CGExprAgg.cpp revision a07398ed98ea2b55ad7a505a3aab18aed93b149f 
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    EmitAggLoadOfLValue(E);
96  }
97  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
98    EmitAggLoadOfLValue(E);
99  }
100  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E) {
101    EmitAggLoadOfLValue(E);
102  }
103  void VisitPredefinedExpr(const PredefinedExpr *E) {
104    EmitAggLoadOfLValue(E);
105  }
106
107  // Operators.
108  void VisitCastExpr(CastExpr *E);
109  void VisitCallExpr(const CallExpr *E);
110  void VisitStmtExpr(const StmtExpr *E);
111  void VisitBinaryOperator(const BinaryOperator *BO);
112  void VisitPointerToDataMemberBinaryOperator(const BinaryOperator *BO);
113  void VisitBinAssign(const BinaryOperator *E);
114  void VisitBinComma(const BinaryOperator *E);
115
116  void VisitObjCMessageExpr(ObjCMessageExpr *E);
117  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
118    EmitAggLoadOfLValue(E);
119  }
120  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
121
122  void VisitAbstractConditionalOperator(const AbstractConditionalOperator *CO);
123  void VisitChooseExpr(const ChooseExpr *CE);
124  void VisitInitListExpr(InitListExpr *E);
125  void VisitImplicitValueInitExpr(ImplicitValueInitExpr *E);
126  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
127    Visit(DAE->getExpr());
128  }
129  void VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E);
130  void VisitCXXConstructExpr(const CXXConstructExpr *E);
131  void VisitExprWithCleanups(ExprWithCleanups *E);
132  void VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E);
133  void VisitCXXTypeidExpr(CXXTypeidExpr *E) { EmitAggLoadOfLValue(E); }
134
135  void VisitOpaqueValueExpr(OpaqueValueExpr *E);
136
137  void VisitVAArgExpr(VAArgExpr *E);
138
139  void EmitInitializationToLValue(Expr *E, LValue Address);
140  void EmitNullInitializationToLValue(LValue Address);
141  //  case Expr::ChooseExprClass:
142  void VisitCXXThrowExpr(const CXXThrowExpr *E) { CGF.EmitCXXThrowExpr(E); }
143};
144}  // end anonymous namespace.
145
146//===----------------------------------------------------------------------===//
147//                                Utilities
148//===----------------------------------------------------------------------===//
149
150/// EmitAggLoadOfLValue - Given an expression with aggregate type that
151/// represents a value lvalue, this method emits the address of the lvalue,
152/// then loads the result into DestPtr.
153void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
154  LValue LV = CGF.EmitLValue(E);
155  EmitFinalDestCopy(E, LV);
156}
157
158/// \brief True if the given aggregate type requires special GC API calls.
159bool AggExprEmitter::TypeRequiresGCollection(QualType T) {
160  // Only record types have members that might require garbage collection.
161  const RecordType *RecordTy = T->getAs<RecordType>();
162  if (!RecordTy) return false;
163
164  // Don't mess with non-trivial C++ types.
165  RecordDecl *Record = RecordTy->getDecl();
166  if (isa<CXXRecordDecl>(Record) &&
167      (!cast<CXXRecordDecl>(Record)->hasTrivialCopyConstructor() ||
168       !cast<CXXRecordDecl>(Record)->hasTrivialDestructor()))
169    return false;
170
171  // Check whether the type has an object member.
172  return Record->hasObjectMember();
173}
174
175/// \brief Perform the final move to DestPtr if RequiresGCollection is set.
176///
177/// The idea is that you do something like this:
178///   RValue Result = EmitSomething(..., getReturnValueSlot());
179///   EmitGCMove(E, Result);
180/// If GC doesn't interfere, this will cause the result to be emitted
181/// directly into the return value slot.  If GC does interfere, a final
182/// move will be performed.
