1 //
2 // The LLVM Compiler Infrastructure
3 //
4 // This file is distributed under the University of Illinois Open Source
5 // License. See LICENSE.TXT for details.
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "llvm/MC/MCStreamer.h"
10
11 #include "llvm/MC/MCAssembler.h"
12 #include "llvm/MC/MCContext.h"
13 #include "llvm/MC/MCCodeEmitter.h"
14 #include "llvm/MC/MCExpr.h"
15 #include "llvm/MC/MCInst.h"
16 #include "llvm/MC/MCObjectStreamer.h"
17 #include "llvm/MC/MCSection.h"
18 #include "llvm/MC/MCSymbol.h"
19 #include "llvm/MC/MCMachOSymbolFlags.h"
20 #include "llvm/MC/MCSectionMachO.h"
21 #include "llvm/MC/MCDwarf.h"
22 #include "llvm/MC/MCAsmBackend.h"
23 #include "llvm/Support/Dwarf.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/raw_ostream.h"
26
27 using namespace llvm;
28
29 namespace {
30
31 class MCMachOStreamer : public MCObjectStreamer {
32 private:
33 virtual void EmitInstToData(const MCInst &Inst);
34
35 void EmitDataRegion(DataRegionData::KindTy Kind);
36 void EmitDataRegionEnd();
37 public:
MCMachOStreamer(MCContext & Context,MCAsmBackend & MAB,raw_ostream & OS,MCCodeEmitter * Emitter)38 MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
39 raw_ostream &OS, MCCodeEmitter *Emitter)
40 : MCObjectStreamer(Context, MAB, OS, Emitter) {}
41
42 /// @name MCStreamer Interface
43 /// @{
44
45 virtual void InitSections();
46 virtual void EmitLabel(MCSymbol *Symbol);
47 virtual void EmitEHSymAttributes(const MCSymbol *Symbol,
48 MCSymbol *EHSymbol);
49 virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
50 virtual void EmitDataRegion(MCDataRegionType Kind);
51 virtual void EmitThumbFunc(MCSymbol *Func);
52 virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
53 virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
54 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
55 virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
56 unsigned ByteAlignment);
BeginCOFFSymbolDef(const MCSymbol * Symbol)57 virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
58 llvm_unreachable("macho doesn't support this directive");
59 }
EmitCOFFSymbolStorageClass(int StorageClass)60 virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
61 llvm_unreachable("macho doesn't support this directive");
62 }
EmitCOFFSymbolType(int Type)63 virtual void EmitCOFFSymbolType(int Type) {
64 llvm_unreachable("macho doesn't support this directive");
65 }
EndCOFFSymbolDef()66 virtual void EndCOFFSymbolDef() {
67 llvm_unreachable("macho doesn't support this directive");
68 }
EmitELFSize(MCSymbol * Symbol,const MCExpr * Value)69 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
70 llvm_unreachable("macho doesn't support this directive");
71 }
72 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
73 unsigned ByteAlignment);
74 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
75 uint64_t Size = 0, unsigned ByteAlignment = 0);
76 virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
77 uint64_t Size, unsigned ByteAlignment = 0);
78 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
79 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
80 unsigned ValueSize = 1,
81 unsigned MaxBytesToEmit = 0);
82 virtual void EmitCodeAlignment(unsigned ByteAlignment,
83 unsigned MaxBytesToEmit = 0);
84
EmitFileDirective(StringRef Filename)85 virtual void EmitFileDirective(StringRef Filename) {
86 // FIXME: Just ignore the .file; it isn't important enough to fail the
87 // entire assembly.
88
89 //report_fatal_error("unsupported directive: '.file'");
90 }
91
92 virtual void FinishImpl();
93
94 /// @}
95 };
96
97 } // end anonymous namespace.
98
InitSections()99 void MCMachOStreamer::InitSections() {
100 SwitchSection(getContext().getMachOSection("__TEXT", "__text",
101 MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
102 0, SectionKind::getText()));
103
104 }
105
EmitEHSymAttributes(const MCSymbol * Symbol,MCSymbol * EHSymbol)106 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
107 MCSymbol *EHSymbol) {
108 MCSymbolData &SD =
109 getAssembler().getOrCreateSymbolData(*Symbol);
110 if (SD.isExternal())
111 EmitSymbolAttribute(EHSymbol, MCSA_Global);
112 if (SD.getFlags() & SF_WeakDefinition)
113 EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
114 if (SD.isPrivateExtern())
115 EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
116 }
117
EmitLabel(MCSymbol * Symbol)118 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
119 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
120
121 // isSymbolLinkerVisible uses the section.
