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 EmitAssemblerFlag(MCAssemblerFlag Flag);
  48   virtual void EmitThumbFunc(MCSymbol *Func);
  49   virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
  50   virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
  51   virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
  52   virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
  53                                 unsigned ByteAlignment);
  54   virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
  55     assert(0 && "macho doesn't support this directive");
  56   }
  57   virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
  58     assert(0 && "macho doesn't support this directive");
  59   }
  60   virtual void EmitCOFFSymbolType(int Type) {
  61     assert(0 && "macho doesn't support this directive");
  62   }
  63   virtual void EndCOFFSymbolDef() {
  64     assert(0 && "macho doesn't support this directive");
  65   }
  66   virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
  67     assert(0 && "macho doesn't support this directive");
  68   }
  69   virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
  70     assert(0 && "macho doesn't support this directive");
  71   }
  72   virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
  73                             unsigned Size = 0, unsigned ByteAlignment = 0);
  74   virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
  75                               uint64_t Size, unsigned ByteAlignment = 0);
  76   virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
  77   virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
  78                                     unsigned ValueSize = 1,
  79                                     unsigned MaxBytesToEmit = 0);
  80   virtual void EmitCodeAlignment(unsigned ByteAlignment,
  81                                  unsigned MaxBytesToEmit = 0);
  82
  83   virtual void EmitFileDirective(StringRef Filename) {
  84     // FIXME: Just ignore the .file; it isn't important enough to fail the
  85     // entire assembly.
  86
  87     //report_fatal_error("unsupported directive: '.file'");
  88   }
  89
  90   virtual void Finish();
  91
  92   /// @}
  93 };
  94
  95 } // end anonymous namespace.
  96
  97 void MCMachOStreamer::InitSections() {
  98   SwitchSection(getContext().getMachOSection("__TEXT", "__text",
  99                                     MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
 100                                     0, SectionKind::getText()));
 101
 102 }
 103
 104 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
 105   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 106
 107   // isSymbolLinkerVisible uses the section.
 108   Symbol->setSection(*getCurrentSection());
 109   // We have to create a new fragment if this is an atom defining symbol,
 110   // fragments cannot span atoms.
 111   if (getAssembler().isSymbolLinkerVisible(*Symbol))
 112     new MCDataFragment(getCurrentSectionData());
 113
 114   MCObjectStreamer::EmitLabel(Symbol);
 115
 116   MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
 117   // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
 118   // to clear the weak reference and weak definition bits too, but the
 119   // implementation was buggy. For now we just try to match 'as', for
 120   // diffability.
 121   //
 122   // FIXME: Cleanup this code, these bits should be emitted based on semantic
 123   // properties, not on the order of definition, etc.
 124   SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
 125 }
 126
 127 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
 128   // Let the target do whatever target specific stuff it needs to do.
 129   getAssembler().getBackend().HandleAssemblerFlag(Flag);
 130   // Do any generic stuff we need to do.
 131   switch (Flag) {
 132   case MCAF_SyntaxUnified: return; // no-op here.
 133   case MCAF_Code16: return; // no-op here.
 134   case MCAF_Code32: return; // no-op here.
 135   case MCAF_SubsectionsViaSymbols:
 136     getAssembler().setSubsectionsViaSymbols(true);
 137     return;
 138   default:
 139     llvm_unreachable("invalid assembler flag!");
 140   }
 141 }
 142
 143 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
 144   // FIXME: Flag the function ISA as thumb with DW_AT_APPLE_isa.
 145
 146   // Remember that the function is a thumb function. Fixup and relocation
 147   // values will need adjusted.
 148   getAssembler().setIsThumbFunc(Symbol);
 149
 150   // Mark the thumb bit on the symbol.
 151   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 152   SD.setFlags(SD.getFlags() | SF_ThumbFunc);
 153 }
 154
 155 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
 156   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 157   // MCObjectStreamer.
 158   // FIXME: Lift context changes into super class.
