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
MCELFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> TAB,std::unique_ptr<MCObjectWriter> OW,std::unique_ptr<MCCodeEmitter> Emitter)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
isBundleLocked() const48 bool MCELFStreamer::isBundleLocked() const {
49 return getCurrentSectionOnly()->isBundleLocked();
50 }
51
mergeFragment(MCDataFragment * DF,MCDataFragment * EF)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
InitSections(bool NoExecStack)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
emitLabel(MCSymbol * S,SMLoc Loc)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
emitLabelAtPos(MCSymbol * S,SMLoc Loc,MCFragment * F,uint64_t Offset)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
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(Align(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_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
emitCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment,TailPaddingAmount TailPadding)290 void MCELFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
291 unsigned ByteAlignment,
292 TailPaddingAmount TailPadding) {
293 auto *Symbol = cast<MCSymbolELF>(S);
294 getAssembler().registerSymbol(*Symbol);
295
296 if (!Symbol->isBindingSet()) {
297 Symbol->setBinding(ELF::STB_GLOBAL);
298 Symbol->setExternal(true);
299 }
300
301 Symbol->setType(ELF::STT_OBJECT);
302
303 if (Symbol->getBinding() == ELF::STB_LOCAL) {
304 MCSection &Section = *getAssembler().getContext().getELFSection(
305 ".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
306 MCSectionSubPair P = getCurrentSection();
307 SwitchSection(&Section);
308
309 emitValueToAlignment(ByteAlignment, 0, 1, 0);
310 emitLabel(Symbol);
311 emitZeros(Size + static_cast<uint64_t>(TailPadding));
312
313 SwitchSection(P.first, P.second);
314 } else {
315 if (Symbol->declareCommon(Size + static_cast<uint64_t>(TailPadding),
316 ByteAlignment))
317 report_fatal_error("Symbol: " + Symbol->getName() +
318 " redeclared as different type");
319 }
320
321 cast<MCSymbolELF>(Symbol)
322 ->setSize(MCConstantExpr::create(Size, getContext()));
323 }
324
emitELFSize(MCSymbol * Symbol,const MCExpr * Value)325 void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
326 cast<MCSymbolELF>(Symbol)->setSize(Value);
327 }
328
emitELFSymverDirective(StringRef AliasName,const MCSymbol * Aliasee)329 void MCELFStreamer::emitELFSymverDirective(StringRef AliasName,
330 const MCSymbol *Aliasee) {
331 getAssembler().Symvers.push_back({AliasName, Aliasee});
332 }
333
emitLocalCommonSymbol(MCSymbol * S,uint64_t Size,unsigned ByteAlignment,TailPaddingAmount TailPadding)334 void MCELFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
335 unsigned ByteAlignment,
336 TailPaddingAmount TailPadding) {
337 auto *Symbol = cast<MCSymbolELF>(S);
338 // FIXME: Should this be caught and done earlier?
339 getAssembler().registerSymbol(*Symbol);
340 Symbol->setBinding(ELF::STB_LOCAL);
341 Symbol->setExternal(false);
342 emitCommonSymbol(Symbol, Size, ByteAlignment, TailPadding);
343 }
344
emitValueImpl(const MCExpr * Value,unsigned Size,SMLoc Loc)345 void MCELFStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,
346 SMLoc Loc) {
347 if (isBundleLocked())
348 report_fatal_error("Emitting values inside a locked bundle is forbidden");
349 fixSymbolsInTLSFixups(Value);
350 MCObjectStreamer::emitValueImpl(Value, Size, Loc);
351 }
352
emitValueToAlignment(unsigned ByteAlignment,int64_t Value,unsigned ValueSize,unsigned MaxBytesToEmit)353 void MCELFStreamer::emitValueToAlignment(unsigned ByteAlignment,
354 int64_t Value,
355 unsigned ValueSize,
356 unsigned MaxBytesToEmit) {
357 if (isBundleLocked())
358 report_fatal_error("Emitting values inside a locked bundle is forbidden");
359 MCObjectStreamer::emitValueToAlignment(ByteAlignment, Value,
360 ValueSize, MaxBytesToEmit);
361 }
362
emitCGProfileEntry(const MCSymbolRefExpr * From,const MCSymbolRefExpr * To,uint64_t Count)363 void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
364 const MCSymbolRefExpr *To,
365 uint64_t Count) {
366 getAssembler().CGProfile.push_back({From, To, Count});
367 }
368
emitIdent(StringRef IdentString)369 void MCELFStreamer::emitIdent(StringRef IdentString) {
370 MCSection *Comment = getAssembler().getContext().getELFSection(
371 ".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
372 PushSection();
373 SwitchSection(Comment);
374 if (!SeenIdent) {
375 emitInt8(0);
376 SeenIdent = true;
377 }
378 emitBytes(IdentString);
379 emitInt8(0);
380 PopSection();
381 }
382
