CGExprAgg.cpp revision 18da88a38b82132faa7794120e17352dfacc5155 
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, QualType T);
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.CreateMemTemp(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                               E->getSubExpr()->getType());
193    break;
194  }
195
196  // FIXME: Remove the CK_Unknown check here.
197  case CastExpr::CK_Unknown:
198  case CastExpr::CK_NoOp:
199  case CastExpr::CK_UserDefinedConversion:
200  case CastExpr::CK_ConstructorConversion:
201    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
202                                                   E->getType()) &&
203           "Implicit cast types must be compatible");
204    Visit(E->getSubExpr());
205    break;
206
207  case CastExpr::CK_NullToMemberPointer: {
208    const llvm::Type *PtrDiffTy =
209      CGF.ConvertType(CGF.getContext().getPointerDiffType());
210
211    llvm::Value *NullValue = llvm::Constant::getNullValue(PtrDiffTy);
212    llvm::Value *Ptr = Builder.CreateStructGEP(DestPtr, 0, "ptr");
213    Builder.CreateStore(NullValue, Ptr, VolatileDest);
214
215    llvm::Value *Adj = Builder.CreateStructGEP(DestPtr, 1, "adj");
216    Builder.CreateStore(NullValue, Adj, VolatileDest);
217
218    break;
219  }
220
221  case CastExpr::CK_BitCast: {
222    // This must be a member function pointer cast.
223    Visit(E->getSubExpr());
224    break;
225  }
226
227  case CastExpr::CK_DerivedToBaseMemberPointer:
228  case CastExpr::CK_BaseToDerivedMemberPointer: {
229    QualType SrcType = E->getSubExpr()->getType();
230
231    llvm::Value *Src = CGF.CreateMemTemp(SrcType, "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    if (llvm::Constant *Adj =
256          CGF.CGM.GetNonVirtualBaseClassOffset(DerivedDecl, BaseDecl)) {
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 =
317    cast<CXXMethodDecl>(DRE->getDecl())->getCanonicalDecl();
318
319  const llvm::Type *PtrDiffTy =
320    CGF.ConvertType(CGF.getContext().getPointerDiffType());
321
322  llvm::Value *DstPtr = Builder.CreateStructGEP(DestPtr, 0, "dst.ptr");
323  llvm::Value *FuncPtr;
324
325  if (MD->isVirtual()) {
326    int64_t Index =
327      CGF.CGM.getVtableInfo().getMethodVtableIndex(MD);
328
329    // Itanium C++ ABI 2.3:
330    //   For a non-virtual function, this field is a simple function pointer.
331    //   For a virtual function, it is 1 plus the virtual table offset
332    //   (in bytes) of the function, represented as a ptrdiff_t.
333    FuncPtr = llvm::ConstantInt::get(PtrDiffTy, (Index * 8) + 1);
334  } else {
335    const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
336    const llvm::Type *Ty =
337      CGF.CGM.getTypes().GetFunctionType(CGF.CGM.getTypes().getFunctionInfo(MD),
338                                         FPT->isVariadic());
339    llvm::Constant *Fn = CGF.CGM.GetAddrOfFunction(MD, Ty);
340    FuncPtr = llvm::ConstantExpr::getPtrToInt(Fn, PtrDiffTy);
341  }
342  Builder.CreateStore(FuncPtr, DstPtr, VolatileDest);
343
344  llvm::Value *AdjPtr = Builder.CreateStructGEP(DestPtr, 1, "dst.adj");
345
346  // The adjustment will always be 0.
347  Builder.CreateStore(llvm::ConstantInt::get(PtrDiffTy, 0), AdjPtr,
348                      VolatileDest);
349}
350
351void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
352  CGF.EmitCompoundStmt(*E->getSubStmt(), true, DestPtr, VolatileDest);
353}
354
355void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
356  if (E->getOpcode() == BinaryOperator::PtrMemD ||
357      E->getOpcode() == BinaryOperator::PtrMemI)
358    VisitPointerToDataMemberBinaryOperator(E);
359  else
360    CGF.ErrorUnsupported(E, "aggregate binary expression");
361}
362
363void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
364                                                    const BinaryOperator *E) {
365  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
366  EmitFinalDestCopy(E, LV);
367}
368
369void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
370  // For an assignment to work, the value on the right has
371  // to be compatible with the value on the left.
372  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
373                                                 E->getRHS()->getType())
374         && "Invalid assignment");
375  LValue LHS = CGF.EmitLValue(E->getLHS());
376
377  // We have to special case property setters, otherwise we must have
378  // a simple lvalue (no aggregates inside vectors, bitfields).
