1 //===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file assembles .s files and emits ELF .o object files.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "llvm/MC/MCELFStreamer.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/SmallPtrSet.h"
17 #include "llvm/MC/MCAsmBackend.h"
18 #include "llvm/MC/MCAsmLayout.h"
19 #include "llvm/MC/MCAsmInfo.h"
20 #include "llvm/MC/MCAssembler.h"
21 #include "llvm/MC/MCCodeEmitter.h"
22 #include "llvm/MC/MCContext.h"
23 #include "llvm/MC/MCExpr.h"
24 #include "llvm/MC/MCInst.h"
25 #include "llvm/MC/MCObjectFileInfo.h"
26 #include "llvm/MC/MCObjectStreamer.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCSectionELF.h"
30 #include "llvm/MC/MCSymbolELF.h"
31 #include "llvm/MC/MCSymbol.h"
32 #include "llvm/MC/MCValue.h"
33 #include "llvm/Support/Debug.h"
34 #include "llvm/Support/ELF.h"
35 #include "llvm/Support/ErrorHandling.h"
36 #include "llvm/Support/TargetRegistry.h"
37 #include "llvm/Support/raw_ostream.h"
38 
39 using namespace llvm;
40 
isBundleLocked() const41 bool MCELFStreamer::isBundleLocked() const {
42   return getCurrentSectionOnly()->isBundleLocked();
43 }
44 
~MCELFStreamer()45 MCELFStreamer::~MCELFStreamer() {
46 }
47 
mergeFragment(MCDataFragment * DF,MCDataFragment * EF)48 void MCELFStreamer::mergeFragment(MCDataFragment *DF,
49                                   MCDataFragment *EF) {
50   MCAssembler &Assembler = getAssembler();
51 
52   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
53     uint64_t FSize = EF->getContents().size();
54 
55     if (FSize > Assembler.getBundleAlignSize())
56       report_fatal_error("Fragment can't be larger than a bundle size");
57 
58     uint64_t RequiredBundlePadding = computeBundlePadding(
59         Assembler, EF, DF->getContents().size(), FSize);
60 
61     if (RequiredBundlePadding > UINT8_MAX)
62       report_fatal_error("Padding cannot exceed 255 bytes");
63 
64     if (RequiredBundlePadding > 0) {
65       SmallString<256> Code;
66       raw_svector_ostream VecOS(Code);
67       MCObjectWriter *OW = Assembler.getBackend().createObjectWriter(VecOS);
68 
69       EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
70 
71       Assembler.writeFragmentPadding(*EF, FSize, OW);
72       delete OW;
73 
74       DF->getContents().append(Code.begin(), Code.end());
75     }
76   }
77 
78   flushPendingLabels(DF, DF->getContents().size());
79 
80   for (unsigned i = 0, e = EF->getFixups().size(); i != e; ++i) {
81     EF->getFixups()[i].setOffset(EF->getFixups()[i].getOffset() +
82                                  DF->getContents().size());
83     DF->getFixups().push_back(EF->getFixups()[i]);
84   }
85   DF->setHasInstructions(true);
86   DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
87 }
88 
InitSections(bool NoExecStack)89 void MCELFStreamer::InitSections(bool NoExecStack) {
90   MCContext &Ctx = getContext();
91   SwitchSection(Ctx.getObjectFileInfo()->getTextSection());
92   EmitCodeAlignment(4);
93 
94   if (NoExecStack)
95     SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
96 }
97 
EmitLabel(MCSymbol * S)98 void MCELFStreamer::EmitLabel(MCSymbol *S) {
99   auto *Symbol = cast<MCSymbolELF>(S);
100   assert(Symbol->isUndefined() && "Cannot define a symbol twice!");
101 
102   MCObjectStreamer::EmitLabel(Symbol);
103 
104   const MCSectionELF &Section =
105       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
106   if (Section.getFlags() & ELF::SHF_TLS)
107     Symbol->setType(ELF::STT_TLS);
108 }
109 
EmitAssemblerFlag(MCAssemblerFlag Flag)110 void MCELFStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
111   // Let the target do whatever target specific stuff it needs to do.
112   getAssembler().getBackend().handleAssemblerFlag(Flag);
113   // Do any generic stuff we need to do.
