MCMachOStreamer.cpp revision 263508 
1//===-- MCMachOStreamer.cpp - MachO Streamer ------------------------------===//
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#include "llvm/MC/MCAsmBackend.h"
12#include "llvm/MC/MCAssembler.h"
13#include "llvm/MC/MCCodeEmitter.h"
14#include "llvm/MC/MCContext.h"
15#include "llvm/MC/MCDwarf.h"
16#include "llvm/MC/MCExpr.h"
17#include "llvm/MC/MCInst.h"
18#include "llvm/MC/MCMachOSymbolFlags.h"
19#include "llvm/MC/MCObjectStreamer.h"
20#include "llvm/MC/MCSection.h"
21#include "llvm/MC/MCSectionMachO.h"
22#include "llvm/MC/MCSymbol.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, raw_ostream &OS,
39                  MCCodeEmitter *Emitter)
40      : MCObjectStreamer(Context, 0, MAB, OS, Emitter) {}
41
42  /// @name MCStreamer Interface
43  /// @{
44
45  virtual void InitSections();
46  virtual void InitToTextSection();
47  virtual void EmitLabel(MCSymbol *Symbol);
48  virtual void EmitDebugLabel(MCSymbol *Symbol);
49  virtual void EmitEHSymAttributes(const MCSymbol *Symbol,
50                                   MCSymbol *EHSymbol);
51  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
52  virtual void EmitLinkerOptions(ArrayRef<std::string> Options);
53  virtual void EmitDataRegion(MCDataRegionType Kind);
54  virtual void EmitThumbFunc(MCSymbol *Func);
55  virtual bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
56  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
57  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
58                                unsigned ByteAlignment);
59  virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
60    llvm_unreachable("macho doesn't support this directive");
61  }
62  virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
63    llvm_unreachable("macho doesn't support this directive");
64  }
65  virtual void EmitCOFFSymbolType(int Type) {
66    llvm_unreachable("macho doesn't support this directive");
67  }
68  virtual void EndCOFFSymbolDef() {
69    llvm_unreachable("macho doesn't support this directive");
70  }
71  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
72    llvm_unreachable("macho doesn't support this directive");
73  }
74  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
75                                     unsigned ByteAlignment);
76  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
77                            uint64_t Size = 0, unsigned ByteAlignment = 0);
78  virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
79                              uint64_t Size, unsigned ByteAlignment = 0);
80
81  virtual void EmitFileDirective(StringRef Filename) {
82    // FIXME: Just ignore the .file; it isn't important enough to fail the
83    // entire assembly.
84
85    // report_fatal_error("unsupported directive: '.file'");
86  }
87
88  virtual void EmitIdent(StringRef IdentString) {
89    llvm_unreachable("macho doesn't support this directive");
90  }
91
92  virtual void FinishImpl();
93};
94
95} // end anonymous namespace.
96
97void MCMachOStreamer::InitSections() {
98  InitToTextSection();
99}
100
101void MCMachOStreamer::InitToTextSection() {
102  SwitchSection(getContext().getMachOSection(
103                                    "__TEXT", "__text",
104                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS, 0,
105                                    SectionKind::getText()));
106}
107
108void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
109                                          MCSymbol *EHSymbol) {
110  MCSymbolData &SD =
111    getAssembler().getOrCreateSymbolData(*Symbol);
112  if (SD.isExternal())
113    EmitSymbolAttribute(EHSymbol, MCSA_Global);
114  if (SD.getFlags() & SF_WeakDefinition)
115    EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
116  if (SD.isPrivateExtern())
117    EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
118}
119
120void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
121  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
122
123  // isSymbolLinkerVisible uses the section.
124  AssignSection(Symbol, getCurrentSection().first);
125  // We have to create a new fragment if this is an atom defining symbol,
126  // fragments cannot span atoms.
127  if (getAssembler().isSymbolLinkerVisible(*Symbol))
128    insert(new MCDataFragment());
129
130  MCObjectStreamer::EmitLabel(Symbol);
131
132  MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
133  // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
134  // to clear the weak reference and weak definition bits too, but the
135  // implementation was buggy. For now we just try to match 'as', for
136  // diffability.
137  //
138  // FIXME: Cleanup this code, these bits should be emitted based on semantic
139  // properties, not on the order of definition, etc.
140  SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
141}
142
143void MCMachOStreamer::EmitDebugLabel(MCSymbol *Symbol) {
144  EmitLabel(Symbol);
145}
146void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
147  if (!getAssembler().getBackend().hasDataInCodeSupport())
148    return;
149  // Create a temporary label to mark the start of the data region.