183void AggExprEmitter::EmitGCMove(const Expr *E, RValue Src) {
184  if (Dest.requiresGCollection()) {
185    CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
186    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
187    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
188    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF, Dest.getAddr(),
189                                                    Src.getAggregateAddr(),
190                                                    SizeVal);
191  }
192}
193
194/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
195void AggExprEmitter::EmitFinalDestCopy(const Expr *E, RValue Src, bool Ignore) {
196  assert(Src.isAggregate() && "value must be aggregate value!");
197
198  // If Dest is ignored, then we're evaluating an aggregate expression
199  // in a context (like an expression statement) that doesn't care
200  // about the result.  C says that an lvalue-to-rvalue conversion is
201  // performed in these cases; C++ says that it is not.  In either
202  // case, we don't actually need to do anything unless the value is
203  // volatile.
204  if (Dest.isIgnored()) {
205    if (!Src.isVolatileQualified() ||
206        CGF.CGM.getLangOptions().CPlusPlus ||
207        (IgnoreResult && Ignore))
208      return;
209
210    // If the source is volatile, we must read from it; to do that, we need
211    // some place to put it.
212    Dest = CGF.CreateAggTemp(E->getType(), "agg.tmp");
213  }
214
215  if (Dest.requiresGCollection()) {
216    CharUnits size = CGF.getContext().getTypeSizeInChars(E->getType());
217    const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType());
218    llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
219    CGF.CGM.getObjCRuntime().EmitGCMemmoveCollectable(CGF,
220                                                      Dest.getAddr(),
221                                                      Src.getAggregateAddr(),
222                                                      SizeVal);
223    return;
224  }
225  // If the result of the assignment is used, copy the LHS there also.
226  // FIXME: Pass VolatileDest as well.  I think we also need to merge volatile
227  // from the source as well, as we can't eliminate it if either operand
228  // is volatile, unless copy has volatile for both source and destination..
229  CGF.EmitAggregateCopy(Dest.getAddr(), Src.getAggregateAddr(), E->getType(),
230                        Dest.isVolatile()|Src.isVolatileQualified());
231}
232
233/// EmitFinalDestCopy - Perform the final copy to DestPtr, if desired.
234void AggExprEmitter::EmitFinalDestCopy(const Expr *E, LValue Src, bool Ignore) {
235  assert(Src.isSimple() && "Can't have aggregate bitfield, vector, etc");
236
237  EmitFinalDestCopy(E, RValue::getAggregate(Src.getAddress(),
238                                            Src.isVolatileQualified()),
239                    Ignore);
240}
241
242//===----------------------------------------------------------------------===//
243//                            Visitor Methods
244//===----------------------------------------------------------------------===//
245
246void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
247  EmitFinalDestCopy(e, CGF.getOpaqueLValueMapping(e));
248}
249
250void AggExprEmitter::VisitCastExpr(CastExpr *E) {
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    if (Dest.isIgnored()) break;
268
269    // GCC union extension
270    QualType Ty = E->getSubExpr()->getType();
271    QualType PtrTy = CGF.getContext().getPointerType(Ty);
272    llvm::Value *CastPtr = Builder.CreateBitCast(Dest.getAddr(),
273                                                 CGF.ConvertType(PtrTy));
274    EmitInitializationToLValue(E->getSubExpr(),
275                               CGF.MakeAddrLValue(CastPtr, Ty));
276    break;
277  }
278
279  case CK_DerivedToBase:
280  case CK_BaseToDerived:
281  case CK_UncheckedDerivedToBase: {
282    assert(0 && "cannot perform hierarchy conversion in EmitAggExpr: "
283                "should have been unpacked before we got here");
284    break;
285  }
286
287  case CK_GetObjCProperty: {
