lib/MC/MCMachOStreamer.cpp

   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
  29 using namespace llvm;
  30
  31 namespace {
  32
  33 class MCMachOStreamer : public MCObjectStreamer {
  34 private:
  35   virtual void EmitInstToData(const MCInst &Inst);
  36
  37 public:
  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
  99 void MCMachOStreamer::InitSections() {
 100   SwitchSection(getContext().getMachOSection("__TEXT", "__text",
 101                                     MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
 102                                     0, SectionKind::getText()));
 103
 104 }
 105
 106 void 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 }
 115
 116 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
 117   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 118
 119   // isSymbolLinkerVisible uses the section.
 120   Symbol->setSection(*getCurrentSection());
 121   // We have to create a new fragment if this is an atom defining symbol,
 122   // fragments cannot span atoms.
 123   if (getAssembler().isSymbolLinkerVisible(*Symbol))
 124     new MCDataFragment(getCurrentSectionData());
 125
 126   MCObjectStreamer::EmitLabel(Symbol);
 127
 128   MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
 129   // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
 130   // to clear the weak reference and weak definition bits too, but the
 131   // implementation was buggy. For now we just try to match 'as', for
 132   // diffability.
 133   //
 134   // FIXME: Cleanup this code, these bits should be emitted based on semantic
 135   // properties, not on the order of definition, etc.
 136   SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
 137 }
 138
 139 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
 140   // Let the target do whatever target specific stuff it needs to do.
 141   getAssembler().getBackend().HandleAssemblerFlag(Flag);
 142   // Do any generic stuff we need to do.
 143   switch (Flag) {
 144   case MCAF_SyntaxUnified: return; // no-op here.
 145   case MCAF_Code16: return; // no-op here.
 146   case MCAF_Code32: return; // no-op here.
 147   case MCAF_SubsectionsViaSymbols:
 148     getAssembler().setSubsectionsViaSymbols(true);
 149     return;
 150   default:
 151     llvm_unreachable("invalid assembler flag!");
 152   }
 153 }
 154
 155 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
 156   // FIXME: Flag the function ISA as thumb with DW_AT_APPLE_isa.
 157
 158   // Remember that the function is a thumb function. Fixup and relocation
 159   // values will need adjusted.
 160   getAssembler().setIsThumbFunc(Symbol);
 161
 162   // Mark the thumb bit on the symbol.
 163   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 164   SD.setFlags(SD.getFlags() | SF_ThumbFunc);
 165 }
 166
 167 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
 168   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 169   // MCObjectStreamer.
 170   // FIXME: Lift context changes into super class.
 171   getAssembler().getOrCreateSymbolData(*Symbol);
 172   Symbol->setVariableValue(AddValueSymbols(Value));
 173 }
 174
 175 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
 176                                           MCSymbolAttr Attribute) {
 177   // Indirect symbols are handled differently, to match how 'as' handles
 178   // them. This makes writing matching .o files easier.
 179   if (Attribute == MCSA_IndirectSymbol) {
 180     // Note that we intentionally cannot use the symbol data here; this is
 181     // important for matching the string table that 'as' generates.
 182     IndirectSymbolData ISD;
 183     ISD.Symbol = Symbol;
 184     ISD.SectionData = getCurrentSectionData();
 185     getAssembler().getIndirectSymbols().push_back(ISD);
 186     return;
 187   }
 188
 189   // Adding a symbol attribute always introduces the symbol, note that an
 190   // important side effect of calling getOrCreateSymbolData here is to register
 191   // the symbol with the assembler.
 192   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 193
 194   // The implementation of symbol attributes is designed to match 'as', but it
 195   // leaves much to desired. It doesn't really make sense to arbitrarily add and
 196   // remove flags, but 'as' allows this (in particular, see .desc).
 197   //
 198   // In the future it might be worth trying to make these operations more well
 199   // defined.
 200   switch (Attribute) {
 201   case MCSA_Invalid:
 202   case MCSA_ELF_TypeFunction:
 203   case MCSA_ELF_TypeIndFunction:
 204   case MCSA_ELF_TypeObject:
 205   case MCSA_ELF_TypeTLS:
 206   case MCSA_ELF_TypeCommon:
 207   case MCSA_ELF_TypeNoType:
 208   case MCSA_ELF_TypeGnuUniqueObject:
 209   case MCSA_IndirectSymbol:
 210   case MCSA_Hidden:
 211   case MCSA_Internal:
 212   case MCSA_Protected:
 213   case MCSA_Weak:
 214   case MCSA_Local:
 215     assert(0 && "Invalid symbol attribute for Mach-O!");
 216     break;
 217
 218   case MCSA_Global:
 219     SD.setExternal(true);
 220     // This effectively clears the undefined lazy bit, in Darwin 'as', although
 221     // it isn't very consistent because it implements this as part of symbol
 222     // lookup.
 223     //
 224     // FIXME: Cleanup this code, these bits should be emitted based on semantic
 225     // properties, not on the order of definition, etc.
 226     SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
 227     break;
 228
 229   case MCSA_LazyReference:
 230     // FIXME: This requires -dynamic.
 231     SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
 232     if (Symbol->isUndefined())
 233       SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
 234     break;
 235
 236     // Since .reference sets the no dead strip bit, it is equivalent to
 237     // .no_dead_strip in practice.
