MCMachOStreamer.cpp revision c25dad8750083829d9a8935ce40d0734e5488f8e 
1//===- lib/MC/MCMachOStreamer.cpp - Mach-O Object Output ------------===//
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
12#include "llvm/MC/MCAssembler.h"
13#include "llvm/MC/MCContext.h"
14#include "llvm/MC/MCCodeEmitter.h"
15#include "llvm/MC/MCExpr.h"
16#include "llvm/MC/MCInst.h"
17#include "llvm/MC/MCObjectStreamer.h"
18#include "llvm/MC/MCSection.h"
19#include "llvm/MC/MCSymbol.h"
20#include "llvm/MC/MCMachOSymbolFlags.h"
21#include "llvm/MC/MCSectionMachO.h"
22#include "llvm/MC/MCDwarf.h"
23#include "llvm/Support/Dwarf.h"
24#include "llvm/Support/ErrorHandling.h"
25#include "llvm/Support/raw_ostream.h"
26#include "llvm/Target/TargetAsmBackend.h"
27#include "llvm/Target/TargetAsmInfo.h"
28
29using namespace llvm;
30
31namespace {
32
33class MCMachOStreamer : public MCObjectStreamer {
34private:
35  virtual void EmitInstToData(const MCInst &Inst);
36
37public:
38  MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
39                  raw_ostream &OS, MCCodeEmitter *Emitter)
40    : MCObjectStreamer(Context, TAB, 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 EmitThumbFunc(MCSymbol *Func);
51  virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
52  virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
53  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
54  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
55                                unsigned ByteAlignment);
56  virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
57    assert(0 && "macho doesn't support this directive");
58  }
59  virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
60    assert(0 && "macho doesn't support this directive");
61  }
62  virtual void EmitCOFFSymbolType(int Type) {
63    assert(0 && "macho doesn't support this directive");
64  }
65  virtual void EndCOFFSymbolDef() {
66    assert(0 && "macho doesn't support this directive");
67  }
68  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
69    assert(0 && "macho doesn't support this directive");
70  }
71  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
72    assert(0 && "macho doesn't support this directive");
73  }
74  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
75                            unsigned 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 Finish();
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::EmitAssemblerFlag(MCAssemblerFlag Flag) {
142  // Let the target do whatever target specific stuff it needs to do.
143  getAssembler().getBackend().HandleAssemblerFlag(Flag);
144  // Do any generic stuff we need to do.
145  switch (Flag) {
146  case MCAF_SyntaxUnified: return; // no-op here.
147  case MCAF_Code16: return; // no-op here.
148  case MCAF_Code32: return; // no-op here.
149  case MCAF_SubsectionsViaSymbols:
150    getAssembler().setSubsectionsViaSymbols(true);
151    return;
152  default:
153    llvm_unreachable("invalid assembler flag!");
154  }
155}
156
157void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
158  // FIXME: Flag the function ISA as thumb with DW_AT_APPLE_isa.
159
160  // Remember that the function is a thumb function. Fixup and relocation
161  // values will need adjusted.
162  getAssembler().setIsThumbFunc(Symbol);
163
164  // Mark the thumb bit on the symbol.
165  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
166  SD.setFlags(SD.getFlags() | SF_ThumbFunc);
167}
168
169void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
170  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
171  // MCObjectStreamer.
172  // FIXME: Lift context changes into super class.
173  getAssembler().getOrCreateSymbolData(*Symbol);
174  Symbol->setVariableValue(AddValueSymbols(Value));
175}
176
177void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
178                                          MCSymbolAttr Attribute) {
179  // Indirect symbols are handled differently, to match how 'as' handles
180  // them. This makes writing matching .o files easier.
181  if (Attribute == MCSA_IndirectSymbol) {
182    // Note that we intentionally cannot use the symbol data here; this is
183    // important for matching the string table that 'as' generates.
184    IndirectSymbolData ISD;
185    ISD.Symbol = Symbol;
186    ISD.SectionData = getCurrentSectionData();
187    getAssembler().getIndirectSymbols().push_back(ISD);
188    return;
189  }
190
191  // Adding a symbol attribute always introduces the symbol, note that an
192  // important side effect of calling getOrCreateSymbolData here is to register
193  // the symbol with the assembler.
194  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
195
196  // The implementation of symbol attributes is designed to match 'as', but it
197  // leaves much to desired. It doesn't really make sense to arbitrarily add and
198  // remove flags, but 'as' allows this (in particular, see .desc).
199  //
200  // In the future it might be worth trying to make these operations more well
201  // defined.
202  switch (Attribute) {
203  case MCSA_Invalid:
204  case MCSA_ELF_TypeFunction:
205  case MCSA_ELF_TypeIndFunction:
206  case MCSA_ELF_TypeObject:
207  case MCSA_ELF_TypeTLS:
208  case MCSA_ELF_TypeCommon:
209  case MCSA_ELF_TypeNoType:
210  case MCSA_ELF_TypeGnuUniqueObject:
211  case MCSA_IndirectSymbol:
212  case MCSA_Hidden:
213  case MCSA_Internal:
214  case MCSA_Protected:
215  case MCSA_Weak:
216  case MCSA_Local:
217    assert(0 && "Invalid symbol attribute for Mach-O!");
218    break;
219
220  case MCSA_Global:
221    SD.setExternal(true);
222    // This effectively clears the undefined lazy bit, in Darwin 'as', although
223    // it isn't very consistent because it implements this as part of symbol
224    // lookup.
225    //
226    // FIXME: Cleanup this code, these bits should be emitted based on semantic
227    // properties, not on the order of definition, etc.
