CGExprAgg.cpp revision 32cf1f27ae8620e7b79bb4e81a067187c0aab7ae 
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(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(InitListExpr *initList) {
307  // We emit an array containing the elements, then have the init list point
308  // at the array.
309  ASTContext &ctx = CGF.getContext();
310  unsigned numInits = initList->getNumInits();
311  QualType element = GetStdInitializerListElementType(initList->getType());
312  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
313  QualType array = ctx.getConstantArrayType(element, size, ArrayType::Normal,0);
314  llvm::Type *LTy = CGF.ConvertTypeForMem(array);
315  llvm::AllocaInst *alloc = CGF.CreateTempAlloca(LTy);
316  alloc->setAlignment(ctx.getTypeAlignInChars(array).getQuantity());
317  alloc->setName(".initlist.");
318
319  EmitArrayInit(alloc, cast<llvm::ArrayType>(LTy), element, initList);
320
321  // FIXME: The diagnostics are somewhat out of place here.
322  RecordDecl *record = initList->getType()->castAs<RecordType>()->getDecl();
323  RecordDecl::field_iterator field = record->field_begin();
324  if (field == record->field_end()) {
325    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
326  }
327
328  QualType elementPtr = ctx.getPointerType(element.withConst());
329  llvm::Value *destPtr = Dest.getAddr();
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    LValue elementLV = CGF.MakeAddrLValue(element, elementType);
420    EmitInitializationToLValue(E->getInit(i), elementLV);
421  }
422
423  // Check whether there's a non-trivial array-fill expression.
424  // Note that this will be a CXXConstructExpr even if the element
425  // type is an array (or array of array, etc.) of class type.
426  Expr *filler = E->getArrayFiller();
427  bool hasTrivialFiller = true;
428  if (CXXConstructExpr *cons = dyn_cast_or_null<CXXConstructExpr>(filler)) {
429    assert(cons->getConstructor()->isDefaultConstructor());
430    hasTrivialFiller = cons->getConstructor()->isTrivial();
431  }
432
433  // Any remaining elements need to be zero-initialized, possibly
434  // using the filler expression.  We can skip this if the we're
435  // emitting to zeroed memory.
436  if (NumInitElements != NumArrayElements &&
437      !(Dest.isZeroed() && hasTrivialFiller &&
438        CGF.getTypes().isZeroInitializable(elementType))) {
439
440    // Use an actual loop.  This is basically
441    //   do { *array++ = filler; } while (array != end);
442
443    // Advance to the start of the rest of the array.
444    if (NumInitElements) {
445      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
446      if (endOfInit) Builder.CreateStore(element, endOfInit);
447    }
448
449    // Compute the end of the array.
450    llvm::Value *end = Builder.CreateInBoundsGEP(begin,
451                      llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
452                                                 "arrayinit.end");
453
454    llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
455    llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
456
457    // Jump into the body.
458    CGF.EmitBlock(bodyBB);
459    llvm::PHINode *currentElement =
460      Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
461    currentElement->addIncoming(element, entryBB);
462
463    // Emit the actual filler expression.
464    LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
465    if (filler)
466      EmitInitializationToLValue(filler, elementLV);
467    else
468      EmitNullInitializationToLValue(elementLV);
469
470    // Move on to the next element.
471    llvm::Value *nextElement =
472      Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
473
474    // Tell the EH cleanup that we finished with the last element.
475    if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
476
477    // Leave the loop if we're done.
478    llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
479                                             "arrayinit.done");
480    llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
481    Builder.CreateCondBr(done, endBB, bodyBB);
482    currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
483
484    CGF.EmitBlock(endBB);
485  }
486
487  // Leave the partial-array cleanup if we entered one.
488  if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
489}
490
491//===----------------------------------------------------------------------===//
492//                            Visitor Methods
493//===----------------------------------------------------------------------===//
494
495void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
496  Visit(E->GetTemporaryExpr());
497}
498
499void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
500  EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
501}
502
503void
504AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
505  if (E->getType().isPODType(CGF.getContext())) {
506    // For a POD type, just emit a load of the lvalue + a copy, because our
507    // compound literal might alias the destination.
