xref: /freebsd/contrib/llvm-project/llvm/lib/MC/MCELFStreamer.cpp (revision cfd6422a5217410fbd66f7a7a8a64d9d85e61229) 
1 //===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file assembles .s files and emits ELF .o object files.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "llvm/MC/MCELFStreamer.h"
14 #include "llvm/ADT/SmallString.h"
15 #include "llvm/ADT/SmallVector.h"
16 #include "llvm/BinaryFormat/ELF.h"
17 #include "llvm/MC/MCAsmBackend.h"
18 #include "llvm/MC/MCAsmInfo.h"
19 #include "llvm/MC/MCAssembler.h"
20 #include "llvm/MC/MCCodeEmitter.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCExpr.h"
23 #include "llvm/MC/MCFixup.h"
24 #include "llvm/MC/MCFragment.h"
25 #include "llvm/MC/MCObjectFileInfo.h"
26 #include "llvm/MC/MCObjectWriter.h"
27 #include "llvm/MC/MCSection.h"
28 #include "llvm/MC/MCSectionELF.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/MC/MCSymbol.h"
31 #include "llvm/MC/MCSymbolELF.h"
32 #include "llvm/Support/Casting.h"
33 #include "llvm/Support/ErrorHandling.h"
34 #include "llvm/Support/TargetRegistry.h"
35 #include "llvm/Support/raw_ostream.h"
36 #include <cassert>
37 #include <cstdint>
38 
39 using namespace llvm;
40 
41 MCELFStreamer::MCELFStreamer(MCContext &Context,
42                              std::unique_ptr<MCAsmBackend> TAB,
43                              std::unique_ptr<MCObjectWriter> OW,
44                              std::unique_ptr<MCCodeEmitter> Emitter)
45     : MCObjectStreamer(Context, std::move(TAB), std::move(OW),
46                        std::move(Emitter)) {}
47 
48 bool MCELFStreamer::isBundleLocked() const {
49   return getCurrentSectionOnly()->isBundleLocked();
50 }
51 
52 void MCELFStreamer::mergeFragment(MCDataFragment *DF,
53                                   MCDataFragment *EF) {
54   MCAssembler &Assembler = getAssembler();
55 
56   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
57     uint64_t FSize = EF->getContents().size();
58 
59     if (FSize > Assembler.getBundleAlignSize())
60       report_fatal_error("Fragment can't be larger than a bundle size");
61 
62     uint64_t RequiredBundlePadding = computeBundlePadding(
63         Assembler, EF, DF->getContents().size(), FSize);
64 
65     if (RequiredBundlePadding > UINT8_MAX)
66       report_fatal_error("Padding cannot exceed 255 bytes");
67 
68     if (RequiredBundlePadding > 0) {
69       SmallString<256> Code;
70       raw_svector_ostream VecOS(Code);
71       EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
72       Assembler.writeFragmentPadding(VecOS, *EF, FSize);
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   if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
86     DF->setHasInstructions(*EF->getSubtargetInfo());
87   DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
88 }
89 
90 void MCELFStreamer::InitSections(bool NoExecStack) {
91   MCContext &Ctx = getContext();
92   SwitchSection(Ctx.getObjectFileInfo()->getTextSection());
93   emitCodeAlignment(4);
94 
95   if (NoExecStack)
96     SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
97 }
98 
99 void MCELFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
100   auto *Symbol = cast<MCSymbolELF>(S);
101   MCObjectStreamer::emitLabel(Symbol, Loc);
102 
103   const MCSectionELF &Section =
104       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
105   if (Section.getFlags() & ELF::SHF_TLS)
106     Symbol->setType(ELF::STT_TLS);
107 }
108 
109 void MCELFStreamer::emitLabelAtPos(MCSymbol *S, SMLoc Loc, MCFragment *F,
110                                    uint64_t Offset) {
111   auto *Symbol = cast<MCSymbolELF>(S);
112   MCObjectStreamer::emitLabelAtPos(Symbol, Loc, F, Offset);
113 
114   const MCSectionELF &Section =
115       static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
116   if (Section.getFlags() & ELF::SHF_TLS)
117     Symbol->setType(ELF::STT_TLS);
118 }
119 
120 void MCELFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
121   // Let the target do whatever target specific stuff it needs to do.
