CGExprAgg.cpp revision e996ffd240f20a1048179d7727a6ee3227261921 
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  ReturnValueSlot getReturnValueSlot() const {
39    // If the destination slot requires garbage collection, we can't
40    // use the real return value slot, because we have to use the GC
41    // API.
42    if (Dest.requiresGCollection()) return ReturnValueSlot();
43
44    return ReturnValueSlot(Dest.getAddr(), Dest.isVolatile());
45  }
46
47  AggValueSlot EnsureSlot(QualType T) {
48    if (!Dest.isIgnored()) return Dest;
49    return CGF.CreateAggTemp(T, "agg.tmp.ensured");
50  }
51
52public:
53  AggExprEmitter(CodeGenFunction &cgf, AggValueSlot Dest,
54                 bool ignore)
55    : CGF(cgf), Builder(CGF.Builder), Dest(Dest),
56      IgnoreResult(ignore) {
57  }
58
59  //===--------------------------------------------------------------------===//
60  //                               Utilities
61  //===--------------------------------------------------------------------===//
62
63  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
64  /// represents a value lvalue, this method emits the address of the lvalue,
65  /// then loads the result into DestPtr.
66  void EmitAggLoadOfLValue(const Expr *E);
67
68  /// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
69  void EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore = false);
70  void EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore = false);
71
72  void EmitGCMove(const Expr *E, RValue Src);
73
74  bool TypeRequiresGCollection(QualType T);
75
76  //===--------------------------------------------------------------------===//
77  //                            Visitor Methods
78  //===--------------------------------------------------------------------===//
79
80  void VisitStmt(Stmt *S) {
81    CGF.ErrorUnsupported(S, "aggregate expression");
82  }
83  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
84  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
85
86  // l-values.
87  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
88  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
89  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
90  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
91  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
92    EmitAggLoadOfLValue(E);
93  }
94  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
95    EmitAggLoadOfLValue(E);
96  }
97  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
98    EmitAggLoadOfLValue(E);
99  }
100  void VisitPredefinedExpr(const PredefinedExpr *E) {
101    EmitAggLoadOfLValue(E);
102  }
103
104  // Operators.
105  void VisitCastExpr(CastExpr *E);
106  void VisitCallExpr(const CallExpr *E);
107  void VisitStmtExpr(const StmtExpr *E);
108  void VisitBinaryOperator(const BinaryOperator *BO);
109  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
110  void VisitBinAssign(const BinaryOperator *E);
111  void VisitBinComma(const BinaryOperator *E);
112
113  void VisitObjCMessageExpr(ObjCMessageExpr *E);
114  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
115    EmitAggLoadOfLValue(E);
116  }
117  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
118
119  void VisitConditionalOperator(const ConditionalOperator *CO);
120  void VisitChooseExpr(const ChooseExpr *CE);
121  void VisitInitListExpr(InitListExpr *E);
122  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
123  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
124    Visit(DAE->getExpr());
125  }
126  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
127  void VisitCXXConstructExpr(const CXXConstructExpr *E);
128  void VisitExprWithCleanups(ExprWithCleanups *E);
129  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
130  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
131
132  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
133
134  void VisitVAArgExpr(VAArgExpr *E);
135
136  void EmitInitializationToLValue(Expr *E, LValue Address, QualType T);
137  void EmitNullInitializationToLValue(LValue Address, QualType T);
138  //  case Expr::ChooseExprClass:
139  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
140};
141}  // end anonymous namespace.
142
143//===----------------------------------------------------------------------===//
144//                                Utilities
145//===----------------------------------------------------------------------===//
146
147/// EmitAggLoadOfLValue - Given an expression with aggregate type that
148/// represents a value lvalue, this method emits the address of the lvalue,
149/// then loads the result into DestPtr.
150void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
151  LValue LV = CGF.EmitLValue(E);
152  EmitFinalDestCopy(E, LV);
153}
154
155/// \brief True if the given aggregate type requires special GC API calls.
156bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
157  // Only record types have members that might require garbage collection.
158  const RecordType *RecordTy = T->getAs<RecordType>();
159  if (!RecordTy) return false;
160
161  // Don't mess with non-trivial C++ types.
