X86MachObjectWriter.cpp revision e54726a87a49e3254696b05787f4635dc59fe750 
1//===-- X86MachObjectWriter.cpp - X86 Mach-O Writer -----------------------===//
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 "MCTargetDesc/X86MCTargetDesc.h"
11#include "MCTargetDesc/X86FixupKinds.h"
12#include "llvm/ADT/Twine.h"
13#include "llvm/MC/MCAsmLayout.h"
14#include "llvm/MC/MCAssembler.h"
15#include "llvm/MC/MCContext.h"
16#include "llvm/MC/MCMachObjectWriter.h"
17#include "llvm/MC/MCSectionMachO.h"
18#include "llvm/MC/MCValue.h"
19#include "llvm/Object/MachOFormat.h"
20#include "llvm/Support/ErrorHandling.h"
21#include "llvm/Support/Format.h"
22
23using namespace llvm;
24using namespace llvm::object;
25
26namespace {
27class X86MachObjectWriter : public MCMachObjectTargetWriter {
28  bool RecordScatteredRelocation(MachObjectWriter *Writer,
29                                 const MCAssembler &Asm,
30                                 const MCAsmLayout &Layout,
31                                 const MCFragment *Fragment,
32                                 const MCFixup &Fixup,
33                                 MCValue Target,
34                                 unsigned Log2Size,
35                                 uint64_t &FixedValue);
36  void RecordTLVPRelocation(MachObjectWriter *Writer,
37                            const MCAssembler &Asm,
38                            const MCAsmLayout &Layout,
39                            const MCFragment *Fragment,
40                            const MCFixup &Fixup,
41                            MCValue Target,
42                            uint64_t &FixedValue);
43
44  void RecordX86Relocation(MachObjectWriter *Writer,
45                              const MCAssembler &Asm,
46                              const MCAsmLayout &Layout,
47                              const MCFragment *Fragment,
48                              const MCFixup &Fixup,
49                              MCValue Target,
50                              uint64_t &FixedValue);
51  void RecordX86_64Relocation(MachObjectWriter *Writer,
52                              const MCAssembler &Asm,
53                              const MCAsmLayout &Layout,
54                              const MCFragment *Fragment,
55                              const MCFixup &Fixup,
56                              MCValue Target,
57                              uint64_t &FixedValue);
58public:
59  X86MachObjectWriter(bool Is64Bit, uint32_t CPUType,
60                      uint32_t CPUSubtype)
61    : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype,
62                               /*UseAggressiveSymbolFolding=*/Is64Bit) {}
63
64  void RecordRelocation(MachObjectWriter *Writer,
65                        const MCAssembler &Asm, const MCAsmLayout &Layout,
66                        const MCFragment *Fragment, const MCFixup &Fixup,
67                        MCValue Target, uint64_t &FixedValue) {
68    if (Writer->is64Bit())
69      RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
70                             FixedValue);
71    else
72      RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
73                          FixedValue);
74  }
75};
76}
77
78static bool isFixupKindRIPRel(unsigned Kind) {
79  return Kind == X86::reloc_riprel_4byte ||
80    Kind == X86::reloc_riprel_4byte_movq_load;
81}
82
83static unsigned getFixupKindLog2Size(unsigned Kind) {
84  switch (Kind) {
85  default:
86    llvm_unreachable("invalid fixup kind!");
87  case FK_PCRel_1:
88  case FK_Data_1: return 0;
89  case FK_PCRel_2:
90  case FK_Data_2: return 1;
91  case FK_PCRel_4:
92    // FIXME: Remove these!!!
93  case X86::reloc_riprel_4byte:
94  case X86::reloc_riprel_4byte_movq_load:
95  case X86::reloc_signed_4byte:
96  case FK_Data_4: return 2;
97  case FK_Data_8: return 3;
98  }
99}
100
101void X86MachObjectWriter::RecordX86_64Relocation(MachObjectWriter *Writer,
102                                                 const MCAssembler &Asm,
103                                                 const MCAsmLayout &Layout,
104                                                 const MCFragment *Fragment,
105                                                 const MCFixup &Fixup,
106                                                 MCValue Target,
107                                                 uint64_t &FixedValue) {
108  unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
109  unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind());
110  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
111
112  // See <reloc.h>.
