MCMachOStreamer.cpp revision 030f63a397edc20f8f661bac62f7b90cb5cf57bc 
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,
38                  raw_ostream &OS, MCCodeEmitter *Emitter)
39    : MCObjectStreamer(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 EmitDataRegion(MCDataRegionType Kind);
52  virtual void EmitThumbFunc(MCSymbol *Func);
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  InitToTextSection();
95}
96
97void MCMachOStreamer::InitToTextSection() {
98  SwitchSection(getContext().getMachOSection(
99                                    "__TEXT", "__text",
100                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS, 0,
101                                    SectionKind::getText()));
102}
103
104void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
105                                          MCSymbol *EHSymbol) {
106  MCSymbolData &SD =
107    getAssembler().getOrCreateSymbolData(*Symbol);
108  if (SD.isExternal())
109    EmitSymbolAttribute(EHSymbol, MCSA_Global);
110  if (SD.getFlags() & SF_WeakDefinition)
111    EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
112  if (SD.isPrivateExtern())
113    EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
114}
115
116void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
117  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
118
119  // isSymbolLinkerVisible uses the section.
120  Symbol->setSection(*getCurrentSection());
121  // We have to create a new fragment if this is an atom defining symbol,
122  // fragments cannot span atoms.
123  if (getAssembler().isSymbolLinkerVisible(*Symbol))
124    new MCDataFragment(getCurrentSectionData());
125
126  MCObjectStreamer::EmitLabel(Symbol);
127
128  MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
129  // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
130  // to clear the weak reference and weak definition bits too, but the
131  // implementation was buggy. For now we just try to match 'as', for
132  // diffability.
133  //
134  // FIXME: Cleanup this code, these bits should be emitted based on semantic
135  // properties, not on the order of definition, etc.
136  SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
137}
138
139void MCMachOStreamer::EmitDebugLabel(MCSymbol *Symbol) {
140  EmitLabel(Symbol);
141}
142void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
143  if (!getAssembler().getBackend().hasDataInCodeSupport())
144    return;
145  // Create a temporary label to mark the start of the data region.
146  MCSymbol *Start = getContext().CreateTempSymbol();
147  EmitLabel(Start);
148  // Record the region for the object writer to use.
149  DataRegionData Data = { Kind, Start, NULL };
150  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
151  Regions.push_back(Data);
152}
153
154void MCMachOStreamer::EmitDataRegionEnd() {
155  if (!getAssembler().getBackend().hasDataInCodeSupport())
156    return;
157  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
158  assert(Regions.size() && "Mismatched .end_data_region!");
159  DataRegionData &Data = Regions.back();
160  assert(Data.End == NULL && "Mismatched .end_data_region!");
161  // Create a temporary label to mark the end of the data region.
162  Data.End = getContext().CreateTempSymbol();
163  EmitLabel(Data.End);
164}
165
166void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
167  // Let the target do whatever target specific stuff it needs to do.
168  getAssembler().getBackend().handleAssemblerFlag(Flag);
169  // Do any generic stuff we need to do.
170  switch (Flag) {
171  case MCAF_SyntaxUnified: return; // no-op here.
172  case MCAF_Code16: return; // Change parsing mode; no-op here.
173  case MCAF_Code32: return; // Change parsing mode; no-op here.
174  case MCAF_Code64: return; // Change parsing mode; no-op here.
175  case MCAF_SubsectionsViaSymbols:
176    getAssembler().setSubsectionsViaSymbols(true);
177    return;
178  }
179}
180
181void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
182  switch (Kind) {
183  case MCDR_DataRegion:
184    EmitDataRegion(DataRegionData::Data);
185    return;
186  case MCDR_DataRegionJT8:
187    EmitDataRegion(DataRegionData::JumpTable8);
188    return;
189  case MCDR_DataRegionJT16:
190    EmitDataRegion(DataRegionData::JumpTable16);
191    return;
192  case MCDR_DataRegionJT32:
193    EmitDataRegion(DataRegionData::JumpTable32);
194    return;
195  case MCDR_DataRegionEnd:
196    EmitDataRegionEnd();
197    return;
198  }
199}
200
201void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
202  // Remember that the function is a thumb function. Fixup and relocation
203  // values will need adjusted.
204  getAssembler().setIsThumbFunc(Symbol);
205
206  // Mark the thumb bit on the symbol.
207  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
208  SD.setFlags(SD.getFlags() | SF_ThumbFunc);
209}
210
211void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
212                                          MCSymbolAttr Attribute) {
213  // Indirect symbols are handled differently, to match how 'as' handles
214  // them. This makes writing matching .o files easier.
215  if (Attribute == MCSA_IndirectSymbol) {
216    // Note that we intentionally cannot use the symbol data here; this is
217    // important for matching the string table that 'as' generates.
218    IndirectSymbolData ISD;
219    ISD.Symbol = Symbol;
220    ISD.SectionData = getCurrentSectionData();
221    getAssembler().getIndirectSymbols().push_back(ISD);
222    return;
223  }
224
225  // Adding a symbol attribute always introduces the symbol, note that an
226  // important side effect of calling getOrCreateSymbolData here is to register
227  // the symbol with the assembler.
228  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
229
230  // The implementation of symbol attributes is designed to match 'as', but it
231  // leaves much to desired. It doesn't really make sense to arbitrarily add and
232  // remove flags, but 'as' allows this (in particular, see .desc).
233  //
234  // In the future it might be worth trying to make these operations more well
235  // defined.
