CGExprAgg.cpp revision b22c7dc707cf3770ff3b5e5f11f11fd0aaa06d9b 
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
38  /// We want to use 'dest' as the return slot except under two
39  /// conditions:
40  ///   - The destination slot requires garbage collection, so we
41  ///     need to use the GC API.
42  ///   - The destination slot is potentially aliased.
43  bool shouldUseDestForReturnSlot() const {
44    return !(Dest.requiresGCollection() || Dest.isPotentiallyAliased());
45  }
46
47  ReturnValueSlot getReturnValueSlot() const {
48    if (!shouldUseDestForReturnSlot())
49      return ReturnValueSlot();
50
51    return ReturnValueSlot(Dest.getAddr(), Dest.isVolatile());
52  }
53
54  AggValueSlot EnsureSlot(QualType T) {
55    if (!Dest.isIgnored()) return Dest;
56    return CGF.CreateAggTemp(T, "agg.tmp.ensured");
57  }
58  void EnsureDest(QualType T) {
59    if (!Dest.isIgnored()) return;
60    Dest = CGF.CreateAggTemp(T, "agg.tmp.ensured");
61  }
62
63public:
64  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest)
65    : CGF(cgf), Builder(CGF.Builder), Dest(Dest) {
66  }
67
68  //===--------------------------------------------------------------------===//
69  //                               Utilities
70  //===--------------------------------------------------------------------===//
71
72  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
73  /// represents a value lvalue, this method emits the address of the lvalue,
74  /// then loads the result into DestPtr.
75  void EmitAggLoadOfLValue(const Expr *E);
76
77  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
78  void EmitFinalDestCopy(QualType type, const LValue &src);
79  void EmitFinalDestCopy(QualType type, RValue src,
80                         CharUnits srcAlignment = CharUnits::Zero());
81  void EmitCopy(QualType type, const AggValueSlot &dest,
82                const AggValueSlot &src);
83
84  void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
85
86  void EmitStdInitializerList(llvm::Value *DestPtr, InitListExpr *InitList);
87  void EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
88                     QualType elementType, InitListExpr *E);
89
90  AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
91    if (CGF.getLangOpts().getGC() && TypeRequiresGCollection(T))
92      return AggValueSlot::NeedsGCBarriers;
93    return AggValueSlot::DoesNotNeedGCBarriers;
94  }
95
96  bool TypeRequiresGCollection(QualType T);
97
98  //===--------------------------------------------------------------------===//
99  //                            Visitor Methods
100  //===--------------------------------------------------------------------===//
101
102  void VisitStmt(Stmt *S) {
103    CGF.ErrorUnsupported(S, "aggregate expression");
104  }
105  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
106  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
107    Visit(GE->getResultExpr());
108  }
109  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
110  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
111    return Visit(E->getReplacement());
112  }
113
114  // l-values.
115  void VisitDeclRefExpr(DeclRefExpr *E) {
116    // For aggregates, we should always be able to emit the variable
117    // as an l-value unless it's a reference.  This is due to the fact
118    // that we can't actually ever see a normal l2r conversion on an
119    // aggregate in C++, and in C there's no language standard
120    // actively preventing us from listing variables in the captures
121    // list of a block.
122    if (E->getDecl()->getType()->isReferenceType()) {
123      if (CodeGenFunction::ConstantEmission result
124            = CGF.tryEmitAsConstant(E)) {
125        EmitFinalDestCopy(E->getType(), result.getReferenceLValue(CGF, E));
126        return;
127      }
128    }
129
130    EmitAggLoadOfLValue(E);
131  }
132
133  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
134  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
135  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
136  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
137  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
138    EmitAggLoadOfLValue(E);
139  }
140  void VisitPredefinedExpr(const PredefinedExpr *E) {
141    EmitAggLoadOfLValue(E);
142  }
143
144  // Operators.
145  void VisitCastExpr(CastExpr *E);
146  void VisitCallExpr(const CallExpr *E);
147  void VisitStmtExpr(const StmtExpr *E);
148  void VisitBinaryOperator(const BinaryOperator *BO);
149  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
150  void VisitBinAssign(const BinaryOperator *E);
151  void VisitBinComma(const BinaryOperator *E);
152
153  void VisitObjCMessageExpr(ObjCMessageExpr *E);
154  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
155    EmitAggLoadOfLValue(E);
156  }
157
158  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
159  void VisitChooseExpr(const ChooseExpr *CE);
160  void VisitInitListExpr(InitListExpr *E);
161  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
162  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
163    Visit(DAE->getExpr());
164  }
165  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
166  void VisitCXXConstructExpr(const CXXConstructExpr *E);
167  void VisitLambdaExpr(LambdaExpr *E);
168  void VisitExprWithCleanups(ExprWithCleanups *E);
169  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
170  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
171  void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
172  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
173
174  void VisitPseudoObjectExpr(PseudoObjectExpr *E) {
175    if (E->isGLValue()) {
176      LValue LV = CGF.EmitPseudoObjectLValue(E);
177      return EmitFinalDestCopy(E->getType(), LV);
178    }
179
180    CGF.EmitPseudoObjectRValue(E, EnsureSlot(E->getType()));
181  }
182
183  void VisitVAArgExpr(VAArgExpr *E);
184
185  void EmitInitializationToLValue(Expr *E, LValue Address);
186  void EmitNullInitializationToLValue(LValue Address);
187  //  case Expr::ChooseExprClass:
188  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
189  void VisitAtomicExpr(AtomicExpr *E) {
190    CGF.EmitAtomicExpr(E, EnsureSlot(E->getType()).getAddr());
191  }
192};
193}  // end anonymous namespace.
194
195//===----------------------------------------------------------------------===//
196//                                Utilities
197//===----------------------------------------------------------------------===//
198
199/// EmitAggLoadOfLValue - Given an expression with aggregate type that
200/// represents a value lvalue, this method emits the address of the lvalue,
201/// then loads the result into DestPtr.
202void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
203  LValue LV = CGF.EmitLValue(E);
204  EmitFinalDestCopy(E->getType(), LV);
205}
206
207/// \brief True if the given aggregate type requires special GC API calls.
208bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
209  // Only record types have members that might require garbage collection.
