WinCOFFStreamer.cpp revision 288943 
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 Windows COFF object file streamer.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/MC/MCAsmBackend.h"
15#include "llvm/MC/MCAsmLayout.h"
16#include "llvm/MC/MCAssembler.h"
17#include "llvm/MC/MCCodeEmitter.h"
18#include "llvm/MC/MCContext.h"
19#include "llvm/MC/MCExpr.h"
20#include "llvm/MC/MCObjectFileInfo.h"
21#include "llvm/MC/MCObjectStreamer.h"
22#include "llvm/MC/MCSection.h"
23#include "llvm/MC/MCSectionCOFF.h"
24#include "llvm/MC/MCStreamer.h"
25#include "llvm/MC/MCSymbolCOFF.h"
26#include "llvm/MC/MCValue.h"
27#include "llvm/MC/MCWinCOFFStreamer.h"
28#include "llvm/Support/COFF.h"
29#include "llvm/Support/Debug.h"
30#include "llvm/Support/ErrorHandling.h"
31#include "llvm/Support/MathExtras.h"
32#include "llvm/Support/TargetRegistry.h"
33#include "llvm/Support/raw_ostream.h"
34
35using namespace llvm;
36
37#define DEBUG_TYPE "WinCOFFStreamer"
38
39namespace llvm {
40MCWinCOFFStreamer::MCWinCOFFStreamer(MCContext &Context, MCAsmBackend &MAB,
41                                     MCCodeEmitter &CE, raw_pwrite_stream &OS)
42    : MCObjectStreamer(Context, MAB, OS, &CE), CurSymbol(nullptr) {}
43
44void MCWinCOFFStreamer::EmitInstToData(const MCInst &Inst,
45                                       const MCSubtargetInfo &STI) {
46  MCDataFragment *DF = getOrCreateDataFragment();
47
48  SmallVector<MCFixup, 4> Fixups;
49  SmallString<256> Code;
50  raw_svector_ostream VecOS(Code);
51  getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
52  VecOS.flush();
53
54  // Add the fixups and data.
55  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
56    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
57    DF->getFixups().push_back(Fixups[i]);
58  }
59
60  DF->getContents().append(Code.begin(), Code.end());
61}
62
63void MCWinCOFFStreamer::InitSections(bool NoExecStack) {
64  // FIXME: this is identical to the ELF one.
65  // This emulates the same behavior of GNU as. This makes it easier
66  // to compare the output as the major sections are in the same order.
67  SwitchSection(getContext().getObjectFileInfo()->getTextSection());
68  EmitCodeAlignment(4);
69
70  SwitchSection(getContext().getObjectFileInfo()->getDataSection());
71  EmitCodeAlignment(4);
72
73  SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
74  EmitCodeAlignment(4);
75
76  SwitchSection(getContext().getObjectFileInfo()->getTextSection());
77}
78
79void MCWinCOFFStreamer::EmitLabel(MCSymbol *Symbol) {
80  assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
81  MCObjectStreamer::EmitLabel(Symbol);
82}
83
84void MCWinCOFFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
85  llvm_unreachable("not implemented");
86}
87
88void MCWinCOFFStreamer::EmitThumbFunc(MCSymbol *Func) {
89  llvm_unreachable("not implemented");
90}
91
92bool MCWinCOFFStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
93                                            MCSymbolAttr Attribute) {
94  assert(Symbol && "Symbol must be non-null!");
95  assert((!Symbol->isInSection() ||
96          Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
97         "Got non-COFF section in the COFF backend!");
98
99  getAssembler().registerSymbol(*Symbol);
100
101  switch (Attribute) {
102  default: return false;
103  case MCSA_WeakReference:
104  case MCSA_Weak:
105    cast<MCSymbolCOFF>(Symbol)->setIsWeakExternal();
106    Symbol->setExternal(true);
107    break;
108  case MCSA_Global:
109    Symbol->setExternal(true);
110    break;
111  }
112
113  return true;
114}
115
116void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
117  llvm_unreachable("not implemented");
118}
119
120void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *Symbol) {
121  assert((!Symbol->isInSection() ||
122          Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
123         "Got non-COFF section in the COFF backend!");
124
125  if (CurSymbol)
126    FatalError("starting a new symbol definition without completing the "
127               "previous one");
128  CurSymbol = Symbol;
129}
130
131void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
132  if (!CurSymbol)
133    FatalError("storage class specified outside of symbol definition");
134
135  if (StorageClass & ~COFF::SSC_Invalid)
136    FatalError("storage class value '" + Twine(StorageClass) +
137               "' out of range");
138
139  getAssembler().registerSymbol(*CurSymbol);
140  cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
141}
142
143void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
144  if (!CurSymbol)
145    FatalError("symbol type specified outside of a symbol definition");
146
147  if (Type & ~0xffff)
148    FatalError("type value '" + Twine(Type) + "' out of range");
149
150  getAssembler().registerSymbol(*CurSymbol);
151  cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
152}
153
154void MCWinCOFFStreamer::EndCOFFSymbolDef() {
155  if (!CurSymbol)
156    FatalError("ending symbol definition without starting one");
157  CurSymbol = nullptr;
158}
159
160void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
161  // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
162  // unnecessary) on all platforms which use table-based exception dispatch.