113  uint32_t FixupOffset =
114    Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
115  uint32_t FixupAddress =
116    Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
117  int64_t Value = 0;
118  unsigned Index = 0;
119  unsigned IsExtern = 0;
120  unsigned Type = 0;
121
122  Value = Target.getConstant();
123
124  if (IsPCRel) {
125    // Compensate for the relocation offset, Darwin x86_64 relocations only have
126    // the addend and appear to have attempted to define it to be the actual
127    // expression addend without the PCrel bias. However, instructions with data
128    // following the relocation are not accommodated for (see comment below
129    // regarding SIGNED{1,2,4}), so it isn't exactly that either.
130    Value += 1LL << Log2Size;
131  }
132
133  if (Target.isAbsolute()) { // constant
134    // SymbolNum of 0 indicates the absolute section.
135    Type = macho::RIT_X86_64_Unsigned;
136    Index = 0;
137
138    // FIXME: I believe this is broken, I don't think the linker can understand
139    // it. I think it would require a local relocation, but I'm not sure if that
140    // would work either. The official way to get an absolute PCrel relocation
141    // is to use an absolute symbol (which we don't support yet).
142    if (IsPCRel) {
143      IsExtern = 1;
144      Type = macho::RIT_X86_64_Branch;
145    }
146  } else if (Target.getSymB()) { // A - B + constant
147    const MCSymbol *A = &Target.getSymA()->getSymbol();
148    MCSymbolData &A_SD = Asm.getSymbolData(*A);
149    const MCSymbolData *A_Base = Asm.getAtom(&A_SD);
150
151    const MCSymbol *B = &Target.getSymB()->getSymbol();
152    MCSymbolData &B_SD = Asm.getSymbolData(*B);
153    const MCSymbolData *B_Base = Asm.getAtom(&B_SD);
154
155    // Neither symbol can be modified.
156    if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
157        Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
158      report_fatal_error("unsupported relocation of modified symbol");
159
160    // We don't support PCrel relocations of differences. Darwin 'as' doesn't
161    // implement most of these correctly.
162    if (IsPCRel)
163      report_fatal_error("unsupported pc-relative relocation of difference");
164
165    // The support for the situation where one or both of the symbols would
166    // require a local relocation is handled just like if the symbols were
167    // external.  This is certainly used in the case of debug sections where the
168    // section has only temporary symbols and thus the symbols don't have base
169    // symbols.  This is encoded using the section ordinal and non-extern
170    // relocation entries.
171
172    // Darwin 'as' doesn't emit correct relocations for this (it ends up with a
173    // single SIGNED relocation); reject it for now.  Except the case where both
174    // symbols don't have a base, equal but both NULL.
175    if (A_Base == B_Base && A_Base)
176      report_fatal_error("unsupported relocation with identical base");
177
178    // A subtraction expression where both symbols are undefined is a
179    // non-relocatable expression.