114   switch (Flag) {
115   case MCAF_SyntaxUnified: return; // no-op here.
116   case MCAF_Code16: return; // Change parsing mode; no-op here.
117   case MCAF_Code32: return; // Change parsing mode; no-op here.
118   case MCAF_Code64: return; // Change parsing mode; no-op here.
119   case MCAF_SubsectionsViaSymbols:
120     getAssembler().setSubsectionsViaSymbols(true);
121     return;
122   }
123 
124   llvm_unreachable("invalid assembler flag!");
125 }
126 
127 // If bundle alignment is used and there are any instructions in the section, it
128 // needs to be aligned to at least the bundle size.
setSectionAlignmentForBundling(const MCAssembler & Assembler,MCSection * Section)129 static void setSectionAlignmentForBundling(const MCAssembler &Assembler,
130                                            MCSection *Section) {
131   if (Section && Assembler.isBundlingEnabled() && Section->hasInstructions() &&
132       Section->getAlignment() < Assembler.getBundleAlignSize())
133     Section->setAlignment(Assembler.getBundleAlignSize());
134 }
135 
ChangeSection(MCSection * Section,const MCExpr * Subsection)136 void MCELFStreamer::ChangeSection(MCSection *Section,
137                                   const MCExpr *Subsection) {
138   MCSection *CurSection = getCurrentSectionOnly();
139   if (CurSection && isBundleLocked())
140     report_fatal_error("Unterminated .bundle_lock when changing a section");
141 
142   MCAssembler &Asm = getAssembler();
143   // Ensure the previous section gets aligned if necessary.
144   setSectionAlignmentForBundling(Asm, CurSection);
145   auto *SectionELF = static_cast<const MCSectionELF *>(Section);
146   const MCSymbol *Grp = SectionELF->getGroup();
147   if (Grp)
148     Asm.registerSymbol(*Grp);
149 
150   this->MCObjectStreamer::ChangeSection(Section, Subsection);
151   MCContext &Ctx = getContext();
152   auto *Begin = cast_or_null<MCSymbolELF>(Section->getBeginSymbol());
153   if (!Begin) {
154     Begin = Ctx.getOrCreateSectionSymbol(*SectionELF);
155     Section->setBeginSymbol(Begin);
156   }
157   if (Begin->isUndefined()) {
158     Asm.registerSymbol(*Begin);
159     Begin->setType(ELF::STT_SECTION);
160   }
161 }
162 
EmitWeakReference(MCSymbol * Alias,const MCSymbol * Symbol)163 void MCELFStreamer::EmitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
164   getAssembler().registerSymbol(*Symbol);
165   const MCExpr *Value = MCSymbolRefExpr::create(
166       Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
167   Alias->setVariableValue(Value);
168 }
169 
170 // When GNU as encounters more than one .type declaration for an object it seems
171 // to use a mechanism similar to the one below to decide which type is actually
172 // used in the object file.  The greater of T1 and T2 is selected based on the
173 // following ordering:
174 //  STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
175 // If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
176 // provided type).
CombineSymbolTypes(unsigned T1,unsigned T2)177 static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
178   for (unsigned Type : {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
179                         ELF::STT_GNU_IFUNC, ELF::STT_TLS}) {
180     if (T1 == Type)
181       return T2;
182     if (T2 == Type)
183       return T1;
184   }
185 
186   return T2;
187 }
188 
EmitSymbolAttribute(MCSymbol * S,MCSymbolAttr Attribute)189 bool MCELFStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
190   auto *Symbol = cast<MCSymbolELF>(S);
191   // Indirect symbols are handled differently, to match how 'as' handles
192   // them. This makes writing matching .o files easier.
193   if (Attribute == MCSA_IndirectSymbol) {
194     // Note that we intentionally cannot use the symbol data here; this is
195     // important for matching the string table that 'as' generates.
196     IndirectSymbolData ISD;
197     ISD.Symbol = Symbol;
198     ISD.Section = getCurrentSectionOnly();
199     getAssembler().getIndirectSymbols().push_back(ISD);
200     return true;
201   }
202 
203   // Adding a symbol attribute always introduces the symbol, note that an
204   // important side effect of calling registerSymbol here is to register
205   // the symbol with the assembler.
