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/Support/ErrorHandling.h"
22 #include "llvm/Support/raw_ostream.h"
23 #include "llvm/Target/TargetAsmBackend.h"
29 class MCMachOStreamer : public MCObjectStreamer {
31 void EmitInstToFragment(const MCInst &Inst);
32 void EmitInstToData(const MCInst &Inst);
35 MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
36 raw_ostream &OS, MCCodeEmitter *Emitter)
37 : MCObjectStreamer(Context, TAB, OS, Emitter) {}
39 /// @name MCStreamer Interface
42 virtual void EmitLabel(MCSymbol *Symbol);
43 virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
44 virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
45 virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
46 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
47 virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
48 unsigned ByteAlignment);
49 virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
50 assert(0 && "macho doesn't support this directive");
52 virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
53 assert(0 && "macho doesn't support this directive");
55 virtual void EmitCOFFSymbolType(int Type) {
56 assert(0 && "macho doesn't support this directive");
58 virtual void EndCOFFSymbolDef() {
59 assert(0 && "macho doesn't support this directive");
61 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
62 assert(0 && "macho doesn't support this directive");
64 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
65 assert(0 && "macho doesn't support this directive");
67 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
68 unsigned Size = 0, unsigned ByteAlignment = 0);
69 virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
70 uint64_t Size, unsigned ByteAlignment = 0);
71 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
72 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
73 virtual void EmitGPRel32Value(const MCExpr *Value) {
74 assert(0 && "macho doesn't support this directive");
76 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
77 unsigned ValueSize = 1,
78 unsigned MaxBytesToEmit = 0);
79 virtual void EmitCodeAlignment(unsigned ByteAlignment,
80 unsigned MaxBytesToEmit = 0);
81 virtual void EmitValueToOffset(const MCExpr *Offset,
82 unsigned char Value = 0);
84 virtual void EmitFileDirective(StringRef Filename) {
85 // FIXME: Just ignore the .file; it isn't important enough to fail the
88 //report_fatal_error("unsupported directive: '.file'");
90 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
91 // FIXME: Just ignore the .file; it isn't important enough to fail the
94 //report_fatal_error("unsupported directive: '.file'");
97 virtual void EmitInstruction(const MCInst &Inst);
99 virtual void Finish();
104 } // end anonymous namespace.
106 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
107 // TODO: This is almost exactly the same as WinCOFFStreamer. Consider merging
108 // into MCObjectStreamer.
109 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
110 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
111 assert(CurSection && "Cannot emit before setting section!");
113 Symbol->setSection(*CurSection);
115 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
117 // We have to create a new fragment if this is an atom defining symbol,
118 // fragments cannot span atoms.
119 if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()))
120 new MCDataFragment(getCurrentSectionData());
122 // FIXME: This is wasteful, we don't necessarily need to create a data
123 // fragment. Instead, we should mark the symbol as pointing into the data
124 // fragment if it exists, otherwise we should just queue the label and set its
125 // fragment pointer when we emit the next fragment.
126 MCDataFragment *F = getOrCreateDataFragment();
127 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
129 SD.setOffset(F->getContents().size());
131 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
132 // to clear the weak reference and weak definition bits too, but the
133 // implementation was buggy. For now we just try to match 'as', for
136 // FIXME: Cleanup this code, these bits should be emitted based on semantic
137 // properties, not on the order of definition, etc.
138 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
141 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
143 case MCAF_SubsectionsViaSymbols:
144 getAssembler().setSubsectionsViaSymbols(true);
148 assert(0 && "invalid assembler flag!");
151 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
152 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
154 // FIXME: Lift context changes into super class.
155 getAssembler().getOrCreateSymbolData(*Symbol);
156 Symbol->setVariableValue(AddValueSymbols(Value));
159 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
160 MCSymbolAttr Attribute) {
161 // Indirect symbols are handled differently, to match how 'as' handles
162 // them. This makes writing matching .o files easier.
