1//===--- CGExprAgg.cpp - Emit LLVM Code from Aggregate Expressions --------===//
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 to emit Aggregate Expr nodes as LLVM code.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "CGObjCRuntime.h"
16#include "CodeGenModule.h"
17#include "clang/AST/ASTContext.h"
18#include "clang/AST/DeclCXX.h"
19#include "clang/AST/DeclTemplate.h"
20#include "clang/AST/StmtVisitor.h"
21#include "llvm/IR/Constants.h"
22#include "llvm/IR/Function.h"
23#include "llvm/IR/GlobalVariable.h"
24#include "llvm/IR/Intrinsics.h"
25using namespace clang;
26using namespace CodeGen;
27
28//===----------------------------------------------------------------------===//
29//                        Aggregate Expression Emitter
30//===----------------------------------------------------------------------===//
31
32namespace  {
33class AggExprEmitter : public StmtVisitor<AggExprEmitter> {
34  CodeGenFunction &CGF;
35  CGBuilderTy &Builder;
36  AggValueSlot Dest;
37  bool IsResultUnused;
38
39  /// We want to use 'dest' as the return slot except under two
40  /// conditions:
41  ///   - The destination slot requires garbage collection, so we
42  ///     need to use the GC API.
43  ///   - The destination slot is potentially aliased.
44  bool shouldUseDestForReturnSlot() const {
45    return !(Dest.requiresGCollection() || Dest.isPotentiallyAliased());
46  }
47
48  ReturnValueSlot getReturnValueSlot() const {
49    if (!shouldUseDestForReturnSlot())
50      return ReturnValueSlot();
51
52    return ReturnValueSlot(Dest.getAddress(), Dest.isVolatile(),
53                           IsResultUnused);
54  }
55
56  AggValueSlot EnsureSlot(QualType T) {
57    if (!Dest.isIgnored()) return Dest;
58    return CGF.CreateAggTemp(T, "agg.tmp.ensured");
59  }
60  void EnsureDest(QualType T) {
61    if (!Dest.isIgnored()) return;
62    Dest = CGF.CreateAggTemp(T, "agg.tmp.ensured");
63  }
64
65public:
66  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest, bool IsResultUnused)
67    : CGF(cgf), Builder(CGF.Builder), Dest(Dest),
68    IsResultUnused(IsResultUnused) { }
69
70  //===--------------------------------------------------------------------===//
71  //                               Utilities
72  //===--------------------------------------------------------------------===//
73
74  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
75  /// represents a value lvalue, this method emits the address of the lvalue,
76  /// then loads the result into DestPtr.
77  void EmitAggLoadOfLValue(const Expr *E);
78
79  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
80  void EmitFinalDestCopy(QualType type, const LValue &src);
81  void EmitFinalDestCopy(QualType type, RValue src);
82  void EmitCopy(QualType type, const AggValueSlot &dest,
83                const AggValueSlot &src);
84
85  void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
86
87  void EmitArrayInit(Address DestPtr, llvm::ArrayType *AType,
88                     QualType elementType, InitListExpr *E);
89
90  AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
91    if (CGF.getLangOpts().getGC() && TypeRequiresGCollection(T))
92      return AggValueSlot::NeedsGCBarriers;
93    return AggValueSlot::DoesNotNeedGCBarriers;
94  }
95
96  bool TypeRequiresGCollection(QualType T);
97
98  //===--------------------------------------------------------------------===//
99  //                            Visitor Methods
100  //===--------------------------------------------------------------------===//
101
102  void Visit(Expr *E) {
103    ApplyDebugLocation DL(CGF, E);
104    StmtVisitor<AggExprEmitter>::Visit(E);
105  }
106
107  void VisitStmt(Stmt *S) {
108    CGF.ErrorUnsupported(S, "aggregate expression");
109  }
110  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
111  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
112    Visit(GE->getResultExpr());
113  }
114  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
115  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
116    return Visit(E->getReplacement());
117  }
118
119  // l-values.
120  void VisitDeclRefExpr(DeclRefExpr *E) {
121    // For aggregates, we should always be able to emit the variable
122    // as an l-value unless it's a reference.  This is due to the fact
123    // that we can't actually ever see a normal l2r conversion on an
124    // aggregate in C++, and in C there's no language standard
125    // actively preventing us from listing variables in the captures
126    // list of a block.
127    if (E->getDecl()->getType()->isReferenceType()) {
128      if (CodeGenFunction::ConstantEmission result
129            = CGF.tryEmitAsConstant(E)) {
130        EmitFinalDestCopy(E->getType(), result.getReferenceLValue(CGF, E));
131        return;
132      }
133    }
134
135    EmitAggLoadOfLValue(E);
136  }
137
138  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
139  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
140  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
141  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
142  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
143    EmitAggLoadOfLValue(E);
144  }
145  void VisitPredefinedExpr(const PredefinedExpr *E) {
146    EmitAggLoadOfLValue(E);
147  }
148
149  // Operators.
150  void VisitCastExpr(CastExpr *E);
151  void VisitCallExpr(const CallExpr *E);
152  void VisitStmtExpr(const StmtExpr *E);
153  void VisitBinaryOperator(const BinaryOperator *BO);
154  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
155  void VisitBinAssign(const BinaryOperator *E);
156  void VisitBinComma(const BinaryOperator *E);
157
158  void VisitObjCMessageExpr(ObjCMessageExpr *E);
159  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
160    EmitAggLoadOfLValue(E);
161  }
162
163  void VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E);
164  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
165  void VisitChooseExpr(const ChooseExpr *CE);
166  void VisitInitListExpr(InitListExpr *E);
167  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
168  void VisitNoInitExpr(NoInitExpr *E) { } // Do nothing.
169  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
170    Visit(DAE->getExpr());
171  }
172  void VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
173    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
174    Visit(DIE->getExpr());
175  }
176  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
177  void VisitCXXConstructExpr(const CXXConstructExpr *E);
178  void VisitCXXInheritedCtorInitExpr(const CXXInheritedCtorInitExpr *E);
179  void VisitLambdaExpr(LambdaExpr *E);
180  void VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E);
181  void VisitExprWithCleanups(ExprWithCleanups *E);
182  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
183  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
184  void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
185  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
186
187  void VisitPseudoObjectExpr(PseudoObjectExpr *E) {
188    if (E->isGLValue()) {
189      LValue LV = CGF.EmitPseudoObjectLValue(E);
190      return EmitFinalDestCopy(E->getType(), LV);
191    }
192
193    CGF.EmitPseudoObjectRValue(E, EnsureSlot(E->getType()));
194  }
195
196  void VisitVAArgExpr(VAArgExpr *E);
197
198  void EmitInitializationToLValue(Expr *E, LValue Address);
199  void EmitNullInitializationToLValue(LValue Address);
200  //  case Expr::ChooseExprClass:
201  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
202  void VisitAtomicExpr(AtomicExpr *E) {
203    RValue Res = CGF.EmitAtomicExpr(E);
204    EmitFinalDestCopy(E->getType(), Res);
205  }
206};
207}  // end anonymous namespace.
208
209//===----------------------------------------------------------------------===//
210//                                Utilities
211//===----------------------------------------------------------------------===//
212
213/// EmitAggLoadOfLValue - Given an expression with aggregate type that
214/// represents a value lvalue, this method emits the address of the lvalue,
215/// then loads the result into DestPtr.
