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 "CGObjCRuntime.h"
16#include "CodeGenModule.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/IR/Constants.h"
22#include "llvm/IR/Function.h"
23#include "llvm/IR/GlobalVariable.h"
24#include "llvm/IR/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 EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
87                     QualType elementType, InitListExpr *E);
88
89  AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
90    if (CGF.getLangOpts().getGC() && TypeRequiresGCollection(T))
91      return AggValueSlot::NeedsGCBarriers;
92    return AggValueSlot::DoesNotNeedGCBarriers;
93  }
94
95  bool TypeRequiresGCollection(QualType T);
96
97  //===--------------------------------------------------------------------===//
98  //                            Visitor Methods
99  //===--------------------------------------------------------------------===//
100
101  void VisitStmt(Stmt *S) {
102    CGF.ErrorUnsupported(S, "aggregate expression");
103  }
104  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
105  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
106    Visit(GE->getResultExpr());
107  }
108  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
109  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
110    return Visit(E->getReplacement());
111  }
112
113  // l-values.
114  void VisitDeclRefExpr(DeclRefExpr *E) {
115    // For aggregates, we should always be able to emit the variable
116    // as an l-value unless it's a reference.  This is due to the fact
117    // that we can't actually ever see a normal l2r conversion on an
118    // aggregate in C++, and in C there's no language standard
119    // actively preventing us from listing variables in the captures
120    // list of a block.
121    if (E->getDecl()->getType()->isReferenceType()) {
122      if (CodeGenFunction::ConstantEmission result
123            = CGF.tryEmitAsConstant(E)) {
124        EmitFinalDestCopy(E->getType(), result.getReferenceLValue(CGF, E));
125        return;
126      }
127    }
128
129    EmitAggLoadOfLValue(E);
130  }
131
132  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
133  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
134  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
135  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
136  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
137    EmitAggLoadOfLValue(E);
138  }
139  void VisitPredefinedExpr(const PredefinedExpr *E) {
140    EmitAggLoadOfLValue(E);
141  }
142
143  // Operators.
144  void VisitCastExpr(CastExpr *E);
145  void VisitCallExpr(const CallExpr *E);
146  void VisitStmtExpr(const StmtExpr *E);
147  void VisitBinaryOperator(const BinaryOperator *BO);
148  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
149  void VisitBinAssign(const BinaryOperator *E);
150  void VisitBinComma(const BinaryOperator *E);
151
152  void VisitObjCMessageExpr(ObjCMessageExpr *E);
153  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
154    EmitAggLoadOfLValue(E);
155  }
156
157  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
158  void VisitChooseExpr(const ChooseExpr *CE);
159  void VisitInitListExpr(InitListExpr *E);
160  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
161  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
162    Visit(DAE->getExpr());
163  }
164  void VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
165    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
166    Visit(DIE->getExpr());
167  }
168  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
169  void VisitCXXConstructExpr(const CXXConstructExpr *E);
170  void VisitLambdaExpr(LambdaExpr *E);
171  void VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E);
172  void VisitExprWithCleanups(ExprWithCleanups *E);
173  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
174  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
175  void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
176  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
177
178  void VisitPseudoObjectExpr(PseudoObjectExpr *E) {
179    if (E->isGLValue()) {
180      LValue LV = CGF.EmitPseudoObjectLValue(E);
181      return EmitFinalDestCopy(E->getType(), LV);
182    }
183
184    CGF.EmitPseudoObjectRValue(E, EnsureSlot(E->getType()));
185  }
186
187  void VisitVAArgExpr(VAArgExpr *E);
188
189  void EmitInitializationToLValue(Expr *E, LValue Address);
190  void EmitNullInitializationToLValue(LValue Address);
191  //  case Expr::ChooseExprClass:
192  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
193  void VisitAtomicExpr(AtomicExpr *E) {
194    CGF.EmitAtomicExpr(E, EnsureSlot(E->getType()).getAddr());
195  }
196};
197}  // end anonymous namespace.
198
199//===----------------------------------------------------------------------===//
200//                                Utilities
201//===----------------------------------------------------------------------===//
202
203/// EmitAggLoadOfLValue - Given an expression with aggregate type that
204/// represents a value lvalue, this method emits the address of the lvalue,
205/// then loads the result into DestPtr.
206void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
207  LValue LV = CGF.EmitLValue(E);
208
209  // If the type of the l-value is atomic, then do an atomic load.
210  if (LV.getType()->isAtomicType()) {
211    CGF.EmitAtomicLoad(LV, E->getExprLoc(), Dest);
212    return;
213  }
214
215  EmitFinalDestCopy(E->getType(), LV);
216}
217
218/// \brief True if the given aggregate type requires special GC API calls.
219bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
220  // Only record types have members that might require garbage collection.
221  const RecordType *RecordTy = T->getAs<RecordType>();
222  if (!RecordTy) return false;
223
224  // Don't mess with non-trivial C++ types.
225  RecordDecl *Record = RecordTy->getDecl();
226  if (isa<CXXRecordDecl>(Record) &&
227      (cast<CXXRecordDecl>(Record)->hasNonTrivialCopyConstructor() ||
228       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
229    return false;
230
231  // Check whether the type has an object member.
232  return Record->hasObjectMember();
233}
234
235/// \brief Perform the final move to DestPtr if for some reason
236/// getReturnValueSlot() didn't use it directly.
237///
238/// The idea is that you do something like this:
239///   RValue Result = EmitSomething(..., getReturnValueSlot());
240///   EmitMoveFromReturnSlot(E, Result);
241///
242/// If nothing interferes, this will cause the result to be emitted
243/// directly into the return value slot.  Otherwise, a final move
244/// will be performed.
245void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue src) {
246  if (shouldUseDestForReturnSlot()) {
247    // Logically, Dest.getAddr() should equal Src.getAggregateAddr().
248    // The possibility of undef rvalues complicates that a lot,
249    // though, so we can't really assert.
250    return;
251  }
252
253  // Otherwise, copy from there to the destination.
