1 //===- lib/MC/MCMachOStreamer.cpp - Mach-O Object Output ------------===//
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"
12 #include "llvm/MC/MCAssembler.h"
13 #include "llvm/MC/MCContext.h"
14 #include "llvm/MC/MCCodeEmitter.h"
15 #include "llvm/MC/MCExpr.h"
16 #include "llvm/MC/MCInst.h"
17 #include "llvm/MC/MCObjectStreamer.h"
18 #include "llvm/MC/MCSection.h"
19 #include "llvm/MC/MCSymbol.h"
20 #include "llvm/MC/MCMachOSymbolFlags.h"
21 #include "llvm/MC/MCSectionMachO.h"
22 #include "llvm/MC/MCDwarf.h"
23 #include "llvm/Support/Dwarf.h"
24 #include "llvm/Support/ErrorHandling.h"
25 #include "llvm/Support/raw_ostream.h"
26 #include "llvm/Target/TargetAsmBackend.h"
32 class MCMachOStreamer : public MCObjectStreamer {
34 virtual void EmitInstToFragment(const MCInst &Inst);
35 virtual void EmitInstToData(const MCInst &Inst);
38 MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
39 raw_ostream &OS, MCCodeEmitter *Emitter)
40 : MCObjectStreamer(Context, TAB, OS, Emitter, true) {}
42 /// @name MCStreamer Interface
45 virtual void InitSections();
46 virtual void EmitLabel(MCSymbol *Symbol);
47 virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
48 virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
49 virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
50 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
51 virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
52 unsigned ByteAlignment);
53 virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
54 assert(0 && "macho doesn't support this directive");
56 virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
57 assert(0 && "macho doesn't support this directive");
59 virtual void EmitCOFFSymbolType(int Type) {
60 assert(0 && "macho doesn't support this directive");
62 virtual void EndCOFFSymbolDef() {
63 assert(0 && "macho doesn't support this directive");
65 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
66 assert(0 && "macho doesn't support this directive");
68 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
69 assert(0 && "macho doesn't support this directive");
71 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
72 unsigned Size = 0, unsigned ByteAlignment = 0);
73 virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
74 uint64_t Size, unsigned ByteAlignment = 0);
75 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
76 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
77 virtual void EmitGPRel32Value(const MCExpr *Value) {
78 assert(0 && "macho doesn't support this directive");
80 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
81 unsigned ValueSize = 1,
82 unsigned MaxBytesToEmit = 0);
83 virtual void EmitCodeAlignment(unsigned ByteAlignment,
84 unsigned MaxBytesToEmit = 0);
85 virtual void EmitValueToOffset(const MCExpr *Offset,
86 unsigned char Value = 0);
88 virtual void EmitFileDirective(StringRef Filename) {
89 // FIXME: Just ignore the .file; it isn't important enough to fail the
92 //report_fatal_error("unsupported directive: '.file'");
94 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
95 // FIXME: Just ignore the .file; it isn't important enough to fail the
98 //report_fatal_error("unsupported directive: '.file'");
101 virtual void Finish();
106 } // end anonymous namespace.
108 void MCMachOStreamer::InitSections() {
109 SwitchSection(getContext().getMachOSection("__TEXT", "__text",
110 MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
111 0, SectionKind::getText()));
115 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
116 // TODO: This is almost exactly the same as WinCOFFStreamer. Consider merging
117 // into MCObjectStreamer.
118 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
119 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
120 assert(CurSection && "Cannot emit before setting section!");
122 Symbol->setSection(*CurSection);
124 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
126 // We have to create a new fragment if this is an atom defining symbol,
127 // fragments cannot span atoms.
128 if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()))
129 new MCDataFragment(getCurrentSectionData());
131 // FIXME: This is wasteful, we don't necessarily need to create a data
132 // fragment. Instead, we should mark the symbol as pointing into the data
133 // fragment if it exists, otherwise we should just queue the label and set its
134 // fragment pointer when we emit the next fragment.
