CGExprAgg.cpp revision 3026348bd4c13a0f83b59839f64065e0fcbea253 
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                         unsigned Alignment = 0);
79
80  void EmitMoveFromReturnSlot(const Expr *E, RValue Src);
81
82  AggValueSlot::NeedsGCBarriers_t needsGC(QualType T) {
83    if (CGF.getLangOptions().getGC() && TypeRequiresGCollection(T))
84      return AggValueSlot::NeedsGCBarriers;
85    return AggValueSlot::DoesNotNeedGCBarriers;
86  }
87
88  bool TypeRequiresGCollection(QualType T);
89
90  //===--------------------------------------------------------------------===//
91  //                            Visitor Methods
92  //===--------------------------------------------------------------------===//
93
94  void VisitStmt(Stmt *S) {
95    CGF.ErrorUnsupported(S, "aggregate expression");
96  }
97  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
98  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
99    Visit(GE->getResultExpr());
100  }
101  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
102  void VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *E) {
103    return Visit(E->getReplacement());
104  }
105
106  // l-values.
107  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
108  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
109  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
110  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
111  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
112  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
113    EmitAggLoadOfLValue(E);
114  }
115  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
116    EmitAggLoadOfLValue(E);
117  }
118  void VisitPredefinedExpr(const PredefinedExpr *E) {
119    EmitAggLoadOfLValue(E);
120  }
121
122  // Operators.
123  void VisitCastExpr(CastExpr *E);
124  void VisitCallExpr(const CallExpr *E);
125  void VisitStmtExpr(const StmtExpr *E);
126  void VisitBinaryOperator(const BinaryOperator *BO);
127  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
128  void VisitBinAssign(const BinaryOperator *E);
129  void VisitBinComma(const BinaryOperator *E);
130
131  void VisitObjCMessageExpr(ObjCMessageExpr *E);
132  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
133    EmitAggLoadOfLValue(E);
134  }
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 VisitPseudoObjectExpr(PseudoObjectExpr *E) {
152    if (E->isGLValue()) {
153      LValue LV = CGF.EmitPseudoObjectLValue(E);
154      return EmitFinalDestCopy(E, LV);
155    }
156
157    CGF.EmitPseudoObjectRValue(E, EnsureSlot(E->getType()));
158  }
159
160  void VisitVAArgExpr(VAArgExpr *E);
161
162  void EmitInitializationToLValue(Expr *E, LValue Address);
163  void EmitNullInitializationToLValue(LValue Address);
164  //  case Expr::ChooseExprClass:
165  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
166  void VisitAtomicExpr(AtomicExpr *E) {
167    CGF.EmitAtomicExpr(E, EnsureSlot(E->getType()).getAddr());
168  }
169};
170}  // end anonymous namespace.
171
172//===----------------------------------------------------------------------===//
173//                                Utilities
174//===----------------------------------------------------------------------===//
175
176/// EmitAggLoadOfLValue - Given an expression with aggregate type that
177/// represents a value lvalue, this method emits the address of the lvalue,
178/// then loads the result into DestPtr.
179void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
180  LValue LV = CGF.EmitLValue(E);
181  EmitFinalDestCopy(E, LV);
182}
183
184/// \brief True if the given aggregate type requires special GC API calls.
185bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
186  // Only record types have members that might require garbage collection.
187  const RecordType *RecordTy = T->getAs<RecordType>();
188  if (!RecordTy) return false;
189
190  // Don't mess with non-trivial C++ types.
191  RecordDecl *Record = RecordTy->getDecl();
192  if (isa<CXXRecordDecl>(Record) &&
193      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
194       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
195    return false;
196
197  // Check whether the type has an object member.
198  return Record->hasObjectMember();
199}
200
201/// \brief Perform the final move to DestPtr if for some reason
202/// getReturnValueSlot() didn't use it directly.
203///
204/// The idea is that you do something like this:
205///   RValue Result = EmitSomething(..., getReturnValueSlot());
206///   EmitMoveFromReturnSlot(E, Result);
207///
208/// If nothing interferes, this will cause the result to be emitted
209/// directly into the return value slot.  Otherwise, a final move
210/// will be performed.
211void AggExprEmitter::EmitMoveFromReturnSlot(const Expr *E, RValue Src) {
212  if (shouldUseDestForReturnSlot()) {
213    // Logically, Dest.getAddr() should equal Src.getAggregateAddr().
214    // The possibility of undef rvalues complicates that a lot,
215    // though, so we can't really assert.
