CGExprAgg.cpp revision babcf9d04f4ed9d7ac96812e42c9e8fc0f1ae2c2 
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 "CodeGenModule.h"
16#include "CGObjCRuntime.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/Constants.h"
22#include "llvm/Function.h"
23#include "llvm/GlobalVariable.h"
24#include "llvm/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 IgnoreResult;
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.getAddr(), Dest.isVolatile());
53  }
54
55  AggValueSlot EnsureSlot(QualType T) {
56    if (!Dest.isIgnored()) return Dest;
57    return CGF.CreateAggTemp(T, "agg.tmp.ensured");
58  }
59
60public:
61  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest,
62                 bool ignore)
63    : CGF(cgf), Builder(CGF.Builder), Dest(Dest),
64      IgnoreResult(ignore) {
65  }
66
67  //===--------------------------------------------------------------------===//
68  //                               Utilities
69  //===--------------------------------------------------------------------===//
70
71  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
72  /// represents a value lvalue, this method emits the address of the lvalue,
73  /// then loads the result into DestPtr.
74  void EmitAggLoadOfLValue(const Expr *E);
75
76  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
77  void EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore = false);
78  void EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore = false,
79                         unsigned Alignment = 0);
80
81  void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
82
83  void EmitStdInitializerList(llvm::Value *DestPtr, InitListExpr *InitList);
84  void EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
85                     QualType elementType, InitListExpr *E);
86
87  AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
88    if (CGF.getLangOptions().getGC() && TypeRequiresGCollection(T))
89      return AggValueSlot::NeedsGCBarriers;
90    return AggValueSlot::DoesNotNeedGCBarriers;
91  }
92
93  bool TypeRequiresGCollection(QualType T);
94
95  //===--------------------------------------------------------------------===//
96  //                            Visitor Methods
97  //===--------------------------------------------------------------------===//
98
99  void VisitStmt(Stmt *S) {
100    CGF.ErrorUnsupported(S, "aggregate expression");
101  }
102  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
103  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
104    Visit(GE->getResultExpr());
105  }
106  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
107  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
108    return Visit(E->getReplacement());
109  }
110
111  // l-values.
112  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
113  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
114  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
115  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
116  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
117  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
118    EmitAggLoadOfLValue(E);
119  }
120  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
121    EmitAggLoadOfLValue(E);
122  }
123  void VisitPredefinedExpr(const PredefinedExpr *E) {
124    EmitAggLoadOfLValue(E);
125  }
126
127  // Operators.
128  void VisitCastExpr(CastExpr *E);
129  void VisitCallExpr(const CallExpr *E);
130  void VisitStmtExpr(const StmtExpr *E);
131  void VisitBinaryOperator(const BinaryOperator *BO);
132  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
133  void VisitBinAssign(const BinaryOperator *E);
134  void VisitBinComma(const BinaryOperator *E);
135
136  void VisitObjCMessageExpr(ObjCMessageExpr *E);
137  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
138    EmitAggLoadOfLValue(E);
139  }
140
141  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
142  void VisitChooseExpr(const ChooseExpr *CE);
143  void VisitInitListExpr(InitListExpr *E);
144  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
145  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
146    Visit(DAE->getExpr());
147  }
148  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
149  void VisitCXXConstructExpr(const CXXConstructExpr *E);
150  void VisitLambdaExpr(LambdaExpr *E);
151  void VisitExprWithCleanups(ExprWithCleanups *E);
152  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
153  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
154  void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
155  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
156
157  void VisitPseudoObjectExpr(PseudoObjectExpr *E) {
158    if (E->isGLValue()) {
159      LValue LV = CGF.EmitPseudoObjectLValue(E);
160      return EmitFinalDestCopy(E, LV);
161    }
162
163    CGF.EmitPseudoObjectRValue(E, EnsureSlot(E->getType()));
164  }
165
166  void VisitVAArgExpr(VAArgExpr *E);
167
168  void EmitInitializationToLValue(Expr *E, LValue Address);
169  void EmitNullInitializationToLValue(LValue Address);
170  //  case Expr::ChooseExprClass:
171  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
172  void VisitAtomicExpr(AtomicExpr *E) {
173    CGF.EmitAtomicExpr(E, EnsureSlot(E->getType()).getAddr());
174  }
175};
176}  // end anonymous namespace.
177
178//===----------------------------------------------------------------------===//
179//                                Utilities
180//===----------------------------------------------------------------------===//
181
182/// EmitAggLoadOfLValue - Given an expression with aggregate type that
183/// represents a value lvalue, this method emits the address of the lvalue,
184/// then loads the result into DestPtr.
185void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
186  LValue LV = CGF.EmitLValue(E);
187  EmitFinalDestCopy(E, LV);
188}
189
190/// \brief True if the given aggregate type requires special GC API calls.
191bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
192  // Only record types have members that might require garbage collection.
193  const RecordType *RecordTy = T->getAs<RecordType>();
194  if (!RecordTy) return false;
195
196  // Don't mess with non-trivial C++ types.
197  RecordDecl *Record = RecordTy->getDecl();
198  if (isa<CXXRecordDecl>(Record) &&
199      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
200       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
201    return false;
202
203  // Check whether the type has an object member.
204  return Record->hasObjectMember();
205}
206
207/// \brief Perform the final move to DestPtr if for some reason
208/// getReturnValueSlot() didn't use it directly.