288    LValue LV = CGF.EmitLValue(E->getSubExpr());
289    assert(LV.isPropertyRef());
290    RValue RV = CGF.EmitLoadOfPropertyRefLValue(LV, getReturnValueSlot());
291    EmitGCMove(E, RV);
292    break;
293  }
294
295  case CK_LValueToRValue: // hope for downstream optimization
296  case CK_NoOp:
297  case CK_UserDefinedConversion:
298  case CK_ConstructorConversion:
299    assert(CGF.getContext().hasSameUnqualifiedType(E->getSubExpr()->getType(),
300                                                   E->getType()) &&
301           "Implicit cast types must be compatible");
302    Visit(E->getSubExpr());
303    break;
304
305  case CK_LValueBitCast:
306    llvm_unreachable("should not be emitting lvalue bitcast as rvalue");
307    break;
308
309  case CK_Dependent:
310  case CK_BitCast:
311  case CK_ArrayToPointerDecay:
312  case CK_FunctionToPointerDecay:
313  case CK_NullToPointer:
314  case CK_NullToMemberPointer:
315  case CK_BaseToDerivedMemberPointer:
316  case CK_DerivedToBaseMemberPointer:
317  case CK_MemberPointerToBoolean:
318  case CK_IntegralToPointer:
319  case CK_PointerToIntegral:
320  case CK_PointerToBoolean:
321  case CK_ToVoid:
322  case CK_VectorSplat:
323  case CK_IntegralCast:
324  case CK_IntegralToBoolean:
325  case CK_IntegralToFloating:
326  case CK_FloatingToIntegral:
327  case CK_FloatingToBoolean:
328  case CK_FloatingCast:
329  case CK_AnyPointerToObjCPointerCast:
330  case CK_AnyPointerToBlockPointerCast:
331  case CK_ObjCObjectLValueCast:
332  case CK_FloatingRealToComplex:
333  case CK_FloatingComplexToReal:
334  case CK_FloatingComplexToBoolean:
335  case CK_FloatingComplexCast:
336  case CK_FloatingComplexToIntegralComplex:
337  case CK_IntegralRealToComplex:
338  case CK_IntegralComplexToReal:
339  case CK_IntegralComplexToBoolean:
340  case CK_IntegralComplexCast:
341  case CK_IntegralComplexToFloatingComplex:
342  case CK_ObjCProduceObject:
343  case CK_ObjCConsumeObject:
344    llvm_unreachable("cast kind invalid for aggregate types");
345  }
346}
347
348void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
349  if (E->getCallReturnType()->isReferenceType()) {
350    EmitAggLoadOfLValue(E);
351    return;
352  }
353
354  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
355  EmitGCMove(E, RV);
356}
357
358void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
359  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
360  EmitGCMove(E, RV);
361}
362
363void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
364  llvm_unreachable("direct property access not surrounded by "
365                   "lvalue-to-rvalue cast");
366}
367
368void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
369  CGF.EmitIgnoredExpr(E->getLHS());
370  Visit(E->getRHS());
371}
372
373void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
374  CodeGenFunction::StmtExprEvaluation eval(CGF);
375  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
376}
377
378void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
379  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
380    VisitPointerToDataMemberBinaryOperator(E);
381  else
382    CGF.ErrorUnsupported(E, "aggregate binary expression");
383}
384
385void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
386                                                    const BinaryOperator *E) {
387  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
388  EmitFinalDestCopy(E, LV);
389}
390
391void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
392  // For an assignment to work, the value on the right has
393  // to be compatible with the value on the left.
394  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
395                                                 E->getRHS()->getType())
396         && "Invalid assignment");
397
398  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
399    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
400      if (VD->hasAttr<BlocksAttr>() &&
401          E->getRHS()->HasSideEffects(CGF.getContext())) {
402        // When __block variable on LHS, the RHS must be evaluated first
403        // as it may change the 'forwarding' field via call to Block_copy.
