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