CGExprAgg.cpp revision 5a13d4d2c1e45ab611ca857d923caacfaeb3cd07 
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  }
328
329  QualType elementPtr = ctx.getPointerType(element.withConst());
330
331  // Start pointer.
332  if (!ctx.hasSameType(field->getType(), elementPtr)) {
333    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
334  }
335  LValue start = CGF.EmitLValueForFieldInitialization(destPtr, *field, 0);
336  llvm::Value *arrayStart = Builder.CreateStructGEP(alloc, 0, "arraystart");
337  CGF.EmitStoreThroughLValue(RValue::get(arrayStart), start);
338  ++field;
339
340  if (field == record->field_end()) {
341    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
342  }
343  LValue endOrLength = CGF.EmitLValueForFieldInitialization(destPtr, *field, 0);
344  if (ctx.hasSameType(field->getType(), elementPtr)) {
345    // End pointer.
346    llvm::Value *arrayEnd = Builder.CreateStructGEP(alloc,numInits, "arrayend");
347    CGF.EmitStoreThroughLValue(RValue::get(arrayEnd), endOrLength);
348  } else if(ctx.hasSameType(field->getType(), ctx.getSizeType())) {
349    // Length.
350    CGF.EmitStoreThroughLValue(RValue::get(Builder.getInt(size)), endOrLength);
351  } else {
352    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
353  }
354
355  if (!Dest.isExternallyDestructed())
356    EmitStdInitializerListCleanup(CGF, array, alloc, initList);
357}
358
359/// \brief Emit initialization of an array from an initializer list.
360void AggExprEmitter::EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
361                                   QualType elementType, InitListExpr *E) {
362  uint64_t NumInitElements = E->getNumInits();
363
364  uint64_t NumArrayElements = AType->getNumElements();
365  assert(NumInitElements <= NumArrayElements);
366
367  // DestPtr is an array*.  Construct an elementType* by drilling
368  // down a level.
369  llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
370  llvm::Value *indices[] = { zero, zero };
371  llvm::Value *begin =
372    Builder.CreateInBoundsGEP(DestPtr, indices, "arrayinit.begin");
373
374  // Exception safety requires us to destroy all the
375  // already-constructed members if an initializer throws.
376  // For that, we'll need an EH cleanup.
377  QualType::DestructionKind dtorKind = elementType.isDestructedType();
378  llvm::AllocaInst *endOfInit = 0;
379  EHScopeStack::stable_iterator cleanup;
380  llvm::Instruction *cleanupDominator = 0;
381  if (CGF.needsEHCleanup(dtorKind)) {
382    // In principle we could tell the cleanup where we are more
383    // directly, but the control flow can get so varied here that it
384    // would actually be quite complex.  Therefore we go through an
385    // alloca.
386    endOfInit = CGF.CreateTempAlloca(begin->getType(),
387                                     "arrayinit.endOfInit");
388    cleanupDominator = Builder.CreateStore(begin, endOfInit);
389    CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
390                                         CGF.getDestroyer(dtorKind));
391    cleanup = CGF.EHStack.stable_begin();
392
393  // Otherwise, remember that we didn't need a cleanup.
394  } else {
395    dtorKind = QualType::DK_none;
396  }
397
398  llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
399
400  // The 'current element to initialize'.  The invariants on this
401  // variable are complicated.  Essentially, after each iteration of
402  // the loop, it points to the last initialized element, except
403  // that it points to the beginning of the array before any
404  // elements have been initialized.
405  llvm::Value *element = begin;
406
407  // Emit the explicit initializers.
408  for (uint64_t i = 0; i != NumInitElements; ++i) {
409    // Advance to the next element.
410    if (i > 0) {
411      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
412
413      // Tell the cleanup that it needs to destroy up to this
414      // element.  TODO: some of these stores can be trivially
415      // observed to be unnecessary.
416      if (endOfInit) Builder.CreateStore(element, endOfInit);
417    }
418
419    // If these are nested std::initializer_list inits, do them directly,
420    // because they are conceptually the same "location".