404        LValue RHS = CGF.EmitLValue(E->getRHS());
405        LValue LHS = CGF.EmitLValue(E->getLHS());
406        bool GCollection = false;
407        if (CGF.getContext().getLangOptions().getGCMode())
408          GCollection = TypeRequiresGCollection(E->getLHS()->getType());
409        Dest = AggValueSlot::forLValue(LHS, true, GCollection);
410        EmitFinalDestCopy(E, RHS, true);
411        return;
412      }
413
414  LValue LHS = CGF.EmitLValue(E->getLHS());
415
416  // We have to special case property setters, otherwise we must have
417  // a simple lvalue (no aggregates inside vectors, bitfields).
418  if (LHS.isPropertyRef()) {
419    const ObjCPropertyRefExpr *RE = LHS.getPropertyRefExpr();
420    QualType ArgType = RE->getSetterArgType();
421    RValue Src;
422    if (ArgType->isReferenceType())
423      Src = CGF.EmitReferenceBindingToExpr(E->getRHS(), 0);
424    else {
425      AggValueSlot Slot = EnsureSlot(E->getRHS()->getType());
426      CGF.EmitAggExpr(E->getRHS(), Slot);
427      Src = Slot.asRValue();
428    }
429    CGF.EmitStoreThroughPropertyRefLValue(Src, LHS);
430  } else {
431    bool GCollection = false;
432    if (CGF.getContext().getLangOptions().getGCMode())
433      GCollection = TypeRequiresGCollection(E->getLHS()->getType());
434
435    // Codegen the RHS so that it stores directly into the LHS.
436    AggValueSlot LHSSlot = AggValueSlot::forLValue(LHS, true,
437                                                   GCollection);
438    CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
439    EmitFinalDestCopy(E, LHS, true);
440  }
441}
442
443void AggExprEmitter::
444VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
445  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
446  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
447  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
448
449  // Bind the common expression if necessary.
450  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
451
452  CodeGenFunction::ConditionalEvaluation eval(CGF);
453  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
454
455  // Save whether the destination's lifetime is externally managed.
456  bool DestLifetimeManaged = Dest.isLifetimeExternallyManaged();
457
458  eval.begin(CGF);
459  CGF.EmitBlock(LHSBlock);
460  Visit(E->getTrueExpr());
461  eval.end(CGF);
462
463  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
464  CGF.Builder.CreateBr(ContBlock);
465
466  // If the result of an agg expression is unused, then the emission
467  // of the LHS might need to create a destination slot.  That's fine
468  // with us, and we can safely emit the RHS into the same slot, but
469  // we shouldn't claim that its lifetime is externally managed.
470  Dest.setLifetimeExternallyManaged(DestLifetimeManaged);
471
472  eval.begin(CGF);
473  CGF.EmitBlock(RHSBlock);
474  Visit(E->getFalseExpr());
475  eval.end(CGF);
476
477  CGF.EmitBlock(ContBlock);
478}
479
480void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
481  Visit(CE->getChosenSubExpr(CGF.getContext()));
482}
483
484void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
485  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
486  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
487
488  if (!ArgPtr) {
489    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
490    return;
491  }
492
493  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
494}
495
496void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
497  // Ensure that we have a slot, but if we already do, remember
498  // whether its lifetime was externally managed.
499  bool WasManaged = Dest.isLifetimeExternallyManaged();
500  Dest = EnsureSlot(E->getType());
501  Dest.setLifetimeExternallyManaged();
502
503  Visit(E->getSubExpr());
504
505  // Set up the temporary's destructor if its lifetime wasn't already
506  // being managed.
507  if (!WasManaged)
508    CGF.EmitCXXTemporary(E->getTemporary(), Dest.getAddr());
509}
510
511void
512AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
513  AggValueSlot Slot = EnsureSlot(E->getType());
514  CGF.EmitCXXConstructExpr(E, Slot);
515}
516
517void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
518  CGF.EmitExprWithCleanups(E, Dest);
519}
520
521void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
522  QualType T = E->getType();
523  AggValueSlot Slot = EnsureSlot(T);
524  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
525}
526
527void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
528  QualType T = E->getType();
529  AggValueSlot Slot = EnsureSlot(T);
530  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T));
531}
532
533/// isSimpleZero - If emitting this value will obviously just cause a store of
534/// zero to memory, return true.  This can return false if uncertain, so it just
535/// handles simple cases.