180    if (A->isUndefined() && B->isUndefined())
181      report_fatal_error("unsupported relocation with subtraction expression");
182
183    Value += Writer->getSymbolAddress(&A_SD, Layout) -
184      (A_Base == NULL ? 0 : Writer->getSymbolAddress(A_Base, Layout));
185    Value -= Writer->getSymbolAddress(&B_SD, Layout) -
186      (B_Base == NULL ? 0 : Writer->getSymbolAddress(B_Base, Layout));
187
188    if (A_Base) {
189      Index = A_Base->getIndex();
190      IsExtern = 1;
191    }
192    else {
193      Index = A_SD.getFragment()->getParent()->getOrdinal() + 1;
194      IsExtern = 0;
195    }
196    Type = macho::RIT_X86_64_Unsigned;
197
198    macho::RelocationEntry MRE;
199    MRE.Word0 = FixupOffset;
200    MRE.Word1 = ((Index     <<  0) |
201                 (IsPCRel   << 24) |
202                 (Log2Size  << 25) |
203                 (IsExtern  << 27) |
204                 (Type      << 28));
205    Writer->addRelocation(Fragment->getParent(), MRE);
206
207    if (B_Base) {
208      Index = B_Base->getIndex();
209      IsExtern = 1;
210    }
211    else {
212      Index = B_SD.getFragment()->getParent()->getOrdinal() + 1;
213      IsExtern = 0;
214    }
215    Type = macho::RIT_X86_64_Subtractor;
216  } else {
217    const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
218    MCSymbolData &SD = Asm.getSymbolData(*Symbol);
219    const MCSymbolData *Base = Asm.getAtom(&SD);
220
221    // Relocations inside debug sections always use local relocations when
222    // possible. This seems to be done because the debugger doesn't fully
223    // understand x86_64 relocation entries, and expects to find values that
224    // have already been fixed up.
225    if (Symbol->isInSection()) {
226      const MCSectionMachO &Section = static_cast<const MCSectionMachO&>(
227        Fragment->getParent()->getSection());
228      if (Section.hasAttribute(MCSectionMachO::S_ATTR_DEBUG))
229        Base = 0;
230    }
231
232    // x86_64 almost always uses external relocations, except when there is no
233    // symbol to use as a base address (a local symbol with no preceding
234    // non-local symbol).
235    if (Base) {
236      Index = Base->getIndex();
237      IsExtern = 1;
238
239      // Add the local offset, if needed.
240      if (Base != &SD)
241        Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base);
242    } else if (Symbol->isInSection() && !Symbol->isVariable()) {
243      // The index is the section ordinal (1-based).
244      Index = SD.getFragment()->getParent()->getOrdinal() + 1;
245      IsExtern = 0;
246      Value += Writer->getSymbolAddress(&SD, Layout);
247
248      if (IsPCRel)
249        Value -= FixupAddress + (1 << Log2Size);
250    } else if (Symbol->isVariable()) {
251      const MCExpr *Value = Symbol->getVariableValue();
252      int64_t Res;
253      bool isAbs = Value->EvaluateAsAbsolute(Res, Layout,
254                                             Writer->getSectionAddressMap());
255      if (isAbs) {
256        FixedValue = Res;
257        return;
258      } else {
259        report_fatal_error("unsupported relocation of variable '" +
260                           Symbol->getName() + "'");
261      }
262    } else {
263      report_fatal_error("unsupported relocation of undefined symbol '" +
264                         Symbol->getName() + "'");
265    }
266
267    MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
268    if (IsPCRel) {
269      if (IsRIPRel) {
270        if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
271          // x86_64 distinguishes movq foo@GOTPCREL so that the linker can
272          // rewrite the movq to an leaq at link time if the symbol ends up in
273          // the same linkage unit.
274          if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
275            Type = macho::RIT_X86_64_GOTLoad;
276          else
277            Type = macho::RIT_X86_64_GOT;
278        }  else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
279          Type = macho::RIT_X86_64_TLV;
280        }  else if (Modifier != MCSymbolRefExpr::VK_None) {
281          report_fatal_error("unsupported symbol modifier in relocation");
282        } else {
283          Type = macho::RIT_X86_64_Signed;
284
285          // The Darwin x86_64 relocation format has a problem where it cannot
286          // encode an address (L<foo> + <constant>) which is outside the atom
287          // containing L<foo>. Generally, this shouldn't occur but it does
288          // happen when we have a RIPrel instruction with data following the
289          // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
290          // adjustment Darwin x86_64 uses, the offset is still negative and the
291          // linker has no way to recognize this.
