xref: /llvm-project/clang/lib/CodeGen/CodeGenModule.cpp (revision 678632fa42f77ac668b5a8d2b6c5307e034d48a1)
1 //===--- CodeGenModule.cpp - Emit LLVM Code from ASTs for a Module --------===//
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 coordinates the per-module state used while generating code.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CodeGenModule.h"
15 #include "CGDebugInfo.h"
16 #include "CodeGenFunction.h"
17 #include "CodeGenTBAA.h"
18 #include "CGCall.h"
19 #include "CGCXXABI.h"
20 #include "CGObjCRuntime.h"
21 #include "TargetInfo.h"
22 #include "clang/Frontend/CodeGenOptions.h"
23 #include "clang/AST/ASTContext.h"
24 #include "clang/AST/CharUnits.h"
25 #include "clang/AST/DeclObjC.h"
26 #include "clang/AST/DeclCXX.h"
27 #include "clang/AST/DeclTemplate.h"
28 #include "clang/AST/Mangle.h"
29 #include "clang/AST/RecordLayout.h"
30 #include "clang/Basic/Builtins.h"
31 #include "clang/Basic/Diagnostic.h"
32 #include "clang/Basic/SourceManager.h"
33 #include "clang/Basic/TargetInfo.h"
34 #include "clang/Basic/ConvertUTF.h"
35 #include "llvm/CallingConv.h"
36 #include "llvm/Module.h"
37 #include "llvm/Intrinsics.h"
38 #include "llvm/LLVMContext.h"
39 #include "llvm/ADT/Triple.h"
40 #include "llvm/Target/TargetData.h"
41 #include "llvm/Support/CallSite.h"
42 #include "llvm/Support/ErrorHandling.h"
43 using namespace clang;
44 using namespace CodeGen;
45 
46 static CGCXXABI &createCXXABI(CodeGenModule &CGM) {
47   switch (CGM.getContext().Target.getCXXABI()) {
48   case CXXABI_ARM: return *CreateARMCXXABI(CGM);
49   case CXXABI_Itanium: return *CreateItaniumCXXABI(CGM);
50   case CXXABI_Microsoft: return *CreateMicrosoftCXXABI(CGM);
51   }
52 
53   llvm_unreachable("invalid C++ ABI kind");
54   return *CreateItaniumCXXABI(CGM);
55 }
56 
57 
58 CodeGenModule::CodeGenModule(ASTContext &C, const CodeGenOptions &CGO,
59                              llvm::Module &M, const llvm::TargetData &TD,
60                              Diagnostic &diags)
61   : BlockModule(C, M, TD, Types, *this), Context(C),
62     Features(C.getLangOptions()), CodeGenOpts(CGO), TheModule(M),
63     TheTargetData(TD), TheTargetCodeGenInfo(0), Diags(diags),
64     ABI(createCXXABI(*this)),
65     Types(C, M, TD, getTargetCodeGenInfo().getABIInfo(), ABI),
66     TBAA(0),
67     VTables(*this), Runtime(0),
68     CFConstantStringClassRef(0), ConstantStringClassRef(0),
69     VMContext(M.getContext()),
70     NSConcreteGlobalBlockDecl(0), NSConcreteStackBlockDecl(0),
71     NSConcreteGlobalBlock(0), NSConcreteStackBlock(0),
72     BlockObjectAssignDecl(0), BlockObjectDisposeDecl(0),
73     BlockObjectAssign(0), BlockObjectDispose(0){
74 
75   if (!Features.ObjC1)
76     Runtime = 0;
77   else if (!Features.NeXTRuntime)
78     Runtime = CreateGNUObjCRuntime(*this);
79   else if (Features.ObjCNonFragileABI)
80     Runtime = CreateMacNonFragileABIObjCRuntime(*this);
81   else
82     Runtime = CreateMacObjCRuntime(*this);
83 
84   // Enable TBAA unless it's suppressed.
85   if (!CodeGenOpts.RelaxedAliasing && CodeGenOpts.OptimizationLevel > 0)
86     TBAA = new CodeGenTBAA(Context, VMContext, getLangOptions(),
87                            ABI.getMangleContext());
88 
89   // If debug info generation is enabled, create the CGDebugInfo object.
90   DebugInfo = CodeGenOpts.DebugInfo ? new CGDebugInfo(*this) : 0;
91 }
92 
93 CodeGenModule::~CodeGenModule() {
94   delete Runtime;
95   delete &ABI;
96   delete TBAA;
97   delete DebugInfo;
98 }
99 
100 void CodeGenModule::createObjCRuntime() {
101   if (!Features.NeXTRuntime)
102     Runtime = CreateGNUObjCRuntime(*this);
103   else if (Features.ObjCNonFragileABI)
104     Runtime = CreateMacNonFragileABIObjCRuntime(*this);
105   else
106     Runtime = CreateMacObjCRuntime(*this);
107 }
108 
109 void CodeGenModule::Release() {
110   EmitDeferred();
111   EmitCXXGlobalInitFunc();
112   EmitCXXGlobalDtorFunc();
113   if (Runtime)
114     if (llvm::Function *ObjCInitFunction = Runtime->ModuleInitFunction())
115       AddGlobalCtor(ObjCInitFunction);
116   EmitCtorList(GlobalCtors, "llvm.global_ctors");
117   EmitCtorList(GlobalDtors, "llvm.global_dtors");
118   EmitAnnotations();
119   EmitLLVMUsed();
120 
121   SimplifyPersonality();
122 
123   if (getCodeGenOpts().EmitDeclMetadata)
124     EmitDeclMetadata();
125 }
126 
127 llvm::MDNode *CodeGenModule::getTBAAInfo(QualType QTy) {
128   if (!TBAA)
129     return 0;
130   return TBAA->getTBAAInfo(QTy);
131 }
132 
133 void CodeGenModule::DecorateInstruction(llvm::Instruction *Inst,
134                                         llvm::MDNode *TBAAInfo) {
135   Inst->setMetadata(llvm::LLVMContext::MD_tbaa, TBAAInfo);
136 }
137 
138 bool CodeGenModule::isTargetDarwin() const {
139   return getContext().Target.getTriple().getOS() == llvm::Triple::Darwin;
140 }
141 
142 /// ErrorUnsupported - Print out an error that codegen doesn't support the
143 /// specified stmt yet.
144 void CodeGenModule::ErrorUnsupported(const Stmt *S, const char *Type,
145                                      bool OmitOnError) {
146   if (OmitOnError && getDiags().hasErrorOccurred())
147     return;
148   unsigned DiagID = getDiags().getCustomDiagID(Diagnostic::Error,
149                                                "cannot compile this %0 yet");
150   std::string Msg = Type;
151   getDiags().Report(Context.getFullLoc(S->getLocStart()), DiagID)
152     << Msg << S->getSourceRange();
153 }
154 
155 /// ErrorUnsupported - Print out an error that codegen doesn't support the
156 /// specified decl yet.
157 void CodeGenModule::ErrorUnsupported(const Decl *D, const char *Type,
158                                      bool OmitOnError) {
159   if (OmitOnError && getDiags().hasErrorOccurred())
160     return;
161   unsigned DiagID = getDiags().getCustomDiagID(Diagnostic::Error,
162                                                "cannot compile this %0 yet");
163   std::string Msg = Type;
164   getDiags().Report(Context.getFullLoc(D->getLocation()), DiagID) << Msg;
165 }
166 
167 static llvm::GlobalValue::VisibilityTypes GetLLVMVisibility(Visibility V) {
168   switch (V) {
169   case DefaultVisibility:   return llvm::GlobalValue::DefaultVisibility;
170   case HiddenVisibility:    return llvm::GlobalValue::HiddenVisibility;
171   case ProtectedVisibility: return llvm::GlobalValue::ProtectedVisibility;
172   }
173   llvm_unreachable("unknown visibility!");
174   return llvm::GlobalValue::DefaultVisibility;
175 }
176 
177 
178 void CodeGenModule::setGlobalVisibility(llvm::GlobalValue *GV,
179                                         const NamedDecl *D) const {
180   // Internal definitions always have default visibility.
181   if (GV->hasLocalLinkage()) {
182     GV->setVisibility(llvm::GlobalValue::DefaultVisibility);
183     return;
184   }
185 
186   // Set visibility for definitions.
187   NamedDecl::LinkageInfo LV = D->getLinkageAndVisibility();
188   if (LV.visibilityExplicit() || !GV->hasAvailableExternallyLinkage())
189     GV->setVisibility(GetLLVMVisibility(LV.visibility()));
190 }
191 
192 /// Set the symbol visibility of type information (vtable and RTTI)
193 /// associated with the given type.
194 void CodeGenModule::setTypeVisibility(llvm::GlobalValue *GV,
195                                       const CXXRecordDecl *RD,
196                                       TypeVisibilityKind TVK) const {
197   setGlobalVisibility(GV, RD);
198 
199   if (!CodeGenOpts.HiddenWeakVTables)
200     return;
201 
202   // We never want to drop the visibility for RTTI names.
203   if (TVK == TVK_ForRTTIName)
204     return;
205 
206   // We want to drop the visibility to hidden for weak type symbols.
207   // This isn't possible if there might be unresolved references
208   // elsewhere that rely on this symbol being visible.
209 
210   // This should be kept roughly in sync with setThunkVisibility
211   // in CGVTables.cpp.
212 
213   // Preconditions.
214   if (GV->getLinkage() != llvm::GlobalVariable::LinkOnceODRLinkage ||
215       GV->getVisibility() != llvm::GlobalVariable::DefaultVisibility)
216     return;
217 
218   // Don't override an explicit visibility attribute.
219   if (RD->hasAttr<VisibilityAttr>())
220     return;
221 
222   switch (RD->getTemplateSpecializationKind()) {
223   // We have to disable the optimization if this is an EI definition
224   // because there might be EI declarations in other shared objects.
225   case TSK_ExplicitInstantiationDefinition:
226   case TSK_ExplicitInstantiationDeclaration:
227     return;
228 
229   // Every use of a non-template class's type information has to emit it.
230   case TSK_Undeclared:
231     break;
232 
233   // In theory, implicit instantiations can ignore the possibility of
234   // an explicit instantiation declaration because there necessarily
235   // must be an EI definition somewhere with default visibility.  In
236   // practice, it's possible to have an explicit instantiation for
237   // an arbitrary template class, and linkers aren't necessarily able
238   // to deal with mixed-visibility symbols.
239   case TSK_ExplicitSpecialization:
240   case TSK_ImplicitInstantiation:
241     if (!CodeGenOpts.HiddenWeakTemplateVTables)
242       return;
243     break;
244   }
245 
246   // If there's a key function, there may be translation units
247   // that don't have the key function's definition.  But ignore
248   // this if we're emitting RTTI under -fno-rtti.
249   if (!(TVK != TVK_ForRTTI) || Features.RTTI) {
250     if (Context.getKeyFunction(RD))
251       return;
252   }
253 
254   // Otherwise, drop the visibility to hidden.
255   GV->setVisibility(llvm::GlobalValue::HiddenVisibility);
256   GV->setUnnamedAddr(true);
257 }
258 
259 llvm::StringRef CodeGenModule::getMangledName(GlobalDecl GD) {
260   const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
261 
262   llvm::StringRef &Str = MangledDeclNames[GD.getCanonicalDecl()];
263   if (!Str.empty())
264     return Str;
265 
266   if (!getCXXABI().getMangleContext().shouldMangleDeclName(ND)) {
267     IdentifierInfo *II = ND->getIdentifier();
268     assert(II && "Attempt to mangle unnamed decl.");
269 
270     Str = II->getName();
271     return Str;
272   }
273 
274   llvm::SmallString<256> Buffer;
275   if (const CXXConstructorDecl *D = dyn_cast<CXXConstructorDecl>(ND))
276     getCXXABI().getMangleContext().mangleCXXCtor(D, GD.getCtorType(), Buffer);
277   else if (const CXXDestructorDecl *D = dyn_cast<CXXDestructorDecl>(ND))
278     getCXXABI().getMangleContext().mangleCXXDtor(D, GD.getDtorType(), Buffer);
279   else if (const BlockDecl *BD = dyn_cast<BlockDecl>(ND))
280     getCXXABI().getMangleContext().mangleBlock(BD, Buffer);
281   else
282     getCXXABI().getMangleContext().mangleName(ND, Buffer);
283 
284   // Allocate space for the mangled name.
