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/Mangler.h"
26 #include "llvm/Target/TargetData.h"
27 #include "llvm/Target/TargetMachine.h"
28 #include "llvm/Target/TargetOptions.h"
29 #include "llvm/Support/ErrorHandling.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   // Variables with common linkage always get classified as common.
145   if (GVar->hasCommonLinkage())
146     return SectionKind::getCommon();
147 
148   // Variable can be easily put to BSS section.
149   if (isSuitableForBSS(GVar))
150     return SectionKind::getBSS();
151 
152   Constant *C = GVar->getInitializer();
153 
154   // If the global is marked constant, we can put it into a mergable section,
155   // a mergable string section, or general .data if it contains relocations.
156   if (GVar->isConstant()) {
157     // If the initializer for the global contains something that requires a
158     // relocation, then we may have to drop this into a wriable data section
159     // even though it is marked const.
160     switch (C->getRelocationInfo()) {
161     default: assert(0 && "unknown relocation info kind");
162     case Constant::NoRelocation:
163       // If initializer is a null-terminated string, put it in a "cstring"
164       // section of the right width.
165       if (const ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) {
166         if (const IntegerType *ITy =
167               dyn_cast<IntegerType>(ATy->getElementType())) {
168           if ((ITy->getBitWidth() == 8 || ITy->getBitWidth() == 16 ||
169                ITy->getBitWidth() == 32) &&
170               IsNullTerminatedString(C)) {
171             if (ITy->getBitWidth() == 8)
172               return SectionKind::getMergeable1ByteCString();
173             if (ITy->getBitWidth() == 16)
174               return SectionKind::getMergeable2ByteCString();
175 
176             assert(ITy->getBitWidth() == 32 && "Unknown width");
177             return SectionKind::getMergeable4ByteCString();
178           }
179         }
180       }
181 
182       // Otherwise, just drop it into a mergable constant section.  If we have
183       // a section for this size, use it, otherwise use the arbitrary sized
184       // mergable section.
185       switch (TM.getTargetData()->getTypeAllocSize(C->getType())) {
186       case 4:  return SectionKind::getMergeableConst4();
187       case 8:  return SectionKind::getMergeableConst8();
188       case 16: return SectionKind::getMergeableConst16();
189       default: return SectionKind::getMergeableConst();
190       }
191 
192     case Constant::LocalRelocation:
193       // In static relocation model, the linker will resolve all addresses, so
194       // the relocation entries will actually be constants by the time the app
195       // starts up.  However, we can't put this into a mergable section, because
196       // the linker doesn't take relocations into consideration when it tries to
197       // merge entries in the section.
198       if (ReloModel == Reloc::Static)
199         return SectionKind::getReadOnly();
200 
201       // Otherwise, the dynamic linker needs to fix it up, put it in the
202       // writable data.rel.local section.
203       return SectionKind::getReadOnlyWithRelLocal();
204 
205     case Constant::GlobalRelocations:
206       // In static relocation model, the linker will resolve all addresses, so
207       // the relocation entries will actually be constants by the time the app
208       // starts up.  However, we can't put this into a mergable section, because
209       // the linker doesn't take relocations into consideration when it tries to
210       // merge entries in the section.
211       if (ReloModel == Reloc::Static)
212         return SectionKind::getReadOnly();
213 
214       // Otherwise, the dynamic linker needs to fix it up, put it in the
215       // writable data.rel section.
216       return SectionKind::getReadOnlyWithRel();
217     }
218   }
219 
220   // Okay, this isn't a constant.  If the initializer for the global is going
221   // to require a runtime relocation by the dynamic linker, put it into a more
222   // specific section to improve startup time of the app.  This coalesces these
223   // globals together onto fewer pages, improving the locality of the dynamic
224   // linker.
225   if (ReloModel == Reloc::Static)
226     return SectionKind::getDataNoRel();
227 
228   switch (C->getRelocationInfo()) {
229   default: assert(0 && "unknown relocation info kind");
230   case Constant::NoRelocation:
231     return SectionKind::getDataNoRel();
232   case Constant::LocalRelocation:
233     return SectionKind::getDataRelLocal();
234   case Constant::GlobalRelocations:
235     return SectionKind::getDataRel();
236   }
237 }
238 
239 /// SectionForGlobal - This method computes the appropriate section to emit
240 /// the specified global variable or function definition.  This should not
241 /// be passed external (or available externally) globals.
242 const MCSection *TargetLoweringObjectFile::
243 SectionForGlobal(const GlobalValue *GV, SectionKind Kind, Mangler *Mang,
244                  const TargetMachine &TM) const {
245   // Select section name.
246   if (GV->hasSection())
247     return getExplicitSectionGlobal(GV, Kind, Mang, TM);
248 
249 
250   // Use default section depending on the 'type' of global
251   return SelectSectionForGlobal(GV, Kind, Mang, TM);
252 }
253 
254 
255 // Lame default implementation. Calculate the section name for global.