163 if (Attribute == MCSA_IndirectSymbol) {
164 // Note that we intentionally cannot use the symbol data here; this is
165 // important for matching the string table that 'as' generates.
166 IndirectSymbolData ISD;
168 ISD.SectionData = getCurrentSectionData();
169 getAssembler().getIndirectSymbols().push_back(ISD);
173 // Adding a symbol attribute always introduces the symbol, note that an
174 // important side effect of calling getOrCreateSymbolData here is to register
175 // the symbol with the assembler.
176 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
178 // The implementation of symbol attributes is designed to match 'as', but it
179 // leaves much to desired. It doesn't really make sense to arbitrarily add and
180 // remove flags, but 'as' allows this (in particular, see .desc).
182 // In the future it might be worth trying to make these operations more well
186 case MCSA_ELF_TypeFunction:
187 case MCSA_ELF_TypeIndFunction:
188 case MCSA_ELF_TypeObject:
189 case MCSA_ELF_TypeTLS:
190 case MCSA_ELF_TypeCommon:
191 case MCSA_ELF_TypeNoType:
192 case MCSA_IndirectSymbol:
198 assert(0 && "Invalid symbol attribute for Mach-O!");
202 SD.setExternal(true);
203 // This effectively clears the undefined lazy bit, in Darwin 'as', although
204 // it isn't very consistent because it implements this as part of symbol
207 // FIXME: Cleanup this code, these bits should be emitted based on semantic
208 // properties, not on the order of definition, etc.
209 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
212 case MCSA_LazyReference:
213 // FIXME: This requires -dynamic.
214 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
215 if (Symbol->isUndefined())
216 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
219 // Since .reference sets the no dead strip bit, it is equivalent to
220 // .no_dead_strip in practice.
222 case MCSA_NoDeadStrip:
223 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
226 case MCSA_PrivateExtern:
227 SD.setExternal(true);
228 SD.setPrivateExtern(true);
231 case MCSA_WeakReference:
232 // FIXME: This requires -dynamic.
233 if (Symbol->isUndefined())
234 SD.setFlags(SD.getFlags() | SF_WeakReference);
237 case MCSA_WeakDefinition:
238 // FIXME: 'as' enforces that this is defined and global. The manual claims
239 // it has to be in a coalesced section, but this isn't enforced.
240 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
243 case MCSA_WeakDefAutoPrivate:
244 SD.setFlags(SD.getFlags() | SF_WeakDefinition | SF_WeakReference);
249 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
250 // Encode the 'desc' value into the lowest implementation defined bits.
251 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
252 "Invalid .desc value!");
253 getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
254 DescValue & SF_DescFlagsMask);
257 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
258 unsigned ByteAlignment) {
259 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
260 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
262 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
263 SD.setExternal(true);
264 SD.setCommon(Size, ByteAlignment);
267 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
268 unsigned Size, unsigned ByteAlignment) {
269 MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
271 // The symbol may not be present, which only creates the section.
275 // FIXME: Assert that this section has the zerofill type.
277 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
279 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
281 // Emit an align fragment if necessary.
282 if (ByteAlignment != 1)
283 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
285 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
288 Symbol->setSection(*Section);
290 // Update the maximum alignment on the zero fill section if necessary.
291 if (ByteAlignment > SectData.getAlignment())
292 SectData.setAlignment(ByteAlignment);
295 // This should always be called with the thread local bss section. Like the
296 // .zerofill directive this doesn't actually switch sections on us.
297 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
298 uint64_t Size, unsigned ByteAlignment) {
299 EmitZerofill(Section, Symbol, Size, ByteAlignment);
303 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
304 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
306 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
309 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
310 unsigned AddrSpace) {
311 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
313 MCDataFragment *DF = getOrCreateDataFragment();
315 // Avoid fixups when possible.
317 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
318 // FIXME: Endianness assumption.