292          //
293          // To work around this, Darwin uses several special relocation types
294          // to indicate the offsets. However, the specification or
295          // implementation of these seems to also be incomplete; they should
296          // adjust the addend as well based on the actual encoded instruction
297          // (the additional bias), but instead appear to just look at the final
298          // offset.
299          switch (-(Target.getConstant() + (1LL << Log2Size))) {
300          case 1: Type = macho::RIT_X86_64_Signed1; break;
301          case 2: Type = macho::RIT_X86_64_Signed2; break;
302          case 4: Type = macho::RIT_X86_64_Signed4; break;
303          }
304        }
305      } else {
306        if (Modifier != MCSymbolRefExpr::VK_None)
307          report_fatal_error("unsupported symbol modifier in branch "
308                             "relocation");
309
310        Type = macho::RIT_X86_64_Branch;
311      }
312    } else {
313      if (Modifier == MCSymbolRefExpr::VK_GOT) {
314        Type = macho::RIT_X86_64_GOT;
315      } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
316        // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which
317        // case all we do is set the PCrel bit in the relocation entry; this is
318        // used with exception handling, for example. The source is required to
319        // include any necessary offset directly.
320        Type = macho::RIT_X86_64_GOT;
321        IsPCRel = 1;
322      } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
323        report_fatal_error("TLVP symbol modifier should have been rip-rel");
324      } else if (Modifier != MCSymbolRefExpr::VK_None)
325        report_fatal_error("unsupported symbol modifier in relocation");
326      else {
327        Type = macho::RIT_X86_64_Unsigned;
328        unsigned Kind = Fixup.getKind();
329        if (Kind == X86::reloc_signed_4byte)
330          report_fatal_error("32-bit absolute addressing is not supported in "
331                             "64-bit mode");
332      }
333    }
334  }
335
336  // x86_64 always writes custom values into the fixups.
337  FixedValue = Value;
338
339  // struct relocation_info (8 bytes)
340  macho::RelocationEntry MRE;
341  MRE.Word0 = FixupOffset;
342  MRE.Word1 = ((Index     <<  0) |
343               (IsPCRel   << 24) |
344               (Log2Size  << 25) |
345               (IsExtern  << 27) |
346               (Type      << 28));
347  Writer->addRelocation(Fragment->getParent(), MRE);
348}
349
350bool X86MachObjectWriter::RecordScatteredRelocation(MachObjectWriter *Writer,
351                                                    const MCAssembler &Asm,
352                                                    const MCAsmLayout &Layout,
353                                                    const MCFragment *Fragment,
354                                                    const MCFixup &Fixup,
355                                                    MCValue Target,
356                                                    unsigned Log2Size,
357                                                    uint64_t &FixedValue) {
358  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
359  unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
360  unsigned Type = macho::RIT_Vanilla;
361
362  // See <reloc.h>.
363  const MCSymbol *A = &Target.getSymA()->getSymbol();
364  MCSymbolData *A_SD = &Asm.getSymbolData(*A);
365
366  if (!A_SD->getFragment())
367    report_fatal_error("symbol '" + A->getName() +
368                       "' can not be undefined in a subtraction expression");
369
370  uint32_t Value = Writer->getSymbolAddress(A_SD, Layout);
371  uint64_t SecAddr = Writer->getSectionAddress(A_SD->getFragment()->getParent());
372  FixedValue += SecAddr;
373  uint32_t Value2 = 0;
374
375  if (const MCSymbolRefExpr *B = Target.getSymB()) {
376    MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
377
378    if (!B_SD->getFragment())
379      report_fatal_error("symbol '" + B->getSymbol().getName() +
380                         "' can not be undefined in a subtraction expression");
381
382    // Select the appropriate difference relocation type.
383    //
384    // Note that there is no longer any semantic difference between these two
385    // relocation types from the linkers point of view, this is done solely for
386    // pedantic compatibility with 'as'.
