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"
21 #include "llvm/Target/TargetAsmBackend.h"
27 class MCMachOStreamer : public MCStreamer {
28 /// SymbolFlags - We store the value for the 'desc' symbol field in the lowest
29 /// 16 bits of the implementation defined flags.
30 enum SymbolFlags { // See <mach-o/nlist.h>.
31 SF_DescFlagsMask = 0xFFFF,
33 // Reference type flags.
34 SF_ReferenceTypeMask = 0x0007,
35 SF_ReferenceTypeUndefinedNonLazy = 0x0000,
36 SF_ReferenceTypeUndefinedLazy = 0x0001,
37 SF_ReferenceTypeDefined = 0x0002,
38 SF_ReferenceTypePrivateDefined = 0x0003,
39 SF_ReferenceTypePrivateUndefinedNonLazy = 0x0004,
40 SF_ReferenceTypePrivateUndefinedLazy = 0x0005,
42 // Other 'desc' flags.
43 SF_NoDeadStrip = 0x0020,
44 SF_WeakReference = 0x0040,
45 SF_WeakDefinition = 0x0080
49 MCAssembler Assembler;
50 MCSectionData *CurSectionData;
53 MCFragment *getCurrentFragment() const {
54 assert(CurSectionData && "No current section!");
56 if (!CurSectionData->empty())
57 return &CurSectionData->getFragmentList().back();
62 /// Get a data fragment to write into, creating a new one if the current
63 /// fragment is not a data fragment.
64 MCDataFragment *getOrCreateDataFragment() const {
65 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
67 F = new MCDataFragment(CurSectionData);
72 MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
73 raw_ostream &_OS, MCCodeEmitter *_Emitter)
74 : MCStreamer(Context), Assembler(Context, TAB, *_Emitter, _OS),
78 MCAssembler &getAssembler() { return Assembler; }
80 const MCExpr *AddValueSymbols(const MCExpr *Value) {
81 switch (Value->getKind()) {
82 case MCExpr::Target: assert(0 && "Can't handle target exprs yet!");
83 case MCExpr::Constant:
86 case MCExpr::Binary: {
87 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
88 AddValueSymbols(BE->getLHS());
89 AddValueSymbols(BE->getRHS());
93 case MCExpr::SymbolRef:
94 Assembler.getOrCreateSymbolData(
95 cast<MCSymbolRefExpr>(Value)->getSymbol());
99 AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
106 /// @name MCStreamer Interface
109 virtual void SwitchSection(const MCSection *Section);
110 virtual void EmitLabel(MCSymbol *Symbol);
111 virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
112 virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
113 virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
114 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
115 virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
116 unsigned ByteAlignment);
117 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
118 assert(0 && "macho doesn't support this directive");
120 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
121 assert(0 && "macho doesn't support this directive");
123 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
124 unsigned Size = 0, unsigned ByteAlignment = 0);
125 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
126 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
127 virtual void EmitGPRel32Value(const MCExpr *Value) {
128 assert(0 && "macho doesn't support this directive");
130 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
131 unsigned ValueSize = 1,
132 unsigned MaxBytesToEmit = 0);
133 virtual void EmitCodeAlignment(unsigned ByteAlignment,
134 unsigned MaxBytesToEmit = 0);
135 virtual void EmitValueToOffset(const MCExpr *Offset,
136 unsigned char Value = 0);
138 virtual void EmitFileDirective(StringRef Filename) {
139 errs() << "FIXME: MCMachoStreamer:EmitFileDirective not implemented\n";
141 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
142 errs() << "FIXME: MCMachoStreamer:EmitDwarfFileDirective not implemented\n";
145 virtual void EmitInstruction(const MCInst &Inst);
146 virtual void Finish();
151 } // end anonymous namespace.
153 void MCMachOStreamer::SwitchSection(const MCSection *Section) {
154 assert(Section && "Cannot switch to a null section!");
156 // If already in this section, then this is a noop.
157 if (Section == CurSection) return;
159 CurSection = Section;
160 CurSectionData = &Assembler.getOrCreateSectionData(*Section);
163 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
164 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
165 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
166 assert(CurSection && "Cannot emit before setting section!");
168 // FIXME: This is wasteful, we don't necessarily need to create a data
169 // fragment. Instead, we should mark the symbol as pointing into the data
170 // fragment if it exists, otherwise we should just queue the label and set its
171 // fragment pointer when we emit the next fragment.
172 MCDataFragment *F = getOrCreateDataFragment();
173 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
174 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
176 SD.setOffset(F->getContents().size());
178 // This causes the reference type and weak reference flags to be cleared.
179 SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
181 Symbol->setSection(*CurSection);
184 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
186 case MCAF_SubsectionsViaSymbols:
187 Assembler.setSubsectionsViaSymbols(true);
191 assert(0 && "invalid assembler flag!");
194 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
195 // FIXME: Lift context changes into super class.
196 // FIXME: Set associated section.
197 Symbol->setVariableValue(AddValueSymbols(Value));
200 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
201 MCSymbolAttr Attribute) {
202 // Indirect symbols are handled differently, to match how 'as' handles
203 // them. This makes writing matching .o files easier.
204 if (Attribute == MCSA_IndirectSymbol) {
205 // Note that we intentionally cannot use the symbol data here; this is
206 // important for matching the string table that 'as' generates.
