CGExprAgg.cpp revision 7e5e5f4cc36fe50f46ad76dca7a266434c94f475 
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 VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
85    Visit(GE->getResultExpr());
86  }
87  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
88
89  // l-values.
90  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
91  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
92  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
93  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
94  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
95  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
96    EmitAggLoadOfLValue(E);
97  }
98  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
99    EmitAggLoadOfLValue(E);
100  }
101  void VisitPredefinedExpr(const PredefinedExpr *E) {
102    EmitAggLoadOfLValue(E);
103  }
104
105  // Operators.
106  void VisitCastExpr(CastExpr *E);
107  void VisitCallExpr(const CallExpr *E);
108  void VisitStmtExpr(const StmtExpr *E);
109  void VisitBinaryOperator(const BinaryOperator *BO);
110  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
111  void VisitBinAssign(const BinaryOperator *E);
112  void VisitBinComma(const BinaryOperator *E);
113
114  void VisitObjCMessageExpr(ObjCMessageExpr *E);
115  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
116    EmitAggLoadOfLValue(E);
117  }
118  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
119
120  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
121  void VisitChooseExpr(const ChooseExpr *CE);
122  void VisitInitListExpr(InitListExpr *E);
123  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
124  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
125    Visit(DAE->getExpr());
126  }
127  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
128  void VisitCXXConstructExpr(const CXXConstructExpr *E);
129  void VisitExprWithCleanups(ExprWithCleanups *E);
130  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
131  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
132  void VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E);
133  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
134
135  void VisitVAArgExpr(VAArgExpr *E);
136
137  void EmitInitializationToLValue(Expr *E, LValue Address);
138  void EmitNullInitializationToLValue(LValue Address);
139  //  case Expr::ChooseExprClass:
140  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
141};
142}  // end anonymous namespace.
143
144//===----------------------------------------------------------------------===//
145//                                Utilities
146//===----------------------------------------------------------------------===//
147
148/// EmitAggLoadOfLValue - Given an expression with aggregate type that
149/// represents a value lvalue, this method emits the address of the lvalue,
150/// then loads the result into DestPtr.
151void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
152  LValue LV = CGF.EmitLValue(E);
153  EmitFinalDestCopy(E, LV);
154}
155
156/// \brief True if the given aggregate type requires special GC API calls.
157bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
158  // Only record types have members that might require garbage collection.
159  const RecordType *RecordTy = T->getAs<RecordType>();
160  if (!RecordTy) return false;
161
162  // Don't mess with non-trivial C++ types.
163  RecordDecl *Record = RecordTy->getDecl();
164  if (isa<CXXRecordDecl>(Record) &&
165      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
166       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
167    return false;
168
169  // Check whether the type has an object member.
170  return Record->hasObjectMember();
171}
172
173/// \brief Perform the final move to DestPtr if RequiresGCollection is set.
174///
175/// The idea is that you do something like this:
176///   RValue Result = EmitSomething(..., getReturnValueSlot());
177///   EmitGCMove(E, Result);
178/// If GC doesn't interfere, this will cause the result to be emitted
179/// directly into the return value slot.  If GC does interfere, a final
180/// move will be performed.
181void AggExprEmitter::EmitGCMove(const Expr *E, RValue Src) {
182  if (Dest.requiresGCollection()) {
183    CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
184    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
185    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
186    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF, Dest.getAddr(),
187                                                    Src.getAggregateAddr(),
188                                                    SizeVal);
189  }
190}
191
192/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
193void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore) {
194  assert(Src.isAggregate() && "value must be aggregate value!");
195
196  // If Dest is ignored, then we're evaluating an aggregate expression
197  // in a context (like an expression statement) that doesn't care
198  // about the result.  C says that an lvalue-to-rvalue conversion is
199  // performed in these cases; C++ says that it is not.  In either
200  // case, we don't actually need to do anything unless the value is
201  // volatile.
202  if (Dest.isIgnored()) {
203    if (!Src.isVolatileQualified() ||
204        CGF.CGM.getLangOptions().CPlusPlus ||
205        (IgnoreResult && Ignore))
206      return;
207
208    // If the source is volatile, we must read from it; to do that, we need
209    // some place to put it.
210    Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
211  }
212
213  if (Dest.requiresGCollection()) {
214    CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
215    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
216    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
217    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
218                                                      Dest.getAddr(),
219                                                      Src.getAggregateAddr(),
220                                                      SizeVal);
221    return;
222  }
223  // If the result of the assignment is used, copy the LHS there also.
