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/MC/MCValue.h" 19 #include "llvm/Support/Dwarf.h" 20 #include "llvm/Target/TargetLowering.h" 21 22 using namespace llvm; 23 using namespace dwarf; 24 25 const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference( 26 const GlobalValue *GV, unsigned Encoding, Mangler &Mang, 27 const TargetMachine &TM, MachineModuleInfo *MMI, 28 MCStreamer &Streamer) const { 29 30 // On Darwin/X86-64, we can reference dwarf symbols with foo@GOTPCREL+4, which 31 // is an indirect pc-relative reference. 32 if ((Encoding & DW_EH_PE_indirect) && (Encoding & DW_EH_PE_pcrel)) { 33 const MCSymbol *Sym = TM.getSymbol(GV, Mang); 34 const MCExpr *Res = 35 MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext()); 36 const MCExpr *Four = MCConstantExpr::create(4, getContext()); 37 return MCBinaryExpr::createAdd(Res, Four, getContext()); 38 } 39 40 return TargetLoweringObjectFileMachO::getTTypeGlobalReference( 41 GV, Encoding, Mang, TM, MMI, Streamer); 42 } 43 44 MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol( 45 const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM, 46 MachineModuleInfo *MMI) const { 47 return TM.getSymbol(GV, Mang); 48 } 49 50 const MCExpr *X86_64MachoTargetObjectFile::getIndirectSymViaGOTPCRel( 51 const MCSymbol *Sym, const MCValue &MV, int64_t Offset, 52 MachineModuleInfo *MMI, MCStreamer &Streamer) const { 53 // On Darwin/X86-64, we need to use foo@GOTPCREL+4 to access the got entry 54 // from a data section. In case there's an additional offset, then use 55 // foo@GOTPCREL+4+<offset>. 56 unsigned FinalOff = Offset+MV.getConstant()+4; 57 const MCExpr *Res = 58 MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext()); 59 const MCExpr *Off = MCConstantExpr::create(FinalOff, getContext()); 60 return MCBinaryExpr::createAdd(Res, Off, getContext()); 61 } 62 63 const MCExpr *X86ELFTargetObjectFile::getDebugThreadLocalSymbol( 64 const MCSymbol *Sym) const { 65 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext()); 66 } 67 68 void 69 X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx, 70 const TargetMachine &TM) { 71 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 72 InitializeELF(TM.Options.UseInitArray); 73 } 74 75 const MCExpr *X86WindowsTargetObjectFile::getExecutableRelativeSymbol( 76 const ConstantExpr *CE, Mangler &Mang, const TargetMachine &TM) const { 77 // We are looking for the difference of two symbols, need a subtraction 78 // operation. 79 const SubOperator *Sub = dyn_cast<SubOperator>(CE); 80 if (!Sub) 81 return nullptr; 82 83 // Symbols must first be numbers before we can subtract them, we need to see a 84 // ptrtoint on both subtraction operands. 85 const PtrToIntOperator *SubLHS = 86 dyn_cast<PtrToIntOperator>(Sub->getOperand(0)); 87 const PtrToIntOperator *SubRHS = 88 dyn_cast<PtrToIntOperator>(Sub->getOperand(1)); 89 if (!SubLHS || !SubRHS) 90 return nullptr; 91 92 // Our symbols should exist in address space zero, cowardly no-op if 93 // otherwise. 94 if (SubLHS->getPointerAddressSpace() != 0 || 95 SubRHS->getPointerAddressSpace() != 0) 96 return nullptr; 97 98 // Both ptrtoint instructions must wrap global objects: 99 // - Only global variables are eligible for image relative relocations. 100 // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable. 101 const auto *GOLHS = dyn_cast<GlobalObject>(SubLHS->getPointerOperand()); 102 const auto *GVRHS = dyn_cast<GlobalVariable>(SubRHS->getPointerOperand()); 103 if (!GOLHS || !GVRHS) 104 return nullptr; 105 106 // We expect __ImageBase to be a global variable without a section, externally 107 // defined. 108 // 109 // It should look something like this: @__ImageBase = external constant i8 110 if (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" || 111 !GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() || 112 GVRHS->hasSection()) 113 return nullptr; 114 115 // An image-relative, thread-local, symbol makes no sense. 116 if (GOLHS->isThreadLocal()) 117 return nullptr; 118 119 return MCSymbolRefExpr::create(TM.getSymbol(GOLHS, Mang), 120 MCSymbolRefExpr::VK_COFF_IMGREL32, 121 getContext()); 122 } 123 124 static std::string APIntToHexString(const APInt &AI) { 125 unsigned Width = (AI.getBitWidth() / 8) * 2; 126 std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true); 127 unsigned Size = HexString.size(); 128 assert(Width >= Size && "hex string is too large!"); 129 HexString.insert(HexString.begin(), Width - Size, '0'); 130 131 return HexString; 132 } 133 134 static std::string scalarConstantToHexString(const Constant *C) { 135 Type *Ty = C->getType(); 136 if (isa<UndefValue>(C)) { 137 return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits())); 138 } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) { 139 return APIntToHexString(CFP->getValueAPF().bitcastToAPInt()); 140 } else if (const auto *CI = dyn_cast<ConstantInt>(C)) { 141 return APIntToHexString(CI->getValue()); 142 } else { 143 unsigned NumElements; 144 if (isa<VectorType>(Ty)) 145 NumElements = Ty->getVectorNumElements(); 146 else 147 NumElements = Ty->getArrayNumElements(); 148 std::string HexString; 149 for (int I = NumElements - 1, E = -1; I != E; --I) 150 HexString += scalarConstantToHexString(C->getAggregateElement(I)); 151 return HexString; 152 } 153 } 154 155 MCSection * 156 X86WindowsTargetObjectFile::getSectionForConstant(SectionKind Kind, 157 const Constant *C) const { 158 if (Kind.isMergeableConst() && C) { 159 const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 160 COFF::IMAGE_SCN_MEM_READ | 161 COFF::IMAGE_SCN_LNK_COMDAT; 162 std::string COMDATSymName; 163 if (Kind.isMergeableConst4() || Kind.isMergeableConst8()) 164 COMDATSymName = "__real@" + scalarConstantToHexString(C); 165 else if (Kind.isMergeableConst16()) 166 COMDATSymName = "__xmm@" + scalarConstantToHexString(C); 167 168 if (!COMDATSymName.empty()) 169 return getContext().getCOFFSection(".rdata", Characteristics, Kind, 170 COMDATSymName, 171 COFF::IMAGE_COMDAT_SELECT_ANY); 172 } 173 174 return TargetLoweringObjectFile::getSectionForConstant(Kind, C); 175 } 176