CGExprAgg.cpp revision 239462 
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    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
553    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
554    // FIXME: Do we also need to handle property references here?
555    if (LV.isSimple())
556      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
557    else
558      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
559
560    if (!Dest.isIgnored())
561      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
562    break;
563  }
564
565  case CK_ToUnion: {
566    if (Dest.isIgnored()) break;
567
568    // GCC union extension
569    QualType Ty = E->getSubExpr()->getType();
570    QualType PtrTy = CGF.getContext().getPointerType(Ty);
571    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
572                                                 CGF.ConvertType(PtrTy));
573    EmitInitializationToLValue(E->getSubExpr(),
574                               CGF.MakeAddrLValue(CastPtr, Ty));
575    break;
576  }
577
578  case CK_DerivedToBase:
579  case CK_BaseToDerived:
580  case CK_UncheckedDerivedToBase: {
581    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
582                "should have been unpacked before we got here");
583  }
584
585  case CK_LValueToRValue:
586    // If we're loading from a volatile type, force the destination
587    // into existence.
588    if (E->getSubExpr()->getType().isVolatileQualified()) {
589      EnsureDest(E->getType());
590      return Visit(E->getSubExpr());
591    }
592    // fallthrough
593
594  case CK_NoOp:
595  case CK_AtomicToNonAtomic:
596  case CK_NonAtomicToAtomic:
597  case CK_UserDefinedConversion:
598  case CK_ConstructorConversion:
599    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
600                                                   E->getType()) &&
601           "Implicit cast types must be compatible");
602    Visit(E->getSubExpr());
603    break;
604
605  case CK_LValueBitCast:
606    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
607
608  case CK_Dependent:
609  case CK_BitCast:
610  case CK_ArrayToPointerDecay:
611  case CK_FunctionToPointerDecay:
612  case CK_NullToPointer:
613  case CK_NullToMemberPointer:
614  case CK_BaseToDerivedMemberPointer:
615  case CK_DerivedToBaseMemberPointer:
616  case CK_MemberPointerToBoolean:
617  case CK_ReinterpretMemberPointer:
618  case CK_IntegralToPointer:
619  case CK_PointerToIntegral:
620  case CK_PointerToBoolean:
621  case CK_ToVoid:
622  case CK_VectorSplat:
623  case CK_IntegralCast:
624  case CK_IntegralToBoolean:
625  case CK_IntegralToFloating:
626  case CK_FloatingToIntegral:
627  case CK_FloatingToBoolean:
628  case CK_FloatingCast:
629  case CK_CPointerToObjCPointerCast:
630  case CK_BlockPointerToObjCPointerCast:
631  case CK_AnyPointerToBlockPointerCast:
632  case CK_ObjCObjectLValueCast:
633  case CK_FloatingRealToComplex:
634  case CK_FloatingComplexToReal:
635  case CK_FloatingComplexToBoolean:
636  case CK_FloatingComplexCast:
637  case CK_FloatingComplexToIntegralComplex:
638  case CK_IntegralRealToComplex:
639  case CK_IntegralComplexToReal:
640  case CK_IntegralComplexToBoolean:
641  case CK_IntegralComplexCast:
642  case CK_IntegralComplexToFloatingComplex:
643  case CK_ARCProduceObject:
644  case CK_ARCConsumeObject:
645  case CK_ARCReclaimReturnedObject:
646  case CK_ARCExtendBlockObject:
647  case CK_CopyAndAutoreleaseBlockObject:
648    llvm_unreachable("cast kind invalid for aggregate types");
649  }
650}
651
652void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
653  if (E->getCallReturnType()->isReferenceType()) {
654    EmitAggLoadOfLValue(E);
655    return;
656  }
657
658  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
659  EmitMoveFromReturnSlot(E, RV);
660}
661
662void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
663  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
664  EmitMoveFromReturnSlot(E, RV);
665}
666
667void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
668  CGF.EmitIgnoredExpr(E->getLHS());
669  Visit(E->getRHS());
670}
671
672void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
673  CodeGenFunction::StmtExprEvaluation eval(CGF);
674  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
675}
676
677void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
678  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
679    VisitPointerToDataMemberBinaryOperator(E);
680  else
681    CGF.ErrorUnsupported(E, "aggregate binary expression");
682}
683
684void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
685                                                    const BinaryOperator *E) {
686  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
687  EmitFinalDestCopy(E->getType(), LV);
688}
689
690/// Is the value of the given expression possibly a reference to or
691/// into a __block variable?
