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#include "clang/AST/Attr.h"
17
18using namespace clang;
19using namespace CodeGen;
20
21CGCXXABI::~CGCXXABI() { }
22
23void CGCXXABI::ErrorUnsupportedABI(CodeGenFunction &CGF, StringRef S) {
24 DiagnosticsEngine &Diags = CGF.CGM.getDiags();
25 unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
26 "cannot yet compile %0 in this ABI");
27 Diags.Report(CGF.getContext().getFullLoc(CGF.CurCodeDecl->getLocation()),
28 DiagID)
29 << S;
30}
31
32llvm::Constant *CGCXXABI::GetBogusMemberPointer(QualType T) {
33 return llvm::Constant::getNullValue(CGM.getTypes().ConvertType(T));
34}
35
36llvm::Type *
37CGCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
38 return CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
39}
40
41CGCallee CGCXXABI::EmitLoadOfMemberFunctionPointer(
42 CodeGenFunction &CGF, const Expr *E, Address This,
43 llvm::Value *&ThisPtrForCall,
44 llvm::Value *MemPtr, const MemberPointerType *MPT) {
45 ErrorUnsupportedABI(CGF, "calls through member pointers");
46
47 ThisPtrForCall = This.getPointer();
48 const FunctionProtoType *FPT =
49 MPT->getPointeeType()->getAs<FunctionProtoType>();
50 const auto *RD =
51 cast<CXXRecordDecl>(MPT->getClass()->castAs<RecordType>()->getDecl());
52 llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(
53 CGM.getTypes().arrangeCXXMethodType(RD, FPT, /*FD=*/nullptr));
54 llvm::Constant *FnPtr = llvm::Constant::getNullValue(FTy->getPointerTo());
55 return CGCallee::forDirect(FnPtr, FPT);
56}
57
58llvm::Value *
59CGCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
60 Address Base, llvm::Value *MemPtr,
61 const MemberPointerType *MPT) {
62 ErrorUnsupportedABI(CGF, "loads of member pointers");
63 llvm::Type *Ty = CGF.ConvertType(MPT->getPointeeType())
64 ->getPointerTo(Base.getAddressSpace());
65 return llvm::Constant::getNullValue(Ty);
66}
67
68llvm::Value *CGCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
69 const CastExpr *E,
70 llvm::Value *Src) {
71 ErrorUnsupportedABI(CGF, "member function pointer conversions");
72 return GetBogusMemberPointer(E->getType());
73}
74
75llvm::Constant *CGCXXABI::EmitMemberPointerConversion(const CastExpr *E,
76 llvm::Constant *Src) {
77 return GetBogusMemberPointer(E->getType());
78}
79
80llvm::Value *
81CGCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
82 llvm::Value *L,
83 llvm::Value *R,
84 const MemberPointerType *MPT,
85 bool Inequality) {
86 ErrorUnsupportedABI(CGF, "member function pointer comparison");
87 return CGF.Builder.getFalse();
88}
89
90llvm::Value *
91CGCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
92 llvm::Value *MemPtr,
93 const MemberPointerType *MPT) {
94 ErrorUnsupportedABI(CGF, "member function pointer null testing");
95 return CGF.Builder.getFalse();
96}
97
98llvm::Constant *
99CGCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
100 return GetBogusMemberPointer(QualType(MPT, 0));
101}
102
103llvm::Constant *CGCXXABI::EmitMemberFunctionPointer(const CXXMethodDecl *MD) {
104 return GetBogusMemberPointer(CGM.getContext().getMemberPointerType(
105 MD->getType(), MD->getParent()->getTypeForDecl()));
106}
107
108llvm::Constant *CGCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
109 CharUnits offset) {
110 return GetBogusMemberPointer(QualType(MPT, 0));
111}
112
113llvm::Constant *CGCXXABI::EmitMemberPointer(const APValue &MP, QualType MPT) {
114 return GetBogusMemberPointer(MPT);
115}
116
117bool CGCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
118 // Fake answer.
