xref: /freebsd/contrib/llvm-project/llvm/lib/MC/MCELFStreamer.cpp (revision 5b27928474e6a4103d65b347544705c40c9618fd) 
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_LazyReference:
207   case MCSA_Reference:
208   case MCSA_SymbolResolver:
209   case MCSA_PrivateExtern:
210   case MCSA_WeakDefinition:
211   case MCSA_WeakDefAutoPrivate:
212   case MCSA_Invalid:
213   case MCSA_IndirectSymbol:
214     return false;
215 
216   case MCSA_NoDeadStrip:
217     // Ignore for now.
218     break;
219 
220   case MCSA_ELF_TypeGnuUniqueObject:
221     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
222     Symbol->setBinding(ELF::STB_GNU_UNIQUE);
223     Symbol->setExternal(true);
224     break;
225 
226   case MCSA_Global:
227     Symbol->setBinding(ELF::STB_GLOBAL);
228     Symbol->setExternal(true);
229     break;
230 
231   case MCSA_WeakReference:
232   case MCSA_Weak:
233     Symbol->setBinding(ELF::STB_WEAK);
234     Symbol->setExternal(true);
235     break;
236 
237   case MCSA_Local:
238     Symbol->setBinding(ELF::STB_LOCAL);
239     Symbol->setExternal(false);
240     break;
241 
242   case MCSA_ELF_TypeFunction:
243     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
244     break;
245 
246   case MCSA_ELF_TypeIndFunction:
247     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
248     break;
249 
250   case MCSA_ELF_TypeObject:
251     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
252     break;
253 
254   case MCSA_ELF_TypeTLS:
255     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
256     break;
257 
258   case MCSA_ELF_TypeCommon:
259     // TODO: Emit these as a common symbol.
260     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
261     break;
262 
263   case MCSA_ELF_TypeNoType:
264     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
265     break;
266 
267   case MCSA_Protected:
268     Symbol->setVisibility(ELF::STV_PROTECTED);
269     break;
270 
271   case MCSA_Hidden:
272     Symbol->setVisibility(ELF::STV_HIDDEN);
273     break;
274 
275   case MCSA_Internal:
276     Symbol->setVisibility(ELF::STV_INTERNAL);
277     break;
278 
279   case MCSA_AltEntry:
280     llvm_unreachable("ELF doesn't support the .alt_entry attribute");
281 
282   case MCSA_LGlobal:
283     llvm_unreachable("ELF doesn't support the .lglobl attribute");
284   }
285 
286   return true;
287 }
288 
289 void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
290                                      unsigned ByteAlignment) {
291   auto *Symbol = cast<MCSymbolELF>(S);
292   getAssembler().registerSymbol(*Symbol);
293 
294   if (!Symbol->isBindingSet()) {
295     Symbol->setBinding(ELF::STB_GLOBAL);
296     Symbol->setExternal(true);
297   }
298 
299   Symbol->setType(ELF::STT_OBJECT);
300 
301   if (Symbol->getBinding() == ELF::STB_LOCAL) {
302     MCSection &Section = *getAssembler().getContext().getELFSection(
303         ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
304     MCSectionSubPair P = getCurrentSection();
305     SwitchSection(&Section);
306 
307     EmitValueToAlignment(ByteAlignment, 0, 1, 0);
308     EmitLabel(Symbol);
309     EmitZeros(Size);
310 
311     SwitchSection(P.first, P.second);
312   } else {
313     if(Symbol->declareCommon(Size, ByteAlignment))
314       report_fatal_error("Symbol: " + Symbol->getName() +
315                          " redeclared as different type");
316   }
317 
318   cast<MCSymbolELF>(Symbol)
319       ->setSize(MCConstantExpr::create(Size, getContext()));
320 }
321 
322 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
323   cast<MCSymbolELF>(Symbol)->setSize(Value);
324 }
325 
326 void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
327                                            const MCSymbol *Aliasee) {
328   getAssembler().Symvers.push_back({AliasName, Aliasee});
329 }
330 
331 void MCELFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
332                                           unsigned ByteAlignment) {
333   auto *Symbol = cast<MCSymbolELF>(S);
334   // FIXME: Should this be caught and done earlier?