692static bool isBlockVarRef(const Expr *E) {
693  // Make sure we look through parens.
694  E = E->IgnoreParens();
695
696  // Check for a direct reference to a __block variable.
697  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
698    const VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
699    return (var && var->hasAttr<BlocksAttr>());
700  }
701
702  // More complicated stuff.
703
704  // Binary operators.
705  if (const BinaryOperator *op = dyn_cast<BinaryOperator>(E)) {
706    // For an assignment or pointer-to-member operation, just care
707    // about the LHS.
708    if (op->isAssignmentOp() || op->isPtrMemOp())
709      return isBlockVarRef(op->getLHS());
710
711    // For a comma, just care about the RHS.
712    if (op->getOpcode() == BO_Comma)
713      return isBlockVarRef(op->getRHS());
714
715    // FIXME: pointer arithmetic?
716    return false;
717
718  // Check both sides of a conditional operator.
719  } else if (const AbstractConditionalOperator *op
720               = dyn_cast<AbstractConditionalOperator>(E)) {
721    return isBlockVarRef(op->getTrueExpr())
722        || isBlockVarRef(op->getFalseExpr());
723
724  // OVEs are required to support BinaryConditionalOperators.
725  } else if (const OpaqueValueExpr *op
726               = dyn_cast<OpaqueValueExpr>(E)) {
727    if (const Expr *src = op->getSourceExpr())
728      return isBlockVarRef(src);
729
730  // Casts are necessary to get things like (*(int*)&var) = foo().
731  // We don't really care about the kind of cast here, except
732  // we don't want to look through l2r casts, because it's okay
733  // to get the *value* in a __block variable.
734  } else if (const CastExpr *cast = dyn_cast<CastExpr>(E)) {
735    if (cast->getCastKind() == CK_LValueToRValue)
736      return false;
737    return isBlockVarRef(cast->getSubExpr());
738
739  // Handle unary operators.  Again, just aggressively look through
740  // it, ignoring the operation.
741  } else if (const UnaryOperator *uop = dyn_cast<UnaryOperator>(E)) {
742    return isBlockVarRef(uop->getSubExpr());
743
744  // Look into the base of a field access.
745  } else if (const MemberExpr *mem = dyn_cast<MemberExpr>(E)) {
746    return isBlockVarRef(mem->getBase());
747
748  // Look into the base of a subscript.
749  } else if (const ArraySubscriptExpr *sub = dyn_cast<ArraySubscriptExpr>(E)) {
750    return isBlockVarRef(sub->getBase());
751  }
752
753  return false;
754}
755
756void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
757  // For an assignment to work, the value on the right has
758  // to be compatible with the value on the left.
759  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
760                                                 E->getRHS()->getType())
761         && "Invalid assignment");
762
763  // If the LHS might be a __block variable, and the RHS can
764  // potentially cause a block copy, we need to evaluate the RHS first
765  // so that the assignment goes the right place.
766  // This is pretty semantically fragile.
767  if (isBlockVarRef(E->getLHS()) &&
768      E->getRHS()->HasSideEffects(CGF.getContext())) {
769    // Ensure that we have a destination, and evaluate the RHS into that.
770    EnsureDest(E->getRHS()->getType());
771    Visit(E->getRHS());
772
773    // Now emit the LHS and copy into it.
774    LValue LHS = CGF.EmitLValue(E->getLHS());
775
776    EmitCopy(E->getLHS()->getType(),
777             AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
778                                     needsGC(E->getLHS()->getType()),
779                                     AggValueSlot::IsAliased),
780             Dest);
781    return;
782  }
783
784  LValue LHS = CGF.EmitLValue(E->getLHS());
785
786  // Codegen the RHS so that it stores directly into the LHS.
787  AggValueSlot LHSSlot =
788    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
789                            needsGC(E->getLHS()->getType()),
790                            AggValueSlot::IsAliased);
791  CGF.EmitAggExpr(E->getRHS(), LHSSlot);
792
793  // Copy into the destination if the assignment isn't ignored.
