xref: /llvm-project/llvm/lib/Target/TargetLoweringObjectFile.cpp (revision 51d5b43cda213e3cac83700e39e47657c55fd362)
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/GlobalVariable.h"
19 #include "llvm/Support/Mangler.h"
20 #include "llvm/Target/TargetMachine.h"
21 #include "llvm/Target/TargetData.h"
22 #include "llvm/Target/TargetOptions.h"
23 #include "llvm/ADT/StringExtras.h"
24 using namespace llvm;
25 
26 //===----------------------------------------------------------------------===//
27 //                              Generic Code
28 //===----------------------------------------------------------------------===//
29 
30 TargetLoweringObjectFile::TargetLoweringObjectFile() {
31   TextSection = 0;
32   DataSection = 0;
33   BSSSection_ = 0;
34   ReadOnlySection = 0;
35   TLSDataSection = 0;
36   TLSBSSSection = 0;
37   CStringSection_ = 0;
38 }
39 
40 TargetLoweringObjectFile::~TargetLoweringObjectFile() {
41 }
42 
43 static bool isSuitableForBSS(const GlobalVariable *GV) {
44   Constant *C = GV->getInitializer();
45 
46   // Must have zero initializer.
47   if (!C->isNullValue())
48     return false;
49 
50   // Leave constant zeros in readonly constant sections, so they can be shared.
51   if (GV->isConstant())
52     return false;
53 
54   // If the global has an explicit section specified, don't put it in BSS.
55   if (!GV->getSection().empty())
56     return false;
57 
58   // If -nozero-initialized-in-bss is specified, don't ever use BSS.
59   if (NoZerosInBSS)
60     return false;
61 
62   // Otherwise, put it in BSS!
63   return true;
64 }
65 
66 static bool isConstantString(const Constant *C) {
67   // First check: is we have constant array of i8 terminated with zero
68   const ConstantArray *CVA = dyn_cast<ConstantArray>(C);
69   // Check, if initializer is a null-terminated string
70   if (CVA && CVA->isCString())
71     return true;
72 
73   // Another possibility: [1 x i8] zeroinitializer
74   if (isa<ConstantAggregateZero>(C))
75     if (const ArrayType *Ty = dyn_cast<ArrayType>(C->getType()))
76       return (Ty->getElementType() == Type::Int8Ty &&
77               Ty->getNumElements() == 1);
78 
79   return false;
80 }
81 
82 static SectionKind::Kind SectionKindForGlobal(const GlobalValue *GV,
83                                               const TargetMachine &TM) {
84   Reloc::Model ReloModel = TM.getRelocationModel();
85 
86   // Early exit - functions should be always in text sections.
87   const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
88   if (GVar == 0)
89     return SectionKind::Text;
90 
91 
92   // Handle thread-local data first.
93   if (GVar->isThreadLocal()) {
94     if (isSuitableForBSS(GVar))
95       return SectionKind::ThreadBSS;
96     return SectionKind::ThreadData;
97   }
98 
99   // Variable can be easily put to BSS section.
100   if (isSuitableForBSS(GVar))
101     return SectionKind::BSS;
102 
103   Constant *C = GVar->getInitializer();
104 
105   // If the global is marked constant, we can put it into a mergable section,
106   // a mergable string section, or general .data if it contains relocations.
107   if (GVar->isConstant()) {
108     // If the initializer for the global contains something that requires a
109     // relocation, then we may have to drop this into a wriable data section
110     // even though it is marked const.
111     switch (C->getRelocationInfo()) {
112     default: llvm_unreachable("unknown relocation info kind");
113     case Constant::NoRelocation:
114       // If initializer is a null-terminated string, put it in a "cstring"
115       // section if the target has it.
116       if (isConstantString(C))
117         return SectionKind::MergeableCString;
118 
119       // Otherwise, just drop it into a mergable constant section.  If we have
120       // a section for this size, use it, otherwise use the arbitrary sized
121       // mergable section.