335   getAssembler().registerSymbol(*Symbol);
336   Symbol->setBinding(ELF::STB_LOCAL);
337   Symbol->setExternal(false);
338   EmitCommonSymbol(Symbol, Size, ByteAlignment);
339 }
340 
341 void MCELFStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
342                                   SMLoc Loc) {
343   if (isBundleLocked())
344     report_fatal_error("Emitting values inside a locked bundle is forbidden");
345   fixSymbolsInTLSFixups(Value);
346   MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
347 }
348 
349 void MCELFStreamer::EmitValueToAlignment(unsigned ByteAlignment,
350                                          int64_t Value,
351                                          unsigned ValueSize,
352                                          unsigned MaxBytesToEmit) {
353   if (isBundleLocked())
354     report_fatal_error("Emitting values inside a locked bundle is forbidden");
355   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value,
356                                          ValueSize, MaxBytesToEmit);
357 }
358 
359 void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
360                                        const MCSymbolRefExpr *To,
361                                        uint64_t Count) {
362   getAssembler().CGProfile.push_back({From, To, Count});
363 }
364 
365 void MCELFStreamer::EmitIdent(StringRef IdentString) {
366   MCSection *Comment = getAssembler().getContext().getELFSection(
367       ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
368   PushSection();
369   SwitchSection(Comment);
370   if (!SeenIdent) {
371     EmitIntValue(0, 1);
372     SeenIdent = true;
373   }
374   EmitBytes(IdentString);
375   EmitIntValue(0, 1);
376   PopSection();
377 }
378 
379 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
380   switch (expr->getKind()) {
381   case MCExpr::Target:
382     cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
383     break;
384   case MCExpr::Constant:
385     break;
386 
387   case MCExpr::Binary: {
388     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
389     fixSymbolsInTLSFixups(be->getLHS());
390     fixSymbolsInTLSFixups(be->getRHS());
391     break;
392   }
393 
394   case MCExpr::SymbolRef: {
395     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
396     switch (symRef.getKind()) {
397     default:
398       return;
399     case MCSymbolRefExpr::VK_GOTTPOFF:
400     case MCSymbolRefExpr::VK_INDNTPOFF:
401     case MCSymbolRefExpr::VK_NTPOFF:
402     case MCSymbolRefExpr::VK_GOTNTPOFF:
403     case MCSymbolRefExpr::VK_TLSCALL:
404     case MCSymbolRefExpr::VK_TLSDESC:
405     case MCSymbolRefExpr::VK_TLSGD:
406     case MCSymbolRefExpr::VK_TLSLD:
407     case MCSymbolRefExpr::VK_TLSLDM:
408     case MCSymbolRefExpr::VK_TPOFF:
409     case MCSymbolRefExpr::VK_TPREL:
410     case MCSymbolRefExpr::VK_DTPOFF:
411     case MCSymbolRefExpr::VK_DTPREL:
412     case MCSymbolRefExpr::VK_PPC_DTPMOD:
413     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
414     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
415     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
416     case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
417     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
418     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
419     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
420     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
421     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
422     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
423     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
424     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
425     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
426     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
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 
463 void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
464   const MCSymbol *S = &SRE->getSymbol();
465   if (S->isTemporary()) {
466     if (!S->isInSection()) {
467       getContext().reportError(
468           SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
469                              "`" + S->getName() + "`");
470       return;
471     }
472     S = S->getSection().getBeginSymbol();
473     S->setUsedInReloc();
474     SRE =
475         MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
476     return;
477   }
478   // Not a temporary, referece it as a weak undefined.