162  RecordDecl *Record = RecordTy->getDecl();
163  if (isa<CXXRecordDecl>(Record) &&
164      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
165       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
166    return false;
167
168  // Check whether the type has an object member.
169  return Record->hasObjectMember();
170}
171
172/// \brief Perform the final move to DestPtr if RequiresGCollection is set.
173///
174/// The idea is that you do something like this:
175///   RValue Result = EmitSomething(..., getReturnValueSlot());
176///   EmitGCMove(E, Result);
177/// If GC doesn't interfere, this will cause the result to be emitted
178/// directly into the return value slot.  If GC does interfere, a final
179/// move will be performed.
180void AggExprEmitter::EmitGCMove(const Expr *E, RValue Src) {
181  if (Dest.requiresGCollection()) {
182    std::pair<uint64_t, unsigned> TypeInfo =
183      CGF.getContext().getTypeInfo(E->getType());
184    unsigned long size = TypeInfo.first/8;
185    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
186    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
187    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF, Dest.getAddr(),
188                                                    Src.getAggregateAddr(),
189                                                    SizeVal);
190  }
191}
192
193/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
194void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore) {
195  assert(Src.isAggregate() && "value must be aggregate value!");
196
197  // If Dest is ignored, then we're evaluating an aggregate expression
198  // in a context (like an expression statement) that doesn't care
199  // about the result.  C says that an lvalue-to-rvalue conversion is
200  // performed in these cases; C++ says that it is not.  In either
201  // case, we don't actually need to do anything unless the value is
202  // volatile.
203  if (Dest.isIgnored()) {
204    if (!Src.isVolatileQualified() ||
205        CGF.CGM.getLangOptions().CPlusPlus ||
206        (IgnoreResult && Ignore))
207      return;
208
209    // If the source is volatile, we must read from it; to do that, we need
210    // some place to put it.
211    Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
212  }
213
214  if (Dest.requiresGCollection()) {
215    std::pair<uint64_t, unsigned> TypeInfo =
216    CGF.getContext().getTypeInfo(E->getType());
217    unsigned long size = TypeInfo.first/8;
218    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
219    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
220    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
221                                                      Dest.getAddr(),
222                                                      Src.getAggregateAddr(),
223                                                      SizeVal);
224    return;
225  }
226  // If the result of the assignment is used, copy the LHS there also.
227  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
228  // from the source as well, as we can't eliminate it if either operand
229  // is volatile, unless copy has volatile for both source and destination..
230  CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
231                        Dest.isVolatile()|Src.isVolatileQualified());
232}
233
234/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
235void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
236  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
237
238  EmitFinalDestCopy(E, RValue::getAggregate(Src.getAddress(),
239                                            Src.isVolatileQualified()),
240                    Ignore);
241}
242
243//===----------------------------------------------------------------------===//
244//                            Visitor Methods
245//===----------------------------------------------------------------------===//
246
247void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
248  EmitFinalDestCopy(e, CGF.EmitOpaqueValueLValue(e));
249}
250
251void AggExprEmitter::VisitCastExpr(CastExpr *E) {
252  if (Dest.isIgnored() && E->getCastKind() != CK_Dynamic) {
253    Visit(E->getSubExpr());
254    return;
255  }
256
257  switch (E->getCastKind()) {
258  case CK_Dynamic: {
259    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
260    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
261    // FIXME: Do we also need to handle property references here?
