CGExprAgg.cpp revision 33e56f3273457bfa22c7c50bc46cf5a18216863d 
1//===--- CGExprAgg.cpp - Emit LLVM Code from Aggregate Expressions --------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This contains code to emit Aggregate Expr nodes as LLVM code.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "CodeGenModule.h"
16#include "CGObjCRuntime.h"
17#include "clang/AST/ASTContext.h"
18#include "clang/AST/DeclCXX.h"
19#include "clang/AST/StmtVisitor.h"
20#include "llvm/Constants.h"
21#include "llvm/Function.h"
22#include "llvm/GlobalVariable.h"
23#include "llvm/Intrinsics.h"
24using namespace clang;
25using namespace CodeGen;
26
27//===----------------------------------------------------------------------===//
28//                        Aggregate Expression Emitter
29//===----------------------------------------------------------------------===//
30
31namespace  {
32class AggExprEmitter : public StmtVisitor<AggExprEmitter> {
33  CodeGenFunction &CGF;
34  CGBuilderTy &Builder;
35  AggValueSlot Dest;
36  bool IgnoreResult;
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
59public:
60  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest,
61                 bool ignore)
62    : CGF(cgf), Builder(CGF.Builder), Dest(Dest),
63      IgnoreResult(ignore) {
64  }
65
66  //===--------------------------------------------------------------------===//
67  //                               Utilities
68  //===--------------------------------------------------------------------===//
69
70  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
71  /// represents a value lvalue, this method emits the address of the lvalue,
72  /// then loads the result into DestPtr.
73  void EmitAggLoadOfLValue(const Expr *E);
74
75  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
76  void EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore = false);
77  void EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore = false);
78
79  void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
80
81  AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
82    if (CGF.getLangOptions().getGCMode() && TypeRequiresGCollection(T))
83      return AggValueSlot::NeedsGCBarriers;
84    return AggValueSlot::DoesNotNeedGCBarriers;
85  }
86
87  bool TypeRequiresGCollection(QualType T);
88
89  //===--------------------------------------------------------------------===//
90  //                            Visitor Methods
91  //===--------------------------------------------------------------------===//
92
93  void VisitStmt(Stmt *S) {
94    CGF.ErrorUnsupported(S, "aggregate expression");
95  }
96  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
97  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
98    Visit(GE->getResultExpr());
99  }
100  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
101  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
102    return Visit(E->getReplacement());
103  }
104
105  // l-values.
106  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
107  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
108  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
109  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
110  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
111  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
112    EmitAggLoadOfLValue(E);
113  }
114  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
115    EmitAggLoadOfLValue(E);
116  }
117  void VisitPredefinedExpr(const PredefinedExpr *E) {
118    EmitAggLoadOfLValue(E);
119  }
120
121  // Operators.
122  void VisitCastExpr(CastExpr *E);
123  void VisitCallExpr(const CallExpr *E);
124  void VisitStmtExpr(const StmtExpr *E);
125  void VisitBinaryOperator(const BinaryOperator *BO);
126  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
127  void VisitBinAssign(const BinaryOperator *E);
128  void VisitBinComma(const BinaryOperator *E);
129
130  void VisitObjCMessageExpr(ObjCMessageExpr *E);
131  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
132    EmitAggLoadOfLValue(E);
133  }
134  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
135
136  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
137  void VisitChooseExpr(const ChooseExpr *CE);
138  void VisitInitListExpr(InitListExpr *E);
139  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
140  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
141    Visit(DAE->getExpr());
142  }
143  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
144  void VisitCXXConstructExpr(const CXXConstructExpr *E);
145  void VisitExprWithCleanups(ExprWithCleanups *E);
146  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
147  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
148  void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
149  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
150
151  void VisitVAArgExpr(VAArgExpr *E);
152
153  void EmitInitializationToLValue(Expr *E, LValue Address);
154  void EmitNullInitializationToLValue(LValue Address);
155  //  case Expr::ChooseExprClass:
156  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
157};
158}  // end anonymous namespace.
159
160//===----------------------------------------------------------------------===//
161//                                Utilities
162//===----------------------------------------------------------------------===//
163
164/// EmitAggLoadOfLValue - Given an expression with aggregate type that
165/// represents a value lvalue, this method emits the address of the lvalue,
166/// then loads the result into DestPtr.
167void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
168  LValue LV = CGF.EmitLValue(E);
169  EmitFinalDestCopy(E, LV);
170}
171
172/// \brief True if the given aggregate type requires special GC API calls.
173bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
174  // Only record types have members that might require garbage collection.
