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 MCFragment *getCurrentFragment() const {
32 assert(getCurrentSectionData() && "No current section!");
34 if (!getCurrentSectionData()->empty())
35 return &getCurrentSectionData()->getFragmentList().back();
40 /// Get a data fragment to write into, creating a new one if the current
41 /// fragment is not a data fragment.
42 MCDataFragment *getOrCreateDataFragment() const {
43 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
45 F = new MCDataFragment(getCurrentSectionData());
49 void EmitInstToFragment(const MCInst &Inst);
50 void EmitInstToData(const MCInst &Inst);
53 MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
54 raw_ostream &OS, MCCodeEmitter *Emitter)
55 : MCObjectStreamer(Context, TAB, OS, Emitter) {}
57 const MCExpr *AddValueSymbols(const MCExpr *Value) {
58 switch (Value->getKind()) {
59 case MCExpr::Target: assert(0 && "Can't handle target exprs yet!");
60 case MCExpr::Constant:
63 case MCExpr::Binary: {
64 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
65 AddValueSymbols(BE->getLHS());
66 AddValueSymbols(BE->getRHS());
70 case MCExpr::SymbolRef:
71 getAssembler().getOrCreateSymbolData(
72 cast<MCSymbolRefExpr>(Value)->getSymbol());
76 AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
83 /// @name MCStreamer Interface
86 virtual void EmitLabel(MCSymbol *Symbol);
87 virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
88 virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
89 virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
90 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
91 virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
92 unsigned ByteAlignment);
93 virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
94 assert(0 && "macho doesn't support this directive");
96 virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
97 assert(0 && "macho doesn't support this directive");
99 virtual void EmitCOFFSymbolType(int Type) {
100 assert(0 && "macho doesn't support this directive");
102 virtual void EndCOFFSymbolDef() {
103 assert(0 && "macho doesn't support this directive");
105 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
106 assert(0 && "macho doesn't support this directive");
108 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
109 assert(0 && "macho doesn't support this directive");
111 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
112 unsigned Size = 0, unsigned ByteAlignment = 0);
113 virtual void EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
114 uint64_t Size, unsigned ByteAlignment = 0);
115 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
116 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
117 virtual void EmitGPRel32Value(const MCExpr *Value) {
118 assert(0 && "macho doesn't support this directive");
120 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
121 unsigned ValueSize = 1,
122 unsigned MaxBytesToEmit = 0);
123 virtual void EmitCodeAlignment(unsigned ByteAlignment,
124 unsigned MaxBytesToEmit = 0);
125 virtual void EmitValueToOffset(const MCExpr *Offset,
126 unsigned char Value = 0);
128 virtual void EmitFileDirective(StringRef Filename) {
129 report_fatal_error("unsupported directive: '.file'");
131 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
132 report_fatal_error("unsupported directive: '.file'");
135 virtual void EmitInstruction(const MCInst &Inst);
137 virtual void Finish();
142 } // end anonymous namespace.
144 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
145 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
146 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
147 assert(CurSection && "Cannot emit before setting section!");
149 Symbol->setSection(*CurSection);
151 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
153 // We have to create a new fragment if this is an atom defining symbol,
154 // fragments cannot span atoms.
155 if (getAssembler().isSymbolLinkerVisible(SD.getSymbol()))
156 new MCDataFragment(getCurrentSectionData());
158 // FIXME: This is wasteful, we don't necessarily need to create a data
159 // fragment. Instead, we should mark the symbol as pointing into the data
160 // fragment if it exists, otherwise we should just queue the label and set its
161 // fragment pointer when we emit the next fragment.
162 MCDataFragment *F = getOrCreateDataFragment();
163 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
165 SD.setOffset(F->getContents().size());
167 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
168 // to clear the weak reference and weak definition bits too, but the
169 // implementation was buggy. For now we just try to match 'as', for
172 // FIXME: Cleanup this code, these bits should be emitted based on semantic
173 // properties, not on the order of definition, etc.
174 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
177 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
179 case MCAF_SubsectionsViaSymbols:
180 getAssembler().setSubsectionsViaSymbols(true);
184 assert(0 && "invalid assembler flag!");
187 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
188 // FIXME: Lift context changes into super class.
