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 EmitTBSSSymbol(MCSymbol *Symbol, uint64_t Size,
130 unsigned ByteAlignment = 0);
131 virtual void EmitBytes(StringRef Data, unsigned AddrSpace);
132 virtual void EmitValue(const MCExpr *Value, unsigned Size,unsigned AddrSpace);
133 virtual void EmitGPRel32Value(const MCExpr *Value) {
134 assert(0 && "macho doesn't support this directive");
136 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0,
137 unsigned ValueSize = 1,
138 unsigned MaxBytesToEmit = 0);
139 virtual void EmitCodeAlignment(unsigned ByteAlignment,
140 unsigned MaxBytesToEmit = 0);
141 virtual void EmitValueToOffset(const MCExpr *Offset,
142 unsigned char Value = 0);
144 virtual void EmitFileDirective(StringRef Filename) {
145 report_fatal_error("unsupported directive: '.file'");
147 virtual void EmitDwarfFileDirective(unsigned FileNo, StringRef Filename) {
148 report_fatal_error("unsupported directive: '.file'");
151 virtual void EmitInstruction(const MCInst &Inst);
152 virtual void Finish();
157 } // end anonymous namespace.
159 void MCMachOStreamer::SwitchSection(const MCSection *Section) {
160 assert(Section && "Cannot switch to a null section!");
162 // If already in this section, then this is a noop.
163 if (Section == CurSection) return;
165 CurSection = Section;
166 CurSectionData = &Assembler.getOrCreateSectionData(*Section);
169 void MCMachOStreamer::EmitLabel(MCSymbol *Symbol) {
170 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
171 assert(!Symbol->isVariable() && "Cannot emit a variable symbol!");
172 assert(CurSection && "Cannot emit before setting section!");
174 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
176 // Update the current atom map, if necessary.
177 bool MustCreateFragment = false;
178 if (Assembler.isSymbolLinkerVisible(&SD)) {
179 CurrentAtomMap[CurSectionData] = &SD;
181 // We have to create a new fragment, fragments cannot span atoms.
182 MustCreateFragment = true;
185 // FIXME: This is wasteful, we don't necessarily need to create a data
186 // fragment. Instead, we should mark the symbol as pointing into the data
187 // fragment if it exists, otherwise we should just queue the label and set its
188 // fragment pointer when we emit the next fragment.
190 MustCreateFragment ? createDataFragment() : getOrCreateDataFragment();
191 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
193 SD.setOffset(F->getContents().size());
195 // This causes the reference type flag to be cleared. Darwin 'as' was "trying"
196 // to clear the weak reference and weak definition bits too, but the
197 // implementation was buggy. For now we just try to match 'as', for
200 // FIXME: Cleanup this code, these bits should be emitted based on semantic
201 // properties, not on the order of definition, etc.
202 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeMask);
204 Symbol->setSection(*CurSection);
207 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
209 case MCAF_SubsectionsViaSymbols:
210 Assembler.setSubsectionsViaSymbols(true);
214 assert(0 && "invalid assembler flag!");
217 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
218 // FIXME: Lift context changes into super class.
219 Symbol->setVariableValue(AddValueSymbols(Value));
222 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
223 MCSymbolAttr Attribute) {
224 // Indirect symbols are handled differently, to match how 'as' handles
225 // them. This makes writing matching .o files easier.
226 if (Attribute == MCSA_IndirectSymbol) {
227 // Note that we intentionally cannot use the symbol data here; this is
228 // important for matching the string table that 'as' generates.
229 IndirectSymbolData ISD;
231 ISD.SectionData = CurSectionData;
232 Assembler.getIndirectSymbols().push_back(ISD);
236 // Adding a symbol attribute always introduces the symbol, note that an
237 // important side effect of calling getOrCreateSymbolData here is to register
238 // the symbol with the assembler.
239 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
241 // The implementation of symbol attributes is designed to match 'as', but it
242 // leaves much to desired. It doesn't really make sense to arbitrarily add and
243 // remove flags, but 'as' allows this (in particular, see .desc).
245 // In the future it might be worth trying to make these operations more well
249 case MCSA_ELF_TypeFunction:
250 case MCSA_ELF_TypeIndFunction:
251 case MCSA_ELF_TypeObject:
252 case MCSA_ELF_TypeTLS:
253 case MCSA_ELF_TypeCommon:
254 case MCSA_ELF_TypeNoType:
255 case MCSA_IndirectSymbol:
261 assert(0 && "Invalid symbol attribute for Mach-O!");
265 SD.setExternal(true);
266 // This effectively clears the undefined lazy bit, in Darwin 'as', although
267 // it isn't very consistent because it implements this as part of symbol
270 // FIXME: Cleanup this code, these bits should be emitted based on semantic
271 // properties, not on the order of definition, etc.
272 SD.setFlags(SD.getFlags() & ~SF_ReferenceTypeUndefinedLazy);
275 case MCSA_LazyReference:
276 // FIXME: This requires -dynamic.
277 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
278 if (Symbol->isUndefined())
279 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
282 // Since .reference sets the no dead strip bit, it is equivalent to
283 // .no_dead_strip in practice.
285 case MCSA_NoDeadStrip:
286 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
289 case MCSA_PrivateExtern:
290 SD.setExternal(true);
291 SD.setPrivateExtern(true);
294 case MCSA_WeakReference:
295 // FIXME: This requires -dynamic.
296 if (Symbol->isUndefined())
297 SD.setFlags(SD.getFlags() | SF_WeakReference);
300 case MCSA_WeakDefinition:
301 // FIXME: 'as' enforces that this is defined and global. The manual claims
302 // it has to be in a coalesced section, but this isn't enforced.