224  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
225  // from the source as well, as we can't eliminate it if either operand
226  // is volatile, unless copy has volatile for both source and destination..
227  CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
228                        Dest.isVolatile()|Src.isVolatileQualified());
229}
230
231/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
232void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
233  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
234
235  EmitFinalDestCopy(E, RValue::getAggregate(Src.getAddress(),
236                                            Src.isVolatileQualified()),
237                    Ignore);
238}
239
240//===----------------------------------------------------------------------===//
241//                            Visitor Methods
242//===----------------------------------------------------------------------===//
243
244void AggExprEmitter::VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E){
245  Visit(E->GetTemporaryExpr());
246}
247
248void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
249  EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
250}
251
252void
253AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
254  if (E->getType().isPODType(CGF.getContext())) {
255    // For a POD type, just emit a load of the lvalue + a copy, because our
256    // compound literal might alias the destination.
257    // FIXME: This is a band-aid; the real problem appears to be in our handling
258    // of assignments, where we store directly into the LHS without checking
259    // whether anything in the RHS aliases.
260    EmitAggLoadOfLValue(E);
261    return;
262  }
263
264  AggValueSlot Slot = EnsureSlot(E->getType());
265  CGF.EmitAggExpr(E->getInitializer(), Slot);
266}
267
268
269void AggExprEmitter::VisitCastExpr(CastExpr *E) {
270  switch (E->getCastKind()) {
271  case CK_Dynamic: {
272    assert(isa<CXXDynamicCastExpr>(E) && "CK_Dynamic without a dynamic_cast?");
273    LValue LV = CGF.EmitCheckedLValue(E->getSubExpr());
274    // FIXME: Do we also need to handle property references here?
275    if (LV.isSimple())
276      CGF.EmitDynamicCast(LV.getAddress(), cast<CXXDynamicCastExpr>(E));
277    else
278      CGF.CGM.ErrorUnsupported(E, "non-simple lvalue dynamic_cast");
279
280    if (!Dest.isIgnored())
281      CGF.CGM.ErrorUnsupported(E, "lvalue dynamic_cast with a destination");
282    break;
283  }
284
285  case CK_ToUnion: {
286    if (Dest.isIgnored()) break;
287
288    // GCC union extension
289    QualType Ty = E->getSubExpr()->getType();
290    QualType PtrTy = CGF.getContext().getPointerType(Ty);
291    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
292                                                 CGF.ConvertType(PtrTy));
293    EmitInitializationToLValue(E->getSubExpr(),
294                               CGF.MakeAddrLValue(CastPtr, Ty));
295    break;
296  }
297
298  case CK_DerivedToBase:
299  case CK_BaseToDerived:
300  case CK_UncheckedDerivedToBase: {
301    assert(0 && "cannot perform hierarchy conversion in EmitAggExpr: "
302                "should have been unpacked before we got here");
303    break;
304  }
305
306  case CK_GetObjCProperty: {
307    LValue LV = CGF.EmitLValue(E->getSubExpr());
308    assert(LV.isPropertyRef());
309    RValue RV = CGF.EmitLoadOfPropertyRefLValue(LV, getReturnValueSlot());
310    EmitGCMove(E, RV);
311    break;
312  }
313
314  case CK_LValueToRValue: // hope for downstream optimization
315  case CK_NoOp:
316  case CK_UserDefinedConversion:
317  case CK_ConstructorConversion:
318    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
319                                                   E->getType()) &&
320           "Implicit cast types must be compatible");
321    Visit(E->getSubExpr());
322    break;
323
324  case CK_LValueBitCast:
325    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
326    break;
327
328  case CK_Dependent:
329  case CK_BitCast:
330  case CK_ArrayToPointerDecay:
331  case CK_FunctionToPointerDecay:
332  case CK_NullToPointer:
333  case CK_NullToMemberPointer:
334  case CK_BaseToDerivedMemberPointer:
335  case CK_DerivedToBaseMemberPointer:
336  case CK_MemberPointerToBoolean:
337  case CK_IntegralToPointer:
338  case CK_PointerToIntegral:
339  case CK_PointerToBoolean:
340  case CK_ToVoid:
341  case CK_VectorSplat:
342  case CK_IntegralCast:
343  case CK_IntegralToBoolean:
344  case CK_IntegralToFloating:
345  case CK_FloatingToIntegral:
346  case CK_FloatingToBoolean:
347  case CK_FloatingCast:
348  case CK_AnyPointerToObjCPointerCast:
349  case CK_AnyPointerToBlockPointerCast:
350  case CK_ObjCObjectLValueCast:
351  case CK_FloatingRealToComplex:
352  case CK_FloatingComplexToReal:
353  case CK_FloatingComplexToBoolean:
354  case CK_FloatingComplexCast:
355  case CK_FloatingComplexToIntegralComplex:
356  case CK_IntegralRealToComplex:
357  case CK_IntegralComplexToReal:
358  case CK_IntegralComplexToBoolean:
359  case CK_IntegralComplexCast:
360  case CK_IntegralComplexToFloatingComplex:
361  case CK_ObjCProduceObject:
362  case CK_ObjCConsumeObject:
363  case CK_ObjCReclaimReturnedObject:
364    llvm_unreachable("cast kind invalid for aggregate types");
365  }
366}
367
368void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
369  if (E->getCallReturnType()->isReferenceType()) {
370    EmitAggLoadOfLValue(E);
371    return;
372  }
373
374  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
375  EmitGCMove(E, RV);
376}
377
378void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
379  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
380  EmitGCMove(E, RV);
381}
382
383void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
384  llvm_unreachable("direct property access not surrounded by "
385                   "lvalue-to-rvalue cast");
386}
387
388void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
389  CGF.EmitIgnoredExpr(E->getLHS());
390  Visit(E->getRHS());
391}
392
393void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
394  CodeGenFunction::StmtExprEvaluation eval(CGF);
395  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
396}
397
398void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
399  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
400    VisitPointerToDataMemberBinaryOperator(E);
401  else
402    CGF.ErrorUnsupported(E, "aggregate binary expression");
403}
404
405void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
406                                                    const BinaryOperator *E) {
407  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
408  EmitFinalDestCopy(E, LV);
409}
410
411void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
412  // For an assignment to work, the value on the right has
413  // to be compatible with the value on the left.
414  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
415                                                 E->getRHS()->getType())
416         && "Invalid assignment");
417
418  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
419    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
420      if (VD->hasAttr<BlocksAttr>() &&
421          E->getRHS()->HasSideEffects(CGF.getContext())) {
422        // When __block variable on LHS, the RHS must be evaluated first
423        // as it may change the 'forwarding' field via call to Block_copy.
424        LValue RHS = CGF.EmitLValue(E->getRHS());
425        LValue LHS = CGF.EmitLValue(E->getLHS());
426        bool GCollection = false;
427        if (CGF.getContext().getLangOptions().getGCMode())
428          GCollection = TypeRequiresGCollection(E->getLHS()->getType());
429        Dest = AggValueSlot::forLValue(LHS, true, GCollection);
430        EmitFinalDestCopy(E, RHS, true);
431        return;
432      }
433
434  LValue LHS = CGF.EmitLValue(E->getLHS());
435
436  // We have to special case property setters, otherwise we must have
437  // a simple lvalue (no aggregates inside vectors, bitfields).
438  if (LHS.isPropertyRef()) {
439    const ObjCPropertyRefExpr *RE = LHS.getPropertyRefExpr();
440    QualType ArgType = RE->getSetterArgType();
441    RValue Src;
442    if (ArgType->isReferenceType())
443      Src = CGF.EmitReferenceBindingToExpr(E->getRHS(), 0);
444    else {
445      AggValueSlot Slot = EnsureSlot(E->getRHS()->getType());
446      CGF.EmitAggExpr(E->getRHS(), Slot);
447      Src = Slot.asRValue();
448    }
449    CGF.EmitStoreThroughPropertyRefLValue(Src, LHS);
450  } else {
451    bool GCollection = false;
452    if (CGF.getContext().getLangOptions().getGCMode())
453      GCollection = TypeRequiresGCollection(E->getLHS()->getType());
454
455    // Codegen the RHS so that it stores directly into the LHS.
456    AggValueSlot LHSSlot = AggValueSlot::forLValue(LHS, true,
457                                                   GCollection);
458    CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
459    EmitFinalDestCopy(E, LHS, true);
460  }
461}
462
463void AggExprEmitter::
464VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
465  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
466  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
467  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
468
469  // Bind the common expression if necessary.
