xref: /llvm-project/llvm/lib/Target/TargetLoweringObjectFile.cpp (revision a44d8f806b5c4b19c13ec34eecc7b52bec6dcbb3) 
1 //===-- llvm/Target/TargetLoweringObjectFile.cpp - Object File Info -------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements classes used to handle lowerings specific to common
11 // object file formats.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "llvm/Target/TargetLoweringObjectFile.h"
16 #include "llvm/Constants.h"
17 #include "llvm/DerivedTypes.h"
18 #include "llvm/Function.h"
19 #include "llvm/GlobalVariable.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCExpr.h"
22 #include "llvm/MC/MCSectionMachO.h"
23 #include "llvm/MC/MCSectionELF.h"
24 #include "llvm/MC/MCSymbol.h"
25 #include "llvm/Target/TargetData.h"
26 #include "llvm/Target/TargetMachine.h"
27 #include "llvm/Target/TargetOptions.h"
28 #include "llvm/Support/ErrorHandling.h"
29 #include "llvm/Support/Mangler.h"
30 #include "llvm/Support/raw_ostream.h"
31 #include "llvm/ADT/SmallString.h"
32 #include "llvm/ADT/StringExtras.h"
33 using namespace llvm;
34 
35 //===----------------------------------------------------------------------===//
36 //                              Generic Code
37 //===----------------------------------------------------------------------===//
38 
39 TargetLoweringObjectFile::TargetLoweringObjectFile() : Ctx(0) {
40   TextSection = 0;
41   DataSection = 0;
42   BSSSection = 0;
43   ReadOnlySection = 0;
44   StaticCtorSection = 0;
45   StaticDtorSection = 0;
46   LSDASection = 0;
47   EHFrameSection = 0;
48 
49   DwarfAbbrevSection = 0;
50   DwarfInfoSection = 0;
51   DwarfLineSection = 0;
52   DwarfFrameSection = 0;
53   DwarfPubNamesSection = 0;
54   DwarfPubTypesSection = 0;
55   DwarfDebugInlineSection = 0;
56   DwarfStrSection = 0;
57   DwarfLocSection = 0;
58   DwarfARangesSection = 0;
59   DwarfRangesSection = 0;
60   DwarfMacroInfoSection = 0;
61 }
62 
63 TargetLoweringObjectFile::~TargetLoweringObjectFile() {
64 }
65 
66 static bool isSuitableForBSS(const GlobalVariable *GV) {
67   Constant *C = GV->getInitializer();
68 
69   // Must have zero initializer.
70   if (!C->isNullValue())
71     return false;
72 
73   // Leave constant zeros in readonly constant sections, so they can be shared.
74   if (GV->isConstant())
75     return false;
76 
77   // If the global has an explicit section specified, don't put it in BSS.
78   if (!GV->getSection().empty())
79     return false;
80 
81   // If -nozero-initialized-in-bss is specified, don't ever use BSS.
82   if (NoZerosInBSS)
83     return false;
84 
85   // Otherwise, put it in BSS!
86   return true;
87 }
88 
89 /// IsNullTerminatedString - Return true if the specified constant (which is
90 /// known to have a type that is an array of 1/2/4 byte elements) ends with a
91 /// nul value and contains no other nuls in it.
92 static bool IsNullTerminatedString(const Constant *C) {
93   const ArrayType *ATy = cast<ArrayType>(C->getType());
94 
95   // First check: is we have constant array of i8 terminated with zero
96   if (const ConstantArray *CVA = dyn_cast<ConstantArray>(C)) {
97     if (ATy->getNumElements() == 0) return false;
98 
99     ConstantInt *Null =
100       dyn_cast<ConstantInt>(CVA->getOperand(ATy->getNumElements()-1));
101     if (Null == 0 || Null->getZExtValue() != 0)
102       return false; // Not null terminated.
103 
104     // Verify that the null doesn't occur anywhere else in the string.
105     for (unsigned i = 0, e = ATy->getNumElements()-1; i != e; ++i)
106       // Reject constantexpr elements etc.
107       if (!isa<ConstantInt>(CVA->getOperand(i)) ||
108           CVA->getOperand(i) == Null)
109         return false;
110     return true;
111   }
112 
113   // Another possibility: [1 x i8] zeroinitializer
114   if (isa<ConstantAggregateZero>(C))
115     return ATy->getNumElements() == 1;
116 
117   return false;
118 }
119 
120 /// getKindForGlobal - This is a top-level target-independent classifier for
121 /// a global variable.  Given an global variable and information from TM, it
122 /// classifies the global in a variety of ways that make various target
123 /// implementations simpler.  The target implementation is free to ignore this
124 /// extra info of course.
125 SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalValue *GV,
126                                                        const TargetMachine &TM){
127   assert(!GV->isDeclaration() && !GV->hasAvailableExternallyLinkage() &&
128          "Can only be used for global definitions");
129 
130   Reloc::Model ReloModel = TM.getRelocationModel();
131 
132   // Early exit - functions should be always in text sections.
133   const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
134   if (GVar == 0)
135     return SectionKind::getText();
136 
137   // Handle thread-local data first.
138   if (GVar->isThreadLocal()) {
139     if (isSuitableForBSS(GVar))
140       return SectionKind::getThreadBSS();
141     return SectionKind::getThreadData();
142   }
143 
144   // Variable can be easily put to BSS section.
145   if (isSuitableForBSS(GVar))
146     return SectionKind::getBSS();
147 
148   Constant *C = GVar->getInitializer();
149 
150   // If the global is marked constant, we can put it into a mergable section,
151   // a mergable string section, or general .data if it contains relocations.
