1 //===- EscapeEnumerator.cpp -----------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // Defines a helper class that enumerates all possible exits from a function, 11 // including exception handling. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "llvm/Transforms/Utils/EscapeEnumerator.h" 16 #include "llvm/Analysis/EHPersonalities.h" 17 #include "llvm/IR/CallSite.h" 18 #include "llvm/IR/Module.h" 19 #include "llvm/Transforms/Utils/Local.h" 20 using namespace llvm; 21 22 static Constant *getDefaultPersonalityFn(Module *M) { 23 LLVMContext &C = M->getContext(); 24 Triple T(M->getTargetTriple()); 25 EHPersonality Pers = getDefaultEHPersonality(T); 26 return M->getOrInsertFunction(getEHPersonalityName(Pers), 27 FunctionType::get(Type::getInt32Ty(C), true)); 28 } 29 30 IRBuilder<> *EscapeEnumerator::Next() { 31 if (Done) 32 return nullptr; 33 34 // Find all 'return', 'resume', and 'unwind' instructions. 35 while (StateBB != StateE) { 36 BasicBlock *CurBB = &*StateBB++; 37 38 // Branches and invokes do not escape, only unwind, resume, and return 39 // do. 40 TerminatorInst *TI = CurBB->getTerminator(); 41 if (!isa<ReturnInst>(TI) && !isa<ResumeInst>(TI)) 42 continue; 43 44 Builder.SetInsertPoint(TI); 45 return &Builder; 46 } 47 48 Done = true; 49 50 if (!HandleExceptions) 51 return nullptr; 52 53 if (F.doesNotThrow()) 54 return nullptr; 55 56 // Find all 'call' instructions that may throw. 57 SmallVector<Instruction *, 16> Calls; 58 for (BasicBlock &BB : F) 59 for (Instruction &II : BB) 60 if (CallInst *CI = dyn_cast<CallInst>(&II)) 61 if (!CI->doesNotThrow()) 62 Calls.push_back(CI); 63 64 if (Calls.empty()) 65 return nullptr; 66 67 // Create a cleanup block. 68 LLVMContext &C = F.getContext(); 69 BasicBlock *CleanupBB = BasicBlock::Create(C, CleanupBBName, &F); 70 Type *ExnTy = 71 StructType::get(Type::getInt8PtrTy(C), Type::getInt32Ty(C), nullptr); 72 if (!F.hasPersonalityFn()) { 73 Constant *PersFn = getDefaultPersonalityFn(F.getParent()); 74 F.setPersonalityFn(PersFn); 75 } 76 77 if (isFuncletEHPersonality(classifyEHPersonality(F.getPersonalityFn()))) { 78 report_fatal_error("Funclet EH not supported"); 79 } 80 81 LandingPadInst *LPad = 82 LandingPadInst::Create(ExnTy, 1, "cleanup.lpad", CleanupBB); 83 LPad->setCleanup(true); 84 ResumeInst *RI = ResumeInst::Create(LPad, CleanupBB); 85 86 // Transform the 'call' instructions into 'invoke's branching to the 87 // cleanup block. Go in reverse order to make prettier BB names. 88 SmallVector<Value *, 16> Args; 89 for (unsigned I = Calls.size(); I != 0;) { 90 CallInst *CI = cast<CallInst>(Calls[--I]); 91 changeToInvokeAndSplitBasicBlock(CI, CleanupBB); 92 } 93 94 Builder.SetInsertPoint(RI); 95 return &Builder; 96 } 97