MCMachOStreamer.cpp revision 0c7761b3f98fee270d73f5b9c440fe15e82af263 
1//===- lib/MC/MCMachOStreamer.cpp - Mach-O Object Output ------------===//
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 "llvm/MC/MCStreamer.h"
11
12#include "llvm/MC/MCAssembler.h"
13#include "llvm/MC/MCContext.h"
14#include "llvm/MC/MCSection.h"
15#include "llvm/MC/MCSymbol.h"
16#include "llvm/Support/ErrorHandling.h"
17using namespace llvm;
18
19namespace {
20
21class MCMachOStreamer : public MCStreamer {
22  /// SymbolFlags - We store the value for the 'desc' symbol field in the lowest
23  /// 16 bits of the implementation defined flags.
24  enum SymbolFlags { // See <mach-o/nlist.h>.
25    SF_DescFlagsMask                        = 0xFFFF,
26
27    // Reference type flags.
28    SF_ReferenceTypeMask                    = 0x0007,
29    SF_ReferenceTypeUndefinedNonLazy        = 0x0000,
30    SF_ReferenceTypeUndefinedLazy           = 0x0001,
31    SF_ReferenceTypeDefined                 = 0x0002,
32    SF_ReferenceTypePrivateDefined          = 0x0003,
33    SF_ReferenceTypePrivateUndefinedNonLazy = 0x0004,
34    SF_ReferenceTypePrivateUndefinedLazy    = 0x0005,
35
36    // Other 'desc' flags.
37    SF_NoDeadStrip                          = 0x0020,
38    SF_WeakReference                        = 0x0040,
39    SF_WeakDefinition                       = 0x0080
40  };
41
42private:
43  MCAssembler Assembler;
44
45  MCSectionData *CurSectionData;
46
47  DenseMap<const MCSection*, MCSectionData*> SectionMap;
48
49  DenseMap<const MCSymbol*, MCSymbolData*> SymbolMap;
50
51private:
52  MCFragment *getCurrentFragment() const {
53    assert(CurSectionData && "No current section!");
54
55    if (!CurSectionData->empty())
56      return &CurSectionData->getFragmentList().back();
57
58    return 0;
59  }
60
61  MCSymbolData &getSymbolData(MCSymbol &Symbol) {
62    MCSymbolData *&Entry = SymbolMap[&Symbol];
63
64    if (!Entry)
65      Entry = new MCSymbolData(Symbol, 0, 0, &Assembler);
66
67    return *Entry;
68  }
69
70public:
71  MCMachOStreamer(MCContext &Context, raw_ostream &_OS)
72    : MCStreamer(Context), Assembler(_OS), CurSectionData(0) {}
73  ~MCMachOStreamer() {}
74
75  /// @name MCStreamer Interface
76  /// @{
77
78  virtual void SwitchSection(const MCSection *Section);
79
80  virtual void EmitLabel(MCSymbol *Symbol);
81
82  virtual void EmitAssemblerFlag(AssemblerFlag Flag);
83
84  virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
85                              bool MakeAbsolute = false);
86
87  virtual void EmitSymbolAttribute(MCSymbol *Symbol, SymbolAttr Attribute);
88
89  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
90
91  virtual void EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value);
92
93  virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
94                                unsigned Pow2Alignment, bool IsLocal);
95
96  virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = NULL,
97                            unsigned Size = 0, unsigned Pow2Alignment = 0);
98
99  virtual void EmitBytes(const StringRef &Data);
100
101  virtual void EmitValue(const MCValue &Value, unsigned Size);
102
103  virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
104                                    unsigned ValueSize = 1,
105                                    unsigned MaxBytesToEmit = 0);
106
107  virtual void EmitValueToOffset(const MCValue &Offset,
108                                 unsigned char Value = 0);
109
110  virtual void EmitInstruction(const MCInst &Inst);
111
112  virtual void Finish();
113
114  /// @}
115};
116
117} // end anonymous namespace.
118
119void MCMachOStreamer::SwitchSection(const MCSection *Section) {
120  assert(Section && "Cannot switch to a null section!");
121
122  // If already in this section, then this is a noop.
123  if (Section == CurSection) return;
124
125  CurSection = Section;
126  MCSectionData *&Entry = SectionMap[Section];
127
128  if (!Entry)
129    Entry = new MCSectionData(*Section, &Assembler);
130
131  CurSectionData = Entry;
132}
133
134void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
135  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
136
137  MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
138  if (!F)
139    F = new MCDataFragment(CurSectionData);
140
141  MCSymbolData &SD = getSymbolData(*Symbol);
142  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
143  SD.setFragment(F);
144  SD.setOffset(F->getContents().size());
145
146  // This causes the reference type and weak reference flags to be cleared.
