CGExprAgg.cpp revision d2490a91341b57df7a7e54f8a707e7ecde2eeb4e 
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  llvm::Value *DestPtr;
36  bool VolatileDest;
37  bool IgnoreResult;
38  bool IsInitializer;
39  bool RequiresGCollection;
40public:
41  AggExprEmitter(CodeGenFunction &cgf, llvm::Value *destPtr, bool v,
42                 bool ignore, bool isinit, bool requiresGCollection)
43    : CGF(cgf), Builder(CGF.Builder),
44      DestPtr(destPtr), VolatileDest(v), IgnoreResult(ignore),
45      IsInitializer(isinit), RequiresGCollection(requiresGCollection) {
46  }
47
48  //===--------------------------------------------------------------------===//
49  //                               Utilities
50  //===--------------------------------------------------------------------===//
51
52  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
53  /// represents a value lvalue, this method emits the address of the lvalue,
54  /// then loads the result into DestPtr.
55  void EmitAggLoadOfLValue(const Expr *E);
56
57  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
58  void EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore = false);
59  void EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore = false);
60
61  //===--------------------------------------------------------------------===//
62  //                            Visitor Methods
63  //===--------------------------------------------------------------------===//
64
65  void VisitStmt(Stmt *S) {
66    CGF.ErrorUnsupported(S, "aggregate expression");
67  }
68  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
69  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
70
71  // l-values.
72  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
73  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
74  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
75  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
76  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
77    EmitAggLoadOfLValue(E);
78  }
79  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
80    EmitAggLoadOfLValue(E);
81  }
82  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
83    EmitAggLoadOfLValue(E);
84  }
85  void VisitPredefinedExpr(const PredefinedExpr *E) {
86    EmitAggLoadOfLValue(E);
87  }
88
89  // Operators.
90  void VisitCastExpr(CastExpr *E);
91  void VisitCallExpr(const CallExpr *E);
92  void VisitStmtExpr(const StmtExpr *E);
93  void VisitBinaryOperator(const BinaryOperator *BO);
94  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
95  void VisitBinAssign(const BinaryOperator *E);
96  void VisitBinComma(const BinaryOperator *E);
97  void VisitUnaryAddrOf(const UnaryOperator *E);
98
99  void VisitObjCMessageExpr(ObjCMessageExpr *E);
100  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
101    EmitAggLoadOfLValue(E);
102  }
103  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
104  void VisitObjCImplicitSetterGetterRefExpr(ObjCImplicitSetterGetterRefExpr *E);
105
106  void VisitConditionalOperator(const ConditionalOperator *CO);
107  void VisitChooseExpr(const ChooseExpr *CE);
108  void VisitInitListExpr(InitListExpr *E);
109  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *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  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
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  // If the struct doesn't require GC, we can just pass the destination
276  // directly to EmitCall.
277  if (!RequiresGCollection) {
278    CGF.EmitCallExpr(E, ReturnValueSlot(DestPtr, VolatileDest));
279    return;
280  }
281
282  RValue RV = CGF.EmitCallExpr(E);
283  EmitFinalDestCopy(E, RV);
284}
285
286void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
287  RValue RV = CGF.EmitObjCMessageExpr(E);
288  EmitFinalDestCopy(E, RV);
289}
290
291void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
292  RValue RV = CGF.EmitObjCPropertyGet(E);
293  EmitFinalDestCopy(E, RV);
294}
295
296void AggExprEmitter::VisitObjCImplicitSetterGetterRefExpr(
297                                   ObjCImplicitSetterGetterRefExpr *E) {
298  RValue RV = CGF.EmitObjCPropertyGet(E);
299  EmitFinalDestCopy(E, RV);
300}
301
302void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
303  CGF.EmitAnyExpr(E->getLHS(), 0, false, true);
304  CGF.EmitAggExpr(E->getRHS(), DestPtr, VolatileDest,
305                  /*IgnoreResult=*/false, IsInitializer);
306}
307
308void AggExprEmitter::VisitUnaryAddrOf(const UnaryOperator *E) {
309  // We have a member function pointer.