228    SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
229    break;
230
231  case MCSA_LazyReference:
232    // FIXME: This requires -dynamic.
233    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
234    if (Symbol->isUndefined())
235      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
236    break;
237
238    // Since .reference sets the no dead strip bit, it is equivalent to
239    // .no_dead_strip in practice.
240  case MCSA_Reference:
241  case MCSA_NoDeadStrip:
242    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
243    break;
244
245  case MCSA_SymbolResolver:
246    SD.setFlags(SD.getFlags() | SF_SymbolResolver);
247    break;
248
249  case MCSA_PrivateExtern:
250    SD.setExternal(true);
251    SD.setPrivateExtern(true);
252    break;
253
254  case MCSA_WeakReference:
255    // FIXME: This requires -dynamic.
256    if (Symbol->isUndefined())
257      SD.setFlags(SD.getFlags() | SF_WeakReference);
258    break;
259
260  case MCSA_WeakDefinition:
261    // FIXME: 'as' enforces that this is defined and global. The manual claims
262    // it has to be in a coalesced section, but this isn't enforced.
263    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
264    break;
265
266  case MCSA_WeakDefAutoPrivate:
267    SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
268    break;
269  }
270}
271
272void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
273  // Encode the 'desc' value into the lowest implementation defined bits.
274  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
275         "Invalid .desc value!");
276  getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
277    DescValue & SF_DescFlagsMask);
278}
279
280void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
281                                       unsigned ByteAlignment) {
282  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
283  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
284
285  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
286  SD.setExternal(true);
287  SD.setCommon(Size, ByteAlignment);
288}
289
290void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
291                                   unsigned Size, unsigned ByteAlignment) {
292  MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
293
294  // The symbol may not be present, which only creates the section.
295  if (!Symbol)
296    return;
297
298  // FIXME: Assert that this section has the zerofill type.
299
300  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
301
302  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
303
304  // Emit an align fragment if necessary.
305  if (ByteAlignment != 1)
306    new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
307
308  MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
309  SD.setFragment(F);
310
311  Symbol->setSection(*Section);
312
313  // Update the maximum alignment on the zero fill section if necessary.
314  if (ByteAlignment > SectData.getAlignment())
315    SectData.setAlignment(ByteAlignment);
316}
317
318// This should always be called with the thread local bss section.  Like the
319// .zerofill directive this doesn't actually switch sections on us.
320void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
321                                     uint64_t Size, unsigned ByteAlignment) {
322  EmitZerofill(Section, Symbol, Size, ByteAlignment);
323  return;
324}
325
326void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
327  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
328  // MCObjectStreamer.
329  getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
330}
331
332void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
333                                           int64_t Value, unsigned ValueSize,
334                                           unsigned MaxBytesToEmit) {
335  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
336  // MCObjectStreamer.
337  if (MaxBytesToEmit == 0)
338    MaxBytesToEmit = ByteAlignment;
339  new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
340                      getCurrentSectionData());
341
342  // Update the maximum alignment on the current section if necessary.
343  if (ByteAlignment > getCurrentSectionData()->getAlignment())
344    getCurrentSectionData()->setAlignment(ByteAlignment);
345}
346
347void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
348                                        unsigned MaxBytesToEmit) {
349  // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
350  // MCObjectStreamer.
351  if (MaxBytesToEmit == 0)
352    MaxBytesToEmit = ByteAlignment;
353  MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
354                                           getCurrentSectionData());
355  F->setEmitNops(true);
356
357  // Update the maximum alignment on the current section if necessary.
358  if (ByteAlignment > getCurrentSectionData()->getAlignment())
359    getCurrentSectionData()->setAlignment(ByteAlignment);
360}
361
362void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
363  MCDataFragment *DF = getOrCreateDataFragment();
364
365  SmallVector<MCFixup, 4> Fixups;
366  SmallString<256> Code;
367  raw_svector_ostream VecOS(Code);
368  getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
369  VecOS.flush();
370
371  // Add the fixups and data.
372  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
373    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
374    DF->addFixup(Fixups[i]);
375  }
376  DF->getContents().append(Code.begin(), Code.end());
377}
378
379void MCMachOStreamer::Finish() {
380  EmitFrames(true);
381
382  // We have to set the fragment atom associations so we can relax properly for
383  // Mach-O.
384
385  // First, scan the symbol table to build a lookup table from fragments to
386  // defining symbols.
387  DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
388  for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
389         ie = getAssembler().symbol_end(); it != ie; ++it) {
390    if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
391        it->getFragment()) {
392      // An atom defining symbol should never be internal to a fragment.
393      assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
394      DefiningSymbolMap[it->getFragment()] = it;
395    }
396  }
397
398  // Set the fragment atom associations by tracking the last seen atom defining
399  // symbol.
400  for (MCAssembler::iterator it = getAssembler().begin(),
401         ie = getAssembler().end(); it != ie; ++it) {
402    MCSymbolData *CurrentAtom = 0;
403    for (MCSectionData::iterator it2 = it->begin(),
404           ie2 = it->end(); it2 != ie2; ++it2) {
405      if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
406        CurrentAtom = SD;
407      it2->setAtom(CurrentAtom);
408    }
409  }
410
411  this->MCObjectStreamer::Finish();
412}
413
414MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
415                                      raw_ostream &OS, MCCodeEmitter *CE,
416                                      bool RelaxAll) {
417  MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
418  if (RelaxAll)
419    S->getAssembler().setRelaxAll(true);
420  return S;
421}
422