fixSymbolsInTLSFixups(const MCExpr * expr)383 void MCELFStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
384 switch (expr->getKind()) {
385 case MCExpr::Target:
386 cast<MCTargetExpr>(expr)->fixELFSymbolsInTLSFixups(getAssembler());
387 break;
388 case MCExpr::Constant:
389 break;
390
391 case MCExpr::Binary: {
392 const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
393 fixSymbolsInTLSFixups(be->getLHS());
394 fixSymbolsInTLSFixups(be->getRHS());
395 break;
396 }
397
398 case MCExpr::SymbolRef: {
399 const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
400 switch (symRef.getKind()) {
401 default:
402 return;
403 case MCSymbolRefExpr::VK_GOTTPOFF:
404 case MCSymbolRefExpr::VK_INDNTPOFF:
405 case MCSymbolRefExpr::VK_NTPOFF:
406 case MCSymbolRefExpr::VK_GOTNTPOFF:
407 case MCSymbolRefExpr::VK_TLSCALL:
408 case MCSymbolRefExpr::VK_TLSDESC:
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_HIGH:
421 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHA:
422 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHER:
423 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHERA:
424 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHEST:
425 case MCSymbolRefExpr::VK_PPC_TPREL_HIGHESTA:
426 case MCSymbolRefExpr::VK_PPC_DTPREL_LO:
427 case MCSymbolRefExpr::VK_PPC_DTPREL_HI:
428 case MCSymbolRefExpr::VK_PPC_DTPREL_HA:
429 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGH:
430 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHA:
431 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHER:
432 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHERA:
433 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHEST:
434 case MCSymbolRefExpr::VK_PPC_DTPREL_HIGHESTA:
435 case MCSymbolRefExpr::VK_PPC_GOT_TPREL:
436 case MCSymbolRefExpr::VK_PPC_GOT_TPREL_LO:
437 case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HI:
438 case MCSymbolRefExpr::VK_PPC_GOT_TPREL_HA:
439 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL:
440 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_LO:
441 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HI:
442 case MCSymbolRefExpr::VK_PPC_GOT_DTPREL_HA:
443 case MCSymbolRefExpr::VK_PPC_TLS:
444 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD:
445 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_LO:
446 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HI:
447 case MCSymbolRefExpr::VK_PPC_GOT_TLSGD_HA:
448 case MCSymbolRefExpr::VK_PPC_TLSGD:
449 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD:
450 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_LO:
451 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HI:
452 case MCSymbolRefExpr::VK_PPC_GOT_TLSLD_HA:
453 case MCSymbolRefExpr::VK_PPC_TLSLD:
454 break;
455 }
456 getAssembler().registerSymbol(symRef.getSymbol());
457 cast<MCSymbolELF>(symRef.getSymbol()).setType(ELF::STT_TLS);
458 break;
459 }
460
461 case MCExpr::Unary:
462 fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
463 break;
464 }
465 }
466
finalizeCGProfileEntry(const MCSymbolRefExpr * & SRE)467 void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE) {
468 const MCSymbol *S = &SRE->getSymbol();
469 if (S->isTemporary()) {
470 if (!S->isInSection()) {
471 getContext().reportError(
472 SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
473 "`" + S->getName() + "`");
474 return;
475 }
476 S = S->getSection().getBeginSymbol();
477 S->setUsedInReloc();
478 SRE =
479 MCSymbolRefExpr::create(S, SRE->getKind(), getContext(), SRE->getLoc());
480 return;
481 }
482 // Not a temporary, referece it as a weak undefined.
483 bool Created;
484 getAssembler().registerSymbol(*S, &Created);
485 if (Created) {
486 cast<MCSymbolELF>(S)->setBinding(ELF::STB_WEAK);
487 cast<MCSymbolELF>(S)->setExternal(true);
488 }
489 }
490
finalizeCGProfile()491 void MCELFStreamer::finalizeCGProfile() {
492 for (MCAssembler::CGProfileEntry &E : getAssembler().CGProfile) {
493 finalizeCGProfileEntry(E.From);
494 finalizeCGProfileEntry(E.To);
495 }
496 }
497
emitInstToFragment(const MCInst & Inst,const MCSubtargetInfo & STI)498 void MCELFStreamer::emitInstToFragment(const MCInst &Inst,
499 const MCSubtargetInfo &STI) {
500 this->MCObjectStreamer::emitInstToFragment(Inst, STI);
501 MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
502
503 for (unsigned i = 0, e = F.getFixups().size(); i != e; ++i)
504 fixSymbolsInTLSFixups(F.getFixups()[i].getValue());
505 }
506
507 // A fragment can only have one Subtarget, and when bundling is enabled we
508 // sometimes need to use the same fragment. We give an error if there
509 // are conflicting Subtargets.