216void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
217  LValue LV = CGF.EmitLValue(E);
218
219  // If the type of the l-value is atomic, then do an atomic load.
220  if (LV.getType()->isAtomicType() || CGF.LValueIsSuitableForInlineAtomic(LV)) {
221    CGF.EmitAtomicLoad(LV, E->getExprLoc(), Dest);
222    return;
223  }
224
225  EmitFinalDestCopy(E->getType(), LV);
226}
227
228/// \brief True if the given aggregate type requires special GC API calls.
229bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
230  // Only record types have members that might require garbage collection.
231  const RecordType *RecordTy = T->getAs<RecordType>();
232  if (!RecordTy) return false;
233
234  // Don't mess with non-trivial C++ types.
235  RecordDecl *Record = RecordTy->getDecl();
236  if (isa<CXXRecordDecl>(Record) &&
237      (cast<CXXRecordDecl>(Record)->hasNonTrivialCopyConstructor() ||
238       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
239    return false;
240
241  // Check whether the type has an object member.
242  return Record->hasObjectMember();
243}
244
245/// \brief Perform the final move to DestPtr if for some reason
246/// getReturnValueSlot() didn't use it directly.
247///
248/// The idea is that you do something like this:
249///   RValue Result = EmitSomething(..., getReturnValueSlot());
250///   EmitMoveFromReturnSlot(E, Result);
251///
252/// If nothing interferes, this will cause the result to be emitted
253/// directly into the return value slot.  Otherwise, a final move
254/// will be performed.
255void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue src) {
256  if (shouldUseDestForReturnSlot()) {
257    // Logically, Dest.getAddr() should equal Src.getAggregateAddr().
258    // The possibility of undef rvalues complicates that a lot,
259    // though, so we can't really assert.
260    return;
261  }
262
263  // Otherwise, copy from there to the destination.
264  assert(Dest.getPointer() != src.getAggregatePointer());
265  EmitFinalDestCopy(E->getType(), src);
266}
267
268/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
269void AggExprEmitter::EmitFinalDestCopy(QualType type, RValue src) {
270  assert(src.isAggregate() && "value must be aggregate value!");
271  LValue srcLV = CGF.MakeAddrLValue(src.getAggregateAddress(), type);
272  EmitFinalDestCopy(type, srcLV);
273}
274
275/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
276void AggExprEmitter::EmitFinalDestCopy(QualType type, const LValue &src) {
277  // If Dest is ignored, then we're evaluating an aggregate expression
278  // in a context that doesn't care about the result.  Note that loads
279  // from volatile l-values force the existence of a non-ignored
280  // destination.
281  if (Dest.isIgnored())
282    return;
283
284  AggValueSlot srcAgg =
285    AggValueSlot::forLValue(src, AggValueSlot::IsDestructed,
286                            needsGC(type), AggValueSlot::IsAliased);
287  EmitCopy(type, Dest, srcAgg);
288}
289
290/// Perform a copy from the source into the destination.
291///
292/// \param type - the type of the aggregate being copied; qualifiers are
293///   ignored
294void AggExprEmitter::EmitCopy(QualType type, const AggValueSlot &dest,
295                              const AggValueSlot &src) {
296  if (dest.requiresGCollection()) {
297    CharUnits sz = CGF.getContext().getTypeSizeInChars(type);
298    llvm::Value *size = llvm::ConstantInt::get(CGF.SizeTy, sz.getQuantity());
299    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
300                                                      dest.getAddress(),
301                                                      src.getAddress(),
302                                                      size);
303    return;
304  }
305
306  // If the result of the assignment is used, copy the LHS there also.
307  // It's volatile if either side is.  Use the minimum alignment of
308  // the two sides.
309  CGF.EmitAggregateCopy(dest.getAddress(), src.getAddress(), type,
310                        dest.isVolatile() || src.isVolatile());
311}
312
313/// \brief Emit the initializer for a std::initializer_list initialized with a
314/// real initializer list.
315void
316AggExprEmitter::VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E) {
317  // Emit an array containing the elements.  The array is externally destructed
318  // if the std::initializer_list object is.
319  ASTContext &Ctx = CGF.getContext();
320  LValue Array = CGF.EmitLValue(E->getSubExpr());
321  assert(Array.isSimple() && "initializer_list array not a simple lvalue");
322  Address ArrayPtr = Array.getAddress();
323
324  const ConstantArrayType *ArrayType =
325      Ctx.getAsConstantArrayType(E->getSubExpr()->getType());
326  assert(ArrayType && "std::initializer_list constructed from non-array");
327
328  // FIXME: Perform the checks on the field types in SemaInit.
329  RecordDecl *Record = E->getType()->castAs<RecordType>()->getDecl();
330  RecordDecl::field_iterator Field = Record->field_begin();
331  if (Field == Record->field_end()) {
332    CGF.ErrorUnsupported(E, "weird std::initializer_list");
333    return;
334  }
335
336  // Start pointer.
337  if (!Field->getType()->isPointerType() ||
338      !Ctx.hasSameType(Field->getType()->getPointeeType(),
339                       ArrayType->getElementType())) {
340    CGF.ErrorUnsupported(E, "weird std::initializer_list");
341    return;
342  }
343
344  AggValueSlot Dest = EnsureSlot(E->getType());
345  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
346  LValue Start = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
347  llvm::Value *Zero = llvm::ConstantInt::get(CGF.PtrDiffTy, 0);
348  llvm::Value *IdxStart[] = { Zero, Zero };
349  llvm::Value *ArrayStart =
350      Builder.CreateInBoundsGEP(ArrayPtr.getPointer(), IdxStart, "arraystart");
351  CGF.EmitStoreThroughLValue(RValue::get(ArrayStart), Start);
352  ++Field;
353
354  if (Field == Record->field_end()) {
355    CGF.ErrorUnsupported(E, "weird std::initializer_list");
356    return;
357  }
358
359  llvm::Value *Size = Builder.getInt(ArrayType->getSize());
360  LValue EndOrLength = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
361  if (Field->getType()->isPointerType() &&
362      Ctx.hasSameType(Field->getType()->getPointeeType(),
363                      ArrayType->getElementType())) {
364    // End pointer.
365    llvm::Value *IdxEnd[] = { Zero, Size };
366    llvm::Value *ArrayEnd =
367        Builder.CreateInBoundsGEP(ArrayPtr.getPointer(), IdxEnd, "arrayend");
368    CGF.EmitStoreThroughLValue(RValue::get(ArrayEnd), EndOrLength);
369  } else if (Ctx.hasSameType(Field->getType(), Ctx.getSizeType())) {
370    // Length.
371    CGF.EmitStoreThroughLValue(RValue::get(Size), EndOrLength);
372  } else {
373    CGF.ErrorUnsupported(E, "weird std::initializer_list");
374    return;
375  }
376}
377
378/// \brief Determine if E is a trivial array filler, that is, one that is
379/// equivalent to zero-initialization.