387    Type = A_SD->isExternal() ? (unsigned)macho::RIT_Difference :
388      (unsigned)macho::RIT_Generic_LocalDifference;
389    Value2 = Writer->getSymbolAddress(B_SD, Layout);
390    FixedValue -= Writer->getSectionAddress(B_SD->getFragment()->getParent());
391  }
392
393  // Relocations are written out in reverse order, so the PAIR comes first.
394  if (Type == macho::RIT_Difference ||
395      Type == macho::RIT_Generic_LocalDifference) {
396    // If the offset is too large to fit in a scattered relocation,
397    // we're hosed. It's an unfortunate limitation of the MachO format.
398    if (FixupOffset > 0xffffff) {
399      char Buffer[32];
400      format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
401      Asm.getContext().FatalError(Fixup.getLoc(),
402                         Twine("Section too large, can't encode "
403                                "r_address (") + Buffer +
404                         ") into 24 bits of scattered "
405                         "relocation entry.");
406      llvm_unreachable("fatal error returned?!");
407    }
408
409    macho::RelocationEntry MRE;
410    MRE.Word0 = ((0         <<  0) |
411                 (macho::RIT_Pair  << 24) |
412                 (Log2Size  << 28) |
413                 (IsPCRel   << 30) |
414                 macho::RF_Scattered);
415    MRE.Word1 = Value2;
416    Writer->addRelocation(Fragment->getParent(), MRE);
417  } else {
418    // If the offset is more than 24-bits, it won't fit in a scattered
419    // relocation offset field, so we fall back to using a non-scattered
420    // relocation. This is a bit risky, as if the offset reaches out of
421    // the block and the linker is doing scattered loading on this
422    // symbol, things can go badly.
423    //
424    // Required for 'as' compatibility.
425    if (FixupOffset > 0xffffff)
426      return false;
427  }
428
429  macho::RelocationEntry MRE;
430  MRE.Word0 = ((FixupOffset <<  0) |
431               (Type        << 24) |
432               (Log2Size    << 28) |
433               (IsPCRel     << 30) |
434               macho::RF_Scattered);
435  MRE.Word1 = Value;
436  Writer->addRelocation(Fragment->getParent(), MRE);
437  return true;
438}
439
440void X86MachObjectWriter::RecordTLVPRelocation(MachObjectWriter *Writer,
441                                               const MCAssembler &Asm,
442                                               const MCAsmLayout &Layout,
443                                               const MCFragment *Fragment,
444                                               const MCFixup &Fixup,
445                                               MCValue Target,
446                                               uint64_t &FixedValue) {
447  assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
448         !is64Bit() &&
449         "Should only be called with a 32-bit TLVP relocation!");
450
451  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
452  uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
453  unsigned IsPCRel = 0;
454
455  // Get the symbol data.
456  MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol());
457  unsigned Index = SD_A->getIndex();
458
459  // We're only going to have a second symbol in pic mode and it'll be a
460  // subtraction from the picbase. For 32-bit pic the addend is the difference
461  // between the picbase and the next address.  For 32-bit static the addend is
462  // zero.
463  if (Target.getSymB()) {
464    // If this is a subtraction then we're pcrel.
465    uint32_t FixupAddress =
466      Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
467    MCSymbolData *SD_B = &Asm.getSymbolData(Target.getSymB()->getSymbol());
468    IsPCRel = 1;
469    FixedValue = (FixupAddress - Writer->getSymbolAddress(SD_B, Layout) +
470                  Target.getConstant());
471    FixedValue += 1ULL << Log2Size;
472  } else {
473    FixedValue = 0;
474  }
475
476  // struct relocation_info (8 bytes)
477  macho::RelocationEntry MRE;
478  MRE.Word0 = Value;
479  MRE.Word1 = ((Index                  <<  0) |
480               (IsPCRel                << 24) |
481               (Log2Size               << 25) |
482               (1                      << 27) | // Extern
483               (macho::RIT_Generic_TLV << 28)); // Type
484  Writer->addRelocation(Fragment->getParent(), MRE);
485}
486
487void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
488                                              const MCAssembler &Asm,
489                                              const MCAsmLayout &Layout,
490                                              const MCFragment *Fragment,
491                                              const MCFixup &Fixup,
492                                              MCValue Target,
493                                              uint64_t &FixedValue) {
494  unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
495  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
496
497  // If this is a 32-bit TLVP reloc it's handled a bit differently.
