Home | History | Annotate | Download | only in MC 
      1 //===-- llvm/MC/WinCOFFStreamer.cpp -----------------------------*- C++ -*-===//
      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 // This file contains an implementation of a Win32 COFF object file streamer.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #define DEBUG_TYPE "WinCOFFStreamer"
     15 
     16 #include "llvm/MC/MCObjectStreamer.h"
     17 #include "llvm/MC/MCContext.h"
     18 #include "llvm/MC/MCSection.h"
     19 #include "llvm/MC/MCSymbol.h"
     20 #include "llvm/MC/MCExpr.h"
     21 #include "llvm/MC/MCValue.h"
     22 #include "llvm/MC/MCAssembler.h"
     23 #include "llvm/MC/MCAsmLayout.h"
     24 #include "llvm/MC/MCCodeEmitter.h"
     25 #include "llvm/MC/MCSectionCOFF.h"
     26 #include "llvm/MC/MCWin64EH.h"
     27 #include "llvm/Target/TargetRegistry.h"
     28 #include "llvm/Target/TargetAsmBackend.h"
     29 #include "llvm/ADT/StringMap.h"
     30 
     31 #include "llvm/Support/COFF.h"
     32 #include "llvm/Support/Debug.h"
     33 #include "llvm/Support/ErrorHandling.h"
     34 #include "llvm/Support/raw_ostream.h"
     35 using namespace llvm;
     36 
     37 namespace {
     38 class WinCOFFStreamer : public MCObjectStreamer {
     39 public:
     40   MCSymbol const *CurSymbol;
     41 
     42   WinCOFFStreamer(MCContext &Context,
     43                   TargetAsmBackend &TAB,
     44                   MCCodeEmitter &CE,
     45                   raw_ostream &OS);
     46 
     47   void AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
     48                        unsigned ByteAlignment, bool External);
     49 
     50   // MCStreamer interface
     51 
     52   virtual void InitSections();
     53   virtual void EmitLabel(MCSymbol *Symbol);
     54   virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
     55   virtual void EmitThumbFunc(MCSymbol *Func);
     56   virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
     57   virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
     58   virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
     59   virtual void BeginCOFFSymbolDef(MCSymbol const *Symbol);
     60   virtual void EmitCOFFSymbolStorageClass(int StorageClass);
     61   virtual void EmitCOFFSymbolType(int Type);
     62   virtual void EndCOFFSymbolDef();
     63   virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value);
     64   virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
     65                                 unsigned ByteAlignment);
     66   virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size);
     67   virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
     68                             unsigned Size,unsigned ByteAlignment);
     69   virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
     70                               uint64_t Size, unsigned ByteAlignment);
     71   virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
     72   virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
     73                                    unsigned ValueSize, unsigned MaxBytesToEmit);
     74   virtual void EmitCodeAlignment(unsigned ByteAlignment,
     75                                  unsigned MaxBytesToEmit);
     76   virtual void EmitFileDirective(StringRef Filename);
     77   virtual void EmitInstruction(const MCInst &Instruction);
     78   virtual void EmitWin64EHHandlerData();
     79   virtual void Finish();
     80 
     81 private:
     82   virtual void EmitInstToFragment(const MCInst &Inst) {
     83     llvm_unreachable("Not used by WinCOFF.");
     84   }
     85   virtual void EmitInstToData(const MCInst &Inst) {
     86     llvm_unreachable("Not used by WinCOFF.");
     87   }
     88 
     89   void SetSection(StringRef Section,
     90                   unsigned Characteristics,
     91                   SectionKind Kind) {
     92     SwitchSection(getContext().getCOFFSection(Section, Characteristics, Kind));
     93   }
     94 
     95   void SetSectionText() {
     96     SetSection(".text",
     97                COFF::IMAGE_SCN_CNT_CODE
     98              | COFF::IMAGE_SCN_MEM_EXECUTE
     99              | COFF::IMAGE_SCN_MEM_READ,
    100                SectionKind::getText());
    101     EmitCodeAlignment(4, 0);
    102   }
    103 
    104   void SetSectionData() {
    105     SetSection(".data",
    106                COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
    107              | COFF::IMAGE_SCN_MEM_READ
    108              | COFF::IMAGE_SCN_MEM_WRITE,
    109                SectionKind::getDataRel());
    110     EmitCodeAlignment(4, 0);
    111   }
    112 
    113   void SetSectionBSS() {
    114     SetSection(".bss",
    115                COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA
    116              | COFF::IMAGE_SCN_MEM_READ
    117              | COFF::IMAGE_SCN_MEM_WRITE,
    118                SectionKind::getBSS());
    119     EmitCodeAlignment(4, 0);
    120   }
    121 
    122 };
    123 } // end anonymous namespace.
