1 //===----- CGCXXABI.cpp - Interface to C++ ABIs ---------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This provides an abstract class for C++ code generation. Concrete subclasses
10 // of this implement code generation for specific C++ ABIs.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "CGCXXABI.h"
15 #include "CGCleanup.h"
16
17 using namespace clang;
18 using namespace CodeGen;
19
~CGCXXABI()20 CGCXXABI::~CGCXXABI() { }
21
ErrorUnsupportedABI(CodeGenFunction & CGF,StringRef S)22 void CGCXXABI::ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S) {
23 DiagnosticsEngine &Diags = CGF.CGM.getDiags();
24 unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
25 "cannot yet compile %0 in this ABI");
26 Diags.Report(CGF.getContext().getFullLoc(CGF.CurCodeDecl->getLocation()),
27 DiagID)
28 << S;
29 }
30
GetBogusMemberPointer(QualType T)31 llvm::Constant *CGCXXABI::GetBogusMemberPointer(QualType T) {
32 return llvm::Constant::getNullValue(CGM.getTypes().ConvertType(T));
33 }
34
35 llvm::Type *
ConvertMemberPointerType(const MemberPointerType * MPT)36 CGCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
37 return CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
38 }
39
EmitLoadOfMemberFunctionPointer(CodeGenFunction & CGF,const Expr * E,Address This,llvm::Value * & ThisPtrForCall,llvm::Value * MemPtr,const MemberPointerType * MPT)40 CGCallee CGCXXABI::EmitLoadOfMemberFunctionPointer(
41 CodeGenFunction &CGF, const Expr *E, Address This,
42 llvm::Value *&ThisPtrForCall,
43 llvm::Value *MemPtr, const MemberPointerType *MPT) {
44 ErrorUnsupportedABI(CGF, "calls through member pointers");
45
46 ThisPtrForCall = This.getPointer();
47 const FunctionProtoType *FPT =
48 MPT->getPointeeType()->getAs<FunctionProtoType>();
49 const CXXRecordDecl *RD =
50 cast<CXXRecordDecl>(MPT->getClass()->getAs<RecordType>()->getDecl());
51 llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(
52 CGM.getTypes().arrangeCXXMethodType(RD, FPT, /*FD=*/nullptr));
53 llvm::Constant *FnPtr = llvm::Constant::getNullValue(FTy->getPointerTo());
54 return CGCallee::forDirect(FnPtr, FPT);
55 }
56
57 llvm::Value *
EmitMemberDataPointerAddress(CodeGenFunction & CGF,const Expr * E,Address Base,llvm::Value * MemPtr,const MemberPointerType * MPT)58 CGCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
59 Address Base, llvm::Value *MemPtr,
60 const MemberPointerType *MPT) {
61 ErrorUnsupportedABI(CGF, "loads of member pointers");
62 llvm::Type *Ty = CGF.ConvertType(MPT->getPointeeType())
63 ->getPointerTo(Base.getAddressSpace());
64 return llvm::Constant::getNullValue(Ty);
65 }
66
EmitMemberPointerConversion(CodeGenFunction & CGF,const CastExpr * E,llvm::Value * Src)67 llvm::Value *CGCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
68 const CastExpr *E,
69 llvm::Value *Src) {
70 ErrorUnsupportedABI(CGF, "member function pointer conversions");
71 return GetBogusMemberPointer(E->getType());
72 }
73
EmitMemberPointerConversion(const CastExpr * E,llvm::Constant * Src)74 llvm::Constant *CGCXXABI::EmitMemberPointerConversion(const CastExpr *E,
75 llvm::Constant *Src) {
76 return GetBogusMemberPointer(E->getType());
77 }
78
79 llvm::Value *
