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;
35 MCFragment *getCurrentFragment() const {
36 assert(CurSectionData && "No current section!");
38 if (!CurSectionData->empty())
39 return &CurSectionData->getFragmentList().back();
44 /// Get a data fragment to write into, creating a new one if the current
45 /// fragment is not a data fragment.
46 MCDataFragment *getOrCreateDataFragment() const {
47 MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
49 F = new MCDataFragment(CurSectionData);
54 MCMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
55 raw_ostream &_OS, MCCodeEmitter *_Emitter)
56 : MCStreamer(Context), Assembler(Context, TAB, *_Emitter, _OS),
60 MCAssembler &getAssembler() { return Assembler; }
62 const MCExpr *AddValueSymbols(const MCExpr *Value) {
63 switch (Value->getKind()) {
64 case MCExpr::Target: assert(0 && "Can't handle target exprs yet!");
65 case MCExpr::Constant:
68 case MCExpr::Binary: {
69 const MCBinaryExpr *BE = cast<MCBinaryExpr>(Value);
70 AddValueSymbols(BE->getLHS());
71 AddValueSymbols(BE->getRHS());
75 case MCExpr::SymbolRef:
76 Assembler.getOrCreateSymbolData(
77 cast<MCSymbolRefExpr>(Value)->getSymbol());
81 AddValueSymbols(cast<MCUnaryExpr>(Value)->getSubExpr());
88 /// @name MCStreamer Interface
91 virtual void SwitchSection(const MCSection *Section);
92 virtual void EmitLabel(MCSymbol *Symbol);
93 virtual void EmitAssemblerFlag(MCAssemblerFlag Flag);
94 virtual void EmitAssignment(MCSymbol *Symbol, const MCExpr *Value);
95 virtual void EmitSymbolAttribute(MCSymbol *Symbol, MCSymbolAttr Attribute);
96 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue);
97 virtual void EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
98 unsigned ByteAlignment);
99 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
100 assert(0 && "macho doesn't support this directive");
102 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
103 assert(0 && "macho doesn't support this directive");
105 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
106 unsigned Size = 0, unsigned ByteAlignment = 0);
107 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
108 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
109 virtual void EmitGPRel32Value(const MCExpr *Value) {
110 assert(0 && "macho doesn't support this directive");
112 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
113 unsigned ValueSize = 1,
114 unsigned MaxBytesToEmit = 0);
115 virtual void EmitCodeAlignment(unsigned ByteAlignment,
116 unsigned MaxBytesToEmit = 0);
117 virtual void EmitValueToOffset(const MCExpr *Offset,
118 unsigned char Value = 0);
120 virtual void EmitFileDirective(StringRef Filename) {
121 errs() << "FIXME: MCMachoStreamer:EmitFileDirective not implemented\n";
123 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
124 errs() << "FIXME: MCMachoStreamer:EmitDwarfFileDirective not implemented\n";
127 virtual void EmitInstruction(const MCInst &Inst);
128 virtual void Finish();
133 } // end anonymous namespace.
135 void MCMachOStreamer::SwitchSection(const MCSection *Section) {
136 assert(Section && "Cannot switch to a null section!");
138 // If already in this section, then this is a noop.
139 if (Section == CurSection) return;
141 CurSection = Section;
142 CurSectionData = &Assembler.getOrCreateSectionData(*Section);
145 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
146 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
147 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
148 assert(CurSection && "Cannot emit before setting section!");
150 // FIXME: This is wasteful, we don't necessarily need to create a data
151 // fragment. Instead, we should mark the symbol as pointing into the data
152 // fragment if it exists, otherwise we should just queue the label and set its
153 // fragment pointer when we emit the next fragment.
154 MCDataFragment *F = getOrCreateDataFragment();
155 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
156 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
158 SD.setOffset(F->getContents().size());
160 // This causes the reference type and weak reference flags to be cleared.
161 SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
163 Symbol->setSection(*CurSection);
166 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
168 case MCAF_SubsectionsViaSymbols:
169 Assembler.setSubsectionsViaSymbols(true);
173 assert(0 && "invalid assembler flag!");
176 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
177 // FIXME: Lift context changes into super class.
178 Symbol->setVariableValue(AddValueSymbols(Value));
181 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
182 MCSymbolAttr Attribute) {
183 // Indirect symbols are handled differently, to match how 'as' handles
184 // them. This makes writing matching .o files easier.
185 if (Attribute == MCSA_IndirectSymbol) {
186 // Note that we intentionally cannot use the symbol data here; this is
187 // important for matching the string table that 'as' generates.
188 IndirectSymbolData ISD;
190 ISD.SectionData = CurSectionData;
191 Assembler.getIndirectSymbols().push_back(ISD);
195 // Adding a symbol attribute always introduces the symbol, note that an
196 // important side effect of calling getOrCreateSymbolData here is to register
197 // the symbol with the assembler.
198 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
200 // The implementation of symbol attributes is designed to match 'as', but it
201 // leaves much to desired. It doesn't really make sense to arbitrarily add and
202 // remove flags, but 'as' allows this (in particular, see .desc).
