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/Support/Dwarf.h"
19 #include "llvm/Target/TargetLowering.h"
20
21 using namespace llvm;
22 using namespace dwarf;
23
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const24 const MCExpr *X86_64MachoTargetObjectFile::getTTypeGlobalReference(
25 const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
26 const TargetMachine &TM, MachineModuleInfo *MMI,
27 MCStreamer &Streamer) const {
28
29 // On Darwin/X86-64, we can reference dwarf symbols with foo@GOTPCREL+4, which
30 // is an indirect pc-relative reference.
31 if ((Encoding & DW_EH_PE_indirect) && (Encoding & DW_EH_PE_pcrel)) {
32 const MCSymbol *Sym = TM.getSymbol(GV, Mang);
33 const MCExpr *Res =
34 MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_GOTPCREL, getContext());
35 const MCExpr *Four = MCConstantExpr::Create(4, getContext());
36 return MCBinaryExpr::CreateAdd(Res, Four, getContext());
37 }
38
39 return TargetLoweringObjectFileMachO::getTTypeGlobalReference(
40 GV, Encoding, Mang, TM, MMI, Streamer);
41 }
42
getCFIPersonalitySymbol(const GlobalValue * GV,Mangler & Mang,const TargetMachine & TM,MachineModuleInfo * MMI) const43 MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol(
44 const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
45 MachineModuleInfo *MMI) const {
46 return TM.getSymbol(GV, Mang);
47 }
48
49 void
Initialize(MCContext & Ctx,const TargetMachine & TM)50 X86LinuxTargetObjectFile::Initialize(MCContext &Ctx, const TargetMachine &TM) {
51 TargetLoweringObjectFileELF::Initialize(Ctx, TM);
52 InitializeELF(TM.Options.UseInitArray);
53 }
54
55 const MCExpr *
getDebugThreadLocalSymbol(const MCSymbol * Sym) const56 X86LinuxTargetObjectFile::getDebugThreadLocalSymbol(
57 const MCSymbol *Sym) const {
58 return MCSymbolRefExpr::Create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
59 }
60
getExecutableRelativeSymbol(const ConstantExpr * CE,Mangler & Mang,const TargetMachine & TM) const61 const MCExpr *X86WindowsTargetObjectFile::getExecutableRelativeSymbol(
62 const ConstantExpr *CE, Mangler &Mang, const TargetMachine &TM) const {
63 // We are looking for the difference of two symbols, need a subtraction
64 // operation.
65 const SubOperator *Sub = dyn_cast<SubOperator>(CE);
66 if (!Sub)
67 return nullptr;
68
69 // Symbols must first be numbers before we can subtract them, we need to see a
70 // ptrtoint on both subtraction operands.
71 const PtrToIntOperator *SubLHS =
72 dyn_cast<PtrToIntOperator>(Sub->getOperand(0));
73 const PtrToIntOperator *SubRHS =
74 dyn_cast<PtrToIntOperator>(Sub->getOperand(1));
75 if (!SubLHS || !SubRHS)
76 return nullptr;
77
78 // Our symbols should exist in address space zero, cowardly no-op if
79 // otherwise.
80 if (SubLHS->getPointerAddressSpace() != 0 ||
81 SubRHS->getPointerAddressSpace() != 0)
82 return nullptr;
83
84 // Both ptrtoint instructions must wrap global variables:
85 // - Only global variables are eligible for image relative relocations.
86 // - The subtrahend refers to the special symbol __ImageBase, a global.
87 const GlobalVariable *GVLHS =
88 dyn_cast<GlobalVariable>(SubLHS->getPointerOperand());
89 const GlobalVariable *GVRHS =
90 dyn_cast<GlobalVariable>(SubRHS->getPointerOperand());
91 if (!GVLHS || !GVRHS)
92 return nullptr;
93
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 (GVRHS->isThreadLocal() || GVRHS->getName() != "__ImageBase" ||
99 !GVRHS->hasExternalLinkage() || GVRHS->hasInitializer() ||
100 GVRHS->hasSection())
101 return nullptr;
102
103 // An image-relative, thread-local, symbol makes no sense.
104 if (GVLHS->isThreadLocal())
105 return nullptr;
106
107 return MCSymbolRefExpr::Create(TM.getSymbol(GVLHS, Mang),
108 MCSymbolRefExpr::VK_COFF_IMGREL32,
109 getContext());
110 }
111
APIntToHexString(const APInt & AI)112 static std::string APIntToHexString(const APInt &AI) {
113 unsigned Width = (AI.getBitWidth() / 8) * 2;
114 std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
115 unsigned Size = HexString.size();
116 assert(Width >= Size && "hex string is too large!");
117 HexString.insert(HexString.begin(), Width - Size, '0');
118
119 return HexString;
120 }
121
122
scalarConstantToHexString(const Constant * C)123 static std::string scalarConstantToHexString(const Constant *C) {
124 Type *Ty = C->getType();
125 APInt AI;
126 if (isa<UndefValue>(C)) {
127 AI = APInt(Ty->getPrimitiveSizeInBits(), /*val=*/0);
128 } else if (Ty->isFloatTy() || Ty->isDoubleTy()) {
129 const auto *CFP = cast<ConstantFP>(C);
130 AI = CFP->getValueAPF().bitcastToAPInt();
131 } else if (Ty->isIntegerTy()) {
132 const auto *CI = cast<ConstantInt>(C);
133 AI = CI->getValue();
134 } else {
135 llvm_unreachable("unexpected constant pool element type!");
136 }
137 return APIntToHexString(AI);
138 }
139
140 const MCSection *
getSectionForConstant(SectionKind Kind,const Constant * C) const141 X86WindowsTargetObjectFile::getSectionForConstant(SectionKind Kind,
142 const Constant *C) const {
143 if (Kind.isReadOnly()) {
144 if (C) {
145 Type *Ty = C->getType();
146 SmallString<32> COMDATSymName;
147 if (Ty->isFloatTy() || Ty->isDoubleTy()) {
148 COMDATSymName = "__real@";
149 COMDATSymName += scalarConstantToHexString(C);
150 } else if (const auto *VTy = dyn_cast<VectorType>(Ty)) {
151 uint64_t NumBits = VTy->getBitWidth();
152 if (NumBits == 128 || NumBits == 256) {
153 COMDATSymName = NumBits == 128 ? "__xmm@" : "__ymm@";
154 for (int I = VTy->getNumElements() - 1, E = -1; I != E; --I)
155 COMDATSymName +=
156 scalarConstantToHexString(C->getAggregateElement(I));
157 }
158 }
159 if (!COMDATSymName.empty()) {
160 unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
161 COFF::IMAGE_SCN_MEM_READ |
162 COFF::IMAGE_SCN_LNK_COMDAT;
163 return getContext().getCOFFSection(".rdata", Characteristics, Kind,
164 COMDATSymName,
165 COFF::IMAGE_COMDAT_SELECT_ANY);
166 }
167 }
168 }
169
170 return TargetLoweringObjectFile::getSectionForConstant(Kind, C);
171 }
172