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/MCObjectFileInfo.h"
22 #include "llvm/MC/MCObjectStreamer.h"
23 #include "llvm/MC/MCSection.h"
24 #include "llvm/MC/MCSectionMachO.h"
25 #include "llvm/MC/MCSymbolMachO.h"
26 #include "llvm/Support/Dwarf.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/TargetRegistry.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 bool DWARFMustBeAtTheEnd;
43 bool CreatedADWARFSection;
45 /// HasSectionLabel - map of which sections have already had a non-local
46 /// label emitted to them. Used so we don't emit extraneous linker local
47 /// labels in the middle of the section.
48 DenseMap<const MCSection*, bool> HasSectionLabel;
50 void EmitInstToData(const MCInst &Inst, const MCSubtargetInfo &STI) override;
52 void EmitDataRegion(DataRegionData::KindTy Kind);
53 void EmitDataRegionEnd();
56 MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_pwrite_stream &OS,
57 MCCodeEmitter *Emitter, bool DWARFMustBeAtTheEnd, bool label)
58 : MCObjectStreamer(Context, MAB, OS, Emitter), LabelSections(label),
59 DWARFMustBeAtTheEnd(DWARFMustBeAtTheEnd), CreatedADWARFSection(false) {}
62 void reset() override {
63 HasSectionLabel.clear();
64 MCObjectStreamer::reset();
67 /// @name MCStreamer Interface
70 void ChangeSection(MCSection *Sect, const MCExpr *Subsect) override;
71 void EmitLabel(MCSymbol *Symbol) override;
72 void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
73 void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
74 void EmitLinkerOptions(ArrayRef<std::string> Options) override;
75 void EmitDataRegion(MCDataRegionType Kind) override;
76 void EmitVersionMin(MCVersionMinType Kind, unsigned Major,
77 unsigned Minor, unsigned Update) override;
78 void EmitThumbFunc(MCSymbol *Func) override;
79 bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
80 void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
81 void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
82 unsigned ByteAlignment) override;
83 void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {
84 llvm_unreachable("macho doesn't support this directive");
86 void EmitCOFFSymbolStorageClass(int StorageClass) override {
87 llvm_unreachable("macho doesn't support this directive");
89 void EmitCOFFSymbolType(int Type) override {
90 llvm_unreachable("macho doesn't support this directive");
92 void EndCOFFSymbolDef() override {
93 llvm_unreachable("macho doesn't support this directive");
95 void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
96 unsigned ByteAlignment) override;
97 void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
98 uint64_t Size = 0, unsigned ByteAlignment = 0) override;
99 void EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, uint64_t Size,
100 unsigned ByteAlignment = 0) override;
102 void EmitFileDirective(StringRef Filename) override {
103 // FIXME: Just ignore the .file; it isn't important enough to fail the
106 // report_fatal_error("unsupported directive: '.file'");
109 void EmitIdent(StringRef IdentString) override {
110 llvm_unreachable("macho doesn't support this directive");
113 void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override {
114 getAssembler().getLOHContainer().addDirective(Kind, Args);
117 void FinishImpl() override;
120 } // end anonymous namespace.
122 static bool canGoAfterDWARF(const MCSectionMachO &MSec) {
123 // These sections are created by the assembler itself after the end of
125 StringRef SegName = MSec.getSegmentName();
126 StringRef SecName = MSec.getSectionName();
128 if (SegName == "__LD" && SecName == "__compact_unwind")
131 if (SegName == "__IMPORT") {
132 if (SecName == "__jump_table")
135 if (SecName == "__pointers")
139 if (SegName == "__TEXT" && SecName == "__eh_frame")
142 if (SegName == "__DATA" && SecName == "__nl_symbol_ptr")
148 void MCMachOStreamer::ChangeSection(MCSection *Section,
149 const MCExpr *Subsection) {
150 // Change the section normally.
