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
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,Mangler & Mang,const TargetMachine & TM) const76 const MCExpr *X86WindowsTargetObjectFile::lowerRelativeReference(
77 const GlobalValue *LHS, const GlobalValue *RHS, Mangler &Mang,
78 const TargetMachine &TM) const {
79 // Our symbols should exist in address space zero, cowardly no-op if
80 // otherwise.
81 if (LHS->getType()->getPointerAddressSpace() != 0 ||
82 RHS->getType()->getPointerAddressSpace() != 0)
83 return nullptr;
84
85 // Both ptrtoint instructions must wrap global objects:
86 // - Only global variables are eligible for image relative relocations.
87 // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
88 // We expect __ImageBase to be a global variable without a section, externally
89 // defined.
90 //
91 // It should look something like this: @__ImageBase = external constant i8
92 if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
93 LHS->isThreadLocal() || RHS->isThreadLocal() ||
94 RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
95 cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
96 return nullptr;
97
98 return MCSymbolRefExpr::create(
99 TM.getSymbol(LHS, Mang), MCSymbolRefExpr::VK_COFF_IMGREL32, getContext());
100 }
101
APIntToHexString(const APInt & AI)102 static std::string APIntToHexString(const APInt &AI) {
103 unsigned Width = (AI.getBitWidth() / 8) * 2;
104 std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
105 unsigned Size = HexString.size();
106 assert(Width >= Size && "hex string is too large!");
107 HexString.insert(HexString.begin(), Width - Size, '0');
108
109 return HexString;
110 }
111
scalarConstantToHexString(const Constant * C)112 static std::string scalarConstantToHexString(const Constant *C) {
113 Type *Ty = C->getType();
114 if (isa<UndefValue>(C)) {
115 return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
116 } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
117 return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
118 } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
119 return APIntToHexString(CI->getValue());
120 } else {
121 unsigned NumElements;
122 if (isa<VectorType>(Ty))
123 NumElements = Ty->getVectorNumElements();
124 else
125 NumElements = Ty->getArrayNumElements();
126 std::string HexString;
127 for (int I = NumElements - 1, E = -1; I != E; --I)
128 HexString += scalarConstantToHexString(C->getAggregateElement(I));
129 return HexString;
130 }
131 }
132
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const133 MCSection *X86WindowsTargetObjectFile::getSectionForConstant(
134 const DataLayout &DL, SectionKind Kind, const Constant *C,
135 unsigned &Align) const {
136 if (Kind.isMergeableConst() && C) {
137 const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
138 COFF::IMAGE_SCN_MEM_READ |
139 COFF::IMAGE_SCN_LNK_COMDAT;
140 std::string COMDATSymName;
141 if (Kind.isMergeableConst4()) {
142 if (Align <= 4) {
143 COMDATSymName = "__real@" + scalarConstantToHexString(C);
144 Align = 4;
145 }
146 } else if (Kind.isMergeableConst8()) {
147 if (Align <= 8) {
148 COMDATSymName = "__real@" + scalarConstantToHexString(C);
149 Align = 8;
150 }
151 } else if (Kind.isMergeableConst16()) {
152 if (Align <= 16) {
153 COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
154 Align = 16;
155 }
156 } else if (Kind.isMergeableConst32()) {
157 if (Align <= 32) {
158 COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
159 Align = 32;
160 }
161 }
162
163 if (!COMDATSymName.empty())
164 return getContext().getCOFFSection(".rdata", Characteristics, Kind,
165 COMDATSymName,
166 COFF::IMAGE_COMDAT_SELECT_ANY);
167 }
168
169 return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
170 }
171