508    // FIXME: This is a band-aid; the real problem appears to be in our handling
509    // of assignments, where we store directly into the LHS without checking
510    // whether anything in the RHS aliases.
511    EmitAggLoadOfLValue(E);
512    return;
513  }
514
515  AggValueSlot Slot = EnsureSlot(E->getType());
516  CGF.EmitAggExpr(E->getInitializer(), Slot);
517}
518
519
520void AggExprEmitter::VisitCastExpr(CastExpr *E) {
521  switch (E->getCastKind()) {
522  case CK_Dynamic: {
523    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
524    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
525    // FIXME: Do we also need to handle property references here?
526    if (LV.isSimple())
527      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
528    else
529      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
530
531    if (!Dest.isIgnored())
532      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
533    break;
534  }
535
536  case CK_ToUnion: {
537    if (Dest.isIgnored()) break;
538
539    // GCC union extension
540    QualType Ty = E->getSubExpr()->getType();
541    QualType PtrTy = CGF.getContext().getPointerType(Ty);
542    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
543                                                 CGF.ConvertType(PtrTy));
544    EmitInitializationToLValue(E->getSubExpr(),
545                               CGF.MakeAddrLValue(CastPtr, Ty));
546    break;
547  }
548
549  case CK_DerivedToBase:
550  case CK_BaseToDerived:
551  case CK_UncheckedDerivedToBase: {
552    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
553                "should have been unpacked before we got here");
554  }
555
556  case CK_LValueToRValue: // hope for downstream optimization
557  case CK_NoOp:
558  case CK_AtomicToNonAtomic:
559  case CK_NonAtomicToAtomic:
560  case CK_UserDefinedConversion:
561  case CK_ConstructorConversion:
562    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
563                                                   E->getType()) &&
564           "Implicit cast types must be compatible");
565    Visit(E->getSubExpr());
566    break;
567
568  case CK_LValueBitCast:
569    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
570
571  case CK_Dependent:
572  case CK_BitCast:
573  case CK_ArrayToPointerDecay:
574  case CK_FunctionToPointerDecay:
575  case CK_NullToPointer:
576  case CK_NullToMemberPointer:
577  case CK_BaseToDerivedMemberPointer:
578  case CK_DerivedToBaseMemberPointer:
579  case CK_MemberPointerToBoolean:
580  case CK_ReinterpretMemberPointer:
581  case CK_IntegralToPointer:
582  case CK_PointerToIntegral:
583  case CK_PointerToBoolean:
584  case CK_ToVoid:
585  case CK_VectorSplat:
586  case CK_IntegralCast:
587  case CK_IntegralToBoolean:
588  case CK_IntegralToFloating:
589  case CK_FloatingToIntegral:
590  case CK_FloatingToBoolean:
591  case CK_FloatingCast:
592  case CK_CPointerToObjCPointerCast:
593  case CK_BlockPointerToObjCPointerCast:
594  case CK_AnyPointerToBlockPointerCast:
595  case CK_ObjCObjectLValueCast:
596  case CK_FloatingRealToComplex:
597  case CK_FloatingComplexToReal:
598  case CK_FloatingComplexToBoolean:
599  case CK_FloatingComplexCast:
600  case CK_FloatingComplexToIntegralComplex:
601  case CK_IntegralRealToComplex:
602  case CK_IntegralComplexToReal:
603  case CK_IntegralComplexToBoolean:
604  case CK_IntegralComplexCast:
605  case CK_IntegralComplexToFloatingComplex:
606  case CK_ARCProduceObject:
607  case CK_ARCConsumeObject:
608  case CK_ARCReclaimReturnedObject:
609  case CK_ARCExtendBlockObject:
610    llvm_unreachable("cast kind invalid for aggregate types");
611  }
612}
613
614void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
615  if (E->getCallReturnType()->isReferenceType()) {
616    EmitAggLoadOfLValue(E);
617    return;
618  }
619
620  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
621  EmitMoveFromReturnSlot(E, RV);
622}
623
624void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
625  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
626  EmitMoveFromReturnSlot(E, RV);
627}
628
629void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
630  CGF.EmitIgnoredExpr(E->getLHS());
631  Visit(E->getRHS());
632}
633
634void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
635  CodeGenFunction::StmtExprEvaluation eval(CGF);
636  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
637}
638
639void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
640  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
641    VisitPointerToDataMemberBinaryOperator(E);
642  else
643    CGF.ErrorUnsupported(E, "aggregate binary expression");
644}
645
646void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
647                                                    const BinaryOperator *E) {
648  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
649  EmitFinalDestCopy(E, LV);
650}
651
652void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
653  // For an assignment to work, the value on the right has
654  // to be compatible with the value on the left.
