1 //===--- CGNonTrivialStruct.cpp - Emit Special Functions for C Structs ----===//
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 file defines functions to generate various special functions for C
10 // structs.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "CodeGenFunction.h"
15 #include "CodeGenModule.h"
16 #include "clang/AST/NonTrivialTypeVisitor.h"
17 #include "llvm/Support/ScopedPrinter.h"
18 #include <array>
19 
20 using namespace clang;
21 using namespace CodeGen;
22 
23 // Return the size of a field in number of bits.
24 static uint64_t getFieldSize(const FieldDecl *FD, QualType FT,
25                              ASTContext &Ctx) {
26   if (FD && FD->isBitField())
27     return FD->getBitWidthValue(Ctx);
28   return Ctx.getTypeSize(FT);
29 }
30 
31 namespace {
32 enum { DstIdx = 0, SrcIdx = 1 };
33 const char *ValNameStr[2] = {"dst", "src"};
34 
35 template <class Derived> struct StructVisitor {
36   StructVisitor(ASTContext &Ctx) : Ctx(Ctx) {}
37 
38   template <class... Ts>
39   void visitStructFields(QualType QT, CharUnits CurStructOffset, Ts... Args) {
40     const RecordDecl *RD = QT->castAs<RecordType>()->getDecl();
41 
42     // Iterate over the fields of the struct.
43     for (const FieldDecl *FD : RD->fields()) {
44       QualType FT = FD->getType();
45       FT = QT.isVolatileQualified() ? FT.withVolatile() : FT;
46       asDerived().visit(FT, FD, CurStructOffset, Args...);
47     }
48 
49     asDerived().flushTrivialFields(Args...);
50   }
51 
52   template <class... Ts> void visitTrivial(Ts... Args) {}
53 
54   template <class... Ts> void visitCXXDestructor(Ts... Args) {
55     llvm_unreachable("field of a C++ struct type is not expected");
56   }
57 
58   template <class... Ts> void flushTrivialFields(Ts... Args) {}
59 
60   uint64_t getFieldOffsetInBits(const FieldDecl *FD) {
61     return FD ? Ctx.getASTRecordLayout(FD->getParent())
62                     .getFieldOffset(FD->getFieldIndex())
63               : 0;
64   }
65 
66   CharUnits getFieldOffset(const FieldDecl *FD) {
67     return Ctx.toCharUnitsFromBits(getFieldOffsetInBits(FD));
68   }
69 
70   Derived &asDerived() { return static_cast<Derived &>(*this); }
71 
72   ASTContext &getContext() { return Ctx; }
73   ASTContext &Ctx;
74 };
75 
76 template <class Derived, bool IsMove>
77 struct CopyStructVisitor : StructVisitor<Derived>,
78                            CopiedTypeVisitor<Derived, IsMove> {
79   using StructVisitor<Derived>::asDerived;
80   using Super = CopiedTypeVisitor<Derived, IsMove>;
81 
82   CopyStructVisitor(ASTContext &Ctx) : StructVisitor<Derived>(Ctx) {}
83 
84   template <class... Ts>
85   void preVisit(QualType::PrimitiveCopyKind PCK, QualType FT,
86                 const FieldDecl *FD, CharUnits CurStructOffsset,
87                 Ts &&... Args) {
88     if (PCK)
89       asDerived().flushTrivialFields(std::forward<Ts>(Args)...);
90   }
91 
92   template <class... Ts>
93   void visitWithKind(QualType::PrimitiveCopyKind PCK, QualType FT,
94                      const FieldDecl *FD, CharUnits CurStructOffsset,
95                      Ts &&... Args) {
96     if (const auto *AT = asDerived().getContext().getAsArrayType(FT)) {
97       asDerived().visitArray(PCK, AT, FT.isVolatileQualified(), FD,
98                              CurStructOffsset, std::forward<Ts>(Args)...);
99       return;
100     }
101 
102     Super::visitWithKind(PCK, FT, FD, CurStructOffsset,
103                          std::forward<Ts>(Args)...);
104   }
105 
106   template <class... Ts>
107   void visitTrivial(QualType FT, const FieldDecl *FD, CharUnits CurStructOffset,
108                     Ts... Args) {
109     assert(!FT.isVolatileQualified() && "volatile field not expected");
110     ASTContext &Ctx = asDerived().getContext();
111     uint64_t FieldSize = getFieldSize(FD, FT, Ctx);
112 
113     // Ignore zero-sized fields.
114     if (FieldSize == 0)
115       return;
116 
117     uint64_t FStartInBits = asDerived().getFieldOffsetInBits(FD);
118     uint64_t FEndInBits = FStartInBits + FieldSize;
119     uint64_t RoundedFEnd = llvm::alignTo(FEndInBits, Ctx.getCharWidth());
120 
121     // Set Start if this is the first field of a sequence of trivial fields.
