1 //===--- CGCXX.cpp - Emit LLVM Code for declarations ----------------------===//
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 contains code dealing with C++ code generation.
11 //
12 //===----------------------------------------------------------------------===//
13
14 // We might split this into multiple files if it gets too unwieldy
15
16 #include "CGCXXABI.h"
17 #include "CodeGenFunction.h"
18 #include "CodeGenModule.h"
19 #include "clang/AST/ASTContext.h"
20 #include "clang/AST/RecordLayout.h"
21 #include "clang/AST/Decl.h"
22 #include "clang/AST/DeclCXX.h"
23 #include "clang/AST/DeclObjC.h"
24 #include "clang/AST/Mangle.h"
25 #include "clang/AST/StmtCXX.h"
26 #include "clang/Frontend/CodeGenOptions.h"
27 #include "llvm/ADT/StringExtras.h"
28 using namespace clang;
29 using namespace CodeGen;
30
31 /// Try to emit a base destructor as an alias to its primary
32 /// base-class destructor.
TryEmitBaseDestructorAsAlias(const CXXDestructorDecl * D)33 bool CodeGenModule::TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) {
34 if (!getCodeGenOpts().CXXCtorDtorAliases)
35 return true;
36
37 // If the destructor doesn't have a trivial body, we have to emit it
38 // separately.
39 if (!D->hasTrivialBody())
40 return true;
41
42 const CXXRecordDecl *Class = D->getParent();
43
44 // If we need to manipulate a VTT parameter, give up.
45 if (Class->getNumVBases()) {
46 // Extra Credit: passing extra parameters is perfectly safe
47 // in many calling conventions, so only bail out if the ctor's
48 // calling convention is nonstandard.
49 return true;
50 }
51
52 // If any field has a non-trivial destructor, we have to emit the
53 // destructor separately.
54 for (CXXRecordDecl::field_iterator I = Class->field_begin(),
55 E = Class->field_end(); I != E; ++I)
56 if (I->getType().isDestructedType())
57 return true;
58
59 // Try to find a unique base class with a non-trivial destructor.
60 const CXXRecordDecl *UniqueBase = 0;
61 for (CXXRecordDecl::base_class_const_iterator I = Class->bases_begin(),
62 E = Class->bases_end(); I != E; ++I) {
63
64 // We're in the base destructor, so skip virtual bases.
65 if (I->isVirtual()) continue;
66
67 // Skip base classes with trivial destructors.
68 const CXXRecordDecl *Base
69 = cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
70 if (Base->hasTrivialDestructor()) continue;
71
72 // If we've already found a base class with a non-trivial
73 // destructor, give up.
74 if (UniqueBase) return true;
75 UniqueBase = Base;
76 }
77
78 // If we didn't find any bases with a non-trivial destructor, then
79 // the base destructor is actually effectively trivial, which can
80 // happen if it was needlessly user-defined or if there are virtual
81 // bases with non-trivial destructors.
82 if (!UniqueBase)
83 return true;
84
85 /// If we don't have a definition for the destructor yet, don't
86 /// emit. We can't emit aliases to declarations; that's just not
87 /// how aliases work.
88 const CXXDestructorDecl *BaseD = UniqueBase->getDestructor();
89 if (!BaseD->isImplicit() && !BaseD->hasBody())
90 return true;
91
92 // If the base is at a non-zero offset, give up.
93 const ASTRecordLayout &ClassLayout = Context.getASTRecordLayout(Class);
94 if (!ClassLayout.getBaseClassOffset(UniqueBase).isZero())
95 return true;
96
97 return TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Base),
98 GlobalDecl(BaseD, Dtor_Base));
99 }
100
101 /// Try to emit a definition as a global alias for another definition.
TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,GlobalDecl TargetDecl)102 bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
103 GlobalDecl TargetDecl) {
104 if (!getCodeGenOpts().CXXCtorDtorAliases)
105 return true;
106
107 // The alias will use the linkage of the referrent. If we can't
108 // support aliases with that linkage, fail.
109 llvm::GlobalValue::LinkageTypes Linkage
110 = getFunctionLinkage(cast<FunctionDecl>(AliasDecl.getDecl()));
111
112 switch (Linkage) {
113 // We can definitely emit aliases to definitions with external linkage.
114 case llvm::GlobalValue::ExternalLinkage:
115 case llvm::GlobalValue::ExternalWeakLinkage:
116 break;
117
118 // Same with local linkage.
119 case llvm::GlobalValue::InternalLinkage:
120 case llvm::GlobalValue::PrivateLinkage:
121 case llvm::GlobalValue::LinkerPrivateLinkage:
122 break;
123
124 // We should try to support linkonce linkages.
