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/Support/ErrorHandling.h"
20 #include "llvm/Support/raw_ostream.h"
25 class MCMachOStreamer : public MCStreamer {
26 /// SymbolFlags - We store the value for the 'desc' symbol field in the lowest
27 /// 16 bits of the implementation defined flags.
28 enum SymbolFlags { // See <mach-o/nlist.h>.
29 SF_DescFlagsMask = 0xFFFF,
31 // Reference type flags.
32 SF_ReferenceTypeMask = 0x0007,
33 SF_ReferenceTypeUndefinedNonLazy = 0x0000,
34 SF_ReferenceTypeUndefinedLazy = 0x0001,
35 SF_ReferenceTypeDefined = 0x0002,
36 SF_ReferenceTypePrivateDefined = 0x0003,
37 SF_ReferenceTypePrivateUndefinedNonLazy = 0x0004,
38 SF_ReferenceTypePrivateUndefinedLazy = 0x0005,
40 // Other 'desc' flags.
41 SF_NoDeadStrip = 0x0020,
42 SF_WeakReference = 0x0040,
43 SF_WeakDefinition = 0x0080
47 MCAssembler Assembler;
49 MCCodeEmitter *Emitter;
51 MCSectionData *CurSectionData;
53 DenseMap<const MCSection*, MCSectionData*> SectionMap;
55 DenseMap<const MCSymbol*, MCSymbolData*> SymbolMap;
58 MCFragment *getCurrentFragment() const {
59 assert(CurSectionData && "No current section!");
61 if (!CurSectionData->empty())
62 return &CurSectionData->getFragmentList().back();
67 MCSectionData &getSectionData(const MCSection &Section) {
68 MCSectionData *&Entry = SectionMap[&Section];
71 Entry = new MCSectionData(Section, &Assembler);
76 MCSymbolData &getSymbolData(const MCSymbol &Symbol) {
77 MCSymbolData *&Entry = SymbolMap[&Symbol];
80 Entry = new MCSymbolData(Symbol, 0, 0, &Assembler);
86 MCMachOStreamer(MCContext &Context, raw_ostream &_OS, MCCodeEmitter *_Emitter)
87 : MCStreamer(Context), Assembler(Context, _OS), Emitter(_Emitter),
91 const MCValue &AddValueSymbols(const MCValue &Value) {
93 getSymbolData(*const_cast<MCSymbol*>(Value.getSymA()));
95 getSymbolData(*const_cast<MCSymbol*>(Value.getSymB()));
99 const MCExpr *AddValueSymbols(const MCExpr *Value) {
100 switch (Value->getKind()) {
101 case MCExpr::Constant:
104 case MCExpr::Binary: {
105 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
106 AddValueSymbols(BE->getLHS());
107 AddValueSymbols(BE->getRHS());
111 case MCExpr::SymbolRef:
112 getSymbolData(cast<MCSymbolRefExpr>(Value)->getSymbol());
116 AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
123 /// @name MCStreamer Interface
126 virtual void SwitchSection(const MCSection *Section);
128 virtual void EmitLabel(MCSymbol *Symbol);
130 virtual void EmitAssemblerFlag(AssemblerFlag Flag);
132 virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value);
134 virtual void EmitSymbolAttribute(MCSymbol *Symbol, SymbolAttr Attribute);
136 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
138 virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
139 unsigned ByteAlignment);
141 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
142 unsigned Size = 0, unsigned ByteAlignment = 0);
144 virtual void EmitBytes(const StringRef &Data);
146 virtual void EmitValue(const MCValue &Value, unsigned Size);
148 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
149 unsigned ValueSize = 1,
150 unsigned MaxBytesToEmit = 0);
152 virtual void EmitValueToOffset(const MCValue &Offset,
153 unsigned char Value = 0);
155 virtual void EmitInstruction(const MCInst &Inst);
157 virtual void Finish();
162 } // end anonymous namespace.
164 void MCMachOStreamer::SwitchSection(const MCSection *Section) {
165 assert(Section && "Cannot switch to a null section!");
167 // If already in this section, then this is a noop.
168 if (Section == CurSection) return;
170 CurSection = Section;
171 CurSectionData = &getSectionData(*Section);
174 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
175 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
177 // FIXME: We should also use offsets into Fill fragments.
178 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
180 F = new MCDataFragment(CurSectionData);
182 MCSymbolData &SD = getSymbolData(*Symbol);
183 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
185 SD.setOffset(F->getContents().size());
187 // This causes the reference type and weak reference flags to be cleared.
188 SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
190 Symbol->setSection(*CurSection);
193 void MCMachOStreamer::EmitAssemblerFlag(AssemblerFlag Flag) {
195 case SubsectionsViaSymbols:
196 Assembler.setSubsectionsViaSymbols(true);
200 assert(0 && "invalid assembler flag!");
203 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCValue &Value) {
204 // Only absolute symbols can be redefined.