152   if (GVar->isConstant()) {
153     // If the initializer for the global contains something that requires a
154     // relocation, then we may have to drop this into a wriable data section
155     // even though it is marked const.
156     switch (C->getRelocationInfo()) {
157     default: assert(0 && "unknown relocation info kind");
158     case Constant::NoRelocation:
159       // If initializer is a null-terminated string, put it in a "cstring"
160       // section of the right width.
161       if (const ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) {
162         if (const IntegerType *ITy =
163               dyn_cast<IntegerType>(ATy->getElementType())) {
164           if ((ITy->getBitWidth() == 8 || ITy->getBitWidth() == 16 ||
165                ITy->getBitWidth() == 32) &&
166               IsNullTerminatedString(C)) {
167             if (ITy->getBitWidth() == 8)
168               return SectionKind::getMergeable1ByteCString();
169             if (ITy->getBitWidth() == 16)
170               return SectionKind::getMergeable2ByteCString();
171 
172             assert(ITy->getBitWidth() == 32 && "Unknown width");
173             return SectionKind::getMergeable4ByteCString();
174           }
175         }
176       }
177 
178       // Otherwise, just drop it into a mergable constant section.  If we have
179       // a section for this size, use it, otherwise use the arbitrary sized
180       // mergable section.
181       switch (TM.getTargetData()->getTypeAllocSize(C->getType())) {
182       case 4:  return SectionKind::getMergeableConst4();
183       case 8:  return SectionKind::getMergeableConst8();
184       case 16: return SectionKind::getMergeableConst16();
185       default: return SectionKind::getMergeableConst();
186       }
187 
188     case Constant::LocalRelocation:
189       // In static relocation model, the linker will resolve all addresses, so
190       // the relocation entries will actually be constants by the time the app
191       // starts up.  However, we can't put this into a mergable section, because
192       // the linker doesn't take relocations into consideration when it tries to
193       // merge entries in the section.
194       if (ReloModel == Reloc::Static)
195         return SectionKind::getReadOnly();
196 
197       // Otherwise, the dynamic linker needs to fix it up, put it in the
198       // writable data.rel.local section.
199       return SectionKind::getReadOnlyWithRelLocal();
200 
201     case Constant::GlobalRelocations:
202       // In static relocation model, the linker will resolve all addresses, so
203       // the relocation entries will actually be constants by the time the app
204       // starts up.  However, we can't put this into a mergable section, because
205       // the linker doesn't take relocations into consideration when it tries to
206       // merge entries in the section.
207       if (ReloModel == Reloc::Static)
208         return SectionKind::getReadOnly();
209 
210       // Otherwise, the dynamic linker needs to fix it up, put it in the
211       // writable data.rel section.
212       return SectionKind::getReadOnlyWithRel();
213     }
214   }
215 
216   // Okay, this isn't a constant.  If the initializer for the global is going
217   // to require a runtime relocation by the dynamic linker, put it into a more
218   // specific section to improve startup time of the app.  This coalesces these
219   // globals together onto fewer pages, improving the locality of the dynamic
220   // linker.
221   if (ReloModel == Reloc::Static)
222     return SectionKind::getDataNoRel();
223 
224   switch (C->getRelocationInfo()) {
225   default: assert(0 && "unknown relocation info kind");
226   case Constant::NoRelocation:
227     return SectionKind::getDataNoRel();
228   case Constant::LocalRelocation:
229     return SectionKind::getDataRelLocal();
230   case Constant::GlobalRelocations:
231     return SectionKind::getDataRel();
232   }
233 }
234 
235 /// SectionForGlobal - This method computes the appropriate section to emit
236 /// the specified global variable or function definition.  This should not
237 /// be passed external (or available externally) globals.
238 const MCSection *TargetLoweringObjectFile::
239 SectionForGlobal(const GlobalValue *GV, SectionKind Kind, Mangler *Mang,
240                  const TargetMachine &TM) const {
241   // Select section name.
242   if (GV->hasSection())
243     return getExplicitSectionGlobal(GV, Kind, Mang, TM);
244 
245 
246   // Use default section depending on the 'type' of global
247   return SelectSectionForGlobal(GV, Kind, Mang, TM);
248 }
249 
250 
251 // Lame default implementation. Calculate the section name for global.
252 const MCSection *
253 TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
254                                                  SectionKind Kind,
255                                                  Mangler *Mang,
256                                                  const TargetMachine &TM) const{
257   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
258 
259   if (Kind.isText())
260     return getTextSection();
261 
262   if (Kind.isBSS() && BSSSection != 0)
263     return BSSSection;
264 
265   if (Kind.isReadOnly() && ReadOnlySection != 0)
266     return ReadOnlySection;
267 
268   return getDataSection();
269 }
270 
271 /// getSectionForConstant - Given a mergable constant with the
272 /// specified size and relocation information, return a section that it
273 /// should be placed in.
274 const MCSection *
275 TargetLoweringObjectFile::getSectionForConstant(SectionKind Kind) const {
276   if (Kind.isReadOnly() && ReadOnlySection != 0)
277     return ReadOnlySection;
278 
279   return DataSection;
280 }
281 
282 /// getSymbolForDwarfGlobalReference - Return an MCExpr to use for a
283 /// pc-relative reference to the specified global variable from exception
284 /// handling information.  In addition to the symbol, this returns
285 /// by-reference:
286 ///
287 /// IsIndirect - True if the returned symbol is actually a stub that contains
288 ///    the address of the symbol, false if the symbol is the global itself.