    124 
    125 WinCOFFStreamer::WinCOFFStreamer(MCContext &Context,
    126                                  TargetAsmBackend &TAB,
    127                                  MCCodeEmitter &CE,
    128                                  raw_ostream &OS)
    129     : MCObjectStreamer(Context, TAB, OS, &CE)
    130     , CurSymbol(NULL) {
    131 }
    132 
    133 void WinCOFFStreamer::AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    134                                       unsigned ByteAlignment, bool External) {
    135   assert(!Symbol->isInSection() && "Symbol must not already have a section!");
    136 
    137   std::string SectionName(".bss$linkonce");
    138   SectionName.append(Symbol->getName().begin(), Symbol->getName().end());
    139 
    140   MCSymbolData &SymbolData = getAssembler().getOrCreateSymbolData(*Symbol);
    141 
    142   unsigned Characteristics =
    143     COFF::IMAGE_SCN_LNK_COMDAT |
    144     COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
    145     COFF::IMAGE_SCN_MEM_READ |
    146     COFF::IMAGE_SCN_MEM_WRITE;
    147 
    148   int Selection = COFF::IMAGE_COMDAT_SELECT_LARGEST;
    149 
    150   const MCSection *Section = MCStreamer::getContext().getCOFFSection(
    151     SectionName, Characteristics, Selection, SectionKind::getBSS());
    152 
    153   MCSectionData &SectionData = getAssembler().getOrCreateSectionData(*Section);
    154 
    155   if (SectionData.getAlignment() < ByteAlignment)
    156     SectionData.setAlignment(ByteAlignment);
    157 
    158   SymbolData.setExternal(External);
    159 
    160   Symbol->setSection(*Section);
    161 
    162   if (ByteAlignment != 1)
    163       new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectionData);
    164 
    165   SymbolData.setFragment(new MCFillFragment(0, 0, Size, &SectionData));
    166 }
    167 
    168 // MCStreamer interface
    169 
    170 void WinCOFFStreamer::InitSections() {
    171   SetSectionText();
    172   SetSectionData();
    173   SetSectionBSS();
    174   SetSectionText();
    175 }
    176 
    177 void WinCOFFStreamer::EmitLabel(MCSymbol *Symbol) {
    178   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
    179   MCObjectStreamer::EmitLabel(Symbol);
    180 }
    181 
    182 void WinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
    183   llvm_unreachable("not implemented");
    184 }
    185 
    186 void WinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
    187   llvm_unreachable("not implemented");
    188 }
    189 
    190 void WinCOFFStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
    191   assert((Symbol->isInSection()
    192          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    193          : true) && "Got non COFF section in the COFF backend!");
    194   // FIXME: This is all very ugly and depressing. What needs to happen here
    195   // depends on quite a few things that are all part of relaxation, which we
    196   // don't really even do.
    197 
    198   if (Value->getKind() != MCExpr::SymbolRef) {
    199     // TODO: This is exactly the same as MachOStreamer. Consider merging into
    200     // MCObjectStreamer.