256 const MCSection *
257 TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
258                                                  SectionKind Kind,
259                                                  Mangler *Mang,
260                                                  const TargetMachine &TM) const{
261   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
262 
263   if (Kind.isText())
264     return getTextSection();
265 
266   if (Kind.isBSS() && BSSSection != 0)
267     return BSSSection;
268 
269   if (Kind.isReadOnly() && ReadOnlySection != 0)
270     return ReadOnlySection;
271 
272   return getDataSection();
273 }
274 
275 /// getSectionForConstant - Given a mergable constant with the
276 /// specified size and relocation information, return a section that it
277 /// should be placed in.
278 const MCSection *
279 TargetLoweringObjectFile::getSectionForConstant(SectionKind Kind) const {
280   if (Kind.isReadOnly() && ReadOnlySection != 0)
281     return ReadOnlySection;
282 
283   return DataSection;
284 }
285 
286 /// getSymbolForDwarfGlobalReference - Return an MCExpr to use for a
287 /// pc-relative reference to the specified global variable from exception
288 /// handling information.  In addition to the symbol, this returns
289 /// by-reference:
290 ///
291 /// IsIndirect - True if the returned symbol is actually a stub that contains
292 ///    the address of the symbol, false if the symbol is the global itself.
293 ///
294 /// IsPCRel - True if the symbol reference is already pc-relative, false if
295 ///    the caller needs to subtract off the address of the reference from the
296 ///    symbol.
297 ///
298 const MCExpr *TargetLoweringObjectFile::
299 getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
300                                  MachineModuleInfo *MMI,
301                                  bool &IsIndirect, bool &IsPCRel) const {
302   // The generic implementation of this just returns a direct reference to the
303   // symbol.
304   IsIndirect = false;
305   IsPCRel    = false;
306 
307   // FIXME: Use GetGlobalValueSymbol.
308   SmallString<128> Name;
309   Mang->getNameWithPrefix(Name, GV, false);
310   return MCSymbolRefExpr::Create(Name.str(), getContext());
311 }
312 
313 
314 //===----------------------------------------------------------------------===//
315 //                                  ELF
316 //===----------------------------------------------------------------------===//
317 typedef StringMap<const MCSectionELF*> ELFUniqueMapTy;
318 
319 TargetLoweringObjectFileELF::~TargetLoweringObjectFileELF() {
320   // If we have the section uniquing map, free it.
321   delete (ELFUniqueMapTy*)UniquingMap;
322 }
323 
324 const MCSection *TargetLoweringObjectFileELF::
325 getELFSection(StringRef Section, unsigned Type, unsigned Flags,
326               SectionKind Kind, bool IsExplicit) const {
327   if (UniquingMap == 0)
328     UniquingMap = new ELFUniqueMapTy();
329   ELFUniqueMapTy &Map = *(ELFUniqueMapTy*)UniquingMap;
330 
331   // Do the lookup, if we have a hit, return it.
332   const MCSectionELF *&Entry = Map[Section];
333   if (Entry) return Entry;
334 
335   return Entry = MCSectionELF::Create(Section, Type, Flags, Kind, IsExplicit,
336                                       getContext());
337 }
338 
339 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
340                                              const TargetMachine &TM) {
341   if (UniquingMap != 0)
342     ((ELFUniqueMapTy*)UniquingMap)->clear();
343   TargetLoweringObjectFile::Initialize(Ctx, TM);
344 
345   BSSSection =
346     getELFSection(".bss", MCSectionELF::SHT_NOBITS,
347                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
348                   SectionKind::getBSS());
349 
350   TextSection =
351     getELFSection(".text", MCSectionELF::SHT_PROGBITS,
352                   MCSectionELF::SHF_EXECINSTR | MCSectionELF::SHF_ALLOC,
353                   SectionKind::getText());
354 
355   DataSection =
356     getELFSection(".data", MCSectionELF::SHT_PROGBITS,
357                   MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
358                   SectionKind::getDataRel());
359 
360   ReadOnlySection =
361     getELFSection(".rodata", MCSectionELF::SHT_PROGBITS,
362                   MCSectionELF::SHF_ALLOC,
363                   SectionKind::getReadOnly());
364 
365   TLSDataSection =
366     getELFSection(".tdata", MCSectionELF::SHT_PROGBITS,
367                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
368                   MCSectionELF::SHF_WRITE, SectionKind::getThreadData());
369 
370   TLSBSSSection =
371     getELFSection(".tbss", MCSectionELF::SHT_NOBITS,
372                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
373                   MCSectionELF::SHF_WRITE, SectionKind::getThreadBSS());
374 
375   DataRelSection =
376     getELFSection(".data.rel", MCSectionELF::SHT_PROGBITS,
377                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
378                   SectionKind::getDataRel());
379 
380   DataRelLocalSection =
381     getELFSection(".data.rel.local", MCSectionELF::SHT_PROGBITS,
382                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
383                   SectionKind::getDataRelLocal());
384 
385   DataRelROSection =
386     getELFSection(".data.rel.ro", MCSectionELF::SHT_PROGBITS,
387                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
388                   SectionKind::getReadOnlyWithRel());
389 
390   DataRelROLocalSection =
391     getELFSection(".data.rel.ro.local", MCSectionELF::SHT_PROGBITS,
392                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
393                   SectionKind::getReadOnlyWithRelLocal());
394 
395   MergeableConst4Section =
396     getELFSection(".rodata.cst4", MCSectionELF::SHT_PROGBITS,
397                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
398                   SectionKind::getMergeableConst4());
399 
400   MergeableConst8Section =
401     getELFSection(".rodata.cst8", MCSectionELF::SHT_PROGBITS,
402                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
403                   SectionKind::getMergeableConst8());
404 
405   MergeableConst16Section =
406     getELFSection(".rodata.cst16", MCSectionELF::SHT_PROGBITS,
407                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
408                   SectionKind::getMergeableConst16());
409 
410   StaticCtorSection =
411     getELFSection(".ctors", MCSectionELF::SHT_PROGBITS,
412                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
413                   SectionKind::getDataRel());
414 
415   StaticDtorSection =
416     getELFSection(".dtors", MCSectionELF::SHT_PROGBITS,
417                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
418                   SectionKind::getDataRel());
419 
420   // Exception Handling Sections.