310  const MemberPointerType *MPT = E->getType()->getAs<MemberPointerType>();
311  (void) MPT;
312  assert(MPT->getPointeeType()->isFunctionProtoType() &&
313         "Unexpected member pointer type!");
314
315  const DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr());
316  const CXXMethodDecl *MD = cast<CXXMethodDecl>(DRE->getDecl());
317
318  const llvm::Type *PtrDiffTy =
319    CGF.ConvertType(CGF.getContext().getPointerDiffType());
320
321  llvm::Value *DstPtr = Builder.CreateStructGEP(DestPtr, 0, "dst.ptr");
322  llvm::Value *FuncPtr;
323
324  if (MD->isVirtual()) {
325    int64_t Index =
326      CGF.CGM.getVtableInfo().getMethodVtableIndex(MD);
327
328    FuncPtr = llvm::ConstantInt::get(PtrDiffTy, Index + 1);
329  } else {
330    FuncPtr = llvm::ConstantExpr::getPtrToInt(CGF.CGM.GetAddrOfFunction(MD),
331                                              PtrDiffTy);
332  }
333  Builder.CreateStore(FuncPtr, DstPtr, VolatileDest);
334
335  llvm::Value *AdjPtr = Builder.CreateStructGEP(DestPtr, 1, "dst.adj");
336
337  // The adjustment will always be 0.
338  Builder.CreateStore(llvm::ConstantInt::get(PtrDiffTy, 0), AdjPtr,
339                      VolatileDest);
340}
341
342void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
343  CGF.EmitCompoundStmt(*E->getSubStmt(), true, DestPtr, VolatileDest);
344}
345
346void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
347  if (E->getOpcode() == BinaryOperator::PtrMemD ||
348      E->getOpcode() == BinaryOperator::PtrMemI)
349    VisitPointerToDataMemberBinaryOperator(E);
350  else
351    CGF.ErrorUnsupported(E, "aggregate binary expression");
352}
353
354void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
355                                                    const BinaryOperator *E) {
356  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
357  EmitFinalDestCopy(E, LV);
358}
359
360void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
361  // For an assignment to work, the value on the right has
362  // to be compatible with the value on the left.
363  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
364                                                 E->getRHS()->getType())
365         && "Invalid assignment");
366  LValue LHS = CGF.EmitLValue(E->getLHS());
367
368  // We have to special case property setters, otherwise we must have
369  // a simple lvalue (no aggregates inside vectors, bitfields).
370  if (LHS.isPropertyRef()) {
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.getPropertyRefExpr(),
376                            RValue::getAggregate(AggLoc, VolatileDest));
377  } else if (LHS.isKVCRef()) {
378    llvm::Value *AggLoc = DestPtr;
379    if (!AggLoc)
380      AggLoc = CGF.CreateTempAlloca(CGF.ConvertType(E->getRHS()->getType()));
381    CGF.EmitAggExpr(E->getRHS(), AggLoc, VolatileDest);
382    CGF.EmitObjCPropertySet(LHS.getKVCRefExpr(),
383                            RValue::getAggregate(AggLoc, VolatileDest));
384  } else {
385    bool RequiresGCollection = false;
386    if (CGF.getContext().getLangOptions().NeXTRuntime) {
387      QualType LHSTy = E->getLHS()->getType();
388      if (const RecordType *FDTTy = LHSTy.getTypePtr()->getAs<RecordType>())
389        RequiresGCollection = FDTTy->getDecl()->hasObjectMember();
390    }
391    // Codegen the RHS so that it stores directly into the LHS.
