diff options
Diffstat (limited to 'contrib/llvm/lib/CodeGen/SjLjEHPrepare.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/SjLjEHPrepare.cpp | 480 |
1 files changed, 480 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/SjLjEHPrepare.cpp b/contrib/llvm/lib/CodeGen/SjLjEHPrepare.cpp new file mode 100644 index 000000000000..ce01c5f23e57 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/SjLjEHPrepare.cpp @@ -0,0 +1,480 @@ +//===- 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/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/Module.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; + Constant *RegisterFn; + Constant *UnregisterFn; + Constant *BuiltinSetupDispatchFn; + Constant *FrameAddrFn; + Constant *StackAddrFn; + Constant *StackRestoreFn; + Constant *LSDAAddrFn; + 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); + + 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. + + for (BasicBlock *PredBB : predecessors(BB)) + MarkBlocksLiveIn(PredBB, 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(); + 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(); + unsigned Align = DL.getPrefTypeAlignment(FunctionContextTy); + FuncCtx = new AllocaInst(FunctionContextTy, nullptr, Align, "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]. + 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()); + 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()) { + 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)) { + 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), nullptr); + UnregisterFn = M.getOrInsertFunction( + "_Unwind_SjLj_Unregister", Type::getVoidTy(M.getContext()), + PointerType::getUnqual(FunctionContextTy), nullptr); + FrameAddrFn = Intrinsic::getDeclaration(&M, Intrinsic::frameaddress); + 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; +} |