175  const RecordType *RecordTy = T->getAs<RecordType>();
176  if (!RecordTy) return false;
177
178  // Don't mess with non-trivial C++ types.
179  RecordDecl *Record = RecordTy->getDecl();
180  if (isa<CXXRecordDecl>(Record) &&
181      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
182       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
183    return false;
184
185  // Check whether the type has an object member.
186  return Record->hasObjectMember();
187}
188
189/// \brief Perform the final move to DestPtr if for some reason
190/// getReturnValueSlot() didn't use it directly.
191///
192/// The idea is that you do something like this:
193///   RValue Result = EmitSomething(..., getReturnValueSlot());
194///   EmitMoveFromReturnSlot(E, Result);
195///
196/// If nothing interferes, this will cause the result to be emitted
197/// directly into the return value slot.  Otherwise, a final move
198/// will be performed.
199void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue Src) {
200  if (shouldUseDestForReturnSlot()) {
201    // Logically, Dest.getAddr() should equal Src.getAggregateAddr().
202    // The possibility of undef rvalues complicates that a lot,
203    // though, so we can't really assert.
204    return;
205  }
206
207  // Otherwise, do a final copy,
208  assert(Dest.getAddr() != Src.getAggregateAddr());
209  EmitFinalDestCopy(E, Src, /*Ignore*/ true);
210}
211
212/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
213void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore) {
214  assert(Src.isAggregate() && "value must be aggregate value!");
215
216  // If Dest is ignored, then we're evaluating an aggregate expression
217  // in a context (like an expression statement) that doesn't care
218  // about the result.  C says that an lvalue-to-rvalue conversion is
219  // performed in these cases; C++ says that it is not.  In either
220  // case, we don't actually need to do anything unless the value is
221  // volatile.
222  if (Dest.isIgnored()) {
223    if (!Src.isVolatileQualified() ||
224        CGF.CGM.getLangOptions().CPlusPlus ||
225        (IgnoreResult && Ignore))
226      return;
227
228    // If the source is volatile, we must read from it; to do that, we need
229    // some place to put it.
230    Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
231  }
232
233  if (Dest.requiresGCollection()) {
234    CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
235    llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
236    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
237    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
238                                                      Dest.getAddr(),
239                                                      Src.getAggregateAddr(),
240                                                      SizeVal);
241    return;
242  }
243  // If the result of the assignment is used, copy the LHS there also.
244  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
245  // from the source as well, as we can't eliminate it if either operand
246  // is volatile, unless copy has volatile for both source and destination..
247  CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
248                        Dest.isVolatile()|Src.isVolatileQualified());
249}
250
251/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
252void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
253  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
254
255  EmitFinalDestCopy(E, RValue::getAggregate(Src.getAddress(),
256                                            Src.isVolatileQualified()),
257                    Ignore);
258}
259
260//===----------------------------------------------------------------------===//
261//                            Visitor Methods
262//===----------------------------------------------------------------------===//
263
264void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
265  Visit(E->GetTemporaryExpr());
266}
267
268void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
269  EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
270}
271
272void
273AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
274  if (E->getType().isPODType(CGF.getContext())) {
275    // For a POD type, just emit a load of the lvalue + a copy, because our
276    // compound literal might alias the destination.
277    // FIXME: This is a band-aid; the real problem appears to be in our handling
278    // of assignments, where we store directly into the LHS without checking
279    // whether anything in the RHS aliases.
280    EmitAggLoadOfLValue(E);
281    return;
282  }
283
284  AggValueSlot Slot = EnsureSlot(E->getType());
285  CGF.EmitAggExpr(E->getInitializer(), Slot);
286}
287
288
289void AggExprEmitter::VisitCastExpr(CastExpr *E) {
290  switch (E->getCastKind()) {
291  case CK_Dynamic: {
292    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
293    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
294    // FIXME: Do we also need to handle property references here?