498  if (Target.getSymA() &&
499      Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) {
500    RecordTLVPRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
501                         FixedValue);
502    return;
503  }
504
505  // If this is a difference or a defined symbol plus an offset, then we need a
506  // scattered relocation entry. Differences always require scattered
507  // relocations.
508  if (Target.getSymB()) {
509    RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
510                              Target, Log2Size, FixedValue);
511    return;
512  }
513
514  // Get the symbol data, if any.
515  MCSymbolData *SD = 0;
516  if (Target.getSymA())
517    SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
518
519  // If this is an internal relocation with an offset, it also needs a scattered
520  // relocation entry.
521  uint32_t Offset = Target.getConstant();
522  if (IsPCRel)
523    Offset += 1 << Log2Size;
524  // Try to record the scattered relocation if needed. Fall back to non
525  // scattered if necessary (see comments in RecordScatteredRelocation()
526  // for details).
527  if (Offset && SD && !Writer->doesSymbolRequireExternRelocation(SD) &&
528      RecordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
529                                Target, Log2Size, FixedValue))
530    return;
531
532  // See <reloc.h>.
533  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
534  unsigned Index = 0;
535  unsigned IsExtern = 0;
536  unsigned Type = 0;
537
538  if (Target.isAbsolute()) { // constant
539    // SymbolNum of 0 indicates the absolute section.
540    //
541    // FIXME: Currently, these are never generated (see code below). I cannot
542    // find a case where they are actually emitted.
543    Type = macho::RIT_Vanilla;
544  } else {
545    // Resolve constant variables.
546    if (SD->getSymbol().isVariable()) {
547      int64_t Res;
548      if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute(
549            Res, Layout, Writer->getSectionAddressMap())) {
550        FixedValue = Res;
551        return;
552      }
553    }
554
555    // Check whether we need an external or internal relocation.
556    if (Writer->doesSymbolRequireExternRelocation(SD)) {
557      IsExtern = 1;
558      Index = SD->getIndex();
559      // For external relocations, make sure to offset the fixup value to
560      // compensate for the addend of the symbol address, if it was
561      // undefined. This occurs with weak definitions, for example.
562      if (!SD->Symbol->isUndefined())
563        FixedValue -= Layout.getSymbolOffset(SD);
564    } else {
565      // The index is the section ordinal (1-based).
566      const MCSectionData &SymSD = Asm.getSectionData(
567        SD->getSymbol().getSection());
568      Index = SymSD.getOrdinal() + 1;
569      FixedValue += Writer->getSectionAddress(&SymSD);
570    }
571    if (IsPCRel)
572      FixedValue -= Writer->getSectionAddress(Fragment->getParent());
573
574    Type = macho::RIT_Vanilla;
575  }
576
577  // struct relocation_info (8 bytes)
578  macho::RelocationEntry MRE;
579  MRE.Word0 = FixupOffset;
580  MRE.Word1 = ((Index     <<  0) |
581               (IsPCRel   << 24) |
582               (Log2Size  << 25) |
583               (IsExtern  << 27) |
584               (Type      << 28));
585  Writer->addRelocation(Fragment->getParent(), MRE);
586}
587
588MCObjectWriter *llvm::createX86MachObjectWriter(raw_ostream &OS,
589                                                bool Is64Bit,
590                                                uint32_t CPUType,
591                                                uint32_t CPUSubtype) {
592  return createMachObjectWriter(new X86MachObjectWriter(Is64Bit,
593                                                        CPUType,
594                                                        CPUSubtype),
595                                OS, /*IsLittleEndian=*/true);
596}
597