421    InitListExpr *initList = dyn_cast<InitListExpr>(E->getInit(i));
422    if (initList && initList->initializesStdInitializerList()) {
423      EmitStdInitializerList(element, initList);
424    } else {
425      LValue elementLV = CGF.MakeAddrLValue(element, elementType);
426      EmitInitializationToLValue(E->getInit(i), elementLV);
427    }
428  }
429
430  // Check whether there's a non-trivial array-fill expression.
431  // Note that this will be a CXXConstructExpr even if the element
432  // type is an array (or array of array, etc.) of class type.
433  Expr *filler = E->getArrayFiller();
434  bool hasTrivialFiller = true;
435  if (CXXConstructExpr *cons = dyn_cast_or_null<CXXConstructExpr>(filler)) {
436    assert(cons->getConstructor()->isDefaultConstructor());
437    hasTrivialFiller = cons->getConstructor()->isTrivial();
438  }
439
440  // Any remaining elements need to be zero-initialized, possibly
441  // using the filler expression.  We can skip this if the we're
442  // emitting to zeroed memory.
443  if (NumInitElements != NumArrayElements &&
444      !(Dest.isZeroed() && hasTrivialFiller &&
445        CGF.getTypes().isZeroInitializable(elementType))) {
446
447    // Use an actual loop.  This is basically
448    //   do { *array++ = filler; } while (array != end);
449
450    // Advance to the start of the rest of the array.
451    if (NumInitElements) {
452      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
453      if (endOfInit) Builder.CreateStore(element, endOfInit);
454    }
455
456    // Compute the end of the array.
457    llvm::Value *end = Builder.CreateInBoundsGEP(begin,
458                      llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
459                                                 "arrayinit.end");
460
461    llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
462    llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
463
464    // Jump into the body.
465    CGF.EmitBlock(bodyBB);
466    llvm::PHINode *currentElement =
467      Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
468    currentElement->addIncoming(element, entryBB);
469
470    // Emit the actual filler expression.
471    LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
472    if (filler)
473      EmitInitializationToLValue(filler, elementLV);
474    else
475      EmitNullInitializationToLValue(elementLV);
476
477    // Move on to the next element.
478    llvm::Value *nextElement =
479      Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
480
481    // Tell the EH cleanup that we finished with the last element.
482    if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
483
484    // Leave the loop if we're done.
485    llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
486                                             "arrayinit.done");
487    llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
488    Builder.CreateCondBr(done, endBB, bodyBB);
489    currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
490
491    CGF.EmitBlock(endBB);
492  }
493
494  // Leave the partial-array cleanup if we entered one.
495  if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
496}
497
498//===----------------------------------------------------------------------===//
499//                            Visitor Methods
500//===----------------------------------------------------------------------===//
501
502void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
503  Visit(E->GetTemporaryExpr());
504}
505
506void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
507  EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
508}
509
510void
511AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
512  if (E->getType().isPODType(CGF.getContext())) {
513    // For a POD type, just emit a load of the lvalue + a copy, because our
514    // compound literal might alias the destination.
515    // FIXME: This is a band-aid; the real problem appears to be in our handling
516    // of assignments, where we store directly into the LHS without checking
517    // whether anything in the RHS aliases.
518    EmitAggLoadOfLValue(E);
519    return;
520  }
521
522  AggValueSlot Slot = EnsureSlot(E->getType());
523  CGF.EmitAggExpr(E->getInitializer(), Slot);
524}
525
526
527void AggExprEmitter::VisitCastExpr(CastExpr *E) {
528  switch (E->getCastKind()) {
529  case CK_Dynamic: {
530    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
531    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
532    // FIXME: Do we also need to handle property references here?