794  EmitFinalDestCopy(E->getType(), LHS);
795}
796
797void AggExprEmitter::
798VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
799  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
800  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
801  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
802
803  // Bind the common expression if necessary.
804  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
805
806  CodeGenFunction::ConditionalEvaluation eval(CGF);
807  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
808
809  // Save whether the destination's lifetime is externally managed.
810  bool isExternallyDestructed = Dest.isExternallyDestructed();
811
812  eval.begin(CGF);
813  CGF.EmitBlock(LHSBlock);
814  Visit(E->getTrueExpr());
815  eval.end(CGF);
816
817  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
818  CGF.Builder.CreateBr(ContBlock);
819
820  // If the result of an agg expression is unused, then the emission
821  // of the LHS might need to create a destination slot.  That's fine
822  // with us, and we can safely emit the RHS into the same slot, but
823  // we shouldn't claim that it's already being destructed.
824  Dest.setExternallyDestructed(isExternallyDestructed);
825
826  eval.begin(CGF);
827  CGF.EmitBlock(RHSBlock);
828  Visit(E->getFalseExpr());
829  eval.end(CGF);
830
831  CGF.EmitBlock(ContBlock);
832}
833
834void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
835  Visit(CE->getChosenSubExpr(CGF.getContext()));
836}
837
838void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
839  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
840  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
841
842  if (!ArgPtr) {
843    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
844    return;
845  }
846
847  EmitFinalDestCopy(VE->getType(), CGF.MakeAddrLValue(ArgPtr, VE->getType()));
848}
849
850void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
851  // Ensure that we have a slot, but if we already do, remember
852  // whether it was externally destructed.
853  bool wasExternallyDestructed = Dest.isExternallyDestructed();
854  EnsureDest(E->getType());
855
856  // We're going to push a destructor if there isn't already one.
857  Dest.setExternallyDestructed();
858
859  Visit(E->getSubExpr());
860
861  // Push that destructor we promised.
862  if (!wasExternallyDestructed)
863    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
864}
865
866void
867AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
868  AggValueSlot Slot = EnsureSlot(E->getType());
869  CGF.EmitCXXConstructExpr(E, Slot);
870}
871
872void
873AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
874  AggValueSlot Slot = EnsureSlot(E->getType());
875  CGF.EmitLambdaExpr(E, Slot);
876}
877
878void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
879  CGF.enterFullExpression(E);
880  CodeGenFunction::RunCleanupsScope cleanups(CGF);
881  Visit(E->getSubExpr());
882}
883
884void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
885  QualType T = E->getType();
886  AggValueSlot Slot = EnsureSlot(T);
887  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
888}
889
890void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
891  QualType T = E->getType();
892  AggValueSlot Slot = EnsureSlot(T);
893  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
894}
895
896/// isSimpleZero - If emitting this value will obviously just cause a store of
897/// zero to memory, return true.  This can return false if uncertain, so it just
898/// handles simple cases.
899static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
900  E = E->IgnoreParens();
901
902  // 0
903  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
904    return IL->getValue() == 0;
905  // +0.0
906  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
907    return FL->getValue().isPosZero();
908  // int()
909  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
910      CGF.getTypes().isZeroInitializable(E->getType()))
911    return true;
912  // (int*)0 - Null pointer expressions.
913  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
914    return ICE->getCastKind() == CK_NullToPointer;
915  // '\0'
916  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
917    return CL->getValue() == 0;
918
919  // Otherwise, hard case: conservatively return false.
920  return false;
921}
922
923
924void
925AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
926  QualType type = LV.getType();
927  // FIXME: Ignore result?
928  // FIXME: Are initializers affected by volatile?
929  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
930    // Storing "i32 0" to a zero'd memory location is a noop.
931  } else if (isa<ImplicitValueInitExpr>(E)) {
932    EmitNullInitializationToLValue(LV);
933  } else if (type->isReferenceType()) {
934    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
935    CGF.EmitStoreThroughLValue(RV, LV);
936  } else if (type->isAnyComplexType()) {
937    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
938  } else if (CGF.hasAggregateLLVMType(type)) {
939    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
940                                               AggValueSlot::IsDestructed,
941                                      AggValueSlot::DoesNotNeedGCBarriers,
942                                               AggValueSlot::IsNotAliased,
943                                               Dest.isZeroed()));
944  } else if (LV.isSimple()) {
945    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
946  } else {
947    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
948  }
949}
950
951void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
952  QualType type = lv.getType();
953
954  // If the destination slot is already zeroed out before the aggregate is
955  // copied into it, we don't have to emit any zeros here.
