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/MCSection.h"
18 #include "llvm/MC/MCSymbol.h"
19 #include "llvm/MC/MCMachOSymbolFlags.h"
20 #include "llvm/Support/ErrorHandling.h"
21 #include "llvm/Support/raw_ostream.h"
22 #include "llvm/Target/TargetAsmBackend.h"
28 class MCMachOStreamer : public MCStreamer {
31 MCAssembler Assembler;
32 MCSectionData *CurSectionData;
34 /// Track the current atom for each section.
35 DenseMap<const MCSectionData*, MCSymbolData*> CurrentAtomMap;
38 MCFragment *getCurrentFragment() const {
39 assert(CurSectionData && "No current section!");
41 if (!CurSectionData->empty())
42 return &CurSectionData->getFragmentList().back();
47 /// Get a data fragment to write into, creating a new one if the current
48 /// fragment is not a data fragment.
49 MCDataFragment *getOrCreateDataFragment() const {
50 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
52 F = createDataFragment();
56 /// Create a new data fragment in the current section.
57 MCDataFragment *createDataFragment() const {
58 MCDataFragment *DF = new MCDataFragment(CurSectionData);
59 DF->setAtom(CurrentAtomMap.lookup(CurSectionData));
64 MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
65 raw_ostream &_OS, MCCodeEmitter *_Emitter)
66 : MCStreamer(Context), Assembler(Context, TAB, *_Emitter, _OS),
70 MCAssembler &getAssembler() { return Assembler; }
72 const MCExpr *AddValueSymbols(const MCExpr *Value) {
73 switch (Value->getKind()) {
74 case MCExpr::Target: assert(0 && "Can't handle target exprs yet!");
75 case MCExpr::Constant:
78 case MCExpr::Binary: {
79 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
80 AddValueSymbols(BE->getLHS());
81 AddValueSymbols(BE->getRHS());
85 case MCExpr::SymbolRef:
86 Assembler.getOrCreateSymbolData(
87 cast<MCSymbolRefExpr>(Value)->getSymbol());
91 AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
98 /// @name MCStreamer Interface
101 virtual void SwitchSection(const MCSection *Section);
102 virtual void EmitLabel(MCSymbol *Symbol);
103 virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
104 virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
105 virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
106 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
107 virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
108 unsigned ByteAlignment);
109 virtual void BeginCOFFSymbolDef(const MCSymbol *Symbol) {
110 assert(0 && "macho doesn't support this directive");
112 virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
113 assert(0 && "macho doesn't support this directive");
115 virtual void EmitCOFFSymbolType(int Type) {
116 assert(0 && "macho doesn't support this directive");
118 virtual void EndCOFFSymbolDef() {
119 assert(0 && "macho doesn't support this directive");
121 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
122 assert(0 && "macho doesn't support this directive");
124 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
125 assert(0 && "macho doesn't support this directive");
127 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
128 unsigned Size = 0, unsigned ByteAlignment = 0);
129 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
130 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
131 virtual void EmitGPRel32Value(const MCExpr *Value) {
132 assert(0 && "macho doesn't support this directive");
134 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
135 unsigned ValueSize = 1,
136 unsigned MaxBytesToEmit = 0);
137 virtual void EmitCodeAlignment(unsigned ByteAlignment,
138 unsigned MaxBytesToEmit = 0);
139 virtual void EmitValueToOffset(const MCExpr *Offset,
140 unsigned char Value = 0);
142 virtual void EmitFileDirective(StringRef Filename) {
143 errs() << "FIXME: MCMachoStreamer:EmitFileDirective not implemented\n";
145 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
146 errs() << "FIXME: MCMachoStreamer:EmitDwarfFileDirective not implemented\n";
149 virtual void EmitInstruction(const MCInst &Inst);
150 virtual void Finish();
155 } // end anonymous namespace.
157 void MCMachOStreamer::SwitchSection(const MCSection *Section) {
158 assert(Section && "Cannot switch to a null section!");
160 // If already in this section, then this is a noop.
161 if (Section == CurSection) return;
163 CurSection = Section;
164 CurSectionData = &Assembler.getOrCreateSectionData(*Section);
167 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
168 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
169 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
170 assert(CurSection && "Cannot emit before setting section!");
172 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
174 // Update the current atom map, if necessary.