216    return;
217  }
218
219  // Otherwise, do a final copy,
220  assert(Dest.getAddr() != Src.getAggregateAddr());
221  EmitFinalDestCopy(E, Src, /*Ignore*/ true);
222}
223
224/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
225void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore,
226                                       unsigned Alignment) {
227  assert(Src.isAggregate() && "value must be aggregate value!");
228
229  // If Dest is ignored, then we're evaluating an aggregate expression
230  // in a context (like an expression statement) that doesn't care
231  // about the result.  C says that an lvalue-to-rvalue conversion is
232  // performed in these cases; C++ says that it is not.  In either
233  // case, we don't actually need to do anything unless the value is
234  // volatile.
235  if (Dest.isIgnored()) {
236    if (!Src.isVolatileQualified() ||
237        CGF.CGM.getLangOptions().CPlusPlus ||
238        (IgnoreResult && Ignore))
239      return;
240
241    // If the source is volatile, we must read from it; to do that, we need
242    // some place to put it.
243    Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
244  }
245
246  if (Dest.requiresGCollection()) {
247    CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
248    llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
249    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
250    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
251                                                      Dest.getAddr(),
252                                                      Src.getAggregateAddr(),
253                                                      SizeVal);
254    return;
255  }
256  // If the result of the assignment is used, copy the LHS there also.
257  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
258  // from the source as well, as we can't eliminate it if either operand
259  // is volatile, unless copy has volatile for both source and destination..
260  CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
261                        Dest.isVolatile()|Src.isVolatileQualified(),
262                        Alignment);
263}
264
265/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
266void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
267  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
268
269  CharUnits Alignment = std::min(Src.getAlignment(), Dest.getAlignment());
270  EmitFinalDestCopy(E, Src.asAggregateRValue(), Ignore, Alignment.getQuantity());
271}
272
273//===----------------------------------------------------------------------===//
274//                            Visitor Methods
275//===----------------------------------------------------------------------===//
276
277void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
278  Visit(E->GetTemporaryExpr());
279}
280
281void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
282  EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
283}
284
285void
286AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
287  if (E->getType().isPODType(CGF.getContext())) {
288    // For a POD type, just emit a load of the lvalue + a copy, because our
289    // compound literal might alias the destination.
290    // FIXME: This is a band-aid; the real problem appears to be in our handling
291    // of assignments, where we store directly into the LHS without checking
292    // whether anything in the RHS aliases.
293    EmitAggLoadOfLValue(E);
294    return;
295  }
296
297  AggValueSlot Slot = EnsureSlot(E->getType());
298  CGF.EmitAggExpr(E->getInitializer(), Slot);
299}
300
301
302void AggExprEmitter::VisitCastExpr(CastExpr *E) {
303  switch (E->getCastKind()) {
304  case CK_Dynamic: {
305    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
306    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
307    // FIXME: Do we also need to handle property references here?
308    if (LV.isSimple())
309      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
310    else
311      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
312
313    if (!Dest.isIgnored())
314      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
315    break;
316  }
317
318  case CK_ToUnion: {
319    if (Dest.isIgnored()) break;
320
321    // GCC union extension
322    QualType Ty = E->getSubExpr()->getType();
323    QualType PtrTy = CGF.getContext().getPointerType(Ty);
324    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
325                                                 CGF.ConvertType(PtrTy));
326    EmitInitializationToLValue(E->getSubExpr(),
327                               CGF.MakeAddrLValue(CastPtr, Ty));
328    break;
329  }
330
331  case CK_DerivedToBase:
332  case CK_BaseToDerived:
333  case CK_UncheckedDerivedToBase: {
334    llvm_unreachable("cannot perform hierarchy conversion in EmitAggExpr: "
335                "should have been unpacked before we got here");
336  }
337
338  case CK_LValueToRValue: // hope for downstream optimization
