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1 //===--- CodeGenTypes.cpp - Type translation for LLVM CodeGen -------------===//
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 is the code that handles AST -> LLVM type lowering.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CodeGenTypes.h"
15 #include "CGCall.h"
16 #include "CGCXXABI.h"
17 #include "CGRecordLayout.h"
18 #include "TargetInfo.h"
19 #include "clang/AST/ASTContext.h"
20 #include "clang/AST/DeclObjC.h"
21 #include "clang/AST/DeclCXX.h"
22 #include "clang/AST/Expr.h"
23 #include "clang/AST/RecordLayout.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Module.h"
26 #include "llvm/Target/TargetData.h"
27 using namespace clang;
28 using namespace CodeGen;
29 
CodeGenTypes(CodeGenModule & CGM)30 CodeGenTypes::CodeGenTypes(CodeGenModule &CGM)
31   : Context(CGM.getContext()), Target(Context.getTargetInfo()),
32     TheModule(CGM.getModule()), TheTargetData(CGM.getTargetData()),
33     TheABIInfo(CGM.getTargetCodeGenInfo().getABIInfo()),
34     TheCXXABI(CGM.getCXXABI()),
35     CodeGenOpts(CGM.getCodeGenOpts()), CGM(CGM) {
36   SkippedLayout = false;
37 }
38 
~CodeGenTypes()39 CodeGenTypes::~CodeGenTypes() {
40   for (llvm::DenseMap<const Type *, CGRecordLayout *>::iterator
41          I = CGRecordLayouts.begin(), E = CGRecordLayouts.end();
42       I != E; ++I)
43     delete I->second;
44 
45   for (llvm::FoldingSet<CGFunctionInfo>::iterator
46        I = FunctionInfos.begin(), E = FunctionInfos.end(); I != E; )
47     delete &*I++;
48 }
49 
addRecordTypeName(const RecordDecl * RD,llvm::StructType * Ty,StringRef suffix)50 void CodeGenTypes::addRecordTypeName(const RecordDecl *RD,
51                                      llvm::StructType *Ty,
52                                      StringRef suffix) {
53   SmallString<256> TypeName;
54   llvm::raw_svector_ostream OS(TypeName);
55   OS << RD->getKindName() << '.';
56 
57   // Name the codegen type after the typedef name
58   // if there is no tag type name available
59   if (RD->getIdentifier()) {
60     // FIXME: We should not have to check for a null decl context here.
61     // Right now we do it because the implicit Obj-C decls don't have one.
62     if (RD->getDeclContext())
63       OS << RD->getQualifiedNameAsString();
64     else
65       RD->printName(OS);
66   } else if (const TypedefNameDecl *TDD = RD->getTypedefNameForAnonDecl()) {
67     // FIXME: We should not have to check for a null decl context here.
68     // Right now we do it because the implicit Obj-C decls don't have one.
69     if (TDD->getDeclContext())
70       OS << TDD->getQualifiedNameAsString();
71     else
72       TDD->printName(OS);
73   } else
74     OS << "anon";
75 
76   if (!suffix.empty())
77     OS << suffix;
78 
79   Ty->setName(OS.str());
80 }
81 
82 /// ConvertTypeForMem - Convert type T into a llvm::Type.  This differs from
83 /// ConvertType in that it is used to convert to the memory representation for
84 /// a type.  For example, the scalar representation for _Bool is i1, but the
85 /// memory representation is usually i8 or i32, depending on the target.
ConvertTypeForMem(QualType T)86 llvm::Type *CodeGenTypes::ConvertTypeForMem(QualType T){
87   llvm::Type *R = ConvertType(T);
88 
89   // If this is a non-bool type, don't map it.
90   if (!R->isIntegerTy(1))
91     return R;
92 
93   // Otherwise, return an integer of the target-specified size.