    201     getAssembler().getOrCreateSymbolData(*Symbol);
    202     AddValueSymbols(Value);
    203     Symbol->setVariableValue(Value);
    204   } else {
    205     // FIXME: This is a horrible way to do this :(. This should really be
    206     // handled after we are done with the MC* objects and immediately before
    207     // writing out the object file when we know exactly what the symbol should
    208     // look like in the coff symbol table. I'm not doing that now because the
    209     // COFF object writer doesn't have a clearly defined separation between MC
    210     // data structures, the object writers data structures, and the raw, POD,
    211     // data structures that get written to disk.
    212 
    213     // Copy over the aliased data.
    214     MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    215     const MCSymbolData &RealSD = getAssembler().getOrCreateSymbolData(
    216       dyn_cast<const MCSymbolRefExpr>(Value)->getSymbol());
    217 
    218     // FIXME: This is particularly nasty because it breaks as soon as any data
    219     // members of MCSymbolData change.
    220     SD.CommonAlign     = RealSD.CommonAlign;
    221     SD.CommonSize      = RealSD.CommonSize;
    222     SD.Flags           = RealSD.Flags;
    223     SD.Fragment        = RealSD.Fragment;
    224     SD.Index           = RealSD.Index;
    225     SD.IsExternal      = RealSD.IsExternal;
    226     SD.IsPrivateExtern = RealSD.IsPrivateExtern;
    227     SD.Offset          = RealSD.Offset;
    228     SD.SymbolSize      = RealSD.SymbolSize;
    229   }
    230 }
    231 
    232 void WinCOFFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
    233                                           MCSymbolAttr Attribute) {
    234   assert(Symbol && "Symbol must be non-null!");
    235   assert((Symbol->isInSection()
    236          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    237          : true) && "Got non COFF section in the COFF backend!");
    238   switch (Attribute) {
    239   case MCSA_WeakReference:
    240   case MCSA_Weak: {
    241       MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
    242       SD.modifyFlags(COFF::SF_WeakExternal, COFF::SF_WeakExternal);
    243       SD.setExternal(true);
    244     }
    245     break;
    246 
    247   case MCSA_Global:
    248     getAssembler().getOrCreateSymbolData(*Symbol).setExternal(true);
    249     break;
    250 
    251   default:
    252     llvm_unreachable("unsupported attribute");
    253     break;
    254   }
    255 }
    256 
    257 void WinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
    258   llvm_unreachable("not implemented");
    259 }
    260 
    261 void WinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
    262   assert((Symbol->isInSection()
    263          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    264          : true) && "Got non COFF section in the COFF backend!");
    265   assert(CurSymbol == NULL && "EndCOFFSymbolDef must be called between calls "
    266                               "to BeginCOFFSymbolDef!");
    267   CurSymbol = Symbol;
    268 }
    269 
    270 void WinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
    271   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
    272   assert((StorageClass & ~0xFF) == 0 && "StorageClass must only have data in "
    273                                         "the first byte!");
    274 
    275   getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
    276     StorageClass << COFF::SF_ClassShift,
    277     COFF::SF_ClassMask);
    278 }
    279 
    280 void WinCOFFStreamer::EmitCOFFSymbolType(int Type) {
    281   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
    282   assert((Type & ~0xFFFF) == 0 && "Type must only have data in the first 2 "
    283                                   "bytes");
    284 
    285   getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
    286     Type << COFF::SF_TypeShift,
    287     COFF::SF_TypeMask);
    288 }
    289 
    290 void WinCOFFStreamer::EndCOFFSymbolDef() {
    291   assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
    292   CurSymbol = NULL;
    293 }
    294 
    295 void WinCOFFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
    296   llvm_unreachable("not implemented");
    297 }
    298 
    299 void WinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
    300                                        unsigned ByteAlignment) {
    301   assert((Symbol->isInSection()
    302          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    303          : true) && "Got non COFF section in the COFF backend!");
    304   AddCommonSymbol(Symbol, Size, ByteAlignment, true);
    305 }
    306 
    307 void WinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
    308   assert((Symbol->isInSection()
    309          ? Symbol->getSection().getVariant() == MCSection::SV_COFF
    310          : true) && "Got non COFF section in the COFF backend!");
    311   AddCommonSymbol(Symbol, Size, 1, false);
    312 }
    313 
    314 void WinCOFFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
    315                                    unsigned Size,unsigned ByteAlignment) {
    316   llvm_unreachable("not implemented");
    317 }
    318 
    319 void WinCOFFStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
    320                                      uint64_t Size, unsigned ByteAlignment) {
    321   llvm_unreachable("not implemented");
    322 }
    323 
    324 void WinCOFFStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
    325   // TODO: This is copied exactly from the MachOStreamer. Consider merging into
    326   // MCObjectStreamer?