122   getAssembler().getBackend().handleAssemblerFlag(Flag);
123   // Do any generic stuff we need to do.
124   switch (Flag) {
125   case MCAF_SyntaxUnified: return; // no-op here.
126   case MCAF_Code16: return; // Change parsing mode; no-op here.
127   case MCAF_Code32: return; // Change parsing mode; no-op here.
128   case MCAF_Code64: return; // Change parsing mode; no-op here.
129   case MCAF_SubsectionsViaSymbols:
130     getAssembler().setSubsectionsViaSymbols(true);
131     return;
132   }
133 
134   llvm_unreachable("invalid assembler flag!");
135 }
136 
137 // If bundle alignment is used and there are any instructions in the section, it
138 // needs to be aligned to at least the bundle size.
139 static void setSectionAlignmentForBundling(const MCAssembler &Assembler,
140                                            MCSection *Section) {
141   if (Section && Assembler.isBundlingEnabled() && Section->hasInstructions() &&
142       Section->getAlignment() < Assembler.getBundleAlignSize())
143     Section->setAlignment(Align(Assembler.getBundleAlignSize()));
144 }
145 
146 void MCELFStreamer::changeSection(MCSection *Section,
147                                   const MCExpr *Subsection) {
148   MCSection *CurSection = getCurrentSectionOnly();
149   if (CurSection && isBundleLocked())
150     report_fatal_error("Unterminated .bundle_lock when changing a section");
151 
152   MCAssembler &Asm = getAssembler();
153   // Ensure the previous section gets aligned if necessary.
154   setSectionAlignmentForBundling(Asm, CurSection);
155   auto *SectionELF = static_cast<const MCSectionELF *>(Section);
156   const MCSymbol *Grp = SectionELF->getGroup();
157   if (Grp)
158     Asm.registerSymbol(*Grp);
159 
160   changeSectionImpl(Section, Subsection);
161   Asm.registerSymbol(*Section->getBeginSymbol());
162 }
163 
164 void MCELFStreamer::emitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
165   getAssembler().registerSymbol(*Symbol);
166   const MCExpr *Value = MCSymbolRefExpr::create(
167       Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
168   Alias->setVariableValue(Value);
169 }
170 
171 // When GNU as encounters more than one .type declaration for an object it seems
172 // to use a mechanism similar to the one below to decide which type is actually
173 // used in the object file.  The greater of T1 and T2 is selected based on the
174 // following ordering:
175 //  STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
176 // If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
177 // provided type).
178 static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
179   for (unsigned Type : {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
180                         ELF::STT_GNU_IFUNC, ELF::STT_TLS}) {
181     if (T1 == Type)
182       return T2;
183     if (T2 == Type)
184       return T1;
185   }
186 
187   return T2;
188 }
189 
190 bool MCELFStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
191   auto *Symbol = cast<MCSymbolELF>(S);
192 
193   // Adding a symbol attribute always introduces the symbol, note that an
194   // important side effect of calling registerSymbol here is to register
195   // the symbol with the assembler.
196   getAssembler().registerSymbol(*Symbol);
197 
198   // The implementation of symbol attributes is designed to match 'as', but it
199   // leaves much to desired. It doesn't really make sense to arbitrarily add and
200   // remove flags, but 'as' allows this (in particular, see .desc).
201   //
202   // In the future it might be worth trying to make these operations more well
203   // defined.
204   switch (Attribute) {
205   case MCSA_Cold:
206   case MCSA_Extern:
207   case MCSA_LazyReference:
208   case MCSA_Reference:
209   case MCSA_SymbolResolver:
210   case MCSA_PrivateExtern:
211   case MCSA_WeakDefinition:
212   case MCSA_WeakDefAutoPrivate:
213   case MCSA_Invalid:
214   case MCSA_IndirectSymbol:
215     return false;
216 
217   case MCSA_NoDeadStrip:
218     // Ignore for now.
