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