WinCOFFStreamer.cpp revision de2d8694e25a814696358e95141f4b1aa4d8847e 
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
53  // Add the fixups and data.
54  for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
55    Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
56    DF->getFixups().push_back(Fixups[i]);
57  }
58
59  DF->getContents().append(Code.begin(), Code.end());
60}
61
62void MCWinCOFFStreamer::InitSections(bool NoExecStack) {
63  // FIXME: this is identical to the ELF one.
64  // This emulates the same behavior of GNU as. This makes it easier
65  // to compare the output as the major sections are in the same order.
66  SwitchSection(getContext().getObjectFileInfo()->getTextSection());
67  EmitCodeAlignment(4);
68
69  SwitchSection(getContext().getObjectFileInfo()->getDataSection());
70  EmitCodeAlignment(4);
71
72  SwitchSection(getContext().getObjectFileInfo()->getBSSSection());
73  EmitCodeAlignment(4);
74
75  SwitchSection(getContext().getObjectFileInfo()->getTextSection());
76}
77
78void MCWinCOFFStreamer::EmitLabel(MCSymbol *S) {
79  auto *Symbol = cast<MCSymbolCOFF>(S);
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 *S,
93                                            MCSymbolAttr Attribute) {
94  auto *Symbol = cast<MCSymbolCOFF>(S);
95  getAssembler().registerSymbol(*Symbol);
96
97  switch (Attribute) {
98  default: return false;
99  case MCSA_WeakReference:
100  case MCSA_Weak:
101    Symbol->setIsWeakExternal();
102    Symbol->setExternal(true);
103    break;
104  case MCSA_Global:
105    Symbol->setExternal(true);
106    break;
107  case MCSA_AltEntry:
108    llvm_unreachable("COFF doesn't support the .alt_entry attribute");
109  }
110
111  return true;
112}
113
114void MCWinCOFFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
115  llvm_unreachable("not implemented");
116}
117
118void MCWinCOFFStreamer::BeginCOFFSymbolDef(MCSymbol const *S) {
119  auto *Symbol = cast<MCSymbolCOFF>(S);
120  if (CurSymbol)
121    Error("starting a new symbol definition without completing the "
122          "previous one");
123  CurSymbol = Symbol;
124}
125
126void MCWinCOFFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
127  if (!CurSymbol) {
128    Error("storage class specified outside of symbol definition");
129    return;
130  }
131
132  if (StorageClass & ~COFF::SSC_Invalid) {
133    Error("storage class value '" + Twine(StorageClass) +
134               "' out of range");
135    return;
136  }
137
138  getAssembler().registerSymbol(*CurSymbol);
139  cast<MCSymbolCOFF>(CurSymbol)->setClass((uint16_t)StorageClass);
140}
141
142void MCWinCOFFStreamer::EmitCOFFSymbolType(int Type) {
143  if (!CurSymbol) {
144    Error("symbol type specified outside of a symbol definition");
145    return;
146  }
147
148  if (Type & ~0xffff) {
149    Error("type value '" + Twine(Type) + "' out of range");
150    return;
151  }
152
153  getAssembler().registerSymbol(*CurSymbol);
154  cast<MCSymbolCOFF>(CurSymbol)->setType((uint16_t)Type);
155}
156
157void MCWinCOFFStreamer::EndCOFFSymbolDef() {
158  if (!CurSymbol)
159    Error("ending symbol definition without starting one");
160  CurSymbol = nullptr;
161}
162
163void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
164  // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
165  // unnecessary) on all platforms which use table-based exception dispatch.
166  if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
167      Triple::x86)
168    return;
169
170  const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
171  if (CSymbol->isSafeSEH())
172    return;
173
174  MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
175  getAssembler().registerSection(*SXData);
176  if (SXData->getAlignment() < 4)
177    SXData->setAlignment(4);
178
179  new MCSafeSEHFragment(Symbol, SXData);
180
181  getAssembler().registerSymbol(*Symbol);
182  CSymbol->setIsSafeSEH();
183
184  // The Microsoft linker requires that the symbol type of a handler be
185  // function. Go ahead and oblige it here.