380static bool isTrivialFiller(Expr *E) {
381  if (!E)
382    return true;
383
384  if (isa<ImplicitValueInitExpr>(E))
385    return true;
386
387  if (auto *ILE = dyn_cast<InitListExpr>(E)) {
388    if (ILE->getNumInits())
389      return false;
390    return isTrivialFiller(ILE->getArrayFiller());
391  }
392
393  if (auto *Cons = dyn_cast_or_null<CXXConstructExpr>(E))
394    return Cons->getConstructor()->isDefaultConstructor() &&
395           Cons->getConstructor()->isTrivial();
396
397  // FIXME: Are there other cases where we can avoid emitting an initializer?
398  return false;
399}
400
401/// \brief Emit initialization of an array from an initializer list.
402void AggExprEmitter::EmitArrayInit(Address DestPtr, llvm::ArrayType *AType,
403                                   QualType elementType, InitListExpr *E) {
404  uint64_t NumInitElements = E->getNumInits();
405
406  uint64_t NumArrayElements = AType->getNumElements();
407  assert(NumInitElements <= NumArrayElements);
408
409  // DestPtr is an array*.  Construct an elementType* by drilling
410  // down a level.
411  llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
412  llvm::Value *indices[] = { zero, zero };
413  llvm::Value *begin =
414    Builder.CreateInBoundsGEP(DestPtr.getPointer(), indices, "arrayinit.begin");
415
416  CharUnits elementSize = CGF.getContext().getTypeSizeInChars(elementType);
417  CharUnits elementAlign =
418    DestPtr.getAlignment().alignmentOfArrayElement(elementSize);
419
420  // Exception safety requires us to destroy all the
421  // already-constructed members if an initializer throws.
422  // For that, we'll need an EH cleanup.
423  QualType::DestructionKind dtorKind = elementType.isDestructedType();
424  Address endOfInit = Address::invalid();
425  EHScopeStack::stable_iterator cleanup;
426  llvm::Instruction *cleanupDominator = nullptr;
427  if (CGF.needsEHCleanup(dtorKind)) {
428    // In principle we could tell the cleanup where we are more
429    // directly, but the control flow can get so varied here that it
430    // would actually be quite complex.  Therefore we go through an
431    // alloca.
432    endOfInit = CGF.CreateTempAlloca(begin->getType(), CGF.getPointerAlign(),
433                                     "arrayinit.endOfInit");
434    cleanupDominator = Builder.CreateStore(begin, endOfInit);
435    CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
436                                         elementAlign,
437                                         CGF.getDestroyer(dtorKind));
438    cleanup = CGF.EHStack.stable_begin();
439
440  // Otherwise, remember that we didn't need a cleanup.
441  } else {
442    dtorKind = QualType::DK_none;
443  }
444
445  llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
446
447  // The 'current element to initialize'.  The invariants on this
448  // variable are complicated.  Essentially, after each iteration of
449  // the loop, it points to the last initialized element, except
450  // that it points to the beginning of the array before any
451  // elements have been initialized.
452  llvm::Value *element = begin;
453
454  // Emit the explicit initializers.
455  for (uint64_t i = 0; i != NumInitElements; ++i) {
456    // Advance to the next element.
457    if (i > 0) {
458      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
459
460      // Tell the cleanup that it needs to destroy up to this
461      // element.  TODO: some of these stores can be trivially
462      // observed to be unnecessary.
463      if (endOfInit.isValid()) Builder.CreateStore(element, endOfInit);
464    }
465
466    LValue elementLV =
467      CGF.MakeAddrLValue(Address(element, elementAlign), elementType);
468    EmitInitializationToLValue(E->getInit(i), elementLV);
469  }
470
471  // Check whether there's a non-trivial array-fill expression.
472  Expr *filler = E->getArrayFiller();
473  bool hasTrivialFiller = isTrivialFiller(filler);
474
475  // Any remaining elements need to be zero-initialized, possibly
476  // using the filler expression.  We can skip this if the we're
477  // emitting to zeroed memory.
478  if (NumInitElements != NumArrayElements &&
479      !(Dest.isZeroed() && hasTrivialFiller &&
480        CGF.getTypes().isZeroInitializable(elementType))) {
481
482    // Use an actual loop.  This is basically
483    //   do { *array++ = filler; } while (array != end);
484
485    // Advance to the start of the rest of the array.
486    if (NumInitElements) {
487      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
488      if (endOfInit.isValid()) Builder.CreateStore(element, endOfInit);
489    }
490
491    // Compute the end of the array.
492    llvm::Value *end = Builder.CreateInBoundsGEP(begin,
493                      llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
494                                                 "arrayinit.end");
495
496    llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
497    llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
498
499    // Jump into the body.
500    CGF.EmitBlock(bodyBB);
501    llvm::PHINode *currentElement =
502      Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
503    currentElement->addIncoming(element, entryBB);
504
505    // Emit the actual filler expression.
506    LValue elementLV =
507      CGF.MakeAddrLValue(Address(currentElement, elementAlign), elementType);
508    if (filler)
509      EmitInitializationToLValue(filler, elementLV);
510    else
511      EmitNullInitializationToLValue(elementLV);
512
513    // Move on to the next element.
514    llvm::Value *nextElement =
515      Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
516
517    // Tell the EH cleanup that we finished with the last element.
518    if (endOfInit.isValid()) Builder.CreateStore(nextElement, endOfInit);
519
520    // Leave the loop if we're done.
521    llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
522                                             "arrayinit.done");
523    llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
524    Builder.CreateCondBr(done, endBB, bodyBB);
525    currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
526
527    CGF.EmitBlock(endBB);
528  }
529
530  // Leave the partial-array cleanup if we entered one.
531  if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
532}
533
534//===----------------------------------------------------------------------===//
535//                            Visitor Methods
536//===----------------------------------------------------------------------===//
537
538void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
539  Visit(E->GetTemporaryExpr());
540}
541
542void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
543  EmitFinalDestCopy(e->getType(), CGF.getOpaqueLValueMapping(e));
544}
545
546void
547AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
548  if (Dest.isPotentiallyAliased() &&
549      E->getType().isPODType(CGF.getContext())) {
550    // For a POD type, just emit a load of the lvalue + a copy, because our
551    // compound literal might alias the destination.
552    EmitAggLoadOfLValue(E);
553    return;
554  }
555
556  AggValueSlot Slot = EnsureSlot(E->getType());
557  CGF.EmitAggExpr(E->getInitializer(), Slot);
558}
559
560/// Attempt to look through various unimportant expressions to find a
561/// cast of the given kind.
562static Expr *findPeephole(Expr *op, CastKind kind) {
563  while (true) {
564    op = op->IgnoreParens();
565    if (CastExpr *castE = dyn_cast<CastExpr>(op)) {
566      if (castE->getCastKind() == kind)
567        return castE->getSubExpr();
568      if (castE->getCastKind() == CK_NoOp)
569        continue;
570    }
571    return nullptr;
572  }
573}
574
575void AggExprEmitter::VisitCastExpr(CastExpr *E) {
576  if (const auto *ECE = dyn_cast<ExplicitCastExpr>(E))
577    CGF.CGM.EmitExplicitCastExprType(ECE, &CGF);
578  switch (E->getCastKind()) {
579  case CK_Dynamic: {
580    // FIXME: Can this actually happen? We have no test coverage for it.
581    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
582    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr(),
583                                      CodeGenFunction::TCK_Load);
584    // FIXME: Do we also need to handle property references here?
585    if (LV.isSimple())
586      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
587    else
588      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
589
590    if (!Dest.isIgnored())
591      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
592    break;
593  }
594
595  case CK_ToUnion: {
596    // Evaluate even if the destination is ignored.
