CGExprAgg.cpp revision af130fd78267ee9e2395b758a7d827b07ce317a0 
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    llvm_unreachable("cast kind invalid for aggregate types");
618  }
619}
620
621void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
622  if (E->getCallReturnType()->isReferenceType()) {
623    EmitAggLoadOfLValue(E);
624    return;
625  }
626
627  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
628  EmitMoveFromReturnSlot(E, RV);
629}
630
631void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
632  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
633  EmitMoveFromReturnSlot(E, RV);
634}
635
636void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
637  CGF.EmitIgnoredExpr(E->getLHS());
638  Visit(E->getRHS());
639}
640
641void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
642  CodeGenFunction::StmtExprEvaluation eval(CGF);
643  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
644}
645
646void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
647  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
648    VisitPointerToDataMemberBinaryOperator(E);
649  else
650    CGF.ErrorUnsupported(E, "aggregate binary expression");
651}
652
653void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
654                                                    const BinaryOperator *E) {
655  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
656  EmitFinalDestCopy(E, LV);
657}
658
659void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
660  // For an assignment to work, the value on the right has
661  // to be compatible with the value on the left.
662  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
663                                                 E->getRHS()->getType())
664         && "Invalid assignment");
665
666  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
667    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
668      if (VD->hasAttr<BlocksAttr>() &&
669          E->getRHS()->HasSideEffects(CGF.getContext())) {
670        // When __block variable on LHS, the RHS must be evaluated first
671        // as it may change the 'forwarding' field via call to Block_copy.
672        LValue RHS = CGF.EmitLValue(E->getRHS());
673        LValue LHS = CGF.EmitLValue(E->getLHS());
674        Dest = AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
675                                       needsGC(E->getLHS()->getType()),
676                                       AggValueSlot::IsAliased);
677        EmitFinalDestCopy(E, RHS, true);
678        return;
679      }
680
681  LValue LHS = CGF.EmitLValue(E->getLHS());
682
683  // Codegen the RHS so that it stores directly into the LHS.
684  AggValueSlot LHSSlot =
685    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
686                            needsGC(E->getLHS()->getType()),
687                            AggValueSlot::IsAliased);
688  CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
689  EmitFinalDestCopy(E, LHS, true);
690}
691
692void AggExprEmitter::
693VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
694  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
695  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
696  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
697
698  // Bind the common expression if necessary.
699  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
700
701  CodeGenFunction::ConditionalEvaluation eval(CGF);
702  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
703
704  // Save whether the destination's lifetime is externally managed.
705  bool isExternallyDestructed = Dest.isExternallyDestructed();
706
707  eval.begin(CGF);
708  CGF.EmitBlock(LHSBlock);
709  Visit(E->getTrueExpr());
710  eval.end(CGF);
711
712  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
713  CGF.Builder.CreateBr(ContBlock);
714
715  // If the result of an agg expression is unused, then the emission
716  // of the LHS might need to create a destination slot.  That's fine
717  // with us, and we can safely emit the RHS into the same slot, but
718  // we shouldn't claim that it's already being destructed.
719  Dest.setExternallyDestructed(isExternallyDestructed);
720
721  eval.begin(CGF);
722  CGF.EmitBlock(RHSBlock);
723  Visit(E->getFalseExpr());
724  eval.end(CGF);
725
726  CGF.EmitBlock(ContBlock);
727}
728
729void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
730  Visit(CE->getChosenSubExpr(CGF.getContext()));
731}
732
733void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
734  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
735  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
736
737  if (!ArgPtr) {
738    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
739    return;
740  }
741
742  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
743}
744
745void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
746  // Ensure that we have a slot, but if we already do, remember
747  // whether it was externally destructed.
748  bool wasExternallyDestructed = Dest.isExternallyDestructed();
749  Dest = EnsureSlot(E->getType());
750
751  // We're going to push a destructor if there isn't already one.
752  Dest.setExternallyDestructed();
753
754  Visit(E->getSubExpr());
755
756  // Push that destructor we promised.
757  if (!wasExternallyDestructed)
758    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
759}
760
761void
762AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
763  AggValueSlot Slot = EnsureSlot(E->getType());
764  CGF.EmitCXXConstructExpr(E, Slot);
765}
766
767void
768AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
769  AggValueSlot Slot = EnsureSlot(E->getType());
770  CGF.EmitLambdaExpr(E, Slot);
771}
772
773void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
774  CGF.enterFullExpression(E);
775  CodeGenFunction::RunCleanupsScope cleanups(CGF);
776  Visit(E->getSubExpr());
777}
778
779void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
780  QualType T = E->getType();
781  AggValueSlot Slot = EnsureSlot(T);
782  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
783}
784
785void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
786  QualType T = E->getType();
787  AggValueSlot Slot = EnsureSlot(T);
788  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
789}
790
791/// isSimpleZero - If emitting this value will obviously just cause a store of
792/// zero to memory, return true.  This can return false if uncertain, so it just
793/// handles simple cases.
