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, const TargetMachine &TM, 28 MachineModuleInfo *MMI, 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, getMangler()); 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, TM, MMI, Streamer); 42 } 43 44 MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol( 45 const GlobalValue *GV, const TargetMachine &TM, 46 MachineModuleInfo *MMI) const { 47 return TM.getSymbol(GV, getMangler()); 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 X86FreeBSDTargetObjectFile::Initialize(MCContext &Ctx, 70 const TargetMachine &TM) { 71 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 72 InitializeELF(TM.Options.UseInitArray); 73 } 74 75 void 76 X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx, 77 const TargetMachine &TM) { 78 TargetLoweringObjectFileELF::Initialize(Ctx, TM); 79 InitializeELF(TM.Options.UseInitArray); 80 } 81 82 const MCExpr *X86WindowsTargetObjectFile::lowerRelativeReference( 83 const GlobalValue *LHS, const GlobalValue *RHS, 84 const TargetMachine &TM) const { 85 // Our symbols should exist in address space zero, cowardly no-op if 86 // otherwise. 87 if (LHS->getType()->getPointerAddressSpace() != 0 || 88 RHS->getType()->getPointerAddressSpace() != 0) 89 return nullptr; 90 91 // Both ptrtoint instructions must wrap global objects: 92 // - Only global variables are eligible for image relative relocations. 93 // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable. 94 // We expect __ImageBase to be a global variable without a section, externally 95 // defined. 96 // 97 // It should look something like this: @__ImageBase = external constant i8 98 if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) || 99 LHS->isThreadLocal() || RHS->isThreadLocal() || 100 RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() || 101 cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection()) 102 return nullptr; 103 104 return MCSymbolRefExpr::create(TM.getSymbol(LHS, getMangler()), 105 MCSymbolRefExpr::VK_COFF_IMGREL32, 106 getContext()); 107 } 108 109 static std::string APIntToHexString(const APInt &AI) { 110 unsigned Width = (AI.getBitWidth() / 8) * 2; 111 std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true); 112 unsigned Size = HexString.size(); 113 assert(Width >= Size && "hex string is too large!"); 114 HexString.insert(HexString.begin(), Width - Size, '0'); 115 116 return HexString; 117 } 118 119 static std::string scalarConstantToHexString(const Constant *C) { 120 Type *Ty = C->getType(); 121 if (isa<UndefValue>(C)) { 122 return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits())); 123 } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) { 124 return APIntToHexString(CFP->getValueAPF().bitcastToAPInt()); 125 } else if (const auto *CI = dyn_cast<ConstantInt>(C)) { 126 return APIntToHexString(CI->getValue()); 127 } else { 128 unsigned NumElements; 129 if (isa<VectorType>(Ty)) 130 NumElements = Ty->getVectorNumElements(); 131 else 132 NumElements = Ty->getArrayNumElements(); 133 std::string HexString; 134 for (int I = NumElements - 1, E = -1; I != E; --I) 135 HexString += scalarConstantToHexString(C->getAggregateElement(I)); 136 return HexString; 137 } 138 } 139 140 MCSection *X86WindowsTargetObjectFile::getSectionForConstant( 141 const DataLayout &DL, SectionKind Kind, const Constant *C, 142 unsigned &Align) const { 143 if (Kind.isMergeableConst() && C) { 144 const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | 145 COFF::IMAGE_SCN_MEM_READ | 146 COFF::IMAGE_SCN_LNK_COMDAT; 147 std::string COMDATSymName; 148 if (Kind.isMergeableConst4()) { 149 if (Align <= 4) { 150 COMDATSymName = "__real@" + scalarConstantToHexString(C); 151 Align = 4; 152 } 153 } else if (Kind.isMergeableConst8()) { 154 if (Align <= 8) { 155 COMDATSymName = "__real@" + scalarConstantToHexString(C); 156 Align = 8; 157 } 158 } else if (Kind.isMergeableConst16()) { 159 if (Align <= 16) { 160 COMDATSymName = "__xmm@" + scalarConstantToHexString(C); 161 Align = 16; 162 } 163 } else if (Kind.isMergeableConst32()) { 164 if (Align <= 32) { 165 COMDATSymName = "__ymm@" + scalarConstantToHexString(C); 166 Align = 32; 167 } 168 } 169 170 if (!COMDATSymName.empty()) 171 return getContext().getCOFFSection(".rdata", Characteristics, Kind, 172 COMDATSymName, 173 COFF::IMAGE_COMDAT_SELECT_ANY); 174 } 175 176 return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align); 177 } 178