1 //===-- MCMachOStreamer.cpp - MachO Streamer ------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #include "llvm/MC/MCStreamer.h"
11 #include "llvm/ADT/DenseMap.h"
12 #include "llvm/ADT/SmallVector.h"
13 #include "llvm/MC/MCAsmBackend.h"
14 #include "llvm/MC/MCAssembler.h"
15 #include "llvm/MC/MCCodeEmitter.h"
16 #include "llvm/MC/MCContext.h"
17 #include "llvm/MC/MCDwarf.h"
18 #include "llvm/MC/MCExpr.h"
19 #include "llvm/MC/MCInst.h"
20 #include "llvm/MC/MCLinkerOptimizationHint.h"
21 #include "llvm/MC/MCMachOSymbolFlags.h"
22 #include "llvm/MC/MCObjectFileInfo.h"
23 #include "llvm/MC/MCObjectStreamer.h"
24 #include "llvm/MC/MCSection.h"
25 #include "llvm/MC/MCSectionMachO.h"
26 #include "llvm/MC/MCSymbol.h"
27 #include "llvm/Support/Dwarf.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/raw_ostream.h"
35 class MCMachOStreamer : public MCObjectStreamer {
37 /// LabelSections - true if each section change should emit a linker local
38 /// label for use in relocations for assembler local references. Obviates the
39 /// need for local relocations. False by default.
42 /// HasSectionLabel - map of which sections have already had a non-local
43 /// label emitted to them. Used so we don't emit extraneous linker local
44 /// labels in the middle of the section.
45 DenseMap<const MCSection*, bool> HasSectionLabel;
47 void EmitInstToData(const MCInst &Inst, const MCSubtargetInfo &STI) override;
49 void EmitDataRegion(DataRegionData::KindTy Kind);
50 void EmitDataRegionEnd();
53 MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_ostream &OS,
54 MCCodeEmitter *Emitter, bool label)
55 : MCObjectStreamer(Context, MAB, OS, Emitter),
56 LabelSections(label) {}
58 /// @name MCStreamer Interface
61 void ChangeSection(const MCSection *Sect, const MCExpr *Subsect) override;
62 void EmitLabel(MCSymbol *Symbol) override;
63 void EmitDebugLabel(MCSymbol *Symbol) override;
64 void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
65 void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
66 void EmitLinkerOptions(ArrayRef<std::string> Options) override;
67 void EmitDataRegion(MCDataRegionType Kind) override;
68 void EmitVersionMin(MCVersionMinType Kind, unsigned Major,
69 unsigned Minor, unsigned Update) override;
70 void EmitThumbFunc(MCSymbol *Func) override;
71 bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
72 void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
73 void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
74 unsigned ByteAlignment) override;
75 void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {
76 llvm_unreachable("macho doesn't support this directive");
78 void EmitCOFFSymbolStorageClass(int StorageClass) override {
79 llvm_unreachable("macho doesn't support this directive");
81 void EmitCOFFSymbolType(int Type) override {
82 llvm_unreachable("macho doesn't support this directive");
84 void EndCOFFSymbolDef() override {
85 llvm_unreachable("macho doesn't support this directive");
87 void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) override {
88 llvm_unreachable("macho doesn't support this directive");
90 void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
91 unsigned ByteAlignment) override;
92 void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = nullptr,
93 uint64_t Size = 0, unsigned ByteAlignment = 0) override;
94 virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
95 uint64_t Size, unsigned ByteAlignment = 0) override;
97 void EmitFileDirective(StringRef Filename) override {
98 // FIXME: Just ignore the .file; it isn't important enough to fail the
101 // report_fatal_error("unsupported directive: '.file'");
104 void EmitIdent(StringRef IdentString) override {
105 llvm_unreachable("macho doesn't support this directive");
108 void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override {
109 getAssembler().getLOHContainer().addDirective(Kind, Args);
112 void FinishImpl() override;
115 } // end anonymous namespace.
117 void MCMachOStreamer::ChangeSection(const MCSection *Section,
118 const MCExpr *Subsection) {
119 // Change the section normally.
120 MCObjectStreamer::ChangeSection(Section, Subsection);
121 // Output a linker-local symbol so we don't need section-relative local
122 // relocations. The linker hates us when we do that.
123 if (LabelSections && !HasSectionLabel[Section]) {
124 MCSymbol *Label = getContext().CreateLinkerPrivateTempSymbol();
126 HasSectionLabel[Section] = true;
130 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
131 MCSymbol *EHSymbol) {
133 getAssembler().getOrCreateSymbolData(*Symbol);
135 EmitSymbolAttribute(EHSymbol, MCSA_Global);
136 if (SD.getFlags() & SF_WeakDefinition)
137 EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
138 if (SD.isPrivateExtern())
139 EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
142 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
143 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
145 // isSymbolLinkerVisible uses the section.
