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 const MCExpr *X86ELFTargetObjectFile::getDebugThreadLocalSymbol( 66 const MCSymbol *Sym) const { 67 return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext()); 68 } 69 70 void 71 X86LinuxTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM) { 72 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 73 InitializeELF(TM.Options.UseInitArray); 74 } 75 76 const MCExpr *X86WindowsTargetObjectFile::getExecutableRelativeSymbol( 77 const ConstantExpr *CE, Mangler &Mang, const TargetMachine &TM) const { 78 // We are looking for the difference of two symbols, need a subtraction 79 // operation. 80 const SubOperator *Sub = dyn_cast<SubOperator>(CE); 81 if (!Sub) 82 return nullptr; 83 84 // Symbols must first be numbers before we can subtract them, we need to see a 85 // ptrtoint on both subtraction operands. 86 const PtrToIntOperator *SubLHS = 87 dyn_cast<PtrToIntOperator>(Sub->getOperand(0)); 88 const PtrToIntOperator *SubRHS = 89 dyn_cast<PtrToIntOperator>(Sub->getOperand(1)); 90 if (!SubLHS || !SubRHS) 91 return nullptr; 92 93 // Our symbols should exist in address space zero, cowardly no-op if 94 // otherwise. 95 if (SubLHS->getPointerAddressSpace() != 0 || 96 SubRHS->getPointerAddressSpace() != 0) 97 return nullptr; 98 99 // Both ptrtoint instructions must wrap global variables: 100 // - Only global variables are eligible for image relative relocations. 101 // - The subtrahend refers to the special symbol __ImageBase, a global. 102 const GlobalVariable *GVLHS = 103 dyn_cast<GlobalVariable>(SubLHS->getPointerOperand()); 104 const GlobalVariable *GVRHS = 105 dyn_cast<GlobalVariable>(SubRHS->getPointerOperand()); 106 if (!GVLHS || !GVRHS) 107 return nullptr; 108 109 // We expect __ImageBase to be a global variable without a section, externally 110 // defined. 111 // 112 // It should look something like this: @__ImageBase = external constant i8 113 if (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" || 114 !GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() || 115 GVRHS->hasSection()) 116 return nullptr; 117 118 // An image-relative, thread-local, symbol makes no sense. 119 if (GVLHS->isThreadLocal()) 120 return nullptr; 121 122 return MCSymbolRefExpr::Create(TM.getSymbol(GVLHS, Mang), 123 MCSymbolRefExpr::VK_COFF_IMGREL32, 124 getContext()); 125 } 126 127 static std::string APIntToHexString(const APInt &AI) { 128 unsigned Width = (AI.getBitWidth() / 8) * 2; 129 std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true); 130 unsigned Size = HexString.size(); 131 assert(Width >= Size && "hex string is too large!"); 132 HexString.insert(HexString.begin(), Width - Size, '0'); 133 134 return HexString; 135 } 136 137 138 static std::string scalarConstantToHexString(const Constant *C) { 139 Type *Ty = C->getType(); 140 APInt AI; 141 if (isa<UndefValue>(C)) { 142 AI = APInt(Ty->getPrimitiveSizeInBits(), /*val=*/0); 143 } else if (Ty->isFloatTy() || Ty->isDoubleTy()) { 144 const auto *CFP = cast<ConstantFP>(C); 145 AI = CFP->getValueAPF().bitcastToAPInt(); 146 } else if (Ty->isIntegerTy()) { 147 const auto *CI = cast<ConstantInt>(C); 148 AI = CI->getValue(); 149 } else { 150 llvm_unreachable("unexpected constant pool element type!"); 151 } 152 return APIntToHexString(AI); 153 } 154 155 const MCSection * 156 X86WindowsTargetObjectFile::getSectionForConstant(SectionKind Kind, 157 const Constant *C) const { 158 if (Kind.isReadOnly()) { 159 if (C) { 160 Type *Ty = C->getType(); 161 SmallString<32> COMDATSymName; 162 if (Ty->isFloatTy() || Ty->isDoubleTy()) { 163 COMDATSymName = "__real@"; 164 COMDATSymName += scalarConstantToHexString(C); 165 } else if (const auto *VTy = dyn_cast<VectorType>(Ty)) { 166 uint64_t NumBits = VTy->getBitWidth(); 167 if (NumBits == 128 || NumBits == 256) { 168 COMDATSymName = NumBits == 128 ? "__xmm@" : "__ymm@"; 169 for (int I = VTy->getNumElements() - 1, E = -1; I != E; --I) 170 COMDATSymName += 171 scalarConstantToHexString(C->getAggregateElement(I)); 172 } 173 } 174 if (!COMDATSymName.empty()) { 175 unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 176 COFF::IMAGE_SCN_MEM_READ | 177 COFF::IMAGE_SCN_LNK_COMDAT; 178 return getContext().getCOFFSection(".rdata", Characteristics, Kind, 179 COMDATSymName, 180 COFF::IMAGE_COMDAT_SELECT_ANY); 181 } 182 } 183 } 184 185 return TargetLoweringObjectFile::getSectionForConstant(Kind, C); 186 } 187