119 return true;
120}
121
122void CGCXXABI::buildThisParam(CodeGenFunction &CGF, FunctionArgList &params) {
123 const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
124
125 // FIXME: I'm not entirely sure I like using a fake decl just for code
126 // generation. Maybe we can come up with a better way?
127 auto *ThisDecl = ImplicitParamDecl::Create(
128 CGM.getContext(), nullptr, MD->getLocation(),
129 &CGM.getContext().Idents.get("this"), MD->getThisType(),
130 ImplicitParamDecl::CXXThis);
131 params.push_back(ThisDecl);
132 CGF.CXXABIThisDecl = ThisDecl;
133
134 // Compute the presumed alignment of 'this', which basically comes
135 // down to whether we know it's a complete object or not.
136 auto &Layout = CGF.getContext().getASTRecordLayout(MD->getParent());
137 if (MD->getParent()->getNumVBases() == 0 || // avoid vcall in common case
138 MD->getParent()->isEffectivelyFinal() ||
139 isThisCompleteObject(CGF.CurGD)) {
140 CGF.CXXABIThisAlignment = Layout.getAlignment();
141 } else {
142 CGF.CXXABIThisAlignment = Layout.getNonVirtualAlignment();
143 }
144}
145
146llvm::Value *CGCXXABI::loadIncomingCXXThis(CodeGenFunction &CGF) {
147 return CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(getThisDecl(CGF)),
148 "this");
149}
150
151void CGCXXABI::setCXXABIThisValue(CodeGenFunction &CGF, llvm::Value *ThisPtr) {
152 /// Initialize the 'this' slot.
153 assert(getThisDecl(CGF) && "no 'this' variable for function");
154 CGF.CXXABIThisValue = ThisPtr;
155}
156
157void CGCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
158 RValue RV, QualType ResultType) {
159 assert(!CGF.hasAggregateEvaluationKind(ResultType) &&
160 "cannot handle aggregates");
161 CGF.EmitReturnOfRValue(RV, ResultType);
162}
163
164CharUnits CGCXXABI::GetArrayCookieSize(const CXXNewExpr *expr) {
165 if (!requiresArrayCookie(expr))
166 return CharUnits::Zero();
167 return getArrayCookieSizeImpl(expr->getAllocatedType());
168}
169
170CharUnits CGCXXABI::getArrayCookieSizeImpl(QualType elementType) {
171 // BOGUS
172 return CharUnits::Zero();
173}
174
175Address CGCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
176 Address NewPtr,
177 llvm::Value *NumElements,
178 const CXXNewExpr *expr,
179 QualType ElementType) {
180 // Should never be called.
181 ErrorUnsupportedABI(CGF, "array cookie initialization");
182 return Address::invalid();
183}
184
185bool CGCXXABI::requiresArrayCookie(const CXXDeleteExpr *expr,
186 QualType elementType) {
187 // If the class's usual deallocation function takes two arguments,
188 // it needs a cookie.
189 if (expr->doesUsualArrayDeleteWantSize())
190 return true;
191
192 return elementType.isDestructedType();
193}
194
195bool CGCXXABI::requiresArrayCookie(const CXXNewExpr *expr) {
196 // If the class's usual deallocation function takes two arguments,
197 // it needs a cookie.
198 if (expr->doesUsualArrayDeleteWantSize())
199 return true;
200
201 return expr->getAllocatedType().isDestructedType();
202}
203
204void CGCXXABI::ReadArrayCookie(CodeGenFunction &CGF, Address ptr,
205 const CXXDeleteExpr *expr, QualType eltTy,
206 llvm::Value *&numElements,
207 llvm::Value *&allocPtr, CharUnits &cookieSize) {
208 // Derive a char* in the same address space as the pointer.
209 ptr = CGF.Builder.CreateElementBitCast(ptr, CGF.Int8Ty);
210
211 // If we don't need an array cookie, bail out early.
