1 //===-- X86TargetObjectFile.cpp - X86 Object Info -------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #include "X86TargetObjectFile.h" 11 #include "llvm/ADT/StringExtras.h" 12 #include "llvm/IR/Mangler.h" 13 #include "llvm/IR/Operator.h" 14 #include "llvm/MC/MCContext.h" 15 #include "llvm/MC/MCExpr.h" 16 #include "llvm/MC/MCSectionCOFF.h" 17 #include "llvm/MC/MCSectionELF.h" 18 #include "llvm/Support/Dwarf.h" 19 #include "llvm/Target/TargetLowering.h" 20 21 using namespace llvm; 22 using namespace dwarf; 23 24 X86_64MachoTargetObjectFile::X86_64MachoTargetObjectFile() 25 : TargetLoweringObjectFileMachO() { 26 SupportIndirectSymViaGOTPCRel = true; 27 } 28 29 const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference( 30 const GlobalValue *GV, unsigned Encoding, Mangler &Mang, 31 const TargetMachine &TM, MachineModuleInfo *MMI, 32 MCStreamer &Streamer) const { 33 34 // On Darwin/X86-64, we can reference dwarf symbols with foo@GOTPCREL+4, which 35 // is an indirect pc-relative reference. 36 if ((Encoding & DW_EH_PE_indirect) && (Encoding & DW_EH_PE_pcrel)) { 37 const MCSymbol *Sym = TM.getSymbol(GV, Mang); 38 const MCExpr *Res = 39 MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext()); 40 const MCExpr *Four = MCConstantExpr::Create(4, getContext()); 41 return MCBinaryExpr::CreateAdd(Res, Four, getContext()); 42 } 43 44 return TargetLoweringObjectFileMachO::getTTypeGlobalReference( 45 GV, Encoding, Mang, TM, MMI, Streamer); 46 } 47 48 MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol( 49 const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM, 50 MachineModuleInfo *MMI) const { 51 return TM.getSymbol(GV, Mang); 52 } 53 54 const MCExpr *X86_64MachoTargetObjectFile::getIndirectSymViaGOTPCRel( 55 const MCSymbol *Sym, int64_t Offset) const { 56 // On Darwin/X86-64, we need to use foo@GOTPCREL+4 to access the got entry 57 // from a data section. In case there's an additional offset, then use 58 // foo@GOTPCREL+4+<offset>. 59 const MCExpr *Res = 60 MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext()); 61 const MCExpr *Off = MCConstantExpr::Create(Offset+4, getContext()); 62 return MCBinaryExpr::CreateAdd(Res, Off, getContext()); 63 } 64 65 void 66 X86LinuxTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM) { 67 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 68 InitializeELF(TM.Options.UseInitArray); 69 } 70 71 const MCExpr * 72 X86LinuxTargetObjectFile::getDebugThreadLocalSymbol( 73 const MCSymbol *Sym) const { 74 return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext()); 75 } 76 77 const MCExpr *PS4TargetObjectFile::getDebugThreadLocalSymbol( 78 const MCSymbol *Sym) const { 79 return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext()); 80 } 81 82 const MCExpr *X86WindowsTargetObjectFile::getExecutableRelativeSymbol( 83 const ConstantExpr *CE, Mangler &Mang, const TargetMachine &TM) const { 84 // We are looking for the difference of two symbols, need a subtraction 85 // operation. 86 const SubOperator *Sub = dyn_cast<SubOperator>(CE); 87 if (!Sub) 88 return nullptr; 89 90 // Symbols must first be numbers before we can subtract them, we need to see a 91 // ptrtoint on both subtraction operands. 92 const PtrToIntOperator *SubLHS = 93 dyn_cast<PtrToIntOperator>(Sub->getOperand(0)); 94 const PtrToIntOperator *SubRHS = 95 dyn_cast<PtrToIntOperator>(Sub->getOperand(1)); 96 if (!SubLHS || !SubRHS) 97 return nullptr; 98 99 // Our symbols should exist in address space zero, cowardly no-op if 100 // otherwise. 