536static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
537  E = E->IgnoreParens();
538
539  // 0
540  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
541    return IL->getValue() == 0;
542  // +0.0
543  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
544    return FL->getValue().isPosZero();
545  // int()
546  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
547      CGF.getTypes().isZeroInitializable(E->getType()))
548    return true;
549  // (int*)0 - Null pointer expressions.
550  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
551    return ICE->getCastKind() == CK_NullToPointer;
552  // '\0'
553  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
554    return CL->getValue() == 0;
555
556  // Otherwise, hard case: conservatively return false.
557  return false;
558}
559
560
561void
562AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
563  QualType type = LV.getType();
564  // FIXME: Ignore result?
565  // FIXME: Are initializers affected by volatile?
566  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
567    // Storing "i32 0" to a zero'd memory location is a noop.
568  } else if (isa<ImplicitValueInitExpr>(E)) {
569    EmitNullInitializationToLValue(LV);
570  } else if (type->isReferenceType()) {
571    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
572    CGF.EmitStoreThroughLValue(RV, LV, type);
573  } else if (type->isAnyComplexType()) {
574    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
575  } else if (CGF.hasAggregateLLVMType(type)) {
576    CGF.EmitAggExpr(E, AggValueSlot::forLValue(LV, true, false,
577                                               Dest.isZeroed()));
578  } else if (LV.isSimple()) {
579    CGF.EmitScalarInit(E, /*D=*/0, LV, /*Captured=*/false);
580  } else {
581    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV, type);
582  }
583}
584
585void AggExprEmitter::EmitNullInitializationToLValue(LValue lv) {
586  QualType type = lv.getType();
587
588  // If the destination slot is already zeroed out before the aggregate is
589  // copied into it, we don't have to emit any zeros here.
590  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(type))
591    return;
592
593  if (!CGF.hasAggregateLLVMType(type)) {
594    // For non-aggregates, we can store zero
595    llvm::Value *null = llvm::Constant::getNullValue(CGF.ConvertType(type));
596    CGF.EmitStoreThroughLValue(RValue::get(null), lv, type);
597  } else {
598    // There's a potential optimization opportunity in combining
599    // memsets; that would be easy for arrays, but relatively
600    // difficult for structures with the current code.
601    CGF.EmitNullInitialization(lv.getAddress(), lv.getType());
602  }
603}
604
605void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
606#if 0
607  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
608  // (Length of globals? Chunks of zeroed-out space?).
609  //
610  // If we can, prefer a copy from a global; this is a lot less code for long
611  // globals, and it's easier for the current optimizers to analyze.
612  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
613    llvm::GlobalVariable* GV =
614    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
615                             llvm::GlobalValue::InternalLinkage, C, "");
616    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
617    return;
618  }
619#endif
620  if (E->hadArrayRangeDesignator())
621    CGF.ErrorUnsupported(E, "GNU array range designator extension");
622
623  llvm::Value *DestPtr = Dest.getAddr();
624
625  // Handle initialization of an array.
626  if (E->getType()->isArrayType()) {
627    const llvm::PointerType *APType =
628      cast<llvm::PointerType>(DestPtr->getType());
629    const llvm::ArrayType *AType =
630      cast<llvm::ArrayType>(APType->getElementType());
631
632    uint64_t NumInitElements = E->getNumInits();
633
634    if (E->getNumInits() > 0) {
635      QualType T1 = E->getType();
636      QualType T2 = E->getInit(0)->getType();
637      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
638        EmitAggLoadOfLValue(E->getInit(0));
639        return;
640      }
641    }
642
643    uint64_t NumArrayElements = AType->getNumElements();
644    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
645    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
646    ElementType = CGF.getContext().getQualifiedType(ElementType,
647                                                    Dest.getQualifiers());
648
649    bool hasNonTrivialCXXConstructor = false;
650    if (CGF.getContext().getLangOptions().CPlusPlus)
651      if (const RecordType *RT = CGF.getContext()
652                        .getBaseElementType(ElementType)->getAs<RecordType>()) {
653        const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
654        hasNonTrivialCXXConstructor = !RD->hasTrivialDefaultConstructor();
655      }
656
657    for (uint64_t i = 0; i != NumArrayElements; ++i) {
658      // If we're done emitting initializers and the destination is known-zeroed
659      // then we're done.