206   getAssembler().registerSymbol(*Symbol);
207 
208   // The implementation of symbol attributes is designed to match 'as', but it
209   // leaves much to desired. It doesn't really make sense to arbitrarily add and
210   // remove flags, but 'as' allows this (in particular, see .desc).
211   //
212   // In the future it might be worth trying to make these operations more well
213   // defined.
214   switch (Attribute) {
215   case MCSA_LazyReference:
216   case MCSA_Reference:
217   case MCSA_SymbolResolver:
218   case MCSA_PrivateExtern:
219   case MCSA_WeakDefinition:
220   case MCSA_WeakDefAutoPrivate:
221   case MCSA_Invalid:
222   case MCSA_IndirectSymbol:
223     return false;
224 
225   case MCSA_NoDeadStrip:
226     // Ignore for now.
227     break;
228 
229   case MCSA_ELF_TypeGnuUniqueObject:
230     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
231     Symbol->setBinding(ELF::STB_GNU_UNIQUE);
232     Symbol->setExternal(true);
233     break;
234 
235   case MCSA_Global:
236     Symbol->setBinding(ELF::STB_GLOBAL);
237     Symbol->setExternal(true);
238     break;
239 
240   case MCSA_WeakReference:
241   case MCSA_Weak:
242     Symbol->setBinding(ELF::STB_WEAK);
243     Symbol->setExternal(true);
244     break;
245 
246   case MCSA_Local:
247     Symbol->setBinding(ELF::STB_LOCAL);
248     Symbol->setExternal(false);
249     break;
250 
251   case MCSA_ELF_TypeFunction:
252     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
253     break;
254 
255   case MCSA_ELF_TypeIndFunction:
256     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
257     break;
258 
259   case MCSA_ELF_TypeObject:
260     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
261     break;
262 
263   case MCSA_ELF_TypeTLS:
264     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
265     break;
266 
267   case MCSA_ELF_TypeCommon:
268     // TODO: Emit these as a common symbol.
269     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
270     break;
271 
272   case MCSA_ELF_TypeNoType:
273     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
274     break;
275 
276   case MCSA_Protected:
277     Symbol->setVisibility(ELF::STV_PROTECTED);
278     break;
279 
280   case MCSA_Hidden:
281     Symbol->setVisibility(ELF::STV_HIDDEN);
282     break;
283 
284   case MCSA_Internal:
285     Symbol->setVisibility(ELF::STV_INTERNAL);
286     break;
287 
288   case MCSA_AltEntry:
289     llvm_unreachable("ELF doesn't support the .alt_entry attribute");
290   }
291 
292   return true;
293 }
294 
EmitCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)295 void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
296                                      unsigned ByteAlignment) {
297   auto *Symbol = cast<MCSymbolELF>(S);
298   getAssembler().registerSymbol(*Symbol);
299 
300   if (!Symbol->isBindingSet()) {
301     Symbol->setBinding(ELF::STB_GLOBAL);
302     Symbol->setExternal(true);
303   }
304 
305   Symbol->setType(ELF::STT_OBJECT);
306 
307   if (Symbol->getBinding() == ELF::STB_LOCAL) {
308     MCSection &Section = *getAssembler().getContext().getELFSection(
309         ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
310     MCSectionSubPair P = getCurrentSection();
311     SwitchSection(&Section);
312 
313     EmitValueToAlignment(ByteAlignment, 0, 1, 0);
314     EmitLabel(Symbol);
315     EmitZeros(Size);
316 
317     // Update the maximum alignment of the section if necessary.
318     if (ByteAlignment > Section.getAlignment())
319       Section.setAlignment(ByteAlignment);
320 
321     SwitchSection(P.first, P.second);
322   } else {
323     if(Symbol->declareCommon(Size, ByteAlignment))
324       report_fatal_error("Symbol: " + Symbol->getName() +
325                          " redeclared as different type");
326   }
327 
328   cast<MCSymbolELF>(Symbol)
329       ->setSize(MCConstantExpr::create(Size, getContext()));
330 }
331 
emitELFSize(MCSymbolELF * Symbol,const MCExpr * Value)332 void MCELFStreamer::emitELFSize(MCSymbolELF *Symbol, const MCExpr *Value) {
333   Symbol->setSize(Value);
334 }
335 
EmitLocalCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)336 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
337                                           unsigned ByteAlignment) {
338   auto *Symbol = cast<MCSymbolELF>(S);
339   // FIXME: Should this be caught and done earlier?