285   size_t Length = Buffer.size();
286   char *Name = MangledNamesAllocator.Allocate<char>(Length);
287   std::copy(Buffer.begin(), Buffer.end(), Name);
288 
289   Str = llvm::StringRef(Name, Length);
290 
291   return Str;
292 }
293 
294 void CodeGenModule::getBlockMangledName(GlobalDecl GD, MangleBuffer &Buffer,
295                                         const BlockDecl *BD) {
296   MangleContext &MangleCtx = getCXXABI().getMangleContext();
297   const Decl *D = GD.getDecl();
298   if (D == 0)
299     MangleCtx.mangleGlobalBlock(BD, Buffer.getBuffer());
300   else if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(D))
301     MangleCtx.mangleCtorBlock(CD, GD.getCtorType(), BD, Buffer.getBuffer());
302   else if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(D))
303     MangleCtx.mangleDtorBlock(DD, GD.getDtorType(), BD, Buffer.getBuffer());
304   else
305     MangleCtx.mangleBlock(cast<DeclContext>(D), BD, Buffer.getBuffer());
306 }
307 
308 llvm::GlobalValue *CodeGenModule::GetGlobalValue(llvm::StringRef Name) {
309   return getModule().getNamedValue(Name);
310 }
311 
312 /// AddGlobalCtor - Add a function to the list that will be called before
313 /// main() runs.
314 void CodeGenModule::AddGlobalCtor(llvm::Function * Ctor, int Priority) {
315   // FIXME: Type coercion of void()* types.
316   GlobalCtors.push_back(std::make_pair(Ctor, Priority));
317 }
318 
319 /// AddGlobalDtor - Add a function to the list that will be called
320 /// when the module is unloaded.
321 void CodeGenModule::AddGlobalDtor(llvm::Function * Dtor, int Priority) {
322   // FIXME: Type coercion of void()* types.
323   GlobalDtors.push_back(std::make_pair(Dtor, Priority));
324 }
325 
326 void CodeGenModule::EmitCtorList(const CtorList &Fns, const char *GlobalName) {
327   // Ctor function type is void()*.
328   llvm::FunctionType* CtorFTy =
329     llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), false);
330   llvm::Type *CtorPFTy = llvm::PointerType::getUnqual(CtorFTy);
331 
332   // Get the type of a ctor entry, { i32, void ()* }.
333   llvm::StructType* CtorStructTy =
334     llvm::StructType::get(VMContext, llvm::Type::getInt32Ty(VMContext),
335                           llvm::PointerType::getUnqual(CtorFTy), NULL);
336 
337   // Construct the constructor and destructor arrays.
338   std::vector<llvm::Constant*> Ctors;
339   for (CtorList::const_iterator I = Fns.begin(), E = Fns.end(); I != E; ++I) {
340     std::vector<llvm::Constant*> S;
341     S.push_back(llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
342                 I->second, false));
343     S.push_back(llvm::ConstantExpr::getBitCast(I->first, CtorPFTy));
344     Ctors.push_back(llvm::ConstantStruct::get(CtorStructTy, S));
345   }
346 
347   if (!Ctors.empty()) {
348     llvm::ArrayType *AT = llvm::ArrayType::get(CtorStructTy, Ctors.size());
349     new llvm::GlobalVariable(TheModule, AT, false,
350                              llvm::GlobalValue::AppendingLinkage,
351                              llvm::ConstantArray::get(AT, Ctors),
352                              GlobalName);
353   }
354 }
355 
356 void CodeGenModule::EmitAnnotations() {
357   if (Annotations.empty())
358     return;
359 
360   // Create a new global variable for the ConstantStruct in the Module.
361   llvm::Constant *Array =
362   llvm::ConstantArray::get(llvm::ArrayType::get(Annotations[0]->getType(),
363                                                 Annotations.size()),
364                            Annotations);
365   llvm::GlobalValue *gv =
366   new llvm::GlobalVariable(TheModule, Array->getType(), false,
367                            llvm::GlobalValue::AppendingLinkage, Array,
368                            "llvm.global.annotations");
369   gv->setSection("llvm.metadata");
370 }
371 
372 llvm::GlobalValue::LinkageTypes
373 CodeGenModule::getFunctionLinkage(const FunctionDecl *D) {
374   GVALinkage Linkage = getContext().GetGVALinkageForFunction(D);
375 
376   if (Linkage == GVA_Internal)
377     return llvm::Function::InternalLinkage;
378 
379   if (D->hasAttr<DLLExportAttr>())
380     return llvm::Function::DLLExportLinkage;
381 
382   if (D->hasAttr<WeakAttr>())
383     return llvm::Function::WeakAnyLinkage;
384 
385   // In C99 mode, 'inline' functions are guaranteed to have a strong
386   // definition somewhere else, so we can use available_externally linkage.
387   if (Linkage == GVA_C99Inline)
388     return llvm::Function::AvailableExternallyLinkage;
389 
390   // In C++, the compiler has to emit a definition in every translation unit
391   // that references the function.  We should use linkonce_odr because
392   // a) if all references in this translation unit are optimized away, we
393   // don't need to codegen it.  b) if the function persists, it needs to be
394   // merged with other definitions. c) C++ has the ODR, so we know the
395   // definition is dependable.
396   if (Linkage == GVA_CXXInline || Linkage == GVA_TemplateInstantiation)
397     return llvm::Function::LinkOnceODRLinkage;
398 
399   // An explicit instantiation of a template has weak linkage, since
400   // explicit instantiations can occur in multiple translation units
401   // and must all be equivalent. However, we are not allowed to
402   // throw away these explicit instantiations.
403   if (Linkage == GVA_ExplicitTemplateInstantiation)
404     return llvm::Function::WeakODRLinkage;
405 
406   // Otherwise, we have strong external linkage.
407   assert(Linkage == GVA_StrongExternal);
408   return llvm::Function::ExternalLinkage;
409 }
410 
411 
412 /// SetFunctionDefinitionAttributes - Set attributes for a global.
413 ///
414 /// FIXME: This is currently only done for aliases and functions, but not for
415 /// variables (these details are set in EmitGlobalVarDefinition for variables).
416 void CodeGenModule::SetFunctionDefinitionAttributes(const FunctionDecl *D,
417                                                     llvm::GlobalValue *GV) {
418   SetCommonAttributes(D, GV);
419 }
420 
421 void CodeGenModule::SetLLVMFunctionAttributes(const Decl *D,
422                                               const CGFunctionInfo &Info,
423                                               llvm::Function *F) {
424   unsigned CallingConv;
425   AttributeListType AttributeList;
426   ConstructAttributeList(Info, D, AttributeList, CallingConv);
427   F->setAttributes(llvm::AttrListPtr::get(AttributeList.begin(),
428                                           AttributeList.size()));
429   F->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));
430 }
431 
432 void CodeGenModule::SetLLVMFunctionAttributesForDefinition(const Decl *D,
433                                                            llvm::Function *F) {
434   if (!Features.Exceptions && !Features.ObjCNonFragileABI)
435     F->addFnAttr(llvm::Attribute::NoUnwind);
436 
437   if (D->hasAttr<AlwaysInlineAttr>())
438     F->addFnAttr(llvm::Attribute::AlwaysInline);
439 
440   if (D->hasAttr<NakedAttr>())
441     F->addFnAttr(llvm::Attribute::Naked);
442 
443   if (D->hasAttr<NoInlineAttr>())
444     F->addFnAttr(llvm::Attribute::NoInline);
445 
446   if (isa<CXXConstructorDecl>(D) || isa<CXXDestructorDecl>(D))
447     F->setUnnamedAddr(true);
448 
449   if (Features.getStackProtectorMode() == LangOptions::SSPOn)
450     F->addFnAttr(llvm::Attribute::StackProtect);
451   else if (Features.getStackProtectorMode() == LangOptions::SSPReq)
452     F->addFnAttr(llvm::Attribute::StackProtectReq);
453 
454   unsigned alignment = D->getMaxAlignment() / Context.getCharWidth();
455   if (alignment)
456     F->setAlignment(alignment);
457 
458   // C++ ABI requires 2-byte alignment for member functions.
459   if (F->getAlignment() < 2 && isa<CXXMethodDecl>(D))
460     F->setAlignment(2);
461 }
462 
463 void CodeGenModule::SetCommonAttributes(const Decl *D,
464                                         llvm::GlobalValue *GV) {
465   if (const NamedDecl *ND = dyn_cast<NamedDecl>(D))
466     setGlobalVisibility(GV, ND);
467   else
468     GV->setVisibility(llvm::GlobalValue::DefaultVisibility);
469 
470   if (D->hasAttr<UsedAttr>())
471     AddUsedGlobal(GV);
472 
473   if (const SectionAttr *SA = D->getAttr<SectionAttr>())
474     GV->setSection(SA->getName());
475 
476   getTargetCodeGenInfo().SetTargetAttributes(D, GV, *this);
477 }
478 
479 void CodeGenModule::SetInternalFunctionAttributes(const Decl *D,
480                                                   llvm::Function *F,
481                                                   const CGFunctionInfo &FI) {
482   SetLLVMFunctionAttributes(D, FI, F);
483   SetLLVMFunctionAttributesForDefinition(D, F);
484 
485   F->setLinkage(llvm::Function::InternalLinkage);
486 
487   SetCommonAttributes(D, F);
488 }
489 
490 void CodeGenModule::SetFunctionAttributes(GlobalDecl GD,
491                                           llvm::Function *F,
492                                           bool IsIncompleteFunction) {
493   const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
494 
495   if (!IsIncompleteFunction)
496     SetLLVMFunctionAttributes(FD, getTypes().getFunctionInfo(GD), F);
497 
498   // Only a few attributes are set on declarations; these may later be
499   // overridden by a definition.
500 
501   if (FD->hasAttr<DLLImportAttr>()) {
502     F->setLinkage(llvm::Function::DLLImportLinkage);
503   } else if (FD->hasAttr<WeakAttr>() ||
504              FD->hasAttr<WeakImportAttr>()) {
505     // "extern_weak" is overloaded in LLVM; we probably should have
506     // separate linkage types for this.
507     F->setLinkage(llvm::Function::ExternalWeakLinkage);
508   } else {
509     F->setLinkage(llvm::Function::ExternalLinkage);
510 
511     NamedDecl::LinkageInfo LV = FD->getLinkageAndVisibility();
512     if (LV.linkage() == ExternalLinkage && LV.visibilityExplicit()) {
513       F->setVisibility(GetLLVMVisibility(LV.visibility()));
514     }
515   }
516 
517   if (const SectionAttr *SA = FD->getAttr<SectionAttr>())
518     F->setSection(SA->getName());
519 }
520 
521 void CodeGenModule::AddUsedGlobal(llvm::GlobalValue *GV) {
522   assert(!GV->isDeclaration() &&
523          "Only globals with definition can force usage.");
524   LLVMUsed.push_back(GV);
525 }
526 
527 void CodeGenModule::EmitLLVMUsed() {
528   // Don't create llvm.used if there is no need.
529   if (LLVMUsed.empty())
530     return;
531 
532   const llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(VMContext);
533 
534   // Convert LLVMUsed to what ConstantArray needs.
535   std::vector<llvm::Constant*> UsedArray;
536   UsedArray.resize(LLVMUsed.size());
537   for (unsigned i = 0, e = LLVMUsed.size(); i != e; ++i) {
538     UsedArray[i] =
539      llvm::ConstantExpr::getBitCast(cast<llvm::Constant>(&*LLVMUsed[i]),
540                                       i8PTy);
541   }
542 
543   if (UsedArray.empty())
544     return;
545   llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, UsedArray.size());
546 
547   llvm::GlobalVariable *GV =
548     new llvm::GlobalVariable(getModule(), ATy, false,
549                              llvm::GlobalValue::AppendingLinkage,
550                              llvm::ConstantArray::get(ATy, UsedArray),
551                              "llvm.used");
552 
553   GV->setSection("llvm.metadata");
554 }
555 
556 void CodeGenModule::EmitDeferred() {
557   // Emit code for any potentially referenced deferred decls.  Since a
558   // previously unused static decl may become used during the generation of code
559   // for a static function, iterate until no  changes are made.