655  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
656                                                 E->getRHS()->getType())
657         && "Invalid assignment");
658
659  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
660    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
661      if (VD->hasAttr<BlocksAttr>() &&
662          E->getRHS()->HasSideEffects(CGF.getContext())) {
663        // When __block variable on LHS, the RHS must be evaluated first
664        // as it may change the 'forwarding' field via call to Block_copy.
665        LValue RHS = CGF.EmitLValue(E->getRHS());
666        LValue LHS = CGF.EmitLValue(E->getLHS());
667        Dest = AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
668                                       needsGC(E->getLHS()->getType()),
669                                       AggValueSlot::IsAliased);
670        EmitFinalDestCopy(E, RHS, true);
671        return;
672      }
673
674  LValue LHS = CGF.EmitLValue(E->getLHS());
675
676  // Codegen the RHS so that it stores directly into the LHS.
677  AggValueSlot LHSSlot =
678    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
679                            needsGC(E->getLHS()->getType()),
680                            AggValueSlot::IsAliased);
681  CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
682  EmitFinalDestCopy(E, LHS, true);
683}
684
685void AggExprEmitter::
686VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
687  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
688  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
689  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
690
691  // Bind the common expression if necessary.
692  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
693
694  CodeGenFunction::ConditionalEvaluation eval(CGF);
695  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
696
697  // Save whether the destination's lifetime is externally managed.
698  bool isExternallyDestructed = Dest.isExternallyDestructed();
699
700  eval.begin(CGF);
701  CGF.EmitBlock(LHSBlock);
702  Visit(E->getTrueExpr());
703  eval.end(CGF);
704
705  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
706  CGF.Builder.CreateBr(ContBlock);
707
708  // If the result of an agg expression is unused, then the emission
709  // of the LHS might need to create a destination slot.  That's fine
710  // with us, and we can safely emit the RHS into the same slot, but
711  // we shouldn't claim that it's already being destructed.
712  Dest.setExternallyDestructed(isExternallyDestructed);
713
714  eval.begin(CGF);
715  CGF.EmitBlock(RHSBlock);
716  Visit(E->getFalseExpr());
717  eval.end(CGF);
718
719  CGF.EmitBlock(ContBlock);
720}
721
722void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
723  Visit(CE->getChosenSubExpr(CGF.getContext()));
724}
725
726void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
727  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
728  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
729
730  if (!ArgPtr) {
731    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
732    return;
733  }
734
735  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
736}
737
738void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
739  // Ensure that we have a slot, but if we already do, remember
740  // whether it was externally destructed.
741  bool wasExternallyDestructed = Dest.isExternallyDestructed();
742  Dest = EnsureSlot(E->getType());
743
744  // We're going to push a destructor if there isn't already one.
745  Dest.setExternallyDestructed();
746
747  Visit(E->getSubExpr());
748
749  // Push that destructor we promised.
750  if (!wasExternallyDestructed)
751    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
752}
753
754void
755AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
756  AggValueSlot Slot = EnsureSlot(E->getType());
757  CGF.EmitCXXConstructExpr(E, Slot);
758}
759
760void
761AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
762  AggValueSlot Slot = EnsureSlot(E->getType());
763  CGF.EmitLambdaExpr(E, Slot);
764}
765
766void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
767  CGF.enterFullExpression(E);
768  CodeGenFunction::RunCleanupsScope cleanups(CGF);
769  Visit(E->getSubExpr());
770}
771
772void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
773  QualType T = E->getType();
774  AggValueSlot Slot = EnsureSlot(T);
775  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
776}
777
778void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
779  QualType T = E->getType();
780  AggValueSlot Slot = EnsureSlot(T);
781  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
782}
783
784/// isSimpleZero - If emitting this value will obviously just cause a store of
785/// zero to memory, return true.  This can return false if uncertain, so it just
786/// handles simple cases.