794static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
795  E = E->IgnoreParens();
796
797  // 0
798  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
799    return IL->getValue() == 0;
800  // +0.0
801  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
802    return FL->getValue().isPosZero();
803  // int()
804  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
805      CGF.getTypes().isZeroInitializable(E->getType()))
806    return true;
807  // (int*)0 - Null pointer expressions.
808  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
809    return ICE->getCastKind() == CK_NullToPointer;
810  // '\0'
811  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
812    return CL->getValue() == 0;
813
814  // Otherwise, hard case: conservatively return false.
815  return false;
816}
817
818
819void
820AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
821  QualType type = LV.getType();
822  // FIXME: Ignore result?
823  // FIXME: Are initializers affected by volatile?
824  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
825    // Storing "i32 0" to a zero'd memory location is a noop.
826  } else if (isa<ImplicitValueInitExpr>(E)) {
827    EmitNullInitializationToLValue(LV);
828  } else if (type->isReferenceType()) {
829    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
830    CGF.EmitStoreThroughLValue(RV, LV);
831  } else if (type->isAnyComplexType()) {
832    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
833  } else if (CGF.hasAggregateLLVMType(type)) {
834    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
835                                               AggValueSlot::IsDestructed,
836                                      AggValueSlot::DoesNotNeedGCBarriers,
837                                               AggValueSlot::IsNotAliased,
838                                               Dest.isZeroed()));
839  } else if (LV.isSimple()) {
840    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
841  } else {
842    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
843  }
844}
845
846void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
847  QualType type = lv.getType();
848
849  // If the destination slot is already zeroed out before the aggregate is
850  // copied into it, we don't have to emit any zeros here.
851  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
852    return;
853
854  if (!CGF.hasAggregateLLVMType(type)) {
855    // For non-aggregates, we can store zero
856    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
857    CGF.EmitStoreThroughLValue(RValue::get(null), lv);
858  } else {
859    // There's a potential optimization opportunity in combining
860    // memsets; that would be easy for arrays, but relatively
861    // difficult for structures with the current code.
862    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
863  }
864}
865
866void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
867#if 0
868  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
869  // (Length of globals? Chunks of zeroed-out space?).
870  //
871  // If we can, prefer a copy from a global; this is a lot less code for long
872  // globals, and it's easier for the current optimizers to analyze.
873  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
874    llvm::GlobalVariable* GV =
875    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
876                             llvm::GlobalValue::InternalLinkage, C, "");
877    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
878    return;
879  }
880#endif
881  if (E->hadArrayRangeDesignator())
882    CGF.ErrorUnsupported(E, "GNU array range designator extension");
883
884  if (E->initializesStdInitializerList()) {
885    EmitStdInitializerList(Dest.getAddr(), E);
886    return;
887  }
888
889  llvm::Value *DestPtr = Dest.getAddr();
890
891  // Handle initialization of an array.
892  if (E->getType()->isArrayType()) {
893    if (E->getNumInits() > 0) {
894      QualType T1 = E->getType();
895      QualType T2 = E->getInit(0)->getType();
896      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
897        EmitAggLoadOfLValue(E->getInit(0));
898        return;
899      }
900    }
901
902    QualType elementType = E->getType().getCanonicalType();
903    elementType = CGF.getContext().getQualifiedType(
904                    cast<ArrayType>(elementType)->getElementType(),
905                    elementType.getQualifiers() + Dest.getQualifiers());
906
907    llvm::PointerType *APType =
908      cast<llvm::PointerType>(DestPtr->getType());
909    llvm::ArrayType *AType =
910      cast<llvm::ArrayType>(APType->getElementType());
911
912    EmitArrayInit(DestPtr, AType, elementType, E);
913    return;
914  }
915
916  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
917
918  // Do struct initialization; this code just sets each individual member
919  // to the approprate value.  This makes bitfield support automatic;
920  // the disadvantage is that the generated code is more difficult for
921  // the optimizer, especially with bitfields.
922  unsigned NumInitElements = E->getNumInits();
923  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
924
925  if (record->isUnion()) {
926    // Only initialize one field of a union. The field itself is
927    // specified by the initializer list.
928    if (!E->getInitializedFieldInUnion()) {
929      // Empty union; we have nothing to do.
