1 //===- LowerEmuTLS.cpp - Add __emutls_[vt].* variables --------------------===// 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 transformation is required for targets depending on libgcc style 10 // emulated thread local storage variables. For every defined TLS variable xyz, 11 // an __emutls_v.xyz is generated. If there is non-zero initialized value 12 // an __emutls_t.xyz is also generated. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "llvm/ADT/SmallVector.h" 17 #include "llvm/CodeGen/Passes.h" 18 #include "llvm/CodeGen/TargetPassConfig.h" 19 #include "llvm/IR/Constants.h" 20 #include "llvm/IR/Module.h" 21 #include "llvm/InitializePasses.h" 22 #include "llvm/Pass.h" 23 #include "llvm/Target/TargetMachine.h" 24 25 using namespace llvm; 26 27 #define DEBUG_TYPE "loweremutls" 28 29 namespace { 30 31 class LowerEmuTLS : public ModulePass { 32 public: 33 static char ID; // Pass identification, replacement for typeid 34 LowerEmuTLS() : ModulePass(ID) { 35 initializeLowerEmuTLSPass(*PassRegistry::getPassRegistry()); 36 } 37 38 bool runOnModule(Module &M) override; 39 private: 40 bool addEmuTlsVar(Module &M, const GlobalVariable *GV); 41 static void copyLinkageVisibility(Module &M, 42 const GlobalVariable *from, 43 GlobalVariable *to) { 44 to->setLinkage(from->getLinkage()); 45 to->setVisibility(from->getVisibility()); 46 to->setDSOLocal(from->isDSOLocal()); 47 if (from->hasComdat()) { 48 to->setComdat(M.getOrInsertComdat(to->getName())); 49 to->getComdat()->setSelectionKind(from->getComdat()->getSelectionKind()); 50 } 51 } 52 }; 53 } 54 55 char LowerEmuTLS::ID = 0; 56 57 INITIALIZE_PASS(LowerEmuTLS, DEBUG_TYPE, 58 "Add __emutls_[vt]. variables for emultated TLS model", false, 59 false) 60 61 ModulePass *llvm::createLowerEmuTLSPass() { return new LowerEmuTLS(); } 62 63 bool LowerEmuTLS::runOnModule(Module &M) { 64 if (skipModule(M)) 65 return false; 66 67 auto *TPC = getAnalysisIfAvailable<TargetPassConfig>(); 68 if (!TPC) 69 return false; 70 71 auto &TM = TPC->getTM<TargetMachine>(); 72 if (!TM.useEmulatedTLS()) 73 return false; 74 75 bool Changed = false; 76 SmallVector<const GlobalVariable*, 8> TlsVars; 77 for (const auto &G : M.globals()) { 78 if (G.isThreadLocal()) 79 TlsVars.append({&G}); 80 } 81 for (const auto *const G : TlsVars) 82 Changed |= addEmuTlsVar(M, G); 83 return Changed; 84 } 85 86 bool LowerEmuTLS::addEmuTlsVar(Module &M, const GlobalVariable *GV) { 87 LLVMContext &C = M.getContext(); 88 PointerType *VoidPtrType = Type::getInt8PtrTy(C); 89 90 std::string EmuTlsVarName = ("__emutls_v." + GV->getName()).str(); 91 GlobalVariable *EmuTlsVar = M.getNamedGlobal(EmuTlsVarName); 92 if (EmuTlsVar) 93 return false; // It has been added before. 94 95 const DataLayout &DL = M.getDataLayout(); 96 Constant *NullPtr = ConstantPointerNull::get(VoidPtrType); 97 98 // Get non-zero initializer from GV's initializer. 99 const Constant *InitValue = nullptr; 100 if (GV->hasInitializer()) { 101 InitValue = GV->getInitializer(); 102 const ConstantInt *InitIntValue = dyn_cast<ConstantInt>(InitValue); 103 // When GV's init value is all 0, omit the EmuTlsTmplVar and let 104 // the emutls library function to reset newly allocated TLS variables. 105 if (isa<ConstantAggregateZero>(InitValue) || 106 (InitIntValue && InitIntValue->isZero())) 107 InitValue = nullptr; 108 } 109 110 // Create the __emutls_v. symbol, whose type has 4 fields: 111 // word size; // size of GV in bytes 112 // word align; // alignment of GV 113 // void *ptr; // initialized to 0; set at run time per thread. 114 // void *templ; // 0 or point to __emutls_t.* 115 // sizeof(word) should be the same as sizeof(void*) on target. 116 IntegerType *WordType = DL.getIntPtrType(C); 117 PointerType *InitPtrType = InitValue ? 118 PointerType::getUnqual(InitValue->getType()) : VoidPtrType; 119 Type *ElementTypes[4] = {WordType, WordType, VoidPtrType, InitPtrType}; 120 ArrayRef<Type*> ElementTypeArray(ElementTypes, 4); 121 StructType *EmuTlsVarType = StructType::create(ElementTypeArray); 122 EmuTlsVar = cast<GlobalVariable>( 123 M.getOrInsertGlobal(EmuTlsVarName, EmuTlsVarType)); 124 copyLinkageVisibility(M, GV, EmuTlsVar); 125 126 // Define "__emutls_t.*" and "__emutls_v.*" only if GV is defined. 127 if (!GV->hasInitializer()) 128 return true; 129 130 Type *GVType = GV->getValueType(); 131 Align GVAlignment = DL.getValueOrABITypeAlignment(GV->getAlign(), GVType); 132 133 // Define "__emutls_t.*" if there is InitValue 134 GlobalVariable *EmuTlsTmplVar = nullptr; 135 if (InitValue) { 136 std::string EmuTlsTmplName = ("__emutls_t." + GV->getName()).str(); 137 EmuTlsTmplVar = dyn_cast_or_null<GlobalVariable>( 138 M.getOrInsertGlobal(EmuTlsTmplName, GVType)); 139 assert(EmuTlsTmplVar && "Failed to create emualted TLS initializer"); 140 EmuTlsTmplVar->setConstant(true); 141 EmuTlsTmplVar->setInitializer(const_cast<Constant*>(InitValue)); 142 EmuTlsTmplVar->setAlignment(GVAlignment); 143 copyLinkageVisibility(M, GV, EmuTlsTmplVar); 144 } 145 146 // Define "__emutls_v.*" with initializer and alignment. 147 Constant *ElementValues[4] = { 148 ConstantInt::get(WordType, DL.getTypeStoreSize(GVType)), 149 ConstantInt::get(WordType, GVAlignment.value()), NullPtr, 150 EmuTlsTmplVar ? EmuTlsTmplVar : NullPtr}; 151 ArrayRef<Constant*> ElementValueArray(ElementValues, 4); 152 EmuTlsVar->setInitializer( 153 ConstantStruct::get(EmuTlsVarType, ElementValueArray)); 154 Align MaxAlignment = 155 std::max(DL.getABITypeAlign(WordType), DL.getABITypeAlign(VoidPtrType)); 156 EmuTlsVar->setAlignment(MaxAlignment); 157 return true; 158 } 159