340   getAssembler().registerSymbol(*Symbol);
341   Symbol->setBinding(ELF::STB_LOCAL);
342   Symbol->setExternal(false);
343   EmitCommonSymbol(Symbol, Size, ByteAlignment);
344 }
345 
EmitValueImpl(const MCExpr * Value,unsigned Size,SMLoc Loc)346 void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
347                                   SMLoc Loc) {
348   if (isBundleLocked())
349     report_fatal_error("Emitting values inside a locked bundle is forbidden");
350   fixSymbolsInTLSFixups(Value);
351   MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
352 }
353 
EmitValueToAlignment(unsigned ByteAlignment,int64_t Value,unsigned ValueSize,unsigned MaxBytesToEmit)354 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
355                                          int64_t Value,
356                                          unsigned ValueSize,
357                                          unsigned MaxBytesToEmit) {
358   if (isBundleLocked())
359     report_fatal_error("Emitting values inside a locked bundle is forbidden");
360   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
361                                          ValueSize, MaxBytesToEmit);
362 }
363 
364 // Add a symbol for the file name of this module. They start after the
365 // null symbol and don't count as normal symbol, i.e. a non-STT_FILE symbol
366 // with the same name may appear.
EmitFileDirective(StringRef Filename)367 void MCELFStreamer::EmitFileDirective(StringRef Filename) {
368   getAssembler().addFileName(Filename);
369 }
370 
EmitIdent(StringRef IdentString)371 void MCELFStreamer::EmitIdent(StringRef IdentString) {
372   MCSection *Comment = getAssembler().getContext().getELFSection(
373       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
374   PushSection();
375   SwitchSection(Comment);
376   if (!SeenIdent) {
377     EmitIntValue(0, 1);
378     SeenIdent = true;
379   }
380   EmitBytes(IdentString);
381   EmitIntValue(0, 1);
382   PopSection();
383 }
384 
fixSymbolsInTLSFixups(const MCExpr * expr)385 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
386   switch (expr->getKind()) {
387   case MCExpr::Target:
388     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
389     break;
390   case MCExpr::Constant:
391     break;
392 
393   case MCExpr::Binary: {
394     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
395     fixSymbolsInTLSFixups(be->getLHS());
396     fixSymbolsInTLSFixups(be->getRHS());
397     break;
398   }
399 
400   case MCExpr::SymbolRef: {
401     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
402     switch (symRef.getKind()) {
403     default:
404       return;
405     case MCSymbolRefExpr::VK_GOTTPOFF:
406     case MCSymbolRefExpr::VK_INDNTPOFF:
407     case MCSymbolRefExpr::VK_NTPOFF:
408     case MCSymbolRefExpr::VK_GOTNTPOFF:
409     case MCSymbolRefExpr::VK_TLSGD:
410     case MCSymbolRefExpr::VK_TLSLD:
411     case MCSymbolRefExpr::VK_TLSLDM:
412     case MCSymbolRefExpr::VK_TPOFF:
413     case MCSymbolRefExpr::VK_TPREL:
414     case MCSymbolRefExpr::VK_DTPOFF:
415     case MCSymbolRefExpr::VK_DTPREL:
416     case MCSymbolRefExpr::VK_PPC_DTPMOD:
417     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
418     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
419     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
420     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
421     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
422     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
423     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
424     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
425     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
426     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
427     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
428     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
429     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
430     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
431     case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
432     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
433     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
434     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
435     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
436     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
437     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
438     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
439     case MCSymbolRefExpr::VK_PPC_TLS:
440     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
441     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
442     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
443     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
444     case MCSymbolRefExpr::VK_PPC_TLSGD:
445     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
446     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
447     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
448     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
449     case MCSymbolRefExpr::VK_PPC_TLSLD:
450       break;
451     }
452     getAssembler().registerSymbol(symRef.getSymbol());
453     cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
454     break;
455   }
456 
457   case MCExpr::Unary:
458     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
459     break;
460   }
461 }
462 
EmitInstToFragment(const MCInst & Inst,const MCSubtargetInfo & STI)463 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
464                                        const MCSubtargetInfo &STI) {
465   this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
466   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
467 
468   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
469     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
470 }
471 
EmitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)472 void MCELFStreamer::EmitInstToData(const MCInst &Inst,
473                                    const MCSubtargetInfo &STI) {
474   MCAssembler &Assembler = getAssembler();
475   SmallVector<MCFixup, 4> Fixups;
476   SmallString<256> Code;
477   raw_svector_ostream VecOS(Code);
478   Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
479 
480   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
481     fixSymbolsInTLSFixups(Fixups[i].getValue());
482 
483   // There are several possibilities here:
484   //
485   // If bundling is disabled, append the encoded instruction to the current data
486   // fragment (or create a new such fragment if the current fragment is not a
487   // data fragment).
