| //===- SjLjEHPrepare.cpp - Eliminate Invoke & Unwind instructions ---------===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This transformation is designed for use by code generators which use SjLj |
| // based exception handling. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/CodeGen/Passes.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/Module.h" |
| #include "llvm/InitializePasses.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| 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; |
| FunctionCallee RegisterFn; |
| FunctionCallee UnregisterFn; |
| Function *BuiltinSetupDispatchFn; |
| Function *FrameAddrFn; |
| Function *StackAddrFn; |
| Function *StackRestoreFn; |
| Function *LSDAAddrFn; |
| Function *CallSiteFn; |
| Function *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 {} |
| StringRef 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, DEBUG_TYPE, "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 |
| ); |
| |
| 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 predecessors 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. |
| |
| df_iterator_default_set<BasicBlock*> Visited; |
| |
| for (BasicBlock *B : inverse_depth_first_ext(BB, Visited)) |
| LiveBBs.insert(B); |
| |
| } |
| |
| /// 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(); |
| auto *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->use_empty()) |
| EVI->eraseFromParent(); |
| } |
| |
| if (LPI->use_empty()) |
| 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); |
| auto *SelI = cast<Instruction>(SelVal); |
| IRBuilder<> Builder(SelI->getParent(), std::next(SelI->getIterator())); |
| 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.front(); |
| |
| // 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(); |
| const Align Alignment(DL.getPrefTypeAlignment(FunctionContextTy)); |
| FuncCtx = new AllocaInst(FunctionContextTy, DL.getAllocaAddrSpace(), nullptr, |
| Alignment, "fn_context", &EntryBB->front()); |
| |
| // Fill in the function context structure. |
| for (LandingPadInst *LPI : LPads) { |
| IRBuilder<> Builder(LPI->getParent(), |
| 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]. |
| Type *Int32Ty = Type::getInt32Ty(F.getContext()); |
| Value *ExceptionAddr = Builder.CreateConstGEP2_32(doubleUnderDataTy, FCData, |
| 0, 0, "exception_gep"); |
| Value *ExnVal = Builder.CreateLoad(Int32Ty, 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(Int32Ty, SelectorAddr, true, "exn_selector_val"); |
| |
| substituteLPadValues(LPI, ExnVal, SelVal); |
| } |
| |
| // Personality function |
| IRBuilder<> Builder(EntryBB->getTerminator()); |
| Value *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) && |
| cast<AllocaInst>(AfterAllocaInsPt)->isStaticAlloca()) |
| ++AfterAllocaInsPt; |
| assert(AfterAllocaInsPt != F.front().end()); |
| |
| for (auto &AI : F.args()) { |
| // Swift error really is a register that we model as memory -- instruction |
| // selection will perform mem-to-reg for us and spill/reload appropriately |
| // around calls that clobber it. There is no need to spill this |
| // value to the stack and doing so would not be allowed. |
| if (AI.isSwiftError()) |
| continue; |
| |
| 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 (BasicBlock &BB : F) { |
| for (Instruction &Inst : BB) { |
| // 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. |
| 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 (auto *AI = dyn_cast<AllocaInst>(&Inst)) |
| if (AI->isStaticAlloca()) |
| 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 *, 32> LiveBBs; |
| LiveBBs.insert(&BB); |
| while (!Users.empty()) { |
| Instruction *U = Users.pop_back_val(); |
| |
| 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 (InvokeInst *Invoke : Invokes) { |
| BasicBlock *UnwindBlock = Invoke->getUnwindDest(); |
| if (UnwindBlock != &BB && LiveBBs.count(UnwindBlock)) { |
| LLVM_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 (InvokeInst *Invoke : Invokes) { |
| BasicBlock *UnwindBlock = Invoke->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->front()); |
| } |
| } |
| |
| /// 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 (BasicBlock &BB : F) |
| if (auto *II = dyn_cast<InvokeInst>(BB.getTerminator())) { |
| if (Function *Callee = II->getCalledFunction()) |
| if (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 (auto *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.front(); |
| 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 setup_dispatch instrinsic. It fills in the rest of the jmpbuf. |
| Builder.CreateCall(BuiltinSetupDispatchFn, {}); |
| |
| // 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 (BasicBlock &BB : F) { |
| if (&BB == &F.front()) |
| continue; |
| for (Instruction &I : BB) |
| if (I.mayThrow()) |
| insertCallSiteStore(&I, -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 (BasicBlock &BB : F) { |
| if (&BB == &F.front()) |
| continue; |
| for (Instruction &I : BB) { |
| if (auto *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 (ReturnInst *Return : Returns) |
| CallInst::Create(UnregisterFn, FuncCtx, "", Return); |
| |
| return true; |
| } |
| |
| bool SjLjEHPrepare::runOnFunction(Function &F) { |
| Module &M = *F.getParent(); |
| RegisterFn = M.getOrInsertFunction( |
| "_Unwind_SjLj_Register", Type::getVoidTy(M.getContext()), |
| PointerType::getUnqual(FunctionContextTy)); |
| UnregisterFn = M.getOrInsertFunction( |
| "_Unwind_SjLj_Unregister", Type::getVoidTy(M.getContext()), |
| PointerType::getUnqual(FunctionContextTy)); |
| FrameAddrFn = Intrinsic::getDeclaration( |
| &M, Intrinsic::frameaddress, |
| {Type::getInt8PtrTy(M.getContext(), |
| M.getDataLayout().getAllocaAddrSpace())}); |
| StackAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::stacksave); |
| StackRestoreFn = Intrinsic::getDeclaration(&M, Intrinsic::stackrestore); |
| BuiltinSetupDispatchFn = |
| Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_setup_dispatch); |
| LSDAAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_lsda); |
| CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite); |
| FuncCtxFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_functioncontext); |
| |
| bool Res = setupEntryBlockAndCallSites(F); |
| return Res; |
| } |