209///
210/// The idea is that you do something like this:
211///   RValue Result = EmitSomething(..., getReturnValueSlot());
212///   EmitMoveFromReturnSlot(E, Result);
213///
214/// If nothing interferes, this will cause the result to be emitted
215/// directly into the return value slot.  Otherwise, a final move
216/// will be performed.
217void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue Src) {
218  if (shouldUseDestForReturnSlot()) {
219    // Logically, Dest.getAddr() should equal Src.getAggregateAddr().
220    // The possibility of undef rvalues complicates that a lot,
221    // though, so we can't really assert.
222    return;
223  }
224
225  // Otherwise, do a final copy,
226  assert(Dest.getAddr() != Src.getAggregateAddr());
227  EmitFinalDestCopy(E, Src, /*Ignore*/ true);
228}
229
230/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
231void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore,
232                                       unsigned Alignment) {
233  assert(Src.isAggregate() && "value must be aggregate value!");
234
235  // If Dest is ignored, then we're evaluating an aggregate expression
236  // in a context (like an expression statement) that doesn't care
237  // about the result.  C says that an lvalue-to-rvalue conversion is
238  // performed in these cases; C++ says that it is not.  In either
239  // case, we don't actually need to do anything unless the value is
240  // volatile.
241  if (Dest.isIgnored()) {
242    if (!Src.isVolatileQualified() ||
243        CGF.CGM.getLangOptions().CPlusPlus ||
244        (IgnoreResult && Ignore))
245      return;
246
247    // If the source is volatile, we must read from it; to do that, we need
248    // some place to put it.
249    Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
250  }
251
252  if (Dest.requiresGCollection()) {
253    CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
254    llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
255    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
256    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
257                                                      Dest.getAddr(),
258                                                      Src.getAggregateAddr(),
259                                                      SizeVal);
260    return;
261  }
262  // If the result of the assignment is used, copy the LHS there also.
263  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
264  // from the source as well, as we can't eliminate it if either operand
265  // is volatile, unless copy has volatile for both source and destination..
266  CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
267                        Dest.isVolatile()|Src.isVolatileQualified(),
268                        Alignment);
269}
270
271/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
272void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
273  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
274
275  CharUnits Alignment = std::min(Src.getAlignment(), Dest.getAlignment());
276  EmitFinalDestCopy(E, Src.asAggregateRValue(), Ignore, Alignment.getQuantity());
277}
278
279static QualType GetStdInitializerListElementType(QualType T) {
280  // Just assume that this is really std::initializer_list.
281  ClassTemplateSpecializationDecl *specialization =
282      cast<ClassTemplateSpecializationDecl>(T->castAs<RecordType>()->getDecl());
283  return specialization->getTemplateArgs()[0].getAsType();
284}
285
286/// \brief Prepare cleanup for the temporary array.
287static void EmitStdInitializerListCleanup(CodeGenFunction &CGF,
288                                          QualType arrayType,
289                                          llvm::Value *addr,
290                                          const InitListExpr *initList) {
291  QualType::DestructionKind dtorKind = arrayType.isDestructedType();
292  if (!dtorKind)
293    return; // Type doesn't need destroying.
294  if (dtorKind != QualType::DK_cxx_destructor) {
295    CGF.ErrorUnsupported(initList, "ObjC ARC type in initializer_list");
296    return;
297  }
298
299  CodeGenFunction::Destroyer *destroyer = CGF.getDestroyer(dtorKind);
300  CGF.pushDestroy(NormalAndEHCleanup, addr, arrayType, destroyer,
301                  /*EHCleanup=*/true);
302}
303
304/// \brief Emit the initializer for a std::initializer_list initialized with a
305/// real initializer list.
306void AggExprEmitter::EmitStdInitializerList(llvm::Value *destPtr,
307                                            InitListExpr *initList) {
308  // We emit an array containing the elements, then have the init list point
309  // at the array.
310  ASTContext &ctx = CGF.getContext();
311  unsigned numInits = initList->getNumInits();
312  QualType element = GetStdInitializerListElementType(initList->getType());
313  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
314  QualType array = ctx.getConstantArrayType(element, size, ArrayType::Normal,0);
315  llvm::Type *LTy = CGF.ConvertTypeForMem(array);
316  llvm::AllocaInst *alloc = CGF.CreateTempAlloca(LTy);
317  alloc->setAlignment(ctx.getTypeAlignInChars(array).getQuantity());
318  alloc->setName(".initlist.");
319
320  EmitArrayInit(alloc, cast<llvm::ArrayType>(LTy), element, initList);
321
322  // FIXME: The diagnostics are somewhat out of place here.
323  RecordDecl *record = initList->getType()->castAs<RecordType>()->getDecl();
324  RecordDecl::field_iterator field = record->field_begin();
325  if (field == record->field_end()) {
326    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
327    return;
328  }
329
330  QualType elementPtr = ctx.getPointerType(element.withConst());
331
332  // Start pointer.
333  if (!ctx.hasSameType(field->getType(), elementPtr)) {
334    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
335    return;
336  }
337  LValue start = CGF.EmitLValueForFieldInitialization(destPtr, *field, 0);
338  llvm::Value *arrayStart = Builder.CreateStructGEP(alloc, 0, "arraystart");
339  CGF.EmitStoreThroughLValue(RValue::get(arrayStart), start);
340  ++field;
341
342  if (field == record->field_end()) {
343    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
344    return;
345  }
346  LValue endOrLength = CGF.EmitLValueForFieldInitialization(destPtr, *field, 0);
347  if (ctx.hasSameType(field->getType(), elementPtr)) {
348    // End pointer.
