1 //===- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info ---===//
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 implements classes used to handle lowerings specific to common
10 // object file formats.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
15 #include "llvm/ADT/SmallString.h"
16 #include "llvm/ADT/SmallVector.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Triple.h"
20 #include "llvm/BinaryFormat/COFF.h"
21 #include "llvm/BinaryFormat/Dwarf.h"
22 #include "llvm/BinaryFormat/ELF.h"
23 #include "llvm/BinaryFormat/MachO.h"
24 #include "llvm/CodeGen/MachineModuleInfo.h"
25 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
26 #include "llvm/IR/Comdat.h"
27 #include "llvm/IR/Constants.h"
28 #include "llvm/IR/DataLayout.h"
29 #include "llvm/IR/DerivedTypes.h"
30 #include "llvm/IR/Function.h"
31 #include "llvm/IR/GlobalAlias.h"
32 #include "llvm/IR/GlobalObject.h"
33 #include "llvm/IR/GlobalValue.h"
34 #include "llvm/IR/GlobalVariable.h"
35 #include "llvm/IR/Mangler.h"
36 #include "llvm/IR/Metadata.h"
37 #include "llvm/IR/Module.h"
38 #include "llvm/IR/Type.h"
39 #include "llvm/MC/MCAsmInfo.h"
40 #include "llvm/MC/MCContext.h"
41 #include "llvm/MC/MCExpr.h"
42 #include "llvm/MC/MCSectionCOFF.h"
43 #include "llvm/MC/MCSectionELF.h"
44 #include "llvm/MC/MCSectionMachO.h"
45 #include "llvm/MC/MCSectionWasm.h"
46 #include "llvm/MC/MCSectionXCOFF.h"
47 #include "llvm/MC/MCStreamer.h"
48 #include "llvm/MC/MCSymbol.h"
49 #include "llvm/MC/MCSymbolELF.h"
50 #include "llvm/MC/MCValue.h"
51 #include "llvm/MC/SectionKind.h"
52 #include "llvm/ProfileData/InstrProf.h"
53 #include "llvm/Support/Casting.h"
54 #include "llvm/Support/CodeGen.h"
55 #include "llvm/Support/Format.h"
56 #include "llvm/Support/ErrorHandling.h"
57 #include "llvm/Support/raw_ostream.h"
58 #include "llvm/Target/TargetMachine.h"
59 #include <cassert>
60 #include <string>
61
62 using namespace llvm;
63 using namespace dwarf;
64
GetObjCImageInfo(Module & M,unsigned & Version,unsigned & Flags,StringRef & Section)65 static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
66 StringRef &Section) {
67 SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
68 M.getModuleFlagsMetadata(ModuleFlags);
69
70 for (const auto &MFE: ModuleFlags) {
71 // Ignore flags with 'Require' behaviour.
72 if (MFE.Behavior == Module::Require)
73 continue;
74
75 StringRef Key = MFE.Key->getString();
76 if (Key == "Objective-C Image Info Version") {
77 Version = mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
78 } else if (Key == "Objective-C Garbage Collection" ||
79 Key == "Objective-C GC Only" ||
80 Key == "Objective-C Is Simulated" ||
81 Key == "Objective-C Class Properties" ||
82 Key == "Objective-C Image Swift Version") {
83 Flags |= mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
84 } else if (Key == "Objective-C Image Info Section") {
85 Section = cast<MDString>(MFE.Val)->getString();
86 }
87 }
88 }
89
90 //===----------------------------------------------------------------------===//
91 // ELF
92 //===----------------------------------------------------------------------===//
93
Initialize(MCContext & Ctx,const TargetMachine & TgtM)94 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
95 const TargetMachine &TgtM) {
96 TargetLoweringObjectFile::Initialize(Ctx, TgtM);
97 TM = &TgtM;
98
99 CodeModel::Model CM = TgtM.getCodeModel();
100
101 switch (TgtM.getTargetTriple().getArch()) {
102 case Triple::arm:
103 case Triple::armeb:
104 case Triple::thumb:
105 case Triple::thumbeb:
106 if (Ctx.getAsmInfo()->getExceptionHandlingType() == ExceptionHandling::ARM)
107 break;
108 // Fallthrough if not using EHABI
109 LLVM_FALLTHROUGH;
110 case Triple::ppc:
111 case Triple::x86:
112 PersonalityEncoding = isPositionIndependent()
113 ? dwarf::DW_EH_PE_indirect |
114 dwarf::DW_EH_PE_pcrel |
115 dwarf::DW_EH_PE_sdata4
116 : dwarf::DW_EH_PE_absptr;
117 LSDAEncoding = isPositionIndependent()
118 ? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
119 : dwarf::DW_EH_PE_absptr;
120 TTypeEncoding = isPositionIndependent()
121 ? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
122 dwarf::DW_EH_PE_sdata4
123 : dwarf::DW_EH_PE_absptr;
124 break;
125 case Triple::x86_64:
126 if (isPositionIndependent()) {
127 PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
128 ((CM == CodeModel::Small || CM == CodeModel::Medium)
129 ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
130 LSDAEncoding = dwarf::DW_EH_PE_pcrel |
131 (CM == CodeModel::Small
132 ? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
133 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
134 ((CM == CodeModel::Small || CM == CodeModel::Medium)
135 ? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
136 } else {
137 PersonalityEncoding =
138 (CM == CodeModel::Small || CM == CodeModel::Medium)
139 ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
140 LSDAEncoding = (CM == CodeModel::Small)
141 ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
142 TTypeEncoding = (CM == CodeModel::Small)
143 ? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
144 }
145 break;
146 case Triple::hexagon:
147 PersonalityEncoding = dwarf::DW_EH_PE_absptr;
148 LSDAEncoding = dwarf::DW_EH_PE_absptr;
149 TTypeEncoding = dwarf::DW_EH_PE_absptr;
150 if (isPositionIndependent()) {
151 PersonalityEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
152 LSDAEncoding |= dwarf::DW_EH_PE_pcrel;
153 TTypeEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
154 }
155 break;
156 case Triple::aarch64:
157 case Triple::aarch64_be:
158 case Triple::aarch64_32:
159 // The small model guarantees static code/data size < 4GB, but not where it
160 // will be in memory. Most of these could end up >2GB away so even a signed
161 // pc-relative 32-bit address is insufficient, theoretically.
162 if (isPositionIndependent()) {
163 PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
164 dwarf::DW_EH_PE_sdata8;
165 LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8;
166 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
167 dwarf::DW_EH_PE_sdata8;
168 } else {
169 PersonalityEncoding = dwarf::DW_EH_PE_absptr;
170 LSDAEncoding = dwarf::DW_EH_PE_absptr;
171 TTypeEncoding = dwarf::DW_EH_PE_absptr;
172 }
173 break;
174 case Triple::lanai:
175 LSDAEncoding = dwarf::DW_EH_PE_absptr;
176 PersonalityEncoding = dwarf::DW_EH_PE_absptr;
177 TTypeEncoding = dwarf::DW_EH_PE_absptr;
178 break;
179 case Triple::mips:
180 case Triple::mipsel:
181 case Triple::mips64:
182 case Triple::mips64el:
183 // MIPS uses indirect pointer to refer personality functions and types, so
184 // that the eh_frame section can be read-only. DW.ref.personality will be
185 // generated for relocation.
186 PersonalityEncoding = dwarf::DW_EH_PE_indirect;
187 // FIXME: The N64 ABI probably ought to use DW_EH_PE_sdata8 but we can't
188 // identify N64 from just a triple.
189 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
190 dwarf::DW_EH_PE_sdata4;
191 // We don't support PC-relative LSDA references in GAS so we use the default
192 // DW_EH_PE_absptr for those.
193
194 // FreeBSD must be explicit about the data size and using pcrel since it's
195 // assembler/linker won't do the automatic conversion that the Linux tools
196 // do.
197 if (TgtM.getTargetTriple().isOSFreeBSD()) {
198 PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
199 LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
200 }
201 break;
202 case Triple::ppc64:
203 case Triple::ppc64le:
204 PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
205 dwarf::DW_EH_PE_udata8;
206 LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8;
207 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
208 dwarf::DW_EH_PE_udata8;
209 break;
210 case Triple::sparcel:
211 case Triple::sparc:
212 if (isPositionIndependent()) {
213 LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
214 PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
215 dwarf::DW_EH_PE_sdata4;
216 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
217 dwarf::DW_EH_PE_sdata4;
218 } else {
219 LSDAEncoding = dwarf::DW_EH_PE_absptr;
220 PersonalityEncoding = dwarf::DW_EH_PE_absptr;
221 TTypeEncoding = dwarf::DW_EH_PE_absptr;
222 }
223 CallSiteEncoding = dwarf::DW_EH_PE_udata4;
224 break;
225 case Triple::riscv32:
226 case Triple::riscv64:
227 LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
228 PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
229 dwarf::DW_EH_PE_sdata4;
230 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
231 dwarf::DW_EH_PE_sdata4;
232 CallSiteEncoding = dwarf::DW_EH_PE_udata4;
233 break;
234 case Triple::sparcv9:
235 LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
236 if (isPositionIndependent()) {
237 PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
238 dwarf::DW_EH_PE_sdata4;
239 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
240 dwarf::DW_EH_PE_sdata4;
241 } else {
242 PersonalityEncoding = dwarf::DW_EH_PE_absptr;
243 TTypeEncoding = dwarf::DW_EH_PE_absptr;
244 }
245 break;
246 case Triple::systemz:
247 // All currently-defined code models guarantee that 4-byte PC-relative
248 // values will be in range.
