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/COFF.h" 20 #include "llvm/Support/Dwarf.h" 21 #include "llvm/Target/TargetLowering.h" 22 23 using namespace llvm; 24 using namespace dwarf; 25 26 const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference( 27 const GlobalValue *GV, unsigned Encoding, Mangler &Mang, 28 const TargetMachine &TM, MachineModuleInfo *MMI, 29 MCStreamer &Streamer) const { 30 31 // On Darwin/X86-64, we can reference dwarf symbols with foo@GOTPCREL+4, which 32 // is an indirect pc-relative reference. 33 if ((Encoding & DW_EH_PE_indirect) && (Encoding & DW_EH_PE_pcrel)) { 34 const MCSymbol *Sym = TM.getSymbol(GV, Mang); 35 const MCExpr *Res = 36 MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext()); 37 const MCExpr *Four = MCConstantExpr::create(4, getContext()); 38 return MCBinaryExpr::createAdd(Res, Four, getContext()); 39 } 40 41 return TargetLoweringObjectFileMachO::getTTypeGlobalReference( 42 GV, Encoding, Mang, TM, MMI, Streamer); 43 } 44 45 MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol( 46 const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM, 47 MachineModuleInfo *MMI) const { 48 return TM.getSymbol(GV, Mang); 49 } 50 51 const MCExpr *X86_64MachoTargetObjectFile::getIndirectSymViaGOTPCRel( 52 const MCSymbol *Sym, const MCValue &MV, int64_t Offset, 53 MachineModuleInfo *MMI, MCStreamer &Streamer) const { 54 // On Darwin/X86-64, we need to use foo@GOTPCREL+4 to access the got entry 55 // from a data section. In case there's an additional offset, then use 56 // foo@GOTPCREL+4+<offset>. 57 unsigned FinalOff = Offset+MV.getConstant()+4; 58 const MCExpr *Res = 59 MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext()); 60 const MCExpr *Off = MCConstantExpr::create(FinalOff, getContext()); 61 return MCBinaryExpr::createAdd(Res, Off, getContext()); 62 } 63 64 const MCExpr *X86ELFTargetObjectFile::getDebugThreadLocalSymbol( 65 const MCSymbol *Sym) const { 66 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext()); 67 } 68 69 void 70 X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx, 71 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 objects: 100 // - Only global variables are eligible for image relative relocations. 101 // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable. 102 const auto *GOLHS = dyn_cast<GlobalObject>(SubLHS->getPointerOperand()); 103 const auto *GVRHS = dyn_cast<GlobalVariable>(SubRHS->getPointerOperand()); 104 if (!GOLHS || !GVRHS) 105 return nullptr; 106 107 // We expect __ImageBase to be a global variable without a section, externally 108 // defined. 109 // 110 // It should look something like this: @__ImageBase = external constant i8 111 if (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" || 112 !GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() || 113 GVRHS->hasSection()) 114 return nullptr; 115 116 // An image-relative, thread-local, symbol makes no sense. 117 if (GOLHS->isThreadLocal()) 118 return nullptr; 119 120 return MCSymbolRefExpr::create(TM.getSymbol(GOLHS, Mang), 121 MCSymbolRefExpr::VK_COFF_IMGREL32, 122 getContext()); 123 } 124 125 static std::string APIntToHexString(const APInt &AI) { 126 unsigned Width = (AI.getBitWidth() / 8) * 2; 127 std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true); 128 unsigned Size = HexString.size(); 129 assert(Width >= Size && "hex string is too large!"); 130 HexString.insert(HexString.begin(), Width - Size, '0'); 131 132 return HexString; 133 } 134 135 static std::string scalarConstantToHexString(const Constant *C) { 136 Type *Ty = C->getType(); 137 if (isa<UndefValue>(C)) { 138 return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits())); 139 } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) { 140 return APIntToHexString(CFP->getValueAPF().bitcastToAPInt()); 141 } else if (const auto *CI = dyn_cast<ConstantInt>(C)) { 142 return APIntToHexString(CI->getValue()); 143 } else { 144 unsigned NumElements; 145 if (isa<VectorType>(Ty)) 146 NumElements = Ty->getVectorNumElements(); 147 else 148 NumElements = Ty->getArrayNumElements(); 149 std::string HexString; 150 for (int I = NumElements - 1, E = -1; I != E; --I) 151 HexString += scalarConstantToHexString(C->getAggregateElement(I)); 152 return HexString; 153 } 154 } 155 156 MCSection *X86WindowsTargetObjectFile::getSectionForConstant( 157 const DataLayout &DL, SectionKind Kind, 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(DL, Kind, C); 175 } 176
