CGExprAgg.cpp revision c6fdb7765fc872eea8dfc5fb0ee984c0fbac1068 
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/Support/Compiler.h"
24#include "llvm/Intrinsics.h"
25using namespace clang;
26using namespace CodeGen;
27
28//===----------------------------------------------------------------------===//
29//                        Aggregate Expression Emitter
30//===----------------------------------------------------------------------===//
31
32namespace  {
33class VISIBILITY_HIDDEN AggExprEmitter : public StmtVisitor<AggExprEmitter> {
34  CodeGenFunction &CGF;
35  CGBuilderTy &Builder;
36  llvm::Value *DestPtr;
37  bool VolatileDest;
38  bool IgnoreResult;
39  bool IsInitializer;
40  bool RequiresGCollection;
41public:
42  AggExprEmitter(CodeGenFunction &cgf, llvm::Value *destPtr, bool v,
43                 bool ignore, bool isinit, bool requiresGCollection)
44    : CGF(cgf), Builder(CGF.Builder),
45      DestPtr(destPtr), VolatileDest(v), IgnoreResult(ignore),
46      IsInitializer(isinit), RequiresGCollection(requiresGCollection) {
47  }
48
49  //===--------------------------------------------------------------------===//
50  //                               Utilities
51  //===--------------------------------------------------------------------===//
52
53  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
54  /// represents a value lvalue, this method emits the address of the lvalue,
55  /// then loads the result into DestPtr.
56  void EmitAggLoadOfLValue(const Expr *E);
57
58  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
59  void EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore = false);
60  void EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore = false);
61
62  //===--------------------------------------------------------------------===//
63  //                            Visitor Methods
64  //===--------------------------------------------------------------------===//
65
66  void VisitStmt(Stmt *S) {
67    CGF.ErrorUnsupported(S, "aggregate expression");
68  }
69  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
70  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
71
72  // l-values.
73  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
74  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
75  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
76  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
77  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
78    EmitAggLoadOfLValue(E);
79  }
80  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
81    EmitAggLoadOfLValue(E);
82  }
83  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
84    EmitAggLoadOfLValue(E);
85  }
86  void VisitPredefinedExpr(const PredefinedExpr *E) {
87    EmitAggLoadOfLValue(E);
88  }
89
90  // Operators.
91  void VisitCastExpr(CastExpr *E);
92  void VisitCallExpr(const CallExpr *E);
93  void VisitStmtExpr(const StmtExpr *E);
94  void VisitBinaryOperator(const BinaryOperator *BO);
95  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
96  void VisitBinAssign(const BinaryOperator *E);
97  void VisitBinComma(const BinaryOperator *E);
98  void VisitUnaryAddrOf(const UnaryOperator *E);
99
100  void VisitObjCMessageExpr(ObjCMessageExpr *E);
101  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
102    EmitAggLoadOfLValue(E);
103  }
104  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
105  void VisitObjCImplicitSetterGetterRefExpr(ObjCImplicitSetterGetterRefExpr *E);
106
107  void VisitConditionalOperator(const ConditionalOperator *CO);
108  void VisitChooseExpr(const ChooseExpr *CE);
109  void VisitInitListExpr(InitListExpr *E);
110  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
111    Visit(DAE->getExpr());
112  }
113  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
114  void VisitCXXConstructExpr(const CXXConstructExpr *E);
115  void VisitCXXExprWithTemporaries(CXXExprWithTemporaries *E);
116  void VisitCXXZeroInitValueExpr(CXXZeroInitValueExpr *E);
117  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
118
119  void VisitVAArgExpr(VAArgExpr *E);
120
121  void EmitInitializationToLValue(Expr *E, LValue Address);
122  void EmitNullInitializationToLValue(LValue Address, QualType T);
123  //  case Expr::ChooseExprClass:
124
125};
126}  // end anonymous namespace.
127
128//===----------------------------------------------------------------------===//
129//                                Utilities
130//===----------------------------------------------------------------------===//
131
132/// EmitAggLoadOfLValue - Given an expression with aggregate type that
133/// represents a value lvalue, this method emits the address of the lvalue,
134/// then loads the result into DestPtr.
135void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
136  LValue LV = CGF.EmitLValue(E);
137  EmitFinalDestCopy(E, LV);
138}
139
140/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
141void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore) {
142  assert(Src.isAggregate() && "value must be aggregate value!");
143
144  // If the result is ignored, don't copy from the value.