295    if (LV.isSimple())
296      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
297    else
298      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
299
300    if (!Dest.isIgnored())
301      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
302    break;
303  }
304
305  case CK_ToUnion: {
306    if (Dest.isIgnored()) break;
307
308    // GCC union extension
309    QualType Ty = E->getSubExpr()->getType();
310    QualType PtrTy = CGF.getContext().getPointerType(Ty);
311    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
312                                                 CGF.ConvertType(PtrTy));
313    EmitInitializationToLValue(E->getSubExpr(),
314                               CGF.MakeAddrLValue(CastPtr, Ty));
315    break;
316  }
317
318  case CK_DerivedToBase:
319  case CK_BaseToDerived:
320  case CK_UncheckedDerivedToBase: {
321    assert(0 && "cannot perform hierarchy conversion in EmitAggExpr: "
322                "should have been unpacked before we got here");
323    break;
324  }
325
326  case CK_GetObjCProperty: {
327    LValue LV = CGF.EmitLValue(E->getSubExpr());
328    assert(LV.isPropertyRef());
329    RValue RV = CGF.EmitLoadOfPropertyRefLValue(LV, getReturnValueSlot());
330    EmitMoveFromReturnSlot(E, RV);
331    break;
332  }
333
334  case CK_LValueToRValue: // hope for downstream optimization
335  case CK_NoOp:
336  case CK_UserDefinedConversion:
337  case CK_ConstructorConversion:
338    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
339                                                   E->getType()) &&
340           "Implicit cast types must be compatible");
341    Visit(E->getSubExpr());
342    break;
343
344  case CK_LValueBitCast:
345    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
346    break;
347
348  case CK_Dependent:
349  case CK_BitCast:
350  case CK_ArrayToPointerDecay:
351  case CK_FunctionToPointerDecay:
352  case CK_NullToPointer:
353  case CK_NullToMemberPointer:
354  case CK_BaseToDerivedMemberPointer:
355  case CK_DerivedToBaseMemberPointer:
356  case CK_MemberPointerToBoolean:
357  case CK_IntegralToPointer:
358  case CK_PointerToIntegral:
359  case CK_PointerToBoolean:
360  case CK_ToVoid:
361  case CK_VectorSplat:
362  case CK_IntegralCast:
363  case CK_IntegralToBoolean:
364  case CK_IntegralToFloating:
365  case CK_FloatingToIntegral:
366  case CK_FloatingToBoolean:
367  case CK_FloatingCast:
368  case CK_CPointerToObjCPointerCast:
369  case CK_BlockPointerToObjCPointerCast:
370  case CK_AnyPointerToBlockPointerCast:
371  case CK_ObjCObjectLValueCast:
372  case CK_FloatingRealToComplex:
373  case CK_FloatingComplexToReal:
374  case CK_FloatingComplexToBoolean:
375  case CK_FloatingComplexCast:
376  case CK_FloatingComplexToIntegralComplex:
377  case CK_IntegralRealToComplex:
378  case CK_IntegralComplexToReal:
379  case CK_IntegralComplexToBoolean:
380  case CK_IntegralComplexCast:
381  case CK_IntegralComplexToFloatingComplex:
382  case CK_ARCProduceObject:
383  case CK_ARCConsumeObject:
384  case CK_ARCReclaimReturnedObject:
385  case CK_ARCExtendBlockObject:
386    llvm_unreachable("cast kind invalid for aggregate types");
387  }
388}
389
390void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
391  if (E->getCallReturnType()->isReferenceType()) {
392    EmitAggLoadOfLValue(E);
393    return;
394  }
395
396  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
397  EmitMoveFromReturnSlot(E, RV);
398}
399
400void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
401  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
402  EmitMoveFromReturnSlot(E, RV);
403}
404
405void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
406  llvm_unreachable("direct property access not surrounded by "
407                   "lvalue-to-rvalue cast");
408}
409
410void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
411  CGF.EmitIgnoredExpr(E->getLHS());
412  Visit(E->getRHS());
413}
414
415void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
416  CodeGenFunction::StmtExprEvaluation eval(CGF);
417  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
418}
419
420void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
421  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
422    VisitPointerToDataMemberBinaryOperator(E);
423  else
424    CGF.ErrorUnsupported(E, "aggregate binary expression");
425}
426
427void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
428                                                    const BinaryOperator *E) {
429  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
430  EmitFinalDestCopy(E, LV);
431}
432
433void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
434  // For an assignment to work, the value on the right has
435  // to be compatible with the value on the left.
436  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
437                                                 E->getRHS()->getType())
438         && "Invalid assignment");
439
440  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
441    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
442      if (VD->hasAttr<BlocksAttr>() &&
443          E->getRHS()->HasSideEffects(CGF.getContext())) {
444        // When __block variable on LHS, the RHS must be evaluated first
445        // as it may change the 'forwarding' field via call to Block_copy.
446        LValue RHS = CGF.EmitLValue(E->getRHS());
447        LValue LHS = CGF.EmitLValue(E->getLHS());
448        Dest = AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
449                                       needsGC(E->getLHS()->getType()),
450                                       AggValueSlot::IsAliased);
451        EmitFinalDestCopy(E, RHS, true);
452        return;
453      }
454
455  LValue LHS = CGF.EmitLValue(E->getLHS());
456
457  // We have to special case property setters, otherwise we must have
458  // a simple lvalue (no aggregates inside vectors, bitfields).