249 if (isPositionIndependent()) {
250 PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
251 dwarf::DW_EH_PE_sdata4;
252 LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
253 TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
254 dwarf::DW_EH_PE_sdata4;
255 } else {
256 PersonalityEncoding = dwarf::DW_EH_PE_absptr;
257 LSDAEncoding = dwarf::DW_EH_PE_absptr;
258 TTypeEncoding = dwarf::DW_EH_PE_absptr;
259 }
260 break;
261 default:
262 break;
263 }
264 }
265
emitModuleMetadata(MCStreamer & Streamer,Module & M) const266 void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
267 Module &M) const {
268 auto &C = getContext();
269
270 if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
271 auto *S = C.getELFSection(".linker-options", ELF::SHT_LLVM_LINKER_OPTIONS,
272 ELF::SHF_EXCLUDE);
273
274 Streamer.SwitchSection(S);
275
276 for (const auto *Operand : LinkerOptions->operands()) {
277 if (cast<MDNode>(Operand)->getNumOperands() != 2)
278 report_fatal_error("invalid llvm.linker.options");
279 for (const auto &Option : cast<MDNode>(Operand)->operands()) {
280 Streamer.EmitBytes(cast<MDString>(Option)->getString());
281 Streamer.EmitIntValue(0, 1);
282 }
283 }
284 }
285
286 if (NamedMDNode *DependentLibraries = M.getNamedMetadata("llvm.dependent-libraries")) {
287 auto *S = C.getELFSection(".deplibs", ELF::SHT_LLVM_DEPENDENT_LIBRARIES,
288 ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
289
290 Streamer.SwitchSection(S);
291
292 for (const auto *Operand : DependentLibraries->operands()) {
293 Streamer.EmitBytes(
294 cast<MDString>(cast<MDNode>(Operand)->getOperand(0))->getString());
295 Streamer.EmitIntValue(0, 1);
296 }
297 }
298
299 unsigned Version = 0;
300 unsigned Flags = 0;
301 StringRef Section;
302
303 GetObjCImageInfo(M, Version, Flags, Section);
304 if (!Section.empty()) {
305 auto *S = C.getELFSection(Section, ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
306 Streamer.SwitchSection(S);
307 Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
308 Streamer.EmitIntValue(Version, 4);
309 Streamer.EmitIntValue(Flags, 4);
310 Streamer.AddBlankLine();
311 }
312
313 SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
314 M.getModuleFlagsMetadata(ModuleFlags);
315
316 MDNode *CFGProfile = nullptr;
317
318 for (const auto &MFE : ModuleFlags) {
319 StringRef Key = MFE.Key->getString();
320 if (Key == "CG Profile") {
321 CFGProfile = cast<MDNode>(MFE.Val);
322 break;
323 }
324 }
325
326 if (!CFGProfile)
327 return;
328
329 auto GetSym = [this](const MDOperand &MDO) -> MCSymbol * {
330 if (!MDO)
331 return nullptr;
332 auto V = cast<ValueAsMetadata>(MDO);
333 const Function *F = cast<Function>(V->getValue());
334 return TM->getSymbol(F);
335 };
336
337 for (const auto &Edge : CFGProfile->operands()) {
338 MDNode *E = cast<MDNode>(Edge);
339 const MCSymbol *From = GetSym(E->getOperand(0));
340 const MCSymbol *To = GetSym(E->getOperand(1));
341 // Skip null functions. This can happen if functions are dead stripped after
342 // the CGProfile pass has been run.
343 if (!From || !To)
344 continue;
345 uint64_t Count = cast<ConstantAsMetadata>(E->getOperand(2))
346 ->getValue()
347 ->getUniqueInteger()
348 .getZExtValue();
349 Streamer.emitCGProfileEntry(
350 MCSymbolRefExpr::create(From, MCSymbolRefExpr::VK_None, C),
351 MCSymbolRefExpr::create(To, MCSymbolRefExpr::VK_None, C), Count);
352 }
353 }
354
getCFIPersonalitySymbol(const GlobalValue * GV,const TargetMachine & TM,MachineModuleInfo * MMI) const355 MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
356 const GlobalValue *GV, const TargetMachine &TM,
357 MachineModuleInfo *MMI) const {
358 unsigned Encoding = getPersonalityEncoding();
359 if ((Encoding & 0x80) == DW_EH_PE_indirect)
360 return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
361 TM.getSymbol(GV)->getName());
362 if ((Encoding & 0x70) == DW_EH_PE_absptr)
363 return TM.getSymbol(GV);
364 report_fatal_error("We do not support this DWARF encoding yet!");
365 }
366
emitPersonalityValue(MCStreamer & Streamer,const DataLayout & DL,const MCSymbol * Sym) const367 void TargetLoweringObjectFileELF::emitPersonalityValue(
368 MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
369 SmallString<64> NameData("DW.ref.");
370 NameData += Sym->getName();
371 MCSymbolELF *Label =
372 cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
373 Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
374 Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
375 unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
376 MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
377 ELF::SHT_PROGBITS, Flags, 0);
378 unsigned Size = DL.getPointerSize();
379 Streamer.SwitchSection(Sec);
380 Streamer.EmitValueToAlignment(DL.getPointerABIAlignment(0).value());
381 Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
382 const MCExpr *E = MCConstantExpr::create(Size, getContext());
383 Streamer.emitELFSize(Label, E);
384 Streamer.EmitLabel(Label);
385
386 Streamer.EmitSymbolValue(Sym, Size);
387 }
388
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const389 const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
390 const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
391 MachineModuleInfo *MMI, MCStreamer &Streamer) const {
392 if (Encoding & DW_EH_PE_indirect) {
393 MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
394
395 MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
396
397 // Add information about the stub reference to ELFMMI so that the stub
398 // gets emitted by the asmprinter.
399 MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
400 if (!StubSym.getPointer()) {
401 MCSymbol *Sym = TM.getSymbol(GV);
402 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
403 }
404
405 return TargetLoweringObjectFile::
406 getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
407 Encoding & ~DW_EH_PE_indirect, Streamer);
408 }
409
410 return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
411 MMI, Streamer);
412 }
413
getELFKindForNamedSection(StringRef Name,SectionKind K)414 static SectionKind getELFKindForNamedSection(StringRef Name, SectionKind K) {
415 // N.B.: The defaults used in here are not the same ones used in MC.
416 // We follow gcc, MC follows gas. For example, given ".section .eh_frame",
417 // both gas and MC will produce a section with no flags. Given
418 // section(".eh_frame") gcc will produce:
419 //
420 // .section .eh_frame,"a",@progbits
421
422 if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
423 /*AddSegmentInfo=*/false))
424 return SectionKind::getMetadata();
425
426 if (Name.empty() || Name[0] != '.') return K;
427
428 // Default implementation based on some magic section names.
429 if (Name == ".bss" ||
430 Name.startswith(".bss.") ||
431 Name.startswith(".gnu.linkonce.b.") ||
432 Name.startswith(".llvm.linkonce.b.") ||
433 Name == ".sbss" ||
434 Name.startswith(".sbss.") ||
435 Name.startswith(".gnu.linkonce.sb.") ||
436 Name.startswith(".llvm.linkonce.sb."))
437 return SectionKind::getBSS();
438
439 if (Name == ".tdata" ||
440 Name.startswith(".tdata.") ||
441 Name.startswith(".gnu.linkonce.td.") ||
442 Name.startswith(".llvm.linkonce.td."))
443 return SectionKind::getThreadData();
444
445 if (Name == ".tbss" ||
446 Name.startswith(".tbss.") ||
447 Name.startswith(".gnu.linkonce.tb.") ||
448 Name.startswith(".llvm.linkonce.tb."))
449 return SectionKind::getThreadBSS();
450
451 return K;
452 }
453
getELFSectionType(StringRef Name,SectionKind K)454 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
455 // Use SHT_NOTE for section whose name starts with ".note" to allow
456 // emitting ELF notes from C variable declaration.
