MCMachOStreamer.cpp revision 204642 
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 EmitCodeAlignment(unsigned ByteAlignment,
141                                 unsigned MaxBytesToEmit = 0);
142  virtual void EmitValueToOffset(const MCExpr *Offset,
143                                 unsigned char Value = 0);
144
145  virtual void EmitFileDirective(StringRef Filename) {
146    errs() << "FIXME: MCMachoStreamer:EmitFileDirective not implemented\n";
147  }
148  virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
149    errs() << "FIXME: MCMachoStreamer:EmitDwarfFileDirective not implemented\n";
150  }
151
152  virtual void EmitInstruction(const MCInst &Inst);
153  virtual void Finish();
154
155  /// @}
156};
157
158} // end anonymous namespace.
159
160void MCMachOStreamer::SwitchSection(const MCSection *Section) {
161  assert(Section && "Cannot switch to a null section!");
162
163  // If already in this section, then this is a noop.
164  if (Section == CurSection) return;
165
166  CurSection = Section;
167  CurSectionData = &getSectionData(*Section);
168}
169
170void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
171  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
172
173  // FIXME: We should also use offsets into Fill fragments.
174  MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
175  if (!F)
176    F = new MCDataFragment(CurSectionData);
177
178  MCSymbolData &SD = getSymbolData(*Symbol);
179  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
180  SD.setFragment(F);
181  SD.setOffset(F->getContents().size());
182
183  // This causes the reference type and weak reference flags to be cleared.
184  SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
185
186  Symbol->setSection(*CurSection);
187}
188
189void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
190  switch (Flag) {
191  case MCAF_SubsectionsViaSymbols:
192    Assembler.setSubsectionsViaSymbols(true);
193    return;
194  }
195
196  assert(0 && "invalid assembler flag!");
197}
198
199void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
200  // Only absolute symbols can be redefined.
201  assert((Symbol->isUndefined() || Symbol->isAbsolute()) &&
202         "Cannot define a symbol twice!");
203
204  // FIXME: Lift context changes into super class.
205  // FIXME: Set associated section.
206  Symbol->setValue(Value);
207}
208
209void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
210                                          MCSymbolAttr Attribute) {
211  // Indirect symbols are handled differently, to match how 'as' handles
212  // them. This makes writing matching .o files easier.
213  if (Attribute == MCSA_IndirectSymbol) {
214    // Note that we intentionally cannot use the symbol data here; this is
215    // important for matching the string table that 'as' generates.
216    IndirectSymbolData ISD;
217    ISD.Symbol = Symbol;
218    ISD.SectionData = CurSectionData;
219    Assembler.getIndirectSymbols().push_back(ISD);
220    return;
221  }
222
223  // Adding a symbol attribute always introduces the symbol, note that an
224  // important side effect of calling getSymbolData here is to register the
225  // symbol with the assembler.
226  MCSymbolData &SD = getSymbolData(*Symbol);
227
228  // The implementation of symbol attributes is designed to match 'as', but it
229  // leaves much to desired. It doesn't really make sense to arbitrarily add and
230  // remove flags, but 'as' allows this (in particular, see .desc).
231  //
232  // In the future it might be worth trying to make these operations more well
233  // defined.
234  switch (Attribute) {
235  case MCSA_Invalid:
236  case MCSA_ELF_TypeFunction:
237  case MCSA_ELF_TypeIndFunction:
238  case MCSA_ELF_TypeObject:
239  case MCSA_ELF_TypeTLS:
240  case MCSA_ELF_TypeCommon:
241  case MCSA_ELF_TypeNoType:
242  case MCSA_IndirectSymbol:
243  case MCSA_Hidden:
244  case MCSA_Internal:
245  case MCSA_Protected:
246  case MCSA_Weak:
247  case MCSA_Local:
248    assert(0 && "Invalid symbol attribute for Mach-O!");
249    break;
250
251  case MCSA_Global:
252    SD.setExternal(true);
253    break;
254
255  case MCSA_LazyReference:
256    // FIXME: This requires -dynamic.
257    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
258    if (Symbol->isUndefined())
259      SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
260    break;
261
262    // Since .reference sets the no dead strip bit, it is equivalent to
263    // .no_dead_strip in practice.