EmitMemberPointerComparison(CodeGenFunction & CGF,llvm::Value * L,llvm::Value * R,const MemberPointerType * MPT,bool Inequality)80 CGCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
81 llvm::Value *L,
82 llvm::Value *R,
83 const MemberPointerType *MPT,
84 bool Inequality) {
85 ErrorUnsupportedABI(CGF, "member function pointer comparison");
86 return CGF.Builder.getFalse();
87 }
88
89 llvm::Value *
EmitMemberPointerIsNotNull(CodeGenFunction & CGF,llvm::Value * MemPtr,const MemberPointerType * MPT)90 CGCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
91 llvm::Value *MemPtr,
92 const MemberPointerType *MPT) {
93 ErrorUnsupportedABI(CGF, "member function pointer null testing");
94 return CGF.Builder.getFalse();
95 }
96
97 llvm::Constant *
EmitNullMemberPointer(const MemberPointerType * MPT)98 CGCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
99 return GetBogusMemberPointer(QualType(MPT, 0));
100 }
101
EmitMemberFunctionPointer(const CXXMethodDecl * MD)102 llvm::Constant *CGCXXABI::EmitMemberFunctionPointer(const CXXMethodDecl *MD) {
103 return GetBogusMemberPointer(CGM.getContext().getMemberPointerType(
104 MD->getType(), MD->getParent()->getTypeForDecl()));
105 }
106
EmitMemberDataPointer(const MemberPointerType * MPT,CharUnits offset)107 llvm::Constant *CGCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
108 CharUnits offset) {
109 return GetBogusMemberPointer(QualType(MPT, 0));
110 }
111
EmitMemberPointer(const APValue & MP,QualType MPT)112 llvm::Constant *CGCXXABI::EmitMemberPointer(const APValue &MP, QualType MPT) {
113 return GetBogusMemberPointer(MPT);
114 }
115
isZeroInitializable(const MemberPointerType * MPT)116 bool CGCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
117 // Fake answer.
118 return true;
119 }
120
buildThisParam(CodeGenFunction & CGF,FunctionArgList & params)121 void CGCXXABI::buildThisParam(CodeGenFunction &CGF, FunctionArgList ¶ms) {
122 const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
123
124 // FIXME: I'm not entirely sure I like using a fake decl just for code
125 // generation. Maybe we can come up with a better way?
126 auto *ThisDecl = ImplicitParamDecl::Create(
127 CGM.getContext(), nullptr, MD->getLocation(),
128 &CGM.getContext().Idents.get("this"), MD->getThisType(),
129 ImplicitParamDecl::CXXThis);
130 params.push_back(ThisDecl);
131 CGF.CXXABIThisDecl = ThisDecl;
132
133 // Compute the presumed alignment of 'this', which basically comes
134 // down to whether we know it's a complete object or not.
135 auto &Layout = CGF.getContext().getASTRecordLayout(MD->getParent());
136 if (MD->getParent()->getNumVBases() == 0 || // avoid vcall in common case
137 MD->getParent()->hasAttr<FinalAttr>() ||
138 !isThisCompleteObject(CGF.CurGD)) {
139 CGF.CXXABIThisAlignment = Layout.getAlignment();
140 } else {
141 CGF.CXXABIThisAlignment = Layout.getNonVirtualAlignment();
142 }
143 }
144
loadIncomingCXXThis(CodeGenFunction & CGF)145 llvm::Value *CGCXXABI::loadIncomingCXXThis(CodeGenFunction &CGF) {
146 return CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getThisDecl(CGF)),
147 "this");
148 }
149
setCXXABIThisValue(CodeGenFunction & CGF,llvm::Value * ThisPtr)150 void CGCXXABI::setCXXABIThisValue(CodeGenFunction &CGF, llvm::Value *ThisPtr) {
151 /// Initialize the 'this' slot.
