CGExprAgg.cpp revision 9f0c7cc36d29cf591c33962931f5862847145f3e 
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 VisitVAArgExpr(VAArgExpr *E);
133
134  void EmitInitializationToLValue(Expr *E, LValue Address, QualType T);
135  void EmitNullInitializationToLValue(LValue Address, QualType T);
136  //  case Expr::ChooseExprClass:
137  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
138};
139}  // end anonymous namespace.
140
141//===----------------------------------------------------------------------===//
142//                                Utilities
143//===----------------------------------------------------------------------===//
144
145/// EmitAggLoadOfLValue - Given an expression with aggregate type that
146/// represents a value lvalue, this method emits the address of the lvalue,
147/// then loads the result into DestPtr.
148void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
149  LValue LV = CGF.EmitLValue(E);
150  EmitFinalDestCopy(E, LV);
151}
152
153/// \brief True if the given aggregate type requires special GC API calls.
154bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
155  // Only record types have members that might require garbage collection.
156  const RecordType *RecordTy = T->getAs<RecordType>();
157  if (!RecordTy) return false;
158
159  // Don't mess with non-trivial C++ types.
160  RecordDecl *Record = RecordTy->getDecl();
161  if (isa<CXXRecordDecl>(Record) &&
162      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
163       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
164    return false;
165
166  // Check whether the type has an object member.
167  return Record->hasObjectMember();
168}
169
170/// \brief Perform the final move to DestPtr if RequiresGCollection is set.
171///
172/// The idea is that you do something like this:
173///   RValue Result = EmitSomething(..., getReturnValueSlot());
174///   EmitGCMove(E, Result);
175/// If GC doesn't interfere, this will cause the result to be emitted
176/// directly into the return value slot.  If GC does interfere, a final
177/// move will be performed.
178void AggExprEmitter::EmitGCMove(const Expr *E, RValue Src) {
179  if (Dest.requiresGCollection()) {
180    std::pair<uint64_t, unsigned> TypeInfo =
181      CGF.getContext().getTypeInfo(E->getType());
182    unsigned long size = TypeInfo.first/8;
183    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
184    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
185    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF, Dest.getAddr(),
186                                                    Src.getAggregateAddr(),
187                                                    SizeVal);
188  }
189}
190
191/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
192void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore) {
193  assert(Src.isAggregate() && "value must be aggregate value!");
194
195  // If Dest is ignored, then we're evaluating an aggregate expression
196  // in a context (like an expression statement) that doesn't care
197  // about the result.  C says that an lvalue-to-rvalue conversion is
198  // performed in these cases; C++ says that it is not.  In either
199  // case, we don't actually need to do anything unless the value is
200  // volatile.
201  if (Dest.isIgnored()) {
202    if (!Src.isVolatileQualified() ||
203        CGF.CGM.getLangOptions().CPlusPlus ||
204        (IgnoreResult && Ignore))
205      return;
206
207    // If the source is volatile, we must read from it; to do that, we need
208    // some place to put it.
209    Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
210  }
211
212  if (Dest.requiresGCollection()) {
213    std::pair<uint64_t, unsigned> TypeInfo =
214    CGF.getContext().getTypeInfo(E->getType());
215    unsigned long size = TypeInfo.first/8;
216    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
217    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
218    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
219                                                      Dest.getAddr(),
220                                                      Src.getAggregateAddr(),
221                                                      SizeVal);
222    return;
223  }
224  // If the result of the assignment is used, copy the LHS there also.
225  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
226  // from the source as well, as we can't eliminate it if either operand
227  // is volatile, unless copy has volatile for both source and destination..
228  CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
229                        Dest.isVolatile()|Src.isVolatileQualified());
230}
231
232/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
233void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
234  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
235
236  EmitFinalDestCopy(E, RValue::getAggregate(Src.getAddress(),
237                                            Src.isVolatileQualified()),
238                    Ignore);
239}
240
241//===----------------------------------------------------------------------===//
242//                            Visitor Methods
243//===----------------------------------------------------------------------===//
244
245void AggExprEmitter::VisitCastExpr(CastExpr *E) {
246  if (Dest.isIgnored() && E->getCastKind() != CK_Dynamic) {
247    Visit(E->getSubExpr());
248    return;
249  }
250
251  switch (E->getCastKind()) {
252  case CK_Dynamic: {
253    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
254    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
255    // FIXME: Do we also need to handle property references here?