479   bool Created;
480   getAssembler().registerSymbol(*S, &Created);
481   if (Created) {
482     cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
483     cast<MCSymbolELF>(S)->setExternal(true);
484   }
485 }
486 
487 void MCELFStreamer::finalizeCGProfile() {
488   for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
489     finalizeCGProfileEntry(E.From);
490     finalizeCGProfileEntry(E.To);
491   }
492 }
493 
494 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
495                                        const MCSubtargetInfo &STI) {
496   this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
497   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
498 
499   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
500     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
501 }
502 
503 // A fragment can only have one Subtarget, and when bundling is enabled we
504 // sometimes need to use the same fragment. We give an error if there
505 // are conflicting Subtargets.
506 static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
507                                   const MCSubtargetInfo *NewSTI) {
508   if (OldSTI && NewSTI && OldSTI != NewSTI)
509     report_fatal_error("A Bundle can only have one Subtarget.");
510 }
511 
512 void MCELFStreamer::EmitInstToData(const MCInst &Inst,
513                                    const MCSubtargetInfo &STI) {
514   MCAssembler &Assembler = getAssembler();
515   SmallVector<MCFixup, 4> Fixups;
516   SmallString<256> Code;
517   raw_svector_ostream VecOS(Code);
518   Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
519 
520   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
521     fixSymbolsInTLSFixups(Fixups[i].getValue());
522 
523   // There are several possibilities here:
524   //
525   // If bundling is disabled, append the encoded instruction to the current data
526   // fragment (or create a new such fragment if the current fragment is not a
527   // data fragment, or the Subtarget has changed).
528   //
529   // If bundling is enabled:
530   // - If we're not in a bundle-locked group, emit the instruction into a
531   //   fragment of its own. If there are no fixups registered for the
532   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
533   //   MCDataFragment.
534   // - If we're in a bundle-locked group, append the instruction to the current
535   //   data fragment because we want all the instructions in a group to get into
536   //   the same fragment. Be careful not to do that for the first instruction in
537   //   the group, though.
538   MCDataFragment *DF;
539 
540   if (Assembler.isBundlingEnabled()) {
541     MCSection &Sec = *getCurrentSectionOnly();
542     if (Assembler.getRelaxAll() && isBundleLocked()) {
543       // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
544       // the current bundle group.
545       DF = BundleGroups.back();
546       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
547     }
548     else if (Assembler.getRelaxAll() && !isBundleLocked())
549       // When not in a bundle-locked group and the -mc-relax-all flag is used,
550       // we create a new temporary fragment which will be later merged into
551       // the current fragment.
552       DF = new MCDataFragment();
553     else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
554       // If we are bundle-locked, we re-use the current fragment.
555       // The bundle-locking directive ensures this is a new data fragment.
556       DF = cast<MCDataFragment>(getCurrentFragment());
557       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
558     }
559     else if (!isBundleLocked() && Fixups.size() == 0) {
560       // Optimize memory usage by emitting the instruction to a
561       // MCCompactEncodedInstFragment when not in a bundle-locked group and
562       // there are no fixups registered.
563       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
564       insert(CEIF);
565       CEIF->getContents().append(Code.begin(), Code.end());
566       CEIF->setHasInstructions(STI);
567       return;
568     } else {
569       DF = new MCDataFragment();
570       insert(DF);
571     }
572     if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
573       // If this fragment is for a group marked "align_to_end", set a flag
574       // in the fragment. This can happen after the fragment has already been
575       // created if there are nested bundle_align groups and an inner one
576       // is the one marked align_to_end.
577       DF->setAlignToBundleEnd(true);
578     }
579 
580     // We're now emitting an instruction in a bundle group, so this flag has
581     // to be turned off.
582     Sec.setBundleGroupBeforeFirstInst(false);
583   } else {
584     DF = getOrCreateDataFragment(&STI);
585   }
586 
587   // Add the fixups and data.
