MCMachOStreamer.cpp revision 203954 
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/MCSection.h"
18#include "llvm/MC/MCSymbol.h"
19#include "llvm/MC/MCValue.h"
20#include "llvm/Support/ErrorHandling.h"
21#include "llvm/Support/raw_ostream.h"
22using namespace llvm;
23
24namespace {
25
26class MCMachOStreamer : public MCStreamer {
27  /// SymbolFlags - We store the value for the 'desc' symbol field in the lowest
28  /// 16 bits of the implementation defined flags.
29  enum SymbolFlags { // See <mach-o/nlist.h>.
30    SF_DescFlagsMask                        = 0xFFFF,
31
32    // Reference type flags.
33    SF_ReferenceTypeMask                    = 0x0007,
34    SF_ReferenceTypeUndefinedNonLazy        = 0x0000,
35    SF_ReferenceTypeUndefinedLazy           = 0x0001,
36    SF_ReferenceTypeDefined                 = 0x0002,
37    SF_ReferenceTypePrivateDefined          = 0x0003,
38    SF_ReferenceTypePrivateUndefinedNonLazy = 0x0004,
39    SF_ReferenceTypePrivateUndefinedLazy    = 0x0005,
40
41    // Other 'desc' flags.
42    SF_NoDeadStrip                          = 0x0020,
43    SF_WeakReference                        = 0x0040,
44    SF_WeakDefinition                       = 0x0080
45  };
46
47private:
48  MCAssembler Assembler;
49  MCCodeEmitter *Emitter;
50  MCSectionData *CurSectionData;
51  DenseMap<const MCSection*, MCSectionData*> SectionMap;
52  DenseMap<const MCSymbol*, MCSymbolData*> SymbolMap;
53
54private:
55  MCFragment *getCurrentFragment() const {
56    assert(CurSectionData && "No current section!");
57
58    if (!CurSectionData->empty())
59      return &CurSectionData->getFragmentList().back();
60
61    return 0;
62  }
63
64  MCSectionData &getSectionData(const MCSection &Section) {
65    MCSectionData *&Entry = SectionMap[&Section];
66
67    if (!Entry)
68      Entry = new MCSectionData(Section, &Assembler);
69
70    return *Entry;
71  }
72
73  MCSymbolData &getSymbolData(const MCSymbol &Symbol) {
74    MCSymbolData *&Entry = SymbolMap[&Symbol];
75
76    if (!Entry)
77      Entry = new MCSymbolData(Symbol, 0, 0, &Assembler);
78
79    return *Entry;
80  }
81
82public:
83  MCMachOStreamer(MCContext &Context, raw_ostream &_OS, MCCodeEmitter *_Emitter)
84    : MCStreamer(Context), Assembler(Context, _OS), Emitter(_Emitter),
85      CurSectionData(0) {}
86  ~MCMachOStreamer() {}
87
88  const MCExpr *AddValueSymbols(const MCExpr *Value) {
89    switch (Value->getKind()) {
90    case MCExpr::Target: assert(0 && "Can't handle target exprs yet!");
91    case MCExpr::Constant:
92      break;
93
94    case MCExpr::Binary: {
95      const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
96      AddValueSymbols(BE->getLHS());
97      AddValueSymbols(BE->getRHS());
98      break;
99    }
100
101    case MCExpr::SymbolRef:
102      getSymbolData(cast<MCSymbolRefExpr>(Value)->getSymbol());
103      break;
104
105    case MCExpr::Unary:
106      AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
107      break;
108    }
109
110    return Value;
111  }
112
113  /// @name MCStreamer Interface
114  /// @{
115
116  virtual void SwitchSection(const MCSection *Section);
117  virtual void EmitLabel(MCSymbol *Symbol);
118  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
119  virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
120  virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
121  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
122  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
123                                unsigned ByteAlignment);
124  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
125    assert(0 && "macho doesn't support this directive");
126  }
127  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
128    assert(0 && "macho doesn't support this directive");
129  }
130  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
131                            unsigned Size = 0, unsigned ByteAlignment = 0);
132  virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
133  virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
134  virtual void EmitGPRel32Value(const MCExpr *Value) {
135    assert(0 && "macho doesn't support this directive");
136  }
137  virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
138                                    unsigned ValueSize = 1,
139                                    unsigned MaxBytesToEmit = 0);
140  virtual void EmitValueToOffset(const MCExpr *Offset,
141                                 unsigned char Value = 0);
142
143  virtual void EmitFileDirective(StringRef Filename) {
144    errs() << "FIXME: MCMachoStreamer:EmitFileDirective not implemented\n";
145  }
146  virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
147    errs() << "FIXME: MCMachoStreamer:EmitDwarfFileDirective not implemented\n";
148  }
149
150  virtual void EmitInstruction(const MCInst &Inst);
151  virtual void Finish();
152
153  /// @}
154};
155
156} // end anonymous namespace.
