WinCOFFStreamer.cpp revision ba210243ef7d325ef6954d459091edf580a241f9 
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/Target/TargetRegistry.h"
27#include "llvm/Target/TargetAsmBackend.h"
28#include "llvm/ADT/StringMap.h"
29
30#include "llvm/Support/COFF.h"
31#include "llvm/Support/Debug.h"
32#include "llvm/Support/ErrorHandling.h"
33#include "llvm/Support/raw_ostream.h"
34using namespace llvm;
35
36namespace {
37class WinCOFFStreamer : public MCObjectStreamer {
38public:
39  MCSymbol const *CurSymbol;
40
41  WinCOFFStreamer(MCContext &Context,
42                  TargetAsmBackend &TAB,
43                  MCCodeEmitter &CE,
44                  raw_ostream &OS);
45
46  void AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
47                       unsigned ByteAlignment, bool External);
48
49  // MCStreamer interface
50
51  virtual void InitSections();
52  virtual void EmitLabel(MCSymbol *Symbol);
53  virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
54  virtual void EmitThumbFunc(MCSymbol *Func);
55  virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
56  virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
57  virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
58  virtual void BeginCOFFSymbolDef(MCSymbol const *Symbol);
59  virtual void EmitCOFFSymbolStorageClass(int StorageClass);
60  virtual void EmitCOFFSymbolType(int Type);
61  virtual void EndCOFFSymbolDef();
62  virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value);
63  virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
64                                unsigned ByteAlignment);
65  virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size);
66  virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
67                            unsigned Size,unsigned ByteAlignment);
68  virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
69                              uint64_t Size, unsigned ByteAlignment);
70  virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
71  virtual void EmitValue(const MCExpr *Value, unsigned Size,
72                         unsigned AddrSpace);
73  virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
74                                   unsigned ValueSize, unsigned MaxBytesToEmit);
75  virtual void EmitCodeAlignment(unsigned ByteAlignment,
76                                 unsigned MaxBytesToEmit);
77  virtual void EmitValueToOffset(const MCExpr *Offset, unsigned char Value);
78  virtual void EmitFileDirective(StringRef Filename);
79  virtual void EmitInstruction(const MCInst &Instruction);
80  virtual void Finish();
81
82private:
83  virtual void EmitInstToFragment(const MCInst &Inst) {
84    llvm_unreachable("Not used by WinCOFF.");
85  }
86  virtual void EmitInstToData(const MCInst &Inst) {
87    llvm_unreachable("Not used by WinCOFF.");
88  }
89
90  void SetSection(StringRef Section,
91                  unsigned Characteristics,
92                  SectionKind Kind) {
93    SwitchSection(getContext().getCOFFSection(Section, Characteristics, Kind));
94  }
95
96  void SetSectionText() {
97    SetSection(".text",
98               COFF::IMAGE_SCN_CNT_CODE
99             | COFF::IMAGE_SCN_MEM_EXECUTE
100             | COFF::IMAGE_SCN_MEM_READ,
101               SectionKind::getText());
102    EmitCodeAlignment(4, 0);
103  }
104
105  void SetSectionData() {
106    SetSection(".data",
107               COFF::IMAGE_SCN_CNT_INITIALIZED_DATA
108             | COFF::IMAGE_SCN_MEM_READ
109             | COFF::IMAGE_SCN_MEM_WRITE,
110               SectionKind::getDataRel());
111    EmitCodeAlignment(4, 0);
112  }
113
114  void SetSectionBSS() {
115    SetSection(".bss",
116               COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA
117             | COFF::IMAGE_SCN_MEM_READ
118             | COFF::IMAGE_SCN_MEM_WRITE,
119               SectionKind::getBSS());
120    EmitCodeAlignment(4, 0);
121  }
122
123};
124} // end anonymous namespace.