349    llvm::Value *arrayEnd = Builder.CreateStructGEP(alloc,numInits, "arrayend");
350    CGF.EmitStoreThroughLValue(RValue::get(arrayEnd), endOrLength);
351  } else if(ctx.hasSameType(field->getType(), ctx.getSizeType())) {
352    // Length.
353    CGF.EmitStoreThroughLValue(RValue::get(Builder.getInt(size)), endOrLength);
354  } else {
355    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
356    return;
357  }
358
359  if (!Dest.isExternallyDestructed())
360    EmitStdInitializerListCleanup(CGF, array, alloc, initList);
361}
362
363/// \brief Emit initialization of an array from an initializer list.
364void AggExprEmitter::EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
365                                   QualType elementType, InitListExpr *E) {
366  uint64_t NumInitElements = E->getNumInits();
367
368  uint64_t NumArrayElements = AType->getNumElements();
369  assert(NumInitElements <= NumArrayElements);
370
371  // DestPtr is an array*.  Construct an elementType* by drilling
372  // down a level.
373  llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
374  llvm::Value *indices[] = { zero, zero };
375  llvm::Value *begin =
376    Builder.CreateInBoundsGEP(DestPtr, indices, "arrayinit.begin");
377
378  // Exception safety requires us to destroy all the
379  // already-constructed members if an initializer throws.
380  // For that, we'll need an EH cleanup.
381  QualType::DestructionKind dtorKind = elementType.isDestructedType();
382  llvm::AllocaInst *endOfInit = 0;
383  EHScopeStack::stable_iterator cleanup;
384  llvm::Instruction *cleanupDominator = 0;
385  if (CGF.needsEHCleanup(dtorKind)) {
386    // In principle we could tell the cleanup where we are more
387    // directly, but the control flow can get so varied here that it
388    // would actually be quite complex.  Therefore we go through an
389    // alloca.
390    endOfInit = CGF.CreateTempAlloca(begin->getType(),
391                                     "arrayinit.endOfInit");
392    cleanupDominator = Builder.CreateStore(begin, endOfInit);
393    CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
394                                         CGF.getDestroyer(dtorKind));
395    cleanup = CGF.EHStack.stable_begin();
396
397  // Otherwise, remember that we didn't need a cleanup.
398  } else {
399    dtorKind = QualType::DK_none;
400  }
401
402  llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
403
404  // The 'current element to initialize'.  The invariants on this
405  // variable are complicated.  Essentially, after each iteration of
406  // the loop, it points to the last initialized element, except
407  // that it points to the beginning of the array before any
408  // elements have been initialized.
409  llvm::Value *element = begin;
410
411  // Emit the explicit initializers.
412  for (uint64_t i = 0; i != NumInitElements; ++i) {
413    // Advance to the next element.
414    if (i > 0) {
415      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
416
417      // Tell the cleanup that it needs to destroy up to this
418      // element.  TODO: some of these stores can be trivially
419      // observed to be unnecessary.
420      if (endOfInit) Builder.CreateStore(element, endOfInit);
421    }
422
423    // If these are nested std::initializer_list inits, do them directly,
424    // because they are conceptually the same "location".
425    InitListExpr *initList = dyn_cast<InitListExpr>(E->getInit(i));
426    if (initList && initList->initializesStdInitializerList()) {
427      EmitStdInitializerList(element, initList);
428    } else {
429      LValue elementLV = CGF.MakeAddrLValue(element, elementType);
430      EmitInitializationToLValue(E->getInit(i), elementLV);
431    }
432  }
433
434  // Check whether there's a non-trivial array-fill expression.
435  // Note that this will be a CXXConstructExpr even if the element
436  // type is an array (or array of array, etc.) of class type.
437  Expr *filler = E->getArrayFiller();
438  bool hasTrivialFiller = true;
439  if (CXXConstructExpr *cons = dyn_cast_or_null<CXXConstructExpr>(filler)) {
440    assert(cons->getConstructor()->isDefaultConstructor());
441    hasTrivialFiller = cons->getConstructor()->isTrivial();
442  }
443
444  // Any remaining elements need to be zero-initialized, possibly
445  // using the filler expression.  We can skip this if the we're
446  // emitting to zeroed memory.
447  if (NumInitElements != NumArrayElements &&
448      !(Dest.isZeroed() && hasTrivialFiller &&
449        CGF.getTypes().isZeroInitializable(elementType))) {
450
451    // Use an actual loop.  This is basically
452    //   do { *array++ = filler; } while (array != end);
453
454    // Advance to the start of the rest of the array.
455    if (NumInitElements) {
456      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
457      if (endOfInit) Builder.CreateStore(element, endOfInit);
458    }
459
460    // Compute the end of the array.
461    llvm::Value *end = Builder.CreateInBoundsGEP(begin,
462                      llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
463                                                 "arrayinit.end");
464
465    llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
466    llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
467
468    // Jump into the body.
469    CGF.EmitBlock(bodyBB);
470    llvm::PHINode *currentElement =
471      Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
472    currentElement->addIncoming(element, entryBB);
473
474    // Emit the actual filler expression.
475    LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
476    if (filler)
477      EmitInitializationToLValue(filler, elementLV);
478    else
479      EmitNullInitializationToLValue(elementLV);
480
481    // Move on to the next element.
482    llvm::Value *nextElement =
483      Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
484
485    // Tell the EH cleanup that we finished with the last element.