189 getAssembler().getOrCreateSymbolData(*Symbol);
190 Symbol->setVariableValue(AddValueSymbols(Value));
193 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
194 MCSymbolAttr Attribute) {
195 // Indirect symbols are handled differently, to match how 'as' handles
196 // them. This makes writing matching .o files easier.
197 if (Attribute == MCSA_IndirectSymbol) {
198 // Note that we intentionally cannot use the symbol data here; this is
199 // important for matching the string table that 'as' generates.
200 IndirectSymbolData ISD;
202 ISD.SectionData = getCurrentSectionData();
203 getAssembler().getIndirectSymbols().push_back(ISD);
207 // Adding a symbol attribute always introduces the symbol, note that an
208 // important side effect of calling getOrCreateSymbolData here is to register
209 // the symbol with the assembler.
210 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
212 // The implementation of symbol attributes is designed to match 'as', but it
213 // leaves much to desired. It doesn't really make sense to arbitrarily add and
214 // remove flags, but 'as' allows this (in particular, see .desc).
216 // In the future it might be worth trying to make these operations more well
220 case MCSA_ELF_TypeFunction:
221 case MCSA_ELF_TypeIndFunction:
222 case MCSA_ELF_TypeObject:
223 case MCSA_ELF_TypeTLS:
224 case MCSA_ELF_TypeCommon:
225 case MCSA_ELF_TypeNoType:
226 case MCSA_IndirectSymbol:
232 assert(0 && "Invalid symbol attribute for Mach-O!");
236 SD.setExternal(true);
237 // This effectively clears the undefined lazy bit, in Darwin 'as', although
238 // it isn't very consistent because it implements this as part of symbol
241 // FIXME: Cleanup this code, these bits should be emitted based on semantic
242 // properties, not on the order of definition, etc.
243 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
246 case MCSA_LazyReference:
247 // FIXME: This requires -dynamic.
248 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
249 if (Symbol->isUndefined())
250 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
253 // Since .reference sets the no dead strip bit, it is equivalent to
254 // .no_dead_strip in practice.
256 case MCSA_NoDeadStrip:
257 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
260 case MCSA_PrivateExtern:
261 SD.setExternal(true);
262 SD.setPrivateExtern(true);
265 case MCSA_WeakReference:
266 // FIXME: This requires -dynamic.
267 if (Symbol->isUndefined())
268 SD.setFlags(SD.getFlags() | SF_WeakReference);
271 case MCSA_WeakDefinition:
272 // FIXME: 'as' enforces that this is defined and global. The manual claims
273 // it has to be in a coalesced section, but this isn't enforced.
274 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
279 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
280 // Encode the 'desc' value into the lowest implementation defined bits.
281 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
282 "Invalid .desc value!");
283 getAssembler().getOrCreateSymbolData(*Symbol).setFlags(
284 DescValue & SF_DescFlagsMask);
287 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
288 unsigned ByteAlignment) {
289 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
290 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
292 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
293 SD.setExternal(true);
294 SD.setCommon(Size, ByteAlignment);
297 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
298 unsigned Size, unsigned ByteAlignment) {
299 MCSectionData &SectData = getAssembler().getOrCreateSectionData(*Section);
301 // The symbol may not be present, which only creates the section.
305 // FIXME: Assert that this section has the zerofill type.
307 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
309 MCSymbolData &SD = getAssembler().getOrCreateSymbolData(*Symbol);
311 // Emit an align fragment if necessary.
312 if (ByteAlignment != 1)
313 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
315 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
318 Symbol->setSection(*Section);
320 // Update the maximum alignment on the zero fill section if necessary.
321 if (ByteAlignment > SectData.getAlignment())
322 SectData.setAlignment(ByteAlignment);
325 // This should always be called with the thread local bss section. Like the
326 // .zerofill directive this doesn't actually switch sections on us.
327 void MCMachOStreamer::EmitTBSSSymbol(const MCSection *Section, MCSymbol *Symbol,
328 uint64_t Size, unsigned ByteAlignment) {
329 EmitZerofill(Section, Symbol, Size, ByteAlignment);
333 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
334 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
337 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
338 unsigned AddrSpace) {
339 MCDataFragment *DF = getOrCreateDataFragment();
341 // Avoid fixups when possible.
343 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
344 // FIXME: Endianness assumption.