956  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
957    return;
958
959  if (!CGF.hasAggregateLLVMType(type)) {
960    // For non-aggregates, we can store zero.
961    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
962    // Note that the following is not equivalent to
963    // EmitStoreThroughBitfieldLValue for ARC types.
964    if (lv.isBitField()) {
965      CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
966    } else {
967      assert(lv.isSimple());
968      CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
969    }
970  } else {
971    // There's a potential optimization opportunity in combining
972    // memsets; that would be easy for arrays, but relatively
973    // difficult for structures with the current code.
974    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
975  }
976}
977
978void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
979#if 0
980  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
981  // (Length of globals? Chunks of zeroed-out space?).
982  //
983  // If we can, prefer a copy from a global; this is a lot less code for long
984  // globals, and it's easier for the current optimizers to analyze.
985  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
986    llvm::GlobalVariable* GV =
987    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
988                             llvm::GlobalValue::InternalLinkage, C, "");
989    EmitFinalDestCopy(E->getType(), CGF.MakeAddrLValue(GV, E->getType()));
990    return;
991  }
992#endif
993  if (E->hadArrayRangeDesignator())
994    CGF.ErrorUnsupported(E, "GNU array range designator extension");
995
996  if (E->initializesStdInitializerList()) {
997    EmitStdInitializerList(Dest.getAddr(), E);
998    return;
999  }
1000
1001  AggValueSlot Dest = EnsureSlot(E->getType());
1002  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddr(), E->getType(),
1003                                     Dest.getAlignment());
1004
1005  // Handle initialization of an array.
1006  if (E->getType()->isArrayType()) {
1007    if (E->isStringLiteralInit())
1008      return Visit(E->getInit(0));
1009
1010    QualType elementType =
1011        CGF.getContext().getAsArrayType(E->getType())->getElementType();
1012
1013    llvm::PointerType *APType =
1014      cast<llvm::PointerType>(Dest.getAddr()->getType());
1015    llvm::ArrayType *AType =
1016      cast<llvm::ArrayType>(APType->getElementType());
1017
1018    EmitArrayInit(Dest.getAddr(), AType, elementType, E);
1019    return;
1020  }
1021
1022  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
1023
1024  // Do struct initialization; this code just sets each individual member
1025  // to the approprate value.  This makes bitfield support automatic;
1026  // the disadvantage is that the generated code is more difficult for
1027  // the optimizer, especially with bitfields.
1028  unsigned NumInitElements = E->getNumInits();
1029  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
1030
1031  if (record->isUnion()) {
1032    // Only initialize one field of a union. The field itself is
1033    // specified by the initializer list.
1034    if (!E->getInitializedFieldInUnion()) {
1035      // Empty union; we have nothing to do.
1036
1037#ifndef NDEBUG
1038      // Make sure that it's really an empty and not a failure of
1039      // semantic analysis.
1040      for (RecordDecl::field_iterator Field = record->field_begin(),
1041                                   FieldEnd = record->field_end();
1042           Field != FieldEnd; ++Field)
1043        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
1044#endif
1045      return;
1046    }
1047
1048    // FIXME: volatility
1049    FieldDecl *Field = E->getInitializedFieldInUnion();
1050
1051    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestLV, Field);
1052    if (NumInitElements) {
1053      // Store the initializer into the field
1054      EmitInitializationToLValue(E->getInit(0), FieldLoc);
1055    } else {
1056      // Default-initialize to null.
1057      EmitNullInitializationToLValue(FieldLoc);
1058    }
1059
1060    return;
1061  }
1062
1063  // We'll need to enter cleanup scopes in case any of the member
1064  // initializers throw an exception.
1065  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
1066  llvm::Instruction *cleanupDominator = 0;
1067
1068  // Here we iterate over the fields; this makes it simpler to both
1069  // default-initialize fields and skip over unnamed fields.
1070  unsigned curInitIndex = 0;
1071  for (RecordDecl::field_iterator field = record->field_begin(),
1072                               fieldEnd = record->field_end();
1073       field != fieldEnd; ++field) {
1074    // We're done once we hit the flexible array member.