150  MCSymbol *Start = getContext().CreateTempSymbol();
151  EmitLabel(Start);
152  // Record the region for the object writer to use.
153  DataRegionData Data = { Kind, Start, NULL };
154  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
155  Regions.push_back(Data);
156}
157
158void MCMachOStreamer::EmitDataRegionEnd() {
159  if (!getAssembler().getBackend().hasDataInCodeSupport())
160    return;
161  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
162  assert(Regions.size() && "Mismatched .end_data_region!");
163  DataRegionData &Data = Regions.back();
164  assert(Data.End == NULL && "Mismatched .end_data_region!");
165  // Create a temporary label to mark the end of the data region.
166  Data.End = getContext().CreateTempSymbol();
167  EmitLabel(Data.End);
168}
169
170void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
171  // Let the target do whatever target specific stuff it needs to do.
172  getAssembler().getBackend().handleAssemblerFlag(Flag);
173  // Do any generic stuff we need to do.
174  switch (Flag) {
175  case MCAF_SyntaxUnified: return; // no-op here.
176  case MCAF_Code16: return; // Change parsing mode; no-op here.
177  case MCAF_Code32: return; // Change parsing mode; no-op here.
178  case MCAF_Code64: return; // Change parsing mode; no-op here.
179  case MCAF_SubsectionsViaSymbols:
180    getAssembler().setSubsectionsViaSymbols(true);
181    return;
182  }
183}
184
185void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
186  getAssembler().getLinkerOptions().push_back(Options);
187}
188
189void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
190  switch (Kind) {
191  case MCDR_DataRegion:
192    EmitDataRegion(DataRegionData::Data);
193    return;
194  case MCDR_DataRegionJT8:
195    EmitDataRegion(DataRegionData::JumpTable8);
196    return;
197  case MCDR_DataRegionJT16:
198    EmitDataRegion(DataRegionData::JumpTable16);
199    return;
200  case MCDR_DataRegionJT32:
201    EmitDataRegion(DataRegionData::JumpTable32);
202    return;
203  case MCDR_DataRegionEnd:
204    EmitDataRegionEnd();
205    return;
206  }
207}
208
209void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
210  // Remember that the function is a thumb function. Fixup and relocation
211  // values will need adjusted.
212  getAssembler().setIsThumbFunc(Symbol);
213
214  // Mark the thumb bit on the symbol.
215  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
216  SD.setFlags(SD.getFlags() | SF_ThumbFunc);
217}
218
219bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
220                                          MCSymbolAttr Attribute) {
221  // Indirect symbols are handled differently, to match how 'as' handles
222  // them. This makes writing matching .o files easier.
223  if (Attribute == MCSA_IndirectSymbol) {
224    // Note that we intentionally cannot use the symbol data here; this is
225    // important for matching the string table that 'as' generates.
226    IndirectSymbolData ISD;
227    ISD.Symbol = Symbol;
228    ISD.SectionData = getCurrentSectionData();
229    getAssembler().getIndirectSymbols().push_back(ISD);
230    return true;
231  }
232
233  // Adding a symbol attribute always introduces the symbol, note that an
234  // important side effect of calling getOrCreateSymbolData here is to register
235  // the symbol with the assembler.
236  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
237
238  // The implementation of symbol attributes is designed to match 'as', but it
239  // leaves much to desired. It doesn't really make sense to arbitrarily add and
240  // remove flags, but 'as' allows this (in particular, see .desc).
241  //
242  // In the future it might be worth trying to make these operations more well
243  // defined.
244  switch (Attribute) {
245  case MCSA_Invalid:
246  case MCSA_ELF_TypeFunction:
247  case MCSA_ELF_TypeIndFunction:
248  case MCSA_ELF_TypeObject:
249  case MCSA_ELF_TypeTLS:
250  case MCSA_ELF_TypeCommon:
251  case MCSA_ELF_TypeNoType:
252  case MCSA_ELF_TypeGnuUniqueObject:
253  case MCSA_Hidden:
254  case MCSA_IndirectSymbol:
255  case MCSA_Internal:
256  case MCSA_Protected:
257  case MCSA_Weak:
258  case MCSA_Local:
259    return false;
260
261  case MCSA_Global:
262    SD.setExternal(true);
263    // This effectively clears the undefined lazy bit, in Darwin 'as', although
264    // it isn't very consistent because it implements this as part of symbol
265    // lookup.
266    //
267    // FIXME: Cleanup this code, these bits should be emitted based on semantic
268    // properties, not on the order of definition, etc.
269    SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
270    break;
271
272  case MCSA_LazyReference:
273    // FIXME: This requires -dynamic.
274    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
275    if (Symbol->isUndefined())
276      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
277    break;
278
279    // Since .reference sets the no dead strip bit, it is equivalent to
280    // .no_dead_strip in practice.