205 assert((Symbol->isUndefined() || Symbol->isAbsolute()) &&
206 "Cannot define a symbol twice!");
208 llvm_unreachable("FIXME: Not yet implemented!");
211 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
212 SymbolAttr Attribute) {
213 // Indirect symbols are handled differently, to match how 'as' handles
214 // them. This makes writing matching .o files easier.
215 if (Attribute == MCStreamer::IndirectSymbol) {
216 // Note that we intentionally cannot use the symbol data here; this is
217 // important for matching the string table that 'as' generates.
218 IndirectSymbolData ISD;
220 ISD.SectionData = CurSectionData;
221 Assembler.getIndirectSymbols().push_back(ISD);
225 // Adding a symbol attribute always introduces the symbol, note that an
226 // important side effect of calling getSymbolData here is to register the
227 // symbol with the assembler.
228 MCSymbolData &SD = getSymbolData(*Symbol);
230 // The implementation of symbol attributes is designed to match 'as', but it
231 // leaves much to desired. It doesn't really make sense to arbitrarily add and
232 // remove flags, but 'as' allows this (in particular, see .desc).
234 // In the future it might be worth trying to make these operations more well
237 case MCStreamer::IndirectSymbol:
238 case MCStreamer::Hidden:
239 case MCStreamer::Internal:
240 case MCStreamer::Protected:
241 case MCStreamer::Weak:
242 assert(0 && "Invalid symbol attribute for Mach-O!");
245 case MCStreamer::Global:
246 SD.setExternal(true);
249 case MCStreamer::LazyReference:
250 // FIXME: This requires -dynamic.
251 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
252 if (Symbol->isUndefined())
253 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
256 // Since .reference sets the no dead strip bit, it is equivalent to
257 // .no_dead_strip in practice.
258 case MCStreamer::Reference:
259 case MCStreamer::NoDeadStrip:
260 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
263 case MCStreamer::PrivateExtern:
264 SD.setExternal(true);
265 SD.setPrivateExtern(true);
268 case MCStreamer::WeakReference:
269 // FIXME: This requires -dynamic.
270 if (Symbol->isUndefined())
271 SD.setFlags(SD.getFlags() | SF_WeakReference);
274 case MCStreamer::WeakDefinition:
275 // FIXME: 'as' enforces that this is defined and global. The manual claims
276 // it has to be in a coalesced section, but this isn't enforced.
277 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
282 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
283 // Encode the 'desc' value into the lowest implementation defined bits.
284 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
285 "Invalid .desc value!");
286 getSymbolData(*Symbol).setFlags(DescValue & SF_DescFlagsMask);
289 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, unsigned Size,
290 unsigned ByteAlignment) {
291 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
292 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
294 MCSymbolData &SD = getSymbolData(*Symbol);
295 SD.setExternal(true);
296 SD.setCommon(Size, ByteAlignment);
299 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
300 unsigned Size, unsigned ByteAlignment) {
301 MCSectionData &SectData = getSectionData(*Section);
303 // The symbol may not be present, which only creates the section.
307 // FIXME: Assert that this section has the zerofill type.
309 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
311 MCSymbolData &SD = getSymbolData(*Symbol);
313 MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
316 Symbol->setSection(*Section);
318 // Update the maximum alignment on the zero fill section if necessary.
319 if (ByteAlignment > SectData.getAlignment())
320 SectData.setAlignment(ByteAlignment);
323 void MCMachOStreamer::EmitBytes(const StringRef &Data) {
324 MCDataFragment *DF = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
326 DF = new MCDataFragment(CurSectionData);
327 DF->getContents().append(Data.begin(), Data.end());
330 void MCMachOStreamer::EmitValue(const MCValue &Value, unsigned Size) {
331 new MCFillFragment(AddValueSymbols(Value), Size, 1, CurSectionData);
334 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
335 int64_t Value, unsigned ValueSize,
336 unsigned MaxBytesToEmit) {
337 if (MaxBytesToEmit == 0)
338 MaxBytesToEmit = ByteAlignment;
339 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
342 // Update the maximum alignment on the current section if necessary.
343 if (ByteAlignment > CurSectionData->getAlignment())
344 CurSectionData->setAlignment(ByteAlignment);
347 void MCMachOStreamer::EmitValueToOffset(const MCValue &Offset,
348 unsigned char Value) {
349 new MCOrgFragment(AddValueSymbols(Offset), Value, CurSectionData);
352 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
354 for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
355 if (Inst.getOperand(i).isExpr())
356 AddValueSymbols(Inst.getOperand(i).getExpr());
359 llvm_unreachable("no code emitter available!");
361 // FIXME: Relocations!
362 SmallString<256> Code;
363 raw_svector_ostream VecOS(Code);
364 Emitter->EncodeInstruction(Inst, VecOS);
365 EmitBytes(VecOS.str());
368 void MCMachOStreamer::Finish() {
372 MCStreamer *llvm::createMachOStreamer(MCContext &Context, raw_ostream &OS,
374 return new MCMachOStreamer(Context, OS, CE);