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 CreatedADWARFSection = false;
64 HasSectionLabel.clear();
65 MCObjectStreamer::reset();
68 /// @name MCStreamer Interface
71 void ChangeSection(MCSection *Sect, const MCExpr *Subsect) override;
72 void EmitLabel(MCSymbol *Symbol) override;
73 void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
74 void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
75 void EmitLinkerOptions(ArrayRef<std::string> Options) override;
76 void EmitDataRegion(MCDataRegionType Kind) override;
77 void EmitVersionMin(MCVersionMinType Kind, unsigned Major,
78 unsigned Minor, unsigned Update) override;
79 void EmitThumbFunc(MCSymbol *Func) override;
80 bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
81 void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
82 void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
83 unsigned ByteAlignment) override;
84 void BeginCOFFSymbolDef(const MCSymbol *Symbol) override {
85 llvm_unreachable("macho doesn't support this directive");
87 void EmitCOFFSymbolStorageClass(int StorageClass) override {
88 llvm_unreachable("macho doesn't support this directive");
90 void EmitCOFFSymbolType(int Type) override {
91 llvm_unreachable("macho doesn't support this directive");
93 void EndCOFFSymbolDef() override {
94 llvm_unreachable("macho doesn't support this directive");
96 void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
97 unsigned ByteAlignment) override;
98 void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
99 uint64_t Size = 0, unsigned ByteAlignment = 0) override;
100 void EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, uint64_t Size,
101 unsigned ByteAlignment = 0) override;
103 void EmitFileDirective(StringRef Filename) override {
104 // FIXME: Just ignore the .file; it isn't important enough to fail the
107 // report_fatal_error("unsupported directive: '.file'");
110 void EmitIdent(StringRef IdentString) override {
111 llvm_unreachable("macho doesn't support this directive");
114 void EmitLOHDirective(MCLOHType Kind, const MCLOHArgs &Args) override {
115 getAssembler().getLOHContainer().addDirective(Kind, Args);
118 void FinishImpl() override;
121 } // end anonymous namespace.
123 static bool canGoAfterDWARF(const MCSectionMachO &MSec) {
124 // These sections are created by the assembler itself after the end of
126 StringRef SegName = MSec.getSegmentName();
127 StringRef SecName = MSec.getSectionName();
129 if (SegName == "__LD" && SecName == "__compact_unwind")
132 if (SegName == "__IMPORT") {
133 if (SecName == "__jump_table")
136 if (SecName == "__pointers")
140 if (SegName == "__TEXT" && SecName == "__eh_frame")
143 if (SegName == "__DATA" && SecName == "__nl_symbol_ptr")
149 void MCMachOStreamer::ChangeSection(MCSection *Section,
150 const MCExpr *Subsection) {
151 // Change the section normally.
152 bool Created = MCObjectStreamer::changeSectionImpl(Section, Subsection);
153 const MCSectionMachO &MSec = *cast<MCSectionMachO>(Section);
154 StringRef SegName = MSec.getSegmentName();
155 if (SegName == "__DWARF")
156 CreatedADWARFSection = true;
157 else if (Created && DWARFMustBeAtTheEnd && !canGoAfterDWARF(MSec))
158 assert(!CreatedADWARFSection && "Creating regular section after DWARF");
160 // Output a linker-local symbol so we don't need section-relative local
161 // relocations. The linker hates us when we do that.
162 if (LabelSections && !HasSectionLabel[Section] &&
163 !Section->getBeginSymbol()) {
164 MCSymbol *Label = getContext().createLinkerPrivateTempSymbol();
165 Section->setBeginSymbol(Label);
166 HasSectionLabel[Section] = true;
170 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
171 MCSymbol *EHSymbol) {
172 getAssembler().registerSymbol(*Symbol);
173 if (Symbol->isExternal())
174 EmitSymbolAttribute(EHSymbol, MCSA_Global);
175 if (cast<MCSymbolMachO>(Symbol)->isWeakDefinition())
176 EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
177 if (Symbol->isPrivateExtern())
178 EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
181 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
182 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
184 // We have to create a new fragment if this is an atom defining symbol,
185 // fragments cannot span atoms.
186 if (getAssembler().isSymbolLinkerVisible(*Symbol))
187 insert(new MCDataFragment());
189 MCObjectStreamer::EmitLabel(Symbol);
191 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
192 // to clear the weak reference and weak definition bits too, but the
193 // implementation was buggy. For now we just try to match 'as', for
196 // FIXME: Cleanup this code, these bits should be emitted based on semantic
197 // properties, not on the order of definition, etc.
198 cast<MCSymbolMachO>(Symbol)->clearReferenceType();
201 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
202 if (!getAssembler().getBackend().hasDataInCodeSupport())
204 // Create a temporary label to mark the start of the data region.
205 MCSymbol *Start = getContext().createTempSymbol();
207 // Record the region for the object writer to use.