125
126WinCOFFStreamer::WinCOFFStreamer(MCContext &Context,
127                                 TargetAsmBackend &TAB,
128                                 MCCodeEmitter &CE,
129                                 raw_ostream &OS)
130    : MCObjectStreamer(Context, TAB, OS, &CE, true)
131    , CurSymbol(NULL) {
132}
133
134void WinCOFFStreamer::AddCommonSymbol(MCSymbol *Symbol, uint64_t Size,
135                                      unsigned ByteAlignment, bool External) {
136  assert(!Symbol->isInSection() && "Symbol must not already have a section!");
137
138  std::string SectionName(".bss$linkonce");
139  SectionName.append(Symbol->getName().begin(), Symbol->getName().end());
140
141  MCSymbolData &SymbolData = getAssembler().getOrCreateSymbolData(*Symbol);
142
143  unsigned Characteristics =
144    COFF::IMAGE_SCN_LNK_COMDAT |
145    COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
146    COFF::IMAGE_SCN_MEM_READ |
147    COFF::IMAGE_SCN_MEM_WRITE;
148
149  int Selection = COFF::IMAGE_COMDAT_SELECT_LARGEST;
150
151  const MCSection *Section = MCStreamer::getContext().getCOFFSection(
152    SectionName, Characteristics, Selection, SectionKind::getBSS());
153
154  MCSectionData &SectionData = getAssembler().getOrCreateSectionData(*Section);
155
156  if (SectionData.getAlignment() < ByteAlignment)
157    SectionData.setAlignment(ByteAlignment);
158
159  SymbolData.setExternal(External);
160
161  Symbol->setSection(*Section);
162
163  if (ByteAlignment != 1)
164      new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectionData);
165
166  SymbolData.setFragment(new MCFillFragment(0, 0, Size, &SectionData));
167}
168
169// MCStreamer interface
170
171void WinCOFFStreamer::InitSections() {
172  SetSectionText();
173  SetSectionData();
174  SetSectionBSS();
175  SetSectionText();
176}
177
178void WinCOFFStreamer::EmitLabel(MCSymbol *Symbol) {
179  // TODO: This is copied almost exactly from the MachOStreamer. Consider
180  // merging into MCObjectStreamer?
181  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
182  assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
183  assert(CurSection && "Cannot emit before setting section!");
184
185  Symbol->setSection(*CurSection);
186
187  MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
188
189  // FIXME: This is wasteful, we don't necessarily need to create a data
190  // fragment. Instead, we should mark the symbol as pointing into the data
191  // fragment if it exists, otherwise we should just queue the label and set its
192  // fragment pointer when we emit the next fragment.
193  MCDataFragment *DF = getOrCreateDataFragment();
194
195  assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
196  SD.setFragment(DF);
197  SD.setOffset(DF->getContents().size());
198}
199
200void WinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
201  llvm_unreachable("not implemented");
202}
203
204void WinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
205  llvm_unreachable("not implemented");
206}
207
208void WinCOFFStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
209  assert((Symbol->isInSection()
210         ? Symbol->getSection().getVariant() == MCSection::SV_COFF
211         : true) && "Got non COFF section in the COFF backend!");
212  // FIXME: This is all very ugly and depressing. What needs to happen here
213  // depends on quite a few things that are all part of relaxation, which we
214  // don't really even do.
215
216  if (Value->getKind() != MCExpr::SymbolRef) {
217    // TODO: This is exactly the same as MachOStreamer. Consider merging into
218    // MCObjectStreamer.
219    getAssembler().getOrCreateSymbolData(*Symbol);
220    AddValueSymbols(Value);
221    Symbol->setVariableValue(Value);
222  } else {
223    // FIXME: This is a horrible way to do this :(. This should really be
224    // handled after we are done with the MC* objects and immediately before
225    // writing out the object file when we know exactly what the symbol should
226    // look like in the coff symbol table. I'm not doing that now because the
227    // COFF object writer doesn't have a clearly defined separation between MC
228    // data structures, the object writers data structures, and the raw, POD,
229    // data structures that get written to disk.
230
231    // Copy over the aliased data.