319 for (unsigned i = 0; i != Size; ++i)
320 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
322 DF->addFixup(MCFixup::Create(DF->getContents().size(),
323 AddValueSymbols(Value),
324 MCFixup::getKindForSize(Size)));
325 DF->getContents().resize(DF->getContents().size() + Size, 0);
329 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
330 int64_t Value, unsigned ValueSize,
331 unsigned MaxBytesToEmit) {
332 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
334 if (MaxBytesToEmit == 0)
335 MaxBytesToEmit = ByteAlignment;
336 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
337 getCurrentSectionData());
339 // Update the maximum alignment on the current section if necessary.
340 if (ByteAlignment > getCurrentSectionData()->getAlignment())
341 getCurrentSectionData()->setAlignment(ByteAlignment);
344 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
345 unsigned MaxBytesToEmit) {
346 // TODO: This is exactly the same as WinCOFFStreamer. Consider merging into
348 if (MaxBytesToEmit == 0)
349 MaxBytesToEmit = ByteAlignment;
350 MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
351 getCurrentSectionData());
352 F->setEmitNops(true);
354 // Update the maximum alignment on the current section if necessary.
355 if (ByteAlignment > getCurrentSectionData()->getAlignment())
356 getCurrentSectionData()->setAlignment(ByteAlignment);
359 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
360 unsigned char Value) {
361 new MCOrgFragment(*Offset, Value, getCurrentSectionData());
364 void MCMachOStreamer::EmitInstToFragment(const MCInst &Inst) {
365 MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
367 // Add the fixups and data.
369 // FIXME: Revisit this design decision when relaxation is done, we may be
370 // able to get away with not storing any extra data in the MCInst.
371 SmallVector<MCFixup, 4> Fixups;
372 SmallString<256> Code;
373 raw_svector_ostream VecOS(Code);
374 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
377 IF->getCode() = Code;
378 IF->getFixups() = Fixups;
381 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
382 MCDataFragment *DF = getOrCreateDataFragment();
384 SmallVector<MCFixup, 4> Fixups;
385 SmallString<256> Code;
386 raw_svector_ostream VecOS(Code);
387 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
390 // Add the fixups and data.
391 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
392 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
393 DF->addFixup(Fixups[i]);
395 DF->getContents().append(Code.begin(), Code.end());
398 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
400 for (unsigned i = Inst.getNumOperands(); i--; )
401 if (Inst.getOperand(i).isExpr())
402 AddValueSymbols(Inst.getOperand(i).getExpr());
404 getCurrentSectionData()->setHasInstructions(true);
406 // If this instruction doesn't need relaxation, just emit it as data.
407 if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
408 EmitInstToData(Inst);
412 // Otherwise, if we are relaxing everything, relax the instruction as much as
413 // possible and emit it as data.
414 if (getAssembler().getRelaxAll()) {
416 getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
417 while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
418 getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
419 EmitInstToData(Relaxed);
423 // Otherwise emit to a separate fragment.
424 EmitInstToFragment(Inst);
427 void MCMachOStreamer::Finish() {
428 // We have to set the fragment atom associations so we can relax properly for
431 // First, scan the symbol table to build a lookup table from fragments to
433 DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
434 for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
435 ie = getAssembler().symbol_end(); it != ie; ++it) {
436 if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
438 // An atom defining symbol should never be internal to a fragment.
439 assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
440 DefiningSymbolMap[it->getFragment()] = it;
444 // Set the fragment atom associations by tracking the last seen atom defining
446 for (MCAssembler::iterator it = getAssembler().begin(),
447 ie = getAssembler().end(); it != ie; ++it) {
448 MCSymbolData *CurrentAtom = 0;
449 for (MCSectionData::iterator it2 = it->begin(),
450 ie2 = it->end(); it2 != ie2; ++it2) {
451 if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
453 it2->setAtom(CurrentAtom);
457 this->MCObjectStreamer::Finish();
460 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
461 raw_ostream &OS, MCCodeEmitter *CE,
463 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
465 S->getAssembler().setRelaxAll(true);