339  case CK_NoOp:
340  case CK_AtomicToNonAtomic:
341  case CK_NonAtomicToAtomic:
342  case CK_UserDefinedConversion:
343  case CK_ConstructorConversion:
344    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
345                                                   E->getType()) &&
346           "Implicit cast types must be compatible");
347    Visit(E->getSubExpr());
348    break;
349
350  case CK_LValueBitCast:
351    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
352
353  case CK_Dependent:
354  case CK_BitCast:
355  case CK_ArrayToPointerDecay:
356  case CK_FunctionToPointerDecay:
357  case CK_NullToPointer:
358  case CK_NullToMemberPointer:
359  case CK_BaseToDerivedMemberPointer:
360  case CK_DerivedToBaseMemberPointer:
361  case CK_MemberPointerToBoolean:
362  case CK_IntegralToPointer:
363  case CK_PointerToIntegral:
364  case CK_PointerToBoolean:
365  case CK_ToVoid:
366  case CK_VectorSplat:
367  case CK_IntegralCast:
368  case CK_IntegralToBoolean:
369  case CK_IntegralToFloating:
370  case CK_FloatingToIntegral:
371  case CK_FloatingToBoolean:
372  case CK_FloatingCast:
373  case CK_CPointerToObjCPointerCast:
374  case CK_BlockPointerToObjCPointerCast:
375  case CK_AnyPointerToBlockPointerCast:
376  case CK_ObjCObjectLValueCast:
377  case CK_FloatingRealToComplex:
378  case CK_FloatingComplexToReal:
379  case CK_FloatingComplexToBoolean:
380  case CK_FloatingComplexCast:
381  case CK_FloatingComplexToIntegralComplex:
382  case CK_IntegralRealToComplex:
383  case CK_IntegralComplexToReal:
384  case CK_IntegralComplexToBoolean:
385  case CK_IntegralComplexCast:
386  case CK_IntegralComplexToFloatingComplex:
387  case CK_ARCProduceObject:
388  case CK_ARCConsumeObject:
389  case CK_ARCReclaimReturnedObject:
390  case CK_ARCExtendBlockObject:
391    llvm_unreachable("cast kind invalid for aggregate types");
392  }
393}
394
395void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
396  if (E->getCallReturnType()->isReferenceType()) {
397    EmitAggLoadOfLValue(E);
398    return;
399  }
400
401  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
402  EmitMoveFromReturnSlot(E, RV);
403}
404
405void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
406  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
407  EmitMoveFromReturnSlot(E, RV);
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  // Codegen the RHS so that it stores directly into the LHS.
458  AggValueSlot LHSSlot =
459    AggValueSlot::forLValue(LHS, AggValueSlot::IsDestructed,
460                            needsGC(E->getLHS()->getType()),
461                            AggValueSlot::IsAliased);
462  CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
463  EmitFinalDestCopy(E, LHS, true);
464}
465
466void AggExprEmitter::
467VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
468  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
469  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
470  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
471
472  // Bind the common expression if necessary.
473  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
474
475  CodeGenFunction::ConditionalEvaluation eval(CGF);
476  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
477
478  // Save whether the destination's lifetime is externally managed.
479  bool isExternallyDestructed = Dest.isExternallyDestructed();
480
481  eval.begin(CGF);
482  CGF.EmitBlock(LHSBlock);
483  Visit(E->getTrueExpr());
484  eval.end(CGF);
485
486  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
487  CGF.Builder.CreateBr(ContBlock);
488
489  // If the result of an agg expression is unused, then the emission
490  // of the LHS might need to create a destination slot.  That's fine
491  // with us, and we can safely emit the RHS into the same slot, but
492  // we shouldn't claim that it's already being destructed.
493  Dest.setExternallyDestructed(isExternallyDestructed);
494
495  eval.begin(CGF);
496  CGF.EmitBlock(RHSBlock);
497  Visit(E->getFalseExpr());
498  eval.end(CGF);
499
500  CGF.EmitBlock(ContBlock);
501}
502
503void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
504  Visit(CE->getChosenSubExpr(CGF.getContext()));
505}
506
507void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
508  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
509  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
510
511  if (!ArgPtr) {
512    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
513    return;
514  }
515
516  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
517}
518
519void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
520  // Ensure that we have a slot, but if we already do, remember
521  // whether it was externally destructed.
522  bool wasExternallyDestructed = Dest.isExternallyDestructed();
523  Dest = EnsureSlot(E->getType());
524
525  // We're going to push a destructor if there isn't already one.
526  Dest.setExternallyDestructed();
527
528  Visit(E->getSubExpr());
529
530  // Push that destructor we promised.