146 AssignSection(Symbol, getCurrentSection().first);
147 // We have to create a new fragment if this is an atom defining symbol,
148 // fragments cannot span atoms.
149 if (getAssembler().isSymbolLinkerVisible(*Symbol))
150 insert(new MCDataFragment());
152 MCObjectStreamer::EmitLabel(Symbol);
154 MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
155 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
156 // to clear the weak reference and weak definition bits too, but the
157 // implementation was buggy. For now we just try to match 'as', for
160 // FIXME: Cleanup this code, these bits should be emitted based on semantic
161 // properties, not on the order of definition, etc.
162 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
165 void MCMachOStreamer::EmitDebugLabel(MCSymbol *Symbol) {
168 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
169 if (!getAssembler().getBackend().hasDataInCodeSupport())
171 // Create a temporary label to mark the start of the data region.
172 MCSymbol *Start = getContext().CreateTempSymbol();
174 // Record the region for the object writer to use.
175 DataRegionData Data = { Kind, Start, nullptr };
176 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
177 Regions.push_back(Data);
180 void MCMachOStreamer::EmitDataRegionEnd() {
181 if (!getAssembler().getBackend().hasDataInCodeSupport())
183 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
184 assert(Regions.size() && "Mismatched .end_data_region!");
185 DataRegionData &Data = Regions.back();
186 assert(!Data.End && "Mismatched .end_data_region!");
187 // Create a temporary label to mark the end of the data region.
188 Data.End = getContext().CreateTempSymbol();
192 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
193 // Let the target do whatever target specific stuff it needs to do.
194 getAssembler().getBackend().handleAssemblerFlag(Flag);
195 // Do any generic stuff we need to do.
197 case MCAF_SyntaxUnified: return; // no-op here.
198 case MCAF_Code16: return; // Change parsing mode; no-op here.
199 case MCAF_Code32: return; // Change parsing mode; no-op here.
200 case MCAF_Code64: return; // Change parsing mode; no-op here.
201 case MCAF_SubsectionsViaSymbols:
202 getAssembler().setSubsectionsViaSymbols(true);
207 void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
208 getAssembler().getLinkerOptions().push_back(Options);
211 void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
213 case MCDR_DataRegion:
214 EmitDataRegion(DataRegionData::Data);
216 case MCDR_DataRegionJT8:
217 EmitDataRegion(DataRegionData::JumpTable8);
219 case MCDR_DataRegionJT16:
220 EmitDataRegion(DataRegionData::JumpTable16);
222 case MCDR_DataRegionJT32:
223 EmitDataRegion(DataRegionData::JumpTable32);
225 case MCDR_DataRegionEnd:
231 void MCMachOStreamer::EmitVersionMin(MCVersionMinType Kind, unsigned Major,
232 unsigned Minor, unsigned Update) {
233 getAssembler().setVersionMinInfo(Kind, Major, Minor, Update);
236 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
237 // Remember that the function is a thumb function. Fixup and relocation
238 // values will need adjusted.
239 getAssembler().setIsThumbFunc(Symbol);
242 bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
243 MCSymbolAttr Attribute) {
244 // Indirect symbols are handled differently, to match how 'as' handles
245 // them. This makes writing matching .o files easier.
246 if (Attribute == MCSA_IndirectSymbol) {
247 // Note that we intentionally cannot use the symbol data here; this is
248 // important for matching the string table that 'as' generates.
249 IndirectSymbolData ISD;
251 ISD.SectionData = getCurrentSectionData();
252 getAssembler().getIndirectSymbols().push_back(ISD);
256 // Adding a symbol attribute always introduces the symbol, note that an
257 // important side effect of calling getOrCreateSymbolData here is to register
258 // the symbol with the assembler.
259 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
261 // The implementation of symbol attributes is designed to match 'as', but it
262 // leaves much to desired. It doesn't really make sense to arbitrarily add and
263 // remove flags, but 'as' allows this (in particular, see .desc).
265 // In the future it might be worth trying to make these operations more well
269 case MCSA_ELF_TypeFunction:
270 case MCSA_ELF_TypeIndFunction:
271 case MCSA_ELF_TypeObject:
272 case MCSA_ELF_TypeTLS:
273 case MCSA_ELF_TypeCommon:
274 case MCSA_ELF_TypeNoType:
275 case MCSA_ELF_TypeGnuUniqueObject:
277 case MCSA_IndirectSymbol:
285 SD.setExternal(true);
286 // This effectively clears the undefined lazy bit, in Darwin 'as', although
287 // it isn't very consistent because it implements this as part of symbol
290 // FIXME: Cleanup this code, these bits should be emitted based on semantic
291 // properties, not on the order of definition, etc.