660      if (i == NumInitElements &&
661          Dest.isZeroed() &&
662          CGF.getTypes().isZeroInitializable(ElementType) &&
663          !hasNonTrivialCXXConstructor)
664        break;
665
666      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
667      LValue LV = CGF.MakeAddrLValue(NextVal, ElementType);
668
669      if (i < NumInitElements)
670        EmitInitializationToLValue(E->getInit(i), LV);
671      else if (Expr *filler = E->getArrayFiller())
672        EmitInitializationToLValue(filler, LV);
673      else
674        EmitNullInitializationToLValue(LV);
675
676      // If the GEP didn't get used because of a dead zero init or something
677      // else, clean it up for -O0 builds and general tidiness.
678      if (llvm::GetElementPtrInst *GEP =
679            dyn_cast<llvm::GetElementPtrInst>(NextVal))
680        if (GEP->use_empty())
681          GEP->eraseFromParent();
682    }
683    return;
684  }
685
686  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
687
688  // Do struct initialization; this code just sets each individual member
689  // to the approprate value.  This makes bitfield support automatic;
690  // the disadvantage is that the generated code is more difficult for
691  // the optimizer, especially with bitfields.
692  unsigned NumInitElements = E->getNumInits();
693  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
694
695  if (E->getType()->isUnionType()) {
696    // Only initialize one field of a union. The field itself is
697    // specified by the initializer list.
698    if (!E->getInitializedFieldInUnion()) {
699      // Empty union; we have nothing to do.
700
701#ifndef NDEBUG
702      // Make sure that it's really an empty and not a failure of
703      // semantic analysis.
704      for (RecordDecl::field_iterator Field = SD->field_begin(),
705                                   FieldEnd = SD->field_end();
706           Field != FieldEnd; ++Field)
707        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
708#endif
709      return;
710    }
711
712    // FIXME: volatility
713    FieldDecl *Field = E->getInitializedFieldInUnion();
714
715    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
716    if (NumInitElements) {
717      // Store the initializer into the field
718      EmitInitializationToLValue(E->getInit(0), FieldLoc);
719    } else {
720      // Default-initialize to null.
721      EmitNullInitializationToLValue(FieldLoc);
722    }
723
724    return;
725  }
726
727  // Here we iterate over the fields; this makes it simpler to both
728  // default-initialize fields and skip over unnamed fields.
729  unsigned CurInitVal = 0;
730  for (RecordDecl::field_iterator Field = SD->field_begin(),
731                               FieldEnd = SD->field_end();
732       Field != FieldEnd; ++Field) {
733    // We're done once we hit the flexible array member
734    if (Field->getType()->isIncompleteArrayType())
735      break;
736
737    if (Field->isUnnamedBitfield())
738      continue;
739
740    // Don't emit GEP before a noop store of zero.
741    if (CurInitVal == NumInitElements && Dest.isZeroed() &&
742        CGF.getTypes().isZeroInitializable(E->getType()))
743      break;
744
745    // FIXME: volatility
746    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, *Field, 0);
747    // We never generate write-barries for initialized fields.
748    FieldLoc.setNonGC(true);
749
750    if (CurInitVal < NumInitElements) {
751      // Store the initializer into the field.