289 ///
290 /// IsPCRel - True if the symbol reference is already pc-relative, false if
291 ///    the caller needs to subtract off the address of the reference from the
292 ///    symbol.
293 ///
294 const MCExpr *TargetLoweringObjectFile::
295 getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
296                                  MachineModuleInfo *MMI,
297                                  bool &IsIndirect, bool &IsPCRel) const {
298   // The generic implementation of this just returns a direct reference to the
299   // symbol.
300   IsIndirect = false;
301   IsPCRel    = false;
302 
303   SmallString<128> Name;
304   Mang->getNameWithPrefix(Name, GV, false);
305   return MCSymbolRefExpr::Create(Name.str(), getContext());
306 }
307 
308 
309 //===----------------------------------------------------------------------===//
310 //                                  ELF
311 //===----------------------------------------------------------------------===//
312 typedef StringMap<const MCSectionELF*> ELFUniqueMapTy;
313 
314 TargetLoweringObjectFileELF::~TargetLoweringObjectFileELF() {
315   // If we have the section uniquing map, free it.
316   delete (ELFUniqueMapTy*)UniquingMap;
317 }
318 
319 const MCSection *TargetLoweringObjectFileELF::
320 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
321               SectionKind Kind, bool IsExplicit) const {
322   if (UniquingMap == 0)
323     UniquingMap = new ELFUniqueMapTy();
324   ELFUniqueMapTy &Map = *(ELFUniqueMapTy*)UniquingMap;
325 
326   // Do the lookup, if we have a hit, return it.
327   const MCSectionELF *&Entry = Map[Section];
328   if (Entry) return Entry;
329 
330   return Entry = MCSectionELF::Create(Section, Type, Flags, Kind, IsExplicit,
331                                       getContext());
332 }
333 
334 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
335                                              const TargetMachine &TM) {
336   if (UniquingMap != 0)
337     ((ELFUniqueMapTy*)UniquingMap)->clear();
338   TargetLoweringObjectFile::Initialize(Ctx, TM);
339 
340   BSSSection =
341     getELFSection(".bss", MCSectionELF::SHT_NOBITS,
342                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
343                   SectionKind::getBSS());
344 
345   TextSection =
346     getELFSection(".text", MCSectionELF::SHT_PROGBITS,
347                   MCSectionELF::SHF_EXECINSTR | MCSectionELF::SHF_ALLOC,
348                   SectionKind::getText());
349 
350   DataSection =
351     getELFSection(".data", MCSectionELF::SHT_PROGBITS,
352                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
353                   SectionKind::getDataRel());
354 
355   ReadOnlySection =
356     getELFSection(".rodata", MCSectionELF::SHT_PROGBITS,
357                   MCSectionELF::SHF_ALLOC,
358                   SectionKind::getReadOnly());
359 
360   TLSDataSection =
361     getELFSection(".tdata", MCSectionELF::SHT_PROGBITS,
362                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
363                   MCSectionELF::SHF_WRITE, SectionKind::getThreadData());
364 
365   TLSBSSSection =
366     getELFSection(".tbss", MCSectionELF::SHT_NOBITS,
367                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
368                   MCSectionELF::SHF_WRITE, SectionKind::getThreadBSS());
369 
370   DataRelSection =
371     getELFSection(".data.rel", MCSectionELF::SHT_PROGBITS,
372                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
373                   SectionKind::getDataRel());
374 
375   DataRelLocalSection =
376     getELFSection(".data.rel.local", MCSectionELF::SHT_PROGBITS,
377                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
378                   SectionKind::getDataRelLocal());
379 
380   DataRelROSection =
381     getELFSection(".data.rel.ro", MCSectionELF::SHT_PROGBITS,
382                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
383                   SectionKind::getReadOnlyWithRel());
384 
385   DataRelROLocalSection =
386     getELFSection(".data.rel.ro.local", MCSectionELF::SHT_PROGBITS,
387                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
388                   SectionKind::getReadOnlyWithRelLocal());
389 
390   MergeableConst4Section =
391     getELFSection(".rodata.cst4", MCSectionELF::SHT_PROGBITS,
392                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
393                   SectionKind::getMergeableConst4());
394 
395   MergeableConst8Section =
396     getELFSection(".rodata.cst8", MCSectionELF::SHT_PROGBITS,
397                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
398                   SectionKind::getMergeableConst8());
399 
400   MergeableConst16Section =
401     getELFSection(".rodata.cst16", MCSectionELF::SHT_PROGBITS,
402                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
403                   SectionKind::getMergeableConst16());
404 
405   StaticCtorSection =
406     getELFSection(".ctors", MCSectionELF::SHT_PROGBITS,
407                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
408                   SectionKind::getDataRel());
409 
410   StaticDtorSection =
411     getELFSection(".dtors", MCSectionELF::SHT_PROGBITS,
412                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
413                   SectionKind::getDataRel());
414 
415   // Exception Handling Sections.
416 
417   // FIXME: We're emitting LSDA info into a readonly section on ELF, even though
418   // it contains relocatable pointers.  In PIC mode, this is probably a big
419   // runtime hit for C++ apps.  Either the contents of the LSDA need to be
420   // adjusted or this should be a data section.
421   LSDASection =
422     getELFSection(".gcc_except_table", MCSectionELF::SHT_PROGBITS,
423                   MCSectionELF::SHF_ALLOC, SectionKind::getReadOnly());
424   EHFrameSection =
425     getELFSection(".eh_frame", MCSectionELF::SHT_PROGBITS,
426                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
427                   SectionKind::getDataRel());
428 
429   // Debug Info Sections.