262    if (LV.isSimple())
263      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
264    else
265      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
266
267    if (!Dest.isIgnored())
268      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
269    break;
270  }
271
272  case CK_ToUnion: {
273    // GCC union extension
274    QualType Ty = E->getSubExpr()->getType();
275    QualType PtrTy = CGF.getContext().getPointerType(Ty);
276    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
277                                                 CGF.ConvertType(PtrTy));
278    EmitInitializationToLValue(E->getSubExpr(), CGF.MakeAddrLValue(CastPtr, Ty),
279                               Ty);
280    break;
281  }
282
283  case CK_DerivedToBase:
284  case CK_BaseToDerived:
285  case CK_UncheckedDerivedToBase: {
286    assert(0 && "cannot perform hierarchy conversion in EmitAggExpr: "
287                "should have been unpacked before we got here");
288    break;
289  }
290
291  case CK_GetObjCProperty: {
292    LValue LV = CGF.EmitLValue(E->getSubExpr());
293    assert(LV.isPropertyRef());
294    RValue RV = CGF.EmitLoadOfPropertyRefLValue(LV, getReturnValueSlot());
295    EmitGCMove(E, RV);
296    break;
297  }
298
299  case CK_LValueToRValue: // hope for downstream optimization
300  case CK_NoOp:
301  case CK_UserDefinedConversion:
302  case CK_ConstructorConversion:
303    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
304                                                   E->getType()) &&
305           "Implicit cast types must be compatible");
306    Visit(E->getSubExpr());
307    break;
308
309  case CK_LValueBitCast:
310    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
311    break;
312
313  case CK_Dependent:
314  case CK_BitCast:
315  case CK_ArrayToPointerDecay:
316  case CK_FunctionToPointerDecay:
317  case CK_NullToPointer:
318  case CK_NullToMemberPointer:
319  case CK_BaseToDerivedMemberPointer:
320  case CK_DerivedToBaseMemberPointer:
321  case CK_MemberPointerToBoolean:
322  case CK_IntegralToPointer:
323  case CK_PointerToIntegral:
324  case CK_PointerToBoolean:
325  case CK_ToVoid:
326  case CK_VectorSplat:
327  case CK_IntegralCast:
328  case CK_IntegralToBoolean:
329  case CK_IntegralToFloating:
330  case CK_FloatingToIntegral:
331  case CK_FloatingToBoolean:
332  case CK_FloatingCast:
333  case CK_AnyPointerToObjCPointerCast:
334  case CK_AnyPointerToBlockPointerCast:
335  case CK_ObjCObjectLValueCast:
336  case CK_FloatingRealToComplex:
337  case CK_FloatingComplexToReal:
338  case CK_FloatingComplexToBoolean:
339  case CK_FloatingComplexCast:
340  case CK_FloatingComplexToIntegralComplex:
341  case CK_IntegralRealToComplex:
342  case CK_IntegralComplexToReal:
343  case CK_IntegralComplexToBoolean:
344  case CK_IntegralComplexCast:
345  case CK_IntegralComplexToFloatingComplex:
346    llvm_unreachable("cast kind invalid for aggregate types");
347  }
348}
349
350void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
351  if (E->getCallReturnType()->isReferenceType()) {
352    EmitAggLoadOfLValue(E);
353    return;
354  }
355
356  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
357  EmitGCMove(E, RV);
358}
359
360void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
361  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
362  EmitGCMove(E, RV);
363}
364
365void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
366  llvm_unreachable("direct property access not surrounded by "
367                   "lvalue-to-rvalue cast");
368}
369
370void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
371  CGF.EmitIgnoredExpr(E->getLHS());
372  Visit(E->getRHS());
373}
374
375void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
376  CodeGenFunction::StmtExprEvaluation eval(CGF);
377  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
378}
379
380void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
381  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
382    VisitPointerToDataMemberBinaryOperator(E);
383  else
384    CGF.ErrorUnsupported(E, "aggregate binary expression");
385}
386
387void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
388                                                    const BinaryOperator *E) {
389  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
390  EmitFinalDestCopy(E, LV);
391}
392
393void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
394  // For an assignment to work, the value on the right has
395  // to be compatible with the value on the left.
396  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
397                                                 E->getRHS()->getType())
398         && "Invalid assignment");
399
400  // FIXME:  __block variables need the RHS evaluated first!
401  LValue LHS = CGF.EmitLValue(E->getLHS());
402
403  // We have to special case property setters, otherwise we must have
404  // a simple lvalue (no aggregates inside vectors, bitfields).
405  if (LHS.isPropertyRef()) {
406    AggValueSlot Slot = EnsureSlot(E->getRHS()->getType());
407    CGF.EmitAggExpr(E->getRHS(), Slot);
408    CGF.EmitStoreThroughPropertyRefLValue(Slot.asRValue(), LHS);
409  } else {
410    bool GCollection = false;
411    if (CGF.getContext().getLangOptions().getGCMode())
412      GCollection = TypeRequiresGCollection(E->getLHS()->getType());
413
414    // Codegen the RHS so that it stores directly into the LHS.