122 Symbol->setSection(*getCurrentSection());
123 // We have to create a new fragment if this is an atom defining symbol,
124 // fragments cannot span atoms.
125 if (getAssembler().isSymbolLinkerVisible(*Symbol))
126 new MCDataFragment(getCurrentSectionData());
127
128 MCObjectStreamer::EmitLabel(Symbol);
129
130 MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
131 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
132 // to clear the weak reference and weak definition bits too, but the
133 // implementation was buggy. For now we just try to match 'as', for
134 // diffability.
135 //
136 // FIXME: Cleanup this code, these bits should be emitted based on semantic
137 // properties, not on the order of definition, etc.
138 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
139 }
140
EmitDataRegion(DataRegionData::KindTy Kind)141 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
142 // Create a temporary label to mark the start of the data region.
143 MCSymbol *Start = getContext().CreateTempSymbol();
144 EmitLabel(Start);
145 // Record the region for the object writer to use.
146 DataRegionData Data = { Kind, Start, NULL };
147 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
148 Regions.push_back(Data);
149 }
150
EmitDataRegionEnd()151 void MCMachOStreamer::EmitDataRegionEnd() {
152 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
153 assert(Regions.size() && "Mismatched .end_data_region!");
154 DataRegionData &Data = Regions.back();
155 assert(Data.End == NULL && "Mismatched .end_data_region!");
156 // Create a temporary label to mark the end of the data region.
157 Data.End = getContext().CreateTempSymbol();
158 EmitLabel(Data.End);
159 }
160
EmitAssemblerFlag(MCAssemblerFlag Flag)161 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
162 // Let the target do whatever target specific stuff it needs to do.
163 getAssembler().getBackend().handleAssemblerFlag(Flag);
164 // Do any generic stuff we need to do.
165 switch (Flag) {
166 case MCAF_SyntaxUnified: return; // no-op here.
167 case MCAF_Code16: return; // Change parsing mode; no-op here.
168 case MCAF_Code32: return; // Change parsing mode; no-op here.
169 case MCAF_Code64: return; // Change parsing mode; no-op here.
170 case MCAF_SubsectionsViaSymbols:
171 getAssembler().setSubsectionsViaSymbols(true);
172 return;
173 }
174 }
175
EmitDataRegion(MCDataRegionType Kind)176 void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
177 switch (Kind) {
178 case MCDR_DataRegion:
179 EmitDataRegion(DataRegionData::Data);
180 return;
181 case MCDR_DataRegionJT8:
182 EmitDataRegion(DataRegionData::JumpTable8);
183 return;
184 case MCDR_DataRegionJT16:
185 EmitDataRegion(DataRegionData::JumpTable16);
186 return;
187 case MCDR_DataRegionJT32:
188 EmitDataRegion(DataRegionData::JumpTable32);
189 return;
190 case MCDR_DataRegionEnd:
191 EmitDataRegionEnd();
192 return;
193 }
194 }
195
EmitThumbFunc(MCSymbol * Symbol)196 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
197 // Remember that the function is a thumb function. Fixup and relocation
198 // values will need adjusted.
199 getAssembler().setIsThumbFunc(Symbol);
200
201 // Mark the thumb bit on the symbol.
202 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
203 SD.setFlags(SD.getFlags() | SF_ThumbFunc);
204 }
205
EmitAssignment(MCSymbol * Symbol,const MCExpr * Value)206 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
207 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
208 // MCObjectStreamer.
209 // FIXME: Lift context changes into super class.
210 getAssembler().getOrCreateSymbolData(*Symbol);
211 Symbol->setVariableValue(AddValueSymbols(Value));
212 }
213
EmitSymbolAttribute(MCSymbol * Symbol,MCSymbolAttr Attribute)214 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
215 MCSymbolAttr Attribute) {
216 // Indirect symbols are handled differently, to match how 'as' handles
217 // them. This makes writing matching .o files easier.