488   //
489   // If bundling is enabled:
490   // - If we're not in a bundle-locked group, emit the instruction into a
491   //   fragment of its own. If there are no fixups registered for the
492   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
493   //   MCDataFragment.
494   // - If we're in a bundle-locked group, append the instruction to the current
495   //   data fragment because we want all the instructions in a group to get into
496   //   the same fragment. Be careful not to do that for the first instruction in
497   //   the group, though.
498   MCDataFragment *DF;
499 
500   if (Assembler.isBundlingEnabled()) {
501     MCSection &Sec = *getCurrentSectionOnly();
502     if (Assembler.getRelaxAll() && isBundleLocked())
503       // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
504       // the current bundle group.
505       DF = BundleGroups.back();
506     else if (Assembler.getRelaxAll() && !isBundleLocked())
507       // When not in a bundle-locked group and the -mc-relax-all flag is used,
508       // we create a new temporary fragment which will be later merged into
509       // the current fragment.
510       DF = new MCDataFragment();
511     else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst())
512       // If we are bundle-locked, we re-use the current fragment.
513       // The bundle-locking directive ensures this is a new data fragment.
514       DF = cast<MCDataFragment>(getCurrentFragment());
515     else if (!isBundleLocked() && Fixups.size() == 0) {
516       // Optimize memory usage by emitting the instruction to a
517       // MCCompactEncodedInstFragment when not in a bundle-locked group and
518       // there are no fixups registered.
519       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
520       insert(CEIF);
521       CEIF->getContents().append(Code.begin(), Code.end());
522       return;
523     } else {
524       DF = new MCDataFragment();
525       insert(DF);
526     }
527     if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
528       // If this fragment is for a group marked "align_to_end", set a flag
529       // in the fragment. This can happen after the fragment has already been
530       // created if there are nested bundle_align groups and an inner one
531       // is the one marked align_to_end.
532       DF->setAlignToBundleEnd(true);
533     }
534 
535     // We're now emitting an instruction in a bundle group, so this flag has
536     // to be turned off.
537     Sec.setBundleGroupBeforeFirstInst(false);
538   } else {
539     DF = getOrCreateDataFragment();
540   }
541 
542   // Add the fixups and data.
543   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
544     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
545     DF->getFixups().push_back(Fixups[i]);
546   }
547   DF->setHasInstructions(true);
548   DF->getContents().append(Code.begin(), Code.end());
549 
550   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
551     if (!isBundleLocked()) {
552       mergeFragment(getOrCreateDataFragment(), DF);
553       delete DF;
554     }
555   }
556 }
557 
EmitBundleAlignMode(unsigned AlignPow2)558 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
559   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
560   MCAssembler &Assembler = getAssembler();
561   if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
562                         Assembler.getBundleAlignSize() == 1U << AlignPow2))
563     Assembler.setBundleAlignSize(1U << AlignPow2);
564   else
565     report_fatal_error(".bundle_align_mode cannot be changed once set");
566 }
567 
EmitBundleLock(bool AlignToEnd)568 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
569   MCSection &Sec = *getCurrentSectionOnly();
570 
571   // Sanity checks
572   //
573   if (!getAssembler().isBundlingEnabled())
574     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
575 
576   if (!isBundleLocked())
577     Sec.setBundleGroupBeforeFirstInst(true);
578 
579   if (getAssembler().getRelaxAll() && !isBundleLocked()) {
580     // TODO: drop the lock state and set directly in the fragment
581     MCDataFragment *DF = new MCDataFragment();
582     BundleGroups.push_back(DF);
583   }
584 
585   Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
586                                     : MCSection::BundleLocked);
587 }
588 
EmitBundleUnlock()589 void MCELFStreamer::EmitBundleUnlock() {
590   MCSection &Sec = *getCurrentSectionOnly();
591 
592   // Sanity checks
593   if (!getAssembler().isBundlingEnabled())
594     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
595   else if (!isBundleLocked())
596     report_fatal_error(".bundle_unlock without matching lock");
597   else if (Sec.isBundleGroupBeforeFirstInst())
598     report_fatal_error("Empty bundle-locked group is forbidden");
599 
600   // When the -mc-relax-all flag is used, we emit instructions to fragments
601   // stored on a stack. When the bundle unlock is emitted, we pop a fragment
602   // from the stack a merge it to the one below.