 159   getAssembler().getOrCreateSymbolData(*Symbol);
 160   Symbol->setVariableValue(AddValueSymbols(Value));
 161 }
 162
 163 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
 164                                           MCSymbolAttr Attribute) {
 165   // Indirect symbols are handled differently, to match how 'as' handles
 166   // them. This makes writing matching .o files easier.
 167   if (Attribute == MCSA_IndirectSymbol) {
 168     // Note that we intentionally cannot use the symbol data here; this is
 169     // important for matching the string table that 'as' generates.
 170     IndirectSymbolData ISD;
 171     ISD.Symbol = Symbol;
 172     ISD.SectionData = getCurrentSectionData();
 173     getAssembler().getIndirectSymbols().push_back(ISD);
 174     return;
 175   }
 176
 177   // Adding a symbol attribute always introduces the symbol, note that an
 178   // important side effect of calling getOrCreateSymbolData here is to register
 179   // the symbol with the assembler.
 180   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 181
 182   // The implementation of symbol attributes is designed to match 'as', but it
 183   // leaves much to desired. It doesn't really make sense to arbitrarily add and
 184   // remove flags, but 'as' allows this (in particular, see .desc).
 185   //
 186   // In the future it might be worth trying to make these operations more well
 187   // defined.
 188   switch (Attribute) {
 189   case MCSA_Invalid:
 190   case MCSA_ELF_TypeFunction:
 191   case MCSA_ELF_TypeIndFunction:
 192   case MCSA_ELF_TypeObject:
 193   case MCSA_ELF_TypeTLS:
 194   case MCSA_ELF_TypeCommon:
 195   case MCSA_ELF_TypeNoType:
 196   case MCSA_ELF_TypeGnuUniqueObject:
 197   case MCSA_IndirectSymbol:
 198   case MCSA_Hidden:
 199   case MCSA_Internal:
 200   case MCSA_Protected:
 201   case MCSA_Weak:
 202   case MCSA_Local:
 203     assert(0 && "Invalid symbol attribute for Mach-O!");
 204     break;
 205
 206   case MCSA_Global:
 207     SD.setExternal(true);
 208     // This effectively clears the undefined lazy bit, in Darwin 'as', although
 209     // it isn't very consistent because it implements this as part of symbol
 210     // lookup.
 211     //
 212     // FIXME: Cleanup this code, these bits should be emitted based on semantic
 213     // properties, not on the order of definition, etc.
 214     SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
 215     break;
 216
 217   case MCSA_LazyReference:
 218     // FIXME: This requires -dynamic.
 219     SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
 220     if (Symbol->isUndefined())
 221       SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
 222     break;
 223
 224     // Since .reference sets the no dead strip bit, it is equivalent to
 225     // .no_dead_strip in practice.
 226   case MCSA_Reference:
 227   case MCSA_NoDeadStrip:
 228     SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
 229     break;
 230
 231   case MCSA_SymbolResolver:
 232     SD.setFlags(SD.getFlags() | SF_SymbolResolver);
 233     break;
 234
 235   case MCSA_PrivateExtern:
 236     SD.setExternal(true);
 237     SD.setPrivateExtern(true);
 238     break;
 239
 240   case MCSA_WeakReference:
 241     // FIXME: This requires -dynamic.
 242     if (Symbol->isUndefined())
 243       SD.setFlags(SD.getFlags() | SF_WeakReference);
 244     break;
 245
 246   case MCSA_WeakDefinition:
 247     // FIXME: 'as' enforces that this is defined and global. The manual claims
 248     // it has to be in a coalesced section, but this isn't enforced.
 249     SD.setFlags(SD.getFlags() | SF_WeakDefinition);
 250     break;
 251
 252   case MCSA_WeakDefAutoPrivate:
 253     SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
 254     break;
 255   }
 256 }
 257
 258 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 259   // Encode the 'desc' value into the lowest implementation defined bits.
 260   assert(DescValue == (DescValue & SF_DescFlagsMask) &&
 261          "Invalid .desc value!");
 262   getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
 263     DescValue & SF_DescFlagsMask);
 264 }
 265
 266 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
 267                                        unsigned ByteAlignment) {
 268   // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
 269   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 270
 271   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 272   SD.setExternal(true);
 273   SD.setCommon(Size, ByteAlignment);
 274 }
 275
 276 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
 277                                    unsigned Size, unsigned ByteAlignment) {
 278   MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
 279
 280   // The symbol may not be present, which only creates the section.