457 // See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
458 if (Name.startswith(".note"))
459 return ELF::SHT_NOTE;
460
461 if (Name == ".init_array")
462 return ELF::SHT_INIT_ARRAY;
463
464 if (Name == ".fini_array")
465 return ELF::SHT_FINI_ARRAY;
466
467 if (Name == ".preinit_array")
468 return ELF::SHT_PREINIT_ARRAY;
469
470 if (K.isBSS() || K.isThreadBSS())
471 return ELF::SHT_NOBITS;
472
473 return ELF::SHT_PROGBITS;
474 }
475
getELFSectionFlags(SectionKind K)476 static unsigned getELFSectionFlags(SectionKind K) {
477 unsigned Flags = 0;
478
479 if (!K.isMetadata())
480 Flags |= ELF::SHF_ALLOC;
481
482 if (K.isText())
483 Flags |= ELF::SHF_EXECINSTR;
484
485 if (K.isExecuteOnly())
486 Flags |= ELF::SHF_ARM_PURECODE;
487
488 if (K.isWriteable())
489 Flags |= ELF::SHF_WRITE;
490
491 if (K.isThreadLocal())
492 Flags |= ELF::SHF_TLS;
493
494 if (K.isMergeableCString() || K.isMergeableConst())
495 Flags |= ELF::SHF_MERGE;
496
497 if (K.isMergeableCString())
498 Flags |= ELF::SHF_STRINGS;
499
500 return Flags;
501 }
502
getELFComdat(const GlobalValue * GV)503 static const Comdat *getELFComdat(const GlobalValue *GV) {
504 const Comdat *C = GV->getComdat();
505 if (!C)
506 return nullptr;
507
508 if (C->getSelectionKind() != Comdat::Any)
509 report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
510 C->getName() + "' cannot be lowered.");
511
512 return C;
513 }
514
getAssociatedSymbol(const GlobalObject * GO,const TargetMachine & TM)515 static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
516 const TargetMachine &TM) {
517 MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
518 if (!MD)
519 return nullptr;
520
521 const MDOperand &Op = MD->getOperand(0);
522 if (!Op.get())
523 return nullptr;
524
525 auto *VM = dyn_cast<ValueAsMetadata>(Op);
526 if (!VM)
527 report_fatal_error("MD_associated operand is not ValueAsMetadata");
528
529 auto *OtherGV = dyn_cast<GlobalValue>(VM->getValue());
530 return OtherGV ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGV)) : nullptr;
531 }
532
getEntrySizeForKind(SectionKind Kind)533 static unsigned getEntrySizeForKind(SectionKind Kind) {
534 if (Kind.isMergeable1ByteCString())
535 return 1;
536 else if (Kind.isMergeable2ByteCString())
537 return 2;
538 else if (Kind.isMergeable4ByteCString())
539 return 4;
540 else if (Kind.isMergeableConst4())
541 return 4;
542 else if (Kind.isMergeableConst8())
543 return 8;
544 else if (Kind.isMergeableConst16())
545 return 16;
546 else if (Kind.isMergeableConst32())
547 return 32;
548 else {
549 // We shouldn't have mergeable C strings or mergeable constants that we
550 // didn't handle above.
551 assert(!Kind.isMergeableCString() && "unknown string width");
552 assert(!Kind.isMergeableConst() && "unknown data width");
553 return 0;
554 }
555 }
556
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const557 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
558 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
559 StringRef SectionName = GO->getSection();
560
561 // Check if '#pragma clang section' name is applicable.
562 // Note that pragma directive overrides -ffunction-section, -fdata-section
563 // and so section name is exactly as user specified and not uniqued.
564 const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
565 if (GV && GV->hasImplicitSection()) {
566 auto Attrs = GV->getAttributes();
567 if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
568 SectionName = Attrs.getAttribute("bss-section").getValueAsString();
569 } else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
570 SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
571 } else if (Attrs.hasAttribute("relro-section") && Kind.isReadOnlyWithRel()) {
572 SectionName = Attrs.getAttribute("relro-section").getValueAsString();
573 } else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
574 SectionName = Attrs.getAttribute("data-section").getValueAsString();
575 }
576 }
577 const Function *F = dyn_cast<Function>(GO);
578 if (F && F->hasFnAttribute("implicit-section-name")) {
579 SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
580 }
581
582 // Infer section flags from the section name if we can.
583 Kind = getELFKindForNamedSection(SectionName, Kind);
584
585 StringRef Group = "";
586 unsigned Flags = getELFSectionFlags(Kind);
587 if (const Comdat *C = getELFComdat(GO)) {
588 Group = C->getName();
589 Flags |= ELF::SHF_GROUP;
590 }
591
592 // A section can have at most one associated section. Put each global with
593 // MD_associated in a unique section.
594 unsigned UniqueID = MCContext::GenericSectionID;
595 const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
596 if (AssociatedSymbol) {
597 UniqueID = NextUniqueID++;
598 Flags |= ELF::SHF_LINK_ORDER;
599 }
600
601 MCSectionELF *Section = getContext().getELFSection(
602 SectionName, getELFSectionType(SectionName, Kind), Flags,
603 getEntrySizeForKind(Kind), Group, UniqueID, AssociatedSymbol);
604 // Make sure that we did not get some other section with incompatible sh_link.
605 // This should not be possible due to UniqueID code above.
606 assert(Section->getAssociatedSymbol() == AssociatedSymbol &&
607 "Associated symbol mismatch between sections");
608 return Section;
609 }
610
611 /// Return the section prefix name used by options FunctionsSections and
612 /// DataSections.
getSectionPrefixForGlobal(SectionKind Kind)613 static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
614 if (Kind.isText())
615 return ".text";
616 if (Kind.isReadOnly())
617 return ".rodata";
618 if (Kind.isBSS())
619 return ".bss";
620 if (Kind.isThreadData())
621 return ".tdata";
622 if (Kind.isThreadBSS())
623 return ".tbss";
624 if (Kind.isData())
625 return ".data";
626 assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
627 return ".data.rel.ro";
628 }
629
selectELFSectionForGlobal(MCContext & Ctx,const GlobalObject * GO,SectionKind Kind,Mangler & Mang,const TargetMachine & TM,bool EmitUniqueSection,unsigned Flags,unsigned * NextUniqueID,const MCSymbolELF * AssociatedSymbol)630 static MCSectionELF *selectELFSectionForGlobal(
631 MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
632 const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
633 unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
634
635 StringRef Group = "";
636 if (const Comdat *C = getELFComdat(GO)) {
637 Flags |= ELF::SHF_GROUP;
638 Group = C->getName();
639 }
640
641 // Get the section entry size based on the kind.
642 unsigned EntrySize = getEntrySizeForKind(Kind);
643
644 SmallString<128> Name;
645 if (Kind.isMergeableCString()) {
646 // We also need alignment here.
647 // FIXME: this is getting the alignment of the character, not the
648 // alignment of the global!
649 unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
650 cast<GlobalVariable>(GO));
651
652 std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
653 Name = SizeSpec + utostr(Align);
654 } else if (Kind.isMergeableConst()) {
655 Name = ".rodata.cst";
656 Name += utostr(EntrySize);
657 } else {
658 Name = getSectionPrefixForGlobal(Kind);
659 }
660
661 if (const auto *F = dyn_cast<Function>(GO)) {
662 const auto &OptionalPrefix = F->getSectionPrefix();
663 if (OptionalPrefix)
664 Name += *OptionalPrefix;
665 }
666
667 unsigned UniqueID = MCContext::GenericSectionID;
668 if (EmitUniqueSection) {
669 if (TM.getUniqueSectionNames()) {
670 Name.push_back('.');
671 TM.getNameWithPrefix(Name, GO, Mang, true /*MayAlwaysUsePrivate*/);
672 } else {
673 UniqueID = *NextUniqueID;
674 (*NextUniqueID)++;
675 }
676 }
677 // Use 0 as the unique ID for execute-only text.
678 if (Kind.isExecuteOnly())
679 UniqueID = 0;
680 return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
681 EntrySize, Group, UniqueID, AssociatedSymbol);
682 }
683
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const684 MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
685 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
686 unsigned Flags = getELFSectionFlags(Kind);
687
688 // If we have -ffunction-section or -fdata-section then we should emit the
689 // global value to a uniqued section specifically for it.
690 bool EmitUniqueSection = false;
691 if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
692 if (Kind.isText())
693 EmitUniqueSection = TM.getFunctionSections();
694 else
695 EmitUniqueSection = TM.getDataSections();
696 }
697 EmitUniqueSection |= GO->hasComdat();
698
699 const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
700 if (AssociatedSymbol) {
701 EmitUniqueSection = true;
702 Flags |= ELF::SHF_LINK_ORDER;
703 }
704
705 MCSectionELF *Section = selectELFSectionForGlobal(
706 getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
707 &NextUniqueID, AssociatedSymbol);
708 assert(Section->getAssociatedSymbol() == AssociatedSymbol);
709 return Section;
710 }
711
getSectionForJumpTable(const Function & F,const TargetMachine & TM) const712 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
713 const Function &F, const TargetMachine &TM) const {
714 // If the function can be removed, produce a unique section so that
715 // the table doesn't prevent the removal.
716 const Comdat *C = F.getComdat();
717 bool EmitUniqueSection = TM.getFunctionSections() || C;
718 if (!EmitUniqueSection)
719 return ReadOnlySection;
720
721 return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
722 getMangler(), TM, EmitUniqueSection,
723 ELF::SHF_ALLOC, &NextUniqueID,
724 /* AssociatedSymbol */ nullptr);
725 }
726
shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,const Function & F) const727 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
728 bool UsesLabelDifference, const Function &F) const {
729 // We can always create relative relocations, so use another section
730 // that can be marked non-executable.
731 return false;
732 }
733
734 /// Given a mergeable constant with the specified size and relocation
735 /// information, return a section that it should be placed in.