486    if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
487
488    // Leave the loop if we're done.
489    llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
490                                             "arrayinit.done");
491    llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
492    Builder.CreateCondBr(done, endBB, bodyBB);
493    currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
494
495    CGF.EmitBlock(endBB);
496  }
497
498  // Leave the partial-array cleanup if we entered one.
499  if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
500}
501
502//===----------------------------------------------------------------------===//
503//                            Visitor Methods
504//===----------------------------------------------------------------------===//
505
506void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
507  Visit(E->GetTemporaryExpr());
508}
509
510void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
511  EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
512}
513
514void
515AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
516  if (E->getType().isPODType(CGF.getContext())) {
517    // For a POD type, just emit a load of the lvalue + a copy, because our
518    // compound literal might alias the destination.
519    // FIXME: This is a band-aid; the real problem appears to be in our handling
520    // of assignments, where we store directly into the LHS without checking
521    // whether anything in the RHS aliases.
522    EmitAggLoadOfLValue(E);
523    return;
524  }
525
526  AggValueSlot Slot = EnsureSlot(E->getType());
527  CGF.EmitAggExpr(E->getInitializer(), Slot);
528}
529
530
531void AggExprEmitter::VisitCastExpr(CastExpr *E) {
532  switch (E->getCastKind()) {
533  case CK_Dynamic: {
534    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
535    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
536    // FIXME: Do we also need to handle property references here?
537    if (LV.isSimple())
538      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
539    else
540      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
541
542    if (!Dest.isIgnored())
543      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
544    break;
545  }
546
547  case CK_ToUnion: {
548    if (Dest.isIgnored()) break;
549
550    // GCC union extension
551    QualType Ty = E->getSubExpr()->getType();
552    QualType PtrTy = CGF.getContext().getPointerType(Ty);
553    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
554                                                 CGF.ConvertType(PtrTy));
555    EmitInitializationToLValue(E->getSubExpr(),
556                               CGF.MakeAddrLValue(CastPtr, Ty));
557    break;
558  }
559
560  case CK_DerivedToBase:
561  case CK_BaseToDerived:
562  case CK_UncheckedDerivedToBase: {
563    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
564                "should have been unpacked before we got here");
565  }
566
567  case CK_LValueToRValue: // hope for downstream optimization
568  case CK_NoOp:
569  case CK_AtomicToNonAtomic:
570  case CK_NonAtomicToAtomic:
571  case CK_UserDefinedConversion:
572  case CK_ConstructorConversion:
573    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
574                                                   E->getType()) &&
575           "Implicit cast types must be compatible");
576    Visit(E->getSubExpr());
577    break;
578
579  case CK_LValueBitCast:
580    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
581
582  case CK_Dependent:
583  case CK_BitCast:
584  case CK_ArrayToPointerDecay:
585  case CK_FunctionToPointerDecay:
586  case CK_NullToPointer:
587  case CK_NullToMemberPointer:
588  case CK_BaseToDerivedMemberPointer:
589  case CK_DerivedToBaseMemberPointer:
590  case CK_MemberPointerToBoolean:
591  case CK_ReinterpretMemberPointer:
592  case CK_IntegralToPointer:
593  case CK_PointerToIntegral:
594  case CK_PointerToBoolean:
595  case CK_ToVoid:
596  case CK_VectorSplat:
597  case CK_IntegralCast:
598  case CK_IntegralToBoolean:
599  case CK_IntegralToFloating:
600  case CK_FloatingToIntegral:
601  case CK_FloatingToBoolean:
602  case CK_FloatingCast:
603  case CK_CPointerToObjCPointerCast:
604  case CK_BlockPointerToObjCPointerCast:
605  case CK_AnyPointerToBlockPointerCast:
606  case CK_ObjCObjectLValueCast:
607  case CK_FloatingRealToComplex:
608  case CK_FloatingComplexToReal:
609  case CK_FloatingComplexToBoolean:
610  case CK_FloatingComplexCast:
611  case CK_FloatingComplexToIntegralComplex:
612  case CK_IntegralRealToComplex:
613  case CK_IntegralComplexToReal:
614  case CK_IntegralComplexToBoolean:
615  case CK_IntegralComplexCast:
616  case CK_IntegralComplexToFloatingComplex:
617  case CK_ARCProduceObject:
618  case CK_ARCConsumeObject:
619  case CK_ARCReclaimReturnedObject:
620  case CK_ARCExtendBlockObject:
621  case CK_CopyAndAutoreleaseBlockObject:
622    llvm_unreachable("cast kind invalid for aggregate types");
623  }
624}
625
626void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
627  if (E->getCallReturnType()->isReferenceType()) {
628    EmitAggLoadOfLValue(E);
629    return;
630  }
631
632  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
633  EmitMoveFromReturnSlot(E, RV);
634}
635
636void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
637  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
638  EmitMoveFromReturnSlot(E, RV);
639}
640
641void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
642  CGF.EmitIgnoredExpr(E->getLHS());
643  Visit(E->getRHS());
644}
645
646void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
647  CodeGenFunction::StmtExprEvaluation eval(CGF);
648  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
649}
650
651void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
652  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
653    VisitPointerToDataMemberBinaryOperator(E);
654  else
655    CGF.ErrorUnsupported(E, "aggregate binary expression");
656}
657
658void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
659                                                    const BinaryOperator *E) {
660  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
661  EmitFinalDestCopy(E, LV);
662}
663
664void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
665  // For an assignment to work, the value on the right has
666  // to be compatible with the value on the left.