392    CGF.EmitAggExpr(E->getRHS(), LHS.getAddress(), LHS.isVolatileQualified(),
393                    false, false, RequiresGCollection);
394    EmitFinalDestCopy(E, LHS, true);
395  }
396}
397
398void AggExprEmitter::VisitConditionalOperator(const ConditionalOperator *E) {
399  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
400  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
401  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
402
403  llvm::Value *Cond = CGF.EvaluateExprAsBool(E->getCond());
404  Builder.CreateCondBr(Cond, LHSBlock, RHSBlock);
405
406  CGF.StartConditionalBranch();
407  CGF.EmitBlock(LHSBlock);
408
409  // Handle the GNU extension for missing LHS.
410  assert(E->getLHS() && "Must have LHS for aggregate value");
411
412  Visit(E->getLHS());
413  CGF.FinishConditionalBranch();
414  CGF.EmitBranch(ContBlock);
415
416  CGF.StartConditionalBranch();
417  CGF.EmitBlock(RHSBlock);
418
419  Visit(E->getRHS());
420  CGF.FinishConditionalBranch();
421  CGF.EmitBranch(ContBlock);
422
423  CGF.EmitBlock(ContBlock);
424}
425
426void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
427  Visit(CE->getChosenSubExpr(CGF.getContext()));
428}
429
430void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
431  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
432  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
433
434  if (!ArgPtr) {
435    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
436    return;
437  }
438
439  EmitFinalDestCopy(VE, LValue::MakeAddr(ArgPtr, Qualifiers()));
440}
441
442void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
443  llvm::Value *Val = DestPtr;
444
445  if (!Val) {
446    // Create a temporary variable.
447    Val = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(E->getType()), "tmp");
448
449    // FIXME: volatile
450    CGF.EmitAggExpr(E->getSubExpr(), Val, false);
451  } else
452    Visit(E->getSubExpr());
453
454  // Don't make this a live temporary if we're emitting an initializer expr.
455  if (!IsInitializer)
456    CGF.PushCXXTemporary(E->getTemporary(), Val);
457}
458
459void
460AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
461  llvm::Value *Val = DestPtr;
462
463  if (!Val) {
464    // Create a temporary variable.
465    Val = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(E->getType()), "tmp");
466  }
467
468  if (E->requiresZeroInitialization())
469    EmitNullInitializationToLValue(LValue::MakeAddr(Val,
470                                                    // FIXME: Qualifiers()?
471                                                 E->getType().getQualifiers()),
472                                   E->getType());
473
474  CGF.EmitCXXConstructExpr(Val, E);
475}
476
477void AggExprEmitter::VisitCXXExprWithTemporaries(CXXExprWithTemporaries *E) {
478  llvm::Value *Val = DestPtr;
479
480  if (!Val) {
481    // Create a temporary variable.
482    Val = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(E->getType()), "tmp");
483  }
484  CGF.EmitCXXExprWithTemporaries(E, Val, VolatileDest, IsInitializer);
485}
486
487void AggExprEmitter::VisitCXXZeroInitValueExpr(CXXZeroInitValueExpr *E) {
488  llvm::Value *Val = DestPtr;
489
490  if (!Val) {
491    // Create a temporary variable.
492    Val = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(E->getType()), "tmp");
493  }
494  LValue LV = LValue::MakeAddr(Val, Qualifiers());
495  EmitNullInitializationToLValue(LV, E->getType());
496}
497
498void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
499  llvm::Value *Val = DestPtr;
500
501  if (!Val) {
502    // Create a temporary variable.
503    Val = CGF.CreateTempAlloca(CGF.ConvertTypeForMem(E->getType()), "tmp");
504  }
505  LValue LV = LValue::MakeAddr(Val, Qualifiers());
506  EmitNullInitializationToLValue(LV, E->getType());
507}
508
509void AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
510  // FIXME: Ignore result?
511  // FIXME: Are initializers affected by volatile?