459  if (LHS.isPropertyRef()) {
460    const ObjCPropertyRefExpr *RE = LHS.getPropertyRefExpr();
461    QualType ArgType = RE->getSetterArgType();
462    RValue Src;
463    if (ArgType->isReferenceType())
464      Src = CGF.EmitReferenceBindingToExpr(E->getRHS(), 0);
465    else {
466      AggValueSlot Slot = EnsureSlot(E->getRHS()->getType());
467      CGF.EmitAggExpr(E->getRHS(), Slot);
468      Src = Slot.asRValue();
469    }
470    CGF.EmitStoreThroughPropertyRefLValue(Src, LHS);
471  } else {
472    // Codegen the RHS so that it stores directly into the LHS.
473    AggValueSlot LHSSlot =
474      AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
475                              needsGC(E->getLHS()->getType()),
476                              AggValueSlot::IsAliased);
477    CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
478    EmitFinalDestCopy(E, LHS, true);
479  }
480}
481
482void AggExprEmitter::
483VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
484  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
485  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
486  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
487
488  // Bind the common expression if necessary.
489  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
490
491  CodeGenFunction::ConditionalEvaluation eval(CGF);
492  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
493
494  // Save whether the destination's lifetime is externally managed.
495  bool isExternallyDestructed = Dest.isExternallyDestructed();
496
497  eval.begin(CGF);
498  CGF.EmitBlock(LHSBlock);
499  Visit(E->getTrueExpr());
500  eval.end(CGF);
501
502  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
503  CGF.Builder.CreateBr(ContBlock);
504
505  // If the result of an agg expression is unused, then the emission
506  // of the LHS might need to create a destination slot.  That's fine
507  // with us, and we can safely emit the RHS into the same slot, but
508  // we shouldn't claim that it's already being destructed.
509  Dest.setExternallyDestructed(isExternallyDestructed);
510
511  eval.begin(CGF);
512  CGF.EmitBlock(RHSBlock);
513  Visit(E->getFalseExpr());
514  eval.end(CGF);
515
516  CGF.EmitBlock(ContBlock);
517}
518
519void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
520  Visit(CE->getChosenSubExpr(CGF.getContext()));
521}
522
523void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
524  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
525  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
526
527  if (!ArgPtr) {
528    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
529    return;
530  }
531
532  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
533}
534
535void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
536  // Ensure that we have a slot, but if we already do, remember
537  // whether it was externally destructed.
538  bool wasExternallyDestructed = Dest.isExternallyDestructed();
539  Dest = EnsureSlot(E->getType());
540
541  // We're going to push a destructor if there isn't already one.
542  Dest.setExternallyDestructed();
543
544  Visit(E->getSubExpr());
545
546  // Push that destructor we promised.
547  if (!wasExternallyDestructed)
548    CGF.EmitCXXTemporary(E->getTemporary(), Dest.getAddr());
549}
550
551void
552AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
553  AggValueSlot Slot = EnsureSlot(E->getType());
554  CGF.EmitCXXConstructExpr(E, Slot);
555}
556
557void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
558  CGF.EmitExprWithCleanups(E, Dest);
559}
560
561void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
562  QualType T = E->getType();
563  AggValueSlot Slot = EnsureSlot(T);
564  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
565}
566
567void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
568  QualType T = E->getType();
569  AggValueSlot Slot = EnsureSlot(T);
570  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
571}
572
573/// isSimpleZero - If emitting this value will obviously just cause a store of
574/// zero to memory, return true.  This can return false if uncertain, so it just
575/// handles simple cases.
576static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
577  E = E->IgnoreParens();
578
579  // 0
580  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
581    return IL->getValue() == 0;
582  // +0.0
583  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
584    return FL->getValue().isPosZero();
585  // int()
586  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
587      CGF.getTypes().isZeroInitializable(E->getType()))
588    return true;
589  // (int*)0 - Null pointer expressions.
590  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
591    return ICE->getCastKind() == CK_NullToPointer;
592  // '\0'
593  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
594    return CL->getValue() == 0;
595
596  // Otherwise, hard case: conservatively return false.
597  return false;
598}
599
600
601void
602AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
603  QualType type = LV.getType();
604  // FIXME: Ignore result?
605  // FIXME: Are initializers affected by volatile?
606  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
607    // Storing "i32 0" to a zero'd memory location is a noop.