122     if (Start == End)
123       Start = CurStructOffset + Ctx.toCharUnitsFromBits(FStartInBits);
124     End = CurStructOffset + Ctx.toCharUnitsFromBits(RoundedFEnd);
125   }
126 
127   CharUnits Start = CharUnits::Zero(), End = CharUnits::Zero();
128 };
129 
130 // This function creates the mangled name of a special function of a non-trivial
131 // C struct. Since there is no ODR in C, the function is mangled based on the
132 // struct contents and not the name. The mangled name has the following
133 // structure:
134 //
135 // <function-name> ::= <prefix> <alignment-info> "_" <struct-field-info>
136 // <prefix> ::= "__destructor_" | "__default_constructor_" |
137 //              "__copy_constructor_" | "__move_constructor_" |
138 //              "__copy_assignment_" | "__move_assignment_"
139 // <alignment-info> ::= <dst-alignment> ["_" <src-alignment>]
140 // <struct-field-info> ::= <field-info>+
141 // <field-info> ::= <struct-or-scalar-field-info> | <array-field-info>
142 // <struct-or-scalar-field-info> ::= <struct-field-info> | <strong-field-info> |
143 //                                   <trivial-field-info>
144 // <array-field-info> ::= "_AB" <array-offset> "s" <element-size> "n"
145 //                        <num-elements> <innermost-element-info> "_AE"
146 // <innermost-element-info> ::= <struct-or-scalar-field-info>
147 // <strong-field-info> ::= "_s" ["b"] ["v"] <field-offset>
148 // <trivial-field-info> ::= "_t" ["v"] <field-offset> "_" <field-size>
149 
150 template <class Derived> struct GenFuncNameBase {
151   std::string getVolatileOffsetStr(bool IsVolatile, CharUnits Offset) {
152     std::string S;
153     if (IsVolatile)
154       S = "v";
155     S += llvm::to_string(Offset.getQuantity());
156     return S;
157   }
158 
159   void visitARCStrong(QualType FT, const FieldDecl *FD,
160                       CharUnits CurStructOffset) {
161     appendStr("_s");
162     if (FT->isBlockPointerType())
163       appendStr("b");
164     CharUnits FieldOffset = CurStructOffset + asDerived().getFieldOffset(FD);
165     appendStr(getVolatileOffsetStr(FT.isVolatileQualified(), FieldOffset));
166   }
167 
168   void visitARCWeak(QualType FT, const FieldDecl *FD,
169                     CharUnits CurStructOffset) {
170     appendStr("_w");
171     CharUnits FieldOffset = CurStructOffset + asDerived().getFieldOffset(FD);
172     appendStr(getVolatileOffsetStr(FT.isVolatileQualified(), FieldOffset));
173   }
174 
175   void visitStruct(QualType QT, const FieldDecl *FD,
176                    CharUnits CurStructOffset) {
177     CharUnits FieldOffset = CurStructOffset + asDerived().getFieldOffset(FD);
178     asDerived().visitStructFields(QT, FieldOffset);
179   }
180 
181   template <class FieldKind>
182   void visitArray(FieldKind FK, const ArrayType *AT, bool IsVolatile,
183                   const FieldDecl *FD, CharUnits CurStructOffset) {
184     // String for non-volatile trivial fields is emitted when
185     // flushTrivialFields is called.
186     if (!FK)
187       return asDerived().visitTrivial(QualType(AT, 0), FD, CurStructOffset);
188 
189     asDerived().flushTrivialFields();
190     CharUnits FieldOffset = CurStructOffset + asDerived().getFieldOffset(FD);
191     ASTContext &Ctx = asDerived().getContext();
192     const ConstantArrayType *CAT = cast<ConstantArrayType>(AT);
193     unsigned NumElts = Ctx.getConstantArrayElementCount(CAT);
194     QualType EltTy = Ctx.getBaseElementType(CAT);
195     CharUnits EltSize = Ctx.getTypeSizeInChars(EltTy);
196     appendStr("_AB" + llvm::to_string(FieldOffset.getQuantity()) + "s" +
197               llvm::to_string(EltSize.getQuantity()) + "n" +
198               llvm::to_string(NumElts));
199     EltTy = IsVolatile ? EltTy.withVolatile() : EltTy;
200     asDerived().visitWithKind(FK, EltTy, nullptr, FieldOffset);
201     appendStr("_AE");
202   }
203 
204   void appendStr(StringRef Str) { Name += Str; }
205 
206   std::string getName(QualType QT, bool IsVolatile) {
207     QT = IsVolatile ? QT.withVolatile() : QT;
208     asDerived().visitStructFields(QT, CharUnits::Zero());
209     return Name;
210   }
211 
212   Derived &asDerived() { return static_cast<Derived &>(*this); }
213 
214   std::string Name;
215 };
216 
217 template <class Derived>
218 struct GenUnaryFuncName : StructVisitor<Derived>, GenFuncNameBase<Derived> {
219   GenUnaryFuncName(StringRef Prefix, CharUnits DstAlignment, ASTContext &Ctx)
220       : StructVisitor<Derived>(Ctx) {
221     this->appendStr(Prefix);
222     this->appendStr(llvm::to_string(DstAlignment.getQuantity()));
223   }
224 };
225 
226 // Helper function to create a null constant.
227 static llvm::Constant *getNullForVariable(Address Addr) {
228   llvm::Type *Ty = Addr.getElementType();
229   return llvm::ConstantPointerNull::get(cast<llvm::PointerType>(Ty));
230 }
231 
232 template <bool IsMove>
233 struct GenBinaryFuncName : CopyStructVisitor<GenBinaryFuncName<IsMove>, IsMove>,
234                            GenFuncNameBase<GenBinaryFuncName<IsMove>> {
235 
236   GenBinaryFuncName(StringRef Prefix, CharUnits DstAlignment,
237                     CharUnits SrcAlignment, ASTContext &Ctx)
238       : CopyStructVisitor<GenBinaryFuncName<IsMove>, IsMove>(Ctx) {
239     this->appendStr(Prefix);
240     this->appendStr(llvm::to_string(DstAlignment.getQuantity()));
241     this->appendStr("_" + llvm::to_string(SrcAlignment.getQuantity()));
242   }
243 
244   void flushTrivialFields() {
245     if (this->Start == this->End)
246       return;
247 
248     this->appendStr("_t" + llvm::to_string(this->Start.getQuantity()) + "w" +
249                     llvm::to_string((this->End - this->Start).getQuantity()));
250 
251     this->Start = this->End = CharUnits::Zero();
252   }
253 
254   void visitVolatileTrivial(QualType FT, const FieldDecl *FD,
255                             CharUnits CurStackOffset) {
256     // Because volatile fields can be bit-fields and are individually copied,
257     // their offset and width are in bits.