531  if (!wasExternallyDestructed)
532    CGF.EmitCXXTemporary(E->getTemporary(), E->getType(), Dest.getAddr());
533}
534
535void
536AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
537  AggValueSlot Slot = EnsureSlot(E->getType());
538  CGF.EmitCXXConstructExpr(E, Slot);
539}
540
541void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
542  CGF.enterFullExpression(E);
543  CodeGenFunction::RunCleanupsScope cleanups(CGF);
544  Visit(E->getSubExpr());
545}
546
547void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
548  QualType T = E->getType();
549  AggValueSlot Slot = EnsureSlot(T);
550  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
551}
552
553void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
554  QualType T = E->getType();
555  AggValueSlot Slot = EnsureSlot(T);
556  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
557}
558
559/// isSimpleZero - If emitting this value will obviously just cause a store of
560/// zero to memory, return true.  This can return false if uncertain, so it just
561/// handles simple cases.
562static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
563  E = E->IgnoreParens();
564
565  // 0
566  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
567    return IL->getValue() == 0;
568  // +0.0
569  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
570    return FL->getValue().isPosZero();
571  // int()
572  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
573      CGF.getTypes().isZeroInitializable(E->getType()))
574    return true;
575  // (int*)0 - Null pointer expressions.
576  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
577    return ICE->getCastKind() == CK_NullToPointer;
578  // '\0'
579  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
580    return CL->getValue() == 0;
581
582  // Otherwise, hard case: conservatively return false.
583  return false;
584}
585
586
587void
588AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
589  QualType type = LV.getType();
590  // FIXME: Ignore result?
591  // FIXME: Are initializers affected by volatile?
592  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
593    // Storing "i32 0" to a zero'd memory location is a noop.
594  } else if (isa<ImplicitValueInitExpr>(E)) {
595    EmitNullInitializationToLValue(LV);
596  } else if (type->isReferenceType()) {
597    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
598    CGF.EmitStoreThroughLValue(RV, LV);
599  } else if (type->isAnyComplexType()) {
600    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
601  } else if (CGF.hasAggregateLLVMType(type)) {
602    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV,
603                                               AggValueSlot::IsDestructed,
604                                      AggValueSlot::DoesNotNeedGCBarriers,
605                                               AggValueSlot::IsNotAliased,
606                                               Dest.isZeroed()));
607  } else if (LV.isSimple()) {
608    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
609  } else {
610    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
611  }
612}
613
614void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
615  QualType type = lv.getType();
616
617  // If the destination slot is already zeroed out before the aggregate is
618  // copied into it, we don't have to emit any zeros here.
619  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
620    return;
621
622  if (!CGF.hasAggregateLLVMType(type)) {
623    // For non-aggregates, we can store zero
624    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
625    CGF.EmitStoreThroughLValue(RValue::get(null), lv);
626  } else {
627    // There's a potential optimization opportunity in combining
628    // memsets; that would be easy for arrays, but relatively
629    // difficult for structures with the current code.
630    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
631  }
632}
633
634void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
635#if 0
636  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
637  // (Length of globals? Chunks of zeroed-out space?).
638  //
639  // If we can, prefer a copy from a global; this is a lot less code for long
640  // globals, and it's easier for the current optimizers to analyze.
641  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
642    llvm::GlobalVariable* GV =
643    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
644                             llvm::GlobalValue::InternalLinkage, C, "");
645    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
646    return;
647  }
648#endif
649  if (E->hadArrayRangeDesignator())
650    CGF.ErrorUnsupported(E, "GNU array range designator extension");
651
652  llvm::Value *DestPtr = Dest.getAddr();
653
654  // Handle initialization of an array.
655  if (E->getType()->isArrayType()) {
656    llvm::PointerType *APType =
657      cast<llvm::PointerType>(DestPtr->getType());
658    llvm::ArrayType *AType =
659      cast<llvm::ArrayType>(APType->getElementType());
660
661    uint64_t NumInitElements = E->getNumInits();
662
663    if (E->getNumInits() > 0) {
664      QualType T1 = E->getType();
665      QualType T2 = E->getInit(0)->getType();
666      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
667        EmitAggLoadOfLValue(E->getInit(0));
668        return;
669      }
670    }
671
672    uint64_t NumArrayElements = AType->getNumElements();
673    assert(NumInitElements <= NumArrayElements);
674
675    QualType elementType = E->getType().getCanonicalType();
676    elementType = CGF.getContext().getQualifiedType(
677                    cast<ArrayType>(elementType)->getElementType(),
678                    elementType.getQualifiers() + Dest.getQualifiers());
679
680    // DestPtr is an array*.  Construct an elementType* by drilling
681    // down a level.
682    llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, 0);
683    llvm::Value *indices[] = { zero, zero };
684    llvm::Value *begin =
685      Builder.CreateInBoundsGEP(DestPtr, indices, "arrayinit.begin");
686
687    // Exception safety requires us to destroy all the
688    // already-constructed members if an initializer throws.