608  } else if (isa<ImplicitValueInitExpr>(E)) {
609    EmitNullInitializationToLValue(LV);
610  } else if (type->isReferenceType()) {
611    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
612    CGF.EmitStoreThroughLValue(RV, LV);
613  } else if (type->isAnyComplexType()) {
614    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
615  } else if (CGF.hasAggregateLLVMType(type)) {
616    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
617                                               AggValueSlot::IsDestructed,
618                                      AggValueSlot::DoesNotNeedGCBarriers,
619                                               AggValueSlot::IsNotAliased,
620                                               Dest.isZeroed()));
621  } else if (LV.isSimple()) {
622    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
623  } else {
624    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
625  }
626}
627
628void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
629  QualType type = lv.getType();
630
631  // If the destination slot is already zeroed out before the aggregate is
632  // copied into it, we don't have to emit any zeros here.
633  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
634    return;
635
636  if (!CGF.hasAggregateLLVMType(type)) {
637    // For non-aggregates, we can store zero
638    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
639    CGF.EmitStoreThroughLValue(RValue::get(null), lv);
640  } else {
641    // There's a potential optimization opportunity in combining
642    // memsets; that would be easy for arrays, but relatively
643    // difficult for structures with the current code.
644    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
645  }
646}
647
648void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
649#if 0
650  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
651  // (Length of globals? Chunks of zeroed-out space?).
652  //
653  // If we can, prefer a copy from a global; this is a lot less code for long
654  // globals, and it's easier for the current optimizers to analyze.
655  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
656    llvm::GlobalVariable* GV =
657    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
658                             llvm::GlobalValue::InternalLinkage, C, "");
659    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
660    return;
661  }
662#endif
663  if (E->hadArrayRangeDesignator())
664    CGF.ErrorUnsupported(E, "GNU array range designator extension");
665
666  llvm::Value *DestPtr = Dest.getAddr();
667
668  // Handle initialization of an array.
669  if (E->getType()->isArrayType()) {
670    llvm::PointerType *APType =
671      cast<llvm::PointerType>(DestPtr->getType());
672    llvm::ArrayType *AType =
673      cast<llvm::ArrayType>(APType->getElementType());
674
675    uint64_t NumInitElements = E->getNumInits();
676
677    if (E->getNumInits() > 0) {
678      QualType T1 = E->getType();
679      QualType T2 = E->getInit(0)->getType();
680      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
681        EmitAggLoadOfLValue(E->getInit(0));
682        return;
683      }
684    }
685
686    uint64_t NumArrayElements = AType->getNumElements();
687    assert(NumInitElements <= NumArrayElements);
688
689    QualType elementType = E->getType().getCanonicalType();
690    elementType = CGF.getContext().getQualifiedType(
691                    cast<ArrayType>(elementType)->getElementType(),
692                    elementType.getQualifiers() + Dest.getQualifiers());
693
694    // DestPtr is an array*.  Construct an elementType* by drilling
695    // down a level.
696    llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
697    llvm::Value *indices[] = { zero, zero };
698    llvm::Value *begin =
699      Builder.CreateInBoundsGEP(DestPtr, indices, "arrayinit.begin");
700
701    // Exception safety requires us to destroy all the
702    // already-constructed members if an initializer throws.
703    // For that, we'll need an EH cleanup.
704    QualType::DestructionKind dtorKind = elementType.isDestructedType();
705    llvm::AllocaInst *endOfInit = 0;
706    EHScopeStack::stable_iterator cleanup;
707    if (CGF.needsEHCleanup(dtorKind)) {
708      // In principle we could tell the cleanup where we are more
709      // directly, but the control flow can get so varied here that it
710      // would actually be quite complex.  Therefore we go through an
711      // alloca.
712      endOfInit = CGF.CreateTempAlloca(begin->getType(),
713                                       "arrayinit.endOfInit");
714      Builder.CreateStore(begin, endOfInit);
715      CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
716                                           CGF.getDestroyer(dtorKind));
717      cleanup = CGF.EHStack.stable_begin();
718
719    // Otherwise, remember that we didn't need a cleanup.
720    } else {
721      dtorKind = QualType::DK_none;
722    }
723
724    llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
725
726    // The 'current element to initialize'.  The invariants on this
727    // variable are complicated.  Essentially, after each iteration of
728    // the loop, it points to the last initialized element, except
729    // that it points to the beginning of the array before any
730    // elements have been initialized.
731    llvm::Value *element = begin;
732
733    // Emit the explicit initializers.
734    for (uint64_t i = 0; i != NumInitElements; ++i) {
735      // Advance to the next element.
736      if (i > 0) {
737        element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
738
739        // Tell the cleanup that it needs to destroy up to this
740        // element.  TODO: some of these stores can be trivially
741        // observed to be unnecessary.
