1303231Sdim//===- LowerEmuTLS.cpp - Add __emutls_[vt].* variables --------------------===// 2303231Sdim// 3353358Sdim// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4353358Sdim// See https://llvm.org/LICENSE.txt for license information. 5353358Sdim// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6303231Sdim// 7303231Sdim//===----------------------------------------------------------------------===// 8303231Sdim// 9303231Sdim// This transformation is required for targets depending on libgcc style 10303231Sdim// emulated thread local storage variables. For every defined TLS variable xyz, 11303231Sdim// an __emutls_v.xyz is generated. If there is non-zero initialized value 12303231Sdim// an __emutls_t.xyz is also generated. 13303231Sdim// 14303231Sdim//===----------------------------------------------------------------------===// 15303231Sdim 16303231Sdim#include "llvm/ADT/SmallVector.h" 17303231Sdim#include "llvm/CodeGen/Passes.h" 18327952Sdim#include "llvm/CodeGen/TargetLowering.h" 19321369Sdim#include "llvm/CodeGen/TargetPassConfig.h" 20303231Sdim#include "llvm/IR/LLVMContext.h" 21303231Sdim#include "llvm/IR/Module.h" 22360784Sdim#include "llvm/InitializePasses.h" 23303231Sdim#include "llvm/Pass.h" 24303231Sdim 25303231Sdimusing namespace llvm; 26303231Sdim 27303231Sdim#define DEBUG_TYPE "loweremutls" 28303231Sdim 29303231Sdimnamespace { 30303231Sdim 31303231Sdimclass LowerEmuTLS : public ModulePass { 32303231Sdimpublic: 33303231Sdim static char ID; // Pass identification, replacement for typeid 34321369Sdim LowerEmuTLS() : ModulePass(ID) { 35303231Sdim initializeLowerEmuTLSPass(*PassRegistry::getPassRegistry()); 36303231Sdim } 37321369Sdim 38303231Sdim bool runOnModule(Module &M) override; 39303231Sdimprivate: 40303231Sdim bool addEmuTlsVar(Module &M, const GlobalVariable *GV); 41303231Sdim static void copyLinkageVisibility(Module &M, 42303231Sdim const GlobalVariable *from, 43303231Sdim GlobalVariable *to) { 44303231Sdim to->setLinkage(from->getLinkage()); 45303231Sdim to->setVisibility(from->getVisibility()); 46303231Sdim if (from->hasComdat()) { 47303231Sdim to->setComdat(M.getOrInsertComdat(to->getName())); 48303231Sdim to->getComdat()->setSelectionKind(from->getComdat()->getSelectionKind()); 49303231Sdim } 50303231Sdim } 51303231Sdim}; 52303231Sdim} 53303231Sdim 54303231Sdimchar LowerEmuTLS::ID = 0; 55303231Sdim 56321369SdimINITIALIZE_PASS(LowerEmuTLS, DEBUG_TYPE, 57321369Sdim "Add __emutls_[vt]. variables for emultated TLS model", false, 58321369Sdim false) 59303231Sdim 60321369SdimModulePass *llvm::createLowerEmuTLSPass() { return new LowerEmuTLS(); } 61303231Sdim 62303231Sdimbool LowerEmuTLS::runOnModule(Module &M) { 63303231Sdim if (skipModule(M)) 64303231Sdim return false; 65303231Sdim 66321369Sdim auto *TPC = getAnalysisIfAvailable<TargetPassConfig>(); 67321369Sdim if (!TPC) 68303231Sdim return false; 69303231Sdim 70321369Sdim auto &TM = TPC->getTM<TargetMachine>(); 71341825Sdim if (!TM.useEmulatedTLS()) 72321369Sdim return false; 73321369Sdim 74303231Sdim bool Changed = false; 75303231Sdim SmallVector<const GlobalVariable*, 8> TlsVars; 76303231Sdim for (const auto &G : M.globals()) { 77303231Sdim if (G.isThreadLocal()) 78303231Sdim TlsVars.append({&G}); 79303231Sdim } 80303231Sdim for (const auto G : TlsVars) 81303231Sdim Changed |= addEmuTlsVar(M, G); 82303231Sdim return Changed; 83303231Sdim} 84303231Sdim 85303231Sdimbool LowerEmuTLS::addEmuTlsVar(Module &M, const GlobalVariable *GV) { 86303231Sdim LLVMContext &C = M.getContext(); 87303231Sdim PointerType *VoidPtrType = Type::getInt8PtrTy(C); 88303231Sdim 89303231Sdim std::string EmuTlsVarName = ("__emutls_v." + GV->getName()).str(); 90303231Sdim GlobalVariable *EmuTlsVar = M.getNamedGlobal(EmuTlsVarName); 91303231Sdim if (EmuTlsVar) 92303231Sdim return false; // It has been added before. 