689    // For that, we'll need an EH cleanup.
690    QualType::DestructionKind dtorKind = elementType.isDestructedType();
691    llvm::AllocaInst *endOfInit = 0;
692    EHScopeStack::stable_iterator cleanup;
693    llvm::Instruction *cleanupDominator = 0;
694    if (CGF.needsEHCleanup(dtorKind)) {
695      // In principle we could tell the cleanup where we are more
696      // directly, but the control flow can get so varied here that it
697      // would actually be quite complex.  Therefore we go through an
698      // alloca.
699      endOfInit = CGF.CreateTempAlloca(begin->getType(),
700                                       "arrayinit.endOfInit");
701      cleanupDominator = Builder.CreateStore(begin, endOfInit);
702      CGF.pushIrregularPartialArrayCleanup(begin, endOfInit, elementType,
703                                           CGF.getDestroyer(dtorKind));
704      cleanup = CGF.EHStack.stable_begin();
705
706    // Otherwise, remember that we didn't need a cleanup.
707    } else {
708      dtorKind = QualType::DK_none;
709    }
710
711    llvm::Value *one = llvm::ConstantInt::get(CGF.SizeTy, 1);
712
713    // The 'current element to initialize'.  The invariants on this
714    // variable are complicated.  Essentially, after each iteration of
715    // the loop, it points to the last initialized element, except
716    // that it points to the beginning of the array before any
717    // elements have been initialized.
718    llvm::Value *element = begin;
719
720    // Emit the explicit initializers.
721    for (uint64_t i = 0; i != NumInitElements; ++i) {
722      // Advance to the next element.
723      if (i > 0) {
724        element = Builder.CreateInBoundsGEP(element, one, "arrayinit.element");
725
726        // Tell the cleanup that it needs to destroy up to this
727        // element.  TODO: some of these stores can be trivially
728        // observed to be unnecessary.
729        if (endOfInit) Builder.CreateStore(element, endOfInit);
730      }
731
732      LValue elementLV = CGF.MakeAddrLValue(element, elementType);
733      EmitInitializationToLValue(E->getInit(i), elementLV);
734    }
735
736    // Check whether there's a non-trivial array-fill expression.
737    // Note that this will be a CXXConstructExpr even if the element
738    // type is an array (or array of array, etc.) of class type.
739    Expr *filler = E->getArrayFiller();
740    bool hasTrivialFiller = true;
741    if (CXXConstructExpr *cons = dyn_cast_or_null<CXXConstructExpr>(filler)) {
742      assert(cons->getConstructor()->isDefaultConstructor());
743      hasTrivialFiller = cons->getConstructor()->isTrivial();
744    }
745
746    // Any remaining elements need to be zero-initialized, possibly
747    // using the filler expression.  We can skip this if the we're
748    // emitting to zeroed memory.
749    if (NumInitElements != NumArrayElements &&
750        !(Dest.isZeroed() && hasTrivialFiller &&
751          CGF.getTypes().isZeroInitializable(elementType))) {
752
753      // Use an actual loop.  This is basically
754      //   do { *array++ = filler; } while (array != end);
755
756      // Advance to the start of the rest of the array.
757      if (NumInitElements) {
758        element = Builder.CreateInBoundsGEP(element, one, "arrayinit.start");
759        if (endOfInit) Builder.CreateStore(element, endOfInit);
760      }
761
762      // Compute the end of the array.
763      llvm::Value *end = Builder.CreateInBoundsGEP(begin,
764                        llvm::ConstantInt::get(CGF.SizeTy, NumArrayElements),
765                                                   "arrayinit.end");
766
767      llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
768      llvm::BasicBlock *bodyBB = CGF.createBasicBlock("arrayinit.body");
769
770      // Jump into the body.
771      CGF.EmitBlock(bodyBB);
772      llvm::PHINode *currentElement =
773        Builder.CreatePHI(element->getType(), 2, "arrayinit.cur");
774      currentElement->addIncoming(element, entryBB);
775
776      // Emit the actual filler expression.
777      LValue elementLV = CGF.MakeAddrLValue(currentElement, elementType);
778      if (filler)
779        EmitInitializationToLValue(filler, elementLV);
780      else
781        EmitNullInitializationToLValue(elementLV);
782
783      // Move on to the next element.