122       switch (TM.getTargetData()->getTypeAllocSize(C->getType())) {
123       case 4:  return SectionKind::MergeableConst4;
124       case 8:  return SectionKind::MergeableConst8;
125       case 16: return SectionKind::MergeableConst16;
126       default: return SectionKind::MergeableConst;
127       }
128 
129     case Constant::LocalRelocation:
130       // In static relocation model, the linker will resolve all addresses, so
131       // the relocation entries will actually be constants by the time the app
132       // starts up.  However, we can't put this into a mergable section, because
133       // the linker doesn't take relocations into consideration when it tries to
134       // merge entries in the section.
135       if (ReloModel == Reloc::Static)
136         return SectionKind::ReadOnly;
137 
138       // Otherwise, the dynamic linker needs to fix it up, put it in the
139       // writable data.rel.local section.
140       return SectionKind::ReadOnlyWithRelLocal;
141 
142     case Constant::GlobalRelocations:
143       // In static relocation model, the linker will resolve all addresses, so
144       // the relocation entries will actually be constants by the time the app
145       // starts up.  However, we can't put this into a mergable section, because
146       // the linker doesn't take relocations into consideration when it tries to
147       // merge entries in the section.
148       if (ReloModel == Reloc::Static)
149         return SectionKind::ReadOnly;
150 
151       // Otherwise, the dynamic linker needs to fix it up, put it in the
152       // writable data.rel section.
153       return SectionKind::ReadOnlyWithRel;
154     }
155   }
156 
157   // Okay, this isn't a constant.  If the initializer for the global is going
158   // to require a runtime relocation by the dynamic linker, put it into a more
159   // specific section to improve startup time of the app.  This coalesces these
160   // globals together onto fewer pages, improving the locality of the dynamic
161   // linker.
162   if (ReloModel == Reloc::Static)
163     return SectionKind::DataNoRel;
164 
165   switch (C->getRelocationInfo()) {
166   default: llvm_unreachable("unknown relocation info kind");
167   case Constant::NoRelocation:
168     return SectionKind::DataNoRel;
169   case Constant::LocalRelocation:
170     return SectionKind::DataRelLocal;
171   case Constant::GlobalRelocations:
172     return SectionKind::DataRel;
173   }
174 }
175 
176 /// SectionForGlobal - This method computes the appropriate section to emit
177 /// the specified global variable or function definition.  This should not
178 /// be passed external (or available externally) globals.
179 const Section *TargetLoweringObjectFile::
180 SectionForGlobal(const GlobalValue *GV, Mangler *Mang,
181                  const TargetMachine &TM) const {
182   assert(!GV->isDeclaration() && !GV->hasAvailableExternallyLinkage() &&
183          "Can only be used for global definitions");
184 
185   SectionKind::Kind GVKind = SectionKindForGlobal(GV, TM);
186 
187   SectionKind Kind = SectionKind::get(GVKind, GV->isWeakForLinker(),
188                                       GV->hasSection());
189 
190 
191   // Select section name.
192   if (GV->hasSection()) {
193     // If the target has special section hacks for specifically named globals,
194     // return them now.
195     if (const Section *TS = getSpecialCasedSectionGlobals(GV, Mang, Kind))
196       return TS;
197 
198     // If the target has magic semantics for certain section names, make sure to
199     // pick up the flags.  This allows the user to write things with attribute
200     // section and still get the appropriate section flags printed.
201     GVKind = getKindForNamedSection(GV->getSection().c_str(), GVKind);
202 
203     return getOrCreateSection(GV->getSection().c_str(), false, GVKind);
204   }
205 
206 
207   // Use default section depending on the 'type' of global
208   return SelectSectionForGlobal(GV, Kind, Mang, TM);
209 }
210 
211 // Lame default implementation. Calculate the section name for global.
212 const Section*
213 TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
214                                                  SectionKind Kind,
215                                                  Mangler *Mang,
216                                                  const TargetMachine &TM) const{
217   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
218 
219   if (Kind.isText())
220     return getTextSection();
221 
222   if (Kind.isBSS() && BSSSection_ != 0)
223     return BSSSection_;
224 
225   if (Kind.isReadOnly() && ReadOnlySection != 0)
226     return ReadOnlySection;
227 
228   return getDataSection();
229 }
230 
231 /// getSectionForMergableConstant - Given a mergable constant with the
232 /// specified size and relocation information, return a section that it
233 /// should be placed in.