CheckBundleSubtargets(const MCSubtargetInfo * OldSTI,const MCSubtargetInfo * NewSTI)510 static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
511 const MCSubtargetInfo *NewSTI) {
512 if (OldSTI && NewSTI && OldSTI != NewSTI)
513 report_fatal_error("A Bundle can only have one Subtarget.");
514 }
515
emitInstToData(const MCInst & Inst,const MCSubtargetInfo & STI)516 void MCELFStreamer::emitInstToData(const MCInst &Inst,
517 const MCSubtargetInfo &STI) {
518 MCAssembler &Assembler = getAssembler();
519 SmallVector<MCFixup, 4> Fixups;
520 SmallString<256> Code;
521 raw_svector_ostream VecOS(Code);
522 Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
523
524 for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
525 fixSymbolsInTLSFixups(Fixups[i].getValue());
526
527 // There are several possibilities here:
528 //
529 // If bundling is disabled, append the encoded instruction to the current data
530 // fragment (or create a new such fragment if the current fragment is not a
531 // data fragment, or the Subtarget has changed).
532 //
533 // If bundling is enabled:
534 // - If we're not in a bundle-locked group, emit the instruction into a
535 // fragment of its own. If there are no fixups registered for the
536 // instruction, emit a MCCompactEncodedInstFragment. Otherwise, emit a
537 // MCDataFragment.
538 // - If we're in a bundle-locked group, append the instruction to the current
539 // data fragment because we want all the instructions in a group to get into
540 // the same fragment. Be careful not to do that for the first instruction in
541 // the group, though.
542 MCDataFragment *DF;
543
544 if (Assembler.isBundlingEnabled()) {
545 MCSection &Sec = *getCurrentSectionOnly();
546 if (Assembler.getRelaxAll() && isBundleLocked()) {
547 // If the -mc-relax-all flag is used and we are bundle-locked, we re-use
548 // the current bundle group.
549 DF = BundleGroups.back();
550 CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
551 }
552 else if (Assembler.getRelaxAll() && !isBundleLocked())
553 // When not in a bundle-locked group and the -mc-relax-all flag is used,
554 // we create a new temporary fragment which will be later merged into
555 // the current fragment.
556 DF = new MCDataFragment();
557 else if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
558 // If we are bundle-locked, we re-use the current fragment.
559 // The bundle-locking directive ensures this is a new data fragment.
560 DF = cast<MCDataFragment>(getCurrentFragment());
561 CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
562 }
563 else if (!isBundleLocked() && Fixups.size() == 0) {
564 // Optimize memory usage by emitting the instruction to a
565 // MCCompactEncodedInstFragment when not in a bundle-locked group and
566 // there are no fixups registered.
567 MCCompactEncodedInstFragment *CEIF = new MCCompactEncodedInstFragment();
568 insert(CEIF);
569 CEIF->getContents().append(Code.begin(), Code.end());
570 CEIF->setHasInstructions(STI);
571 return;
572 } else {
573 DF = new MCDataFragment();
574 insert(DF);
575 }
576 if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
577 // If this fragment is for a group marked "align_to_end", set a flag
578 // in the fragment. This can happen after the fragment has already been
579 // created if there are nested bundle_align groups and an inner one
580 // is the one marked align_to_end.
581 DF->setAlignToBundleEnd(true);
582 }
583
584 // We're now emitting an instruction in a bundle group, so this flag has
585 // to be turned off.
586 Sec.setBundleGroupBeforeFirstInst(false);
587 } else {
588 DF = getOrCreateDataFragment(&STI);
589 }
590
591 // Add the fixups and data.