784      llvm::Value *nextElement =
785        Builder.CreateInBoundsGEP(currentElement, one, "arrayinit.next");
786
787      // Tell the EH cleanup that we finished with the last element.
788      if (endOfInit) Builder.CreateStore(nextElement, endOfInit);
789
790      // Leave the loop if we're done.
791      llvm::Value *done = Builder.CreateICmpEQ(nextElement, end,
792                                               "arrayinit.done");
793      llvm::BasicBlock *endBB = CGF.createBasicBlock("arrayinit.end");
794      Builder.CreateCondBr(done, endBB, bodyBB);
795      currentElement->addIncoming(nextElement, Builder.GetInsertBlock());
796
797      CGF.EmitBlock(endBB);
798    }
799
800    // Leave the partial-array cleanup if we entered one.
801    if (dtorKind) CGF.DeactivateCleanupBlock(cleanup, cleanupDominator);
802
803    return;
804  }
805
806  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
807
808  // Do struct initialization; this code just sets each individual member
809  // to the approprate value.  This makes bitfield support automatic;
810  // the disadvantage is that the generated code is more difficult for
811  // the optimizer, especially with bitfields.
812  unsigned NumInitElements = E->getNumInits();
813  RecordDecl *record = E->getType()->castAs<RecordType>()->getDecl();
814
815  if (record->isUnion()) {
816    // Only initialize one field of a union. The field itself is
817    // specified by the initializer list.
818    if (!E->getInitializedFieldInUnion()) {
819      // Empty union; we have nothing to do.
820
821#ifndef NDEBUG
822      // Make sure that it's really an empty and not a failure of
823      // semantic analysis.
824      for (RecordDecl::field_iterator Field = record->field_begin(),
825                                   FieldEnd = record->field_end();
826           Field != FieldEnd; ++Field)
827        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
828#endif
829      return;
830    }
831
832    // FIXME: volatility
833    FieldDecl *Field = E->getInitializedFieldInUnion();
834
835    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
836    if (NumInitElements) {
837      // Store the initializer into the field
838      EmitInitializationToLValue(E->getInit(0), FieldLoc);
839    } else {
840      // Default-initialize to null.
841      EmitNullInitializationToLValue(FieldLoc);
842    }
843
844    return;
845  }
846
847  // We'll need to enter cleanup scopes in case any of the member
848  // initializers throw an exception.
849  SmallVector<EHScopeStack::stable_iterator, 16> cleanups;
850  llvm::Instruction *cleanupDominator = 0;
851
852  // Here we iterate over the fields; this makes it simpler to both
853  // default-initialize fields and skip over unnamed fields.
854  unsigned curInitIndex = 0;
855  for (RecordDecl::field_iterator field = record->field_begin(),
856                               fieldEnd = record->field_end();
857       field != fieldEnd; ++field) {
858    // We're done once we hit the flexible array member.
859    if (field->getType()->isIncompleteArrayType())
860      break;
861
862    // Always skip anonymous bitfields.
863    if (field->isUnnamedBitfield())
864      continue;
865
866    // We're done if we reach the end of the explicit initializers, we
867    // have a zeroed object, and the rest of the fields are
868    // zero-initializable.
869    if (curInitIndex == NumInitElements && Dest.isZeroed() &&
870        CGF.getTypes().isZeroInitializable(E->getType()))
871      break;
872
873    // FIXME: volatility
874    LValue LV = CGF.EmitLValueForFieldInitialization(DestPtr, *field, 0);
875    // We never generate write-barries for initialized fields.
876    LV.setNonGC(true);
877
878    if (curInitIndex < NumInitElements) {
879      // Store the initializer into the field.
880      EmitInitializationToLValue(E->getInit(curInitIndex++), LV);
881    } else {
882      // We're out of initalizers; default-initialize to null
883      EmitNullInitializationToLValue(LV);
884    }
885
886    // Push a destructor if necessary.
887    // FIXME: if we have an array of structures, all explicitly
888    // initialized, we can end up pushing a linear number of cleanups.
889    bool pushedCleanup = false;
890    if (QualType::DestructionKind dtorKind
891          = field->getType().isDestructedType()) {
892      assert(LV.isSimple());
893      if (CGF.needsEHCleanup(dtorKind)) {
894        if (!cleanupDominator)
895          cleanupDominator = CGF.Builder.CreateUnreachable(); // placeholder
896
897        CGF.pushDestroy(EHCleanup, LV.getAddress(), field->getType(),
898                        CGF.getDestroyer(dtorKind), false);
899        cleanups.push_back(CGF.EHStack.stable_begin());
900        pushedCleanup = true;
901      }
902    }
903
904    // If the GEP didn't get used because of a dead zero init or something
905    // else, clean it up for -O0 builds and general tidiness.