752      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc);
753    } else {
754      // We're out of initalizers; default-initialize to null
755      EmitNullInitializationToLValue(FieldLoc);
756    }
757
758    // If the GEP didn't get used because of a dead zero init or something
759    // else, clean it up for -O0 builds and general tidiness.
760    if (FieldLoc.isSimple())
761      if (llvm::GetElementPtrInst *GEP =
762            dyn_cast<llvm::GetElementPtrInst>(FieldLoc.getAddress()))
763        if (GEP->use_empty())
764          GEP->eraseFromParent();
765  }
766}
767
768//===----------------------------------------------------------------------===//
769//                        Entry Points into this File
770//===----------------------------------------------------------------------===//
771
772/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
773/// non-zero bytes that will be stored when outputting the initializer for the
774/// specified initializer expression.
775static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
776  E = E->IgnoreParens();
777
778  // 0 and 0.0 won't require any non-zero stores!
779  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
780
781  // If this is an initlist expr, sum up the size of sizes of the (present)
782  // elements.  If this is something weird, assume the whole thing is non-zero.
783  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
784  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
785    return CGF.getContext().getTypeSizeInChars(E->getType());
786
787  // InitListExprs for structs have to be handled carefully.  If there are
788  // reference members, we need to consider the size of the reference, not the
789  // referencee.  InitListExprs for unions and arrays can't have references.
790  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
791    if (!RT->isUnionType()) {
792      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
793      CharUnits NumNonZeroBytes = CharUnits::Zero();
794
795      unsigned ILEElement = 0;
796      for (RecordDecl::field_iterator Field = SD->field_begin(),
797           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
798        // We're done once we hit the flexible array member or run out of
799        // InitListExpr elements.
800        if (Field->getType()->isIncompleteArrayType() ||
801            ILEElement == ILE->getNumInits())
802          break;
803        if (Field->isUnnamedBitfield())
804          continue;
805
806        const Expr *E = ILE->getInit(ILEElement++);
807
808        // Reference values are always non-null and have the width of a pointer.
809        if (Field->getType()->isReferenceType())
810          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
811              CGF.getContext().Target.getPointerWidth(0));
812        else
813          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
814      }
815
816      return NumNonZeroBytes;
817    }
818  }
819
820
821  CharUnits NumNonZeroBytes = CharUnits::Zero();
822  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
823    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
824  return NumNonZeroBytes;
825}
826
827/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
828/// zeros in it, emit a memset and avoid storing the individual zeros.
829///
830static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
831                                     CodeGenFunction &CGF) {
832  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
833  // volatile stores.
834  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
835
836  // C++ objects with a user-declared constructor don't need zero'ing.
837  if (CGF.getContext().getLangOptions().CPlusPlus)
838    if (const RecordType *RT = CGF.getContext()
839                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
840      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
841      if (RD->hasUserDeclaredConstructor())
842        return;
843    }
844
845  // If the type is 16-bytes or smaller, prefer individual stores over memset.
846  std::pair<CharUnits, CharUnits> TypeInfo =
847    CGF.getContext().getTypeInfoInChars(E->getType());
848  if (TypeInfo.first <= CharUnits::fromQuantity(16))
849    return;
850
851  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
852  // we prefer to emit memset + individual stores for the rest.
853  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
854  if (NumNonZeroBytes*4 > TypeInfo.first)
855    return;
856
857  // Okay, it seems like a good idea to use an initial memset, emit the call.
858  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
859  CharUnits Align = TypeInfo.second;
860
861  llvm::Value *Loc = Slot.getAddr();
862  const llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
863
864  Loc = CGF.Builder.CreateBitCast(Loc, BP);
865  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
866                           Align.getQuantity(), false);
867
868  // Tell the AggExprEmitter that the slot is known zero.
869  Slot.setZeroed();
870}
871
872
873
874
875/// EmitAggExpr - Emit the computation of the specified expression of aggregate
876/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
877/// the value of the aggregate expression is not needed.  If VolatileDest is
878/// true, DestPtr cannot be 0.