151 bool Created = MCObjectStreamer::changeSectionImpl(Section, Subsection);
152 const MCSectionMachO &MSec = *cast<MCSectionMachO>(Section);
153 StringRef SegName = MSec.getSegmentName();
154 if (SegName == "__DWARF")
155 CreatedADWARFSection = true;
156 else if (Created && DWARFMustBeAtTheEnd && !canGoAfterDWARF(MSec))
157 assert(!CreatedADWARFSection && "Creating regular section after DWARF");
159 // Output a linker-local symbol so we don't need section-relative local
160 // relocations. The linker hates us when we do that.
161 if (LabelSections && !HasSectionLabel[Section] &&
162 !Section->getBeginSymbol()) {
163 MCSymbol *Label = getContext().createLinkerPrivateTempSymbol();
164 Section->setBeginSymbol(Label);
165 HasSectionLabel[Section] = true;
169 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
170 MCSymbol *EHSymbol) {
171 getAssembler().registerSymbol(*Symbol);
172 if (Symbol->isExternal())
173 EmitSymbolAttribute(EHSymbol, MCSA_Global);
174 if (cast<MCSymbolMachO>(Symbol)->isWeakDefinition())
175 EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
176 if (Symbol->isPrivateExtern())
177 EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
180 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
181 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
183 // We have to create a new fragment if this is an atom defining symbol,
184 // fragments cannot span atoms.
185 if (getAssembler().isSymbolLinkerVisible(*Symbol))
186 insert(new MCDataFragment());
188 MCObjectStreamer::EmitLabel(Symbol);
190 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
191 // to clear the weak reference and weak definition bits too, but the
192 // implementation was buggy. For now we just try to match 'as', for
195 // FIXME: Cleanup this code, these bits should be emitted based on semantic
196 // properties, not on the order of definition, etc.
197 cast<MCSymbolMachO>(Symbol)->clearReferenceType();
200 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
201 if (!getAssembler().getBackend().hasDataInCodeSupport())
203 // Create a temporary label to mark the start of the data region.
204 MCSymbol *Start = getContext().createTempSymbol();
206 // Record the region for the object writer to use.
207 DataRegionData Data = { Kind, Start, nullptr };
208 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
209 Regions.push_back(Data);
212 void MCMachOStreamer::EmitDataRegionEnd() {
213 if (!getAssembler().getBackend().hasDataInCodeSupport())
215 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
216 assert(!Regions.empty() && "Mismatched .end_data_region!");
217 DataRegionData &Data = Regions.back();
218 assert(!Data.End && "Mismatched .end_data_region!");
219 // Create a temporary label to mark the end of the data region.
220 Data.End = getContext().createTempSymbol();
224 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
225 // Let the target do whatever target specific stuff it needs to do.
226 getAssembler().getBackend().handleAssemblerFlag(Flag);
227 // Do any generic stuff we need to do.
229 case MCAF_SyntaxUnified: return; // no-op here.
230 case MCAF_Code16: return; // Change parsing mode; no-op here.
231 case MCAF_Code32: return; // Change parsing mode; no-op here.
232 case MCAF_Code64: return; // Change parsing mode; no-op here.
233 case MCAF_SubsectionsViaSymbols:
234 getAssembler().setSubsectionsViaSymbols(true);
239 void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
240 getAssembler().getLinkerOptions().push_back(Options);
243 void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
245 case MCDR_DataRegion:
246 EmitDataRegion(DataRegionData::Data);
248 case MCDR_DataRegionJT8:
249 EmitDataRegion(DataRegionData::JumpTable8);
251 case MCDR_DataRegionJT16:
252 EmitDataRegion(DataRegionData::JumpTable16);
254 case MCDR_DataRegionJT32:
255 EmitDataRegion(DataRegionData::JumpTable32);
257 case MCDR_DataRegionEnd:
263 void MCMachOStreamer::EmitVersionMin(MCVersionMinType Kind, unsigned Major,
264 unsigned Minor, unsigned Update) {
265 getAssembler().setVersionMinInfo(Kind, Major, Minor, Update);
268 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
269 // Remember that the function is a thumb function. Fixup and relocation
270 // values will need adjusted.