906    if (!pushedCleanup && LV.isSimple())
907      if (llvm::GetElementPtrInst *GEP =
908            dyn_cast<llvm::GetElementPtrInst>(LV.getAddress()))
909        if (GEP->use_empty())
910          GEP->eraseFromParent();
911  }
912
913  // Deactivate all the partial cleanups in reverse order, which
914  // generally means popping them.
915  for (unsigned i = cleanups.size(); i != 0; --i)
916    CGF.DeactivateCleanupBlock(cleanups[i-1], cleanupDominator);
917
918  // Destroy the placeholder if we made one.
919  if (cleanupDominator)
920    cleanupDominator->eraseFromParent();
921}
922
923//===----------------------------------------------------------------------===//
924//                        Entry Points into this File
925//===----------------------------------------------------------------------===//
926
927/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
928/// non-zero bytes that will be stored when outputting the initializer for the
929/// specified initializer expression.
930static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
931  E = E->IgnoreParens();
932
933  // 0 and 0.0 won't require any non-zero stores!
934  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
935
936  // If this is an initlist expr, sum up the size of sizes of the (present)
937  // elements.  If this is something weird, assume the whole thing is non-zero.
938  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
939  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
940    return CGF.getContext().getTypeSizeInChars(E->getType());
941
942  // InitListExprs for structs have to be handled carefully.  If there are
943  // reference members, we need to consider the size of the reference, not the
944  // referencee.  InitListExprs for unions and arrays can't have references.
945  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
946    if (!RT->isUnionType()) {
947      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
948      CharUnits NumNonZeroBytes = CharUnits::Zero();
949
950      unsigned ILEElement = 0;
951      for (RecordDecl::field_iterator Field = SD->field_begin(),
952           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
953        // We're done once we hit the flexible array member or run out of
954        // InitListExpr elements.
955        if (Field->getType()->isIncompleteArrayType() ||
956            ILEElement == ILE->getNumInits())
957          break;
958        if (Field->isUnnamedBitfield())
959          continue;
960
961        const Expr *E = ILE->getInit(ILEElement++);
962
963        // Reference values are always non-null and have the width of a pointer.
964        if (Field->getType()->isReferenceType())
965          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
966              CGF.getContext().getTargetInfo().getPointerWidth(0));
967        else
968          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
969      }
970
971      return NumNonZeroBytes;
972    }
973  }
974
975
976  CharUnits NumNonZeroBytes = CharUnits::Zero();
977  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
978    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
979  return NumNonZeroBytes;
980}
981
982/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
983/// zeros in it, emit a memset and avoid storing the individual zeros.
984///
985static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
986                                     CodeGenFunction &CGF) {
987  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
988  // volatile stores.
989  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
990
991  // C++ objects with a user-declared constructor don't need zero'ing.
992  if (CGF.getContext().getLangOptions().CPlusPlus)
993    if (const RecordType *RT = CGF.getContext()
994                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
995      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
996      if (RD->hasUserDeclaredConstructor())
997        return;
998    }
999
1000  // If the type is 16-bytes or smaller, prefer individual stores over memset.
1001  std::pair<CharUnits, CharUnits> TypeInfo =
1002    CGF.getContext().getTypeInfoInChars(E->getType());
1003  if (TypeInfo.first <= CharUnits::fromQuantity(16))
1004    return;
1005
1006  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
1007  // we prefer to emit memset + individual stores for the rest.
1008  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
1009  if (NumNonZeroBytes*4 > TypeInfo.first)
1010    return;
1011
1012  // Okay, it seems like a good idea to use an initial memset, emit the call.
1013  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
1014  CharUnits Align = TypeInfo.second;
1015
1016  llvm::Value *Loc = Slot.getAddr();
1017  llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
1018
1019  Loc = CGF.Builder.CreateBitCast(Loc, BP);
1020  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
1021                           Align.getQuantity(), false);
1022
1023  // Tell the AggExprEmitter that the slot is known zero.
1024  Slot.setZeroed();
1025}
1026
1027
1028
1029
1030/// EmitAggExpr - Emit the computation of the specified expression of aggregate
1031/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
1032/// the value of the aggregate expression is not needed.  If VolatileDest is
1033/// true, DestPtr cannot be 0.
