CGExprAgg.cpp revision 296417 
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  bool IsResultUnused;
38
39  /// We want to use 'dest' as the return slot except under two
40  /// conditions:
41  ///   - The destination slot requires garbage collection, so we
42  ///     need to use the GC API.
43  ///   - The destination slot is potentially aliased.
44  bool shouldUseDestForReturnSlot() const {
45    return !(Dest.requiresGCollection() || Dest.isPotentiallyAliased());
46  }
47
48  ReturnValueSlot getReturnValueSlot() const {
49    if (!shouldUseDestForReturnSlot())
50      return ReturnValueSlot();
51
52    return ReturnValueSlot(Dest.getAddress(), Dest.isVolatile(),
53                           IsResultUnused);
54  }
55
56  AggValueSlot EnsureSlot(QualType T) {
57    if (!Dest.isIgnored()) return Dest;
58    return CGF.CreateAggTemp(T, "agg.tmp.ensured");
59  }
60  void EnsureDest(QualType T) {
61    if (!Dest.isIgnored()) return;
62    Dest = CGF.CreateAggTemp(T, "agg.tmp.ensured");
63  }
64
65public:
66  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest, bool IsResultUnused)
67    : CGF(cgf), Builder(CGF.Builder), Dest(Dest),
68    IsResultUnused(IsResultUnused) { }
69
70  //===--------------------------------------------------------------------===//
71  //                               Utilities
72  //===--------------------------------------------------------------------===//
73
74  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
75  /// represents a value lvalue, this method emits the address of the lvalue,
76  /// then loads the result into DestPtr.
77  void EmitAggLoadOfLValue(const Expr *E);
78
79  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
80  void EmitFinalDestCopy(QualType type, const LValue &src);
81  void EmitFinalDestCopy(QualType type, RValue src);
82  void EmitCopy(QualType type, const AggValueSlot &dest,
83                const AggValueSlot &src);
84
85  void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
86
87  void EmitArrayInit(Address 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 Visit(Expr *E) {
103    ApplyDebugLocation DL(CGF, E);
104    StmtVisitor<AggExprEmitter>::Visit(E);
105  }
106
107  void VisitStmt(Stmt *S) {
108    CGF.ErrorUnsupported(S, "aggregate expression");
109  }
110  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
111  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
112    Visit(GE->getResultExpr());
113  }
114  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
115  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
116    return Visit(E->getReplacement());
117  }
118
119  // l-values.
120  void VisitDeclRefExpr(DeclRefExpr *E) {
121    // For aggregates, we should always be able to emit the variable
122    // as an l-value unless it's a reference.  This is due to the fact
123    // that we can't actually ever see a normal l2r conversion on an
124    // aggregate in C++, and in C there's no language standard
125    // actively preventing us from listing variables in the captures
126    // list of a block.
127    if (E->getDecl()->getType()->isReferenceType()) {
128      if (CodeGenFunction::ConstantEmission result
129            = CGF.tryEmitAsConstant(E)) {
130        EmitFinalDestCopy(E->getType(), result.getReferenceLValue(CGF, E));
131        return;
132      }
133    }
134
135    EmitAggLoadOfLValue(E);
136  }
137
138  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
139  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
140  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
141  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
142  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
143    EmitAggLoadOfLValue(E);
144  }
145  void VisitPredefinedExpr(const PredefinedExpr *E) {
146    EmitAggLoadOfLValue(E);
147  }
148
149  // Operators.
150  void VisitCastExpr(CastExpr *E);
151  void VisitCallExpr(const CallExpr *E);
152  void VisitStmtExpr(const StmtExpr *E);
153  void VisitBinaryOperator(const BinaryOperator *BO);
154  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
155  void VisitBinAssign(const BinaryOperator *E);
156  void VisitBinComma(const BinaryOperator *E);
157
158  void VisitObjCMessageExpr(ObjCMessageExpr *E);
159  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
160    EmitAggLoadOfLValue(E);
161  }
162
163  void VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E);
164  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
165  void VisitChooseExpr(const ChooseExpr *CE);
166  void VisitInitListExpr(InitListExpr *E);
167  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
168  void VisitNoInitExpr(NoInitExpr *E) { } // Do nothing.
169  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
170    Visit(DAE->getExpr());
171  }
172  void VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
173    CodeGenFunction::CXXDefaultInitExprScope Scope(CGF);
174    Visit(DIE->getExpr());
175  }
176  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
177  void VisitCXXConstructExpr(const CXXConstructExpr *E);
178  void VisitLambdaExpr(LambdaExpr *E);
179  void VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E);
180  void VisitExprWithCleanups(ExprWithCleanups *E);
181  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
182  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
183  void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
184  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
185
186  void VisitPseudoObjectExpr(PseudoObjectExpr *E) {
187    if (E->isGLValue()) {
188      LValue LV = CGF.EmitPseudoObjectLValue(E);
189      return EmitFinalDestCopy(E->getType(), LV);
190    }
191
192    CGF.EmitPseudoObjectRValue(E, EnsureSlot(E->getType()));
193  }
194
195  void VisitVAArgExpr(VAArgExpr *E);
196
197  void EmitInitializationToLValue(Expr *E, LValue Address);
198  void EmitNullInitializationToLValue(LValue Address);
199  //  case Expr::ChooseExprClass:
200  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
201  void VisitAtomicExpr(AtomicExpr *E) {
202    RValue Res = CGF.EmitAtomicExpr(E);
203    EmitFinalDestCopy(E->getType(), Res);
204  }
205};
206}  // end anonymous namespace.
207
208//===----------------------------------------------------------------------===//
209//                                Utilities
210//===----------------------------------------------------------------------===//
211
212/// EmitAggLoadOfLValue - Given an expression with aggregate type that
213/// represents a value lvalue, this method emits the address of the lvalue,
214/// then loads the result into DestPtr.
215void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
216  LValue LV = CGF.EmitLValue(E);
217
218  // If the type of the l-value is atomic, then do an atomic load.
219  if (LV.getType()->isAtomicType() || CGF.LValueIsSuitableForInlineAtomic(LV)) {
220    CGF.EmitAtomicLoad(LV, E->getExprLoc(), Dest);
221    return;
222  }
223
224  EmitFinalDestCopy(E->getType(), LV);
225}
226
227/// \brief True if the given aggregate type requires special GC API calls.
228bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
229  // Only record types have members that might require garbage collection.
230  const RecordType *RecordTy = T->getAs<RecordType>();
231  if (!RecordTy) return false;
232
233  // Don't mess with non-trivial C++ types.
234  RecordDecl *Record = RecordTy->getDecl();
235  if (isa<CXXRecordDecl>(Record) &&
236      (cast<CXXRecordDecl>(Record)->hasNonTrivialCopyConstructor() ||
237       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
238    return false;
239
240  // Check whether the type has an object member.
241  return Record->hasObjectMember();
242}
243
244/// \brief Perform the final move to DestPtr if for some reason
245/// getReturnValueSlot() didn't use it directly.
