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  virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
79  virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
80                                    unsigned ValueSize = 1,
81                                    unsigned MaxBytesToEmit = 0);
82  virtual void EmitCodeAlignment(unsigned ByteAlignment,
83                                 unsigned MaxBytesToEmit = 0);
84
85  virtual void EmitFileDirective(StringRef Filename) {
86    // FIXME: Just ignore the .file; it isn't important enough to fail the
87    // entire assembly.
88
89    //report_fatal_error("unsupported directive: '.file'");
90  }
91
92  virtual void FinishImpl();
93
94  /// @}
95};
96
97} // end anonymous namespace.
98
99void MCMachOStreamer::InitSections() {
100  SwitchSection(getContext().getMachOSection("__TEXT", "__text",
101                                    MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
102                                    0, SectionKind::getText()));
103
104}
105
106void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
107                                          MCSymbol *EHSymbol) {
108  MCSymbolData &SD =
109    getAssembler().getOrCreateSymbolData(*Symbol);
110  if (SD.isExternal())
111    EmitSymbolAttribute(EHSymbol, MCSA_Global);
112  if (SD.getFlags() & SF_WeakDefinition)
113    EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
114  if (SD.isPrivateExtern())
115    EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
116}
117
118void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
119  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
120
121  // isSymbolLinkerVisible uses the section.
122  Symbol->setSection(*getCurrentSection());
123  // We have to create a new fragment if this is an atom defining symbol,
124  // fragments cannot span atoms.
125  if (getAssembler().isSymbolLinkerVisible(*Symbol))
126    new MCDataFragment(getCurrentSectionData());
127
128  MCObjectStreamer::EmitLabel(Symbol);
129
130  MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
131  // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
132  // to clear the weak reference and weak definition bits too, but the
133  // implementation was buggy. For now we just try to match 'as', for
134  // diffability.
135  //
136  // FIXME: Cleanup this code, these bits should be emitted based on semantic
137  // properties, not on the order of definition, etc.
138  SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
139}
140
141void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
142  if (!getAssembler().getBackend().hasDataInCodeSupport())
143    return;
144  // Create a temporary label to mark the start of the data region.
145  MCSymbol *Start = getContext().CreateTempSymbol();
146  EmitLabel(Start);
147  // Record the region for the object writer to use.
148  DataRegionData Data = { Kind, Start, NULL };
149  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
150  Regions.push_back(Data);
151}
152
153void MCMachOStreamer::EmitDataRegionEnd() {
154  if (!getAssembler().getBackend().hasDataInCodeSupport())
155    return;
156  std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
157  assert(Regions.size() && "Mismatched .end_data_region!");
158  DataRegionData &Data = Regions.back();
159  assert(Data.End == NULL && "Mismatched .end_data_region!");
160  // Create a temporary label to mark the end of the data region.
161  Data.End = getContext().CreateTempSymbol();
162  EmitLabel(Data.End);
163}
164
165void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
166  // Let the target do whatever target specific stuff it needs to do.
167  getAssembler().getBackend().handleAssemblerFlag(Flag);
168  // Do any generic stuff we need to do.
169  switch (Flag) {
170  case MCAF_SyntaxUnified: return; // no-op here.
171  case MCAF_Code16: return; // Change parsing mode; no-op here.
172  case MCAF_Code32: return; // Change parsing mode; no-op here.
173  case MCAF_Code64: return; // Change parsing mode; no-op here.
174  case MCAF_SubsectionsViaSymbols:
175    getAssembler().setSubsectionsViaSymbols(true);
176    return;
177  }
178}
179
180void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
181  switch (Kind) {
182  case MCDR_DataRegion:
183    EmitDataRegion(DataRegionData::Data);
184    return;
185  case MCDR_DataRegionJT8:
186    EmitDataRegion(DataRegionData::JumpTable8);
187    return;
188  case MCDR_DataRegionJT16:
189    EmitDataRegion(DataRegionData::JumpTable16);
190    return;
191  case MCDR_DataRegionJT32:
192    EmitDataRegion(DataRegionData::JumpTable32);
193    return;
194  case MCDR_DataRegionEnd:
195    EmitDataRegionEnd();
196    return;
197  }
198}
199
200void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
201  // Remember that the function is a thumb function. Fixup and relocation
202  // values will need adjusted.