533    if (LV.isSimple())
534      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
535    else
536      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
537
538    if (!Dest.isIgnored())
539      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
540    break;
541  }
542
543  case CK_ToUnion: {
544    if (Dest.isIgnored()) break;
545
546    // GCC union extension
547    QualType Ty = E->getSubExpr()->getType();
548    QualType PtrTy = CGF.getContext().getPointerType(Ty);
549    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
550                                                 CGF.ConvertType(PtrTy));
551    EmitInitializationToLValue(E->getSubExpr(),
552                               CGF.MakeAddrLValue(CastPtr, Ty));
553    break;
554  }
555
556  case CK_DerivedToBase:
557  case CK_BaseToDerived:
558  case CK_UncheckedDerivedToBase: {
559    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
560                "should have been unpacked before we got here");
561  }
562
563  case CK_LValueToRValue: // hope for downstream optimization
564  case CK_NoOp:
565  case CK_AtomicToNonAtomic:
566  case CK_NonAtomicToAtomic:
567  case CK_UserDefinedConversion:
568  case CK_ConstructorConversion:
569    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
570                                                   E->getType()) &&
571           "Implicit cast types must be compatible");
572    Visit(E->getSubExpr());
573    break;
574
575  case CK_LValueBitCast:
576    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
577
578  case CK_Dependent:
579  case CK_BitCast:
580  case CK_ArrayToPointerDecay:
581  case CK_FunctionToPointerDecay:
582  case CK_NullToPointer:
583  case CK_NullToMemberPointer:
584  case CK_BaseToDerivedMemberPointer:
585  case CK_DerivedToBaseMemberPointer:
586  case CK_MemberPointerToBoolean:
587  case CK_ReinterpretMemberPointer:
588  case CK_IntegralToPointer:
589  case CK_PointerToIntegral:
590  case CK_PointerToBoolean:
591  case CK_ToVoid:
592  case CK_VectorSplat:
593  case CK_IntegralCast:
594  case CK_IntegralToBoolean:
595  case CK_IntegralToFloating:
596  case CK_FloatingToIntegral:
597  case CK_FloatingToBoolean:
598  case CK_FloatingCast:
599  case CK_CPointerToObjCPointerCast:
600  case CK_BlockPointerToObjCPointerCast:
601  case CK_AnyPointerToBlockPointerCast:
602  case CK_ObjCObjectLValueCast:
603  case CK_FloatingRealToComplex:
604  case CK_FloatingComplexToReal:
605  case CK_FloatingComplexToBoolean:
606  case CK_FloatingComplexCast:
607  case CK_FloatingComplexToIntegralComplex:
608  case CK_IntegralRealToComplex:
609  case CK_IntegralComplexToReal:
610  case CK_IntegralComplexToBoolean:
611  case CK_IntegralComplexCast:
612  case CK_IntegralComplexToFloatingComplex:
613  case CK_ARCProduceObject:
614  case CK_ARCConsumeObject:
615  case CK_ARCReclaimReturnedObject:
616  case CK_ARCExtendBlockObject:
617  case CK_CopyAndAutoreleaseBlockObject:
618    llvm_unreachable("cast kind invalid for aggregate types");
619  }
620}
621
622void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
623  if (E->getCallReturnType()->isReferenceType()) {
624    EmitAggLoadOfLValue(E);
625    return;
626  }
627
628  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
629  EmitMoveFromReturnSlot(E, RV);
630}
631
632void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
633  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
634  EmitMoveFromReturnSlot(E, RV);
635}
636
637void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
638  CGF.EmitIgnoredExpr(E->getLHS());
639  Visit(E->getRHS());
640}
641
642void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
643  CodeGenFunction::StmtExprEvaluation eval(CGF);
644  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
645}
646
647void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
648  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
649    VisitPointerToDataMemberBinaryOperator(E);
650  else
651    CGF.ErrorUnsupported(E, "aggregate binary expression");
652}
653
654void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
655                                                    const BinaryOperator *E) {
656  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
657  EmitFinalDestCopy(E, LV);
658}
659
660void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
661  // For an assignment to work, the value on the right has
662  // to be compatible with the value on the left.
663  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
664                                                 E->getRHS()->getType())
665         && "Invalid assignment");
666
667  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
668    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
669      if (VD->hasAttr<BlocksAttr>() &&
670          E->getRHS()->HasSideEffects(CGF.getContext())) {
671        // When __block variable on LHS, the RHS must be evaluated first
672        // as it may change the 'forwarding' field via call to Block_copy.
673        LValue RHS = CGF.EmitLValue(E->getRHS());
674        LValue LHS = CGF.EmitLValue(E->getLHS());
675        Dest = AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
676                                       needsGC(E->getLHS()->getType()),
677                                       AggValueSlot::IsAliased);
678        EmitFinalDestCopy(E, RHS, true);
679        return;
680      }
681
682  LValue LHS = CGF.EmitLValue(E->getLHS());
683
684  // Codegen the RHS so that it stores directly into the LHS.