135 MCDataFragment *F = getOrCreateDataFragment();
136 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
138 SD.setOffset(F->getContents().size());
140 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
141 // to clear the weak reference and weak definition bits too, but the
142 // implementation was buggy. For now we just try to match 'as', for
145 // FIXME: Cleanup this code, these bits should be emitted based on semantic
146 // properties, not on the order of definition, etc.
147 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
150 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
152 case MCAF_SyntaxUnified: return; // no-op here.
153 case MCAF_SubsectionsViaSymbols:
154 getAssembler().setSubsectionsViaSymbols(true);
157 llvm_unreachable("invalid assembler flag!");
161 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
162 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
164 // FIXME: Lift context changes into super class.
165 getAssembler().getOrCreateSymbolData(*Symbol);
166 Symbol->setVariableValue(AddValueSymbols(Value));
169 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
170 MCSymbolAttr Attribute) {
171 // Indirect symbols are handled differently, to match how 'as' handles
172 // them. This makes writing matching .o files easier.
173 if (Attribute == MCSA_IndirectSymbol) {
174 // Note that we intentionally cannot use the symbol data here; this is
175 // important for matching the string table that 'as' generates.
176 IndirectSymbolData ISD;
178 ISD.SectionData = getCurrentSectionData();
179 getAssembler().getIndirectSymbols().push_back(ISD);
183 // Adding a symbol attribute always introduces the symbol, note that an
184 // important side effect of calling getOrCreateSymbolData here is to register
185 // the symbol with the assembler.
186 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
188 // The implementation of symbol attributes is designed to match 'as', but it
189 // leaves much to desired. It doesn't really make sense to arbitrarily add and
190 // remove flags, but 'as' allows this (in particular, see .desc).
192 // In the future it might be worth trying to make these operations more well
196 case MCSA_ELF_TypeFunction:
197 case MCSA_ELF_TypeIndFunction:
198 case MCSA_ELF_TypeObject:
199 case MCSA_ELF_TypeTLS:
200 case MCSA_ELF_TypeCommon:
201 case MCSA_ELF_TypeNoType:
202 case MCSA_IndirectSymbol:
208 assert(0 && "Invalid symbol attribute for Mach-O!");
212 SD.setExternal(true);
213 // This effectively clears the undefined lazy bit, in Darwin 'as', although
214 // it isn't very consistent because it implements this as part of symbol
217 // FIXME: Cleanup this code, these bits should be emitted based on semantic
218 // properties, not on the order of definition, etc.
219 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
222 case MCSA_LazyReference:
223 // FIXME: This requires -dynamic.
224 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
225 if (Symbol->isUndefined())
226 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
229 // Since .reference sets the no dead strip bit, it is equivalent to
230 // .no_dead_strip in practice.
232 case MCSA_NoDeadStrip:
233 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
236 case MCSA_PrivateExtern:
237 SD.setExternal(true);
238 SD.setPrivateExtern(true);
241 case MCSA_WeakReference:
242 // FIXME: This requires -dynamic.
243 if (Symbol->isUndefined())
244 SD.setFlags(SD.getFlags() | SF_WeakReference);
247 case MCSA_WeakDefinition:
248 // FIXME: 'as' enforces that this is defined and global. The manual claims
249 // it has to be in a coalesced section, but this isn't enforced.
250 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
253 case MCSA_WeakDefAutoPrivate:
254 SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
259 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
260 // Encode the 'desc' value into the lowest implementation defined bits.
261 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
262 "Invalid .desc value!");
263 getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
264 DescValue & SF_DescFlagsMask);
267 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
268 unsigned ByteAlignment) {
269 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
270 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
272 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
273 SD.setExternal(true);
274 SD.setCommon(Size, ByteAlignment);
277 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
278 unsigned Size, unsigned ByteAlignment) {
279 MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
281 // The symbol may not be present, which only creates the section.
285 // FIXME: Assert that this section has the zerofill type.
287 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
289 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
291 // Emit an align fragment if necessary.