175 bool MustCreateFragment = false;
176 if (Assembler.isSymbolLinkerVisible(&SD)) {
177 CurrentAtomMap[CurSectionData] = &SD;
179 // We have to create a new fragment, fragments cannot span atoms.
180 MustCreateFragment = true;
183 // FIXME: This is wasteful, we don't necessarily need to create a data
184 // fragment. Instead, we should mark the symbol as pointing into the data
185 // fragment if it exists, otherwise we should just queue the label and set its
186 // fragment pointer when we emit the next fragment.
188 MustCreateFragment ? createDataFragment() : getOrCreateDataFragment();
189 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
191 SD.setOffset(F->getContents().size());
193 // This causes the reference type and weak reference flags to be cleared.
194 SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
196 Symbol->setSection(*CurSection);
199 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
201 case MCAF_SubsectionsViaSymbols:
202 Assembler.setSubsectionsViaSymbols(true);
206 assert(0 && "invalid assembler flag!");
209 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
210 // FIXME: Lift context changes into super class.
211 Symbol->setVariableValue(AddValueSymbols(Value));
214 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
215 MCSymbolAttr Attribute) {
216 // Indirect symbols are handled differently, to match how 'as' handles
217 // them. This makes writing matching .o files easier.
218 if (Attribute == MCSA_IndirectSymbol) {
219 // Note that we intentionally cannot use the symbol data here; this is
220 // important for matching the string table that 'as' generates.
221 IndirectSymbolData ISD;
223 ISD.SectionData = CurSectionData;
224 Assembler.getIndirectSymbols().push_back(ISD);
228 // Adding a symbol attribute always introduces the symbol, note that an
229 // important side effect of calling getOrCreateSymbolData here is to register
230 // the symbol with the assembler.
231 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
233 // The implementation of symbol attributes is designed to match 'as', but it
234 // leaves much to desired. It doesn't really make sense to arbitrarily add and
235 // remove flags, but 'as' allows this (in particular, see .desc).
237 // In the future it might be worth trying to make these operations more well
241 case MCSA_ELF_TypeFunction:
242 case MCSA_ELF_TypeIndFunction:
243 case MCSA_ELF_TypeObject:
244 case MCSA_ELF_TypeTLS:
245 case MCSA_ELF_TypeCommon:
246 case MCSA_ELF_TypeNoType:
247 case MCSA_IndirectSymbol:
253 assert(0 && "Invalid symbol attribute for Mach-O!");
257 SD.setExternal(true);
260 case MCSA_LazyReference:
261 // FIXME: This requires -dynamic.
262 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
263 if (Symbol->isUndefined())
264 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
267 // Since .reference sets the no dead strip bit, it is equivalent to
268 // .no_dead_strip in practice.
270 case MCSA_NoDeadStrip:
271 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
274 case MCSA_PrivateExtern:
275 SD.setExternal(true);
276 SD.setPrivateExtern(true);
279 case MCSA_WeakReference:
280 // FIXME: This requires -dynamic.
281 if (Symbol->isUndefined())
282 SD.setFlags(SD.getFlags() | SF_WeakReference);
285 case MCSA_WeakDefinition:
286 // FIXME: 'as' enforces that this is defined and global. The manual claims
287 // it has to be in a coalesced section, but this isn't enforced.
288 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
293 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
294 // Encode the 'desc' value into the lowest implementation defined bits.
295 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
296 "Invalid .desc value!");
297 Assembler.getOrCreateSymbolData(*Symbol).setFlags(DescValue&SF_DescFlagsMask);
300 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
301 unsigned ByteAlignment) {
302 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
303 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
305 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
306 SD.setExternal(true);
307 SD.setCommon(Size, ByteAlignment);
310 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
311 unsigned Size, unsigned ByteAlignment) {
312 MCSectionData &SectData = Assembler.getOrCreateSectionData(*Section);
314 // The symbol may not be present, which only creates the section.
318 // FIXME: Assert that this section has the zerofill type.
320 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
322 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
324 MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
326 if (Assembler.isSymbolLinkerVisible(&SD))
329 Symbol->setSection(*Section);
331 // Update the maximum alignment on the zero fill section if necessary.