246///
247/// The idea is that you do something like this:
248///   RValue Result = EmitSomething(..., getReturnValueSlot());
249///   EmitMoveFromReturnSlot(E, Result);
250///
251/// If nothing interferes, this will cause the result to be emitted
252/// directly into the return value slot.  Otherwise, a final move
253/// will be performed.
254void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue src) {
255  if (shouldUseDestForReturnSlot()) {
256    // Logically, Dest.getAddr() should equal Src.getAggregateAddr().
257    // The possibility of undef rvalues complicates that a lot,
258    // though, so we can't really assert.
259    return;
260  }
261
262  // Otherwise, copy from there to the destination.
263  assert(Dest.getPointer() != src.getAggregatePointer());
264  EmitFinalDestCopy(E->getType(), src);
265}
266
267/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
268void AggExprEmitter::EmitFinalDestCopy(QualType type, RValue src) {
269  assert(src.isAggregate() && "value must be aggregate value!");
270  LValue srcLV = CGF.MakeAddrLValue(src.getAggregateAddress(), type);
271  EmitFinalDestCopy(type, srcLV);
272}
273
274/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
275void AggExprEmitter::EmitFinalDestCopy(QualType type, const LValue &src) {
276  // If Dest is ignored, then we're evaluating an aggregate expression
277  // in a context that doesn't care about the result.  Note that loads
278  // from volatile l-values force the existence of a non-ignored
279  // destination.
280  if (Dest.isIgnored())
281    return;
282
283  AggValueSlot srcAgg =
284    AggValueSlot::forLValue(src, AggValueSlot::IsDestructed,
285                            needsGC(type), AggValueSlot::IsAliased);
286  EmitCopy(type, Dest, srcAgg);
287}
288
289/// Perform a copy from the source into the destination.
290///
291/// \param type - the type of the aggregate being copied; qualifiers are
292///   ignored
293void AggExprEmitter::EmitCopy(QualType type, const AggValueSlot &dest,
294                              const AggValueSlot &src) {
295  if (dest.requiresGCollection()) {
296    CharUnits sz = CGF.getContext().getTypeSizeInChars(type);
297    llvm::Value *size = llvm::ConstantInt::get(CGF.SizeTy, sz.getQuantity());
298    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
299                                                      dest.getAddress(),
300                                                      src.getAddress(),
301                                                      size);
302    return;
303  }
304
305  // If the result of the assignment is used, copy the LHS there also.
306  // It's volatile if either side is.  Use the minimum alignment of
307  // the two sides.
308  CGF.EmitAggregateCopy(dest.getAddress(), src.getAddress(), type,
309                        dest.isVolatile() || src.isVolatile());
310}
311
312/// \brief Emit the initializer for a std::initializer_list initialized with a
313/// real initializer list.
314void
315AggExprEmitter::VisitCXXStdInitializerListExpr(CXXStdInitializerListExpr *E) {
316  // Emit an array containing the elements.  The array is externally destructed
317  // if the std::initializer_list object is.
318  ASTContext &Ctx = CGF.getContext();
319  LValue Array = CGF.EmitLValue(E->getSubExpr());
320  assert(Array.isSimple() && "initializer_list array not a simple lvalue");
321  Address ArrayPtr = Array.getAddress();
322
323  const ConstantArrayType *ArrayType =
324      Ctx.getAsConstantArrayType(E->getSubExpr()->getType());
325  assert(ArrayType && "std::initializer_list constructed from non-array");
326
327  // FIXME: Perform the checks on the field types in SemaInit.
328  RecordDecl *Record = E->getType()->castAs<RecordType>()->getDecl();
329  RecordDecl::field_iterator Field = Record->field_begin();
330  if (Field == Record->field_end()) {
331    CGF.ErrorUnsupported(E, "weird std::initializer_list");
332    return;
333  }
334
335  // Start pointer.
336  if (!Field->getType()->isPointerType() ||
337      !Ctx.hasSameType(Field->getType()->getPointeeType(),
338                       ArrayType->getElementType())) {
339    CGF.ErrorUnsupported(E, "weird std::initializer_list");
340    return;
341  }
342
343  AggValueSlot Dest = EnsureSlot(E->getType());
344  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
345  LValue Start = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
346  llvm::Value *Zero = llvm::ConstantInt::get(CGF.PtrDiffTy, 0);
347  llvm::Value *IdxStart[] = { Zero, Zero };
348  llvm::Value *ArrayStart =
349      Builder.CreateInBoundsGEP(ArrayPtr.getPointer(), IdxStart, "arraystart");
350  CGF.EmitStoreThroughLValue(RValue::get(ArrayStart), Start);
351  ++Field;
352
353  if (Field == Record->field_end()) {
354    CGF.ErrorUnsupported(E, "weird std::initializer_list");
355    return;
356  }
357
358  llvm::Value *Size = Builder.getInt(ArrayType->getSize());
359  LValue EndOrLength = CGF.EmitLValueForFieldInitialization(DestLV, *Field);
360  if (Field->getType()->isPointerType() &&
361      Ctx.hasSameType(Field->getType()->getPointeeType(),
362                      ArrayType->getElementType())) {
363    // End pointer.
364    llvm::Value *IdxEnd[] = { Zero, Size };
365    llvm::Value *ArrayEnd =
366        Builder.CreateInBoundsGEP(ArrayPtr.getPointer(), IdxEnd, "arrayend");
367    CGF.EmitStoreThroughLValue(RValue::get(ArrayEnd), EndOrLength);
368  } else if (Ctx.hasSameType(Field->getType(), Ctx.getSizeType())) {
369    // Length.
370    CGF.EmitStoreThroughLValue(RValue::get(Size), EndOrLength);
371  } else {
372    CGF.ErrorUnsupported(E, "weird std::initializer_list");
373    return;
374  }
375}
376
377/// \brief Determine if E is a trivial array filler, that is, one that is
378/// equivalent to zero-initialization.
379static bool isTrivialFiller(Expr *E) {
380  if (!E)
381    return true;
382
383  if (isa<ImplicitValueInitExpr>(E))
384    return true;
385
386  if (auto *ILE = dyn_cast<InitListExpr>(E)) {
387    if (ILE->getNumInits())
388      return false;
389    return isTrivialFiller(ILE->getArrayFiller());
390  }
391
392  if (auto *Cons = dyn_cast_or_null<CXXConstructExpr>(E))
393    return Cons->getConstructor()->isDefaultConstructor() &&
394           Cons->getConstructor()->isTrivial();
395
396  // FIXME: Are there other cases where we can avoid emitting an initializer?
397  return false;
398}
399
400/// \brief Emit initialization of an array from an initializer list.
401void AggExprEmitter::EmitArrayInit(Address DestPtr, llvm::ArrayType *AType,
402                                   QualType elementType, InitListExpr *E) {
403  uint64_t NumInitElements = E->getNumInits();
404
405  uint64_t NumArrayElements = AType->getNumElements();
406  assert(NumInitElements <= NumArrayElements);
407
408  // DestPtr is an array*.  Construct an elementType* by drilling
409  // down a level.