152 assert(getThisDecl(CGF) && "no 'this' variable for function");
153 CGF.CXXABIThisValue = ThisPtr;
154 }
155
EmitReturnFromThunk(CodeGenFunction & CGF,RValue RV,QualType ResultType)156 void CGCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
157 RValue RV, QualType ResultType) {
158 CGF.EmitReturnOfRValue(RV, ResultType);
159 }
160
GetArrayCookieSize(const CXXNewExpr * expr)161 CharUnits CGCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
162 if (!requiresArrayCookie(expr))
163 return CharUnits::Zero();
164 return getArrayCookieSizeImpl(expr->getAllocatedType());
165 }
166
getArrayCookieSizeImpl(QualType elementType)167 CharUnits CGCXXABI::getArrayCookieSizeImpl(QualType elementType) {
168 // BOGUS
169 return CharUnits::Zero();
170 }
171
InitializeArrayCookie(CodeGenFunction & CGF,Address NewPtr,llvm::Value * NumElements,const CXXNewExpr * expr,QualType ElementType)172 Address CGCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
173 Address NewPtr,
174 llvm::Value *NumElements,
175 const CXXNewExpr *expr,
176 QualType ElementType) {
177 // Should never be called.
178 ErrorUnsupportedABI(CGF, "array cookie initialization");
179 return Address::invalid();
180 }
181
requiresArrayCookie(const CXXDeleteExpr * expr,QualType elementType)182 bool CGCXXABI::requiresArrayCookie(const CXXDeleteExpr *expr,
183 QualType elementType) {
184 // If the class's usual deallocation function takes two arguments,
185 // it needs a cookie.
186 if (expr->doesUsualArrayDeleteWantSize())
187 return true;
188
189 return elementType.isDestructedType();
190 }
191
requiresArrayCookie(const CXXNewExpr * expr)192 bool CGCXXABI::requiresArrayCookie(const CXXNewExpr *expr) {
193 // If the class's usual deallocation function takes two arguments,
194 // it needs a cookie.
195 if (expr->doesUsualArrayDeleteWantSize())
196 return true;
197
198 return expr->getAllocatedType().isDestructedType();
199 }
200
ReadArrayCookie(CodeGenFunction & CGF,Address ptr,const CXXDeleteExpr * expr,QualType eltTy,llvm::Value * & numElements,llvm::Value * & allocPtr,CharUnits & cookieSize)201 void CGCXXABI::ReadArrayCookie(CodeGenFunction &CGF, Address ptr,
202 const CXXDeleteExpr *expr, QualType eltTy,
203 llvm::Value *&numElements,
204 llvm::Value *&allocPtr, CharUnits &cookieSize) {
205 // Derive a char* in the same address space as the pointer.
206 ptr = CGF.Builder.CreateElementBitCast(ptr, CGF.Int8Ty);
207
208 // If we don't need an array cookie, bail out early.
209 if (!requiresArrayCookie(expr, eltTy)) {
210 allocPtr = ptr.getPointer();
211 numElements = nullptr;
212 cookieSize = CharUnits::Zero();
213 return;
214 }
215
216 cookieSize = getArrayCookieSizeImpl(eltTy);
217 Address allocAddr =
218 CGF.Builder.CreateConstInBoundsByteGEP(ptr, -cookieSize);
219 allocPtr = allocAddr.getPointer();
220 numElements = readArrayCookieImpl(CGF, allocAddr, cookieSize);
221 }
222
readArrayCookieImpl(CodeGenFunction & CGF,Address ptr,CharUnits cookieSize)223 llvm::Value *CGCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
224 Address ptr,
225 CharUnits cookieSize) {
226 ErrorUnsupportedABI(CGF, "reading a new[] cookie");
227 return llvm::ConstantInt::get(CGF.SizeTy, 0);
228 }
229
230 /// Returns the adjustment, in bytes, required for the given
231 /// member-pointer operation. Returns null if no adjustment is
232 /// required.
getMemberPointerAdjustment(const CastExpr * E)233 llvm::Constant *CGCXXABI::getMemberPointerAdjustment(const CastExpr *E) {
234 assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
235 E->getCastKind() == CK_BaseToDerivedMemberPointer);
236
237 QualType derivedType;
238 if (E->getCastKind() == CK_DerivedToBaseMemberPointer)
239 derivedType = E->getSubExpr()->getType();
240 else
241 derivedType = E->getType();
242
243 const CXXRecordDecl *derivedClass =
244 derivedType->castAs<MemberPointerType>()->getClass()->getAsCXXRecordDecl();
245
246 return CGM.GetNonVirtualBaseClassOffset(derivedClass,
247 E->path_begin(),
248 E->path_end());
249 }
250
getMemberPointerPathAdjustment(const APValue & MP)251 CharUnits CGCXXABI::getMemberPointerPathAdjustment(const APValue &MP) {
252 // TODO: Store base specifiers in APValue member pointer paths so we can
253 // easily reuse CGM.GetNonVirtualBaseClassOffset().
