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/ADT/DenseMap.h"
11 #include "llvm/ADT/SmallString.h"
12 #include "llvm/ADT/SmallVector.h"
13 #include "llvm/ADT/StringRef.h"
14 #include "llvm/ADT/Triple.h"
15 #include "llvm/MC/MCAsmBackend.h"
16 #include "llvm/MC/MCAssembler.h"
17 #include "llvm/MC/MCCodeEmitter.h"
18 #include "llvm/MC/MCContext.h"
19 #include "llvm/MC/MCDirectives.h"
20 #include "llvm/MC/MCExpr.h"
21 #include "llvm/MC/MCFixup.h"
22 #include "llvm/MC/MCFragment.h"
23 #include "llvm/MC/MCInst.h"
24 #include "llvm/MC/MCLinkerOptimizationHint.h"
25 #include "llvm/MC/MCObjectFileInfo.h"
26 #include "llvm/MC/MCObjectStreamer.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCSectionMachO.h"
30 #include "llvm/MC/MCStreamer.h"
31 #include "llvm/MC/MCSymbol.h"
32 #include "llvm/MC/MCSymbolMachO.h"
33 #include "llvm/MC/MCValue.h"
34 #include "llvm/Support/Casting.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/TargetRegistry.h"
37 #include "llvm/Support/raw_ostream.h"
45 class MCMachOStreamer : public MCObjectStreamer {
47 /// LabelSections - true if each section change should emit a linker local
48 /// label for use in relocations for assembler local references. Obviates the
49 /// need for local relocations. False by default.
52 bool DWARFMustBeAtTheEnd;
53 bool CreatedADWARFSection;
55 /// HasSectionLabel - map of which sections have already had a non-local
56 /// label emitted to them. Used so we don't emit extraneous linker local
57 /// labels in the middle of the section.
58 DenseMap<const MCSection*, bool> HasSectionLabel;
60 void EmitInstToData(const MCInst &Inst, const MCSubtargetInfo &STI) override;
62 void EmitDataRegion(DataRegionData::KindTy Kind);
63 void EmitDataRegionEnd();
66 MCMachOStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> MAB,
67 std::unique_ptr<MCObjectWriter> OW,
68 std::unique_ptr<MCCodeEmitter> Emitter,
69 bool DWARFMustBeAtTheEnd, bool label)
70 : MCObjectStreamer(Context, std::move(MAB), std::move(OW),
72 LabelSections(label), DWARFMustBeAtTheEnd(DWARFMustBeAtTheEnd),
73 CreatedADWARFSection(false) {}
76 void reset() override {
77 CreatedADWARFSection = false;
78 HasSectionLabel.clear();
79 MCObjectStreamer::reset();
82 /// @name MCStreamer Interface
85 void ChangeSection(MCSection *Sect, const MCExpr *Subsect) override;
86 void EmitLabel(MCSymbol *Symbol, SMLoc Loc = SMLoc()) override;
87 void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) override;
88 void EmitEHSymAttributes(const MCSymbol *Symbol, MCSymbol *EHSymbol) override;
89 void EmitAssemblerFlag(MCAssemblerFlag Flag) override;
90 void EmitLinkerOptions(ArrayRef<std::string> Options) override;
91 void EmitDataRegion(MCDataRegionType Kind) override;
92 void EmitVersionMin(MCVersionMinType Kind, unsigned Major,
93 unsigned Minor, unsigned Update) override;
94 void EmitBuildVersion(unsigned Platform, unsigned Major,
95 unsigned Minor, unsigned Update) override;
96 void EmitThumbFunc(MCSymbol *Func) override;
97 bool EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute) override;
98 void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) override;
99 void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
100 unsigned ByteAlignment) override;
102 void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
103 unsigned ByteAlignment) override;
104 void EmitZerofill(MCSection *Section, MCSymbol *Symbol = nullptr,
105 uint64_t Size = 0, unsigned ByteAlignment = 0,
106 SMLoc Loc = SMLoc()) override;
107 void EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol, uint64_t Size,
108 unsigned ByteAlignment = 0) override;
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" ||
144 SecName == "__thread_ptr"))
150 void MCMachOStreamer::ChangeSection(MCSection *Section,
151 const MCExpr *Subsection) {
152 // Change the section normally.