592 for (unsigned i = 0, e = Fixups.size(); i != e; ++i) {
593 Fixups[i].setOffset(Fixups[i].getOffset() + DF->getContents().size());
594 DF->getFixups().push_back(Fixups[i]);
595 }
596 DF->setHasInstructions(STI);
597 DF->getContents().append(Code.begin(), Code.end());
598
599 if (Assembler.isBundlingEnabled() && Assembler.getRelaxAll()) {
600 if (!isBundleLocked()) {
601 mergeFragment(getOrCreateDataFragment(&STI), DF);
602 delete DF;
603 }
604 }
605 }
606
emitBundleAlignMode(unsigned AlignPow2)607 void MCELFStreamer::emitBundleAlignMode(unsigned AlignPow2) {
608 assert(AlignPow2 <= 30 && "Invalid bundle alignment");
609 MCAssembler &Assembler = getAssembler();
610 if (AlignPow2 > 0 && (Assembler.getBundleAlignSize() == 0 ||
611 Assembler.getBundleAlignSize() == 1U << AlignPow2))
612 Assembler.setBundleAlignSize(1U << AlignPow2);
613 else
614 report_fatal_error(".bundle_align_mode cannot be changed once set");
615 }
616
emitBundleLock(bool AlignToEnd)617 void MCELFStreamer::emitBundleLock(bool AlignToEnd) {
618 MCSection &Sec = *getCurrentSectionOnly();
619
620 // Sanity checks
621 //
622 if (!getAssembler().isBundlingEnabled())
623 report_fatal_error(".bundle_lock forbidden when bundling is disabled");
624
625 if (!isBundleLocked())
626 Sec.setBundleGroupBeforeFirstInst(true);
627
628 if (getAssembler().getRelaxAll() && !isBundleLocked()) {
629 // TODO: drop the lock state and set directly in the fragment
630 MCDataFragment *DF = new MCDataFragment();
631 BundleGroups.push_back(DF);
632 }
633
634 Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
635 : MCSection::BundleLocked);
636 }
637
emitBundleUnlock()638 void MCELFStreamer::emitBundleUnlock() {
639 MCSection &Sec = *getCurrentSectionOnly();
640
641 // Sanity checks
642 if (!getAssembler().isBundlingEnabled())
643 report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
644 else if (!isBundleLocked())
645 report_fatal_error(".bundle_unlock without matching lock");
646 else if (Sec.isBundleGroupBeforeFirstInst())
647 report_fatal_error("Empty bundle-locked group is forbidden");
648
649 // When the -mc-relax-all flag is used, we emit instructions to fragments
650 // stored on a stack. When the bundle unlock is emitted, we pop a fragment
651 // from the stack a merge it to the one below.
652 if (getAssembler().getRelaxAll()) {
653 assert(!BundleGroups.empty() && "There are no bundle groups");
654 MCDataFragment *DF = BundleGroups.back();
655
656 // FIXME: Use BundleGroups to track the lock state instead.
657 Sec.setBundleLockState(MCSection::NotBundleLocked);
658
659 // FIXME: Use more separate fragments for nested groups.
660 if (!isBundleLocked()) {
661 mergeFragment(getOrCreateDataFragment(DF->getSubtargetInfo()), DF);
662 BundleGroups.pop_back();
663 delete DF;
664 }
665
666 if (Sec.getBundleLockState() != MCSection::BundleLockedAlignToEnd)
667 getOrCreateDataFragment()->setAlignToBundleEnd(false);
668 } else
669 Sec.setBundleLockState(MCSection::NotBundleLocked);
670 }
671
finishImpl()672 void MCELFStreamer::finishImpl() {
673 // Ensure the last section gets aligned if necessary.
674 MCSection *CurSection = getCurrentSectionOnly();
675 setSectionAlignmentForBundling(getAssembler(), CurSection);
676
677 finalizeCGProfile();
678 emitFrames(nullptr);
679
680 this->MCObjectStreamer::finishImpl();
681 }
682
emitThumbFunc(MCSymbol * Func)683 void MCELFStreamer::emitThumbFunc(MCSymbol *Func) {
684 llvm_unreachable("Generic ELF doesn't support this directive");
685 }
686
emitSymbolDesc(MCSymbol * Symbol,unsigned DescValue)687 void MCELFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
688 llvm_unreachable("ELF doesn't support this directive");
689 }
690
emitZerofill(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment,TailPaddingAmount TailPadding,SMLoc Loc)691 void MCELFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
692 uint64_t Size, unsigned ByteAlignment,
693 TailPaddingAmount TailPadding, SMLoc Loc) {
694 llvm_unreachable("ELF doesn't support this directive");
695 }
696
emitTBSSSymbol(MCSection * Section,MCSymbol * Symbol,uint64_t Size,unsigned ByteAlignment,TailPaddingAmount TailPadding)697 void MCELFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
698 uint64_t Size, unsigned ByteAlignment,
699 TailPaddingAmount TailPadding) {
700 llvm_unreachable("ELF doesn't support this directive");
701 }
702
createELFStreamer(MCContext & Context,std::unique_ptr<MCAsmBackend> && MAB,std::unique_ptr<MCObjectWriter> && OW,std::unique_ptr<MCCodeEmitter> && CE,bool RelaxAll)703 MCStreamer *llvm::createELFStreamer(MCContext &Context,
704 std::unique_ptr<MCAsmBackend> &&MAB,
705 std::unique_ptr<MCObjectWriter> &&OW,
706 std::unique_ptr<MCCodeEmitter> &&CE,
707 bool RelaxAll) {
708 MCELFStreamer *S =
709 new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
710 if (RelaxAll)
711 S->getAssembler().setRelaxAll(true);
712 return S;
713 }
714