292 if (ByteAlignment != 1)
293 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
295 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
298 Symbol->setSection(*Section);
300 // Update the maximum alignment on the zero fill section if necessary.
301 if (ByteAlignment > SectData.getAlignment())
302 SectData.setAlignment(ByteAlignment);
305 // This should always be called with the thread local bss section. Like the
306 // .zerofill directive this doesn't actually switch sections on us.
307 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
308 uint64_t Size, unsigned ByteAlignment) {
309 EmitZerofill(Section, Symbol, Size, ByteAlignment);
313 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
314 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
316 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
319 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
320 unsigned AddrSpace) {
321 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
323 MCDataFragment *DF = getOrCreateDataFragment();
325 // Avoid fixups when possible.
327 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
328 // FIXME: Endianness assumption.
329 for (unsigned i = 0; i != Size; ++i)
330 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
332 DF->addFixup(MCFixup::Create(DF->getContents().size(),
333 AddValueSymbols(Value),
334 MCFixup::getKindForSize(Size)));
335 DF->getContents().resize(DF->getContents().size() + Size, 0);
339 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
340 int64_t Value, unsigned ValueSize,
341 unsigned MaxBytesToEmit) {
342 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
344 if (MaxBytesToEmit == 0)
345 MaxBytesToEmit = ByteAlignment;
346 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
347 getCurrentSectionData());
349 // Update the maximum alignment on the current section if necessary.
350 if (ByteAlignment > getCurrentSectionData()->getAlignment())
351 getCurrentSectionData()->setAlignment(ByteAlignment);
354 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
355 unsigned MaxBytesToEmit) {
356 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
358 if (MaxBytesToEmit == 0)
359 MaxBytesToEmit = ByteAlignment;
360 MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
361 getCurrentSectionData());
362 F->setEmitNops(true);
364 // Update the maximum alignment on the current section if necessary.
365 if (ByteAlignment > getCurrentSectionData()->getAlignment())
366 getCurrentSectionData()->setAlignment(ByteAlignment);
369 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
370 unsigned char Value) {
371 new MCOrgFragment(*Offset, Value, getCurrentSectionData());
374 void MCMachOStreamer::EmitInstToFragment(const MCInst &Inst) {
375 MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
377 // Add the fixups and data.
379 // FIXME: Revisit this design decision when relaxation is done, we may be
380 // able to get away with not storing any extra data in the MCInst.
381 SmallVector<MCFixup, 4> Fixups;
382 SmallString<256> Code;
383 raw_svector_ostream VecOS(Code);
384 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
387 IF->getCode() = Code;
388 IF->getFixups() = Fixups;
391 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
392 MCDataFragment *DF = getOrCreateDataFragment();
394 SmallVector<MCFixup, 4> Fixups;
395 SmallString<256> Code;
396 raw_svector_ostream VecOS(Code);
397 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
400 // Add the fixups and data.
401 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
402 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
403 DF->addFixup(Fixups[i]);
405 DF->getContents().append(Code.begin(), Code.end());
408 void MCMachOStreamer::Finish() {
409 // Dump out the dwarf file & directory tables and line tables.
410 if (getContext().hasDwarfFiles()) {
411 const MCSection *DwarfLineSection = getContext().getMachOSection("__DWARF",
413 MCSectionMachO::S_ATTR_DEBUG,
414 0, SectionKind::getDataRelLocal());
415 MCDwarfFileTable::Emit(this, DwarfLineSection);
418 // We have to set the fragment atom associations so we can relax properly for
421 // First, scan the symbol table to build a lookup table from fragments to
423 DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
424 for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
425 ie = getAssembler().symbol_end(); it != ie; ++it) {
426 if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
428 // An atom defining symbol should never be internal to a fragment.
429 assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
430 DefiningSymbolMap[it->getFragment()] = it;
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 = 0;
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::Finish();
450 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
451 raw_ostream &OS, MCCodeEmitter *CE,
453 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
455 S->getAssembler().setRelaxAll(true);