258     uint64_t OffsetInBits =
259         this->Ctx.toBits(CurStackOffset) + this->getFieldOffsetInBits(FD);
260     this->appendStr("_tv" + llvm::to_string(OffsetInBits) + "w" +
261                     llvm::to_string(getFieldSize(FD, FT, this->Ctx)));
262   }
263 };
264 
265 struct GenDefaultInitializeFuncName
266     : GenUnaryFuncName<GenDefaultInitializeFuncName>,
267       DefaultInitializedTypeVisitor<GenDefaultInitializeFuncName> {
268   using Super = DefaultInitializedTypeVisitor<GenDefaultInitializeFuncName>;
269   GenDefaultInitializeFuncName(CharUnits DstAlignment, ASTContext &Ctx)
270       : GenUnaryFuncName<GenDefaultInitializeFuncName>("__default_constructor_",
271                                                        DstAlignment, Ctx) {}
272   void visitWithKind(QualType::PrimitiveDefaultInitializeKind PDIK, QualType FT,
273                      const FieldDecl *FD, CharUnits CurStructOffset) {
274     if (const auto *AT = getContext().getAsArrayType(FT)) {
275       visitArray(PDIK, AT, FT.isVolatileQualified(), FD, CurStructOffset);
276       return;
277     }
278 
279     Super::visitWithKind(PDIK, FT, FD, CurStructOffset);
280   }
281 };
282 
283 struct GenDestructorFuncName : GenUnaryFuncName<GenDestructorFuncName>,
284                                DestructedTypeVisitor<GenDestructorFuncName> {
285   using Super = DestructedTypeVisitor<GenDestructorFuncName>;
286   GenDestructorFuncName(const char *Prefix, CharUnits DstAlignment,
287                         ASTContext &Ctx)
288       : GenUnaryFuncName<GenDestructorFuncName>(Prefix, DstAlignment,
289                                                 Ctx) {}
290   void visitWithKind(QualType::DestructionKind DK, QualType FT,
291                      const FieldDecl *FD, CharUnits CurStructOffset) {
292     if (const auto *AT = getContext().getAsArrayType(FT)) {
293       visitArray(DK, AT, FT.isVolatileQualified(), FD, CurStructOffset);
294       return;
295     }
296 
297     Super::visitWithKind(DK, FT, FD, CurStructOffset);
298   }
299 };
300 
301 // Helper function that creates CGFunctionInfo for an N-ary special function.
302 template <size_t N>
303 static const CGFunctionInfo &getFunctionInfo(CodeGenModule &CGM,
304                                              FunctionArgList &Args) {
305   ASTContext &Ctx = CGM.getContext();
306   llvm::SmallVector<ImplicitParamDecl *, N> Params;
307   QualType ParamTy = Ctx.getPointerType(Ctx.VoidPtrTy);
308 
309   for (unsigned I = 0; I < N; ++I)
310     Params.push_back(ImplicitParamDecl::Create(
311         Ctx, nullptr, SourceLocation(), &Ctx.Idents.get(ValNameStr[I]), ParamTy,
312         ImplicitParamDecl::Other));
313 
314   for (auto &P : Params)
315     Args.push_back(P);
316 
317   return CGM.getTypes().arrangeBuiltinFunctionDeclaration(Ctx.VoidTy, Args);
318 }
319 
320 // Template classes that are used as bases for classes that emit special
321 // functions.
322 template <class Derived> struct GenFuncBase {
323   template <size_t N>
324   void visitStruct(QualType FT, const FieldDecl *FD, CharUnits CurStackOffset,
325                    std::array<Address, N> Addrs) {
326     this->asDerived().callSpecialFunction(
327         FT, CurStackOffset + asDerived().getFieldOffset(FD), Addrs);
328   }
329 
330   template <class FieldKind, size_t N>
331   void visitArray(FieldKind FK, const ArrayType *AT, bool IsVolatile,
332                   const FieldDecl *FD, CharUnits CurStackOffset,
333                   std::array<Address, N> Addrs) {
334     // Non-volatile trivial fields are copied when flushTrivialFields is called.
335     if (!FK)
336       return asDerived().visitTrivial(QualType(AT, 0), FD, CurStackOffset,
337                                       Addrs);
338 
339     asDerived().flushTrivialFields(Addrs);
340     CodeGenFunction &CGF = *this->CGF;
341     ASTContext &Ctx = CGF.getContext();
342 
343     // Compute the end address.
344     QualType BaseEltQT;
345     std::array<Address, N> StartAddrs = Addrs;
346     for (unsigned I = 0; I < N; ++I)
347       StartAddrs[I] = getAddrWithOffset(Addrs[I], CurStackOffset, FD);
348     Address DstAddr = StartAddrs[DstIdx];
349     llvm::Value *NumElts = CGF.emitArrayLength(AT, BaseEltQT, DstAddr);
350     unsigned BaseEltSize = Ctx.getTypeSizeInChars(BaseEltQT).getQuantity();
351     llvm::Value *BaseEltSizeVal =
352         llvm::ConstantInt::get(NumElts->getType(), BaseEltSize);
353     llvm::Value *SizeInBytes =
354         CGF.Builder.CreateNUWMul(BaseEltSizeVal, NumElts);
355     Address BC = CGF.Builder.CreateBitCast(DstAddr, CGF.CGM.Int8PtrTy);
356     llvm::Value *DstArrayEnd =
357         CGF.Builder.CreateInBoundsGEP(BC.getPointer(), SizeInBytes);
358     DstArrayEnd = CGF.Builder.CreateBitCast(DstArrayEnd, CGF.CGM.Int8PtrPtrTy,
359                                             "dstarray.end");
360     llvm::BasicBlock *PreheaderBB = CGF.Builder.GetInsertBlock();
361 
362     // Create the header block and insert the phi instructions.