125 case llvm::GlobalValue::LinkOnceAnyLinkage:
126 case llvm::GlobalValue::LinkOnceODRLinkage:
127 return true;
128
129 // Other linkages will probably never be supported.
130 default:
131 return true;
132 }
133
134 llvm::GlobalValue::LinkageTypes TargetLinkage
135 = getFunctionLinkage(cast<FunctionDecl>(TargetDecl.getDecl()));
136
137 if (llvm::GlobalValue::isWeakForLinker(TargetLinkage))
138 return true;
139
140 // Derive the type for the alias.
141 llvm::PointerType *AliasType
142 = getTypes().GetFunctionType(AliasDecl)->getPointerTo();
143
144 // Find the referrent. Some aliases might require a bitcast, in
145 // which case the caller is responsible for ensuring the soundness
146 // of these semantics.
147 llvm::GlobalValue *Ref = cast<llvm::GlobalValue>(GetAddrOfGlobal(TargetDecl));
148 llvm::Constant *Aliasee = Ref;
149 if (Ref->getType() != AliasType)
150 Aliasee = llvm::ConstantExpr::getBitCast(Ref, AliasType);
151
152 // Create the alias with no name.
153 llvm::GlobalAlias *Alias =
154 new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule());
155
156 // Switch any previous uses to the alias.
157 StringRef MangledName = getMangledName(AliasDecl);
158 llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
159 if (Entry) {
160 assert(Entry->isDeclaration() && "definition already exists for alias");
161 assert(Entry->getType() == AliasType &&
162 "declaration exists with different type");
163 Alias->takeName(Entry);
164 Entry->replaceAllUsesWith(Alias);
165 Entry->eraseFromParent();
166 } else {
167 Alias->setName(MangledName);
168 }
169
170 // Finally, set up the alias with its proper name and attributes.
171 SetCommonAttributes(cast<NamedDecl>(AliasDecl.getDecl()), Alias);
172
173 return false;
174 }
175
EmitCXXConstructors(const CXXConstructorDecl * D)176 void CodeGenModule::EmitCXXConstructors(const CXXConstructorDecl *D) {
177 // The constructor used for constructing this as a complete class;
178 // constucts the virtual bases, then calls the base constructor.
179 if (!D->getParent()->isAbstract()) {
180 // We don't need to emit the complete ctor if the class is abstract.
181 EmitGlobal(GlobalDecl(D, Ctor_Complete));
182 }
183
184 // The constructor used for constructing this as a base class;
185 // ignores virtual bases.
186 EmitGlobal(GlobalDecl(D, Ctor_Base));
187 }
188
EmitCXXConstructor(const CXXConstructorDecl * ctor,CXXCtorType ctorType)189 void CodeGenModule::EmitCXXConstructor(const CXXConstructorDecl *ctor,
190 CXXCtorType ctorType) {
191 // The complete constructor is equivalent to the base constructor
192 // for classes with no virtual bases. Try to emit it as an alias.
193 if (ctorType == Ctor_Complete &&
194 !ctor->getParent()->getNumVBases() &&
195 !TryEmitDefinitionAsAlias(GlobalDecl(ctor, Ctor_Complete),
196 GlobalDecl(ctor, Ctor_Base)))
197 return;
198
199 const CGFunctionInfo &fnInfo =
200 getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType);
201
202 llvm::Function *fn =
203 cast<llvm::Function>(GetAddrOfCXXConstructor(ctor, ctorType, &fnInfo));
204 setFunctionLinkage(ctor, fn);
205
206 CodeGenFunction(*this).GenerateCode(GlobalDecl(ctor, ctorType), fn, fnInfo);
207
208 SetFunctionDefinitionAttributes(ctor, fn);
209 SetLLVMFunctionAttributesForDefinition(ctor, fn);
210 }
211
212 llvm::GlobalValue *
GetAddrOfCXXConstructor(const CXXConstructorDecl * ctor,CXXCtorType ctorType,const CGFunctionInfo * fnInfo)213 CodeGenModule::GetAddrOfCXXConstructor(const CXXConstructorDecl *ctor,
214 CXXCtorType ctorType,
215 const CGFunctionInfo *fnInfo) {
216 GlobalDecl GD(ctor, ctorType);
217
218 StringRef name = getMangledName(GD);
219 if (llvm::GlobalValue *existing = GetGlobalValue(name))
220 return existing;
221
222 if (!fnInfo)
223 fnInfo = &getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType);
224
225 llvm::FunctionType *fnType = getTypes().GetFunctionType(*fnInfo);
226 return cast<llvm::Function>(GetOrCreateLLVMFunction(name, fnType, GD,
227 /*ForVTable=*/false));
228 }
229
EmitCXXDestructors(const CXXDestructorDecl * D)230 void CodeGenModule::EmitCXXDestructors(const CXXDestructorDecl *D) {
231 // The destructor in a virtual table is always a 'deleting'
232 // destructor, which calls the complete destructor and then uses the
233 // appropriate operator delete.