421 
422   // FIXME: We're emitting LSDA info into a readonly section on ELF, even though
423   // it contains relocatable pointers.  In PIC mode, this is probably a big
424   // runtime hit for C++ apps.  Either the contents of the LSDA need to be
425   // adjusted or this should be a data section.
426   LSDASection =
427     getELFSection(".gcc_except_table", MCSectionELF::SHT_PROGBITS,
428                   MCSectionELF::SHF_ALLOC, SectionKind::getReadOnly());
429   EHFrameSection =
430     getELFSection(".eh_frame", MCSectionELF::SHT_PROGBITS,
431                   MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
432                   SectionKind::getDataRel());
433 
434   // Debug Info Sections.
435   DwarfAbbrevSection =
436     getELFSection(".debug_abbrev", MCSectionELF::SHT_PROGBITS, 0,
437                   SectionKind::getMetadata());
438   DwarfInfoSection =
439     getELFSection(".debug_info", MCSectionELF::SHT_PROGBITS, 0,
440                   SectionKind::getMetadata());
441   DwarfLineSection =
442     getELFSection(".debug_line", MCSectionELF::SHT_PROGBITS, 0,
443                   SectionKind::getMetadata());
444   DwarfFrameSection =
445     getELFSection(".debug_frame", MCSectionELF::SHT_PROGBITS, 0,
446                   SectionKind::getMetadata());
447   DwarfPubNamesSection =
448     getELFSection(".debug_pubnames", MCSectionELF::SHT_PROGBITS, 0,
449                   SectionKind::getMetadata());
450   DwarfPubTypesSection =
451     getELFSection(".debug_pubtypes", MCSectionELF::SHT_PROGBITS, 0,
452                   SectionKind::getMetadata());
453   DwarfStrSection =
454     getELFSection(".debug_str", MCSectionELF::SHT_PROGBITS, 0,
455                   SectionKind::getMetadata());
456   DwarfLocSection =
457     getELFSection(".debug_loc", MCSectionELF::SHT_PROGBITS, 0,
458                   SectionKind::getMetadata());
459   DwarfARangesSection =
460     getELFSection(".debug_aranges", MCSectionELF::SHT_PROGBITS, 0,
461                   SectionKind::getMetadata());
462   DwarfRangesSection =
463     getELFSection(".debug_ranges", MCSectionELF::SHT_PROGBITS, 0,
464                   SectionKind::getMetadata());
465   DwarfMacroInfoSection =
466     getELFSection(".debug_macinfo", MCSectionELF::SHT_PROGBITS, 0,
467                   SectionKind::getMetadata());
468 }
469 
470 
471 static SectionKind
472 getELFKindForNamedSection(const char *Name, SectionKind K) {
473   if (Name[0] != '.') return K;
474 
475   // Some lame default implementation based on some magic section names.