597    if (Dest.isIgnored()) {
598      CGF.EmitAnyExpr(E->getSubExpr(), AggValueSlot::ignored(),
599                      /*ignoreResult=*/true);
600      break;
601    }
602
603    // GCC union extension
604    QualType Ty = E->getSubExpr()->getType();
605    Address CastPtr =
606      Builder.CreateElementBitCast(Dest.getAddress(), CGF.ConvertType(Ty));
607    EmitInitializationToLValue(E->getSubExpr(),
608                               CGF.MakeAddrLValue(CastPtr, Ty));
609    break;
610  }
611
612  case CK_DerivedToBase:
613  case CK_BaseToDerived:
614  case CK_UncheckedDerivedToBase: {
615    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
616                "should have been unpacked before we got here");
617  }
618
619  case CK_NonAtomicToAtomic:
620  case CK_AtomicToNonAtomic: {
621    bool isToAtomic = (E->getCastKind() == CK_NonAtomicToAtomic);
622
623    // Determine the atomic and value types.
624    QualType atomicType = E->getSubExpr()->getType();
625    QualType valueType = E->getType();
626    if (isToAtomic) std::swap(atomicType, valueType);
627
628    assert(atomicType->isAtomicType());
629    assert(CGF.getContext().hasSameUnqualifiedType(valueType,
630                          atomicType->castAs<AtomicType>()->getValueType()));
631
632    // Just recurse normally if we're ignoring the result or the
633    // atomic type doesn't change representation.
634    if (Dest.isIgnored() || !CGF.CGM.isPaddedAtomicType(atomicType)) {
635      return Visit(E->getSubExpr());
636    }
637
638    CastKind peepholeTarget =
639      (isToAtomic ? CK_AtomicToNonAtomic : CK_NonAtomicToAtomic);
640
641    // These two cases are reverses of each other; try to peephole them.
642    if (Expr *op = findPeephole(E->getSubExpr(), peepholeTarget)) {
643      assert(CGF.getContext().hasSameUnqualifiedType(op->getType(),
644                                                     E->getType()) &&
645           "peephole significantly changed types?");
646      return Visit(op);
647    }
648
649    // If we're converting an r-value of non-atomic type to an r-value
650    // of atomic type, just emit directly into the relevant sub-object.
651    if (isToAtomic) {
652      AggValueSlot valueDest = Dest;
653      if (!valueDest.isIgnored() && CGF.CGM.isPaddedAtomicType(atomicType)) {
654        // Zero-initialize.  (Strictly speaking, we only need to intialize
655        // the padding at the end, but this is simpler.)
656        if (!Dest.isZeroed())
657          CGF.EmitNullInitialization(Dest.getAddress(), atomicType);
658
659        // Build a GEP to refer to the subobject.
660        Address valueAddr =
661            CGF.Builder.CreateStructGEP(valueDest.getAddress(), 0,
662                                        CharUnits());
663        valueDest = AggValueSlot::forAddr(valueAddr,
664                                          valueDest.getQualifiers(),
665                                          valueDest.isExternallyDestructed(),
666                                          valueDest.requiresGCollection(),
667                                          valueDest.isPotentiallyAliased(),
668                                          AggValueSlot::IsZeroed);
669      }
670
671      CGF.EmitAggExpr(E->getSubExpr(), valueDest);
672      return;
673    }
674
675    // Otherwise, we're converting an atomic type to a non-atomic type.
676    // Make an atomic temporary, emit into that, and then copy the value out.
677    AggValueSlot atomicSlot =
678      CGF.CreateAggTemp(atomicType, "atomic-to-nonatomic.temp");
679    CGF.EmitAggExpr(E->getSubExpr(), atomicSlot);
680
681    Address valueAddr =
682      Builder.CreateStructGEP(atomicSlot.getAddress(), 0, CharUnits());
683    RValue rvalue = RValue::getAggregate(valueAddr, atomicSlot.isVolatile());
684    return EmitFinalDestCopy(valueType, rvalue);
685  }
686
687  case CK_LValueToRValue:
688    // If we're loading from a volatile type, force the destination
689    // into existence.
690    if (E->getSubExpr()->getType().isVolatileQualified()) {
691      EnsureDest(E->getType());
692      return Visit(E->getSubExpr());
693    }
694
695    // fallthrough
696
697  case CK_NoOp:
698  case CK_UserDefinedConversion:
699  case CK_ConstructorConversion:
700    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
701                                                   E->getType()) &&
702           "Implicit cast types must be compatible");
703    Visit(E->getSubExpr());
704    break;
705
706  case CK_LValueBitCast:
707    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
708
709  case CK_Dependent:
710  case CK_BitCast:
711  case CK_ArrayToPointerDecay:
712  case CK_FunctionToPointerDecay:
713  case CK_NullToPointer:
714  case CK_NullToMemberPointer:
715  case CK_BaseToDerivedMemberPointer:
716  case CK_DerivedToBaseMemberPointer:
717  case CK_MemberPointerToBoolean:
718  case CK_ReinterpretMemberPointer:
719  case CK_IntegralToPointer:
720  case CK_PointerToIntegral:
721  case CK_PointerToBoolean:
722  case CK_ToVoid:
723  case CK_VectorSplat:
724  case CK_IntegralCast:
725  case CK_BooleanToSignedIntegral:
726  case CK_IntegralToBoolean:
727  case CK_IntegralToFloating:
728  case CK_FloatingToIntegral:
729  case CK_FloatingToBoolean:
730  case CK_FloatingCast:
731  case CK_CPointerToObjCPointerCast:
732  case CK_BlockPointerToObjCPointerCast:
733  case CK_AnyPointerToBlockPointerCast:
734  case CK_ObjCObjectLValueCast:
735  case CK_FloatingRealToComplex:
736  case CK_FloatingComplexToReal:
737  case CK_FloatingComplexToBoolean:
738  case CK_FloatingComplexCast:
739  case CK_FloatingComplexToIntegralComplex:
740  case CK_IntegralRealToComplex:
741  case CK_IntegralComplexToReal:
742  case CK_IntegralComplexToBoolean:
743  case CK_IntegralComplexCast:
744  case CK_IntegralComplexToFloatingComplex:
745  case CK_ARCProduceObject:
746  case CK_ARCConsumeObject:
747  case CK_ARCReclaimReturnedObject:
748  case CK_ARCExtendBlockObject:
749  case CK_CopyAndAutoreleaseBlockObject:
750  case CK_BuiltinFnToFnPtr:
751  case CK_ZeroToOCLEvent:
752  case CK_AddressSpaceConversion:
753    llvm_unreachable("cast kind invalid for aggregate types");
754  }
755}
756
757void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
758  if (E->getCallReturnType(CGF.getContext())->isReferenceType()) {
759    EmitAggLoadOfLValue(E);
760    return;
761  }
762
763  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
764  EmitMoveFromReturnSlot(E, RV);
765}
766
767void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
768  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
769  EmitMoveFromReturnSlot(E, RV);
770}
771
772void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
773  CGF.EmitIgnoredExpr(E->getLHS());
774  Visit(E->getRHS());
775}
776
777void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
778  CodeGenFunction::StmtExprEvaluation eval(CGF);
779  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
780}
781
782void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
783  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
784    VisitPointerToDataMemberBinaryOperator(E);
785  else
786    CGF.ErrorUnsupported(E, "aggregate binary expression");
787}
788
789void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
790                                                    const BinaryOperator *E) {
791  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
792  EmitFinalDestCopy(E->getType(), LV);
793}
794
795/// Is the value of the given expression possibly a reference to or
796/// into a __block variable?