879///
880/// \param IsInitializer - true if this evaluation is initializing an
881/// object whose lifetime is already being managed.
882void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
883                                  bool IgnoreResult) {
884  assert(E && hasAggregateLLVMType(E->getType()) &&
885         "Invalid aggregate expression to emit");
886  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
887         "slot has bits but no address");
888
889  // Optimize the slot if possible.
890  CheckAggExprForMemSetUse(Slot, E, *this);
891
892  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
893}
894
895LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
896  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
897  llvm::Value *Temp = CreateMemTemp(E->getType());
898  LValue LV = MakeAddrLValue(Temp, E->getType());
899  EmitAggExpr(E, AggValueSlot::forLValue(LV, false));
900  return LV;
901}
902
903void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
904                                        llvm::Value *SrcPtr, QualType Ty,
905                                        bool isVolatile) {
906  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
907
908  if (getContext().getLangOptions().CPlusPlus) {
909    if (const RecordType *RT = Ty->getAs<RecordType>()) {
910      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
911      assert((Record->hasTrivialCopyConstructor() ||
912              Record->hasTrivialCopyAssignment()) &&
913             "Trying to aggregate-copy a type without a trivial copy "
914             "constructor or assignment operator");
915      // Ignore empty classes in C++.
916      if (Record->isEmpty())
917        return;
918    }
919  }
920
921  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
922  // C99 6.5.16.1p3, which states "If the value being stored in an object is
923  // read from another object that overlaps in anyway the storage of the first
924  // object, then the overlap shall be exact and the two objects shall have
925  // qualified or unqualified versions of a compatible type."
926  //
927  // memcpy is not defined if the source and destination pointers are exactly
928  // equal, but other compilers do this optimization, and almost every memcpy
929  // implementation handles this case safely.  If there is a libc that does not
930  // safely handle this, we can add a target hook.
931
932  // Get size and alignment info for this aggregate.
933  std::pair<CharUnits, CharUnits> TypeInfo =
934    getContext().getTypeInfoInChars(Ty);
935
936  // FIXME: Handle variable sized types.
937
938  // FIXME: If we have a volatile struct, the optimizer can remove what might
939  // appear to be `extra' memory ops:
940  //
941  // volatile struct { int i; } a, b;
942  //
943  // int main() {
944  //   a = b;
945  //   a = b;
946  // }
947  //
948  // we need to use a different call here.  We use isVolatile to indicate when
949  // either the source or the destination is volatile.
950
951  const llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
952  const llvm::Type *DBP =
953    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
954  DestPtr = Builder.CreateBitCast(DestPtr, DBP, "tmp");
955
956  const llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
957  const llvm::Type *SBP =
958    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
959  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP, "tmp");
960
961  // Don't do any of the memmove_collectable tests if GC isn't set.
962  if (CGM.getLangOptions().getGCMode() == LangOptions::NonGC) {
963    // fall through
964  } else if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
965    RecordDecl *Record = RecordTy->getDecl();
966    if (Record->hasObjectMember()) {
967      CharUnits size = TypeInfo.first;
968      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
969      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
970      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
971                                                    SizeVal);
972      return;
973    }
974  } else if (Ty->isArrayType()) {
975    QualType BaseType = getContext().getBaseElementType(Ty);
976    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
977      if (RecordTy->getDecl()->hasObjectMember()) {
978        CharUnits size = TypeInfo.first;
979        const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
980        llvm::Value *SizeVal =
981          llvm::ConstantInt::get(SizeTy, size.getQuantity());
982        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
983                                                      SizeVal);
984        return;
985      }
986    }
987  }
988
989  Builder.CreateMemCpy(DestPtr, SrcPtr,
990                       llvm::ConstantInt::get(IntPtrTy,
991                                              TypeInfo.first.getQuantity()),
992                       TypeInfo.second.getQuantity(), isVolatile);
993}
994