685  AggValueSlot LHSSlot =
686    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
687                            needsGC(E->getLHS()->getType()),
688                            AggValueSlot::IsAliased);
689  CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
690  EmitFinalDestCopy(E, LHS, true);
691}
692
693void AggExprEmitter::
694VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
695  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
696  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
697  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
698
699  // Bind the common expression if necessary.
700  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
701
702  CodeGenFunction::ConditionalEvaluation eval(CGF);
703  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
704
705  // Save whether the destination's lifetime is externally managed.
706  bool isExternallyDestructed = Dest.isExternallyDestructed();
707
708  eval.begin(CGF);
709  CGF.EmitBlock(LHSBlock);
710  Visit(E->getTrueExpr());
711  eval.end(CGF);
712
713  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
714  CGF.Builder.CreateBr(ContBlock);
715
716  // If the result of an agg expression is unused, then the emission
717  // of the LHS might need to create a destination slot.  That's fine
718  // with us, and we can safely emit the RHS into the same slot, but
719  // we shouldn't claim that it's already being destructed.
720  Dest.setExternallyDestructed(isExternallyDestructed);
721
722  eval.begin(CGF);
723  CGF.EmitBlock(RHSBlock);
724  Visit(E->getFalseExpr());
725  eval.end(CGF);
726
727  CGF.EmitBlock(ContBlock);
728}
729
730void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
731  Visit(CE->getChosenSubExpr(CGF.getContext()));
732}
733
734void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
735  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
736  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
737
738  if (!ArgPtr) {
739    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
740    return;
741  }
742
743  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
744}
745
746void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
747  // Ensure that we have a slot, but if we already do, remember
748  // whether it was externally destructed.
749  bool wasExternallyDestructed = Dest.isExternallyDestructed();
750  Dest = EnsureSlot(E->getType());
751
752  // We're going to push a destructor if there isn't already one.
753  Dest.setExternallyDestructed();
754
755  Visit(E->getSubExpr());
756
757  // Push that destructor we promised.
758  if (!wasExternallyDestructed)
759    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
760}
761
762void
763AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
764  AggValueSlot Slot = EnsureSlot(E->getType());
765  CGF.EmitCXXConstructExpr(E, Slot);
766}
767
768void
769AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
770  AggValueSlot Slot = EnsureSlot(E->getType());
771  CGF.EmitLambdaExpr(E, Slot);
772}
773
774void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
775  CGF.enterFullExpression(E);
776  CodeGenFunction::RunCleanupsScope cleanups(CGF);
777  Visit(E->getSubExpr());
778}
779
780void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
781  QualType T = E->getType();
782  AggValueSlot Slot = EnsureSlot(T);
783  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
784}
785
786void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
787  QualType T = E->getType();
788  AggValueSlot Slot = EnsureSlot(T);
789  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
790}
791
792/// isSimpleZero - If emitting this value will obviously just cause a store of
793/// zero to memory, return true.  This can return false if uncertain, so it just
794/// handles simple cases.
795static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
796  E = E->IgnoreParens();
797
798  // 0
799  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
800    return IL->getValue() == 0;
801  // +0.0
802  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
803    return FL->getValue().isPosZero();
804  // int()
805  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
806      CGF.getTypes().isZeroInitializable(E->getType()))
807    return true;
808  // (int*)0 - Null pointer expressions.
809  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
810    return ICE->getCastKind() == CK_NullToPointer;
811  // '\0'
812  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
813    return CL->getValue() == 0;
814
815  // Otherwise, hard case: conservatively return false.
816  return false;
817}
818
819
820void
821AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
822  QualType type = LV.getType();
823  // FIXME: Ignore result?
824  // FIXME: Are initializers affected by volatile?
825  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
826    // Storing "i32 0" to a zero'd memory location is a noop.