94   return llvm::IntegerType::get(getLLVMContext(),
95                                 (unsigned)Context.getTypeSize(T));
96 }
97 
98 
99 /// isRecordLayoutComplete - Return true if the specified type is already
100 /// completely laid out.
isRecordLayoutComplete(const Type * Ty) const101 bool CodeGenTypes::isRecordLayoutComplete(const Type *Ty) const {
102   llvm::DenseMap<const Type*, llvm::StructType *>::const_iterator I =
103   RecordDeclTypes.find(Ty);
104   return I != RecordDeclTypes.end() && !I->second->isOpaque();
105 }
106 
107 static bool
108 isSafeToConvert(QualType T, CodeGenTypes &CGT,
109                 llvm::SmallPtrSet<const RecordDecl*, 16> &AlreadyChecked);
110 
111 
112 /// isSafeToConvert - Return true if it is safe to convert the specified record
113 /// decl to IR and lay it out, false if doing so would cause us to get into a
114 /// recursive compilation mess.
115 static bool
isSafeToConvert(const RecordDecl * RD,CodeGenTypes & CGT,llvm::SmallPtrSet<const RecordDecl *,16> & AlreadyChecked)116 isSafeToConvert(const RecordDecl *RD, CodeGenTypes &CGT,
117                 llvm::SmallPtrSet<const RecordDecl*, 16> &AlreadyChecked) {
118   // If we have already checked this type (maybe the same type is used by-value
119   // multiple times in multiple structure fields, don't check again.
120   if (!AlreadyChecked.insert(RD)) return true;
121 
122   const Type *Key = CGT.getContext().getTagDeclType(RD).getTypePtr();
123 
124   // If this type is already laid out, converting it is a noop.
125   if (CGT.isRecordLayoutComplete(Key)) return true;
126 
127   // If this type is currently being laid out, we can't recursively compile it.
128   if (CGT.isRecordBeingLaidOut(Key))
129     return false;
130 
131   // If this type would require laying out bases that are currently being laid
132   // out, don't do it.  This includes virtual base classes which get laid out
133   // when a class is translated, even though they aren't embedded by-value into
134   // the class.
135   if (const CXXRecordDecl *CRD = dyn_cast<CXXRecordDecl>(RD)) {
136     for (CXXRecordDecl::base_class_const_iterator I = CRD->bases_begin(),
137          E = CRD->bases_end(); I != E; ++I)
138       if (!isSafeToConvert(I->getType()->getAs<RecordType>()->getDecl(),
139                            CGT, AlreadyChecked))
140         return false;
141   }
142 
143   // If this type would require laying out members that are currently being laid
144   // out, don't do it.
145   for (RecordDecl::field_iterator I = RD->field_begin(),
146        E = RD->field_end(); I != E; ++I)
147     if (!isSafeToConvert(I->getType(), CGT, AlreadyChecked))
148       return false;
149 
150   // If there are no problems, lets do it.
151   return true;
152 }
153 
154 /// isSafeToConvert - Return true if it is safe to convert this field type,
155 /// which requires the structure elements contained by-value to all be
156 /// recursively safe to convert.
157 static bool
isSafeToConvert(QualType T,CodeGenTypes & CGT,llvm::SmallPtrSet<const RecordDecl *,16> & AlreadyChecked)158 isSafeToConvert(QualType T, CodeGenTypes &CGT,
159                 llvm::SmallPtrSet<const RecordDecl*, 16> &AlreadyChecked) {
160   T = T.getCanonicalType();
161 
162   // If this is a record, check it.
163   if (const RecordType *RT = dyn_cast<RecordType>(T))
164     return isSafeToConvert(RT->getDecl(), CGT, AlreadyChecked);
165 
166   // If this is an array, check the elements, which are embedded inline.
167   if (const ArrayType *AT = dyn_cast<ArrayType>(T))
168     return isSafeToConvert(AT->getElementType(), CGT, AlreadyChecked);
169 
170   // Otherwise, there is no concern about transforming this.  We only care about
171   // things that are contained by-value in a structure that can have another
172   // structure as a member.
173   return true;
174 }
175 
176 
177 /// isSafeToConvert - Return true if it is safe to convert the specified record
178 /// decl to IR and lay it out, false if doing so would cause us to get into a
179 /// recursive compilation mess.
isSafeToConvert(const RecordDecl * RD,CodeGenTypes & CGT)180 static bool isSafeToConvert(const RecordDecl *RD, CodeGenTypes &CGT) {
181   // If no structs are being laid out, we can certainly do this one.