603   if (getAssembler().getRelaxAll()) {
604     assert(!BundleGroups.empty() && "There are no bundle groups");
605     MCDataFragment *DF = BundleGroups.back();
606 
607     // FIXME: Use BundleGroups to track the lock state instead.
608     Sec.setBundleLockState(MCSection::NotBundleLocked);
609 
610     // FIXME: Use more separate fragments for nested groups.
611     if (!isBundleLocked()) {
612       mergeFragment(getOrCreateDataFragment(), DF);
613       BundleGroups.pop_back();
614       delete DF;
615     }
616 
617     if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
618       getOrCreateDataFragment()->setAlignToBundleEnd(false);
619   } else
620     Sec.setBundleLockState(MCSection::NotBundleLocked);
621 }
622 
FinishImpl()623 void MCELFStreamer::FinishImpl() {
624   // Ensure the last section gets aligned if necessary.
625   MCSection *CurSection = getCurrentSectionOnly();
626   setSectionAlignmentForBundling(getAssembler(), CurSection);
627 
628   EmitFrames(nullptr);
629 
630   this->MCObjectStreamer::FinishImpl();
631 }
632 
createELFStreamer(MCContext & Context,MCAsmBackend & MAB,raw_pwrite_stream & OS,MCCodeEmitter * CE,bool RelaxAll)633 MCStreamer *llvm::createELFStreamer(MCContext &Context, MCAsmBackend &MAB,
634                                     raw_pwrite_stream &OS, MCCodeEmitter *CE,
635                                     bool RelaxAll) {
636   MCELFStreamer *S = new MCELFStreamer(Context, MAB, OS, CE);
637   if (RelaxAll)
638     S->getAssembler().setRelaxAll(true);
639   return S;
640 }
641 
EmitThumbFunc(MCSymbol * Func)642 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
643   llvm_unreachable("Generic ELF doesn't support this directive");
644 }
645 
EmitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)646 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
647   llvm_unreachable("ELF doesn't support this directive");
648 }
649 
BeginCOFFSymbolDef(const MCSymbol * Symbol)650 void MCELFStreamer::BeginCOFFSymbolDef(const MCSymbol *Symbol) {
651   llvm_unreachable("ELF doesn't support this directive");
652 }
653 
EmitCOFFSymbolStorageClass(int StorageClass)654 void MCELFStreamer::EmitCOFFSymbolStorageClass(int StorageClass) {
655   llvm_unreachable("ELF doesn't support this directive");
656 }
657 
EmitCOFFSymbolType(int Type)658 void MCELFStreamer::EmitCOFFSymbolType(int Type) {
659   llvm_unreachable("ELF doesn't support this directive");
660 }
661 
EndCOFFSymbolDef()662 void MCELFStreamer::EndCOFFSymbolDef() {
663   llvm_unreachable("ELF doesn't support this directive");
664 }
665 
EmitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)666 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
667                                  uint64_t Size, unsigned ByteAlignment) {
668   llvm_unreachable("ELF doesn't support this directive");
669 }
670 
EmitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)671 void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
672                                    uint64_t Size, unsigned ByteAlignment) {
673   llvm_unreachable("ELF doesn't support this directive");
674 }
675