271 getAssembler().setIsThumbFunc(Symbol);
272 cast<MCSymbolMachO>(Symbol)->setThumbFunc();
275 bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Sym,
276 MCSymbolAttr Attribute) {
277 MCSymbolMachO *Symbol = cast<MCSymbolMachO>(Sym);
279 // Indirect symbols are handled differently, to match how 'as' handles
280 // them. This makes writing matching .o files easier.
281 if (Attribute == MCSA_IndirectSymbol) {
282 // Note that we intentionally cannot use the symbol data here; this is
283 // important for matching the string table that 'as' generates.
284 IndirectSymbolData ISD;
286 ISD.Section = getCurrentSectionOnly();
287 getAssembler().getIndirectSymbols().push_back(ISD);
291 // Adding a symbol attribute always introduces the symbol, note that an
292 // important side effect of calling registerSymbol here is to register
293 // the symbol with the assembler.
294 getAssembler().registerSymbol(*Symbol);
296 // The implementation of symbol attributes is designed to match 'as', but it
297 // leaves much to desired. It doesn't really make sense to arbitrarily add and
298 // remove flags, but 'as' allows this (in particular, see .desc).
300 // In the future it might be worth trying to make these operations more well
304 case MCSA_ELF_TypeFunction:
305 case MCSA_ELF_TypeIndFunction:
306 case MCSA_ELF_TypeObject:
307 case MCSA_ELF_TypeTLS:
308 case MCSA_ELF_TypeCommon:
309 case MCSA_ELF_TypeNoType:
310 case MCSA_ELF_TypeGnuUniqueObject:
312 case MCSA_IndirectSymbol:
320 Symbol->setExternal(true);
321 // This effectively clears the undefined lazy bit, in Darwin 'as', although
322 // it isn't very consistent because it implements this as part of symbol
325 // FIXME: Cleanup this code, these bits should be emitted based on semantic
326 // properties, not on the order of definition, etc.
327 Symbol->setReferenceTypeUndefinedLazy(false);
330 case MCSA_LazyReference:
331 // FIXME: This requires -dynamic.
332 Symbol->setNoDeadStrip();
333 if (Symbol->isUndefined())
334 Symbol->setReferenceTypeUndefinedLazy(true);
337 // Since .reference sets the no dead strip bit, it is equivalent to
338 // .no_dead_strip in practice.
340 case MCSA_NoDeadStrip:
341 Symbol->setNoDeadStrip();
344 case MCSA_SymbolResolver:
345 Symbol->setSymbolResolver();
348 case MCSA_PrivateExtern:
349 Symbol->setExternal(true);
350 Symbol->setPrivateExtern(true);
353 case MCSA_WeakReference:
354 // FIXME: This requires -dynamic.
355 if (Symbol->isUndefined())
356 Symbol->setWeakReference();
359 case MCSA_WeakDefinition:
360 // FIXME: 'as' enforces that this is defined and global. The manual claims
361 // it has to be in a coalesced section, but this isn't enforced.
362 Symbol->setWeakDefinition();
365 case MCSA_WeakDefAutoPrivate:
366 Symbol->setWeakDefinition();
367 Symbol->setWeakReference();
374 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
375 // Encode the 'desc' value into the lowest implementation defined bits.
376 getAssembler().registerSymbol(*Symbol);
377 cast<MCSymbolMachO>(Symbol)->setDesc(DescValue);
380 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
381 unsigned ByteAlignment) {
382 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
383 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
385 getAssembler().registerSymbol(*Symbol);
386 Symbol->setExternal(true);
387 Symbol->setCommon(Size, ByteAlignment);
390 void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
391 unsigned ByteAlignment) {
392 // '.lcomm' is equivalent to '.zerofill'.
393 return EmitZerofill(getContext().getObjectFileInfo()->getDataBSSSection(),
394 Symbol, Size, ByteAlignment);
397 void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
398 uint64_t Size, unsigned ByteAlignment) {
399 getAssembler().registerSection(*Section);
401 // The symbol may not be present, which only creates the section.