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const736 MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
737 const DataLayout &DL, SectionKind Kind, const Constant *C,
738 unsigned &Align) const {
739 if (Kind.isMergeableConst4() && MergeableConst4Section)
740 return MergeableConst4Section;
741 if (Kind.isMergeableConst8() && MergeableConst8Section)
742 return MergeableConst8Section;
743 if (Kind.isMergeableConst16() && MergeableConst16Section)
744 return MergeableConst16Section;
745 if (Kind.isMergeableConst32() && MergeableConst32Section)
746 return MergeableConst32Section;
747 if (Kind.isReadOnly())
748 return ReadOnlySection;
749
750 assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
751 return DataRelROSection;
752 }
753
getStaticStructorSection(MCContext & Ctx,bool UseInitArray,bool IsCtor,unsigned Priority,const MCSymbol * KeySym)754 static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
755 bool IsCtor, unsigned Priority,
756 const MCSymbol *KeySym) {
757 std::string Name;
758 unsigned Type;
759 unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
760 StringRef COMDAT = KeySym ? KeySym->getName() : "";
761
762 if (KeySym)
763 Flags |= ELF::SHF_GROUP;
764
765 if (UseInitArray) {
766 if (IsCtor) {
767 Type = ELF::SHT_INIT_ARRAY;
768 Name = ".init_array";
769 } else {
770 Type = ELF::SHT_FINI_ARRAY;
771 Name = ".fini_array";
772 }
773 if (Priority != 65535) {
774 Name += '.';
775 Name += utostr(Priority);
776 }
777 } else {
778 // The default scheme is .ctor / .dtor, so we have to invert the priority
779 // numbering.
780 if (IsCtor)
781 Name = ".ctors";
782 else
783 Name = ".dtors";
784 if (Priority != 65535)
785 raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
786 Type = ELF::SHT_PROGBITS;
787 }
788
789 return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
790 }
791
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const792 MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
793 unsigned Priority, const MCSymbol *KeySym) const {
794 return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
795 KeySym);
796 }
797
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const798 MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
799 unsigned Priority, const MCSymbol *KeySym) const {
800 return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
801 KeySym);
802 }
803
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,const TargetMachine & TM) const804 const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
805 const GlobalValue *LHS, const GlobalValue *RHS,
806 const TargetMachine &TM) const {
807 // We may only use a PLT-relative relocation to refer to unnamed_addr
808 // functions.
809 if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
810 return nullptr;
811
812 // Basic sanity checks.
813 if (LHS->getType()->getPointerAddressSpace() != 0 ||
814 RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
815 RHS->isThreadLocal())
816 return nullptr;
817
818 return MCBinaryExpr::createSub(
819 MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
820 getContext()),
821 MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
822 }
823
getSectionForCommandLines() const824 MCSection *TargetLoweringObjectFileELF::getSectionForCommandLines() const {
825 // Use ".GCC.command.line" since this feature is to support clang's
826 // -frecord-gcc-switches which in turn attempts to mimic GCC's switch of the
827 // same name.
828 return getContext().getELFSection(".GCC.command.line", ELF::SHT_PROGBITS,
829 ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
830 }
831
832 void
InitializeELF(bool UseInitArray_)833 TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
834 UseInitArray = UseInitArray_;
835 MCContext &Ctx = getContext();
836 if (!UseInitArray) {
837 StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
838 ELF::SHF_ALLOC | ELF::SHF_WRITE);
839
840 StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
841 ELF::SHF_ALLOC | ELF::SHF_WRITE);
842 return;
843 }
844
845 StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
846 ELF::SHF_WRITE | ELF::SHF_ALLOC);
847 StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
848 ELF::SHF_WRITE | ELF::SHF_ALLOC);
849 }
850
851 //===----------------------------------------------------------------------===//
852 // MachO
853 //===----------------------------------------------------------------------===//
854
TargetLoweringObjectFileMachO()855 TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
856 : TargetLoweringObjectFile() {
857 SupportIndirectSymViaGOTPCRel = true;
858 }
859
Initialize(MCContext & Ctx,const TargetMachine & TM)860 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
861 const TargetMachine &TM) {
862 TargetLoweringObjectFile::Initialize(Ctx, TM);
863 if (TM.getRelocationModel() == Reloc::Static) {
864 StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
865 SectionKind::getData());
866 StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
867 SectionKind::getData());
868 } else {
869 StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
870 MachO::S_MOD_INIT_FUNC_POINTERS,
871 SectionKind::getData());
872 StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
873 MachO::S_MOD_TERM_FUNC_POINTERS,
874 SectionKind::getData());
875 }
876
877 PersonalityEncoding =
878 dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
879 LSDAEncoding = dwarf::DW_EH_PE_pcrel;
880 TTypeEncoding =
881 dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
882 }
883
emitModuleMetadata(MCStreamer & Streamer,Module & M) const884 void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
885 Module &M) const {
886 // Emit the linker options if present.
887 if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
888 for (const auto *Option : LinkerOptions->operands()) {
889 SmallVector<std::string, 4> StrOptions;
890 for (const auto &Piece : cast<MDNode>(Option)->operands())
891 StrOptions.push_back(cast<MDString>(Piece)->getString());
892 Streamer.EmitLinkerOptions(StrOptions);
893 }
894 }
895
896 unsigned VersionVal = 0;
897 unsigned ImageInfoFlags = 0;
898 StringRef SectionVal;
899
900 GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
901
902 // The section is mandatory. If we don't have it, then we don't have GC info.
903 if (SectionVal.empty())
904 return;
905
906 StringRef Segment, Section;
907 unsigned TAA = 0, StubSize = 0;
908 bool TAAParsed;
909 std::string ErrorCode =
910 MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
911 TAA, TAAParsed, StubSize);
912 if (!ErrorCode.empty())
913 // If invalid, report the error with report_fatal_error.
914 report_fatal_error("Invalid section specifier '" + Section + "': " +
915 ErrorCode + ".");
916
917 // Get the section.
918 MCSectionMachO *S = getContext().getMachOSection(
919 Segment, Section, TAA, StubSize, SectionKind::getData());
920 Streamer.SwitchSection(S);
921 Streamer.EmitLabel(getContext().
922 getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
923 Streamer.EmitIntValue(VersionVal, 4);
924 Streamer.EmitIntValue(ImageInfoFlags, 4);
925 Streamer.AddBlankLine();
926 }
927
checkMachOComdat(const GlobalValue * GV)928 static void checkMachOComdat(const GlobalValue *GV) {
929 const Comdat *C = GV->getComdat();
930 if (!C)
931 return;
932
933 report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
934 "' cannot be lowered.");
935 }
936
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const937 MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
938 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
939 // Parse the section specifier and create it if valid.
940 StringRef Segment, Section;
941 unsigned TAA = 0, StubSize = 0;
942 bool TAAParsed;
943
944 checkMachOComdat(GO);
945
946 std::string ErrorCode =
947 MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
948 TAA, TAAParsed, StubSize);
949 if (!ErrorCode.empty()) {
950 // If invalid, report the error with report_fatal_error.
951 report_fatal_error("Global variable '" + GO->getName() +
952 "' has an invalid section specifier '" +
953 GO->getSection() + "': " + ErrorCode + ".");
954 }
955
956 // Get the section.
957 MCSectionMachO *S =
958 getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
959
960 // If TAA wasn't set by ParseSectionSpecifier() above,
961 // use the value returned by getMachOSection() as a default.
962 if (!TAAParsed)
963 TAA = S->getTypeAndAttributes();
964
965 // Okay, now that we got the section, verify that the TAA & StubSize agree.
966 // If the user declared multiple globals with different section flags, we need
967 // to reject it here.
968 if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
969 // If invalid, report the error with report_fatal_error.
970 report_fatal_error("Global variable '" + GO->getName() +
971 "' section type or attributes does not match previous"
972 " section specifier");
973 }
974
975 return S;
976 }
977
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const978 MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
979 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
980 checkMachOComdat(GO);
981
982 // Handle thread local data.
983 if (Kind.isThreadBSS()) return TLSBSSSection;
984 if (Kind.isThreadData()) return TLSDataSection;
985
986 if (Kind.isText())
987 return GO->isWeakForLinker() ? TextCoalSection : TextSection;
988
989 // If this is weak/linkonce, put this in a coalescable section, either in text
990 // or data depending on if it is writable.
991 if (GO->isWeakForLinker()) {
992 if (Kind.isReadOnly())
993 return ConstTextCoalSection;
994 if (Kind.isReadOnlyWithRel())
995 return ConstDataCoalSection;
996 return DataCoalSection;
997 }
998
999 // FIXME: Alignment check should be handled by section classifier.
1000 if (Kind.isMergeable1ByteCString() &&
1001 GO->getParent()->getDataLayout().getPreferredAlignment(
1002 cast<GlobalVariable>(GO)) < 32)
1003 return CStringSection;
1004
1005 // Do not put 16-bit arrays in the UString section if they have an
1006 // externally visible label, this runs into issues with certain linker
1007 // versions.
1008 if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
1009 GO->getParent()->getDataLayout().getPreferredAlignment(
1010 cast<GlobalVariable>(GO)) < 32)
1011 return UStringSection;
1012
1013 // With MachO only variables whose corresponding symbol starts with 'l' or
1014 // 'L' can be merged, so we only try merging GVs with private linkage.
1015 if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
1016 if (Kind.isMergeableConst4())
1017 return FourByteConstantSection;
1018 if (Kind.isMergeableConst8())
1019 return EightByteConstantSection;
1020 if (Kind.isMergeableConst16())
1021 return SixteenByteConstantSection;
1022 }
1023
1024 // Otherwise, if it is readonly, but not something we can specially optimize,
1025 // just drop it in .const.
1026 if (Kind.isReadOnly())
1027 return ReadOnlySection;
1028
1029 // If this is marked const, put it into a const section. But if the dynamic
1030 // linker needs to write to it, put it in the data segment.