303 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
308 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
309 // Encode the 'desc' value into the lowest implementation defined bits.
310 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
311 "Invalid .desc value!");
312 Assembler.getOrCreateSymbolData(*Symbol).setFlags(DescValue&SF_DescFlagsMask);
315 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
316 unsigned ByteAlignment) {
317 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
318 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
320 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
321 SD.setExternal(true);
322 SD.setCommon(Size, ByteAlignment);
325 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
326 unsigned Size, unsigned ByteAlignment) {
327 MCSectionData &SectData = Assembler.getOrCreateSectionData(*Section);
329 // The symbol may not be present, which only creates the section.
333 // FIXME: Assert that this section has the zerofill type.
335 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
337 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
339 // Emit an align fragment if necessary.
340 if (ByteAlignment != 1)
341 new MCAlignFragment(ByteAlignment, 0, 0, ByteAlignment, &SectData);
343 MCFragment *F = new MCFillFragment(0, 0, Size, &SectData);
345 if (Assembler.isSymbolLinkerVisible(&SD))
348 Symbol->setSection(*Section);
350 // Update the maximum alignment on the zero fill section if necessary.
351 if (ByteAlignment > SectData.getAlignment())
352 SectData.setAlignment(ByteAlignment);
355 void MCMachOStreamer::EmitTBSSSymbol(MCSymbol *Symbol, uint64_t Size,
356 unsigned ByteAlignment) {
357 assert(false && "Implement me!");
360 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
361 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
364 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
365 unsigned AddrSpace) {
366 MCDataFragment *DF = getOrCreateDataFragment();
368 // Avoid fixups when possible.
370 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
371 // FIXME: Endianness assumption.
372 for (unsigned i = 0; i != Size; ++i)
373 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
375 DF->addFixup(MCAsmFixup(DF->getContents().size(), *AddValueSymbols(Value),
376 MCFixup::getKindForSize(Size)));
377 DF->getContents().resize(DF->getContents().size() + Size, 0);
381 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
382 int64_t Value, unsigned ValueSize,
383 unsigned MaxBytesToEmit) {
384 if (MaxBytesToEmit == 0)
385 MaxBytesToEmit = ByteAlignment;
386 MCFragment *F = new MCAlignFragment(ByteAlignment, Value, ValueSize,
387 MaxBytesToEmit, CurSectionData);
388 F->setAtom(CurrentAtomMap.lookup(CurSectionData));
390 // Update the maximum alignment on the current section if necessary.
391 if (ByteAlignment > CurSectionData->getAlignment())
392 CurSectionData->setAlignment(ByteAlignment);
395 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
396 unsigned MaxBytesToEmit) {
397 if (MaxBytesToEmit == 0)
398 MaxBytesToEmit = ByteAlignment;
399 MCAlignFragment *F = new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
401 F->setEmitNops(true);
402 F->setAtom(CurrentAtomMap.lookup(CurSectionData));
404 // Update the maximum alignment on the current section if necessary.
405 if (ByteAlignment > CurSectionData->getAlignment())
406 CurSectionData->setAlignment(ByteAlignment);
409 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
410 unsigned char Value) {
411 MCFragment *F = new MCOrgFragment(*Offset, Value, CurSectionData);
412 F->setAtom(CurrentAtomMap.lookup(CurSectionData));
415 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
417 for (unsigned i = Inst.getNumOperands(); i--; )
418 if (Inst.getOperand(i).isExpr())
419 AddValueSymbols(Inst.getOperand(i).getExpr());
421 CurSectionData->setHasInstructions(true);
423 // FIXME-PERF: Common case is that we don't need to relax, encode directly
424 // onto the data fragments buffers.
426 SmallVector<MCFixup, 4> Fixups;
427 SmallString<256> Code;
428 raw_svector_ostream VecOS(Code);
429 Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
432 // FIXME: Eliminate this copy.
433 SmallVector<MCAsmFixup, 4> AsmFixups;
434 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
435 MCFixup &F = Fixups[i];
436 AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
440 // See if we might need to relax this instruction, if so it needs its own
443 // FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
444 // when we can immediately tell that we will get something which might need
445 // relaxation (and compute its size).
447 // FIXME-PERF: We should also be smart about immediately relaxing instructions
448 // which we can already show will never possibly fit (we can also do a very
449 // good job of this before we do the first relaxation pass, because we have
450 // total knowledge about undefined symbols at that point). Even now, though,
451 // we can do a decent job, especially on Darwin where scattering means that we
452 // are going to often know that we can never fully resolve a fixup.
453 if (Assembler.getBackend().MayNeedRelaxation(Inst, AsmFixups)) {
454 MCInstFragment *IF = new MCInstFragment(Inst, CurSectionData);
455 IF->setAtom(CurrentAtomMap.lookup(CurSectionData));
457 // Add the fixups and data.
459 // FIXME: Revisit this design decision when relaxation is done, we may be
460 // able to get away with not storing any extra data in the MCInst.
461 IF->getCode() = Code;
462 IF->getFixups() = AsmFixups;
467 // Add the fixups and data.
468 MCDataFragment *DF = getOrCreateDataFragment();
469 for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
470 AsmFixups[i].Offset += DF->getContents().size();
471 DF->addFixup(AsmFixups[i]);
473 DF->getContents().append(Code.begin(), Code.end());
476 void MCMachOStreamer::Finish() {
480 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
481 raw_ostream &OS, MCCodeEmitter *CE,
483 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
485 S->getAssembler().setRelaxAll(true);