210  const RecordType *RecordTy = T->getAs<RecordType>();
211  if (!RecordTy) return false;
212
213  // Don't mess with non-trivial C++ types.
214  RecordDecl *Record = RecordTy->getDecl();
215  if (isa<CXXRecordDecl>(Record) &&
216      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
217       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
218    return false;
219
220  // Check whether the type has an object member.
221  return Record->hasObjectMember();
222}
223
224/// \brief Perform the final move to DestPtr if for some reason
225/// getReturnValueSlot() didn't use it directly.
226///
227/// The idea is that you do something like this:
228///   RValue Result = EmitSomething(..., getReturnValueSlot());
229///   EmitMoveFromReturnSlot(E, Result);
230///
231/// If nothing interferes, this will cause the result to be emitted
232/// directly into the return value slot.  Otherwise, a final move
233/// will be performed.
234void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue src) {
235  if (shouldUseDestForReturnSlot()) {
236    // Logically, Dest.getAddr() should equal Src.getAggregateAddr().
237    // The possibility of undef rvalues complicates that a lot,
238    // though, so we can't really assert.
239    return;
240  }
241
242  // Otherwise, copy from there to the destination.
243  assert(Dest.getAddr() != src.getAggregateAddr());
244  std::pair<CharUnits, CharUnits> typeInfo =
245    CGF.getContext().getTypeInfoInChars(E->getType());
246  EmitFinalDestCopy(E->getType(), src, typeInfo.second);
247}
248
249/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
250void AggExprEmitter::EmitFinalDestCopy(QualType type, RValue src,
251                                       CharUnits srcAlign) {
252  assert(src.isAggregate() && "value must be aggregate value!");
253  LValue srcLV = CGF.MakeAddrLValue(src.getAggregateAddr(), type, srcAlign);
254  EmitFinalDestCopy(type, srcLV);
255}
256
257/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
258void AggExprEmitter::EmitFinalDestCopy(QualType type, const LValue &src) {
259  // If Dest is ignored, then we're evaluating an aggregate expression
260  // in a context that doesn't care about the result.  Note that loads
261  // from volatile l-values force the existence of a non-ignored
262  // destination.
263  if (Dest.isIgnored())
264    return;
265
266  AggValueSlot srcAgg =
267    AggValueSlot::forLValue(src, AggValueSlot::IsDestructed,
268                            needsGC(type), AggValueSlot::IsAliased);
269  EmitCopy(type, Dest, srcAgg);
270}
271
272/// Perform a copy from the source into the destination.
273///
274/// \param type - the type of the aggregate being copied; qualifiers are
275///   ignored
276void AggExprEmitter::EmitCopy(QualType type, const AggValueSlot &dest,
277                              const AggValueSlot &src) {
278  if (dest.requiresGCollection()) {
279    CharUnits sz = CGF.getContext().getTypeSizeInChars(type);
280    llvm::Value *size = llvm::ConstantInt::get(CGF.SizeTy, sz.getQuantity());
281    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
282                                                      dest.getAddr(),
283                                                      src.getAddr(),
284                                                      size);
285    return;
286  }
287
288  // If the result of the assignment is used, copy the LHS there also.
289  // It's volatile if either side is.  Use the minimum alignment of
290  // the two sides.
291  CGF.EmitAggregateCopy(dest.getAddr(), src.getAddr(), type,
292                        dest.isVolatile() || src.isVolatile(),
293                        std::min(dest.getAlignment(), src.getAlignment()));
294}
295
296static QualType GetStdInitializerListElementType(QualType T) {
297  // Just assume that this is really std::initializer_list.
298  ClassTemplateSpecializationDecl *specialization =
299      cast<ClassTemplateSpecializationDecl>(T->castAs<RecordType>()->getDecl());
300  return specialization->getTemplateArgs()[0].getAsType();
301}
302
303/// \brief Prepare cleanup for the temporary array.
304static void EmitStdInitializerListCleanup(CodeGenFunction &CGF,
305                                          QualType arrayType,
306                                          llvm::Value *addr,
307                                          const InitListExpr *initList) {
308  QualType::DestructionKind dtorKind = arrayType.isDestructedType();
309  if (!dtorKind)
310    return; // Type doesn't need destroying.
311  if (dtorKind != QualType::DK_cxx_destructor) {
312    CGF.ErrorUnsupported(initList, "ObjC ARC type in initializer_list");
313    return;
314  }
315
316  CodeGenFunction::Destroyer *destroyer = CGF.getDestroyer(dtorKind);
317  CGF.pushDestroy(NormalAndEHCleanup, addr, arrayType, destroyer,
318                  /*EHCleanup=*/true);
319}
320
321/// \brief Emit the initializer for a std::initializer_list initialized with a
322/// real initializer list.
323void AggExprEmitter::EmitStdInitializerList(llvm::Value *destPtr,
324                                            InitListExpr *initList) {
325  // We emit an array containing the elements, then have the init list point
326  // at the array.
327  ASTContext &ctx = CGF.getContext();
328  unsigned numInits = initList->getNumInits();
329  QualType element = GetStdInitializerListElementType(initList->getType());
330  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
331  QualType array = ctx.getConstantArrayType(element, size, ArrayType::Normal,0);
332  llvm::Type *LTy = CGF.ConvertTypeForMem(array);
333  llvm::AllocaInst *alloc = CGF.CreateTempAlloca(LTy);
334  alloc->setAlignment(ctx.getTypeAlignInChars(array).getQuantity());
335  alloc->setName(".initlist.");
336
337  EmitArrayInit(alloc, cast<llvm::ArrayType>(LTy), element, initList);
338
339  // FIXME: The diagnostics are somewhat out of place here.
340  RecordDecl *record = initList->getType()->castAs<RecordType>()->getDecl();
341  RecordDecl::field_iterator field = record->field_begin();
342  if (field == record->field_end()) {
343    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
344    return;
345  }
346
347  QualType elementPtr = ctx.getPointerType(element.withConst());
348
349  // Start pointer.