101 if (SubLHS->getPointerAddressSpace() != 0 || 102 SubRHS->getPointerAddressSpace() != 0) 103 return nullptr; 104 105 // Both ptrtoint instructions must wrap global variables: 106 // - Only global variables are eligible for image relative relocations. 107 // - The subtrahend refers to the special symbol __ImageBase, a global. 108 const GlobalVariable *GVLHS = 109 dyn_cast<GlobalVariable>(SubLHS->getPointerOperand()); 110 const GlobalVariable *GVRHS = 111 dyn_cast<GlobalVariable>(SubRHS->getPointerOperand()); 112 if (!GVLHS || !GVRHS) 113 return nullptr; 114 115 // We expect __ImageBase to be a global variable without a section, externally 116 // defined. 117 // 118 // It should look something like this: @__ImageBase = external constant i8 119 if (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" || 120 !GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() || 121 GVRHS->hasSection()) 122 return nullptr; 123 124 // An image-relative, thread-local, symbol makes no sense. 125 if (GVLHS->isThreadLocal()) 126 return nullptr; 127 128 return MCSymbolRefExpr::Create(TM.getSymbol(GVLHS, Mang), 129 MCSymbolRefExpr::VK_COFF_IMGREL32, 130 getContext()); 131 } 132 133 static std::string APIntToHexString(const APInt &AI) { 134 unsigned Width = (AI.getBitWidth() / 8) * 2; 135 std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true); 136 unsigned Size = HexString.size(); 137 assert(Width >= Size && "hex string is too large!"); 138 HexString.insert(HexString.begin(), Width - Size, '0'); 139 140 return HexString; 141 } 142 143 144 static std::string scalarConstantToHexString(const Constant *C) { 145 Type *Ty = C->getType(); 146 APInt AI; 147 if (isa<UndefValue>(C)) { 148 AI = APInt(Ty->getPrimitiveSizeInBits(), /*val=*/0); 149 } else if (Ty->isFloatTy() || Ty->isDoubleTy()) { 150 const auto *CFP = cast<ConstantFP>(C); 151 AI = CFP->getValueAPF().bitcastToAPInt(); 152 } else if (Ty->isIntegerTy()) { 153 const auto *CI = cast<ConstantInt>(C); 154 AI = CI->getValue(); 155 } else { 156 llvm_unreachable("unexpected constant pool element type!"); 157 } 158 return APIntToHexString(AI); 159 } 160 161 const MCSection * 162 X86WindowsTargetObjectFile::getSectionForConstant(SectionKind Kind, 163 const Constant *C) const { 164 if (Kind.isReadOnly()) { 165 if (C) { 166 Type *Ty = C->getType(); 167 SmallString<32> COMDATSymName; 168 if (Ty->isFloatTy() || Ty->isDoubleTy()) { 169 COMDATSymName = "__real@"; 170 COMDATSymName += scalarConstantToHexString(C); 171 } else if (const auto *VTy = dyn_cast<VectorType>(Ty)) { 172 uint64_t NumBits = VTy->getBitWidth(); 173 if (NumBits == 128 || NumBits == 256) { 174 COMDATSymName = NumBits == 128 ? "__xmm@" : "__ymm@"; 175 for (int I = VTy->getNumElements() - 1, E = -1; I != E; --I) 176 COMDATSymName += 177 scalarConstantToHexString(C->getAggregateElement(I)); 178 } 179 } 180 if (!COMDATSymName.empty()) { 181 unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 182 COFF::IMAGE_SCN_MEM_READ | 183 COFF::IMAGE_SCN_LNK_COMDAT; 184 return getContext().getCOFFSection(".rdata", Characteristics, Kind, 185 COMDATSymName, 186 COFF::IMAGE_COMDAT_SELECT_ANY); 187 } 188 } 189 } 190 191 return TargetLoweringObjectFile::getSectionForConstant(Kind, C); 192 } 193