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/ADT/Triple.h" 16 #include "llvm/Analysis/EHPersonalities.h" 17 #include "llvm/IR/Module.h" 18 #include "llvm/Transforms/Utils/Local.h" 19 20 using namespace llvm; 21 22 static FunctionCallee 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 Instruction *TI = CurBB->getTerminator(); 41 if (!isa<ReturnInst>(TI) && !isa<ResumeInst>(TI)) 42 continue; 43 44 if (CallInst *CI = CurBB->getTerminatingMustTailCall()) 45 TI = CI; 46 Builder.SetInsertPoint(TI); 47 return &Builder; 48 } 49 50 Done = true; 51 52 if (!HandleExceptions) 53 return nullptr; 54 55 if (F.doesNotThrow()) 56 return nullptr; 57 58 // Find all 'call' instructions that may throw. 59 // We cannot tranform calls with musttail tag. 60 SmallVector<Instruction *, 16> Calls; 61 for (BasicBlock &BB : F) 62 for (Instruction &II : BB) 63 if (CallInst *CI = dyn_cast<CallInst>(&II)) 64 if (!CI->doesNotThrow() && !CI->isMustTailCall()) 65 Calls.push_back(CI); 66 67 if (Calls.empty()) 68 return nullptr; 69 70 // Create a cleanup block. 71 LLVMContext &C = F.getContext(); 72 BasicBlock *CleanupBB = BasicBlock::Create(C, CleanupBBName, &F); 73 Type *ExnTy = StructType::get(Type::getInt8PtrTy(C), Type::getInt32Ty(C)); 74 if (!F.hasPersonalityFn()) { 75 FunctionCallee PersFn = getDefaultPersonalityFn(F.getParent()); 76 F.setPersonalityFn(cast<Constant>(PersFn.getCallee())); 77 } 78 79 if (isScopedEHPersonality(classifyEHPersonality(F.getPersonalityFn()))) { 80 report_fatal_error("Scoped EH not supported"); 81 } 82 83 LandingPadInst *LPad = 84 LandingPadInst::Create(ExnTy, 1, "cleanup.lpad", CleanupBB); 85 LPad->setCleanup(true); 86 ResumeInst *RI = ResumeInst::Create(LPad, CleanupBB); 87 88 // Transform the 'call' instructions into 'invoke's branching to the 89 // cleanup block. Go in reverse order to make prettier BB names. 90 SmallVector<Value *, 16> Args; 91 for (unsigned I = Calls.size(); I != 0;) { 92 CallInst *CI = cast<CallInst>(Calls[--I]); 93 changeToInvokeAndSplitBasicBlock(CI, CleanupBB); 94 } 95 96 Builder.SetInsertPoint(RI); 97 return &Builder; 98 } 99