//===- SjLjEHPass.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/Transforms/Scalar.h" #include "llvm/Constants.h" #include "llvm/DerivedTypes.h" #include "llvm/Instructions.h" #include "llvm/Intrinsics.h" #include "llvm/LLVMContext.h" #include "llvm/Module.h" #include "llvm/Pass.h" #include "llvm/CodeGen/Passes.h" #include "llvm/Target/TargetData.h" #include "llvm/Target/TargetLowering.h" #include "llvm/Transforms/Utils/BasicBlockUtils.h" #include "llvm/Transforms/Utils/Local.h" #include "llvm/Support/CommandLine.h" #include "llvm/Support/Debug.h" #include "llvm/Support/IRBuilder.h" #include "llvm/ADT/DenseMap.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" #include using namespace llvm; static cl::opt DisableOldSjLjEH("disable-old-sjlj-eh", cl::Hidden, cl::desc("Disable the old SjLj EH preparation pass")); STATISTIC(NumInvokes, "Number of invokes replaced"); STATISTIC(NumUnwinds, "Number of unwinds replaced"); STATISTIC(NumSpilled, "Number of registers live across unwind edges"); namespace { class SjLjEHPass : public FunctionPass { const TargetLowering *TLI; Type *FunctionContextTy; Constant *RegisterFn; Constant *UnregisterFn; Constant *BuiltinSetjmpFn; Constant *FrameAddrFn; Constant *StackAddrFn; Constant *StackRestoreFn; Constant *LSDAAddrFn; Value *PersonalityFn; Constant *SelectorFn; Constant *ExceptionFn; Constant *CallSiteFn; Constant *DispatchSetupFn; Constant *FuncCtxFn; Value *CallSite; DenseMap LPadSuccMap; public: static char ID; // Pass identification, replacement for typeid explicit SjLjEHPass(const TargetLowering *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); Value *setupFunctionContext(Function &F, ArrayRef LPads); void lowerIncomingArguments(Function &F); void lowerAcrossUnwindEdges(Function &F, ArrayRef Invokes); void insertCallSiteStore(Instruction *I, int Number, Value *CallSite); void markInvokeCallSite(InvokeInst *II, int InvokeNo, Value *CallSite, SwitchInst *CatchSwitch); void splitLiveRangesAcrossInvokes(SmallVector &Invokes); void splitLandingPad(InvokeInst *II); bool insertSjLjEHSupport(Function &F); }; } // end anonymous namespace char SjLjEHPass::ID = 0; // Public Interface To the SjLjEHPass pass. FunctionPass *llvm::createSjLjEHPass(const TargetLowering *TLI) { return new SjLjEHPass(TLI); } // doInitialization - Set up decalarations and types needed to process // exceptions. bool SjLjEHPass::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); SelectorFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_selector); ExceptionFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_exception); CallSiteFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_callsite); DispatchSetupFn = Intrinsic::getDeclaration(&M, Intrinsic::eh_sjlj_dispatch_setup); 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 SjLjEHPass::insertCallSiteStore(Instruction *I, int Number, Value *CallSite) { ConstantInt *CallSiteNoC = ConstantInt::get(Type::getInt32Ty(I->getContext()), Number); // Insert a store of the call-site number new StoreInst(CallSiteNoC, CallSite, true, I); // volatile } /// splitLandingPad - Split a landing pad. This takes considerable care because /// of PHIs and other nasties. The problem is that the jump table needs to jump /// to the landing pad block. However, the landing pad block can be jumped to /// only by an invoke instruction. So we clone the landingpad instruction into /// its own basic block, have the invoke jump to there. The landingpad /// instruction's basic block's successor is now the target for the jump table. /// /// But because of PHI nodes, we need to create another basic block for the jump /// table to jump to. This is definitely a hack, because the values for the PHI /// nodes may not be defined on the edge from the jump table. But that's okay, /// because the jump table is simply a construct to mimic what is happening in /// the CFG. So the values are mysteriously there, even though there is no value /// for the PHI from the jump table's edge (hence calling this a hack). void SjLjEHPass::splitLandingPad(InvokeInst *II) { SmallVector NewBBs; SplitLandingPadPredecessors(II->getUnwindDest(), II->getParent(), ".1", ".2", this, NewBBs); // Create an empty block so that the jump table has something to jump to // which doesn't have any PHI nodes. BasicBlock *LPad = NewBBs[0]; BasicBlock *Succ = *succ_begin(LPad); BasicBlock *JumpTo = BasicBlock::Create(II->getContext(), "jt.land", LPad->getParent(), Succ); LPad->getTerminator()->eraseFromParent(); BranchInst::Create(JumpTo, LPad); BranchInst::Create(Succ, JumpTo); LPadSuccMap[II] = JumpTo; for (BasicBlock::iterator I = Succ->begin(); isa(I); ++I) { PHINode *PN = cast(I); Value *Val = PN->removeIncomingValue(LPad, false); PN->addIncoming(Val, JumpTo); } } /// markInvokeCallSite - Insert code to mark the call_site for this invoke void SjLjEHPass::markInvokeCallSite(InvokeInst *II, int InvokeNo, Value *CallSite, SwitchInst *CatchSwitch) { ConstantInt *CallSiteNoC= ConstantInt::get(Type::getInt32Ty(II->getContext()), InvokeNo); // The runtime comes back to the dispatcher with the call_site - 1 in // the context. Odd, but there it is. ConstantInt *SwitchValC = ConstantInt::get(Type::getInt32Ty(II->getContext()), InvokeNo - 1); // If the unwind edge has phi nodes, split the edge. if (isa(II->getUnwindDest()->begin())) { // FIXME: New EH - This if-condition will be always true in the new scheme. if (II->getUnwindDest()->isLandingPad()) splitLandingPad(II); else SplitCriticalEdge(II, 1, this); // If there are any phi nodes left, they must have a single predecessor. while (PHINode *PN = dyn_cast(II->getUnwindDest()->begin())) { PN->replaceAllUsesWith(PN->getIncomingValue(0)); PN->eraseFromParent(); } } // Insert the store of the call site value insertCallSiteStore(II, InvokeNo, CallSite); // Record the call site value for the back end so it stays associated with // the invoke. CallInst::Create(CallSiteFn, CallSiteNoC, "", II); // Add a switch case to our unwind block. if (BasicBlock *SuccBB = LPadSuccMap[II]) { CatchSwitch->addCase(SwitchValC, SuccBB); } else { CatchSwitch->addCase(SwitchValC, II->getUnwindDest()); } // We still want this to look like an invoke so we emit the LSDA properly, // so we don't transform the invoke into a call here. } /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until /// we reach blocks we've already seen. static void MarkBlocksLiveIn(BasicBlock *BB, std::set &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); } /// splitLiveRangesAcrossInvokes - Each value that is live across an unwind edge /// we spill into a stack location, guaranteeing that there is nothing live /// across the unwind edge. This process also splits all critical edges /// coming out of invoke's. /// FIXME: Move this function to a common utility file (Local.cpp?) so /// both SjLj and LowerInvoke can use it. void SjLjEHPass:: splitLiveRangesAcrossInvokes(SmallVector &Invokes) { // First step, split all critical edges from invoke instructions. for (unsigned i = 0, e = Invokes.size(); i != e; ++i) { InvokeInst *II = Invokes[i]; SplitCriticalEdge(II, 0, this); // FIXME: New EH - This if-condition will be always true in the new scheme. if (II->getUnwindDest()->isLandingPad()) splitLandingPad(II); else SplitCriticalEdge(II, 1, this); assert(!isa(II->getNormalDest()) && !isa(II->getUnwindDest()) && "Critical edge splitting left single entry phi nodes?"); } Function *F = Invokes.back()->getParent()->getParent(); // 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 across the entry block. BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin(); while (isa(AfterAllocaInsertPt) && isa(cast(AfterAllocaInsertPt)->getArraySize())) ++AfterAllocaInsertPt; for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; ++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(Ty) || isa(Ty) || isa(Ty)) { Instruction *EI = ExtractValueInst::Create(AI, 0, "",AfterAllocaInsertPt); 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", AfterAllocaInsertPt); 