264  case MCSA_Reference:
265  case MCSA_NoDeadStrip:
266    SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
267    break;
268
269  case MCSA_PrivateExtern:
270    SD.setExternal(true);
271    SD.setPrivateExtern(true);
272    break;
273
274  case MCSA_WeakReference:
275    // FIXME: This requires -dynamic.
276    if (Symbol->isUndefined())
277      SD.setFlags(SD.getFlags() | SF_WeakReference);
278    break;
279
280  case MCSA_WeakDefinition:
281    // FIXME: 'as' enforces that this is defined and global. The manual claims
282    // it has to be in a coalesced section, but this isn't enforced.
283    SD.setFlags(SD.getFlags() | SF_WeakDefinition);
284    break;
285  }
286}
287
288void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
289  // Encode the 'desc' value into the lowest implementation defined bits.
290  assert(DescValue == (DescValue & SF_DescFlagsMask) &&
291         "Invalid .desc value!");
292  getSymbolData(*Symbol).setFlags(DescValue & SF_DescFlagsMask);
293}
294
295void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
296                                       unsigned ByteAlignment) {
297  // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
298  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
299
300  MCSymbolData &SD = getSymbolData(*Symbol);
301  SD.setExternal(true);
302  SD.setCommon(Size, ByteAlignment);
303}
304
305void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
306                                   unsigned Size, unsigned ByteAlignment) {
307  MCSectionData &SectData = getSectionData(*Section);
308
309  // The symbol may not be present, which only creates the section.
310  if (!Symbol)
311    return;
312
313  // FIXME: Assert that this section has the zerofill type.
314
315  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
316
317  MCSymbolData &SD = getSymbolData(*Symbol);
318
319  MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
320  SD.setFragment(F);
321
322  Symbol->setSection(*Section);
323
324  // Update the maximum alignment on the zero fill section if necessary.
325  if (ByteAlignment > SectData.getAlignment())
326    SectData.setAlignment(ByteAlignment);
327}
328
329void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
330  MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
331  if (!DF)
332    DF = new MCDataFragment(CurSectionData);
333  DF->getContents().append(Data.begin(), Data.end());
334}
335
336void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
337                                unsigned AddrSpace) {
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 (AddValueSymbols(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                      false /* EmitNops */, 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::EmitCodeAlignment(unsigned ByteAlignment,
370                                        unsigned MaxBytesToEmit) {
371  if (MaxBytesToEmit == 0)
372    MaxBytesToEmit = ByteAlignment;
373  // FIXME the 0x90 is the default x86 1 byte nop opcode.
374  new MCAlignFragment(ByteAlignment, 0x90, 1, MaxBytesToEmit,
375                      true /* EmitNops */, CurSectionData);
376
377  // Update the maximum alignment on the current section if necessary.
378  if (ByteAlignment > CurSectionData->getAlignment())
379    CurSectionData->setAlignment(ByteAlignment);
380}
381
382void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
383                                        unsigned char Value) {
384  new MCOrgFragment(*Offset, Value, CurSectionData);
385}
386
387void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
388  // Scan for values.
389  for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
390    if (Inst.getOperand(i).isExpr())
391      AddValueSymbols(Inst.getOperand(i).getExpr());
392
393  if (!Emitter)
394    llvm_unreachable("no code emitter available!");
395
396  CurSectionData->setHasInstructions(true);
397
398  SmallVector<MCFixup, 4> Fixups;
399  SmallString<256> Code;
400  raw_svector_ostream VecOS(Code);
401  Emitter->EncodeInstruction(Inst, VecOS, Fixups);
402  VecOS.flush();
403
404  // Add the fixups and data.
405  MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
406  if (!DF)
407    DF = new MCDataFragment(CurSectionData);
408  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
409    MCFixup &F = Fixups[i];
410    DF->getFixups().push_back(MCAsmFixup(DF->getContents().size()+F.getOffset(),
411                                         *F.getValue(),
412                                         F.getKind()));
413  }
414  DF->getContents().append(Code.begin(), Code.end());
415}
416
417void MCMachOStreamer::Finish() {
418  Assembler.Finish();
419}
420
421MCStreamer *llvm::createMachOStreamer(MCContext &Context, raw_ostream &OS,
422                                      MCCodeEmitter *CE) {
423  return new MCMachOStreamer(Context, OS, CE);
424}
425