667  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
668                                                 E->getRHS()->getType())
669         && "Invalid assignment");
670
671  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
672    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
673      if (VD->hasAttr<BlocksAttr>() &&
674          E->getRHS()->HasSideEffects(CGF.getContext())) {
675        // When __block variable on LHS, the RHS must be evaluated first
676        // as it may change the 'forwarding' field via call to Block_copy.
677        LValue RHS = CGF.EmitLValue(E->getRHS());
678        LValue LHS = CGF.EmitLValue(E->getLHS());
679        Dest = AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
680                                       needsGC(E->getLHS()->getType()),
681                                       AggValueSlot::IsAliased);
682        EmitFinalDestCopy(E, RHS, true);
683        return;
684      }
685
686  LValue LHS = CGF.EmitLValue(E->getLHS());
687
688  // Codegen the RHS so that it stores directly into the LHS.
689  AggValueSlot LHSSlot =
690    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
691                            needsGC(E->getLHS()->getType()),
692                            AggValueSlot::IsAliased);
693  CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
694  EmitFinalDestCopy(E, LHS, true);
695}
696
697void AggExprEmitter::
698VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
699  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
700  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
701  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
702
703  // Bind the common expression if necessary.
704  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
705
706  CodeGenFunction::ConditionalEvaluation eval(CGF);
707  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
708
709  // Save whether the destination's lifetime is externally managed.
710  bool isExternallyDestructed = Dest.isExternallyDestructed();
711
712  eval.begin(CGF);
713  CGF.EmitBlock(LHSBlock);
714  Visit(E->getTrueExpr());
715  eval.end(CGF);
716
717  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
718  CGF.Builder.CreateBr(ContBlock);
719
720  // If the result of an agg expression is unused, then the emission
721  // of the LHS might need to create a destination slot.  That's fine
722  // with us, and we can safely emit the RHS into the same slot, but
723  // we shouldn't claim that it's already being destructed.
724  Dest.setExternallyDestructed(isExternallyDestructed);
725
726  eval.begin(CGF);
727  CGF.EmitBlock(RHSBlock);
728  Visit(E->getFalseExpr());
729  eval.end(CGF);
730
731  CGF.EmitBlock(ContBlock);
732}
733
734void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
735  Visit(CE->getChosenSubExpr(CGF.getContext()));
736}
737
738void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
739  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
740  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
741
742  if (!ArgPtr) {
743    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
744    return;
745  }
746
747  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
748}
749
750void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
751  // Ensure that we have a slot, but if we already do, remember
752  // whether it was externally destructed.
753  bool wasExternallyDestructed = Dest.isExternallyDestructed();
754  Dest = EnsureSlot(E->getType());
755
756  // We're going to push a destructor if there isn't already one.
757  Dest.setExternallyDestructed();
758
759  Visit(E->getSubExpr());
760
761  // Push that destructor we promised.
762  if (!wasExternallyDestructed)
763    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
764}
765
766void
767AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
768  AggValueSlot Slot = EnsureSlot(E->getType());
769  CGF.EmitCXXConstructExpr(E, Slot);
770}
771
772void
773AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
774  AggValueSlot Slot = EnsureSlot(E->getType());
775  CGF.EmitLambdaExpr(E, Slot);
776}
777
778void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
779  CGF.enterFullExpression(E);
780  CodeGenFunction::RunCleanupsScope cleanups(CGF);
781  Visit(E->getSubExpr());
782}
783
784void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
785  QualType T = E->getType();
786  AggValueSlot Slot = EnsureSlot(T);
787  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
788}
789
790void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
791  QualType T = E->getType();
792  AggValueSlot Slot = EnsureSlot(T);
793  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
794}
795
796/// isSimpleZero - If emitting this value will obviously just cause a store of
797/// zero to memory, return true.  This can return false if uncertain, so it just
798/// handles simple cases.
799static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
800  E = E->IgnoreParens();
801
802  // 0
803  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
804    return IL->getValue() == 0;
805  // +0.0
806  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
807    return FL->getValue().isPosZero();
808  // int()
809  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
810      CGF.getTypes().isZeroInitializable(E->getType()))
811    return true;
812  // (int*)0 - Null pointer expressions.
813  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
814    return ICE->getCastKind() == CK_NullToPointer;
815  // '\0'
816  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
817    return CL->getValue() == 0;
818
819  // Otherwise, hard case: conservatively return false.
820  return false;
821}
822
823
824void
825AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
826  QualType type = LV.getType();
827  // FIXME: Ignore result?
828  // FIXME: Are initializers affected by volatile?
829  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
830    // Storing "i32 0" to a zero'd memory location is a noop.
831  } else if (isa<ImplicitValueInitExpr>(E)) {
832    EmitNullInitializationToLValue(LV);
833  } else if (type->isReferenceType()) {
834    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
835    CGF.EmitStoreThroughLValue(RV, LV);
836  } else if (type->isAnyComplexType()) {
837    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
838  } else if (CGF.hasAggregateLLVMType(type)) {
839    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
840                                               AggValueSlot::IsDestructed,
841                                      AggValueSlot::DoesNotNeedGCBarriers,
842                                               AggValueSlot::IsNotAliased,
843                                               Dest.isZeroed()));
844  } else if (LV.isSimple()) {
845    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
846  } else {
847    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
848  }
849}
850
851void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
852  QualType type = lv.getType();
853
854  // If the destination slot is already zeroed out before the aggregate is
855  // copied into it, we don't have to emit any zeros here.