415    AggValueSlot LHSSlot = AggValueSlot::forLValue(LHS, true,
416                                                   GCollection);
417    CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
418    EmitFinalDestCopy(E, LHS, true);
419  }
420}
421
422void AggExprEmitter::VisitConditionalOperator(const ConditionalOperator *E) {
423  if (!E->getLHS()) {
424    CGF.ErrorUnsupported(E, "conditional operator with missing LHS");
425    return;
426  }
427
428  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
429  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
430  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
431
432  CodeGenFunction::ConditionalEvaluation eval(CGF);
433  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
434
435  // Save whether the destination's lifetime is externally managed.
436  bool DestLifetimeManaged = Dest.isLifetimeExternallyManaged();
437
438  eval.begin(CGF);
439  CGF.EmitBlock(LHSBlock);
440  Visit(E->getLHS());
441  eval.end(CGF);
442
443  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
444  CGF.Builder.CreateBr(ContBlock);
445
446  // If the result of an agg expression is unused, then the emission
447  // of the LHS might need to create a destination slot.  That's fine
448  // with us, and we can safely emit the RHS into the same slot, but
449  // we shouldn't claim that its lifetime is externally managed.
450  Dest.setLifetimeExternallyManaged(DestLifetimeManaged);
451
452  eval.begin(CGF);
453  CGF.EmitBlock(RHSBlock);
454  Visit(E->getRHS());
455  eval.end(CGF);
456
457  CGF.EmitBlock(ContBlock);
458}
459
460void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
461  Visit(CE->getChosenSubExpr(CGF.getContext()));
462}
463
464void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
465  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
466  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
467
468  if (!ArgPtr) {
469    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
470    return;
471  }
472
473  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
474}
475
476void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
477  // Ensure that we have a slot, but if we already do, remember
478  // whether its lifetime was externally managed.
479  bool WasManaged = Dest.isLifetimeExternallyManaged();
480  Dest = EnsureSlot(E->getType());
481  Dest.setLifetimeExternallyManaged();
482
483  Visit(E->getSubExpr());
484
485  // Set up the temporary's destructor if its lifetime wasn't already
486  // being managed.
487  if (!WasManaged)
488    CGF.EmitCXXTemporary(E->getTemporary(), Dest.getAddr());
489}
490
491void
492AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
493  AggValueSlot Slot = EnsureSlot(E->getType());
494  CGF.EmitCXXConstructExpr(E, Slot);
495}
496
497void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
498  CGF.EmitExprWithCleanups(E, Dest);
499}
500
501void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
502  QualType T = E->getType();
503  AggValueSlot Slot = EnsureSlot(T);
504  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
505}
506
507void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
508  QualType T = E->getType();
509  AggValueSlot Slot = EnsureSlot(T);
510  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
511}
512
513/// isSimpleZero - If emitting this value will obviously just cause a store of
514/// zero to memory, return true.  This can return false if uncertain, so it just
515/// handles simple cases.
516static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
517  // (0)
518  if (const ParenExpr *PE = dyn_cast<ParenExpr>(E))
519    return isSimpleZero(PE->getSubExpr(), CGF);
520  // 0
521  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
522    return IL->getValue() == 0;
523  // +0.0
524  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
525    return FL->getValue().isPosZero();
526  // int()
527  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
528      CGF.getTypes().isZeroInitializable(E->getType()))
529    return true;
530  // (int*)0 - Null pointer expressions.
531  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
532    return ICE->getCastKind() == CK_NullToPointer;
533  // '\0'
534  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
535    return CL->getValue() == 0;
536
537  // Otherwise, hard case: conservatively return false.
538  return false;
539}
540
541
542void
543AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV, QualType T) {
544  // FIXME: Ignore result?
545  // FIXME: Are initializers affected by volatile?
546  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
547    // Storing "i32 0" to a zero'd memory location is a noop.
548  } else if (isa<ImplicitValueInitExpr>(E)) {
549    EmitNullInitializationToLValue(LV, T);
550  } else if (T->isReferenceType()) {
551    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
552    CGF.EmitStoreThroughLValue(RV, LV, T);
553  } else if (T->isAnyComplexType()) {
554    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
555  } else if (CGF.hasAggregateLLVMType(T)) {
556    CGF.EmitAggExpr(E, AggValueSlot::forAddr(LV.getAddress(), false, true,
557                                             false, Dest.isZeroed()));
558  } else {
559    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV, T);
560  }
561}
562
563void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
564  // If the destination slot is already zeroed out before the aggregate is
565  // copied into it, we don't have to emit any zeros here.
