1 //===- EscapeEnumerator.cpp -----------------------------------------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // Defines a helper class that enumerates all possible exits from a function, 10 // including exception handling. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Transforms/Utils/EscapeEnumerator.h" 15 #include "llvm/Analysis/EHPersonalities.h" 16 #include "llvm/Transforms/Utils/Local.h" 17 #include "llvm/IR/Module.h" 18 using namespace llvm; 19 20 static FunctionCallee getDefaultPersonalityFn(Module *M) { 21 LLVMContext &C = M->getContext(); 22 Triple T(M->getTargetTriple()); 23 EHPersonality Pers = getDefaultEHPersonality(T); 24 return M->getOrInsertFunction(getEHPersonalityName(Pers), 25 FunctionType::get(Type::getInt32Ty(C), true)); 26 } 27 28 IRBuilder<> *EscapeEnumerator::Next() { 29 if (Done) 30 return nullptr; 31 32 // Find all 'return', 'resume', and 'unwind' instructions. 33 while (StateBB != StateE) { 34 BasicBlock *CurBB = &*StateBB++; 35 36 // Branches and invokes do not escape, only unwind, resume, and return 37 // do. 38 Instruction *TI = CurBB->getTerminator(); 39 if (!isa<ReturnInst>(TI) && !isa<ResumeInst>(TI)) 40 continue; 41 42 Builder.SetInsertPoint(TI); 43 return &Builder; 44 } 45 46 Done = true; 47 48 if (!HandleExceptions) 49 return nullptr; 50 51 if (F.doesNotThrow()) 52 return nullptr; 53 54 // Find all 'call' instructions that may throw. 55 SmallVector<Instruction *, 16> Calls; 56 for (BasicBlock &BB : F) 57 for (Instruction &II : BB) 58 if (CallInst *CI = dyn_cast<CallInst>(&II)) 59 if (!CI->doesNotThrow()) 60 Calls.push_back(CI); 61 62 if (Calls.empty()) 63 return nullptr; 64 65 // Create a cleanup block. 66 LLVMContext &C = F.getContext(); 67 BasicBlock *CleanupBB = BasicBlock::Create(C, CleanupBBName, &F); 68 Type *ExnTy = StructType::get(Type::getInt8PtrTy(C), Type::getInt32Ty(C)); 69 if (!F.hasPersonalityFn()) { 70 FunctionCallee PersFn = getDefaultPersonalityFn(F.getParent()); 71 F.setPersonalityFn(cast<Constant>(PersFn.getCallee())); 72 } 73 74 if (isScopedEHPersonality(classifyEHPersonality(F.getPersonalityFn()))) { 75 report_fatal_error("Scoped EH not supported"); 76 } 77 78 LandingPadInst *LPad = 79 LandingPadInst::Create(ExnTy, 1, "cleanup.lpad", CleanupBB); 80 LPad->setCleanup(true); 81 ResumeInst *RI = ResumeInst::Create(LPad, CleanupBB); 82 83 // Transform the 'call' instructions into 'invoke's branching to the 84 // cleanup block. Go in reverse order to make prettier BB names. 85 SmallVector<Value *, 16> Args; 86 for (unsigned I = Calls.size(); I != 0;) { 87 CallInst *CI = cast<CallInst>(Calls[--I]); 88 changeToInvokeAndSplitBasicBlock(CI, CleanupBB); 89 } 90 91 Builder.SetInsertPoint(RI); 92 return &Builder; 93 } 94