93303231Sdim 94303231Sdim const DataLayout &DL = M.getDataLayout(); 95303231Sdim Constant *NullPtr = ConstantPointerNull::get(VoidPtrType); 96303231Sdim 97303231Sdim // Get non-zero initializer from GV's initializer. 98303231Sdim const Constant *InitValue = nullptr; 99303231Sdim if (GV->hasInitializer()) { 100303231Sdim InitValue = GV->getInitializer(); 101303231Sdim const ConstantInt *InitIntValue = dyn_cast<ConstantInt>(InitValue); 102303231Sdim // When GV's init value is all 0, omit the EmuTlsTmplVar and let 103303231Sdim // the emutls library function to reset newly allocated TLS variables. 104303231Sdim if (isa<ConstantAggregateZero>(InitValue) || 105303231Sdim (InitIntValue && InitIntValue->isZero())) 106303231Sdim InitValue = nullptr; 107303231Sdim } 108303231Sdim 109303231Sdim // Create the __emutls_v. symbol, whose type has 4 fields: 110303231Sdim // word size; // size of GV in bytes 111303231Sdim // word align; // alignment of GV 112303231Sdim // void *ptr; // initialized to 0; set at run time per thread. 113303231Sdim // void *templ; // 0 or point to __emutls_t.* 114303231Sdim // sizeof(word) should be the same as sizeof(void*) on target. 115303231Sdim IntegerType *WordType = DL.getIntPtrType(C); 116303231Sdim PointerType *InitPtrType = InitValue ? 117303231Sdim PointerType::getUnqual(InitValue->getType()) : VoidPtrType; 118303231Sdim Type *ElementTypes[4] = {WordType, WordType, VoidPtrType, InitPtrType}; 119303231Sdim ArrayRef<Type*> ElementTypeArray(ElementTypes, 4); 120303231Sdim StructType *EmuTlsVarType = StructType::create(ElementTypeArray); 121303231Sdim EmuTlsVar = cast<GlobalVariable>( 122303231Sdim M.getOrInsertGlobal(EmuTlsVarName, EmuTlsVarType)); 123303231Sdim copyLinkageVisibility(M, GV, EmuTlsVar); 124303231Sdim 125303231Sdim // Define "__emutls_t.*" and "__emutls_v.*" only if GV is defined. 126303231Sdim if (!GV->hasInitializer()) 127303231Sdim return true; 128303231Sdim 129303231Sdim Type *GVType = GV->getValueType(); 130303231Sdim unsigned GVAlignment = GV->getAlignment(); 131303231Sdim if (!GVAlignment) { 132303231Sdim // When LLVM IL declares a variable without alignment, use 133303231Sdim // the ABI default alignment for the type. 134303231Sdim GVAlignment = DL.getABITypeAlignment(GVType); 135303231Sdim } 136303231Sdim 137303231Sdim // Define "__emutls_t.*" if there is InitValue 138303231Sdim GlobalVariable *EmuTlsTmplVar = nullptr; 139303231Sdim if (InitValue) { 140303231Sdim std::string EmuTlsTmplName = ("__emutls_t." + GV->getName()).str(); 141303231Sdim EmuTlsTmplVar = dyn_cast_or_null<GlobalVariable>( 142303231Sdim M.getOrInsertGlobal(EmuTlsTmplName, GVType)); 143303231Sdim assert(EmuTlsTmplVar && "Failed to create emualted TLS initializer"); 144303231Sdim EmuTlsTmplVar->setConstant(true); 145303231Sdim EmuTlsTmplVar->setInitializer(const_cast<Constant*>(InitValue)); 146360784Sdim EmuTlsTmplVar->setAlignment(Align(GVAlignment)); 147303231Sdim copyLinkageVisibility(M, GV, EmuTlsTmplVar); 148303231Sdim } 149303231Sdim 150303231Sdim // Define "__emutls_v.*" with initializer and alignment. 151303231Sdim Constant *ElementValues[4] = { 152303231Sdim ConstantInt::get(WordType, DL.getTypeStoreSize(GVType)), 153303231Sdim ConstantInt::get(WordType, GVAlignment), 154303231Sdim NullPtr, EmuTlsTmplVar ? EmuTlsTmplVar : NullPtr 155303231Sdim }; 156303231Sdim ArrayRef<Constant*> ElementValueArray(ElementValues, 4); 157303231Sdim EmuTlsVar->setInitializer( 158303231Sdim ConstantStruct::get(EmuTlsVarType, ElementValueArray)); 159360784Sdim Align MaxAlignment(std::max(DL.getABITypeAlignment(WordType), 160360784Sdim DL.getABITypeAlignment(VoidPtrType))); 161303231Sdim EmuTlsVar->setAlignment(MaxAlignment); 162303231Sdim return true; 163303231Sdim} 164