182   if (CGT.noRecordsBeingLaidOut()) return true;
183 
184   llvm::SmallPtrSet<const RecordDecl*, 16> AlreadyChecked;
185   return isSafeToConvert(RD, CGT, AlreadyChecked);
186 }
187 
188 
189 /// isFuncTypeArgumentConvertible - Return true if the specified type in a
190 /// function argument or result position can be converted to an IR type at this
191 /// point.  This boils down to being whether it is complete, as well as whether
192 /// we've temporarily deferred expanding the type because we're in a recursive
193 /// context.
isFuncTypeArgumentConvertible(QualType Ty)194 bool CodeGenTypes::isFuncTypeArgumentConvertible(QualType Ty) {
195   // If this isn't a tagged type, we can convert it!
196   const TagType *TT = Ty->getAs<TagType>();
197   if (TT == 0) return true;
198 
199   // Incomplete types cannot be converted.
200   if (TT->isIncompleteType())
201     return false;
202 
203   // If this is an enum, then it is always safe to convert.
204   const RecordType *RT = dyn_cast<RecordType>(TT);
205   if (RT == 0) return true;
206 
207   // Otherwise, we have to be careful.  If it is a struct that we're in the
208   // process of expanding, then we can't convert the function type.  That's ok
209   // though because we must be in a pointer context under the struct, so we can
210   // just convert it to a dummy type.
211   //
212   // We decide this by checking whether ConvertRecordDeclType returns us an
213   // opaque type for a struct that we know is defined.
214   return isSafeToConvert(RT->getDecl(), *this);
215 }
216 
217 
218 /// Code to verify a given function type is complete, i.e. the return type
219 /// and all of the argument types are complete.  Also check to see if we are in
220 /// a RS_StructPointer context, and if so whether any struct types have been
221 /// pended.  If so, we don't want to ask the ABI lowering code to handle a type
222 /// that cannot be converted to an IR type.
isFuncTypeConvertible(const FunctionType * FT)223 bool CodeGenTypes::isFuncTypeConvertible(const FunctionType *FT) {
224   if (!isFuncTypeArgumentConvertible(FT->getResultType()))
225     return false;
226 
227   if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(FT))
228     for (unsigned i = 0, e = FPT->getNumArgs(); i != e; i++)
229       if (!isFuncTypeArgumentConvertible(FPT->getArgType(i)))
230         return false;
231 
232   return true;
233 }
234 
235 /// UpdateCompletedType - When we find the full definition for a TagDecl,
236 /// replace the 'opaque' type we previously made for it if applicable.
UpdateCompletedType(const TagDecl * TD)237 void CodeGenTypes::UpdateCompletedType(const TagDecl *TD) {
238   // If this is an enum being completed, then we flush all non-struct types from
239   // the cache.  This allows function types and other things that may be derived
240   // from the enum to be recomputed.
241   if (const EnumDecl *ED = dyn_cast<EnumDecl>(TD)) {
242     // Only flush the cache if we've actually already converted this type.
243     if (TypeCache.count(ED->getTypeForDecl())) {
244       // Okay, we formed some types based on this.  We speculated that the enum
245       // would be lowered to i32, so we only need to flush the cache if this
246       // didn't happen.
247       if (!ConvertType(ED->getIntegerType())->isIntegerTy(32))
248         TypeCache.clear();
249     }
250     return;
251   }
252 
253   // If we completed a RecordDecl that we previously used and converted to an
254   // anonymous type, then go ahead and complete it now.
255   const RecordDecl *RD = cast<RecordDecl>(TD);
256   if (RD->isDependentType()) return;
257 
258   // Only complete it if we converted it already.  If we haven't converted it
259   // yet, we'll just do it lazily.
260   if (RecordDeclTypes.count(Context.getTagDeclType(RD).getTypePtr()))
261     ConvertRecordDeclType(RD);
262 }
263 
getTypeForFormat(llvm::LLVMContext & VMContext,const llvm::fltSemantics & format)264 static llvm::Type *getTypeForFormat(llvm::LLVMContext &VMContext,
265                                     const llvm::fltSemantics &format) {
266   if (&format == &llvm::APFloat::IEEEhalf)
267     return llvm::Type::getInt16Ty(VMContext);
268   if (&format == &llvm::APFloat::IEEEsingle)
269     return llvm::Type::getFloatTy(VMContext);
270   if (&format == &llvm::APFloat::IEEEdouble)
271     return llvm::Type::getDoubleTy(VMContext);
272   if (&format == &llvm::APFloat::IEEEquad)
273     return llvm::Type::getFP128Ty(VMContext);
274   if (&format == &llvm::APFloat::PPCDoubleDouble)
275     return llvm::Type::getPPC_FP128Ty(VMContext);
276   if (&format == &llvm::APFloat::x87DoubleExtended)
277     return llvm::Type::getX86_FP80Ty(VMContext);
278   llvm_unreachable("Unknown float format!");
279 }
280 
281 /// ConvertType - Convert the specified type to its LLVM form.