212 if (!requiresArrayCookie(expr, eltTy)) {
213 allocPtr = ptr.getPointer();
214 numElements = nullptr;
215 cookieSize = CharUnits::Zero();
216 return;
217 }
218
219 cookieSize = getArrayCookieSizeImpl(eltTy);
220 Address allocAddr =
221 CGF.Builder.CreateConstInBoundsByteGEP(ptr, -cookieSize);
222 allocPtr = allocAddr.getPointer();
223 numElements = readArrayCookieImpl(CGF, allocAddr, cookieSize);
224}
225
226llvm::Value *CGCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
227 Address ptr,
228 CharUnits cookieSize) {
229 ErrorUnsupportedABI(CGF, "reading a new[] cookie");
230 return llvm::ConstantInt::get(CGF.SizeTy, 0);
231}
232
233/// Returns the adjustment, in bytes, required for the given
234/// member-pointer operation. Returns null if no adjustment is
235/// required.
236llvm::Constant *CGCXXABI::getMemberPointerAdjustment(const CastExpr *E) {
237 assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
238 E->getCastKind() == CK_BaseToDerivedMemberPointer);
239
240 QualType derivedType;
241 if (E->getCastKind() == CK_DerivedToBaseMemberPointer)
242 derivedType = E->getSubExpr()->getType();
243 else
244 derivedType = E->getType();
245
246 const CXXRecordDecl *derivedClass =
247 derivedType->castAs<MemberPointerType>()->getClass()->getAsCXXRecordDecl();
248
249 return CGM.GetNonVirtualBaseClassOffset(derivedClass,
250 E->path_begin(),
251 E->path_end());
252}
253
254llvm::BasicBlock *
255CGCXXABI::EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
256 const CXXRecordDecl *RD) {
257 if (CGM.getTarget().getCXXABI().hasConstructorVariants())
258 llvm_unreachable("shouldn't be called in this ABI");
259
260 ErrorUnsupportedABI(CGF, "complete object detection in ctor");
261 return nullptr;
262}
263
264void CGCXXABI::setCXXDestructorDLLStorage(llvm::GlobalValue *GV,
265 const CXXDestructorDecl *Dtor,
266 CXXDtorType DT) const {
267 // Assume the base C++ ABI has no special rules for destructor variants.
268 CGM.setDLLImportDLLExport(GV, Dtor);
269}
270
271llvm::GlobalValue::LinkageTypes CGCXXABI::getCXXDestructorLinkage(
272 GVALinkage Linkage, const CXXDestructorDecl *Dtor, CXXDtorType DT) const {
273 // Delegate back to CGM by default.
274 return CGM.getLLVMLinkageForDeclarator(Dtor, Linkage,
275 /*IsConstantVariable=*/false);
276}
277
278bool CGCXXABI::NeedsVTTParameter(GlobalDecl GD) {
279 return false;
280}
281
282llvm::CallInst *
283CGCXXABI::emitTerminateForUnexpectedException(CodeGenFunction &CGF,
284 llvm::Value *Exn) {
285 // Just call std::terminate and ignore the violating exception.
286 return CGF.EmitNounwindRuntimeCall(CGF.CGM.getTerminateFn());
287}
288
289CatchTypeInfo CGCXXABI::getCatchAllTypeInfo() {
290 return CatchTypeInfo{nullptr, 0};
291}
292
293std::vector<CharUnits> CGCXXABI::getVBPtrOffsets(const CXXRecordDecl *RD) {
294 return std::vector<CharUnits>();
295}
296
297CGCXXABI::AddedStructorArgCounts CGCXXABI::addImplicitConstructorArgs(
298 CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
299 bool ForVirtualBase, bool Delegating, CallArgList &Args) {
300 AddedStructorArgs AddedArgs =
301 getImplicitConstructorArgs(CGF, D, Type, ForVirtualBase, Delegating);
302 for (size_t i = 0; i < AddedArgs.Prefix.size(); ++i) {
303 Args.insert(Args.begin() + 1 + i,
304 CallArg(RValue::get(AddedArgs.Prefix[i].Value),
305 AddedArgs.Prefix[i].Type));
306 }
307 for (const auto &arg : AddedArgs.Suffix) {
308 Args.add(RValue::get(arg.Value), arg.Type);
309 }
310 return AddedStructorArgCounts(AddedArgs.Prefix.size(),
311 AddedArgs.Suffix.size());
312}
313