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/TargetRegistry.h"
30 #include "llvm/Support/raw_ostream.h"
36 class MCMachOStreamer : public MCObjectStreamer {
38 /// LabelSections - true if each section change should emit a linker local
39 /// label for use in relocations for assembler local references. Obviates the
40 /// need for local relocations. False by default.
43 bool DWARFMustBeAtTheEnd;
44 bool CreatedADWARFSection;
46 /// HasSectionLabel - map of which sections have already had a non-local
47 /// label emitted to them. Used so we don't emit extraneous linker local
48 /// labels in the middle of the section.
49 DenseMap<const MCSection*, bool> HasSectionLabel;
51 void EmitInstToData(const MCInst &Inst, const MCSubtargetInfo &STI) override;
53 void EmitDataRegion(DataRegionData::KindTy Kind);
54 void EmitDataRegionEnd();
57 MCMachOStreamer(MCContext &Context, MCAsmBackend &MAB, raw_pwrite_stream &OS,
58 MCCodeEmitter *Emitter, bool DWARFMustBeAtTheEnd, bool label)
59 : MCObjectStreamer(Context, MAB, OS, Emitter), LabelSections(label),
60 DWARFMustBeAtTheEnd(DWARFMustBeAtTheEnd), CreatedADWARFSection(false) {}
63 void reset() override {
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 (Symbol->getFlags() & SF_WeakDefinition)
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 // isSymbolLinkerVisible uses the section.
185 AssignSection(Symbol, getCurrentSection().first);
186 // We have to create a new fragment if this is an atom defining symbol,
187 // fragments cannot span atoms.
188 if (getAssembler().isSymbolLinkerVisible(*Symbol))
189 insert(new MCDataFragment());
191 MCObjectStreamer::EmitLabel(Symbol);
193 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
194 // to clear the weak reference and weak definition bits too, but the
195 // implementation was buggy. For now we just try to match 'as', for
198 // FIXME: Cleanup this code, these bits should be emitted based on semantic
199 // properties, not on the order of definition, etc.
200 Symbol->setFlags(Symbol->getFlags() & ~SF_ReferenceTypeMask);
203 void MCMachOStreamer::EmitDataRegion(DataRegionData::KindTy Kind) {
204 if (!getAssembler().getBackend().hasDataInCodeSupport())
206 // Create a temporary label to mark the start of the data region.
207 MCSymbol *Start = getContext().createTempSymbol();
209 // Record the region for the object writer to use.
210 DataRegionData Data = { Kind, Start, nullptr };
211 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
212 Regions.push_back(Data);
215 void MCMachOStreamer::EmitDataRegionEnd() {
216 if (!getAssembler().getBackend().hasDataInCodeSupport())
218 std::vector<DataRegionData> &Regions = getAssembler().getDataRegions();
219 assert(!Regions.empty() && "Mismatched .end_data_region!");
220 DataRegionData &Data = Regions.back();
221 assert(!Data.End && "Mismatched .end_data_region!");
222 // Create a temporary label to mark the end of the data region.
223 Data.End = getContext().createTempSymbol();
227 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
228 // Let the target do whatever target specific stuff it needs to do.
229 getAssembler().getBackend().handleAssemblerFlag(Flag);
230 // Do any generic stuff we need to do.
232 case MCAF_SyntaxUnified: return; // no-op here.
233 case MCAF_Code16: return; // Change parsing mode; no-op here.
234 case MCAF_Code32: return; // Change parsing mode; no-op here.
235 case MCAF_Code64: return; // Change parsing mode; no-op here.
236 case MCAF_SubsectionsViaSymbols:
237 getAssembler().setSubsectionsViaSymbols(true);
242 void MCMachOStreamer::EmitLinkerOptions(ArrayRef<std::string> Options) {
243 getAssembler().getLinkerOptions().push_back(Options);
246 void MCMachOStreamer::EmitDataRegion(MCDataRegionType Kind) {
248 case MCDR_DataRegion:
249 EmitDataRegion(DataRegionData::Data);
251 case MCDR_DataRegionJT8:
252 EmitDataRegion(DataRegionData::JumpTable8);
254 case MCDR_DataRegionJT16:
255 EmitDataRegion(DataRegionData::JumpTable16);
257 case MCDR_DataRegionJT32:
258 EmitDataRegion(DataRegionData::JumpTable32);
260 case MCDR_DataRegionEnd:
266 void MCMachOStreamer::EmitVersionMin(MCVersionMinType Kind, unsigned Major,
267 unsigned Minor, unsigned Update) {
268 getAssembler().setVersionMinInfo(Kind, Major, Minor, Update);
271 void MCMachOStreamer::EmitThumbFunc(MCSymbol *Symbol) {
272 // Remember that the function is a thumb function. Fixup and relocation
273 // values will need adjusted.
274 getAssembler().setIsThumbFunc(Symbol);
277 bool MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
278 MCSymbolAttr Attribute) {
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->setFlags(Symbol->getFlags() & ~SF_ReferenceTypeUndefinedLazy);
330 case MCSA_LazyReference:
331 // FIXME: This requires -dynamic.