234 const Section *
235 TargetLoweringObjectFile::
236 getSectionForMergeableConstant(SectionKind Kind) const {
237   if (Kind.isReadOnly() && ReadOnlySection != 0)
238     return ReadOnlySection;
239 
240   return DataSection;
241 }
242 
243 
244 const Section *TargetLoweringObjectFile::
245 getOrCreateSection(const char *Name, bool isDirective,
246                    SectionKind::Kind Kind) const {
247   Section &S = Sections[Name];
248 
249   // This is newly-created section, set it up properly.
250   if (S.Name.empty()) {
251     S.Kind = SectionKind::get(Kind, false /*weak*/, !isDirective);
252     S.Name = Name;
253   }
254 
255   return &S;
256 }
257 
258 
259 
260 //===----------------------------------------------------------------------===//
261 //                                  ELF
262 //===----------------------------------------------------------------------===//
263 
264 void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
265                                              const TargetMachine &TM) {
266   if (!HasCrazyBSS)
267     BSSSection_ = getOrCreateSection("\t.bss", true, SectionKind::BSS);
268   else
269     // PPC/Linux doesn't support the .bss directive, it needs .section .bss.
270     // FIXME: Does .section .bss work everywhere??
271     BSSSection_ = getOrCreateSection("\t.bss", false, SectionKind::BSS);
272 
273 
274   TextSection = getOrCreateSection("\t.text", true, SectionKind::Text);
275   DataSection = getOrCreateSection("\t.data", true, SectionKind::DataRel);
276   ReadOnlySection =
277     getOrCreateSection("\t.rodata", false, SectionKind::ReadOnly);
278   TLSDataSection =
279     getOrCreateSection("\t.tdata", false, SectionKind::ThreadData);
280   CStringSection_ = getOrCreateSection("\t.rodata.str", true,
281                                        SectionKind::MergeableCString);
282 
283   TLSBSSSection = getOrCreateSection("\t.tbss", false, SectionKind::ThreadBSS);
284 
285   DataRelSection = getOrCreateSection("\t.data.rel", false,
286                                       SectionKind::DataRel);
287   DataRelLocalSection = getOrCreateSection("\t.data.rel.local", false,
288                                            SectionKind::DataRelLocal);
289   DataRelROSection = getOrCreateSection("\t.data.rel.ro", false,
290                                         SectionKind::ReadOnlyWithRel);
291   DataRelROLocalSection =
292     getOrCreateSection("\t.data.rel.ro.local", false,
293                        SectionKind::ReadOnlyWithRelLocal);
294 
295   MergeableConst4Section = getOrCreateSection(".rodata.cst4", false,
296                                               SectionKind::MergeableConst4);
297   MergeableConst8Section = getOrCreateSection(".rodata.cst8", false,
298                                               SectionKind::MergeableConst8);
299   MergeableConst16Section = getOrCreateSection(".rodata.cst16", false,
300                                                SectionKind::MergeableConst16);
301 }
302 
303 
304 SectionKind::Kind TargetLoweringObjectFileELF::
305 getKindForNamedSection(const char *Name, SectionKind::Kind K) const {
306   if (Name[0] != '.') return K;
307 
308   // Some lame default implementation based on some magic section names.