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); } } // Finally, scan the code looking for instructions with bad live ranges. for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++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(Inst->use_back())->getParent() == BB && !isa(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(Inst)) if (isa(AI->getArraySize()) && BB == F->begin()) continue; // Avoid iterator invalidation by copying users to a temporary vector. SmallVector Users; for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end(); UI != E; ++UI) { Instruction *User = cast(*UI); if (User->getParent() != BB || isa(User)) Users.push_back(User); } // Find all of the blocks that this value is live in. std::set LiveBBs; LiveBBs.insert(Inst->getParent()); while (!Users.empty()) { Instruction *U = Users.back(); Users.pop_back(); if (!isa(U)) { MarkBlocksLiveIn(U->getParent(), LiveBBs); } else { // Uses for a PHI node occur in their predecessor block. PHINode *PN = cast(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)) NeedsSpill = true; } // 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) { ++NumSpilled; DemoteRegToStack(*Inst, true); } } } /// CreateLandingPadLoad - Load the exception handling values and insert them /// into a structure. static Instruction *CreateLandingPadLoad(Function &F, Value *ExnAddr, Value *SelAddr, BasicBlock::iterator InsertPt) { Value *Exn = new LoadInst(ExnAddr, "exn", false, InsertPt); Type *Ty = Type::getInt8PtrTy(F.getContext()); Exn = CastInst::Create(Instruction::IntToPtr, Exn, Ty, "", InsertPt); Value *Sel = new LoadInst(SelAddr, "sel", false, InsertPt); Ty = StructType::get(Exn->getType(), Sel->getType(), NULL); InsertValueInst *LPadVal = InsertValueInst::Create(llvm::UndefValue::get(Ty), Exn, 0, "lpad.val", InsertPt); return InsertValueInst::Create(LPadVal, Sel, 1, "lpad.val", InsertPt); } /// ReplaceLandingPadVal - Replace the landingpad instruction's value with a /// load from the stored values (via CreateLandingPadLoad). This looks through /// PHI nodes, and removes them if they are dead. static void ReplaceLandingPadVal(Function &F, Instruction *Inst, Value *ExnAddr, Value *SelAddr) { if (Inst->use_empty()) return; while (!Inst->use_empty()) { Instruction *I = cast(Inst->use_back()); if (PHINode *PN = dyn_cast(I)) { ReplaceLandingPadVal(F, PN, ExnAddr, SelAddr); if (PN->use_empty()) PN->eraseFromParent(); continue; } I->replaceUsesOfWith(Inst, CreateLandingPadLoad(F, ExnAddr, SelAddr, I)); } } bool SjLjEHPass::insertSjLjEHSupport(Function &F) { SmallVector Returns; SmallVector Unwinds; SmallVector Invokes; // Look through the terminators of the basic blocks to find invokes, returns // and unwinds. for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { if (ReturnInst *RI = dyn_cast(BB->getTerminator())) { // Remember all return instructions in case we insert an invoke into this // function. Returns.push_back(RI); } else if (InvokeInst *II = dyn_cast(BB->getTerminator())) { Invokes.push_back(II); } else if (UnwindInst *UI = dyn_cast(BB->getTerminator())) { Unwinds.push_back(UI); } } NumInvokes += Invokes.size(); NumUnwinds += Unwinds.size(); // If we don't have any invokes, there's nothing to do. if (Invokes.empty()) return false; // Find the eh.selector.*, eh.exception and alloca calls. // // Remember any allocas() that aren't in the entry block, as the // jmpbuf saved SP will need to be updated for them. // // We'll use the first eh.selector to determine the right personality // function to use. For SJLJ, we always use the same personality for the // whole function, not on a per-selector basis. // FIXME: That's a bit ugly. Better way? SmallVector EH_Selectors; SmallVector EH_Exceptions; SmallVector JmpbufUpdatePoints; for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { // Note: Skip the entry block since there's nothing there that interests // us. eh.selector and eh.exception shouldn't ever be there, and we // want to