234 if (D->isVirtual())
235 EmitGlobal(GlobalDecl(D, Dtor_Deleting));
236
237 // The destructor used for destructing this as a most-derived class;
238 // call the base destructor and then destructs any virtual bases.
239 EmitGlobal(GlobalDecl(D, Dtor_Complete));
240
241 // The destructor used for destructing this as a base class; ignores
242 // virtual bases.
243 EmitGlobal(GlobalDecl(D, Dtor_Base));
244 }
245
EmitCXXDestructor(const CXXDestructorDecl * dtor,CXXDtorType dtorType)246 void CodeGenModule::EmitCXXDestructor(const CXXDestructorDecl *dtor,
247 CXXDtorType dtorType) {
248 // The complete destructor is equivalent to the base destructor for
249 // classes with no virtual bases, so try to emit it as an alias.
250 if (dtorType == Dtor_Complete &&
251 !dtor->getParent()->getNumVBases() &&
252 !TryEmitDefinitionAsAlias(GlobalDecl(dtor, Dtor_Complete),
253 GlobalDecl(dtor, Dtor_Base)))
254 return;
255
256 // The base destructor is equivalent to the base destructor of its
257 // base class if there is exactly one non-virtual base class with a
258 // non-trivial destructor, there are no fields with a non-trivial
259 // destructor, and the body of the destructor is trivial.
260 if (dtorType == Dtor_Base && !TryEmitBaseDestructorAsAlias(dtor))
261 return;
262
263 const CGFunctionInfo &fnInfo =
264 getTypes().arrangeCXXDestructor(dtor, dtorType);
265
266 llvm::Function *fn =
267 cast<llvm::Function>(GetAddrOfCXXDestructor(dtor, dtorType, &fnInfo));
268 setFunctionLinkage(dtor, fn);
269
270 CodeGenFunction(*this).GenerateCode(GlobalDecl(dtor, dtorType), fn, fnInfo);
271
272 SetFunctionDefinitionAttributes(dtor, fn);
273 SetLLVMFunctionAttributesForDefinition(dtor, fn);
274 }
275
276 llvm::GlobalValue *
GetAddrOfCXXDestructor(const CXXDestructorDecl * dtor,CXXDtorType dtorType,const CGFunctionInfo * fnInfo)277 CodeGenModule::GetAddrOfCXXDestructor(const CXXDestructorDecl *dtor,
278 CXXDtorType dtorType,
279 const CGFunctionInfo *fnInfo) {
280 GlobalDecl GD(dtor, dtorType);
281
282 StringRef name = getMangledName(GD);
283 if (llvm::GlobalValue *existing = GetGlobalValue(name))
284 return existing;
285
286 if (!fnInfo) fnInfo = &getTypes().arrangeCXXDestructor(dtor, dtorType);
287
288 llvm::FunctionType *fnType = getTypes().GetFunctionType(*fnInfo);
289 return cast<llvm::Function>(GetOrCreateLLVMFunction(name, fnType, GD,
290 /*ForVTable=*/false));
291 }
292
BuildVirtualCall(CodeGenFunction & CGF,uint64_t VTableIndex,llvm::Value * This,llvm::Type * Ty)293 static llvm::Value *BuildVirtualCall(CodeGenFunction &CGF, uint64_t VTableIndex,
294 llvm::Value *This, llvm::Type *Ty) {
295 Ty = Ty->getPointerTo()->getPointerTo();
296
297 llvm::Value *VTable = CGF.GetVTablePtr(This, Ty);
298 llvm::Value *VFuncPtr =
299 CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfn");
300 return CGF.Builder.CreateLoad(VFuncPtr);
301 }
302
303 llvm::Value *
BuildVirtualCall(const CXXMethodDecl * MD,llvm::Value * This,llvm::Type * Ty)304 CodeGenFunction::BuildVirtualCall(const CXXMethodDecl *MD, llvm::Value *This,
305 llvm::Type *Ty) {
306 MD = MD->getCanonicalDecl();
307 uint64_t VTableIndex = CGM.getVTableContext().getMethodVTableIndex(MD);
308
309 return ::BuildVirtualCall(*this, VTableIndex, This, Ty);
310 }
311
312 /// BuildVirtualCall - This routine is to support gcc's kext ABI making
313 /// indirect call to virtual functions. It makes the call through indexing
314 /// into the vtable.