153 bool Created = changeSectionImpl(Section, Subsection);
154 const MCSectionMachO &MSec = *cast<MCSectionMachO>(Section);
155 StringRef SegName = MSec.getSegmentName();
156 if (SegName == "__DWARF")
157 CreatedADWARFSection = true;
158 else if (Created && DWARFMustBeAtTheEnd && !canGoAfterDWARF(MSec))
159 assert(!CreatedADWARFSection && "Creating regular section after DWARF");
161 // Output a linker-local symbol so we don't need section-relative local
162 // relocations. The linker hates us when we do that.
163 if (LabelSections && !HasSectionLabel[Section] &&
164 !Section->getBeginSymbol()) {
165 MCSymbol *Label = getContext().createLinkerPrivateTempSymbol();
166 Section->setBeginSymbol(Label);
167 HasSectionLabel[Section] = true;
171 void MCMachOStreamer::EmitEHSymAttributes(const MCSymbol *Symbol,
172 MCSymbol *EHSymbol) {
173 getAssembler().registerSymbol(*Symbol);
174 if (Symbol->isExternal())
175 EmitSymbolAttribute(EHSymbol, MCSA_Global);
176 if (cast<MCSymbolMachO>(Symbol)->isWeakDefinition())
177 EmitSymbolAttribute(EHSymbol, MCSA_WeakDefinition);
178 if (Symbol->isPrivateExtern())
179 EmitSymbolAttribute(EHSymbol, MCSA_PrivateExtern);
182 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol, SMLoc Loc) {
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, Loc);
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::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
203 if (Value->evaluateAsRelocatable(Res, nullptr, nullptr)) {
204 if (const MCSymbolRefExpr *SymAExpr = Res.getSymA()) {
205 const MCSymbol &SymA = SymAExpr->getSymbol();
206 if (!Res.getSymB() && (SymA.getName() == "" || Res.getConstant() != 0))
207 cast<MCSymbolMachO>(Symbol)->setAltEntry();
210 MCObjectStreamer::EmitAssignment(Symbol, Value);
213 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
214 // Create a temporary label to mark the start of the data region.
215 MCSymbol *Start = getContext().createTempSymbol();
217 // Record the region for the object writer to use.
218 DataRegionData Data = { Kind, Start, nullptr };
219 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
220 Regions.push_back(Data);
223 void MCMachOStreamer::EmitDataRegionEnd() {
224 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
225 assert(!Regions.empty() && "Mismatched .end_data_region!");
226 DataRegionData &Data = Regions.back();
227 assert(!Data.End && "Mismatched .end_data_region!");
228 // Create a temporary label to mark the end of the data region.
229 Data.End = getContext().createTempSymbol();
233 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
234 // Let the target do whatever target specific stuff it needs to do.
235 getAssembler().getBackend().handleAssemblerFlag(Flag);
236 // Do any generic stuff we need to do.
238 case MCAF_SyntaxUnified: return; // no-op here.
239 case MCAF_Code16: return; // Change parsing mode; no-op here.
240 case MCAF_Code32: return; // Change parsing mode; no-op here.
241 case MCAF_Code64: return; // Change parsing mode; no-op here.
242 case MCAF_SubsectionsViaSymbols:
243 getAssembler().setSubsectionsViaSymbols(true);
248 void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
249 getAssembler().getLinkerOptions().push_back(Options);
252 void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
254 case MCDR_DataRegion:
255 EmitDataRegion(DataRegionData::Data);
257 case MCDR_DataRegionJT8:
258 EmitDataRegion(DataRegionData::JumpTable8);
260 case MCDR_DataRegionJT16:
261 EmitDataRegion(DataRegionData::JumpTable16);
263 case MCDR_DataRegionJT32:
264 EmitDataRegion(DataRegionData::JumpTable32);
266 case MCDR_DataRegionEnd:
272 void MCMachOStreamer::EmitVersionMin(MCVersionMinType Kind, unsigned Major,
273 unsigned Minor, unsigned Update) {
274 getAssembler().setVersionMin(Kind, Major, Minor, Update);
277 void MCMachOStreamer::EmitBuildVersion(unsigned Platform, unsigned Major,
278 unsigned Minor, unsigned Update) {
279 getAssembler().setBuildVersion((MachO::PlatformType)Platform, Major, Minor,
283 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
284 // Remember that the function is a thumb function. Fixup and relocation
285 // values will need adjusted.