787static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
788  E = E->IgnoreParens();
789
790  // 0
791  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
792    return IL->getValue() == 0;
793  // +0.0
794  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
795    return FL->getValue().isPosZero();
796  // int()
797  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
798      CGF.getTypes().isZeroInitializable(E->getType()))
799    return true;
800  // (int*)0 - Null pointer expressions.
801  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
802    return ICE->getCastKind() == CK_NullToPointer;
803  // '\0'
804  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
805    return CL->getValue() == 0;
806
807  // Otherwise, hard case: conservatively return false.
808  return false;
809}
810
811
812void
813AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
814  QualType type = LV.getType();
815  // FIXME: Ignore result?
816  // FIXME: Are initializers affected by volatile?
817  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
818    // Storing "i32 0" to a zero'd memory location is a noop.
819  } else if (isa<ImplicitValueInitExpr>(E)) {
820    EmitNullInitializationToLValue(LV);
821  } else if (type->isReferenceType()) {
822    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
823    CGF.EmitStoreThroughLValue(RV, LV);
824  } else if (type->isAnyComplexType()) {
825    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
826  } else if (CGF.hasAggregateLLVMType(type)) {
827    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
828                                               AggValueSlot::IsDestructed,
829                                      AggValueSlot::DoesNotNeedGCBarriers,
830                                               AggValueSlot::IsNotAliased,
831                                               Dest.isZeroed()));
832  } else if (LV.isSimple()) {
833    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
834  } else {
835    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
836  }
837}
838
839void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
840  QualType type = lv.getType();
841
842  // If the destination slot is already zeroed out before the aggregate is
843  // copied into it, we don't have to emit any zeros here.
844  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
845    return;
846
847  if (!CGF.hasAggregateLLVMType(type)) {
848    // For non-aggregates, we can store zero
849    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
850    CGF.EmitStoreThroughLValue(RValue::get(null), lv);
851  } else {
852    // There's a potential optimization opportunity in combining
853    // memsets; that would be easy for arrays, but relatively
854    // difficult for structures with the current code.
855    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
856  }
857}
858
859void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
860#if 0
861  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
862  // (Length of globals? Chunks of zeroed-out space?).
863  //
864  // If we can, prefer a copy from a global; this is a lot less code for long
865  // globals, and it's easier for the current optimizers to analyze.
866  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
867    llvm::GlobalVariable* GV =
868    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
869                             llvm::GlobalValue::InternalLinkage, C, "");
870    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
871    return;
872  }
873#endif
874  if (E->hadArrayRangeDesignator())
875    CGF.ErrorUnsupported(E, "GNU array range designator extension");
876
877  if (E->initializesStdInitializerList()) {
878    EmitStdInitializerList(E);
879    return;
880  }
881
882  llvm::Value *DestPtr = Dest.getAddr();
883
884  // Handle initialization of an array.
885  if (E->getType()->isArrayType()) {
886    if (E->getNumInits() > 0) {
887      QualType T1 = E->getType();
888      QualType T2 = E->getInit(0)->getType();
889      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
890        EmitAggLoadOfLValue(E->getInit(0));
891        return;
892      }
893    }
894
895    QualType elementType = E->getType().getCanonicalType();
896    elementType = CGF.getContext().getQualifiedType(
897                    cast<ArrayType>(elementType)->getElementType(),
898                    elementType.getQualifiers() + Dest.getQualifiers());
899
900    llvm::PointerType *APType =
901      cast<llvm::PointerType>(DestPtr->getType());
902    llvm::ArrayType *AType =
903      cast<llvm::ArrayType>(APType->getElementType());
904
905    EmitArrayInit(DestPtr, AType, elementType, E);
906    return;
907  }
908
909  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
910
911  // Do struct initialization; this code just sets each individual member
912  // to the approprate value.  This makes bitfield support automatic;
913  // the disadvantage is that the generated code is more difficult for
914  // the optimizer, especially with bitfields.
915  unsigned NumInitElements = E->getNumInits();
916  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
917
918  if (record->isUnion()) {
919    // Only initialize one field of a union. The field itself is
920    // specified by the initializer list.
921    if (!E->getInitializedFieldInUnion()) {
922      // Empty union; we have nothing to do.