145  if (DestPtr == 0) {
146    if (!Src.isVolatileQualified() || (IgnoreResult && Ignore))
147      return;
148    // If the source is volatile, we must read from it; to do that, we need
149    // some place to put it.
150    DestPtr = CGF.CreateTempAlloca(CGF.ConvertType(E->getType()), "agg.tmp");
151  }
152
153  if (RequiresGCollection) {
154    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
155                                              DestPtr, Src.getAggregateAddr(),
156                                              E->getType());
157    return;
158  }
159  // If the result of the assignment is used, copy the LHS there also.
160  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
161  // from the source as well, as we can't eliminate it if either operand
162  // is volatile, unless copy has volatile for both source and destination..
163  CGF.EmitAggregateCopy(DestPtr, Src.getAggregateAddr(), E->getType(),
164                        VolatileDest|Src.isVolatileQualified());
165}
166
167/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
168void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
169  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
170
171  EmitFinalDestCopy(E, RValue::getAggregate(Src.getAddress(),
172                                            Src.isVolatileQualified()),
173                    Ignore);
174}
175
176//===----------------------------------------------------------------------===//
177//                            Visitor Methods
178//===----------------------------------------------------------------------===//
179
180void AggExprEmitter::VisitCastExpr(CastExpr *E) {
181  switch (E->getCastKind()) {
182  default: assert(0 && "Unhandled cast kind!");
183
184  case CastExpr::CK_ToUnion: {
185    // GCC union extension
186    QualType PtrTy =
187    CGF.getContext().getPointerType(E->getSubExpr()->getType());
188    llvm::Value *CastPtr = Builder.CreateBitCast(DestPtr,
189                                                 CGF.ConvertType(PtrTy));
190    EmitInitializationToLValue(E->getSubExpr(),
191                               LValue::MakeAddr(CastPtr, Qualifiers()));
192    break;
193  }
194
195  // FIXME: Remove the CK_Unknown check here.
196  case CastExpr::CK_Unknown:
197  case CastExpr::CK_NoOp:
198  case CastExpr::CK_UserDefinedConversion:
199  case CastExpr::CK_ConstructorConversion:
200    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
201                                                   E->getType()) &&
202           "Implicit cast types must be compatible");
203    Visit(E->getSubExpr());
204    break;
205
206  case CastExpr::CK_NullToMemberPointer: {
207    const llvm::Type *PtrDiffTy =
208      CGF.ConvertType(CGF.getContext().getPointerDiffType());
209
210    llvm::Value *NullValue = llvm::Constant::getNullValue(PtrDiffTy);
211    llvm::Value *Ptr = Builder.CreateStructGEP(DestPtr, 0, "ptr");
212    Builder.CreateStore(NullValue, Ptr, VolatileDest);
213
214    llvm::Value *Adj = Builder.CreateStructGEP(DestPtr, 1, "adj");
215    Builder.CreateStore(NullValue, Adj, VolatileDest);
216
217    break;
218  }
219
220  case CastExpr::CK_BitCast: {
221    // This must be a member function pointer cast.
222    Visit(E->getSubExpr());
223    break;
224  }
225
226  case CastExpr::CK_DerivedToBaseMemberPointer:
227  case CastExpr::CK_BaseToDerivedMemberPointer: {
228    QualType SrcType = E->getSubExpr()->getType();
229
230    llvm::Value *Src = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(SrcType),
231                                            "tmp");
232    CGF.EmitAggExpr(E->getSubExpr(), Src, SrcType.isVolatileQualified());
233
234    llvm::Value *SrcPtr = Builder.CreateStructGEP(Src, 0, "src.ptr");
235    SrcPtr = Builder.CreateLoad(SrcPtr);
236
237    llvm::Value *SrcAdj = Builder.CreateStructGEP(Src, 1, "src.adj");
238    SrcAdj = Builder.CreateLoad(SrcAdj);
239
240    llvm::Value *DstPtr = Builder.CreateStructGEP(DestPtr, 0, "dst.ptr");
241    Builder.CreateStore(SrcPtr, DstPtr, VolatileDest);
242
243    llvm::Value *DstAdj = Builder.CreateStructGEP(DestPtr, 1, "dst.adj");
244
245    // Now See if we need to update the adjustment.