410  llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
411  llvm::Value *indices[] = { zero, zero };
412  llvm::Value *begin =
413    Builder.CreateInBoundsGEP(DestPtr.getPointer(), indices, "arrayinit.begin");
414
415  CharUnits elementSize = CGF.getContext().getTypeSizeInChars(elementType);
416  CharUnits elementAlign =
417    DestPtr.getAlignment().alignmentOfArrayElement(elementSize);
418
419  // Exception safety requires us to destroy all the
420  // already-constructed members if an initializer throws.
421  // For that, we'll need an EH cleanup.
422  QualType::DestructionKind dtorKind = elementType.isDestructedType();
423  Address endOfInit = Address::invalid();
424  EHScopeStack::stable_iterator cleanup;
425  llvm::Instruction *cleanupDominator = nullptr;
426  if (CGF.needsEHCleanup(dtorKind)) {
427    // In principle we could tell the cleanup where we are more
428    // directly, but the control flow can get so varied here that it
429    // would actually be quite complex.  Therefore we go through an
430    // alloca.
431    endOfInit = CGF.CreateTempAlloca(begin->getType(), CGF.getPointerAlign(),
432                                     "arrayinit.endOfInit");
433    cleanupDominator = Builder.CreateStore(begin, endOfInit);
434    CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
435                                         elementAlign,
436                                         CGF.getDestroyer(dtorKind));
437    cleanup = CGF.EHStack.stable_begin();
438
439  // Otherwise, remember that we didn't need a cleanup.
440  } else {
441    dtorKind = QualType::DK_none;
442  }
443
444  llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
445
446  // The 'current element to initialize'.  The invariants on this
447  // variable are complicated.  Essentially, after each iteration of
448  // the loop, it points to the last initialized element, except
449  // that it points to the beginning of the array before any
450  // elements have been initialized.
451  llvm::Value *element = begin;
452
453  // Emit the explicit initializers.
454  for (uint64_t i = 0; i != NumInitElements; ++i) {
455    // Advance to the next element.
456    if (i > 0) {
457      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
458
459      // Tell the cleanup that it needs to destroy up to this
460      // element.  TODO: some of these stores can be trivially
461      // observed to be unnecessary.
462      if (endOfInit.isValid()) Builder.CreateStore(element, endOfInit);
463    }
464
465    LValue elementLV =
466      CGF.MakeAddrLValue(Address(element, elementAlign), elementType);
467    EmitInitializationToLValue(E->getInit(i), elementLV);
468  }
469
470  // Check whether there's a non-trivial array-fill expression.
471  Expr *filler = E->getArrayFiller();
472  bool hasTrivialFiller = isTrivialFiller(filler);
473
474  // Any remaining elements need to be zero-initialized, possibly
475  // using the filler expression.  We can skip this if the we're
476  // emitting to zeroed memory.
477  if (NumInitElements != NumArrayElements &&
478      !(Dest.isZeroed() && hasTrivialFiller &&
479        CGF.getTypes().isZeroInitializable(elementType))) {
480
481    // Use an actual loop.  This is basically
482    //   do { *array++ = filler; } while (array != end);
483
484    // Advance to the start of the rest of the array.
485    if (NumInitElements) {
486      element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
487      if (endOfInit.isValid()) Builder.CreateStore(element, endOfInit);
488    }
489
490    // Compute the end of the array.
491    llvm::Value *end = Builder.CreateInBoundsGEP(begin,
492                      llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
493                                                 "arrayinit.end");
494
495    llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
496    llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
497
498    // Jump into the body.
499    CGF.EmitBlock(bodyBB);
500    llvm::PHINode *currentElement =
501      Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
502    currentElement->addIncoming(element, entryBB);
503
504    // Emit the actual filler expression.
505    LValue elementLV =
506      CGF.MakeAddrLValue(Address(currentElement, elementAlign), elementType);
507    if (filler)
508      EmitInitializationToLValue(filler, elementLV);
509    else
510      EmitNullInitializationToLValue(elementLV);
511
512    // Move on to the next element.
513    llvm::Value *nextElement =
514      Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
515
516    // Tell the EH cleanup that we finished with the last element.
517    if (endOfInit.isValid()) Builder.CreateStore(nextElement, endOfInit);
518
519    // Leave the loop if we're done.
520    llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
521                                             "arrayinit.done");
522    llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
523    Builder.CreateCondBr(done, endBB, bodyBB);
524    currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
525
526    CGF.EmitBlock(endBB);
527  }
528
529  // Leave the partial-array cleanup if we entered one.
530  if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
531}
532
533//===----------------------------------------------------------------------===//
534//                            Visitor Methods
535//===----------------------------------------------------------------------===//
536
537void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
538  Visit(E->GetTemporaryExpr());
539}
540
541void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
542  EmitFinalDestCopy(e->getType(), CGF.getOpaqueLValueMapping(e));
543}
544
545void
546AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
547  if (Dest.isPotentiallyAliased() &&
548      E->getType().isPODType(CGF.getContext())) {
549    // For a POD type, just emit a load of the lvalue + a copy, because our
550    // compound literal might alias the destination.
551    EmitAggLoadOfLValue(E);
552    return;
553  }
554
555  AggValueSlot Slot = EnsureSlot(E->getType());
556  CGF.EmitAggExpr(E->getInitializer(), Slot);
557}
558
559/// Attempt to look through various unimportant expressions to find a
560/// cast of the given kind.
561static Expr *findPeephole(Expr *op, CastKind kind) {
562  while (true) {
563    op = op->IgnoreParens();
564    if (CastExpr *castE = dyn_cast<CastExpr>(op)) {
565      if (castE->getCastKind() == kind)
566        return castE->getSubExpr();
567      if (castE->getCastKind() == CK_NoOp)
568        continue;
569    }
570    return nullptr;
571  }
572}
573
574void AggExprEmitter::VisitCastExpr(CastExpr *E) {
575  if (const auto *ECE = dyn_cast<ExplicitCastExpr>(E))
576    CGF.CGM.EmitExplicitCastExprType(ECE, &CGF);
577  switch (E->getCastKind()) {
578  case CK_Dynamic: {
579    // FIXME: Can this actually happen? We have no test coverage for it.
580    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
581    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr(),
582                                      CodeGenFunction::TCK_Load);
583    // FIXME: Do we also need to handle property references here?
584    if (LV.isSimple())
585      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
586    else
587      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
588
589    if (!Dest.isIgnored())
590      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
591    break;
592  }
593
594  case CK_ToUnion: {
595    // Evaluate even if the destination is ignored.