254  assert(Dest.getAddr() != src.getAggregateAddr());
255  std::pair<CharUnits, CharUnits> typeInfo =
256    CGF.getContext().getTypeInfoInChars(E->getType());
257  EmitFinalDestCopy(E->getType(), src, typeInfo.second);
258}
259
260/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
261void AggExprEmitter::EmitFinalDestCopy(QualType type, RValue src,
262                                       CharUnits srcAlign) {
263  assert(src.isAggregate() && "value must be aggregate value!");
264  LValue srcLV = CGF.MakeAddrLValue(src.getAggregateAddr(), type, srcAlign);
265  EmitFinalDestCopy(type, srcLV);
266}
267
268/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
269void AggExprEmitter::EmitFinalDestCopy(QualType type, const LValue &src) {
270  // If Dest is ignored, then we're evaluating an aggregate expression
271  // in a context that doesn't care about the result.  Note that loads
272  // from volatile l-values force the existence of a non-ignored
273  // destination.
274  if (Dest.isIgnored())
275    return;
276
277  AggValueSlot srcAgg =
278    AggValueSlot::forLValue(src, AggValueSlot::IsDestructed,
279                            needsGC(type), AggValueSlot::IsAliased);
280  EmitCopy(type, Dest, srcAgg);
281}
282
283/// Perform a copy from the source into the destination.
284///
285/// \param type - the type of the aggregate being copied; qualifiers are
286///   ignored
287void AggExprEmitter::EmitCopy(QualType type, const AggValueSlot &dest,
288                              const AggValueSlot &src) {
289  if (dest.requiresGCollection()) {
290    CharUnits sz = CGF.getContext().getTypeSizeInChars(type);
291    llvm::Value *size = llvm::ConstantInt::get(CGF.SizeTy, sz.getQuantity());
292    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
293                                                      dest.getAddr(),
294                                                      src.getAddr(),
295                                                      size);
296    return;
297  }
298
299  // If the result of the assignment is used, copy the LHS there also.
300  // It's volatile if either side is.  Use the minimum alignment of
301  // the two sides.
302  CGF.EmitAggregateCopy(dest.getAddr(), src.getAddr(), type,
303                        dest.isVolatile() || src.isVolatile(),
304                        std::min(dest.getAlignment(), src.getAlignment()));
305}
306
307/// \brief Emit the initializer for a std::initializer_list initialized with a
308/// real initializer list.
309void
310AggExprEmitter::VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E) {
311  // Emit an array containing the elements.  The array is externally destructed
312  // if the std::initializer_list object is.
313  ASTContext &Ctx = CGF.getContext();
314  LValue Array = CGF.EmitLValue(E->getSubExpr());
315  assert(Array.isSimple() && "initializer_list array not a simple lvalue");
316  llvm::Value *ArrayPtr = Array.getAddress();
317
318  const ConstantArrayType *ArrayType =
319      Ctx.getAsConstantArrayType(E->getSubExpr()->getType());
320  assert(ArrayType && "std::initializer_list constructed from non-array");
321
322  // FIXME: Perform the checks on the field types in SemaInit.
323  RecordDecl *Record = E->getType()->castAs<RecordType>()->getDecl();
324  RecordDecl::field_iterator Field = Record->field_begin();
325  if (Field == Record->field_end()) {
326    CGF.ErrorUnsupported(E, "weird std::initializer_list");
327    return;
328  }
329
330  // Start pointer.
331  if (!Field->getType()->isPointerType() ||
332      !Ctx.hasSameType(Field->getType()->getPointeeType(),
333                       ArrayType->getElementType())) {
334    CGF.ErrorUnsupported(E, "weird std::initializer_list");
335    return;
336  }
337
338  AggValueSlot Dest = EnsureSlot(E->getType());
339  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddr(), E->getType(),
340                                     Dest.getAlignment());
341  LValue Start = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
342  llvm::Value *Zero = llvm::ConstantInt::get(CGF.PtrDiffTy, 0);
343  llvm::Value *IdxStart[] = { Zero, Zero };
344  llvm::Value *ArrayStart =
345      Builder.CreateInBoundsGEP(ArrayPtr, IdxStart, "arraystart");
346  CGF.EmitStoreThroughLValue(RValue::get(ArrayStart), Start);
347  ++Field;
348
349  if (Field == Record->field_end()) {
350    CGF.ErrorUnsupported(E, "weird std::initializer_list");
351    return;
352  }
353
354  llvm::Value *Size = Builder.getInt(ArrayType->getSize());
355  LValue EndOrLength = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
356  if (Field->getType()->isPointerType() &&
357      Ctx.hasSameType(Field->getType()->getPointeeType(),
358                      ArrayType->getElementType())) {
359    // End pointer.
360    llvm::Value *IdxEnd[] = { Zero, Size };
361    llvm::Value *ArrayEnd =
362        Builder.CreateInBoundsGEP(ArrayPtr, IdxEnd, "arrayend");
363    CGF.EmitStoreThroughLValue(RValue::get(ArrayEnd), EndOrLength);
364  } else if (Ctx.hasSameType(Field->getType(), Ctx.getSizeType())) {
365    // Length.
366    CGF.EmitStoreThroughLValue(RValue::get(Size), EndOrLength);
367  } else {
368    CGF.ErrorUnsupported(E, "weird std::initializer_list");
369    return;
370  }
371}
372
373/// \brief Determine if E is a trivial array filler, that is, one that is
374/// equivalent to zero-initialization.
375static bool isTrivialFiller(Expr *E) {
376  if (!E)
377    return true;
378
379  if (isa<ImplicitValueInitExpr>(E))
380    return true;
381
382  if (auto *ILE = dyn_cast<InitListExpr>(E)) {
383    if (ILE->getNumInits())
384      return false;
385    return isTrivialFiller(ILE->getArrayFiller());
386  }
387
388  if (auto *Cons = dyn_cast_or_null<CXXConstructExpr>(E))
389    return Cons->getConstructor()->isDefaultConstructor() &&
390           Cons->getConstructor()->isTrivial();
391
392  // FIXME: Are there other cases where we can avoid emitting an initializer?
393  return false;
394}
395
396/// \brief Emit initialization of an array from an initializer list.
397void AggExprEmitter::EmitArrayInit(llvm::Value *DestPtr, llvm::ArrayType *AType,
398                                   QualType elementType, InitListExpr *E) {
399  uint64_t NumInitElements = E->getNumInits();
400
401  uint64_t NumArrayElements = AType->getNumElements();
402  assert(NumInitElements <= NumArrayElements);
403
404  // DestPtr is an array*.  Construct an elementType* by drilling
405  // down a level.