246    const CXXRecordDecl *BaseDecl =
247      cast<CXXRecordDecl>(SrcType->getAs<MemberPointerType>()->
248                          getClass()->getAs<RecordType>()->getDecl());
249    const CXXRecordDecl *DerivedDecl =
250      cast<CXXRecordDecl>(E->getType()->getAs<MemberPointerType>()->
251                          getClass()->getAs<RecordType>()->getDecl());
252    if (E->getCastKind() == CastExpr::CK_DerivedToBaseMemberPointer)
253      std::swap(DerivedDecl, BaseDecl);
254
255    llvm::Constant *Adj = CGF.CGM.GetCXXBaseClassOffset(DerivedDecl, BaseDecl);
256    if (Adj) {
257      if (E->getCastKind() == CastExpr::CK_DerivedToBaseMemberPointer)
258        SrcAdj = Builder.CreateSub(SrcAdj, Adj, "adj");
259      else
260        SrcAdj = Builder.CreateAdd(SrcAdj, Adj, "adj");
261    }
262
263    Builder.CreateStore(SrcAdj, DstAdj, VolatileDest);
264    break;
265  }
266  }
267}
268
269void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
270  if (E->getCallReturnType()->isReferenceType()) {
271    EmitAggLoadOfLValue(E);
272    return;
273  }
274
275  RValue RV = CGF.EmitCallExpr(E);
276  EmitFinalDestCopy(E, RV);
277}
278
279void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
280  RValue RV = CGF.EmitObjCMessageExpr(E);
281  EmitFinalDestCopy(E, RV);
282}
283
284void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
285  RValue RV = CGF.EmitObjCPropertyGet(E);
286  EmitFinalDestCopy(E, RV);
287}
288
289void AggExprEmitter::VisitObjCImplicitSetterGetterRefExpr(
290                                   ObjCImplicitSetterGetterRefExpr *E) {
291  RValue RV = CGF.EmitObjCPropertyGet(E);
292  EmitFinalDestCopy(E, RV);
293}
294
295void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
296  CGF.EmitAnyExpr(E->getLHS(), 0, false, true);
297  CGF.EmitAggExpr(E->getRHS(), DestPtr, VolatileDest,
298                  /*IgnoreResult=*/false, IsInitializer);
299}
300
301void AggExprEmitter::VisitUnaryAddrOf(const UnaryOperator *E) {
302  // We have a member function pointer.
303  const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>();
304  (void) MPT;
305  assert(MPT->getPointeeType()->isFunctionProtoType() &&
306         "Unexpected member pointer type!");
307
308  const DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr());
309  const CXXMethodDecl *MD = cast<CXXMethodDecl>(DRE->getDecl());
310
311  const llvm::Type *PtrDiffTy =
312    CGF.ConvertType(CGF.getContext().getPointerDiffType());
313
314  llvm::Value *DstPtr = Builder.CreateStructGEP(DestPtr, 0, "dst.ptr");
315  llvm::Value *FuncPtr;
316
317  if (MD->isVirtual()) {
318    int64_t Index =
319      CGF.CGM.getVtableInfo().getMethodVtableIndex(MD);
320
321    FuncPtr = llvm::ConstantInt::get(PtrDiffTy, Index + 1);
322  } else {
323    FuncPtr = llvm::ConstantExpr::getPtrToInt(CGF.CGM.GetAddrOfFunction(MD),
324                                              PtrDiffTy);
325  }
326  Builder.CreateStore(FuncPtr, DstPtr, VolatileDest);
327
328  llvm::Value *AdjPtr = Builder.CreateStructGEP(DestPtr, 1, "dst.adj");
329
330  // The adjustment will always be 0.
331  Builder.CreateStore(llvm::ConstantInt::get(PtrDiffTy, 0), AdjPtr,
332                      VolatileDest);
333}
334
335void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
336  CGF.EmitCompoundStmt(*E->getSubStmt(), true, DestPtr, VolatileDest);
337}
338
339void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
340  if (E->getOpcode() == BinaryOperator::PtrMemD ||
341      E->getOpcode() == BinaryOperator::PtrMemI)
342    VisitPointerToDataMemberBinaryOperator(E);
343  else
344    CGF.ErrorUnsupported(E, "aggregate binary expression");
345}
346
347void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
348                                                    const BinaryOperator *E) {
349  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
350  EmitFinalDestCopy(E, LV);
351}
352
353void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
354  // For an assignment to work, the value on the right has
355  // to be compatible with the value on the left.