596    if (Dest.isIgnored()) {
597      CGF.EmitAnyExpr(E->getSubExpr(), AggValueSlot::ignored(),
598                      /*ignoreResult=*/true);
599      break;
600    }
601
602    // GCC union extension
603    QualType Ty = E->getSubExpr()->getType();
604    Address CastPtr =
605      Builder.CreateElementBitCast(Dest.getAddress(), CGF.ConvertType(Ty));
606    EmitInitializationToLValue(E->getSubExpr(),
607                               CGF.MakeAddrLValue(CastPtr, Ty));
608    break;
609  }
610
611  case CK_DerivedToBase:
612  case CK_BaseToDerived:
613  case CK_UncheckedDerivedToBase: {
614    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
615                "should have been unpacked before we got here");
616  }
617
618  case CK_NonAtomicToAtomic:
619  case CK_AtomicToNonAtomic: {
620    bool isToAtomic = (E->getCastKind() == CK_NonAtomicToAtomic);
621
622    // Determine the atomic and value types.
623    QualType atomicType = E->getSubExpr()->getType();
624    QualType valueType = E->getType();
625    if (isToAtomic) std::swap(atomicType, valueType);
626
627    assert(atomicType->isAtomicType());
628    assert(CGF.getContext().hasSameUnqualifiedType(valueType,
629                          atomicType->castAs<AtomicType>()->getValueType()));
630
631    // Just recurse normally if we're ignoring the result or the
632    // atomic type doesn't change representation.
633    if (Dest.isIgnored() || !CGF.CGM.isPaddedAtomicType(atomicType)) {
634      return Visit(E->getSubExpr());
635    }
636
637    CastKind peepholeTarget =
638      (isToAtomic ? CK_AtomicToNonAtomic : CK_NonAtomicToAtomic);
639
640    // These two cases are reverses of each other; try to peephole them.
641    if (Expr *op = findPeephole(E->getSubExpr(), peepholeTarget)) {
642      assert(CGF.getContext().hasSameUnqualifiedType(op->getType(),
643                                                     E->getType()) &&
644           "peephole significantly changed types?");
645      return Visit(op);
646    }
647
648    // If we're converting an r-value of non-atomic type to an r-value
649    // of atomic type, just emit directly into the relevant sub-object.
650    if (isToAtomic) {
651      AggValueSlot valueDest = Dest;
652      if (!valueDest.isIgnored() && CGF.CGM.isPaddedAtomicType(atomicType)) {
653        // Zero-initialize.  (Strictly speaking, we only need to intialize
654        // the padding at the end, but this is simpler.)
655        if (!Dest.isZeroed())
656          CGF.EmitNullInitialization(Dest.getAddress(), atomicType);
657
658        // Build a GEP to refer to the subobject.
659        Address valueAddr =
660            CGF.Builder.CreateStructGEP(valueDest.getAddress(), 0,
661                                        CharUnits());
662        valueDest = AggValueSlot::forAddr(valueAddr,
663                                          valueDest.getQualifiers(),
664                                          valueDest.isExternallyDestructed(),
665                                          valueDest.requiresGCollection(),
666                                          valueDest.isPotentiallyAliased(),
667                                          AggValueSlot::IsZeroed);
668      }
669
670      CGF.EmitAggExpr(E->getSubExpr(), valueDest);
671      return;
672    }
673
674    // Otherwise, we're converting an atomic type to a non-atomic type.
675    // Make an atomic temporary, emit into that, and then copy the value out.
676    AggValueSlot atomicSlot =
677      CGF.CreateAggTemp(atomicType, "atomic-to-nonatomic.temp");
678    CGF.EmitAggExpr(E->getSubExpr(), atomicSlot);
679
680    Address valueAddr =
681      Builder.CreateStructGEP(atomicSlot.getAddress(), 0, CharUnits());
682    RValue rvalue = RValue::getAggregate(valueAddr, atomicSlot.isVolatile());
683    return EmitFinalDestCopy(valueType, rvalue);
684  }
685
686  case CK_LValueToRValue:
687    // If we're loading from a volatile type, force the destination
688    // into existence.
689    if (E->getSubExpr()->getType().isVolatileQualified()) {
690      EnsureDest(E->getType());
691      return Visit(E->getSubExpr());
692    }
693
694    // fallthrough
695
696  case CK_NoOp:
697  case CK_UserDefinedConversion:
698  case CK_ConstructorConversion:
699    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
700                                                   E->getType()) &&
701           "Implicit cast types must be compatible");
702    Visit(E->getSubExpr());
703    break;
704
705  case CK_LValueBitCast:
706    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
707
708  case CK_Dependent:
709  case CK_BitCast:
710  case CK_ArrayToPointerDecay:
711  case CK_FunctionToPointerDecay:
712  case CK_NullToPointer:
713  case CK_NullToMemberPointer:
714  case CK_BaseToDerivedMemberPointer:
715  case CK_DerivedToBaseMemberPointer:
716  case CK_MemberPointerToBoolean:
717  case CK_ReinterpretMemberPointer:
718  case CK_IntegralToPointer:
719  case CK_PointerToIntegral:
720  case CK_PointerToBoolean:
721  case CK_ToVoid:
722  case CK_VectorSplat:
723  case CK_IntegralCast:
724  case CK_BooleanToSignedIntegral:
725  case CK_IntegralToBoolean:
726  case CK_IntegralToFloating:
727  case CK_FloatingToIntegral:
728  case CK_FloatingToBoolean:
729  case CK_FloatingCast:
730  case CK_CPointerToObjCPointerCast:
731  case CK_BlockPointerToObjCPointerCast:
732  case CK_AnyPointerToBlockPointerCast:
733  case CK_ObjCObjectLValueCast:
734  case CK_FloatingRealToComplex:
735  case CK_FloatingComplexToReal:
736  case CK_FloatingComplexToBoolean:
737  case CK_FloatingComplexCast:
738  case CK_FloatingComplexToIntegralComplex:
739  case CK_IntegralRealToComplex:
740  case CK_IntegralComplexToReal:
741  case CK_IntegralComplexToBoolean:
742  case CK_IntegralComplexCast:
743  case CK_IntegralComplexToFloatingComplex:
744  case CK_ARCProduceObject:
745  case CK_ARCConsumeObject:
746  case CK_ARCReclaimReturnedObject:
747  case CK_ARCExtendBlockObject:
748  case CK_CopyAndAutoreleaseBlockObject:
749  case CK_BuiltinFnToFnPtr:
750  case CK_ZeroToOCLEvent:
751  case CK_AddressSpaceConversion:
752    llvm_unreachable("cast kind invalid for aggregate types");
753  }
754}
755
756void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
757  if (E->getCallReturnType(CGF.getContext())->isReferenceType()) {
758    EmitAggLoadOfLValue(E);
759    return;
760  }
761
762  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
763  EmitMoveFromReturnSlot(E, RV);
764}
765
766void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
767  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
768  EmitMoveFromReturnSlot(E, RV);
769}
770
771void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
772  CGF.EmitIgnoredExpr(E->getLHS());
773  Visit(E->getRHS());
774}
775
776void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
777  CodeGenFunction::StmtExprEvaluation eval(CGF);
778  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
779}
780
781void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
782  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
783    VisitPointerToDataMemberBinaryOperator(E);
784  else
785    CGF.ErrorUnsupported(E, "aggregate binary expression");
786}
787
788void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
789                                                    const BinaryOperator *E) {
790  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
791  EmitFinalDestCopy(E->getType(), LV);
792}
793
794/// Is the value of the given expression possibly a reference to or
795/// into a __block variable?