560 
561   while (!DeferredDeclsToEmit.empty() || !DeferredVTables.empty()) {
562     if (!DeferredVTables.empty()) {
563       const CXXRecordDecl *RD = DeferredVTables.back();
564       DeferredVTables.pop_back();
565       getVTables().GenerateClassData(getVTableLinkage(RD), RD);
566       continue;
567     }
568 
569     GlobalDecl D = DeferredDeclsToEmit.back();
570     DeferredDeclsToEmit.pop_back();
571 
572     // Check to see if we've already emitted this.  This is necessary
573     // for a couple of reasons: first, decls can end up in the
574     // deferred-decls queue multiple times, and second, decls can end
575     // up with definitions in unusual ways (e.g. by an extern inline
576     // function acquiring a strong function redefinition).  Just
577     // ignore these cases.
578     //
579     // TODO: That said, looking this up multiple times is very wasteful.
580     llvm::StringRef Name = getMangledName(D);
581     llvm::GlobalValue *CGRef = GetGlobalValue(Name);
582     assert(CGRef && "Deferred decl wasn't referenced?");
583 
584     if (!CGRef->isDeclaration())
585       continue;
586 
587     // GlobalAlias::isDeclaration() defers to the aliasee, but for our
588     // purposes an alias counts as a definition.
589     if (isa<llvm::GlobalAlias>(CGRef))
590       continue;
591 
592     // Otherwise, emit the definition and move on to the next one.
593     EmitGlobalDefinition(D);
594   }
595 }
596 
597 /// EmitAnnotateAttr - Generate the llvm::ConstantStruct which contains the
598 /// annotation information for a given GlobalValue.  The annotation struct is
599 /// {i8 *, i8 *, i8 *, i32}.  The first field is a constant expression, the
600 /// GlobalValue being annotated.  The second field is the constant string
601 /// created from the AnnotateAttr's annotation.  The third field is a constant
602 /// string containing the name of the translation unit.  The fourth field is
603 /// the line number in the file of the annotated value declaration.
604 ///
605 /// FIXME: this does not unique the annotation string constants, as llvm-gcc
606 ///        appears to.
607 ///
608 llvm::Constant *CodeGenModule::EmitAnnotateAttr(llvm::GlobalValue *GV,
609                                                 const AnnotateAttr *AA,
610                                                 unsigned LineNo) {
611   llvm::Module *M = &getModule();
612 
613   // get [N x i8] constants for the annotation string, and the filename string
614   // which are the 2nd and 3rd elements of the global annotation structure.
615   const llvm::Type *SBP = llvm::Type::getInt8PtrTy(VMContext);
616   llvm::Constant *anno = llvm::ConstantArray::get(VMContext,
617                                                   AA->getAnnotation(), true);
618   llvm::Constant *unit = llvm::ConstantArray::get(VMContext,
619                                                   M->getModuleIdentifier(),
620                                                   true);
621 
622   // Get the two global values corresponding to the ConstantArrays we just
623   // created to hold the bytes of the strings.
624   llvm::GlobalValue *annoGV =
625     new llvm::GlobalVariable(*M, anno->getType(), false,
626                              llvm::GlobalValue::PrivateLinkage, anno,
627                              GV->getName());
628   // translation unit name string, emitted into the llvm.metadata section.
629   llvm::GlobalValue *unitGV =
630     new llvm::GlobalVariable(*M, unit->getType(), false,
631                              llvm::GlobalValue::PrivateLinkage, unit,
632                              ".str");
633   unitGV->setUnnamedAddr(true);
634 
635   // Create the ConstantStruct for the global annotation.
636   llvm::Constant *Fields[4] = {
637     llvm::ConstantExpr::getBitCast(GV, SBP),
638     llvm::ConstantExpr::getBitCast(annoGV, SBP),
639     llvm::ConstantExpr::getBitCast(unitGV, SBP),
640     llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), LineNo)
641   };
642   return llvm::ConstantStruct::get(VMContext, Fields, 4, false);
643 }
644 
645 bool CodeGenModule::MayDeferGeneration(const ValueDecl *Global) {
646   // Never defer when EmitAllDecls is specified.
647   if (Features.EmitAllDecls)
648     return false;
649 
650   return !getContext().DeclMustBeEmitted(Global);
651 }
652 
653 llvm::Constant *CodeGenModule::GetWeakRefReference(const ValueDecl *VD) {
654   const AliasAttr *AA = VD->getAttr<AliasAttr>();
655   assert(AA && "No alias?");
656 
657   const llvm::Type *DeclTy = getTypes().ConvertTypeForMem(VD->getType());
658 
659   // See if there is already something with the target's name in the module.
660   llvm::GlobalValue *Entry = GetGlobalValue(AA->getAliasee());
661 
662   llvm::Constant *Aliasee;
663   if (isa<llvm::FunctionType>(DeclTy))
664     Aliasee = GetOrCreateLLVMFunction(AA->getAliasee(), DeclTy, GlobalDecl());
665   else
666     Aliasee = GetOrCreateLLVMGlobal(AA->getAliasee(),
667                                     llvm::PointerType::getUnqual(DeclTy), 0);
668   if (!Entry) {
669     llvm::GlobalValue* F = cast<llvm::GlobalValue>(Aliasee);
670     F->setLinkage(llvm::Function::ExternalWeakLinkage);
671     WeakRefReferences.insert(F);
672   }
673 
674   return Aliasee;
675 }
676 
677 void CodeGenModule::EmitGlobal(GlobalDecl GD) {
678   const ValueDecl *Global = cast<ValueDecl>(GD.getDecl());
679 
680   // Weak references don't produce any output by themselves.
681   if (Global->hasAttr<WeakRefAttr>())
682     return;
683 
684   // If this is an alias definition (which otherwise looks like a declaration)
685   // emit it now.
686   if (Global->hasAttr<AliasAttr>())
687     return EmitAliasDefinition(GD);
688 
689   // Ignore declarations, they will be emitted on their first use.
690   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Global)) {
691     if (FD->getIdentifier()) {
692       llvm::StringRef Name = FD->getName();
693       if (Name == "_Block_object_assign") {
694         BlockObjectAssignDecl = FD;
695       } else if (Name == "_Block_object_dispose") {
696         BlockObjectDisposeDecl = FD;
697       }
698     }
699 
700     // Forward declarations are emitted lazily on first use.
701     if (!FD->isThisDeclarationADefinition())
702       return;
703   } else {
704     const VarDecl *VD = cast<VarDecl>(Global);
705     assert(VD->isFileVarDecl() && "Cannot emit local var decl as global.");
706 
707     if (VD->getIdentifier()) {
708       llvm::StringRef Name = VD->getName();
709       if (Name == "_NSConcreteGlobalBlock") {
710         NSConcreteGlobalBlockDecl = VD;
711       } else if (Name == "_NSConcreteStackBlock") {
712         NSConcreteStackBlockDecl = VD;
713       }
714     }
715 
716 
717     if (VD->isThisDeclarationADefinition() != VarDecl::Definition)
718       return;
719   }
720 
721   // Defer code generation when possible if this is a static definition, inline
722   // function etc.  These we only want to emit if they are used.
723   if (!MayDeferGeneration(Global)) {
724     // Emit the definition if it can't be deferred.
725     EmitGlobalDefinition(GD);
726     return;
727   }
728 
729   // If we're deferring emission of a C++ variable with an
730   // initializer, remember the order in which it appeared in the file.
731   if (getLangOptions().CPlusPlus && isa<VarDecl>(Global) &&
732       cast<VarDecl>(Global)->hasInit()) {
733     DelayedCXXInitPosition[Global] = CXXGlobalInits.size();
734     CXXGlobalInits.push_back(0);
735   }
736 
737   // If the value has already been used, add it directly to the
738   // DeferredDeclsToEmit list.
739   llvm::StringRef MangledName = getMangledName(GD);
740   if (GetGlobalValue(MangledName))
741     DeferredDeclsToEmit.push_back(GD);
742   else {
743     // Otherwise, remember that we saw a deferred decl with this name.  The
744     // first use of the mangled name will cause it to move into
745     // DeferredDeclsToEmit.
746     DeferredDecls[MangledName] = GD;
747   }
748 }
749 
750 void CodeGenModule::EmitGlobalDefinition(GlobalDecl GD) {
751   const ValueDecl *D = cast<ValueDecl>(GD.getDecl());
752 
753   PrettyStackTraceDecl CrashInfo(const_cast<ValueDecl *>(D), D->getLocation(),
754                                  Context.getSourceManager(),
755                                  "Generating code for declaration");
756 
757   if (const FunctionDecl *Function = dyn_cast<FunctionDecl>(D)) {
758     // At -O0, don't generate IR for functions with available_externally
759     // linkage.
760     if (CodeGenOpts.OptimizationLevel == 0 &&
761         !Function->hasAttr<AlwaysInlineAttr>() &&
762         getFunctionLinkage(Function)
763                                   == llvm::Function::AvailableExternallyLinkage)
764       return;
765 
766     if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(D)) {
767       if (Method->isVirtual())
768         getVTables().EmitThunks(GD);
769 
770       if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(Method))
771         return EmitCXXConstructor(CD, GD.getCtorType());
772 
773       if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(Method))
774         return EmitCXXDestructor(DD, GD.getDtorType());
775     }
776 
777     return EmitGlobalFunctionDefinition(GD);
778   }
779 
780   if (const VarDecl *VD = dyn_cast<VarDecl>(D))
781     return EmitGlobalVarDefinition(VD);
782 
783   assert(0 && "Invalid argument to EmitGlobalDefinition()");
784 }
785 
786 /// GetOrCreateLLVMFunction - If the specified mangled name is not in the
787 /// module, create and return an llvm Function with the specified type. If there
788 /// is something in the module with the specified name, return it potentially
789 /// bitcasted to the right type.
790 ///
791 /// If D is non-null, it specifies a decl that correspond to this.  This is used
792 /// to set the attributes on the function when it is first created.
793 llvm::Constant *
794 CodeGenModule::GetOrCreateLLVMFunction(llvm::StringRef MangledName,
795                                        const llvm::Type *Ty,
796                                        GlobalDecl D) {
797   // Lookup the entry, lazily creating it if necessary.
798   llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
799   if (Entry) {
800     if (WeakRefReferences.count(Entry)) {
801       const FunctionDecl *FD = cast_or_null<FunctionDecl>(D.getDecl());
802       if (FD && !FD->hasAttr<WeakAttr>())
803         Entry->setLinkage(llvm::Function::ExternalLinkage);
804 
805       WeakRefReferences.erase(Entry);
806     }
807 
808     if (Entry->getType()->getElementType() == Ty)
809       return Entry;
810 
811     // Make sure the result is of the correct type.
812     const llvm::Type *PTy = llvm::PointerType::getUnqual(Ty);
813     return llvm::ConstantExpr::getBitCast(Entry, PTy);
814   }
815 
816   // This function doesn't have a complete type (for example, the return
817   // type is an incomplete struct). Use a fake type instead, and make
818   // sure not to try to set attributes.
819   bool IsIncompleteFunction = false;
820 
821   const llvm::FunctionType *FTy;
822   if (isa<llvm::FunctionType>(Ty)) {
823     FTy = cast<llvm::FunctionType>(Ty);
824   } else {
825     FTy = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), false);
826     IsIncompleteFunction = true;
827   }
828 
829   llvm::Function *F = llvm::Function::Create(FTy,
830                                              llvm::Function::ExternalLinkage,
831                                              MangledName, &getModule());
832   assert(F->getName() == MangledName && "name was uniqued!");
833   if (D.getDecl())
834     SetFunctionAttributes(D, F, IsIncompleteFunction);
835 
836   // This is the first use or definition of a mangled name.  If there is a
837   // deferred decl with this name, remember that we need to emit it at the end
838   // of the file.
839   llvm::StringMap<GlobalDecl>::iterator DDI = DeferredDecls.find(MangledName);
840   if (DDI != DeferredDecls.end()) {
841     // Move the potentially referenced deferred decl to the DeferredDeclsToEmit
842     // list, and remove it from DeferredDecls (since we don't need it anymore).
843     DeferredDeclsToEmit.push_back(DDI->second);
844     DeferredDecls.erase(DDI);
845 
846   // Otherwise, there are cases we have to worry about where we're
847   // using a declaration for which we must emit a definition but where
848   // we might not find a top-level definition:
849   //   - member functions defined inline in their classes
850   //   - friend functions defined inline in some class
851   //   - special member functions with implicit definitions
852   // If we ever change our AST traversal to walk into class methods,
853   // this will be unnecessary.
854   } else if (getLangOptions().CPlusPlus && D.getDecl()) {
855     // Look for a declaration that's lexically in a record.