ConvertType(QualType T)282 llvm::Type *CodeGenTypes::ConvertType(QualType T) {
283   T = Context.getCanonicalType(T);
284 
285   const Type *Ty = T.getTypePtr();
286 
287   // RecordTypes are cached and processed specially.
288   if (const RecordType *RT = dyn_cast<RecordType>(Ty))
289     return ConvertRecordDeclType(RT->getDecl());
290 
291   // See if type is already cached.
292   llvm::DenseMap<const Type *, llvm::Type *>::iterator TCI = TypeCache.find(Ty);
293   // If type is found in map then use it. Otherwise, convert type T.
294   if (TCI != TypeCache.end())
295     return TCI->second;
296 
297   // If we don't have it in the cache, convert it now.
298   llvm::Type *ResultType = 0;
299   switch (Ty->getTypeClass()) {
300   case Type::Record: // Handled above.
301 #define TYPE(Class, Base)
302 #define ABSTRACT_TYPE(Class, Base)
303 #define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
304 #define DEPENDENT_TYPE(Class, Base) case Type::Class:
305 #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base) case Type::Class:
306 #include "clang/AST/TypeNodes.def"
307     llvm_unreachable("Non-canonical or dependent types aren't possible.");
308 
309   case Type::Builtin: {
310     switch (cast<BuiltinType>(Ty)->getKind()) {
311     case BuiltinType::Void:
312     case BuiltinType::ObjCId:
313     case BuiltinType::ObjCClass:
314     case BuiltinType::ObjCSel:
315       // LLVM void type can only be used as the result of a function call.  Just
316       // map to the same as char.
317       ResultType = llvm::Type::getInt8Ty(getLLVMContext());
318       break;
319 
320     case BuiltinType::Bool:
321       // Note that we always return bool as i1 for use as a scalar type.
322       ResultType = llvm::Type::getInt1Ty(getLLVMContext());
323       break;
324 
325     case BuiltinType::Char_S:
326     case BuiltinType::Char_U:
327     case BuiltinType::SChar:
328     case BuiltinType::UChar:
329     case BuiltinType::Short:
330     case BuiltinType::UShort:
331     case BuiltinType::Int:
332     case BuiltinType::UInt:
333     case BuiltinType::Long:
334     case BuiltinType::ULong:
335     case BuiltinType::LongLong:
336     case BuiltinType::ULongLong:
337     case BuiltinType::WChar_S:
338     case BuiltinType::WChar_U:
339     case BuiltinType::Char16:
340     case BuiltinType::Char32:
341       ResultType = llvm::IntegerType::get(getLLVMContext(),
342                                  static_cast<unsigned>(Context.getTypeSize(T)));
343       break;
344 
345     case BuiltinType::Half:
346       // Half is special: it might be lowered to i16 (and will be storage-only
347       // type),. or can be represented as a set of native operations.
348 
349       // FIXME: Ask target which kind of half FP it prefers (storage only vs
350       // native).