363     llvm::BasicBlock *HeaderBB = CGF.createBasicBlock("loop.header");
364     CGF.EmitBlock(HeaderBB);
365     llvm::PHINode *PHIs[N];
366 
367     for (unsigned I = 0; I < N; ++I) {
368       PHIs[I] = CGF.Builder.CreatePHI(CGF.CGM.Int8PtrPtrTy, 2, "addr.cur");
369       PHIs[I]->addIncoming(StartAddrs[I].getPointer(), PreheaderBB);
370     }
371 
372     // Create the exit and loop body blocks.
373     llvm::BasicBlock *ExitBB = CGF.createBasicBlock("loop.exit");
374     llvm::BasicBlock *LoopBB = CGF.createBasicBlock("loop.body");
375 
376     // Emit the comparison and conditional branch instruction that jumps to
377     // either the exit or the loop body.
378     llvm::Value *Done =
379         CGF.Builder.CreateICmpEQ(PHIs[DstIdx], DstArrayEnd, "done");
380     CGF.Builder.CreateCondBr(Done, ExitBB, LoopBB);
381 
382     // Visit the element of the array in the loop body.
383     CGF.EmitBlock(LoopBB);
384     QualType EltQT = AT->getElementType();
385     CharUnits EltSize = Ctx.getTypeSizeInChars(EltQT);
386     std::array<Address, N> NewAddrs = Addrs;
387 
388     for (unsigned I = 0; I < N; ++I)
389       NewAddrs[I] = Address(
390           PHIs[I], StartAddrs[I].getAlignment().alignmentAtOffset(EltSize));
391 
392     EltQT = IsVolatile ? EltQT.withVolatile() : EltQT;
393     this->asDerived().visitWithKind(FK, EltQT, nullptr, CharUnits::Zero(),
394                                     NewAddrs);
395 
396     LoopBB = CGF.Builder.GetInsertBlock();
397 
398     for (unsigned I = 0; I < N; ++I) {
399       // Instrs to update the destination and source addresses.
400       // Update phi instructions.
401       NewAddrs[I] = getAddrWithOffset(NewAddrs[I], EltSize);
402       PHIs[I]->addIncoming(NewAddrs[I].getPointer(), LoopBB);
403     }
404 
405     // Insert an unconditional branch to the header block.
406     CGF.Builder.CreateBr(HeaderBB);
407     CGF.EmitBlock(ExitBB);
408   }
409 
410   /// Return an address with the specified offset from the passed address.
411   Address getAddrWithOffset(Address Addr, CharUnits Offset) {
412     assert(Addr.isValid() && "invalid address");
413     if (Offset.getQuantity() == 0)
414       return Addr;
415     Addr = CGF->Builder.CreateBitCast(Addr, CGF->CGM.Int8PtrTy);
416     Addr = CGF->Builder.CreateConstInBoundsGEP(Addr, Offset.getQuantity());
417     return CGF->Builder.CreateBitCast(Addr, CGF->CGM.Int8PtrPtrTy);
418   }
419 
420   Address getAddrWithOffset(Address Addr, CharUnits StructFieldOffset,
421                             const FieldDecl *FD) {
422     return getAddrWithOffset(Addr, StructFieldOffset +
423                                        asDerived().getFieldOffset(FD));
424   }
425 
426   template <size_t N>
427   llvm::Function *
428   getFunction(StringRef FuncName, QualType QT, std::array<Address, N> Addrs,
429               std::array<CharUnits, N> Alignments, CodeGenModule &CGM) {
430     // If the special function already exists in the module, return it.
431     if (llvm::Function *F = CGM.getModule().getFunction(FuncName)) {
432       bool WrongType = false;
433       if (!F->getReturnType()->isVoidTy())
434         WrongType = true;
435       else {
436         for (const llvm::Argument &Arg : F->args())
437           if (Arg.getType() != CGM.Int8PtrPtrTy)
438             WrongType = true;
439       }
440 
441       if (WrongType) {
442         std::string FuncName = F->getName();
443         SourceLocation Loc = QT->castAs<RecordType>()->getDecl()->getLocation();
444         CGM.Error(Loc, "special function " + FuncName +
445                            " for non-trivial C struct has incorrect type");
446         return nullptr;
447       }
448       return F;
449     }
450 
451     ASTContext &Ctx = CGM.getContext();
452     FunctionArgList Args;
453     const CGFunctionInfo &FI = getFunctionInfo<N>(CGM, Args);
454     llvm::FunctionType *FuncTy = CGM.getTypes().GetFunctionType(FI);
455     llvm::Function *F =
456         llvm::Function::Create(FuncTy, llvm::GlobalValue::LinkOnceODRLinkage,
457                                FuncName, &CGM.getModule());
458     F->setVisibility(llvm::GlobalValue::HiddenVisibility);
459     CGM.SetLLVMFunctionAttributes(GlobalDecl(), FI, F);
460     CGM.SetLLVMFunctionAttributesForDefinition(nullptr, F);
461     IdentifierInfo *II = &Ctx.Idents.get(FuncName);
462     FunctionDecl *FD = FunctionDecl::Create(
463         Ctx, Ctx.getTranslationUnitDecl(), SourceLocation(), SourceLocation(),
464         II, Ctx.getFunctionType(Ctx.VoidTy, llvm::None, {}), nullptr,