827  } else if (isa<ImplicitValueInitExpr>(E)) {
828    EmitNullInitializationToLValue(LV);
829  } else if (type->isReferenceType()) {
830    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
831    CGF.EmitStoreThroughLValue(RV, LV);
832  } else if (type->isAnyComplexType()) {
833    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
834  } else if (CGF.hasAggregateLLVMType(type)) {
835    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
836                                               AggValueSlot::IsDestructed,
837                                      AggValueSlot::DoesNotNeedGCBarriers,
838                                               AggValueSlot::IsNotAliased,
839                                               Dest.isZeroed()));
840  } else if (LV.isSimple()) {
841    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
842  } else {
843    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
844  }
845}
846
847void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
848  QualType type = lv.getType();
849
850  // If the destination slot is already zeroed out before the aggregate is
851  // copied into it, we don't have to emit any zeros here.
852  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
853    return;
854
855  if (!CGF.hasAggregateLLVMType(type)) {
856    // For non-aggregates, we can store zero.
857    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
858    // Note that the following is not equivalent to
859    // EmitStoreThroughBitfieldLValue for ARC types.
860    if (lv.isBitField()) {
861      CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
862    } else {
863      assert(lv.isSimple());
864      CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
865    }
866  } else {
867    // There's a potential optimization opportunity in combining
868    // memsets; that would be easy for arrays, but relatively
869    // difficult for structures with the current code.
870    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
871  }
872}
873
874void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
875#if 0
876  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
877  // (Length of globals? Chunks of zeroed-out space?).
878  //
879  // If we can, prefer a copy from a global; this is a lot less code for long
880  // globals, and it's easier for the current optimizers to analyze.
881  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
882    llvm::GlobalVariable* GV =
883    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
884                             llvm::GlobalValue::InternalLinkage, C, "");
885    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
886    return;
887  }
888#endif
889  if (E->hadArrayRangeDesignator())
890    CGF.ErrorUnsupported(E, "GNU array range designator extension");
891
892  if (E->initializesStdInitializerList()) {
893    EmitStdInitializerList(Dest.getAddr(), E);
894    return;
895  }
896
897  llvm::Value *DestPtr = Dest.getAddr();
898
899  // Handle initialization of an array.
900  if (E->getType()->isArrayType()) {
901    if (E->getNumInits() > 0) {
902      QualType T1 = E->getType();
903      QualType T2 = E->getInit(0)->getType();
904      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
905        EmitAggLoadOfLValue(E->getInit(0));
906        return;
907      }
908    }
909
910    QualType elementType =
911        CGF.getContext().getAsArrayType(E->getType())->getElementType();
912
913    llvm::PointerType *APType =
914      cast<llvm::PointerType>(DestPtr->getType());
915    llvm::ArrayType *AType =
916      cast<llvm::ArrayType>(APType->getElementType());
917
918    EmitArrayInit(DestPtr, AType, elementType, E);
919    return;
920  }
921
922  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
923
924  // Do struct initialization; this code just sets each individual member
925  // to the approprate value.  This makes bitfield support automatic;
926  // the disadvantage is that the generated code is more difficult for
927  // the optimizer, especially with bitfields.
928  unsigned NumInitElements = E->getNumInits();
929  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
930
931  if (record->isUnion()) {
932    // Only initialize one field of a union. The field itself is
933    // specified by the initializer list.
934    if (!E->getInitializedFieldInUnion()) {
935      // Empty union; we have nothing to do.
936
937#ifndef NDEBUG
938      // Make sure that it's really an empty and not a failure of
939      // semantic analysis.
940      for (RecordDecl::field_iterator Field = record->field_begin(),
941                                   FieldEnd = record->field_end();
942           Field != FieldEnd; ++Field)
943        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
944#endif
945      return;
946    }
947
948    // FIXME: volatility
949    FieldDecl *Field = E->getInitializedFieldInUnion();
950
951    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
952    if (NumInitElements) {
953      // Store the initializer into the field
954      EmitInitializationToLValue(E->getInit(0), FieldLoc);
955    } else {
956      // Default-initialize to null.
957      EmitNullInitializationToLValue(FieldLoc);
958    }
959
960    return;
961  }
962
963  // We'll need to enter cleanup scopes in case any of the member
964  // initializers throw an exception.
965  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
966  llvm::Instruction *cleanupDominator = 0;
967
968  // Here we iterate over the fields; this makes it simpler to both
969  // default-initialize fields and skip over unnamed fields.
970  unsigned curInitIndex = 0;
971  for (RecordDecl::field_iterator field = record->field_begin(),
972                               fieldEnd = record->field_end();
973       field != fieldEnd; ++field) {
974    // We're done once we hit the flexible array member.