1075    if (field->getType()->isIncompleteArrayType())
1076      break;
1077
1078    // Always skip anonymous bitfields.
1079    if (field->isUnnamedBitfield())
1080      continue;
1081
1082    // We're done if we reach the end of the explicit initializers, we
1083    // have a zeroed object, and the rest of the fields are
1084    // zero-initializable.
1085    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
1086        CGF.getTypes().isZeroInitializable(E->getType()))
1087      break;
1088
1089
1090    LValue LV = CGF.EmitLValueForFieldInitialization(DestLV, *field);
1091    // We never generate write-barries for initialized fields.
1092    LV.setNonGC(true);
1093
1094    if (curInitIndex < NumInitElements) {
1095      // Store the initializer into the field.
1096      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
1097    } else {
1098      // We're out of initalizers; default-initialize to null
1099      EmitNullInitializationToLValue(LV);
1100    }
1101
1102    // Push a destructor if necessary.
1103    // FIXME: if we have an array of structures, all explicitly
1104    // initialized, we can end up pushing a linear number of cleanups.
1105    bool pushedCleanup = false;
1106    if (QualType::DestructionKind dtorKind
1107          = field->getType().isDestructedType()) {
1108      assert(LV.isSimple());
1109      if (CGF.needsEHCleanup(dtorKind)) {
1110        if (!cleanupDominator)
1111          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
1112
1113        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1114                        CGF.getDestroyer(dtorKind), false);
1115        cleanups.push_back(CGF.EHStack.stable_begin());
1116        pushedCleanup = true;
1117      }
1118    }
1119
1120    // If the GEP didn't get used because of a dead zero init or something
1121    // else, clean it up for -O0 builds and general tidiness.
1122    if (!pushedCleanup && LV.isSimple())
1123      if (llvm::GetElementPtrInst *GEP =
1124            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
1125        if (GEP->use_empty())
1126          GEP->eraseFromParent();
1127  }
1128
1129  // Deactivate all the partial cleanups in reverse order, which
1130  // generally means popping them.
1131  for (unsigned i = cleanups.size(); i != 0; --i)
1132    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1133
1134  // Destroy the placeholder if we made one.
1135  if (cleanupDominator)
1136    cleanupDominator->eraseFromParent();
1137}
1138
1139//===----------------------------------------------------------------------===//
1140//                        Entry Points into this File
1141//===----------------------------------------------------------------------===//
1142
1143/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1144/// non-zero bytes that will be stored when outputting the initializer for the
1145/// specified initializer expression.
1146static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1147  E = E->IgnoreParens();
1148
1149  // 0 and 0.0 won't require any non-zero stores!
1150  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1151
1152  // If this is an initlist expr, sum up the size of sizes of the (present)
1153  // elements.  If this is something weird, assume the whole thing is non-zero.
1154  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1155  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1156    return CGF.getContext().getTypeSizeInChars(E->getType());
1157
1158  // InitListExprs for structs have to be handled carefully.  If there are
1159  // reference members, we need to consider the size of the reference, not the
1160  // referencee.  InitListExprs for unions and arrays can't have references.
1161  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1162    if (!RT->isUnionType()) {
1163      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1164      CharUnits NumNonZeroBytes = CharUnits::Zero();
1165
1166      unsigned ILEElement = 0;
1167      for (RecordDecl::field_iterator Field = SD->field_begin(),
1168           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
1169        // We're done once we hit the flexible array member or run out of
1170        // InitListExpr elements.
1171        if (Field->getType()->isIncompleteArrayType() ||
1172            ILEElement == ILE->getNumInits())
1173          break;
1174        if (Field->isUnnamedBitfield())
1175          continue;
1176
1177        const Expr *E = ILE->getInit(ILEElement++);
1178
1179        // Reference values are always non-null and have the width of a pointer.
1180        if (Field->getType()->isReferenceType())
1181          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1182              CGF.getContext().getTargetInfo().getPointerWidth(0));
1183        else
1184          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1185      }
1186
1187      return NumNonZeroBytes;
1188    }
1189  }
1190
1191
1192  CharUnits NumNonZeroBytes = CharUnits::Zero();
1193  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1194    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1195  return NumNonZeroBytes;
1196}
1197
1198/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1199/// zeros in it, emit a memset and avoid storing the individual zeros.