147  SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
148
149  Symbol->setSection(*CurSection);
150}
151
152void MCMachOStreamer::EmitAssemblerFlag(AssemblerFlag Flag) {
153  llvm_unreachable("FIXME: Not yet implemented!");
154}
155
156void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol,
157                                     const MCValue &Value,
158                                     bool MakeAbsolute) {
159  // Only absolute symbols can be redefined.
160  assert((Symbol->isUndefined() || Symbol->isAbsolute()) &&
161         "Cannot define a symbol twice!");
162
163  llvm_unreachable("FIXME: Not yet implemented!");
164}
165
166void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
167                                          SymbolAttr Attribute) {
168  // Indirect symbols are handled differently, to match how 'as' handles
169  // them. This makes writing matching .o files easier.
170  if (Attribute == MCStreamer::IndirectSymbol) {
171    IndirectSymbolData ISD;
172    ISD.Symbol = Symbol;
173    ISD.SectionData = CurSectionData;
174    Assembler.getIndirectSymbols().push_back(ISD);
175    return;
176  }
177
178  // Adding a symbol attribute always introduces the symbol, note that an
179  // important side effect of calling getSymbolData here is to register the
180  // symbol with the assembler.
181  MCSymbolData &SD = getSymbolData(*Symbol);
182
183  // The implementation of symbol attributes is designed to match 'as', but it
184  // leaves much to desired. It doesn't really make sense to arbitrarily add and
185  // remove flags, but 'as' allows this (in particular, see .desc).
186  //
187  // In the future it might be worth trying to make these operations more well
188  // defined.
189  switch (Attribute) {
190  case MCStreamer::IndirectSymbol:
191  case MCStreamer::Hidden:
192  case MCStreamer::Internal:
193  case MCStreamer::Protected:
194  case MCStreamer::Weak:
195    assert(0 && "Invalid symbol attribute for Mach-O!");
196    break;
197
198  case MCStreamer::Global:
199    getSymbolData(*Symbol).setExternal(true);
200    break;
201
202  case MCStreamer::LazyReference:
203    // FIXME: This requires -dynamic.
204    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
205    if (Symbol->isUndefined())
206      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
207    break;
208
209    // Since .reference sets the no dead strip bit, it is equivalent to
210    // .no_dead_strip in practice.
211  case MCStreamer::Reference:
212  case MCStreamer::NoDeadStrip:
213    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
214    break;
215
216  case MCStreamer::PrivateExtern:
217    SD.setExternal(true);
218    SD.setPrivateExtern(true);
219    break;
220
221  case MCStreamer::WeakReference:
222    // FIXME: This requires -dynamic.
223    if (Symbol->isUndefined())
224      SD.setFlags(SD.getFlags() | SF_WeakReference);
225    break;
226
227  case MCStreamer::WeakDefinition:
228    // FIXME: 'as' enforces that this is defined and global. The manual claims
229    // it has to be in a coalesced section, but this isn't enforced.
230    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
231    break;
232  }
233}
234
235void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
236  // Encode the 'desc' value into the lowest implementation defined bits.
237  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
238         "Invalid .desc value!");
239  getSymbolData(*Symbol).setFlags(DescValue & SF_DescFlagsMask);
240}
241
242void MCMachOStreamer::EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value) {
243  llvm_unreachable("FIXME: Not yet implemented!");
244}
245
246void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
247                                       unsigned Pow2Alignment,
248                                       bool IsLocal) {
249  llvm_unreachable("FIXME: Not yet implemented!");
250}
251
252void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
253                                   unsigned Size, unsigned Pow2Alignment) {
254  llvm_unreachable("FIXME: Not yet implemented!");
255}
256
257void MCMachOStreamer::EmitBytes(const StringRef &Data) {
258  MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
259  if (!DF)
260    DF = new MCDataFragment(CurSectionData);
261  DF->getContents().append(Data.begin(), Data.end());
262}
263
264void MCMachOStreamer::EmitValue(const MCValue &Value, unsigned Size) {
265  new MCFillFragment(Value, Size, 1, CurSectionData);
266}
267
268void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
269                                           int64_t Value, unsigned ValueSize,
270                                           unsigned MaxBytesToEmit) {
271  if (MaxBytesToEmit == 0)
272    MaxBytesToEmit = ByteAlignment;
273  new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
274                      CurSectionData);
275
276  // Update the maximum alignment on the current section if necessary.
277  if (ByteAlignment > CurSectionData->getAlignment())
278    CurSectionData->setAlignment(ByteAlignment);
279}
280
281void MCMachOStreamer::EmitValueToOffset(const MCValue &Offset,
282                                        unsigned char Value) {
283  new MCOrgFragment(Offset, Value, CurSectionData);
284}
285
286void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
287  llvm_unreachable("FIXME: Not yet implemented!");
288}
289
290void MCMachOStreamer::Finish() {
291  Assembler.Finish();
292}
293
294MCStreamer *llvm::createMachOStreamer(MCContext &Context, raw_ostream &OS) {
295  return new MCMachOStreamer(Context, OS);
296}
297