 238   case MCSA_Reference:
 239   case MCSA_NoDeadStrip:
 240     SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
 241     break;
 242
 243   case MCSA_SymbolResolver:
 244     SD.setFlags(SD.getFlags() | SF_SymbolResolver);
 245     break;
 246
 247   case MCSA_PrivateExtern:
 248     SD.setExternal(true);
 249     SD.setPrivateExtern(true);
 250     break;
 251
 252   case MCSA_WeakReference:
 253     // FIXME: This requires -dynamic.
 254     if (Symbol->isUndefined())
 255       SD.setFlags(SD.getFlags() | SF_WeakReference);
 256     break;
 257
 258   case MCSA_WeakDefinition:
 259     // FIXME: 'as' enforces that this is defined and global. The manual claims
 260     // it has to be in a coalesced section, but this isn't enforced.
 261     SD.setFlags(SD.getFlags() | SF_WeakDefinition);
 262     break;
 263
 264   case MCSA_WeakDefAutoPrivate:
 265     SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
 266     break;
 267   }
 268 }
 269
 270 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 271   // Encode the 'desc' value into the lowest implementation defined bits.
 272   assert(DescValue == (DescValue & SF_DescFlagsMask) &&
 273          "Invalid .desc value!");
 274   getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
 275     DescValue & SF_DescFlagsMask);
 276 }
 277
 278 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
 279                                        unsigned ByteAlignment) {
 280   // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
 281   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 282
 283   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 284   SD.setExternal(true);
 285   SD.setCommon(Size, ByteAlignment);
 286 }
 287
 288 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
 289                                    unsigned Size, unsigned ByteAlignment) {
 290   MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
 291
 292   // The symbol may not be present, which only creates the section.
 293   if (!Symbol)
 294     return;
 295
 296   // FIXME: Assert that this section has the zerofill type.
 297
 298   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 299
 300   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 301
 302   // Emit an align fragment if necessary.
 303   if (ByteAlignment != 1)
 304     new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
 305
 306   MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
 307   SD.setFragment(F);
 308
 309   Symbol->setSection(*Section);
 310
 311   // Update the maximum alignment on the zero fill section if necessary.
 312   if (ByteAlignment > SectData.getAlignment())
 313     SectData.setAlignment(ByteAlignment);
 314 }
 315
 316 // This should always be called with the thread local bss section.  Like the
 317 // .zerofill directive this doesn't actually switch sections on us.
 318 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
 319                                      uint64_t Size, unsigned ByteAlignment) {
 320   EmitZerofill(Section, Symbol, Size, ByteAlignment);
 321   return;
 322 }
 323
 324 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
 325   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 326   // MCObjectStreamer.
 327   getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
 328 }
 329
 330 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
 331                                            int64_t Value, unsigned ValueSize,
 332                                            unsigned MaxBytesToEmit) {
 333   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 334   // MCObjectStreamer.
 335   if (MaxBytesToEmit == 0)
 336     MaxBytesToEmit = ByteAlignment;
 337   new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
 338                       getCurrentSectionData());
 339
 340   // Update the maximum alignment on the current section if necessary.
 341   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 342     getCurrentSectionData()->setAlignment(ByteAlignment);
 343 }
 344
 345 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
 346                                         unsigned MaxBytesToEmit) {
 347   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 348   // MCObjectStreamer.
 349   if (MaxBytesToEmit == 0)
 350     MaxBytesToEmit = ByteAlignment;
 351   MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
 352                                            getCurrentSectionData());
 353   F->setEmitNops(true);
 354
 355   // Update the maximum alignment on the current section if necessary.
 356   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 357     getCurrentSectionData()->setAlignment(ByteAlignment);
 358 }
 359
 360 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
 361   MCDataFragment *DF = getOrCreateDataFragment();
 362
 363   SmallVector<MCFixup, 4> Fixups;
 364   SmallString<256> Code;
 365   raw_svector_ostream VecOS(Code);
 366   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
 367   VecOS.flush();
 368
 369   // Add the fixups and data.
 370   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
 371     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
 372     DF->addFixup(Fixups[i]);
 373   }
 374   DF->getContents().append(Code.begin(), Code.end());
 375 }
 376
 377 void MCMachOStreamer::Finish() {
 378   // We have to set the fragment atom associations so we can relax properly for
 379   // Mach-O.
 380
 381   // First, scan the symbol table to build a lookup table from fragments to
 382   // defining symbols.
 383   DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
 384   for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
 385          ie = getAssembler().symbol_end(); it != ie; ++it) {
 386     if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
 387         it->getFragment()) {
 388       // An atom defining symbol should never be internal to a fragment.
 389       assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
 390       DefiningSymbolMap[it->getFragment()] = it;
 391     }
 392   }
 393
 394   // Set the fragment atom associations by tracking the last seen atom defining
 395   // symbol.
 396   for (MCAssembler::iterator it = getAssembler().begin(),
 397          ie = getAssembler().end(); it != ie; ++it) {
 398     MCSymbolData *CurrentAtom = 0;
 399     for (MCSectionData::iterator it2 = it->begin(),
 400            ie2 = it->end(); it2 != ie2; ++it2) {
 401       if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
 402         CurrentAtom = SD;
 403       it2->setAtom(CurrentAtom);
 404     }
 405   }
 406
 407   this->MCObjectStreamer::Finish();
 408 }
 409
 410 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
 411                                       raw_ostream &OS, MCCodeEmitter *CE,
 412                                       bool RelaxAll) {
 413   MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
 414   if (RelaxAll)
 415     S->getAssembler().setRelaxAll(true);
 416   return S;
 417 }