309   if (strncmp(Name, ".gnu.linkonce.b.", 16) == 0 ||
310       strncmp(Name, ".llvm.linkonce.b.", 17) == 0 ||
311       strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 ||
312       strncmp(Name, ".llvm.linkonce.sb.", 18) == 0)
313     return SectionKind::BSS;
314 
315   if (strcmp(Name, ".tdata") == 0 ||
316       strncmp(Name, ".tdata.", 7) == 0 ||
317       strncmp(Name, ".gnu.linkonce.td.", 17) == 0 ||
318       strncmp(Name, ".llvm.linkonce.td.", 18) == 0)
319     return SectionKind::ThreadData;
320 
321   if (strcmp(Name, ".tbss") == 0 ||
322       strncmp(Name, ".tbss.", 6) == 0 ||
323       strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 ||
324       strncmp(Name, ".llvm.linkonce.tb.", 18) == 0)
325     return SectionKind::ThreadBSS;
326 
327   return K;
328 }
329 
330 void TargetLoweringObjectFileELF::
331 getSectionFlagsAsString(SectionKind Kind, SmallVectorImpl<char> &Str) const {
332   Str.push_back(',');
333   Str.push_back('"');
334 
335   if (!Kind.isMetadata())
336     Str.push_back('a');
337   if (Kind.isText())
338     Str.push_back('x');
339   if (Kind.isWriteable())
340     Str.push_back('w');
341   if (Kind.isMergeableCString() ||
342       Kind.isMergeableConst4() ||
343       Kind.isMergeableConst8() ||
344       Kind.isMergeableConst16())
345     Str.push_back('M');
346   if (Kind.isMergeableCString())
347     Str.push_back('S');
348   if (Kind.isThreadLocal())
349     Str.push_back('T');
350 
351   Str.push_back('"');
352   Str.push_back(',');
353 
354   // If comment string is '@', e.g. as on ARM - use '%' instead
355   if (AtIsCommentChar)
356     Str.push_back('%');
357   else
358     Str.push_back('@');
359 
360   const char *KindStr;
361   if (Kind.isBSS() || Kind.isThreadBSS())
362     KindStr = "nobits";
363   else
364     KindStr = "progbits";
365 
366   Str.append(KindStr, KindStr+strlen(KindStr));
367 
368   if (Kind.isMergeableCString()) {
369     // TODO: Eventually handle multiple byte character strings.  For now, all
370     // mergable C strings are single byte.
371     Str.push_back(',');
372     Str.push_back('1');
373   } else if (Kind.isMergeableConst4()) {
374     Str.push_back(',');
375     Str.push_back('4');
376   } else if (Kind.isMergeableConst8()) {
377     Str.push_back(',');
378     Str.push_back('8');
379   } else if (Kind.isMergeableConst16()) {
380     Str.push_back(',');
381     Str.push_back('1');
382     Str.push_back('6');
383   }
384 }
385 
386 
387 static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) {
388   if (Kind.isText())                 return ".gnu.linkonce.t.";
389   if (Kind.isReadOnly())             return ".gnu.linkonce.r.";
390 
391   if (Kind.isThreadData())           return ".gnu.linkonce.td.";
392   if (Kind.isThreadBSS())            return ".gnu.linkonce.tb.";
393 
394   if (Kind.isBSS())                  return ".gnu.linkonce.b.";
395   if (Kind.isDataNoRel())            return ".gnu.linkonce.d.";
396   if (Kind.isDataRelLocal())         return ".gnu.linkonce.d.rel.local.";
397   if (Kind.isDataRel())              return ".gnu.linkonce.d.rel.";
398   if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local.";
399 
400   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
401   return ".gnu.linkonce.d.rel.ro.";
402 }
403 
404 const Section *TargetLoweringObjectFileELF::
405 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
406                        Mangler *Mang, const TargetMachine &TM) const {
407 
408   // If this global is linkonce/weak and the target handles this by emitting it
409   // into a 'uniqued' section name, create and return the section now.
410   if (Kind.isWeak()) {
411     const char *Prefix = getSectionPrefixForUniqueGlobal(Kind);
412     std::string Name = Mang->makeNameProper(GV->getNameStr());
413     return getOrCreateSection((Prefix+Name).c_str(), false, Kind.getKind());
414   }
415 
416   if (Kind.isText()) return TextSection;
417 
418   if (Kind.isMergeableCString()) {
419    assert(CStringSection_ && "Should have string section prefix");
420 
421     // We also need alignment here.
422     // FIXME: this is getting the alignment of the character, not the
423     // alignment of the global!