476   if (strcmp(Name, ".bss") == 0 ||
477       strncmp(Name, ".bss.", 5) == 0 ||
478       strncmp(Name, ".gnu.linkonce.b.", 16) == 0 ||
479       strncmp(Name, ".llvm.linkonce.b.", 17) == 0 ||
480       strcmp(Name, ".sbss") == 0 ||
481       strncmp(Name, ".sbss.", 6) == 0 ||
482       strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 ||
483       strncmp(Name, ".llvm.linkonce.sb.", 18) == 0)
484     return SectionKind::getBSS();
485 
486   if (strcmp(Name, ".tdata") == 0 ||
487       strncmp(Name, ".tdata.", 7) == 0 ||
488       strncmp(Name, ".gnu.linkonce.td.", 17) == 0 ||
489       strncmp(Name, ".llvm.linkonce.td.", 18) == 0)
490     return SectionKind::getThreadData();
491 
492   if (strcmp(Name, ".tbss") == 0 ||
493       strncmp(Name, ".tbss.", 6) == 0 ||
494       strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 ||
495       strncmp(Name, ".llvm.linkonce.tb.", 18) == 0)
496     return SectionKind::getThreadBSS();
497 
498   return K;
499 }
500 
501 
502 static unsigned getELFSectionType(StringRef Name, SectionKind K) {
503 
504   if (Name == ".init_array")
505     return MCSectionELF::SHT_INIT_ARRAY;
506 
507   if (Name == ".fini_array")
508     return MCSectionELF::SHT_FINI_ARRAY;
509 
510   if (Name == ".preinit_array")
511     return MCSectionELF::SHT_PREINIT_ARRAY;
512 
513   if (K.isBSS() || K.isThreadBSS())
514     return MCSectionELF::SHT_NOBITS;
515 
516   return MCSectionELF::SHT_PROGBITS;
517 }
518 
519 
520 static unsigned
521 getELFSectionFlags(SectionKind K) {
522   unsigned Flags = 0;
523 
524   if (!K.isMetadata())
525     Flags |= MCSectionELF::SHF_ALLOC;
526 
527   if (K.isText())
528     Flags |= MCSectionELF::SHF_EXECINSTR;
529 
530   if (K.isWriteable())
531     Flags |= MCSectionELF::SHF_WRITE;
532 
533   if (K.isThreadLocal())
534     Flags |= MCSectionELF::SHF_TLS;
535 
536   // K.isMergeableConst() is left out to honour PR4650
537   if (K.isMergeableCString() || K.isMergeableConst4() ||
538       K.isMergeableConst8() || K.isMergeableConst16())
539     Flags |= MCSectionELF::SHF_MERGE;
540 
541   if (K.isMergeableCString())
542     Flags |= MCSectionELF::SHF_STRINGS;
543 
544   return Flags;
545 }
546 
547 
548 const MCSection *TargetLoweringObjectFileELF::
549 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
550                          Mangler *Mang, const TargetMachine &TM) const {
551   const char *SectionName = GV->getSection().c_str();
552 
553   // Infer section flags from the section name if we can.
554   Kind = getELFKindForNamedSection(SectionName, Kind);
555 
556   return getELFSection(SectionName,
557                        getELFSectionType(SectionName, Kind),
558                        getELFSectionFlags(Kind), Kind, true);
559 }
560 
561 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) {
562   if (Kind.isText())                 return ".gnu.linkonce.t.";
563   if (Kind.isReadOnly())             return ".gnu.linkonce.r.";
564 
565   if (Kind.isThreadData())           return ".gnu.linkonce.td.";
566   if (Kind.isThreadBSS())            return ".gnu.linkonce.tb.";
567 
568   if (Kind.isBSS())                  return ".gnu.linkonce.b.";
569   if (Kind.isDataNoRel())            return ".gnu.linkonce.d.";
570   if (Kind.isDataRelLocal())         return ".gnu.linkonce.d.rel.local.";
571   if (Kind.isDataRel())              return ".gnu.linkonce.d.rel.";
572   if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local.";
573 
574   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
575   return ".gnu.linkonce.d.rel.ro.";
576 }
577 
578 const MCSection *TargetLoweringObjectFileELF::
579 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
580                        Mangler *Mang, const TargetMachine &TM) const {
581 
582   // If this global is linkonce/weak and the target handles this by emitting it
583   // into a 'uniqued' section name, create and return the section now.
584   if (GV->isWeakForLinker() && !Kind.isCommon()) {
585     const char *Prefix = getSectionPrefixForUniqueGlobal(Kind);
586     SmallString<128> Name;
587     Name.append(Prefix, Prefix+strlen(Prefix));
588     Mang->getNameWithPrefix(Name, GV, false);
589     return getELFSection(Name.str(), getELFSectionType(Name.str(), Kind),
590                          getELFSectionFlags(Kind), Kind);
591   }
592 
593   if (Kind.isText()) return TextSection;
594 
595   if (Kind.isMergeable1ByteCString() ||
596       Kind.isMergeable2ByteCString() ||
597       Kind.isMergeable4ByteCString()) {
598 
599     // We also need alignment here.
600     // FIXME: this is getting the alignment of the character, not the
601     // alignment of the global!
602     unsigned Align =
603       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
604 
605     const char *SizeSpec = ".rodata.str1.";
606     if (Kind.isMergeable2ByteCString())
607       SizeSpec = ".rodata.str2.";
608     else if (Kind.isMergeable4ByteCString())
609       SizeSpec = ".rodata.str4.";
610     else
611       assert(Kind.isMergeable1ByteCString() && "unknown string width");
612 
613 
614     std::string Name = SizeSpec + utostr(Align);
615     return getELFSection(Name.c_str(), MCSectionELF::SHT_PROGBITS,
616                          MCSectionELF::SHF_ALLOC |
617                          MCSectionELF::SHF_MERGE |
618                          MCSectionELF::SHF_STRINGS,
619                          Kind);
620   }
621 
622   if (Kind.isMergeableConst()) {
623     if (Kind.isMergeableConst4() && MergeableConst4Section)
624       return MergeableConst4Section;
625     if (Kind.isMergeableConst8() && MergeableConst8Section)
626       return MergeableConst8Section;
627     if (Kind.isMergeableConst16() && MergeableConst16Section)
628       return MergeableConst16Section;
629     return ReadOnlySection;  // .const
630   }
631 
632   if (Kind.isReadOnly())             return ReadOnlySection;
633 
634   if (Kind.isThreadData())           return TLSDataSection;
635   if (Kind.isThreadBSS())            return TLSBSSSection;
636 
637   if (Kind.isBSS() || Kind.isCommon()) return BSSSection;
638 
639   if (Kind.isDataNoRel())            return DataSection;
640   if (Kind.isDataRelLocal())         return DataRelLocalSection;
641   if (Kind.isDataRel())              return DataRelSection;
642   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
643 
644   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
645   return DataRelROSection;
646 }
647 
648 /// getSectionForConstant - Given a mergeable constant with the
649 /// specified size and relocation information, return a section that it
650 /// should be placed in.