207 IndirectSymbolData ISD;
209 ISD.SectionData = CurSectionData;
210 Assembler.getIndirectSymbols().push_back(ISD);
214 // Adding a symbol attribute always introduces the symbol, note that an
215 // important side effect of calling getOrCreateSymbolData here is to register
216 // the symbol with the assembler.
217 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
219 // The implementation of symbol attributes is designed to match 'as', but it
220 // leaves much to desired. It doesn't really make sense to arbitrarily add and
221 // remove flags, but 'as' allows this (in particular, see .desc).
223 // In the future it might be worth trying to make these operations more well
227 case MCSA_ELF_TypeFunction:
228 case MCSA_ELF_TypeIndFunction:
229 case MCSA_ELF_TypeObject:
230 case MCSA_ELF_TypeTLS:
231 case MCSA_ELF_TypeCommon:
232 case MCSA_ELF_TypeNoType:
233 case MCSA_IndirectSymbol:
239 assert(0 && "Invalid symbol attribute for Mach-O!");
243 SD.setExternal(true);
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 Assembler.getOrCreateSymbolData(*Symbol).setFlags(DescValue&SF_DescFlagsMask);
286 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
287 unsigned ByteAlignment) {
288 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
289 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
291 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
292 SD.setExternal(true);
293 SD.setCommon(Size, ByteAlignment);
296 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
297 unsigned Size, unsigned ByteAlignment) {
298 MCSectionData &SectData = Assembler.getOrCreateSectionData(*Section);
300 // The symbol may not be present, which only creates the section.
304 // FIXME: Assert that this section has the zerofill type.
306 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
308 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
310 MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
313 Symbol->setSection(*Section);
315 // Update the maximum alignment on the zero fill section if necessary.
316 if (ByteAlignment > SectData.getAlignment())
317 SectData.setAlignment(ByteAlignment);
320 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
321 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
324 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
325 unsigned AddrSpace) {
326 MCDataFragment *DF = getOrCreateDataFragment();
328 // Avoid fixups when possible.
330 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
331 // FIXME: Endianness assumption.
332 for (unsigned i = 0; i != Size; ++i)
333 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
335 DF->addFixup(MCAsmFixup(DF->getContents().size(), *AddValueSymbols(Value),
336 MCFixup::getKindForSize(Size)));
337 DF->getContents().resize(DF->getContents().size() + Size, 0);
341 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
342 int64_t Value, unsigned ValueSize,
343 unsigned MaxBytesToEmit) {
344 if (MaxBytesToEmit == 0)
345 MaxBytesToEmit = ByteAlignment;
346 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
347 false /* EmitNops */, CurSectionData);
349 // Update the maximum alignment on the current section if necessary.
350 if (ByteAlignment > CurSectionData->getAlignment())
351 CurSectionData->setAlignment(ByteAlignment);
354 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
355 unsigned MaxBytesToEmit) {
356 if (MaxBytesToEmit == 0)
357 MaxBytesToEmit = ByteAlignment;
358 new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
359 true /* EmitNops */, CurSectionData);
361 // Update the maximum alignment on the current section if necessary.
362 if (ByteAlignment > CurSectionData->getAlignment())
363 CurSectionData->setAlignment(ByteAlignment);
366 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
367 unsigned char Value) {
368 new MCOrgFragment(*Offset, Value, CurSectionData);
371 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
373 for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
374 if (Inst.getOperand(i).isExpr())
375 AddValueSymbols(Inst.getOperand(i).getExpr());
377 CurSectionData->setHasInstructions(true);
379 // FIXME-PERF: Common case is that we don't need to relax, encode directly
380 // onto the data fragments buffers.
382 SmallVector<MCFixup, 4> Fixups;
383 SmallString<256> Code;
384 raw_svector_ostream VecOS(Code);
385 Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
388 // FIXME: Eliminate this copy.
389 SmallVector<MCAsmFixup, 4> AsmFixups;
390 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
391 MCFixup &F = Fixups[i];
392 AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
396 // See if we might need to relax this instruction, if so it needs its own
399 // FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
400 // when we can immediately tell that we will get something which might need
401 // relaxation (and compute its size).
403 // FIXME-PERF: We should also be smart about immediately relaxing instructions
404 // which we can already show will never possibly fit (we can also do a very
405 // good job of this before we do the first relaxation pass, because we have
406 // total knowledge about undefined symbols at that point). Even now, though,
407 // we can do a decent job, especially on Darwin where scattering means that we
408 // are going to often know that we can never fully resolve a fixup.
409 if (Assembler.getBackend().MayNeedRelaxation(Inst, AsmFixups)) {
410 MCInstFragment *IF = new MCInstFragment(Inst, CurSectionData);
412 // Add the fixups and data.
414 // FIXME: Revisit this design decision when relaxation is done, we may be
415 // able to get away with not storing any extra data in the MCInst.
416 IF->getCode() = Code;
417 IF->getFixups() = AsmFixups;
422 // Add the fixups and data.
423 MCDataFragment *DF = getOrCreateDataFragment();
424 for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
425 AsmFixups[i].Offset += DF->getContents().size();
426 DF->addFixup(AsmFixups[i]);
428 DF->getContents().append(Code.begin(), Code.end());
431 void MCMachOStreamer::Finish() {
435 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
436 raw_ostream &OS, MCCodeEmitter *CE,
438 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
440 S->getAssembler().setRelaxAll(true);