465         SC_PrivateExtern, false, false);
466     CodeGenFunction NewCGF(CGM);
467     setCGF(&NewCGF);
468     CGF->StartFunction(FD, Ctx.VoidTy, F, FI, Args);
469 
470     for (unsigned I = 0; I < N; ++I) {
471       llvm::Value *V = CGF->Builder.CreateLoad(CGF->GetAddrOfLocalVar(Args[I]));
472       Addrs[I] = Address(V, Alignments[I]);
473     }
474 
475     asDerived().visitStructFields(QT, CharUnits::Zero(), Addrs);
476     CGF->FinishFunction();
477     return F;
478   }
479 
480   template <size_t N>
481   void callFunc(StringRef FuncName, QualType QT, std::array<Address, N> Addrs,
482                 CodeGenFunction &CallerCGF) {
483     std::array<CharUnits, N> Alignments;
484     llvm::Value *Ptrs[N];
485 
486     for (unsigned I = 0; I < N; ++I) {
487       Alignments[I] = Addrs[I].getAlignment();
488       Ptrs[I] =
489           CallerCGF.Builder.CreateBitCast(Addrs[I], CallerCGF.CGM.Int8PtrPtrTy)
490               .getPointer();
491     }
492 
493     if (llvm::Function *F =
494             getFunction(FuncName, QT, Addrs, Alignments, CallerCGF.CGM))
495       CallerCGF.EmitNounwindRuntimeCall(F, Ptrs);
496   }
497 
498   Derived &asDerived() { return static_cast<Derived &>(*this); }
499 
500   void setCGF(CodeGenFunction *F) { CGF = F; }
501 
502   CodeGenFunction *CGF = nullptr;
503 };
504 
505 template <class Derived, bool IsMove>
506 struct GenBinaryFunc : CopyStructVisitor<Derived, IsMove>,
507                        GenFuncBase<Derived> {
508   GenBinaryFunc(ASTContext &Ctx) : CopyStructVisitor<Derived, IsMove>(Ctx) {}
509 
510   void flushTrivialFields(std::array<Address, 2> Addrs) {
511     CharUnits Size = this->End - this->Start;
512 
513     if (Size.getQuantity() == 0)
514       return;
515 
516     Address DstAddr = this->getAddrWithOffset(Addrs[DstIdx], this->Start);
517     Address SrcAddr = this->getAddrWithOffset(Addrs[SrcIdx], this->Start);
518 
519     // Emit memcpy.
520     if (Size.getQuantity() >= 16 || !llvm::isPowerOf2_32(Size.getQuantity())) {
521       llvm::Value *SizeVal =
522           llvm::ConstantInt::get(this->CGF->SizeTy, Size.getQuantity());
523       DstAddr =
524           this->CGF->Builder.CreateElementBitCast(DstAddr, this->CGF->Int8Ty);
525       SrcAddr =
526           this->CGF->Builder.CreateElementBitCast(SrcAddr, this->CGF->Int8Ty);
527       this->CGF->Builder.CreateMemCpy(DstAddr, SrcAddr, SizeVal, false);
528     } else {
529       llvm::Type *Ty = llvm::Type::getIntNTy(
530           this->CGF->getLLVMContext(),
531           Size.getQuantity() * this->CGF->getContext().getCharWidth());
532       DstAddr = this->CGF->Builder.CreateElementBitCast(DstAddr, Ty);
533       SrcAddr = this->CGF->Builder.CreateElementBitCast(SrcAddr, Ty);
534       llvm::Value *SrcVal = this->CGF->Builder.CreateLoad(SrcAddr, false);
535       this->CGF->Builder.CreateStore(SrcVal, DstAddr, false);
536     }
537 
538     this->Start = this->End = CharUnits::Zero();
539   }
540 
541   template <class... Ts>
542   void visitVolatileTrivial(QualType FT, const FieldDecl *FD, CharUnits Offset,
543                             std::array<Address, 2> Addrs) {
544     LValue DstLV, SrcLV;
545     if (FD) {
546       QualType RT = QualType(FD->getParent()->getTypeForDecl(), 0);
547       llvm::PointerType *PtrTy = this->CGF->ConvertType(RT)->getPointerTo();
548       Address DstAddr = this->getAddrWithOffset(Addrs[DstIdx], Offset);
549       LValue DstBase = this->CGF->MakeAddrLValue(
550           this->CGF->Builder.CreateBitCast(DstAddr, PtrTy), FT);
551       DstLV = this->CGF->EmitLValueForField(DstBase, FD);
552       Address SrcAddr = this->getAddrWithOffset(Addrs[SrcIdx], Offset);
553       LValue SrcBase = this->CGF->MakeAddrLValue(
554           this->CGF->Builder.CreateBitCast(SrcAddr, PtrTy), FT);
555       SrcLV = this->CGF->EmitLValueForField(SrcBase, FD);
556     } else {
557       llvm::PointerType *Ty = this->CGF->ConvertType(FT)->getPointerTo();
558       Address DstAddr = this->CGF->Builder.CreateBitCast(Addrs[DstIdx], Ty);
559       Address SrcAddr = this->CGF->Builder.CreateBitCast(Addrs[SrcIdx], Ty);
560       DstLV = this->CGF->MakeAddrLValue(DstAddr, FT);
561       SrcLV = this->CGF->MakeAddrLValue(SrcAddr, FT);
562     }
563     RValue SrcVal = this->CGF->EmitLoadOfLValue(SrcLV, SourceLocation());
564     this->CGF->EmitStoreThroughLValue(SrcVal, DstLV);
565   }
566 };
567 
568 // These classes that emit the special functions for a non-trivial struct.
