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!");
166 // FIXME: This is wasteful, we don't necessarily need to create a data
167 // fragment. Instead, we should mark the symbol as pointing into the data
168 // fragment if it exists, otherwise we should just queue the label and set its
169 // fragment pointer when we emit the next fragment.
170 MCDataFragment *F = getOrCreateDataFragment();
171 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
172 assert(!SD.getFragment() && "Unexpected fragment on symbol data!");
174 SD.setOffset(F->getContents().size());
176 // This causes the reference type and weak reference flags to be cleared.
177 SD.setFlags(SD.getFlags() & ~(SF_WeakReference | SF_ReferenceTypeMask));
179 Symbol->setSection(*CurSection);
182 void MCMachOStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
184 case MCAF_SubsectionsViaSymbols:
185 Assembler.setSubsectionsViaSymbols(true);
189 assert(0 && "invalid assembler flag!");
192 void MCMachOStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
193 // Only absolute symbols can be redefined.
194 assert((Symbol->isUndefined() || Symbol->isAbsolute()) &&
195 "Cannot define a symbol twice!");
197 // FIXME: Lift context changes into super class.
198 // FIXME: Set associated section.
199 Symbol->setValue(AddValueSymbols(Value));
202 void MCMachOStreamer::EmitSymbolAttribute(MCSymbol *Symbol,
203 MCSymbolAttr Attribute) {
204 // Indirect symbols are handled differently, to match how 'as' handles
205 // them. This makes writing matching .o files easier.
206 if (Attribute == MCSA_IndirectSymbol) {
207 // Note that we intentionally cannot use the symbol data here; this is
208 // important for matching the string table that 'as' generates.
209 IndirectSymbolData ISD;
211 ISD.SectionData = CurSectionData;
212 Assembler.getIndirectSymbols().push_back(ISD);
216 // Adding a symbol attribute always introduces the symbol, note that an
217 // important side effect of calling getOrCreateSymbolData here is to register
218 // the symbol with the assembler.
219 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
221 // The implementation of symbol attributes is designed to match 'as', but it
222 // leaves much to desired. It doesn't really make sense to arbitrarily add and
223 // remove flags, but 'as' allows this (in particular, see .desc).
225 // In the future it might be worth trying to make these operations more well
229 case MCSA_ELF_TypeFunction:
230 case MCSA_ELF_TypeIndFunction:
231 case MCSA_ELF_TypeObject:
232 case MCSA_ELF_TypeTLS:
233 case MCSA_ELF_TypeCommon:
234 case MCSA_ELF_TypeNoType:
235 case MCSA_IndirectSymbol:
241 assert(0 && "Invalid symbol attribute for Mach-O!");
245 SD.setExternal(true);
248 case MCSA_LazyReference:
249 // FIXME: This requires -dynamic.
250 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
251 if (Symbol->isUndefined())
252 SD.setFlags(SD.getFlags() | SF_ReferenceTypeUndefinedLazy);
255 // Since .reference sets the no dead strip bit, it is equivalent to
256 // .no_dead_strip in practice.
258 case MCSA_NoDeadStrip:
259 SD.setFlags(SD.getFlags() | SF_NoDeadStrip);
262 case MCSA_PrivateExtern:
263 SD.setExternal(true);
264 SD.setPrivateExtern(true);
267 case MCSA_WeakReference:
268 // FIXME: This requires -dynamic.
269 if (Symbol->isUndefined())
270 SD.setFlags(SD.getFlags() | SF_WeakReference);
273 case MCSA_WeakDefinition:
274 // FIXME: 'as' enforces that this is defined and global. The manual claims
275 // it has to be in a coalesced section, but this isn't enforced.
276 SD.setFlags(SD.getFlags() | SF_WeakDefinition);
281 void MCMachOStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
282 // Encode the 'desc' value into the lowest implementation defined bits.
283 assert(DescValue == (DescValue & SF_DescFlagsMask) &&
284 "Invalid .desc value!");
285 Assembler.getOrCreateSymbolData(*Symbol).setFlags(DescValue&SF_DescFlagsMask);
288 void MCMachOStreamer::EmitCommonSymbol(MCSymbol *Symbol, uint64_t Size,
289 unsigned ByteAlignment) {
290 // FIXME: Darwin 'as' does appear to allow redef of a .comm by itself.
291 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
293 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
294 SD.setExternal(true);
295 SD.setCommon(Size, ByteAlignment);
298 void MCMachOStreamer::EmitZerofill(const MCSection *Section, MCSymbol *Symbol,
299 unsigned Size, unsigned ByteAlignment) {
300 MCSectionData &SectData = Assembler.getOrCreateSectionData(*Section);
302 // The symbol may not be present, which only creates the section.
306 // FIXME: Assert that this section has the zerofill type.
308 assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
310 MCSymbolData &SD = Assembler.getOrCreateSymbolData(*Symbol);
312 MCFragment *F = new MCZeroFillFragment(Size, ByteAlignment, &SectData);
315 Symbol->setSection(*Section);
317 // Update the maximum alignment on the zero fill section if necessary.