 281   if (!Symbol)
 282     return;
 283
 284   // FIXME: Assert that this section has the zerofill type.
 285
 286   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
 287
 288   MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
 289
 290   // Emit an align fragment if necessary.
 291   if (ByteAlignment != 1)
 292     new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
 293
 294   MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
 295   SD.setFragment(F);
 296
 297   Symbol->setSection(*Section);
 298
 299   // Update the maximum alignment on the zero fill section if necessary.
 300   if (ByteAlignment > SectData.getAlignment())
 301     SectData.setAlignment(ByteAlignment);
 302 }
 303
 304 // This should always be called with the thread local bss section.  Like the
 305 // .zerofill directive this doesn't actually switch sections on us.
 306 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
 307                                      uint64_t Size, unsigned ByteAlignment) {
 308   EmitZerofill(Section, Symbol, Size, ByteAlignment);
 309   return;
 310 }
 311
 312 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
 313   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 314   // MCObjectStreamer.
 315   getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
 316 }
 317
 318 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
 319                                            int64_t Value, unsigned ValueSize,
 320                                            unsigned MaxBytesToEmit) {
 321   // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
 322   // MCObjectStreamer.
 323   if (MaxBytesToEmit == 0)
 324     MaxBytesToEmit = ByteAlignment;
 325   new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
 326                       getCurrentSectionData());
 327
 328   // Update the maximum alignment on the current section if necessary.
 329   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 330     getCurrentSectionData()->setAlignment(ByteAlignment);
 331 }
 332
 333 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
 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   MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
 340                                            getCurrentSectionData());
 341   F->setEmitNops(true);
 342
 343   // Update the maximum alignment on the current section if necessary.
 344   if (ByteAlignment > getCurrentSectionData()->getAlignment())
 345     getCurrentSectionData()->setAlignment(ByteAlignment);
 346 }
 347
 348 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
 349   MCDataFragment *DF = getOrCreateDataFragment();
 350
 351   SmallVector<MCFixup, 4> Fixups;
 352   SmallString<256> Code;
 353   raw_svector_ostream VecOS(Code);
 354   getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
 355   VecOS.flush();
 356
 357   // Add the fixups and data.
 358   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
 359     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
 360     DF->addFixup(Fixups[i]);
 361   }
 362   DF->getContents().append(Code.begin(), Code.end());
 363 }
 364
 365 void MCMachOStreamer::Finish() {
 366   // We have to set the fragment atom associations so we can relax properly for
 367   // Mach-O.
 368
 369   // First, scan the symbol table to build a lookup table from fragments to
 370   // defining symbols.
 371   DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
 372   for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
 373          ie = getAssembler().symbol_end(); it != ie; ++it) {
 374     if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
 375         it->getFragment()) {
 376       // An atom defining symbol should never be internal to a fragment.
 377       assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
 378       DefiningSymbolMap[it->getFragment()] = it;
 379     }
 380   }
 381
 382   // Set the fragment atom associations by tracking the last seen atom defining
 383   // symbol.
 384   for (MCAssembler::iterator it = getAssembler().begin(),
 385          ie = getAssembler().end(); it != ie; ++it) {
 386     MCSymbolData *CurrentAtom = 0;
 387     for (MCSectionData::iterator it2 = it->begin(),
 388            ie2 = it->end(); it2 != ie2; ++it2) {
 389       if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
 390         CurrentAtom = SD;
 391       it2->setAtom(CurrentAtom);
 392     }
 393   }
 394
 395   this->MCObjectStreamer::Finish();
 396 }
 397
 398 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
 399                                       raw_ostream &OS, MCCodeEmitter *CE,
 400                                       bool RelaxAll) {
 401   MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
 402   if (RelaxAll)
 403     S->getAssembler().setRelaxAll(true);
 404   return S;
 405 }