350  if (!ctx.hasSameType(field->getType(), elementPtr)) {
351    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
352    return;
353  }
354  LValue DestLV = CGF.MakeNaturalAlignAddrLValue(destPtr, initList->getType());
355  LValue start = CGF.EmitLValueForFieldInitialization(DestLV, *field);
356  llvm::Value *arrayStart = Builder.CreateStructGEP(alloc, 0, "arraystart");
357  CGF.EmitStoreThroughLValue(RValue::get(arrayStart), start);
358  ++field;
359
360  if (field == record->field_end()) {
361    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
362    return;
363  }
364  LValue endOrLength = CGF.EmitLValueForFieldInitialization(DestLV, *field);
365  if (ctx.hasSameType(field->getType(), elementPtr)) {
366    // End pointer.
367    llvm::Value *arrayEnd = Builder.CreateStructGEP(alloc,numInits, "arrayend");
368    CGF.EmitStoreThroughLValue(RValue::get(arrayEnd), endOrLength);
369  } else if(ctx.hasSameType(field->getType(), ctx.getSizeType())) {
370    // Length.
371    CGF.EmitStoreThroughLValue(RValue::get(Builder.getInt(size)), endOrLength);
372  } else {
373    CGF.ErrorUnsupported(initList, "weird std::initializer_list");
374    return;
375  }
376
377  if (!Dest.isExternallyDestructed())
378    EmitStdInitializerListCleanup(CGF, array, alloc, initList);
379}
380
381/// \brief Emit initialization of an array from an initializer list.
382void AggExprEmitter::EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
383                                   QualType elementType, InitListExpr *E) {
384  uint64_t NumInitElements = E->getNumInits();
385
386  uint64_t NumArrayElements = AType->getNumElements();
387  assert(NumInitElements <= NumArrayElements);
388
389  // DestPtr is an array*.  Construct an elementType* by drilling
390  // down a level.
391  llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
392  llvm::Value *indices[] = { zero, zero };
393  llvm::Value *begin =
394    Builder.CreateInBoundsGEP(DestPtr, indices, "arrayinit.begin");
395
396  // Exception safety requires us to destroy all the
397  // already-constructed members if an initializer throws.
398  // For that, we'll need an EH cleanup.
399  QualType::DestructionKind dtorKind = elementType.isDestructedType();
400  llvm::AllocaInst *endOfInit = 0;
401  EHScopeStack::stable_iterator cleanup;
402  llvm::Instruction *cleanupDominator = 0;
403  if (CGF.needsEHCleanup(dtorKind)) {
404    // In principle we could tell the cleanup where we are more
405    // directly, but the control flow can get so varied here that it
406    // would actually be quite complex.  Therefore we go through an
407    // alloca.
408    endOfInit = CGF.CreateTempAlloca(begin->getType(),
409                                     "arrayinit.endOfInit");
410    cleanupDominator = Builder.CreateStore(begin, endOfInit);
411    CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
412                                         CGF.getDestroyer(dtorKind));
413    cleanup = CGF.EHStack.stable_begin();
414
415  // Otherwise, remember that we didn't need a cleanup.
416  } else {
417    dtorKind = QualType::DK_none;
418  }
419
420  llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
421
422  // The 'current element to initialize'.  The invariants on this
423  // variable are complicated.  Essentially, after each iteration of
424  // the loop, it points to the last initialized element, except
425  // that it points to the beginning of the array before any
426  // elements have been initialized.
427  llvm::Value *element = begin;
428
429  // Emit the explicit initializers.
430  for (uint64_t i = 0; i != NumInitElements; ++i) {
431    // Advance to the next element.
432    if (i > 0) {
433      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
434
435      // Tell the cleanup that it needs to destroy up to this
436      // element.  TODO: some of these stores can be trivially
437      // observed to be unnecessary.
438      if (endOfInit) Builder.CreateStore(element, endOfInit);
439    }
440
441    // If these are nested std::initializer_list inits, do them directly,
442    // because they are conceptually the same "location".
443    InitListExpr *initList = dyn_cast<InitListExpr>(E->getInit(i));
444    if (initList && initList->initializesStdInitializerList()) {
445      EmitStdInitializerList(element, initList);
446    } else {
447      LValue elementLV = CGF.MakeAddrLValue(element, elementType);
448      EmitInitializationToLValue(E->getInit(i), elementLV);
449    }
450  }
451
452  // Check whether there's a non-trivial array-fill expression.
453  // Note that this will be a CXXConstructExpr even if the element
454  // type is an array (or array of array, etc.) of class type.
455  Expr *filler = E->getArrayFiller();
456  bool hasTrivialFiller = true;
457  if (CXXConstructExpr *cons = dyn_cast_or_null<CXXConstructExpr>(filler)) {
458    assert(cons->getConstructor()->isDefaultConstructor());
459    hasTrivialFiller = cons->getConstructor()->isTrivial();
460  }
461
462  // Any remaining elements need to be zero-initialized, possibly
463  // using the filler expression.  We can skip this if the we're
464  // emitting to zeroed memory.
465  if (NumInitElements != NumArrayElements &&
466      !(Dest.isZeroed() && hasTrivialFiller &&
467        CGF.getTypes().isZeroInitializable(elementType))) {
468
469    // Use an actual loop.  This is basically
470    //   do { *array++ = filler; } while (array != end);
471
472    // Advance to the start of the rest of the array.
473    if (NumInitElements) {
474      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
475      if (endOfInit) Builder.CreateStore(element, endOfInit);
476    }
477
478    // Compute the end of the array.
479    llvm::Value *end = Builder.CreateInBoundsGEP(begin,
480                      llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
481                                                 "arrayinit.end");
482
483    llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
484    llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
485
486    // Jump into the body.
487    CGF.EmitBlock(bodyBB);
488    llvm::PHINode *currentElement =
489      Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
490    currentElement->addIncoming(element, entryBB);
491
492    // Emit the actual filler expression.
493    LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
494    if (filler)
495      EmitInitializationToLValue(filler, elementLV);
496    else
497      EmitNullInitializationToLValue(elementLV);
498
499    // Move on to the next element.
500    llvm::Value *nextElement =
501      Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
502
503    // Tell the EH cleanup that we finished with the last element.
504    if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
505
506    // Leave the loop if we're done.
507    llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
508                                             "arrayinit.done");
509    llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
510    Builder.CreateCondBr(done, endBB, bodyBB);
511    currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
512
513    CGF.EmitBlock(endBB);
514  }
515
516  // Leave the partial-array cleanup if we entered one.