356  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
357                                                 E->getRHS()->getType())
358         && "Invalid assignment");
359  LValue LHS = CGF.EmitLValue(E->getLHS());
360
361  // We have to special case property setters, otherwise we must have
362  // a simple lvalue (no aggregates inside vectors, bitfields).
363  if (LHS.isPropertyRef()) {
364    llvm::Value *AggLoc = DestPtr;
365    if (!AggLoc)
366      AggLoc = CGF.CreateTempAlloca(CGF.ConvertType(E->getRHS()->getType()));
367    CGF.EmitAggExpr(E->getRHS(), AggLoc, VolatileDest);
368    CGF.EmitObjCPropertySet(LHS.getPropertyRefExpr(),
369                            RValue::getAggregate(AggLoc, VolatileDest));
370  } else if (LHS.isKVCRef()) {
371    llvm::Value *AggLoc = DestPtr;
372    if (!AggLoc)
373      AggLoc = CGF.CreateTempAlloca(CGF.ConvertType(E->getRHS()->getType()));
374    CGF.EmitAggExpr(E->getRHS(), AggLoc, VolatileDest);
375    CGF.EmitObjCPropertySet(LHS.getKVCRefExpr(),
376                            RValue::getAggregate(AggLoc, VolatileDest));
377  } else {
378    bool RequiresGCollection = false;
379    if (CGF.getContext().getLangOptions().NeXTRuntime) {
380      QualType LHSTy = E->getLHS()->getType();
381      if (const RecordType *FDTTy = LHSTy.getTypePtr()->getAs<RecordType>())
382        RequiresGCollection = FDTTy->getDecl()->hasObjectMember();
383    }
384    // Codegen the RHS so that it stores directly into the LHS.
385    CGF.EmitAggExpr(E->getRHS(), LHS.getAddress(), LHS.isVolatileQualified(),
386                    false, false, RequiresGCollection);
387    EmitFinalDestCopy(E, LHS, true);
388  }
389}
390
391void AggExprEmitter::VisitConditionalOperator(const ConditionalOperator *E) {
392  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
393  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
394  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
395
396  llvm::Value *Cond = CGF.EvaluateExprAsBool(E->getCond());
397  Builder.CreateCondBr(Cond, LHSBlock, RHSBlock);
398
399  CGF.StartConditionalBranch();
400  CGF.EmitBlock(LHSBlock);
401
402  // Handle the GNU extension for missing LHS.
403  assert(E->getLHS() && "Must have LHS for aggregate value");
404
405  Visit(E->getLHS());
406  CGF.FinishConditionalBranch();
407  CGF.EmitBranch(ContBlock);
408
409  CGF.StartConditionalBranch();
410  CGF.EmitBlock(RHSBlock);
411
412  Visit(E->getRHS());
413  CGF.FinishConditionalBranch();
414  CGF.EmitBranch(ContBlock);
415
416  CGF.EmitBlock(ContBlock);
417}
418
419void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
420  Visit(CE->getChosenSubExpr(CGF.getContext()));
421}
422
423void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
424  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
425  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
426
427  if (!ArgPtr) {
428    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
429    return;
430  }
431
432  EmitFinalDestCopy(VE, LValue::MakeAddr(ArgPtr, Qualifiers()));
433}
434
435void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
436  llvm::Value *Val = DestPtr;
437
438  if (!Val) {
439    // Create a temporary variable.
440    Val = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(E->getType()), "tmp");
441
442    // FIXME: volatile
443    CGF.EmitAggExpr(E->getSubExpr(), Val, false);
444  } else
445    Visit(E->getSubExpr());
446
447  // Don't make this a live temporary if we're emitting an initializer expr.
448  if (!IsInitializer)
449    CGF.PushCXXTemporary(E->getTemporary(), Val);
450}
451
452void
453AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
454  llvm::Value *Val = DestPtr;
455
456  if (!Val) {
457    // Create a temporary variable.
458    Val = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(E->getType()), "tmp");
459  }
460
461  CGF.EmitCXXConstructExpr(Val, E);
462}
463
464void AggExprEmitter::VisitCXXExprWithTemporaries(CXXExprWithTemporaries *E) {
465  CGF.EmitCXXExprWithTemporaries(E, DestPtr, VolatileDest, IsInitializer);
466}
467
468void AggExprEmitter::VisitCXXZeroInitValueExpr(CXXZeroInitValueExpr *E) {
469  LValue lvalue = LValue::MakeAddr(DestPtr, Qualifiers());
470  EmitNullInitializationToLValue(lvalue, E->getType());
471}
472
473void AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
474  // FIXME: Ignore result?