796static bool isBlockVarRef(const Expr *E) {
797  // Make sure we look through parens.
798  E = E->IgnoreParens();
799
800  // Check for a direct reference to a __block variable.
801  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
802    const VarDecl *var = dyn_cast<VarDecl>(DRE->getDecl());
803    return (var && var->hasAttr<BlocksAttr>());
804  }
805
806  // More complicated stuff.
807
808  // Binary operators.
809  if (const BinaryOperator *op = dyn_cast<BinaryOperator>(E)) {
810    // For an assignment or pointer-to-member operation, just care
811    // about the LHS.
812    if (op->isAssignmentOp() || op->isPtrMemOp())
813      return isBlockVarRef(op->getLHS());
814
815    // For a comma, just care about the RHS.
816    if (op->getOpcode() == BO_Comma)
817      return isBlockVarRef(op->getRHS());
818
819    // FIXME: pointer arithmetic?
820    return false;
821
822  // Check both sides of a conditional operator.
823  } else if (const AbstractConditionalOperator *op
824               = dyn_cast<AbstractConditionalOperator>(E)) {
825    return isBlockVarRef(op->getTrueExpr())
826        || isBlockVarRef(op->getFalseExpr());
827
828  // OVEs are required to support BinaryConditionalOperators.
829  } else if (const OpaqueValueExpr *op
830               = dyn_cast<OpaqueValueExpr>(E)) {
831    if (const Expr *src = op->getSourceExpr())
832      return isBlockVarRef(src);
833
834  // Casts are necessary to get things like (*(int*)&var) = foo().
835  // We don't really care about the kind of cast here, except
836  // we don't want to look through l2r casts, because it's okay
837  // to get the *value* in a __block variable.
838  } else if (const CastExpr *cast = dyn_cast<CastExpr>(E)) {
839    if (cast->getCastKind() == CK_LValueToRValue)
840      return false;
841    return isBlockVarRef(cast->getSubExpr());
842
843  // Handle unary operators.  Again, just aggressively look through
844  // it, ignoring the operation.
845  } else if (const UnaryOperator *uop = dyn_cast<UnaryOperator>(E)) {
846    return isBlockVarRef(uop->getSubExpr());
847
848  // Look into the base of a field access.
849  } else if (const MemberExpr *mem = dyn_cast<MemberExpr>(E)) {
850    return isBlockVarRef(mem->getBase());
851
852  // Look into the base of a subscript.
853  } else if (const ArraySubscriptExpr *sub = dyn_cast<ArraySubscriptExpr>(E)) {
854    return isBlockVarRef(sub->getBase());
855  }
856
857  return false;
858}
859
860void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
861  // For an assignment to work, the value on the right has
862  // to be compatible with the value on the left.
863  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
864                                                 E->getRHS()->getType())
865         && "Invalid assignment");
866
867  // If the LHS might be a __block variable, and the RHS can
868  // potentially cause a block copy, we need to evaluate the RHS first
869  // so that the assignment goes the right place.
870  // This is pretty semantically fragile.
871  if (isBlockVarRef(E->getLHS()) &&
872      E->getRHS()->HasSideEffects(CGF.getContext())) {
873    // Ensure that we have a destination, and evaluate the RHS into that.
874    EnsureDest(E->getRHS()->getType());
875    Visit(E->getRHS());
876
877    // Now emit the LHS and copy into it.
878    LValue LHS = CGF.EmitCheckedLValue(E->getLHS(), CodeGenFunction::TCK_Store);
879
880    // That copy is an atomic copy if the LHS is atomic.
881    if (LHS.getType()->isAtomicType() ||
882        CGF.LValueIsSuitableForInlineAtomic(LHS)) {
883      CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
884      return;
885    }
886
887    EmitCopy(E->getLHS()->getType(),
888             AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
889                                     needsGC(E->getLHS()->getType()),
890                                     AggValueSlot::IsAliased),
891             Dest);
892    return;
893  }
894
895  LValue LHS = CGF.EmitLValue(E->getLHS());
896
897  // If we have an atomic type, evaluate into the destination and then
898  // do an atomic copy.
899  if (LHS.getType()->isAtomicType() ||
900      CGF.LValueIsSuitableForInlineAtomic(LHS)) {
901    EnsureDest(E->getRHS()->getType());
902    Visit(E->getRHS());
903    CGF.EmitAtomicStore(Dest.asRValue(), LHS, /*isInit*/ false);
904    return;
905  }
906
907  // Codegen the RHS so that it stores directly into the LHS.
908  AggValueSlot LHSSlot =
909    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
910                            needsGC(E->getLHS()->getType()),
911                            AggValueSlot::IsAliased);
912  // A non-volatile aggregate destination might have volatile member.
913  if (!LHSSlot.isVolatile() &&
914      CGF.hasVolatileMember(E->getLHS()->getType()))
915    LHSSlot.setVolatile(true);
916
917  CGF.EmitAggExpr(E->getRHS(), LHSSlot);
918
919  // Copy into the destination if the assignment isn't ignored.
920  EmitFinalDestCopy(E->getType(), LHS);
921}
922
923void AggExprEmitter::
924VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
925  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
926  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
927  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
928
929  // Bind the common expression if necessary.
930  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
931
932  CodeGenFunction::ConditionalEvaluation eval(CGF);
933  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock,
934                           CGF.getProfileCount(E));
935
936  // Save whether the destination's lifetime is externally managed.
937  bool isExternallyDestructed = Dest.isExternallyDestructed();
938
939  eval.begin(CGF);
940  CGF.EmitBlock(LHSBlock);
941  CGF.incrementProfileCounter(E);
942  Visit(E->getTrueExpr());
943  eval.end(CGF);
944
945  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
946  CGF.Builder.CreateBr(ContBlock);
947
948  // If the result of an agg expression is unused, then the emission
949  // of the LHS might need to create a destination slot.  That's fine
950  // with us, and we can safely emit the RHS into the same slot, but
951  // we shouldn't claim that it's already being destructed.
952  Dest.setExternallyDestructed(isExternallyDestructed);
953
954  eval.begin(CGF);
955  CGF.EmitBlock(RHSBlock);
956  Visit(E->getFalseExpr());
957  eval.end(CGF);
958
959  CGF.EmitBlock(ContBlock);
960}
961
962void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
963  Visit(CE->getChosenSubExpr());
964}
965
966void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
967  Address ArgValue = Address::invalid();
968  Address ArgPtr = CGF.EmitVAArg(VE, ArgValue);
969
970  if (!ArgPtr.isValid()) {
971    // If EmitVAArg fails, we fall back to the LLVM instruction.