856     const FunctionDecl *FD = cast<FunctionDecl>(D.getDecl());
857     do {
858       if (isa<CXXRecordDecl>(FD->getLexicalDeclContext())) {
859         if (FD->isImplicit()) {
860           assert(FD->isUsed() && "Sema didn't mark implicit function as used!");
861           DeferredDeclsToEmit.push_back(D);
862           break;
863         } else if (FD->isThisDeclarationADefinition()) {
864           DeferredDeclsToEmit.push_back(D);
865           break;
866         }
867       }
868       FD = FD->getPreviousDeclaration();
869     } while (FD);
870   }
871 
872   // Make sure the result is of the requested type.
873   if (!IsIncompleteFunction) {
874     assert(F->getType()->getElementType() == Ty);
875     return F;
876   }
877 
878   const llvm::Type *PTy = llvm::PointerType::getUnqual(Ty);
879   return llvm::ConstantExpr::getBitCast(F, PTy);
880 }
881 
882 /// GetAddrOfFunction - Return the address of the given function.  If Ty is
883 /// non-null, then this function will use the specified type if it has to
884 /// create it (this occurs when we see a definition of the function).
885 llvm::Constant *CodeGenModule::GetAddrOfFunction(GlobalDecl GD,
886                                                  const llvm::Type *Ty) {
887   // If there was no specific requested type, just convert it now.
888   if (!Ty)
889     Ty = getTypes().ConvertType(cast<ValueDecl>(GD.getDecl())->getType());
890 
891   llvm::StringRef MangledName = getMangledName(GD);
892   return GetOrCreateLLVMFunction(MangledName, Ty, GD);
893 }
894 
895 /// CreateRuntimeFunction - Create a new runtime function with the specified
896 /// type and name.
897 llvm::Constant *
898 CodeGenModule::CreateRuntimeFunction(const llvm::FunctionType *FTy,
899                                      llvm::StringRef Name) {
900   return GetOrCreateLLVMFunction(Name, FTy, GlobalDecl());
901 }
902 
903 static bool DeclIsConstantGlobal(ASTContext &Context, const VarDecl *D) {
904   if (!D->getType().isConstant(Context) && !D->getType()->isReferenceType())
905     return false;
906   if (Context.getLangOptions().CPlusPlus &&
907       Context.getBaseElementType(D->getType())->getAs<RecordType>()) {
908     // FIXME: We should do something fancier here!
909     return false;
910   }
911   return true;
912 }
913 
914 /// GetOrCreateLLVMGlobal - If the specified mangled name is not in the module,
915 /// create and return an llvm GlobalVariable with the specified type.  If there
916 /// is something in the module with the specified name, return it potentially
917 /// bitcasted to the right type.
918 ///
919 /// If D is non-null, it specifies a decl that correspond to this.  This is used
920 /// to set the attributes on the global when it is first created.
921 llvm::Constant *
922 CodeGenModule::GetOrCreateLLVMGlobal(llvm::StringRef MangledName,
923                                      const llvm::PointerType *Ty,
924                                      const VarDecl *D,
925                                      bool UnnamedAddr) {
926   // Lookup the entry, lazily creating it if necessary.
927   llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
928   if (Entry) {
929     if (WeakRefReferences.count(Entry)) {
930       if (D && !D->hasAttr<WeakAttr>())
931         Entry->setLinkage(llvm::Function::ExternalLinkage);
932 
933       WeakRefReferences.erase(Entry);
934     }
935 
936     if (UnnamedAddr)
937       Entry->setUnnamedAddr(true);
938 
939     if (Entry->getType() == Ty)
940       return Entry;
941 
942     // Make sure the result is of the correct type.
943     return llvm::ConstantExpr::getBitCast(Entry, Ty);
944   }
945 
946   // This is the first use or definition of a mangled name.  If there is a
947   // deferred decl with this name, remember that we need to emit it at the end
948   // of the file.
949   llvm::StringMap<GlobalDecl>::iterator DDI = DeferredDecls.find(MangledName);
950   if (DDI != DeferredDecls.end()) {
951     // Move the potentially referenced deferred decl to the DeferredDeclsToEmit
952     // list, and remove it from DeferredDecls (since we don't need it anymore).
953     DeferredDeclsToEmit.push_back(DDI->second);
954     DeferredDecls.erase(DDI);
955   }
956 
957   llvm::GlobalVariable *GV =
958     new llvm::GlobalVariable(getModule(), Ty->getElementType(), false,
959                              llvm::GlobalValue::ExternalLinkage,
960                              0, MangledName, 0,
961                              false, Ty->getAddressSpace());
962 
963   // Handle things which are present even on external declarations.
964   if (D) {
965     // FIXME: This code is overly simple and should be merged with other global
966     // handling.
967     GV->setConstant(DeclIsConstantGlobal(Context, D));
968 
969     // Set linkage and visibility in case we never see a definition.
970     NamedDecl::LinkageInfo LV = D->getLinkageAndVisibility();
971     if (LV.linkage() != ExternalLinkage) {
972       GV->setLinkage(llvm::GlobalValue::InternalLinkage);
973     } else {
974       if (D->hasAttr<DLLImportAttr>())
975         GV->setLinkage(llvm::GlobalValue::DLLImportLinkage);
976       else if (D->hasAttr<WeakAttr>() || D->hasAttr<WeakImportAttr>())
977         GV->setLinkage(llvm::GlobalValue::ExternalWeakLinkage);
978 
979       // Set visibility on a declaration only if it's explicit.
980       if (LV.visibilityExplicit())
981         GV->setVisibility(GetLLVMVisibility(LV.visibility()));
982     }
983 
984     GV->setThreadLocal(D->isThreadSpecified());
985   }
986 
987   return GV;
988 }
989 
990 
991 llvm::GlobalVariable *
992 CodeGenModule::CreateOrReplaceCXXRuntimeVariable(llvm::StringRef Name,
993                                       const llvm::Type *Ty,
994                                       llvm::GlobalValue::LinkageTypes Linkage) {
995   llvm::GlobalVariable *GV = getModule().getNamedGlobal(Name);
996   llvm::GlobalVariable *OldGV = 0;
997 
998 
999   if (GV) {
1000     // Check if the variable has the right type.
1001     if (GV->getType()->getElementType() == Ty)
1002       return GV;
1003 
1004     // Because C++ name mangling, the only way we can end up with an already
1005     // existing global with the same name is if it has been declared extern "C".
1006       assert(GV->isDeclaration() && "Declaration has wrong type!");
1007     OldGV = GV;
1008   }
1009 
1010   // Create a new variable.
1011   GV = new llvm::GlobalVariable(getModule(), Ty, /*isConstant=*/true,
1012                                 Linkage, 0, Name);
1013 
1014   if (OldGV) {
1015     // Replace occurrences of the old variable if needed.
1016     GV->takeName(OldGV);
1017 
1018     if (!OldGV->use_empty()) {
1019       llvm::Constant *NewPtrForOldDecl =
1020       llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
1021       OldGV->replaceAllUsesWith(NewPtrForOldDecl);
1022     }
1023 
1024     OldGV->eraseFromParent();
1025   }
1026 
1027   return GV;
1028 }
1029 
1030 /// GetAddrOfGlobalVar - Return the llvm::Constant for the address of the
1031 /// given global variable.  If Ty is non-null and if the global doesn't exist,
1032 /// then it will be greated with the specified type instead of whatever the
1033 /// normal requested type would be.
1034 llvm::Constant *CodeGenModule::GetAddrOfGlobalVar(const VarDecl *D,
1035                                                   const llvm::Type *Ty) {
1036   assert(D->hasGlobalStorage() && "Not a global variable");
1037   QualType ASTTy = D->getType();
1038   if (Ty == 0)
1039     Ty = getTypes().ConvertTypeForMem(ASTTy);
1040 
1041   const llvm::PointerType *PTy =
1042     llvm::PointerType::get(Ty, ASTTy.getAddressSpace());
1043 
1044   llvm::StringRef MangledName = getMangledName(D);
1045   return GetOrCreateLLVMGlobal(MangledName, PTy, D);
1046 }
1047 
1048 /// CreateRuntimeVariable - Create a new runtime global variable with the
1049 /// specified type and name.
1050 llvm::Constant *
1051 CodeGenModule::CreateRuntimeVariable(const llvm::Type *Ty,
1052                                      llvm::StringRef Name) {
1053   return GetOrCreateLLVMGlobal(Name,  llvm::PointerType::getUnqual(Ty), 0,
1054                                true);
1055 }
1056 
1057 void CodeGenModule::EmitTentativeDefinition(const VarDecl *D) {
1058   assert(!D->getInit() && "Cannot emit definite definitions here!");
1059 
1060   if (MayDeferGeneration(D)) {
1061     // If we have not seen a reference to this variable yet, place it
1062     // into the deferred declarations table to be emitted if needed
1063     // later.
1064     llvm::StringRef MangledName = getMangledName(D);
1065     if (!GetGlobalValue(MangledName)) {
1066       DeferredDecls[MangledName] = D;
1067       return;
1068     }
1069   }
1070 
1071   // The tentative definition is the only definition.
1072   EmitGlobalVarDefinition(D);
1073 }
1074 
1075 void CodeGenModule::EmitVTable(CXXRecordDecl *Class, bool DefinitionRequired) {
1076   if (DefinitionRequired)
1077     getVTables().GenerateClassData(getVTableLinkage(Class), Class);
1078 }
1079 
1080 llvm::GlobalVariable::LinkageTypes
1081 CodeGenModule::getVTableLinkage(const CXXRecordDecl *RD) {
1082   if (RD->isInAnonymousNamespace() || !RD->hasLinkage())
1083     return llvm::GlobalVariable::InternalLinkage;
1084 
1085   if (const CXXMethodDecl *KeyFunction
1086                                     = RD->getASTContext().getKeyFunction(RD)) {
1087     // If this class has a key function, use that to determine the linkage of
1088     // the vtable.
1089     const FunctionDecl *Def = 0;
1090     if (KeyFunction->hasBody(Def))
1091       KeyFunction = cast<CXXMethodDecl>(Def);
1092 
1093     switch (KeyFunction->getTemplateSpecializationKind()) {
1094       case TSK_Undeclared:
1095       case TSK_ExplicitSpecialization:
1096         if (KeyFunction->isInlined())
1097           return llvm::GlobalVariable::LinkOnceODRLinkage;
1098 
1099         return llvm::GlobalVariable::ExternalLinkage;
1100 
1101       case TSK_ImplicitInstantiation:
1102         return llvm::GlobalVariable::LinkOnceODRLinkage;
1103 
1104       case TSK_ExplicitInstantiationDefinition:
1105         return llvm::GlobalVariable::WeakODRLinkage;
1106 
1107       case TSK_ExplicitInstantiationDeclaration:
1108         // FIXME: Use available_externally linkage. However, this currently
1109         // breaks LLVM's build due to undefined symbols.
1110         //      return llvm::GlobalVariable::AvailableExternallyLinkage;
1111         return llvm::GlobalVariable::LinkOnceODRLinkage;
1112     }
1113   }
1114 
1115   switch (RD->getTemplateSpecializationKind()) {
1116   case TSK_Undeclared:
1117   case TSK_ExplicitSpecialization:
1118   case TSK_ImplicitInstantiation:
1119     return llvm::GlobalVariable::LinkOnceODRLinkage;
1120 
1121   case TSK_ExplicitInstantiationDefinition:
1122     return llvm::GlobalVariable::WeakODRLinkage;
1123 
1124   case TSK_ExplicitInstantiationDeclaration:
1125     // FIXME: Use available_externally linkage. However, this currently
1126     // breaks LLVM's build due to undefined symbols.
1127     //   return llvm::GlobalVariable::AvailableExternallyLinkage;
1128     return llvm::GlobalVariable::LinkOnceODRLinkage;
1129   }
1130 
1131   // Silence GCC warning.
1132   return llvm::GlobalVariable::LinkOnceODRLinkage;
1133 }
1134 
1135 CharUnits CodeGenModule::GetTargetTypeStoreSize(const llvm::Type *Ty) const {
1136     return Context.toCharUnitsFromBits(
1137       TheTargetData.getTypeStoreSizeInBits(Ty));
1138 }
1139 
1140 void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D) {
1141   llvm::Constant *Init = 0;
1142   QualType ASTTy = D->getType();
1143   bool NonConstInit = false;
1144 
1145   const Expr *InitExpr = D->getAnyInitializer();
1146 
1147   if (!InitExpr) {
1148     // This is a tentative definition; tentative definitions are
1149     // implicitly initialized with { 0 }.