475  // FIXME: Are initializers affected by volatile?
476  if (isa<ImplicitValueInitExpr>(E)) {
477    EmitNullInitializationToLValue(LV, E->getType());
478  } else if (E->getType()->isComplexType()) {
479    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
480  } else if (CGF.hasAggregateLLVMType(E->getType())) {
481    CGF.EmitAnyExpr(E, LV.getAddress(), false);
482  } else {
483    CGF.EmitStoreThroughLValue(CGF.EmitAnyExpr(E), LV, E->getType());
484  }
485}
486
487void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
488  if (!CGF.hasAggregateLLVMType(T)) {
489    // For non-aggregates, we can store zero
490    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
491    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
492  } else {
493    // Otherwise, just memset the whole thing to zero.  This is legal
494    // because in LLVM, all default initializers are guaranteed to have a
495    // bit pattern of all zeros.
496    // FIXME: That isn't true for member pointers!
497    // There's a potential optimization opportunity in combining
498    // memsets; that would be easy for arrays, but relatively
499    // difficult for structures with the current code.
500    CGF.EmitMemSetToZero(LV.getAddress(), T);
501  }
502}
503
504void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
505#if 0
506  // FIXME: Disabled while we figure out what to do about
507  // test/CodeGen/bitfield.c
508  //
509  // If we can, prefer a copy from a global; this is a lot less code for long
510  // globals, and it's easier for the current optimizers to analyze.
511  // FIXME: Should we really be doing this? Should we try to avoid cases where
512  // we emit a global with a lot of zeros?  Should we try to avoid short
513  // globals?
514  if (E->isConstantInitializer(CGF.getContext(), 0)) {
515    llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, &CGF);
516    llvm::GlobalVariable* GV =
517    new llvm::GlobalVariable(C->getType(), true,
518                             llvm::GlobalValue::InternalLinkage,
519                             C, "", &CGF.CGM.getModule(), 0);
520    EmitFinalDestCopy(E, LValue::MakeAddr(GV, 0));
521    return;
522  }
523#endif
524  if (E->hadArrayRangeDesignator()) {
525    CGF.ErrorUnsupported(E, "GNU array range designator extension");
526  }
527
528  // Handle initialization of an array.
529  if (E->getType()->isArrayType()) {
530    const llvm::PointerType *APType =
531      cast<llvm::PointerType>(DestPtr->getType());
532    const llvm::ArrayType *AType =
533      cast<llvm::ArrayType>(APType->getElementType());
534
535    uint64_t NumInitElements = E->getNumInits();
536
537    if (E->getNumInits() > 0) {
538      QualType T1 = E->getType();
539      QualType T2 = E->getInit(0)->getType();
540      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
541        EmitAggLoadOfLValue(E->getInit(0));
542        return;
543      }
544    }
545
546    uint64_t NumArrayElements = AType->getNumElements();
547    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
548    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
549
550    // FIXME: were we intentionally ignoring address spaces and GC attributes?
551    Qualifiers Quals = CGF.MakeQualifiers(ElementType);
552
553    for (uint64_t i = 0; i != NumArrayElements; ++i) {
554      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
555      if (i < NumInitElements)
556        EmitInitializationToLValue(E->getInit(i),
557                                   LValue::MakeAddr(NextVal, Quals));
558      else
559        EmitNullInitializationToLValue(LValue::MakeAddr(NextVal, Quals),
560                                       ElementType);
561    }
562    return;
563  }
564
565  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
566
567  // Do struct initialization; this code just sets each individual member
568  // to the approprate value.  This makes bitfield support automatic;
569  // the disadvantage is that the generated code is more difficult for
570  // the optimizer, especially with bitfields.
571  unsigned NumInitElements = E->getNumInits();
572  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
573  unsigned CurInitVal = 0;
574
575  if (E->getType()->isUnionType()) {
576    // Only initialize one field of a union. The field itself is
577    // specified by the initializer list.
578    if (!E->getInitializedFieldInUnion()) {
579      // Empty union; we have nothing to do.
580
581#ifndef NDEBUG
582      // Make sure that it's really an empty and not a failure of
583      // semantic analysis.