219     break;
220 
221   case MCSA_ELF_TypeGnuUniqueObject:
222     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
223     Symbol->setBinding(ELF::STB_GNU_UNIQUE);
224     Symbol->setExternal(true);
225     break;
226 
227   case MCSA_Global:
228     Symbol->setBinding(ELF::STB_GLOBAL);
229     Symbol->setExternal(true);
230     break;
231 
232   case MCSA_WeakReference:
233   case MCSA_Weak:
234     Symbol->setBinding(ELF::STB_WEAK);
235     Symbol->setExternal(true);
236     break;
237 
238   case MCSA_Local:
239     Symbol->setBinding(ELF::STB_LOCAL);
240     Symbol->setExternal(false);
241     break;
242 
243   case MCSA_ELF_TypeFunction:
244     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
245     break;
246 
247   case MCSA_ELF_TypeIndFunction:
248     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
249     break;
250 
251   case MCSA_ELF_TypeObject:
252     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
253     break;
254 
255   case MCSA_ELF_TypeTLS:
256     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
257     break;
258 
259   case MCSA_ELF_TypeCommon:
260     // TODO: Emit these as a common symbol.
261     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
262     break;
263 
264   case MCSA_ELF_TypeNoType:
265     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
266     break;
267 
268   case MCSA_Protected:
269     Symbol->setVisibility(ELF::STV_PROTECTED);
270     break;
271 
272   case MCSA_Hidden:
273     Symbol->setVisibility(ELF::STV_HIDDEN);
274     break;
275 
276   case MCSA_Internal:
277     Symbol->setVisibility(ELF::STV_INTERNAL);
278     break;
279 
280   case MCSA_AltEntry:
281     llvm_unreachable("ELF doesn't support the .alt_entry attribute");
282 
283   case MCSA_LGlobal:
284     llvm_unreachable("ELF doesn't support the .lglobl attribute");
285   }
286 
287   return true;
288 }
289 
290 void MCELFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
291                                      unsigned ByteAlignment) {
292   auto *Symbol = cast<MCSymbolELF>(S);
293   getAssembler().registerSymbol(*Symbol);
294 
295   if (!Symbol->isBindingSet()) {
296     Symbol->setBinding(ELF::STB_GLOBAL);
297     Symbol->setExternal(true);
298   }
299 
300   Symbol->setType(ELF::STT_OBJECT);
301 
302   if (Symbol->getBinding() == ELF::STB_LOCAL) {
303     MCSection &Section = *getAssembler().getContext().getELFSection(
304         ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
305     MCSectionSubPair P = getCurrentSection();
306     SwitchSection(&Section);
307 
308     emitValueToAlignment(ByteAlignment, 0, 1, 0);
309     emitLabel(Symbol);
310     emitZeros(Size);
311 
312     SwitchSection(P.first, P.second);
313   } else {
314     if(Symbol->declareCommon(Size, ByteAlignment))
315       report_fatal_error("Symbol: " + Symbol->getName() +
316                          " redeclared as different type");
317   }
318 
319   cast<MCSymbolELF>(Symbol)
320       ->setSize(MCConstantExpr::create(Size, getContext()));
321 }
322 
323 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
324   cast<MCSymbolELF>(Symbol)->setSize(Value);
325 }
326 
327 void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
328                                            const MCSymbol *Aliasee) {
329   getAssembler().Symvers.push_back({AliasName, Aliasee});
330 }
331 
332 void MCELFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
333                                           unsigned ByteAlignment) {
334   auto *Symbol = cast<MCSymbolELF>(S);
335   // FIXME: Should this be caught and done earlier?