256    if (LV.isSimple())
257      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
258    else
259      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
260
261    if (!Dest.isIgnored())
262      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
263    break;
264  }
265
266  case CK_ToUnion: {
267    // GCC union extension
268    QualType Ty = E->getSubExpr()->getType();
269    QualType PtrTy = CGF.getContext().getPointerType(Ty);
270    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
271                                                 CGF.ConvertType(PtrTy));
272    EmitInitializationToLValue(E->getSubExpr(), CGF.MakeAddrLValue(CastPtr, Ty),
273                               Ty);
274    break;
275  }
276
277  case CK_DerivedToBase:
278  case CK_BaseToDerived:
279  case CK_UncheckedDerivedToBase: {
280    assert(0 && "cannot perform hierarchy conversion in EmitAggExpr: "
281                "should have been unpacked before we got here");
282    break;
283  }
284
285  case CK_GetObjCProperty: {
286    LValue LV = CGF.EmitLValue(E->getSubExpr());
287    assert(LV.isPropertyRef());
288    RValue RV = CGF.EmitLoadOfPropertyRefLValue(LV, getReturnValueSlot());
289    EmitGCMove(E, RV);
290    break;
291  }
292
293  case CK_LValueToRValue: // hope for downstream optimization
294  case CK_NoOp:
295  case CK_UserDefinedConversion:
296  case CK_ConstructorConversion:
297    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
298                                                   E->getType()) &&
299           "Implicit cast types must be compatible");
300    Visit(E->getSubExpr());
301    break;
302
303  case CK_LValueBitCast:
304    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
305    break;
306
307  case CK_Dependent:
308  case CK_BitCast:
309  case CK_ArrayToPointerDecay:
310  case CK_FunctionToPointerDecay:
311  case CK_NullToPointer:
312  case CK_NullToMemberPointer:
313  case CK_BaseToDerivedMemberPointer:
314  case CK_DerivedToBaseMemberPointer:
315  case CK_MemberPointerToBoolean:
316  case CK_IntegralToPointer:
317  case CK_PointerToIntegral:
318  case CK_PointerToBoolean:
319  case CK_ToVoid:
320  case CK_VectorSplat:
321  case CK_IntegralCast:
322  case CK_IntegralToBoolean:
323  case CK_IntegralToFloating:
324  case CK_FloatingToIntegral:
325  case CK_FloatingToBoolean:
326  case CK_FloatingCast:
327  case CK_AnyPointerToObjCPointerCast:
328  case CK_AnyPointerToBlockPointerCast:
329  case CK_ObjCObjectLValueCast:
330  case CK_FloatingRealToComplex:
331  case CK_FloatingComplexToReal:
332  case CK_FloatingComplexToBoolean:
333  case CK_FloatingComplexCast:
334  case CK_FloatingComplexToIntegralComplex:
335  case CK_IntegralRealToComplex:
336  case CK_IntegralComplexToReal:
337  case CK_IntegralComplexToBoolean:
338  case CK_IntegralComplexCast:
339  case CK_IntegralComplexToFloatingComplex:
340    llvm_unreachable("cast kind invalid for aggregate types");
341  }
342}
343
344void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
345  if (E->getCallReturnType()->isReferenceType()) {
346    EmitAggLoadOfLValue(E);
347    return;
348  }
349
350  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
351  EmitGCMove(E, RV);
352}
353
354void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
355  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
356  EmitGCMove(E, RV);
357}
358
359void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
360  llvm_unreachable("direct property access not surrounded by "
361                   "lvalue-to-rvalue cast");
362}
363
364void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
365  CGF.EmitIgnoredExpr(E->getLHS());
366  Visit(E->getRHS());
367}
368
369void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
370  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
371}
372
373void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
374  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
375    VisitPointerToDataMemberBinaryOperator(E);
376  else
377    CGF.ErrorUnsupported(E, "aggregate binary expression");
378}
379
380void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
381                                                    const BinaryOperator *E) {
382  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
383  EmitFinalDestCopy(E, LV);
384}
385
386void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
387  // For an assignment to work, the value on the right has
388  // to be compatible with the value on the left.
389  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
390                                                 E->getRHS()->getType())
391         && "Invalid assignment");
392
393  // FIXME:  __block variables need the RHS evaluated first!
394  LValue LHS = CGF.EmitLValue(E->getLHS());
395
396  // We have to special case property setters, otherwise we must have
397  // a simple lvalue (no aggregates inside vectors, bitfields).