351       ResultType = llvm::Type::getInt16Ty(getLLVMContext());
352       break;
353     case BuiltinType::Float:
354     case BuiltinType::Double:
355     case BuiltinType::LongDouble:
356       ResultType = getTypeForFormat(getLLVMContext(),
357                                     Context.getFloatTypeSemantics(T));
358       break;
359 
360     case BuiltinType::NullPtr:
361       // Model std::nullptr_t as i8*
362       ResultType = llvm::Type::getInt8PtrTy(getLLVMContext());
363       break;
364 
365     case BuiltinType::UInt128:
366     case BuiltinType::Int128:
367       ResultType = llvm::IntegerType::get(getLLVMContext(), 128);
368       break;
369 
370     case BuiltinType::Dependent:
371 #define BUILTIN_TYPE(Id, SingletonId)
372 #define PLACEHOLDER_TYPE(Id, SingletonId) \
373     case BuiltinType::Id:
374 #include "clang/AST/BuiltinTypes.def"
375       llvm_unreachable("Unexpected placeholder builtin type!");
376     }
377     break;
378   }
379   case Type::Complex: {
380     llvm::Type *EltTy = ConvertType(cast<ComplexType>(Ty)->getElementType());
381     ResultType = llvm::StructType::get(EltTy, EltTy, NULL);
382     break;
383   }
384   case Type::LValueReference:
385   case Type::RValueReference: {
386     const ReferenceType *RTy = cast<ReferenceType>(Ty);
387     QualType ETy = RTy->getPointeeType();
388     llvm::Type *PointeeType = ConvertTypeForMem(ETy);
389     unsigned AS = Context.getTargetAddressSpace(ETy);
390     ResultType = llvm::PointerType::get(PointeeType, AS);
391     break;
392   }
393   case Type::Pointer: {
394     const PointerType *PTy = cast<PointerType>(Ty);
395     QualType ETy = PTy->getPointeeType();
396     llvm::Type *PointeeType = ConvertTypeForMem(ETy);
397     if (PointeeType->isVoidTy())
398       PointeeType = llvm::Type::getInt8Ty(getLLVMContext());
399     unsigned AS = Context.getTargetAddressSpace(ETy);
400     ResultType = llvm::PointerType::get(PointeeType, AS);
401     break;
402   }
403 
404   case Type::VariableArray: {
405     const VariableArrayType *A = cast<VariableArrayType>(Ty);
406     assert(A->getIndexTypeCVRQualifiers() == 0 &&
407            "FIXME: We only handle trivial array types so far!");
408     // VLAs resolve to the innermost element type; this matches
409     // the return of alloca, and there isn't any obviously better choice.
410     ResultType = ConvertTypeForMem(A->getElementType());
411     break;
412   }
413   case Type::IncompleteArray: {
414     const IncompleteArrayType *A = cast<IncompleteArrayType>(Ty);
415     assert(A->getIndexTypeCVRQualifiers() == 0 &&
416            "FIXME: We only handle trivial array types so far!");
417     // int X[] -> [0 x int], unless the element type is not sized.  If it is
418     // unsized (e.g. an incomplete struct) just use [0 x i8].
419     ResultType = ConvertTypeForMem(A->getElementType());
420     if (!ResultType->isSized()) {
421       SkippedLayout = true;
422       ResultType = llvm::Type::getInt8Ty(getLLVMContext());
423     }
424     ResultType = llvm::ArrayType::get(ResultType, 0);
425     break;
426   }
427   case Type::ConstantArray: {
428     const ConstantArrayType *A = cast<ConstantArrayType>(Ty);
429     llvm::Type *EltTy = ConvertTypeForMem(A->getElementType());
430 
431     // Lower arrays of undefined struct type to arrays of i8 just to have a
432     // concrete type.
433     if (!EltTy->isSized()) {
434       SkippedLayout = true;
435       EltTy = llvm::Type::getInt8Ty(getLLVMContext());
436     }
437 
438     ResultType = llvm::ArrayType::get(EltTy, A->getSize().getZExtValue());
439     break;
440   }
441   case Type::ExtVector:
442   case Type::Vector: {
443     const VectorType *VT = cast<VectorType>(Ty);
444     ResultType = llvm::VectorType::get(ConvertType(VT->getElementType()),
445                                        VT->getNumElements());
446     break;
447   }
448   case Type::FunctionNoProto:
449   case Type::FunctionProto: {
450     const FunctionType *FT = cast<FunctionType>(Ty);
451     // First, check whether we can build the full function type.  If the
452     // function type depends on an incomplete type (e.g. a struct or enum), we
453     // cannot lower the function type.
454     if (!isFuncTypeConvertible(FT)) {
455       // This function's type depends on an incomplete tag type.
456       // Return a placeholder type.
457       ResultType = llvm::StructType::get(getLLVMContext());
458 
459       SkippedLayout = true;
460       break;
461     }
462 
463     // While we're converting the argument types for a function, we don't want
464     // to recursively convert any pointed-to structs.  Converting directly-used
465     // structs is ok though.