566  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(T))
567    return;
568
569  if (!CGF.hasAggregateLLVMType(T)) {
570    // For non-aggregates, we can store zero
571    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
572    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
573  } else {
574    // There's a potential optimization opportunity in combining
575    // memsets; that would be easy for arrays, but relatively
576    // difficult for structures with the current code.
577    CGF.EmitNullInitialization(LV.getAddress(), T);
578  }
579}
580
581void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
582#if 0
583  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
584  // (Length of globals? Chunks of zeroed-out space?).
585  //
586  // If we can, prefer a copy from a global; this is a lot less code for long
587  // globals, and it's easier for the current optimizers to analyze.
588  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
589    llvm::GlobalVariable* GV =
590    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
591                             llvm::GlobalValue::InternalLinkage, C, "");
592    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
593    return;
594  }
595#endif
596  if (E->hadArrayRangeDesignator())
597    CGF.ErrorUnsupported(E, "GNU array range designator extension");
598
599  llvm::Value *DestPtr = Dest.getAddr();
600
601  // Handle initialization of an array.
602  if (E->getType()->isArrayType()) {
603    const llvm::PointerType *APType =
604      cast<llvm::PointerType>(DestPtr->getType());
605    const llvm::ArrayType *AType =
606      cast<llvm::ArrayType>(APType->getElementType());
607
608    uint64_t NumInitElements = E->getNumInits();
609
610    if (E->getNumInits() > 0) {
611      QualType T1 = E->getType();
612      QualType T2 = E->getInit(0)->getType();
613      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
614        EmitAggLoadOfLValue(E->getInit(0));
615        return;
616      }
617    }
618
619    uint64_t NumArrayElements = AType->getNumElements();
620    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
621    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
622
623    // FIXME: were we intentionally ignoring address spaces and GC attributes?
624
625    for (uint64_t i = 0; i != NumArrayElements; ++i) {
626      // If we're done emitting initializers and the destination is known-zeroed
627      // then we're done.
628      if (i == NumInitElements &&
629          Dest.isZeroed() &&
630          CGF.getTypes().isZeroInitializable(ElementType))
631        break;
632
633      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
634      LValue LV = CGF.MakeAddrLValue(NextVal, ElementType);
635
636      if (i < NumInitElements)
637        EmitInitializationToLValue(E->getInit(i), LV, ElementType);
638      else
639        EmitNullInitializationToLValue(LV, ElementType);
640
641      // If the GEP didn't get used because of a dead zero init or something
642      // else, clean it up for -O0 builds and general tidiness.
643      if (llvm::GetElementPtrInst *GEP =
644            dyn_cast<llvm::GetElementPtrInst>(NextVal))
645        if (GEP->use_empty())
646          GEP->eraseFromParent();
647    }
648    return;
649  }
650
651  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
652
653  // Do struct initialization; this code just sets each individual member
654  // to the approprate value.  This makes bitfield support automatic;
655  // the disadvantage is that the generated code is more difficult for
656  // the optimizer, especially with bitfields.
657  unsigned NumInitElements = E->getNumInits();
658  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
659
660  if (E->getType()->isUnionType()) {
661    // Only initialize one field of a union. The field itself is
662    // specified by the initializer list.
663    if (!E->getInitializedFieldInUnion()) {
664      // Empty union; we have nothing to do.
665
666#ifndef NDEBUG
667      // Make sure that it's really an empty and not a failure of
668      // semantic analysis.
669      for (RecordDecl::field_iterator Field = SD->field_begin(),
670                                   FieldEnd = SD->field_end();
671           Field != FieldEnd; ++Field)
672        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
673#endif
674      return;
675    }
676
677    // FIXME: volatility
678    FieldDecl *Field = E->getInitializedFieldInUnion();
679
680    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
681    if (NumInitElements) {
682      // Store the initializer into the field
683      EmitInitializationToLValue(E->getInit(0), FieldLoc, Field->getType());
684    } else {
685      // Default-initialize to null.