208 DataRegionData Data = { Kind, Start, nullptr };
209 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
210 Regions.push_back(Data);
213 void MCMachOStreamer::EmitDataRegionEnd() {
214 if (!getAssembler().getBackend().hasDataInCodeSupport())
216 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
217 assert(!Regions.empty() && "Mismatched .end_data_region!");
218 DataRegionData &Data = Regions.back();
219 assert(!Data.End && "Mismatched .end_data_region!");
220 // Create a temporary label to mark the end of the data region.
221 Data.End = getContext().createTempSymbol();
225 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
226 // Let the target do whatever target specific stuff it needs to do.
227 getAssembler().getBackend().handleAssemblerFlag(Flag);
228 // Do any generic stuff we need to do.
230 case MCAF_SyntaxUnified: return; // no-op here.
231 case MCAF_Code16: return; // Change parsing mode; no-op here.
232 case MCAF_Code32: return; // Change parsing mode; no-op here.
233 case MCAF_Code64: return; // Change parsing mode; no-op here.
234 case MCAF_SubsectionsViaSymbols:
235 getAssembler().setSubsectionsViaSymbols(true);
240 void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
241 getAssembler().getLinkerOptions().push_back(Options);
244 void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
246 case MCDR_DataRegion:
247 EmitDataRegion(DataRegionData::Data);
249 case MCDR_DataRegionJT8:
250 EmitDataRegion(DataRegionData::JumpTable8);
252 case MCDR_DataRegionJT16:
253 EmitDataRegion(DataRegionData::JumpTable16);
255 case MCDR_DataRegionJT32:
256 EmitDataRegion(DataRegionData::JumpTable32);
258 case MCDR_DataRegionEnd:
264 void MCMachOStreamer::EmitVersionMin(MCVersionMinType Kind, unsigned Major,
265 unsigned Minor, unsigned Update) {
266 getAssembler().setVersionMinInfo(Kind, Major, Minor, Update);
269 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
270 // Remember that the function is a thumb function. Fixup and relocation
271 // values will need adjusted.
272 getAssembler().setIsThumbFunc(Symbol);
273 cast<MCSymbolMachO>(Symbol)->setThumbFunc();
276 bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Sym,
277 MCSymbolAttr Attribute) {
278 MCSymbolMachO *Symbol = cast<MCSymbolMachO>(Sym);
280 // Indirect symbols are handled differently, to match how 'as' handles
281 // them. This makes writing matching .o files easier.
282 if (Attribute == MCSA_IndirectSymbol) {
283 // Note that we intentionally cannot use the symbol data here; this is
284 // important for matching the string table that 'as' generates.
285 IndirectSymbolData ISD;
287 ISD.Section = getCurrentSectionOnly();
288 getAssembler().getIndirectSymbols().push_back(ISD);
292 // Adding a symbol attribute always introduces the symbol, note that an
293 // important side effect of calling registerSymbol here is to register
294 // the symbol with the assembler.
295 getAssembler().registerSymbol(*Symbol);
297 // The implementation of symbol attributes is designed to match 'as', but it
298 // leaves much to desired. It doesn't really make sense to arbitrarily add and
299 // remove flags, but 'as' allows this (in particular, see .desc).
301 // In the future it might be worth trying to make these operations more well
305 case MCSA_ELF_TypeFunction:
306 case MCSA_ELF_TypeIndFunction:
307 case MCSA_ELF_TypeObject:
308 case MCSA_ELF_TypeTLS:
309 case MCSA_ELF_TypeCommon:
310 case MCSA_ELF_TypeNoType:
311 case MCSA_ELF_TypeGnuUniqueObject:
313 case MCSA_IndirectSymbol:
321 Symbol->setExternal(true);
322 // This effectively clears the undefined lazy bit, in Darwin 'as', although
323 // it isn't very consistent because it implements this as part of symbol
326 // FIXME: Cleanup this code, these bits should be emitted based on semantic
327 // properties, not on the order of definition, etc.
328 Symbol->setReferenceTypeUndefinedLazy(false);
331 case MCSA_LazyReference:
332 // FIXME: This requires -dynamic.
333 Symbol->setNoDeadStrip();
334 if (Symbol->isUndefined())
335 Symbol->setReferenceTypeUndefinedLazy(true);
338 // Since .reference sets the no dead strip bit, it is equivalent to
339 // .no_dead_strip in practice.
341 case MCSA_NoDeadStrip:
342 Symbol->setNoDeadStrip();
345 case MCSA_SymbolResolver:
346 Symbol->setSymbolResolver();
349 case MCSA_PrivateExtern:
350 Symbol->setExternal(true);
351 Symbol->setPrivateExtern(true);
354 case MCSA_WeakReference:
355 // FIXME: This requires -dynamic.
356 if (Symbol->isUndefined())
357 Symbol->setWeakReference();
360 case MCSA_WeakDefinition:
361 // FIXME: 'as' enforces that this is defined and global. The manual claims
362 // it has to be in a coalesced section, but this isn't enforced.