797static bool isBlockVarRef(const Expr *E) {
798  // Make sure we look through parens.
799  E = E->IgnoreParens();
800
801  // Check for a direct reference to a __block variable.
802  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
803    const VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
804    return (var && var->hasAttr<BlocksAttr>());
805  }
806
807  // More complicated stuff.
808
809  // Binary operators.
810  if (const BinaryOperator *op = dyn_cast<BinaryOperator>(E)) {
811    // For an assignment or pointer-to-member operation, just care
812    // about the LHS.
813    if (op->isAssignmentOp() || op->isPtrMemOp())
814      return isBlockVarRef(op->getLHS());
815
816    // For a comma, just care about the RHS.
817    if (op->getOpcode() == BO_Comma)
818      return isBlockVarRef(op->getRHS());
819
820    // FIXME: pointer arithmetic?
821    return false;
822
823  // Check both sides of a conditional operator.
824  } else if (const AbstractConditionalOperator *op
825               = dyn_cast<AbstractConditionalOperator>(E)) {
826    return isBlockVarRef(op->getTrueExpr())
827        || isBlockVarRef(op->getFalseExpr());
828
829  // OVEs are required to support BinaryConditionalOperators.
830  } else if (const OpaqueValueExpr *op
831               = dyn_cast<OpaqueValueExpr>(E)) {
832    if (const Expr *src = op->getSourceExpr())
833      return isBlockVarRef(src);
834
835  // Casts are necessary to get things like (*(int*)&var) = foo().
836  // We don't really care about the kind of cast here, except
837  // we don't want to look through l2r casts, because it's okay
838  // to get the *value* in a __block variable.
839  } else if (const CastExpr *cast = dyn_cast<CastExpr>(E)) {
840    if (cast->getCastKind() == CK_LValueToRValue)
841      return false;
842    return isBlockVarRef(cast->getSubExpr());
843
844  // Handle unary operators.  Again, just aggressively look through
845  // it, ignoring the operation.
846  } else if (const UnaryOperator *uop = dyn_cast<UnaryOperator>(E)) {
847    return isBlockVarRef(uop->getSubExpr());
848
849  // Look into the base of a field access.
850  } else if (const MemberExpr *mem = dyn_cast<MemberExpr>(E)) {
851    return isBlockVarRef(mem->getBase());
852
853  // Look into the base of a subscript.
854  } else if (const ArraySubscriptExpr *sub = dyn_cast<ArraySubscriptExpr>(E)) {
855    return isBlockVarRef(sub->getBase());
856  }
857
858  return false;
859}
860
861void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
862  // For an assignment to work, the value on the right has
863  // to be compatible with the value on the left.
864  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
865                                                 E->getRHS()->getType())
866         && "Invalid assignment");
867
868  // If the LHS might be a __block variable, and the RHS can
869  // potentially cause a block copy, we need to evaluate the RHS first
870  // so that the assignment goes the right place.
871  // This is pretty semantically fragile.
872  if (isBlockVarRef(E->getLHS()) &&
873      E->getRHS()->HasSideEffects(CGF.getContext())) {
874    // Ensure that we have a destination, and evaluate the RHS into that.
875    EnsureDest(E->getRHS()->getType());
876    Visit(E->getRHS());
877
878    // Now emit the LHS and copy into it.
879    LValue LHS = CGF.EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
880
881    // That copy is an atomic copy if the LHS is atomic.
882    if (LHS.getType()->isAtomicType() ||
883        CGF.LValueIsSuitableForInlineAtomic(LHS)) {
884      CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
885      return;
886    }
887
888    EmitCopy(E->getLHS()->getType(),
889             AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
890                                     needsGC(E->getLHS()->getType()),
891                                     AggValueSlot::IsAliased),
892             Dest);
893    return;
894  }
895
896  LValue LHS = CGF.EmitLValue(E->getLHS());
897
898  // If we have an atomic type, evaluate into the destination and then
899  // do an atomic copy.
900  if (LHS.getType()->isAtomicType() ||
901      CGF.LValueIsSuitableForInlineAtomic(LHS)) {
902    EnsureDest(E->getRHS()->getType());
903    Visit(E->getRHS());
904    CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
905    return;
906  }
907
908  // Codegen the RHS so that it stores directly into the LHS.
909  AggValueSlot LHSSlot =
910    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
911                            needsGC(E->getLHS()->getType()),
912                            AggValueSlot::IsAliased);
913  // A non-volatile aggregate destination might have volatile member.
914  if (!LHSSlot.isVolatile() &&
915      CGF.hasVolatileMember(E->getLHS()->getType()))
916    LHSSlot.setVolatile(true);
917
918  CGF.EmitAggExpr(E->getRHS(), LHSSlot);
919
920  // Copy into the destination if the assignment isn't ignored.
921  EmitFinalDestCopy(E->getType(), LHS);
922}
923
924void AggExprEmitter::
925VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
926  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
927  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
928  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
929
930  // Bind the common expression if necessary.
931  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
932
933  CodeGenFunction::ConditionalEvaluation eval(CGF);
934  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock,
935                           CGF.getProfileCount(E));
936
937  // Save whether the destination's lifetime is externally managed.
938  bool isExternallyDestructed = Dest.isExternallyDestructed();
939
940  eval.begin(CGF);
941  CGF.EmitBlock(LHSBlock);
942  CGF.incrementProfileCounter(E);
943  Visit(E->getTrueExpr());
944  eval.end(CGF);
945
946  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
947  CGF.Builder.CreateBr(ContBlock);
948
949  // If the result of an agg expression is unused, then the emission
950  // of the LHS might need to create a destination slot.  That's fine
951  // with us, and we can safely emit the RHS into the same slot, but
952  // we shouldn't claim that it's already being destructed.
953  Dest.setExternallyDestructed(isExternallyDestructed);
954
955  eval.begin(CGF);
956  CGF.EmitBlock(RHSBlock);
957  Visit(E->getFalseExpr());
958  eval.end(CGF);
959
960  CGF.EmitBlock(ContBlock);
961}
962
963void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
964  Visit(CE->getChosenSubExpr());
965}
966
967void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
968  Address ArgValue = Address::invalid();
969  Address ArgPtr = CGF.EmitVAArg(VE, ArgValue);
970
971  // If EmitVAArg fails, emit an error.
972  if (!ArgPtr.isValid()) {
973    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
974    return;
975  }
976
977  EmitFinalDestCopy(VE->getType(), CGF.MakeAddrLValue(ArgPtr, VE->getType()));
978}
979
980void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
981  // Ensure that we have a slot, but if we already do, remember
982  // whether it was externally destructed.
983  bool wasExternallyDestructed = Dest.isExternallyDestructed();
984  EnsureDest(E->getType());
985
986  // We're going to push a destructor if there isn't already one.
987  Dest.setExternallyDestructed();
988
989  Visit(E->getSubExpr());
990
991  // Push that destructor we promised.