318 if (ByteAlignment > SectData.getAlignment())
319 SectData.setAlignment(ByteAlignment);
322 void MCMachOStreamer::EmitBytes(StringRef Data, unsigned AddrSpace) {
323 getOrCreateDataFragment()->getContents().append(Data.begin(), Data.end());
326 void MCMachOStreamer::EmitValue(const MCExpr *Value, unsigned Size,
327 unsigned AddrSpace) {
328 MCDataFragment *DF = getOrCreateDataFragment();
330 // Avoid fixups when possible.
332 if (AddValueSymbols(Value)->EvaluateAsAbsolute(AbsValue)) {
333 // FIXME: Endianness assumption.
334 for (unsigned i = 0; i != Size; ++i)
335 DF->getContents().push_back(uint8_t(AbsValue >> (i * 8)));
337 DF->addFixup(MCAsmFixup(DF->getContents().size(), *AddValueSymbols(Value),
338 MCFixup::getKindForSize(Size)));
339 DF->getContents().resize(DF->getContents().size() + Size, 0);
343 void MCMachOStreamer::EmitValueToAlignment(unsigned ByteAlignment,
344 int64_t Value, unsigned ValueSize,
345 unsigned MaxBytesToEmit) {
346 if (MaxBytesToEmit == 0)
347 MaxBytesToEmit = ByteAlignment;
348 new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit,
349 false /* EmitNops */, CurSectionData);
351 // Update the maximum alignment on the current section if necessary.
352 if (ByteAlignment > CurSectionData->getAlignment())
353 CurSectionData->setAlignment(ByteAlignment);
356 void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
357 unsigned MaxBytesToEmit) {
358 if (MaxBytesToEmit == 0)
359 MaxBytesToEmit = ByteAlignment;
360 new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
361 true /* EmitNops */, CurSectionData);
363 // Update the maximum alignment on the current section if necessary.
364 if (ByteAlignment > CurSectionData->getAlignment())
365 CurSectionData->setAlignment(ByteAlignment);
368 void MCMachOStreamer::EmitValueToOffset(const MCExpr *Offset,
369 unsigned char Value) {
370 new MCOrgFragment(*Offset, Value, CurSectionData);
373 void MCMachOStreamer::EmitInstruction(const MCInst &Inst) {
375 for (unsigned i = 0; i != Inst.getNumOperands(); ++i)
376 if (Inst.getOperand(i).isExpr())
377 AddValueSymbols(Inst.getOperand(i).getExpr());
379 CurSectionData->setHasInstructions(true);
381 // FIXME-PERF: Common case is that we don't need to relax, encode directly
382 // onto the data fragments buffers.
384 SmallVector<MCFixup, 4> Fixups;
385 SmallString<256> Code;
386 raw_svector_ostream VecOS(Code);
387 Assembler.getEmitter().EncodeInstruction(Inst, VecOS, Fixups);
390 // FIXME: Eliminate this copy.
391 SmallVector<MCAsmFixup, 4> AsmFixups;
392 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
393 MCFixup &F = Fixups[i];
394 AsmFixups.push_back(MCAsmFixup(F.getOffset(), *F.getValue(),
398 // See if we might need to relax this instruction, if so it needs its own
401 // FIXME-PERF: Support target hook to do a fast path that avoids the encoder,
402 // when we can immediately tell that we will get something which might need
403 // relaxation (and compute its size).
405 // FIXME-PERF: We should also be smart about immediately relaxing instructions
406 // which we can already show will never possibly fit (we can also do a very
407 // good job of this before we do the first relaxation pass, because we have
408 // total knowledge about undefined symbols at that point). Even now, though,
409 // we can do a decent job, especially on Darwin where scattering means that we
410 // are going to often know that we can never fully resolve a fixup.
411 if (Assembler.getBackend().MayNeedRelaxation(Inst, AsmFixups)) {
412 MCInstFragment *IF = new MCInstFragment(Inst, CurSectionData);
414 // Add the fixups and data.
416 // FIXME: Revisit this design decision when relaxation is done, we may be
417 // able to get away with not storing any extra data in the MCInst.
418 IF->getCode() = Code;
419 IF->getFixups() = AsmFixups;
424 // Add the fixups and data.
425 MCDataFragment *DF = getOrCreateDataFragment();
426 for (unsigned i = 0, e = AsmFixups.size(); i != e; ++i) {
427 AsmFixups[i].Offset += DF->getContents().size();
428 DF->addFixup(AsmFixups[i]);
430 DF->getContents().append(Code.begin(), Code.end());
433 void MCMachOStreamer::Finish() {
437 MCStreamer *llvm::createMachOStreamer(MCContext &Context, TargetAsmBackend &TAB,
438 raw_ostream &OS, MCCodeEmitter *CE,
440 MCMachOStreamer *S = new MCMachOStreamer(Context, TAB, OS, CE);
442 S->getAssembler().setRelaxAll(true);