569 struct GenDestructor : StructVisitor<GenDestructor>,
570                        GenFuncBase<GenDestructor>,
571                        DestructedTypeVisitor<GenDestructor> {
572   using Super = DestructedTypeVisitor<GenDestructor>;
573   GenDestructor(ASTContext &Ctx) : StructVisitor<GenDestructor>(Ctx) {}
574 
575   void visitWithKind(QualType::DestructionKind DK, QualType FT,
576                      const FieldDecl *FD, CharUnits CurStructOffset,
577                      std::array<Address, 1> Addrs) {
578     if (const auto *AT = getContext().getAsArrayType(FT)) {
579       visitArray(DK, AT, FT.isVolatileQualified(), FD, CurStructOffset, Addrs);
580       return;
581     }
582 
583     Super::visitWithKind(DK, FT, FD, CurStructOffset, Addrs);
584   }
585 
586   void visitARCStrong(QualType QT, const FieldDecl *FD,
587                       CharUnits CurStackOffset, std::array<Address, 1> Addrs) {
588     CGF->destroyARCStrongImprecise(
589         *CGF, getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD), QT);
590   }
591 
592   void visitARCWeak(QualType QT, const FieldDecl *FD, CharUnits CurStackOffset,
593                     std::array<Address, 1> Addrs) {
594     CGF->destroyARCWeak(
595         *CGF, getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD), QT);
596   }
597 
598   void callSpecialFunction(QualType FT, CharUnits Offset,
599                            std::array<Address, 1> Addrs) {
600     CGF->callCStructDestructor(
601         CGF->MakeAddrLValue(getAddrWithOffset(Addrs[DstIdx], Offset), FT));
602   }
603 };
604 
605 struct GenDefaultInitialize
606     : StructVisitor<GenDefaultInitialize>,
607       GenFuncBase<GenDefaultInitialize>,
608       DefaultInitializedTypeVisitor<GenDefaultInitialize> {
609   using Super = DefaultInitializedTypeVisitor<GenDefaultInitialize>;
610   typedef GenFuncBase<GenDefaultInitialize> GenFuncBaseTy;
611 
612   GenDefaultInitialize(ASTContext &Ctx)
613       : StructVisitor<GenDefaultInitialize>(Ctx) {}
614 
615   void visitWithKind(QualType::PrimitiveDefaultInitializeKind PDIK, QualType FT,
616                      const FieldDecl *FD, CharUnits CurStructOffset,
617                      std::array<Address, 1> Addrs) {
618     if (const auto *AT = getContext().getAsArrayType(FT)) {
619       visitArray(PDIK, AT, FT.isVolatileQualified(), FD, CurStructOffset,
620                  Addrs);
621       return;
622     }
623 
624     Super::visitWithKind(PDIK, FT, FD, CurStructOffset, Addrs);
625   }
626 
627   void visitARCStrong(QualType QT, const FieldDecl *FD,
628                       CharUnits CurStackOffset, std::array<Address, 1> Addrs) {
629     CGF->EmitNullInitialization(
630         getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD), QT);
631   }
632 
633   void visitARCWeak(QualType QT, const FieldDecl *FD, CharUnits CurStackOffset,
634                     std::array<Address, 1> Addrs) {
635     CGF->EmitNullInitialization(
636         getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD), QT);
637   }
638 
639   template <class FieldKind, size_t... Is>
640   void visitArray(FieldKind FK, const ArrayType *AT, bool IsVolatile,
641                   const FieldDecl *FD, CharUnits CurStackOffset,
642                   std::array<Address, 1> Addrs) {
643     if (!FK)
644       return visitTrivial(QualType(AT, 0), FD, CurStackOffset, Addrs);
645 
646     ASTContext &Ctx = getContext();
647     CharUnits Size = Ctx.getTypeSizeInChars(QualType(AT, 0));
648     QualType EltTy = Ctx.getBaseElementType(QualType(AT, 0));
649 
650     if (Size < CharUnits::fromQuantity(16) || EltTy->getAs<RecordType>()) {
651       GenFuncBaseTy::visitArray(FK, AT, IsVolatile, FD, CurStackOffset, Addrs);
652       return;
653     }
654 
655     llvm::Constant *SizeVal = CGF->Builder.getInt64(Size.getQuantity());
656     Address DstAddr = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
657     Address Loc = CGF->Builder.CreateElementBitCast(DstAddr, CGF->Int8Ty);
658     CGF->Builder.CreateMemSet(Loc, CGF->Builder.getInt8(0), SizeVal,
659                               IsVolatile);
660   }
661 
662   void callSpecialFunction(QualType FT, CharUnits Offset,
663                            std::array<Address, 1> Addrs) {
664     CGF->callCStructDefaultConstructor(
665         CGF->MakeAddrLValue(getAddrWithOffset(Addrs[DstIdx], Offset), FT));
666   }
667 };
668 
669 struct GenCopyConstructor : GenBinaryFunc<GenCopyConstructor, false> {
670   GenCopyConstructor(ASTContext &Ctx)
671       : GenBinaryFunc<GenCopyConstructor, false>(Ctx) {}
672 
673   void visitARCStrong(QualType QT, const FieldDecl *FD,
674                       CharUnits CurStackOffset, std::array<Address, 2> Addrs) {
675     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
676     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
677     llvm::Value *SrcVal = CGF->EmitLoadOfScalar(
678         Addrs[SrcIdx], QT.isVolatileQualified(), QT, SourceLocation());
679     llvm::Value *Val = CGF->EmitARCRetain(QT, SrcVal);
680     CGF->EmitStoreOfScalar(Val, CGF->MakeAddrLValue(Addrs[DstIdx], QT), true);
681   }
682 
683   void visitARCWeak(QualType QT, const FieldDecl *FD, CharUnits CurStackOffset,
684                     std::array<Address, 2> Addrs) {
685     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
