MCMachOStreamer.cpp revision 243830 
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
11#include "llvm/MC/MCAssembler.h"
12#include "llvm/MC/MCContext.h"
13#include "llvm/MC/MCCodeEmitter.h"
14#include "llvm/MC/MCExpr.h"
15#include "llvm/MC/MCInst.h"
16#include "llvm/MC/MCObjectStreamer.h"
17#include "llvm/MC/MCSection.h"
18#include "llvm/MC/MCSymbol.h"
19#include "llvm/MC/MCMachOSymbolFlags.h"
20#include "llvm/MC/MCSectionMachO.h"
21#include "llvm/MC/MCDwarf.h"
22#include "llvm/MC/MCAsmBackend.h"
23#include "llvm/Support/Dwarf.h"
24#include "llvm/Support/ErrorHandling.h"
25#include "llvm/Support/raw_ostream.h"
26
27using namespace llvm;
28
29namespace {
30
31class MCMachOStreamer : public MCObjectStreamer {
32private:
33  virtual void EmitInstToData(const MCInst &Inst);
34
35  void EmitDataRegion(DataRegionData::KindTy Kind);
36  void EmitDataRegionEnd();
37public:
38  MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
39                  raw_ostream &OS, MCCodeEmitter *Emitter)
40    : MCObjectStreamer(Context, MAB, OS, Emitter) {}
41
42  /// @name MCStreamer Interface
43  /// @{
44
45  virtual void InitSections();
46  virtual void EmitLabel(MCSymbol *Symbol);
47  virtual void EmitEHSymAttributes(const MCSymbol *Symbol,
48                                   MCSymbol *EHSymbol);
49  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
50  virtual void EmitDataRegion(MCDataRegionType Kind);
51  virtual void EmitThumbFunc(MCSymbol *Func);
52  virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
53  virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
54  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
55  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
56                                unsigned ByteAlignment);
57  virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
58    llvm_unreachable("macho doesn't support this directive");
59  }
60  virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
61    llvm_unreachable("macho doesn't support this directive");
62  }
63  virtual void EmitCOFFSymbolType(int Type) {
64    llvm_unreachable("macho doesn't support this directive");
65  }
66  virtual void EndCOFFSymbolDef() {
67    llvm_unreachable("macho doesn't support this directive");
68  }
69  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
70    llvm_unreachable("macho doesn't support this directive");
71  }
72  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
73                                     unsigned ByteAlignment);
74  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
75                            uint64_t Size = 0, unsigned ByteAlignment = 0);
76  virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
77                              uint64_t Size, unsigned ByteAlignment = 0);
78
79  virtual void EmitFileDirective(StringRef Filename) {
80    // FIXME: Just ignore the .file; it isn't important enough to fail the
81    // entire assembly.
82
83    //report_fatal_error("unsupported directive: '.file'");
84  }
85
86  virtual void FinishImpl();
87
88  /// @}
89};
90
91} // end anonymous namespace.
92
93void MCMachOStreamer::InitSections() {
94  SwitchSection(getContext().getMachOSection("__TEXT", "__text",
95                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
96                                    0, SectionKind::getText()));
97
98}
99
100void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
101                                          MCSymbol *EHSymbol) {
102  MCSymbolData &SD =
103    getAssembler().getOrCreateSymbolData(*Symbol);
104  if (SD.isExternal())
105    EmitSymbolAttribute(EHSymbol, MCSA_Global);
106  if (SD.getFlags() & SF_WeakDefinition)
107    EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
108  if (SD.isPrivateExtern())
109    EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
110}
111
112void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
113  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
114
115  // isSymbolLinkerVisible uses the section.
116  Symbol->setSection(*getCurrentSection());
117  // We have to create a new fragment if this is an atom defining symbol,
118  // fragments cannot span atoms.
119  if (getAssembler().isSymbolLinkerVisible(*Symbol))
120    new MCDataFragment(getCurrentSectionData());
121
122  MCObjectStreamer::EmitLabel(Symbol);
123
124  MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
125  // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
126  // to clear the weak reference and weak definition bits too, but the
127  // implementation was buggy. For now we just try to match 'as', for
128  // diffability.
129  //
130  // FIXME: Cleanup this code, these bits should be emitted based on semantic
131  // properties, not on the order of definition, etc.
132  SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
133}
134
135void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
136  if (!getAssembler().getBackend().hasDataInCodeSupport())
137    return;
138  // Create a temporary label to mark the start of the data region.
139  MCSymbol *Start = getContext().CreateTempSymbol();
140  EmitLabel(Start);
141  // Record the region for the object writer to use.