930
931#ifndef NDEBUG
932      // Make sure that it's really an empty and not a failure of
933      // semantic analysis.
934      for (RecordDecl::field_iterator Field = record->field_begin(),
935                                   FieldEnd = record->field_end();
936           Field != FieldEnd; ++Field)
937        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
938#endif
939      return;
940    }
941
942    // FIXME: volatility
943    FieldDecl *Field = E->getInitializedFieldInUnion();
944
945    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
946    if (NumInitElements) {
947      // Store the initializer into the field
948      EmitInitializationToLValue(E->getInit(0), FieldLoc);
949    } else {
950      // Default-initialize to null.
951      EmitNullInitializationToLValue(FieldLoc);
952    }
953
954    return;
955  }
956
957  // We'll need to enter cleanup scopes in case any of the member
958  // initializers throw an exception.
959  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
960  llvm::Instruction *cleanupDominator = 0;
961
962  // Here we iterate over the fields; this makes it simpler to both
963  // default-initialize fields and skip over unnamed fields.
964  unsigned curInitIndex = 0;
965  for (RecordDecl::field_iterator field = record->field_begin(),
966                               fieldEnd = record->field_end();
967       field != fieldEnd; ++field) {
968    // We're done once we hit the flexible array member.
969    if (field->getType()->isIncompleteArrayType())
970      break;
971
972    // Always skip anonymous bitfields.
973    if (field->isUnnamedBitfield())
974      continue;
975
976    // We're done if we reach the end of the explicit initializers, we
977    // have a zeroed object, and the rest of the fields are
978    // zero-initializable.
979    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
980        CGF.getTypes().isZeroInitializable(E->getType()))
981      break;
982
983    // FIXME: volatility
984    LValue LV = CGF.EmitLValueForFieldInitialization(DestPtr, *field, 0);
985    // We never generate write-barries for initialized fields.
986    LV.setNonGC(true);
987
988    if (curInitIndex < NumInitElements) {
989      // Store the initializer into the field.
990      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
991    } else {
992      // We're out of initalizers; default-initialize to null
993      EmitNullInitializationToLValue(LV);
994    }
995
996    // Push a destructor if necessary.
997    // FIXME: if we have an array of structures, all explicitly
998    // initialized, we can end up pushing a linear number of cleanups.
999    bool pushedCleanup = false;
1000    if (QualType::DestructionKind dtorKind
1001          = field->getType().isDestructedType()) {
1002      assert(LV.isSimple());
1003      if (CGF.needsEHCleanup(dtorKind)) {
1004        if (!cleanupDominator)
1005          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
1006
1007        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1008                        CGF.getDestroyer(dtorKind), false);
1009        cleanups.push_back(CGF.EHStack.stable_begin());
1010        pushedCleanup = true;
1011      }
1012    }
1013
1014    // If the GEP didn't get used because of a dead zero init or something
1015    // else, clean it up for -O0 builds and general tidiness.
1016    if (!pushedCleanup && LV.isSimple())
1017      if (llvm::GetElementPtrInst *GEP =
1018            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
1019        if (GEP->use_empty())
1020          GEP->eraseFromParent();
1021  }
1022
1023  // Deactivate all the partial cleanups in reverse order, which
1024  // generally means popping them.
1025  for (unsigned i = cleanups.size(); i != 0; --i)
1026    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1027
1028  // Destroy the placeholder if we made one.
1029  if (cleanupDominator)
1030    cleanupDominator->eraseFromParent();
1031}
1032
1033//===----------------------------------------------------------------------===//
1034//                        Entry Points into this File
1035//===----------------------------------------------------------------------===//
1036
1037/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1038/// non-zero bytes that will be stored when outputting the initializer for the
1039/// specified initializer expression.
1040static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1041  E = E->IgnoreParens();
1042
1043  // 0 and 0.0 won't require any non-zero stores!
1044  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1045
1046  // If this is an initlist expr, sum up the size of sizes of the (present)
1047  // elements.  If this is something weird, assume the whole thing is non-zero.
1048  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1049  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1050    return CGF.getContext().getTypeSizeInChars(E->getType());
1051
1052  // InitListExprs for structs have to be handled carefully.  If there are
1053  // reference members, we need to consider the size of the reference, not the
1054  // referencee.  InitListExprs for unions and arrays can't have references.
1055  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1056    if (!RT->isUnionType()) {
1057      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1058      CharUnits NumNonZeroBytes = CharUnits::Zero();
1059
1060      unsigned ILEElement = 0;
1061      for (RecordDecl::field_iterator Field = SD->field_begin(),
1062           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
1063        // We're done once we hit the flexible array member or run out of
1064        // InitListExpr elements.