406  llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
407  llvm::Value *indices[] = { zero, zero };
408  llvm::Value *begin =
409    Builder.CreateInBoundsGEP(DestPtr, indices, "arrayinit.begin");
410
411  // Exception safety requires us to destroy all the
412  // already-constructed members if an initializer throws.
413  // For that, we'll need an EH cleanup.
414  QualType::DestructionKind dtorKind = elementType.isDestructedType();
415  llvm::AllocaInst *endOfInit = nullptr;
416  EHScopeStack::stable_iterator cleanup;
417  llvm::Instruction *cleanupDominator = nullptr;
418  if (CGF.needsEHCleanup(dtorKind)) {
419    // In principle we could tell the cleanup where we are more
420    // directly, but the control flow can get so varied here that it
421    // would actually be quite complex.  Therefore we go through an
422    // alloca.
423    endOfInit = CGF.CreateTempAlloca(begin->getType(),
424                                     "arrayinit.endOfInit");
425    cleanupDominator = Builder.CreateStore(begin, endOfInit);
426    CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
427                                         CGF.getDestroyer(dtorKind));
428    cleanup = CGF.EHStack.stable_begin();
429
430  // Otherwise, remember that we didn't need a cleanup.
431  } else {
432    dtorKind = QualType::DK_none;
433  }
434
435  llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
436
437  // The 'current element to initialize'.  The invariants on this
438  // variable are complicated.  Essentially, after each iteration of
439  // the loop, it points to the last initialized element, except
440  // that it points to the beginning of the array before any
441  // elements have been initialized.
442  llvm::Value *element = begin;
443
444  // Emit the explicit initializers.
445  for (uint64_t i = 0; i != NumInitElements; ++i) {
446    // Advance to the next element.
447    if (i > 0) {
448      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
449
450      // Tell the cleanup that it needs to destroy up to this
451      // element.  TODO: some of these stores can be trivially
452      // observed to be unnecessary.
453      if (endOfInit) Builder.CreateStore(element, endOfInit);
454    }
455
456    LValue elementLV = CGF.MakeAddrLValue(element, elementType);
457    EmitInitializationToLValue(E->getInit(i), elementLV);
458  }
459
460  // Check whether there's a non-trivial array-fill expression.
461  Expr *filler = E->getArrayFiller();
462  bool hasTrivialFiller = isTrivialFiller(filler);
463
464  // Any remaining elements need to be zero-initialized, possibly
465  // using the filler expression.  We can skip this if the we're
466  // emitting to zeroed memory.
467  if (NumInitElements != NumArrayElements &&
468      !(Dest.isZeroed() && hasTrivialFiller &&
469        CGF.getTypes().isZeroInitializable(elementType))) {
470
471    // Use an actual loop.  This is basically
472    //   do { *array++ = filler; } while (array != end);
473
474    // Advance to the start of the rest of the array.
475    if (NumInitElements) {
476      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
477      if (endOfInit) Builder.CreateStore(element, endOfInit);
478    }
479
480    // Compute the end of the array.
481    llvm::Value *end = Builder.CreateInBoundsGEP(begin,
482                      llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
483                                                 "arrayinit.end");
484
485    llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
486    llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
487
488    // Jump into the body.
489    CGF.EmitBlock(bodyBB);
490    llvm::PHINode *currentElement =
491      Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
492    currentElement->addIncoming(element, entryBB);
493
494    // Emit the actual filler expression.
495    LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
496    if (filler)
497      EmitInitializationToLValue(filler, elementLV);
498    else
499      EmitNullInitializationToLValue(elementLV);
500
501    // Move on to the next element.
502    llvm::Value *nextElement =
503      Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
504
505    // Tell the EH cleanup that we finished with the last element.
506    if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
507
508    // Leave the loop if we're done.
509    llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
510                                             "arrayinit.done");
511    llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
512    Builder.CreateCondBr(done, endBB, bodyBB);
513    currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
514
515    CGF.EmitBlock(endBB);
516  }
517
518  // Leave the partial-array cleanup if we entered one.
519  if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
520}
521
522//===----------------------------------------------------------------------===//
523//                            Visitor Methods
524//===----------------------------------------------------------------------===//
525
526void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
527  Visit(E->GetTemporaryExpr());
528}
529
530void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
531  EmitFinalDestCopy(e->getType(), CGF.getOpaqueLValueMapping(e));
532}
533
534void
535AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
536  if (Dest.isPotentiallyAliased() &&
537      E->getType().isPODType(CGF.getContext())) {
538    // For a POD type, just emit a load of the lvalue + a copy, because our
539    // compound literal might alias the destination.
540    EmitAggLoadOfLValue(E);
541    return;
542  }
543
544  AggValueSlot Slot = EnsureSlot(E->getType());
545  CGF.EmitAggExpr(E->getInitializer(), Slot);
546}
547
548/// Attempt to look through various unimportant expressions to find a
549/// cast of the given kind.
550static Expr *findPeephole(Expr *op, CastKind kind) {
551  while (true) {
552    op = op->IgnoreParens();
553    if (CastExpr *castE = dyn_cast<CastExpr>(op)) {
554      if (castE->getCastKind() == kind)
555        return castE->getSubExpr();
556      if (castE->getCastKind() == CK_NoOp)
557        continue;
558    }
559    return nullptr;
560  }
561}
562
563void AggExprEmitter::VisitCastExpr(CastExpr *E) {
564  switch (E->getCastKind()) {
565  case CK_Dynamic: {
566    // FIXME: Can this actually happen? We have no test coverage for it.
567    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
568    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr(),
569                                      CodeGenFunction::TCK_Load);
570    // FIXME: Do we also need to handle property references here?
571    if (LV.isSimple())
572      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
573    else
574      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
575
576    if (!Dest.isIgnored())
577      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
578    break;
579  }
580
581  case CK_ToUnion: {
582    if (Dest.isIgnored()) break;
583
584    // GCC union extension
585    QualType Ty = E->getSubExpr()->getType();
586    QualType PtrTy = CGF.getContext().getPointerType(Ty);
587    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
588                                                 CGF.ConvertType(PtrTy));
589    EmitInitializationToLValue(E->getSubExpr(),
590                               CGF.MakeAddrLValue(CastPtr, Ty));
591    break;
592  }
593
594  case CK_DerivedToBase:
595  case CK_BaseToDerived:
596  case CK_UncheckedDerivedToBase: {
597    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
598                "should have been unpacked before we got here");
599  }
600
601  case CK_NonAtomicToAtomic:
602  case CK_AtomicToNonAtomic: {
603    bool isToAtomic = (E->getCastKind() == CK_NonAtomicToAtomic);
604
605    // Determine the atomic and value types.