517  if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
518}
519
520//===----------------------------------------------------------------------===//
521//                            Visitor Methods
522//===----------------------------------------------------------------------===//
523
524void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
525  Visit(E->GetTemporaryExpr());
526}
527
528void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
529  EmitFinalDestCopy(e->getType(), CGF.getOpaqueLValueMapping(e));
530}
531
532void
533AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
534  if (E->getType().isPODType(CGF.getContext())) {
535    // For a POD type, just emit a load of the lvalue + a copy, because our
536    // compound literal might alias the destination.
537    // FIXME: This is a band-aid; the real problem appears to be in our handling
538    // of assignments, where we store directly into the LHS without checking
539    // whether anything in the RHS aliases.
540    EmitAggLoadOfLValue(E);
541    return;
542  }
543
544  AggValueSlot Slot = EnsureSlot(E->getType());
545  CGF.EmitAggExpr(E->getInitializer(), Slot);
546}
547
548
549void AggExprEmitter::VisitCastExpr(CastExpr *E) {
550  switch (E->getCastKind()) {
551  case CK_Dynamic: {
552    // FIXME: Can this actually happen? We have no test coverage for it.
553    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
554    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr(),
555                                      CodeGenFunction::TCK_Load);
556    // FIXME: Do we also need to handle property references here?
557    if (LV.isSimple())
558      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
559    else
560      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
561
562    if (!Dest.isIgnored())
563      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
564    break;
565  }
566
567  case CK_ToUnion: {
568    if (Dest.isIgnored()) break;
569
570    // GCC union extension
571    QualType Ty = E->getSubExpr()->getType();
572    QualType PtrTy = CGF.getContext().getPointerType(Ty);
573    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
574                                                 CGF.ConvertType(PtrTy));
575    EmitInitializationToLValue(E->getSubExpr(),
576                               CGF.MakeAddrLValue(CastPtr, Ty));
577    break;
578  }
579
580  case CK_DerivedToBase:
581  case CK_BaseToDerived:
582  case CK_UncheckedDerivedToBase: {
583    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
584                "should have been unpacked before we got here");
585  }
586
587  case CK_LValueToRValue:
588    // If we're loading from a volatile type, force the destination
589    // into existence.
590    if (E->getSubExpr()->getType().isVolatileQualified()) {
591      EnsureDest(E->getType());
592      return Visit(E->getSubExpr());
593    }
594    // fallthrough
595
596  case CK_NoOp:
597  case CK_AtomicToNonAtomic:
598  case CK_NonAtomicToAtomic:
599  case CK_UserDefinedConversion:
600  case CK_ConstructorConversion:
601    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
602                                                   E->getType()) &&
603           "Implicit cast types must be compatible");
604    Visit(E->getSubExpr());
605    break;
606
607  case CK_LValueBitCast:
608    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
609
610  case CK_Dependent:
611  case CK_BitCast:
612  case CK_ArrayToPointerDecay:
613  case CK_FunctionToPointerDecay:
614  case CK_NullToPointer:
615  case CK_NullToMemberPointer:
616  case CK_BaseToDerivedMemberPointer:
617  case CK_DerivedToBaseMemberPointer:
618  case CK_MemberPointerToBoolean:
619  case CK_ReinterpretMemberPointer:
620  case CK_IntegralToPointer:
621  case CK_PointerToIntegral:
622  case CK_PointerToBoolean:
623  case CK_ToVoid:
624  case CK_VectorSplat:
625  case CK_IntegralCast:
626  case CK_IntegralToBoolean:
627  case CK_IntegralToFloating:
628  case CK_FloatingToIntegral:
629  case CK_FloatingToBoolean:
630  case CK_FloatingCast:
631  case CK_CPointerToObjCPointerCast:
632  case CK_BlockPointerToObjCPointerCast:
633  case CK_AnyPointerToBlockPointerCast:
634  case CK_ObjCObjectLValueCast:
635  case CK_FloatingRealToComplex:
636  case CK_FloatingComplexToReal:
637  case CK_FloatingComplexToBoolean:
638  case CK_FloatingComplexCast:
639  case CK_FloatingComplexToIntegralComplex:
640  case CK_IntegralRealToComplex:
641  case CK_IntegralComplexToReal:
642  case CK_IntegralComplexToBoolean:
643  case CK_IntegralComplexCast:
644  case CK_IntegralComplexToFloatingComplex:
645  case CK_ARCProduceObject:
646  case CK_ARCConsumeObject:
647  case CK_ARCReclaimReturnedObject:
648  case CK_ARCExtendBlockObject:
649  case CK_CopyAndAutoreleaseBlockObject:
650  case CK_BuiltinFnToFnPtr:
651    llvm_unreachable("cast kind invalid for aggregate types");
652  }
653}
654
655void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
656  if (E->getCallReturnType()->isReferenceType()) {
657    EmitAggLoadOfLValue(E);
658    return;
659  }
660
661  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
662  EmitMoveFromReturnSlot(E, RV);
663}
664
665void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
666  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
667  EmitMoveFromReturnSlot(E, RV);
668}
669
670void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
671  CGF.EmitIgnoredExpr(E->getLHS());
672  Visit(E->getRHS());
673}
674
675void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
676  CodeGenFunction::StmtExprEvaluation eval(CGF);
677  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
678}
679
680void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
681  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
682    VisitPointerToDataMemberBinaryOperator(E);
683  else
684    CGF.ErrorUnsupported(E, "aggregate binary expression");
685}
686
687void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
688                                                    const BinaryOperator *E) {
689  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
690  EmitFinalDestCopy(E->getType(), LV);
691}
692
693/// Is the value of the given expression possibly a reference to or
694/// into a __block variable?
695static bool isBlockVarRef(const Expr *E) {
696  // Make sure we look through parens.
697  E = E->IgnoreParens();
698
699  // Check for a direct reference to a __block variable.
700  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
701    const VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
702    return (var && var->hasAttr<BlocksAttr>());
703  }
704
705  // More complicated stuff.
706
707  // Binary operators.
708  if (const BinaryOperator *op = dyn_cast<BinaryOperator>(E)) {
709    // For an assignment or pointer-to-member operation, just care
710    // about the LHS.