424     unsigned Align =
425       TM.getTargetData()->getPreferredAlignment(cast<GlobalVariable>(GV));
426 
427     std::string Name = CStringSection_->getName() + "1." + utostr(Align);
428     return getOrCreateSection(Name.c_str(), false,
429                               SectionKind::MergeableCString);
430   }
431 
432   if (Kind.isMergeableConst()) {
433     if (Kind.isMergeableConst4())
434       return MergeableConst4Section;
435     if (Kind.isMergeableConst8())
436       return MergeableConst8Section;
437     if (Kind.isMergeableConst16())
438       return MergeableConst16Section;
439     return ReadOnlySection;  // .const
440   }
441 
442   if (Kind.isReadOnly())             return ReadOnlySection;
443 
444   if (Kind.isThreadData())           return TLSDataSection;
445   if (Kind.isThreadBSS())            return TLSBSSSection;
446 
447   if (Kind.isBSS())                  return BSSSection_;
448 
449   if (Kind.isDataNoRel())            return DataSection;
450   if (Kind.isDataRelLocal())         return DataRelLocalSection;
451   if (Kind.isDataRel())              return DataRelSection;
452   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
453 
454   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
455   return DataRelROSection;
456 }
457 
458 /// getSectionForMergeableConstant - Given a mergeable constant with the
459 /// specified size and relocation information, return a section that it
460 /// should be placed in.
461 const Section *TargetLoweringObjectFileELF::
462 getSectionForMergeableConstant(SectionKind Kind) const {
463   if (Kind.isMergeableConst4())
464     return MergeableConst4Section;
465   if (Kind.isMergeableConst8())
466     return MergeableConst8Section;
467   if (Kind.isMergeableConst16())
468     return MergeableConst16Section;
469   if (Kind.isReadOnly())
470     return ReadOnlySection;
471 
472   if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
473   assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
474   return DataRelROSection;
475 }
476 
477 //===----------------------------------------------------------------------===//
478 //                                 MachO
479 //===----------------------------------------------------------------------===//
480 
481 void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
482                                                const TargetMachine &TM) {
483   TextSection = getOrCreateSection("\t.text", true, SectionKind::Text);
484   DataSection = getOrCreateSection("\t.data", true, SectionKind::DataRel);
485 
486   CStringSection_ = getOrCreateSection("\t.cstring", true,
487                                        SectionKind::MergeableCString);
488   FourByteConstantSection = getOrCreateSection("\t.literal4\n", true,
489                                                SectionKind::MergeableConst4);
490   EightByteConstantSection = getOrCreateSection("\t.literal8\n", true,
491                                                 SectionKind::MergeableConst8);
492 
493   // ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
494   // to using it in -static mode.
495   if (TM.getRelocationModel() != Reloc::Static &&
496       TM.getTargetData()->getPointerSize() == 32)
497     SixteenByteConstantSection =
498       getOrCreateSection("\t.literal16\n", true, SectionKind::MergeableConst16);
499   else
500     SixteenByteConstantSection = 0;
501 
502   ReadOnlySection = getOrCreateSection("\t.const", true, SectionKind::ReadOnly);
503 
504   TextCoalSection =
505   getOrCreateSection("\t__TEXT,__textcoal_nt,coalesced,pure_instructions",
506                      false, SectionKind::Text);
507   ConstTextCoalSection = getOrCreateSection("\t__TEXT,__const_coal,coalesced",
508                                             false, SectionKind::Text);
509   ConstDataCoalSection = getOrCreateSection("\t__DATA,__const_coal,coalesced",
510                                             false, SectionKind::Text);
511   ConstDataSection = getOrCreateSection("\t.const_data", true,
512                                         SectionKind::ReadOnlyWithRel);
513   DataCoalSection = getOrCreateSection("\t__DATA,__datacoal_nt,coalesced",
514                                        false, SectionKind::DataRel);
515 }
516 
517 const Section *TargetLoweringObjectFileMachO::
518 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
519                        Mangler *Mang, const TargetMachine &TM) const {
520   assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
521 
522   if (Kind.isText())
523     return Kind.isWeak() ? TextCoalSection : TextSection;
524 
525   // If this is weak/linkonce, put this in a coalescable section, either in text
526   // or data depending on if it is writable.
527   if (Kind.isWeak()) {
528     if (Kind.isReadOnly())
529       return ConstTextCoalSection;
530     return DataCoalSection;
531   }
532 
533   // FIXME: Alignment check should be handled by section classifier.
