1 //===-- Instrumentation.cpp - TransformUtils Infrastructure ---------------===// 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 // This file defines the common initialization infrastructure for the 10 // Instrumentation library. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Transforms/Instrumentation.h" 15 #include "llvm/IR/IntrinsicInst.h" 16 #include "llvm/IR/Module.h" 17 #include "llvm/TargetParser/Triple.h" 18 19 using namespace llvm; 20 21 /// Moves I before IP. Returns new insert point. 22 static BasicBlock::iterator moveBeforeInsertPoint(BasicBlock::iterator I, BasicBlock::iterator IP) { 23 // If I is IP, move the insert point down. 24 if (I == IP) { 25 ++IP; 26 } else { 27 // Otherwise, move I before IP and return IP. 28 I->moveBefore(&*IP); 29 } 30 return IP; 31 } 32 33 /// Instrumentation passes often insert conditional checks into entry blocks. 34 /// Call this function before splitting the entry block to move instructions 35 /// that must remain in the entry block up before the split point. Static 36 /// allocas and llvm.localescape calls, for example, must remain in the entry 37 /// block. 38 BasicBlock::iterator llvm::PrepareToSplitEntryBlock(BasicBlock &BB, 39 BasicBlock::iterator IP) { 40 assert(&BB.getParent()->getEntryBlock() == &BB); 41 for (auto I = IP, E = BB.end(); I != E; ++I) { 42 bool KeepInEntry = false; 43 if (auto *AI = dyn_cast<AllocaInst>(I)) { 44 if (AI->isStaticAlloca()) 45 KeepInEntry = true; 46 } else if (auto *II = dyn_cast<IntrinsicInst>(I)) { 47 if (II->getIntrinsicID() == llvm::Intrinsic::localescape) 48 KeepInEntry = true; 49 } 50 if (KeepInEntry) 51 IP = moveBeforeInsertPoint(I, IP); 52 } 53 return IP; 54 } 55 56 // Create a constant for Str so that we can pass it to the run-time lib. 57 GlobalVariable *llvm::createPrivateGlobalForString(Module &M, StringRef Str, 58 bool AllowMerging, 59 const char *NamePrefix) { 60 Constant *StrConst = ConstantDataArray::getString(M.getContext(), Str); 61 // We use private linkage for module-local strings. If they can be merged 62 // with another one, we set the unnamed_addr attribute. 63 GlobalVariable *GV = 64 new GlobalVariable(M, StrConst->getType(), true, 65 GlobalValue::PrivateLinkage, StrConst, NamePrefix); 66 if (AllowMerging) 67 GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global); 68 GV->setAlignment(Align(1)); // Strings may not be merged w/o setting 69 // alignment explicitly. 70 return GV; 71 } 72 73 Comdat *llvm::getOrCreateFunctionComdat(Function &F, Triple &T) { 74 if (auto Comdat = F.getComdat()) return Comdat; 75 assert(F.hasName()); 76 Module *M = F.getParent(); 77 78 // Make a new comdat for the function. Use the "no duplicates" selection kind 79 // if the object file format supports it. For COFF we restrict it to non-weak 80 // symbols. 81 Comdat *C = M->getOrInsertComdat(F.getName()); 82 if (T.isOSBinFormatELF() || (T.isOSBinFormatCOFF() && !F.isWeakForLinker())) 83 C->setSelectionKind(Comdat::NoDeduplicate); 84 F.setComdat(C); 85 return C; 86 } 87 88 void llvm::setGlobalVariableLargeSection(const Triple &TargetTriple, 89 GlobalVariable &GV) { 90 // Limit to x86-64 ELF. 91 if (TargetTriple.getArch() != Triple::x86_64 || 92 TargetTriple.getObjectFormat() != Triple::ELF) 93 return; 94 // Limit to medium/large code models. 95 std::optional<CodeModel::Model> CM = GV.getParent()->getCodeModel(); 96 if (!CM || (*CM != CodeModel::Medium && *CM != CodeModel::Large)) 97 return; 98 GV.setCodeModel(CodeModel::Large); 99 } 100