686     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
687     CGF->EmitARCCopyWeak(Addrs[DstIdx], Addrs[SrcIdx]);
688   }
689 
690   void callSpecialFunction(QualType FT, CharUnits Offset,
691                            std::array<Address, 2> Addrs) {
692     CGF->callCStructCopyConstructor(CGF->MakeAddrLValue(Addrs[DstIdx], FT),
693                                     CGF->MakeAddrLValue(Addrs[SrcIdx], FT));
694   }
695 };
696 
697 struct GenMoveConstructor : GenBinaryFunc<GenMoveConstructor, true> {
698   GenMoveConstructor(ASTContext &Ctx)
699       : GenBinaryFunc<GenMoveConstructor, true>(Ctx) {}
700 
701   void visitARCStrong(QualType QT, const FieldDecl *FD,
702                       CharUnits CurStackOffset, std::array<Address, 2> Addrs) {
703     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
704     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
705     LValue SrcLV = CGF->MakeAddrLValue(Addrs[SrcIdx], QT);
706     llvm::Value *SrcVal =
707         CGF->EmitLoadOfLValue(SrcLV, SourceLocation()).getScalarVal();
708     CGF->EmitStoreOfScalar(getNullForVariable(SrcLV.getAddress()), SrcLV);
709     CGF->EmitStoreOfScalar(SrcVal, CGF->MakeAddrLValue(Addrs[DstIdx], QT),
710                            /* isInitialization */ true);
711   }
712 
713   void visitARCWeak(QualType QT, const FieldDecl *FD, CharUnits CurStackOffset,
714                     std::array<Address, 2> Addrs) {
715     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
716     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
717     CGF->EmitARCMoveWeak(Addrs[DstIdx], Addrs[SrcIdx]);
718   }
719 
720   void callSpecialFunction(QualType FT, CharUnits Offset,
721                            std::array<Address, 2> Addrs) {
722     CGF->callCStructMoveConstructor(CGF->MakeAddrLValue(Addrs[DstIdx], FT),
723                                     CGF->MakeAddrLValue(Addrs[SrcIdx], FT));
724   }
725 };
726 
727 struct GenCopyAssignment : GenBinaryFunc<GenCopyAssignment, false> {
728   GenCopyAssignment(ASTContext &Ctx)
729       : GenBinaryFunc<GenCopyAssignment, false>(Ctx) {}
730 
731   void visitARCStrong(QualType QT, const FieldDecl *FD,
732                       CharUnits CurStackOffset, std::array<Address, 2> Addrs) {
733     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
734     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
735     llvm::Value *SrcVal = CGF->EmitLoadOfScalar(
736         Addrs[SrcIdx], QT.isVolatileQualified(), QT, SourceLocation());
737     CGF->EmitARCStoreStrong(CGF->MakeAddrLValue(Addrs[DstIdx], QT), SrcVal,
738                             false);
739   }
740 
741   void visitARCWeak(QualType QT, const FieldDecl *FD, CharUnits CurStackOffset,
742                     std::array<Address, 2> Addrs) {
743     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
744     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
745     CGF->emitARCCopyAssignWeak(QT, Addrs[DstIdx], Addrs[SrcIdx]);
746   }
747 
748   void callSpecialFunction(QualType FT, CharUnits Offset,
749                            std::array<Address, 2> Addrs) {
750     CGF->callCStructCopyAssignmentOperator(
751         CGF->MakeAddrLValue(Addrs[DstIdx], FT),
752         CGF->MakeAddrLValue(Addrs[SrcIdx], FT));
753   }
754 };
755 
756 struct GenMoveAssignment : GenBinaryFunc<GenMoveAssignment, true> {
757   GenMoveAssignment(ASTContext &Ctx)
758       : GenBinaryFunc<GenMoveAssignment, true>(Ctx) {}
759 
760   void visitARCStrong(QualType QT, const FieldDecl *FD,
761                       CharUnits CurStackOffset, std::array<Address, 2> Addrs) {
762     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
763     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
764     LValue SrcLV = CGF->MakeAddrLValue(Addrs[SrcIdx], QT);
765     llvm::Value *SrcVal =
766         CGF->EmitLoadOfLValue(SrcLV, SourceLocation()).getScalarVal();
767     CGF->EmitStoreOfScalar(getNullForVariable(SrcLV.getAddress()), SrcLV);
768     LValue DstLV = CGF->MakeAddrLValue(Addrs[DstIdx], QT);
769     llvm::Value *DstVal =
770         CGF->EmitLoadOfLValue(DstLV, SourceLocation()).getScalarVal();
771     CGF->EmitStoreOfScalar(SrcVal, DstLV);
772     CGF->EmitARCRelease(DstVal, ARCImpreciseLifetime);
773   }
774 
775   void visitARCWeak(QualType QT, const FieldDecl *FD, CharUnits CurStackOffset,
776                     std::array<Address, 2> Addrs) {
777     Addrs[DstIdx] = getAddrWithOffset(Addrs[DstIdx], CurStackOffset, FD);
778     Addrs[SrcIdx] = getAddrWithOffset(Addrs[SrcIdx], CurStackOffset, FD);
779     CGF->emitARCMoveAssignWeak(QT, Addrs[DstIdx], Addrs[SrcIdx]);
780   }
781 
782   void callSpecialFunction(QualType FT, CharUnits Offset,
783                            std::array<Address, 2> Addrs) {
784     CGF->callCStructMoveAssignmentOperator(
785         CGF->MakeAddrLValue(Addrs[DstIdx], FT),
786         CGF->MakeAddrLValue(Addrs[SrcIdx], FT));
787   }
788 };
789 
790 } // namespace
791 
792 void CodeGenFunction::destroyNonTrivialCStruct(CodeGenFunction &CGF,
793                                                Address Addr, QualType Type) {
794   CGF.callCStructDestructor(CGF.MakeAddrLValue(Addr, Type));
795 }
796 
797 // Default-initialize a variable that is a non-trivial struct or an array of
798 // such structure.
