::get(LPadType); |
| IRBuilder<> Builder( |
| std::next(BasicBlock::iterator(cast<Instruction>(SelVal)))); |
| LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val"); |
| LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val"); |
| |
| LPI->replaceAllUsesWith(LPadVal); |
| } |
| |
| /// setupFunctionContext - Allocate the function context on the stack and fill |
| /// it with all of the data that we know at this point. |
| Value *SjLjEHPrepare::setupFunctionContext(Function &F, |
| ArrayRef<LandingPadInst *> LPads) { |
| BasicBlock *EntryBB = F.begin(); |
| |
| // Create an alloca for the incoming jump buffer ptr and the new jump buffer |
| // that needs to be restored on all exits from the function. This is an alloca |
| // because the value needs to be added to the global context list. |
| auto &DL = F.getParent()->getDataLayout(); |
| unsigned Align = DL.getPrefTypeAlignment(FunctionContextTy); |
| FuncCtx = new AllocaInst(FunctionContextTy, nullptr, Align, "fn_context", |
| EntryBB->begin()); |
| |
| // Fill in the function context structure. |
| for (unsigned I = 0, E = LPads.size(); I != E; ++I) { |
| LandingPadInst *LPI = LPads[I]; |
| IRBuilder<> Builder(LPI->getParent()->getFirstInsertionPt()); |
| |
| // Reference the __data field. |
| Value *FCData = |
| Builder.CreateConstGEP2_32(FunctionContextTy, FuncCtx, 0, 2, "__data"); |
| |
| // The exception values come back in context->__data[0]. |
| Value *ExceptionAddr = Builder.CreateConstGEP2_32(doubleUnderDataTy, FCData, |
| 0, 0, "exception_gep"); |
| Value *ExnVal = Builder.CreateLoad(ExceptionAddr, true, "exn_val"); |
| ExnVal = Builder.CreateIntToPtr(ExnVal, Builder.getInt8PtrTy()); |
| |
| Value *SelectorAddr = Builder.CreateConstGEP2_32(doubleUnderDataTy, FCData, |
| 0, 1, "exn_selector_gep"); |
| Value *SelVal = Builder.CreateLoad(SelectorAddr, true, "exn_selector_val"); |
| |
| substituteLPadValues(LPI, ExnVal, SelVal); |
| } |
| |
| // Personality function |
| IRBuilder<> Builder(EntryBB->getTerminator()); |
| if (!PersonalityFn) |
| PersonalityFn = F.getPersonalityFn(); |
| Value *PersonalityFieldPtr = Builder.CreateConstGEP2_32( |
| FunctionContextTy, FuncCtx, 0, 3, "pers_fn_gep"); |
| Builder.CreateStore( |
| Builder.CreateBitCast(PersonalityFn, Builder.getInt8PtrTy()), |
| PersonalityFieldPtr, /*isVolatile=*/true); |
| |
| // LSDA address |
| Value *LSDA = Builder.CreateCall(LSDAAddrFn, {}, "lsda_addr"); |
| Value *LSDAFieldPtr = |
| Builder.CreateConstGEP2_32(FunctionContextTy, FuncCtx, 0, 4, "lsda_gep"); |
| Builder.CreateStore(LSDA, LSDAFieldPtr, /*isVolatile=*/true); |
| |
| return FuncCtx; |
| } |
| |
| /// lowerIncomingArguments - To avoid having to handle incoming arguments |
| /// specially, we lower each arg to a copy instruction in the entry block. This |
| /// ensures that the argument value itself cannot be live out of the entry |
| /// block. |
| void SjLjEHPrepare::lowerIncomingArguments(Function &F) { |
| BasicBlock::iterator AfterAllocaInsPt = F.begin()->begin(); |
| while (isa<AllocaInst>(AfterAllocaInsPt) && |
| isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsPt)->getArraySize())) |
| ++AfterAllocaInsPt; |
| |
| for (Function::arg_iterator AI = F.arg_begin(), AE = F.arg_end(); AI != AE; |
| ++AI) { |
| Type *Ty = AI->getType(); |
| |
| // Use 'select i8 true, %arg, undef' to simulate a 'no-op' instruction. |
| Value *TrueValue = ConstantInt::getTrue(F.getContext()); |
| Value *UndefValue = UndefValue::get(Ty); |
| Instruction *SI = SelectInst::Create(TrueValue, AI, UndefValue, |
| AI->getName() + ".tmp", |
| AfterAllocaInsPt); |
| AI->replaceAllUsesWith(SI); |
| |
| // Reset the operand, because it was clobbered by the RAUW above. |
| SI->setOperand(1, AI); |
| } |
| } |
| |
| /// lowerAcrossUnwindEdges - Find all variables which are alive across an unwind |
| /// edge and spill them. |
| void SjLjEHPrepare::lowerAcrossUnwindEdges(Function &F, |
| ArrayRef<InvokeInst *> Invokes) { |
| // Finally, scan the code looking for instructions with bad live ranges. |
| for (Function::iterator BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) { |
