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 BeginCOFFSymbolDef(const MCSymbol *Symbol) {
100 assert(0 && "macho doesn't support this directive");
102 virtual void EmitCOFFSymbolStorageClass(int StorageClass) {
103 assert(0 && "macho doesn't support this directive");
105 virtual void EmitCOFFSymbolType(int Type) {
106 assert(0 && "macho doesn't support this directive");
108 virtual void EndCOFFSymbolDef() {
109 assert(0 && "macho doesn't support this directive");
111 virtual void EmitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
112 assert(0 && "macho doesn't support this directive");
114 virtual void EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size) {
115 assert(0 && "macho doesn't support this directive");
117 virtual void EmitZerofill(const MCSection *Section, MCSymbol *Symbol = 0,
118 unsigned Size = 0, unsigned ByteAlignment = 0);
119 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
120 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
121 virtual void EmitGPRel32Value(const MCExpr *Value) {
122 assert(0 && "macho doesn't support this directive");
124 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
125 unsigned ValueSize = 1,
126 unsigned MaxBytesToEmit = 0);
127 virtual void EmitCodeAlignment(unsigned ByteAlignment,
128 unsigned MaxBytesToEmit = 0);
129 virtual void EmitValueToOffset(const MCExpr *Offset,
130 unsigned char Value = 0);
132 virtual void EmitFileDirective(StringRef Filename) {
133 errs() << "FIXME: MCMachoStreamer:EmitFileDirective not implemented\n";
135 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
136 errs() << "FIXME: MCMachoStreamer:EmitDwarfFileDirective not implemented\n";
139 virtual void EmitInstruction(const MCInst &Inst);
140 virtual void Finish();
145 } // end anonymous namespace.
147 void MCMachOStreamer::SwitchSection(const MCSection *Section) {
148 assert(Section && "Cannot switch to a null section!");
150 // If already in this section, then this is a noop.
151 if (Section == CurSection) return;
153 CurSection = Section;
154 CurSectionData = &Assembler.getOrCreateSectionData(*Section);
157 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
158 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
159 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
160 assert(CurSection && "Cannot emit before setting section!");
162 // FIXME: This is wasteful, we don't necessarily need to create a data
163 // fragment. Instead, we should mark the symbol as pointing into the data
164 // fragment if it exists, otherwise we should just queue the label and set its
165 // fragment pointer when we emit the next fragment.
166 MCDataFragment *F = getOrCreateDataFragment();
167 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
168 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
170 SD.setOffset(F->getContents().size());
172 // This causes the reference type and weak reference flags to be cleared.
173 SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
175 Symbol->setSection(*CurSection);
178 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
180 case MCAF_SubsectionsViaSymbols:
181 Assembler.setSubsectionsViaSymbols(true);
185 assert(0 && "invalid assembler flag!");
188 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
189 // FIXME: Lift context changes into super class.
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 = CurSectionData;
203 Assembler.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 = Assembler.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);
239 case MCSA_LazyReference:
240 // FIXME: This requires -dynamic.
241 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
242 if (Symbol->isUndefined())
243 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
246 // Since .reference sets the no dead strip bit, it is equivalent to
247 // .no_dead_strip in practice.
249 case MCSA_NoDeadStrip:
250 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
253 case MCSA_PrivateExtern:
254 SD.setExternal(true);
255 SD.setPrivateExtern(true);
258 case MCSA_WeakReference:
259 // FIXME: This requires -dynamic.
260 if (Symbol->isUndefined())
261 SD.setFlags(SD.getFlags() | SF_WeakReference);
264 case MCSA_WeakDefinition:
265 // FIXME: 'as' enforces that this is defined and global. The manual claims
266 // it has to be in a coalesced section, but this isn't enforced.
267 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
272 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
273 // Encode the 'desc' value into the lowest implementation defined bits.