disregard any allocas that are there. // // FIXME: This is awkward. The new EH scheme won't need to skip the entry // block. if (BB == F.begin()) { if (InvokeInst *II = dyn_cast(F.begin()->getTerminator())) { // FIXME: This will be always non-NULL in the new EH. if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst()) if (!PersonalityFn) PersonalityFn = LPI->getPersonalityFn(); } continue; } for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) { if (CallInst *CI = dyn_cast(I)) { if (CI->getCalledFunction() == SelectorFn) { if (!PersonalityFn) PersonalityFn = CI->getArgOperand(1); EH_Selectors.push_back(CI); } else if (CI->getCalledFunction() == ExceptionFn) { EH_Exceptions.push_back(CI); } else if (CI->getCalledFunction() == StackRestoreFn) { JmpbufUpdatePoints.push_back(CI); } } else if (AllocaInst *AI = dyn_cast(I)) { JmpbufUpdatePoints.push_back(AI); } else if (InvokeInst *II = dyn_cast(I)) { // FIXME: This will be always non-NULL in the new EH. if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst()) if (!PersonalityFn) PersonalityFn = LPI->getPersonalityFn(); } } } // If we don't have any eh.selector calls, we can't determine the personality // function. Without a personality function, we can't process exceptions. if (!PersonalityFn) return false; // We have invokes, so we need to add register/unregister calls to get this // function onto the global unwind stack. // // First thing we need to do is scan the whole function for values that are // live across unwind edges. Each value that is live across an unwind edge we // spill into a stack location, guaranteeing that there is nothing live across // the unwind edge. This process also splits all critical edges coming out of // invoke's. splitLiveRangesAcrossInvokes(Invokes); SmallVector LandingPads; for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) { if (InvokeInst *II = dyn_cast(BB->getTerminator())) // FIXME: This will be always non-NULL in the new EH. if (LandingPadInst *LPI = II->getUnwindDest()->getLandingPadInst()) LandingPads.push_back(LPI); } 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 = 4; // FIXME: Should be a TLI check? AllocaInst *FunctionContext = new AllocaInst(FunctionContextTy, 0, Align, "fcn_context", F.begin()->begin()); Value *Idxs[2]; Type *Int32Ty = Type::getInt32Ty(F.getContext()); Value *Zero = ConstantInt::get(Int32Ty, 0); // We need to also keep around a reference to the call_site field Idxs[0] = Zero; Idxs[1] = ConstantInt::get(Int32Ty, 1); CallSite = GetElementPtrInst::Create(FunctionContext, Idxs, "call_site", EntryBB->getTerminator()); // The exception selector comes back in context->data[1] Idxs[1] = ConstantInt::get(Int32Ty, 2); Value *FCData = GetElementPtrInst::Create(FunctionContext, Idxs, "fc_data", EntryBB->getTerminator()); Idxs[1] = ConstantInt::get(Int32Ty, 1); Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, "exc_selector_gep", EntryBB->getTerminator()); // The exception value comes back in context->data[0] Idxs[1] = Zero; Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, "exception_gep", EntryBB->getTerminator()); // The result of the eh.selector call will be replaced with a a reference to // the selector value returned in the function context. We leave the selector // itself so the EH analysis later can use it. for (int i = 0, e = EH_Selectors.size(); i < e; ++i) { CallInst *I = EH_Selectors[i]; Value *SelectorVal = new LoadInst(SelectorAddr, "select_val", true, I); I->replaceAllUsesWith(SelectorVal); } // eh.exception calls are replaced with references to the proper location in // the context. Unlike eh.selector, the eh.exception calls are removed // entirely. for (int i = 0, e = EH_Exceptions.size(); i < e; ++i) { CallInst *I = EH_Exceptions[i]; // Possible for there to be duplicates, so check to make sure the // instruction hasn't already been removed. if (!I->getParent()) continue; Value *Val = new LoadInst(ExceptionAddr, "exception", true, I); Type *Ty = Type::getInt8PtrTy(F.getContext()); Val = CastInst::Create(Instruction::IntToPtr, Val, Ty, "", I); I->replaceAllUsesWith(Val); I->eraseFromParent(); } for (unsigned i = 0, e = LandingPads.size(); i != e; ++i) ReplaceLandingPadVal(F, LandingPads[i], ExceptionAddr, SelectorAddr); // The entry block changes to have the eh.sjlj.setjmp, with a conditional // branch to a dispatch block for non-zero returns. If we return normally, // we're not handling an exception and just register the function context and // continue. // Create the dispatch block. The dispatch block is basically a big switch // statement that goes to all of the invoke landing pads. BasicBlock *DispatchBlock = BasicBlock::Create(F.getContext(), "eh.sjlj.setjmp.catch", &F); // Insert a load of the callsite in the dispatch block, and a switch on its // value. By default, we issue a trap statement. BasicBlock *TrapBlock = BasicBlock::Create(F.getContext(), "trapbb", &F); CallInst::Create(Intrinsic::getDeclaration(F.getParent(), Intrinsic::trap), "", TrapBlock); new UnreachableInst(F.getContext(), TrapBlock); Value *DispatchLoad = new LoadInst(CallSite, "invoke.num", true, DispatchBlock); SwitchInst *DispatchSwitch = SwitchInst::Create(DispatchLoad, TrapBlock, Invokes.size(), DispatchBlock); // Split the entry block to insert the conditional branch for the setjmp. BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(), "eh.sjlj.setjmp.cont"); // Populate the Function Context // 1. LSDA address // 2. Personality function address // 3. jmpbuf (save SP, FP and call eh.sjlj.setjmp) // LSDA address Idxs[0] = Zero; Idxs[1] = ConstantInt::get(Int32Ty, 4); Value *LSDAFieldPtr = GetElementPtrInst::Create(FunctionContext, Idxs, "lsda_gep", EntryBB->getTerminator()); Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr", EntryBB->getTerminator()); new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator()); Idxs[1] = ConstantInt::get(Int32Ty, 3); Value *PersonalityFieldPtr = GetElementPtrInst::Create(FunctionContext, Idxs, "lsda_gep", EntryBB->getTerminator()); new StoreInst(PersonalityFn, PersonalityFieldPtr, true, EntryBB->getTerminator()); // Save the frame pointer. Idxs[1] = ConstantInt::get(Int32Ty, 5); Value *JBufPtr = GetElementPtrInst::Create(FunctionContext, Idxs, "jbuf_gep", EntryBB->getTerminator()); Idxs[1] = ConstantInt::get(Int32Ty, 0); Value *FramePtr = GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_fp_gep", EntryBB->getTerminator()); Value *Val = CallInst::Create(FrameAddrFn, ConstantInt::get(Int32Ty, 0), "fp", EntryBB->getTerminator()); new StoreInst(Val, FramePtr, true, EntryBB->getTerminator()); // Save the stack pointer. Idxs[1] = ConstantInt::get(Int32Ty, 2); Value *StackPtr = GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_sp_gep", EntryBB->getTerminator()); Val = CallInst::Create(StackAddrFn, "sp", EntryBB->getTerminator()); new StoreInst(Val, StackPtr, true, EntryBB->getTerminator()); // Call the setjmp instrinsic. It fills in the rest of the jmpbuf. Value *SetjmpArg = CastInst::Create(Instruction::BitCast, JBufPtr, Type::getInt8PtrTy(F.getContext()), "", EntryBB->getTerminator()); Value *DispatchVal = CallInst::Create(BuiltinSetjmpFn, SetjmpArg, "", EntryBB->getTerminator()); // Add a call to dispatch_setup after the setjmp call. This is expanded to any // target-specific setup that needs to be done. CallInst::Create(DispatchSetupFn, DispatchVal, "", EntryBB->getTerminator()); // check the return value of the setjmp. non-zero goes to dispatcher. Value *IsNormal = new ICmpInst(EntryBB->getTerminator(), ICmpInst::ICMP_EQ, DispatchVal, Zero, "notunwind"); // Nuke the uncond branch. EntryBB->getTerminator()->eraseFromParent(); // Put in a new condbranch in its place. BranchInst::Create(ContBlock, DispatchBlock, IsNormal, EntryBB); // Register the function context and make sure it's known to not throw CallInst *Register = CallInst::Create(RegisterFn, FunctionContext, "", ContBlock->getTerminator()); Register->setDoesNotThrow(); // At this point, we are all set