742        if (endOfInit) Builder.CreateStore(element, endOfInit);
743      }
744
745      LValue elementLV = CGF.MakeAddrLValue(element, elementType);
746      EmitInitializationToLValue(E->getInit(i), elementLV);
747    }
748
749    // Check whether there's a non-trivial array-fill expression.
750    // Note that this will be a CXXConstructExpr even if the element
751    // type is an array (or array of array, etc.) of class type.
752    Expr *filler = E->getArrayFiller();
753    bool hasTrivialFiller = true;
754    if (CXXConstructExpr *cons = dyn_cast_or_null<CXXConstructExpr>(filler)) {
755      assert(cons->getConstructor()->isDefaultConstructor());
756      hasTrivialFiller = cons->getConstructor()->isTrivial();
757    }
758
759    // Any remaining elements need to be zero-initialized, possibly
760    // using the filler expression.  We can skip this if the we're
761    // emitting to zeroed memory.
762    if (NumInitElements != NumArrayElements &&
763        !(Dest.isZeroed() && hasTrivialFiller &&
764          CGF.getTypes().isZeroInitializable(elementType))) {
765
766      // Use an actual loop.  This is basically
767      //   do { *array++ = filler; } while (array != end);
768
769      // Advance to the start of the rest of the array.
770      if (NumInitElements) {
771        element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
772        if (endOfInit) Builder.CreateStore(element, endOfInit);
773      }
774
775      // Compute the end of the array.
776      llvm::Value *end = Builder.CreateInBoundsGEP(begin,
777                        llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
778                                                   "arrayinit.end");
779
780      llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
781      llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
782
783      // Jump into the body.
784      CGF.EmitBlock(bodyBB);
785      llvm::PHINode *currentElement =
786        Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
787      currentElement->addIncoming(element, entryBB);
788
789      // Emit the actual filler expression.
790      LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
791      if (filler)
792        EmitInitializationToLValue(filler, elementLV);
793      else
794        EmitNullInitializationToLValue(elementLV);
795
796      // Move on to the next element.
797      llvm::Value *nextElement =
798        Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
799
800      // Tell the EH cleanup that we finished with the last element.
801      if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
802
803      // Leave the loop if we're done.
804      llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
805                                               "arrayinit.done");
806      llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
807      Builder.CreateCondBr(done, endBB, bodyBB);
808      currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
809
810      CGF.EmitBlock(endBB);
811    }
812
813    // Leave the partial-array cleanup if we entered one.
814    if (dtorKind) CGF.DeactivateCleanupBlock(cleanup);
815
816    return;
817  }
818
819  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
820
821  // Do struct initialization; this code just sets each individual member
822  // to the approprate value.  This makes bitfield support automatic;
823  // the disadvantage is that the generated code is more difficult for
824  // the optimizer, especially with bitfields.
825  unsigned NumInitElements = E->getNumInits();
826  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
827
828  if (record->isUnion()) {
829    // Only initialize one field of a union. The field itself is
830    // specified by the initializer list.
831    if (!E->getInitializedFieldInUnion()) {
832      // Empty union; we have nothing to do.
833
834#ifndef NDEBUG
835      // Make sure that it's really an empty and not a failure of
836      // semantic analysis.
837      for (RecordDecl::field_iterator Field = record->field_begin(),
838                                   FieldEnd = record->field_end();
839           Field != FieldEnd; ++Field)
840        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
841#endif
842      return;
843    }
844
845    // FIXME: volatility
846    FieldDecl *Field = E->getInitializedFieldInUnion();
847
848    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
849    if (NumInitElements) {
850      // Store the initializer into the field
851      EmitInitializationToLValue(E->getInit(0), FieldLoc);
852    } else {
853      // Default-initialize to null.
854      EmitNullInitializationToLValue(FieldLoc);
855    }
856
857    return;
858  }
859
860  // We'll need to enter cleanup scopes in case any of the member
861  // initializers throw an exception.
862  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
863
864  // Here we iterate over the fields; this makes it simpler to both
865  // default-initialize fields and skip over unnamed fields.
866  unsigned curInitIndex = 0;
867  for (RecordDecl::field_iterator field = record->field_begin(),
868                               fieldEnd = record->field_end();
869       field != fieldEnd; ++field) {
870    // We're done once we hit the flexible array member.
871    if (field->getType()->isIncompleteArrayType())
872      break;
873
874    // Always skip anonymous bitfields.
875    if (field->isUnnamedBitfield())
876      continue;
877
878    // We're done if we reach the end of the explicit initializers, we
879    // have a zeroed object, and the rest of the fields are
880    // zero-initializable.
