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
23using namespace llvm;
24using namespace dwarf;
25
26const 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
45MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol(
46    const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
47    MachineModuleInfo *MMI) const {
48  return TM.getSymbol(GV, Mang);
49}
50
51const 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
64const MCExpr *X86ELFTargetObjectFile::getDebugThreadLocalSymbol(
65    const MCSymbol *Sym) const {
66  return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
67}
68
69void
70X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx,
71                                         const TargetMachine &TM) {
72  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
73  InitializeELF(TM.Options.UseInitArray);
74}
75
76const 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
102static 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
112static 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
133MCSection *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