651 const MCSection *TargetLoweringObjectFileELF::
652 getSectionForConstant(SectionKind Kind) const {
653   if (Kind.isMergeableConst4() && MergeableConst4Section)
654     return MergeableConst4Section;
655   if (Kind.isMergeableConst8() && MergeableConst8Section)
656     return MergeableConst8Section;
657   if (Kind.isMergeableConst16() && MergeableConst16Section)
658     return MergeableConst16Section;
659   if (Kind.isReadOnly())
660     return ReadOnlySection;
661 
662   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
663   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
664   return DataRelROSection;
665 }
666 
667 //===----------------------------------------------------------------------===//
668 //                                 MachO
669 //===----------------------------------------------------------------------===//
670 
671 typedef StringMap<const MCSectionMachO*> MachOUniqueMapTy;
672 
673 TargetLoweringObjectFileMachO::~TargetLoweringObjectFileMachO() {
674   // If we have the MachO uniquing map, free it.
675   delete (MachOUniqueMapTy*)UniquingMap;
676 }
677 
678 
679 const MCSectionMachO *TargetLoweringObjectFileMachO::
680 getMachOSection(StringRef Segment, StringRef Section,
681                 unsigned TypeAndAttributes,
682                 unsigned Reserved2, SectionKind Kind) const {
683   // We unique sections by their segment/section pair.  The returned section
684   // may not have the same flags as the requested section, if so this should be
685   // diagnosed by the client as an error.
686 
687   // Create the map if it doesn't already exist.
688   if (UniquingMap == 0)
689     UniquingMap = new MachOUniqueMapTy();
690   MachOUniqueMapTy &Map = *(MachOUniqueMapTy*)UniquingMap;
691 
692   // Form the name to look up.
693   SmallString<64> Name;
694   Name += Segment;
695   Name.push_back(',');
696   Name += Section;
697 
698   // Do the lookup, if we have a hit, return it.
699   const MCSectionMachO *&Entry = Map[Name.str()];
700   if (Entry) return Entry;
701 
702   // Otherwise, return a new section.
703   return Entry = MCSectionMachO::Create(Segment, Section, TypeAndAttributes,
704                                         Reserved2, Kind, getContext());
705 }
706 
707 
708 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
709                                                const TargetMachine &TM) {
710   if (UniquingMap != 0)
711     ((MachOUniqueMapTy*)UniquingMap)->clear();
712   TargetLoweringObjectFile::Initialize(Ctx, TM);
713 
714   TextSection // .text
715     = getMachOSection("__TEXT", "__text",
716                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
717                       SectionKind::getText());
718   DataSection // .data
719     = getMachOSection("__DATA", "__data", 0, SectionKind::getDataRel());
720 
721   CStringSection // .cstring
722     = getMachOSection("__TEXT", "__cstring", MCSectionMachO::S_CSTRING_LITERALS,
723                       SectionKind::getMergeable1ByteCString());
724   UStringSection
725     = getMachOSection("__TEXT","__ustring", 0,
726                       SectionKind::getMergeable2ByteCString());
727   FourByteConstantSection // .literal4
728     = getMachOSection("__TEXT", "__literal4", MCSectionMachO::S_4BYTE_LITERALS,
729                       SectionKind::getMergeableConst4());
730   EightByteConstantSection // .literal8
731     = getMachOSection("__TEXT", "__literal8", MCSectionMachO::S_8BYTE_LITERALS,
732                       SectionKind::getMergeableConst8());
733 
734   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
735   // to using it in -static mode.
