CGExprAgg.cpp revision 221345 
1181643Skmacy//===--- CGExprAgg.cpp - Emit LLVM Code from Aggregate Expressions --------===//
2181643Skmacy//
3181643Skmacy//                     The LLVM Compiler Infrastructure
4181643Skmacy//
5181643Skmacy// This file is distributed under the University of Illinois Open Source
6181643Skmacy// License. See LICENSE.TXT for details.
7181643Skmacy//
8192003Skmacy//===----------------------------------------------------------------------===//
9192003Skmacy//
10192003Skmacy// This contains code to emit Aggregate Expr nodes as LLVM code.
11192003Skmacy//
12192003Skmacy//===----------------------------------------------------------------------===//
13192003Skmacy
14192003Skmacy#include "CodeGenFunction.h"
15192003Skmacy#include "CodeGenModule.h"
16192003Skmacy#include "CGObjCRuntime.h"
17192003Skmacy#include "clang/AST/ASTContext.h"
18192003Skmacy#include "clang/AST/DeclCXX.h"
19181643Skmacy#include "clang/AST/StmtVisitor.h"
20181643Skmacy#include "llvm/Constants.h"
21181643Skmacy#include "llvm/Function.h"
22181643Skmacy#include "llvm/GlobalVariable.h"
23181643Skmacy#include "llvm/Intrinsics.h"
24181643Skmacyusing namespace clang;
25181643Skmacyusing namespace CodeGen;
26181643Skmacy
27181643Skmacy//===----------------------------------------------------------------------===//
28181643Skmacy//                        Aggregate Expression Emitter
29181643Skmacy//===----------------------------------------------------------------------===//
30181643Skmacy
31181643Skmacynamespace  {
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  if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E->getLHS()))
397    if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl()))
398      if (VD->hasAttr<BlocksAttr>() &&
399          E->getRHS()->HasSideEffects(CGF.getContext())) {
400        // When __block variable on LHS, the RHS must be evaluated first
401        // as it may change the 'forwarding' field via call to Block_copy.
402        LValue RHS = CGF.EmitLValue(E->getRHS());
403        LValue LHS = CGF.EmitLValue(E->getLHS());
404        bool GCollection = false;
405        if (CGF.getContext().getLangOptions().getGCMode())
406          GCollection = TypeRequiresGCollection(E->getLHS()->getType());
407        Dest = AggValueSlot::forLValue(LHS, true, GCollection);
408        EmitFinalDestCopy(E, RHS, true);
409        return;
410      }
411
412  LValue LHS = CGF.EmitLValue(E->getLHS());
413
414  // We have to special case property setters, otherwise we must have
415  // a simple lvalue (no aggregates inside vectors, bitfields).
416  if (LHS.isPropertyRef()) {
417    const ObjCPropertyRefExpr *RE = LHS.getPropertyRefExpr();
418    QualType ArgType = RE->getSetterArgType();
419    RValue Src;
420    if (ArgType->isReferenceType())
421      Src = CGF.EmitReferenceBindingToExpr(E->getRHS(), 0);
422    else {
423      AggValueSlot Slot = EnsureSlot(E->getRHS()->getType());
424      CGF.EmitAggExpr(E->getRHS(), Slot);
425      Src = Slot.asRValue();
426    }
427    CGF.EmitStoreThroughPropertyRefLValue(Src, LHS);
428  } else {
429    bool GCollection = false;
430    if (CGF.getContext().getLangOptions().getGCMode())
431      GCollection = TypeRequiresGCollection(E->getLHS()->getType());
432
433    // Codegen the RHS so that it stores directly into the LHS.
434    AggValueSlot LHSSlot = AggValueSlot::forLValue(LHS, true,
435                                                   GCollection);
436    CGF.EmitAggExpr(E->getRHS(), LHSSlot, false);
437    EmitFinalDestCopy(E, LHS, true);
438  }
439}
440
441void AggExprEmitter::
442VisitAbstractConditionalOperator(const AbstractConditionalOperator *E) {
443  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
444  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
445  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
446
447  // Bind the common expression if necessary.
448  CodeGenFunction::OpaqueValueMapping binding(CGF, E);
449
450  CodeGenFunction::ConditionalEvaluation eval(CGF);
451  CGF.EmitBranchOnBoolExpr(E->getCond(), LHSBlock, RHSBlock);
452
453  // Save whether the destination's lifetime is externally managed.
454  bool DestLifetimeManaged = Dest.isLifetimeExternallyManaged();
455
456  eval.begin(CGF);
457  CGF.EmitBlock(LHSBlock);
458  Visit(E->getTrueExpr());
459  eval.end(CGF);
460
461  assert(CGF.HaveInsertPoint() && "expression evaluation ended with no IP!");
462  CGF.Builder.CreateBr(ContBlock);
463
464  // If the result of an agg expression is unused, then the emission
465  // of the LHS might need to create a destination slot.  That's fine
466  // with us, and we can safely emit the RHS into the same slot, but
467  // we shouldn't claim that its lifetime is externally managed.