470  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
471
472  CodeGenFunction::ConditionalEvaluation eval(CGF);
473  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
474
475  // Save whether the destination's lifetime is externally managed.
476  bool DestLifetimeManaged = Dest.isLifetimeExternallyManaged();
477
478  eval.begin(CGF);
479  CGF.EmitBlock(LHSBlock);
480  Visit(E->getTrueExpr());
481  eval.end(CGF);
482
483  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
484  CGF.Builder.CreateBr(ContBlock);
485
486  // If the result of an agg expression is unused, then the emission
487  // of the LHS might need to create a destination slot.  That's fine
488  // with us, and we can safely emit the RHS into the same slot, but
489  // we shouldn't claim that its lifetime is externally managed.
490  Dest.setLifetimeExternallyManaged(DestLifetimeManaged);
491
492  eval.begin(CGF);
493  CGF.EmitBlock(RHSBlock);
494  Visit(E->getFalseExpr());
495  eval.end(CGF);
496
497  CGF.EmitBlock(ContBlock);
498}
499
500void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
501  Visit(CE->getChosenSubExpr(CGF.getContext()));
502}
503
504void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
505  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
506  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
507
508  if (!ArgPtr) {
509    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
510    return;
511  }
512
513  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
514}
515
516void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
517  // Ensure that we have a slot, but if we already do, remember
518  // whether its lifetime was externally managed.
519  bool WasManaged = Dest.isLifetimeExternallyManaged();
520  Dest = EnsureSlot(E->getType());
521  Dest.setLifetimeExternallyManaged();
522
523  Visit(E->getSubExpr());
524
525  // Set up the temporary's destructor if its lifetime wasn't already
526  // being managed.
527  if (!WasManaged)
528    CGF.EmitCXXTemporary(E->getTemporary(), Dest.getAddr());
529}
530
531void
532AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
533  AggValueSlot Slot = EnsureSlot(E->getType());
534  CGF.EmitCXXConstructExpr(E, Slot);
535}
536
537void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
538  CGF.EmitExprWithCleanups(E, Dest);
539}
540
541void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
542  QualType T = E->getType();
543  AggValueSlot Slot = EnsureSlot(T);
544  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
545}
546
547void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
548  QualType T = E->getType();
549  AggValueSlot Slot = EnsureSlot(T);
550  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
551}
552
553/// isSimpleZero - If emitting this value will obviously just cause a store of
554/// zero to memory, return true.  This can return false if uncertain, so it just
555/// handles simple cases.
556static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
557  E = E->IgnoreParens();
558
559  // 0
560  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
561    return IL->getValue() == 0;
562  // +0.0
563  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
564    return FL->getValue().isPosZero();
565  // int()
566  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
567      CGF.getTypes().isZeroInitializable(E->getType()))
568    return true;
569  // (int*)0 - Null pointer expressions.
570  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
571    return ICE->getCastKind() == CK_NullToPointer;
572  // '\0'
573  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
574    return CL->getValue() == 0;
575
576  // Otherwise, hard case: conservatively return false.
577  return false;
578}
579
580
581void
582AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
583  QualType type = LV.getType();
584  // FIXME: Ignore result?
585  // FIXME: Are initializers affected by volatile?
586  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
587    // Storing "i32 0" to a zero'd memory location is a noop.
588  } else if (isa<ImplicitValueInitExpr>(E)) {
589    EmitNullInitializationToLValue(LV);
590  } else if (type->isReferenceType()) {
591    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
592    CGF.EmitStoreThroughLValue(RV, LV);
593  } else if (type->isAnyComplexType()) {
594    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
595  } else if (CGF.hasAggregateLLVMType(type)) {
596    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV, true, false,
597                                               Dest.isZeroed()));
598  } else if (LV.isSimple()) {
599    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
600  } else {
601    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV);
602  }
603}
604
605void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
606  QualType type = lv.getType();
607
608  // If the destination slot is already zeroed out before the aggregate is
609  // copied into it, we don't have to emit any zeros here.
610  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
611    return;
612
613  if (!CGF.hasAggregateLLVMType(type)) {
614    // For non-aggregates, we can store zero
615    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
616    CGF.EmitStoreThroughLValue(RValue::get(null), lv);
617  } else {
618    // There's a potential optimization opportunity in combining
619    // memsets; that would be easy for arrays, but relatively
620    // difficult for structures with the current code.