232    MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
233    const MCSymbolData &RealSD = getAssembler().getOrCreateSymbolData(
234      dyn_cast<const MCSymbolRefExpr>(Value)->getSymbol());
235
236    // FIXME: This is particularly nasty because it breaks as soon as any data
237    // members of MCSymbolData change.
238    SD.CommonAlign     = RealSD.CommonAlign;
239    SD.CommonSize      = RealSD.CommonSize;
240    SD.Flags           = RealSD.Flags;
241    SD.Fragment        = RealSD.Fragment;
242    SD.Index           = RealSD.Index;
243    SD.IsExternal      = RealSD.IsExternal;
244    SD.IsPrivateExtern = RealSD.IsPrivateExtern;
245    SD.Offset          = RealSD.Offset;
246    SD.SymbolSize      = RealSD.SymbolSize;
247  }
248}
249
250void WinCOFFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
251                                          MCSymbolAttr Attribute) {
252  assert(Symbol && "Symbol must be non-null!");
253  assert((Symbol->isInSection()
254         ? Symbol->getSection().getVariant() == MCSection::SV_COFF
255         : true) && "Got non COFF section in the COFF backend!");
256  switch (Attribute) {
257  case MCSA_WeakReference:
258  case MCSA_Weak: {
259      MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
260      SD.modifyFlags(COFF::SF_WeakExternal, COFF::SF_WeakExternal);
261      SD.setExternal(true);
262    }
263    break;
264
265  case MCSA_Global:
266    getAssembler().getOrCreateSymbolData(*Symbol).setExternal(true);
267    break;
268
269  default:
270    llvm_unreachable("unsupported attribute");
271    break;
272  }
273}
274
275void WinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
276  llvm_unreachable("not implemented");
277}
278
279void WinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
280  assert((Symbol->isInSection()
281         ? Symbol->getSection().getVariant() == MCSection::SV_COFF
282         : true) && "Got non COFF section in the COFF backend!");
283  assert(CurSymbol == NULL && "EndCOFFSymbolDef must be called between calls "
284                              "to BeginCOFFSymbolDef!");
285  CurSymbol = Symbol;
286}
287
288void WinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
289  assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
290  assert((StorageClass & ~0xFF) == 0 && "StorageClass must only have data in "
291                                        "the first byte!");
292
293  getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
294    StorageClass << COFF::SF_ClassShift,
295    COFF::SF_ClassMask);
296}
297
298void WinCOFFStreamer::EmitCOFFSymbolType(int Type) {
299  assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
300  assert((Type & ~0xFFFF) == 0 && "Type must only have data in the first 2 "
301                                  "bytes");
302
303  getAssembler().getOrCreateSymbolData(*CurSymbol).modifyFlags(
304    Type << COFF::SF_TypeShift,
305    COFF::SF_TypeMask);
306}
307
308void WinCOFFStreamer::EndCOFFSymbolDef() {
309  assert(CurSymbol != NULL && "BeginCOFFSymbolDef must be called first!");
310  CurSymbol = NULL;
311}
312
313void WinCOFFStreamer::EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
314  llvm_unreachable("not implemented");
315}
316
317void WinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
318                                       unsigned ByteAlignment) {
319  assert((Symbol->isInSection()
320         ? Symbol->getSection().getVariant() == MCSection::SV_COFF
321         : true) && "Got non COFF section in the COFF backend!");
322  AddCommonSymbol(Symbol, Size, ByteAlignment, true);
323}
324
325void WinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
326  assert((Symbol->isInSection()
327         ? Symbol->getSection().getVariant() == MCSection::SV_COFF
328         : true) && "Got non COFF section in the COFF backend!");
329  AddCommonSymbol(Symbol, Size, 1, false);
330}
331
332void WinCOFFStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
333                                   unsigned Size,unsigned ByteAlignment) {
334  llvm_unreachable("not implemented");
335}
336
337void WinCOFFStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
338                                     uint64_t Size, unsigned ByteAlignment) {
339  llvm_unreachable("not implemented");
340}
341
342void WinCOFFStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
343  // TODO: This is copied exactly from the MachOStreamer. Consider merging into
344  // MCObjectStreamer?