992  if (!wasExternallyDestructed)
993    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddress());
994}
995
996void
997AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
998  AggValueSlot Slot = EnsureSlot(E->getType());
999  CGF.EmitCXXConstructExpr(E, Slot);
1000}
1001
1002void AggExprEmitter::VisitCXXInheritedCtorInitExpr(
1003    const CXXInheritedCtorInitExpr *E) {
1004  AggValueSlot Slot = EnsureSlot(E->getType());
1005  CGF.EmitInheritedCXXConstructorCall(
1006      E->getConstructor(), E->constructsVBase(), Slot.getAddress(),
1007      E->inheritedFromVBase(), E);
1008}
1009
1010void
1011AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
1012  AggValueSlot Slot = EnsureSlot(E->getType());
1013  CGF.EmitLambdaExpr(E, Slot);
1014}
1015
1016void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
1017  CGF.enterFullExpression(E);
1018  CodeGenFunction::RunCleanupsScope cleanups(CGF);
1019  Visit(E->getSubExpr());
1020}
1021
1022void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
1023  QualType T = E->getType();
1024  AggValueSlot Slot = EnsureSlot(T);
1025  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddress(), T));
1026}
1027
1028void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
1029  QualType T = E->getType();
1030  AggValueSlot Slot = EnsureSlot(T);
1031  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddress(), T));
1032}
1033
1034/// isSimpleZero - If emitting this value will obviously just cause a store of
1035/// zero to memory, return true.  This can return false if uncertain, so it just
1036/// handles simple cases.
1037static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
1038  E = E->IgnoreParens();
1039
1040  // 0
1041  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
1042    return IL->getValue() == 0;
1043  // +0.0
1044  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
1045    return FL->getValue().isPosZero();
1046  // int()
1047  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
1048      CGF.getTypes().isZeroInitializable(E->getType()))
1049    return true;
1050  // (int*)0 - Null pointer expressions.
1051  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
1052    return ICE->getCastKind() == CK_NullToPointer;
1053  // '\0'
1054  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
1055    return CL->getValue() == 0;
1056
1057  // Otherwise, hard case: conservatively return false.
1058  return false;
1059}
1060
1061
1062void
1063AggExprEmitter::EmitInitializationToLValue(Expr *E, LValue LV) {
1064  QualType type = LV.getType();
1065  // FIXME: Ignore result?
1066  // FIXME: Are initializers affected by volatile?
1067  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
1068    // Storing "i32 0" to a zero'd memory location is a noop.
1069    return;
1070  } else if (isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) {
1071    return EmitNullInitializationToLValue(LV);
1072  } else if (isa<NoInitExpr>(E)) {
1073    // Do nothing.
1074    return;
1075  } else if (type->isReferenceType()) {
1076    RValue RV = CGF.EmitReferenceBindingToExpr(E);
1077    return CGF.EmitStoreThroughLValue(RV, LV);
1078  }
1079
1080  switch (CGF.getEvaluationKind(type)) {
1081  case TEK_Complex:
1082    CGF.EmitComplexExprIntoLValue(E, LV, /*isInit*/ true);
1083    return;
1084  case TEK_Aggregate:
1085    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
1086                                               AggValueSlot::IsDestructed,
1087                                      AggValueSlot::DoesNotNeedGCBarriers,
1088                                               AggValueSlot::IsNotAliased,
1089                                               Dest.isZeroed()));
1090    return;
1091  case TEK_Scalar:
1092    if (LV.isSimple()) {
1093      CGF.EmitScalarInit(E, /*D=*/nullptr, LV, /*Captured=*/false);
1094    } else {
1095      CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
1096    }
1097    return;
1098  }
1099  llvm_unreachable("bad evaluation kind");
1100}
1101
1102void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
1103  QualType type = lv.getType();
1104
1105  // If the destination slot is already zeroed out before the aggregate is
1106  // copied into it, we don't have to emit any zeros here.
1107  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
1108    return;
1109
1110  if (CGF.hasScalarEvaluationKind(type)) {
1111    // For non-aggregates, we can store the appropriate null constant.
1112    llvm::Value *null = CGF.CGM.EmitNullConstant(type);
1113    // Note that the following is not equivalent to
1114    // EmitStoreThroughBitfieldLValue for ARC types.
1115    if (lv.isBitField()) {
1116      CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
1117    } else {
1118      assert(lv.isSimple());
1119      CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
1120    }
1121  } else {
1122    // There's a potential optimization opportunity in combining
1123    // memsets; that would be easy for arrays, but relatively
1124    // difficult for structures with the current code.
1125    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
1126  }
1127}
1128
1129void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
1130#if 0
1131  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
1132  // (Length of globals? Chunks of zeroed-out space?).
1133  //
1134  // If we can, prefer a copy from a global; this is a lot less code for long
1135  // globals, and it's easier for the current optimizers to analyze.
1136  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
1137    llvm::GlobalVariable* GV =
1138    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
1139                             llvm::GlobalValue::InternalLinkage, C, "");
1140    EmitFinalDestCopy(E->getType(), CGF.MakeAddrLValue(GV, E->getType()));
1141    return;
1142  }
1143#endif
1144  if (E->hadArrayRangeDesignator())
1145    CGF.ErrorUnsupported(E, "GNU array range designator extension");
1146
1147  AggValueSlot Dest = EnsureSlot(E->getType());
1148
1149  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
1150
1151  // Handle initialization of an array.
1152  if (E->getType()->isArrayType()) {
1153    if (E->isStringLiteralInit())
1154      return Visit(E->getInit(0));
1155
1156    QualType elementType =
1157        CGF.getContext().getAsArrayType(E->getType())->getElementType();
1158
1159    auto AType = cast<llvm::ArrayType>(Dest.getAddress().getElementType());
1160    EmitArrayInit(Dest.getAddress(), AType, elementType, E);
1161    return;
1162  }
1163
1164  if (E->getType()->isAtomicType()) {
1165    // An _Atomic(T) object can be list-initialized from an expression
1166    // of the same type.
1167    assert(E->getNumInits() == 1 &&
1168           CGF.getContext().hasSameUnqualifiedType(E->getInit(0)->getType(),
1169                                                   E->getType()) &&
1170           "unexpected list initialization for atomic object");
1171    return Visit(E->getInit(0));
1172  }
1173
1174  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
1175
1176  // Do struct initialization; this code just sets each individual member
1177  // to the approprate value.  This makes bitfield support automatic;
1178  // the disadvantage is that the generated code is more difficult for
1179  // the optimizer, especially with bitfields.
1180  unsigned NumInitElements = E->getNumInits();
1181  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
1182
1183  // We'll need to enter cleanup scopes in case any of the element
1184  // initializers throws an exception.
1185  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
1186  llvm::Instruction *cleanupDominator = nullptr;
1187
1188  unsigned curInitIndex = 0;
1189
1190  // Emit initialization of base classes.
