MCMachOStreamer.cpp revision 249423 
1//
2//                     The LLVM Compiler Infrastructure
3//
4// This file is distributed under the University of Illinois Open Source
5// License. See LICENSE.TXT for details.
6//
7//===----------------------------------------------------------------------===//
8
9#include "llvm/MC/MCStreamer.h"
10#include "llvm/MC/MCAsmBackend.h"
11#include "llvm/MC/MCAssembler.h"
12#include "llvm/MC/MCCodeEmitter.h"
13#include "llvm/MC/MCContext.h"
14#include "llvm/MC/MCDwarf.h"
15#include "llvm/MC/MCExpr.h"
16#include "llvm/MC/MCInst.h"
17#include "llvm/MC/MCMachOSymbolFlags.h"
18#include "llvm/MC/MCObjectStreamer.h"
19#include "llvm/MC/MCSection.h"
20#include "llvm/MC/MCSectionMachO.h"
21#include "llvm/MC/MCSymbol.h"
22#include "llvm/Support/Dwarf.h"
23#include "llvm/Support/ErrorHandling.h"
24#include "llvm/Support/raw_ostream.h"
25
26using namespace llvm;
27
28namespace {
29
30class MCMachOStreamer : public MCObjectStreamer {
31private:
32  virtual void EmitInstToData(const MCInst &Inst);
33
34  void EmitDataRegion(DataRegionData::KindTy Kind);
35  void EmitDataRegionEnd();
36public:
37  MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_ostream &OS,
38                  MCCodeEmitter *Emitter)
39      : MCObjectStreamer(SK_MachOStreamer, Context, MAB, OS, Emitter) {}
40
41  /// @name MCStreamer Interface
42  /// @{
43
44  virtual void InitSections();
45  virtual void InitToTextSection();
46  virtual void EmitLabel(MCSymbol *Symbol);
47  virtual void EmitDebugLabel(MCSymbol *Symbol);
48  virtual void EmitEHSymAttributes(const MCSymbol *Symbol,
49                                   MCSymbol *EHSymbol);
50  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
51  virtual void EmitLinkerOptions(ArrayRef<std::string> Options);
52  virtual void EmitDataRegion(MCDataRegionType Kind);
53  virtual void EmitThumbFunc(MCSymbol *Func);
54  virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
55  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
56  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
57                                unsigned ByteAlignment);
58  virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
59    llvm_unreachable("macho doesn't support this directive");
60  }
61  virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
62    llvm_unreachable("macho doesn't support this directive");
63  }
64  virtual void EmitCOFFSymbolType(int Type) {
65    llvm_unreachable("macho doesn't support this directive");
66  }
67  virtual void EndCOFFSymbolDef() {
68    llvm_unreachable("macho doesn't support this directive");
69  }
70  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
71    llvm_unreachable("macho doesn't support this directive");
72  }
73  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
74                                     unsigned ByteAlignment);
75  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
76                            uint64_t Size = 0, unsigned ByteAlignment = 0);
77  virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
78                              uint64_t Size, unsigned ByteAlignment = 0);
79
80  virtual void EmitFileDirective(StringRef Filename) {
81    // FIXME: Just ignore the .file; it isn't important enough to fail the
82    // entire assembly.
83
84    //report_fatal_error("unsupported directive: '.file'");
85  }
86
87  virtual void FinishImpl();
88
89  /// @}
90
91  static bool classof(const MCStreamer *S) {
92    return S->getKind() == SK_MachOStreamer;
93  }
94};
95
96} // end anonymous namespace.
97
98void MCMachOStreamer::InitSections() {
99  InitToTextSection();
100}
101
102void MCMachOStreamer::InitToTextSection() {
103  SwitchSection(getContext().getMachOSection(
104                                    "__TEXT", "__text",
105                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS, 0,
106                                    SectionKind::getText()));
107}
108
109void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
110                                          MCSymbol *EHSymbol) {
111  MCSymbolData &SD =
112    getAssembler().getOrCreateSymbolData(*Symbol);
113  if (SD.isExternal())
114    EmitSymbolAttribute(EHSymbol, MCSA_Global);
115  if (SD.getFlags() & SF_WeakDefinition)
116    EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
117  if (SD.isPrivateExtern())
118    EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
119}
120
121void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
122  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
123
124  // isSymbolLinkerVisible uses the section.
125  Symbol->setSection(*getCurrentSection());
126  // We have to create a new fragment if this is an atom defining symbol,
127  // fragments cannot span atoms.
128  if (getAssembler().isSymbolLinkerVisible(*Symbol))
129    new MCDataFragment(getCurrentSectionData());
130
131  MCObjectStreamer::EmitLabel(Symbol);
132
133  MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
134  // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
135  // to clear the weak reference and weak definition bits too, but the
136  // implementation was buggy. For now we just try to match 'as', for
137  // diffability.