398  if (LHS.isPropertyRef()) {
399    AggValueSlot Slot = EnsureSlot(E->getRHS()->getType());
400    CGF.EmitAggExpr(E->getRHS(), Slot);
401    CGF.EmitStoreThroughPropertyRefLValue(Slot.asRValue(), LHS);
402  } else {
403    bool GCollection = false;
404    if (CGF.getContext().getLangOptions().getGCMode())
405      GCollection = TypeRequiresGCollection(E->getLHS()->getType());
406
407    // Codegen the RHS so that it stores directly into the LHS.
408    AggValueSlot LHSSlot = AggValueSlot::forLValue(LHS, true,
409                                                   GCollection);
410    CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
411    EmitFinalDestCopy(E, LHS, true);
412  }
413}
414
415void AggExprEmitter::VisitConditionalOperator(const ConditionalOperator *E) {
416  if (!E->getLHS()) {
417    CGF.ErrorUnsupported(E, "conditional operator with missing LHS");
418    return;
419  }
420
421  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
422  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
423  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
424
425  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
426
427  CGF.BeginConditionalBranch();
428  CGF.EmitBlock(LHSBlock);
429
430  // Save whether the destination's lifetime is externally managed.
431  bool DestLifetimeManaged = Dest.isLifetimeExternallyManaged();
432
433  Visit(E->getLHS());
434  CGF.EndConditionalBranch();
435  CGF.EmitBranch(ContBlock);
436
437  CGF.BeginConditionalBranch();
438  CGF.EmitBlock(RHSBlock);
439
440  // If the result of an agg expression is unused, then the emission
441  // of the LHS might need to create a destination slot.  That's fine
442  // with us, and we can safely emit the RHS into the same slot, but
443  // we shouldn't claim that its lifetime is externally managed.
444  Dest.setLifetimeExternallyManaged(DestLifetimeManaged);
445
446  Visit(E->getRHS());
447  CGF.EndConditionalBranch();
448  CGF.EmitBranch(ContBlock);
449
450  CGF.EmitBlock(ContBlock);
451}
452
453void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
454  Visit(CE->getChosenSubExpr(CGF.getContext()));
455}
456
457void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
458  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
459  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
460
461  if (!ArgPtr) {
462    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
463    return;
464  }
465
466  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
467}
468
469void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
470  // Ensure that we have a slot, but if we already do, remember
471  // whether its lifetime was externally managed.
472  bool WasManaged = Dest.isLifetimeExternallyManaged();
473  Dest = EnsureSlot(E->getType());
474  Dest.setLifetimeExternallyManaged();
475
476  Visit(E->getSubExpr());
477
478  // Set up the temporary's destructor if its lifetime wasn't already
479  // being managed.
480  if (!WasManaged)
481    CGF.EmitCXXTemporary(E->getTemporary(), Dest.getAddr());
482}
483
484void
485AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
486  AggValueSlot Slot = EnsureSlot(E->getType());
487  CGF.EmitCXXConstructExpr(E, Slot);
488}
489
490void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
491  CGF.EmitExprWithCleanups(E, Dest);
492}
493
494void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
495  QualType T = E->getType();
496  AggValueSlot Slot = EnsureSlot(T);
497  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
498}
499
500void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
501  QualType T = E->getType();
502  AggValueSlot Slot = EnsureSlot(T);
503  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
504}
505
506/// isSimpleZero - If emitting this value will obviously just cause a store of
507/// zero to memory, return true.  This can return false if uncertain, so it just
508/// handles simple cases.
509static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
510  // (0)
511  if (const ParenExpr *PE = dyn_cast<ParenExpr>(E))
512    return isSimpleZero(PE->getSubExpr(), CGF);
513  // 0
514  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
515    return IL->getValue() == 0;
516  // +0.0
517  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
518    return FL->getValue().isPosZero();
519  // int()
520  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
521      CGF.getTypes().isZeroInitializable(E->getType()))
522    return true;
523  // (int*)0 - Null pointer expressions.
524  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
525    return ICE->getCastKind() == CK_NullToPointer;
526  // '\0'
527  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
528    return CL->getValue() == 0;
529
530  // Otherwise, hard case: conservatively return false.
531  return false;
532}
533
534
535void
536AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV, QualType T) {
537  // FIXME: Ignore result?
538  // FIXME: Are initializers affected by volatile?
539  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
540    // Storing "i32 0" to a zero'd memory location is a noop.