972    llvm::Value *Val = Builder.CreateVAArg(ArgValue.getPointer(),
973                                           CGF.ConvertType(VE->getType()));
974    if (!Dest.isIgnored())
975      Builder.CreateStore(Val, Dest.getAddress());
976    return;
977  }
978
979  EmitFinalDestCopy(VE->getType(), CGF.MakeAddrLValue(ArgPtr, VE->getType()));
980}
981
982void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
983  // Ensure that we have a slot, but if we already do, remember
984  // whether it was externally destructed.
985  bool wasExternallyDestructed = Dest.isExternallyDestructed();
986  EnsureDest(E->getType());
987
988  // We're going to push a destructor if there isn't already one.
989  Dest.setExternallyDestructed();
990
991  Visit(E->getSubExpr());
992
993  // Push that destructor we promised.
994  if (!wasExternallyDestructed)
995    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddress());
996}
997
998void
999AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
1000  AggValueSlot Slot = EnsureSlot(E->getType());
1001  CGF.EmitCXXConstructExpr(E, Slot);
1002}
1003
1004void
1005AggExprEmitter::VisitLambdaExpr(LambdaExpr *E) {
1006  AggValueSlot Slot = EnsureSlot(E->getType());
1007  CGF.EmitLambdaExpr(E, Slot);
1008}
1009
1010void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
1011  CGF.enterFullExpression(E);
1012  CodeGenFunction::RunCleanupsScope cleanups(CGF);
1013  Visit(E->getSubExpr());
1014}
1015
1016void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
1017  QualType T = E->getType();
1018  AggValueSlot Slot = EnsureSlot(T);
1019  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddress(), T));
1020}
1021
1022void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
1023  QualType T = E->getType();
1024  AggValueSlot Slot = EnsureSlot(T);
1025  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddress(), T));
1026}
1027
1028/// isSimpleZero - If emitting this value will obviously just cause a store of
1029/// zero to memory, return true.  This can return false if uncertain, so it just
1030/// handles simple cases.
1031static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
1032  E = E->IgnoreParens();
1033
1034  // 0
1035  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
1036    return IL->getValue() == 0;
1037  // +0.0
1038  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
1039    return FL->getValue().isPosZero();
1040  // int()
1041  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
1042      CGF.getTypes().isZeroInitializable(E->getType()))
1043    return true;
1044  // (int*)0 - Null pointer expressions.
1045  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
1046    return ICE->getCastKind() == CK_NullToPointer;
1047  // '\0'
1048  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
1049    return CL->getValue() == 0;
1050
1051  // Otherwise, hard case: conservatively return false.
1052  return false;
1053}
1054
1055
1056void
1057AggExprEmitter::EmitInitializationToLValue(Expr *E, LValue LV) {
1058  QualType type = LV.getType();
1059  // FIXME: Ignore result?
1060  // FIXME: Are initializers affected by volatile?
1061  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
1062    // Storing "i32 0" to a zero'd memory location is a noop.
1063    return;
1064  } else if (isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) {
1065    return EmitNullInitializationToLValue(LV);
1066  } else if (isa<NoInitExpr>(E)) {
1067    // Do nothing.
1068    return;
1069  } else if (type->isReferenceType()) {
1070    RValue RV = CGF.EmitReferenceBindingToExpr(E);
1071    return CGF.EmitStoreThroughLValue(RV, LV);
1072  }
1073
1074  switch (CGF.getEvaluationKind(type)) {
1075  case TEK_Complex:
1076    CGF.EmitComplexExprIntoLValue(E, LV, /*isInit*/ true);
1077    return;
1078  case TEK_Aggregate:
1079    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
1080                                               AggValueSlot::IsDestructed,
1081                                      AggValueSlot::DoesNotNeedGCBarriers,
1082                                               AggValueSlot::IsNotAliased,
1083                                               Dest.isZeroed()));
1084    return;
1085  case TEK_Scalar:
1086    if (LV.isSimple()) {
1087      CGF.EmitScalarInit(E, /*D=*/nullptr, LV, /*Captured=*/false);
1088    } else {
1089      CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
1090    }
1091    return;
1092  }
1093  llvm_unreachable("bad evaluation kind");
1094}
1095
1096void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
1097  QualType type = lv.getType();
1098
1099  // If the destination slot is already zeroed out before the aggregate is
1100  // copied into it, we don't have to emit any zeros here.
1101  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
1102    return;
1103
1104  if (CGF.hasScalarEvaluationKind(type)) {
1105    // For non-aggregates, we can store the appropriate null constant.
1106    llvm::Value *null = CGF.CGM.EmitNullConstant(type);
1107    // Note that the following is not equivalent to
1108    // EmitStoreThroughBitfieldLValue for ARC types.
1109    if (lv.isBitField()) {
1110      CGF.EmitStoreThroughBitfieldLValue(RValue::get(null), lv);
1111    } else {
1112      assert(lv.isSimple());
1113      CGF.EmitStoreOfScalar(null, lv, /* isInitialization */ true);
1114    }
1115  } else {
1116    // There's a potential optimization opportunity in combining
1117    // memsets; that would be easy for arrays, but relatively
1118    // difficult for structures with the current code.
1119    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
1120  }
1121}
1122
1123void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
1124#if 0
1125  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
1126  // (Length of globals? Chunks of zeroed-out space?).
1127  //
1128  // If we can, prefer a copy from a global; this is a lot less code for long
1129  // globals, and it's easier for the current optimizers to analyze.
1130  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
1131    llvm::GlobalVariable* GV =
1132    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
1133                             llvm::GlobalValue::InternalLinkage, C, "");
1134    EmitFinalDestCopy(E->getType(), CGF.MakeAddrLValue(GV, E->getType()));
1135    return;
1136  }
1137#endif
1138  if (E->hadArrayRangeDesignator())
1139    CGF.ErrorUnsupported(E, "GNU array range designator extension");
1140
1141  AggValueSlot Dest = EnsureSlot(E->getType());
1142
1143  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
1144
1145  // Handle initialization of an array.
1146  if (E->getType()->isArrayType()) {
1147    if (E->isStringLiteralInit())
1148      return Visit(E->getInit(0));
1149
1150    QualType elementType =
1151        CGF.getContext().getAsArrayType(E->getType())->getElementType();
1152
1153    auto AType = cast<llvm::ArrayType>(Dest.getAddress().getElementType());
1154    EmitArrayInit(Dest.getAddress(), AType, elementType, E);
1155    return;
1156  }
1157
1158  if (E->getType()->isAtomicType()) {
1159    // An _Atomic(T) object can be list-initialized from an expression
1160    // of the same type.
1161    assert(E->getNumInits() == 1 &&
1162           CGF.getContext().hasSameUnqualifiedType(E->getInit(0)->getType(),
1163                                                   E->getType()) &&
1164           "unexpected list initialization for atomic object");
1165    return Visit(E->getInit(0));
1166  }
1167
1168  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
1169
1170  // Do struct initialization; this code just sets each individual member
1171  // to the approprate value.  This makes bitfield support automatic;
1172  // the disadvantage is that the generated code is more difficult for
1173  // the optimizer, especially with bitfields.
1174  unsigned NumInitElements = E->getNumInits();
1175  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
1176
1177  // Prepare a 'this' for CXXDefaultInitExprs.