345 for (unsigned i = 0; i != Size; ++i)
346 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
348 DF->addFixup(MCFixup::Create(DF->getContents().size(),
349 AddValueSymbols(Value),
350 MCFixup::getKindForSize(Size)));
351 DF->getContents().resize(DF->getContents().size() + Size, 0);
355 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
356 int64_t Value, unsigned ValueSize,
357 unsigned MaxBytesToEmit) {
358 if (MaxBytesToEmit == 0)
359 MaxBytesToEmit = ByteAlignment;
360 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
361 getCurrentSectionData());
363 // Update the maximum alignment on the current section if necessary.
364 if (ByteAlignment > getCurrentSectionData()->getAlignment())
365 getCurrentSectionData()->setAlignment(ByteAlignment);
368 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
369 unsigned MaxBytesToEmit) {
370 if (MaxBytesToEmit == 0)
371 MaxBytesToEmit = ByteAlignment;
372 MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
373 getCurrentSectionData());
374 F->setEmitNops(true);
376 // Update the maximum alignment on the current section if necessary.
377 if (ByteAlignment > getCurrentSectionData()->getAlignment())
378 getCurrentSectionData()->setAlignment(ByteAlignment);
381 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
382 unsigned char Value) {
383 new MCOrgFragment(*Offset, Value, getCurrentSectionData());
386 void MCMachOStreamer::EmitInstToFragment(const MCInst &Inst) {
387 MCInstFragment *IF = new MCInstFragment(Inst, getCurrentSectionData());
389 // Add the fixups and data.
391 // FIXME: Revisit this design decision when relaxation is done, we may be
392 // able to get away with not storing any extra data in the MCInst.
393 SmallVector<MCFixup, 4> Fixups;
394 SmallString<256> Code;
395 raw_svector_ostream VecOS(Code);
396 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
399 IF->getCode() = Code;
400 IF->getFixups() = Fixups;
403 void MCMachOStreamer::EmitInstToData(const MCInst &Inst) {
404 MCDataFragment *DF = getOrCreateDataFragment();
406 SmallVector<MCFixup, 4> Fixups;
407 SmallString<256> Code;
408 raw_svector_ostream VecOS(Code);
409 getAssembler().getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
412 // Add the fixups and data.
413 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
414 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
415 DF->addFixup(Fixups[i]);
417 DF->getContents().append(Code.begin(), Code.end());
420 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
422 for (unsigned i = Inst.getNumOperands(); i--; )
423 if (Inst.getOperand(i).isExpr())
424 AddValueSymbols(Inst.getOperand(i).getExpr());
426 getCurrentSectionData()->setHasInstructions(true);
428 // If this instruction doesn't need relaxation, just emit it as data.
429 if (!getAssembler().getBackend().MayNeedRelaxation(Inst)) {
430 EmitInstToData(Inst);
434 // Otherwise, if we are relaxing everything, relax the instruction as much as
435 // possible and emit it as data.
436 if (getAssembler().getRelaxAll()) {
438 getAssembler().getBackend().RelaxInstruction(Inst, Relaxed);
439 while (getAssembler().getBackend().MayNeedRelaxation(Relaxed))
440 getAssembler().getBackend().RelaxInstruction(Relaxed, Relaxed);
441 EmitInstToData(Relaxed);
445 // Otherwise emit to a separate fragment.
446 EmitInstToFragment(Inst);
449 void MCMachOStreamer::Finish() {
450 // We have to set the fragment atom associations so we can relax properly for
453 // First, scan the symbol table to build a lookup table from fragments to
455 DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
456 for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
457 ie = getAssembler().symbol_end(); it != ie; ++it) {
458 if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
460 // An atom defining symbol should never be internal to a fragment.
461 assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
462 DefiningSymbolMap[it->getFragment()] = it;
466 // Set the fragment atom associations by tracking the last seen atom defining
468 for (MCAssembler::iterator it = getAssembler().begin(),
469 ie = getAssembler().end(); it != ie; ++it) {
470 MCSymbolData *CurrentAtom = 0;
471 for (MCSectionData::iterator it2 = it->begin(),
472 ie2 = it->end(); it2 != ie2; ++it2) {
473 if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
475 it2->setAtom(CurrentAtom);
479 this->MCObjectStreamer::Finish();
482 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
483 raw_ostream &OS, MCCodeEmitter *CE,
485 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
487 S->getAssembler().setRelaxAll(true);