286 getAssembler().setIsThumbFunc(Symbol);
287 cast<MCSymbolMachO>(Symbol)->setThumbFunc();
290 bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Sym,
291 MCSymbolAttr Attribute) {
292 MCSymbolMachO *Symbol = cast<MCSymbolMachO>(Sym);
294 // Indirect symbols are handled differently, to match how 'as' handles
295 // them. This makes writing matching .o files easier.
296 if (Attribute == MCSA_IndirectSymbol) {
297 // Note that we intentionally cannot use the symbol data here; this is
298 // important for matching the string table that 'as' generates.
299 IndirectSymbolData ISD;
301 ISD.Section = getCurrentSectionOnly();
302 getAssembler().getIndirectSymbols().push_back(ISD);
306 // Adding a symbol attribute always introduces the symbol, note that an
307 // important side effect of calling registerSymbol here is to register
308 // the symbol with the assembler.
309 getAssembler().registerSymbol(*Symbol);
311 // The implementation of symbol attributes is designed to match 'as', but it
312 // leaves much to desired. It doesn't really make sense to arbitrarily add and
313 // remove flags, but 'as' allows this (in particular, see .desc).
315 // In the future it might be worth trying to make these operations more well
319 case MCSA_ELF_TypeFunction:
320 case MCSA_ELF_TypeIndFunction:
321 case MCSA_ELF_TypeObject:
322 case MCSA_ELF_TypeTLS:
323 case MCSA_ELF_TypeCommon:
324 case MCSA_ELF_TypeNoType:
325 case MCSA_ELF_TypeGnuUniqueObject:
327 case MCSA_IndirectSymbol:
335 Symbol->setExternal(true);
336 // This effectively clears the undefined lazy bit, in Darwin 'as', although
337 // it isn't very consistent because it implements this as part of symbol
340 // FIXME: Cleanup this code, these bits should be emitted based on semantic
341 // properties, not on the order of definition, etc.
342 Symbol->setReferenceTypeUndefinedLazy(false);
345 case MCSA_LazyReference:
346 // FIXME: This requires -dynamic.
347 Symbol->setNoDeadStrip();
348 if (Symbol->isUndefined())
349 Symbol->setReferenceTypeUndefinedLazy(true);
352 // Since .reference sets the no dead strip bit, it is equivalent to
353 // .no_dead_strip in practice.
355 case MCSA_NoDeadStrip:
356 Symbol->setNoDeadStrip();
359 case MCSA_SymbolResolver:
360 Symbol->setSymbolResolver();
364 Symbol->setAltEntry();
367 case MCSA_PrivateExtern:
368 Symbol->setExternal(true);
369 Symbol->setPrivateExtern(true);
372 case MCSA_WeakReference:
373 // FIXME: This requires -dynamic.
374 if (Symbol->isUndefined())
375 Symbol->setWeakReference();
378 case MCSA_WeakDefinition:
379 // FIXME: 'as' enforces that this is defined and global. The manual claims
380 // it has to be in a coalesced section, but this isn't enforced.
381 Symbol->setWeakDefinition();
384 case MCSA_WeakDefAutoPrivate:
385 Symbol->setWeakDefinition();
386 Symbol->setWeakReference();
393 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
394 // Encode the 'desc' value into the lowest implementation defined bits.