923
924#ifndef NDEBUG
925      // Make sure that it's really an empty and not a failure of
926      // semantic analysis.
927      for (RecordDecl::field_iterator Field = record->field_begin(),
928                                   FieldEnd = record->field_end();
929           Field != FieldEnd; ++Field)
930        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
931#endif
932      return;
933    }
934
935    // FIXME: volatility
936    FieldDecl *Field = E->getInitializedFieldInUnion();
937
938    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
939    if (NumInitElements) {
940      // Store the initializer into the field
941      EmitInitializationToLValue(E->getInit(0), FieldLoc);
942    } else {
943      // Default-initialize to null.
944      EmitNullInitializationToLValue(FieldLoc);
945    }
946
947    return;
948  }
949
950  // We'll need to enter cleanup scopes in case any of the member
951  // initializers throw an exception.
952  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
953  llvm::Instruction *cleanupDominator = 0;
954
955  // Here we iterate over the fields; this makes it simpler to both
956  // default-initialize fields and skip over unnamed fields.
957  unsigned curInitIndex = 0;
958  for (RecordDecl::field_iterator field = record->field_begin(),
959                               fieldEnd = record->field_end();
960       field != fieldEnd; ++field) {
961    // We're done once we hit the flexible array member.
962    if (field->getType()->isIncompleteArrayType())
963      break;
964
965    // Always skip anonymous bitfields.
966    if (field->isUnnamedBitfield())
967      continue;
968
969    // We're done if we reach the end of the explicit initializers, we
970    // have a zeroed object, and the rest of the fields are
971    // zero-initializable.
972    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
973        CGF.getTypes().isZeroInitializable(E->getType()))
974      break;
975
976    // FIXME: volatility
977    LValue LV = CGF.EmitLValueForFieldInitialization(DestPtr, *field, 0);
978    // We never generate write-barries for initialized fields.
979    LV.setNonGC(true);
980
981    if (curInitIndex < NumInitElements) {
982      // Store the initializer into the field.
983      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
984    } else {
985      // We're out of initalizers; default-initialize to null
986      EmitNullInitializationToLValue(LV);
987    }
988
989    // Push a destructor if necessary.
990    // FIXME: if we have an array of structures, all explicitly
991    // initialized, we can end up pushing a linear number of cleanups.
992    bool pushedCleanup = false;
993    if (QualType::DestructionKind dtorKind
994          = field->getType().isDestructedType()) {
995      assert(LV.isSimple());
996      if (CGF.needsEHCleanup(dtorKind)) {
997        if (!cleanupDominator)
998          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
999
1000        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1001                        CGF.getDestroyer(dtorKind), false);
1002        cleanups.push_back(CGF.EHStack.stable_begin());
1003        pushedCleanup = true;
1004      }
1005    }
1006
1007    // If the GEP didn't get used because of a dead zero init or something
1008    // else, clean it up for -O0 builds and general tidiness.
1009    if (!pushedCleanup && LV.isSimple())
1010      if (llvm::GetElementPtrInst *GEP =
1011            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
1012        if (GEP->use_empty())
1013          GEP->eraseFromParent();
1014  }
1015
1016  // Deactivate all the partial cleanups in reverse order, which
1017  // generally means popping them.
1018  for (unsigned i = cleanups.size(); i != 0; --i)
1019    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1020
1021  // Destroy the placeholder if we made one.
1022  if (cleanupDominator)
1023    cleanupDominator->eraseFromParent();
1024}
1025
1026//===----------------------------------------------------------------------===//
1027//                        Entry Points into this File
1028//===----------------------------------------------------------------------===//
1029
1030/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1031/// non-zero bytes that will be stored when outputting the initializer for the
1032/// specified initializer expression.
1033static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1034  E = E->IgnoreParens();
1035
1036  // 0 and 0.0 won't require any non-zero stores!
1037  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1038
1039  // If this is an initlist expr, sum up the size of sizes of the (present)
1040  // elements.  If this is something weird, assume the whole thing is non-zero.
1041  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1042  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1043    return CGF.getContext().getTypeSizeInChars(E->getType());
1044
1045  // InitListExprs for structs have to be handled carefully.  If there are
1046  // reference members, we need to consider the size of the reference, not the
1047  // referencee.  InitListExprs for unions and arrays can't have references.