1178  CodeGenFunction::FieldConstructionScope FCS(CGF, Dest.getAddress());
1179
1180  if (record->isUnion()) {
1181    // Only initialize one field of a union. The field itself is
1182    // specified by the initializer list.
1183    if (!E->getInitializedFieldInUnion()) {
1184      // Empty union; we have nothing to do.
1185
1186#ifndef NDEBUG
1187      // Make sure that it's really an empty and not a failure of
1188      // semantic analysis.
1189      for (const auto *Field : record->fields())
1190        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
1191#endif
1192      return;
1193    }
1194
1195    // FIXME: volatility
1196    FieldDecl *Field = E->getInitializedFieldInUnion();
1197
1198    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestLV, Field);
1199    if (NumInitElements) {
1200      // Store the initializer into the field
1201      EmitInitializationToLValue(E->getInit(0), FieldLoc);
1202    } else {
1203      // Default-initialize to null.
1204      EmitNullInitializationToLValue(FieldLoc);
1205    }
1206
1207    return;
1208  }
1209
1210  // We'll need to enter cleanup scopes in case any of the member
1211  // initializers throw an exception.
1212  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
1213  llvm::Instruction *cleanupDominator = nullptr;
1214
1215  // Here we iterate over the fields; this makes it simpler to both
1216  // default-initialize fields and skip over unnamed fields.
1217  unsigned curInitIndex = 0;
1218  for (const auto *field : record->fields()) {
1219    // We're done once we hit the flexible array member.
1220    if (field->getType()->isIncompleteArrayType())
1221      break;
1222
1223    // Always skip anonymous bitfields.
1224    if (field->isUnnamedBitfield())
1225      continue;
1226
1227    // We're done if we reach the end of the explicit initializers, we
1228    // have a zeroed object, and the rest of the fields are
1229    // zero-initializable.
1230    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
1231        CGF.getTypes().isZeroInitializable(E->getType()))
1232      break;
1233
1234
1235    LValue LV = CGF.EmitLValueForFieldInitialization(DestLV, field);
1236    // We never generate write-barries for initialized fields.
1237    LV.setNonGC(true);
1238
1239    if (curInitIndex < NumInitElements) {
1240      // Store the initializer into the field.
1241      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
1242    } else {
1243      // We're out of initalizers; default-initialize to null
1244      EmitNullInitializationToLValue(LV);
1245    }
1246
1247    // Push a destructor if necessary.
1248    // FIXME: if we have an array of structures, all explicitly
1249    // initialized, we can end up pushing a linear number of cleanups.
1250    bool pushedCleanup = false;
1251    if (QualType::DestructionKind dtorKind
1252          = field->getType().isDestructedType()) {
1253      assert(LV.isSimple());
1254      if (CGF.needsEHCleanup(dtorKind)) {
1255        if (!cleanupDominator)
1256          cleanupDominator = CGF.Builder.CreateAlignedLoad(
1257              CGF.Int8Ty,
1258              llvm::Constant::getNullValue(CGF.Int8PtrTy),
1259              CharUnits::One()); // placeholder
1260
1261        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
1262                        CGF.getDestroyer(dtorKind), false);
1263        cleanups.push_back(CGF.EHStack.stable_begin());
1264        pushedCleanup = true;
1265      }
1266    }
1267
1268    // If the GEP didn't get used because of a dead zero init or something
1269    // else, clean it up for -O0 builds and general tidiness.
1270    if (!pushedCleanup && LV.isSimple())
1271      if (llvm::GetElementPtrInst *GEP =
1272            dyn_cast<llvm::GetElementPtrInst>(LV.getPointer()))
1273        if (GEP->use_empty())
1274          GEP->eraseFromParent();
1275  }
1276
1277  // Deactivate all the partial cleanups in reverse order, which
1278  // generally means popping them.
1279  for (unsigned i = cleanups.size(); i != 0; --i)
1280    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
1281
1282  // Destroy the placeholder if we made one.
1283  if (cleanupDominator)
1284    cleanupDominator->eraseFromParent();
1285}
1286
1287void AggExprEmitter::VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E) {
1288  AggValueSlot Dest = EnsureSlot(E->getType());
1289
1290  LValue DestLV = CGF.MakeAddrLValue(Dest.getAddress(), E->getType());
1291  EmitInitializationToLValue(E->getBase(), DestLV);
1292  VisitInitListExpr(E->getUpdater());
1293}
1294
1295//===----------------------------------------------------------------------===//
1296//                        Entry Points into this File
1297//===----------------------------------------------------------------------===//
1298
1299/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
1300/// non-zero bytes that will be stored when outputting the initializer for the
1301/// specified initializer expression.
1302static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
1303  E = E->IgnoreParens();
1304
1305  // 0 and 0.0 won't require any non-zero stores!
1306  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
1307
1308  // If this is an initlist expr, sum up the size of sizes of the (present)
1309  // elements.  If this is something weird, assume the whole thing is non-zero.
1310  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
1311  if (!ILE || !CGF.getTypes().isZeroInitializable(ILE->getType()))
1312    return CGF.getContext().getTypeSizeInChars(E->getType());
1313
1314  // InitListExprs for structs have to be handled carefully.  If there are
1315  // reference members, we need to consider the size of the reference, not the
1316  // referencee.  InitListExprs for unions and arrays can't have references.
1317  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
1318    if (!RT->isUnionType()) {
1319      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
1320      CharUnits NumNonZeroBytes = CharUnits::Zero();
1321
1322      unsigned ILEElement = 0;
1323      for (const auto *Field : SD->fields()) {
1324        // We're done once we hit the flexible array member or run out of
1325        // InitListExpr elements.
1326        if (Field->getType()->isIncompleteArrayType() ||
1327            ILEElement == ILE->getNumInits())
1328          break;
1329        if (Field->isUnnamedBitfield())
1330          continue;
1331
1332        const Expr *E = ILE->getInit(ILEElement++);
1333
1334        // Reference values are always non-null and have the width of a pointer.
1335        if (Field->getType()->isReferenceType())
1336          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
1337              CGF.getTarget().getPointerWidth(0));
1338        else
1339          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
1340      }
1341
1342      return NumNonZeroBytes;
1343    }
1344  }
1345
1346
1347  CharUnits NumNonZeroBytes = CharUnits::Zero();
1348  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
1349    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
1350  return NumNonZeroBytes;
1351}
1352
1353/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
1354/// zeros in it, emit a memset and avoid storing the individual zeros.
1355///
1356static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
1357                                     CodeGenFunction &CGF) {
1358  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
1359  // volatile stores.
1360  if (Slot.isZeroed() || Slot.isVolatile() || !Slot.getAddress().isValid())
1361    return;
1362
1363  // C++ objects with a user-declared constructor don't need zero'ing.