512  if (isa<ImplicitValueInitExpr>(E)) {
513    EmitNullInitializationToLValue(LV, E->getType());
514  } else if (E->getType()->isComplexType()) {
515    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
516  } else if (CGF.hasAggregateLLVMType(E->getType())) {
517    CGF.EmitAnyExpr(E, LV.getAddress(), false);
518  } else {
519    CGF.EmitStoreThroughLValue(CGF.EmitAnyExpr(E), LV, E->getType());
520  }
521}
522
523void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
524  if (!CGF.hasAggregateLLVMType(T)) {
525    // For non-aggregates, we can store zero
526    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
527    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
528  } else {
529    // Otherwise, just memset the whole thing to zero.  This is legal
530    // because in LLVM, all default initializers are guaranteed to have a
531    // bit pattern of all zeros.
532    // FIXME: That isn't true for member pointers!
533    // There's a potential optimization opportunity in combining
534    // memsets; that would be easy for arrays, but relatively
535    // difficult for structures with the current code.
536    CGF.EmitMemSetToZero(LV.getAddress(), T);
537  }
538}
539
540void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
541#if 0
542  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
543  // (Length of globals? Chunks of zeroed-out space?).
544  //
545  // If we can, prefer a copy from a global; this is a lot less code for long
546  // globals, and it's easier for the current optimizers to analyze.
547  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
548    llvm::GlobalVariable* GV =
549    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
550                             llvm::GlobalValue::InternalLinkage, C, "");
551    EmitFinalDestCopy(E, LValue::MakeAddr(GV, Qualifiers()));
552    return;
553  }
554#endif
555  if (E->hadArrayRangeDesignator()) {
556    CGF.ErrorUnsupported(E, "GNU array range designator extension");
557  }
558
559  // Handle initialization of an array.
560  if (E->getType()->isArrayType()) {
561    const llvm::PointerType *APType =
562      cast<llvm::PointerType>(DestPtr->getType());
563    const llvm::ArrayType *AType =
564      cast<llvm::ArrayType>(APType->getElementType());
565
566    uint64_t NumInitElements = E->getNumInits();
567
568    if (E->getNumInits() > 0) {
569      QualType T1 = E->getType();
570      QualType T2 = E->getInit(0)->getType();
571      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
572        EmitAggLoadOfLValue(E->getInit(0));
573        return;
574      }
575    }
576
577    uint64_t NumArrayElements = AType->getNumElements();
578    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
579    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
580
581    // FIXME: were we intentionally ignoring address spaces and GC attributes?
582    Qualifiers Quals = CGF.MakeQualifiers(ElementType);
583
584    for (uint64_t i = 0; i != NumArrayElements; ++i) {
585      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
586      if (i < NumInitElements)
587        EmitInitializationToLValue(E->getInit(i),
588                                   LValue::MakeAddr(NextVal, Quals));
589      else
590        EmitNullInitializationToLValue(LValue::MakeAddr(NextVal, Quals),
591                                       ElementType);
592    }
593    return;
594  }
595
596  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
597
598  // Do struct initialization; this code just sets each individual member
599  // to the approprate value.  This makes bitfield support automatic;
600  // the disadvantage is that the generated code is more difficult for
601  // the optimizer, especially with bitfields.
602  unsigned NumInitElements = E->getNumInits();
603  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
604  unsigned CurInitVal = 0;
605
606  if (E->getType()->isUnionType()) {
607    // Only initialize one field of a union. The field itself is
608    // specified by the initializer list.
609    if (!E->getInitializedFieldInUnion()) {
610      // Empty union; we have nothing to do.
611
612#ifndef NDEBUG
613      // Make sure that it's really an empty and not a failure of
614      // semantic analysis.
615      for (RecordDecl::field_iterator Field = SD->field_begin(),
616                                   FieldEnd = SD->field_end();
617           Field != FieldEnd; ++Field)
618        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
619#endif
620      return;
621    }
622
623    // FIXME: volatility
624    FieldDecl *Field = E->getInitializedFieldInUnion();
625    LValue FieldLoc = CGF.EmitLValueForField(DestPtr, Field, true, 0);
626
627    if (NumInitElements) {
628      // Store the initializer into the field
629      EmitInitializationToLValue(E->getInit(0), FieldLoc);
630    } else {
631      // Default-initialize to null
632      EmitNullInitializationToLValue(FieldLoc, Field->getType());
633    }
634
635    return;
636  }
637
638  // Here we iterate over the fields; this makes it simpler to both
639  // default-initialize fields and skip over unnamed fields.