254 const ValueDecl *MPD = MP.getMemberPointerDecl();
255 CharUnits ThisAdjustment = CharUnits::Zero();
256 ArrayRef<const CXXRecordDecl*> Path = MP.getMemberPointerPath();
257 bool DerivedMember = MP.isMemberPointerToDerivedMember();
258 const CXXRecordDecl *RD = cast<CXXRecordDecl>(MPD->getDeclContext());
259 for (unsigned I = 0, N = Path.size(); I != N; ++I) {
260 const CXXRecordDecl *Base = RD;
261 const CXXRecordDecl *Derived = Path[I];
262 if (DerivedMember)
263 std::swap(Base, Derived);
264 ThisAdjustment +=
265 getContext().getASTRecordLayout(Derived).getBaseClassOffset(Base);
266 RD = Path[I];
267 }
268 if (DerivedMember)
269 ThisAdjustment = -ThisAdjustment;
270 return ThisAdjustment;
271 }
272
273 llvm::BasicBlock *
EmitCtorCompleteObjectHandler(CodeGenFunction & CGF,const CXXRecordDecl * RD)274 CGCXXABI::EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
275 const CXXRecordDecl *RD) {
276 if (CGM.getTarget().getCXXABI().hasConstructorVariants())
277 llvm_unreachable("shouldn't be called in this ABI");
278
279 ErrorUnsupportedABI(CGF, "complete object detection in ctor");
280 return nullptr;
281 }
282
setCXXDestructorDLLStorage(llvm::GlobalValue * GV,const CXXDestructorDecl * Dtor,CXXDtorType DT) const283 void CGCXXABI::setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
284 const CXXDestructorDecl *Dtor,
285 CXXDtorType DT) const {
286 // Assume the base C++ ABI has no special rules for destructor variants.
287 CGM.setDLLImportDLLExport(GV, Dtor);
288 }
289
getCXXDestructorLinkage(GVALinkage Linkage,const CXXDestructorDecl * Dtor,CXXDtorType DT) const290 llvm::GlobalValue::LinkageTypes CGCXXABI::getCXXDestructorLinkage(
291 GVALinkage Linkage, const CXXDestructorDecl *Dtor, CXXDtorType DT) const {
292 // Delegate back to CGM by default.
293 return CGM.getLLVMLinkageForDeclarator(Dtor, Linkage,
294 /*IsConstantVariable=*/false);
295 }
296
NeedsVTTParameter(GlobalDecl GD)297 bool CGCXXABI::NeedsVTTParameter(GlobalDecl GD) {
298 return false;
299 }
300
301 llvm::CallInst *
emitTerminateForUnexpectedException(CodeGenFunction & CGF,llvm::Value * Exn)302 CGCXXABI::emitTerminateForUnexpectedException(CodeGenFunction &CGF,
303 llvm::Value *Exn) {
304 // Just call std::terminate and ignore the violating exception.
305 return CGF.EmitNounwindRuntimeCall(CGF.CGM.getTerminateFn());
306 }
307
getCatchAllTypeInfo()308 CatchTypeInfo CGCXXABI::getCatchAllTypeInfo() {
309 return CatchTypeInfo{nullptr, 0};
310 }
311
getVBPtrOffsets(const CXXRecordDecl * RD)312 std::vector<CharUnits> CGCXXABI::getVBPtrOffsets(const CXXRecordDecl *RD) {
313 return std::vector<CharUnits>();
314 }
315