236  switch (Attribute) {
237  case MCSA_Invalid:
238  case MCSA_ELF_TypeFunction:
239  case MCSA_ELF_TypeIndFunction:
240  case MCSA_ELF_TypeObject:
241  case MCSA_ELF_TypeTLS:
242  case MCSA_ELF_TypeCommon:
243  case MCSA_ELF_TypeNoType:
244  case MCSA_ELF_TypeGnuUniqueObject:
245  case MCSA_Hidden:
246  case MCSA_IndirectSymbol:
247  case MCSA_Internal:
248  case MCSA_Protected:
249  case MCSA_Weak:
250  case MCSA_Local:
251    llvm_unreachable("Invalid symbol attribute for Mach-O!");
252
253  case MCSA_Global:
254    SD.setExternal(true);
255    // This effectively clears the undefined lazy bit, in Darwin 'as', although
256    // it isn't very consistent because it implements this as part of symbol
257    // lookup.
258    //
259    // FIXME: Cleanup this code, these bits should be emitted based on semantic
260    // properties, not on the order of definition, etc.
261    SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
262    break;
263
264  case MCSA_LazyReference:
265    // FIXME: This requires -dynamic.
266    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
267    if (Symbol->isUndefined())
268      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
269    break;
270
271    // Since .reference sets the no dead strip bit, it is equivalent to
272    // .no_dead_strip in practice.
273  case MCSA_Reference:
274  case MCSA_NoDeadStrip:
275    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
276    break;
277
278  case MCSA_SymbolResolver:
279    SD.setFlags(SD.getFlags() | SF_SymbolResolver);
280    break;
281
282  case MCSA_PrivateExtern:
283    SD.setExternal(true);
284    SD.setPrivateExtern(true);
285    break;
286
287  case MCSA_WeakReference:
288    // FIXME: This requires -dynamic.
289    if (Symbol->isUndefined())
290      SD.setFlags(SD.getFlags() | SF_WeakReference);
291    break;
292
293  case MCSA_WeakDefinition:
294    // FIXME: 'as' enforces that this is defined and global. The manual claims
295    // it has to be in a coalesced section, but this isn't enforced.
296    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
297    break;
298
299  case MCSA_WeakDefAutoPrivate:
300    SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
301    break;
302  }
303}
304
305void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
306  // Encode the 'desc' value into the lowest implementation defined bits.
307  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
308         "Invalid .desc value!");
309  getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
310    DescValue & SF_DescFlagsMask);
311}
312
313void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
314                                       unsigned ByteAlignment) {
315  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
316  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
317
318  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
319  SD.setExternal(true);
320  SD.setCommon(Size, ByteAlignment);
321}
322
323void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
324                                            unsigned ByteAlignment) {
325  // '.lcomm' is equivalent to '.zerofill'.
326  return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
327                                                   MCSectionMachO::S_ZEROFILL,
328                                                   0, SectionKind::getBSS()),
329                      Symbol, Size, ByteAlignment);
330}
331
332void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
333                                   uint64_t Size, unsigned ByteAlignment) {
334  MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
335
336  // The symbol may not be present, which only creates the section.
337  if (!Symbol)
338    return;
339
340  // FIXME: Assert that this section has the zerofill type.
341
342  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
343
344  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
345
346  // Emit an align fragment if necessary.
347  if (ByteAlignment != 1)
348    new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
349
350  MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
351  SD.setFragment(F);
352
353  Symbol->setSection(*Section);
354
355  // Update the maximum alignment on the zero fill section if necessary.
356  if (ByteAlignment > SectData.getAlignment())
357    SectData.setAlignment(ByteAlignment);
358}
359
360// This should always be called with the thread local bss section.  Like the
361// .zerofill directive this doesn't actually switch sections on us.
362void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
363                                     uint64_t Size, unsigned ByteAlignment) {
364  EmitZerofill(Section, Symbol, Size, ByteAlignment);
365  return;
366}
367
368void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
369  MCDataFragment *DF = getOrCreateDataFragment();
370
371  SmallVector<MCFixup, 4> Fixups;
372  SmallString<256> Code;
373  raw_svector_ostream VecOS(Code);
374  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
375  VecOS.flush();
376
377  // Add the fixups and data.
378  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
379    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
380    DF->getFixups().push_back(Fixups[i]);
381  }
382  DF->getContents().append(Code.begin(), Code.end());
383}
384
385void MCMachOStreamer::FinishImpl() {
386  EmitFrames(true);
387
388  // We have to set the fragment atom associations so we can relax properly for
389  // Mach-O.
390
391  // First, scan the symbol table to build a lookup table from fragments to
392  // defining symbols.
393  DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
394  for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
395         ie = getAssembler().symbol_end(); it != ie; ++it) {
396    if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
397        it->getFragment()) {
398      // An atom defining symbol should never be internal to a fragment.
399      assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
400      DefiningSymbolMap[it->getFragment()] = it;
401    }
402  }
403
404  // Set the fragment atom associations by tracking the last seen atom defining
405  // symbol.
406  for (MCAssembler::iterator it = getAssembler().begin(),
407         ie = getAssembler().end(); it != ie; ++it) {
408    MCSymbolData *CurrentAtom = 0;
409    for (MCSectionData::iterator it2 = it->begin(),
410           ie2 = it->end(); it2 != ie2; ++it2) {
411      if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
412        CurrentAtom = SD;
413      it2->setAtom(CurrentAtom);
414    }
415  }
416
417  this->MCObjectStreamer::FinishImpl();
418}
419
420MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
421                                      raw_ostream &OS, MCCodeEmitter *CE,
422                                      bool RelaxAll) {
423  MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
424  if (RelaxAll)
425    S->getAssembler().setRelaxAll(true);
426  return S;
427}
428