up, update the invoke instructions to mark // their call_site values, and fill in the dispatch switch accordingly. for (unsigned i = 0, e = Invokes.size(); i != e; ++i) markInvokeCallSite(Invokes[i], i+1, CallSite, DispatchSwitch); // 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(I)) { // Ignore calls to the EH builtins (eh.selector, eh.exception) Constant *Callee = CI->getCalledFunction(); if (Callee != SelectorFn && Callee != ExceptionFn && !CI->doesNotThrow()) insertCallSiteStore(CI, -1, CallSite); } else if (ResumeInst *RI = dyn_cast(I)) { insertCallSiteStore(RI, -1, CallSite); } } // Replace all unwinds with a branch to the unwind handler. // ??? Should this ever happen with sjlj exceptions? for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) { BranchInst::Create(TrapBlock, Unwinds[i]); Unwinds[i]->eraseFromParent(); } // Following any allocas not in the entry block, update the saved SP in the // jmpbuf to the new value. for (unsigned i = 0, e = JmpbufUpdatePoints.size(); i != e; ++i) { Instruction *AI = JmpbufUpdatePoints[i]; Instruction *StackAddr = CallInst::Create(StackAddrFn, "sp"); StackAddr->insertAfter(AI); 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, FunctionContext, "", Returns[i]); return true; } /// setupFunctionContext - Allocate the function context on the stack and fill /// it with all of the data that we know at this point. Value *SjLjEHPass:: setupFunctionContext(Function &F, ArrayRef 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->getTargetData()->getPrefTypeAlignment(FunctionContextTy); AllocaInst *FuncCtx = new AllocaInst(FunctionContextTy, 0, Align, "fn_context", EntryBB->begin()); // Fill in the function context structure. Value *Idxs[2]; Type *Int32Ty = Type::getInt32Ty(F.getContext()); Value *Zero = ConstantInt::get(Int32Ty, 0); Value *One = ConstantInt::get(Int32Ty, 1); // Keep around a reference to the call_site field. Idxs[0] = Zero; Idxs[1] = One; CallSite = GetElementPtrInst::Create(FuncCtx, Idxs, "call_site", EntryBB->getTerminator()); // Reference the __data field. Idxs[1] = ConstantInt::get(Int32Ty, 2); Value *FCData = GetElementPtrInst::Create(FuncCtx, Idxs, "__data", EntryBB->getTerminator()); // The exception value comes back in context->__data[0]. Idxs[1] = Zero; Value *ExceptionAddr = GetElementPtrInst::Create(FCData, Idxs, "exception_gep", EntryBB->getTerminator()); // The exception selector comes back in context->__data[1]. Idxs[1] = One; Value *SelectorAddr = GetElementPtrInst::Create(FCData, Idxs, "exn_selector_gep", EntryBB->getTerminator()); for (unsigned I = 0, E = LPads.size(); I != E; ++I) { LandingPadInst *LPI = LPads[I]; IRBuilder<> Builder(LPI->getParent()->getFirstInsertionPt()); Value *ExnVal = Builder.CreateLoad(ExceptionAddr, true, "exn_val"); ExnVal = Builder.CreateIntToPtr(ExnVal, Type::getInt8PtrTy(F.getContext())); Value *SelVal = Builder.CreateLoad(SelectorAddr, true, "exn_selector_val"); Type *LPadType = LPI->getType(); Value *LPadVal = UndefValue::get(LPadType); LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val"); LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val"); LPI->replaceAllUsesWith(LPadVal); } // Personality function Idxs[1] = ConstantInt::get(Int32Ty, 3); if (!PersonalityFn) PersonalityFn = LPads[0]->getPersonalityFn(); Value *PersonalityFieldPtr = GetElementPtrInst::Create(FuncCtx, Idxs, "pers_fn_gep", EntryBB->getTerminator()); new StoreInst(PersonalityFn, PersonalityFieldPtr, true, EntryBB->getTerminator()); // LSDA address Idxs[1] = ConstantInt::get(Int32Ty, 4); Value *LSDAFieldPtr = GetElementPtrInst::Create(FuncCtx, Idxs, "lsda_gep", EntryBB->getTerminator()); Value *LSDA = CallInst::Create(LSDAAddrFn, "lsda_addr", EntryBB->getTerminator()); new StoreInst(LSDA, LSDAFieldPtr, true, EntryBB->getTerminator()); 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 SjLjEHPass::lowerIncomingArguments(Function &F) { BasicBlock::iterator AfterAllocaInsPt = F.begin()->begin(); while (isa(AfterAllocaInsPt) && isa(cast(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(Ty) || isa(Ty) || isa(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 SjLjEHPass::lowerAcrossUnwindEdges(Function &F, ArrayRef 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(Inst->use_back())->getParent() == BB && !isa(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(Inst)) if (isa(AI->getArraySize()) && BB == F.begin()) continue; // Avoid iterator invalidation by copying users to a temporary vector. SmallVector Users; for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end(); UI != E; ++UI) { Instruction *User = cast(*UI); if (User->getParent() != BB || isa(User)) Users.push_back(User); } // Find all of the blocks that this value is live in. std::set LiveBBs; LiveBBs.insert(Inst->getParent()); while (!Users.empty()) { Instruction *U = Users.back(); Users.pop_back(); if (!isa(U)) { MarkBlocksLiveIn(U->getParent(), LiveBBs); } else { // Uses for a PHI node occur in their predecessor block. PHINode *PN = cast(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)) { NeedsSpill = true; } } // 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) { ++NumSpilled; DemoteRegToStack(*Inst, true); } } } } /// 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 SjLjEHPass::setupEntryBlockAndCallSites(Function &F) { SmallVector Returns; SmallVector Invokes; SmallVector 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(BB->getTerminator())) { Invokes.push_back(II); LPads.push_back(II->getUnwindDest()->getLandingPadInst()); } else if (ReturnInst *RI = dyn_cast(BB->getTerminator())) { Returns.push_back(RI); } if (Invokes.empty()) return false; lowerIncomingArguments(F); lowerAcrossUnwindEdges(F, Invokes); Value *FuncCtx = setupFunctionContext(F, LPads); BasicBlock *EntryBB = F.begin(); Type *Int32Ty = Type::getInt32Ty(F.getContext()); Value *Idxs[2] = { ConstantInt::get(Int32Ty, 0), 0 }; // Get a reference to the jump buffer. Idxs[1] = ConstantInt::get(Int32Ty, 5); Value *JBufPtr = GetElementPtrInst::Create(FuncCtx, Idxs, "jbuf_gep", EntryBB->getTerminator()); // Save the frame pointer. Idxs[1] = ConstantInt::get(Int32Ty, 0); Value *FramePtr = GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_fp_gep", EntryBB->getTerminator()); Value *Val = CallInst::Create(FrameAddrFn, ConstantInt::get(Int32Ty, 0), "fp", EntryBB->getTerminator()); new StoreInst(Val, FramePtr, true, EntryBB->getTerminator()); // Save the stack pointer. Idxs[1] = ConstantInt::get(Int32Ty, 2); Value *StackPtr = GetElementPtrInst::Create(JBufPtr, Idxs, "jbuf_sp_gep", EntryBB->getTerminator()); Val = CallInst::Create(StackAddrFn, "sp", EntryBB->getTerminator()); new StoreInst(Val, StackPtr, true, EntryBB->getTerminator()); // Call the setjmp instrinsic. It fills in the rest of the jmpbuf. Value *SetjmpArg = CastInst::Create(Instruction::BitCast, JBufPtr, Type::getInt8PtrTy(F.getContext()), "", EntryBB->getTerminator()); CallInst::Create(BuiltinSetjmpFn, SetjmpArg, "", EntryBB->getTerminator()); // Store a pointer to the function context so that the back-end will know // where to look for it. Value *FuncCtxArg = CastInst::Create(Instruction::BitCast, FuncCtx, Type::getInt8PtrTy(F.getContext()), "", EntryBB->getTerminator()); CallInst::Create(FuncCtxFn, FuncCtxArg, "", EntryBB->getTerminator()); // 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, CallSite); 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(I)) { if (!CI->doesNotThrow()) insertCallSiteStore(CI, -1, CallSite); } else if (ResumeInst *RI = dyn_cast(I)) { insertCallSiteStore(RI, -1, CallSite); } // Register the function context and make sure it's known to not throw CallInst *Register = CallInst::Create(RegisterFn, FuncCtx, "", EntryBB->getTerminator()); Register->setDoesNotThrow(); // 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 SjLjEHPass::runOnFunction(Function &F) { bool Res = false; if (!DisableOldSjLjEH) Res = insertSjLjEHSupport(F); else Res = setupEntryBlockAndCallSites(F); return Res; }