1150     //
1151     // Note that tentative definitions are only emitted at the end of
1152     // a translation unit, so they should never have incomplete
1153     // type. In addition, EmitTentativeDefinition makes sure that we
1154     // never attempt to emit a tentative definition if a real one
1155     // exists. A use may still exists, however, so we still may need
1156     // to do a RAUW.
1157     assert(!ASTTy->isIncompleteType() && "Unexpected incomplete type");
1158     Init = EmitNullConstant(D->getType());
1159   } else {
1160     Init = EmitConstantExpr(InitExpr, D->getType());
1161     if (!Init) {
1162       QualType T = InitExpr->getType();
1163       if (D->getType()->isReferenceType())
1164         T = D->getType();
1165 
1166       if (getLangOptions().CPlusPlus) {
1167         Init = EmitNullConstant(T);
1168         NonConstInit = true;
1169       } else {
1170         ErrorUnsupported(D, "static initializer");
1171         Init = llvm::UndefValue::get(getTypes().ConvertType(T));
1172       }
1173     } else {
1174       // We don't need an initializer, so remove the entry for the delayed
1175       // initializer position (just in case this entry was delayed).
1176       if (getLangOptions().CPlusPlus)
1177         DelayedCXXInitPosition.erase(D);
1178     }
1179   }
1180 
1181   const llvm::Type* InitType = Init->getType();
1182   llvm::Constant *Entry = GetAddrOfGlobalVar(D, InitType);
1183 
1184   // Strip off a bitcast if we got one back.
1185   if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(Entry)) {
1186     assert(CE->getOpcode() == llvm::Instruction::BitCast ||
1187            // all zero index gep.
1188            CE->getOpcode() == llvm::Instruction::GetElementPtr);
1189     Entry = CE->getOperand(0);
1190   }
1191 
1192   // Entry is now either a Function or GlobalVariable.
1193   llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Entry);
1194 
1195   // We have a definition after a declaration with the wrong type.
1196   // We must make a new GlobalVariable* and update everything that used OldGV
1197   // (a declaration or tentative definition) with the new GlobalVariable*
1198   // (which will be a definition).
1199   //
1200   // This happens if there is a prototype for a global (e.g.
1201   // "extern int x[];") and then a definition of a different type (e.g.
1202   // "int x[10];"). This also happens when an initializer has a different type
1203   // from the type of the global (this happens with unions).
1204   if (GV == 0 ||
1205       GV->getType()->getElementType() != InitType ||
1206       GV->getType()->getAddressSpace() != ASTTy.getAddressSpace()) {
1207 
1208     // Move the old entry aside so that we'll create a new one.
1209     Entry->setName(llvm::StringRef());
1210 
1211     // Make a new global with the correct type, this is now guaranteed to work.
1212     GV = cast<llvm::GlobalVariable>(GetAddrOfGlobalVar(D, InitType));
1213 
1214     // Replace all uses of the old global with the new global
1215     llvm::Constant *NewPtrForOldDecl =
1216         llvm::ConstantExpr::getBitCast(GV, Entry->getType());
1217     Entry->replaceAllUsesWith(NewPtrForOldDecl);
1218 
1219     // Erase the old global, since it is no longer used.
1220     cast<llvm::GlobalValue>(Entry)->eraseFromParent();
1221   }
1222 
1223   if (const AnnotateAttr *AA = D->getAttr<AnnotateAttr>()) {
1224     SourceManager &SM = Context.getSourceManager();
1225     AddAnnotation(EmitAnnotateAttr(GV, AA,
1226                               SM.getInstantiationLineNumber(D->getLocation())));
1227   }
1228 
1229   GV->setInitializer(Init);
1230 
1231   // If it is safe to mark the global 'constant', do so now.
1232   GV->setConstant(false);
1233   if (!NonConstInit && DeclIsConstantGlobal(Context, D))
1234     GV->setConstant(true);
1235 
1236   GV->setAlignment(getContext().getDeclAlign(D).getQuantity());
1237 
1238   // Set the llvm linkage type as appropriate.
1239   llvm::GlobalValue::LinkageTypes Linkage =
1240     GetLLVMLinkageVarDefinition(D, GV);
1241   GV->setLinkage(Linkage);
1242   if (Linkage == llvm::GlobalVariable::CommonLinkage)
1243     // common vars aren't constant even if declared const.
1244     GV->setConstant(false);
1245 
1246   SetCommonAttributes(D, GV);
1247 
1248   // Emit the initializer function if necessary.
1249   if (NonConstInit)
1250     EmitCXXGlobalVarDeclInitFunc(D, GV);
1251 
1252   // Emit global variable debug information.
1253   if (CGDebugInfo *DI = getDebugInfo()) {
1254     DI->setLocation(D->getLocation());
1255     DI->EmitGlobalVariable(GV, D);
1256   }
1257 }
1258 
1259 llvm::GlobalValue::LinkageTypes
1260 CodeGenModule::GetLLVMLinkageVarDefinition(const VarDecl *D,
1261                                            llvm::GlobalVariable *GV) {
1262   GVALinkage Linkage = getContext().GetGVALinkageForVariable(D);
1263   if (Linkage == GVA_Internal)
1264     return llvm::Function::InternalLinkage;
1265   else if (D->hasAttr<DLLImportAttr>())
1266     return llvm::Function::DLLImportLinkage;
1267   else if (D->hasAttr<DLLExportAttr>())
1268     return llvm::Function::DLLExportLinkage;
1269   else if (D->hasAttr<WeakAttr>()) {
1270     if (GV->isConstant())
1271       return llvm::GlobalVariable::WeakODRLinkage;
1272     else
1273       return llvm::GlobalVariable::WeakAnyLinkage;
1274   } else if (Linkage == GVA_TemplateInstantiation ||
1275              Linkage == GVA_ExplicitTemplateInstantiation)
1276     // FIXME: It seems like we can provide more specific linkage here
1277     // (LinkOnceODR, WeakODR).
1278     return llvm::GlobalVariable::WeakAnyLinkage;
1279   else if (!getLangOptions().CPlusPlus &&
1280            ((!CodeGenOpts.NoCommon && !D->getAttr<NoCommonAttr>()) ||
1281              D->getAttr<CommonAttr>()) &&
1282            !D->hasExternalStorage() && !D->getInit() &&
1283            !D->getAttr<SectionAttr>() && !D->isThreadSpecified()) {
1284     // Thread local vars aren't considered common linkage.
1285     return llvm::GlobalVariable::CommonLinkage;
1286   }
1287   return llvm::GlobalVariable::ExternalLinkage;
1288 }
1289 
1290 /// ReplaceUsesOfNonProtoTypeWithRealFunction - This function is called when we
1291 /// implement a function with no prototype, e.g. "int foo() {}".  If there are
1292 /// existing call uses of the old function in the module, this adjusts them to
1293 /// call the new function directly.
1294 ///
1295 /// This is not just a cleanup: the always_inline pass requires direct calls to
1296 /// functions to be able to inline them.  If there is a bitcast in the way, it
1297 /// won't inline them.  Instcombine normally deletes these calls, but it isn't
1298 /// run at -O0.
1299 static void ReplaceUsesOfNonProtoTypeWithRealFunction(llvm::GlobalValue *Old,
1300                                                       llvm::Function *NewFn) {
1301   // If we're redefining a global as a function, don't transform it.
1302   llvm::Function *OldFn = dyn_cast<llvm::Function>(Old);
1303   if (OldFn == 0) return;
1304 
1305   const llvm::Type *NewRetTy = NewFn->getReturnType();
1306   llvm::SmallVector<llvm::Value*, 4> ArgList;
1307 
1308   for (llvm::Value::use_iterator UI = OldFn->use_begin(), E = OldFn->use_end();
1309        UI != E; ) {
1310     // TODO: Do invokes ever occur in C code?  If so, we should handle them too.
1311     llvm::Value::use_iterator I = UI++; // Increment before the CI is erased.
1312     llvm::CallInst *CI = dyn_cast<llvm::CallInst>(*I);
1313     if (!CI) continue; // FIXME: when we allow Invoke, just do CallSite CS(*I)
1314     llvm::CallSite CS(CI);
1315     if (!CI || !CS.isCallee(I)) continue;
1316 
1317     // If the return types don't match exactly, and if the call isn't dead, then
1318     // we can't transform this call.
1319     if (CI->getType() != NewRetTy && !CI->use_empty())
1320       continue;
1321 
1322     // If the function was passed too few arguments, don't transform.  If extra
1323     // arguments were passed, we silently drop them.  If any of the types
1324     // mismatch, we don't transform.
1325     unsigned ArgNo = 0;
1326     bool DontTransform = false;
1327     for (llvm::Function::arg_iterator AI = NewFn->arg_begin(),
1328          E = NewFn->arg_end(); AI != E; ++AI, ++ArgNo) {
1329       if (CS.arg_size() == ArgNo ||
1330           CS.getArgument(ArgNo)->getType() != AI->getType()) {
1331         DontTransform = true;
1332         break;
1333       }
1334     }
1335     if (DontTransform)
1336       continue;
1337 
1338     // Okay, we can transform this.  Create the new call instruction and copy
1339     // over the required information.
1340     ArgList.append(CS.arg_begin(), CS.arg_begin() + ArgNo);
1341     llvm::CallInst *NewCall = llvm::CallInst::Create(NewFn, ArgList.begin(),
1342                                                      ArgList.end(), "", CI);
1343     ArgList.clear();
1344     if (!NewCall->getType()->isVoidTy())
1345       NewCall->takeName(CI);
1346     NewCall->setAttributes(CI->getAttributes());
1347     NewCall->setCallingConv(CI->getCallingConv());
1348 
1349     // Finally, remove the old call, replacing any uses with the new one.
1350     if (!CI->use_empty())
1351       CI->replaceAllUsesWith(NewCall);
1352 
1353     // Copy debug location attached to CI.
1354     if (!CI->getDebugLoc().isUnknown())
1355       NewCall->setDebugLoc(CI->getDebugLoc());
1356     CI->eraseFromParent();
1357   }
1358 }
1359 
1360 
1361 void CodeGenModule::EmitGlobalFunctionDefinition(GlobalDecl GD) {
1362   const FunctionDecl *D = cast<FunctionDecl>(GD.getDecl());
1363   const llvm::FunctionType *Ty = getTypes().GetFunctionType(GD);
1364   // Get or create the prototype for the function.
1365   llvm::Constant *Entry = GetAddrOfFunction(GD, Ty);
1366 
1367   // Strip off a bitcast if we got one back.
1368   if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(Entry)) {
1369     assert(CE->getOpcode() == llvm::Instruction::BitCast);
1370     Entry = CE->getOperand(0);
1371   }
1372 
1373 
1374   if (cast<llvm::GlobalValue>(Entry)->getType()->getElementType() != Ty) {
1375     llvm::GlobalValue *OldFn = cast<llvm::GlobalValue>(Entry);
1376 
1377     // If the types mismatch then we have to rewrite the definition.
1378     assert(OldFn->isDeclaration() &&
1379            "Shouldn't replace non-declaration");
1380 
1381     // F is the Function* for the one with the wrong type, we must make a new
1382     // Function* and update everything that used F (a declaration) with the new
1383     // Function* (which will be a definition).
1384     //
1385     // This happens if there is a prototype for a function
1386     // (e.g. "int f()") and then a definition of a different type
1387     // (e.g. "int f(int x)").  Move the old function aside so that it
1388     // doesn't interfere with GetAddrOfFunction.
1389     OldFn->setName(llvm::StringRef());
1390     llvm::Function *NewFn = cast<llvm::Function>(GetAddrOfFunction(GD, Ty));
1391 
1392     // If this is an implementation of a function without a prototype, try to
1393     // replace any existing uses of the function (which may be calls) with uses
1394     // of the new function
1395     if (D->getType()->isFunctionNoProtoType()) {
1396       ReplaceUsesOfNonProtoTypeWithRealFunction(OldFn, NewFn);
1397       OldFn->removeDeadConstantUsers();
1398     }
1399 
1400     // Replace uses of F with the Function we will endow with a body.
1401     if (!Entry->use_empty()) {
1402       llvm::Constant *NewPtrForOldDecl =
1403         llvm::ConstantExpr::getBitCast(NewFn, Entry->getType());
1404       Entry->replaceAllUsesWith(NewPtrForOldDecl);
1405     }
1406 
1407     // Ok, delete the old function now, which is dead.