315 llvm::Value *
BuildAppleKextVirtualCall(const CXXMethodDecl * MD,NestedNameSpecifier * Qual,llvm::Type * Ty)316 CodeGenFunction::BuildAppleKextVirtualCall(const CXXMethodDecl *MD,
317 NestedNameSpecifier *Qual,
318 llvm::Type *Ty) {
319 llvm::Value *VTable = 0;
320 assert((Qual->getKind() == NestedNameSpecifier::TypeSpec) &&
321 "BuildAppleKextVirtualCall - bad Qual kind");
322
323 const Type *QTy = Qual->getAsType();
324 QualType T = QualType(QTy, 0);
325 const RecordType *RT = T->getAs<RecordType>();
326 assert(RT && "BuildAppleKextVirtualCall - Qual type must be record");
327 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
328
329 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD))
330 return BuildAppleKextVirtualDestructorCall(DD, Dtor_Complete, RD);
331
332 VTable = CGM.getVTables().GetAddrOfVTable(RD);
333 Ty = Ty->getPointerTo()->getPointerTo();
334 VTable = Builder.CreateBitCast(VTable, Ty);
335 assert(VTable && "BuildVirtualCall = kext vtbl pointer is null");
336 MD = MD->getCanonicalDecl();
337 uint64_t VTableIndex = CGM.getVTableContext().getMethodVTableIndex(MD);
338 uint64_t AddressPoint =
339 CGM.getVTableContext().getVTableLayout(RD)
340 .getAddressPoint(BaseSubobject(RD, CharUnits::Zero()));
341 VTableIndex += AddressPoint;
342 llvm::Value *VFuncPtr =
343 Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfnkxt");
344 return Builder.CreateLoad(VFuncPtr);
345 }
346
347 /// BuildVirtualCall - This routine makes indirect vtable call for
348 /// call to virtual destructors. It returns 0 if it could not do it.
349 llvm::Value *
BuildAppleKextVirtualDestructorCall(const CXXDestructorDecl * DD,CXXDtorType Type,const CXXRecordDecl * RD)350 CodeGenFunction::BuildAppleKextVirtualDestructorCall(
351 const CXXDestructorDecl *DD,
352 CXXDtorType Type,
353 const CXXRecordDecl *RD) {
354 llvm::Value * Callee = 0;
355 const CXXMethodDecl *MD = cast<CXXMethodDecl>(DD);
356 // FIXME. Dtor_Base dtor is always direct!!
357 // It need be somehow inline expanded into the caller.
358 // -O does that. But need to support -O0 as well.
359 if (MD->isVirtual() && Type != Dtor_Base) {
360 // Compute the function type we're calling.
361 const CGFunctionInfo &FInfo =
362 CGM.getTypes().arrangeCXXDestructor(cast<CXXDestructorDecl>(MD),
363 Dtor_Complete);
364 llvm::Type *Ty = CGM.getTypes().GetFunctionType(FInfo);
365
366 llvm::Value *VTable = CGM.getVTables().GetAddrOfVTable(RD);
367 Ty = Ty->getPointerTo()->getPointerTo();
368 VTable = Builder.CreateBitCast(VTable, Ty);
369 DD = cast<CXXDestructorDecl>(DD->getCanonicalDecl());
370 uint64_t VTableIndex =
371 CGM.getVTableContext().getMethodVTableIndex(GlobalDecl(DD, Type));
372 uint64_t AddressPoint =
373 CGM.getVTableContext().getVTableLayout(RD)
374 .getAddressPoint(BaseSubobject(RD, CharUnits::Zero()));
375 VTableIndex += AddressPoint;
376 llvm::Value *VFuncPtr =
377 Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfnkxt");
378 Callee = Builder.CreateLoad(VFuncPtr);
379 }
380 return Callee;
381 }
382
383 llvm::Value *
BuildVirtualCall(const CXXDestructorDecl * DD,CXXDtorType Type,llvm::Value * This,llvm::Type * Ty)384 CodeGenFunction::BuildVirtualCall(const CXXDestructorDecl *DD, CXXDtorType Type,
385 llvm::Value *This, llvm::Type *Ty) {
386 DD = cast<CXXDestructorDecl>(DD->getCanonicalDecl());
387 uint64_t VTableIndex =
388 CGM.getVTableContext().getMethodVTableIndex(GlobalDecl(DD, Type));
389
390 return ::BuildVirtualCall(*this, VTableIndex, This, Ty);
391 }
392
393