203  getAssembler().setIsThumbFunc(Symbol);
204
205  // Mark the thumb bit on the symbol.
206  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
207  SD.setFlags(SD.getFlags() | SF_ThumbFunc);
208}
209
210void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
211  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
212  // MCObjectStreamer.
213  // FIXME: Lift context changes into super class.
214  getAssembler().getOrCreateSymbolData(*Symbol);
215  Symbol->setVariableValue(AddValueSymbols(Value));
216}
217
218void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
219                                          MCSymbolAttr Attribute) {
220  // Indirect symbols are handled differently, to match how 'as' handles
221  // them. This makes writing matching .o files easier.
222  if (Attribute == MCSA_IndirectSymbol) {
223    // Note that we intentionally cannot use the symbol data here; this is
224    // important for matching the string table that 'as' generates.
225    IndirectSymbolData ISD;
226    ISD.Symbol = Symbol;
227    ISD.SectionData = getCurrentSectionData();
228    getAssembler().getIndirectSymbols().push_back(ISD);
229    return;
230  }
231
232  // Adding a symbol attribute always introduces the symbol, note that an
233  // important side effect of calling getOrCreateSymbolData here is to register
234  // the symbol with the assembler.
235  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
236
237  // The implementation of symbol attributes is designed to match 'as', but it
238  // leaves much to desired. It doesn't really make sense to arbitrarily add and
239  // remove flags, but 'as' allows this (in particular, see .desc).
240  //
241  // In the future it might be worth trying to make these operations more well
242  // defined.
243  switch (Attribute) {
244  case MCSA_Invalid:
245  case MCSA_ELF_TypeFunction:
246  case MCSA_ELF_TypeIndFunction:
247  case MCSA_ELF_TypeObject:
248  case MCSA_ELF_TypeTLS:
249  case MCSA_ELF_TypeCommon:
250  case MCSA_ELF_TypeNoType:
251  case MCSA_ELF_TypeGnuUniqueObject:
252  case MCSA_Hidden:
253  case MCSA_IndirectSymbol:
254  case MCSA_Internal:
255  case MCSA_Protected:
256  case MCSA_Weak:
257  case MCSA_Local:
258    llvm_unreachable("Invalid symbol attribute for Mach-O!");
259
260  case MCSA_Global:
261    SD.setExternal(true);
262    // This effectively clears the undefined lazy bit, in Darwin 'as', although
263    // it isn't very consistent because it implements this as part of symbol
264    // lookup.
265    //
266    // FIXME: Cleanup this code, these bits should be emitted based on semantic
267    // properties, not on the order of definition, etc.
268    SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
269    break;
270
271  case MCSA_LazyReference:
272    // FIXME: This requires -dynamic.
273    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
274    if (Symbol->isUndefined())
275      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
276    break;
277
278    // Since .reference sets the no dead strip bit, it is equivalent to
279    // .no_dead_strip in practice.
280  case MCSA_Reference:
281  case MCSA_NoDeadStrip:
282    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
283    break;
284
285  case MCSA_SymbolResolver:
286    SD.setFlags(SD.getFlags() | SF_SymbolResolver);
287    break;
288
289  case MCSA_PrivateExtern:
290    SD.setExternal(true);
291    SD.setPrivateExtern(true);
292    break;
293
294  case MCSA_WeakReference:
295    // FIXME: This requires -dynamic.
296    if (Symbol->isUndefined())
297      SD.setFlags(SD.getFlags() | SF_WeakReference);
298    break;
299
300  case MCSA_WeakDefinition:
301    // FIXME: 'as' enforces that this is defined and global. The manual claims
302    // it has to be in a coalesced section, but this isn't enforced.
303    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
304    break;
305
306  case MCSA_WeakDefAutoPrivate:
307    SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
308    break;
309  }
310}
311
312void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
313  // Encode the 'desc' value into the lowest implementation defined bits.
314  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
315         "Invalid .desc value!");
316  getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
317    DescValue & SF_DescFlagsMask);
318}
319
320void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
321                                       unsigned ByteAlignment) {
322  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
323  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
324
325  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
326  SD.setExternal(true);
327  SD.setCommon(Size, ByteAlignment);
328}
329
330void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
331                                            unsigned ByteAlignment) {
332  // '.lcomm' is equivalent to '.zerofill'.