363 Symbol->setWeakDefinition();
366 case MCSA_WeakDefAutoPrivate:
367 Symbol->setWeakDefinition();
368 Symbol->setWeakReference();
375 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
376 // Encode the 'desc' value into the lowest implementation defined bits.
377 getAssembler().registerSymbol(*Symbol);
378 cast<MCSymbolMachO>(Symbol)->setDesc(DescValue);
381 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
382 unsigned ByteAlignment) {
383 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
384 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
386 getAssembler().registerSymbol(*Symbol);
387 Symbol->setExternal(true);
388 Symbol->setCommon(Size, ByteAlignment);
391 void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
392 unsigned ByteAlignment) {
393 // '.lcomm' is equivalent to '.zerofill'.
394 return EmitZerofill(getContext().getObjectFileInfo()->getDataBSSSection(),
395 Symbol, Size, ByteAlignment);
398 void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
399 uint64_t Size, unsigned ByteAlignment) {
400 getAssembler().registerSection(*Section);
402 // The symbol may not be present, which only creates the section.
406 // On darwin all virtual sections have zerofill type.
407 assert(Section->isVirtualSection() && "Section does not have zerofill type!");
409 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
411 getAssembler().registerSymbol(*Symbol);
413 // Emit an align fragment if necessary.
414 if (ByteAlignment != 1)
415 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, Section);
417 MCFragment *F = new MCFillFragment(0, 0, Size, Section);
418 Symbol->setFragment(F);
420 // Update the maximum alignment on the zero fill section if necessary.
421 if (ByteAlignment > Section->getAlignment())
422 Section->setAlignment(ByteAlignment);
425 // This should always be called with the thread local bss section. Like the
426 // .zerofill directive this doesn't actually switch sections on us.
427 void MCMachOStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
428 uint64_t Size, unsigned ByteAlignment) {
429 EmitZerofill(Section, Symbol, Size, ByteAlignment);
433 void MCMachOStreamer::EmitInstToData(const MCInst &Inst,
434 const MCSubtargetInfo &STI) {
435 MCDataFragment *DF = getOrCreateDataFragment();
437 SmallVector<MCFixup, 4> Fixups;
438 SmallString<256> Code;
439 raw_svector_ostream VecOS(Code);
440 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
442 // Add the fixups and data.
443 for (MCFixup &Fixup : Fixups) {
444 Fixup.setOffset(Fixup.getOffset() + DF->getContents().size());
445 DF->getFixups().push_back(Fixup);
447 DF->getContents().append(Code.begin(), Code.end());
450 void MCMachOStreamer::FinishImpl() {
451 EmitFrames(&getAssembler().getBackend());
453 // We have to set the fragment atom associations so we can relax properly for
456 // First, scan the symbol table to build a lookup table from fragments to
458 DenseMap<const MCFragment *, const MCSymbol *> DefiningSymbolMap;
459 for (const MCSymbol &Symbol : getAssembler().symbols()) {
460 if (getAssembler().isSymbolLinkerVisible(Symbol) && Symbol.isInSection() &&
461 !Symbol.isVariable()) {
462 // An atom defining symbol should never be internal to a fragment.
463 assert(Symbol.getOffset() == 0 &&
464 "Invalid offset in atom defining symbol!");
465 DefiningSymbolMap[Symbol.getFragment()] = &Symbol;
469 // Set the fragment atom associations by tracking the last seen atom defining
471 for (MCSection &Sec : getAssembler()) {
472 const MCSymbol *CurrentAtom = nullptr;
473 for (MCFragment &Frag : Sec) {
474 if (const MCSymbol *Symbol = DefiningSymbolMap.lookup(&Frag))
475 CurrentAtom = Symbol;
476 Frag.setAtom(CurrentAtom);
480 this->MCObjectStreamer::FinishImpl();
483 MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
484 raw_pwrite_stream &OS, MCCodeEmitter *CE,
485 bool RelaxAll, bool DWARFMustBeAtTheEnd,
486 bool LabelSections) {
487 MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE,
488 DWARFMustBeAtTheEnd, LabelSections);
489 const Triple &TT = Context.getObjectFileInfo()->getTargetTriple();
490 if (TT.isOSDarwin()) {
491 unsigned Major, Minor, Update;
492 TT.getOSVersion(Major, Minor, Update);
493 // If there is a version specified, Major will be non-zero.
495 MCVersionMinType VersionType;
497 VersionType = MCVM_WatchOSVersionMin;
498 else if (TT.isTvOS())
499 VersionType = MCVM_TvOSVersionMin;
500 else if (TT.isMacOSX())
501 VersionType = MCVM_OSXVersionMin;
503 assert(TT.isiOS() && "Must only be iOS platform left");
504 VersionType = MCVM_IOSVersionMin;
506 S->EmitVersionMin(VersionType, Major, Minor, Update);
510 S->getAssembler().setRelaxAll(true);