142  DataRegionData Data = { Kind, Start, NULL };
143  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
144  Regions.push_back(Data);
145}
146
147void MCMachOStreamer::EmitDataRegionEnd() {
148  if (!getAssembler().getBackend().hasDataInCodeSupport())
149    return;
150  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
151  assert(Regions.size() && "Mismatched .end_data_region!");
152  DataRegionData &Data = Regions.back();
153  assert(Data.End == NULL && "Mismatched .end_data_region!");
154  // Create a temporary label to mark the end of the data region.
155  Data.End = getContext().CreateTempSymbol();
156  EmitLabel(Data.End);
157}
158
159void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
160  // Let the target do whatever target specific stuff it needs to do.
161  getAssembler().getBackend().handleAssemblerFlag(Flag);
162  // Do any generic stuff we need to do.
163  switch (Flag) {
164  case MCAF_SyntaxUnified: return; // no-op here.
165  case MCAF_Code16: return; // Change parsing mode; no-op here.
166  case MCAF_Code32: return; // Change parsing mode; no-op here.
167  case MCAF_Code64: return; // Change parsing mode; no-op here.
168  case MCAF_SubsectionsViaSymbols:
169    getAssembler().setSubsectionsViaSymbols(true);
170    return;
171  }
172}
173
174void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
175  switch (Kind) {
176  case MCDR_DataRegion:
177    EmitDataRegion(DataRegionData::Data);
178    return;
179  case MCDR_DataRegionJT8:
180    EmitDataRegion(DataRegionData::JumpTable8);
181    return;
182  case MCDR_DataRegionJT16:
183    EmitDataRegion(DataRegionData::JumpTable16);
184    return;
185  case MCDR_DataRegionJT32:
186    EmitDataRegion(DataRegionData::JumpTable32);
187    return;
188  case MCDR_DataRegionEnd:
189    EmitDataRegionEnd();
190    return;
191  }
192}
193
194void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
195  // Remember that the function is a thumb function. Fixup and relocation
196  // values will need adjusted.
197  getAssembler().setIsThumbFunc(Symbol);
198
199  // Mark the thumb bit on the symbol.
200  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
201  SD.setFlags(SD.getFlags() | SF_ThumbFunc);
202}
203
204void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
205  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
206  // MCObjectStreamer.
207  // FIXME: Lift context changes into super class.
208  getAssembler().getOrCreateSymbolData(*Symbol);
209  Symbol->setVariableValue(AddValueSymbols(Value));
210}
211
212void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
213                                          MCSymbolAttr Attribute) {
214  // Indirect symbols are handled differently, to match how 'as' handles
215  // them. This makes writing matching .o files easier.
216  if (Attribute == MCSA_IndirectSymbol) {
217    // Note that we intentionally cannot use the symbol data here; this is
218    // important for matching the string table that 'as' generates.
219    IndirectSymbolData ISD;
220    ISD.Symbol = Symbol;
221    ISD.SectionData = getCurrentSectionData();
222    getAssembler().getIndirectSymbols().push_back(ISD);
223    return;
224  }
225
226  // Adding a symbol attribute always introduces the symbol, note that an
227  // important side effect of calling getOrCreateSymbolData here is to register
228  // the symbol with the assembler.
229  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
230
231  // The implementation of symbol attributes is designed to match 'as', but it
232  // leaves much to desired. It doesn't really make sense to arbitrarily add and
233  // remove flags, but 'as' allows this (in particular, see .desc).
234  //
235  // In the future it might be worth trying to make these operations more well
236  // defined.
237  switch (Attribute) {
238  case MCSA_Invalid:
239  case MCSA_ELF_TypeFunction:
240  case MCSA_ELF_TypeIndFunction:
241  case MCSA_ELF_TypeObject:
242  case MCSA_ELF_TypeTLS:
243  case MCSA_ELF_TypeCommon:
244  case MCSA_ELF_TypeNoType:
245  case MCSA_ELF_TypeGnuUniqueObject:
246  case MCSA_Hidden:
247  case MCSA_IndirectSymbol:
248  case MCSA_Internal:
249  case MCSA_Protected:
250  case MCSA_Weak:
251  case MCSA_Local:
252    llvm_unreachable("Invalid symbol attribute for Mach-O!");
253
254  case MCSA_Global:
255    SD.setExternal(true);
256    // This effectively clears the undefined lazy bit, in Darwin 'as', although
257    // it isn't very consistent because it implements this as part of symbol
258    // lookup.
259    //
260    // FIXME: Cleanup this code, these bits should be emitted based on semantic
261    // properties, not on the order of definition, etc.
262    SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
263    break;
264
265  case MCSA_LazyReference:
266    // FIXME: This requires -dynamic.
