MCMachOStreamer.cpp revision a421de11df9d2a07b9f95a1ad817467af426803a 
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  const MCValue &AddValueSymbols(const MCValue &Value) {
76    if (Value.getSymA())
77      getSymbolData(*const_cast<MCSymbol*>(Value.getSymA()));
78    if (Value.getSymB())
79      getSymbolData(*const_cast<MCSymbol*>(Value.getSymB()));
80    return Value;
81  }
82
83  /// @name MCStreamer Interface
84  /// @{
85
86  virtual void SwitchSection(const MCSection *Section);
87
88  virtual void EmitLabel(MCSymbol *Symbol);
89
90  virtual void EmitAssemblerFlag(AssemblerFlag Flag);
91
92  virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value,
93                              bool MakeAbsolute = false);
94
95  virtual void EmitSymbolAttribute(MCSymbol *Symbol, SymbolAttr Attribute);
96
97  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
98
99  virtual void EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value);
100
101  virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
102                                unsigned Pow2Alignment, bool IsLocal);
103
104  virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = NULL,
105                            unsigned Size = 0, unsigned Pow2Alignment = 0);
106
107  virtual void EmitBytes(const StringRef &Data);
108
109  virtual void EmitValue(const MCValue &Value, unsigned Size);
110
111  virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
112                                    unsigned ValueSize = 1,
113                                    unsigned MaxBytesToEmit = 0);
114
115  virtual void EmitValueToOffset(const MCValue &Offset,
116                                 unsigned char Value = 0);
117
118  virtual void EmitInstruction(const MCInst &Inst);
119
120  virtual void Finish();
121
122  /// @}
123};
124
125} // end anonymous namespace.
126
127void MCMachOStreamer::SwitchSection(const MCSection *Section) {
128  assert(Section && "Cannot switch to a null section!");
129
130  // If already in this section, then this is a noop.
131  if (Section == CurSection) return;
132
133  CurSection = Section;
134  MCSectionData *&Entry = SectionMap[Section];
135
136  if (!Entry)
137    Entry = new MCSectionData(*Section, &Assembler);
138
139  CurSectionData = Entry;
140}
141
142void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
143  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
144
145  // FIXME: We should also use offsets into Fill fragments.
146  MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
147  if (!F)
148    F = new MCDataFragment(CurSectionData);
149
150  MCSymbolData &SD = getSymbolData(*Symbol);
151  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
152  SD.setFragment(F);
153  SD.setOffset(F->getContents().size());
154
155  // This causes the reference type and weak reference flags to be cleared.
156  SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
157
158  Symbol->setSection(*CurSection);
159}
160
161void MCMachOStreamer::EmitAssemblerFlag(AssemblerFlag Flag) {
162  llvm_unreachable("FIXME: Not yet implemented!");
163}
164
165void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol,
166                                     const MCValue &Value,
167                                     bool MakeAbsolute) {
168  // Only absolute symbols can be redefined.
169  assert((Symbol->isUndefined() || Symbol->isAbsolute()) &&
170         "Cannot define a symbol twice!");
171
172  llvm_unreachable("FIXME: Not yet implemented!");
173}
174
175void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
176                                          SymbolAttr Attribute) {
177  // Indirect symbols are handled differently, to match how 'as' handles
178  // them. This makes writing matching .o files easier.
179  if (Attribute == MCStreamer::IndirectSymbol) {
180    // Note that we intentionally cannot use the symbol data here; this is
181    // important for matching the string table that 'as' generates.
182    IndirectSymbolData ISD;
183    ISD.Symbol = Symbol;
184    ISD.SectionData = CurSectionData;
185    Assembler.getIndirectSymbols().push_back(ISD);
186    return;
187  }
188
189  // Adding a symbol attribute always introduces the symbol, note that an
190  // important side effect of calling getSymbolData here is to register the
191  // symbol with the assembler.