218 if (Attribute == MCSA_IndirectSymbol) {
219 // Note that we intentionally cannot use the symbol data here; this is
220 // important for matching the string table that 'as' generates.
221 IndirectSymbolData ISD;
222 ISD.Symbol = Symbol;
223 ISD.SectionData = getCurrentSectionData();
224 getAssembler().getIndirectSymbols().push_back(ISD);
225 return;
226 }
227
228 // Adding a symbol attribute always introduces the symbol, note that an
229 // important side effect of calling getOrCreateSymbolData here is to register
230 // the symbol with the assembler.
231 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
232
233 // The implementation of symbol attributes is designed to match 'as', but it
234 // leaves much to desired. It doesn't really make sense to arbitrarily add and
235 // remove flags, but 'as' allows this (in particular, see .desc).
236 //
237 // In the future it might be worth trying to make these operations more well
238 // defined.
239 switch (Attribute) {
240 case MCSA_Invalid:
241 case MCSA_ELF_TypeFunction:
242 case MCSA_ELF_TypeIndFunction:
243 case MCSA_ELF_TypeObject:
244 case MCSA_ELF_TypeTLS:
245 case MCSA_ELF_TypeCommon:
246 case MCSA_ELF_TypeNoType:
247 case MCSA_ELF_TypeGnuUniqueObject:
248 case MCSA_Hidden:
249 case MCSA_IndirectSymbol:
250 case MCSA_Internal:
251 case MCSA_Protected:
252 case MCSA_Weak:
253 case MCSA_Local:
254 llvm_unreachable("Invalid symbol attribute for Mach-O!");
255
256 case MCSA_Global:
257 SD.setExternal(true);
258 // This effectively clears the undefined lazy bit, in Darwin 'as', although
259 // it isn't very consistent because it implements this as part of symbol
260 // lookup.
261 //
262 // FIXME: Cleanup this code, these bits should be emitted based on semantic
263 // properties, not on the order of definition, etc.
264 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
265 break;
266
267 case MCSA_LazyReference:
268 // FIXME: This requires -dynamic.
269 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
270 if (Symbol->isUndefined())
271 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
272 break;
273
274 // Since .reference sets the no dead strip bit, it is equivalent to
275 // .no_dead_strip in practice.
276 case MCSA_Reference:
277 case MCSA_NoDeadStrip:
278 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
279 break;
280
281 case MCSA_SymbolResolver:
282 SD.setFlags(SD.getFlags() | SF_SymbolResolver);
283 break;
284
285 case MCSA_PrivateExtern:
286 SD.setExternal(true);
287 SD.setPrivateExtern(true);
288 break;
289
290 case MCSA_WeakReference:
291 // FIXME: This requires -dynamic.
292 if (Symbol->isUndefined())
293 SD.setFlags(SD.getFlags() | SF_WeakReference);
294 break;
295
296 case MCSA_WeakDefinition:
297 // FIXME: 'as' enforces that this is defined and global. The manual claims
298 // it has to be in a coalesced section, but this isn't enforced.
299 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
300 break;
301
302 case MCSA_WeakDefAutoPrivate:
303 SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
304 break;
305 }
306 }
307
EmitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)308 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
309 // Encode the 'desc' value into the lowest implementation defined bits.
310 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
311 "Invalid .desc value!");
312 getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
313 DescValue & SF_DescFlagsMask);
314 }
315
EmitCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)316 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
317 unsigned ByteAlignment) {
318 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
319 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
320
321 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
322 SD.setExternal(true);
323 SD.setCommon(Size, ByteAlignment);
324 }
325
EmitLocalCommonSymbol(MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)326 void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
327 unsigned ByteAlignment) {
328 // '.lcomm' is equivalent to '.zerofill'.
329 return EmitZerofill(getContext().getMachOSection("__DATA", "__bss",
330 MCSectionMachO::S_ZEROFILL,
331 0, SectionKind::getBSS()),
332 Symbol, Size, ByteAlignment);
333 }
334
EmitZerofill(const MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)335 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
336 uint64_t Size, unsigned ByteAlignment) {
337 MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
338
339 // The symbol may not be present, which only creates the section.
340 if (!Symbol)
341 return;
342
343 // FIXME: Assert that this section has the zerofill type.
