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/SmallString.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/BinaryFormat/ELF.h"
18 #include "llvm/MC/MCAsmBackend.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/MCFixup.h"
25 #include "llvm/MC/MCFragment.h"
26 #include "llvm/MC/MCObjectFileInfo.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCSection.h"
29 #include "llvm/MC/MCSectionELF.h"
30 #include "llvm/MC/MCStreamer.h"
31 #include "llvm/MC/MCSymbol.h"
32 #include "llvm/MC/MCSymbolELF.h"
33 #include "llvm/Support/Casting.h"
34 #include "llvm/Support/ErrorHandling.h"
35 #include "llvm/Support/TargetRegistry.h"
36 #include "llvm/Support/raw_ostream.h"
37 #include <cassert>
38 #include <cstdint>
39 
40 using namespace llvm;
41 
MCELFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> TAB,std::unique_ptr<MCObjectWriter> OW,std::unique_ptr<MCCodeEmitter> Emitter)42 MCELFStreamer::MCELFStreamer(MCContext &Context,
43                              std::unique_ptr<MCAsmBackend> TAB,
44                              std::unique_ptr<MCObjectWriter> OW,
45                              std::unique_ptr<MCCodeEmitter> Emitter)
46     : MCObjectStreamer(Context, std::move(TAB), std::move(OW),
47                        std::move(Emitter)) {}
48 
isBundleLocked() const49 bool MCELFStreamer::isBundleLocked() const {
50   return getCurrentSectionOnly()->isBundleLocked();
51 }
52 
mergeFragment(MCDataFragment * DF,MCDataFragment * EF)53 void MCELFStreamer::mergeFragment(MCDataFragment *DF,
54                                   MCDataFragment *EF) {
55   MCAssembler &Assembler = getAssembler();
56 
57   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
58     uint64_t FSize = EF->getContents().size();
59 
60     if (FSize > Assembler.getBundleAlignSize())
61       report_fatal_error("Fragment can't be larger than a bundle size");
62 
63     uint64_t RequiredBundlePadding = computeBundlePadding(
64         Assembler, EF, DF->getContents().size(), FSize);
65 
66     if (RequiredBundlePadding > UINT8_MAX)
67       report_fatal_error("Padding cannot exceed 255 bytes");
68 
69     if (RequiredBundlePadding > 0) {
70       SmallString<256> Code;
71       raw_svector_ostream VecOS(Code);
72       EF->setBundlePadding(static_cast<uint8_t>(RequiredBundlePadding));
73       Assembler.writeFragmentPadding(VecOS, *EF, FSize);
74 
75       DF->getContents().append(Code.begin(), Code.end());
76     }
77   }
78 
79   flushPendingLabels(DF, DF->getContents().size());
80 
81   for (unsigned i = 0, e = EF->getFixups().size(); i != e; ++i) {
82     EF->getFixups()[i].setOffset(EF->getFixups()[i].getOffset() +
83                                  DF->getContents().size());
84     DF->getFixups().push_back(EF->getFixups()[i]);
85   }
86   if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
87     DF->setHasInstructions(*EF->getSubtargetInfo());
88   DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
89 }
90 
InitSections(bool NoExecStack)91 void MCELFStreamer::InitSections(bool NoExecStack) {
92   MCContext &Ctx = getContext();
93   SwitchSection(Ctx.getObjectFileInfo()->getTextSection());
94   EmitCodeAlignment(4);
95 
96   if (NoExecStack)
97     SwitchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
98 }
99 
EmitLabel(MCSymbol * S,SMLoc Loc)100 void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc) {
101   auto *Symbol = cast<MCSymbolELF>(S);
102   MCObjectStreamer::EmitLabel(Symbol, Loc);
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 
EmitLabel(MCSymbol * S,SMLoc Loc,MCFragment * F)110 void MCELFStreamer::EmitLabel(MCSymbol *S, SMLoc Loc, MCFragment *F) {
111   auto *Symbol = cast<MCSymbolELF>(S);
112   MCObjectStreamer::EmitLabel(Symbol, Loc, F);
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 
EmitAssemblerFlag(MCAssemblerFlag Flag)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.
setSectionAlignmentForBundling(const MCAssembler & Assembler,MCSection * Section)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(Assembler.getBundleAlignSize());
144 }
145 
ChangeSection(MCSection * Section,const MCExpr * Subsection)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 
EmitWeakReference(MCSymbol * Alias,const MCSymbol * Symbol)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).