1408     OldFn->eraseFromParent();
1409 
1410     Entry = NewFn;
1411   }
1412 
1413   // We need to set linkage and visibility on the function before
1414   // generating code for it because various parts of IR generation
1415   // want to propagate this information down (e.g. to local static
1416   // declarations).
1417   llvm::Function *Fn = cast<llvm::Function>(Entry);
1418   setFunctionLinkage(D, Fn);
1419 
1420   // FIXME: this is redundant with part of SetFunctionDefinitionAttributes
1421   setGlobalVisibility(Fn, D);
1422 
1423   CodeGenFunction(*this).GenerateCode(D, Fn);
1424 
1425   SetFunctionDefinitionAttributes(D, Fn);
1426   SetLLVMFunctionAttributesForDefinition(D, Fn);
1427 
1428   if (const ConstructorAttr *CA = D->getAttr<ConstructorAttr>())
1429     AddGlobalCtor(Fn, CA->getPriority());
1430   if (const DestructorAttr *DA = D->getAttr<DestructorAttr>())
1431     AddGlobalDtor(Fn, DA->getPriority());
1432 }
1433 
1434 void CodeGenModule::EmitAliasDefinition(GlobalDecl GD) {
1435   const ValueDecl *D = cast<ValueDecl>(GD.getDecl());
1436   const AliasAttr *AA = D->getAttr<AliasAttr>();
1437   assert(AA && "Not an alias?");
1438 
1439   llvm::StringRef MangledName = getMangledName(GD);
1440 
1441   // If there is a definition in the module, then it wins over the alias.
1442   // This is dubious, but allow it to be safe.  Just ignore the alias.
1443   llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
1444   if (Entry && !Entry->isDeclaration())
1445     return;
1446 
1447   const llvm::Type *DeclTy = getTypes().ConvertTypeForMem(D->getType());
1448 
1449   // Create a reference to the named value.  This ensures that it is emitted
1450   // if a deferred decl.
1451   llvm::Constant *Aliasee;
1452   if (isa<llvm::FunctionType>(DeclTy))
1453     Aliasee = GetOrCreateLLVMFunction(AA->getAliasee(), DeclTy, GlobalDecl());
1454   else
1455     Aliasee = GetOrCreateLLVMGlobal(AA->getAliasee(),
1456                                     llvm::PointerType::getUnqual(DeclTy), 0);
1457 
1458   // Create the new alias itself, but don't set a name yet.
1459   llvm::GlobalValue *GA =
1460     new llvm::GlobalAlias(Aliasee->getType(),
1461                           llvm::Function::ExternalLinkage,
1462                           "", Aliasee, &getModule());
1463 
1464   if (Entry) {
1465     assert(Entry->isDeclaration());
1466 
1467     // If there is a declaration in the module, then we had an extern followed
1468     // by the alias, as in:
1469     //   extern int test6();
1470     //   ...
1471     //   int test6() __attribute__((alias("test7")));
1472     //
1473     // Remove it and replace uses of it with the alias.
1474     GA->takeName(Entry);
1475 
1476     Entry->replaceAllUsesWith(llvm::ConstantExpr::getBitCast(GA,
1477                                                           Entry->getType()));
1478     Entry->eraseFromParent();
1479   } else {
1480     GA->setName(MangledName);
1481   }
1482 
1483   // Set attributes which are particular to an alias; this is a
1484   // specialization of the attributes which may be set on a global
1485   // variable/function.
1486   if (D->hasAttr<DLLExportAttr>()) {
1487     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
1488       // The dllexport attribute is ignored for undefined symbols.
1489       if (FD->hasBody())
1490         GA->setLinkage(llvm::Function::DLLExportLinkage);
1491     } else {
1492       GA->setLinkage(llvm::Function::DLLExportLinkage);
1493     }
1494   } else if (D->hasAttr<WeakAttr>() ||
1495              D->hasAttr<WeakRefAttr>() ||
1496              D->hasAttr<WeakImportAttr>()) {
1497     GA->setLinkage(llvm::Function::WeakAnyLinkage);
1498   }
1499 
1500   SetCommonAttributes(D, GA);
1501 }
1502 
1503 /// getBuiltinLibFunction - Given a builtin id for a function like
1504 /// "__builtin_fabsf", return a Function* for "fabsf".
1505 llvm::Value *CodeGenModule::getBuiltinLibFunction(const FunctionDecl *FD,
1506                                                   unsigned BuiltinID) {
1507   assert((Context.BuiltinInfo.isLibFunction(BuiltinID) ||
1508           Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID)) &&
1509          "isn't a lib fn");
1510 
1511   // Get the name, skip over the __builtin_ prefix (if necessary).
1512   const char *Name = Context.BuiltinInfo.GetName(BuiltinID);
1513   if (Context.BuiltinInfo.isLibFunction(BuiltinID))
1514     Name += 10;
1515 
1516   const llvm::FunctionType *Ty =
1517     cast<llvm::FunctionType>(getTypes().ConvertType(FD->getType()));
1518 
1519   return GetOrCreateLLVMFunction(Name, Ty, GlobalDecl(FD));
1520 }
1521 
1522 llvm::Function *CodeGenModule::getIntrinsic(unsigned IID,const llvm::Type **Tys,
1523                                             unsigned NumTys) {
1524   return llvm::Intrinsic::getDeclaration(&getModule(),
1525                                          (llvm::Intrinsic::ID)IID, Tys, NumTys);
1526 }
1527 
1528 static llvm::StringMapEntry<llvm::Constant*> &
1529 GetConstantCFStringEntry(llvm::StringMap<llvm::Constant*> &Map,
1530                          const StringLiteral *Literal,
1531                          bool TargetIsLSB,
1532                          bool &IsUTF16,
1533                          unsigned &StringLength) {
1534   llvm::StringRef String = Literal->getString();
1535   unsigned NumBytes = String.size();
1536 
1537   // Check for simple case.
1538   if (!Literal->containsNonAsciiOrNull()) {
1539     StringLength = NumBytes;
1540     return Map.GetOrCreateValue(String);
1541   }
1542 
1543   // Otherwise, convert the UTF8 literals into a byte string.
1544   llvm::SmallVector<UTF16, 128> ToBuf(NumBytes);
1545   const UTF8 *FromPtr = (UTF8 *)String.data();
1546   UTF16 *ToPtr = &ToBuf[0];
1547 
1548   (void)ConvertUTF8toUTF16(&FromPtr, FromPtr + NumBytes,
1549                            &ToPtr, ToPtr + NumBytes,
1550                            strictConversion);
1551 
1552   // ConvertUTF8toUTF16 returns the length in ToPtr.
1553   StringLength = ToPtr - &ToBuf[0];
1554 
1555   // Render the UTF-16 string into a byte array and convert to the target byte
1556   // order.
1557   //
1558   // FIXME: This isn't something we should need to do here.
1559   llvm::SmallString<128> AsBytes;
1560   AsBytes.reserve(StringLength * 2);
1561   for (unsigned i = 0; i != StringLength; ++i) {
1562     unsigned short Val = ToBuf[i];
1563     if (TargetIsLSB) {
1564       AsBytes.push_back(Val & 0xFF);
1565       AsBytes.push_back(Val >> 8);
1566     } else {
1567       AsBytes.push_back(Val >> 8);
1568       AsBytes.push_back(Val & 0xFF);
1569     }
1570   }
1571   // Append one extra null character, the second is automatically added by our
1572   // caller.
1573   AsBytes.push_back(0);
1574 
1575   IsUTF16 = true;
1576   return Map.GetOrCreateValue(llvm::StringRef(AsBytes.data(), AsBytes.size()));
1577 }
1578 
1579 llvm::Constant *
1580 CodeGenModule::GetAddrOfConstantCFString(const StringLiteral *Literal) {
1581   unsigned StringLength = 0;
1582   bool isUTF16 = false;
1583   llvm::StringMapEntry<llvm::Constant*> &Entry =
1584     GetConstantCFStringEntry(CFConstantStringMap, Literal,
1585                              getTargetData().isLittleEndian(),
1586                              isUTF16, StringLength);
1587 
1588   if (llvm::Constant *C = Entry.getValue())
1589     return C;
1590 
1591   llvm::Constant *Zero =
1592       llvm::Constant::getNullValue(llvm::Type::getInt32Ty(VMContext));
1593   llvm::Constant *Zeros[] = { Zero, Zero };
1594 
1595   // If we don't already have it, get __CFConstantStringClassReference.
1596   if (!CFConstantStringClassRef) {
1597     const llvm::Type *Ty = getTypes().ConvertType(getContext().IntTy);
1598     Ty = llvm::ArrayType::get(Ty, 0);
1599     llvm::Constant *GV = CreateRuntimeVariable(Ty,
1600                                            "__CFConstantStringClassReference");
1601     // Decay array -> ptr
1602     CFConstantStringClassRef =
1603       llvm::ConstantExpr::getGetElementPtr(GV, Zeros, 2);
1604   }
1605 
1606   QualType CFTy = getContext().getCFConstantStringType();
1607 
1608   const llvm::StructType *STy =
1609     cast<llvm::StructType>(getTypes().ConvertType(CFTy));
1610 
1611   std::vector<llvm::Constant*> Fields(4);
1612 
1613   // Class pointer.
1614   Fields[0] = CFConstantStringClassRef;
1615 
1616   // Flags.
1617   const llvm::Type *Ty = getTypes().ConvertType(getContext().UnsignedIntTy);
1618   Fields[1] = isUTF16 ? llvm::ConstantInt::get(Ty, 0x07d0) :
1619     llvm::ConstantInt::get(Ty, 0x07C8);
1620 
1621   // String pointer.
1622   llvm::Constant *C = llvm::ConstantArray::get(VMContext, Entry.getKey().str());
1623 
1624   llvm::GlobalValue::LinkageTypes Linkage;
1625   bool isConstant;
1626   if (isUTF16) {
1627     // FIXME: why do utf strings get "_" labels instead of "L" labels?
1628     Linkage = llvm::GlobalValue::InternalLinkage;
1629     // Note: -fwritable-strings doesn't make unicode CFStrings writable, but
1630     // does make plain ascii ones writable.
1631     isConstant = true;
1632   } else {
1633     Linkage = llvm::GlobalValue::PrivateLinkage;
1634     isConstant = !Features.WritableStrings;
1635   }
1636 
1637   llvm::GlobalVariable *GV =
1638     new llvm::GlobalVariable(getModule(), C->getType(), isConstant, Linkage, C,
1639                              ".str");
1640   GV->setUnnamedAddr(true);
1641   if (isUTF16) {
1642     CharUnits Align = getContext().getTypeAlignInChars(getContext().ShortTy);
1643     GV->setAlignment(Align.getQuantity());
1644   }
1645   Fields[2] = llvm::ConstantExpr::getGetElementPtr(GV, Zeros, 2);
1646 
1647   // String length.
1648   Ty = getTypes().ConvertType(getContext().LongTy);
1649   Fields[3] = llvm::ConstantInt::get(Ty, StringLength);
1650 
1651   // The struct.
1652   C = llvm::ConstantStruct::get(STy, Fields);
1653   GV = new llvm::GlobalVariable(getModule(), C->getType(), true,
1654                                 llvm::GlobalVariable::PrivateLinkage, C,
1655                                 "_unnamed_cfstring_");
1656   if (const char *Sect = getContext().Target.getCFStringSection())
1657     GV->setSection(Sect);
1658   Entry.setValue(GV);
1659 
1660   return GV;
1661 }
1662 
1663 llvm::Constant *
1664 CodeGenModule::GetAddrOfConstantString(const StringLiteral *Literal) {
1665   unsigned StringLength = 0;
1666   bool isUTF16 = false;
1667   llvm::StringMapEntry<llvm::Constant*> &Entry =
1668     GetConstantCFStringEntry(CFConstantStringMap, Literal,
1669                              getTargetData().isLittleEndian(),
1670                              isUTF16, StringLength);
1671 
1672   if (llvm::Constant *C = Entry.getValue())
1673     return C;
1674 
1675   llvm::Constant *Zero =
1676   llvm::Constant::getNullValue(llvm::Type::getInt32Ty(VMContext));
1677   llvm::Constant *Zeros[] = { Zero, Zero };
1678 
1679   // If we don't already have it, get _NSConstantStringClassReference.