621    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
622  }
623}
624
625void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
626#if 0
627  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
628  // (Length of globals? Chunks of zeroed-out space?).
629  //
630  // If we can, prefer a copy from a global; this is a lot less code for long
631  // globals, and it's easier for the current optimizers to analyze.
632  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
633    llvm::GlobalVariable* GV =
634    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
635                             llvm::GlobalValue::InternalLinkage, C, "");
636    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
637    return;
638  }
639#endif
640  if (E->hadArrayRangeDesignator())
641    CGF.ErrorUnsupported(E, "GNU array range designator extension");
642
643  llvm::Value *DestPtr = Dest.getAddr();
644
645  // Handle initialization of an array.
646  if (E->getType()->isArrayType()) {
647    const llvm::PointerType *APType =
648      cast<llvm::PointerType>(DestPtr->getType());
649    const llvm::ArrayType *AType =
650      cast<llvm::ArrayType>(APType->getElementType());
651
652    uint64_t NumInitElements = E->getNumInits();
653
654    if (E->getNumInits() > 0) {
655      QualType T1 = E->getType();
656      QualType T2 = E->getInit(0)->getType();
657      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
658        EmitAggLoadOfLValue(E->getInit(0));
659        return;
660      }
661    }
662
663    uint64_t NumArrayElements = AType->getNumElements();
664    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
665    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
666    ElementType = CGF.getContext().getQualifiedType(ElementType,
667                                                    Dest.getQualifiers());
668
669    bool hasNonTrivialCXXConstructor = false;
670    if (CGF.getContext().getLangOptions().CPlusPlus)
671      if (const RecordType *RT = CGF.getContext()
672                        .getBaseElementType(ElementType)->getAs<RecordType>()) {
673        const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
674        hasNonTrivialCXXConstructor = !RD->hasTrivialDefaultConstructor();
675      }
676
677    for (uint64_t i = 0; i != NumArrayElements; ++i) {
678      // If we're done emitting initializers and the destination is known-zeroed
679      // then we're done.
680      if (i == NumInitElements &&
681          Dest.isZeroed() &&
682          CGF.getTypes().isZeroInitializable(ElementType) &&
683          !hasNonTrivialCXXConstructor)
684        break;
685
686      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
687      LValue LV = CGF.MakeAddrLValue(NextVal, ElementType);
688
689      if (i < NumInitElements)
690        EmitInitializationToLValue(E->getInit(i), LV);
691      else if (Expr *filler = E->getArrayFiller())
692        EmitInitializationToLValue(filler, LV);
693      else
694        EmitNullInitializationToLValue(LV);
695
696      // If the GEP didn't get used because of a dead zero init or something
697      // else, clean it up for -O0 builds and general tidiness.
698      if (llvm::GetElementPtrInst *GEP =
699            dyn_cast<llvm::GetElementPtrInst>(NextVal))
700        if (GEP->use_empty())
701          GEP->eraseFromParent();
702    }
703    return;
704  }
705
706  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
707
708  // Do struct initialization; this code just sets each individual member
709  // to the approprate value.  This makes bitfield support automatic;
710  // the disadvantage is that the generated code is more difficult for
711  // the optimizer, especially with bitfields.
712  unsigned NumInitElements = E->getNumInits();
713  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
714
715  if (E->getType()->isUnionType()) {
716    // Only initialize one field of a union. The field itself is
717    // specified by the initializer list.
718    if (!E->getInitializedFieldInUnion()) {
719      // Empty union; we have nothing to do.
720
721#ifndef NDEBUG
722      // Make sure that it's really an empty and not a failure of
723      // semantic analysis.
724      for (RecordDecl::field_iterator Field = SD->field_begin(),
725                                   FieldEnd = SD->field_end();
726           Field != FieldEnd; ++Field)
727        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
728#endif
729      return;
730    }
731
732    // FIXME: volatility
733    FieldDecl *Field = E->getInitializedFieldInUnion();
734
735    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
736    if (NumInitElements) {
737      // Store the initializer into the field
738      EmitInitializationToLValue(E->getInit(0), FieldLoc);
739    } else {
740      // Default-initialize to null.
741      EmitNullInitializationToLValue(FieldLoc);
742    }
743
744    return;
745  }
746
747  // Here we iterate over the fields; this makes it simpler to both
748  // default-initialize fields and skip over unnamed fields.