344
345 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
346
347 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
348
349 // Emit an align fragment if necessary.
350 if (ByteAlignment != 1)
351 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
352
353 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
354 SD.setFragment(F);
355
356 Symbol->setSection(*Section);
357
358 // Update the maximum alignment on the zero fill section if necessary.
359 if (ByteAlignment > SectData.getAlignment())
360 SectData.setAlignment(ByteAlignment);
361 }
362
363 // This should always be called with the thread local bss section. Like the
364 // .zerofill directive this doesn't actually switch sections on us.
EmitTBSSSymbol(const MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)365 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
366 uint64_t Size, unsigned ByteAlignment) {
367 EmitZerofill(Section, Symbol, Size, ByteAlignment);
368 return;
369 }
370
EmitBytes(StringRef Data,unsigned AddrSpace)371 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
372 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
373 // MCObjectStreamer.
374 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
375 }
376
EmitValueToAlignment(unsigned ByteAlignment,int64_t Value,unsigned ValueSize,unsigned MaxBytesToEmit)377 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
378 int64_t Value, unsigned ValueSize,
379 unsigned MaxBytesToEmit) {
380 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
381 // MCObjectStreamer.
382 if (MaxBytesToEmit == 0)
383 MaxBytesToEmit = ByteAlignment;
384 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
385 getCurrentSectionData());
386
387 // Update the maximum alignment on the current section if necessary.
388 if (ByteAlignment > getCurrentSectionData()->getAlignment())
389 getCurrentSectionData()->setAlignment(ByteAlignment);
390 }
391
EmitCodeAlignment(unsigned ByteAlignment,unsigned MaxBytesToEmit)392 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
393 unsigned MaxBytesToEmit) {
394 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
395 // MCObjectStreamer.
396 if (MaxBytesToEmit == 0)
397 MaxBytesToEmit = ByteAlignment;
398 MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
399 getCurrentSectionData());
400 F->setEmitNops(true);
401
402 // Update the maximum alignment on the current section if necessary.
403 if (ByteAlignment > getCurrentSectionData()->getAlignment())
404 getCurrentSectionData()->setAlignment(ByteAlignment);
405 }
406
EmitInstToData(const MCInst & Inst)407 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
408 MCDataFragment *DF = getOrCreateDataFragment();
409
410 SmallVector<MCFixup, 4> Fixups;
411 SmallString<256> Code;
412 raw_svector_ostream VecOS(Code);
413 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
414 VecOS.flush();
415
416 // Add the fixups and data.
417 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
418 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
419 DF->addFixup(Fixups[i]);
420 }
421 DF->getContents().append(Code.begin(), Code.end());
422 }
423
FinishImpl()424 void MCMachOStreamer::FinishImpl() {
425 EmitFrames(true);
426
427 // We have to set the fragment atom associations so we can relax properly for
428 // Mach-O.
429
430 // First, scan the symbol table to build a lookup table from fragments to
431 // defining symbols.
432 DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
433 for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
434 ie = getAssembler().symbol_end(); it != ie; ++it) {
435 if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
436 it->getFragment()) {
437 // An atom defining symbol should never be internal to a fragment.
438 assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
439 DefiningSymbolMap[it->getFragment()] = it;
440 }
441 }
442
443 // Set the fragment atom associations by tracking the last seen atom defining
444 // symbol.
445 for (MCAssembler::iterator it = getAssembler().begin(),
446 ie = getAssembler().end(); it != ie; ++it) {
447 MCSymbolData *CurrentAtom = 0;
448 for (MCSectionData::iterator it2 = it->begin(),
449 ie2 = it->end(); it2 != ie2; ++it2) {
450 if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
451 CurrentAtom = SD;
452 it2->setAtom(CurrentAtom);
453 }
454 }
455
456 this->MCObjectStreamer::FinishImpl();
457 }
458
createMachOStreamer(MCContext & Context,MCAsmBackend & MAB,raw_ostream & OS,MCCodeEmitter * CE,bool RelaxAll)459 MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
460 raw_ostream &OS, MCCodeEmitter *CE,
461 bool RelaxAll) {
462 MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE);
463 if (RelaxAll)
464 S->getAssembler().setRelaxAll(true);
465 return S;
466 }
467