736   SixteenByteConstantSection = 0;
737   if (TM.getRelocationModel() != Reloc::Static &&
738       TM.getTargetData()->getPointerSize() == 32)
739     SixteenByteConstantSection =   // .literal16
740       getMachOSection("__TEXT", "__literal16",MCSectionMachO::S_16BYTE_LITERALS,
741                       SectionKind::getMergeableConst16());
742 
743   ReadOnlySection  // .const
744     = getMachOSection("__TEXT", "__const", 0, SectionKind::getReadOnly());
745 
746   TextCoalSection
747     = getMachOSection("__TEXT", "__textcoal_nt",
748                       MCSectionMachO::S_COALESCED |
749                       MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
750                       SectionKind::getText());
751   ConstTextCoalSection
752     = getMachOSection("__TEXT", "__const_coal", MCSectionMachO::S_COALESCED,
753                       SectionKind::getText());
754   ConstDataCoalSection
755     = getMachOSection("__DATA","__const_coal", MCSectionMachO::S_COALESCED,
756                       SectionKind::getText());
757   DataCommonSection
758     = getMachOSection("__DATA","__common", MCSectionMachO::S_ZEROFILL,
759                       SectionKind::getBSS());
760   ConstDataSection  // .const_data
761     = getMachOSection("__DATA", "__const", 0,
762                       SectionKind::getReadOnlyWithRel());
763   DataCoalSection
764     = getMachOSection("__DATA","__datacoal_nt", MCSectionMachO::S_COALESCED,
765                       SectionKind::getDataRel());
766 
767 
768   LazySymbolPointerSection
769     = getMachOSection("__DATA", "__la_symbol_ptr",
770                       MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
771                       SectionKind::getMetadata());
772   NonLazySymbolPointerSection
773     = getMachOSection("__DATA", "__nl_symbol_ptr",
774                       MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
775                       SectionKind::getMetadata());
776 
777   if (TM.getRelocationModel() == Reloc::Static) {
778     StaticCtorSection
779       = getMachOSection("__TEXT", "__constructor", 0,SectionKind::getDataRel());
780     StaticDtorSection
781       = getMachOSection("__TEXT", "__destructor", 0, SectionKind::getDataRel());
782   } else {
783     StaticCtorSection
784       = getMachOSection("__DATA", "__mod_init_func",
785                         MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
786                         SectionKind::getDataRel());
787     StaticDtorSection
788       = getMachOSection("__DATA", "__mod_term_func",
789                         MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
790                         SectionKind::getDataRel());
791   }
792 
793   // Exception Handling.
794   LSDASection = getMachOSection("__DATA", "__gcc_except_tab", 0,
795                                 SectionKind::getDataRel());
796   EHFrameSection =
797     getMachOSection("__TEXT", "__eh_frame",
798                     MCSectionMachO::S_COALESCED |
799                     MCSectionMachO::S_ATTR_NO_TOC |
800                     MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
801                     MCSectionMachO::S_ATTR_LIVE_SUPPORT,
802                     SectionKind::getReadOnly());
803 
804   // Debug Information.
805   DwarfAbbrevSection =
806     getMachOSection("__DWARF", "__debug_abbrev", MCSectionMachO::S_ATTR_DEBUG,
807                     SectionKind::getMetadata());
808   DwarfInfoSection =
809     getMachOSection("__DWARF", "__debug_info", MCSectionMachO::S_ATTR_DEBUG,
810                     SectionKind::getMetadata());
811   DwarfLineSection =
812     getMachOSection("__DWARF", "__debug_line", MCSectionMachO::S_ATTR_DEBUG,
813                     SectionKind::getMetadata());
814   DwarfFrameSection =
815     getMachOSection("__DWARF", "__debug_frame", MCSectionMachO::S_ATTR_DEBUG,
816                     SectionKind::getMetadata());
817   DwarfPubNamesSection =
818     getMachOSection("__DWARF", "__debug_pubnames", MCSectionMachO::S_ATTR_DEBUG,
819                     SectionKind::getMetadata());
820   DwarfPubTypesSection =
821     getMachOSection("__DWARF", "__debug_pubtypes", MCSectionMachO::S_ATTR_DEBUG,
822                     SectionKind::getMetadata());
823   DwarfStrSection =
824     getMachOSection("__DWARF", "__debug_str", MCSectionMachO::S_ATTR_DEBUG,
825                     SectionKind::getMetadata());
826   DwarfLocSection =
827     getMachOSection("__DWARF", "__debug_loc", MCSectionMachO::S_ATTR_DEBUG,
828                     SectionKind::getMetadata());
829   DwarfARangesSection =
830     getMachOSection("__DWARF", "__debug_aranges", MCSectionMachO::S_ATTR_DEBUG,
831                     SectionKind::getMetadata());
832   DwarfRangesSection =
833     getMachOSection("__DWARF", "__debug_ranges", MCSectionMachO::S_ATTR_DEBUG,
834                     SectionKind::getMetadata());
835   DwarfMacroInfoSection =
836     getMachOSection("__DWARF", "__debug_macinfo", MCSectionMachO::S_ATTR_DEBUG,
837                     SectionKind::getMetadata());
838   DwarfDebugInlineSection =
839     getMachOSection("__DWARF", "__debug_inlined", MCSectionMachO::S_ATTR_DEBUG,
840                     SectionKind::getMetadata());
841 }
842 
843 const MCSection *TargetLoweringObjectFileMachO::
844 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
845                          Mangler *Mang, const TargetMachine &TM) const {
846   // Parse the section specifier and create it if valid.
847   StringRef Segment, Section;
848   unsigned TAA, StubSize;
849   std::string ErrorCode =
850     MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
851                                           TAA, StubSize);
852   if (!ErrorCode.empty()) {
853     // If invalid, report the error with llvm_report_error.
