CGExprAgg.cpp revision 3b4d490b09347e0b68ec0511ddfae79dfaba77a6 
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, QualType T);
140  void EmitNullInitializationToLValue(LValue Address, QualType T);
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(), CGF.MakeAddrLValue(CastPtr, Ty),
275                               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    llvm_unreachable("cast kind invalid for aggregate types");
343  }
344}
345
346void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
347  if (E->getCallReturnType()->isReferenceType()) {
348    EmitAggLoadOfLValue(E);
349    return;
350  }
351
352  RValue RV = CGF.EmitCallExpr(E, getReturnValueSlot());
353  EmitGCMove(E, RV);
354}
355
356void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
357  RValue RV = CGF.EmitObjCMessageExpr(E, getReturnValueSlot());
358  EmitGCMove(E, RV);
359}
360
361void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
362  llvm_unreachable("direct property access not surrounded by "
363                   "lvalue-to-rvalue cast");
364}
365
366void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
367  CGF.EmitIgnoredExpr(E->getLHS());
368  Visit(E->getRHS());
369}
370
371void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
372  CodeGenFunction::StmtExprEvaluation eval(CGF);
373  CGF.EmitCompoundStmt(*E->getSubStmt(), true, Dest);
374}
375
376void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
377  if (E->getOpcode() == BO_PtrMemD || E->getOpcode() == BO_PtrMemI)
378    VisitPointerToDataMemberBinaryOperator(E);
379  else
380    CGF.ErrorUnsupported(E, "aggregate binary expression");
381}
382
383void AggExprEmitter::VisitPointerToDataMemberBinaryOperator(
384                                                    const BinaryOperator *E) {
385  LValue LV = CGF.EmitPointerToDataMemberBinaryExpr(E);
386  EmitFinalDestCopy(E, LV);
387}
388
389void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
390  // For an assignment to work, the value on the right has
391  // to be compatible with the value on the left.
392  assert(CGF.getContext().hasSameUnqualifiedType(E->getLHS()->getType(),
393                                                 E->getRHS()->getType())
394         && "Invalid assignment");
395
396  // FIXME:  __block variables need the RHS evaluated first!
397  LValue LHS = CGF.EmitLValue(E->getLHS());
398
399  // We have to special case property setters, otherwise we must have
400  // a simple lvalue (no aggregates inside vectors, bitfields).
401  if (LHS.isPropertyRef()) {
402    const ObjCPropertyRefExpr *RE = LHS.getPropertyRefExpr();
403    QualType ArgType = RE->getSetterArgType();
404    RValue Src;
405    if (ArgType->isReferenceType())
406      Src = CGF.EmitReferenceBindingToExpr(E->getRHS(), 0);
407    else {
408      AggValueSlot Slot = EnsureSlot(E->getRHS()->getType());
409      CGF.EmitAggExpr(E->getRHS(), Slot);
410      Src = Slot.asRValue();
411    }
412    CGF.EmitStoreThroughPropertyRefLValue(Src, LHS);
413  } else {
414    bool GCollection = false;
415    if (CGF.getContext().getLangOptions().getGCMode())
416      GCollection = TypeRequiresGCollection(E->getLHS()->getType());
417
418    // Codegen the RHS so that it stores directly into the LHS.
419    AggValueSlot LHSSlot = AggValueSlot::forLValue(LHS, true,
420                                                   GCollection);
421    CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
422    EmitFinalDestCopy(E, LHS, true);
423  }
424}
425
426void AggExprEmitter::
427VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
428  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
429  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
430  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
431
432  // Bind the common expression if necessary.
433  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
434
435  CodeGenFunction::ConditionalEvaluation eval(CGF);
436  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
437
438  // Save whether the destination's lifetime is externally managed.
439  bool DestLifetimeManaged = Dest.isLifetimeExternallyManaged();
440
441  eval.begin(CGF);
442  CGF.EmitBlock(LHSBlock);
443  Visit(E->getTrueExpr());
444  eval.end(CGF);
445
446  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
447  CGF.Builder.CreateBr(ContBlock);
448
449  // If the result of an agg expression is unused, then the emission
450  // of the LHS might need to create a destination slot.  That's fine
451  // with us, and we can safely emit the RHS into the same slot, but
452  // we shouldn't claim that its lifetime is externally managed.