856  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
857    return;
858
859  if (!CGF.hasAggregateLLVMType(type)) {
860    // For non-aggregates, we can store zero.
861    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
862    // Note that the following is not equivalent to
863    // EmitStoreThroughBitfieldLValue for ARC types.
864    if (lv.isBitField()) {
865      CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
866    } else {
867      assert(lv.isSimple());
868      CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
869    }
870  } else {
871    // There's a potential optimization opportunity in combining
872    // memsets; that would be easy for arrays, but relatively
873    // difficult for structures with the current code.
874    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
875  }
876}
877
878void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
879#if 0
880  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
881  // (Length of globals? Chunks of zeroed-out space?).
882  //
883  // If we can, prefer a copy from a global; this is a lot less code for long
884  // globals, and it's easier for the current optimizers to analyze.
885  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
886    llvm::GlobalVariable* GV =
887    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
888                             llvm::GlobalValue::InternalLinkage, C, "");
889    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
890    return;
891  }
892#endif
893  if (E->hadArrayRangeDesignator())
894    CGF.ErrorUnsupported(E, "GNU array range designator extension");
895
896  if (E->initializesStdInitializerList()) {
897    EmitStdInitializerList(Dest.getAddr(), E);
898    return;
899  }
900
901  llvm::Value *DestPtr = Dest.getAddr();
902
903  // Handle initialization of an array.
904  if (E->getType()->isArrayType()) {
905    if (E->getNumInits() > 0) {
906      QualType T1 = E->getType();
907      QualType T2 = E->getInit(0)->getType();
908      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
909        EmitAggLoadOfLValue(E->getInit(0));
910        return;
911      }
912    }
913
914    QualType elementType =
915        CGF.getContext().getAsArrayType(E->getType())->getElementType();
916
917    llvm::PointerType *APType =
918      cast<llvm::PointerType>(DestPtr->getType());
919    llvm::ArrayType *AType =
920      cast<llvm::ArrayType>(APType->getElementType());
921
922    EmitArrayInit(DestPtr, AType, elementType, E);
923    return;
924  }
925
926  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
927
928  // Do struct initialization; this code just sets each individual member
929  // to the approprate value.  This makes bitfield support automatic;
930  // the disadvantage is that the generated code is more difficult for
931  // the optimizer, especially with bitfields.
932  unsigned NumInitElements = E->getNumInits();
933  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
934
935  if (record->isUnion()) {
936    // Only initialize one field of a union. The field itself is
937    // specified by the initializer list.
938    if (!E->getInitializedFieldInUnion()) {
939      // Empty union; we have nothing to do.
940
941#ifndef NDEBUG
942      // Make sure that it's really an empty and not a failure of
943      // semantic analysis.
944      for (RecordDecl::field_iterator Field = record->field_begin(),
945                                   FieldEnd = record->field_end();
946           Field != FieldEnd; ++Field)
947        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
948#endif
949      return;
950    }
951
952    // FIXME: volatility
953    FieldDecl *Field = E->getInitializedFieldInUnion();
954
955    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
956    if (NumInitElements) {
957      // Store the initializer into the field
958      EmitInitializationToLValue(E->getInit(0), FieldLoc);
959    } else {
960      // Default-initialize to null.
961      EmitNullInitializationToLValue(FieldLoc);
962    }
963
964    return;
965  }
966
967  // We'll need to enter cleanup scopes in case any of the member
968  // initializers throw an exception.
969  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
970  llvm::Instruction *cleanupDominator = 0;
971
972  // Here we iterate over the fields; this makes it simpler to both
973  // default-initialize fields and skip over unnamed fields.
974  unsigned curInitIndex = 0;
975  for (RecordDecl::field_iterator field = record->field_begin(),
976                               fieldEnd = record->field_end();
977       field != fieldEnd; ++field) {
978    // We're done once we hit the flexible array member.
979    if (field->getType()->isIncompleteArrayType())
980      break;
981
982    // Always skip anonymous bitfields.
983    if (field->isUnnamedBitfield())
984      continue;
985
986    // We're done if we reach the end of the explicit initializers, we
987    // have a zeroed object, and the rest of the fields are
988    // zero-initializable.
989    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
990        CGF.getTypes().isZeroInitializable(E->getType()))
991      break;
992
993    // FIXME: volatility
994    LValue LV = CGF.EmitLValueForFieldInitialization(DestPtr, *field, 0);
995    // We never generate write-barries for initialized fields.
996    LV.setNonGC(true);
997
998    if (curInitIndex < NumInitElements) {
999      // Store the initializer into the field.
1000      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
1001    } else {
1002      // We're out of initalizers; default-initialize to null
1003      EmitNullInitializationToLValue(LV);
1004    }
1005
1006    // Push a destructor if necessary.
1007    // FIXME: if we have an array of structures, all explicitly
1008    // initialized, we can end up pushing a linear number of cleanups.
1009    bool pushedCleanup = false;
1010    if (QualType::DestructionKind dtorKind
1011          = field->getType().isDestructedType()) {
1012      assert(LV.isSimple());
1013      if (CGF.needsEHCleanup(dtorKind)) {
1014        if (!cleanupDominator)
1015          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
1016
1017        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1018                        CGF.getDestroyer(dtorKind), false);
1019        cleanups.push_back(CGF.EHStack.stable_begin());
1020        pushedCleanup = true;
1021      }
1022    }
1023
1024    // If the GEP didn't get used because of a dead zero init or something
1025    // else, clean it up for -O0 builds and general tidiness.