345  getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
346}
347
348void WinCOFFStreamer::EmitValue(const MCExpr *Value, unsigned Size,
349                                unsigned AddrSpace) {
350  assert(AddrSpace == 0 && "Address space must be 0!");
351
352  // TODO: This is copied exactly from the MachOStreamer. Consider merging into
353  // MCObjectStreamer?
354  MCDataFragment *DF = getOrCreateDataFragment();
355
356  // Avoid fixups when possible.
357  int64_t AbsValue;
358  if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
359    // FIXME: Endianness assumption.
360    for (unsigned i = 0; i != Size; ++i)
361      DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
362  } else {
363    DF->addFixup(MCFixup::Create(DF->getContents().size(),
364                                 AddValueSymbols(Value),
365                                 MCFixup::getKindForSize(Size, false)));
366    DF->getContents().resize(DF->getContents().size() + Size, 0);
367  }
368}
369
370void WinCOFFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
371                                           int64_t Value,
372                                           unsigned ValueSize,
373                                           unsigned MaxBytesToEmit) {
374  // TODO: This is copied exactly from the MachOStreamer. Consider merging into
375  // MCObjectStreamer?
376  if (MaxBytesToEmit == 0)
377    MaxBytesToEmit = ByteAlignment;
378  new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
379                      getCurrentSectionData());
380
381  // Update the maximum alignment on the current section if necessary.
382  if (ByteAlignment > getCurrentSectionData()->getAlignment())
383    getCurrentSectionData()->setAlignment(ByteAlignment);
384}
385
386void WinCOFFStreamer::EmitCodeAlignment(unsigned ByteAlignment,
387                                        unsigned MaxBytesToEmit) {
388  // TODO: This is copied exactly from the MachOStreamer. Consider merging into
389  // MCObjectStreamer?
390  if (MaxBytesToEmit == 0)
391    MaxBytesToEmit = ByteAlignment;
392  MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
393                                           getCurrentSectionData());
394  F->setEmitNops(true);
395
396  // Update the maximum alignment on the current section if necessary.
397  if (ByteAlignment > getCurrentSectionData()->getAlignment())
398    getCurrentSectionData()->setAlignment(ByteAlignment);
399}
400
401void WinCOFFStreamer::EmitValueToOffset(const MCExpr *Offset,
402                                        unsigned char Value) {
403  llvm_unreachable("not implemented");
404}
405
406void WinCOFFStreamer::EmitFileDirective(StringRef Filename) {
407  // Ignore for now, linkers don't care, and proper debug
408  // info will be a much large effort.
409}
410
411void WinCOFFStreamer::EmitInstruction(const MCInst &Instruction) {
412  for (unsigned i = 0, e = Instruction.getNumOperands(); i != e; ++i)
413    if (Instruction.getOperand(i).isExpr())
414      AddValueSymbols(Instruction.getOperand(i).getExpr());
415
416  getCurrentSectionData()->setHasInstructions(true);
417
418  MCInstFragment *Fragment =
419    new MCInstFragment(Instruction, getCurrentSectionData());
420
421  raw_svector_ostream VecOS(Fragment->getCode());
422
423  getAssembler().getEmitter().EncodeInstruction(Instruction, VecOS,
424                                                Fragment->getFixups());
425}
426
427void WinCOFFStreamer::Finish() {
428  MCObjectStreamer::Finish();
429}
430
431namespace llvm
432{
433  MCStreamer *createWinCOFFStreamer(MCContext &Context,
434                                    TargetAsmBackend &TAB,
435                                    MCCodeEmitter &CE,
436                                    raw_ostream &OS,
437                                    bool RelaxAll) {
438    WinCOFFStreamer *S = new WinCOFFStreamer(Context, TAB, CE, OS);
439    S->getAssembler().setRelaxAll(RelaxAll);
440    return S;
441  }
442}
443