path: root/lib/MC/MCAssembler.cpp

//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "assembler"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Target/TargetMachOWriterInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <vector>
using namespace llvm;

class MachObjectWriter;

STATISTIC(EmittedFragments, "Number of emitted assembler fragments");

// FIXME FIXME FIXME: There are number of places in this file where we convert
// what is a 64-bit assembler value used for computation into a value in the
// object file, which may truncate it. We should detect that truncation where
// invalid and report errors back.

static void WriteFileData(raw_ostream &OS, const MCSectionData &SD,
                          MachObjectWriter &MOW);

/// isVirtualSection - Check if this is a section which does not actually exist
/// in the object file.
static bool isVirtualSection(const MCSection &Section) {
  // FIXME: Lame.
  const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
  unsigned Type = SMO.getTypeAndAttributes() & MCSectionMachO::SECTION_TYPE;
  return (Type == MCSectionMachO::S_ZEROFILL);
}

class MachObjectWriter {
  // See <mach-o/loader.h>.
  enum {
    Header_Magic32 = 0xFEEDFACE,
    Header_Magic64 = 0xFEEDFACF
  };
  
  static const unsigned Header32Size = 28;
  static const unsigned Header64Size = 32;
  static const unsigned SegmentLoadCommand32Size = 56;
  static const unsigned Section32Size = 68;
  static const unsigned SymtabLoadCommandSize = 24;
  static const unsigned DysymtabLoadCommandSize = 80;
  static const unsigned Nlist32Size = 12;
  static const unsigned RelocationInfoSize = 8;

  enum HeaderFileType {
    HFT_Object = 0x1
  };

  enum HeaderFlags {
    HF_SubsectionsViaSymbols = 0x2000
  };

  enum LoadCommandType {
    LCT_Segment = 0x1,
    LCT_Symtab = 0x2,
    LCT_Dysymtab = 0xb
  };

  // See <mach-o/nlist.h>.
  enum SymbolTypeType {
    STT_Undefined = 0x00,
    STT_Absolute  = 0x02,
    STT_Section   = 0x0e
  };

  enum SymbolTypeFlags {
    // If any of these bits are set, then the entry is a stab entry number (see
    // <mach-o/stab.h>. Otherwise the other masks apply.
    STF_StabsEntryMask = 0xe0,

    STF_TypeMask       = 0x0e,
    STF_External       = 0x01,
    STF_PrivateExtern  = 0x10
  };

  /// IndirectSymbolFlags - Flags for encoding special values in the indirect
  /// symbol entry.
  enum IndirectSymbolFlags {
    ISF_Local    = 0x80000000,
    ISF_Absolute = 0x40000000
  };

  /// RelocationFlags - Special flags for addresses.
  enum RelocationFlags {
    RF_Scattered = 0x80000000
  };

  enum RelocationInfoType {
    RIT_Vanilla             = 0,
    RIT_Pair                = 1,
    RIT_Difference          = 2,