138  //
139  // FIXME: Cleanup this code, these bits should be emitted based on semantic
140  // properties, not on the order of definition, etc.
141  SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
142}
143
144void MCMachOStreamer::EmitDebugLabel(MCSymbol *Symbol) {
145  EmitLabel(Symbol);
146}
147void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
148  if (!getAssembler().getBackend().hasDataInCodeSupport())
149    return;
150  // Create a temporary label to mark the start of the data region.
151  MCSymbol *Start = getContext().CreateTempSymbol();
152  EmitLabel(Start);
153  // Record the region for the object writer to use.
154  DataRegionData Data = { Kind, Start, NULL };
155  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
156  Regions.push_back(Data);
157}
158
159void MCMachOStreamer::EmitDataRegionEnd() {
160  if (!getAssembler().getBackend().hasDataInCodeSupport())
161    return;
162  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
163  assert(Regions.size() && "Mismatched .end_data_region!");
164  DataRegionData &Data = Regions.back();
165  assert(Data.End == NULL && "Mismatched .end_data_region!");
166  // Create a temporary label to mark the end of the data region.
167  Data.End = getContext().CreateTempSymbol();
168  EmitLabel(Data.End);
169}
170
171void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
172  // Let the target do whatever target specific stuff it needs to do.
173  getAssembler().getBackend().handleAssemblerFlag(Flag);
174  // Do any generic stuff we need to do.
175  switch (Flag) {
176  case MCAF_SyntaxUnified: return; // no-op here.
177  case MCAF_Code16: return; // Change parsing mode; no-op here.
178  case MCAF_Code32: return; // Change parsing mode; no-op here.
179  case MCAF_Code64: return; // Change parsing mode; no-op here.
180  case MCAF_SubsectionsViaSymbols:
181    getAssembler().setSubsectionsViaSymbols(true);
182    return;
183  }
184}
185
186void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
187  getAssembler().getLinkerOptions().push_back(Options);
188}
189
190void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
191  switch (Kind) {
192  case MCDR_DataRegion:
193    EmitDataRegion(DataRegionData::Data);
194    return;
195  case MCDR_DataRegionJT8:
196    EmitDataRegion(DataRegionData::JumpTable8);
197    return;
198  case MCDR_DataRegionJT16:
199    EmitDataRegion(DataRegionData::JumpTable16);
200    return;
201  case MCDR_DataRegionJT32:
202    EmitDataRegion(DataRegionData::JumpTable32);
203    return;
204  case MCDR_DataRegionEnd:
205    EmitDataRegionEnd();
206    return;
207  }
208}
209
210void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
211  // Remember that the function is a thumb function. Fixup and relocation
212  // values will need adjusted.
213  getAssembler().setIsThumbFunc(Symbol);
214
215  // Mark the thumb bit on the symbol.
216  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
217  SD.setFlags(SD.getFlags() | SF_ThumbFunc);
218}
219
220void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
221                                          MCSymbolAttr Attribute) {
222  // Indirect symbols are handled differently, to match how 'as' handles
223  // them. This makes writing matching .o files easier.
224  if (Attribute == MCSA_IndirectSymbol) {
225    // Note that we intentionally cannot use the symbol data here; this is
226    // important for matching the string table that 'as' generates.
227    IndirectSymbolData ISD;
228    ISD.Symbol = Symbol;
229    ISD.SectionData = getCurrentSectionData();
230    getAssembler().getIndirectSymbols().push_back(ISD);
231    return;
232  }
233
234  // Adding a symbol attribute always introduces the symbol, note that an
235  // important side effect of calling getOrCreateSymbolData here is to register
236  // the symbol with the assembler.
237  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
238
239  // The implementation of symbol attributes is designed to match 'as', but it
240  // leaves much to desired. It doesn't really make sense to arbitrarily add and
241  // remove flags, but 'as' allows this (in particular, see .desc).
242  //
243  // In the future it might be worth trying to make these operations more well
244  // defined.
245  switch (Attribute) {
246  case MCSA_Invalid:
247  case MCSA_ELF_TypeFunction:
248  case MCSA_ELF_TypeIndFunction:
249  case MCSA_ELF_TypeObject:
250  case MCSA_ELF_TypeTLS:
251  case MCSA_ELF_TypeCommon:
252  case MCSA_ELF_TypeNoType:
253  case MCSA_ELF_TypeGnuUniqueObject:
254  case MCSA_Hidden:
255  case MCSA_IndirectSymbol:
256  case MCSA_Internal:
257  case MCSA_Protected:
258  case MCSA_Weak:
259  case MCSA_Local:
260    llvm_unreachable("Invalid symbol attribute for Mach-O!");
261
262  case MCSA_Global:
263    SD.setExternal(true);
264    // This effectively clears the undefined lazy bit, in Darwin 'as', although
265    // it isn't very consistent because it implements this as part of symbol
266    // lookup.