186  CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
187                   << COFF::SCT_COMPLEX_TYPE_SHIFT);
188}
189
190void MCWinCOFFStreamer::EmitCOFFSectionIndex(MCSymbol const *Symbol) {
191  MCDataFragment *DF = getOrCreateDataFragment();
192  const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
193  MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_2);
194  DF->getFixups().push_back(Fixup);
195  DF->getContents().resize(DF->getContents().size() + 2, 0);
196}
197
198void MCWinCOFFStreamer::EmitCOFFSecRel32(MCSymbol const *Symbol) {
199  MCDataFragment *DF = getOrCreateDataFragment();
200  const MCSymbolRefExpr *SRE = MCSymbolRefExpr::create(Symbol, getContext());
201  MCFixup Fixup = MCFixup::create(DF->getContents().size(), SRE, FK_SecRel_4);
202  DF->getFixups().push_back(Fixup);
203  DF->getContents().resize(DF->getContents().size() + 4, 0);
204}
205
206void MCWinCOFFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
207                                         unsigned ByteAlignment) {
208  auto *Symbol = cast<MCSymbolCOFF>(S);
209
210  const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
211  if (T.isKnownWindowsMSVCEnvironment()) {
212    if (ByteAlignment > 32)
213      report_fatal_error("alignment is limited to 32-bytes");
214
215    // Round size up to alignment so that we will honor the alignment request.
216    Size = std::max(Size, static_cast<uint64_t>(ByteAlignment));
217  }
218
219  getAssembler().registerSymbol(*Symbol);
220  Symbol->setExternal(true);
221  Symbol->setCommon(Size, ByteAlignment);
222
223  if (!T.isKnownWindowsMSVCEnvironment() && ByteAlignment > 1) {
224    SmallString<128> Directive;
225    raw_svector_ostream OS(Directive);
226    const MCObjectFileInfo *MFI = getContext().getObjectFileInfo();
227
228    OS << " -aligncomm:\"" << Symbol->getName() << "\","
229       << Log2_32_Ceil(ByteAlignment);
230
231    PushSection();
232    SwitchSection(MFI->getDrectveSection());
233    EmitBytes(Directive);
234    PopSection();
235  }
236}
237
238void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
239                                              unsigned ByteAlignment) {
240  auto *Symbol = cast<MCSymbolCOFF>(S);
241
242  MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
243  getAssembler().registerSection(*Section);
244  if (Section->getAlignment() < ByteAlignment)
245    Section->setAlignment(ByteAlignment);
246
247  getAssembler().registerSymbol(*Symbol);
248  Symbol->setExternal(false);
249
250  if (ByteAlignment != 1)
251    new MCAlignFragment(ByteAlignment, /*Value=*/0, /*ValueSize=*/0,
252                        ByteAlignment, Section);
253
254  MCFillFragment *Fragment = new MCFillFragment(
255      /*Value=*/0, Size, Section);
256  Symbol->setFragment(Fragment);
257}
258
259void MCWinCOFFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
260                                     uint64_t Size, unsigned ByteAlignment) {
261  llvm_unreachable("not implemented");
262}
263
264void MCWinCOFFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
265                                       uint64_t Size, unsigned ByteAlignment) {
266  llvm_unreachable("not implemented");
267}
268
269void MCWinCOFFStreamer::EmitFileDirective(StringRef Filename) {
270  getAssembler().addFileName(Filename);
271}
272
273// TODO: Implement this if you want to emit .comment section in COFF obj files.
274void MCWinCOFFStreamer::EmitIdent(StringRef IdentString) {
275  llvm_unreachable("not implemented");
276}
277
278void MCWinCOFFStreamer::EmitWinEHHandlerData() {
279  llvm_unreachable("not implemented");
280}
281
282void MCWinCOFFStreamer::FinishImpl() {
283  MCObjectStreamer::FinishImpl();
284}
285
286void MCWinCOFFStreamer::Error(const Twine &Msg) const {
287  getContext().reportError(SMLoc(), Msg);
288}
289}
290
291