CombineSymbolTypes(unsigned T1,unsigned T2)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 
EmitSymbolAttribute(MCSymbol * S,MCSymbolAttr Attribute)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_LazyReference:
206   case MCSA_Reference:
207   case MCSA_SymbolResolver:
208   case MCSA_PrivateExtern:
209   case MCSA_WeakDefinition:
210   case MCSA_WeakDefAutoPrivate:
211   case MCSA_Invalid:
212   case MCSA_IndirectSymbol:
213     return false;
214 
215   case MCSA_NoDeadStrip:
216     // Ignore for now.
217     break;
218 
219   case MCSA_ELF_TypeGnuUniqueObject:
220     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
221     Symbol->setBinding(ELF::STB_GNU_UNIQUE);
222     Symbol->setExternal(true);
223     break;
224 
225   case MCSA_Global:
226     Symbol->setBinding(ELF::STB_GLOBAL);
227     Symbol->setExternal(true);
228     break;
229 
230   case MCSA_WeakReference:
231   case MCSA_Weak:
232     Symbol->setBinding(ELF::STB_WEAK);
233     Symbol->setExternal(true);
234     break;
235 
236   case MCSA_Local:
237     Symbol->setBinding(ELF::STB_LOCAL);
238     Symbol->setExternal(false);
239     break;
240 
241   case MCSA_ELF_TypeFunction:
242     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
243     break;
244 
245   case MCSA_ELF_TypeIndFunction:
246     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
247     break;
248 
249   case MCSA_ELF_TypeObject:
250     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
251     break;
252 
253   case MCSA_ELF_TypeTLS:
254     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
255     break;
256 
257   case MCSA_ELF_TypeCommon:
258     // TODO: Emit these as a common symbol.
259     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
260     break;
261 
262   case MCSA_ELF_TypeNoType:
263     Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
264     break;
265 
266   case MCSA_Protected:
267     Symbol->setVisibility(ELF::STV_PROTECTED);
268     break;
269 
270   case MCSA_Hidden:
271     Symbol->setVisibility(ELF::STV_HIDDEN);
272     break;
273 
274   case MCSA_Internal:
275     Symbol->setVisibility(ELF::STV_INTERNAL);
276     break;
277 
278   case MCSA_AltEntry:
279     llvm_unreachable("ELF doesn't support the .alt_entry attribute");
280   }
281 
282   return true;
283 }
284 
EmitCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)285 void MCELFStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
286                                      unsigned ByteAlignment) {
287   auto *Symbol = cast<MCSymbolELF>(S);
288   getAssembler().registerSymbol(*Symbol);
289 
290   if (!Symbol->isBindingSet()) {
291     Symbol->setBinding(ELF::STB_GLOBAL);
292     Symbol->setExternal(true);
293   }
294 
295   Symbol->setType(ELF::STT_OBJECT);
296 
297   if (Symbol->getBinding() == ELF::STB_LOCAL) {
298     MCSection &Section = *getAssembler().getContext().getELFSection(
299         ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
300     MCSectionSubPair P = getCurrentSection();
301     SwitchSection(&Section);
302 
303     EmitValueToAlignment(ByteAlignment, 0, 1, 0);
304     EmitLabel(Symbol);
305     EmitZeros(Size);
306 
307     // Update the maximum alignment of the section if necessary.