192  MCSymbolData &SD = getSymbolData(*Symbol);
193
194  // The implementation of symbol attributes is designed to match 'as', but it
195  // leaves much to desired. It doesn't really make sense to arbitrarily add and
196  // remove flags, but 'as' allows this (in particular, see .desc).
197  //
198  // In the future it might be worth trying to make these operations more well
199  // defined.
200  switch (Attribute) {
201  case MCStreamer::IndirectSymbol:
202  case MCStreamer::Hidden:
203  case MCStreamer::Internal:
204  case MCStreamer::Protected:
205  case MCStreamer::Weak:
206    assert(0 && "Invalid symbol attribute for Mach-O!");
207    break;
208
209  case MCStreamer::Global:
210    getSymbolData(*Symbol).setExternal(true);
211    break;
212
213  case MCStreamer::LazyReference:
214    // FIXME: This requires -dynamic.
215    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
216    if (Symbol->isUndefined())
217      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
218    break;
219
220    // Since .reference sets the no dead strip bit, it is equivalent to
221    // .no_dead_strip in practice.
222  case MCStreamer::Reference:
223  case MCStreamer::NoDeadStrip:
224    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
225    break;
226
227  case MCStreamer::PrivateExtern:
228    SD.setExternal(true);
229    SD.setPrivateExtern(true);
230    break;
231
232  case MCStreamer::WeakReference:
233    // FIXME: This requires -dynamic.
234    if (Symbol->isUndefined())
235      SD.setFlags(SD.getFlags() | SF_WeakReference);
236    break;
237
238  case MCStreamer::WeakDefinition:
239    // FIXME: 'as' enforces that this is defined and global. The manual claims
240    // it has to be in a coalesced section, but this isn't enforced.
241    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
242    break;
243  }
244}
245
246void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
247  // Encode the 'desc' value into the lowest implementation defined bits.
248  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
249         "Invalid .desc value!");
250  getSymbolData(*Symbol).setFlags(DescValue & SF_DescFlagsMask);
251}
252
253void MCMachOStreamer::EmitLocalSymbol(MCSymbol *Symbol, const MCValue &Value) {
254  llvm_unreachable("FIXME: Not yet implemented!");
255}
256
257void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
258                                       unsigned Pow2Alignment,
259                                       bool IsLocal) {
260  llvm_unreachable("FIXME: Not yet implemented!");
261}
262
263void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
264                                   unsigned Size, unsigned Pow2Alignment) {
265  llvm_unreachable("FIXME: Not yet implemented!");
266}
267
268void MCMachOStreamer::EmitBytes(const StringRef &Data) {
269  MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
270  if (!DF)
271    DF = new MCDataFragment(CurSectionData);
272  DF->getContents().append(Data.begin(), Data.end());
273}
274
275void MCMachOStreamer::EmitValue(const MCValue &Value, unsigned Size) {
276  new MCFillFragment(AddValueSymbols(Value), Size, 1, CurSectionData);
277}
278
279void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
280                                           int64_t Value, unsigned ValueSize,
281                                           unsigned MaxBytesToEmit) {
282  if (MaxBytesToEmit == 0)
283    MaxBytesToEmit = ByteAlignment;
284  new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
285                      CurSectionData);
286
287  // Update the maximum alignment on the current section if necessary.
288  if (ByteAlignment > CurSectionData->getAlignment())
289    CurSectionData->setAlignment(ByteAlignment);
290}
291
292void MCMachOStreamer::EmitValueToOffset(const MCValue &Offset,
293                                        unsigned char Value) {
294  new MCOrgFragment(AddValueSymbols(Offset), Value, CurSectionData);
295}
296
297void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
298  llvm_unreachable("FIXME: Not yet implemented!");
299}
300
301void MCMachOStreamer::Finish() {
302  Assembler.Finish();
303}
304
305MCStreamer *llvm::createMachOStreamer(MCContext &Context, raw_ostream &OS) {
306  return new MCMachOStreamer(Context, OS);
307}
308