468  Dest.setLifetimeExternallyManaged(DestLifetimeManaged);
469
470  eval.begin(CGF);
471  CGF.EmitBlock(RHSBlock);
472  Visit(E->getFalseExpr());
473  eval.end(CGF);
474
475  CGF.EmitBlock(ContBlock);
476}
477
478void AggExprEmitter::VisitChooseExpr(const ChooseExpr *CE) {
479  Visit(CE->getChosenSubExpr(CGF.getContext()));
480}
481
482void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
483  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
484  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
485
486  if (!ArgPtr) {
487    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
488    return;
489  }
490
491  EmitFinalDestCopy(VE, CGF.MakeAddrLValue(ArgPtr, VE->getType()));
492}
493
494void AggExprEmitter::VisitCXXBindTemporaryExpr(CXXBindTemporaryExpr *E) {
495  // Ensure that we have a slot, but if we already do, remember
496  // whether its lifetime was externally managed.
497  bool WasManaged = Dest.isLifetimeExternallyManaged();
498  Dest = EnsureSlot(E->getType());
499  Dest.setLifetimeExternallyManaged();
500
501  Visit(E->getSubExpr());
502
503  // Set up the temporary's destructor if its lifetime wasn't already
504  // being managed.
505  if (!WasManaged)
506    CGF.EmitCXXTemporary(E->getTemporary(), Dest.getAddr());
507}
508
509void
510AggExprEmitter::VisitCXXConstructExpr(const CXXConstructExpr *E) {
511  AggValueSlot Slot = EnsureSlot(E->getType());
512  CGF.EmitCXXConstructExpr(E, Slot);
513}
514
515void AggExprEmitter::VisitExprWithCleanups(ExprWithCleanups *E) {
516  CGF.EmitExprWithCleanups(E, Dest);
517}
518
519void AggExprEmitter::VisitCXXScalarValueInitExpr(CXXScalarValueInitExpr *E) {
520  QualType T = E->getType();
521  AggValueSlot Slot = EnsureSlot(T);
522  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
523}
524
525void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
526  QualType T = E->getType();
527  AggValueSlot Slot = EnsureSlot(T);
528  EmitNullInitializationToLValue(CGF.MakeAddrLValue(Slot.getAddr(), T), T);
529}
530
531/// isSimpleZero - If emitting this value will obviously just cause a store of
532/// zero to memory, return true.  This can return false if uncertain, so it just
533/// handles simple cases.
534static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
535  E = E->IgnoreParens();
536
537  // 0
538  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
539    return IL->getValue() == 0;
540  // +0.0
541  if (const FloatingLiteral *FL = dyn_cast<FloatingLiteral>(E))
542    return FL->getValue().isPosZero();
543  // int()
544  if ((isa<ImplicitValueInitExpr>(E) || isa<CXXScalarValueInitExpr>(E)) &&
545      CGF.getTypes().isZeroInitializable(E->getType()))
546    return true;
547  // (int*)0 - Null pointer expressions.
548  if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
549    return ICE->getCastKind() == CK_NullToPointer;
550  // '\0'
551  if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
552    return CL->getValue() == 0;
553
554  // Otherwise, hard case: conservatively return false.
555  return false;
556}
557
558
559void
560AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV, QualType T) {
561  // FIXME: Ignore result?
562  // FIXME: Are initializers affected by volatile?
563  if (Dest.isZeroed() && isSimpleZero(E, CGF)) {
564    // Storing "i32 0" to a zero'd memory location is a noop.
565  } else if (isa<ImplicitValueInitExpr>(E)) {
566    EmitNullInitializationToLValue(LV, T);
567  } else if (T->isReferenceType()) {
568    RValue RV = CGF.EmitReferenceBindingToExpr(E, /*InitializedDecl=*/0);
569    CGF.EmitStoreThroughLValue(RV, LV, T);
570  } else if (T->isAnyComplexType()) {
571    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
572  } else if (CGF.hasAggregateLLVMType(T)) {
573    CGF.EmitAggExpr(E, AggValueSlot::forAddr(LV.getAddress(), false, true,
574                                             false, Dest.isZeroed()));
575  } else {
576    CGF.EmitStoreThroughLValue(RValue::get(CGF.EmitScalarExpr(E)), LV, T);
577  }
578}
579
580void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
581  // If the destination slot is already zeroed out before the aggregate is
582  // copied into it, we don't have to emit any zeros here.
583  if (Dest.isZeroed() && CGF.getTypes().isZeroInitializable(T))
584    return;
585
586  if (!CGF.hasAggregateLLVMType(T)) {
587    // For non-aggregates, we can store zero
588    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
589    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
590  } else {
591    // There's a potential optimization opportunity in combining
592    // memsets; that would be easy for arrays, but relatively
593    // difficult for structures with the current code.