308     if (ByteAlignment > Section.getAlignment())
309       Section.setAlignment(ByteAlignment);
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 
emitELFSize(MCSymbol * Symbol,const MCExpr * Value)322 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
323   cast<MCSymbolELF>(Symbol)->setSize(Value);
324 }
325 
emitELFSymverDirective(StringRef AliasName,const MCSymbol * Aliasee)326 void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
327                                            const MCSymbol *Aliasee) {
328   getAssembler().Symvers.push_back({AliasName, Aliasee});
329 }
330 
EmitLocalCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment)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 
EmitValueImpl(const MCExpr * Value,unsigned Size,SMLoc Loc)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 
EmitValueToAlignment(unsigned ByteAlignment,int64_t Value,unsigned ValueSize,unsigned MaxBytesToEmit)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 
emitCGProfileEntry(const MCSymbolRefExpr * From,const MCSymbolRefExpr * To,uint64_t Count)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 
EmitIdent(StringRef IdentString)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 
fixSymbolsInTLSFixups(const MCExpr * expr)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_TLSGD:
404     case MCSymbolRefExpr::VK_TLSLD:
405     case MCSymbolRefExpr::VK_TLSLDM:
406     case MCSymbolRefExpr::VK_TPOFF:
407     case MCSymbolRefExpr::VK_TPREL:
408     case MCSymbolRefExpr::VK_DTPOFF:
409     case MCSymbolRefExpr::VK_DTPREL:
410     case MCSymbolRefExpr::VK_PPC_DTPMOD:
411     case MCSymbolRefExpr::VK_PPC_TPREL_LO:
412     case MCSymbolRefExpr::VK_PPC_TPREL_HI:
413     case MCSymbolRefExpr::VK_PPC_TPREL_HA:
414     case MCSymbolRefExpr::VK_PPC_TPREL_HIGH:
415     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
416     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
417     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
418     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
419     case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
420     case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
421     case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
422     case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
423     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
424     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
425     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
426     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
427     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
428     case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
429     case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
430     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
431     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
432     case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
433     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
434     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
435     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
436     case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
437     case MCSymbolRefExpr::VK_PPC_TLS:
438     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
439     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
440     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
441     case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
442     case MCSymbolRefExpr::VK_PPC_TLSGD:
443     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
444     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
445     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
446     case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
447     case MCSymbolRefExpr::VK_PPC_TLSLD:
448       break;
449     }
450     getAssembler().registerSymbol(symRef.getSymbol());
451     cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
452     break;
453   }
454 
455   case MCExpr::Unary:
456     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
457     break;
458   }
459 }
460 
finalizeCGProfileEntry(const MCSymbolRefExpr * & SRE)461 void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
462   const MCSymbol *S = &SRE->getSymbol();
463   if (S->isTemporary()) {
464     if (!S->isInSection()) {
465       getContext().reportError(
466           SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
467                              "`" + S->getName() + "`");
468       return;
469     }
470     S = S->getSection().getBeginSymbol();
471     S->setUsedInReloc();
472     SRE =
473         MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
474     return;
475   }
476   // Not a temporary, referece it as a weak undefined.
477   bool Created;
478   getAssembler().registerSymbol(*S, &Created);
479   if (Created) {
480     cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
481     cast<MCSymbolELF>(S)->setExternal(true);
482   }
483 }
484 
finalizeCGProfile()485 void MCELFStreamer::finalizeCGProfile() {
486   for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
487     finalizeCGProfileEntry(E.From);
488     finalizeCGProfileEntry(E.To);
489   }
490 }
491 
EmitInstToFragment(const MCInst & Inst,const MCSubtargetInfo & STI)492 void MCELFStreamer::EmitInstToFragment(const MCInst &Inst,
493                                        const MCSubtargetInfo &STI) {
494   this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
495   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
496 
497   for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
498     fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
499 }
500 
501 // A fragment can only have one Subtarget, and when bundling is enabled we
502 // sometimes need to use the same fragment. We give an error if there
503 // are conflicting Subtargets.