1364  if (CGF.getLangOpts().CPlusPlus)
1365    if (const RecordType *RT = CGF.getContext()
1366                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1367      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1368      if (RD->hasUserDeclaredConstructor())
1369        return;
1370    }
1371
1372  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1373  CharUnits Size = CGF.getContext().getTypeSizeInChars(E->getType());
1374  if (Size <= CharUnits::fromQuantity(16))
1375    return;
1376
1377  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1378  // we prefer to emit memset + individual stores for the rest.
1379  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1380  if (NumNonZeroBytes*4 > Size)
1381    return;
1382
1383  // Okay, it seems like a good idea to use an initial memset, emit the call.
1384  llvm::Constant *SizeVal = CGF.Builder.getInt64(Size.getQuantity());
1385
1386  Address Loc = Slot.getAddress();
1387  Loc = CGF.Builder.CreateElementBitCast(Loc, CGF.Int8Ty);
1388  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, false);
1389
1390  // Tell the AggExprEmitter that the slot is known zero.
1391  Slot.setZeroed();
1392}
1393
1394
1395
1396
1397/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1398/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1399/// the value of the aggregate expression is not needed.  If VolatileDest is
1400/// true, DestPtr cannot be 0.
1401void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot) {
1402  assert(E && hasAggregateEvaluationKind(E->getType()) &&
1403         "Invalid aggregate expression to emit");
1404  assert((Slot.getAddress().isValid() || Slot.isIgnored()) &&
1405         "slot has bits but no address");
1406
1407  // Optimize the slot if possible.
1408  CheckAggExprForMemSetUse(Slot, E, *this);
1409
1410  AggExprEmitter(*this, Slot, Slot.isIgnored()).Visit(const_cast<Expr*>(E));
1411}
1412
1413LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1414  assert(hasAggregateEvaluationKind(E->getType()) && "Invalid argument!");
1415  Address Temp = CreateMemTemp(E->getType());
1416  LValue LV = MakeAddrLValue(Temp, E->getType());
1417  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1418                                         AggValueSlot::DoesNotNeedGCBarriers,
1419                                         AggValueSlot::IsNotAliased));
1420  return LV;
1421}
1422
1423void CodeGenFunction::EmitAggregateCopy(Address DestPtr,
1424                                        Address SrcPtr, QualType Ty,
1425                                        bool isVolatile,
1426                                        bool isAssignment) {
1427  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1428
1429  if (getLangOpts().CPlusPlus) {
1430    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1431      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1432      assert((Record->hasTrivialCopyConstructor() ||
1433              Record->hasTrivialCopyAssignment() ||
1434              Record->hasTrivialMoveConstructor() ||
1435              Record->hasTrivialMoveAssignment() ||
1436              Record->isUnion()) &&
1437             "Trying to aggregate-copy a type without a trivial copy/move "
1438             "constructor or assignment operator");
1439      // Ignore empty classes in C++.
1440      if (Record->isEmpty())
1441        return;
1442    }
1443  }
1444
1445  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1446  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1447  // read from another object that overlaps in anyway the storage of the first
1448  // object, then the overlap shall be exact and the two objects shall have
1449  // qualified or unqualified versions of a compatible type."
1450  //
1451  // memcpy is not defined if the source and destination pointers are exactly
1452  // equal, but other compilers do this optimization, and almost every memcpy
1453  // implementation handles this case safely.  If there is a libc that does not
1454  // safely handle this, we can add a target hook.
1455
1456  // Get data size info for this aggregate. If this is an assignment,
1457  // don't copy the tail padding, because we might be assigning into a
1458  // base subobject where the tail padding is claimed.  Otherwise,
1459  // copying it is fine.
1460  std::pair<CharUnits, CharUnits> TypeInfo;
1461  if (isAssignment)
1462    TypeInfo = getContext().getTypeInfoDataSizeInChars(Ty);
1463  else
1464    TypeInfo = getContext().getTypeInfoInChars(Ty);
1465
1466  llvm::Value *SizeVal = nullptr;
1467  if (TypeInfo.first.isZero()) {
1468    // But note that getTypeInfo returns 0 for a VLA.
1469    if (auto *VAT = dyn_cast_or_null<VariableArrayType>(
1470            getContext().getAsArrayType(Ty))) {
1471      QualType BaseEltTy;
1472      SizeVal = emitArrayLength(VAT, BaseEltTy, DestPtr);
1473      TypeInfo = getContext().getTypeInfoDataSizeInChars(BaseEltTy);
1474      std::pair<CharUnits, CharUnits> LastElementTypeInfo;
1475      if (!isAssignment)
1476        LastElementTypeInfo = getContext().getTypeInfoInChars(BaseEltTy);
1477      assert(!TypeInfo.first.isZero());
1478      SizeVal = Builder.CreateNUWMul(
1479          SizeVal,
1480          llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity()));
1481      if (!isAssignment) {
1482        SizeVal = Builder.CreateNUWSub(
1483            SizeVal,
1484            llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity()));
1485        SizeVal = Builder.CreateNUWAdd(
1486            SizeVal, llvm::ConstantInt::get(
1487                         SizeTy, LastElementTypeInfo.first.getQuantity()));
1488      }
1489    }
1490  }
1491  if (!SizeVal) {
1492    SizeVal = llvm::ConstantInt::get(SizeTy, TypeInfo.first.getQuantity());
1493  }
1494
1495  // FIXME: If we have a volatile struct, the optimizer can remove what might
1496  // appear to be `extra' memory ops:
1497  //
1498  // volatile struct { int i; } a, b;
1499  //
1500  // int main() {
1501  //   a = b;
1502  //   a = b;
1503  // }
1504  //
1505  // we need to use a different call here.  We use isVolatile to indicate when
1506  // either the source or the destination is volatile.
1507
1508  DestPtr = Builder.CreateElementBitCast(DestPtr, Int8Ty);
1509  SrcPtr = Builder.CreateElementBitCast(SrcPtr, Int8Ty);
1510
1511  // Don't do any of the memmove_collectable tests if GC isn't set.
1512  if (CGM.getLangOpts().getGC() == LangOptions::NonGC) {
1513    // fall through
1514  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1515    RecordDecl *Record = RecordTy->getDecl();
1516    if (Record->hasObjectMember()) {
1517      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1518                                                    SizeVal);
1519      return;
1520    }
1521  } else if (Ty->isArrayType()) {
1522    QualType BaseType = getContext().getBaseElementType(Ty);
1523    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1524      if (RecordTy->getDecl()->hasObjectMember()) {
1525        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1526                                                      SizeVal);
1527        return;
1528      }
1529    }
1530  }
1531
1532  auto Inst = Builder.CreateMemCpy(DestPtr, SrcPtr, SizeVal, isVolatile);
1533
1534  // Determine the metadata to describe the position of any padding in this
1535  // memcpy, as well as the TBAA tags for the members of the struct, in case
1536  // the optimizer wishes to expand it in to scalar memory operations.
1537  if (llvm::MDNode *TBAAStructTag = CGM.getTBAAStructInfo(Ty))
1538    Inst->setMetadata(llvm::LLVMContext::MD_tbaa_struct, TBAAStructTag);
1539}
1540