466     if (!RecordsBeingLaidOut.insert(Ty)) {
467       ResultType = llvm::StructType::get(getLLVMContext());
468 
469       SkippedLayout = true;
470       break;
471     }
472 
473     // The function type can be built; call the appropriate routines to
474     // build it.
475     const CGFunctionInfo *FI;
476     if (const FunctionProtoType *FPT = dyn_cast<FunctionProtoType>(FT)) {
477       FI = &arrangeFreeFunctionType(
478                    CanQual<FunctionProtoType>::CreateUnsafe(QualType(FPT, 0)));
479     } else {
480       const FunctionNoProtoType *FNPT = cast<FunctionNoProtoType>(FT);
481       FI = &arrangeFreeFunctionType(
482                 CanQual<FunctionNoProtoType>::CreateUnsafe(QualType(FNPT, 0)));
483     }
484 
485     // If there is something higher level prodding our CGFunctionInfo, then
486     // don't recurse into it again.
487     if (FunctionsBeingProcessed.count(FI)) {
488 
489       ResultType = llvm::StructType::get(getLLVMContext());
490       SkippedLayout = true;
491     } else {
492 
493       // Otherwise, we're good to go, go ahead and convert it.
494       ResultType = GetFunctionType(*FI);
495     }
496 
497     RecordsBeingLaidOut.erase(Ty);
498 
499     if (SkippedLayout)
500       TypeCache.clear();
501 
502     if (RecordsBeingLaidOut.empty())
503       while (!DeferredRecords.empty())
504         ConvertRecordDeclType(DeferredRecords.pop_back_val());
505     break;
506   }
507 
508   case Type::ObjCObject:
509     ResultType = ConvertType(cast<ObjCObjectType>(Ty)->getBaseType());
510     break;
511 
512   case Type::ObjCInterface: {
513     // Objective-C interfaces are always opaque (outside of the
514     // runtime, which can do whatever it likes); we never refine
515     // these.
516     llvm::Type *&T = InterfaceTypes[cast<ObjCInterfaceType>(Ty)];
517     if (!T)
518       T = llvm::StructType::create(getLLVMContext());
519     ResultType = T;
520     break;
521   }
522 
523   case Type::ObjCObjectPointer: {
524     // Protocol qualifications do not influence the LLVM type, we just return a
525     // pointer to the underlying interface type. We don't need to worry about
526     // recursive conversion.
527     llvm::Type *T =
528       ConvertTypeForMem(cast<ObjCObjectPointerType>(Ty)->getPointeeType());
529     ResultType = T->getPointerTo();
530     break;
531   }
532 
533   case Type::Enum: {
534     const EnumDecl *ED = cast<EnumType>(Ty)->getDecl();
535     if (ED->isCompleteDefinition() || ED->isFixed())
536       return ConvertType(ED->getIntegerType());
537     // Return a placeholder 'i32' type.  This can be changed later when the
538     // type is defined (see UpdateCompletedType), but is likely to be the
539     // "right" answer.
540     ResultType = llvm::Type::getInt32Ty(getLLVMContext());
541     break;
542   }
543 
544   case Type::BlockPointer: {
545     const QualType FTy = cast<BlockPointerType>(Ty)->getPointeeType();
546     llvm::Type *PointeeType = ConvertTypeForMem(FTy);
547     unsigned AS = Context.getTargetAddressSpace(FTy);
548     ResultType = llvm::PointerType::get(PointeeType, AS);
549     break;
550   }
551 
552   case Type::MemberPointer: {
553     ResultType =
554       getCXXABI().ConvertMemberPointerType(cast<MemberPointerType>(Ty));
555     break;
556   }
557 
558   case Type::Atomic: {
559     ResultType = ConvertType(cast<AtomicType>(Ty)->getValueType());
560     break;
561   }
562   }
563 
564   assert(ResultType && "Didn't convert a type?");
565 
566   TypeCache[Ty] = ResultType;
567   return ResultType;
568 }
569 
570 /// ConvertRecordDeclType - Lay out a tagged decl type like struct or union.
ConvertRecordDeclType(const RecordDecl * RD)571 llvm::StructType *CodeGenTypes::ConvertRecordDeclType(const RecordDecl *RD) {
572   // TagDecl's are not necessarily unique, instead use the (clang)
573   // type connected to the decl.