1026    if (!pushedCleanup && LV.isSimple())
1027      if (llvm::GetElementPtrInst *GEP =
1028            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
1029        if (GEP->use_empty())
1030          GEP->eraseFromParent();
1031  }
1032
1033  // Deactivate all the partial cleanups in reverse order, which
1034  // generally means popping them.
1035  for (unsigned i = cleanups.size(); i != 0; --i)
1036    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1037
1038  // Destroy the placeholder if we made one.
1039  if (cleanupDominator)
1040    cleanupDominator->eraseFromParent();
1041}
1042
1043//===----------------------------------------------------------------------===//
1044//                        Entry Points into this File
1045//===----------------------------------------------------------------------===//
1046
1047/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1048/// non-zero bytes that will be stored when outputting the initializer for the
1049/// specified initializer expression.
1050static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1051  E = E->IgnoreParens();
1052
1053  // 0 and 0.0 won't require any non-zero stores!
1054  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1055
1056  // If this is an initlist expr, sum up the size of sizes of the (present)
1057  // elements.  If this is something weird, assume the whole thing is non-zero.
1058  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1059  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1060    return CGF.getContext().getTypeSizeInChars(E->getType());
1061
1062  // InitListExprs for structs have to be handled carefully.  If there are
1063  // reference members, we need to consider the size of the reference, not the
1064  // referencee.  InitListExprs for unions and arrays can't have references.
1065  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1066    if (!RT->isUnionType()) {
1067      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1068      CharUnits NumNonZeroBytes = CharUnits::Zero();
1069
1070      unsigned ILEElement = 0;
1071      for (RecordDecl::field_iterator Field = SD->field_begin(),
1072           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
1073        // We're done once we hit the flexible array member or run out of
1074        // InitListExpr elements.
1075        if (Field->getType()->isIncompleteArrayType() ||
1076            ILEElement == ILE->getNumInits())
1077          break;
1078        if (Field->isUnnamedBitfield())
1079          continue;
1080
1081        const Expr *E = ILE->getInit(ILEElement++);
1082
1083        // Reference values are always non-null and have the width of a pointer.
1084        if (Field->getType()->isReferenceType())
1085          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1086              CGF.getContext().getTargetInfo().getPointerWidth(0));
1087        else
1088          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1089      }
1090
1091      return NumNonZeroBytes;
1092    }
1093  }
1094
1095
1096  CharUnits NumNonZeroBytes = CharUnits::Zero();
1097  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1098    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1099  return NumNonZeroBytes;
1100}
1101
1102/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1103/// zeros in it, emit a memset and avoid storing the individual zeros.
1104///
1105static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1106                                     CodeGenFunction &CGF) {
1107  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1108  // volatile stores.
1109  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
1110
1111  // C++ objects with a user-declared constructor don't need zero'ing.
1112  if (CGF.getContext().getLangOptions().CPlusPlus)
1113    if (const RecordType *RT = CGF.getContext()
1114                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1115      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1116      if (RD->hasUserDeclaredConstructor())
1117        return;
1118    }
1119
1120  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1121  std::pair<CharUnits, CharUnits> TypeInfo =
1122    CGF.getContext().getTypeInfoInChars(E->getType());
1123  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1124    return;
1125
1126  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1127  // we prefer to emit memset + individual stores for the rest.
1128  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1129  if (NumNonZeroBytes*4 > TypeInfo.first)
1130    return;
1131
1132  // Okay, it seems like a good idea to use an initial memset, emit the call.
1133  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1134  CharUnits Align = TypeInfo.second;
1135
1136  llvm::Value *Loc = Slot.getAddr();
1137
1138  Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
1139  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1140                           Align.getQuantity(), false);
1141
1142  // Tell the AggExprEmitter that the slot is known zero.
1143  Slot.setZeroed();
1144}
1145
1146
1147
1148
1149/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1150/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1151/// the value of the aggregate expression is not needed.  If VolatileDest is
1152/// true, DestPtr cannot be 0.
1153///
1154/// \param IsInitializer - true if this evaluation is initializing an
1155/// object whose lifetime is already being managed.
1156void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
1157                                  bool IgnoreResult) {
1158  assert(E && hasAggregateLLVMType(E->getType()) &&
1159         "Invalid aggregate expression to emit");
1160  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1161         "slot has bits but no address");
1162
1163  // Optimize the slot if possible.
1164  CheckAggExprForMemSetUse(Slot, E, *this);
1165
1166  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
1167}
1168
1169LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1170  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1171  llvm::Value *Temp = CreateMemTemp(E->getType());
1172  LValue LV = MakeAddrLValue(Temp, E->getType());
1173  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1174                                         AggValueSlot::DoesNotNeedGCBarriers,
1175                                         AggValueSlot::IsNotAliased));
1176  return LV;
1177}
1178
1179void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1180                                        llvm::Value *SrcPtr, QualType Ty,
1181                                        bool isVolatile, unsigned Alignment) {
1182  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1183
1184  if (getContext().getLangOptions().CPlusPlus) {
1185    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1186      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1187      assert((Record->hasTrivialCopyConstructor() ||
1188              Record->hasTrivialCopyAssignment() ||
1189              Record->hasTrivialMoveConstructor() ||
1190              Record->hasTrivialMoveAssignment()) &&
1191             "Trying to aggregate-copy a type without a trivial copy "
1192             "constructor or assignment operator");
1193      // Ignore empty classes in C++.