430   DwarfAbbrevSection =
431     getELFSection(".debug_abbrev", MCSectionELF::SHT_PROGBITS, 0,
432                   SectionKind::getMetadata());
433   DwarfInfoSection =
434     getELFSection(".debug_info", MCSectionELF::SHT_PROGBITS, 0,
435                   SectionKind::getMetadata());
436   DwarfLineSection =
437     getELFSection(".debug_line", MCSectionELF::SHT_PROGBITS, 0,
438                   SectionKind::getMetadata());
439   DwarfFrameSection =
440     getELFSection(".debug_frame", MCSectionELF::SHT_PROGBITS, 0,
441                   SectionKind::getMetadata());
442   DwarfPubNamesSection =
443     getELFSection(".debug_pubnames", MCSectionELF::SHT_PROGBITS, 0,
444                   SectionKind::getMetadata());
445   DwarfPubTypesSection =
446     getELFSection(".debug_pubtypes", MCSectionELF::SHT_PROGBITS, 0,
447                   SectionKind::getMetadata());
448   DwarfStrSection =
449     getELFSection(".debug_str", MCSectionELF::SHT_PROGBITS, 0,
450                   SectionKind::getMetadata());
451   DwarfLocSection =
452     getELFSection(".debug_loc", MCSectionELF::SHT_PROGBITS, 0,
453                   SectionKind::getMetadata());
454   DwarfARangesSection =
455     getELFSection(".debug_aranges", MCSectionELF::SHT_PROGBITS, 0,
456                   SectionKind::getMetadata());
457   DwarfRangesSection =
458     getELFSection(".debug_ranges", MCSectionELF::SHT_PROGBITS, 0,
459                   SectionKind::getMetadata());
460   DwarfMacroInfoSection =
461     getELFSection(".debug_macinfo", MCSectionELF::SHT_PROGBITS, 0,
462                   SectionKind::getMetadata());
463 }
464 
465 
466 static SectionKind
467 getELFKindForNamedSection(const char *Name, SectionKind K) {
468   if (Name[0] != '.') return K;
469 
470   // Some lame default implementation based on some magic section names.
471   if (strcmp(Name, ".bss") == 0 ||
472       strncmp(Name, ".bss.", 5) == 0 ||
473       strncmp(Name, ".gnu.linkonce.b.", 16) == 0 ||
474       strncmp(Name, ".llvm.linkonce.b.", 17) == 0 ||
475       strcmp(Name, ".sbss") == 0 ||
476       strncmp(Name, ".sbss.", 6) == 0 ||
477       strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 ||
478       strncmp(Name, ".llvm.linkonce.sb.", 18) == 0)
479     return SectionKind::getBSS();
480 
481   if (strcmp(Name, ".tdata") == 0 ||
482       strncmp(Name, ".tdata.", 7) == 0 ||
483       strncmp(Name, ".gnu.linkonce.td.", 17) == 0 ||
484       strncmp(Name, ".llvm.linkonce.td.", 18) == 0)
485     return SectionKind::getThreadData();
486 
487   if (strcmp(Name, ".tbss") == 0 ||
488       strncmp(Name, ".tbss.", 6) == 0 ||
489       strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 ||
490       strncmp(Name, ".llvm.linkonce.tb.", 18) == 0)
491     return SectionKind::getThreadBSS();
492 
493   return K;
494 }
495 
496 
497 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
498 
499   if (Name == ".init_array")
500     return MCSectionELF::SHT_INIT_ARRAY;
501 
502   if (Name == ".fini_array")
503     return MCSectionELF::SHT_FINI_ARRAY;
504 
505   if (Name == ".preinit_array")
506     return MCSectionELF::SHT_PREINIT_ARRAY;
507 
508   if (K.isBSS() || K.isThreadBSS())
509     return MCSectionELF::SHT_NOBITS;
510 
511   return MCSectionELF::SHT_PROGBITS;
512 }
513 
514 
515 static unsigned
516 getELFSectionFlags(SectionKind K) {
517   unsigned Flags = 0;
518 
519   if (!K.isMetadata())
520     Flags |= MCSectionELF::SHF_ALLOC;
521 
522   if (K.isText())
523     Flags |= MCSectionELF::SHF_EXECINSTR;
524 
525   if (K.isWriteable())
526     Flags |= MCSectionELF::SHF_WRITE;
527 
528   if (K.isThreadLocal())
529     Flags |= MCSectionELF::SHF_TLS;
530 
531   // K.isMergeableConst() is left out to honour PR4650
532   if (K.isMergeableCString() || K.isMergeableConst4() ||
533       K.isMergeableConst8() || K.isMergeableConst16())
534     Flags |= MCSectionELF::SHF_MERGE;
535 
536   if (K.isMergeableCString())
537     Flags |= MCSectionELF::SHF_STRINGS;
538 
539   return Flags;
540 }
541 
542 
543 const MCSection *TargetLoweringObjectFileELF::
544 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
545                          Mangler *Mang, const TargetMachine &TM) const {
546   const char *SectionName = GV->getSection().c_str();
547 
548   // Infer section flags from the section name if we can.