1048  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1049    if (!RT->isUnionType()) {
1050      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1051      CharUnits NumNonZeroBytes = CharUnits::Zero();
1052
1053      unsigned ILEElement = 0;
1054      for (RecordDecl::field_iterator Field = SD->field_begin(),
1055           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
1056        // We're done once we hit the flexible array member or run out of
1057        // InitListExpr elements.
1058        if (Field->getType()->isIncompleteArrayType() ||
1059            ILEElement == ILE->getNumInits())
1060          break;
1061        if (Field->isUnnamedBitfield())
1062          continue;
1063
1064        const Expr *E = ILE->getInit(ILEElement++);
1065
1066        // Reference values are always non-null and have the width of a pointer.
1067        if (Field->getType()->isReferenceType())
1068          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1069              CGF.getContext().getTargetInfo().getPointerWidth(0));
1070        else
1071          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1072      }
1073
1074      return NumNonZeroBytes;
1075    }
1076  }
1077
1078
1079  CharUnits NumNonZeroBytes = CharUnits::Zero();
1080  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1081    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1082  return NumNonZeroBytes;
1083}
1084
1085/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1086/// zeros in it, emit a memset and avoid storing the individual zeros.
1087///
1088static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1089                                     CodeGenFunction &CGF) {
1090  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1091  // volatile stores.
1092  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
1093
1094  // C++ objects with a user-declared constructor don't need zero'ing.
1095  if (CGF.getContext().getLangOptions().CPlusPlus)
1096    if (const RecordType *RT = CGF.getContext()
1097                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1098      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1099      if (RD->hasUserDeclaredConstructor())
1100        return;
1101    }
1102
1103  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1104  std::pair<CharUnits, CharUnits> TypeInfo =
1105    CGF.getContext().getTypeInfoInChars(E->getType());
1106  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1107    return;
1108
1109  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1110  // we prefer to emit memset + individual stores for the rest.
1111  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1112  if (NumNonZeroBytes*4 > TypeInfo.first)
1113    return;
1114
1115  // Okay, it seems like a good idea to use an initial memset, emit the call.
1116  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1117  CharUnits Align = TypeInfo.second;
1118
1119  llvm::Value *Loc = Slot.getAddr();
1120
1121  Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
1122  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1123                           Align.getQuantity(), false);
1124
1125  // Tell the AggExprEmitter that the slot is known zero.
1126  Slot.setZeroed();
1127}
1128
1129
1130
1131
1132/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1133/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1134/// the value of the aggregate expression is not needed.  If VolatileDest is
1135/// true, DestPtr cannot be 0.
1136///
1137/// \param IsInitializer - true if this evaluation is initializing an
1138/// object whose lifetime is already being managed.
1139void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
1140                                  bool IgnoreResult) {
1141  assert(E && hasAggregateLLVMType(E->getType()) &&
1142         "Invalid aggregate expression to emit");
1143  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1144         "slot has bits but no address");
1145
1146  // Optimize the slot if possible.
1147  CheckAggExprForMemSetUse(Slot, E, *this);
1148
1149  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
1150}
1151
1152LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1153  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1154  llvm::Value *Temp = CreateMemTemp(E->getType());
1155  LValue LV = MakeAddrLValue(Temp, E->getType());
1156  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1157                                         AggValueSlot::DoesNotNeedGCBarriers,
1158                                         AggValueSlot::IsNotAliased));
1159  return LV;
1160}
1161
1162void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1163                                        llvm::Value *SrcPtr, QualType Ty,
1164                                        bool isVolatile, unsigned Alignment) {
1165  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1166
1167  if (getContext().getLangOptions().CPlusPlus) {
1168    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1169      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1170      assert((Record->hasTrivialCopyConstructor() ||
1171              Record->hasTrivialCopyAssignment() ||
1172              Record->hasTrivialMoveConstructor() ||
1173              Record->hasTrivialMoveAssignment()) &&
1174             "Trying to aggregate-copy a type without a trivial copy "
1175             "constructor or assignment operator");
1176      // Ignore empty classes in C++.