1191  if (auto *CXXRD = dyn_cast<CXXRecordDecl>(record)) {
1192    assert(E->getNumInits() >= CXXRD->getNumBases() &&
1193           "missing initializer for base class");
1194    for (auto &Base : CXXRD->bases()) {
1195      assert(!Base.isVirtual() && "should not see vbases here");
1196      auto *BaseRD = Base.getType()->getAsCXXRecordDecl();
1197      Address V = CGF.GetAddressOfDirectBaseInCompleteClass(
1198          Dest.getAddress(), CXXRD, BaseRD,
1199          /*isBaseVirtual*/ false);
1200      AggValueSlot AggSlot =
1201        AggValueSlot::forAddr(V, Qualifiers(),
1202                              AggValueSlot::IsDestructed,
1203                              AggValueSlot::DoesNotNeedGCBarriers,
1204                              AggValueSlot::IsNotAliased);
1205      CGF.EmitAggExpr(E->getInit(curInitIndex++), AggSlot);
1206
1207      if (QualType::DestructionKind dtorKind =
1208              Base.getType().isDestructedType()) {
1209        CGF.pushDestroy(dtorKind, V, Base.getType());
1210        cleanups.push_back(CGF.EHStack.stable_begin());
1211      }
1212    }
1213  }
1214
1215  // Prepare a 'this' for CXXDefaultInitExprs.
1216  CodeGenFunction::FieldConstructionScope FCS(CGF, Dest.getAddress());
1217
1218  if (record->isUnion()) {
1219    // Only initialize one field of a union. The field itself is
1220    // specified by the initializer list.
1221    if (!E->getInitializedFieldInUnion()) {
1222      // Empty union; we have nothing to do.
1223
1224#ifndef NDEBUG
1225      // Make sure that it's really an empty and not a failure of
1226      // semantic analysis.
1227      for (const auto *Field : record->fields())
1228        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
1229#endif
1230      return;
1231    }
1232
1233    // FIXME: volatility
1234    FieldDecl *Field = E->getInitializedFieldInUnion();
1235
1236    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestLV, Field);
1237    if (NumInitElements) {
1238      // Store the initializer into the field
1239      EmitInitializationToLValue(E->getInit(0), FieldLoc);
1240    } else {
1241      // Default-initialize to null.
1242      EmitNullInitializationToLValue(FieldLoc);
1243    }
1244
1245    return;
1246  }
1247
1248  // Here we iterate over the fields; this makes it simpler to both
1249  // default-initialize fields and skip over unnamed fields.
1250  for (const auto *field : record->fields()) {
1251    // We're done once we hit the flexible array member.
1252    if (field->getType()->isIncompleteArrayType())
1253      break;
1254
1255    // Always skip anonymous bitfields.
1256    if (field->isUnnamedBitfield())
1257      continue;
1258
1259    // We're done if we reach the end of the explicit initializers, we
1260    // have a zeroed object, and the rest of the fields are
1261    // zero-initializable.
1262    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
1263        CGF.getTypes().isZeroInitializable(E->getType()))
1264      break;
1265
1266
1267    LValue LV = CGF.EmitLValueForFieldInitialization(DestLV, field);
1268    // We never generate write-barries for initialized fields.
1269    LV.setNonGC(true);
1270
1271    if (curInitIndex < NumInitElements) {
1272      // Store the initializer into the field.
1273      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
1274    } else {
1275      // We're out of initalizers; default-initialize to null
1276      EmitNullInitializationToLValue(LV);
1277    }
1278
1279    // Push a destructor if necessary.
1280    // FIXME: if we have an array of structures, all explicitly
1281    // initialized, we can end up pushing a linear number of cleanups.
1282    bool pushedCleanup = false;
1283    if (QualType::DestructionKind dtorKind
1284          = field->getType().isDestructedType()) {
1285      assert(LV.isSimple());
1286      if (CGF.needsEHCleanup(dtorKind)) {
1287        if (!cleanupDominator)
1288          cleanupDominator = CGF.Builder.CreateAlignedLoad(
1289              CGF.Int8Ty,
1290              llvm::Constant::getNullValue(CGF.Int8PtrTy),
1291              CharUnits::One()); // placeholder
1292
1293        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1294                        CGF.getDestroyer(dtorKind), false);
1295        cleanups.push_back(CGF.EHStack.stable_begin());
1296        pushedCleanup = true;
1297      }
1298    }
1299
1300    // If the GEP didn't get used because of a dead zero init or something
1301    // else, clean it up for -O0 builds and general tidiness.
1302    if (!pushedCleanup && LV.isSimple())
1303      if (llvm::GetElementPtrInst *GEP =
1304            dyn_cast<llvm::GetElementPtrInst>(LV.getPointer()))
1305        if (GEP->use_empty())
1306          GEP->eraseFromParent();
1307  }
1308
1309  // Deactivate all the partial cleanups in reverse order, which
1310  // generally means popping them.
1311  for (unsigned i = cleanups.size(); i != 0; --i)
1312    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1313
1314  // Destroy the placeholder if we made one.
1315  if (cleanupDominator)
1316    cleanupDominator->eraseFromParent();
1317}
1318
1319void AggExprEmitter::VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E) {
1320  AggValueSlot Dest = EnsureSlot(E->getType());
1321
1322  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
1323  EmitInitializationToLValue(E->getBase(), DestLV);
1324  VisitInitListExpr(E->getUpdater());
1325}
1326
1327//===----------------------------------------------------------------------===//
1328//                        Entry Points into this File
1329//===----------------------------------------------------------------------===//
1330
1331/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1332/// non-zero bytes that will be stored when outputting the initializer for the
1333/// specified initializer expression.
1334static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1335  E = E->IgnoreParens();
1336
1337  // 0 and 0.0 won't require any non-zero stores!
1338  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1339
1340  // If this is an initlist expr, sum up the size of sizes of the (present)
1341  // elements.  If this is something weird, assume the whole thing is non-zero.
1342  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1343  if (!ILE || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1344    return CGF.getContext().getTypeSizeInChars(E->getType());
1345
1346  // InitListExprs for structs have to be handled carefully.  If there are
1347  // reference members, we need to consider the size of the reference, not the
1348  // referencee.  InitListExprs for unions and arrays can't have references.
1349  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1350    if (!RT->isUnionType()) {
1351      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1352      CharUnits NumNonZeroBytes = CharUnits::Zero();
1353
1354      unsigned ILEElement = 0;
1355      if (auto *CXXRD = dyn_cast<CXXRecordDecl>(SD))
1356        while (ILEElement != CXXRD->getNumBases())
1357          NumNonZeroBytes +=
1358              GetNumNonZeroBytesInInit(ILE->getInit(ILEElement++), CGF);
1359      for (const auto *Field : SD->fields()) {
1360        // We're done once we hit the flexible array member or run out of
1361        // InitListExpr elements.
1362        if (Field->getType()->isIncompleteArrayType() ||
1363            ILEElement == ILE->getNumInits())
1364          break;
1365        if (Field->isUnnamedBitfield())
1366          continue;
1367
1368        const Expr *E = ILE->getInit(ILEElement++);
1369
1370        // Reference values are always non-null and have the width of a pointer.
1371        if (Field->getType()->isReferenceType())
1372          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1373              CGF.getTarget().getPointerWidth(0));
1374        else
1375          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1376      }
1377
1378      return NumNonZeroBytes;
1379    }
1380  }
1381
1382
1383  CharUnits NumNonZeroBytes = CharUnits::Zero();
1384  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1385    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1386  return NumNonZeroBytes;
1387}
1388
1389/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1390/// zeros in it, emit a memset and avoid storing the individual zeros.
1391///
1392static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1393                                     CodeGenFunction &CGF) {
1394  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1395  // volatile stores.