| for (BasicBlock::iterator II = BB->begin(), IIE = BB->end(); II != IIE; |
| ++II) { |
| // Ignore obvious cases we don't have to handle. In particular, most |
| // instructions either have no uses or only have a single use inside the |
| // current block. Ignore them quickly. |
| Instruction *Inst = II; |
| if (Inst->use_empty()) |
| continue; |
| if (Inst->hasOneUse() && |
| cast<Instruction>(Inst->user_back())->getParent() == BB && |
| !isa<PHINode>(Inst->user_back())) |
| continue; |
| |
| // If this is an alloca in the entry block, it's not a real register |
| // value. |
| if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst)) |
| if (isa<ConstantInt>(AI->getArraySize()) && BB == F.begin()) |
| continue; |
| |
| // Avoid iterator invalidation by copying users to a temporary vector. |
| SmallVector<Instruction *, 16> Users; |
| for (User *U : Inst->users()) { |
| Instruction *UI = cast<Instruction>(U); |
| if (UI->getParent() != BB || isa<PHINode>(UI)) |
| Users.push_back(UI); |
| } |
| |
| // Find all of the blocks that this value is live in. |
| SmallPtrSet<BasicBlock *, 64> LiveBBs; |
| LiveBBs.insert(Inst->getParent()); |
| while (!Users.empty()) { |
| Instruction *U = Users.back(); |
| Users.pop_back(); |
| |
| if (!isa<PHINode>(U)) { |
| MarkBlocksLiveIn(U->getParent(), LiveBBs); |
| } else { |
| // Uses for a PHI node occur in their predecessor block. |
| PHINode *PN = cast<PHINode>(U); |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) |
| if (PN->getIncomingValue(i) == Inst) |
| MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs); |
| } |
| } |
| |
| // Now that we know all of the blocks that this thing is live in, see if |
| // it includes any of the unwind locations. |
| bool NeedsSpill = false; |
| for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { |
| BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); |
| if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) { |
| DEBUG(dbgs() << "SJLJ Spill: " << *Inst << " around " |
| << UnwindBlock->getName() << "\n"); |
| NeedsSpill = true; |
| break; |
| } |
| } |
| |
| // If we decided we need a spill, do it. |
| // FIXME: Spilling this way is overkill, as it forces all uses of |
| // the value to be reloaded from the stack slot, even those that aren't |
| // in the unwind blocks. We should be more selective. |
| if (NeedsSpill) { |
| DemoteRegToStack(*Inst, true); |
| ++NumSpilled; |
| } |
| } |
| } |
| |
| // Go through the landing pads and remove any PHIs there. |
| for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { |
| BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest(); |
| LandingPadInst *LPI = UnwindBlock->getLandingPadInst(); |
| |
| // Place PHIs into a set to avoid invalidating the iterator. |
| SmallPtrSet<PHINode *, 8> PHIsToDemote; |
| for (BasicBlock::iterator PN = UnwindBlock->begin(); isa<PHINode>(PN); ++PN) |
| PHIsToDemote.insert(cast<PHINode>(PN)); |
| if (PHIsToDemote.empty()) |
| continue; |
| |
| // Demote the PHIs to the stack. |
| for (PHINode *PN : PHIsToDemote) |
| DemotePHIToStack(PN); |
| |
| // Move the landingpad instruction back to the top of the landing pad block. |
| LPI->moveBefore(UnwindBlock->begin()); |
| } |
| } |
| |
| /// setupEntryBlockAndCallSites - Setup the entry block by creating and filling |
| /// the function context and marking the call sites with the appropriate |
| /// values. These values are used by the DWARF EH emitter. |
| bool SjLjEHPrepare::setupEntryBlockAndCallSites(Function &F) { |
| SmallVector<ReturnInst *, 16> Returns; |
| SmallVector<InvokeInst *, 16> Invokes; |
| SmallSetVector<LandingPadInst *, 16> LPads; |
| |
| // Look through the terminators of the basic blocks to find invokes. |
| for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) |
| if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) { |
| if (Function *Callee = II->getCalledFunction()) |
| if (Callee->isIntrinsic() && |
| Callee->getIntrinsicID() == Intrinsic::donothing) { |
| // Remove the NOP invoke. |
| BranchInst::Create(II->getNormalDest(), II); |
| II->eraseFromParent(); |
| continue; |
| } |
| |
| Invokes.push_back(II); |