163  if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
164      Triple::x86)
165    return;
166
167  const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
168  if (CSymbol->isSafeSEH())
169    return;
170
171  MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
172  getAssembler().registerSection(*SXData);
173  if (SXData->getAlignment() < 4)
174    SXData->setAlignment(4);
175
176  new MCSafeSEHFragment(Symbol, SXData);
177
178  getAssembler().registerSymbol(*Symbol);
179  CSymbol->setIsSafeSEH();
180
181  // The Microsoft linker requires that the symbol type of a handler be
182  // function. Go ahead and oblige it here.
183  CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
184                   << COFF::SCT_COMPLEX_TYPE_SHIFT);
185}
186
187void MCWinCOFFStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) {
188  MCDataFragment *DF = getOrCreateDataFragment();
189  const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
190  MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
191  DF->getFixups().push_back(Fixup);
192  DF->getContents().resize(DF->getContents().size() + 2, 0);
193}
194
195void MCWinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol) {
196  MCDataFragment *DF = getOrCreateDataFragment();
197  const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
198  MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_4);
199  DF->getFixups().push_back(Fixup);
200  DF->getContents().resize(DF->getContents().size() + 4, 0);
201}
202
203void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
204                                         unsigned ByteAlignment) {
205  assert((!Symbol->isInSection() ||
206          Symbol->getSection().getVariant() == MCSection::SV_COFF) &&
207         "Got non-COFF section in the COFF backend!");
208
209  const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
210  if (T.isKnownWindowsMSVCEnvironment()) {
211    if (ByteAlignment > 32)
212      report_fatal_error("alignment is limited to 32-bytes");
213
214    // Round size up to alignment so that we will honor the alignment request.
215    Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
216  }
217
218  AssignSection(Symbol, nullptr);
219
220  getAssembler().registerSymbol(*Symbol);
221  Symbol->setExternal(true);
222  Symbol->setCommon(Size, ByteAlignment);
223
224  if (!T.isKnownWindowsMSVCEnvironment() && ByteAlignment > 1) {
225    SmallString<128> Directive;
226    raw_svector_ostream OS(Directive);
227    const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
228
229    OS << " -aligncomm:\"" << Symbol->getName() << "\","
230       << Log2_32_Ceil(ByteAlignment);
231    OS.flush();
232
233    PushSection();
234    SwitchSection(MFI->getDrectveSection());
235    EmitBytes(Directive);
236    PopSection();
237  }
238}
239
240void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
241                                              unsigned ByteAlignment) {
242  assert(!Symbol->isInSection() && "Symbol must not already have a section!");
243
244  MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
245  getAssembler().registerSection(*Section);
246  if (Section->getAlignment() < ByteAlignment)
247    Section->setAlignment(ByteAlignment);
248
249  getAssembler().registerSymbol(*Symbol);
250  Symbol->setExternal(false);
251
252  AssignSection(Symbol, Section);
253
254  if (ByteAlignment != 1)
255    new MCAlignFragment(ByteAlignment, /*Value=*/0, /*ValueSize=*/0,
256                        ByteAlignment, Section);
257
258  MCFillFragment *Fragment = new MCFillFragment(
259      /*Value=*/0, /*ValueSize=*/0, Size, Section);
260  Symbol->setFragment(Fragment);
261}
262
263void MCWinCOFFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
264                                     uint64_t Size, unsigned ByteAlignment) {
265  llvm_unreachable("not implemented");
266}
267
268void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
269                                       uint64_t Size, unsigned ByteAlignment) {
270  llvm_unreachable("not implemented");
271}
272
273void MCWinCOFFStreamer::EmitFileDirective(StringRef Filename) {
274  getAssembler().addFileName(Filename);
275}
276
277// TODO: Implement this if you want to emit .comment section in COFF obj files.
278void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
279  llvm_unreachable("not implemented");
280}
281
282void MCWinCOFFStreamer::EmitWinEHHandlerData() {
283  llvm_unreachable("not implemented");
284}
285
286void MCWinCOFFStreamer::FinishImpl() {
287  MCObjectStreamer::FinishImpl();
288}
289
290LLVM_ATTRIBUTE_NORETURN
291void MCWinCOFFStreamer::FatalError(const Twine &Msg) const {
292  getContext().reportFatalError(SMLoc(), Msg);
293}
294}
295
296