336   getAssembler().registerSymbol(*Symbol);
337   Symbol->setBinding(ELF::STB_LOCAL);
338   Symbol->setExternal(false);
339   emitCommonSymbol(Symbol, Size, ByteAlignment);
340 }
341 
342 void MCELFStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,
343                                   SMLoc Loc) {
344   if (isBundleLocked())
345     report_fatal_error("Emitting values inside a locked bundle is forbidden");
346   fixSymbolsInTLSFixups(Value);
347   MCObjectStreamer::emitValueImpl(Value, Size, Loc);
348 }
349 
350 void MCELFStreamer::emitValueToAlignment(unsigned ByteAlignment,
351                                          int64_t Value,
352                                          unsigned ValueSize,
353                                          unsigned MaxBytesToEmit) {
354   if (isBundleLocked())
355     report_fatal_error("Emitting values inside a locked bundle is forbidden");
356   MCObjectStreamer::emitValueToAlignment(ByteAlignment, Value,
357                                          ValueSize, MaxBytesToEmit);
358 }
359 
360 void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
361                                        const MCSymbolRefExpr *To,
362                                        uint64_t Count) {
363   getAssembler().CGProfile.push_back({From, To, Count});
364 }
365 
366 void MCELFStreamer::emitIdent(StringRef IdentString) {
367   MCSection *Comment = getAssembler().getContext().getELFSection(
368       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
369   PushSection();
370   SwitchSection(Comment);
371   if (!SeenIdent) {
372     emitInt8(0);
373     SeenIdent = true;
374   }
375   emitBytes(IdentString);
376   emitInt8(0);
377   PopSection();
378 }
379 
380 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
381   switch (expr->getKind()) {
382   case MCExpr::Target:
383     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
384     break;
385   case MCExpr::Constant:
386     break;
387 
388   case MCExpr::Binary: {
389     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
390     fixSymbolsInTLSFixups(be->getLHS());
391     fixSymbolsInTLSFixups(be->getRHS());
392     break;
393   }
394 
395   case MCExpr::SymbolRef: {
396     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
397     switch (symRef.getKind()) {
398     default:
399       return;
400     case MCSymbolRefExpr::VK_GOTTPOFF:
401     case MCSymbolRefExpr::VK_INDNTPOFF:
402     case MCSymbolRefExpr::VK_NTPOFF:
403     case MCSymbolRefExpr::VK_GOTNTPOFF:
404     case MCSymbolRefExpr::VK_TLSCALL:
405     case MCSymbolRefExpr::VK_TLSDESC:
406     case MCSymbolRefExpr::VK_TLSGD:
407     case MCSymbolRefExpr::VK_TLSLD:
408     case MCSymbolRefExpr::VK_TLSLDM:
409     case MCSymbolRefExpr::VK_TPOFF:
410     case MCSymbolRefExpr::VK_TPREL:
411     case MCSymbolRefExpr::VK_DTPOFF:
412     case MCSymbolRefExpr::VK_DTPREL:
413     case MCSymbolRefExpr::VK_PPC_DTPMOD:
414     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
415     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
416     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
417     case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
418     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
419     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
420     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
421     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
422     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
423     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
424     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
425     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
426     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
427     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
428     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
429     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
430     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
431     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
432     case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
433     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
434     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
435     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
436     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
437     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
438     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
439     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
440     case MCSymbolRefExpr::VK_PPC_TLS:
441     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
442     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
443     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
444     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
445     case MCSymbolRefExpr::VK_PPC_TLSGD:
446     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
447     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
448     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
449     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
450     case MCSymbolRefExpr::VK_PPC_TLSLD:
451       break;
452     }
453     getAssembler().registerSymbol(symRef.getSymbol());
454     cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
455     break;
456   }
457 
458   case MCExpr::Unary:
459     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
460     break;
461   }
462 }
463 
464 void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
465   const MCSymbol *S = &SRE->getSymbol();
466   if (S->isTemporary()) {
467     if (!S->isInSection()) {
468       getContext().reportError(
469           SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
470                              "`" + S->getName() + "`");
471       return;
472     }
473     S = S->getSection().getBeginSymbol();
474     S->setUsedInReloc();
475     SRE =
476         MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
477     return;
478   }
479   // Not a temporary, referece it as a weak undefined.