| LPads.insert(II->getUnwindDest()->getLandingPadInst()); |
| } else if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) { |
| Returns.push_back(RI); |
| } |
| |
| if (Invokes.empty()) |
| return false; |
| |
| NumInvokes += Invokes.size(); |
| |
| lowerIncomingArguments(F); |
| lowerAcrossUnwindEdges(F, Invokes); |
| |
| Value *FuncCtx = |
| setupFunctionContext(F, makeArrayRef(LPads.begin(), LPads.end())); |
| BasicBlock *EntryBB = F.begin(); |
| IRBuilder<> Builder(EntryBB->getTerminator()); |
| |
| // Get a reference to the jump buffer. |
| Value *JBufPtr = |
| Builder.CreateConstGEP2_32(FunctionContextTy, FuncCtx, 0, 5, "jbuf_gep"); |
| |
| // Save the frame pointer. |
| Value *FramePtr = Builder.CreateConstGEP2_32(doubleUnderJBufTy, JBufPtr, 0, 0, |
| "jbuf_fp_gep"); |
| |
| Value *Val = Builder.CreateCall(FrameAddrFn, Builder.getInt32(0), "fp"); |
| Builder.CreateStore(Val, FramePtr, /*isVolatile=*/true); |
| |
| // Save the stack pointer. |
| Value *StackPtr = Builder.CreateConstGEP2_32(doubleUnderJBufTy, JBufPtr, 0, 2, |
| "jbuf_sp_gep"); |
| |
| Val = Builder.CreateCall(StackAddrFn, {}, "sp"); |
| Builder.CreateStore(Val, StackPtr, /*isVolatile=*/true); |
| |
| // Call the setjmp instrinsic. It fills in the rest of the jmpbuf. |
| Value *SetjmpArg = Builder.CreateBitCast(JBufPtr, Builder.getInt8PtrTy()); |
| Builder.CreateCall(BuiltinSetjmpFn, SetjmpArg); |
| |
| // Store a pointer to the function context so that the back-end will know |
| // where to look for it. |
| Value *FuncCtxArg = Builder.CreateBitCast(FuncCtx, Builder.getInt8PtrTy()); |
| Builder.CreateCall(FuncCtxFn, FuncCtxArg); |
| |
| // At this point, we are all set up, update the invoke instructions to mark |
| // their call_site values. |
| for (unsigned I = 0, E = Invokes.size(); I != E; ++I) { |
| insertCallSiteStore(Invokes[I], I + 1); |
| |
| ConstantInt *CallSiteNum = |
| ConstantInt::get(Type::getInt32Ty(F.getContext()), I + 1); |
| |
| // Record the call site value for the back end so it stays associated with |
| // the invoke. |
| CallInst::Create(CallSiteFn, CallSiteNum, "", Invokes[I]); |
| } |
| |
| // Mark call instructions that aren't nounwind as no-action (call_site == |
| // -1). Skip the entry block, as prior to then, no function context has been |
| // created for this function and any unexpected exceptions thrown will go |
| // directly to the caller's context, which is what we want anyway, so no need |
| // to do anything here. |
| for (Function::iterator BB = F.begin(), E = F.end(); ++BB != E;) |
| for (BasicBlock::iterator I = BB->begin(), end = BB->end(); I != end; ++I) |
| if (CallInst *CI = dyn_cast<CallInst>(I)) { |
| if (!CI->doesNotThrow()) |
| insertCallSiteStore(CI, -1); |
| } else if (ResumeInst *RI = dyn_cast<ResumeInst>(I)) { |
| insertCallSiteStore(RI, -1); |
| } |
| |
| // Register the function context and make sure it's known to not throw |
| CallInst *Register = |
| CallInst::Create(RegisterFn, FuncCtx, "", EntryBB->getTerminator()); |
| Register->setDoesNotThrow(); |
| |
| // Following any allocas not in the entry block, update the saved SP in the |
| // jmpbuf to the new value. |
| for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { |
| if (BB == F.begin()) |
| continue; |
| for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { |
| if (CallInst *CI = dyn_cast<CallInst>(I)) { |
| if (CI->getCalledFunction() != StackRestoreFn) |
| continue; |
| } else if (!isa<AllocaInst>(I)) { |
| continue; |
| } |
| Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp"); |
| StackAddr->insertAfter(I); |
| Instruction *StoreStackAddr = new StoreInst(StackAddr, StackPtr, true); |
| StoreStackAddr->insertAfter(StackAddr); |
| } |
| } |
| |
| // Finally, for any returns from this function, if this function contains an |
| // invoke, add a call to unregister the function context. |
| for (unsigned I = 0, E = Returns.size(); I != E; ++I) |
| CallInst::Create(UnregisterFn, FuncCtx, "", Returns[I]); |
| |
| return true; |
| } |
| |
| bool SjLjEHPrepare::runOnFunction(Function &F) { |
| bool Res = setupEntryBlockAndCallSites(F); |
| return Res; |
| } |