1680   if (!ConstantStringClassRef) {
1681     std::string StringClass(getLangOptions().ObjCConstantStringClass);
1682     const llvm::Type *Ty = getTypes().ConvertType(getContext().IntTy);
1683     Ty = llvm::ArrayType::get(Ty, 0);
1684     llvm::Constant *GV;
1685     if (StringClass.empty())
1686       GV = CreateRuntimeVariable(Ty,
1687                                  Features.ObjCNonFragileABI ?
1688                                  "OBJC_CLASS_$_NSConstantString" :
1689                                  "_NSConstantStringClassReference");
1690     else {
1691       std::string str;
1692       if (Features.ObjCNonFragileABI)
1693         str = "OBJC_CLASS_$_" + StringClass;
1694       else
1695         str = "_" + StringClass + "ClassReference";
1696       GV = CreateRuntimeVariable(Ty, str);
1697     }
1698     // Decay array -> ptr
1699     ConstantStringClassRef =
1700     llvm::ConstantExpr::getGetElementPtr(GV, Zeros, 2);
1701   }
1702 
1703   QualType NSTy = getContext().getNSConstantStringType();
1704 
1705   const llvm::StructType *STy =
1706   cast<llvm::StructType>(getTypes().ConvertType(NSTy));
1707 
1708   std::vector<llvm::Constant*> Fields(3);
1709 
1710   // Class pointer.
1711   Fields[0] = ConstantStringClassRef;
1712 
1713   // String pointer.
1714   llvm::Constant *C = llvm::ConstantArray::get(VMContext, Entry.getKey().str());
1715 
1716   llvm::GlobalValue::LinkageTypes Linkage;
1717   bool isConstant;
1718   if (isUTF16) {
1719     // FIXME: why do utf strings get "_" labels instead of "L" labels?
1720     Linkage = llvm::GlobalValue::InternalLinkage;
1721     // Note: -fwritable-strings doesn't make unicode NSStrings writable, but
1722     // does make plain ascii ones writable.
1723     isConstant = true;
1724   } else {
1725     Linkage = llvm::GlobalValue::PrivateLinkage;
1726     isConstant = !Features.WritableStrings;
1727   }
1728 
1729   llvm::GlobalVariable *GV =
1730   new llvm::GlobalVariable(getModule(), C->getType(), isConstant, Linkage, C,
1731                            ".str");
1732   GV->setUnnamedAddr(true);
1733   if (isUTF16) {
1734     CharUnits Align = getContext().getTypeAlignInChars(getContext().ShortTy);
1735     GV->setAlignment(Align.getQuantity());
1736   }
1737   Fields[1] = llvm::ConstantExpr::getGetElementPtr(GV, Zeros, 2);
1738 
1739   // String length.
1740   const llvm::Type *Ty = getTypes().ConvertType(getContext().UnsignedIntTy);
1741   Fields[2] = llvm::ConstantInt::get(Ty, StringLength);
1742 
1743   // The struct.
1744   C = llvm::ConstantStruct::get(STy, Fields);
1745   GV = new llvm::GlobalVariable(getModule(), C->getType(), true,
1746                                 llvm::GlobalVariable::PrivateLinkage, C,
1747                                 "_unnamed_nsstring_");
1748   // FIXME. Fix section.
1749   if (const char *Sect =
1750         Features.ObjCNonFragileABI
1751           ? getContext().Target.getNSStringNonFragileABISection()
1752           : getContext().Target.getNSStringSection())
1753     GV->setSection(Sect);
1754   Entry.setValue(GV);
1755 
1756   return GV;
1757 }
1758 
1759 /// GetStringForStringLiteral - Return the appropriate bytes for a
1760 /// string literal, properly padded to match the literal type.
1761 std::string CodeGenModule::GetStringForStringLiteral(const StringLiteral *E) {
1762   const ASTContext &Context = getContext();
1763   const ConstantArrayType *CAT =
1764     Context.getAsConstantArrayType(E->getType());
1765   assert(CAT && "String isn't pointer or array!");
1766 
1767   // Resize the string to the right size.
1768   uint64_t RealLen = CAT->getSize().getZExtValue();
1769 
1770   if (E->isWide())
1771     RealLen *= Context.Target.getWCharWidth() / Context.getCharWidth();
1772 
1773   std::string Str = E->getString().str();
1774   Str.resize(RealLen, '\0');
1775 
1776   return Str;
1777 }
1778 
1779 /// GetAddrOfConstantStringFromLiteral - Return a pointer to a
1780 /// constant array for the given string literal.
1781 llvm::Constant *
1782 CodeGenModule::GetAddrOfConstantStringFromLiteral(const StringLiteral *S) {
1783   // FIXME: This can be more efficient.
1784   // FIXME: We shouldn't need to bitcast the constant in the wide string case.
1785   llvm::Constant *C = GetAddrOfConstantString(GetStringForStringLiteral(S));
1786   if (S->isWide()) {
1787     llvm::Type *DestTy =
1788         llvm::PointerType::getUnqual(getTypes().ConvertType(S->getType()));
1789     C = llvm::ConstantExpr::getBitCast(C, DestTy);
1790   }
1791   return C;
1792 }
1793 
1794 /// GetAddrOfConstantStringFromObjCEncode - Return a pointer to a constant
1795 /// array for the given ObjCEncodeExpr node.
1796 llvm::Constant *
1797 CodeGenModule::GetAddrOfConstantStringFromObjCEncode(const ObjCEncodeExpr *E) {
1798   std::string Str;
1799   getContext().getObjCEncodingForType(E->getEncodedType(), Str);
1800 
1801   return GetAddrOfConstantCString(Str);
1802 }
1803 
1804 
1805 /// GenerateWritableString -- Creates storage for a string literal.
1806 static llvm::Constant *GenerateStringLiteral(const std::string &str,
1807                                              bool constant,
1808                                              CodeGenModule &CGM,
1809                                              const char *GlobalName) {
1810   // Create Constant for this string literal. Don't add a '\0'.
1811   llvm::Constant *C =
1812       llvm::ConstantArray::get(CGM.getLLVMContext(), str, false);
1813 
1814   // Create a global variable for this string
1815   llvm::GlobalVariable *GV =
1816     new llvm::GlobalVariable(CGM.getModule(), C->getType(), constant,
1817                              llvm::GlobalValue::PrivateLinkage,
1818                              C, GlobalName);
1819   GV->setUnnamedAddr(true);
1820   return GV;
1821 }
1822 
1823 /// GetAddrOfConstantString - Returns a pointer to a character array
1824 /// containing the literal. This contents are exactly that of the
1825 /// given string, i.e. it will not be null terminated automatically;
1826 /// see GetAddrOfConstantCString. Note that whether the result is
1827 /// actually a pointer to an LLVM constant depends on
1828 /// Feature.WriteableStrings.
1829 ///
1830 /// The result has pointer to array type.
1831 llvm::Constant *CodeGenModule::GetAddrOfConstantString(const std::string &str,
1832                                                        const char *GlobalName) {
1833   bool IsConstant = !Features.WritableStrings;
1834 
1835   // Get the default prefix if a name wasn't specified.
1836   if (!GlobalName)
1837     GlobalName = ".str";
1838 
1839   // Don't share any string literals if strings aren't constant.
1840   if (!IsConstant)
1841     return GenerateStringLiteral(str, false, *this, GlobalName);
1842 
1843   llvm::StringMapEntry<llvm::Constant *> &Entry =
1844     ConstantStringMap.GetOrCreateValue(&str[0], &str[str.length()]);
1845 
1846   if (Entry.getValue())
1847     return Entry.getValue();
1848 
1849   // Create a global variable for this.
1850   llvm::Constant *C = GenerateStringLiteral(str, true, *this, GlobalName);
1851   Entry.setValue(C);
1852   return C;
1853 }
1854 
1855 /// GetAddrOfConstantCString - Returns a pointer to a character
1856 /// array containing the literal and a terminating '\-'
1857 /// character. The result has pointer to array type.
1858 llvm::Constant *CodeGenModule::GetAddrOfConstantCString(const std::string &str,
1859                                                         const char *GlobalName){
1860   return GetAddrOfConstantString(str + '\0', GlobalName);
1861 }
1862 
1863 /// EmitObjCPropertyImplementations - Emit information for synthesized
1864 /// properties for an implementation.
1865 void CodeGenModule::EmitObjCPropertyImplementations(const
1866                                                     ObjCImplementationDecl *D) {
1867   for (ObjCImplementationDecl::propimpl_iterator
1868          i = D->propimpl_begin(), e = D->propimpl_end(); i != e; ++i) {
1869     ObjCPropertyImplDecl *PID = *i;
1870 
1871     // Dynamic is just for type-checking.
1872     if (PID->getPropertyImplementation() == ObjCPropertyImplDecl::Synthesize) {
1873       ObjCPropertyDecl *PD = PID->getPropertyDecl();
1874 
1875       // Determine which methods need to be implemented, some may have
1876       // been overridden. Note that ::isSynthesized is not the method
1877       // we want, that just indicates if the decl came from a
1878       // property. What we want to know is if the method is defined in
1879       // this implementation.
1880       if (!D->getInstanceMethod(PD->getGetterName()))
1881         CodeGenFunction(*this).GenerateObjCGetter(
1882                                  const_cast<ObjCImplementationDecl *>(D), PID);
1883       if (!PD->isReadOnly() &&
1884           !D->getInstanceMethod(PD->getSetterName()))
1885         CodeGenFunction(*this).GenerateObjCSetter(
1886                                  const_cast<ObjCImplementationDecl *>(D), PID);
1887     }
1888   }
1889 }
1890 
1891 /// EmitObjCIvarInitializations - Emit information for ivar initialization
1892 /// for an implementation.
1893 void CodeGenModule::EmitObjCIvarInitializations(ObjCImplementationDecl *D) {
1894   if (!Features.NeXTRuntime || D->getNumIvarInitializers() == 0)
1895     return;
1896   DeclContext* DC = const_cast<DeclContext*>(dyn_cast<DeclContext>(D));
1897   assert(DC && "EmitObjCIvarInitializations - null DeclContext");
1898   IdentifierInfo *II = &getContext().Idents.get(".cxx_destruct");
1899   Selector cxxSelector = getContext().Selectors.getSelector(0, &II);
1900   ObjCMethodDecl *DTORMethod = ObjCMethodDecl::Create(getContext(),
1901                                                   D->getLocation(),
1902                                                   D->getLocation(), cxxSelector,
1903                                                   getContext().VoidTy, 0,
1904                                                   DC, true, false, true, false,
1905                                                   ObjCMethodDecl::Required);
1906   D->addInstanceMethod(DTORMethod);
1907   CodeGenFunction(*this).GenerateObjCCtorDtorMethod(D, DTORMethod, false);
1908 
1909   II = &getContext().Idents.get(".cxx_construct");
1910   cxxSelector = getContext().Selectors.getSelector(0, &II);
1911   // The constructor returns 'self'.
1912   ObjCMethodDecl *CTORMethod = ObjCMethodDecl::Create(getContext(),
1913                                                 D->getLocation(),
1914                                                 D->getLocation(), cxxSelector,
1915                                                 getContext().getObjCIdType(), 0,
1916                                                 DC, true, false, true, false,
1917                                                 ObjCMethodDecl::Required);
1918   D->addInstanceMethod(CTORMethod);
1919   CodeGenFunction(*this).GenerateObjCCtorDtorMethod(D, CTORMethod, true);
1920 
1921 
1922 }
1923 
1924 /// EmitNamespace - Emit all declarations in a namespace.
1925 void CodeGenModule::EmitNamespace(const NamespaceDecl *ND) {
1926   for (RecordDecl::decl_iterator I = ND->decls_begin(), E = ND->decls_end();
1927        I != E; ++I)
1928     EmitTopLevelDecl(*I);
1929 }
1930 
1931 // EmitLinkageSpec - Emit all declarations in a linkage spec.
1932 void CodeGenModule::EmitLinkageSpec(const LinkageSpecDecl *LSD) {
1933   if (LSD->getLanguage() != LinkageSpecDecl::lang_c &&
1934       LSD->getLanguage() != LinkageSpecDecl::lang_cxx) {
1935     ErrorUnsupported(LSD, "linkage spec");
1936     return;
1937   }
1938 
1939   for (RecordDecl::decl_iterator I = LSD->decls_begin(), E = LSD->decls_end();
1940        I != E; ++I)
1941     EmitTopLevelDecl(*I);
1942 }
1943 
1944 /// EmitTopLevelDecl - Emit code for a single top level declaration.