799 void CodeGenFunction::defaultInitNonTrivialCStructVar(LValue Dst) {
800   GenDefaultInitialize Gen(getContext());
801   Address DstPtr = Builder.CreateBitCast(Dst.getAddress(), CGM.Int8PtrPtrTy);
802   Gen.setCGF(this);
803   QualType QT = Dst.getType();
804   QT = Dst.isVolatile() ? QT.withVolatile() : QT;
805   Gen.visit(QT, nullptr, CharUnits::Zero(), std::array<Address, 1>({{DstPtr}}));
806 }
807 
808 template <class G, size_t N>
809 static void callSpecialFunction(G &&Gen, StringRef FuncName, QualType QT,
810                                 bool IsVolatile, CodeGenFunction &CGF,
811                                 std::array<Address, N> Addrs) {
812   for (unsigned I = 0; I < N; ++I)
813     Addrs[I] = CGF.Builder.CreateBitCast(Addrs[I], CGF.CGM.Int8PtrPtrTy);
814   QT = IsVolatile ? QT.withVolatile() : QT;
815   Gen.callFunc(FuncName, QT, Addrs, CGF);
816 }
817 
818 // Functions to emit calls to the special functions of a non-trivial C struct.
819 void CodeGenFunction::callCStructDefaultConstructor(LValue Dst) {
820   bool IsVolatile = Dst.isVolatile();
821   Address DstPtr = Dst.getAddress();
822   QualType QT = Dst.getType();
823   GenDefaultInitializeFuncName GenName(DstPtr.getAlignment(), getContext());
824   std::string FuncName = GenName.getName(QT, IsVolatile);
825   callSpecialFunction(GenDefaultInitialize(getContext()), FuncName, QT,
826                       IsVolatile, *this, std::array<Address, 1>({{DstPtr}}));
827 }
828 
829 std::string
830 CodeGenFunction::getNonTrivialCopyConstructorStr(QualType QT,
831                                                  CharUnits Alignment,
832                                                  bool IsVolatile,
833                                                  ASTContext &Ctx) {
834   GenBinaryFuncName<false> GenName("", Alignment, Alignment, Ctx);
835   return GenName.getName(QT, IsVolatile);
836 }
837 
838 std::string
839 CodeGenFunction::getNonTrivialDestructorStr(QualType QT, CharUnits Alignment,
840                                             bool IsVolatile, ASTContext &Ctx) {
841   GenDestructorFuncName GenName("", Alignment, Ctx);
842   return GenName.getName(QT, IsVolatile);
843 }
844 
845 void CodeGenFunction::callCStructDestructor(LValue Dst) {
846   bool IsVolatile = Dst.isVolatile();
847   Address DstPtr = Dst.getAddress();
848   QualType QT = Dst.getType();
849   GenDestructorFuncName GenName("__destructor_", DstPtr.getAlignment(),
850                                 getContext());
851   std::string FuncName = GenName.getName(QT, IsVolatile);
852   callSpecialFunction(GenDestructor(getContext()), FuncName, QT, IsVolatile,
853                       *this, std::array<Address, 1>({{DstPtr}}));
854 }
855 
856 void CodeGenFunction::callCStructCopyConstructor(LValue Dst, LValue Src) {
857   bool IsVolatile = Dst.isVolatile() || Src.isVolatile();
858   Address DstPtr = Dst.getAddress(), SrcPtr = Src.getAddress();
859   QualType QT = Dst.getType();
860   GenBinaryFuncName<false> GenName("__copy_constructor_", DstPtr.getAlignment(),
861                                    SrcPtr.getAlignment(), getContext());
862   std::string FuncName = GenName.getName(QT, IsVolatile);
863   callSpecialFunction(GenCopyConstructor(getContext()), FuncName, QT,
864                       IsVolatile, *this,
865                       std::array<Address, 2>({{DstPtr, SrcPtr}}));
866 }
867 
868 void CodeGenFunction::callCStructCopyAssignmentOperator(LValue Dst, LValue Src
869 
870 ) {
871   bool IsVolatile = Dst.isVolatile() || Src.isVolatile();
872   Address DstPtr = Dst.getAddress(), SrcPtr = Src.getAddress();
873   QualType QT = Dst.getType();
874   GenBinaryFuncName<false> GenName("__copy_assignment_", DstPtr.getAlignment(),
875                                    SrcPtr.getAlignment(), getContext());
876   std::string FuncName = GenName.getName(QT, IsVolatile);
877   callSpecialFunction(GenCopyAssignment(getContext()), FuncName, QT, IsVolatile,
878                       *this, std::array<Address, 2>({{DstPtr, SrcPtr}}));
879 }
880 
881 void CodeGenFunction::callCStructMoveConstructor(LValue Dst, LValue Src) {
882   bool IsVolatile = Dst.isVolatile() || Src.isVolatile();
883   Address DstPtr = Dst.getAddress(), SrcPtr = Src.getAddress();
884   QualType QT = Dst.getType();
885   GenBinaryFuncName<true> GenName("__move_constructor_", DstPtr.getAlignment(),
886                                   SrcPtr.getAlignment(), getContext());
887   std::string FuncName = GenName.getName(QT, IsVolatile);
888   callSpecialFunction(GenMoveConstructor(getContext()), FuncName, QT,
889                       IsVolatile, *this,
890                       std::array<Address, 2>({{DstPtr, SrcPtr}}));
891 }
892 
893 void CodeGenFunction::callCStructMoveAssignmentOperator(LValue Dst, LValue Src
894 
895 ) {
896   bool IsVolatile = Dst.isVolatile() || Src.isVolatile();
897   Address DstPtr = Dst.getAddress(), SrcPtr = Src.getAddress();
898   QualType QT = Dst.getType();
899   GenBinaryFuncName<true> GenName("__move_assignment_", DstPtr.getAlignment(),
900                                   SrcPtr.getAlignment(), getContext());
901   std::string FuncName = GenName.getName(QT, IsVolatile);
902   callSpecialFunction(GenMoveAssignment(getContext()), FuncName, QT, IsVolatile,
903                       *this, std::array<Address, 2>({{DstPtr, SrcPtr}}));
904 }
905