541  } else if (isa<ImplicitValueInitExpr>(E)) {
542    EmitNullInitializationToLValue(LV, T);
543  } else if (T->isReferenceType()) {
544    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
545    CGF.EmitStoreThroughLValue(RV, LV, T);
546  } else if (T->isAnyComplexType()) {
547    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
548  } else if (CGF.hasAggregateLLVMType(T)) {
549    CGF.EmitAggExpr(E, AggValueSlot::forAddr(LV.getAddress(), false, true,
550                                             false, Dest.isZeroed()));
551  } else {
552    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV, T);
553  }
554}
555
556void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
557  // If the destination slot is already zeroed out before the aggregate is
558  // copied into it, we don't have to emit any zeros here.
559  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(T))
560    return;
561
562  if (!CGF.hasAggregateLLVMType(T)) {
563    // For non-aggregates, we can store zero
564    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
565    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
566  } else {
567    // There's a potential optimization opportunity in combining
568    // memsets; that would be easy for arrays, but relatively
569    // difficult for structures with the current code.
570    CGF.EmitNullInitialization(LV.getAddress(), T);
571  }
572}
573
574void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
575#if 0
576  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
577  // (Length of globals? Chunks of zeroed-out space?).
578  //
579  // If we can, prefer a copy from a global; this is a lot less code for long
580  // globals, and it's easier for the current optimizers to analyze.
581  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
582    llvm::GlobalVariable* GV =
583    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
584                             llvm::GlobalValue::InternalLinkage, C, "");
585    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
586    return;
587  }
588#endif
589  if (E->hadArrayRangeDesignator())
590    CGF.ErrorUnsupported(E, "GNU array range designator extension");
591
592  llvm::Value *DestPtr = Dest.getAddr();
593
594  // Handle initialization of an array.
595  if (E->getType()->isArrayType()) {
596    const llvm::PointerType *APType =
597      cast<llvm::PointerType>(DestPtr->getType());
598    const llvm::ArrayType *AType =
599      cast<llvm::ArrayType>(APType->getElementType());
600
601    uint64_t NumInitElements = E->getNumInits();
602
603    if (E->getNumInits() > 0) {
604      QualType T1 = E->getType();
605      QualType T2 = E->getInit(0)->getType();
606      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
607        EmitAggLoadOfLValue(E->getInit(0));
608        return;
609      }
610    }
611
612    uint64_t NumArrayElements = AType->getNumElements();
613    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
614    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
615
616    // FIXME: were we intentionally ignoring address spaces and GC attributes?
617
618    for (uint64_t i = 0; i != NumArrayElements; ++i) {
619      // If we're done emitting initializers and the destination is known-zeroed
620      // then we're done.
621      if (i == NumInitElements &&
622          Dest.isZeroed() &&
623          CGF.getTypes().isZeroInitializable(ElementType))
624        break;
625
626      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
627      LValue LV = CGF.MakeAddrLValue(NextVal, ElementType);
628
629      if (i < NumInitElements)
630        EmitInitializationToLValue(E->getInit(i), LV, ElementType);
631      else
632        EmitNullInitializationToLValue(LV, ElementType);
633
634      // If the GEP didn't get used because of a dead zero init or something
635      // else, clean it up for -O0 builds and general tidiness.
636      if (llvm::GetElementPtrInst *GEP =
637            dyn_cast<llvm::GetElementPtrInst>(NextVal))
638        if (GEP->use_empty())
639          GEP->eraseFromParent();
640    }
641    return;
642  }
643
644  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
645
646  // Do struct initialization; this code just sets each individual member
647  // to the approprate value.  This makes bitfield support automatic;
648  // the disadvantage is that the generated code is more difficult for
649  // the optimizer, especially with bitfields.
650  unsigned NumInitElements = E->getNumInits();
651  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
652
653  if (E->getType()->isUnionType()) {
654    // Only initialize one field of a union. The field itself is
655    // specified by the initializer list.
656    if (!E->getInitializedFieldInUnion()) {
657      // Empty union; we have nothing to do.
658
659#ifndef NDEBUG
660      // Make sure that it's really an empty and not a failure of
661      // semantic analysis.
662      for (RecordDecl::field_iterator Field = SD->field_begin(),
663                                   FieldEnd = SD->field_end();
664           Field != FieldEnd; ++Field)
665        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
666#endif
667      return;
668    }
669
670    // FIXME: volatility
671    FieldDecl *Field = E->getInitializedFieldInUnion();
672
673    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
674    if (NumInitElements) {
675      // Store the initializer into the field
676      EmitInitializationToLValue(E->getInit(0), FieldLoc, Field->getType());
677    } else {
678      // Default-initialize to null.