711    if (op->isAssignmentOp() || op->isPtrMemOp())
712      return isBlockVarRef(op->getLHS());
713
714    // For a comma, just care about the RHS.
715    if (op->getOpcode() == BO_Comma)
716      return isBlockVarRef(op->getRHS());
717
718    // FIXME: pointer arithmetic?
719    return false;
720
721  // Check both sides of a conditional operator.
722  } else if (const AbstractConditionalOperator *op
723               = dyn_cast<AbstractConditionalOperator>(E)) {
724    return isBlockVarRef(op->getTrueExpr())
725        || isBlockVarRef(op->getFalseExpr());
726
727  // OVEs are required to support BinaryConditionalOperators.
728  } else if (const OpaqueValueExpr *op
729               = dyn_cast<OpaqueValueExpr>(E)) {
730    if (const Expr *src = op->getSourceExpr())
731      return isBlockVarRef(src);
732
733  // Casts are necessary to get things like (*(int*)&var) = foo().
734  // We don't really care about the kind of cast here, except
735  // we don't want to look through l2r casts, because it's okay
736  // to get the *value* in a __block variable.
737  } else if (const CastExpr *cast = dyn_cast<CastExpr>(E)) {
738    if (cast->getCastKind() == CK_LValueToRValue)
739      return false;
740    return isBlockVarRef(cast->getSubExpr());
741
742  // Handle unary operators.  Again, just aggressively look through
743  // it, ignoring the operation.
744  } else if (const UnaryOperator *uop = dyn_cast<UnaryOperator>(E)) {
745    return isBlockVarRef(uop->getSubExpr());
746
747  // Look into the base of a field access.
748  } else if (const MemberExpr *mem = dyn_cast<MemberExpr>(E)) {
749    return isBlockVarRef(mem->getBase());
750
751  // Look into the base of a subscript.
752  } else if (const ArraySubscriptExpr *sub = dyn_cast<ArraySubscriptExpr>(E)) {
753    return isBlockVarRef(sub->getBase());
754  }
755
756  return false;
757}
758
759void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
760  // For an assignment to work, the value on the right has
761  // to be compatible with the value on the left.
762  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
763                                                 E->getRHS()->getType())
764         && "Invalid assignment");
765
766  // If the LHS might be a __block variable, and the RHS can
767  // potentially cause a block copy, we need to evaluate the RHS first
768  // so that the assignment goes the right place.
769  // This is pretty semantically fragile.
770  if (isBlockVarRef(E->getLHS()) &&
771      E->getRHS()->HasSideEffects(CGF.getContext())) {
772    // Ensure that we have a destination, and evaluate the RHS into that.
773    EnsureDest(E->getRHS()->getType());
774    Visit(E->getRHS());
775
776    // Now emit the LHS and copy into it.
777    LValue LHS = CGF.EmitLValue(E->getLHS());
778
779    EmitCopy(E->getLHS()->getType(),
780             AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
781                                     needsGC(E->getLHS()->getType()),
782                                     AggValueSlot::IsAliased),
783             Dest);
784    return;
785  }
786
787  LValue LHS = CGF.EmitLValue(E->getLHS());
788
789  // Codegen the RHS so that it stores directly into the LHS.
790  AggValueSlot LHSSlot =
791    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
792                            needsGC(E->getLHS()->getType()),
793                            AggValueSlot::IsAliased);
794  CGF.EmitAggExpr(E->getRHS(), LHSSlot);
795
796  // Copy into the destination if the assignment isn't ignored.
797  EmitFinalDestCopy(E->getType(), LHS);
798}
799
800void AggExprEmitter::
801VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
802  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
803  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
804  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
805
806  // Bind the common expression if necessary.
807  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
808
809  CodeGenFunction::ConditionalEvaluation eval(CGF);
810  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
811
812  // Save whether the destination's lifetime is externally managed.
813  bool isExternallyDestructed = Dest.isExternallyDestructed();
814
815  eval.begin(CGF);
816  CGF.EmitBlock(LHSBlock);
817  Visit(E->getTrueExpr());
818  eval.end(CGF);
819
820  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
821  CGF.Builder.CreateBr(ContBlock);
822
823  // If the result of an agg expression is unused, then the emission
824  // of the LHS might need to create a destination slot.  That's fine
825  // with us, and we can safely emit the RHS into the same slot, but
826  // we shouldn't claim that it's already being destructed.
827  Dest.setExternallyDestructed(isExternallyDestructed);
828
829  eval.begin(CGF);
830  CGF.EmitBlock(RHSBlock);
831  Visit(E->getFalseExpr());
832  eval.end(CGF);
833
834  CGF.EmitBlock(ContBlock);
835}
836
837void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
838  Visit(CE->getChosenSubExpr(CGF.getContext()));
839}
840
841void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
842  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
843  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
844
845  if (!ArgPtr) {
846    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
847    return;
848  }
849
850  EmitFinalDestCopy(VE->getType(), CGF.MakeAddrLValue(ArgPtr, VE->getType()));
851}
852
853void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
854  // Ensure that we have a slot, but if we already do, remember
855  // whether it was externally destructed.
856  bool wasExternallyDestructed = Dest.isExternallyDestructed();
857  EnsureDest(E->getType());
858
859  // We're going to push a destructor if there isn't already one.
860  Dest.setExternallyDestructed();
861
862  Visit(E->getSubExpr());
863
864  // Push that destructor we promised.
865  if (!wasExternallyDestructed)
866    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
867}
868
869void
870AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
871  AggValueSlot Slot = EnsureSlot(E->getType());
872  CGF.EmitCXXConstructExpr(E, Slot);
873}
874
875void
876AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
877  AggValueSlot Slot = EnsureSlot(E->getType());
878  CGF.EmitLambdaExpr(E, Slot);
879}
880
881void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
882  CGF.enterFullExpression(E);
883  CodeGenFunction::RunCleanupsScope cleanups(CGF);
884  Visit(E->getSubExpr());
885}
886
887void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
888  QualType T = E->getType();
889  AggValueSlot Slot = EnsureSlot(T);
890  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
891}
892
893void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
894  QualType T = E->getType();
895  AggValueSlot Slot = EnsureSlot(T);
896  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
897}
898
899/// isSimpleZero - If emitting this value will obviously just cause a store of
900/// zero to memory, return true.  This can return false if uncertain, so it just
901/// handles simple cases.