333  return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
334                                                   MCSectionMachO::S_ZEROFILL,
335                                                   0, SectionKind::getBSS()),
336                      Symbol, Size, ByteAlignment);
337}
338
339void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
340                                   uint64_t Size, unsigned ByteAlignment) {
341  MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
342
343  // The symbol may not be present, which only creates the section.
344  if (!Symbol)
345    return;
346
347  // FIXME: Assert that this section has the zerofill type.
348
349  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
350
351  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
352
353  // Emit an align fragment if necessary.
354  if (ByteAlignment != 1)
355    new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
356
357  MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
358  SD.setFragment(F);
359
360  Symbol->setSection(*Section);
361
362  // Update the maximum alignment on the zero fill section if necessary.
363  if (ByteAlignment > SectData.getAlignment())
364    SectData.setAlignment(ByteAlignment);
365}
366
367// This should always be called with the thread local bss section.  Like the
368// .zerofill directive this doesn't actually switch sections on us.
369void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
370                                     uint64_t Size, unsigned ByteAlignment) {
371  EmitZerofill(Section, Symbol, Size, ByteAlignment);
372  return;
373}
374
375void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
376  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
377  // MCObjectStreamer.
378  getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
379}
380
381void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
382                                           int64_t Value, unsigned ValueSize,
383                                           unsigned MaxBytesToEmit) {
384  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
385  // MCObjectStreamer.
386  if (MaxBytesToEmit == 0)
387    MaxBytesToEmit = ByteAlignment;
388  new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
389                      getCurrentSectionData());
390
391  // Update the maximum alignment on the current section if necessary.
392  if (ByteAlignment > getCurrentSectionData()->getAlignment())
393    getCurrentSectionData()->setAlignment(ByteAlignment);
394}
395
396void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
397                                        unsigned MaxBytesToEmit) {
398  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
399  // MCObjectStreamer.
400  if (MaxBytesToEmit == 0)
401    MaxBytesToEmit = ByteAlignment;
402  MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
403                                           getCurrentSectionData());
404  F->setEmitNops(true);
405
406  // Update the maximum alignment on the current section if necessary.
407  if (ByteAlignment > getCurrentSectionData()->getAlignment())
408    getCurrentSectionData()->setAlignment(ByteAlignment);
409}
410
411void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
412  MCDataFragment *DF = getOrCreateDataFragment();
413
414  SmallVector<MCFixup, 4> Fixups;
415  SmallString<256> Code;
416  raw_svector_ostream VecOS(Code);
417  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
418  VecOS.flush();
419
420  // Add the fixups and data.
421  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
422    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
423    DF->addFixup(Fixups[i]);
424  }
425  DF->getContents().append(Code.begin(), Code.end());
426}
427
428void MCMachOStreamer::FinishImpl() {
429  EmitFrames(true);
430
431  // We have to set the fragment atom associations so we can relax properly for
432  // Mach-O.
433
434  // First, scan the symbol table to build a lookup table from fragments to
435  // defining symbols.
436  DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
437  for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
438         ie = getAssembler().symbol_end(); it != ie; ++it) {
439    if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
440        it->getFragment()) {
441      // An atom defining symbol should never be internal to a fragment.
442      assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
443      DefiningSymbolMap[it->getFragment()] = it;
444    }
445  }
446
447  // Set the fragment atom associations by tracking the last seen atom defining
448  // symbol.
449  for (MCAssembler::iterator it = getAssembler().begin(),
450         ie = getAssembler().end(); it != ie; ++it) {
451    MCSymbolData *CurrentAtom = 0;
452    for (MCSectionData::iterator it2 = it->begin(),
453           ie2 = it->end(); it2 != ie2; ++it2) {
454      if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
455        CurrentAtom = SD;
456      it2->setAtom(CurrentAtom);
457    }
458  }
459
460  this->MCObjectStreamer::FinishImpl();
461}
462
463MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
464                                      raw_ostream &OS, MCCodeEmitter *CE,
465                                      bool RelaxAll) {
466  MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
467  if (RelaxAll)
468    S->getAssembler().setRelaxAll(true);
469  return S;
470}
471