157
158void MCMachOStreamer::SwitchSection(const MCSection *Section) {
159  assert(Section && "Cannot switch to a null section!");
160
161  // If already in this section, then this is a noop.
162  if (Section == CurSection) return;
163
164  CurSection = Section;
165  CurSectionData = &getSectionData(*Section);
166}
167
168void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
169  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
170
171  // FIXME: We should also use offsets into Fill fragments.
172  MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
173  if (!F)
174    F = new MCDataFragment(CurSectionData);
175
176  MCSymbolData &SD = getSymbolData(*Symbol);
177  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
178  SD.setFragment(F);
179  SD.setOffset(F->getContents().size());
180
181  // This causes the reference type and weak reference flags to be cleared.
182  SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
183
184  Symbol->setSection(*CurSection);
185}
186
187void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
188  switch (Flag) {
189  case MCAF_SubsectionsViaSymbols:
190    Assembler.setSubsectionsViaSymbols(true);
191    return;
192  }
193
194  assert(0 && "invalid assembler flag!");
195}
196
197void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
198  // Only absolute symbols can be redefined.
199  assert((Symbol->isUndefined() || Symbol->isAbsolute()) &&
200         "Cannot define a symbol twice!");
201
202  // FIXME: Lift context changes into super class.
203  // FIXME: Set associated section.
204  Symbol->setValue(Value);
205}
206
207void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
208                                          MCSymbolAttr Attribute) {
209  // Indirect symbols are handled differently, to match how 'as' handles
210  // them. This makes writing matching .o files easier.
211  if (Attribute == MCSA_IndirectSymbol) {
212    // Note that we intentionally cannot use the symbol data here; this is
213    // important for matching the string table that 'as' generates.
214    IndirectSymbolData ISD;
215    ISD.Symbol = Symbol;
216    ISD.SectionData = CurSectionData;
217    Assembler.getIndirectSymbols().push_back(ISD);
218    return;
219  }
220
221  // Adding a symbol attribute always introduces the symbol, note that an
222  // important side effect of calling getSymbolData here is to register the
223  // symbol with the assembler.
224  MCSymbolData &SD = getSymbolData(*Symbol);
225
226  // The implementation of symbol attributes is designed to match 'as', but it
227  // leaves much to desired. It doesn't really make sense to arbitrarily add and
228  // remove flags, but 'as' allows this (in particular, see .desc).
229  //
230  // In the future it might be worth trying to make these operations more well
231  // defined.
232  switch (Attribute) {
233  case MCSA_Invalid:
234  case MCSA_ELF_TypeFunction:
235  case MCSA_ELF_TypeIndFunction:
236  case MCSA_ELF_TypeObject:
237  case MCSA_ELF_TypeTLS:
238  case MCSA_ELF_TypeCommon:
239  case MCSA_ELF_TypeNoType:
240  case MCSA_IndirectSymbol:
241  case MCSA_Hidden:
242  case MCSA_Internal:
243  case MCSA_Protected:
244  case MCSA_Weak:
245  case MCSA_Local:
246    assert(0 && "Invalid symbol attribute for Mach-O!");
247    break;
248
249  case MCSA_Global:
250    SD.setExternal(true);
251    break;
252
253  case MCSA_LazyReference:
254    // FIXME: This requires -dynamic.
255    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
256    if (Symbol->isUndefined())
257      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
258    break;
259
260    // Since .reference sets the no dead strip bit, it is equivalent to
261    // .no_dead_strip in practice.
262  case MCSA_Reference:
263  case MCSA_NoDeadStrip:
264    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
265    break;
266
267  case MCSA_PrivateExtern:
268    SD.setExternal(true);
269    SD.setPrivateExtern(true);
270    break;
271
272  case MCSA_WeakReference:
273    // FIXME: This requires -dynamic.