    327   getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
    328 }
    329 
    330 void WinCOFFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
    331                                            int64_t Value,
    332                                            unsigned ValueSize,
    333                                            unsigned MaxBytesToEmit) {
    334   // TODO: This is copied exactly from the MachOStreamer. Consider merging into
    335   // MCObjectStreamer?
    336   if (MaxBytesToEmit == 0)
    337     MaxBytesToEmit = ByteAlignment;
    338   new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
    339                       getCurrentSectionData());
    340 
    341   // Update the maximum alignment on the current section if necessary.
    342   if (ByteAlignment > getCurrentSectionData()->getAlignment())
    343     getCurrentSectionData()->setAlignment(ByteAlignment);
    344 }
    345 
    346 void WinCOFFStreamer::EmitCodeAlignment(unsigned ByteAlignment,
    347                                         unsigned MaxBytesToEmit) {
    348   // TODO: This is copied exactly from the MachOStreamer. Consider merging into
    349   // MCObjectStreamer?
    350   if (MaxBytesToEmit == 0)
    351     MaxBytesToEmit = ByteAlignment;
    352   MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
    353                                            getCurrentSectionData());
    354   F->setEmitNops(true);
    355 
    356   // Update the maximum alignment on the current section if necessary.
    357   if (ByteAlignment > getCurrentSectionData()->getAlignment())
    358     getCurrentSectionData()->setAlignment(ByteAlignment);
    359 }
    360 
    361 void WinCOFFStreamer::EmitFileDirective(StringRef Filename) {
    362   // Ignore for now, linkers don't care, and proper debug
    363   // info will be a much large effort.
    364 }
    365 
    366 void WinCOFFStreamer::EmitInstruction(const MCInst &Instruction) {
    367   for (unsigned i = 0, e = Instruction.getNumOperands(); i != e; ++i)
    368     if (Instruction.getOperand(i).isExpr())
    369       AddValueSymbols(Instruction.getOperand(i).getExpr());
    370 
    371   getCurrentSectionData()->setHasInstructions(true);
    372 
    373   MCInstFragment *Fragment =
    374     new MCInstFragment(Instruction, getCurrentSectionData());
    375 
    376   raw_svector_ostream VecOS(Fragment->getCode());
    377 
    378   getAssembler().getEmitter().EncodeInstruction(Instruction, VecOS,
    379                                                 Fragment->getFixups());
    380 }
    381 
    382 void WinCOFFStreamer::EmitWin64EHHandlerData() {
    383   MCStreamer::EmitWin64EHHandlerData();
    384 
    385   // We have to emit the unwind info now, because this directive
    386   // actually switches to the .xdata section!
    387   MCWin64EHUnwindEmitter::EmitUnwindInfo(*this, getCurrentW64UnwindInfo());
    388 }
    389 
    390 void WinCOFFStreamer::Finish() {
    391   EmitW64Tables();
    392   MCObjectStreamer::Finish();
    393 }
    394 
    395 namespace llvm
    396 {
    397   MCStreamer *createWinCOFFStreamer(MCContext &Context,
    398                                     TargetAsmBackend &TAB,
    399                                     MCCodeEmitter &CE,
    400                                     raw_ostream &OS,
    401                                     bool RelaxAll) {
    402     WinCOFFStreamer *S = new WinCOFFStreamer(Context, TAB, CE, OS);
    403     S->getAssembler().setRelaxAll(RelaxAll);
    404     return S;
    405   }
    406 }
    407