1031 if (Kind.isReadOnlyWithRel())
1032 return ConstDataSection;
1033
1034 // Put zero initialized globals with strong external linkage in the
1035 // DATA, __common section with the .zerofill directive.
1036 if (Kind.isBSSExtern())
1037 return DataCommonSection;
1038
1039 // Put zero initialized globals with local linkage in __DATA,__bss directive
1040 // with the .zerofill directive (aka .lcomm).
1041 if (Kind.isBSSLocal())
1042 return DataBSSSection;
1043
1044 // Otherwise, just drop the variable in the normal data section.
1045 return DataSection;
1046 }
1047
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const1048 MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
1049 const DataLayout &DL, SectionKind Kind, const Constant *C,
1050 unsigned &Align) const {
1051 // If this constant requires a relocation, we have to put it in the data
1052 // segment, not in the text segment.
1053 if (Kind.isData() || Kind.isReadOnlyWithRel())
1054 return ConstDataSection;
1055
1056 if (Kind.isMergeableConst4())
1057 return FourByteConstantSection;
1058 if (Kind.isMergeableConst8())
1059 return EightByteConstantSection;
1060 if (Kind.isMergeableConst16())
1061 return SixteenByteConstantSection;
1062 return ReadOnlySection; // .const
1063 }
1064
getTTypeGlobalReference(const GlobalValue * GV,unsigned Encoding,const TargetMachine & TM,MachineModuleInfo * MMI,MCStreamer & Streamer) const1065 const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
1066 const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
1067 MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1068 // The mach-o version of this method defaults to returning a stub reference.
1069
1070 if (Encoding & DW_EH_PE_indirect) {
1071 MachineModuleInfoMachO &MachOMMI =
1072 MMI->getObjFileInfo<MachineModuleInfoMachO>();
1073
1074 MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
1075
1076 // Add information about the stub reference to MachOMMI so that the stub
1077 // gets emitted by the asmprinter.
1078 MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
1079 if (!StubSym.getPointer()) {
1080 MCSymbol *Sym = TM.getSymbol(GV);
1081 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
1082 }
1083
1084 return TargetLoweringObjectFile::
1085 getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
1086 Encoding & ~DW_EH_PE_indirect, Streamer);
1087 }
1088
1089 return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
1090 MMI, Streamer);
1091 }
1092
getCFIPersonalitySymbol(const GlobalValue * GV,const TargetMachine & TM,MachineModuleInfo * MMI) const1093 MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
1094 const GlobalValue *GV, const TargetMachine &TM,
1095 MachineModuleInfo *MMI) const {
1096 // The mach-o version of this method defaults to returning a stub reference.
1097 MachineModuleInfoMachO &MachOMMI =
1098 MMI->getObjFileInfo<MachineModuleInfoMachO>();
1099
1100 MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
1101
1102 // Add information about the stub reference to MachOMMI so that the stub
1103 // gets emitted by the asmprinter.
1104 MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
1105 if (!StubSym.getPointer()) {
1106 MCSymbol *Sym = TM.getSymbol(GV);
1107 StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
1108 }
1109
1110 return SSym;
1111 }
1112
getIndirectSymViaGOTPCRel(const GlobalValue * GV,const MCSymbol * Sym,const MCValue & MV,int64_t Offset,MachineModuleInfo * MMI,MCStreamer & Streamer) const1113 const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
1114 const GlobalValue *GV, const MCSymbol *Sym, const MCValue &MV,
1115 int64_t Offset, MachineModuleInfo *MMI, MCStreamer &Streamer) const {
1116 // Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
1117 // as 64-bit do, we replace the GOT equivalent by accessing the final symbol
1118 // through a non_lazy_ptr stub instead. One advantage is that it allows the
1119 // computation of deltas to final external symbols. Example:
1120 //
1121 // _extgotequiv:
1122 // .long _extfoo
1123 //
1124 // _delta:
1125 // .long _extgotequiv-_delta
1126 //
1127 // is transformed to:
1128 //
1129 // _delta:
1130 // .long L_extfoo$non_lazy_ptr-(_delta+0)
1131 //
1132 // .section __IMPORT,__pointers,non_lazy_symbol_pointers
1133 // L_extfoo$non_lazy_ptr:
1134 // .indirect_symbol _extfoo
1135 // .long 0
1136 //
1137 // The indirect symbol table (and sections of non_lazy_symbol_pointers type)
1138 // may point to both local (same translation unit) and global (other
1139 // translation units) symbols. Example:
1140 //
1141 // .section __DATA,__pointers,non_lazy_symbol_pointers
1142 // L1:
1143 // .indirect_symbol _myGlobal
1144 // .long 0
1145 // L2:
1146 // .indirect_symbol _myLocal
1147 // .long _myLocal
1148 //
1149 // If the symbol is local, instead of the symbol's index, the assembler
1150 // places the constant INDIRECT_SYMBOL_LOCAL into the indirect symbol table.
1151 // Then the linker will notice the constant in the table and will look at the
1152 // content of the symbol.
1153 MachineModuleInfoMachO &MachOMMI =
1154 MMI->getObjFileInfo<MachineModuleInfoMachO>();
1155 MCContext &Ctx = getContext();
1156
1157 // The offset must consider the original displacement from the base symbol
1158 // since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
1159 Offset = -MV.getConstant();
1160 const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
1161
1162 // Access the final symbol via sym$non_lazy_ptr and generate the appropriated
1163 // non_lazy_ptr stubs.
1164 SmallString<128> Name;
1165 StringRef Suffix = "$non_lazy_ptr";
1166 Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
1167 Name += Sym->getName();
1168 Name += Suffix;
1169 MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
1170
1171 MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
1172
1173 if (!StubSym.getPointer())
1174 StubSym = MachineModuleInfoImpl::StubValueTy(const_cast<MCSymbol *>(Sym),
1175 !GV->hasLocalLinkage());
1176
1177 const MCExpr *BSymExpr =
1178 MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
1179 const MCExpr *LHS =
1180 MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
1181
1182 if (!Offset)
1183 return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
1184
1185 const MCExpr *RHS =
1186 MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
1187 return MCBinaryExpr::createSub(LHS, RHS, Ctx);
1188 }
1189
canUsePrivateLabel(const MCAsmInfo & AsmInfo,const MCSection & Section)1190 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
1191 const MCSection &Section) {
1192 if (!AsmInfo.isSectionAtomizableBySymbols(Section))
1193 return true;
1194
1195 // If it is not dead stripped, it is safe to use private labels.
1196 const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
1197 if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
1198 return true;
1199
1200 return false;
1201 }
1202
getNameWithPrefix(SmallVectorImpl<char> & OutName,const GlobalValue * GV,const TargetMachine & TM) const1203 void TargetLoweringObjectFileMachO::getNameWithPrefix(
1204 SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1205 const TargetMachine &TM) const {
1206 bool CannotUsePrivateLabel = true;
1207 if (auto *GO = GV->getBaseObject()) {
1208 SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
1209 const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
1210 CannotUsePrivateLabel =
1211 !canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
1212 }
1213 getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1214 }
1215
1216 //===----------------------------------------------------------------------===//
1217 // COFF
1218 //===----------------------------------------------------------------------===//
1219
1220 static unsigned
getCOFFSectionFlags(SectionKind K,const TargetMachine & TM)1221 getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
1222 unsigned Flags = 0;
1223 bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
1224
1225 if (K.isMetadata())
1226 Flags |=
1227 COFF::IMAGE_SCN_MEM_DISCARDABLE;
1228 else if (K.isText())
1229 Flags |=
1230 COFF::IMAGE_SCN_MEM_EXECUTE |
1231 COFF::IMAGE_SCN_MEM_READ |
1232 COFF::IMAGE_SCN_CNT_CODE |
1233 (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
1234 else if (K.isBSS())
1235 Flags |=
1236 COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
1237 COFF::IMAGE_SCN_MEM_READ |
1238 COFF::IMAGE_SCN_MEM_WRITE;
1239 else if (K.isThreadLocal())
1240 Flags |=
1241 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1242 COFF::IMAGE_SCN_MEM_READ |
1243 COFF::IMAGE_SCN_MEM_WRITE;
1244 else if (K.isReadOnly() || K.isReadOnlyWithRel())
1245 Flags |=
1246 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1247 COFF::IMAGE_SCN_MEM_READ;
1248 else if (K.isWriteable())
1249 Flags |=
1250 COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1251 COFF::IMAGE_SCN_MEM_READ |
1252 COFF::IMAGE_SCN_MEM_WRITE;
1253
1254 return Flags;
1255 }
1256
getComdatGVForCOFF(const GlobalValue * GV)1257 static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
1258 const Comdat *C = GV->getComdat();
1259 assert(C && "expected GV to have a Comdat!");
1260
1261 StringRef ComdatGVName = C->getName();
1262 const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
1263 if (!ComdatGV)
1264 report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1265 "' does not exist.");
1266
1267 if (ComdatGV->getComdat() != C)
1268 report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
1269 "' is not a key for its COMDAT.");
1270
1271 return ComdatGV;
1272 }
1273
getSelectionForCOFF(const GlobalValue * GV)1274 static int getSelectionForCOFF(const GlobalValue *GV) {
1275 if (const Comdat *C = GV->getComdat()) {
1276 const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
1277 if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
1278 ComdatKey = GA->getBaseObject();
1279 if (ComdatKey == GV) {
1280 switch (C->getSelectionKind()) {
1281 case Comdat::Any:
1282 return COFF::IMAGE_COMDAT_SELECT_ANY;
1283 case Comdat::ExactMatch:
1284 return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
1285 case Comdat::Largest:
1286 return COFF::IMAGE_COMDAT_SELECT_LARGEST;
1287 case Comdat::NoDuplicates:
1288 return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1289 case Comdat::SameSize:
1290 return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
1291 }
1292 } else {
1293 return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
1294 }
1295 }
1296 return 0;
1297 }
1298
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1299 MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
1300 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1301 int Selection = 0;
1302 unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1303 StringRef Name = GO->getSection();
1304 StringRef COMDATSymName = "";
1305 if (GO->hasComdat()) {
1306 Selection = getSelectionForCOFF(GO);
1307 const GlobalValue *ComdatGV;
1308 if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1309 ComdatGV = getComdatGVForCOFF(GO);
1310 else
1311 ComdatGV = GO;
1312
1313 if (!ComdatGV->hasPrivateLinkage()) {
1314 MCSymbol *Sym = TM.getSymbol(ComdatGV);
1315 COMDATSymName = Sym->getName();
1316 Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1317 } else {
1318 Selection = 0;
1319 }
1320 }
1321
1322 return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
1323 Selection);
1324 }
1325
getCOFFSectionNameForUniqueGlobal(SectionKind Kind)1326 static StringRef getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
1327 if (Kind.isText())
1328 return ".text";
1329 if (Kind.isBSS())
1330 return ".bss";
1331 if (Kind.isThreadLocal())
1332 return ".tls$";
1333 if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1334 return ".rdata";
1335 return ".data";
1336 }
1337
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1338 MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
1339 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1340 // If we have -ffunction-sections then we should emit the global value to a
1341 // uniqued section specifically for it.
