| //===- 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. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "sjljehprepare" |
| #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/Transforms/Scalar.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include <set> |
| using namespace llvm; |
| |
| STATISTIC(NumInvokes, "Number of invokes replaced"); |
| STATISTIC(NumSpilled, "Number of registers live across unwind edges"); |
| |
| namespace { |
| class SjLjEHPrepare : public FunctionPass { |
| const TargetLoweringBase *TLI; |
| 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(const TargetLoweringBase *tli = NULL) |
| : FunctionPass(ID), TLI(tli) { } |
| bool doInitialization(Module &M); |
| bool runOnFunction(Function &F); |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const {} |
| const char *getPassName() const { |
| 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; |
| |
| // Public Interface To the SjLjEHPrepare pass. |
| FunctionPass *llvm::createSjLjEHPreparePass(const TargetLoweringBase *TLI) { |
| return new SjLjEHPrepare(TLI); |
| } |
| // 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()); |
| FunctionContextTy = |
| StructType::get(VoidPtrTy, // __prev |
| Int32Ty, // call_site |
| ArrayType::get(Int32Ty, 4), // __data |
| VoidPtrTy, // __personality |
| VoidPtrTy, // __lsda |
| ArrayType::get(VoidPtrTy, 5), // __jbuf |
| NULL); |
| RegisterFn = M.getOrInsertFunction("_Unwind_SjLj_Register", |
| Type::getVoidTy(M.getContext()), |
| PointerType::getUnqual(FunctionContextTy), |
| (Type *)0); |
| UnregisterFn = |
| M.getOrInsertFunction("_Unwind_SjLj_Unregister", |
| Type::getVoidTy(M.getContext()), |
| PointerType::getUnqual(FunctionContextTy), |
| (Type *)0); |
| 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 = 0; |
| |
| 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(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, |
| SmallPtrSet<BasicBlock*, 64> &LiveBBs) { |
| if (!LiveBBs.insert(BB)) 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->use_begin(), LPI->use_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(llvm::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. |
| unsigned Align = |
| TLI->getDataLayout()->getPrefTypeAlignment(FunctionContextTy); |
| FuncCtx = |
| new AllocaInst(FunctionContextTy, 0, 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(FuncCtx, 0, 2, "__data"); |
| |
| // The exception values come back in context->__data[0]. |
| Value *ExceptionAddr = Builder.CreateConstGEP2_32(FCData, 0, 0, |
| "exception_gep"); |
| Value *ExnVal = Builder.CreateLoad(ExceptionAddr, true, "exn_val"); |
| ExnVal = Builder.CreateIntToPtr(ExnVal, Builder.getInt8PtrTy()); |
| |
| Value *SelectorAddr = Builder.CreateConstGEP2_32(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 = LPads[0]->getPersonalityFn(); |
| Value *PersonalityFieldPtr = Builder.CreateConstGEP2_32(FuncCtx, 0, 3, |
| "pers_fn_gep"); |
| Builder.CreateStore(PersonalityFn, PersonalityFieldPtr, /*isVolatile=*/true); |
| |
| // LSDA address |
| Value *LSDA = Builder.CreateCall(LSDAAddrFn, "lsda_addr"); |
| Value *LSDAFieldPtr = Builder.CreateConstGEP2_32(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(); |
| |
| // Aggregate types can't be cast, but are legal argument types, so we have |
| // to handle them differently. We use an extract/insert pair as a |
| // lightweight method to achieve the same goal. |
| if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) { |
| Instruction *EI = ExtractValueInst::Create(AI, 0, "", AfterAllocaInsPt); |
| Instruction *NI = InsertValueInst::Create(AI, EI, 0); |
| NI->insertAfter(EI); |
| AI->replaceAllUsesWith(NI); |
| |
| // Set the operand of the instructions back to the AllocaInst. |
| EI->setOperand(0, AI); |
| NI->setOperand(0, AI); |
| } else { |
| // This is always a no-op cast because we're casting AI to AI->getType() |
| // so src and destination types are identical. BitCast is the only |
| // possibility. |
| CastInst *NC = |
| new BitCastInst(AI, AI->getType(), AI->getName() + ".tmp", |
| AfterAllocaInsPt); |
| AI->replaceAllUsesWith(NC); |
| |
| // Set the operand of the cast instruction back to the AllocaInst. |
| // Normally it's forbidden to replace a CastInst's operand because it |
| // could cause the opcode to reflect an illegal conversion. However, we're |
| // replacing it here with the same value it was constructed with. We do |
| // this because the above replaceAllUsesWith() clobbered the operand, but |
| // we want this one to remain. |
| NC->setOperand(0, 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->use_back())->getParent() == BB && |
| !isa<PHINode>(Inst->use_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 (Value::use_iterator |
| UI = Inst->use_begin(), E = Inst->use_end(); UI != E; ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| if (User->getParent() != BB || isa<PHINode>(User)) |
| Users.push_back(User); |
| } |
| |
| // 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 (SmallPtrSet<PHINode*, 8>::iterator |
| I = PHIsToDemote.begin(), E = PHIsToDemote.end(); I != E; ++I) |
| DemotePHIToStack(*I); |
| |
| // 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(FuncCtx, 0, 5, "jbuf_gep"); |
| |
| // Save the frame pointer. |
| Value *FramePtr = Builder.CreateConstGEP2_32(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(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; |
| } |