292 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
295 case MCSA_LazyReference:
296 // FIXME: This requires -dynamic.
297 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
298 if (Symbol->isUndefined())
299 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
302 // Since .reference sets the no dead strip bit, it is equivalent to
303 // .no_dead_strip in practice.
305 case MCSA_NoDeadStrip:
306 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
309 case MCSA_SymbolResolver:
310 SD.setFlags(SD.getFlags() | SF_SymbolResolver);
313 case MCSA_PrivateExtern:
314 SD.setExternal(true);
315 SD.setPrivateExtern(true);
318 case MCSA_WeakReference:
319 // FIXME: This requires -dynamic.
320 if (Symbol->isUndefined())
321 SD.setFlags(SD.getFlags() | SF_WeakReference);
324 case MCSA_WeakDefinition:
325 // FIXME: 'as' enforces that this is defined and global. The manual claims
326 // it has to be in a coalesced section, but this isn't enforced.
327 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
330 case MCSA_WeakDefAutoPrivate:
331 SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
338 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
339 // Encode the 'desc' value into the lowest implementation defined bits.
340 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
341 "Invalid .desc value!");
342 getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
343 DescValue & SF_DescFlagsMask);
346 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
347 unsigned ByteAlignment) {
348 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
349 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
351 AssignSection(Symbol, nullptr);
353 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
354 SD.setExternal(true);
355 SD.setCommon(Size, ByteAlignment);
358 void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
359 unsigned ByteAlignment) {
360 // '.lcomm' is equivalent to '.zerofill'.
361 return EmitZerofill(getContext().getObjectFileInfo()->getDataBSSSection(),
362 Symbol, Size, ByteAlignment);
365 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
366 uint64_t Size, unsigned ByteAlignment) {
367 MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
369 // The symbol may not be present, which only creates the section.
373 // On darwin all virtual sections have zerofill type.
374 assert(Section->isVirtualSection() && "Section does not have zerofill type!");
376 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
378 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
380 // Emit an align fragment if necessary.
381 if (ByteAlignment != 1)
382 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
384 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
387 AssignSection(Symbol, Section);
389 // Update the maximum alignment on the zero fill section if necessary.
390 if (ByteAlignment > SectData.getAlignment())
391 SectData.setAlignment(ByteAlignment);
394 // This should always be called with the thread local bss section. Like the
395 // .zerofill directive this doesn't actually switch sections on us.
396 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
397 uint64_t Size, unsigned ByteAlignment) {
398 EmitZerofill(Section, Symbol, Size, ByteAlignment);
402 void MCMachOStreamer::EmitInstToData(const MCInst &Inst,
403 const MCSubtargetInfo &STI) {
404 MCDataFragment *DF = getOrCreateDataFragment();
406 SmallVector<MCFixup, 4> Fixups;
407 SmallString<256> Code;
408 raw_svector_ostream VecOS(Code);
409 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups, STI);
412 // Add the fixups and data.
413 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
414 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
415 DF->getFixups().push_back(Fixups[i]);
417 DF->getContents().append(Code.begin(), Code.end());
420 void MCMachOStreamer::FinishImpl() {
421 EmitFrames(&getAssembler().getBackend(), true);
423 // We have to set the fragment atom associations so we can relax properly for
426 // First, scan the symbol table to build a lookup table from fragments to
428 DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
429 for (MCSymbolData &SD : getAssembler().symbols()) {
430 if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()) &&
432 // An atom defining symbol should never be internal to a fragment.
433 assert(SD.getOffset() == 0 && "Invalid offset in atom defining symbol!");
434 DefiningSymbolMap[SD.getFragment()] = &SD;
438 // Set the fragment atom associations by tracking the last seen atom defining
440 for (MCAssembler::iterator it = getAssembler().begin(),
441 ie = getAssembler().end(); it != ie; ++it) {
442 MCSymbolData *CurrentAtom = nullptr;
443 for (MCSectionData::iterator it2 = it->begin(),
444 ie2 = it->end(); it2 != ie2; ++it2) {
445 if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
447 it2->setAtom(CurrentAtom);
451 this->MCObjectStreamer::FinishImpl();
454 MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
455 raw_ostream &OS, MCCodeEmitter *CE,
457 bool LabelSections) {
458 MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE, LabelSections);
460 S->getAssembler().setRelaxAll(true);