1342 bool EmitUniquedSection;
1343 if (Kind.isText())
1344 EmitUniquedSection = TM.getFunctionSections();
1345 else
1346 EmitUniquedSection = TM.getDataSections();
1347
1348 if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
1349 SmallString<256> Name = getCOFFSectionNameForUniqueGlobal(Kind);
1350
1351 unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1352
1353 Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1354 int Selection = getSelectionForCOFF(GO);
1355 if (!Selection)
1356 Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
1357 const GlobalValue *ComdatGV;
1358 if (GO->hasComdat())
1359 ComdatGV = getComdatGVForCOFF(GO);
1360 else
1361 ComdatGV = GO;
1362
1363 unsigned UniqueID = MCContext::GenericSectionID;
1364 if (EmitUniquedSection)
1365 UniqueID = NextUniqueID++;
1366
1367 if (!ComdatGV->hasPrivateLinkage()) {
1368 MCSymbol *Sym = TM.getSymbol(ComdatGV);
1369 StringRef COMDATSymName = Sym->getName();
1370
1371 // Append "$symbol" to the section name *before* IR-level mangling is
1372 // applied when targetting mingw. This is what GCC does, and the ld.bfd
1373 // COFF linker will not properly handle comdats otherwise.
1374 if (getTargetTriple().isWindowsGNUEnvironment())
1375 raw_svector_ostream(Name) << '$' << ComdatGV->getName();
1376
1377 return getContext().getCOFFSection(Name, Characteristics, Kind,
1378 COMDATSymName, Selection, UniqueID);
1379 } else {
1380 SmallString<256> TmpData;
1381 getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
1382 return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
1383 Selection, UniqueID);
1384 }
1385 }
1386
1387 if (Kind.isText())
1388 return TextSection;
1389
1390 if (Kind.isThreadLocal())
1391 return TLSDataSection;
1392
1393 if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
1394 return ReadOnlySection;
1395
1396 // Note: we claim that common symbols are put in BSSSection, but they are
1397 // really emitted with the magic .comm directive, which creates a symbol table
1398 // entry but not a section.
1399 if (Kind.isBSS() || Kind.isCommon())
1400 return BSSSection;
1401
1402 return DataSection;
1403 }
1404
getNameWithPrefix(SmallVectorImpl<char> & OutName,const GlobalValue * GV,const TargetMachine & TM) const1405 void TargetLoweringObjectFileCOFF::getNameWithPrefix(
1406 SmallVectorImpl<char> &OutName, const GlobalValue *GV,
1407 const TargetMachine &TM) const {
1408 bool CannotUsePrivateLabel = false;
1409 if (GV->hasPrivateLinkage() &&
1410 ((isa<Function>(GV) && TM.getFunctionSections()) ||
1411 (isa<GlobalVariable>(GV) && TM.getDataSections())))
1412 CannotUsePrivateLabel = true;
1413
1414 getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
1415 }
1416
getSectionForJumpTable(const Function & F,const TargetMachine & TM) const1417 MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
1418 const Function &F, const TargetMachine &TM) const {
1419 // If the function can be removed, produce a unique section so that
1420 // the table doesn't prevent the removal.
1421 const Comdat *C = F.getComdat();
1422 bool EmitUniqueSection = TM.getFunctionSections() || C;
1423 if (!EmitUniqueSection)
1424 return ReadOnlySection;
1425
1426 // FIXME: we should produce a symbol for F instead.
1427 if (F.hasPrivateLinkage())
1428 return ReadOnlySection;
1429
1430 MCSymbol *Sym = TM.getSymbol(&F);
1431 StringRef COMDATSymName = Sym->getName();
1432
1433 SectionKind Kind = SectionKind::getReadOnly();
1434 StringRef SecName = getCOFFSectionNameForUniqueGlobal(Kind);
1435 unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
1436 Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
1437 unsigned UniqueID = NextUniqueID++;
1438
1439 return getContext().getCOFFSection(
1440 SecName, Characteristics, Kind, COMDATSymName,
1441 COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
1442 }
1443
emitModuleMetadata(MCStreamer & Streamer,Module & M) const1444 void TargetLoweringObjectFileCOFF::emitModuleMetadata(MCStreamer &Streamer,
1445 Module &M) const {
1446 if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
1447 // Emit the linker options to the linker .drectve section. According to the
1448 // spec, this section is a space-separated string containing flags for
1449 // linker.
1450 MCSection *Sec = getDrectveSection();
1451 Streamer.SwitchSection(Sec);
1452 for (const auto *Option : LinkerOptions->operands()) {
1453 for (const auto &Piece : cast<MDNode>(Option)->operands()) {
1454 // Lead with a space for consistency with our dllexport implementation.
1455 std::string Directive(" ");
1456 Directive.append(cast<MDString>(Piece)->getString());
1457 Streamer.EmitBytes(Directive);
1458 }
1459 }
1460 }
1461
1462 unsigned Version = 0;
1463 unsigned Flags = 0;
1464 StringRef Section;
1465
1466 GetObjCImageInfo(M, Version, Flags, Section);
1467 if (Section.empty())
1468 return;
1469
1470 auto &C = getContext();
1471 auto *S = C.getCOFFSection(
1472 Section, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1473 SectionKind::getReadOnly());
1474 Streamer.SwitchSection(S);
1475 Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
1476 Streamer.EmitIntValue(Version, 4);
1477 Streamer.EmitIntValue(Flags, 4);
1478 Streamer.AddBlankLine();
1479 }
1480
Initialize(MCContext & Ctx,const TargetMachine & TM)1481 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1482 const TargetMachine &TM) {
1483 TargetLoweringObjectFile::Initialize(Ctx, TM);
1484 const Triple &T = TM.getTargetTriple();
1485 if (T.isWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1486 StaticCtorSection =
1487 Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1488 COFF::IMAGE_SCN_MEM_READ,
1489 SectionKind::getReadOnly());
1490 StaticDtorSection =
1491 Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1492 COFF::IMAGE_SCN_MEM_READ,
1493 SectionKind::getReadOnly());
1494 } else {
1495 StaticCtorSection = Ctx.getCOFFSection(
1496 ".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1497 COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1498 SectionKind::getData());
1499 StaticDtorSection = Ctx.getCOFFSection(
1500 ".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1501 COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
1502 SectionKind::getData());
1503 }
1504 }
1505
getCOFFStaticStructorSection(MCContext & Ctx,const Triple & T,bool IsCtor,unsigned Priority,const MCSymbol * KeySym,MCSectionCOFF * Default)1506 static MCSectionCOFF *getCOFFStaticStructorSection(MCContext &Ctx,
1507 const Triple &T, bool IsCtor,
1508 unsigned Priority,
1509 const MCSymbol *KeySym,
1510 MCSectionCOFF *Default) {
1511 if (T.isWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
1512 // If the priority is the default, use .CRT$XCU, possibly associative.
1513 if (Priority == 65535)
1514 return Ctx.getAssociativeCOFFSection(Default, KeySym, 0);
1515
1516 // Otherwise, we need to compute a new section name. Low priorities should
1517 // run earlier. The linker will sort sections ASCII-betically, and we need a
1518 // string that sorts between .CRT$XCA and .CRT$XCU. In the general case, we
1519 // make a name like ".CRT$XCT12345", since that runs before .CRT$XCU. Really
1520 // low priorities need to sort before 'L', since the CRT uses that
1521 // internally, so we use ".CRT$XCA00001" for them.