749  unsigned CurInitVal = 0;
750  for (RecordDecl::field_iterator Field = SD->field_begin(),
751                               FieldEnd = SD->field_end();
752       Field != FieldEnd; ++Field) {
753    // We're done once we hit the flexible array member
754    if (Field->getType()->isIncompleteArrayType())
755      break;
756
757    if (Field->isUnnamedBitfield())
758      continue;
759
760    // Don't emit GEP before a noop store of zero.
761    if (CurInitVal == NumInitElements && Dest.isZeroed() &&
762        CGF.getTypes().isZeroInitializable(E->getType()))
763      break;
764
765    // FIXME: volatility
766    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, *Field, 0);
767    // We never generate write-barries for initialized fields.
768    FieldLoc.setNonGC(true);
769
770    if (CurInitVal < NumInitElements) {
771      // Store the initializer into the field.
772      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc);
773    } else {
774      // We're out of initalizers; default-initialize to null
775      EmitNullInitializationToLValue(FieldLoc);
776    }
777
778    // If the GEP didn't get used because of a dead zero init or something
779    // else, clean it up for -O0 builds and general tidiness.
780    if (FieldLoc.isSimple())
781      if (llvm::GetElementPtrInst *GEP =
782            dyn_cast<llvm::GetElementPtrInst>(FieldLoc.getAddress()))
783        if (GEP->use_empty())
784          GEP->eraseFromParent();
785  }
786}
787
788//===----------------------------------------------------------------------===//
789//                        Entry Points into this File
790//===----------------------------------------------------------------------===//
791
792/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
793/// non-zero bytes that will be stored when outputting the initializer for the
794/// specified initializer expression.
795static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
796  E = E->IgnoreParens();
797
798  // 0 and 0.0 won't require any non-zero stores!
799  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
800
801  // If this is an initlist expr, sum up the size of sizes of the (present)
802  // elements.  If this is something weird, assume the whole thing is non-zero.
803  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
804  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
805    return CGF.getContext().getTypeSizeInChars(E->getType());
806
807  // InitListExprs for structs have to be handled carefully.  If there are
808  // reference members, we need to consider the size of the reference, not the
809  // referencee.  InitListExprs for unions and arrays can't have references.
810  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
811    if (!RT->isUnionType()) {
812      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
813      CharUnits NumNonZeroBytes = CharUnits::Zero();
814
815      unsigned ILEElement = 0;
816      for (RecordDecl::field_iterator Field = SD->field_begin(),
817           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
818        // We're done once we hit the flexible array member or run out of
819        // InitListExpr elements.
820        if (Field->getType()->isIncompleteArrayType() ||
821            ILEElement == ILE->getNumInits())
822          break;
823        if (Field->isUnnamedBitfield())
824          continue;
825
826        const Expr *E = ILE->getInit(ILEElement++);
827
828        // Reference values are always non-null and have the width of a pointer.
829        if (Field->getType()->isReferenceType())
830          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
831              CGF.getContext().Target.getPointerWidth(0));
832        else
833          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
834      }
835
836      return NumNonZeroBytes;
837    }
838  }
839
840
841  CharUnits NumNonZeroBytes = CharUnits::Zero();
842  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
843    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
844  return NumNonZeroBytes;
845}
846
847/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
848/// zeros in it, emit a memset and avoid storing the individual zeros.
849///
850static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
851                                     CodeGenFunction &CGF) {
852  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
853  // volatile stores.
854  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
855
856  // C++ objects with a user-declared constructor don't need zero'ing.
857  if (CGF.getContext().getLangOptions().CPlusPlus)
858    if (const RecordType *RT = CGF.getContext()
859                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
860      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
861      if (RD->hasUserDeclaredConstructor())
862        return;
863    }
864
865  // If the type is 16-bytes or smaller, prefer individual stores over memset.
866  std::pair<CharUnits, CharUnits> TypeInfo =
867    CGF.getContext().getTypeInfoInChars(E->getType());
868  if (TypeInfo.first <= CharUnits::fromQuantity(16))
869    return;
870
871  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
872  // we prefer to emit memset + individual stores for the rest.
873  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
874  if (NumNonZeroBytes*4 > TypeInfo.first)
875    return;
876
877  // Okay, it seems like a good idea to use an initial memset, emit the call.