CheckBundleSubtargets(const MCSubtargetInfo * OldSTI,const MCSubtargetInfo * NewSTI)504 static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
505                                   const MCSubtargetInfo *NewSTI) {
506   if (OldSTI && NewSTI && OldSTI != NewSTI)
507     report_fatal_error("A Bundle can only have one Subtarget.");
508 }
509 
EmitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)510 void MCELFStreamer::EmitInstToData(const MCInst &Inst,
511                                    const MCSubtargetInfo &STI) {
512   MCAssembler &Assembler = getAssembler();
513   SmallVector<MCFixup, 4> Fixups;
514   SmallString<256> Code;
515   raw_svector_ostream VecOS(Code);
516   Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
517 
518   for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
519     fixSymbolsInTLSFixups(Fixups[i].getValue());
520 
521   // There are several possibilities here:
522   //
523   // If bundling is disabled, append the encoded instruction to the current data
524   // fragment (or create a new such fragment if the current fragment is not a
525   // data fragment, or the Subtarget has changed).
526   //
527   // If bundling is enabled:
528   // - If we're not in a bundle-locked group, emit the instruction into a
529   //   fragment of its own. If there are no fixups registered for the
530   //   instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
531   //   MCDataFragment.
532   // - If we're in a bundle-locked group, append the instruction to the current
533   //   data fragment because we want all the instructions in a group to get into
534   //   the same fragment. Be careful not to do that for the first instruction in
535   //   the group, though.
536   MCDataFragment *DF;
537 
538   if (Assembler.isBundlingEnabled()) {
539     MCSection &Sec = *getCurrentSectionOnly();
540     if (Assembler.getRelaxAll() && isBundleLocked()) {
541       // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
542       // the current bundle group.
543       DF = BundleGroups.back();
544       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
545     }
546     else if (Assembler.getRelaxAll() && !isBundleLocked())
547       // When not in a bundle-locked group and the -mc-relax-all flag is used,
548       // we create a new temporary fragment which will be later merged into
549       // the current fragment.
550       DF = new MCDataFragment();
551     else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
552       // If we are bundle-locked, we re-use the current fragment.
553       // The bundle-locking directive ensures this is a new data fragment.
554       DF = cast<MCDataFragment>(getCurrentFragment());
555       CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
556     }
557     else if (!isBundleLocked() && Fixups.size() == 0) {
558       // Optimize memory usage by emitting the instruction to a
559       // MCCompactEncodedInstFragment when not in a bundle-locked group and
560       // there are no fixups registered.
561       MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
562       insert(CEIF);
563       CEIF->getContents().append(Code.begin(), Code.end());
564       CEIF->setHasInstructions(STI);
565       return;
566     } else {
567       DF = new MCDataFragment();
568       insert(DF);
569     }
570     if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
571       // If this fragment is for a group marked "align_to_end", set a flag
572       // in the fragment. This can happen after the fragment has already been
573       // created if there are nested bundle_align groups and an inner one
574       // is the one marked align_to_end.
575       DF->setAlignToBundleEnd(true);
576     }
577 
578     // We're now emitting an instruction in a bundle group, so this flag has
579     // to be turned off.
580     Sec.setBundleGroupBeforeFirstInst(false);
581   } else {
582     DF = getOrCreateDataFragment(&STI);
583   }
584 
585   // Add the fixups and data.