854     llvm_report_error("Global variable '" + GV->getNameStr() +
855                       "' has an invalid section specifier '" + GV->getSection()+
856                       "': " + ErrorCode + ".");
857     // Fall back to dropping it into the data section.
858     return DataSection;
859   }
860 
861   // Get the section.
862   const MCSectionMachO *S =
863     getMachOSection(Segment, Section, TAA, StubSize, Kind);
864 
865   // Okay, now that we got the section, verify that the TAA & StubSize agree.
866   // If the user declared multiple globals with different section flags, we need
867   // to reject it here.
868   if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
869     // If invalid, report the error with llvm_report_error.
870     llvm_report_error("Global variable '" + GV->getNameStr() +
871                       "' section type or attributes does not match previous"
872                       " section specifier");
873   }
874 
875   return S;
876 }
877 
878 const MCSection *TargetLoweringObjectFileMachO::
879 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
880                        Mangler *Mang, const TargetMachine &TM) const {
881   assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
882 
883   if (Kind.isText())
884     return GV->isWeakForLinker() ? TextCoalSection : TextSection;
885 
886   // If this is weak/linkonce, put this in a coalescable section, either in text
887   // or data depending on if it is writable.
888   if (GV->isWeakForLinker()) {
889     if (Kind.isReadOnly())
890       return ConstTextCoalSection;
891     return DataCoalSection;
892   }
893 
894   // FIXME: Alignment check should be handled by section classifier.
895   if (Kind.isMergeable1ByteCString() ||
896       Kind.isMergeable2ByteCString()) {
897     if (TM.getTargetData()->getPreferredAlignment(
898                                               cast<GlobalVariable>(GV)) < 32) {
899       if (Kind.isMergeable1ByteCString())
900         return CStringSection;
901       assert(Kind.isMergeable2ByteCString());
902       return UStringSection;
903     }
904   }
905 
906   if (Kind.isMergeableConst()) {
907     if (Kind.isMergeableConst4())
908       return FourByteConstantSection;
909     if (Kind.isMergeableConst8())
910       return EightByteConstantSection;
911     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
912       return SixteenByteConstantSection;
913   }
914 
915   // Otherwise, if it is readonly, but not something we can specially optimize,
916   // just drop it in .const.
917   if (Kind.isReadOnly())
918     return ReadOnlySection;
919 
920   // If this is marked const, put it into a const section.  But if the dynamic
921   // linker needs to write to it, put it in the data segment.
922   if (Kind.isReadOnlyWithRel())
923     return ConstDataSection;
924 
925   // Put zero initialized globals with strong external linkage in the
926   // DATA, __common section with the .zerofill directive.
927   if (Kind.isBSS() && GV->hasExternalLinkage())
928     return DataCommonSection;
929 
930   // Otherwise, just drop the variable in the normal data section.
931   return DataSection;
932 }
933 
934 const MCSection *
935 TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind) const {
936   // If this constant requires a relocation, we have to put it in the data
937   // segment, not in the text segment.
938   if (Kind.isDataRel() || Kind.isReadOnlyWithRel())
939     return ConstDataSection;
940 
941   if (Kind.isMergeableConst4())
942     return FourByteConstantSection;
943   if (Kind.isMergeableConst8())
944     return EightByteConstantSection;
945   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
946     return SixteenByteConstantSection;
947   return ReadOnlySection;  // .const
948 }
949 
950 /// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
951 /// not to emit the UsedDirective for some symbols in llvm.used.
952 // FIXME: REMOVE this (rdar://7071300)
953 bool TargetLoweringObjectFileMachO::
954 shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
955   /// On Darwin, internally linked data beginning with "L" or "l" does not have
956   /// the directive emitted (this occurs in ObjC metadata).
957   if (!GV) return false;
958 
959   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
960   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
961     // FIXME: ObjC metadata is currently emitted as internal symbols that have
962     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
963     // this horrible hack can go away.
964     SmallString<64> Name;
965     Mang->getNameWithPrefix(Name, GV, false);
966     if (Name[0] == 'L' || Name[0] == 'l')
967       return false;
968   }
969 
970   return true;
971 }
972 
973 const MCExpr *TargetLoweringObjectFileMachO::
974 getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
975                                  MachineModuleInfo *MMI,
976                                  bool &IsIndirect, bool &IsPCRel) const {
977   // The mach-o version of this method defaults to returning a stub reference.
978   IsIndirect = true;
979   IsPCRel    = false;
980 
981   SmallString<128> Name;
982   Mang->getNameWithPrefix(Name, GV, true);
983   Name += "$non_lazy_ptr";
984   return MCSymbolRefExpr::Create(Name.str(), getContext());
985 }
986 
987 
988 //===----------------------------------------------------------------------===//
989 //                                  COFF
990 //===----------------------------------------------------------------------===//
991 
992 typedef StringMap<const MCSectionCOFF*> COFFUniqueMapTy;
993 
994 TargetLoweringObjectFileCOFF::~TargetLoweringObjectFileCOFF() {
995   delete (COFFUniqueMapTy*)UniquingMap;
996 }
997 
998 
999 const MCSection *TargetLoweringObjectFileCOFF::
1000 getCOFFSection(StringRef Name, bool isDirective, SectionKind Kind) const {
1001   // Create the map if it doesn't already exist.