640  for (RecordDecl::field_iterator Field = SD->field_begin(),
641                               FieldEnd = SD->field_end();
642       Field != FieldEnd; ++Field) {
643    // We're done once we hit the flexible array member
644    if (Field->getType()->isIncompleteArrayType())
645      break;
646
647    if (Field->isUnnamedBitfield())
648      continue;
649
650    // FIXME: volatility
651    LValue FieldLoc = CGF.EmitLValueForField(DestPtr, *Field, false, 0);
652    // We never generate write-barries for initialized fields.
653    LValue::SetObjCNonGC(FieldLoc, true);
654    if (CurInitVal < NumInitElements) {
655      // Store the initializer into the field
656      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc);
657    } else {
658      // We're out of initalizers; default-initialize to null
659      EmitNullInitializationToLValue(FieldLoc, Field->getType());
660    }
661  }
662}
663
664//===----------------------------------------------------------------------===//
665//                        Entry Points into this File
666//===----------------------------------------------------------------------===//
667
668/// EmitAggExpr - Emit the computation of the specified expression of aggregate
669/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
670/// the value of the aggregate expression is not needed.  If VolatileDest is
671/// true, DestPtr cannot be 0.
672void CodeGenFunction::EmitAggExpr(const Expr *E, llvm::Value *DestPtr,
673                                  bool VolatileDest, bool IgnoreResult,
674                                  bool IsInitializer,
675                                  bool RequiresGCollection) {
676  assert(E && hasAggregateLLVMType(E->getType()) &&
677         "Invalid aggregate expression to emit");
678  assert ((DestPtr != 0 || VolatileDest == false)
679          && "volatile aggregate can't be 0");
680
681  AggExprEmitter(*this, DestPtr, VolatileDest, IgnoreResult, IsInitializer,
682                 RequiresGCollection)
683    .Visit(const_cast<Expr*>(E));
684}
685
686void CodeGenFunction::EmitAggregateClear(llvm::Value *DestPtr, QualType Ty) {
687  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
688
689  EmitMemSetToZero(DestPtr, Ty);
690}
691
692void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
693                                        llvm::Value *SrcPtr, QualType Ty,
694                                        bool isVolatile) {
695  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
696
697  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
698  // C99 6.5.16.1p3, which states "If the value being stored in an object is
699  // read from another object that overlaps in anyway the storage of the first
700  // object, then the overlap shall be exact and the two objects shall have
701  // qualified or unqualified versions of a compatible type."
702  //
703  // memcpy is not defined if the source and destination pointers are exactly
704  // equal, but other compilers do this optimization, and almost every memcpy
705  // implementation handles this case safely.  If there is a libc that does not
706  // safely handle this, we can add a target hook.
707  const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
708  if (DestPtr->getType() != BP)
709    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
710  if (SrcPtr->getType() != BP)
711    SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp");
712
713  // Get size and alignment info for this aggregate.
714  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
715
716  // FIXME: Handle variable sized types.
717  const llvm::Type *IntPtr =
718          llvm::IntegerType::get(VMContext, LLVMPointerWidth);
719
720  // FIXME: If we have a volatile struct, the optimizer can remove what might
721  // appear to be `extra' memory ops:
722  //
723  // volatile struct { int i; } a, b;
724  //
725  // int main() {
726  //   a = b;
727  //   a = b;
728  // }
729  //
730  // we need to use a differnt call here.  We use isVolatile to indicate when
731  // either the source or the destination is volatile.
732  Builder.CreateCall4(CGM.getMemCpyFn(),
733                      DestPtr, SrcPtr,
734                      // TypeInfo.first describes size in bits.
735                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
736                      llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
737                                             TypeInfo.second/8));
738}
739