1194      if (Record->isEmpty())
1195        return;
1196    }
1197  }
1198
1199  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1200  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1201  // read from another object that overlaps in anyway the storage of the first
1202  // object, then the overlap shall be exact and the two objects shall have
1203  // qualified or unqualified versions of a compatible type."
1204  //
1205  // memcpy is not defined if the source and destination pointers are exactly
1206  // equal, but other compilers do this optimization, and almost every memcpy
1207  // implementation handles this case safely.  If there is a libc that does not
1208  // safely handle this, we can add a target hook.
1209
1210  // Get size and alignment info for this aggregate.
1211  std::pair<CharUnits, CharUnits> TypeInfo =
1212    getContext().getTypeInfoInChars(Ty);
1213
1214  if (!Alignment)
1215    Alignment = TypeInfo.second.getQuantity();
1216
1217  // FIXME: Handle variable sized types.
1218
1219  // FIXME: If we have a volatile struct, the optimizer can remove what might
1220  // appear to be `extra' memory ops:
1221  //
1222  // volatile struct { int i; } a, b;
1223  //
1224  // int main() {
1225  //   a = b;
1226  //   a = b;
1227  // }
1228  //
1229  // we need to use a different call here.  We use isVolatile to indicate when
1230  // either the source or the destination is volatile.
1231
1232  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1233  llvm::Type *DBP =
1234    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1235  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1236
1237  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1238  llvm::Type *SBP =
1239    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1240  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1241
1242  // Don't do any of the memmove_collectable tests if GC isn't set.
1243  if (CGM.getLangOptions().getGC() == LangOptions::NonGC) {
1244    // fall through
1245  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1246    RecordDecl *Record = RecordTy->getDecl();
1247    if (Record->hasObjectMember()) {
1248      CharUnits size = TypeInfo.first;
1249      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1250      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1251      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1252                                                    SizeVal);
1253      return;
1254    }
1255  } else if (Ty->isArrayType()) {
1256    QualType BaseType = getContext().getBaseElementType(Ty);
1257    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1258      if (RecordTy->getDecl()->hasObjectMember()) {
1259        CharUnits size = TypeInfo.first;
1260        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1261        llvm::Value *SizeVal =
1262          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1263        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1264                                                      SizeVal);
1265        return;
1266      }
1267    }
1268  }
1269
1270  Builder.CreateMemCpy(DestPtr, SrcPtr,
1271                       llvm::ConstantInt::get(IntPtrTy,
1272                                              TypeInfo.first.getQuantity()),
1273                       Alignment, isVolatile);
1274}
1275
1276void CodeGenFunction::MaybeEmitStdInitializerListCleanup(llvm::Value *loc,
1277                                                         const Expr *init) {
1278  const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(init);
1279  if (cleanups)
1280    init = cleanups->getSubExpr();
1281
1282  if (isa<InitListExpr>(init) &&
1283      cast<InitListExpr>(init)->initializesStdInitializerList()) {
1284    // We initialized this std::initializer_list with an initializer list.
1285    // A backing array was created. Push a cleanup for it.
1286    EmitStdInitializerListCleanup(loc, cast<InitListExpr>(init));
1287  }
1288}
1289
1290static void EmitRecursiveStdInitializerListCleanup(CodeGenFunction &CGF,
1291                                                   llvm::Value *arrayStart,
1292                                                   const InitListExpr *init) {
1293  // Check if there are any recursive cleanups to do, i.e. if we have
1294  //   std::initializer_list<std::initializer_list<obj>> list = {{obj()}};
1295  // then we need to destroy the inner array as well.
1296  for (unsigned i = 0, e = init->getNumInits(); i != e; ++i) {
1297    const InitListExpr *subInit = dyn_cast<InitListExpr>(init->getInit(i));
1298    if (!subInit || !subInit->initializesStdInitializerList())
1299      continue;
1300
1301    // This one needs to be destroyed. Get the address of the std::init_list.
1302    llvm::Value *offset = llvm::ConstantInt::get(CGF.SizeTy, i);
1303    llvm::Value *loc = CGF.Builder.CreateInBoundsGEP(arrayStart, offset,
1304                                                 "std.initlist");
1305    CGF.EmitStdInitializerListCleanup(loc, subInit);
1306  }
1307}
1308
1309void CodeGenFunction::EmitStdInitializerListCleanup(llvm::Value *loc,
1310                                                    const InitListExpr *init) {
1311  ASTContext &ctx = getContext();
1312  QualType element = GetStdInitializerListElementType(init->getType());
1313  unsigned numInits = init->getNumInits();
1314  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
1315  QualType array =ctx.getConstantArrayType(element, size, ArrayType::Normal, 0);
1316  QualType arrayPtr = ctx.getPointerType(array);
1317  llvm::Type *arrayPtrType = ConvertType(arrayPtr);
1318
1319  // lvalue is the location of a std::initializer_list, which as its first
1320  // element has a pointer to the array we want to destroy.
1321  llvm::Value *startPointer = Builder.CreateStructGEP(loc, 0, "startPointer");
1322  llvm::Value *startAddress = Builder.CreateLoad(startPointer, "startAddress");
1323
1324  ::EmitRecursiveStdInitializerListCleanup(*this, startAddress, init);
1325
1326  llvm::Value *arrayAddress =
1327      Builder.CreateBitCast(startAddress, arrayPtrType, "arrayAddress");
1328  ::EmitStdInitializerListCleanup(*this, array, arrayAddress, init);
1329}
1330