453  Dest.setLifetimeExternallyManaged(DestLifetimeManaged);
454
455  eval.begin(CGF);
456  CGF.EmitBlock(RHSBlock);
457  Visit(E->getFalseExpr());
458  eval.end(CGF);
459
460  CGF.EmitBlock(ContBlock);
461}
462
463void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
464  Visit(CE->getChosenSubExpr(CGF.getContext()));
465}
466
467void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
468  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
469  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
470
471  if (!ArgPtr) {
472    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
473    return;
474  }
475
476  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
477}
478
479void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
480  // Ensure that we have a slot, but if we already do, remember
481  // whether its lifetime was externally managed.
482  bool WasManaged = Dest.isLifetimeExternallyManaged();
483  Dest = EnsureSlot(E->getType());
484  Dest.setLifetimeExternallyManaged();
485
486  Visit(E->getSubExpr());
487
488  // Set up the temporary's destructor if its lifetime wasn't already
489  // being managed.
490  if (!WasManaged)
491    CGF.EmitCXXTemporary(E->getTemporary(), Dest.getAddr());
492}
493
494void
495AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
496  AggValueSlot Slot = EnsureSlot(E->getType());
497  CGF.EmitCXXConstructExpr(E, Slot);
498}
499
500void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
501  CGF.EmitExprWithCleanups(E, Dest);
502}
503
504void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
505  QualType T = E->getType();
506  AggValueSlot Slot = EnsureSlot(T);
507  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
508}
509
510void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
511  QualType T = E->getType();
512  AggValueSlot Slot = EnsureSlot(T);
513  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
514}
515
516/// isSimpleZero - If emitting this value will obviously just cause a store of
517/// zero to memory, return true.  This can return false if uncertain, so it just
518/// handles simple cases.
519static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
520  E = E->IgnoreParens();
521
522  // 0
523  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
524    return IL->getValue() == 0;
525  // +0.0
526  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
527    return FL->getValue().isPosZero();
528  // int()
529  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
530      CGF.getTypes().isZeroInitializable(E->getType()))
531    return true;
532  // (int*)0 - Null pointer expressions.
533  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
534    return ICE->getCastKind() == CK_NullToPointer;
535  // '\0'
536  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
537    return CL->getValue() == 0;
538
539  // Otherwise, hard case: conservatively return false.
540  return false;
541}
542
543
544void
545AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV, QualType T) {
546  // FIXME: Ignore result?
547  // FIXME: Are initializers affected by volatile?
548  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
549    // Storing "i32 0" to a zero'd memory location is a noop.
550  } else if (isa<ImplicitValueInitExpr>(E)) {
551    EmitNullInitializationToLValue(LV, T);
552  } else if (T->isReferenceType()) {
553    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
554    CGF.EmitStoreThroughLValue(RV, LV, T);
555  } else if (T->isAnyComplexType()) {
556    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
557  } else if (CGF.hasAggregateLLVMType(T)) {
558    CGF.EmitAggExpr(E, AggValueSlot::forAddr(LV.getAddress(), false, true,
559                                             false, Dest.isZeroed()));
560  } else {
561    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV, T);
562  }
563}
564
565void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
566  // If the destination slot is already zeroed out before the aggregate is
567  // copied into it, we don't have to emit any zeros here.
568  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(T))
569    return;
570
571  if (!CGF.hasAggregateLLVMType(T)) {
572    // For non-aggregates, we can store zero
573    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
574    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
575  } else {
576    // There's a potential optimization opportunity in combining
577    // memsets; that would be easy for arrays, but relatively
578    // difficult for structures with the current code.
579    CGF.EmitNullInitialization(LV.getAddress(), T);
580  }
581}
582
583void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
584#if 0
585  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
586  // (Length of globals? Chunks of zeroed-out space?).
587  //
588  // If we can, prefer a copy from a global; this is a lot less code for long
589  // globals, and it's easier for the current optimizers to analyze.