332 Symbol->setFlags(Symbol->getFlags() | SF_NoDeadStrip);
333 if (Symbol->isUndefined())
334 Symbol->setFlags(Symbol->getFlags() | SF_ReferenceTypeUndefinedLazy);
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->setFlags(Symbol->getFlags() | SF_NoDeadStrip);
344 case MCSA_SymbolResolver:
345 Symbol->setFlags(Symbol->getFlags() | SF_SymbolResolver);
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->setFlags(Symbol->getFlags() | SF_WeakReference);
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->setFlags(Symbol->getFlags() | SF_WeakDefinition);
365 case MCSA_WeakDefAutoPrivate:
366 Symbol->setFlags(Symbol->getFlags() | SF_WeakDefinition | SF_WeakReference);
373 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
374 // Encode the 'desc' value into the lowest implementation defined bits.
375 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
376 "Invalid .desc value!");
377 getAssembler().registerSymbol(*Symbol);
378 Symbol->setFlags(DescValue & SF_DescFlagsMask);
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 AssignSection(Symbol, nullptr);
388 getAssembler().registerSymbol(*Symbol);
389 Symbol->setExternal(true);
390 Symbol->setCommon(Size, ByteAlignment);
393 void MCMachOStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
394 unsigned ByteAlignment) {
395 // '.lcomm' is equivalent to '.zerofill'.
396 return EmitZerofill(getContext().getObjectFileInfo()->getDataBSSSection(),
397 Symbol, Size, ByteAlignment);
400 void MCMachOStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
401 uint64_t Size, unsigned ByteAlignment) {
402 getAssembler().registerSection(*Section);
404 // The symbol may not be present, which only creates the section.
408 // On darwin all virtual sections have zerofill type.
409 assert(Section->isVirtualSection() && "Section does not have zerofill type!");
411 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
413 getAssembler().registerSymbol(*Symbol);
415 // Emit an align fragment if necessary.
416 if (ByteAlignment != 1)
417 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, Section);
419 AssignSection(Symbol, Section);
421 MCFragment *F = new MCFillFragment(0, 0, Size, Section);
422 Symbol->setFragment(F);
424 // Update the maximum alignment on the zero fill section if necessary.
425 if (ByteAlignment > Section->getAlignment())
426 Section->setAlignment(ByteAlignment);
429 // This should always be called with the thread local bss section. Like the
430 // .zerofill directive this doesn't actually switch sections on us.
431 void MCMachOStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
432 uint64_t Size, unsigned ByteAlignment) {
433 EmitZerofill(Section, Symbol, Size, ByteAlignment);
437 void MCMachOStreamer::EmitInstToData(const MCInst &Inst,
438 const MCSubtargetInfo &STI) {
439 MCDataFragment *DF = getOrCreateDataFragment();
441 SmallVector<MCFixup, 4> Fixups;
442 SmallString<256> Code;
443 raw_svector_ostream VecOS(Code);
444 getAssembler().getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
447 // Add the fixups and data.
448 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
449 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
450 DF->getFixups().push_back(Fixups[i]);
452 DF->getContents().append(Code.begin(), Code.end());
455 void MCMachOStreamer::FinishImpl() {
456 EmitFrames(&getAssembler().getBackend());
458 // We have to set the fragment atom associations so we can relax properly for
461 // First, scan the symbol table to build a lookup table from fragments to
463 DenseMap<const MCFragment *, const MCSymbol *> DefiningSymbolMap;
464 for (const MCSymbol &Symbol : getAssembler().symbols()) {
465 if (getAssembler().isSymbolLinkerVisible(Symbol) && Symbol.getFragment()) {
466 // An atom defining symbol should never be internal to a fragment.
467 assert(Symbol.getOffset() == 0 &&
468 "Invalid offset in atom defining symbol!");
469 DefiningSymbolMap[Symbol.getFragment()] = &Symbol;
473 // Set the fragment atom associations by tracking the last seen atom defining
475 for (MCAssembler::iterator it = getAssembler().begin(),
476 ie = getAssembler().end(); it != ie; ++it) {
477 const MCSymbol *CurrentAtom = nullptr;
478 for (MCSection::iterator it2 = it->begin(), ie2 = it->end(); it2 != ie2;
480 if (const MCSymbol *Symbol = DefiningSymbolMap.lookup(it2))
481 CurrentAtom = Symbol;
482 it2->setAtom(CurrentAtom);
486 this->MCObjectStreamer::FinishImpl();
489 MCStreamer *llvm::createMachOStreamer(MCContext &Context, MCAsmBackend &MAB,
490 raw_pwrite_stream &OS, MCCodeEmitter *CE,
491 bool RelaxAll, bool DWARFMustBeAtTheEnd,
492 bool LabelSections) {
493 MCMachOStreamer *S = new MCMachOStreamer(Context, MAB, OS, CE,
494 DWARFMustBeAtTheEnd, LabelSections);
496 S->getAssembler().setRelaxAll(true);