881    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
882        CGF.getTypes().isZeroInitializable(E->getType()))
883      break;
884
885    // FIXME: volatility
886    LValue LV = CGF.EmitLValueForFieldInitialization(DestPtr, *field, 0);
887    // We never generate write-barries for initialized fields.
888    LV.setNonGC(true);
889
890    if (curInitIndex < NumInitElements) {
891      // Store the initializer into the field.
892      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
893    } else {
894      // We're out of initalizers; default-initialize to null
895      EmitNullInitializationToLValue(LV);
896    }
897
898    // Push a destructor if necessary.
899    // FIXME: if we have an array of structures, all explicitly
900    // initialized, we can end up pushing a linear number of cleanups.
901    bool pushedCleanup = false;
902    if (QualType::DestructionKind dtorKind
903          = field->getType().isDestructedType()) {
904      assert(LV.isSimple());
905      if (CGF.needsEHCleanup(dtorKind)) {
906        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
907                        CGF.getDestroyer(dtorKind), false);
908        cleanups.push_back(CGF.EHStack.stable_begin());
909        pushedCleanup = true;
910      }
911    }
912
913    // If the GEP didn't get used because of a dead zero init or something
914    // else, clean it up for -O0 builds and general tidiness.
915    if (!pushedCleanup && LV.isSimple())
916      if (llvm::GetElementPtrInst *GEP =
917            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
918        if (GEP->use_empty())
919          GEP->eraseFromParent();
920  }
921
922  // Deactivate all the partial cleanups in reverse order, which
923  // generally means popping them.
924  for (unsigned i = cleanups.size(); i != 0; --i)
925    CGF.DeactivateCleanupBlock(cleanups[i-1]);
926}
927
928//===----------------------------------------------------------------------===//
929//                        Entry Points into this File
930//===----------------------------------------------------------------------===//
931
932/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
933/// non-zero bytes that will be stored when outputting the initializer for the
934/// specified initializer expression.
935static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
936  E = E->IgnoreParens();
937
938  // 0 and 0.0 won't require any non-zero stores!
939  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
940
941  // If this is an initlist expr, sum up the size of sizes of the (present)
942  // elements.  If this is something weird, assume the whole thing is non-zero.
943  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
944  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
945    return CGF.getContext().getTypeSizeInChars(E->getType());
946
947  // InitListExprs for structs have to be handled carefully.  If there are
948  // reference members, we need to consider the size of the reference, not the
949  // referencee.  InitListExprs for unions and arrays can't have references.
950  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
951    if (!RT->isUnionType()) {
952      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
953      CharUnits NumNonZeroBytes = CharUnits::Zero();
954
955      unsigned ILEElement = 0;
956      for (RecordDecl::field_iterator Field = SD->field_begin(),
957           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
958        // We're done once we hit the flexible array member or run out of
959        // InitListExpr elements.
960        if (Field->getType()->isIncompleteArrayType() ||
961            ILEElement == ILE->getNumInits())
962          break;
963        if (Field->isUnnamedBitfield())
964          continue;
965
966        const Expr *E = ILE->getInit(ILEElement++);
967
968        // Reference values are always non-null and have the width of a pointer.
969        if (Field->getType()->isReferenceType())
970          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
971              CGF.getContext().getTargetInfo().getPointerWidth(0));
972        else
973          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
974      }
975
976      return NumNonZeroBytes;
977    }
978  }
979
980
981  CharUnits NumNonZeroBytes = CharUnits::Zero();
982  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
983    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
984  return NumNonZeroBytes;
985}
986
987/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
988/// zeros in it, emit a memset and avoid storing the individual zeros.
989///
990static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
991                                     CodeGenFunction &CGF) {
992  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
993  // volatile stores.
994  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
995
996  // C++ objects with a user-declared constructor don't need zero'ing.
997  if (CGF.getContext().getLangOptions().CPlusPlus)
998    if (const RecordType *RT = CGF.getContext()
999                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
1000      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1001      if (RD->hasUserDeclaredConstructor())
1002        return;
1003    }
1004
1005  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1006  std::pair<CharUnits, CharUnits> TypeInfo =
1007    CGF.getContext().getTypeInfoInChars(E->getType());
1008  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1009    return;
1010
1011  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1012  // we prefer to emit memset + individual stores for the rest.
1013  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1014  if (NumNonZeroBytes*4 > TypeInfo.first)
1015    return;
1016
1017  // Okay, it seems like a good idea to use an initial memset, emit the call.