574   const Type *Key = Context.getTagDeclType(RD).getTypePtr();
575 
576   llvm::StructType *&Entry = RecordDeclTypes[Key];
577 
578   // If we don't have a StructType at all yet, create the forward declaration.
579   if (Entry == 0) {
580     Entry = llvm::StructType::create(getLLVMContext());
581     addRecordTypeName(RD, Entry, "");
582   }
583   llvm::StructType *Ty = Entry;
584 
585   // If this is still a forward declaration, or the LLVM type is already
586   // complete, there's nothing more to do.
587   RD = RD->getDefinition();
588   if (RD == 0 || !RD->isCompleteDefinition() || !Ty->isOpaque())
589     return Ty;
590 
591   // If converting this type would cause us to infinitely loop, don't do it!
592   if (!isSafeToConvert(RD, *this)) {
593     DeferredRecords.push_back(RD);
594     return Ty;
595   }
596 
597   // Okay, this is a definition of a type.  Compile the implementation now.
598   bool InsertResult = RecordsBeingLaidOut.insert(Key); (void)InsertResult;
599   assert(InsertResult && "Recursively compiling a struct?");
600 
601   // Force conversion of non-virtual base classes recursively.
602   if (const CXXRecordDecl *CRD = dyn_cast<CXXRecordDecl>(RD)) {
603     for (CXXRecordDecl::base_class_const_iterator i = CRD->bases_begin(),
604          e = CRD->bases_end(); i != e; ++i) {
605       if (i->isVirtual()) continue;
606 
607       ConvertRecordDeclType(i->getType()->getAs<RecordType>()->getDecl());
608     }
609   }
610 
611   // Layout fields.
612   CGRecordLayout *Layout = ComputeRecordLayout(RD, Ty);
613   CGRecordLayouts[Key] = Layout;
614 
615   // We're done laying out this struct.
616   bool EraseResult = RecordsBeingLaidOut.erase(Key); (void)EraseResult;
617   assert(EraseResult && "struct not in RecordsBeingLaidOut set?");
618 
619   // If this struct blocked a FunctionType conversion, then recompute whatever
620   // was derived from that.
621   // FIXME: This is hugely overconservative.
622   if (SkippedLayout)
623     TypeCache.clear();
624 
625   // If we're done converting the outer-most record, then convert any deferred
626   // structs as well.
627   if (RecordsBeingLaidOut.empty())
628     while (!DeferredRecords.empty())
629       ConvertRecordDeclType(DeferredRecords.pop_back_val());
630 
631   return Ty;
632 }
633 
634 /// getCGRecordLayout - Return record layout info for the given record decl.
635 const CGRecordLayout &
getCGRecordLayout(const RecordDecl * RD)636 CodeGenTypes::getCGRecordLayout(const RecordDecl *RD) {
637   const Type *Key = Context.getTagDeclType(RD).getTypePtr();
638 
639   const CGRecordLayout *Layout = CGRecordLayouts.lookup(Key);
640   if (!Layout) {
641     // Compute the type information.
642     ConvertRecordDeclType(RD);
643 
644     // Now try again.
645     Layout = CGRecordLayouts.lookup(Key);
646   }
647 
648   assert(Layout && "Unable to find record layout information for type");
649   return *Layout;
650 }
651 
isZeroInitializable(QualType T)652 bool CodeGenTypes::isZeroInitializable(QualType T) {
653   // No need to check for member pointers when not compiling C++.
654   if (!Context.getLangOpts().CPlusPlus)
655     return true;
656 
657   T = Context.getBaseElementType(T);
658 
659   // Records are non-zero-initializable if they contain any
660   // non-zero-initializable subobjects.
661   if (const RecordType *RT = T->getAs<RecordType>()) {
662     const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
663     return isZeroInitializable(RD);
664   }
665 
666   // We have to ask the ABI about member pointers.
667   if (const MemberPointerType *MPT = T->getAs<MemberPointerType>())
668     return getCXXABI().isZeroInitializable(MPT);
669 
670   // Everything else is okay.
671   return true;
672 }
673 
isZeroInitializable(const CXXRecordDecl * RD)674 bool CodeGenTypes::isZeroInitializable(const CXXRecordDecl *RD) {
675   return getCGRecordLayout(RD).isZeroInitializable();
676 }
677