549   Kind = getELFKindForNamedSection(SectionName, Kind);
550 
551   return getELFSection(SectionName,
552                        getELFSectionType(SectionName, Kind),
553                        getELFSectionFlags(Kind), Kind, true);
554 }
555 
556 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) {
557   if (Kind.isText())                 return ".gnu.linkonce.t.";
558   if (Kind.isReadOnly())             return ".gnu.linkonce.r.";
559 
560   if (Kind.isThreadData())           return ".gnu.linkonce.td.";
561   if (Kind.isThreadBSS())            return ".gnu.linkonce.tb.";
562 
563   if (Kind.isBSS())                  return ".gnu.linkonce.b.";
564   if (Kind.isDataNoRel())            return ".gnu.linkonce.d.";
565   if (Kind.isDataRelLocal())         return ".gnu.linkonce.d.rel.local.";
566   if (Kind.isDataRel())              return ".gnu.linkonce.d.rel.";
567   if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local.";
568 
569   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
570   return ".gnu.linkonce.d.rel.ro.";
571 }
572 
573 const MCSection *TargetLoweringObjectFileELF::
574 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
575                        Mangler *Mang, const TargetMachine &TM) const {
576 
577   // If this global is linkonce/weak and the target handles this by emitting it
578   // into a 'uniqued' section name, create and return the section now.
579   if (GV->isWeakForLinker()) {
580     const char *Prefix = getSectionPrefixForUniqueGlobal(Kind);
581     SmallString<128> Name, MangledName;
582     Name.append(Prefix, Prefix+strlen(Prefix));
583     Mang->getNameWithPrefix(Name, GV, false);
584 
585     raw_svector_ostream OS(MangledName);
586     MCSymbol::printMangledName(Name, OS, 0);
587     OS.flush();
588 
589     return getELFSection(MangledName.str(),
590                          getELFSectionType(MangledName.str(), Kind),
591                          getELFSectionFlags(Kind),
592                          Kind);
593   }
594 
595   if (Kind.isText()) return TextSection;
596 
597   if (Kind.isMergeable1ByteCString() ||
598       Kind.isMergeable2ByteCString() ||
599       Kind.isMergeable4ByteCString()) {
600 
601     // We also need alignment here.
602     // FIXME: this is getting the alignment of the character, not the
603     // alignment of the global!
604     unsigned Align =
605       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
606 
607     const char *SizeSpec = ".rodata.str1.";
608     if (Kind.isMergeable2ByteCString())
609       SizeSpec = ".rodata.str2.";
610     else if (Kind.isMergeable4ByteCString())
611       SizeSpec = ".rodata.str4.";
612     else
613       assert(Kind.isMergeable1ByteCString() && "unknown string width");
614 
615 
616     std::string Name = SizeSpec + utostr(Align);
617     return getELFSection(Name.c_str(), MCSectionELF::SHT_PROGBITS,
618                          MCSectionELF::SHF_ALLOC |
619                          MCSectionELF::SHF_MERGE |
620                          MCSectionELF::SHF_STRINGS,
621                          Kind);
622   }
623 
624   if (Kind.isMergeableConst()) {
625     if (Kind.isMergeableConst4() && MergeableConst4Section)
626       return MergeableConst4Section;
627     if (Kind.isMergeableConst8() && MergeableConst8Section)
628       return MergeableConst8Section;
629     if (Kind.isMergeableConst16() && MergeableConst16Section)
630       return MergeableConst16Section;
631     return ReadOnlySection;  // .const
632   }
633 
634   if (Kind.isReadOnly())             return ReadOnlySection;
635 
636   if (Kind.isThreadData())           return TLSDataSection;
637   if (Kind.isThreadBSS())            return TLSBSSSection;
638 
639   if (Kind.isBSS())                  return BSSSection;
640 
641   if (Kind.isDataNoRel())            return DataSection;
642   if (Kind.isDataRelLocal())         return DataRelLocalSection;
643   if (Kind.isDataRel())              return DataRelSection;
644   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
645 
646   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
647   return DataRelROSection;
648 }
649 
650 /// getSectionForConstant - Given a mergeable constant with the
651 /// specified size and relocation information, return a section that it
652 /// should be placed in.
653 const MCSection *TargetLoweringObjectFileELF::
654 getSectionForConstant(SectionKind Kind) const {
655   if (Kind.isMergeableConst4() && MergeableConst4Section)
656     return MergeableConst4Section;
657   if (Kind.isMergeableConst8() && MergeableConst8Section)
658     return MergeableConst8Section;
659   if (Kind.isMergeableConst16() && MergeableConst16Section)
660     return MergeableConst16Section;
661   if (Kind.isReadOnly())
662     return ReadOnlySection;
663 
664   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
665   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
666   return DataRelROSection;
667 }
668 
669 //===----------------------------------------------------------------------===//
670 //                                 MachO
671 //===----------------------------------------------------------------------===//
672 
673 typedef StringMap<const MCSectionMachO*> MachOUniqueMapTy;
674 
675 TargetLoweringObjectFileMachO::~TargetLoweringObjectFileMachO() {
676   // If we have the MachO uniquing map, free it.
677   delete (MachOUniqueMapTy*)UniquingMap;
678 }
679 
680 
681 const MCSectionMachO *TargetLoweringObjectFileMachO::
682 getMachOSection(StringRef Segment, StringRef Section,
683                 unsigned TypeAndAttributes,
684                 unsigned Reserved2, SectionKind Kind) const {
685   // We unique sections by their segment/section pair.  The returned section
686   // may not have the same flags as the requested section, if so this should be
687   // diagnosed by the client as an error.
688 
689   // Create the map if it doesn't already exist.
690   if (UniquingMap == 0)
691     UniquingMap = new MachOUniqueMapTy();
692   MachOUniqueMapTy &Map = *(MachOUniqueMapTy*)UniquingMap;
693 
694   // Form the name to look up.
695   SmallString<64> Name;
696   Name += Segment;
697   Name.push_back(',');
698   Name += Section;
699 
700   // Do the lookup, if we have a hit, return it.
701   const MCSectionMachO *&Entry = Map[Name.str()];
702   if (Entry) return Entry;
703 
704   // Otherwise, return a new section.