584      for (RecordDecl::field_iterator Field = SD->field_begin(),
585                                   FieldEnd = SD->field_end();
586           Field != FieldEnd; ++Field)
587        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
588#endif
589      return;
590    }
591
592    // FIXME: volatility
593    FieldDecl *Field = E->getInitializedFieldInUnion();
594    LValue FieldLoc = CGF.EmitLValueForField(DestPtr, Field, true, 0);
595
596    if (NumInitElements) {
597      // Store the initializer into the field
598      EmitInitializationToLValue(E->getInit(0), FieldLoc);
599    } else {
600      // Default-initialize to null
601      EmitNullInitializationToLValue(FieldLoc, Field->getType());
602    }
603
604    return;
605  }
606
607  // Here we iterate over the fields; this makes it simpler to both
608  // default-initialize fields and skip over unnamed fields.
609  for (RecordDecl::field_iterator Field = SD->field_begin(),
610                               FieldEnd = SD->field_end();
611       Field != FieldEnd; ++Field) {
612    // We're done once we hit the flexible array member
613    if (Field->getType()->isIncompleteArrayType())
614      break;
615
616    if (Field->isUnnamedBitfield())
617      continue;
618
619    // FIXME: volatility
620    LValue FieldLoc = CGF.EmitLValueForField(DestPtr, *Field, false, 0);
621    // We never generate write-barries for initialized fields.
622    LValue::SetObjCNonGC(FieldLoc, true);
623    if (CurInitVal < NumInitElements) {
624      // Store the initializer into the field
625      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc);
626    } else {
627      // We're out of initalizers; default-initialize to null
628      EmitNullInitializationToLValue(FieldLoc, Field->getType());
629    }
630  }
631}
632
633//===----------------------------------------------------------------------===//
634//                        Entry Points into this File
635//===----------------------------------------------------------------------===//
636
637/// EmitAggExpr - Emit the computation of the specified expression of aggregate
638/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
639/// the value of the aggregate expression is not needed.  If VolatileDest is
640/// true, DestPtr cannot be 0.
641void CodeGenFunction::EmitAggExpr(const Expr *E, llvm::Value *DestPtr,
642                                  bool VolatileDest, bool IgnoreResult,
643                                  bool IsInitializer,
644                                  bool RequiresGCollection) {
645  assert(E && hasAggregateLLVMType(E->getType()) &&
646         "Invalid aggregate expression to emit");
647  assert ((DestPtr != 0 || VolatileDest == false)
648          && "volatile aggregate can't be 0");
649
650  AggExprEmitter(*this, DestPtr, VolatileDest, IgnoreResult, IsInitializer,
651                 RequiresGCollection)
652    .Visit(const_cast<Expr*>(E));
653}
654
655void CodeGenFunction::EmitAggregateClear(llvm::Value *DestPtr, QualType Ty) {
656  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
657
658  EmitMemSetToZero(DestPtr, Ty);
659}
660
661void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
662                                        llvm::Value *SrcPtr, QualType Ty,
663                                        bool isVolatile) {
664  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
665
666  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
667  // C99 6.5.16.1p3, which states "If the value being stored in an object is
668  // read from another object that overlaps in anyway the storage of the first
669  // object, then the overlap shall be exact and the two objects shall have
670  // qualified or unqualified versions of a compatible type."
671  //
672  // memcpy is not defined if the source and destination pointers are exactly
673  // equal, but other compilers do this optimization, and almost every memcpy
674  // implementation handles this case safely.  If there is a libc that does not
675  // safely handle this, we can add a target hook.
676  const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
677  if (DestPtr->getType() != BP)
678    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
679  if (SrcPtr->getType() != BP)
680    SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp");
681
682  // Get size and alignment info for this aggregate.
683  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
684
685  // FIXME: Handle variable sized types.
686  const llvm::Type *IntPtr =
687          llvm::IntegerType::get(VMContext, LLVMPointerWidth);
688
689  // FIXME: If we have a volatile struct, the optimizer can remove what might
690  // appear to be `extra' memory ops:
691  //
692  // volatile struct { int i; } a, b;
693  //
694  // int main() {
695  //   a = b;
696  //   a = b;
697  // }
698  //
699  // we need to use a differnt call here.  We use isVolatile to indicate when
700  // either the source or the destination is volatile.
701  Builder.CreateCall4(CGM.getMemCpyFn(),
702                      DestPtr, SrcPtr,
703                      // TypeInfo.first describes size in bits.
704                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
705                      llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
706                                             TypeInfo.second/8));
707}
708