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 EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
64 void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
65 void EmitLinkerOptions(ArrayRef<std::string> Options) override;
66 void EmitDataRegion(MCDataRegionType Kind) override;
67 void EmitVersionMin(MCVersionMinType Kind, unsigned Major,
68 unsigned Minor, unsigned Update) override;
69 void EmitThumbFunc(MCSymbol *Func) override;
70 bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
71 void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
72 void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
73 unsigned ByteAlignment) override;
74 void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {
75 llvm_unreachable("macho doesn't support this directive");
77 void EmitCOFFSymbolStorageClass(int StorageClass) override {
78 llvm_unreachable("macho doesn't support this directive");
80 void EmitCOFFSymbolType(int Type) override {
81 llvm_unreachable("macho doesn't support this directive");
83 void EndCOFFSymbolDef() override {
84 llvm_unreachable("macho doesn't support this directive");
86 void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) override {
87 llvm_unreachable("macho doesn't support this directive");
89 void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
90 unsigned ByteAlignment) override;
91 void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = nullptr,
92 uint64_t Size = 0, unsigned ByteAlignment = 0) override;
93 void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol, uint64_t Size,
94 unsigned ByteAlignment = 0) override;
96 void EmitFileDirective(StringRef Filename) override {
97 // FIXME: Just ignore the .file; it isn't important enough to fail the
100 // report_fatal_error("unsupported directive: '.file'");
103 void EmitIdent(StringRef IdentString) override {
104 llvm_unreachable("macho doesn't support this directive");
107 void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override {
108 getAssembler().getLOHContainer().addDirective(Kind, Args);
111 void FinishImpl() override;
114 } // end anonymous namespace.
116 void MCMachOStreamer::ChangeSection(const MCSection *Section,
117 const MCExpr *Subsection) {
118 // Change the section normally.
119 MCObjectStreamer::ChangeSection(Section, Subsection);
120 // Output a linker-local symbol so we don't need section-relative local
121 // relocations. The linker hates us when we do that.
122 if (LabelSections && !HasSectionLabel[Section]) {
123 MCSymbol *Label = getContext().CreateLinkerPrivateTempSymbol();
125 HasSectionLabel[Section] = true;
129 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
130 MCSymbol *EHSymbol) {
132 getAssembler().getOrCreateSymbolData(*Symbol);
134 EmitSymbolAttribute(EHSymbol, MCSA_Global);
135 if (SD.getFlags() & SF_WeakDefinition)
136 EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
137 if (SD.isPrivateExtern())
138 EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
141 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
142 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
144 // isSymbolLinkerVisible uses the section.
145 AssignSection(Symbol, getCurrentSection().first);
146 // We have to create a new fragment if this is an atom defining symbol,
147 // fragments cannot span atoms.
148 if (getAssembler().isSymbolLinkerVisible(*Symbol))
149 insert(new MCDataFragment());
151 MCObjectStreamer::EmitLabel(Symbol);
153 MCSymbolData &SD = getAssembler().getSymbolData(*Symbol);
154 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
155 // to clear the weak reference and weak definition bits too, but the
156 // implementation was buggy. For now we just try to match 'as', for
159 // FIXME: Cleanup this code, these bits should be emitted based on semantic
160 // properties, not on the order of definition, etc.
161 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
164 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
165 if (!getAssembler().getBackend().hasDataInCodeSupport())
167 // Create a temporary label to mark the start of the data region.
168 MCSymbol *Start = getContext().CreateTempSymbol();
170 // Record the region for the object writer to use.
171 DataRegionData Data = { Kind, Start, nullptr };
172 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
173 Regions.push_back(Data);
176 void MCMachOStreamer::EmitDataRegionEnd() {
177 if (!getAssembler().getBackend().hasDataInCodeSupport())
179 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
180 assert(Regions.size() && "Mismatched .end_data_region!");
181 DataRegionData &Data = Regions.back();
182 assert(!Data.End && "Mismatched .end_data_region!");
183 // Create a temporary label to mark the end of the data region.
184 Data.End = getContext().CreateTempSymbol();
188 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
189 // Let the target do whatever target specific stuff it needs to do.
190 getAssembler().getBackend().handleAssemblerFlag(Flag);
191 // Do any generic stuff we need to do.
193 case MCAF_SyntaxUnified: return; // no-op here.
194 case MCAF_Code16: return; // Change parsing mode; no-op here.
195 case MCAF_Code32: return; // Change parsing mode; no-op here.
196 case MCAF_Code64: return; // Change parsing mode; no-op here.
197 case MCAF_SubsectionsViaSymbols:
198 getAssembler().setSubsectionsViaSymbols(true);
203 void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
204 getAssembler().getLinkerOptions().push_back(Options);
207 void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
209 case MCDR_DataRegion:
210 EmitDataRegion(DataRegionData::Data);
212 case MCDR_DataRegionJT8:
213 EmitDataRegion(DataRegionData::JumpTable8);
215 case MCDR_DataRegionJT16:
216 EmitDataRegion(DataRegionData::JumpTable16);
218 case MCDR_DataRegionJT32:
219 EmitDataRegion(DataRegionData::JumpTable32);
221 case MCDR_DataRegionEnd:
227 void MCMachOStreamer::EmitVersionMin(MCVersionMinType Kind, unsigned Major,
228 unsigned Minor, unsigned Update) {
229 getAssembler().setVersionMinInfo(Kind, Major, Minor, Update);
232 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
233 // Remember that the function is a thumb function. Fixup and relocation
234 // values will need adjusted.
235 getAssembler().setIsThumbFunc(Symbol);
238 bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
239 MCSymbolAttr Attribute) {
240 // Indirect symbols are handled differently, to match how 'as' handles
241 // them. This makes writing matching .o files easier.