902static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
903  E = E->IgnoreParens();
904
905  // 0
906  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
907    return IL->getValue() == 0;
908  // +0.0
909  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
910    return FL->getValue().isPosZero();
911  // int()
912  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
913      CGF.getTypes().isZeroInitializable(E->getType()))
914    return true;
915  // (int*)0 - Null pointer expressions.
916  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
917    return ICE->getCastKind() == CK_NullToPointer;
918  // '\0'
919  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
920    return CL->getValue() == 0;
921
922  // Otherwise, hard case: conservatively return false.
923  return false;
924}
925
926
927void
928AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
929  QualType type = LV.getType();
930  // FIXME: Ignore result?
931  // FIXME: Are initializers affected by volatile?
932  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
933    // Storing "i32 0" to a zero'd memory location is a noop.
934  } else if (isa<ImplicitValueInitExpr>(E)) {
935    EmitNullInitializationToLValue(LV);
936  } else if (type->isReferenceType()) {
937    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
938    CGF.EmitStoreThroughLValue(RV, LV);
939  } else if (type->isAnyComplexType()) {
940    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
941  } else if (CGF.hasAggregateLLVMType(type)) {
942    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
943                                               AggValueSlot::IsDestructed,
944                                      AggValueSlot::DoesNotNeedGCBarriers,
945                                               AggValueSlot::IsNotAliased,
946                                               Dest.isZeroed()));
947  } else if (LV.isSimple()) {
948    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
949  } else {
950    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
951  }
952}
953
954void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
955  QualType type = lv.getType();
956
957  // If the destination slot is already zeroed out before the aggregate is
958  // copied into it, we don't have to emit any zeros here.
959  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
960    return;
961
962  if (!CGF.hasAggregateLLVMType(type)) {
963    // For non-aggregates, we can store zero.
964    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
965    // Note that the following is not equivalent to
966    // EmitStoreThroughBitfieldLValue for ARC types.
967    if (lv.isBitField()) {
968      CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
969    } else {
970      assert(lv.isSimple());
971      CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
972    }
973  } else {
974    // There's a potential optimization opportunity in combining
975    // memsets; that would be easy for arrays, but relatively
976    // difficult for structures with the current code.
977    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
978  }
979}
980
981void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
982#if 0
983  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
984  // (Length of globals? Chunks of zeroed-out space?).
985  //
986  // If we can, prefer a copy from a global; this is a lot less code for long
987  // globals, and it's easier for the current optimizers to analyze.
988  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
989    llvm::GlobalVariable* GV =
990    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
991                             llvm::GlobalValue::InternalLinkage, C, "");
992    EmitFinalDestCopy(E->getType(), CGF.MakeAddrLValue(GV, E->getType()));
993    return;
994  }
995#endif
996  if (E->hadArrayRangeDesignator())
997    CGF.ErrorUnsupported(E, "GNU array range designator extension");
998
999  if (E->initializesStdInitializerList()) {
1000    EmitStdInitializerList(Dest.getAddr(), E);
1001    return;
1002  }
1003
1004  AggValueSlot Dest = EnsureSlot(E->getType());
1005  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddr(), E->getType(),
1006                                     Dest.getAlignment());
1007
1008  // Handle initialization of an array.
1009  if (E->getType()->isArrayType()) {
1010    if (E->isStringLiteralInit())
1011      return Visit(E->getInit(0));
1012
1013    QualType elementType =
1014        CGF.getContext().getAsArrayType(E->getType())->getElementType();
1015
1016    llvm::PointerType *APType =
1017      cast<llvm::PointerType>(Dest.getAddr()->getType());
1018    llvm::ArrayType *AType =
1019      cast<llvm::ArrayType>(APType->getElementType());
1020
1021    EmitArrayInit(Dest.getAddr(), AType, elementType, E);
1022    return;
1023  }
1024
1025  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
1026
1027  // Do struct initialization; this code just sets each individual member
1028  // to the approprate value.  This makes bitfield support automatic;
1029  // the disadvantage is that the generated code is more difficult for
1030  // the optimizer, especially with bitfields.
1031  unsigned NumInitElements = E->getNumInits();
1032  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
1033
1034  if (record->isUnion()) {
1035    // Only initialize one field of a union. The field itself is
1036    // specified by the initializer list.
1037    if (!E->getInitializedFieldInUnion()) {
1038      // Empty union; we have nothing to do.
1039
1040#ifndef NDEBUG
1041      // Make sure that it's really an empty and not a failure of
1042      // semantic analysis.
1043      for (RecordDecl::field_iterator Field = record->field_begin(),
1044                                   FieldEnd = record->field_end();
1045           Field != FieldEnd; ++Field)
1046        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
1047#endif
1048      return;
1049    }
1050
1051    // FIXME: volatility
1052    FieldDecl *Field = E->getInitializedFieldInUnion();
1053
1054    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestLV, Field);
1055    if (NumInitElements) {
1056      // Store the initializer into the field
1057      EmitInitializationToLValue(E->getInit(0), FieldLoc);
1058    } else {
1059      // Default-initialize to null.
1060      EmitNullInitializationToLValue(FieldLoc);
1061    }
1062
1063    return;
1064  }
1065
1066  // We'll need to enter cleanup scopes in case any of the member
1067  // initializers throw an exception.
1068  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
1069  llvm::Instruction *cleanupDominator = 0;
1070
1071  // Here we iterate over the fields; this makes it simpler to both
1072  // default-initialize fields and skip over unnamed fields.
1073  unsigned curInitIndex = 0;
1074  for (RecordDecl::field_iterator field = record->field_begin(),
1075                               fieldEnd = record->field_end();
1076       field != fieldEnd; ++field) {
1077    // We're done once we hit the flexible array member.
1078    if (field->getType()->isIncompleteArrayType())
1079      break;
1080
1081    // Always skip anonymous bitfields.
1082    if (field->isUnnamedBitfield())
1083      continue;
1084
1085    // We're done if we reach the end of the explicit initializers, we
1086    // have a zeroed object, and the rest of the fields are
1087    // zero-initializable.
