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
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const26 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
getCFIPersonalitySymbol(const GlobalValue * GV,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI) const45 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
getIndirectSymViaGOTPCRel(const MCSymbol * Sym,const MCValue & MV,int64_t Offset,MachineModuleInfo * MMI,MCStreamer & Streamer) const51 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
getDebugThreadLocalSymbol(const MCSymbol * Sym) const64 const MCExpr *X86ELFTargetObjectFile::getDebugThreadLocalSymbol(
65 const MCSymbol *Sym) const {
66 return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
67 }
68
69 void
Initialize(MCContext & Ctx,const TargetMachine & TM)70 X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx,
71 const TargetMachine &TM) {
72 TargetLoweringObjectFileELF::Initialize(Ctx, TM);
73 InitializeELF(TM.Options.UseInitArray);
74 }
75
getExecutableRelativeSymbol(const ConstantExpr * CE,Mangler & Mang,const TargetMachine & TM) const76 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
APIntToHexString(const APInt & AI)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
scalarConstantToHexString(const Constant * C)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
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C) const156 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