1522 SmallString<24> Name;
1523 raw_svector_ostream OS(Name);
1524 OS << ".CRT$X" << (IsCtor ? "C" : "T") <<
1525 (Priority < 200 ? 'A' : 'T') << format("%05u", Priority);
1526 MCSectionCOFF *Sec = Ctx.getCOFFSection(
1527 Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
1528 SectionKind::getReadOnly());
1529 return Ctx.getAssociativeCOFFSection(Sec, KeySym, 0);
1530 }
1531
1532 std::string Name = IsCtor ? ".ctors" : ".dtors";
1533 if (Priority != 65535)
1534 raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
1535
1536 return Ctx.getAssociativeCOFFSection(
1537 Ctx.getCOFFSection(Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1538 COFF::IMAGE_SCN_MEM_READ |
1539 COFF::IMAGE_SCN_MEM_WRITE,
1540 SectionKind::getData()),
1541 KeySym, 0);
1542 }
1543
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const1544 MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
1545 unsigned Priority, const MCSymbol *KeySym) const {
1546 return getCOFFStaticStructorSection(getContext(), getTargetTriple(), true,
1547 Priority, KeySym,
1548 cast<MCSectionCOFF>(StaticCtorSection));
1549 }
1550
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const1551 MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
1552 unsigned Priority, const MCSymbol *KeySym) const {
1553 return getCOFFStaticStructorSection(getContext(), getTargetTriple(), false,
1554 Priority, KeySym,
1555 cast<MCSectionCOFF>(StaticDtorSection));
1556 }
1557
emitLinkerFlagsForGlobal(raw_ostream & OS,const GlobalValue * GV) const1558 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
1559 raw_ostream &OS, const GlobalValue *GV) const {
1560 emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
1561 }
1562
emitLinkerFlagsForUsed(raw_ostream & OS,const GlobalValue * GV) const1563 void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
1564 raw_ostream &OS, const GlobalValue *GV) const {
1565 emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
1566 }
1567
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,const TargetMachine & TM) const1568 const MCExpr *TargetLoweringObjectFileCOFF::lowerRelativeReference(
1569 const GlobalValue *LHS, const GlobalValue *RHS,
1570 const TargetMachine &TM) const {
1571 const Triple &T = TM.getTargetTriple();
1572 if (T.isOSCygMing())
1573 return nullptr;
1574
1575 // Our symbols should exist in address space zero, cowardly no-op if
1576 // otherwise.
1577 if (LHS->getType()->getPointerAddressSpace() != 0 ||
1578 RHS->getType()->getPointerAddressSpace() != 0)
1579 return nullptr;
1580
1581 // Both ptrtoint instructions must wrap global objects:
1582 // - Only global variables are eligible for image relative relocations.
1583 // - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
1584 // We expect __ImageBase to be a global variable without a section, externally
1585 // defined.
1586 //
1587 // It should look something like this: @__ImageBase = external constant i8
1588 if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
1589 LHS->isThreadLocal() || RHS->isThreadLocal() ||
1590 RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
1591 cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
1592 return nullptr;
1593
1594 return MCSymbolRefExpr::create(TM.getSymbol(LHS),
1595 MCSymbolRefExpr::VK_COFF_IMGREL32,
1596 getContext());
1597 }
1598
APIntToHexString(const APInt & AI)1599 static std::string APIntToHexString(const APInt &AI) {
1600 unsigned Width = (AI.getBitWidth() / 8) * 2;
1601 std::string HexString = AI.toString(16, /*Signed=*/false);
1602 transform(HexString.begin(), HexString.end(), HexString.begin(), tolower);
1603 unsigned Size = HexString.size();
1604 assert(Width >= Size && "hex string is too large!");
1605 HexString.insert(HexString.begin(), Width - Size, '0');
1606
1607 return HexString;
1608 }
1609
scalarConstantToHexString(const Constant * C)1610 static std::string scalarConstantToHexString(const Constant *C) {
1611 Type *Ty = C->getType();
1612 if (isa<UndefValue>(C)) {
1613 return APIntToHexString(APInt::getNullValue(Ty->getPrimitiveSizeInBits()));
1614 } else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
1615 return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
1616 } else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
1617 return APIntToHexString(CI->getValue());
1618 } else {
1619 unsigned NumElements;
1620 if (isa<VectorType>(Ty))
1621 NumElements = Ty->getVectorNumElements();
1622 else
1623 NumElements = Ty->getArrayNumElements();
1624 std::string HexString;
1625 for (int I = NumElements - 1, E = -1; I != E; --I)
1626 HexString += scalarConstantToHexString(C->getAggregateElement(I));
1627 return HexString;
1628 }
1629 }
1630
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const1631 MCSection *TargetLoweringObjectFileCOFF::getSectionForConstant(
1632 const DataLayout &DL, SectionKind Kind, const Constant *C,
1633 unsigned &Align) const {
1634 if (Kind.isMergeableConst() && C &&
1635 getContext().getAsmInfo()->hasCOFFComdatConstants()) {
1636 // This creates comdat sections with the given symbol name, but unless
1637 // AsmPrinter::GetCPISymbol actually makes the symbol global, the symbol
1638 // will be created with a null storage class, which makes GNU binutils
1639 // error out.
1640 const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
1641 COFF::IMAGE_SCN_MEM_READ |
1642 COFF::IMAGE_SCN_LNK_COMDAT;
1643 std::string COMDATSymName;
1644 if (Kind.isMergeableConst4()) {
1645 if (Align <= 4) {
1646 COMDATSymName = "__real@" + scalarConstantToHexString(C);
1647 Align = 4;
1648 }
1649 } else if (Kind.isMergeableConst8()) {
1650 if (Align <= 8) {
1651 COMDATSymName = "__real@" + scalarConstantToHexString(C);
1652 Align = 8;
1653 }
1654 } else if (Kind.isMergeableConst16()) {
1655 // FIXME: These may not be appropriate for non-x86 architectures.
1656 if (Align <= 16) {
1657 COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
1658 Align = 16;
1659 }
1660 } else if (Kind.isMergeableConst32()) {
1661 if (Align <= 32) {
1662 COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
1663 Align = 32;
1664 }
1665 }
1666
1667 if (!COMDATSymName.empty())
1668 return getContext().getCOFFSection(".rdata", Characteristics, Kind,
1669 COMDATSymName,
1670 COFF::IMAGE_COMDAT_SELECT_ANY);
1671 }
1672
1673 return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C, Align);
1674 }
1675
1676
1677 //===----------------------------------------------------------------------===//
1678 // Wasm
1679 //===----------------------------------------------------------------------===//
1680
getWasmComdat(const GlobalValue * GV)1681 static const Comdat *getWasmComdat(const GlobalValue *GV) {
1682 const Comdat *C = GV->getComdat();
1683 if (!C)
1684 return nullptr;
1685
1686 if (C->getSelectionKind() != Comdat::Any)
1687 report_fatal_error("WebAssembly COMDATs only support "
1688 "SelectionKind::Any, '" + C->getName() + "' cannot be "
1689 "lowered.");
1690
1691 return C;
1692 }
1693
getWasmKindForNamedSection(StringRef Name,SectionKind K)1694 static SectionKind getWasmKindForNamedSection(StringRef Name, SectionKind K) {
1695 // If we're told we have function data, then use that.
1696 if (K.isText())
1697 return SectionKind::getText();
1698
1699 // Otherwise, ignore whatever section type the generic impl detected and use
1700 // a plain data section.
1701 return SectionKind::getData();
1702 }
1703
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1704 MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
1705 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1706 // We don't support explict section names for functions in the wasm object
1707 // format. Each function has to be in its own unique section.
1708 if (isa<Function>(GO)) {
1709 return SelectSectionForGlobal(GO, Kind, TM);
1710 }
1711
1712 StringRef Name = GO->getSection();
1713
1714 Kind = getWasmKindForNamedSection(Name, Kind);
1715
1716 StringRef Group = "";
1717 if (const Comdat *C = getWasmComdat(GO)) {
1718 Group = C->getName();
1719 }
1720
1721 MCSectionWasm* Section =
1722 getContext().getWasmSection(Name, Kind, Group,
1723 MCContext::GenericSectionID);
1724
1725 return Section;
1726 }
1727
selectWasmSectionForGlobal(MCContext & Ctx,const GlobalObject * GO,SectionKind Kind,Mangler & Mang,const TargetMachine & TM,bool EmitUniqueSection,unsigned * NextUniqueID)1728 static MCSectionWasm *selectWasmSectionForGlobal(
1729 MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
1730 const TargetMachine &TM, bool EmitUniqueSection, unsigned *NextUniqueID) {
1731 StringRef Group = "";
1732 if (const Comdat *C = getWasmComdat(GO)) {
1733 Group = C->getName();
1734 }
1735
1736 bool UniqueSectionNames = TM.getUniqueSectionNames();
1737 SmallString<128> Name = getSectionPrefixForGlobal(Kind);
1738
1739 if (const auto *F = dyn_cast<Function>(GO)) {
1740 const auto &OptionalPrefix = F->getSectionPrefix();
1741 if (OptionalPrefix)
1742 Name += *OptionalPrefix;
1743 }
1744
1745 if (EmitUniqueSection && UniqueSectionNames) {
1746 Name.push_back('.');
1747 TM.getNameWithPrefix(Name, GO, Mang, true);
1748 }
1749 unsigned UniqueID = MCContext::GenericSectionID;
1750 if (EmitUniqueSection && !UniqueSectionNames) {
1751 UniqueID = *NextUniqueID;
1752 (*NextUniqueID)++;
1753 }
1754
1755 return Ctx.getWasmSection(Name, Kind, Group, UniqueID);
1756 }
1757
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1758 MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
1759 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1760
1761 if (Kind.isCommon())
1762 report_fatal_error("mergable sections not supported yet on wasm");
1763
1764 // If we have -ffunction-section or -fdata-section then we should emit the
1765 // global value to a uniqued section specifically for it.