705   return Entry = MCSectionMachO::Create(Segment, Section, TypeAndAttributes,
706                                         Reserved2, Kind, getContext());
707 }
708 
709 
710 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
711                                                const TargetMachine &TM) {
712   if (UniquingMap != 0)
713     ((MachOUniqueMapTy*)UniquingMap)->clear();
714   TargetLoweringObjectFile::Initialize(Ctx, TM);
715 
716   TextSection // .text
717     = getMachOSection("__TEXT", "__text",
718                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
719                       SectionKind::getText());
720   DataSection // .data
721     = getMachOSection("__DATA", "__data", 0, SectionKind::getDataRel());
722 
723   CStringSection // .cstring
724     = getMachOSection("__TEXT", "__cstring", MCSectionMachO::S_CSTRING_LITERALS,
725                       SectionKind::getMergeable1ByteCString());
726   UStringSection
727     = getMachOSection("__TEXT","__ustring", 0,
728                       SectionKind::getMergeable2ByteCString());
729   FourByteConstantSection // .literal4
730     = getMachOSection("__TEXT", "__literal4", MCSectionMachO::S_4BYTE_LITERALS,
731                       SectionKind::getMergeableConst4());
732   EightByteConstantSection // .literal8
733     = getMachOSection("__TEXT", "__literal8", MCSectionMachO::S_8BYTE_LITERALS,
734                       SectionKind::getMergeableConst8());
735 
736   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
737   // to using it in -static mode.
738   SixteenByteConstantSection = 0;
739   if (TM.getRelocationModel() != Reloc::Static &&
740       TM.getTargetData()->getPointerSize() == 32)
741     SixteenByteConstantSection =   // .literal16
742       getMachOSection("__TEXT", "__literal16",MCSectionMachO::S_16BYTE_LITERALS,
743                       SectionKind::getMergeableConst16());
744 
745   ReadOnlySection  // .const
746     = getMachOSection("__TEXT", "__const", 0, SectionKind::getReadOnly());
747 
748   TextCoalSection
749     = getMachOSection("__TEXT", "__textcoal_nt",
750                       MCSectionMachO::S_COALESCED |
751                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
752                       SectionKind::getText());
753   ConstTextCoalSection
754     = getMachOSection("__TEXT", "__const_coal", MCSectionMachO::S_COALESCED,
755                       SectionKind::getText());
756   ConstDataCoalSection
757     = getMachOSection("__DATA","__const_coal", MCSectionMachO::S_COALESCED,
758                       SectionKind::getText());
759   ConstDataSection  // .const_data
760     = getMachOSection("__DATA", "__const", 0,
761                       SectionKind::getReadOnlyWithRel());
762   DataCoalSection
763     = getMachOSection("__DATA","__datacoal_nt", MCSectionMachO::S_COALESCED,
764                       SectionKind::getDataRel());
765 
766 
767   LazySymbolPointerSection
768     = getMachOSection("__DATA", "__la_symbol_ptr",
769                       MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
770                       SectionKind::getMetadata());
771   NonLazySymbolPointerSection
772     = getMachOSection("__DATA", "__nl_symbol_ptr",
773                       MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
774                       SectionKind::getMetadata());
775 
776   if (TM.getRelocationModel() == Reloc::Static) {
777     StaticCtorSection
778       = getMachOSection("__TEXT", "__constructor", 0,SectionKind::getDataRel());
779     StaticDtorSection
780       = getMachOSection("__TEXT", "__destructor", 0, SectionKind::getDataRel());
781   } else {
782     StaticCtorSection
783       = getMachOSection("__DATA", "__mod_init_func",
784                         MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
785                         SectionKind::getDataRel());
786     StaticDtorSection
787       = getMachOSection("__DATA", "__mod_term_func",
788                         MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
789                         SectionKind::getDataRel());
790   }
791 
792   // Exception Handling.
793   LSDASection = getMachOSection("__DATA", "__gcc_except_tab", 0,
794                                 SectionKind::getDataRel());
795   EHFrameSection =
796     getMachOSection("__TEXT", "__eh_frame",
797                     MCSectionMachO::S_COALESCED |
798                     MCSectionMachO::S_ATTR_NO_TOC |
799                     MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
800                     MCSectionMachO::S_ATTR_LIVE_SUPPORT,
801                     SectionKind::getReadOnly());
802 
803   // Debug Information.