1065        if (Field->getType()->isIncompleteArrayType() ||
1066            ILEElement == ILE->getNumInits())
1067          break;
1068        if (Field->isUnnamedBitfield())
1069          continue;
1070
1071        const Expr *E = ILE->getInit(ILEElement++);
1072
1073        // Reference values are always non-null and have the width of a pointer.
1074        if (Field->getType()->isReferenceType())
1075          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1076              CGF.getContext().getTargetInfo().getPointerWidth(0));
1077        else
1078          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1079      }
1080
1081      return NumNonZeroBytes;
1082    }
1083  }
1084
1085
1086  CharUnits NumNonZeroBytes = CharUnits::Zero();
1087  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1088    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1089  return NumNonZeroBytes;
1090}
1091
1092/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1093/// zeros in it, emit a memset and avoid storing the individual zeros.
1094///
1095static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1096                                     CodeGenFunction &CGF) {
1097  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1098  // volatile stores.
1099  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
1100
1101  // C++ objects with a user-declared constructor don't need zero'ing.
1102  if (CGF.getContext().getLangOptions().CPlusPlus)
1103    if (const RecordType *RT = CGF.getContext()
1104                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1105      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1106      if (RD->hasUserDeclaredConstructor())
1107        return;
1108    }
1109
1110  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1111  std::pair<CharUnits, CharUnits> TypeInfo =
1112    CGF.getContext().getTypeInfoInChars(E->getType());
1113  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1114    return;
1115
1116  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1117  // we prefer to emit memset + individual stores for the rest.
1118  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1119  if (NumNonZeroBytes*4 > TypeInfo.first)
1120    return;
1121
1122  // Okay, it seems like a good idea to use an initial memset, emit the call.
1123  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1124  CharUnits Align = TypeInfo.second;
1125
1126  llvm::Value *Loc = Slot.getAddr();
1127
1128  Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
1129  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1130                           Align.getQuantity(), false);
1131
1132  // Tell the AggExprEmitter that the slot is known zero.
1133  Slot.setZeroed();
1134}
1135
1136
1137
1138
1139/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1140/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1141/// the value of the aggregate expression is not needed.  If VolatileDest is
1142/// true, DestPtr cannot be 0.
1143///
1144/// \param IsInitializer - true if this evaluation is initializing an
1145/// object whose lifetime is already being managed.
1146void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
1147                                  bool IgnoreResult) {
1148  assert(E && hasAggregateLLVMType(E->getType()) &&
1149         "Invalid aggregate expression to emit");
1150  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1151         "slot has bits but no address");
1152
1153  // Optimize the slot if possible.
1154  CheckAggExprForMemSetUse(Slot, E, *this);
1155
1156  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
1157}
1158
1159LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1160  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1161  llvm::Value *Temp = CreateMemTemp(E->getType());
1162  LValue LV = MakeAddrLValue(Temp, E->getType());
1163  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1164                                         AggValueSlot::DoesNotNeedGCBarriers,
1165                                         AggValueSlot::IsNotAliased));
1166  return LV;
1167}
1168
1169void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1170                                        llvm::Value *SrcPtr, QualType Ty,
1171                                        bool isVolatile, unsigned Alignment) {
1172  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1173
1174  if (getContext().getLangOptions().CPlusPlus) {
1175    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1176      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1177      assert((Record->hasTrivialCopyConstructor() ||
1178              Record->hasTrivialCopyAssignment() ||
1179              Record->hasTrivialMoveConstructor() ||
1180              Record->hasTrivialMoveAssignment()) &&
1181             "Trying to aggregate-copy a type without a trivial copy "
1182             "constructor or assignment operator");
1183      // Ignore empty classes in C++.
1184      if (Record->isEmpty())
1185        return;
1186    }
1187  }
1188
1189  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1190  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1191  // read from another object that overlaps in anyway the storage of the first
1192  // object, then the overlap shall be exact and the two objects shall have
1193  // qualified or unqualified versions of a compatible type."
1194  //
1195  // memcpy is not defined if the source and destination pointers are exactly
1196  // equal, but other compilers do this optimization, and almost every memcpy
1197  // implementation handles this case safely.  If there is a libc that does not
1198  // safely handle this, we can add a target hook.
1199
1200  // Get size and alignment info for this aggregate.
1201  std::pair<CharUnits, CharUnits> TypeInfo =
1202    getContext().getTypeInfoInChars(Ty);
1203
1204  if (!Alignment)
1205    Alignment = TypeInfo.second.getQuantity();
1206
1207  // FIXME: Handle variable sized types.