395 getAssembler().registerSymbol(*Symbol);
396 cast<MCSymbolMachO>(Symbol)->setDesc(DescValue);
399 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
400 unsigned ByteAlignment) {
401 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
402 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
404 getAssembler().registerSymbol(*Symbol);
405 Symbol->setExternal(true);
406 Symbol->setCommon(Size, ByteAlignment);
409 void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
410 unsigned ByteAlignment) {
411 // '.lcomm' is equivalent to '.zerofill'.
412 return EmitZerofill(getContext().getObjectFileInfo()->getDataBSSSection(),
413 Symbol, Size, ByteAlignment);
416 void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
417 uint64_t Size, unsigned ByteAlignment,
419 // On darwin all virtual sections have zerofill type. Disallow the usage of
420 // .zerofill in non-virtual functions. If something similar is needed, use
422 if (!Section->isVirtualSection()) {
423 getContext().reportError(
424 Loc, "The usage of .zerofill is restricted to sections of "
425 "ZEROFILL type. Use .zero or .space instead.");
426 return; // Early returning here shouldn't harm. EmitZeros should work on any
431 SwitchSection(Section);
433 // The symbol may not be present, which only creates the section.
435 EmitValueToAlignment(ByteAlignment, 0, 1, 0);
442 // This should always be called with the thread local bss section. Like the
443 // .zerofill directive this doesn't actually switch sections on us.
444 void MCMachOStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
445 uint64_t Size, unsigned ByteAlignment) {
446 EmitZerofill(Section, Symbol, Size, ByteAlignment);
449 void MCMachOStreamer::EmitInstToData(const MCInst &Inst,
450 const MCSubtargetInfo &STI) {
451 MCDataFragment *DF = getOrCreateDataFragment();
453 SmallVector<MCFixup, 4> Fixups;
454 SmallString<256> Code;
455 raw_svector_ostream VecOS(Code);
456 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
458 // Add the fixups and data.
459 for (MCFixup &Fixup : Fixups) {
460 Fixup.setOffset(Fixup.getOffset() + DF->getContents().size());
461 DF->getFixups().push_back(Fixup);
463 DF->setHasInstructions(STI);
464 DF->getContents().append(Code.begin(), Code.end());
467 void MCMachOStreamer::FinishImpl() {
468 EmitFrames(&getAssembler().getBackend());
470 // We have to set the fragment atom associations so we can relax properly for
473 // First, scan the symbol table to build a lookup table from fragments to
475 DenseMap<const MCFragment *, const MCSymbol *> DefiningSymbolMap;
476 for (const MCSymbol &Symbol : getAssembler().symbols()) {
477 if (getAssembler().isSymbolLinkerVisible(Symbol) && Symbol.isInSection() &&
478 !Symbol.isVariable()) {
479 // An atom defining symbol should never be internal to a fragment.
480 assert(Symbol.getOffset() == 0 &&
481 "Invalid offset in atom defining symbol!");
482 DefiningSymbolMap[Symbol.getFragment()] = &Symbol;
486 // Set the fragment atom associations by tracking the last seen atom defining
488 for (MCSection &Sec : getAssembler()) {
489 const MCSymbol *CurrentAtom = nullptr;
490 for (MCFragment &Frag : Sec) {
491 if (const MCSymbol *Symbol = DefiningSymbolMap.lookup(&Frag))
492 CurrentAtom = Symbol;
493 Frag.setAtom(CurrentAtom);
497 this->MCObjectStreamer::FinishImpl();
500 MCStreamer *llvm::createMachOStreamer(MCContext &Context,
501 std::unique_ptr<MCAsmBackend> &&MAB,
502 std::unique_ptr<MCObjectWriter> &&OW,
503 std::unique_ptr<MCCodeEmitter> &&CE,
504 bool RelaxAll, bool DWARFMustBeAtTheEnd,
505 bool LabelSections) {
507 new MCMachOStreamer(Context, std::move(MAB), std::move(OW), std::move(CE),
508 DWARFMustBeAtTheEnd, LabelSections);
509 const Triple &Target = Context.getObjectFileInfo()->getTargetTriple();
510 S->EmitVersionForTarget(Target);
512 S->getAssembler().setRelaxAll(true);