686      EmitNullInitializationToLValue(FieldLoc, Field->getType());
687    }
688
689    return;
690  }
691
692  // Here we iterate over the fields; this makes it simpler to both
693  // default-initialize fields and skip over unnamed fields.
694  unsigned CurInitVal = 0;
695  for (RecordDecl::field_iterator Field = SD->field_begin(),
696                               FieldEnd = SD->field_end();
697       Field != FieldEnd; ++Field) {
698    // We're done once we hit the flexible array member
699    if (Field->getType()->isIncompleteArrayType())
700      break;
701
702    if (Field->isUnnamedBitfield())
703      continue;
704
705    // Don't emit GEP before a noop store of zero.
706    if (CurInitVal == NumInitElements && Dest.isZeroed() &&
707        CGF.getTypes().isZeroInitializable(E->getType()))
708      break;
709
710    // FIXME: volatility
711    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, *Field, 0);
712    // We never generate write-barries for initialized fields.
713    FieldLoc.setNonGC(true);
714
715    if (CurInitVal < NumInitElements) {
716      // Store the initializer into the field.
717      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc,
718                                 Field->getType());
719    } else {
720      // We're out of initalizers; default-initialize to null
721      EmitNullInitializationToLValue(FieldLoc, Field->getType());
722    }
723
724    // If the GEP didn't get used because of a dead zero init or something
725    // else, clean it up for -O0 builds and general tidiness.
726    if (FieldLoc.isSimple())
727      if (llvm::GetElementPtrInst *GEP =
728            dyn_cast<llvm::GetElementPtrInst>(FieldLoc.getAddress()))
729        if (GEP->use_empty())
730          GEP->eraseFromParent();
731  }
732}
733
734//===----------------------------------------------------------------------===//
735//                        Entry Points into this File
736//===----------------------------------------------------------------------===//
737
738/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
739/// non-zero bytes that will be stored when outputting the initializer for the
740/// specified initializer expression.
741static uint64_t GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
742  if (const ParenExpr *PE = dyn_cast<ParenExpr>(E))
743    return GetNumNonZeroBytesInInit(PE->getSubExpr(), CGF);
744
745  // 0 and 0.0 won't require any non-zero stores!
746  if (isSimpleZero(E, CGF)) return 0;
747
748  // If this is an initlist expr, sum up the size of sizes of the (present)
749  // elements.  If this is something weird, assume the whole thing is non-zero.
750  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
751  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
752    return CGF.getContext().getTypeSize(E->getType())/8;
753
754  // InitListExprs for structs have to be handled carefully.  If there are
755  // reference members, we need to consider the size of the reference, not the
756  // referencee.  InitListExprs for unions and arrays can't have references.
757  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
758    if (!RT->isUnionType()) {
759      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
760      uint64_t NumNonZeroBytes = 0;
761
762      unsigned ILEElement = 0;
763      for (RecordDecl::field_iterator Field = SD->field_begin(),
764           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
765        // We're done once we hit the flexible array member or run out of
766        // InitListExpr elements.
767        if (Field->getType()->isIncompleteArrayType() ||
768            ILEElement == ILE->getNumInits())
769          break;
770        if (Field->isUnnamedBitfield())
771          continue;
772
773        const Expr *E = ILE->getInit(ILEElement++);
774
775        // Reference values are always non-null and have the width of a pointer.
776        if (Field->getType()->isReferenceType())
777          NumNonZeroBytes += CGF.getContext().Target.getPointerWidth(0);
778        else
779          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
780      }
781
782      return NumNonZeroBytes;
783    }
784  }
785
786
787  uint64_t NumNonZeroBytes = 0;
788  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
789    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
790  return NumNonZeroBytes;
791}
792
793/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
794/// zeros in it, emit a memset and avoid storing the individual zeros.
795///
796static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
797                                     CodeGenFunction &CGF) {
798  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
799  // volatile stores.
800  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
801
802  // If the type is 16-bytes or smaller, prefer individual stores over memset.
803  std::pair<uint64_t, unsigned> TypeInfo =
804    CGF.getContext().getTypeInfo(E->getType());
805  if (TypeInfo.first/8 <= 16)
806    return;
807
808  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
809  // we prefer to emit memset + individual stores for the rest.