204 // In the future it might be worth trying to make these operations more well
208 case MCSA_ELF_TypeFunction:
209 case MCSA_ELF_TypeIndFunction:
210 case MCSA_ELF_TypeObject:
211 case MCSA_ELF_TypeTLS:
212 case MCSA_ELF_TypeCommon:
213 case MCSA_ELF_TypeNoType:
214 case MCSA_IndirectSymbol:
220 assert(0 && "Invalid symbol attribute for Mach-O!");
224 SD.setExternal(true);
227 case MCSA_LazyReference:
228 // FIXME: This requires -dynamic.
229 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
230 if (Symbol->isUndefined())
231 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
234 // Since .reference sets the no dead strip bit, it is equivalent to
235 // .no_dead_strip in practice.
237 case MCSA_NoDeadStrip:
238 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
241 case MCSA_PrivateExtern:
242 SD.setExternal(true);
243 SD.setPrivateExtern(true);
246 case MCSA_WeakReference:
247 // FIXME: This requires -dynamic.
248 if (Symbol->isUndefined())
249 SD.setFlags(SD.getFlags() | SF_WeakReference);
252 case MCSA_WeakDefinition:
253 // FIXME: 'as' enforces that this is defined and global. The manual claims
254 // it has to be in a coalesced section, but this isn't enforced.
255 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
260 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
261 // Encode the 'desc' value into the lowest implementation defined bits.
262 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
263 "Invalid .desc value!");
264 Assembler.getOrCreateSymbolData(*Symbol).setFlags(DescValue&SF_DescFlagsMask);
267 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
268 unsigned ByteAlignment) {
269 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
270 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
272 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
273 SD.setExternal(true);
274 SD.setCommon(Size, ByteAlignment);
277 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
278 unsigned Size, unsigned ByteAlignment) {
279 MCSectionData &SectData = Assembler.getOrCreateSectionData(*Section);
281 // The symbol may not be present, which only creates the section.
285 // FIXME: Assert that this section has the zerofill type.
287 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
289 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
291 MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
294 Symbol->setSection(*Section);
296 // Update the maximum alignment on the zero fill section if necessary.
297 if (ByteAlignment > SectData.getAlignment())
298 SectData.setAlignment(ByteAlignment);
301 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
302 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
305 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
306 unsigned AddrSpace) {
307 MCDataFragment *DF = getOrCreateDataFragment();
309 // Avoid fixups when possible.
311 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
312 // FIXME: Endianness assumption.
313 for (unsigned i = 0; i != Size; ++i)
314 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
316 DF->addFixup(MCAsmFixup(DF->getContents().size(), *AddValueSymbols(Value),
317 MCFixup::getKindForSize(Size)));
318 DF->getContents().resize(DF->getContents().size() + Size, 0);
322 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
323 int64_t Value, unsigned ValueSize,
324 unsigned MaxBytesToEmit) {
325 if (MaxBytesToEmit == 0)
326 MaxBytesToEmit = ByteAlignment;
327 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
328 false /* EmitNops */, CurSectionData);
330 // Update the maximum alignment on the current section if necessary.
331 if (ByteAlignment > CurSectionData->getAlignment())
332 CurSectionData->setAlignment(ByteAlignment);
335 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
336 unsigned MaxBytesToEmit) {
337 if (MaxBytesToEmit == 0)
338 MaxBytesToEmit = ByteAlignment;
339 new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
340 true /* EmitNops */, CurSectionData);
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 MCExpr *Offset,
348 unsigned char Value) {
349 new MCOrgFragment(*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());
358 CurSectionData->setHasInstructions(true);
360 // FIXME-PERF: Common case is that we don't need to relax, encode directly
361 // onto the data fragments buffers.
363 SmallVector<MCFixup, 4> Fixups;
364 SmallString<256> Code;
365 raw_svector_ostream VecOS(Code);
366 Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
369 // FIXME: Eliminate this copy.
370 SmallVector<MCAsmFixup, 4> AsmFixups;
371 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
372 MCFixup &F = Fixups[i];
373 AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
377 // See if we might need to relax this instruction, if so it needs its own
380 // FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
381 // when we can immediately tell that we will get something which might need
382 // relaxation (and compute its size).
384 // FIXME-PERF: We should also be smart about immediately relaxing instructions
385 // which we can already show will never possibly fit (we can also do a very
386 // good job of this before we do the first relaxation pass, because we have
387 // total knowledge about undefined symbols at that point). Even now, though,
388 // we can do a decent job, especially on Darwin where scattering means that we
389 // are going to often know that we can never fully resolve a fixup.
390 if (Assembler.getBackend().MayNeedRelaxation(Inst, AsmFixups)) {
391 MCInstFragment *IF = new MCInstFragment(Inst, CurSectionData);
393 // Add the fixups and data.
395 // FIXME: Revisit this design decision when relaxation is done, we may be
396 // able to get away with not storing any extra data in the MCInst.
397 IF->getCode() = Code;
398 IF->getFixups() = AsmFixups;
403 // Add the fixups and data.
404 MCDataFragment *DF = getOrCreateDataFragment();
405 for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
406 AsmFixups[i].Offset += DF->getContents().size();
407 DF->addFixup(AsmFixups[i]);
409 DF->getContents().append(Code.begin(), Code.end());
412 void MCMachOStreamer::Finish() {
416 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
417 raw_ostream &OS, MCCodeEmitter *CE,
419 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
421 S->getAssembler().setRelaxAll(true);