242 if (Attribute == MCSA_IndirectSymbol) {
243 // Note that we intentionally cannot use the symbol data here; this is
244 // important for matching the string table that 'as' generates.
245 IndirectSymbolData ISD;
247 ISD.SectionData = getCurrentSectionData();
248 getAssembler().getIndirectSymbols().push_back(ISD);
252 // Adding a symbol attribute always introduces the symbol, note that an
253 // important side effect of calling getOrCreateSymbolData here is to register
254 // the symbol with the assembler.
255 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
257 // The implementation of symbol attributes is designed to match 'as', but it
258 // leaves much to desired. It doesn't really make sense to arbitrarily add and
259 // remove flags, but 'as' allows this (in particular, see .desc).
261 // In the future it might be worth trying to make these operations more well
265 case MCSA_ELF_TypeFunction:
266 case MCSA_ELF_TypeIndFunction:
267 case MCSA_ELF_TypeObject:
268 case MCSA_ELF_TypeTLS:
269 case MCSA_ELF_TypeCommon:
270 case MCSA_ELF_TypeNoType:
271 case MCSA_ELF_TypeGnuUniqueObject:
273 case MCSA_IndirectSymbol:
281 SD.setExternal(true);
282 // This effectively clears the undefined lazy bit, in Darwin 'as', although
283 // it isn't very consistent because it implements this as part of symbol
286 // FIXME: Cleanup this code, these bits should be emitted based on semantic
287 // properties, not on the order of definition, etc.
288 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
291 case MCSA_LazyReference:
292 // FIXME: This requires -dynamic.
293 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
294 if (Symbol->isUndefined())
295 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
298 // Since .reference sets the no dead strip bit, it is equivalent to
299 // .no_dead_strip in practice.
301 case MCSA_NoDeadStrip:
302 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
305 case MCSA_SymbolResolver:
306 SD.setFlags(SD.getFlags() | SF_SymbolResolver);
309 case MCSA_PrivateExtern:
310 SD.setExternal(true);
311 SD.setPrivateExtern(true);
314 case MCSA_WeakReference:
315 // FIXME: This requires -dynamic.
316 if (Symbol->isUndefined())
317 SD.setFlags(SD.getFlags() | SF_WeakReference);
320 case MCSA_WeakDefinition:
321 // FIXME: 'as' enforces that this is defined and global. The manual claims
322 // it has to be in a coalesced section, but this isn't enforced.
323 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
326 case MCSA_WeakDefAutoPrivate:
327 SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
334 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
335 // Encode the 'desc' value into the lowest implementation defined bits.
336 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
337 "Invalid .desc value!");
338 getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
339 DescValue & SF_DescFlagsMask);
342 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
343 unsigned ByteAlignment) {
344 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
345 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
347 AssignSection(Symbol, nullptr);
349 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
350 SD.setExternal(true);
351 SD.setCommon(Size, ByteAlignment);
354 void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
355 unsigned ByteAlignment) {
356 // '.lcomm' is equivalent to '.zerofill'.
357 return EmitZerofill(getContext().getObjectFileInfo()->getDataBSSSection(),
358 Symbol, Size, ByteAlignment);
361 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
362 uint64_t Size, unsigned ByteAlignment) {
363 MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
365 // The symbol may not be present, which only creates the section.
369 // On darwin all virtual sections have zerofill type.
370 assert(Section->isVirtualSection() && "Section does not have zerofill type!");
372 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
374 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
376 // Emit an align fragment if necessary.
377 if (ByteAlignment != 1)
378 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
380 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
383 AssignSection(Symbol, Section);
385 // Update the maximum alignment on the zero fill section if necessary.
386 if (ByteAlignment > SectData.getAlignment())
387 SectData.setAlignment(ByteAlignment);
390 // This should always be called with the thread local bss section. Like the
391 // .zerofill directive this doesn't actually switch sections on us.
392 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
393 uint64_t Size, unsigned ByteAlignment) {
394 EmitZerofill(Section, Symbol, Size, ByteAlignment);
398 void MCMachOStreamer::EmitInstToData(const MCInst &Inst,
399 const MCSubtargetInfo &STI) {
400 MCDataFragment *DF = getOrCreateDataFragment();
402 SmallVector<MCFixup, 4> Fixups;
403 SmallString<256> Code;
404 raw_svector_ostream VecOS(Code);
405 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups, STI);
408 // Add the fixups and data.
409 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
410 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
411 DF->getFixups().push_back(Fixups[i]);
413 DF->getContents().append(Code.begin(), Code.end());
416 void MCMachOStreamer::FinishImpl() {
417 EmitFrames(&getAssembler().getBackend());
419 // We have to set the fragment atom associations so we can relax properly for
422 // First, scan the symbol table to build a lookup table from fragments to
424 DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
425 for (MCSymbolData &SD : getAssembler().symbols()) {
426 if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()) &&
428 // An atom defining symbol should never be internal to a fragment.
429 assert(SD.getOffset() == 0 && "Invalid offset in atom defining symbol!");
430 DefiningSymbolMap[SD.getFragment()] = &SD;
434 // Set the fragment atom associations by tracking the last seen atom defining
436 for (MCAssembler::iterator it = getAssembler().begin(),
437 ie = getAssembler().end(); it != ie; ++it) {
438 MCSymbolData *CurrentAtom = nullptr;
439 for (MCSectionData::iterator it2 = it->begin(),
440 ie2 = it->end(); it2 != ie2; ++it2) {
441 if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
443 it2->setAtom(CurrentAtom);
447 this->MCObjectStreamer::FinishImpl();
450 MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
451 raw_ostream &OS, MCCodeEmitter *CE,
453 bool LabelSections) {
454 MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE, LabelSections);
456 S->getAssembler().setRelaxAll(true);