810  uint64_t NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
811  if (NumNonZeroBytes*4 > TypeInfo.first/8)
812    return;
813
814  // Okay, it seems like a good idea to use an initial memset, emit the call.
815  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first/8);
816  unsigned Align = TypeInfo.second/8;
817
818  llvm::Value *Loc = Slot.getAddr();
819  const llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
820
821  Loc = CGF.Builder.CreateBitCast(Loc, BP);
822  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, Align, false);
823
824  // Tell the AggExprEmitter that the slot is known zero.
825  Slot.setZeroed();
826}
827
828
829
830
831/// EmitAggExpr - Emit the computation of the specified expression of aggregate
832/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
833/// the value of the aggregate expression is not needed.  If VolatileDest is
834/// true, DestPtr cannot be 0.
835///
836/// \param IsInitializer - true if this evaluation is initializing an
837/// object whose lifetime is already being managed.
838//
839// FIXME: Take Qualifiers object.
840void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
841                                  bool IgnoreResult) {
842  assert(E && hasAggregateLLVMType(E->getType()) &&
843         "Invalid aggregate expression to emit");
844  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
845         "slot has bits but no address");
846
847  // Optimize the slot if possible.
848  CheckAggExprForMemSetUse(Slot, E, *this);
849
850  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
851}
852
853LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
854  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
855  llvm::Value *Temp = CreateMemTemp(E->getType());
856  LValue LV = MakeAddrLValue(Temp, E->getType());
857  EmitAggExpr(E, AggValueSlot::forAddr(Temp, LV.isVolatileQualified(), false));
858  return LV;
859}
860
861void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
862                                        llvm::Value *SrcPtr, QualType Ty,
863                                        bool isVolatile) {
864  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
865
866  if (getContext().getLangOptions().CPlusPlus) {
867    if (const RecordType *RT = Ty->getAs<RecordType>()) {
868      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
869      assert((Record->hasTrivialCopyConstructor() ||
870              Record->hasTrivialCopyAssignment()) &&
871             "Trying to aggregate-copy a type without a trivial copy "
872             "constructor or assignment operator");
873      // Ignore empty classes in C++.
874      if (Record->isEmpty())
875        return;
876    }
877  }
878
879  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
880  // C99 6.5.16.1p3, which states "If the value being stored in an object is
881  // read from another object that overlaps in anyway the storage of the first
882  // object, then the overlap shall be exact and the two objects shall have
883  // qualified or unqualified versions of a compatible type."
884  //
885  // memcpy is not defined if the source and destination pointers are exactly
886  // equal, but other compilers do this optimization, and almost every memcpy
887  // implementation handles this case safely.  If there is a libc that does not
888  // safely handle this, we can add a target hook.
889
890  // Get size and alignment info for this aggregate.
891  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
892
893  // FIXME: Handle variable sized types.
894
895  // FIXME: If we have a volatile struct, the optimizer can remove what might
896  // appear to be `extra' memory ops:
897  //
898  // volatile struct { int i; } a, b;
899  //
900  // int main() {
901  //   a = b;
902  //   a = b;
903  // }
904  //
905  // we need to use a different call here.  We use isVolatile to indicate when
906  // either the source or the destination is volatile.
907
908  const llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
909  const llvm::Type *DBP =
910    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
911  DestPtr = Builder.CreateBitCast(DestPtr, DBP, "tmp");
912
913  const llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
914  const llvm::Type *SBP =
915    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
916  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP, "tmp");
917
918  if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
919    RecordDecl *Record = RecordTy->getDecl();
920    if (Record->hasObjectMember()) {
921      unsigned long size = TypeInfo.first/8;
922      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
923      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
924      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
925                                                    SizeVal);
926      return;
927    }
928  } else if (getContext().getAsArrayType(Ty)) {
929    QualType BaseType = getContext().getBaseElementType(Ty);
930    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
931      if (RecordTy->getDecl()->hasObjectMember()) {
932        unsigned long size = TypeInfo.first/8;
933        const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
934        llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
935        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
936                                                      SizeVal);
937        return;
938      }
939    }
940  }
941
942  Builder.CreateMemCpy(DestPtr, SrcPtr,
943                       llvm::ConstantInt::get(IntPtrTy, TypeInfo.first/8),
944                       TypeInfo.second/8, isVolatile);
945}
946