1177      if (Record->isEmpty())
1178        return;
1179    }
1180  }
1181
1182  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1183  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1184  // read from another object that overlaps in anyway the storage of the first
1185  // object, then the overlap shall be exact and the two objects shall have
1186  // qualified or unqualified versions of a compatible type."
1187  //
1188  // memcpy is not defined if the source and destination pointers are exactly
1189  // equal, but other compilers do this optimization, and almost every memcpy
1190  // implementation handles this case safely.  If there is a libc that does not
1191  // safely handle this, we can add a target hook.
1192
1193  // Get size and alignment info for this aggregate.
1194  std::pair<CharUnits, CharUnits> TypeInfo =
1195    getContext().getTypeInfoInChars(Ty);
1196
1197  if (!Alignment)
1198    Alignment = TypeInfo.second.getQuantity();
1199
1200  // FIXME: Handle variable sized types.
1201
1202  // FIXME: If we have a volatile struct, the optimizer can remove what might
1203  // appear to be `extra' memory ops:
1204  //
1205  // volatile struct { int i; } a, b;
1206  //
1207  // int main() {
1208  //   a = b;
1209  //   a = b;
1210  // }
1211  //
1212  // we need to use a different call here.  We use isVolatile to indicate when
1213  // either the source or the destination is volatile.
1214
1215  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1216  llvm::Type *DBP =
1217    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1218  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1219
1220  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1221  llvm::Type *SBP =
1222    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1223  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1224
1225  // Don't do any of the memmove_collectable tests if GC isn't set.
1226  if (CGM.getLangOptions().getGC() == LangOptions::NonGC) {
1227    // fall through
1228  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1229    RecordDecl *Record = RecordTy->getDecl();
1230    if (Record->hasObjectMember()) {
1231      CharUnits size = TypeInfo.first;
1232      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1233      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1234      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1235                                                    SizeVal);
1236      return;
1237    }
1238  } else if (Ty->isArrayType()) {
1239    QualType BaseType = getContext().getBaseElementType(Ty);
1240    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1241      if (RecordTy->getDecl()->hasObjectMember()) {
1242        CharUnits size = TypeInfo.first;
1243        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1244        llvm::Value *SizeVal =
1245          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1246        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1247                                                      SizeVal);
1248        return;
1249      }
1250    }
1251  }
1252
1253  Builder.CreateMemCpy(DestPtr, SrcPtr,
1254                       llvm::ConstantInt::get(IntPtrTy,
1255                                              TypeInfo.first.getQuantity()),
1256                       Alignment, isVolatile);
1257}
1258
1259void CodeGenFunction::MaybeEmitStdInitializerListCleanup(LValue lvalue,
1260                                                    const Expr *init) {
1261  const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(init);
1262  if (!cleanups)
1263    return; // Nothing interesting here.
1264  init = cleanups->getSubExpr();
1265
1266  if (isa<InitListExpr>(init) &&
1267      cast<InitListExpr>(init)->initializesStdInitializerList()) {
1268    // We initialized this std::initializer_list with an initializer list.
1269    // A backing array was created. Push a cleanup for it.
1270    EmitStdInitializerListCleanup(lvalue, cast<InitListExpr>(init));
1271  }
1272}
1273
1274void CodeGenFunction::EmitStdInitializerListCleanup(LValue lvalue,
1275                                                    const InitListExpr *init) {
1276  ASTContext &ctx = getContext();
1277  QualType element = GetStdInitializerListElementType(init->getType());
1278  unsigned numInits = init->getNumInits();
1279  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
1280  QualType array =ctx.getConstantArrayType(element, size, ArrayType::Normal, 0);
1281  QualType arrayPtr = ctx.getPointerType(array);
1282  llvm::Type *arrayPtrType = ConvertType(arrayPtr);
1283
1284  // lvalue is the location of a std::initializer_list, which as its first
1285  // element has a pointer to the array we want to destroy.
1286  llvm::Value *startPointer = Builder.CreateStructGEP(lvalue.getAddress(), 0,
1287                                                      "startPointer");
1288  llvm::Value *arrayAddress =
1289      Builder.CreateBitCast(startPointer, arrayPtrType, "arrayAddress");
1290
1291  ::EmitStdInitializerListCleanup(*this, array, arrayAddress, init);
1292}
1293