274    if (Symbol->isUndefined())
275      SD.setFlags(SD.getFlags() | SF_WeakReference);
276    break;
277
278  case MCSA_WeakDefinition:
279    // FIXME: 'as' enforces that this is defined and global. The manual claims
280    // it has to be in a coalesced section, but this isn't enforced.
281    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
282    break;
283  }
284}
285
286void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
287  // Encode the 'desc' value into the lowest implementation defined bits.
288  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
289         "Invalid .desc value!");
290  getSymbolData(*Symbol).setFlags(DescValue & SF_DescFlagsMask);
291}
292
293void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
294                                       unsigned ByteAlignment) {
295  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
296  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
297
298  MCSymbolData &SD = getSymbolData(*Symbol);
299  SD.setExternal(true);
300  SD.setCommon(Size, ByteAlignment);
301}
302
303void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
304                                   unsigned Size, unsigned ByteAlignment) {
305  MCSectionData &SectData = getSectionData(*Section);
306
307  // The symbol may not be present, which only creates the section.
308  if (!Symbol)
309    return;
310
311  // FIXME: Assert that this section has the zerofill type.
312
313  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
314
315  MCSymbolData &SD = getSymbolData(*Symbol);
316
317  MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
318  SD.setFragment(F);
319
320  Symbol->setSection(*Section);
321
322  // Update the maximum alignment on the zero fill section if necessary.
323  if (ByteAlignment > SectData.getAlignment())
324    SectData.setAlignment(ByteAlignment);
325}
326
327void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
328  MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
329  if (!DF)
330    DF = new MCDataFragment(CurSectionData);
331  DF->getContents().append(Data.begin(), Data.end());
332}
333
334void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
335                                unsigned AddrSpace) {
336  // Assume the front-end will have evaluate things absolute expressions, so
337  // just create data + fixup.
338  MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
339  if (!DF)
340    DF = new MCDataFragment(CurSectionData);
341
342  // Avoid fixups when possible.
343  int64_t AbsValue;
344  if (Value->EvaluateAsAbsolute(AbsValue)) {
345    // FIXME: Endianness assumption.
346    for (unsigned i = 0; i != Size; ++i)
347      DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
348  } else {
349    DF->getFixups().push_back(MCAsmFixup(DF->getContents().size(),
350                                         *AddValueSymbols(Value),
351                                         MCFixup::getKindForSize(Size)));
352    DF->getContents().resize(DF->getContents().size() + Size, 0);
353  }
354}
355
356void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
357                                           int64_t Value, unsigned ValueSize,
358                                           unsigned MaxBytesToEmit) {
359  if (MaxBytesToEmit == 0)
360    MaxBytesToEmit = ByteAlignment;
361  new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
362                      CurSectionData);
363
364  // Update the maximum alignment on the current section if necessary.
365  if (ByteAlignment > CurSectionData->getAlignment())
366    CurSectionData->setAlignment(ByteAlignment);
367}
368
369void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
370                                        unsigned char Value) {
371  new MCOrgFragment(*Offset, Value, CurSectionData);
372}
373
374void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
375  // Scan for values.
376  for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
377    if (Inst.getOperand(i).isExpr())
378      AddValueSymbols(Inst.getOperand(i).getExpr());
379
380  if (!Emitter)
381    llvm_unreachable("no code emitter available!");
382
383  CurSectionData->setHasInstructions(true);
384
385  SmallVector<MCFixup, 4> Fixups;
386  SmallString<256> Code;
387  raw_svector_ostream VecOS(Code);
388  Emitter->EncodeInstruction(Inst, VecOS, Fixups);
389  VecOS.flush();
390
391  // Add the fixups and data.
392  MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
393  if (!DF)
394    DF = new MCDataFragment(CurSectionData);
395  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
396    MCFixup &F = Fixups[i];
397    DF->getFixups().push_back(MCAsmFixup(DF->getContents().size()+F.getOffset(),
398                                         *F.getValue(),
399                                         F.getKind()));
400  }
401  DF->getContents().append(Code.begin(), Code.end());
402}
403
404void MCMachOStreamer::Finish() {
405  Assembler.Finish();
406}
407
408MCStreamer *llvm::createMachOStreamer(MCContext &Context, raw_ostream &OS,
409                                      MCCodeEmitter *CE) {
410  return new MCMachOStreamer(Context, OS, CE);
411}
412