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 void EmitInstToFragment(const MCInst &Inst);
35 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 EmitInstruction(const MCInst &Inst);
103 virtual void Finish();
108 } // end anonymous namespace.
110 void MCMachOStreamer::InitSections() {
111 SwitchSection(getContext().getMachOSection("__TEXT", "__text",
112 MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
113 0, SectionKind::getText()));
117 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
118 // TODO: This is almost exactly the same as WinCOFFStreamer. Consider merging
119 // into MCObjectStreamer.
120 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
121 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
122 assert(CurSection && "Cannot emit before setting section!");
124 Symbol->setSection(*CurSection);
126 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
128 // We have to create a new fragment if this is an atom defining symbol,
129 // fragments cannot span atoms.
130 if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()))
131 new MCDataFragment(getCurrentSectionData());
133 // FIXME: This is wasteful, we don't necessarily need to create a data
134 // fragment. Instead, we should mark the symbol as pointing into the data
135 // fragment if it exists, otherwise we should just queue the label and set its
136 // fragment pointer when we emit the next fragment.
137 MCDataFragment *F = getOrCreateDataFragment();
138 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
140 SD.setOffset(F->getContents().size());
142 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
143 // to clear the weak reference and weak definition bits too, but the
144 // implementation was buggy. For now we just try to match 'as', for
147 // FIXME: Cleanup this code, these bits should be emitted based on semantic
148 // properties, not on the order of definition, etc.
149 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
152 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
154 case MCAF_SubsectionsViaSymbols:
155 getAssembler().setSubsectionsViaSymbols(true);
158 llvm_unreachable("invalid assembler flag!");
162 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
163 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
165 // FIXME: Lift context changes into super class.
166 getAssembler().getOrCreateSymbolData(*Symbol);
167 Symbol->setVariableValue(AddValueSymbols(Value));
170 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
171 MCSymbolAttr Attribute) {
172 // Indirect symbols are handled differently, to match how 'as' handles
173 // them. This makes writing matching .o files easier.
174 if (Attribute == MCSA_IndirectSymbol) {
175 // Note that we intentionally cannot use the symbol data here; this is
176 // important for matching the string table that 'as' generates.
177 IndirectSymbolData ISD;
179 ISD.SectionData = getCurrentSectionData();
180 getAssembler().getIndirectSymbols().push_back(ISD);
184 // Adding a symbol attribute always introduces the symbol, note that an
185 // important side effect of calling getOrCreateSymbolData here is to register
186 // the symbol with the assembler.
187 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
189 // The implementation of symbol attributes is designed to match 'as', but it
190 // leaves much to desired. It doesn't really make sense to arbitrarily add and
191 // remove flags, but 'as' allows this (in particular, see .desc).
193 // In the future it might be worth trying to make these operations more well
197 case MCSA_ELF_TypeFunction:
198 case MCSA_ELF_TypeIndFunction:
199 case MCSA_ELF_TypeObject:
200 case MCSA_ELF_TypeTLS:
201 case MCSA_ELF_TypeCommon:
202 case MCSA_ELF_TypeNoType:
203 case MCSA_IndirectSymbol:
209 assert(0 && "Invalid symbol attribute for Mach-O!");
213 SD.setExternal(true);
214 // This effectively clears the undefined lazy bit, in Darwin 'as', although
215 // it isn't very consistent because it implements this as part of symbol
218 // FIXME: Cleanup this code, these bits should be emitted based on semantic
219 // properties, not on the order of definition, etc.
220 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
223 case MCSA_LazyReference:
224 // FIXME: This requires -dynamic.
225 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
226 if (Symbol->isUndefined())
227 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
230 // Since .reference sets the no dead strip bit, it is equivalent to
231 // .no_dead_strip in practice.
233 case MCSA_NoDeadStrip:
234 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
237 case MCSA_PrivateExtern:
238 SD.setExternal(true);
239 SD.setPrivateExtern(true);
242 case MCSA_WeakReference:
243 // FIXME: This requires -dynamic.
244 if (Symbol->isUndefined())
245 SD.setFlags(SD.getFlags() | SF_WeakReference);
248 case MCSA_WeakDefinition:
249 // FIXME: 'as' enforces that this is defined and global. The manual claims
250 // it has to be in a coalesced section, but this isn't enforced.
251 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
254 case MCSA_WeakDefAutoPrivate:
255 SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
260 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
261 // Encode the 'desc' value into the lowest implementation defined bits.
262 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
263 "Invalid .desc value!");
264 getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
265 DescValue & SF_DescFlagsMask);
268 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
269 unsigned ByteAlignment) {
270 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
271 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
273 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
274 SD.setExternal(true);
275 SD.setCommon(Size, ByteAlignment);
278 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
279 unsigned Size, unsigned ByteAlignment) {
280 MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
282 // The symbol may not be present, which only creates the section.
286 // FIXME: Assert that this section has the zerofill type.
288 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
290 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
292 // Emit an align fragment if necessary.
293 if (ByteAlignment != 1)
294 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
296 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
299 Symbol->setSection(*Section);
301 // Update the maximum alignment on the zero fill section if necessary.