590  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
591    llvm::GlobalVariable* GV =
592    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
593                             llvm::GlobalValue::InternalLinkage, C, "");
594    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
595    return;
596  }
597#endif
598  if (E->hadArrayRangeDesignator())
599    CGF.ErrorUnsupported(E, "GNU array range designator extension");
600
601  llvm::Value *DestPtr = Dest.getAddr();
602
603  // Handle initialization of an array.
604  if (E->getType()->isArrayType()) {
605    const llvm::PointerType *APType =
606      cast<llvm::PointerType>(DestPtr->getType());
607    const llvm::ArrayType *AType =
608      cast<llvm::ArrayType>(APType->getElementType());
609
610    uint64_t NumInitElements = E->getNumInits();
611
612    if (E->getNumInits() > 0) {
613      QualType T1 = E->getType();
614      QualType T2 = E->getInit(0)->getType();
615      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
616        EmitAggLoadOfLValue(E->getInit(0));
617        return;
618      }
619    }
620
621    uint64_t NumArrayElements = AType->getNumElements();
622    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
623    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
624
625    bool hasNonTrivialCXXConstructor = false;
626    if (CGF.getContext().getLangOptions().CPlusPlus)
627      if (const RecordType *RT = ElementType->getAs<RecordType>()) {
628        const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
629        hasNonTrivialCXXConstructor = !RD->hasTrivialConstructor();
630      }
631
632    // FIXME: were we intentionally ignoring address spaces and GC attributes?
633
634    for (uint64_t i = 0; i != NumArrayElements; ++i) {
635      // If we're done emitting initializers and the destination is known-zeroed
636      // then we're done.
637      if (i == NumInitElements &&
638          Dest.isZeroed() &&
639          CGF.getTypes().isZeroInitializable(ElementType) &&
640          !hasNonTrivialCXXConstructor)
641        break;
642
643      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
644      LValue LV = CGF.MakeAddrLValue(NextVal, ElementType);
645
646      if (i < NumInitElements)
647        EmitInitializationToLValue(E->getInit(i), LV, ElementType);
648      else if (Expr *filler = E->getArrayFiller())
649        EmitInitializationToLValue(filler, LV, ElementType);
650      else
651        EmitNullInitializationToLValue(LV, ElementType);
652
653      // If the GEP didn't get used because of a dead zero init or something
654      // else, clean it up for -O0 builds and general tidiness.
655      if (llvm::GetElementPtrInst *GEP =
656            dyn_cast<llvm::GetElementPtrInst>(NextVal))
657        if (GEP->use_empty())
658          GEP->eraseFromParent();
659    }
660    return;
661  }
662
663  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
664
665  // Do struct initialization; this code just sets each individual member
666  // to the approprate value.  This makes bitfield support automatic;
667  // the disadvantage is that the generated code is more difficult for
668  // the optimizer, especially with bitfields.
669  unsigned NumInitElements = E->getNumInits();
670  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
671
672  if (E->getType()->isUnionType()) {
673    // Only initialize one field of a union. The field itself is
674    // specified by the initializer list.
675    if (!E->getInitializedFieldInUnion()) {
676      // Empty union; we have nothing to do.
677
678#ifndef NDEBUG
679      // Make sure that it's really an empty and not a failure of
680      // semantic analysis.
681      for (RecordDecl::field_iterator Field = SD->field_begin(),
682                                   FieldEnd = SD->field_end();
683           Field != FieldEnd; ++Field)
684        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
685#endif
686      return;
687    }
688
689    // FIXME: volatility
690    FieldDecl *Field = E->getInitializedFieldInUnion();
691
692    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
693    if (NumInitElements) {
694      // Store the initializer into the field
695      EmitInitializationToLValue(E->getInit(0), FieldLoc, Field->getType());
696    } else {
697      // Default-initialize to null.
698      EmitNullInitializationToLValue(FieldLoc, Field->getType());
699    }
700
701    return;
702  }
703
704  // Here we iterate over the fields; this makes it simpler to both
705  // default-initialize fields and skip over unnamed fields.
