X86TargetObjectFile.cpp revision 314564 
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, 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);
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
44MCSymbol *X86_64MachoTargetObjectFile::getCFIPersonalitySymbol(
45    const GlobalValue *GV, const TargetMachine &TM,
46    MachineModuleInfo *MMI) const {
47  return TM.getSymbol(GV);
48}
49
50const 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
63const MCExpr *X86ELFTargetObjectFile::getDebugThreadLocalSymbol(
64    const MCSymbol *Sym) const {
65  return MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_DTPOFF, getContext());
66}
67
68void
69X86FreeBSDTargetObjectFile::Initialize(MCContext &Ctx,
70                                       const TargetMachine &TM) {
71  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
72  InitializeELF(TM.Options.UseInitArray);
73}
74
75void
76X86FuchsiaTargetObjectFile::Initialize(MCContext &Ctx,
77                                       const TargetMachine &TM) {
78  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
79  InitializeELF(TM.Options.UseInitArray);
80}
81
82void
83X86LinuxNaClTargetObjectFile::Initialize(MCContext &Ctx,
84                                         const TargetMachine &TM) {
85  TargetLoweringObjectFileELF::Initialize(Ctx, TM);
86  InitializeELF(TM.Options.UseInitArray);
87}
88
89const MCExpr *X86WindowsTargetObjectFile::lowerRelativeReference(
90    const GlobalValue *LHS, const GlobalValue *RHS,
91    const TargetMachine &TM) const {
92  // Our symbols should exist in address space zero, cowardly no-op if
93  // otherwise.
94  if (LHS->getType()->getPointerAddressSpace() != 0 ||
95      RHS->getType()->getPointerAddressSpace() != 0)
96    return nullptr;
97
98  // Both ptrtoint instructions must wrap global objects:
99  // - Only global variables are eligible for image relative relocations.
100  // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
101  // We expect __ImageBase to be a global variable without a section, externally
102  // defined.
103  //
104  // It should look something like this: @__ImageBase = external constant i8
105  if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
106      LHS->isThreadLocal() || RHS->isThreadLocal() ||
107      RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
108      cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
109    return nullptr;
110
111  return MCSymbolRefExpr::create(TM.getSymbol(LHS),
112                                 MCSymbolRefExpr::VK_COFF_IMGREL32,
113                                 getContext());
114}
115
116static std::string APIntToHexString(const APInt &AI) {
117  unsigned Width = (AI.getBitWidth() / 8) * 2;
118  std::string HexString = utohexstr(AI.getLimitedValue(), /*LowerCase=*/true);
119  unsigned Size = HexString.size();
120  assert(Width >= Size && "hex string is too large!");
121  HexString.insert(HexString.begin(), Width - Size, '0');
122
123  return HexString;
124}
125
126static std::string scalarConstantToHexString(const Constant *C) {
127  Type *Ty = C->getType();
128  if (isa<UndefValue>(C)) {
129    return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
130  } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
131    return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
132  } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
133    return APIntToHexString(CI->getValue());
134  } else {
135    unsigned NumElements;
136    if (isa<VectorType>(Ty))
137      NumElements = Ty->getVectorNumElements();
138    else
139      NumElements = Ty->getArrayNumElements();
140    std::string HexString;
141    for (int I = NumElements - 1, E = -1; I != E; --I)
142      HexString += scalarConstantToHexString(C->getAggregateElement(I));
143    return HexString;
144  }
145}
146
147MCSection *X86WindowsTargetObjectFile::getSectionForConstant(
148    const DataLayout &DL, SectionKind Kind, const Constant *C,
149    unsigned &Align) const {
150  if (Kind.isMergeableConst() && C) {
151    const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
152                                     COFF::IMAGE_SCN_MEM_READ |
153                                     COFF::IMAGE_SCN_LNK_COMDAT;
154    std::string COMDATSymName;
155    if (Kind.isMergeableConst4()) {
156      if (Align <= 4) {
157        COMDATSymName = "__real@" + scalarConstantToHexString(C);
158        Align = 4;
159      }
160    } else if (Kind.isMergeableConst8()) {
161      if (Align <= 8) {
162        COMDATSymName = "__real@" + scalarConstantToHexString(C);
163        Align = 8;
164      }
165    } else if (Kind.isMergeableConst16()) {
166      if (Align <= 16) {
167        COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
168        Align = 16;
169      }
170    } else if (Kind.isMergeableConst32()) {
171      if (Align <= 32) {
172        COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
173        Align = 32;
174      }
175    }
176
177    if (!COMDATSymName.empty())
178      return getContext().getCOFFSection(".rdata", Characteristics, Kind,
179                                         COMDATSymName,
180                                         COFF::IMAGE_COMDAT_SELECT_ANY);
181  }
182
183  return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
184}
185