975    if (field->getType()->isIncompleteArrayType())
976      break;
977
978    // Always skip anonymous bitfields.
979    if (field->isUnnamedBitfield())
980      continue;
981
982    // We're done if we reach the end of the explicit initializers, we
983    // have a zeroed object, and the rest of the fields are
984    // zero-initializable.
985    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
986        CGF.getTypes().isZeroInitializable(E->getType()))
987      break;
988
989    // FIXME: volatility
990    LValue LV = CGF.EmitLValueForFieldInitialization(DestPtr, *field, 0);
991    // We never generate write-barries for initialized fields.
992    LV.setNonGC(true);
993
994    if (curInitIndex < NumInitElements) {
995      // Store the initializer into the field.
996      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
997    } else {
998      // We're out of initalizers; default-initialize to null
999      EmitNullInitializationToLValue(LV);
1000    }
1001
1002    // Push a destructor if necessary.
1003    // FIXME: if we have an array of structures, all explicitly
1004    // initialized, we can end up pushing a linear number of cleanups.
1005    bool pushedCleanup = false;
1006    if (QualType::DestructionKind dtorKind
1007          = field->getType().isDestructedType()) {
1008      assert(LV.isSimple());
1009      if (CGF.needsEHCleanup(dtorKind)) {
1010        if (!cleanupDominator)
1011          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
1012
1013        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1014                        CGF.getDestroyer(dtorKind), false);
1015        cleanups.push_back(CGF.EHStack.stable_begin());
1016        pushedCleanup = true;
1017      }
1018    }
1019
1020    // If the GEP didn't get used because of a dead zero init or something
1021    // else, clean it up for -O0 builds and general tidiness.
1022    if (!pushedCleanup && LV.isSimple())
1023      if (llvm::GetElementPtrInst *GEP =
1024            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
1025        if (GEP->use_empty())
1026          GEP->eraseFromParent();
1027  }
1028
1029  // Deactivate all the partial cleanups in reverse order, which
1030  // generally means popping them.
1031  for (unsigned i = cleanups.size(); i != 0; --i)
1032    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1033
1034  // Destroy the placeholder if we made one.
1035  if (cleanupDominator)
1036    cleanupDominator->eraseFromParent();
1037}
1038
1039//===----------------------------------------------------------------------===//
1040//                        Entry Points into this File
1041//===----------------------------------------------------------------------===//
1042
1043/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1044/// non-zero bytes that will be stored when outputting the initializer for the
1045/// specified initializer expression.
1046static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1047  E = E->IgnoreParens();
1048
1049  // 0 and 0.0 won't require any non-zero stores!
1050  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1051
1052  // If this is an initlist expr, sum up the size of sizes of the (present)
1053  // elements.  If this is something weird, assume the whole thing is non-zero.
1054  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1055  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1056    return CGF.getContext().getTypeSizeInChars(E->getType());
1057
1058  // InitListExprs for structs have to be handled carefully.  If there are
1059  // reference members, we need to consider the size of the reference, not the
1060  // referencee.  InitListExprs for unions and arrays can't have references.
1061  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1062    if (!RT->isUnionType()) {
1063      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1064      CharUnits NumNonZeroBytes = CharUnits::Zero();
1065
1066      unsigned ILEElement = 0;
1067      for (RecordDecl::field_iterator Field = SD->field_begin(),
1068           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
1069        // We're done once we hit the flexible array member or run out of
1070        // InitListExpr elements.
1071        if (Field->getType()->isIncompleteArrayType() ||
1072            ILEElement == ILE->getNumInits())
1073          break;
1074        if (Field->isUnnamedBitfield())
1075          continue;
1076
1077        const Expr *E = ILE->getInit(ILEElement++);
1078
1079        // Reference values are always non-null and have the width of a pointer.
1080        if (Field->getType()->isReferenceType())
1081          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1082              CGF.getContext().getTargetInfo().getPointerWidth(0));
1083        else
1084          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1085      }
1086
1087      return NumNonZeroBytes;
1088    }
1089  }
1090
1091
1092  CharUnits NumNonZeroBytes = CharUnits::Zero();
1093  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1094    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1095  return NumNonZeroBytes;
1096}
1097
1098/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1099/// zeros in it, emit a memset and avoid storing the individual zeros.