1002   if (UniquingMap == 0)
1003     UniquingMap = new MachOUniqueMapTy();
1004   COFFUniqueMapTy &Map = *(COFFUniqueMapTy*)UniquingMap;
1005 
1006   // Do the lookup, if we have a hit, return it.
1007   const MCSectionCOFF *&Entry = Map[Name];
1008   if (Entry) return Entry;
1009 
1010   return Entry = MCSectionCOFF::Create(Name, isDirective, Kind, getContext());
1011 }
1012 
1013 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
1014                                               const TargetMachine &TM) {
1015   if (UniquingMap != 0)
1016     ((COFFUniqueMapTy*)UniquingMap)->clear();
1017   TargetLoweringObjectFile::Initialize(Ctx, TM);
1018   TextSection = getCOFFSection("\t.text", true, SectionKind::getText());
1019   DataSection = getCOFFSection("\t.data", true, SectionKind::getDataRel());
1020   StaticCtorSection =
1021     getCOFFSection(".ctors", false, SectionKind::getDataRel());
1022   StaticDtorSection =
1023     getCOFFSection(".dtors", false, SectionKind::getDataRel());
1024 
1025   // FIXME: We're emitting LSDA info into a readonly section on COFF, even
1026   // though it contains relocatable pointers.  In PIC mode, this is probably a
1027   // big runtime hit for C++ apps.  Either the contents of the LSDA need to be
1028   // adjusted or this should be a data section.
1029   LSDASection =
1030     getCOFFSection(".gcc_except_table", false, SectionKind::getReadOnly());
1031   EHFrameSection =
1032     getCOFFSection(".eh_frame", false, SectionKind::getDataRel());
1033 
1034   // Debug info.
1035   // FIXME: Don't use 'directive' mode here.
1036   DwarfAbbrevSection =
1037     getCOFFSection("\t.section\t.debug_abbrev,\"dr\"",
1038                    true, SectionKind::getMetadata());
1039   DwarfInfoSection =
1040     getCOFFSection("\t.section\t.debug_info,\"dr\"",
1041                    true, SectionKind::getMetadata());
1042   DwarfLineSection =
1043     getCOFFSection("\t.section\t.debug_line,\"dr\"",
1044                    true, SectionKind::getMetadata());
1045   DwarfFrameSection =
1046     getCOFFSection("\t.section\t.debug_frame,\"dr\"",
1047                    true, SectionKind::getMetadata());
1048   DwarfPubNamesSection =
1049     getCOFFSection("\t.section\t.debug_pubnames,\"dr\"",
1050                    true, SectionKind::getMetadata());
1051   DwarfPubTypesSection =
1052     getCOFFSection("\t.section\t.debug_pubtypes,\"dr\"",
1053                    true, SectionKind::getMetadata());
1054   DwarfStrSection =
1055     getCOFFSection("\t.section\t.debug_str,\"dr\"",
1056                    true, SectionKind::getMetadata());
1057   DwarfLocSection =
1058     getCOFFSection("\t.section\t.debug_loc,\"dr\"",
1059                    true, SectionKind::getMetadata());
1060   DwarfARangesSection =
1061     getCOFFSection("\t.section\t.debug_aranges,\"dr\"",
1062                    true, SectionKind::getMetadata());
1063   DwarfRangesSection =
1064     getCOFFSection("\t.section\t.debug_ranges,\"dr\"",
1065                    true, SectionKind::getMetadata());
1066   DwarfMacroInfoSection =
1067     getCOFFSection("\t.section\t.debug_macinfo,\"dr\"",
1068                    true, SectionKind::getMetadata());
1069 }
1070 
1071 const MCSection *TargetLoweringObjectFileCOFF::
1072 getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
1073                          Mangler *Mang, const TargetMachine &TM) const {
1074   return getCOFFSection(GV->getSection().c_str(), false, Kind);
1075 }
1076 
1077 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
1078   if (Kind.isText())
1079     return ".text$linkonce";
1080   if (Kind.isWriteable())
1081     return ".data$linkonce";
1082   return ".rdata$linkonce";
1083 }
1084 
1085 
1086 const MCSection *TargetLoweringObjectFileCOFF::
1087 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
1088                        Mangler *Mang, const TargetMachine &TM) const {
1089   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
1090 
1091   // If this global is linkonce/weak and the target handles this by emitting it
1092   // into a 'uniqued' section name, create and return the section now.
1093   if (GV->isWeakForLinker()) {
1094     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
1095     SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
1096     Mang->getNameWithPrefix(Name, GV, false);
1097     return getCOFFSection(Name.str(), false, Kind);
1098   }
1099 
1100   if (Kind.isText())
1101     return getTextSection();
1102 
1103   return getDataSection();
1104 }
1105 
1106