302 if (ByteAlignment > SectData.getAlignment())
303 SectData.setAlignment(ByteAlignment);
306 // This should always be called with the thread local bss section. Like the
307 // .zerofill directive this doesn't actually switch sections on us.
308 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
309 uint64_t Size, unsigned ByteAlignment) {
310 EmitZerofill(Section, Symbol, Size, ByteAlignment);
314 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
315 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
317 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
320 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
321 unsigned AddrSpace) {
322 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
324 MCDataFragment *DF = getOrCreateDataFragment();
326 // Avoid fixups when possible.
328 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
329 // FIXME: Endianness assumption.
330 for (unsigned i = 0; i != Size; ++i)
331 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
333 DF->addFixup(MCFixup::Create(DF->getContents().size(),
334 AddValueSymbols(Value),
335 MCFixup::getKindForSize(Size)));
336 DF->getContents().resize(DF->getContents().size() + Size, 0);
340 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
341 int64_t Value, unsigned ValueSize,
342 unsigned MaxBytesToEmit) {
343 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
345 if (MaxBytesToEmit == 0)
346 MaxBytesToEmit = ByteAlignment;
347 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
348 getCurrentSectionData());
350 // Update the maximum alignment on the current section if necessary.
351 if (ByteAlignment > getCurrentSectionData()->getAlignment())
352 getCurrentSectionData()->setAlignment(ByteAlignment);
355 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
356 unsigned MaxBytesToEmit) {
357 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
359 if (MaxBytesToEmit == 0)
360 MaxBytesToEmit = ByteAlignment;
361 MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
362 getCurrentSectionData());
363 F->setEmitNops(true);
365 // Update the maximum alignment on the current section if necessary.
366 if (ByteAlignment > getCurrentSectionData()->getAlignment())
367 getCurrentSectionData()->setAlignment(ByteAlignment);
370 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
371 unsigned char Value) {
372 new MCOrgFragment(*Offset, Value, getCurrentSectionData());
375 void MCMachOStreamer::EmitInstToFragment(const MCInst &Inst) {
376 MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
378 // Add the fixups and data.
380 // FIXME: Revisit this design decision when relaxation is done, we may be
381 // able to get away with not storing any extra data in the MCInst.
382 SmallVector<MCFixup, 4> Fixups;
383 SmallString<256> Code;
384 raw_svector_ostream VecOS(Code);
385 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
388 IF->getCode() = Code;
389 IF->getFixups() = Fixups;
392 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
393 MCDataFragment *DF = getOrCreateDataFragment();
395 SmallVector<MCFixup, 4> Fixups;
396 SmallString<256> Code;
397 raw_svector_ostream VecOS(Code);
398 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
401 // Add the fixups and data.
402 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
403 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
404 DF->addFixup(Fixups[i]);
406 DF->getContents().append(Code.begin(), Code.end());
409 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
411 for (unsigned i = Inst.getNumOperands(); i--; )
412 if (Inst.getOperand(i).isExpr())
413 AddValueSymbols(Inst.getOperand(i).getExpr());
415 getCurrentSectionData()->setHasInstructions(true);
417 // Now that a machine instruction has been assembled into this section, make
418 // a line entry for any .loc directive that has been seen.
419 MCLineEntry::Make(this, getCurrentSection());
421 // If this instruction doesn't need relaxation, just emit it as data.
422 if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
423 EmitInstToData(Inst);
427 // Otherwise, if we are relaxing everything, relax the instruction as much as
428 // possible and emit it as data.
429 if (getAssembler().getRelaxAll()) {
431 getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
432 while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
433 getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
434 EmitInstToData(Relaxed);
438 // Otherwise emit to a separate fragment.
439 EmitInstToFragment(Inst);
442 void MCMachOStreamer::Finish() {
443 // Dump out the dwarf file & directory tables and line tables.
444 if (getContext().hasDwarfFiles()) {
445 const MCSection *DwarfLineSection = getContext().getMachOSection("__DWARF",
447 MCSectionMachO::S_ATTR_DEBUG,
448 0, SectionKind::getDataRelLocal());
449 MCDwarfFileTable::Emit(this, DwarfLineSection);
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*, MCSymbolData*> DefiningSymbolMap;
458 for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
459 ie = getAssembler().symbol_end(); it != ie; ++it) {
460 if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
462 // An atom defining symbol should never be internal to a fragment.
463 assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
464 DefiningSymbolMap[it->getFragment()] = it;
468 // Set the fragment atom associations by tracking the last seen atom defining
470 for (MCAssembler::iterator it = getAssembler().begin(),
471 ie = getAssembler().end(); it != ie; ++it) {
472 MCSymbolData *CurrentAtom = 0;
473 for (MCSectionData::iterator it2 = it->begin(),
474 ie2 = it->end(); it2 != ie2; ++it2) {
475 if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
477 it2->setAtom(CurrentAtom);
481 this->MCObjectStreamer::Finish();
484 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
485 raw_ostream &OS, MCCodeEmitter *CE,
487 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
489 S->getAssembler().setRelaxAll(true);