405 // On darwin all virtual sections have zerofill type.
406 assert(Section->isVirtualSection() && "Section does not have zerofill type!");
408 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
410 getAssembler().registerSymbol(*Symbol);
412 // Emit an align fragment if necessary.
413 if (ByteAlignment != 1)
414 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, Section);
416 MCFragment *F = new MCFillFragment(0, 0, Size, Section);
417 Symbol->setFragment(F);
419 // Update the maximum alignment on the zero fill section if necessary.
420 if (ByteAlignment > Section->getAlignment())
421 Section->setAlignment(ByteAlignment);
424 // This should always be called with the thread local bss section. Like the
425 // .zerofill directive this doesn't actually switch sections on us.
426 void MCMachOStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
427 uint64_t Size, unsigned ByteAlignment) {
428 EmitZerofill(Section, Symbol, Size, ByteAlignment);
432 void MCMachOStreamer::EmitInstToData(const MCInst &Inst,
433 const MCSubtargetInfo &STI) {
434 MCDataFragment *DF = getOrCreateDataFragment();
436 SmallVector<MCFixup, 4> Fixups;
437 SmallString<256> Code;
438 raw_svector_ostream VecOS(Code);
439 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
441 // Add the fixups and data.
442 for (MCFixup &Fixup : Fixups) {
443 Fixup.setOffset(Fixup.getOffset() + DF->getContents().size());
444 DF->getFixups().push_back(Fixup);
446 DF->getContents().append(Code.begin(), Code.end());
449 void MCMachOStreamer::FinishImpl() {
450 EmitFrames(&getAssembler().getBackend());
452 // We have to set the fragment atom associations so we can relax properly for
455 // First, scan the symbol table to build a lookup table from fragments to
457 DenseMap<const MCFragment *, const MCSymbol *> DefiningSymbolMap;
458 for (const MCSymbol &Symbol : getAssembler().symbols()) {
459 if (getAssembler().isSymbolLinkerVisible(Symbol) && Symbol.isInSection() &&
460 !Symbol.isVariable()) {
461 // An atom defining symbol should never be internal to a fragment.
462 assert(Symbol.getOffset() == 0 &&
463 "Invalid offset in atom defining symbol!");
464 DefiningSymbolMap[Symbol.getFragment()] = &Symbol;
468 // Set the fragment atom associations by tracking the last seen atom defining
470 for (MCSection &Sec : getAssembler()) {
471 const MCSymbol *CurrentAtom = nullptr;
472 for (MCFragment &Frag : Sec) {
473 if (const MCSymbol *Symbol = DefiningSymbolMap.lookup(&Frag))
474 CurrentAtom = Symbol;
475 Frag.setAtom(CurrentAtom);
479 this->MCObjectStreamer::FinishImpl();
482 MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
483 raw_pwrite_stream &OS, MCCodeEmitter *CE,
484 bool RelaxAll, bool DWARFMustBeAtTheEnd,
485 bool LabelSections) {
486 MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE,
487 DWARFMustBeAtTheEnd, LabelSections);
488 const Triple &TT = Context.getObjectFileInfo()->getTargetTriple();
489 if (TT.isOSDarwin()) {
490 unsigned Major, Minor, Update;
491 TT.getOSVersion(Major, Minor, Update);
492 // If there is a version specified, Major will be non-zero.
494 MCVersionMinType VersionType;
496 VersionType = MCVM_WatchOSVersionMin;
497 else if (TT.isTvOS())
498 VersionType = MCVM_TvOSVersionMin;
499 else if (TT.isMacOSX())
500 VersionType = MCVM_OSXVersionMin;
502 assert(TT.isiOS() && "Must only be iOS platform left");
503 VersionType = MCVM_IOSVersionMin;
505 S->EmitVersionMin(VersionType, Major, Minor, Update);
509 S->getAssembler().setRelaxAll(true);