586   for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
587     Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
588     DF->getFixups().push_back(Fixups[i]);
589   }
590   DF->setHasInstructions(STI);
591   DF->getContents().append(Code.begin(), Code.end());
592 
593   if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
594     if (!isBundleLocked()) {
595       mergeFragment(getOrCreateDataFragment(&STI), DF);
596       delete DF;
597     }
598   }
599 }
600 
EmitBundleAlignMode(unsigned AlignPow2)601 void MCELFStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
602   assert(AlignPow2 <= 30 && "Invalid bundle alignment");
603   MCAssembler &Assembler = getAssembler();
604   if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
605                         Assembler.getBundleAlignSize() == 1U << AlignPow2))
606     Assembler.setBundleAlignSize(1U << AlignPow2);
607   else
608     report_fatal_error(".bundle_align_mode cannot be changed once set");
609 }
610 
EmitBundleLock(bool AlignToEnd)611 void MCELFStreamer::EmitBundleLock(bool AlignToEnd) {
612   MCSection &Sec = *getCurrentSectionOnly();
613 
614   // Sanity checks
615   //
616   if (!getAssembler().isBundlingEnabled())
617     report_fatal_error(".bundle_lock forbidden when bundling is disabled");
618 
619   if (!isBundleLocked())
620     Sec.setBundleGroupBeforeFirstInst(true);
621 
622   if (getAssembler().getRelaxAll() && !isBundleLocked()) {
623     // TODO: drop the lock state and set directly in the fragment
624     MCDataFragment *DF = new MCDataFragment();
625     BundleGroups.push_back(DF);
626   }
627 
628   Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
629                                     : MCSection::BundleLocked);
630 }
631 
EmitBundleUnlock()632 void MCELFStreamer::EmitBundleUnlock() {
633   MCSection &Sec = *getCurrentSectionOnly();
634 
635   // Sanity checks
636   if (!getAssembler().isBundlingEnabled())
637     report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
638   else if (!isBundleLocked())
639     report_fatal_error(".bundle_unlock without matching lock");
640   else if (Sec.isBundleGroupBeforeFirstInst())
641     report_fatal_error("Empty bundle-locked group is forbidden");
642 
643   // When the -mc-relax-all flag is used, we emit instructions to fragments
644   // stored on a stack. When the bundle unlock is emitted, we pop a fragment
645   // from the stack a merge it to the one below.
646   if (getAssembler().getRelaxAll()) {
647     assert(!BundleGroups.empty() && "There are no bundle groups");
648     MCDataFragment *DF = BundleGroups.back();
649 
650     // FIXME: Use BundleGroups to track the lock state instead.
651     Sec.setBundleLockState(MCSection::NotBundleLocked);
652 
653     // FIXME: Use more separate fragments for nested groups.
654     if (!isBundleLocked()) {
655       mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
656       BundleGroups.pop_back();
657       delete DF;
658     }
659 
660     if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
661       getOrCreateDataFragment()->setAlignToBundleEnd(false);
662   } else
663     Sec.setBundleLockState(MCSection::NotBundleLocked);
664 }
665 
FinishImpl()666 void MCELFStreamer::FinishImpl() {
667   // Ensure the last section gets aligned if necessary.
668   MCSection *CurSection = getCurrentSectionOnly();
669   setSectionAlignmentForBundling(getAssembler(), CurSection);
670 
671   finalizeCGProfile();
672   EmitFrames(nullptr);
673 
674   this->MCObjectStreamer::FinishImpl();
675 }
676 
EmitThumbFunc(MCSymbol * Func)677 void MCELFStreamer::EmitThumbFunc(MCSymbol *Func) {
678   llvm_unreachable("Generic ELF doesn't support this directive");
679 }
680 
EmitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)681 void MCELFStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
682   llvm_unreachable("ELF doesn't support this directive");
683 }
684 
EmitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment,SMLoc Loc)685 void MCELFStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
686                                  uint64_t Size, unsigned ByteAlignment,
687                                  SMLoc Loc) {
688   llvm_unreachable("ELF doesn't support this directive");
689 }
690 
EmitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment)691 void MCELFStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
692                                    uint64_t Size, unsigned ByteAlignment) {
693   llvm_unreachable("ELF doesn't support this directive");
694 }
695 
createELFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> && MAB,std::unique_ptr<MCObjectWriter> && OW,std::unique_ptr<MCCodeEmitter> && CE,bool RelaxAll)696 MCStreamer *llvm::createELFStreamer(MCContext &Context,
697                                     std::unique_ptr<MCAsmBackend> &&MAB,
698                                     std::unique_ptr<MCObjectWriter> &&OW,
699                                     std::unique_ptr<MCCodeEmitter> &&CE,
700                                     bool RelaxAll) {
701   MCELFStreamer *S =
702       new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
703   if (RelaxAll)
704     S->getAssembler().setRelaxAll(true);
705   return S;
706 }
707