379  if (LHS.isPropertyRef()) {
380    llvm::Value *AggLoc = DestPtr;
381    if (!AggLoc)
382      AggLoc = CGF.CreateMemTemp(E->getRHS()->getType());
383    CGF.EmitAggExpr(E->getRHS(), AggLoc, VolatileDest);
384    CGF.EmitObjCPropertySet(LHS.getPropertyRefExpr(),
385                            RValue::getAggregate(AggLoc, VolatileDest));
386  } else if (LHS.isKVCRef()) {
387    llvm::Value *AggLoc = DestPtr;
388    if (!AggLoc)
389      AggLoc = CGF.CreateMemTemp(E->getRHS()->getType());
390    CGF.EmitAggExpr(E->getRHS(), AggLoc, VolatileDest);
391    CGF.EmitObjCPropertySet(LHS.getKVCRefExpr(),
392                            RValue::getAggregate(AggLoc, VolatileDest));
393  } else {
394    bool RequiresGCollection = false;
395    if (CGF.getContext().getLangOptions().NeXTRuntime) {
396      QualType LHSTy = E->getLHS()->getType();
397      if (const RecordType *FDTTy = LHSTy.getTypePtr()->getAs<RecordType>())
398        RequiresGCollection = FDTTy->getDecl()->hasObjectMember();
399    }
400    // Codegen the RHS so that it stores directly into the LHS.
401    CGF.EmitAggExpr(E->getRHS(), LHS.getAddress(), LHS.isVolatileQualified(),
402                    false, false, RequiresGCollection);
403    EmitFinalDestCopy(E, LHS, true);
404  }
405}
406
407void AggExprEmitter::VisitConditionalOperator(const ConditionalOperator *E) {
408  if (!E->getLHS()) {
409    CGF.ErrorUnsupported(E, "conditional operator with missing LHS");
410    return;
411  }
412
413  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
414  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
415  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
416
417  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
418
419  CGF.BeginConditionalBranch();
420  CGF.EmitBlock(LHSBlock);
421
422  // Handle the GNU extension for missing LHS.
423  assert(E->getLHS() && "Must have LHS for aggregate value");
424
425  Visit(E->getLHS());
426  CGF.EndConditionalBranch();
427  CGF.EmitBranch(ContBlock);
428
429  CGF.BeginConditionalBranch();
430  CGF.EmitBlock(RHSBlock);
431
432  Visit(E->getRHS());
433  CGF.EndConditionalBranch();
434  CGF.EmitBranch(ContBlock);
435
436  CGF.EmitBlock(ContBlock);
437}
438
439void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
440  Visit(CE->getChosenSubExpr(CGF.getContext()));
441}
442
443void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
444  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
445  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
446
447  if (!ArgPtr) {
448    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
449    return;
450  }
451
452  EmitFinalDestCopy(VE, LValue::MakeAddr(ArgPtr, Qualifiers()));
453}
454
455void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
456  llvm::Value *Val = DestPtr;
457
458  if (!Val) {
459    // Create a temporary variable.
460    Val = CGF.CreateMemTemp(E->getType(), "tmp");
461
462    // FIXME: volatile
463    CGF.EmitAggExpr(E->getSubExpr(), Val, false);
464  } else
465    Visit(E->getSubExpr());
466
467  // Don't make this a live temporary if we're emitting an initializer expr.
468  if (!IsInitializer)
469    CGF.PushCXXTemporary(E->getTemporary(), Val);
470}
471
472void
473AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
474  llvm::Value *Val = DestPtr;
475
476  if (!Val) {
477    // Create a temporary variable.
478    Val = CGF.CreateMemTemp(E->getType(), "tmp");
479  }
480
481  if (E->requiresZeroInitialization())
482    EmitNullInitializationToLValue(LValue::MakeAddr(Val,
483                                                    // FIXME: Qualifiers()?
484                                                 E->getType().getQualifiers()),
485                                   E->getType());
486
487  CGF.EmitCXXConstructExpr(Val, E);
488}
489
490void AggExprEmitter::VisitCXXExprWithTemporaries(CXXExprWithTemporaries *E) {
491  llvm::Value *Val = DestPtr;
492
493  if (!Val) {
494    // Create a temporary variable.
495    Val = CGF.CreateMemTemp(E->getType(), "tmp");
496  }
497  CGF.EmitCXXExprWithTemporaries(E, Val, VolatileDest, IsInitializer);
498}
499
500void AggExprEmitter::VisitCXXZeroInitValueExpr(CXXZeroInitValueExpr *E) {
501  llvm::Value *Val = DestPtr;
502
503  if (!Val) {
504    // Create a temporary variable.