1200///
1201static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1202                                     CodeGenFunction &CGF) {
1203  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1204  // volatile stores.
1205  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
1206
1207  // C++ objects with a user-declared constructor don't need zero'ing.
1208  if (CGF.getContext().getLangOpts().CPlusPlus)
1209    if (const RecordType *RT = CGF.getContext()
1210                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1211      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1212      if (RD->hasUserDeclaredConstructor())
1213        return;
1214    }
1215
1216  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1217  std::pair<CharUnits, CharUnits> TypeInfo =
1218    CGF.getContext().getTypeInfoInChars(E->getType());
1219  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1220    return;
1221
1222  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1223  // we prefer to emit memset + individual stores for the rest.
1224  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1225  if (NumNonZeroBytes*4 > TypeInfo.first)
1226    return;
1227
1228  // Okay, it seems like a good idea to use an initial memset, emit the call.
1229  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1230  CharUnits Align = TypeInfo.second;
1231
1232  llvm::Value *Loc = Slot.getAddr();
1233
1234  Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
1235  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1236                           Align.getQuantity(), false);
1237
1238  // Tell the AggExprEmitter that the slot is known zero.
1239  Slot.setZeroed();
1240}
1241
1242
1243
1244
1245/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1246/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1247/// the value of the aggregate expression is not needed.  If VolatileDest is
1248/// true, DestPtr cannot be 0.
1249void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot) {
1250  assert(E && hasAggregateLLVMType(E->getType()) &&
1251         "Invalid aggregate expression to emit");
1252  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1253         "slot has bits but no address");
1254
1255  // Optimize the slot if possible.
1256  CheckAggExprForMemSetUse(Slot, E, *this);
1257
1258  AggExprEmitter(*this, Slot).Visit(const_cast<Expr*>(E));
1259}
1260
1261LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1262  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1263  llvm::Value *Temp = CreateMemTemp(E->getType());
1264  LValue LV = MakeAddrLValue(Temp, E->getType());
1265  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1266                                         AggValueSlot::DoesNotNeedGCBarriers,
1267                                         AggValueSlot::IsNotAliased));
1268  return LV;
1269}
1270
1271void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1272                                        llvm::Value *SrcPtr, QualType Ty,
1273                                        bool isVolatile,
1274                                        CharUnits alignment) {
1275  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1276
1277  if (getContext().getLangOpts().CPlusPlus) {
1278    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1279      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1280      assert((Record->hasTrivialCopyConstructor() ||
1281              Record->hasTrivialCopyAssignment() ||
1282              Record->hasTrivialMoveConstructor() ||
1283              Record->hasTrivialMoveAssignment()) &&
1284             "Trying to aggregate-copy a type without a trivial copy "
1285             "constructor or assignment operator");
1286      // Ignore empty classes in C++.
1287      if (Record->isEmpty())
1288        return;
1289    }
1290  }
1291
1292  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1293  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1294  // read from another object that overlaps in anyway the storage of the first
1295  // object, then the overlap shall be exact and the two objects shall have
1296  // qualified or unqualified versions of a compatible type."
1297  //
1298  // memcpy is not defined if the source and destination pointers are exactly
1299  // equal, but other compilers do this optimization, and almost every memcpy
1300  // implementation handles this case safely.  If there is a libc that does not
1301  // safely handle this, we can add a target hook.
1302
1303  // Get size and alignment info for this aggregate.
1304  std::pair<CharUnits, CharUnits> TypeInfo =
1305    getContext().getTypeInfoInChars(Ty);
1306
1307  if (alignment.isZero())
1308    alignment = TypeInfo.second;
1309
1310  // FIXME: Handle variable sized types.
1311
1312  // FIXME: If we have a volatile struct, the optimizer can remove what might
1313  // appear to be `extra' memory ops:
1314  //
1315  // volatile struct { int i; } a, b;
1316  //
1317  // int main() {
1318  //   a = b;
1319  //   a = b;
1320  // }
1321  //
1322  // we need to use a different call here.  We use isVolatile to indicate when
1323  // either the source or the destination is volatile.