1088    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
1089        CGF.getTypes().isZeroInitializable(E->getType()))
1090      break;
1091
1092
1093    LValue LV = CGF.EmitLValueForFieldInitialization(DestLV, *field);
1094    // We never generate write-barries for initialized fields.
1095    LV.setNonGC(true);
1096
1097    if (curInitIndex < NumInitElements) {
1098      // Store the initializer into the field.
1099      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
1100    } else {
1101      // We're out of initalizers; default-initialize to null
1102      EmitNullInitializationToLValue(LV);
1103    }
1104
1105    // Push a destructor if necessary.
1106    // FIXME: if we have an array of structures, all explicitly
1107    // initialized, we can end up pushing a linear number of cleanups.
1108    bool pushedCleanup = false;
1109    if (QualType::DestructionKind dtorKind
1110          = field->getType().isDestructedType()) {
1111      assert(LV.isSimple());
1112      if (CGF.needsEHCleanup(dtorKind)) {
1113        if (!cleanupDominator)
1114          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
1115
1116        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1117                        CGF.getDestroyer(dtorKind), false);
1118        cleanups.push_back(CGF.EHStack.stable_begin());
1119        pushedCleanup = true;
1120      }
1121    }
1122
1123    // If the GEP didn't get used because of a dead zero init or something
1124    // else, clean it up for -O0 builds and general tidiness.
1125    if (!pushedCleanup && LV.isSimple())
1126      if (llvm::GetElementPtrInst *GEP =
1127            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
1128        if (GEP->use_empty())
1129          GEP->eraseFromParent();
1130  }
1131
1132  // Deactivate all the partial cleanups in reverse order, which
1133  // generally means popping them.
1134  for (unsigned i = cleanups.size(); i != 0; --i)
1135    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1136
1137  // Destroy the placeholder if we made one.
1138  if (cleanupDominator)
1139    cleanupDominator->eraseFromParent();
1140}
1141
1142//===----------------------------------------------------------------------===//
1143//                        Entry Points into this File
1144//===----------------------------------------------------------------------===//
1145
1146/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1147/// non-zero bytes that will be stored when outputting the initializer for the
1148/// specified initializer expression.
1149static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1150  E = E->IgnoreParens();
1151
1152  // 0 and 0.0 won't require any non-zero stores!
1153  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1154
1155  // If this is an initlist expr, sum up the size of sizes of the (present)
1156  // elements.  If this is something weird, assume the whole thing is non-zero.
1157  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1158  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1159    return CGF.getContext().getTypeSizeInChars(E->getType());
1160
1161  // InitListExprs for structs have to be handled carefully.  If there are
1162  // reference members, we need to consider the size of the reference, not the
1163  // referencee.  InitListExprs for unions and arrays can't have references.
1164  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1165    if (!RT->isUnionType()) {
1166      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1167      CharUnits NumNonZeroBytes = CharUnits::Zero();
1168
1169      unsigned ILEElement = 0;
1170      for (RecordDecl::field_iterator Field = SD->field_begin(),
1171           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
1172        // We're done once we hit the flexible array member or run out of
1173        // InitListExpr elements.
1174        if (Field->getType()->isIncompleteArrayType() ||
1175            ILEElement == ILE->getNumInits())
1176          break;
1177        if (Field->isUnnamedBitfield())
1178          continue;
1179
1180        const Expr *E = ILE->getInit(ILEElement++);
1181
1182        // Reference values are always non-null and have the width of a pointer.
1183        if (Field->getType()->isReferenceType())
1184          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1185              CGF.getContext().getTargetInfo().getPointerWidth(0));
1186        else
1187          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1188      }
1189
1190      return NumNonZeroBytes;
1191    }
1192  }
1193
1194
1195  CharUnits NumNonZeroBytes = CharUnits::Zero();
1196  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1197    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1198  return NumNonZeroBytes;
1199}
1200
1201/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1202/// zeros in it, emit a memset and avoid storing the individual zeros.
1203///
1204static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1205                                     CodeGenFunction &CGF) {
1206  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1207  // volatile stores.
1208  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
1209
1210  // C++ objects with a user-declared constructor don't need zero'ing.
1211  if (CGF.getContext().getLangOpts().CPlusPlus)
1212    if (const RecordType *RT = CGF.getContext()
1213                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1214      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1215      if (RD->hasUserDeclaredConstructor())
1216        return;
1217    }
1218
1219  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1220  std::pair<CharUnits, CharUnits> TypeInfo =
1221    CGF.getContext().getTypeInfoInChars(E->getType());
1222  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1223    return;
1224
1225  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1226  // we prefer to emit memset + individual stores for the rest.
1227  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1228  if (NumNonZeroBytes*4 > TypeInfo.first)
1229    return;
1230
1231  // Okay, it seems like a good idea to use an initial memset, emit the call.
1232  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1233  CharUnits Align = TypeInfo.second;
1234
1235  llvm::Value *Loc = Slot.getAddr();
1236
1237  Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
1238  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1239                           Align.getQuantity(), false);
1240
1241  // Tell the AggExprEmitter that the slot is known zero.
1242  Slot.setZeroed();
1243}
1244
1245
1246
1247
1248/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1249/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1250/// the value of the aggregate expression is not needed.  If VolatileDest is
1251/// true, DestPtr cannot be 0.
1252void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot) {
1253  assert(E && hasAggregateLLVMType(E->getType()) &&
1254         "Invalid aggregate expression to emit");
1255  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1256         "slot has bits but no address");
1257
1258  // Optimize the slot if possible.
1259  CheckAggExprForMemSetUse(Slot, E, *this);
1260
1261  AggExprEmitter(*this, Slot).Visit(const_cast<Expr*>(E));
1262}
1263
1264LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1265  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1266  llvm::Value *Temp = CreateMemTemp(E->getType());
1267  LValue LV = MakeAddrLValue(Temp, E->getType());
1268  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1269                                         AggValueSlot::DoesNotNeedGCBarriers,
1270                                         AggValueSlot::IsNotAliased));
1271  return LV;
1272}
1273
1274void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1275                                        llvm::Value *SrcPtr, QualType Ty,
1276                                        bool isVolatile,
1277                                        CharUnits alignment) {
1278  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1279
1280  if (getContext().getLangOpts().CPlusPlus) {
1281    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1282      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1283      assert((Record->hasTrivialCopyConstructor() ||
1284              Record->hasTrivialCopyAssignment() ||
1285              Record->hasTrivialMoveConstructor() ||
1286              Record->hasTrivialMoveAssignment()) &&
1287             "Trying to aggregate-copy a type without a trivial copy "
1288             "constructor or assignment operator");
1289      // Ignore empty classes in C++.