1766 bool EmitUniqueSection = false;
1767 if (Kind.isText())
1768 EmitUniqueSection = TM.getFunctionSections();
1769 else
1770 EmitUniqueSection = TM.getDataSections();
1771 EmitUniqueSection |= GO->hasComdat();
1772
1773 return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
1774 EmitUniqueSection, &NextUniqueID);
1775 }
1776
shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,const Function & F) const1777 bool TargetLoweringObjectFileWasm::shouldPutJumpTableInFunctionSection(
1778 bool UsesLabelDifference, const Function &F) const {
1779 // We can always create relative relocations, so use another section
1780 // that can be marked non-executable.
1781 return false;
1782 }
1783
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,const TargetMachine & TM) const1784 const MCExpr *TargetLoweringObjectFileWasm::lowerRelativeReference(
1785 const GlobalValue *LHS, const GlobalValue *RHS,
1786 const TargetMachine &TM) const {
1787 // We may only use a PLT-relative relocation to refer to unnamed_addr
1788 // functions.
1789 if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
1790 return nullptr;
1791
1792 // Basic sanity checks.
1793 if (LHS->getType()->getPointerAddressSpace() != 0 ||
1794 RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
1795 RHS->isThreadLocal())
1796 return nullptr;
1797
1798 return MCBinaryExpr::createSub(
1799 MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
1800 getContext()),
1801 MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
1802 }
1803
InitializeWasm()1804 void TargetLoweringObjectFileWasm::InitializeWasm() {
1805 StaticCtorSection =
1806 getContext().getWasmSection(".init_array", SectionKind::getData());
1807
1808 // We don't use PersonalityEncoding and LSDAEncoding because we don't emit
1809 // .cfi directives. We use TTypeEncoding to encode typeinfo global variables.
1810 TTypeEncoding = dwarf::DW_EH_PE_absptr;
1811 }
1812
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const1813 MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
1814 unsigned Priority, const MCSymbol *KeySym) const {
1815 return Priority == UINT16_MAX ?
1816 StaticCtorSection :
1817 getContext().getWasmSection(".init_array." + utostr(Priority),
1818 SectionKind::getData());
1819 }
1820
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const1821 MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
1822 unsigned Priority, const MCSymbol *KeySym) const {
1823 llvm_unreachable("@llvm.global_dtors should have been lowered already");
1824 return nullptr;
1825 }
1826
1827 //===----------------------------------------------------------------------===//
1828 // XCOFF
1829 //===----------------------------------------------------------------------===//
getExplicitSectionGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1830 MCSection *TargetLoweringObjectFileXCOFF::getExplicitSectionGlobal(
1831 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1832 report_fatal_error("XCOFF explicit sections not yet implemented.");
1833 }
1834
SelectSectionForGlobal(const GlobalObject * GO,SectionKind Kind,const TargetMachine & TM) const1835 MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal(
1836 const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
1837 assert(!TM.getFunctionSections() && !TM.getDataSections() &&
1838 "XCOFF unique sections not yet implemented.");
1839
1840 // Common symbols go into a csect with matching name which will get mapped
1841 // into the .bss section.
1842 if (Kind.isBSSLocal() || Kind.isCommon()) {
1843 SmallString<128> Name;
1844 getNameWithPrefix(Name, GO, TM);
1845 XCOFF::StorageClass SC =
1846 TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(GO);
1847 return getContext().getXCOFFSection(
1848 Name, Kind.isBSSLocal() ? XCOFF::XMC_BS : XCOFF::XMC_RW, XCOFF::XTY_CM,
1849 SC, Kind, /* BeginSymbolName */ nullptr);
1850 }
1851
1852 if (Kind.isMergeableCString()) {
1853 if (!Kind.isMergeable1ByteCString())
1854 report_fatal_error("Unhandled multi-byte mergeable string kind.");
1855
1856 unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
1857 cast<GlobalVariable>(GO));
1858
1859 unsigned EntrySize = getEntrySizeForKind(Kind);
1860 std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
1861 SmallString<128> Name;
1862 Name = SizeSpec + utostr(Align);
1863
1864 return getContext().getXCOFFSection(
1865 Name, XCOFF::XMC_RO, XCOFF::XTY_SD,
1866 TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(GO),
1867 Kind, /* BeginSymbolName */ nullptr);
1868 }
1869
1870 if (Kind.isText())
1871 return TextSection;
1872
1873 if (Kind.isData() || Kind.isReadOnlyWithRel())
1874 // TODO: We may put this under option control, because user may want to
1875 // have read-only data with relocations placed into a read-only section by
1876 // the compiler.
1877 return DataSection;
1878
1879 // Zero initialized data must be emitted to the .data section because external
1880 // linkage control sections that get mapped to the .bss section will be linked
1881 // as tentative defintions, which is only appropriate for SectionKind::Common.
1882 if (Kind.isBSS())
1883 return DataSection;
1884
1885 if (Kind.isReadOnly())
1886 return ReadOnlySection;
1887
1888 report_fatal_error("XCOFF other section types not yet implemented.");
1889 }
1890
getSectionForJumpTable(const Function & F,const TargetMachine & TM) const1891 MCSection *TargetLoweringObjectFileXCOFF::getSectionForJumpTable(
1892 const Function &F, const TargetMachine &TM) const {
1893 assert (!TM.getFunctionSections() && "Unique sections not supported on XCOFF"
1894 " yet.");
1895 assert (!F.getComdat() && "Comdat not supported on XCOFF.");
1896 //TODO: Enable emiting jump table to unique sections when we support it.
1897 return ReadOnlySection;
1898 }
1899
shouldPutJumpTableInFunctionSection(bool UsesLabelDifference,const Function & F) const1900 bool TargetLoweringObjectFileXCOFF::shouldPutJumpTableInFunctionSection(
1901 bool UsesLabelDifference, const Function &F) const {
1902 return false;
1903 }
1904
1905 /// Given a mergeable constant with the specified size and relocation
1906 /// information, return a section that it should be placed in.
getSectionForConstant(const DataLayout & DL,SectionKind Kind,const Constant * C,unsigned & Align) const1907 MCSection *TargetLoweringObjectFileXCOFF::getSectionForConstant(
1908 const DataLayout &DL, SectionKind Kind, const Constant *C,
1909 unsigned &Align) const {
1910 //TODO: Enable emiting constant pool to unique sections when we support it.
1911 return ReadOnlySection;
1912 }
1913
Initialize(MCContext & Ctx,const TargetMachine & TgtM)1914 void TargetLoweringObjectFileXCOFF::Initialize(MCContext &Ctx,
1915 const TargetMachine &TgtM) {
1916 TargetLoweringObjectFile::Initialize(Ctx, TgtM);
1917 TTypeEncoding = 0;
1918 PersonalityEncoding = 0;
1919 LSDAEncoding = 0;
1920 }
1921
getStaticCtorSection(unsigned Priority,const MCSymbol * KeySym) const1922 MCSection *TargetLoweringObjectFileXCOFF::getStaticCtorSection(
1923 unsigned Priority, const MCSymbol *KeySym) const {
1924 report_fatal_error("XCOFF ctor section not yet implemented.");
1925 }
1926
getStaticDtorSection(unsigned Priority,const MCSymbol * KeySym) const1927 MCSection *TargetLoweringObjectFileXCOFF::getStaticDtorSection(
1928 unsigned Priority, const MCSymbol *KeySym) const {
1929 report_fatal_error("XCOFF dtor section not yet implemented.");
1930 }
1931
lowerRelativeReference(const GlobalValue * LHS,const GlobalValue * RHS,const TargetMachine & TM) const1932 const MCExpr *TargetLoweringObjectFileXCOFF::lowerRelativeReference(
1933 const GlobalValue *LHS, const GlobalValue *RHS,
1934 const TargetMachine &TM) const {
1935 report_fatal_error("XCOFF not yet implemented.");
1936 }
1937
getStorageClassForGlobal(const GlobalObject * GO)1938 XCOFF::StorageClass TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(
1939 const GlobalObject *GO) {
1940 switch (GO->getLinkage()) {
1941 case GlobalValue::InternalLinkage:
1942 case GlobalValue::PrivateLinkage:
1943 return XCOFF::C_HIDEXT;
1944 case GlobalValue::ExternalLinkage:
1945 case GlobalValue::CommonLinkage:
1946 return XCOFF::C_EXT;
1947 case GlobalValue::ExternalWeakLinkage:
1948 return XCOFF::C_WEAKEXT;
1949 default:
1950 report_fatal_error(
1951 "Unhandled linkage when mapping linkage to StorageClass.");
1952 }
1953 }
1954