606    QualType atomicType = E->getSubExpr()->getType();
607    QualType valueType = E->getType();
608    if (isToAtomic) std::swap(atomicType, valueType);
609
610    assert(atomicType->isAtomicType());
611    assert(CGF.getContext().hasSameUnqualifiedType(valueType,
612                          atomicType->castAs<AtomicType>()->getValueType()));
613
614    // Just recurse normally if we're ignoring the result or the
615    // atomic type doesn't change representation.
616    if (Dest.isIgnored() || !CGF.CGM.isPaddedAtomicType(atomicType)) {
617      return Visit(E->getSubExpr());
618    }
619
620    CastKind peepholeTarget =
621      (isToAtomic ? CK_AtomicToNonAtomic : CK_NonAtomicToAtomic);
622
623    // These two cases are reverses of each other; try to peephole them.
624    if (Expr *op = findPeephole(E->getSubExpr(), peepholeTarget)) {
625      assert(CGF.getContext().hasSameUnqualifiedType(op->getType(),
626                                                     E->getType()) &&
627           "peephole significantly changed types?");
628      return Visit(op);
629    }
630
631    // If we're converting an r-value of non-atomic type to an r-value
632    // of atomic type, just emit directly into the relevant sub-object.
633    if (isToAtomic) {
634      AggValueSlot valueDest = Dest;
635      if (!valueDest.isIgnored() && CGF.CGM.isPaddedAtomicType(atomicType)) {
636        // Zero-initialize.  (Strictly speaking, we only need to intialize
637        // the padding at the end, but this is simpler.)
638        if (!Dest.isZeroed())
639          CGF.EmitNullInitialization(Dest.getAddr(), atomicType);
640
641        // Build a GEP to refer to the subobject.
642        llvm::Value *valueAddr =
643            CGF.Builder.CreateStructGEP(valueDest.getAddr(), 0);
644        valueDest = AggValueSlot::forAddr(valueAddr,
645                                          valueDest.getAlignment(),
646                                          valueDest.getQualifiers(),
647                                          valueDest.isExternallyDestructed(),
648                                          valueDest.requiresGCollection(),
649                                          valueDest.isPotentiallyAliased(),
650                                          AggValueSlot::IsZeroed);
651      }
652
653      CGF.EmitAggExpr(E->getSubExpr(), valueDest);
654      return;
655    }
656
657    // Otherwise, we're converting an atomic type to a non-atomic type.
658    // Make an atomic temporary, emit into that, and then copy the value out.
659    AggValueSlot atomicSlot =
660      CGF.CreateAggTemp(atomicType, "atomic-to-nonatomic.temp");
661    CGF.EmitAggExpr(E->getSubExpr(), atomicSlot);
662
663    llvm::Value *valueAddr =
664      Builder.CreateStructGEP(atomicSlot.getAddr(), 0);
665    RValue rvalue = RValue::getAggregate(valueAddr, atomicSlot.isVolatile());
666    return EmitFinalDestCopy(valueType, rvalue);
667  }
668
669  case CK_LValueToRValue:
670    // If we're loading from a volatile type, force the destination
671    // into existence.
672    if (E->getSubExpr()->getType().isVolatileQualified()) {
673      EnsureDest(E->getType());
674      return Visit(E->getSubExpr());
675    }
676
677    // fallthrough
678
679  case CK_NoOp:
680  case CK_UserDefinedConversion:
681  case CK_ConstructorConversion:
682    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
683                                                   E->getType()) &&
684           "Implicit cast types must be compatible");
685    Visit(E->getSubExpr());
686    break;
687
688  case CK_LValueBitCast:
689    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
690
691  case CK_Dependent:
692  case CK_BitCast:
693  case CK_ArrayToPointerDecay:
694  case CK_FunctionToPointerDecay:
695  case CK_NullToPointer:
696  case CK_NullToMemberPointer:
697  case CK_BaseToDerivedMemberPointer:
698  case CK_DerivedToBaseMemberPointer:
699  case CK_MemberPointerToBoolean:
700  case CK_ReinterpretMemberPointer:
701  case CK_IntegralToPointer:
702  case CK_PointerToIntegral:
703  case CK_PointerToBoolean:
704  case CK_ToVoid:
705  case CK_VectorSplat:
706  case CK_IntegralCast:
707  case CK_IntegralToBoolean:
708  case CK_IntegralToFloating:
709  case CK_FloatingToIntegral:
710  case CK_FloatingToBoolean:
711  case CK_FloatingCast:
712  case CK_CPointerToObjCPointerCast:
713  case CK_BlockPointerToObjCPointerCast:
714  case CK_AnyPointerToBlockPointerCast:
715  case CK_ObjCObjectLValueCast:
716  case CK_FloatingRealToComplex:
717  case CK_FloatingComplexToReal:
718  case CK_FloatingComplexToBoolean:
719  case CK_FloatingComplexCast:
720  case CK_FloatingComplexToIntegralComplex:
721  case CK_IntegralRealToComplex:
722  case CK_IntegralComplexToReal:
723  case CK_IntegralComplexToBoolean:
724  case CK_IntegralComplexCast:
725  case CK_IntegralComplexToFloatingComplex:
726  case CK_ARCProduceObject:
727  case CK_ARCConsumeObject:
728  case CK_ARCReclaimReturnedObject:
729  case CK_ARCExtendBlockObject:
730  case CK_CopyAndAutoreleaseBlockObject:
731  case CK_BuiltinFnToFnPtr:
732  case CK_ZeroToOCLEvent:
733  case CK_AddressSpaceConversion:
734    llvm_unreachable("cast kind invalid for aggregate types");
735  }
736}
737
738void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
739  if (E->getCallReturnType()->isReferenceType()) {
740    EmitAggLoadOfLValue(E);
741    return;
742  }
743
744  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
745  EmitMoveFromReturnSlot(E, RV);
746}
747
748void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
749  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
750  EmitMoveFromReturnSlot(E, RV);
751}
752
753void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
754  CGF.EmitIgnoredExpr(E->getLHS());
755  Visit(E->getRHS());
756}
757
758void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
759  CodeGenFunction::StmtExprEvaluation eval(CGF);
760  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
761}
762
763void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
764  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
765    VisitPointerToDataMemberBinaryOperator(E);
766  else
767    CGF.ErrorUnsupported(E, "aggregate binary expression");
768}
769
770void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
771                                                    const BinaryOperator *E) {
772  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
773  EmitFinalDestCopy(E->getType(), LV);
774}
775
776/// Is the value of the given expression possibly a reference to or
777/// into a __block variable?