1324
1325  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1326  llvm::Type *DBP =
1327    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1328  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1329
1330  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1331  llvm::Type *SBP =
1332    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1333  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1334
1335  // Don't do any of the memmove_collectable tests if GC isn't set.
1336  if (CGM.getLangOpts().getGC() == LangOptions::NonGC) {
1337    // fall through
1338  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1339    RecordDecl *Record = RecordTy->getDecl();
1340    if (Record->hasObjectMember()) {
1341      CharUnits size = TypeInfo.first;
1342      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1343      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1344      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1345                                                    SizeVal);
1346      return;
1347    }
1348  } else if (Ty->isArrayType()) {
1349    QualType BaseType = getContext().getBaseElementType(Ty);
1350    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1351      if (RecordTy->getDecl()->hasObjectMember()) {
1352        CharUnits size = TypeInfo.first;
1353        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1354        llvm::Value *SizeVal =
1355          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1356        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1357                                                      SizeVal);
1358        return;
1359      }
1360    }
1361  }
1362
1363  Builder.CreateMemCpy(DestPtr, SrcPtr,
1364                       llvm::ConstantInt::get(IntPtrTy,
1365                                              TypeInfo.first.getQuantity()),
1366                       alignment.getQuantity(), isVolatile);
1367}
1368
1369void CodeGenFunction::MaybeEmitStdInitializerListCleanup(llvm::Value *loc,
1370                                                         const Expr *init) {
1371  const ExprWithCleanups *cleanups = dyn_cast<ExprWithCleanups>(init);
1372  if (cleanups)
1373    init = cleanups->getSubExpr();
1374
1375  if (isa<InitListExpr>(init) &&
1376      cast<InitListExpr>(init)->initializesStdInitializerList()) {
1377    // We initialized this std::initializer_list with an initializer list.
1378    // A backing array was created. Push a cleanup for it.
1379    EmitStdInitializerListCleanup(loc, cast<InitListExpr>(init));
1380  }
1381}
1382
1383static void EmitRecursiveStdInitializerListCleanup(CodeGenFunction &CGF,
1384                                                   llvm::Value *arrayStart,
1385                                                   const InitListExpr *init) {
1386  // Check if there are any recursive cleanups to do, i.e. if we have
1387  //   std::initializer_list<std::initializer_list<obj>> list = {{obj()}};
1388  // then we need to destroy the inner array as well.
1389  for (unsigned i = 0, e = init->getNumInits(); i != e; ++i) {
1390    const InitListExpr *subInit = dyn_cast<InitListExpr>(init->getInit(i));
1391    if (!subInit || !subInit->initializesStdInitializerList())
1392      continue;
1393
1394    // This one needs to be destroyed. Get the address of the std::init_list.
1395    llvm::Value *offset = llvm::ConstantInt::get(CGF.SizeTy, i);
1396    llvm::Value *loc = CGF.Builder.CreateInBoundsGEP(arrayStart, offset,
1397                                                 "std.initlist");
1398    CGF.EmitStdInitializerListCleanup(loc, subInit);
1399  }
1400}
1401
1402void CodeGenFunction::EmitStdInitializerListCleanup(llvm::Value *loc,
1403                                                    const InitListExpr *init) {
1404  ASTContext &ctx = getContext();
1405  QualType element = GetStdInitializerListElementType(init->getType());
1406  unsigned numInits = init->getNumInits();
1407  llvm::APInt size(ctx.getTypeSize(ctx.getSizeType()), numInits);
1408  QualType array =ctx.getConstantArrayType(element, size, ArrayType::Normal, 0);
1409  QualType arrayPtr = ctx.getPointerType(array);
1410  llvm::Type *arrayPtrType = ConvertType(arrayPtr);
1411
1412  // lvalue is the location of a std::initializer_list, which as its first
1413  // element has a pointer to the array we want to destroy.
1414  llvm::Value *startPointer = Builder.CreateStructGEP(loc, 0, "startPointer");
1415  llvm::Value *startAddress = Builder.CreateLoad(startPointer, "startAddress");
1416
1417  ::EmitRecursiveStdInitializerListCleanup(*this, startAddress, init);
1418
1419  llvm::Value *arrayAddress =
1420      Builder.CreateBitCast(startAddress, arrayPtrType, "arrayAddress");
1421  ::EmitStdInitializerListCleanup(*this, array, arrayAddress, init);
1422}
1423