1100///
1101static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1102                                     CodeGenFunction &CGF) {
1103  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1104  // volatile stores.
1105  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
1106
1107  // C++ objects with a user-declared constructor don't need zero'ing.
1108  if (CGF.getContext().getLangOptions().CPlusPlus)
1109    if (const RecordType *RT = CGF.getContext()
1110                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1111      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1112      if (RD->hasUserDeclaredConstructor())
1113        return;
1114    }
1115
1116  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1117  std::pair<CharUnits, CharUnits> TypeInfo =
1118    CGF.getContext().getTypeInfoInChars(E->getType());
1119  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1120    return;
1121
1122  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1123  // we prefer to emit memset + individual stores for the rest.
1124  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1125  if (NumNonZeroBytes*4 > TypeInfo.first)
1126    return;
1127
1128  // Okay, it seems like a good idea to use an initial memset, emit the call.
1129  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1130  CharUnits Align = TypeInfo.second;
1131
1132  llvm::Value *Loc = Slot.getAddr();
1133
1134  Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
1135  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1136                           Align.getQuantity(), false);
1137
1138  // Tell the AggExprEmitter that the slot is known zero.
1139  Slot.setZeroed();
1140}
1141
1142
1143
1144
1145/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1146/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1147/// the value of the aggregate expression is not needed.  If VolatileDest is
1148/// true, DestPtr cannot be 0.
1149///
1150/// \param IsInitializer - true if this evaluation is initializing an
1151/// object whose lifetime is already being managed.
1152void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
1153                                  bool IgnoreResult) {
1154  assert(E && hasAggregateLLVMType(E->getType()) &&
1155         "Invalid aggregate expression to emit");
1156  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1157         "slot has bits but no address");
1158
1159  // Optimize the slot if possible.
1160  CheckAggExprForMemSetUse(Slot, E, *this);
1161
1162  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
1163}
1164
1165LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1166  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1167  llvm::Value *Temp = CreateMemTemp(E->getType());
1168  LValue LV = MakeAddrLValue(Temp, E->getType());
1169  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1170                                         AggValueSlot::DoesNotNeedGCBarriers,
1171                                         AggValueSlot::IsNotAliased));
1172  return LV;
1173}
1174
1175void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1176                                        llvm::Value *SrcPtr, QualType Ty,
1177                                        bool isVolatile, unsigned Alignment) {
1178  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1179
1180  if (getContext().getLangOptions().CPlusPlus) {
1181    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1182      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1183      assert((Record->hasTrivialCopyConstructor() ||
1184              Record->hasTrivialCopyAssignment() ||
1185              Record->hasTrivialMoveConstructor() ||
1186              Record->hasTrivialMoveAssignment()) &&
1187             "Trying to aggregate-copy a type without a trivial copy "
1188             "constructor or assignment operator");
1189      // Ignore empty classes in C++.
1190      if (Record->isEmpty())
1191        return;
1192    }
1193  }
1194
1195  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1196  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1197  // read from another object that overlaps in anyway the storage of the first
1198  // object, then the overlap shall be exact and the two objects shall have
1199  // qualified or unqualified versions of a compatible type."
1200  //
1201  // memcpy is not defined if the source and destination pointers are exactly
1202  // equal, but other compilers do this optimization, and almost every memcpy
1203  // implementation handles this case safely.  If there is a libc that does not
1204  // safely handle this, we can add a target hook.
1205
1206  // Get size and alignment info for this aggregate.
1207  std::pair<CharUnits, CharUnits> TypeInfo =
1208    getContext().getTypeInfoInChars(Ty);
1209
1210  if (!Alignment)
1211    Alignment = TypeInfo.second.getQuantity();
1212
1213  // FIXME: Handle variable sized types.
1214
1215  // FIXME: If we have a volatile struct, the optimizer can remove what might
1216  // appear to be `extra' memory ops:
1217  //
1218  // volatile struct { int i; } a, b;
1219  //
1220  // int main() {
1221  //   a = b;
1222  //   a = b;
1223  // }
1224  //
1225  // we need to use a different call here.  We use isVolatile to indicate when
1226  // either the source or the destination is volatile.