778static bool isBlockVarRef(const Expr *E) {
779  // Make sure we look through parens.
780  E = E->IgnoreParens();
781
782  // Check for a direct reference to a __block variable.
783  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
784    const VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
785    return (var && var->hasAttr<BlocksAttr>());
786  }
787
788  // More complicated stuff.
789
790  // Binary operators.
791  if (const BinaryOperator *op = dyn_cast<BinaryOperator>(E)) {
792    // For an assignment or pointer-to-member operation, just care
793    // about the LHS.
794    if (op->isAssignmentOp() || op->isPtrMemOp())
795      return isBlockVarRef(op->getLHS());
796
797    // For a comma, just care about the RHS.
798    if (op->getOpcode() == BO_Comma)
799      return isBlockVarRef(op->getRHS());
800
801    // FIXME: pointer arithmetic?
802    return false;
803
804  // Check both sides of a conditional operator.
805  } else if (const AbstractConditionalOperator *op
806               = dyn_cast<AbstractConditionalOperator>(E)) {
807    return isBlockVarRef(op->getTrueExpr())
808        || isBlockVarRef(op->getFalseExpr());
809
810  // OVEs are required to support BinaryConditionalOperators.
811  } else if (const OpaqueValueExpr *op
812               = dyn_cast<OpaqueValueExpr>(E)) {
813    if (const Expr *src = op->getSourceExpr())
814      return isBlockVarRef(src);
815
816  // Casts are necessary to get things like (*(int*)&var) = foo().
817  // We don't really care about the kind of cast here, except
818  // we don't want to look through l2r casts, because it's okay
819  // to get the *value* in a __block variable.
820  } else if (const CastExpr *cast = dyn_cast<CastExpr>(E)) {
821    if (cast->getCastKind() == CK_LValueToRValue)
822      return false;
823    return isBlockVarRef(cast->getSubExpr());
824
825  // Handle unary operators.  Again, just aggressively look through
826  // it, ignoring the operation.
827  } else if (const UnaryOperator *uop = dyn_cast<UnaryOperator>(E)) {
828    return isBlockVarRef(uop->getSubExpr());
829
830  // Look into the base of a field access.
831  } else if (const MemberExpr *mem = dyn_cast<MemberExpr>(E)) {
832    return isBlockVarRef(mem->getBase());
833
834  // Look into the base of a subscript.
835  } else if (const ArraySubscriptExpr *sub = dyn_cast<ArraySubscriptExpr>(E)) {
836    return isBlockVarRef(sub->getBase());
837  }
838
839  return false;
840}
841
842void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
843  // For an assignment to work, the value on the right has
844  // to be compatible with the value on the left.
845  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
846                                                 E->getRHS()->getType())
847         && "Invalid assignment");
848
849  // If the LHS might be a __block variable, and the RHS can
850  // potentially cause a block copy, we need to evaluate the RHS first
851  // so that the assignment goes the right place.
852  // This is pretty semantically fragile.
853  if (isBlockVarRef(E->getLHS()) &&
854      E->getRHS()->HasSideEffects(CGF.getContext())) {
855    // Ensure that we have a destination, and evaluate the RHS into that.
856    EnsureDest(E->getRHS()->getType());
857    Visit(E->getRHS());
858
859    // Now emit the LHS and copy into it.
860    LValue LHS = CGF.EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
861
862    // That copy is an atomic copy if the LHS is atomic.
863    if (LHS.getType()->isAtomicType()) {
864      CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
865      return;
866    }
867
868    EmitCopy(E->getLHS()->getType(),
869             AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
870                                     needsGC(E->getLHS()->getType()),
871                                     AggValueSlot::IsAliased),
872             Dest);
873    return;
874  }
875
876  LValue LHS = CGF.EmitLValue(E->getLHS());
877
878  // If we have an atomic type, evaluate into the destination and then
879  // do an atomic copy.
880  if (LHS.getType()->isAtomicType()) {
881    EnsureDest(E->getRHS()->getType());
882    Visit(E->getRHS());
883    CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
884    return;
885  }
886
887  // Codegen the RHS so that it stores directly into the LHS.
888  AggValueSlot LHSSlot =
889    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
890                            needsGC(E->getLHS()->getType()),
891                            AggValueSlot::IsAliased);
892  // A non-volatile aggregate destination might have volatile member.
893  if (!LHSSlot.isVolatile() &&
894      CGF.hasVolatileMember(E->getLHS()->getType()))
895    LHSSlot.setVolatile(true);
896
897  CGF.EmitAggExpr(E->getRHS(), LHSSlot);
898
899  // Copy into the destination if the assignment isn't ignored.
900  EmitFinalDestCopy(E->getType(), LHS);
901}
902
903void AggExprEmitter::
904VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
905  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
906  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
907  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
908
909  // Bind the common expression if necessary.
910  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
911
912  RegionCounter Cnt = CGF.getPGORegionCounter(E);
913  CodeGenFunction::ConditionalEvaluation eval(CGF);
914  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock, Cnt.getCount());
915
916  // Save whether the destination's lifetime is externally managed.
917  bool isExternallyDestructed = Dest.isExternallyDestructed();
918
919  eval.begin(CGF);
920  CGF.EmitBlock(LHSBlock);
921  Cnt.beginRegion(Builder);
922  Visit(E->getTrueExpr());
923  eval.end(CGF);
924
925  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
926  CGF.Builder.CreateBr(ContBlock);
927
928  // If the result of an agg expression is unused, then the emission
929  // of the LHS might need to create a destination slot.  That's fine
930  // with us, and we can safely emit the RHS into the same slot, but
931  // we shouldn't claim that it's already being destructed.