1945 void CodeGenModule::EmitTopLevelDecl(Decl *D) {
1946   // If an error has occurred, stop code generation, but continue
1947   // parsing and semantic analysis (to ensure all warnings and errors
1948   // are emitted).
1949   if (Diags.hasErrorOccurred())
1950     return;
1951 
1952   // Ignore dependent declarations.
1953   if (D->getDeclContext() && D->getDeclContext()->isDependentContext())
1954     return;
1955 
1956   switch (D->getKind()) {
1957   case Decl::CXXConversion:
1958   case Decl::CXXMethod:
1959   case Decl::Function:
1960     // Skip function templates
1961     if (cast<FunctionDecl>(D)->getDescribedFunctionTemplate())
1962       return;
1963 
1964     EmitGlobal(cast<FunctionDecl>(D));
1965     break;
1966 
1967   case Decl::Var:
1968     EmitGlobal(cast<VarDecl>(D));
1969     break;
1970 
1971   // C++ Decls
1972   case Decl::Namespace:
1973     EmitNamespace(cast<NamespaceDecl>(D));
1974     break;
1975     // No code generation needed.
1976   case Decl::UsingShadow:
1977   case Decl::Using:
1978   case Decl::UsingDirective:
1979   case Decl::ClassTemplate:
1980   case Decl::FunctionTemplate:
1981   case Decl::NamespaceAlias:
1982     break;
1983   case Decl::CXXConstructor:
1984     // Skip function templates
1985     if (cast<FunctionDecl>(D)->getDescribedFunctionTemplate())
1986       return;
1987 
1988     EmitCXXConstructors(cast<CXXConstructorDecl>(D));
1989     break;
1990   case Decl::CXXDestructor:
1991     EmitCXXDestructors(cast<CXXDestructorDecl>(D));
1992     break;
1993 
1994   case Decl::StaticAssert:
1995     // Nothing to do.
1996     break;
1997 
1998   // Objective-C Decls
1999 
2000   // Forward declarations, no (immediate) code generation.
2001   case Decl::ObjCClass:
2002   case Decl::ObjCForwardProtocol:
2003   case Decl::ObjCInterface:
2004     break;
2005 
2006     case Decl::ObjCCategory: {
2007       ObjCCategoryDecl *CD = cast<ObjCCategoryDecl>(D);
2008       if (CD->IsClassExtension() && CD->hasSynthBitfield())
2009         Context.ResetObjCLayout(CD->getClassInterface());
2010       break;
2011     }
2012 
2013 
2014   case Decl::ObjCProtocol:
2015     Runtime->GenerateProtocol(cast<ObjCProtocolDecl>(D));
2016     break;
2017 
2018   case Decl::ObjCCategoryImpl:
2019     // Categories have properties but don't support synthesize so we
2020     // can ignore them here.
2021     Runtime->GenerateCategory(cast<ObjCCategoryImplDecl>(D));
2022     break;
2023 
2024   case Decl::ObjCImplementation: {
2025     ObjCImplementationDecl *OMD = cast<ObjCImplementationDecl>(D);
2026     if (Features.ObjCNonFragileABI2 && OMD->hasSynthBitfield())
2027       Context.ResetObjCLayout(OMD->getClassInterface());
2028     EmitObjCPropertyImplementations(OMD);
2029     EmitObjCIvarInitializations(OMD);
2030     Runtime->GenerateClass(OMD);
2031     break;
2032   }
2033   case Decl::ObjCMethod: {
2034     ObjCMethodDecl *OMD = cast<ObjCMethodDecl>(D);
2035     // If this is not a prototype, emit the body.
2036     if (OMD->getBody())
2037       CodeGenFunction(*this).GenerateObjCMethod(OMD);
2038     break;
2039   }
2040   case Decl::ObjCCompatibleAlias:
2041     // compatibility-alias is a directive and has no code gen.
2042     break;
2043 
2044   case Decl::LinkageSpec:
2045     EmitLinkageSpec(cast<LinkageSpecDecl>(D));
2046     break;
2047 
2048   case Decl::FileScopeAsm: {
2049     FileScopeAsmDecl *AD = cast<FileScopeAsmDecl>(D);
2050     llvm::StringRef AsmString = AD->getAsmString()->getString();
2051 
2052     const std::string &S = getModule().getModuleInlineAsm();
2053     if (S.empty())
2054       getModule().setModuleInlineAsm(AsmString);
2055     else
2056       getModule().setModuleInlineAsm(S + '\n' + AsmString.str());
2057     break;
2058   }
2059 
2060   default:
2061     // Make sure we handled everything we should, every other kind is a
2062     // non-top-level decl.  FIXME: Would be nice to have an isTopLevelDeclKind
2063     // function. Need to recode Decl::Kind to do that easily.
2064     assert(isa<TypeDecl>(D) && "Unsupported decl kind");
2065   }
2066 }
2067 
2068 /// Turns the given pointer into a constant.
2069 static llvm::Constant *GetPointerConstant(llvm::LLVMContext &Context,
2070                                           const void *Ptr) {
2071   uintptr_t PtrInt = reinterpret_cast<uintptr_t>(Ptr);
2072   const llvm::Type *i64 = llvm::Type::getInt64Ty(Context);
2073   return llvm::ConstantInt::get(i64, PtrInt);
2074 }
2075 
2076 static void EmitGlobalDeclMetadata(CodeGenModule &CGM,
2077                                    llvm::NamedMDNode *&GlobalMetadata,
2078                                    GlobalDecl D,
2079                                    llvm::GlobalValue *Addr) {
2080   if (!GlobalMetadata)
2081     GlobalMetadata =
2082       CGM.getModule().getOrInsertNamedMetadata("clang.global.decl.ptrs");
2083 
2084   // TODO: should we report variant information for ctors/dtors?
2085   llvm::Value *Ops[] = {
2086     Addr,
2087     GetPointerConstant(CGM.getLLVMContext(), D.getDecl())
2088   };
2089   GlobalMetadata->addOperand(llvm::MDNode::get(CGM.getLLVMContext(), Ops, 2));
2090 }
2091 
2092 /// Emits metadata nodes associating all the global values in the
2093 /// current module with the Decls they came from.  This is useful for
2094 /// projects using IR gen as a subroutine.
2095 ///
2096 /// Since there's currently no way to associate an MDNode directly
2097 /// with an llvm::GlobalValue, we create a global named metadata
2098 /// with the name 'clang.global.decl.ptrs'.
2099 void CodeGenModule::EmitDeclMetadata() {
2100   llvm::NamedMDNode *GlobalMetadata = 0;
2101 
2102   // StaticLocalDeclMap
2103   for (llvm::DenseMap<GlobalDecl,llvm::StringRef>::iterator
2104          I = MangledDeclNames.begin(), E = MangledDeclNames.end();
2105        I != E; ++I) {
2106     llvm::GlobalValue *Addr = getModule().getNamedValue(I->second);
2107     EmitGlobalDeclMetadata(*this, GlobalMetadata, I->first, Addr);
2108   }
2109 }
2110 
2111 /// Emits metadata nodes for all the local variables in the current
2112 /// function.
2113 void CodeGenFunction::EmitDeclMetadata() {
2114   if (LocalDeclMap.empty()) return;
2115 
2116   llvm::LLVMContext &Context = getLLVMContext();
2117 
2118   // Find the unique metadata ID for this name.
2119   unsigned DeclPtrKind = Context.getMDKindID("clang.decl.ptr");
2120 
2121   llvm::NamedMDNode *GlobalMetadata = 0;
2122 
2123   for (llvm::DenseMap<const Decl*, llvm::Value*>::iterator
2124          I = LocalDeclMap.begin(), E = LocalDeclMap.end(); I != E; ++I) {
2125     const Decl *D = I->first;
2126     llvm::Value *Addr = I->second;
2127 
2128     if (llvm::AllocaInst *Alloca = dyn_cast<llvm::AllocaInst>(Addr)) {
2129       llvm::Value *DAddr = GetPointerConstant(getLLVMContext(), D);
2130       Alloca->setMetadata(DeclPtrKind, llvm::MDNode::get(Context, &DAddr, 1));
2131     } else if (llvm::GlobalValue *GV = dyn_cast<llvm::GlobalValue>(Addr)) {
2132       GlobalDecl GD = GlobalDecl(cast<VarDecl>(D));
2133       EmitGlobalDeclMetadata(CGM, GlobalMetadata, GD, GV);
2134     }
2135   }
2136 }
2137 
2138 ///@name Custom Runtime Function Interfaces
2139 ///@{
2140 //
2141 // FIXME: These can be eliminated once we can have clients just get the required
2142 // AST nodes from the builtin tables.
2143 
2144 llvm::Constant *CodeGenModule::getBlockObjectDispose() {
2145   if (BlockObjectDispose)
2146     return BlockObjectDispose;
2147 
2148   // If we saw an explicit decl, use that.
2149   if (BlockObjectDisposeDecl) {
2150     return BlockObjectDispose = GetAddrOfFunction(
2151       BlockObjectDisposeDecl,
2152       getTypes().GetFunctionType(BlockObjectDisposeDecl));
2153   }
2154 
2155   // Otherwise construct the function by hand.
2156   const llvm::FunctionType *FTy;
2157   std::vector<const llvm::Type*> ArgTys;
2158   const llvm::Type *ResultType = llvm::Type::getVoidTy(VMContext);
2159   ArgTys.push_back(PtrToInt8Ty);
2160   ArgTys.push_back(llvm::Type::getInt32Ty(VMContext));
2161   FTy = llvm::FunctionType::get(ResultType, ArgTys, false);
2162   return BlockObjectDispose =
2163     CreateRuntimeFunction(FTy, "_Block_object_dispose");
2164 }
2165 
2166 llvm::Constant *CodeGenModule::getBlockObjectAssign() {
2167   if (BlockObjectAssign)
2168     return BlockObjectAssign;
2169 
2170   // If we saw an explicit decl, use that.
2171   if (BlockObjectAssignDecl) {
2172     return BlockObjectAssign = GetAddrOfFunction(
2173       BlockObjectAssignDecl,
2174       getTypes().GetFunctionType(BlockObjectAssignDecl));
2175   }
2176 
2177   // Otherwise construct the function by hand.
2178   const llvm::FunctionType *FTy;
2179   std::vector<const llvm::Type*> ArgTys;
2180   const llvm::Type *ResultType = llvm::Type::getVoidTy(VMContext);
2181   ArgTys.push_back(PtrToInt8Ty);
2182   ArgTys.push_back(PtrToInt8Ty);
2183   ArgTys.push_back(llvm::Type::getInt32Ty(VMContext));
2184   FTy = llvm::FunctionType::get(ResultType, ArgTys, false);
2185   return BlockObjectAssign =
2186     CreateRuntimeFunction(FTy, "_Block_object_assign");
2187 }
2188 
2189 llvm::Constant *CodeGenModule::getNSConcreteGlobalBlock() {
2190   if (NSConcreteGlobalBlock)
2191     return NSConcreteGlobalBlock;
2192 
2193   // If we saw an explicit decl, use that.
2194   if (NSConcreteGlobalBlockDecl) {
2195     return NSConcreteGlobalBlock = GetAddrOfGlobalVar(
2196       NSConcreteGlobalBlockDecl,
2197       getTypes().ConvertType(NSConcreteGlobalBlockDecl->getType()));
2198   }
2199 
2200   // Otherwise construct the variable by hand.
2201   return NSConcreteGlobalBlock = CreateRuntimeVariable(
2202     PtrToInt8Ty, "_NSConcreteGlobalBlock");
2203 }
2204 
2205 llvm::Constant *CodeGenModule::getNSConcreteStackBlock() {
2206   if (NSConcreteStackBlock)
2207     return NSConcreteStackBlock;
2208 
2209   // If we saw an explicit decl, use that.
2210   if (NSConcreteStackBlockDecl) {
2211     return NSConcreteStackBlock = GetAddrOfGlobalVar(
2212       NSConcreteStackBlockDecl,
2213       getTypes().ConvertType(NSConcreteStackBlockDecl->getType()));
2214   }
2215 
2216   // Otherwise construct the variable by hand.
2217   return NSConcreteStackBlock = CreateRuntimeVariable(
2218     PtrToInt8Ty, "_NSConcreteStackBlock");
2219 }
2220 
2221 ///@}
2222