480   bool Created;
481   getAssembler().registerSymbol(*S, &Created);
482   if (Created) {
483     cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
484     cast<MCSymbolELF>(S)->setExternal(true);
485   }
486 }
487 
488 void MCELFStreamer::finalizeCGProfile() {
489   for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
490     finalizeCGProfileEntry(E.From);
491     finalizeCGProfileEntry(E.To);
492   }
493 }
494 
495 void MCELFStreamer::emitInstToFragment(const MCInst &Inst,
496                                        const MCSubtargetInfo &STI) {
497   this->MCObjectStreamer::emitInstToFragment(Inst, STI);
498   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
499 
500   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
501     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
502 }
503 
504 // A fragment can only have one Subtarget, and when bundling is enabled we
505 // sometimes need to use the same fragment. We give an error if there
506 // are conflicting Subtargets.
507 static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
508                                   const MCSubtargetInfo *NewSTI) {
509   if (OldSTI && NewSTI && OldSTI != NewSTI)
510     report_fatal_error("A Bundle can only have one Subtarget.");
511 }
512 
513 void MCELFStreamer::emitInstToData(const MCInst &Inst,
514                                    const MCSubtargetInfo &STI) {
515   MCAssembler &Assembler = getAssembler();
516   SmallVector<MCFixup, 4> Fixups;
517   SmallString<256> Code;
518   raw_svector_ostream VecOS(Code);
519   Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
520 
521   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
522     fixSymbolsInTLSFixups(Fixups[i].getValue());
523 
524   // There are several possibilities here:
525   //
526   // If bundling is disabled, append the encoded instruction to the current data
527   // fragment (or create a new such fragment if the current fragment is not a
528   // data fragment, or the Subtarget has changed).
529   //
530   // If bundling is enabled:
531   // - If we're not in a bundle-locked group, emit the instruction into a
532   //   fragment of its own. If there are no fixups registered for the
533   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
534   //   MCDataFragment.
535   // - If we're in a bundle-locked group, append the instruction to the current
536   //   data fragment because we want all the instructions in a group to get into
537   //   the same fragment. Be careful not to do that for the first instruction in
538   //   the group, though.
539   MCDataFragment *DF;
540 
541   if (Assembler.isBundlingEnabled()) {
542     MCSection &Sec = *getCurrentSectionOnly();
543     if (Assembler.getRelaxAll() && isBundleLocked()) {
544       // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
545       // the current bundle group.
546       DF = BundleGroups.back();
547       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
548     }
549     else if (Assembler.getRelaxAll() && !isBundleLocked())
550       // When not in a bundle-locked group and the -mc-relax-all flag is used,
551       // we create a new temporary fragment which will be later merged into
552       // the current fragment.
553       DF = new MCDataFragment();
554     else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
555       // If we are bundle-locked, we re-use the current fragment.
556       // The bundle-locking directive ensures this is a new data fragment.
557       DF = cast<MCDataFragment>(getCurrentFragment());
558       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
559     }
560     else if (!isBundleLocked() && Fixups.size() == 0) {
561       // Optimize memory usage by emitting the instruction to a
562       // MCCompactEncodedInstFragment when not in a bundle-locked group and
563       // there are no fixups registered.
564       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
565       insert(CEIF);
566       CEIF->getContents().append(Code.begin(), Code.end());
567       CEIF->setHasInstructions(STI);
568       return;
569     } else {
570       DF = new MCDataFragment();
571       insert(DF);
572     }
573     if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
574       // If this fragment is for a group marked "align_to_end", set a flag
575       // in the fragment. This can happen after the fragment has already been
576       // created if there are nested bundle_align groups and an inner one
577       // is the one marked align_to_end.
578       DF->setAlignToBundleEnd(true);
579     }
580 
581     // We're now emitting an instruction in a bundle group, so this flag has
582     // to be turned off.
583     Sec.setBundleGroupBeforeFirstInst(false);
584   } else {
585     DF = getOrCreateDataFragment(&STI);
586   }
587 
588   // Add the fixups and data.