932  Dest.setExternallyDestructed(isExternallyDestructed);
933
934  eval.begin(CGF);
935  CGF.EmitBlock(RHSBlock);
936  Visit(E->getFalseExpr());
937  eval.end(CGF);
938
939  CGF.EmitBlock(ContBlock);
940}
941
942void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
943  Visit(CE->getChosenSubExpr());
944}
945
946void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
947  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
948  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
949
950  if (!ArgPtr) {
951    // If EmitVAArg fails, we fall back to the LLVM instruction.
952    llvm::Value *Val =
953        Builder.CreateVAArg(ArgValue, CGF.ConvertType(VE->getType()));
954    if (!Dest.isIgnored())
955      Builder.CreateStore(Val, Dest.getAddr());
956    return;
957  }
958
959  EmitFinalDestCopy(VE->getType(), CGF.MakeAddrLValue(ArgPtr, VE->getType()));
960}
961
962void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
963  // Ensure that we have a slot, but if we already do, remember
964  // whether it was externally destructed.
965  bool wasExternallyDestructed = Dest.isExternallyDestructed();
966  EnsureDest(E->getType());
967
968  // We're going to push a destructor if there isn't already one.
969  Dest.setExternallyDestructed();
970
971  Visit(E->getSubExpr());
972
973  // Push that destructor we promised.
974  if (!wasExternallyDestructed)
975    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
976}
977
978void
979AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
980  AggValueSlot Slot = EnsureSlot(E->getType());
981  CGF.EmitCXXConstructExpr(E, Slot);
982}
983
984void
985AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
986  AggValueSlot Slot = EnsureSlot(E->getType());
987  CGF.EmitLambdaExpr(E, Slot);
988}
989
990void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
991  CGF.enterFullExpression(E);
992  CodeGenFunction::RunCleanupsScope cleanups(CGF);
993  Visit(E->getSubExpr());
994}
995
996void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
997  QualType T = E->getType();
998  AggValueSlot Slot = EnsureSlot(T);
999  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
1000}
1001
1002void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
1003  QualType T = E->getType();
1004  AggValueSlot Slot = EnsureSlot(T);
1005  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
1006}
1007
1008/// isSimpleZero - If emitting this value will obviously just cause a store of
1009/// zero to memory, return true.  This can return false if uncertain, so it just
1010/// handles simple cases.
1011static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
1012  E = E->IgnoreParens();
1013
1014  // 0
1015  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
1016    return IL->getValue() == 0;
1017  // +0.0
1018  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
1019    return FL->getValue().isPosZero();
1020  // int()
1021  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
1022      CGF.getTypes().isZeroInitializable(E->getType()))
1023    return true;
1024  // (int*)0 - Null pointer expressions.
1025  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
1026    return ICE->getCastKind() == CK_NullToPointer;
1027  // '\0'
1028  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
1029    return CL->getValue() == 0;
1030
1031  // Otherwise, hard case: conservatively return false.
1032  return false;
1033}
1034
1035
1036void
1037AggExprEmitter::EmitInitializationToLValue(Expr *E, LValue LV) {
1038  QualType type = LV.getType();
1039  // FIXME: Ignore result?
1040  // FIXME: Are initializers affected by volatile?
1041  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
1042    // Storing "i32 0" to a zero'd memory location is a noop.
1043    return;
1044  } else if (isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) {
1045    return EmitNullInitializationToLValue(LV);
1046  } else if (type->isReferenceType()) {
1047    RValue RV = CGF.EmitReferenceBindingToExpr(E);
1048    return CGF.EmitStoreThroughLValue(RV, LV);
1049  }
1050
1051  switch (CGF.getEvaluationKind(type)) {
1052  case TEK_Complex:
1053    CGF.EmitComplexExprIntoLValue(E, LV, /*isInit*/ true);
1054    return;
1055  case TEK_Aggregate:
1056    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
1057                                               AggValueSlot::IsDestructed,
1058                                      AggValueSlot::DoesNotNeedGCBarriers,
1059                                               AggValueSlot::IsNotAliased,
1060                                               Dest.isZeroed()));
1061    return;
1062  case TEK_Scalar:
1063    if (LV.isSimple()) {
1064      CGF.EmitScalarInit(E, /*D=*/nullptr, LV, /*Captured=*/false);
1065    } else {
1066      CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
1067    }
1068    return;
1069  }
1070  llvm_unreachable("bad evaluation kind");
1071}
1072
1073void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
1074  QualType type = lv.getType();
1075
1076  // If the destination slot is already zeroed out before the aggregate is
1077  // copied into it, we don't have to emit any zeros here.
1078  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
1079    return;
1080
1081  if (CGF.hasScalarEvaluationKind(type)) {
1082    // For non-aggregates, we can store the appropriate null constant.
1083    llvm::Value *null = CGF.CGM.EmitNullConstant(type);
1084    // Note that the following is not equivalent to
1085    // EmitStoreThroughBitfieldLValue for ARC types.
1086    if (lv.isBitField()) {
1087      CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
1088    } else {
1089      assert(lv.isSimple());
1090      CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
1091    }
1092  } else {
1093    // There's a potential optimization opportunity in combining
1094    // memsets; that would be easy for arrays, but relatively
1095    // difficult for structures with the current code.
1096    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
1097  }
1098}
1099
1100void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
1101#if 0
1102  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
1103  // (Length of globals? Chunks of zeroed-out space?).
1104  //
1105  // If we can, prefer a copy from a global; this is a lot less code for long
1106  // globals, and it's easier for the current optimizers to analyze.
1107  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
1108    llvm::GlobalVariable* GV =
1109    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
1110                             llvm::GlobalValue::InternalLinkage, C, "");
1111    EmitFinalDestCopy(E->getType(), CGF.MakeAddrLValue(GV, E->getType()));
1112    return;
1113  }
1114#endif
1115  if (E->hadArrayRangeDesignator())
1116    CGF.ErrorUnsupported(E, "GNU array range designator extension");
1117
1118  AggValueSlot Dest = EnsureSlot(E->getType());
1119
1120  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddr(), E->getType(),
1121                                     Dest.getAlignment());
1122
1123  // Handle initialization of an array.