706  unsigned CurInitVal = 0;
707  for (RecordDecl::field_iterator Field = SD->field_begin(),
708                               FieldEnd = SD->field_end();
709       Field != FieldEnd; ++Field) {
710    // We're done once we hit the flexible array member
711    if (Field->getType()->isIncompleteArrayType())
712      break;
713
714    if (Field->isUnnamedBitfield())
715      continue;
716
717    // Don't emit GEP before a noop store of zero.
718    if (CurInitVal == NumInitElements && Dest.isZeroed() &&
719        CGF.getTypes().isZeroInitializable(E->getType()))
720      break;
721
722    // FIXME: volatility
723    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, *Field, 0);
724    // We never generate write-barries for initialized fields.
725    FieldLoc.setNonGC(true);
726
727    if (CurInitVal < NumInitElements) {
728      // Store the initializer into the field.
729      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc,
730                                 Field->getType());
731    } else {
732      // We're out of initalizers; default-initialize to null
733      EmitNullInitializationToLValue(FieldLoc, Field->getType());
734    }
735
736    // If the GEP didn't get used because of a dead zero init or something
737    // else, clean it up for -O0 builds and general tidiness.
738    if (FieldLoc.isSimple())
739      if (llvm::GetElementPtrInst *GEP =
740            dyn_cast<llvm::GetElementPtrInst>(FieldLoc.getAddress()))
741        if (GEP->use_empty())
742          GEP->eraseFromParent();
743  }
744}
745
746//===----------------------------------------------------------------------===//
747//                        Entry Points into this File
748//===----------------------------------------------------------------------===//
749
750/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
751/// non-zero bytes that will be stored when outputting the initializer for the
752/// specified initializer expression.
753static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
754  E = E->IgnoreParens();
755
756  // 0 and 0.0 won't require any non-zero stores!
757  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
758
759  // If this is an initlist expr, sum up the size of sizes of the (present)
760  // elements.  If this is something weird, assume the whole thing is non-zero.
761  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
762  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
763    return CGF.getContext().getTypeSizeInChars(E->getType());
764
765  // InitListExprs for structs have to be handled carefully.  If there are
766  // reference members, we need to consider the size of the reference, not the
767  // referencee.  InitListExprs for unions and arrays can't have references.
768  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
769    if (!RT->isUnionType()) {
770      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
771      CharUnits NumNonZeroBytes = CharUnits::Zero();
772
773      unsigned ILEElement = 0;
774      for (RecordDecl::field_iterator Field = SD->field_begin(),
775           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
776        // We're done once we hit the flexible array member or run out of
777        // InitListExpr elements.
778        if (Field->getType()->isIncompleteArrayType() ||
779            ILEElement == ILE->getNumInits())
780          break;
781        if (Field->isUnnamedBitfield())
782          continue;
783
784        const Expr *E = ILE->getInit(ILEElement++);
785
786        // Reference values are always non-null and have the width of a pointer.
787        if (Field->getType()->isReferenceType())
788          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
789              CGF.getContext().Target.getPointerWidth(0));
790        else
791          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
792      }
793
794      return NumNonZeroBytes;
795    }
796  }
797
798
799  CharUnits NumNonZeroBytes = CharUnits::Zero();
800  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
801    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
802  return NumNonZeroBytes;
803}
804
805/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
806/// zeros in it, emit a memset and avoid storing the individual zeros.
807///
808static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
809                                     CodeGenFunction &CGF) {
810  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
811  // volatile stores.
812  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
813
814  // If the type is 16-bytes or smaller, prefer individual stores over memset.
815  std::pair<CharUnits, CharUnits> TypeInfo =
816    CGF.getContext().getTypeInfoInChars(E->getType());
817  if (TypeInfo.first <= CharUnits::fromQuantity(16))
818    return;
819
820  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
821  // we prefer to emit memset + individual stores for the rest.
822  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
823  if (NumNonZeroBytes*4 > TypeInfo.first)
824    return;
825
826  // Okay, it seems like a good idea to use an initial memset, emit the call.
827  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
828  CharUnits Align = TypeInfo.second;
829
830  llvm::Value *Loc = Slot.getAddr();
831  const llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
832
833  Loc = CGF.Builder.CreateBitCast(Loc, BP);
834  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
835                           Align.getQuantity(), false);
836
837  // Tell the AggExprEmitter that the slot is known zero.