505    Val = CGF.CreateMemTemp(E->getType(), "tmp");
506  }
507  LValue LV = LValue::MakeAddr(Val, Qualifiers());
508  EmitNullInitializationToLValue(LV, E->getType());
509}
510
511void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
512  llvm::Value *Val = DestPtr;
513
514  if (!Val) {
515    // Create a temporary variable.
516    Val = CGF.CreateMemTemp(E->getType(), "tmp");
517  }
518  LValue LV = LValue::MakeAddr(Val, Qualifiers());
519  EmitNullInitializationToLValue(LV, E->getType());
520}
521
522void
523AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV, QualType T) {
524  // FIXME: Ignore result?
525  // FIXME: Are initializers affected by volatile?
526  if (isa<ImplicitValueInitExpr>(E)) {
527    EmitNullInitializationToLValue(LV, T);
528  } else if (T->isReferenceType()) {
529    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*IsInitializer=*/false);
530    CGF.EmitStoreThroughLValue(RV, LV, T);
531  } else if (T->isAnyComplexType()) {
532    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
533  } else if (CGF.hasAggregateLLVMType(T)) {
534    CGF.EmitAnyExpr(E, LV.getAddress(), false);
535  } else {
536    CGF.EmitStoreThroughLValue(CGF.EmitAnyExpr(E), LV, T);
537  }
538}
539
540void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
541  if (!CGF.hasAggregateLLVMType(T)) {
542    // For non-aggregates, we can store zero
543    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
544    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
545  } else {
546    // Otherwise, just memset the whole thing to zero.  This is legal
547    // because in LLVM, all default initializers are guaranteed to have a
548    // bit pattern of all zeros.
549    // FIXME: That isn't true for member pointers!
550    // There's a potential optimization opportunity in combining
551    // memsets; that would be easy for arrays, but relatively
552    // difficult for structures with the current code.
553    CGF.EmitMemSetToZero(LV.getAddress(), T);
554  }
555}
556
557void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
558#if 0
559  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
560  // (Length of globals? Chunks of zeroed-out space?).
561  //
562  // If we can, prefer a copy from a global; this is a lot less code for long
563  // globals, and it's easier for the current optimizers to analyze.
564  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
565    llvm::GlobalVariable* GV =
566    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
567                             llvm::GlobalValue::InternalLinkage, C, "");
568    EmitFinalDestCopy(E, LValue::MakeAddr(GV, Qualifiers()));
569    return;
570  }
571#endif
572  if (E->hadArrayRangeDesignator()) {
573    CGF.ErrorUnsupported(E, "GNU array range designator extension");
574  }
575
576  // Handle initialization of an array.
577  if (E->getType()->isArrayType()) {
578    const llvm::PointerType *APType =
579      cast<llvm::PointerType>(DestPtr->getType());
580    const llvm::ArrayType *AType =
581      cast<llvm::ArrayType>(APType->getElementType());
582
583    uint64_t NumInitElements = E->getNumInits();
584
585    if (E->getNumInits() > 0) {
586      QualType T1 = E->getType();
587      QualType T2 = E->getInit(0)->getType();
588      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
589        EmitAggLoadOfLValue(E->getInit(0));
590        return;
591      }
592    }
593
594    uint64_t NumArrayElements = AType->getNumElements();
595    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
596    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
597
598    // FIXME: were we intentionally ignoring address spaces and GC attributes?
599    Qualifiers Quals = CGF.MakeQualifiers(ElementType);
600
601    for (uint64_t i = 0; i != NumArrayElements; ++i) {
602      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
603      if (i < NumInitElements)
604        EmitInitializationToLValue(E->getInit(i),
605                                   LValue::MakeAddr(NextVal, Quals),
606                                   ElementType);
607      else
608        EmitNullInitializationToLValue(LValue::MakeAddr(NextVal, Quals),
609                                       ElementType);
610    }
611    return;
612  }
613
614  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
615
616  // Do struct initialization; this code just sets each individual member
617  // to the approprate value.  This makes bitfield support automatic;
618  // the disadvantage is that the generated code is more difficult for
619  // the optimizer, especially with bitfields.
620  unsigned NumInitElements = E->getNumInits();
621  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
622  unsigned CurInitVal = 0;
623
624  if (E->getType()->isUnionType()) {
625    // Only initialize one field of a union. The field itself is
626    // specified by the initializer list.
627    if (!E->getInitializedFieldInUnion()) {
628      // Empty union; we have nothing to do.
629
630#ifndef NDEBUG
631      // Make sure that it's really an empty and not a failure of
632      // semantic analysis.