1227
1228  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1229  llvm::Type *DBP =
1230    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1231  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1232
1233  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1234  llvm::Type *SBP =
1235    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1236  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1237
1238  // Don't do any of the memmove_collectable tests if GC isn't set.
1239  if (CGM.getLangOptions().getGC() == LangOptions::NonGC) {
1240    // fall through
1241  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1242    RecordDecl *Record = RecordTy->getDecl();
1243    if (Record->hasObjectMember()) {
1244      CharUnits size = TypeInfo.first;
1245      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1246      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1247      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1248                                                    SizeVal);
1249      return;
1250    }
1251  } else if (Ty->isArrayType()) {
1252    QualType BaseType = getContext().getBaseElementType(Ty);
1253    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1254      if (RecordTy->getDecl()->hasObjectMember()) {
1255        CharUnits size = TypeInfo.first;
1256        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1257        llvm::Value *SizeVal =
1258          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1259        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1260                                                      SizeVal);
1261        return;
1262      }
1263    }
1264  }
1265
1266  Builder.CreateMemCpy(DestPtr, SrcPtr,
1267                       llvm::ConstantInt::get(IntPtrTy,
1268                                              TypeInfo.first.getQuantity()),
1269                       Alignment, isVolatile);
1270}
1271
1272void CodeGenFunction::MaybeEmitStdInitializerListCleanup(llvm::Value *loc,
1273                                                         const Expr *init) {
1274  const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(init);
1275  if (cleanups)
1276    init = cleanups->getSubExpr();
1277
1278  if (isa<InitListExpr>(init) &&
1279      cast<InitListExpr>(init)->initializesStdInitializerList()) {
1280    // We initialized this std::initializer_list with an initializer list.
1281    // A backing array was created. Push a cleanup for it.
1282    EmitStdInitializerListCleanup(loc, cast<InitListExpr>(init));
1283  }
1284}
1285
1286static void EmitRecursiveStdInitializerListCleanup(CodeGenFunction &CGF,
1287                                                   llvm::Value *arrayStart,
1288                                                   const InitListExpr *init) {
1289  // Check if there are any recursive cleanups to do, i.e. if we have
1290  //   std::initializer_list<std::initializer_list<obj>> list = {{obj()}};
1291  // then we need to destroy the inner array as well.
1292  for (unsigned i = 0, e = init->getNumInits(); i != e; ++i) {
1293    const InitListExpr *subInit = dyn_cast<InitListExpr>(init->getInit(i));
1294    if (!subInit || !subInit->initializesStdInitializerList())
1295      continue;
1296
1297    // This one needs to be destroyed. Get the address of the std::init_list.
1298    llvm::Value *offset = llvm::ConstantInt::get(CGF.SizeTy, i);
1299    llvm::Value *loc = CGF.Builder.CreateInBoundsGEP(arrayStart, offset,
1300                                                 "std.initlist");
1301    CGF.EmitStdInitializerListCleanup(loc, subInit);
1302  }
1303}
1304
1305void CodeGenFunction::EmitStdInitializerListCleanup(llvm::Value *loc,
1306                                                    const InitListExpr *init) {
1307  ASTContext &ctx = getContext();
1308  QualType element = GetStdInitializerListElementType(init->getType());
1309  unsigned numInits = init->getNumInits();
1310  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
1311  QualType array =ctx.getConstantArrayType(element, size, ArrayType::Normal, 0);
1312  QualType arrayPtr = ctx.getPointerType(array);
1313  llvm::Type *arrayPtrType = ConvertType(arrayPtr);
1314
1315  // lvalue is the location of a std::initializer_list, which as its first
1316  // element has a pointer to the array we want to destroy.
1317  llvm::Value *startPointer = Builder.CreateStructGEP(loc, 0, "startPointer");
1318  llvm::Value *startAddress = Builder.CreateLoad(startPointer, "startAddress");
1319
1320  ::EmitRecursiveStdInitializerListCleanup(*this, startAddress, init);
1321
1322  llvm::Value *arrayAddress =
1323      Builder.CreateBitCast(startAddress, arrayPtrType, "arrayAddress");
1324  ::EmitStdInitializerListCleanup(*this, array, arrayAddress, init);
1325}
1326