1124  if (E->getType()->isArrayType()) {
1125    if (E->isStringLiteralInit())
1126      return Visit(E->getInit(0));
1127
1128    QualType elementType =
1129        CGF.getContext().getAsArrayType(E->getType())->getElementType();
1130
1131    llvm::PointerType *APType =
1132      cast<llvm::PointerType>(Dest.getAddr()->getType());
1133    llvm::ArrayType *AType =
1134      cast<llvm::ArrayType>(APType->getElementType());
1135
1136    EmitArrayInit(Dest.getAddr(), AType, elementType, E);
1137    return;
1138  }
1139
1140  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
1141
1142  // Do struct initialization; this code just sets each individual member
1143  // to the approprate value.  This makes bitfield support automatic;
1144  // the disadvantage is that the generated code is more difficult for
1145  // the optimizer, especially with bitfields.
1146  unsigned NumInitElements = E->getNumInits();
1147  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
1148
1149  // Prepare a 'this' for CXXDefaultInitExprs.
1150  CodeGenFunction::FieldConstructionScope FCS(CGF, Dest.getAddr());
1151
1152  if (record->isUnion()) {
1153    // Only initialize one field of a union. The field itself is
1154    // specified by the initializer list.
1155    if (!E->getInitializedFieldInUnion()) {
1156      // Empty union; we have nothing to do.
1157
1158#ifndef NDEBUG
1159      // Make sure that it's really an empty and not a failure of
1160      // semantic analysis.
1161      for (const auto *Field : record->fields())
1162        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
1163#endif
1164      return;
1165    }
1166
1167    // FIXME: volatility
1168    FieldDecl *Field = E->getInitializedFieldInUnion();
1169
1170    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestLV, Field);
1171    if (NumInitElements) {
1172      // Store the initializer into the field
1173      EmitInitializationToLValue(E->getInit(0), FieldLoc);
1174    } else {
1175      // Default-initialize to null.
1176      EmitNullInitializationToLValue(FieldLoc);
1177    }
1178
1179    return;
1180  }
1181
1182  // We'll need to enter cleanup scopes in case any of the member
1183  // initializers throw an exception.
1184  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
1185  llvm::Instruction *cleanupDominator = nullptr;
1186
1187  // Here we iterate over the fields; this makes it simpler to both
1188  // default-initialize fields and skip over unnamed fields.
1189  unsigned curInitIndex = 0;
1190  for (const auto *field : record->fields()) {
1191    // We're done once we hit the flexible array member.
1192    if (field->getType()->isIncompleteArrayType())
1193      break;
1194
1195    // Always skip anonymous bitfields.
1196    if (field->isUnnamedBitfield())
1197      continue;
1198
1199    // We're done if we reach the end of the explicit initializers, we
1200    // have a zeroed object, and the rest of the fields are
1201    // zero-initializable.
1202    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
1203        CGF.getTypes().isZeroInitializable(E->getType()))
1204      break;
1205
1206
1207    LValue LV = CGF.EmitLValueForFieldInitialization(DestLV, field);
1208    // We never generate write-barries for initialized fields.
1209    LV.setNonGC(true);
1210
1211    if (curInitIndex < NumInitElements) {
1212      // Store the initializer into the field.
1213      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
1214    } else {
1215      // We're out of initalizers; default-initialize to null
1216      EmitNullInitializationToLValue(LV);
1217    }
1218
1219    // Push a destructor if necessary.
1220    // FIXME: if we have an array of structures, all explicitly
1221    // initialized, we can end up pushing a linear number of cleanups.
1222    bool pushedCleanup = false;
1223    if (QualType::DestructionKind dtorKind
1224          = field->getType().isDestructedType()) {
1225      assert(LV.isSimple());
1226      if (CGF.needsEHCleanup(dtorKind)) {
1227        if (!cleanupDominator)
1228          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
1229
1230        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1231                        CGF.getDestroyer(dtorKind), false);
1232        cleanups.push_back(CGF.EHStack.stable_begin());
1233        pushedCleanup = true;
1234      }
1235    }
1236
1237    // If the GEP didn't get used because of a dead zero init or something
1238    // else, clean it up for -O0 builds and general tidiness.
1239    if (!pushedCleanup && LV.isSimple())
1240      if (llvm::GetElementPtrInst *GEP =
1241            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
1242        if (GEP->use_empty())
1243          GEP->eraseFromParent();
1244  }
1245
1246  // Deactivate all the partial cleanups in reverse order, which
1247  // generally means popping them.
1248  for (unsigned i = cleanups.size(); i != 0; --i)
1249    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1250
1251  // Destroy the placeholder if we made one.
1252  if (cleanupDominator)
1253    cleanupDominator->eraseFromParent();
1254}
1255
1256//===----------------------------------------------------------------------===//
1257//                        Entry Points into this File
1258//===----------------------------------------------------------------------===//
1259
1260/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1261/// non-zero bytes that will be stored when outputting the initializer for the
1262/// specified initializer expression.
1263static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1264  E = E->IgnoreParens();
1265
1266  // 0 and 0.0 won't require any non-zero stores!
1267  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1268
1269  // If this is an initlist expr, sum up the size of sizes of the (present)
1270  // elements.  If this is something weird, assume the whole thing is non-zero.
1271  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1272  if (!ILE || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1273    return CGF.getContext().getTypeSizeInChars(E->getType());
1274
1275  // InitListExprs for structs have to be handled carefully.  If there are
1276  // reference members, we need to consider the size of the reference, not the
1277  // referencee.  InitListExprs for unions and arrays can't have references.
1278  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1279    if (!RT->isUnionType()) {
1280      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1281      CharUnits NumNonZeroBytes = CharUnits::Zero();
1282
1283      unsigned ILEElement = 0;
1284      for (const auto *Field : SD->fields()) {
1285        // We're done once we hit the flexible array member or run out of
1286        // InitListExpr elements.
1287        if (Field->getType()->isIncompleteArrayType() ||
1288            ILEElement == ILE->getNumInits())
1289          break;
1290        if (Field->isUnnamedBitfield())
1291          continue;
1292
1293        const Expr *E = ILE->getInit(ILEElement++);
1294
1295        // Reference values are always non-null and have the width of a pointer.
1296        if (Field->getType()->isReferenceType())
1297          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1298              CGF.getTarget().getPointerWidth(0));
1299        else
1300          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1301      }
1302
1303      return NumNonZeroBytes;
1304    }
1305  }
1306
1307
1308  CharUnits NumNonZeroBytes = CharUnits::Zero();
1309  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1310    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1311  return NumNonZeroBytes;
1312}
1313
1314/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1315/// zeros in it, emit a memset and avoid storing the individual zeros.