332 if (ByteAlignment > SectData.getAlignment())
333 SectData.setAlignment(ByteAlignment);
336 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
337 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
340 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
341 unsigned AddrSpace) {
342 MCDataFragment *DF = getOrCreateDataFragment();
344 // Avoid fixups when possible.
346 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
347 // FIXME: Endianness assumption.
348 for (unsigned i = 0; i != Size; ++i)
349 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
351 DF->addFixup(MCAsmFixup(DF->getContents().size(), *AddValueSymbols(Value),
352 MCFixup::getKindForSize(Size)));
353 DF->getContents().resize(DF->getContents().size() + Size, 0);
357 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
358 int64_t Value, unsigned ValueSize,
359 unsigned MaxBytesToEmit) {
360 if (MaxBytesToEmit == 0)
361 MaxBytesToEmit = ByteAlignment;
362 MCFragment *F = new MCAlignFragment(ByteAlignment, Value, ValueSize,
363 MaxBytesToEmit, /*EmitNops=*/false,
365 F->setAtom(CurrentAtomMap.lookup(CurSectionData));
367 // Update the maximum alignment on the current section if necessary.
368 if (ByteAlignment > CurSectionData->getAlignment())
369 CurSectionData->setAlignment(ByteAlignment);
372 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
373 unsigned MaxBytesToEmit) {
374 if (MaxBytesToEmit == 0)
375 MaxBytesToEmit = ByteAlignment;
376 MCFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
377 /*EmitNops=*/true, CurSectionData);
378 F->setAtom(CurrentAtomMap.lookup(CurSectionData));
380 // Update the maximum alignment on the current section if necessary.
381 if (ByteAlignment > CurSectionData->getAlignment())
382 CurSectionData->setAlignment(ByteAlignment);
385 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
386 unsigned char Value) {
387 MCFragment *F = new MCOrgFragment(*Offset, Value, CurSectionData);
388 F->setAtom(CurrentAtomMap.lookup(CurSectionData));
391 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
393 for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
394 if (Inst.getOperand(i).isExpr())
395 AddValueSymbols(Inst.getOperand(i).getExpr());
397 CurSectionData->setHasInstructions(true);
399 // FIXME-PERF: Common case is that we don't need to relax, encode directly
400 // onto the data fragments buffers.
402 SmallVector<MCFixup, 4> Fixups;
403 SmallString<256> Code;
404 raw_svector_ostream VecOS(Code);
405 Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
408 // FIXME: Eliminate this copy.
409 SmallVector<MCAsmFixup, 4> AsmFixups;
410 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
411 MCFixup &F = Fixups[i];
412 AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
416 // See if we might need to relax this instruction, if so it needs its own
419 // FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
420 // when we can immediately tell that we will get something which might need
421 // relaxation (and compute its size).
423 // FIXME-PERF: We should also be smart about immediately relaxing instructions
424 // which we can already show will never possibly fit (we can also do a very
425 // good job of this before we do the first relaxation pass, because we have
426 // total knowledge about undefined symbols at that point). Even now, though,
427 // we can do a decent job, especially on Darwin where scattering means that we
428 // are going to often know that we can never fully resolve a fixup.
429 if (Assembler.getBackend().MayNeedRelaxation(Inst, AsmFixups)) {
430 MCInstFragment *IF = new MCInstFragment(Inst, CurSectionData);
431 IF->setAtom(CurrentAtomMap.lookup(CurSectionData));
433 // Add the fixups and data.
435 // FIXME: Revisit this design decision when relaxation is done, we may be
436 // able to get away with not storing any extra data in the MCInst.
437 IF->getCode() = Code;
438 IF->getFixups() = AsmFixups;
443 // Add the fixups and data.
444 MCDataFragment *DF = getOrCreateDataFragment();
445 for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
446 AsmFixups[i].Offset += DF->getContents().size();
447 DF->addFixup(AsmFixups[i]);
449 DF->getContents().append(Code.begin(), Code.end());
452 void MCMachOStreamer::Finish() {
456 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
457 raw_ostream &OS, MCCodeEmitter *CE,
459 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
461 S->getAssembler().setRelaxAll(true);