281  case MCSA_Reference:
282  case MCSA_NoDeadStrip:
283    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
284    break;
285
286  case MCSA_SymbolResolver:
287    SD.setFlags(SD.getFlags() | SF_SymbolResolver);
288    break;
289
290  case MCSA_PrivateExtern:
291    SD.setExternal(true);
292    SD.setPrivateExtern(true);
293    break;
294
295  case MCSA_WeakReference:
296    // FIXME: This requires -dynamic.
297    if (Symbol->isUndefined())
298      SD.setFlags(SD.getFlags() | SF_WeakReference);
299    break;
300
301  case MCSA_WeakDefinition:
302    // FIXME: 'as' enforces that this is defined and global. The manual claims
303    // it has to be in a coalesced section, but this isn't enforced.
304    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
305    break;
306
307  case MCSA_WeakDefAutoPrivate:
308    SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
309    break;
310  }
311
312  return true;
313}
314
315void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
316  // Encode the 'desc' value into the lowest implementation defined bits.
317  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
318         "Invalid .desc value!");
319  getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
320    DescValue & SF_DescFlagsMask);
321}
322
323void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
324                                       unsigned ByteAlignment) {
325  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
326  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
327
328  AssignSection(Symbol, NULL);
329
330  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
331  SD.setExternal(true);
332  SD.setCommon(Size, ByteAlignment);
333}
334
335void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
336                                            unsigned ByteAlignment) {
337  // '.lcomm' is equivalent to '.zerofill'.
338  return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
339                                                   MCSectionMachO::S_ZEROFILL,
340                                                   0, SectionKind::getBSS()),
341                      Symbol, Size, ByteAlignment);
342}
343
344void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
345                                   uint64_t Size, unsigned ByteAlignment) {
346  MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
347
348  // The symbol may not be present, which only creates the section.
349  if (!Symbol)
350    return;
351
352  // On darwin all virtual sections have zerofill type.
353  assert(Section->isVirtualSection() && "Section does not have zerofill type!");
354
355  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
356
357  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
358
359  // Emit an align fragment if necessary.
360  if (ByteAlignment != 1)
361    new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
362
363  MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
364  SD.setFragment(F);
365
366  AssignSection(Symbol, Section);
367
368  // Update the maximum alignment on the zero fill section if necessary.
369  if (ByteAlignment > SectData.getAlignment())
370    SectData.setAlignment(ByteAlignment);
371}
372
373// This should always be called with the thread local bss section.  Like the
374// .zerofill directive this doesn't actually switch sections on us.
375void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
376                                     uint64_t Size, unsigned ByteAlignment) {
377  EmitZerofill(Section, Symbol, Size, ByteAlignment);
378  return;
379}
380
381void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
382  MCDataFragment *DF = getOrCreateDataFragment();
383
384  SmallVector<MCFixup, 4> Fixups;
385  SmallString<256> Code;
386  raw_svector_ostream VecOS(Code);
387  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
388  VecOS.flush();
389
390  // Add the fixups and data.
391  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
392    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
393    DF->getFixups().push_back(Fixups[i]);
394  }
395  DF->getContents().append(Code.begin(), Code.end());
396}
397
398void MCMachOStreamer::FinishImpl() {
399  EmitFrames(&getAssembler().getBackend(), true);
400
401  // We have to set the fragment atom associations so we can relax properly for
402  // Mach-O.
403
404  // First, scan the symbol table to build a lookup table from fragments to
405  // defining symbols.
406  DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
407  for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
408         ie = getAssembler().symbol_end(); it != ie; ++it) {
409    if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
410        it->getFragment()) {
411      // An atom defining symbol should never be internal to a fragment.
412      assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
413      DefiningSymbolMap[it->getFragment()] = it;
414    }
415  }
416
417  // Set the fragment atom associations by tracking the last seen atom defining
418  // symbol.
419  for (MCAssembler::iterator it = getAssembler().begin(),
420         ie = getAssembler().end(); it != ie; ++it) {
421    MCSymbolData *CurrentAtom = 0;
422    for (MCSectionData::iterator it2 = it->begin(),
423           ie2 = it->end(); it2 != ie2; ++it2) {
424      if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
425        CurrentAtom = SD;
426      it2->setAtom(CurrentAtom);
427    }
428  }
429
430  this->MCObjectStreamer::FinishImpl();
431}
432
433MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
434                                      raw_ostream &OS, MCCodeEmitter *CE,
435                                      bool RelaxAll) {
436  MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
437  if (RelaxAll)
438    S->getAssembler().setRelaxAll(true);
439  return S;
440}
441