804   DwarfAbbrevSection =
805     getMachOSection("__DWARF", "__debug_abbrev", MCSectionMachO::S_ATTR_DEBUG,
806                     SectionKind::getMetadata());
807   DwarfInfoSection =
808     getMachOSection("__DWARF", "__debug_info", MCSectionMachO::S_ATTR_DEBUG,
809                     SectionKind::getMetadata());
810   DwarfLineSection =
811     getMachOSection("__DWARF", "__debug_line", MCSectionMachO::S_ATTR_DEBUG,
812                     SectionKind::getMetadata());
813   DwarfFrameSection =
814     getMachOSection("__DWARF", "__debug_frame", MCSectionMachO::S_ATTR_DEBUG,
815                     SectionKind::getMetadata());
816   DwarfPubNamesSection =
817     getMachOSection("__DWARF", "__debug_pubnames", MCSectionMachO::S_ATTR_DEBUG,
818                     SectionKind::getMetadata());
819   DwarfPubTypesSection =
820     getMachOSection("__DWARF", "__debug_pubtypes", MCSectionMachO::S_ATTR_DEBUG,
821                     SectionKind::getMetadata());
822   DwarfStrSection =
823     getMachOSection("__DWARF", "__debug_str", MCSectionMachO::S_ATTR_DEBUG,
824                     SectionKind::getMetadata());
825   DwarfLocSection =
826     getMachOSection("__DWARF", "__debug_loc", MCSectionMachO::S_ATTR_DEBUG,
827                     SectionKind::getMetadata());
828   DwarfARangesSection =
829     getMachOSection("__DWARF", "__debug_aranges", MCSectionMachO::S_ATTR_DEBUG,
830                     SectionKind::getMetadata());
831   DwarfRangesSection =
832     getMachOSection("__DWARF", "__debug_ranges", MCSectionMachO::S_ATTR_DEBUG,
833                     SectionKind::getMetadata());
834   DwarfMacroInfoSection =
835     getMachOSection("__DWARF", "__debug_macinfo", MCSectionMachO::S_ATTR_DEBUG,
836                     SectionKind::getMetadata());
837   DwarfDebugInlineSection =
838     getMachOSection("__DWARF", "__debug_inlined", MCSectionMachO::S_ATTR_DEBUG,
839                     SectionKind::getMetadata());
840 }
841 
842 const MCSection *TargetLoweringObjectFileMachO::
843 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
844                          Mangler *Mang, const TargetMachine &TM) const {
845   // Parse the section specifier and create it if valid.
846   StringRef Segment, Section;
847   unsigned TAA, StubSize;
848   std::string ErrorCode =
849     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
850                                           TAA, StubSize);
851   if (!ErrorCode.empty()) {
852     // If invalid, report the error with llvm_report_error.
853     llvm_report_error("Global variable '" + GV->getNameStr() +
854                       "' has an invalid section specifier '" + GV->getSection()+
855                       "': " + ErrorCode + ".");
856     // Fall back to dropping it into the data section.
857     return DataSection;
858   }
859 
860   // Get the section.
861   const MCSectionMachO *S =
862     getMachOSection(Segment, Section, TAA, StubSize, Kind);
863 
864   // Okay, now that we got the section, verify that the TAA & StubSize agree.
865   // If the user declared multiple globals with different section flags, we need
866   // to reject it here.
867   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
868     // If invalid, report the error with llvm_report_error.
869     llvm_report_error("Global variable '" + GV->getNameStr() +
870                       "' section type or attributes does not match previous"
871                       " section specifier");
872   }
873 
874   return S;
875 }
876 
877 const MCSection *TargetLoweringObjectFileMachO::
878 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
879                        Mangler *Mang, const TargetMachine &TM) const {
880   assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
881 
882   if (Kind.isText())
883     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
884 
885   // If this is weak/linkonce, put this in a coalescable section, either in text
886   // or data depending on if it is writable.
887   if (GV->isWeakForLinker()) {
888     if (Kind.isReadOnly())
889       return ConstTextCoalSection;
890     return DataCoalSection;
891   }
892 
893   // FIXME: Alignment check should be handled by section classifier.
894   if (Kind.isMergeable1ByteCString() ||
895       Kind.isMergeable2ByteCString()) {
896     if (TM.getTargetData()->getPreferredAlignment(
897                                               cast<GlobalVariable>(GV)) < 32) {
898       if (Kind.isMergeable1ByteCString())
899         return CStringSection;
900       assert(Kind.isMergeable2ByteCString());
901       return UStringSection;
902     }
903   }
904 
905   if (Kind.isMergeableConst()) {
906     if (Kind.isMergeableConst4())
907       return FourByteConstantSection;
908     if (Kind.isMergeableConst8())
909       return EightByteConstantSection;
910     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
911       return SixteenByteConstantSection;
912   }
913 
914   // Otherwise, if it is readonly, but not something we can specially optimize,
915   // just drop it in .const.
916   if (Kind.isReadOnly())
917     return ReadOnlySection;
918 
919   // If this is marked const, put it into a const section.  But if the dynamic
920   // linker needs to write to it, put it in the data segment.
921   if (Kind.isReadOnlyWithRel())
922     return ConstDataSection;
923 
924   // Otherwise, just drop the variable in the normal data section.
925   return DataSection;
926 }
927 
928 const MCSection *
929 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
930   // If this constant requires a relocation, we have to put it in the data
931   // segment, not in the text segment.
932   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
933     return ConstDataSection;
934 
935   if (Kind.isMergeableConst4())
936     return FourByteConstantSection;
937   if (Kind.isMergeableConst8())
938     return EightByteConstantSection;
939   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
940     return SixteenByteConstantSection;
941   return ReadOnlySection;  // .const
942 }
943 
944 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
945 /// not to emit the UsedDirective for some symbols in llvm.used.
946 // FIXME: REMOVE this (rdar://7071300)
947 bool TargetLoweringObjectFileMachO::
948 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
949   /// On Darwin, internally linked data beginning with "L" or "l" does not have
950   /// the directive emitted (this occurs in ObjC metadata).
951   if (!GV) return false;
952 
953   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
954   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
955     // FIXME: ObjC metadata is currently emitted as internal symbols that have
956     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
957     // this horrible hack can go away.
958     SmallString<64> Name;
959     Mang->getNameWithPrefix(Name, GV, false);
960     if (Name[0] == 'L' || Name[0] == 'l')
961       return false;
962   }
963 
964   return true;
965 }
966 
967 const MCExpr *TargetLoweringObjectFileMachO::
968 getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
969                                  MachineModuleInfo *MMI,
970                                  bool &IsIndirect, bool &IsPCRel) const {
971   // The mach-o version of this method defaults to returning a stub reference.