878  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
879  CharUnits Align = TypeInfo.second;
880
881  llvm::Value *Loc = Slot.getAddr();
882  const llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
883
884  Loc = CGF.Builder.CreateBitCast(Loc, BP);
885  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
886                           Align.getQuantity(), false);
887
888  // Tell the AggExprEmitter that the slot is known zero.
889  Slot.setZeroed();
890}
891
892
893
894
895/// EmitAggExpr - Emit the computation of the specified expression of aggregate
896/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
897/// the value of the aggregate expression is not needed.  If VolatileDest is
898/// true, DestPtr cannot be 0.
899///
900/// \param IsInitializer - true if this evaluation is initializing an
901/// object whose lifetime is already being managed.
902void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
903                                  bool IgnoreResult) {
904  assert(E && hasAggregateLLVMType(E->getType()) &&
905         "Invalid aggregate expression to emit");
906  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
907         "slot has bits but no address");
908
909  // Optimize the slot if possible.
910  CheckAggExprForMemSetUse(Slot, E, *this);
911
912  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
913}
914
915LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
916  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
917  llvm::Value *Temp = CreateMemTemp(E->getType());
918  LValue LV = MakeAddrLValue(Temp, E->getType());
919  EmitAggExpr(E, AggValueSlot::forLValue(LV, false));
920  return LV;
921}
922
923void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
924                                        llvm::Value *SrcPtr, QualType Ty,
925                                        bool isVolatile) {
926  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
927
928  if (getContext().getLangOptions().CPlusPlus) {
929    if (const RecordType *RT = Ty->getAs<RecordType>()) {
930      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
931      assert((Record->hasTrivialCopyConstructor() ||
932              Record->hasTrivialCopyAssignment()) &&
933             "Trying to aggregate-copy a type without a trivial copy "
934             "constructor or assignment operator");
935      // Ignore empty classes in C++.
936      if (Record->isEmpty())
937        return;
938    }
939  }
940
941  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
942  // C99 6.5.16.1p3, which states "If the value being stored in an object is
943  // read from another object that overlaps in anyway the storage of the first
944  // object, then the overlap shall be exact and the two objects shall have
945  // qualified or unqualified versions of a compatible type."
946  //
947  // memcpy is not defined if the source and destination pointers are exactly
948  // equal, but other compilers do this optimization, and almost every memcpy
949  // implementation handles this case safely.  If there is a libc that does not
950  // safely handle this, we can add a target hook.
951
952  // Get size and alignment info for this aggregate.
953  std::pair<CharUnits, CharUnits> TypeInfo =
954    getContext().getTypeInfoInChars(Ty);
955
956  // FIXME: Handle variable sized types.
957
958  // FIXME: If we have a volatile struct, the optimizer can remove what might
959  // appear to be `extra' memory ops:
960  //
961  // volatile struct { int i; } a, b;
962  //
963  // int main() {
964  //   a = b;
965  //   a = b;
966  // }
967  //
968  // we need to use a different call here.  We use isVolatile to indicate when
969  // either the source or the destination is volatile.
970
971  const llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
972  const llvm::Type *DBP =
973    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
974  DestPtr = Builder.CreateBitCast(DestPtr, DBP, "tmp");
975
976  const llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
977  const llvm::Type *SBP =
978    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
979  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP, "tmp");
980
981  // Don't do any of the memmove_collectable tests if GC isn't set.
982  if (CGM.getLangOptions().getGCMode() == LangOptions::NonGC) {
983    // fall through
984  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
985    RecordDecl *Record = RecordTy->getDecl();
986    if (Record->hasObjectMember()) {
987      CharUnits size = TypeInfo.first;
988      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
989      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
990      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
991                                                    SizeVal);
992      return;
993    }
994  } else if (Ty->isArrayType()) {
995    QualType BaseType = getContext().getBaseElementType(Ty);
996    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
997      if (RecordTy->getDecl()->hasObjectMember()) {
998        CharUnits size = TypeInfo.first;
999        const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
1000        llvm::Value *SizeVal =
1001          llvm::ConstantInt::get(SizeTy, size.getQuantity());
1002        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
1003                                                      SizeVal);
1004        return;
1005      }
1006    }
1007  }
1008
1009  Builder.CreateMemCpy(DestPtr, SrcPtr,
1010                       llvm::ConstantInt::get(IntPtrTy,
1011                                              TypeInfo.first.getQuantity()),
1012                       TypeInfo.second.getQuantity(), isVolatile);
1013}
1014