838  Slot.setZeroed();
839}
840
841
842
843
844/// EmitAggExpr - Emit the computation of the specified expression of aggregate
845/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
846/// the value of the aggregate expression is not needed.  If VolatileDest is
847/// true, DestPtr cannot be 0.
848///
849/// \param IsInitializer - true if this evaluation is initializing an
850/// object whose lifetime is already being managed.
851//
852// FIXME: Take Qualifiers object.
853void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
854                                  bool IgnoreResult) {
855  assert(E && hasAggregateLLVMType(E->getType()) &&
856         "Invalid aggregate expression to emit");
857  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
858         "slot has bits but no address");
859
860  // Optimize the slot if possible.
861  CheckAggExprForMemSetUse(Slot, E, *this);
862
863  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
864}
865
866LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
867  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
868  llvm::Value *Temp = CreateMemTemp(E->getType());
869  LValue LV = MakeAddrLValue(Temp, E->getType());
870  EmitAggExpr(E, AggValueSlot::forAddr(Temp, LV.isVolatileQualified(), false));
871  return LV;
872}
873
874void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
875                                        llvm::Value *SrcPtr, QualType Ty,
876                                        bool isVolatile) {
877  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
878
879  if (getContext().getLangOptions().CPlusPlus) {
880    if (const RecordType *RT = Ty->getAs<RecordType>()) {
881      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
882      assert((Record->hasTrivialCopyConstructor() ||
883              Record->hasTrivialCopyAssignment()) &&
884             "Trying to aggregate-copy a type without a trivial copy "
885             "constructor or assignment operator");
886      // Ignore empty classes in C++.
887      if (Record->isEmpty())
888        return;
889    }
890  }
891
892  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
893  // C99 6.5.16.1p3, which states "If the value being stored in an object is
894  // read from another object that overlaps in anyway the storage of the first
895  // object, then the overlap shall be exact and the two objects shall have
896  // qualified or unqualified versions of a compatible type."
897  //
898  // memcpy is not defined if the source and destination pointers are exactly
899  // equal, but other compilers do this optimization, and almost every memcpy
900  // implementation handles this case safely.  If there is a libc that does not
901  // safely handle this, we can add a target hook.
902
903  // Get size and alignment info for this aggregate.
904  std::pair<CharUnits, CharUnits> TypeInfo =
905    getContext().getTypeInfoInChars(Ty);
906
907  // FIXME: Handle variable sized types.
908
909  // FIXME: If we have a volatile struct, the optimizer can remove what might
910  // appear to be `extra' memory ops:
911  //
912  // volatile struct { int i; } a, b;
913  //
914  // int main() {
915  //   a = b;
916  //   a = b;
917  // }
918  //
919  // we need to use a different call here.  We use isVolatile to indicate when
920  // either the source or the destination is volatile.
921
922  const llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
923  const llvm::Type *DBP =
924    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
925  DestPtr = Builder.CreateBitCast(DestPtr, DBP, "tmp");
926
927  const llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
928  const llvm::Type *SBP =
929    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
930  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP, "tmp");
931
932  if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
933    RecordDecl *Record = RecordTy->getDecl();
934    if (Record->hasObjectMember()) {
935      CharUnits size = TypeInfo.first;
936      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
937      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
938      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
939                                                    SizeVal);
940      return;
941    }
942  } else if (getContext().getAsArrayType(Ty)) {
943    QualType BaseType = getContext().getBaseElementType(Ty);
944    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
945      if (RecordTy->getDecl()->hasObjectMember()) {
946        CharUnits size = TypeInfo.first;
947        const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
948        llvm::Value *SizeVal =
949          llvm::ConstantInt::get(SizeTy, size.getQuantity());
950        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
951                                                      SizeVal);
952        return;
953      }
954    }
955  }
956
957  Builder.CreateMemCpy(DestPtr, SrcPtr,
958                       llvm::ConstantInt::get(IntPtrTy,
959                                              TypeInfo.first.getQuantity()),
960                       TypeInfo.second.getQuantity(), isVolatile);
961}
962