1396  if (Slot.isZeroed() || Slot.isVolatile() || !Slot.getAddress().isValid())
1397    return;
1398
1399  // C++ objects with a user-declared constructor don't need zero'ing.
1400  if (CGF.getLangOpts().CPlusPlus)
1401    if (const RecordType *RT = CGF.getContext()
1402                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1403      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1404      if (RD->hasUserDeclaredConstructor())
1405        return;
1406    }
1407
1408  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1409  CharUnits Size = CGF.getContext().getTypeSizeInChars(E->getType());
1410  if (Size <= CharUnits::fromQuantity(16))
1411    return;
1412
1413  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1414  // we prefer to emit memset + individual stores for the rest.
1415  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1416  if (NumNonZeroBytes*4 > Size)
1417    return;
1418
1419  // Okay, it seems like a good idea to use an initial memset, emit the call.
1420  llvm::Constant *SizeVal = CGF.Builder.getInt64(Size.getQuantity());
1421
1422  Address Loc = Slot.getAddress();
1423  Loc = CGF.Builder.CreateElementBitCast(Loc, CGF.Int8Ty);
1424  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, false);
1425
1426  // Tell the AggExprEmitter that the slot is known zero.
1427  Slot.setZeroed();
1428}
1429
1430
1431
1432
1433/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1434/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1435/// the value of the aggregate expression is not needed.  If VolatileDest is
1436/// true, DestPtr cannot be 0.
1437void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot) {
1438  assert(E && hasAggregateEvaluationKind(E->getType()) &&
1439         "Invalid aggregate expression to emit");
1440  assert((Slot.getAddress().isValid() || Slot.isIgnored()) &&
1441         "slot has bits but no address");
1442
1443  // Optimize the slot if possible.
1444  CheckAggExprForMemSetUse(Slot, E, *this);
1445
1446  AggExprEmitter(*this, Slot, Slot.isIgnored()).Visit(const_cast<Expr*>(E));
1447}
1448
1449LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1450  assert(hasAggregateEvaluationKind(E->getType()) && "Invalid argument!");
1451  Address Temp = CreateMemTemp(E->getType());
1452  LValue LV = MakeAddrLValue(Temp, E->getType());
1453  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1454                                         AggValueSlot::DoesNotNeedGCBarriers,
1455                                         AggValueSlot::IsNotAliased));
1456  return LV;
1457}
1458
1459void CodeGenFunction::EmitAggregateCopy(Address DestPtr,
1460                                        Address SrcPtr, QualType Ty,
1461                                        bool isVolatile,
1462                                        bool isAssignment) {
1463  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1464
1465  if (getLangOpts().CPlusPlus) {
1466    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1467      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1468      assert((Record->hasTrivialCopyConstructor() ||
1469              Record->hasTrivialCopyAssignment() ||
1470              Record->hasTrivialMoveConstructor() ||
1471              Record->hasTrivialMoveAssignment() ||
1472              Record->isUnion()) &&
1473             "Trying to aggregate-copy a type without a trivial copy/move "
1474             "constructor or assignment operator");
1475      // Ignore empty classes in C++.
1476      if (Record->isEmpty())
1477        return;
1478    }
1479  }
1480
1481  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1482  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1483  // read from another object that overlaps in anyway the storage of the first
1484  // object, then the overlap shall be exact and the two objects shall have
1485  // qualified or unqualified versions of a compatible type."
1486  //
1487  // memcpy is not defined if the source and destination pointers are exactly
1488  // equal, but other compilers do this optimization, and almost every memcpy
1489  // implementation handles this case safely.  If there is a libc that does not
1490  // safely handle this, we can add a target hook.
1491
1492  // Get data size info for this aggregate. If this is an assignment,
1493  // don't copy the tail padding, because we might be assigning into a
1494  // base subobject where the tail padding is claimed.  Otherwise,
1495  // copying it is fine.
1496  std::pair<CharUnits, CharUnits> TypeInfo;
1497  if (isAssignment)
1498    TypeInfo = getContext().getTypeInfoDataSizeInChars(Ty);
1499  else
1500    TypeInfo = getContext().getTypeInfoInChars(Ty);
1501
1502  llvm::Value *SizeVal = nullptr;
1503  if (TypeInfo.first.isZero()) {
1504    // But note that getTypeInfo returns 0 for a VLA.
1505    if (auto *VAT = dyn_cast_or_null<VariableArrayType>(
1506            getContext().getAsArrayType(Ty))) {
1507      QualType BaseEltTy;
1508      SizeVal = emitArrayLength(VAT, BaseEltTy, DestPtr);
1509      TypeInfo = getContext().getTypeInfoDataSizeInChars(BaseEltTy);
1510      std::pair<CharUnits, CharUnits> LastElementTypeInfo;
1511      if (!isAssignment)
1512        LastElementTypeInfo = getContext().getTypeInfoInChars(BaseEltTy);
1513      assert(!TypeInfo.first.isZero());
1514      SizeVal = Builder.CreateNUWMul(
1515          SizeVal,
1516          llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity()));
1517      if (!isAssignment) {
1518        SizeVal = Builder.CreateNUWSub(
1519            SizeVal,
1520            llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity()));
1521        SizeVal = Builder.CreateNUWAdd(
1522            SizeVal, llvm::ConstantInt::get(
1523                         SizeTy, LastElementTypeInfo.first.getQuantity()));
1524      }
1525    }
1526  }
1527  if (!SizeVal) {
1528    SizeVal = llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity());
1529  }
1530
1531  // FIXME: If we have a volatile struct, the optimizer can remove what might
1532  // appear to be `extra' memory ops:
1533  //
1534  // volatile struct { int i; } a, b;
1535  //
1536  // int main() {
1537  //   a = b;
1538  //   a = b;
1539  // }
1540  //
1541  // we need to use a different call here.  We use isVolatile to indicate when
1542  // either the source or the destination is volatile.
1543
1544  DestPtr = Builder.CreateElementBitCast(DestPtr, Int8Ty);
1545  SrcPtr = Builder.CreateElementBitCast(SrcPtr, Int8Ty);
1546
1547  // Don't do any of the memmove_collectable tests if GC isn't set.
1548  if (CGM.getLangOpts().getGC() == LangOptions::NonGC) {
1549    // fall through
1550  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1551    RecordDecl *Record = RecordTy->getDecl();
1552    if (Record->hasObjectMember()) {
1553      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1554                                                    SizeVal);
1555      return;
1556    }
1557  } else if (Ty->isArrayType()) {
1558    QualType BaseType = getContext().getBaseElementType(Ty);
1559    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1560      if (RecordTy->getDecl()->hasObjectMember()) {
1561        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1562                                                      SizeVal);
1563        return;
1564      }
1565    }
1566  }
1567
1568  auto Inst = Builder.CreateMemCpy(DestPtr, SrcPtr, SizeVal, isVolatile);
1569
1570  // Determine the metadata to describe the position of any padding in this
1571  // memcpy, as well as the TBAA tags for the members of the struct, in case
1572  // the optimizer wishes to expand it in to scalar memory operations.
1573  if (llvm::MDNode *TBAAStructTag = CGM.getTBAAStructInfo(Ty))
1574    Inst->setMetadata(llvm::LLVMContext::MD_tbaa_struct, TBAAStructTag);
1575}
1576