1316///
1317static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1318                                     CodeGenFunction &CGF) {
1319  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1320  // volatile stores.
1321  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == nullptr)
1322    return;
1323
1324  // C++ objects with a user-declared constructor don't need zero'ing.
1325  if (CGF.getLangOpts().CPlusPlus)
1326    if (const RecordType *RT = CGF.getContext()
1327                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1328      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1329      if (RD->hasUserDeclaredConstructor())
1330        return;
1331    }
1332
1333  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1334  std::pair<CharUnits, CharUnits> TypeInfo =
1335    CGF.getContext().getTypeInfoInChars(E->getType());
1336  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1337    return;
1338
1339  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1340  // we prefer to emit memset + individual stores for the rest.
1341  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1342  if (NumNonZeroBytes*4 > TypeInfo.first)
1343    return;
1344
1345  // Okay, it seems like a good idea to use an initial memset, emit the call.
1346  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1347  CharUnits Align = TypeInfo.second;
1348
1349  llvm::Value *Loc = Slot.getAddr();
1350
1351  Loc = CGF.Builder.CreateBitCast(Loc, CGF.Int8PtrTy);
1352  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1353                           Align.getQuantity(), false);
1354
1355  // Tell the AggExprEmitter that the slot is known zero.
1356  Slot.setZeroed();
1357}
1358
1359
1360
1361
1362/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1363/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1364/// the value of the aggregate expression is not needed.  If VolatileDest is
1365/// true, DestPtr cannot be 0.
1366void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot) {
1367  assert(E && hasAggregateEvaluationKind(E->getType()) &&
1368         "Invalid aggregate expression to emit");
1369  assert((Slot.getAddr() != nullptr || Slot.isIgnored()) &&
1370         "slot has bits but no address");
1371
1372  // Optimize the slot if possible.
1373  CheckAggExprForMemSetUse(Slot, E, *this);
1374
1375  AggExprEmitter(*this, Slot).Visit(const_cast<Expr*>(E));
1376}
1377
1378LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1379  assert(hasAggregateEvaluationKind(E->getType()) && "Invalid argument!");
1380  llvm::Value *Temp = CreateMemTemp(E->getType());
1381  LValue LV = MakeAddrLValue(Temp, E->getType());
1382  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1383                                         AggValueSlot::DoesNotNeedGCBarriers,
1384                                         AggValueSlot::IsNotAliased));
1385  return LV;
1386}
1387
1388void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1389                                        llvm::Value *SrcPtr, QualType Ty,
1390                                        bool isVolatile,
1391                                        CharUnits alignment,
1392                                        bool isAssignment) {
1393  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1394
1395  if (getLangOpts().CPlusPlus) {
1396    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1397      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1398      assert((Record->hasTrivialCopyConstructor() ||
1399              Record->hasTrivialCopyAssignment() ||
1400              Record->hasTrivialMoveConstructor() ||
1401              Record->hasTrivialMoveAssignment()) &&
1402             "Trying to aggregate-copy a type without a trivial copy/move "
1403             "constructor or assignment operator");
1404      // Ignore empty classes in C++.
1405      if (Record->isEmpty())
1406        return;
1407    }
1408  }
1409
1410  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1411  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1412  // read from another object that overlaps in anyway the storage of the first
1413  // object, then the overlap shall be exact and the two objects shall have
1414  // qualified or unqualified versions of a compatible type."
1415  //
1416  // memcpy is not defined if the source and destination pointers are exactly
1417  // equal, but other compilers do this optimization, and almost every memcpy
1418  // implementation handles this case safely.  If there is a libc that does not
1419  // safely handle this, we can add a target hook.
1420
1421  // Get data size and alignment info for this aggregate. If this is an
1422  // assignment don't copy the tail padding. Otherwise copying it is fine.
1423  std::pair<CharUnits, CharUnits> TypeInfo;
1424  if (isAssignment)
1425    TypeInfo = getContext().getTypeInfoDataSizeInChars(Ty);
1426  else
1427    TypeInfo = getContext().getTypeInfoInChars(Ty);
1428
1429  if (alignment.isZero())
1430    alignment = TypeInfo.second;
1431
1432  // FIXME: Handle variable sized types.
1433
1434  // FIXME: If we have a volatile struct, the optimizer can remove what might
1435  // appear to be `extra' memory ops:
1436  //
1437  // volatile struct { int i; } a, b;
1438  //
1439  // int main() {
1440  //   a = b;
1441  //   a = b;
1442  // }
1443  //
1444  // we need to use a different call here.  We use isVolatile to indicate when
1445  // either the source or the destination is volatile.
1446
1447  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1448  llvm::Type *DBP =
1449    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1450  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1451
1452  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1453  llvm::Type *SBP =
1454    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1455  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1456
1457  // Don't do any of the memmove_collectable tests if GC isn't set.
1458  if (CGM.getLangOpts().getGC() == LangOptions::NonGC) {
1459    // fall through
1460  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1461    RecordDecl *Record = RecordTy->getDecl();
1462    if (Record->hasObjectMember()) {
1463      CharUnits size = TypeInfo.first;
1464      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1465      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1466      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1467                                                    SizeVal);
1468      return;
1469    }
1470  } else if (Ty->isArrayType()) {
1471    QualType BaseType = getContext().getBaseElementType(Ty);
1472    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1473      if (RecordTy->getDecl()->hasObjectMember()) {
1474        CharUnits size = TypeInfo.first;
1475        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1476        llvm::Value *SizeVal =
1477          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1478        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1479                                                      SizeVal);
1480        return;
1481      }
1482    }
1483  }
1484
1485  // Determine the metadata to describe the position of any padding in this
1486  // memcpy, as well as the TBAA tags for the members of the struct, in case
1487  // the optimizer wishes to expand it in to scalar memory operations.
1488  llvm::MDNode *TBAAStructTag = CGM.getTBAAStructInfo(Ty);
1489
1490  Builder.CreateMemCpy(DestPtr, SrcPtr,
1491                       llvm::ConstantInt::get(IntPtrTy,
1492                                              TypeInfo.first.getQuantity()),
1493                       alignment.getQuantity(), isVolatile,
1494                       /*TBAATag=*/nullptr, TBAAStructTag);
1495}
1496