589   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
590     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
591     DF->getFixups().push_back(Fixups[i]);
592   }
593   DF->setHasInstructions(STI);
594   DF->getContents().append(Code.begin(), Code.end());
595 
596   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
597     if (!isBundleLocked()) {
598       mergeFragment(getOrCreateDataFragment(&STI), DF);
599       delete DF;
600     }
601   }
602 }
603 
604 void MCELFStreamer::emitBundleAlignMode(unsigned AlignPow2) {
605   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
606   MCAssembler &Assembler = getAssembler();
607   if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
608                         Assembler.getBundleAlignSize() == 1U << AlignPow2))
609     Assembler.setBundleAlignSize(1U << AlignPow2);
610   else
611     report_fatal_error(".bundle_align_mode cannot be changed once set");
612 }
613 
614 void MCELFStreamer::emitBundleLock(bool AlignToEnd) {
615   MCSection &Sec = *getCurrentSectionOnly();
616 
617   // Sanity checks
618   //
619   if (!getAssembler().isBundlingEnabled())
620     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
621 
622   if (!isBundleLocked())
623     Sec.setBundleGroupBeforeFirstInst(true);
624 
625   if (getAssembler().getRelaxAll() && !isBundleLocked()) {
626     // TODO: drop the lock state and set directly in the fragment
627     MCDataFragment *DF = new MCDataFragment();
628     BundleGroups.push_back(DF);
629   }
630 
631   Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
632                                     : MCSection::BundleLocked);
633 }
634 
635 void MCELFStreamer::emitBundleUnlock() {
636   MCSection &Sec = *getCurrentSectionOnly();
637 
638   // Sanity checks
639   if (!getAssembler().isBundlingEnabled())
640     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
641   else if (!isBundleLocked())
642     report_fatal_error(".bundle_unlock without matching lock");
643   else if (Sec.isBundleGroupBeforeFirstInst())
644     report_fatal_error("Empty bundle-locked group is forbidden");
645 
646   // When the -mc-relax-all flag is used, we emit instructions to fragments
647   // stored on a stack. When the bundle unlock is emitted, we pop a fragment
648   // from the stack a merge it to the one below.
649   if (getAssembler().getRelaxAll()) {
650     assert(!BundleGroups.empty() && "There are no bundle groups");
651     MCDataFragment *DF = BundleGroups.back();
652 
653     // FIXME: Use BundleGroups to track the lock state instead.
654     Sec.setBundleLockState(MCSection::NotBundleLocked);
655 
656     // FIXME: Use more separate fragments for nested groups.
657     if (!isBundleLocked()) {
658       mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
659       BundleGroups.pop_back();
660       delete DF;
661     }
662 
663     if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
664       getOrCreateDataFragment()->setAlignToBundleEnd(false);
665   } else
666     Sec.setBundleLockState(MCSection::NotBundleLocked);
667 }
668 
669 void MCELFStreamer::finishImpl() {
670   // Ensure the last section gets aligned if necessary.
671   MCSection *CurSection = getCurrentSectionOnly();
672   setSectionAlignmentForBundling(getAssembler(), CurSection);
673 
674   finalizeCGProfile();
675   emitFrames(nullptr);
676 
677   this->MCObjectStreamer::finishImpl();
678 }
679 
680 void MCELFStreamer::emitThumbFunc(MCSymbol *Func) {
681   llvm_unreachable("Generic ELF doesn't support this directive");
682 }
683 
684 void MCELFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
685   llvm_unreachable("ELF doesn't support this directive");
686 }
687 
688 void MCELFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
689                                  uint64_t Size, unsigned ByteAlignment,
690                                  SMLoc Loc) {
691   llvm_unreachable("ELF doesn't support this directive");
692 }
693 
694 void MCELFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
695                                    uint64_t Size, unsigned ByteAlignment) {
696   llvm_unreachable("ELF doesn't support this directive");
697 }
698 
699 MCStreamer *llvm::createELFStreamer(MCContext &Context,
700                                     std::unique_ptr<MCAsmBackend> &&MAB,
701                                     std::unique_ptr<MCObjectWriter> &&OW,
702                                     std::unique_ptr<MCCodeEmitter> &&CE,
703                                     bool RelaxAll) {
704   MCELFStreamer *S =
705       new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
706   if (RelaxAll)
707     S->getAssembler().setRelaxAll(true);
708   return S;
709 }
710