633      for (RecordDecl::field_iterator Field = SD->field_begin(),
634                                   FieldEnd = SD->field_end();
635           Field != FieldEnd; ++Field)
636        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
637#endif
638      return;
639    }
640
641    // FIXME: volatility
642    FieldDecl *Field = E->getInitializedFieldInUnion();
643    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
644
645    if (NumInitElements) {
646      // Store the initializer into the field
647      EmitInitializationToLValue(E->getInit(0), FieldLoc, Field->getType());
648    } else {
649      // Default-initialize to null
650      EmitNullInitializationToLValue(FieldLoc, Field->getType());
651    }
652
653    return;
654  }
655
656  // Here we iterate over the fields; this makes it simpler to both
657  // default-initialize fields and skip over unnamed fields.
658  for (RecordDecl::field_iterator Field = SD->field_begin(),
659                               FieldEnd = SD->field_end();
660       Field != FieldEnd; ++Field) {
661    // We're done once we hit the flexible array member
662    if (Field->getType()->isIncompleteArrayType())
663      break;
664
665    if (Field->isUnnamedBitfield())
666      continue;
667
668    // FIXME: volatility
669    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, *Field, 0);
670    // We never generate write-barries for initialized fields.
671    LValue::SetObjCNonGC(FieldLoc, true);
672    if (CurInitVal < NumInitElements) {
673      // Store the initializer into the field
674      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc,
675                                 Field->getType());
676    } else {
677      // We're out of initalizers; default-initialize to null
678      EmitNullInitializationToLValue(FieldLoc, Field->getType());
679    }
680  }
681}
682
683//===----------------------------------------------------------------------===//
684//                        Entry Points into this File
685//===----------------------------------------------------------------------===//
686
687/// EmitAggExpr - Emit the computation of the specified expression of aggregate
688/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
689/// the value of the aggregate expression is not needed.  If VolatileDest is
690/// true, DestPtr cannot be 0.
691//
692// FIXME: Take Qualifiers object.
693void CodeGenFunction::EmitAggExpr(const Expr *E, llvm::Value *DestPtr,
694                                  bool VolatileDest, bool IgnoreResult,
695                                  bool IsInitializer,
696                                  bool RequiresGCollection) {
697  assert(E && hasAggregateLLVMType(E->getType()) &&
698         "Invalid aggregate expression to emit");
699  assert ((DestPtr != 0 || VolatileDest == false)
700          && "volatile aggregate can't be 0");
701
702  AggExprEmitter(*this, DestPtr, VolatileDest, IgnoreResult, IsInitializer,
703                 RequiresGCollection)
704    .Visit(const_cast<Expr*>(E));
705}
706
707LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
708  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
709  Qualifiers Q = MakeQualifiers(E->getType());
710  llvm::Value *Temp = CreateMemTemp(E->getType());
711  EmitAggExpr(E, Temp, Q.hasVolatile());
712  return LValue::MakeAddr(Temp, Q);
713}
714
715void CodeGenFunction::EmitAggregateClear(llvm::Value *DestPtr, QualType Ty) {
716  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
717
718  EmitMemSetToZero(DestPtr, Ty);
719}
720
721void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
722                                        llvm::Value *SrcPtr, QualType Ty,
723                                        bool isVolatile) {
724  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
725
726  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
727  // C99 6.5.16.1p3, which states "If the value being stored in an object is
728  // read from another object that overlaps in anyway the storage of the first
729  // object, then the overlap shall be exact and the two objects shall have
730  // qualified or unqualified versions of a compatible type."
731  //
732  // memcpy is not defined if the source and destination pointers are exactly
733  // equal, but other compilers do this optimization, and almost every memcpy
734  // implementation handles this case safely.  If there is a libc that does not
735  // safely handle this, we can add a target hook.
736  const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
737  if (DestPtr->getType() != BP)
738    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
739  if (SrcPtr->getType() != BP)
740    SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp");
741
742  // Get size and alignment info for this aggregate.
743  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
744
745  // FIXME: Handle variable sized types.
746  const llvm::Type *IntPtr =
747          llvm::IntegerType::get(VMContext, LLVMPointerWidth);
748
749  // FIXME: If we have a volatile struct, the optimizer can remove what might
750  // appear to be `extra' memory ops:
751  //
752  // volatile struct { int i; } a, b;
753  //
754  // int main() {
755  //   a = b;
756  //   a = b;
757  // }
758  //
759  // we need to use a differnt call here.  We use isVolatile to indicate when
760  // either the source or the destination is volatile.
761  Builder.CreateCall4(CGM.getMemCpyFn(),
762                      DestPtr, SrcPtr,
763                      // TypeInfo.first describes size in bits.
764                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
765                      llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
766                                             TypeInfo.second/8));
767}
768