972   IsIndirect = true;
973   IsPCRel    = false;
974 
975   SmallString<128> Name;
976   Mang->getNameWithPrefix(Name, GV, true);
977   Name += "$non_lazy_ptr";
978   return MCSymbolRefExpr::Create(Name.str(), getContext());
979 }
980 
981 
982 //===----------------------------------------------------------------------===//
983 //                                  COFF
984 //===----------------------------------------------------------------------===//
985 
986 typedef StringMap<const MCSectionCOFF*> COFFUniqueMapTy;
987 
988 TargetLoweringObjectFileCOFF::~TargetLoweringObjectFileCOFF() {
989   delete (COFFUniqueMapTy*)UniquingMap;
990 }
991 
992 
993 const MCSection *TargetLoweringObjectFileCOFF::
994 getCOFFSection(StringRef Name, bool isDirective, SectionKind Kind) const {
995   // Create the map if it doesn't already exist.
996   if (UniquingMap == 0)
997     UniquingMap = new MachOUniqueMapTy();
998   COFFUniqueMapTy &Map = *(COFFUniqueMapTy*)UniquingMap;
999 
1000   // Do the lookup, if we have a hit, return it.
1001   const MCSectionCOFF *&Entry = Map[Name];
1002   if (Entry) return Entry;
1003 
1004   return Entry = MCSectionCOFF::Create(Name, isDirective, Kind, getContext());
1005 }
1006 
1007 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1008                                               const TargetMachine &TM) {
1009   if (UniquingMap != 0)
1010     ((COFFUniqueMapTy*)UniquingMap)->clear();
1011   TargetLoweringObjectFile::Initialize(Ctx, TM);
1012   TextSection = getCOFFSection("\t.text", true, SectionKind::getText());
1013   DataSection = getCOFFSection("\t.data", true, SectionKind::getDataRel());
1014   StaticCtorSection =
1015     getCOFFSection(".ctors", false, SectionKind::getDataRel());
1016   StaticDtorSection =
1017     getCOFFSection(".dtors", false, SectionKind::getDataRel());
1018 
1019   // FIXME: We're emitting LSDA info into a readonly section on COFF, even
1020   // though it contains relocatable pointers.  In PIC mode, this is probably a
1021   // big runtime hit for C++ apps.  Either the contents of the LSDA need to be
1022   // adjusted or this should be a data section.
1023   LSDASection =
1024     getCOFFSection(".gcc_except_table", false, SectionKind::getReadOnly());
1025   EHFrameSection =
1026     getCOFFSection(".eh_frame", false, SectionKind::getDataRel());
1027 
1028   // Debug info.
1029   // FIXME: Don't use 'directive' mode here.
1030   DwarfAbbrevSection =
1031     getCOFFSection("\t.section\t.debug_abbrev,\"dr\"",
1032                    true, SectionKind::getMetadata());
1033   DwarfInfoSection =
1034     getCOFFSection("\t.section\t.debug_info,\"dr\"",
1035                    true, SectionKind::getMetadata());
1036   DwarfLineSection =
1037     getCOFFSection("\t.section\t.debug_line,\"dr\"",
1038                    true, SectionKind::getMetadata());
1039   DwarfFrameSection =
1040     getCOFFSection("\t.section\t.debug_frame,\"dr\"",
1041                    true, SectionKind::getMetadata());
1042   DwarfPubNamesSection =
1043     getCOFFSection("\t.section\t.debug_pubnames,\"dr\"",
1044                    true, SectionKind::getMetadata());
1045   DwarfPubTypesSection =
1046     getCOFFSection("\t.section\t.debug_pubtypes,\"dr\"",
1047                    true, SectionKind::getMetadata());
1048   DwarfStrSection =
1049     getCOFFSection("\t.section\t.debug_str,\"dr\"",
1050                    true, SectionKind::getMetadata());
1051   DwarfLocSection =
1052     getCOFFSection("\t.section\t.debug_loc,\"dr\"",
1053                    true, SectionKind::getMetadata());
1054   DwarfARangesSection =
1055     getCOFFSection("\t.section\t.debug_aranges,\"dr\"",
1056                    true, SectionKind::getMetadata());
1057   DwarfRangesSection =
1058     getCOFFSection("\t.section\t.debug_ranges,\"dr\"",
1059                    true, SectionKind::getMetadata());
1060   DwarfMacroInfoSection =
1061     getCOFFSection("\t.section\t.debug_macinfo,\"dr\"",
1062                    true, SectionKind::getMetadata());
1063 }
1064 
1065 const MCSection *TargetLoweringObjectFileCOFF::
1066 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
1067                          Mangler *Mang, const TargetMachine &TM) const {
1068   return getCOFFSection(GV->getSection().c_str(), false, Kind);
1069 }
1070 
1071 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
1072   if (Kind.isText())
1073     return ".text$linkonce";
1074   if (Kind.isWriteable())
1075     return ".data$linkonce";
1076   return ".rdata$linkonce";
1077 }
1078 
1079 
1080 const MCSection *TargetLoweringObjectFileCOFF::
1081 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
1082                        Mangler *Mang, const TargetMachine &TM) const {
1083   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
1084 
1085   // If this global is linkonce/weak and the target handles this by emitting it
1086   // into a 'uniqued' section name, create and return the section now.
1087   if (GV->isWeakForLinker()) {
1088     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
1089     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
1090     Mang->getNameWithPrefix(Name, GV, false);
1091     return getCOFFSection(Name.str(), false, Kind);
1092   }
1093 
1094   if (Kind.isText())
1095     return getTextSection();
1096 
1097   return getDataSection();
1098 }
1099 
1100