1018  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1019  CharUnits Align = TypeInfo.second;
1020
1021  llvm::Value *Loc = Slot.getAddr();
1022  llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
1023
1024  Loc = CGF.Builder.CreateBitCast(Loc, BP);
1025  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1026                           Align.getQuantity(), false);
1027
1028  // Tell the AggExprEmitter that the slot is known zero.
1029  Slot.setZeroed();
1030}
1031
1032
1033
1034
1035/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1036/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1037/// the value of the aggregate expression is not needed.  If VolatileDest is
1038/// true, DestPtr cannot be 0.
1039///
1040/// \param IsInitializer - true if this evaluation is initializing an
1041/// object whose lifetime is already being managed.
1042void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
1043                                  bool IgnoreResult) {
1044  assert(E && hasAggregateLLVMType(E->getType()) &&
1045         "Invalid aggregate expression to emit");
1046  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1047         "slot has bits but no address");
1048
1049  // Optimize the slot if possible.
1050  CheckAggExprForMemSetUse(Slot, E, *this);
1051
1052  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
1053}
1054
1055LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1056  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1057  llvm::Value *Temp = CreateMemTemp(E->getType());
1058  LValue LV = MakeAddrLValue(Temp, E->getType());
1059  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1060                                         AggValueSlot::DoesNotNeedGCBarriers,
1061                                         AggValueSlot::IsNotAliased));
1062  return LV;
1063}
1064
1065void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1066                                        llvm::Value *SrcPtr, QualType Ty,
1067                                        bool isVolatile) {
1068  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1069
1070  if (getContext().getLangOptions().CPlusPlus) {
1071    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1072      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1073      assert((Record->hasTrivialCopyConstructor() ||
1074              Record->hasTrivialCopyAssignment() ||
1075              Record->hasTrivialMoveConstructor() ||
1076              Record->hasTrivialMoveAssignment()) &&
1077             "Trying to aggregate-copy a type without a trivial copy "
1078             "constructor or assignment operator");
1079      // Ignore empty classes in C++.
1080      if (Record->isEmpty())
1081        return;
1082    }
1083  }
1084
1085  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1086  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1087  // read from another object that overlaps in anyway the storage of the first
1088  // object, then the overlap shall be exact and the two objects shall have
1089  // qualified or unqualified versions of a compatible type."
1090  //
1091  // memcpy is not defined if the source and destination pointers are exactly
1092  // equal, but other compilers do this optimization, and almost every memcpy
1093  // implementation handles this case safely.  If there is a libc that does not
1094  // safely handle this, we can add a target hook.
1095
1096  // Get size and alignment info for this aggregate.
1097  std::pair<CharUnits, CharUnits> TypeInfo =
1098    getContext().getTypeInfoInChars(Ty);
1099
1100  // FIXME: Handle variable sized types.
1101
1102  // FIXME: If we have a volatile struct, the optimizer can remove what might
1103  // appear to be `extra' memory ops:
1104  //
1105  // volatile struct { int i; } a, b;
1106  //
1107  // int main() {
1108  //   a = b;
1109  //   a = b;
1110  // }
1111  //
1112  // we need to use a different call here.  We use isVolatile to indicate when
1113  // either the source or the destination is volatile.
1114
1115  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1116  llvm::Type *DBP =
1117    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1118  DestPtr = Builder.CreateBitCast(DestPtr, DBP, "tmp");
1119
1120  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1121  llvm::Type *SBP =
1122    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1123  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP, "tmp");
1124
1125  // Don't do any of the memmove_collectable tests if GC isn't set.
1126  if (CGM.getLangOptions().getGCMode() == LangOptions::NonGC) {
1127    // fall through
1128  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1129    RecordDecl *Record = RecordTy->getDecl();
1130    if (Record->hasObjectMember()) {
1131      CharUnits size = TypeInfo.first;
1132      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1133      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1134      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1135                                                    SizeVal);
1136      return;
1137    }
1138  } else if (Ty->isArrayType()) {
1139    QualType BaseType = getContext().getBaseElementType(Ty);
1140    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1141      if (RecordTy->getDecl()->hasObjectMember()) {
1142        CharUnits size = TypeInfo.first;
1143        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1144        llvm::Value *SizeVal =
1145          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1146        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1147                                                      SizeVal);
1148        return;
1149      }
1150    }
1151  }
1152
1153  Builder.CreateMemCpy(DestPtr, SrcPtr,
1154                       llvm::ConstantInt::get(IntPtrTy,
1155                                              TypeInfo.first.getQuantity()),
1156                       TypeInfo.second.getQuantity(), isVolatile);
1157}
1158