1034///
1035/// \param IsInitializer - true if this evaluation is initializing an
1036/// object whose lifetime is already being managed.
1037void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
1038                                  bool IgnoreResult) {
1039  assert(E && hasAggregateLLVMType(E->getType()) &&
1040         "Invalid aggregate expression to emit");
1041  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
1042         "slot has bits but no address");
1043
1044  // Optimize the slot if possible.
1045  CheckAggExprForMemSetUse(Slot, E, *this);
1046
1047  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
1048}
1049
1050LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
1051  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
1052  llvm::Value *Temp = CreateMemTemp(E->getType());
1053  LValue LV = MakeAddrLValue(Temp, E->getType());
1054  EmitAggExpr(E, AggValueSlot::forLValue(LV, AggValueSlot::IsNotDestructed,
1055                                         AggValueSlot::DoesNotNeedGCBarriers,
1056                                         AggValueSlot::IsNotAliased));
1057  return LV;
1058}
1059
1060void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
1061                                        llvm::Value *SrcPtr, QualType Ty,
1062                                        bool isVolatile, unsigned Alignment) {
1063  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
1064
1065  if (getContext().getLangOptions().CPlusPlus) {
1066    if (const RecordType *RT = Ty->getAs<RecordType>()) {
1067      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
1068      assert((Record->hasTrivialCopyConstructor() ||
1069              Record->hasTrivialCopyAssignment() ||
1070              Record->hasTrivialMoveConstructor() ||
1071              Record->hasTrivialMoveAssignment()) &&
1072             "Trying to aggregate-copy a type without a trivial copy "
1073             "constructor or assignment operator");
1074      // Ignore empty classes in C++.
1075      if (Record->isEmpty())
1076        return;
1077    }
1078  }
1079
1080  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
1081  // C99 6.5.16.1p3, which states "If the value being stored in an object is
1082  // read from another object that overlaps in anyway the storage of the first
1083  // object, then the overlap shall be exact and the two objects shall have
1084  // qualified or unqualified versions of a compatible type."
1085  //
1086  // memcpy is not defined if the source and destination pointers are exactly
1087  // equal, but other compilers do this optimization, and almost every memcpy
1088  // implementation handles this case safely.  If there is a libc that does not
1089  // safely handle this, we can add a target hook.
1090
1091  // Get size and alignment info for this aggregate.
1092  std::pair<CharUnits, CharUnits> TypeInfo =
1093    getContext().getTypeInfoInChars(Ty);
1094
1095  if (!Alignment)
1096    Alignment = TypeInfo.second.getQuantity();
1097
1098  // FIXME: Handle variable sized types.
1099
1100  // FIXME: If we have a volatile struct, the optimizer can remove what might
1101  // appear to be `extra' memory ops:
1102  //
1103  // volatile struct { int i; } a, b;
1104  //
1105  // int main() {
1106  //   a = b;
1107  //   a = b;
1108  // }
1109  //
1110  // we need to use a different call here.  We use isVolatile to indicate when
1111  // either the source or the destination is volatile.
1112
1113  llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
1114  llvm::Type *DBP =
1115    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
1116  DestPtr = Builder.CreateBitCast(DestPtr, DBP);
1117
1118  llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
1119  llvm::Type *SBP =
1120    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
1121  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP);
1122
1123  // Don't do any of the memmove_collectable tests if GC isn't set.
1124  if (CGM.getLangOptions().getGC() == LangOptions::NonGC) {
1125    // fall through
1126  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
1127    RecordDecl *Record = RecordTy->getDecl();
1128    if (Record->hasObjectMember()) {
1129      CharUnits size = TypeInfo.first;
1130      llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1131      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
1132      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1133                                                    SizeVal);
1134      return;
1135    }
1136  } else if (Ty->isArrayType()) {
1137    QualType BaseType = getContext().getBaseElementType(Ty);
1138    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
1139      if (RecordTy->getDecl()->hasObjectMember()) {
1140        CharUnits size = TypeInfo.first;
1141        llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1142        llvm::Value *SizeVal =
1143          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1144        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1145                                                      SizeVal);
1146        return;
1147      }
1148    }
1149  }
1150
1151  Builder.CreateMemCpy(DestPtr, SrcPtr,
1152                       llvm::ConstantInt::get(IntPtrTy,
1153                                              TypeInfo.first.getQuantity()),
1154                       Alignment, isVolatile);
1155}
1156