679      EmitNullInitializationToLValue(FieldLoc, Field->getType());
680    }
681
682    return;
683  }
684
685  // Here we iterate over the fields; this makes it simpler to both
686  // default-initialize fields and skip over unnamed fields.
687  unsigned CurInitVal = 0;
688  for (RecordDecl::field_iterator Field = SD->field_begin(),
689                               FieldEnd = SD->field_end();
690       Field != FieldEnd; ++Field) {
691    // We're done once we hit the flexible array member
692    if (Field->getType()->isIncompleteArrayType())
693      break;
694
695    if (Field->isUnnamedBitfield())
696      continue;
697
698    // Don't emit GEP before a noop store of zero.
699    if (CurInitVal == NumInitElements && Dest.isZeroed() &&
700        CGF.getTypes().isZeroInitializable(E->getType()))
701      break;
702
703    // FIXME: volatility
704    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, *Field, 0);
705    // We never generate write-barries for initialized fields.
706    FieldLoc.setNonGC(true);
707
708    if (CurInitVal < NumInitElements) {
709      // Store the initializer into the field.
710      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc,
711                                 Field->getType());
712    } else {
713      // We're out of initalizers; default-initialize to null
714      EmitNullInitializationToLValue(FieldLoc, Field->getType());
715    }
716
717    // If the GEP didn't get used because of a dead zero init or something
718    // else, clean it up for -O0 builds and general tidiness.
719    if (FieldLoc.isSimple())
720      if (llvm::GetElementPtrInst *GEP =
721            dyn_cast<llvm::GetElementPtrInst>(FieldLoc.getAddress()))
722        if (GEP->use_empty())
723          GEP->eraseFromParent();
724  }
725}
726
727//===----------------------------------------------------------------------===//
728//                        Entry Points into this File
729//===----------------------------------------------------------------------===//
730
731/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
732/// non-zero bytes that will be stored when outputting the initializer for the
733/// specified initializer expression.
734static uint64_t GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
735  if (const ParenExpr *PE = dyn_cast<ParenExpr>(E))
736    return GetNumNonZeroBytesInInit(PE->getSubExpr(), CGF);
737
738  // 0 and 0.0 won't require any non-zero stores!
739  if (isSimpleZero(E, CGF)) return 0;
740
741  // If this is an initlist expr, sum up the size of sizes of the (present)
742  // elements.  If this is something weird, assume the whole thing is non-zero.
743  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
744  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
745    return CGF.getContext().getTypeSize(E->getType())/8;
746
747  // InitListExprs for structs have to be handled carefully.  If there are
748  // reference members, we need to consider the size of the reference, not the
749  // referencee.  InitListExprs for unions and arrays can't have references.
750  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
751    if (!RT->isUnionType()) {
752      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
753      uint64_t NumNonZeroBytes = 0;
754
755      unsigned ILEElement = 0;
756      for (RecordDecl::field_iterator Field = SD->field_begin(),
757           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
758        // We're done once we hit the flexible array member or run out of
759        // InitListExpr elements.
760        if (Field->getType()->isIncompleteArrayType() ||
761            ILEElement == ILE->getNumInits())
762          break;
763        if (Field->isUnnamedBitfield())
764          continue;
765
766        const Expr *E = ILE->getInit(ILEElement++);
767
768        // Reference values are always non-null and have the width of a pointer.
769        if (Field->getType()->isReferenceType())
770          NumNonZeroBytes += CGF.getContext().Target.getPointerWidth(0);
771        else
772          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
773      }
774
775      return NumNonZeroBytes;
776    }
777  }
778
779
780  uint64_t NumNonZeroBytes = 0;
781  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
782    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
783  return NumNonZeroBytes;
784}
785
786/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
787/// zeros in it, emit a memset and avoid storing the individual zeros.
788///
789static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
790                                     CodeGenFunction &CGF) {
791  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
792  // volatile stores.
793  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
794
795  // If the type is 16-bytes or smaller, prefer individual stores over memset.
796  std::pair<uint64_t, unsigned> TypeInfo =
797    CGF.getContext().getTypeInfo(E->getType());
798  if (TypeInfo.first/8 <= 16)
799    return;
800
801  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
802  // we prefer to emit memset + individual stores for the rest.