267    //
268    // FIXME: Cleanup this code, these bits should be emitted based on semantic
269    // properties, not on the order of definition, etc.
270    SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
271    break;
272
273  case MCSA_LazyReference:
274    // FIXME: This requires -dynamic.
275    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
276    if (Symbol->isUndefined())
277      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
278    break;
279
280    // Since .reference sets the no dead strip bit, it is equivalent to
281    // .no_dead_strip in practice.
282  case MCSA_Reference:
283  case MCSA_NoDeadStrip:
284    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
285    break;
286
287  case MCSA_SymbolResolver:
288    SD.setFlags(SD.getFlags() | SF_SymbolResolver);
289    break;
290
291  case MCSA_PrivateExtern:
292    SD.setExternal(true);
293    SD.setPrivateExtern(true);
294    break;
295
296  case MCSA_WeakReference:
297    // FIXME: This requires -dynamic.
298    if (Symbol->isUndefined())
299      SD.setFlags(SD.getFlags() | SF_WeakReference);
300    break;
301
302  case MCSA_WeakDefinition:
303    // FIXME: 'as' enforces that this is defined and global. The manual claims
304    // it has to be in a coalesced section, but this isn't enforced.
305    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
306    break;
307
308  case MCSA_WeakDefAutoPrivate:
309    SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
310    break;
311  }
312}
313
314void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
315  // Encode the 'desc' value into the lowest implementation defined bits.
316  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
317         "Invalid .desc value!");
318  getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
319    DescValue & SF_DescFlagsMask);
320}
321
322void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
323                                       unsigned ByteAlignment) {
324  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
325  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
326
327  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
328  SD.setExternal(true);
329  SD.setCommon(Size, ByteAlignment);
330}
331
332void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
333                                            unsigned ByteAlignment) {
334  // '.lcomm' is equivalent to '.zerofill'.
335  return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
336                                                   MCSectionMachO::S_ZEROFILL,
337                                                   0, SectionKind::getBSS()),
338                      Symbol, Size, ByteAlignment);
339}
340
341void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
342                                   uint64_t Size, unsigned ByteAlignment) {
343  MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
344
345  // The symbol may not be present, which only creates the section.
346  if (!Symbol)
347    return;
348
349  // FIXME: Assert that this section has the zerofill type.
350
351  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
352
353  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
354
355  // Emit an align fragment if necessary.
356  if (ByteAlignment != 1)
357    new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
358
359  MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
360  SD.setFragment(F);
361
362  Symbol->setSection(*Section);
363
364  // Update the maximum alignment on the zero fill section if necessary.
365  if (ByteAlignment > SectData.getAlignment())
366    SectData.setAlignment(ByteAlignment);
367}
368
369// This should always be called with the thread local bss section.  Like the
370// .zerofill directive this doesn't actually switch sections on us.
371void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
372                                     uint64_t Size, unsigned ByteAlignment) {
373  EmitZerofill(Section, Symbol, Size, ByteAlignment);
374  return;
375}
376
377void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
378  MCDataFragment *DF = getOrCreateDataFragment();
379
380  SmallVector<MCFixup, 4> Fixups;
381  SmallString<256> Code;
382  raw_svector_ostream VecOS(Code);
383  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
384  VecOS.flush();
385
386  // Add the fixups and data.
387  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
388    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
389    DF->getFixups().push_back(Fixups[i]);
390  }
391  DF->getContents().append(Code.begin(), Code.end());
392}
393
394void MCMachOStreamer::FinishImpl() {
395  EmitFrames(true);
396
397  // We have to set the fragment atom associations so we can relax properly for
398  // Mach-O.
399
400  // First, scan the symbol table to build a lookup table from fragments to
401  // defining symbols.
402  DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
403  for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
404         ie = getAssembler().symbol_end(); it != ie; ++it) {
405    if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
406        it->getFragment()) {
407      // An atom defining symbol should never be internal to a fragment.
408      assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
409      DefiningSymbolMap[it->getFragment()] = it;
410    }
411  }
412
413  // Set the fragment atom associations by tracking the last seen atom defining
414  // symbol.
415  for (MCAssembler::iterator it = getAssembler().begin(),
416         ie = getAssembler().end(); it != ie; ++it) {
417    MCSymbolData *CurrentAtom = 0;
418    for (MCSectionData::iterator it2 = it->begin(),
419           ie2 = it->end(); it2 != ie2; ++it2) {
420      if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
421        CurrentAtom = SD;
422      it2->setAtom(CurrentAtom);
423    }
424  }
425
426  this->MCObjectStreamer::FinishImpl();
427}
428
429MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
430                                      raw_ostream &OS, MCCodeEmitter *CE,
431                                      bool RelaxAll) {
432  MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
433  if (RelaxAll)
434    S->getAssembler().setRelaxAll(true);
435  return S;
436}
437