534   if (Kind.isMergeableCString()) {
535     Constant *C = cast<GlobalVariable>(GV)->getInitializer();
536     const Type *Ty = cast<ArrayType>(C->getType())->getElementType();
537     const TargetData &TD = *TM.getTargetData();
538     unsigned Size = TD.getTypeAllocSize(Ty);
539     if (Size) {
540       unsigned Align = TD.getPreferredAlignment(cast<GlobalVariable>(GV));
541       if (Align <= 32)
542         return CStringSection_;
543     }
544 
545     return ReadOnlySection;
546   }
547 
548   if (Kind.isMergeableConst()) {
549     if (Kind.isMergeableConst4())
550       return FourByteConstantSection;
551     if (Kind.isMergeableConst8())
552       return EightByteConstantSection;
553     if (Kind.isMergeableConst16() && SixteenByteConstantSection)
554       return SixteenByteConstantSection;
555     return ReadOnlySection;  // .const
556   }
557 
558   // FIXME: ROData -> const in -static mode that is relocatable but they happen
559   // by the static linker.  Why not mergeable?
560   if (Kind.isReadOnly())
561     return ReadOnlySection;
562 
563   // If this is marked const, put it into a const section.  But if the dynamic
564   // linker needs to write to it, put it in the data segment.
565   if (Kind.isReadOnlyWithRel())
566     return ConstDataSection;
567 
568   // Otherwise, just drop the variable in the normal data section.
569   return DataSection;
570 }
571 
572 const Section *
573 TargetLoweringObjectFileMachO::
574 getSectionForMergeableConstant(SectionKind Kind) const {
575   // If this constant requires a relocation, we have to put it in the data
576   // segment, not in the text segment.
577   if (Kind.isDataRel())
578     return ConstDataSection;
579 
580   if (Kind.isMergeableConst4())
581     return FourByteConstantSection;
582   if (Kind.isMergeableConst8())
583     return EightByteConstantSection;
584   if (Kind.isMergeableConst16() && SixteenByteConstantSection)
585     return SixteenByteConstantSection;
586   return ReadOnlySection;  // .const
587 }
588 
589 //===----------------------------------------------------------------------===//
590 //                                  COFF
591 //===----------------------------------------------------------------------===//
592 
593 void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
594                                               const TargetMachine &TM) {
595   TextSection = getOrCreateSection("\t.text", true, SectionKind::Text);
596   DataSection = getOrCreateSection("\t.data", true, SectionKind::DataRel);
597 }
598 
599 void TargetLoweringObjectFileCOFF::
600 getSectionFlagsAsString(SectionKind Kind, SmallVectorImpl<char> &Str) const {
601   // FIXME: Inefficient.
602   std::string Res = ",\"";
603   if (Kind.isText())
604     Res += 'x';
605   if (Kind.isWriteable())
606     Res += 'w';
607   Res += "\"";
608 
609   Str.append(Res.begin(), Res.end());
610 }
611 
612 static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
613   if (Kind.isText())
614     return ".text$linkonce";
615   if (Kind.isWriteable())
616     return ".data$linkonce";
617   return ".rdata$linkonce";
618 }
619 
620 
621 const Section *TargetLoweringObjectFileCOFF::
622 SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
623                        Mangler *Mang, const TargetMachine &TM) const {
624   assert(!Kind.isThreadLocal() && "Doesn't support TLS");
625 
626   // If this global is linkonce/weak and the target handles this by emitting it
627   // into a 'uniqued' section name, create and return the section now.
628   if (Kind.isWeak()) {
629     const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
630     // FIXME: Use mangler interface (PR4584).
631     std::string Name = Prefix+GV->getNameStr();
632     return getOrCreateSection(Name.c_str(), false, Kind.getKind());
633   }
634 
635   if (Kind.isText())
636     return getTextSection();
637 
638   if (Kind.isBSS())
639     if (const Section *S = BSSSection_)
640       return S;
641 
642   if (Kind.isReadOnly() && ReadOnlySection != 0)
643     return ReadOnlySection;
644 
645   return getDataSection();
646 }
647 
648