803  uint64_t NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
804  if (NumNonZeroBytes*4 > TypeInfo.first/8)
805    return;
806
807  // Okay, it seems like a good idea to use an initial memset, emit the call.
808  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first/8);
809  unsigned Align = TypeInfo.second/8;
810
811  llvm::Value *Loc = Slot.getAddr();
812  const llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
813
814  Loc = CGF.Builder.CreateBitCast(Loc, BP);
815  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal, Align, false);
816
817  // Tell the AggExprEmitter that the slot is known zero.
818  Slot.setZeroed();
819}
820
821
822
823
824/// EmitAggExpr - Emit the computation of the specified expression of aggregate
825/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
826/// the value of the aggregate expression is not needed.  If VolatileDest is
827/// true, DestPtr cannot be 0.
828///
829/// \param IsInitializer - true if this evaluation is initializing an
830/// object whose lifetime is already being managed.
831//
832// FIXME: Take Qualifiers object.
833void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
834                                  bool IgnoreResult) {
835  assert(E && hasAggregateLLVMType(E->getType()) &&
836         "Invalid aggregate expression to emit");
837  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
838         "slot has bits but no address");
839
840  // Optimize the slot if possible.
841  CheckAggExprForMemSetUse(Slot, E, *this);
842
843  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
844}
845
846LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
847  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
848  llvm::Value *Temp = CreateMemTemp(E->getType());
849  LValue LV = MakeAddrLValue(Temp, E->getType());
850  EmitAggExpr(E, AggValueSlot::forAddr(Temp, LV.isVolatileQualified(), false));
851  return LV;
852}
853
854void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
855                                        llvm::Value *SrcPtr, QualType Ty,
856                                        bool isVolatile) {
857  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
858
859  if (getContext().getLangOptions().CPlusPlus) {
860    if (const RecordType *RT = Ty->getAs<RecordType>()) {
861      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
862      assert((Record->hasTrivialCopyConstructor() ||
863              Record->hasTrivialCopyAssignment()) &&
864             "Trying to aggregate-copy a type without a trivial copy "
865             "constructor or assignment operator");
866      // Ignore empty classes in C++.
867      if (Record->isEmpty())
868        return;
869    }
870  }
871
872  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
873  // C99 6.5.16.1p3, which states "If the value being stored in an object is
874  // read from another object that overlaps in anyway the storage of the first
875  // object, then the overlap shall be exact and the two objects shall have
876  // qualified or unqualified versions of a compatible type."
877  //
878  // memcpy is not defined if the source and destination pointers are exactly
879  // equal, but other compilers do this optimization, and almost every memcpy
880  // implementation handles this case safely.  If there is a libc that does not
881  // safely handle this, we can add a target hook.
882
883  // Get size and alignment info for this aggregate.
884  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
885
886  // FIXME: Handle variable sized types.
887
888  // FIXME: If we have a volatile struct, the optimizer can remove what might
889  // appear to be `extra' memory ops:
890  //
891  // volatile struct { int i; } a, b;
892  //
893  // int main() {
894  //   a = b;
895  //   a = b;
896  // }
897  //
898  // we need to use a different call here.  We use isVolatile to indicate when
899  // either the source or the destination is volatile.
900
901  const llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
902  const llvm::Type *DBP =
903    llvm::Type::getInt8PtrTy(VMContext, DPT->getAddressSpace());
904  DestPtr = Builder.CreateBitCast(DestPtr, DBP, "tmp");
905
906  const llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
907  const llvm::Type *SBP =
908    llvm::Type::getInt8PtrTy(VMContext, SPT->getAddressSpace());
909  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP, "tmp");
910
911  if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
912    RecordDecl *Record = RecordTy->getDecl();
913    if (Record->hasObjectMember()) {
914      unsigned long size = TypeInfo.first/8;
915      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
916      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
917      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
918                                                    SizeVal);
919      return;
920    }
921  } else if (getContext().getAsArrayType(Ty)) {
922    QualType BaseType = getContext().getBaseElementType(Ty);
923    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
924      if (RecordTy->getDecl()->hasObjectMember()) {
925        unsigned long size = TypeInfo.first/8;
926        const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
927        llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size);
928        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
929                                                      SizeVal);
930        return;
931      }
932    }
933  }
934
935  Builder.CreateMemCpy(DestPtr, SrcPtr,
936                       llvm::ConstantInt::get(IntPtrTy, TypeInfo.first/8),
937                       TypeInfo.second/8, isVolatile);
938}
939