588   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
589     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
590     DF->getFixups().push_back(Fixups[i]);
591   }
592   DF->setHasInstructions(STI);
593   DF->getContents().append(Code.begin(), Code.end());
594 
595   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
596     if (!isBundleLocked()) {
597       mergeFragment(getOrCreateDataFragment(&STI), DF);
598       delete DF;
599     }
600   }
601 }
602 
603 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
604   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
605   MCAssembler &Assembler = getAssembler();
606   if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
607                         Assembler.getBundleAlignSize() == 1U << AlignPow2))
608     Assembler.setBundleAlignSize(1U << AlignPow2);
609   else
610     report_fatal_error(".bundle_align_mode cannot be changed once set");
611 }
612 
613 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
614   MCSection &Sec = *getCurrentSectionOnly();
615 
616   // Sanity checks
617   //
618   if (!getAssembler().isBundlingEnabled())
619     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
620 
621   if (!isBundleLocked())
622     Sec.setBundleGroupBeforeFirstInst(true);
623 
624   if (getAssembler().getRelaxAll() && !isBundleLocked()) {
625     // TODO: drop the lock state and set directly in the fragment
626     MCDataFragment *DF = new MCDataFragment();
627     BundleGroups.push_back(DF);
628   }
629 
630   Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
631                                     : MCSection::BundleLocked);
632 }
633 
634 void MCELFStreamer::EmitBundleUnlock() {
635   MCSection &Sec = *getCurrentSectionOnly();
636 
637   // Sanity checks
638   if (!getAssembler().isBundlingEnabled())
639     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
640   else if (!isBundleLocked())
641     report_fatal_error(".bundle_unlock without matching lock");
642   else if (Sec.isBundleGroupBeforeFirstInst())
643     report_fatal_error("Empty bundle-locked group is forbidden");
644 
645   // When the -mc-relax-all flag is used, we emit instructions to fragments
646   // stored on a stack. When the bundle unlock is emitted, we pop a fragment
647   // from the stack a merge it to the one below.
648   if (getAssembler().getRelaxAll()) {
649     assert(!BundleGroups.empty() && "There are no bundle groups");
650     MCDataFragment *DF = BundleGroups.back();
651 
652     // FIXME: Use BundleGroups to track the lock state instead.
653     Sec.setBundleLockState(MCSection::NotBundleLocked);
654 
655     // FIXME: Use more separate fragments for nested groups.
656     if (!isBundleLocked()) {
657       mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
658       BundleGroups.pop_back();
659       delete DF;
660     }
661 
662     if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
663       getOrCreateDataFragment()->setAlignToBundleEnd(false);
664   } else
665     Sec.setBundleLockState(MCSection::NotBundleLocked);
666 }
667 
668 void MCELFStreamer::FinishImpl() {
669   // Ensure the last section gets aligned if necessary.
670   MCSection *CurSection = getCurrentSectionOnly();
671   setSectionAlignmentForBundling(getAssembler(), CurSection);
672 
673   finalizeCGProfile();
674   EmitFrames(nullptr);
675 
676   this->MCObjectStreamer::FinishImpl();
677 }
678 
679 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
680   llvm_unreachable("Generic ELF doesn't support this directive");
681 }
682 
683 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
684   llvm_unreachable("ELF doesn't support this directive");
685 }
686 
687 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
688                                  uint64_t Size, unsigned ByteAlignment,
689                                  SMLoc Loc) {
690   llvm_unreachable("ELF doesn't support this directive");
691 }
692 
693 void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
694                                    uint64_t Size, unsigned ByteAlignment) {
695   llvm_unreachable("ELF doesn't support this directive");
696 }
697 
698 MCStreamer *llvm::createELFStreamer(MCContext &Context,
699                                     std::unique_ptr<MCAsmBackend> &&MAB,
700                                     std::unique_ptr<MCObjectWriter> &&OW,
701                                     std::unique_ptr<MCCodeEmitter> &&CE,
702                                     bool RelaxAll) {
703   MCELFStreamer *S =
704       new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
705   if (RelaxAll)
706     S->getAssembler().setRelaxAll(true);
707   return S;
708 }
709