274 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
275 "Invalid .desc value!");
276 Assembler.getOrCreateSymbolData(*Symbol).setFlags(DescValue&SF_DescFlagsMask);
279 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
280 unsigned ByteAlignment) {
281 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
282 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
284 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
285 SD.setExternal(true);
286 SD.setCommon(Size, ByteAlignment);
289 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
290 unsigned Size, unsigned ByteAlignment) {
291 MCSectionData &SectData = Assembler.getOrCreateSectionData(*Section);
293 // The symbol may not be present, which only creates the section.
297 // FIXME: Assert that this section has the zerofill type.
299 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
301 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
303 MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
306 Symbol->setSection(*Section);
308 // Update the maximum alignment on the zero fill section if necessary.
309 if (ByteAlignment > SectData.getAlignment())
310 SectData.setAlignment(ByteAlignment);
313 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
314 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
317 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
318 unsigned AddrSpace) {
319 MCDataFragment *DF = getOrCreateDataFragment();
321 // Avoid fixups when possible.
323 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
324 // FIXME: Endianness assumption.
325 for (unsigned i = 0; i != Size; ++i)
326 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
328 DF->addFixup(MCAsmFixup(DF->getContents().size(), *AddValueSymbols(Value),
329 MCFixup::getKindForSize(Size)));
330 DF->getContents().resize(DF->getContents().size() + Size, 0);
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,
340 false /* 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::EmitCodeAlignment(unsigned ByteAlignment,
348 unsigned MaxBytesToEmit) {
349 if (MaxBytesToEmit == 0)
350 MaxBytesToEmit = ByteAlignment;
351 new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
352 true /* EmitNops */, CurSectionData);
354 // Update the maximum alignment on the current section if necessary.
355 if (ByteAlignment > CurSectionData->getAlignment())
356 CurSectionData->setAlignment(ByteAlignment);
359 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
360 unsigned char Value) {
361 new MCOrgFragment(*Offset, Value, CurSectionData);
364 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
366 for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
367 if (Inst.getOperand(i).isExpr())
368 AddValueSymbols(Inst.getOperand(i).getExpr());
370 CurSectionData->setHasInstructions(true);
372 // FIXME-PERF: Common case is that we don't need to relax, encode directly
373 // onto the data fragments buffers.
375 SmallVector<MCFixup, 4> Fixups;
376 SmallString<256> Code;
377 raw_svector_ostream VecOS(Code);
378 Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
381 // FIXME: Eliminate this copy.
382 SmallVector<MCAsmFixup, 4> AsmFixups;
383 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
384 MCFixup &F = Fixups[i];
385 AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
389 // See if we might need to relax this instruction, if so it needs its own
392 // FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
393 // when we can immediately tell that we will get something which might need
394 // relaxation (and compute its size).
396 // FIXME-PERF: We should also be smart about immediately relaxing instructions
397 // which we can already show will never possibly fit (we can also do a very
398 // good job of this before we do the first relaxation pass, because we have
399 // total knowledge about undefined symbols at that point). Even now, though,
400 // we can do a decent job, especially on Darwin where scattering means that we
401 // are going to often know that we can never fully resolve a fixup.
402 if (Assembler.getBackend().MayNeedRelaxation(Inst, AsmFixups)) {
403 MCInstFragment *IF = new MCInstFragment(Inst, CurSectionData);
405 // Add the fixups and data.
407 // FIXME: Revisit this design decision when relaxation is done, we may be
408 // able to get away with not storing any extra data in the MCInst.
409 IF->getCode() = Code;
410 IF->getFixups() = AsmFixups;
415 // Add the fixups and data.
416 MCDataFragment *DF = getOrCreateDataFragment();
417 for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
418 AsmFixups[i].Offset += DF->getContents().size();
419 DF->addFixup(AsmFixups[i]);
421 DF->getContents().append(Code.begin(), Code.end());
424 void MCMachOStreamer::Finish() {
428 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
429 raw_ostream &OS, MCCodeEmitter *CE,
431 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
433 S->getAssembler().setRelaxAll(true);