1290      if (Record->isEmpty())
1291        return;
1292    }
1293  }
1294
1295  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1296  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1297  // read from another object that overlaps in anyway the storage of the first
1298  // object, then the overlap shall be exact and the two objects shall have
1299  // qualified or unqualified versions of a compatible type."
1300  //
1301  // memcpy is not defined if the source and destination pointers are exactly
1302  // equal, but other compilers do this optimization, and almost every memcpy
1303  // implementation handles this case safely.  If there is a libc that does not
1304  // safely handle this, we can add a target hook.
1305
1306  // Get data size and alignment info for this aggregate.
1307  std::pair<CharUnits, CharUnits> TypeInfo =
1308    getContext().getTypeInfoDataSizeInChars(Ty);
1309
1310  if (alignment.isZero())
1311    alignment = TypeInfo.second;
1312
1313  // FIXME: Handle variable sized types.
1314
1315  // FIXME: If we have a volatile struct, the optimizer can remove what might
1316  // appear to be `extra' memory ops:
1317  //
1318  // volatile struct { int i; } a, b;
1319  //
1320  // int main() {
1321  //   a = b;
1322  //   a = b;
1323  // }
1324  //
1325  // we need to use a different call here.  We use isVolatile to indicate when
1326  // either the source or the destination is volatile.
1327
1328  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1329  llvm::Type *DBP =
1330    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1331  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1332
1333  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1334  llvm::Type *SBP =
1335    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1336  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1337
1338  // Don't do any of the memmove_collectable tests if GC isn't set.
1339  if (CGM.getLangOpts().getGC() == LangOptions::NonGC) {
1340    // fall through
1341  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1342    RecordDecl *Record = RecordTy->getDecl();
1343    if (Record->hasObjectMember()) {
1344      CharUnits size = TypeInfo.first;
1345      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1346      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1347      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1348                                                    SizeVal);
1349      return;
1350    }
1351  } else if (Ty->isArrayType()) {
1352    QualType BaseType = getContext().getBaseElementType(Ty);
1353    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1354      if (RecordTy->getDecl()->hasObjectMember()) {
1355        CharUnits size = TypeInfo.first;
1356        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1357        llvm::Value *SizeVal =
1358          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1359        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1360                                                      SizeVal);
1361        return;
1362      }
1363    }
1364  }
1365
1366  // Determine the metadata to describe the position of any padding in this
1367  // memcpy, as well as the TBAA tags for the members of the struct, in case
1368  // the optimizer wishes to expand it in to scalar memory operations.
1369  llvm::MDNode *TBAAStructTag = CGM.getTBAAStructInfo(Ty);
1370
1371  Builder.CreateMemCpy(DestPtr, SrcPtr,
1372                       llvm::ConstantInt::get(IntPtrTy,
1373                                              TypeInfo.first.getQuantity()),
1374                       alignment.getQuantity(), isVolatile,
1375                       /*TBAATag=*/0, TBAAStructTag);
1376}
1377
1378void CodeGenFunction::MaybeEmitStdInitializerListCleanup(llvm::Value *loc,
1379                                                         const Expr *init) {
1380  const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(init);
1381  if (cleanups)
1382    init = cleanups->getSubExpr();
1383
1384  if (isa<InitListExpr>(init) &&
1385      cast<InitListExpr>(init)->initializesStdInitializerList()) {
1386    // We initialized this std::initializer_list with an initializer list.
1387    // A backing array was created. Push a cleanup for it.
1388    EmitStdInitializerListCleanup(loc, cast<InitListExpr>(init));
1389  }
1390}
1391
1392static void EmitRecursiveStdInitializerListCleanup(CodeGenFunction &CGF,
1393                                                   llvm::Value *arrayStart,
1394                                                   const InitListExpr *init) {
1395  // Check if there are any recursive cleanups to do, i.e. if we have
1396  //   std::initializer_list<std::initializer_list<obj>> list = {{obj()}};
1397  // then we need to destroy the inner array as well.
1398  for (unsigned i = 0, e = init->getNumInits(); i != e; ++i) {
1399    const InitListExpr *subInit = dyn_cast<InitListExpr>(init->getInit(i));
1400    if (!subInit || !subInit->initializesStdInitializerList())
1401      continue;
1402
1403    // This one needs to be destroyed. Get the address of the std::init_list.
1404    llvm::Value *offset = llvm::ConstantInt::get(CGF.SizeTy, i);
1405    llvm::Value *loc = CGF.Builder.CreateInBoundsGEP(arrayStart, offset,
1406                                                 "std.initlist");
1407    CGF.EmitStdInitializerListCleanup(loc, subInit);
1408  }
1409}
1410
1411void CodeGenFunction::EmitStdInitializerListCleanup(llvm::Value *loc,
1412                                                    const InitListExpr *init) {
1413  ASTContext &ctx = getContext();
1414  QualType element = GetStdInitializerListElementType(init->getType());
1415  unsigned numInits = init->getNumInits();
1416  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
1417  QualType array =ctx.getConstantArrayType(element, size, ArrayType::Normal, 0);
1418  QualType arrayPtr = ctx.getPointerType(array);
1419  llvm::Type *arrayPtrType = ConvertType(arrayPtr);
1420
1421  // lvalue is the location of a std::initializer_list, which as its first
1422  // element has a pointer to the array we want to destroy.
1423  llvm::Value *startPointer = Builder.CreateStructGEP(loc, 0, "startPointer");
1424  llvm::Value *startAddress = Builder.CreateLoad(startPointer, "startAddress");
1425
1426  ::EmitRecursiveStdInitializerListCleanup(*this, startAddress, init);
1427
1428  llvm::Value *arrayAddress =
1429      Builder.CreateBitCast(startAddress, arrayPtrType, "arrayAddress");
1430  ::EmitStdInitializerListCleanup(*this, array, arrayAddress, init);
1431}
1432