267    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
268    if (Symbol->isUndefined())
269      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
270    break;
271
272    // Since .reference sets the no dead strip bit, it is equivalent to
273    // .no_dead_strip in practice.
274  case MCSA_Reference:
275  case MCSA_NoDeadStrip:
276    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
277    break;
278
279  case MCSA_SymbolResolver:
280    SD.setFlags(SD.getFlags() | SF_SymbolResolver);
281    break;
282
283  case MCSA_PrivateExtern:
284    SD.setExternal(true);
285    SD.setPrivateExtern(true);
286    break;
287
288  case MCSA_WeakReference:
289    // FIXME: This requires -dynamic.
290    if (Symbol->isUndefined())
291      SD.setFlags(SD.getFlags() | SF_WeakReference);
292    break;
293
294  case MCSA_WeakDefinition:
295    // FIXME: 'as' enforces that this is defined and global. The manual claims
296    // it has to be in a coalesced section, but this isn't enforced.
297    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
298    break;
299
300  case MCSA_WeakDefAutoPrivate:
301    SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
302    break;
303  }
304}
305
306void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
307  // Encode the 'desc' value into the lowest implementation defined bits.
308  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
309         "Invalid .desc value!");
310  getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
311    DescValue & SF_DescFlagsMask);
312}
313
314void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
315                                       unsigned ByteAlignment) {
316  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
317  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
318
319  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
320  SD.setExternal(true);
321  SD.setCommon(Size, ByteAlignment);
322}
323
324void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
325                                            unsigned ByteAlignment) {
326  // '.lcomm' is equivalent to '.zerofill'.
327  return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
328                                                   MCSectionMachO::S_ZEROFILL,
329                                                   0, SectionKind::getBSS()),
330                      Symbol, Size, ByteAlignment);
331}
332
333void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
334                                   uint64_t Size, unsigned ByteAlignment) {
335  MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
336
337  // The symbol may not be present, which only creates the section.
338  if (!Symbol)
339    return;
340
341  // FIXME: Assert that this section has the zerofill type.
342
343  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
344
345  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
346
347  // Emit an align fragment if necessary.
348  if (ByteAlignment != 1)
349    new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
350
351  MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
352  SD.setFragment(F);
353
354  Symbol->setSection(*Section);
355
356  // Update the maximum alignment on the zero fill section if necessary.
357  if (ByteAlignment > SectData.getAlignment())
358    SectData.setAlignment(ByteAlignment);
359}
360
361// This should always be called with the thread local bss section.  Like the
362// .zerofill directive this doesn't actually switch sections on us.
363void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
364                                     uint64_t Size, unsigned ByteAlignment) {
365  EmitZerofill(Section, Symbol, Size, ByteAlignment);
366  return;
367}
368
369void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
370  MCDataFragment *DF = getOrCreateDataFragment();
371
372  SmallVector<MCFixup, 4> Fixups;
373  SmallString<256> Code;
374  raw_svector_ostream VecOS(Code);
375  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
376  VecOS.flush();
377
378  // Add the fixups and data.
379  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
380    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
381    DF->addFixup(Fixups[i]);
382  }
383  DF->getContents().append(Code.begin(), Code.end());
384}
385
386void MCMachOStreamer::FinishImpl() {
387  EmitFrames(true);
388
389  // We have to set the fragment atom associations so we can relax properly for
390  // Mach-O.
391
392  // First, scan the symbol table to build a lookup table from fragments to
393  // defining symbols.
394  DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
395  for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
396         ie = getAssembler().symbol_end(); it != ie; ++it) {
397    if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
398        it->getFragment()) {
399      // An atom defining symbol should never be internal to a fragment.
400      assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
401      DefiningSymbolMap[it->getFragment()] = it;
402    }
403  }
404
405  // Set the fragment atom associations by tracking the last seen atom defining
406  // symbol.
407  for (MCAssembler::iterator it = getAssembler().begin(),
408         ie = getAssembler().end(); it != ie; ++it) {
409    MCSymbolData *CurrentAtom = 0;
410    for (MCSectionData::iterator it2 = it->begin(),
411           ie2 = it->end(); it2 != ie2; ++it2) {
412      if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
413        CurrentAtom = SD;
414      it2->setAtom(CurrentAtom);
415    }
416  }
417
418  this->MCObjectStreamer::FinishImpl();
419}
420
421MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
422                                      raw_ostream &OS, MCCodeEmitter *CE,
423                                      bool RelaxAll) {
424  MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
425  if (RelaxAll)
426    S->getAssembler().setRelaxAll(true);
427  return S;
428}
429