1208
1209  // FIXME: If we have a volatile struct, the optimizer can remove what might
1210  // appear to be `extra' memory ops:
1211  //
1212  // volatile struct { int i; } a, b;
1213  //
1214  // int main() {
1215  //   a = b;
1216  //   a = b;
1217  // }
1218  //
1219  // we need to use a different call here.  We use isVolatile to indicate when
1220  // either the source or the destination is volatile.
1221
1222  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1223  llvm::Type *DBP =
1224    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1225  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1226
1227  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1228  llvm::Type *SBP =
1229    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1230  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1231
1232  // Don't do any of the memmove_collectable tests if GC isn't set.
1233  if (CGM.getLangOptions().getGC() == LangOptions::NonGC) {
1234    // fall through
1235  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1236    RecordDecl *Record = RecordTy->getDecl();
1237    if (Record->hasObjectMember()) {
1238      CharUnits size = TypeInfo.first;
1239      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1240      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1241      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1242                                                    SizeVal);
1243      return;
1244    }
1245  } else if (Ty->isArrayType()) {
1246    QualType BaseType = getContext().getBaseElementType(Ty);
1247    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1248      if (RecordTy->getDecl()->hasObjectMember()) {
1249        CharUnits size = TypeInfo.first;
1250        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1251        llvm::Value *SizeVal =
1252          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1253        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1254                                                      SizeVal);
1255        return;
1256      }
1257    }
1258  }
1259
1260  Builder.CreateMemCpy(DestPtr, SrcPtr,
1261                       llvm::ConstantInt::get(IntPtrTy,
1262                                              TypeInfo.first.getQuantity()),
1263                       Alignment, isVolatile);
1264}
1265
1266void CodeGenFunction::MaybeEmitStdInitializerListCleanup(LValue lvalue,
1267                                                    const Expr *init) {
1268  const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(init);
1269  if (!cleanups)
1270    return; // Nothing interesting here.
1271  init = cleanups->getSubExpr();
1272
1273  if (isa<InitListExpr>(init) &&
1274      cast<InitListExpr>(init)->initializesStdInitializerList()) {
1275    // We initialized this std::initializer_list with an initializer list.
1276    // A backing array was created. Push a cleanup for it.
1277    EmitStdInitializerListCleanup(lvalue.getAddress(),
1278                                  cast<InitListExpr>(init));
1279  }
1280}
1281
1282static void EmitRecursiveStdInitializerListCleanup(CodeGenFunction &CGF,
1283                                                   llvm::Value *arrayStart,
1284                                                   const InitListExpr *init) {
1285  // Check if there are any recursive cleanups to do, i.e. if we have
1286  //   std::initializer_list<std::initializer_list<obj>> list = {{obj()}};
1287  // then we need to destroy the inner array as well.
1288  for (unsigned i = 0, e = init->getNumInits(); i != e; ++i) {
1289    const InitListExpr *subInit = dyn_cast<InitListExpr>(init->getInit(i));
1290    if (!subInit || !subInit->initializesStdInitializerList())
1291      continue;
1292
1293    // This one needs to be destroyed. Get the address of the std::init_list.
1294    llvm::Value *offset = llvm::ConstantInt::get(CGF.SizeTy, i);
1295    llvm::Value *loc = CGF.Builder.CreateInBoundsGEP(arrayStart, offset,
1296                                                 "std.initlist");
1297    CGF.EmitStdInitializerListCleanup(loc, subInit);
1298  }
1299}
1300
1301void CodeGenFunction::EmitStdInitializerListCleanup(llvm::Value *loc,
1302                                                    const InitListExpr *init) {
1303  ASTContext &ctx = getContext();
1304  QualType element = GetStdInitializerListElementType(init->getType());
1305  unsigned numInits = init->getNumInits();
1306  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
1307  QualType array =ctx.getConstantArrayType(element, size, ArrayType::Normal, 0);
1308  QualType arrayPtr = ctx.getPointerType(array);
1309  llvm::Type *arrayPtrType = ConvertType(arrayPtr);
1310
1311  // lvalue is the location of a std::initializer_list, which as its first
1312  // element has a pointer to the array we want to destroy.
1313  llvm::Value *startPointer = Builder.CreateStructGEP(loc, 0, "startPointer");
1314  llvm::Value *startAddress = Builder.CreateLoad(startPointer, "startAddress");
1315
1316  ::EmitRecursiveStdInitializerListCleanup(*this, startAddress, init);
1317
1318  llvm::Value *arrayAddress =
1319      Builder.CreateBitCast(startAddress, arrayPtrType, "arrayAddress");
1320  ::EmitStdInitializerListCleanup(*this, array, arrayAddress, init);
1321}
1322