594    CGF.EmitNullInitialization(LV.getAddress(), T);
595  }
596}
597
598void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
599#if 0
600  // FIXME: Assess perf here?  Figure out what cases are worth optimizing here
601  // (Length of globals? Chunks of zeroed-out space?).
602  //
603  // If we can, prefer a copy from a global; this is a lot less code for long
604  // globals, and it's easier for the current optimizers to analyze.
605  if (llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, E->getType(), &CGF)) {
606    llvm::GlobalVariable* GV =
607    new llvm::GlobalVariable(CGF.CGM.getModule(), C->getType(), true,
608                             llvm::GlobalValue::InternalLinkage, C, "");
609    EmitFinalDestCopy(E, CGF.MakeAddrLValue(GV, E->getType()));
610    return;
611  }
612#endif
613  if (E->hadArrayRangeDesignator())
614    CGF.ErrorUnsupported(E, "GNU array range designator extension");
615
616  llvm::Value *DestPtr = Dest.getAddr();
617
618  // Handle initialization of an array.
619  if (E->getType()->isArrayType()) {
620    const llvm::PointerType *APType =
621      cast<llvm::PointerType>(DestPtr->getType());
622    const llvm::ArrayType *AType =
623      cast<llvm::ArrayType>(APType->getElementType());
624
625    uint64_t NumInitElements = E->getNumInits();
626
627    if (E->getNumInits() > 0) {
628      QualType T1 = E->getType();
629      QualType T2 = E->getInit(0)->getType();
630      if (CGF.getContext().hasSameUnqualifiedType(T1, T2)) {
631        EmitAggLoadOfLValue(E->getInit(0));
632        return;
633      }
634    }
635
636    uint64_t NumArrayElements = AType->getNumElements();
637    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
638    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
639
640    bool hasNonTrivialCXXConstructor = false;
641    if (CGF.getContext().getLangOptions().CPlusPlus)
642      if (const RecordType *RT = CGF.getContext()
643                        .getBaseElementType(ElementType)->getAs<RecordType>()) {
644        const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
645        hasNonTrivialCXXConstructor = !RD->hasTrivialConstructor();
646      }
647
648    // FIXME: were we intentionally ignoring address spaces and GC attributes?
649
650    for (uint64_t i = 0; i != NumArrayElements; ++i) {
651      // If we're done emitting initializers and the destination is known-zeroed
652      // then we're done.
653      if (i == NumInitElements &&
654          Dest.isZeroed() &&
655          CGF.getTypes().isZeroInitializable(ElementType) &&
656          !hasNonTrivialCXXConstructor)
657        break;
658
659      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
660      LValue LV = CGF.MakeAddrLValue(NextVal, ElementType);
661
662      if (i < NumInitElements)
663        EmitInitializationToLValue(E->getInit(i), LV, ElementType);
664      else if (Expr *filler = E->getArrayFiller())
665        EmitInitializationToLValue(filler, LV, ElementType);
666      else
667        EmitNullInitializationToLValue(LV, ElementType);
668
669      // If the GEP didn't get used because of a dead zero init or something
670      // else, clean it up for -O0 builds and general tidiness.
671      if (llvm::GetElementPtrInst *GEP =
672            dyn_cast<llvm::GetElementPtrInst>(NextVal))
673        if (GEP->use_empty())
674          GEP->eraseFromParent();
675    }
676    return;
677  }
678
679  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
680
681  // Do struct initialization; this code just sets each individual member
682  // to the approprate value.  This makes bitfield support automatic;
683  // the disadvantage is that the generated code is more difficult for
684  // the optimizer, especially with bitfields.
685  unsigned NumInitElements = E->getNumInits();
686  RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
687
688  if (E->getType()->isUnionType()) {
689    // Only initialize one field of a union. The field itself is
690    // specified by the initializer list.
691    if (!E->getInitializedFieldInUnion()) {
692      // Empty union; we have nothing to do.
693
694#ifndef NDEBUG
695      // Make sure that it's really an empty and not a failure of
696      // semantic analysis.
697      for (RecordDecl::field_iterator Field = SD->field_begin(),
698                                   FieldEnd = SD->field_end();
699           Field != FieldEnd; ++Field)
700        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
701#endif
702      return;
703    }
704
705    // FIXME: volatility
706    FieldDecl *Field = E->getInitializedFieldInUnion();
707
708    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, Field, 0);
709    if (NumInitElements) {
710      // Store the initializer into the field
711      EmitInitializationToLValue(E->getInit(0), FieldLoc, Field->getType());
712    } else {
713      // Default-initialize to null.
714      EmitNullInitializationToLValue(FieldLoc, Field->getType());
715    }
716
717    return;
718  }
719
720  // Here we iterate over the fields; this makes it simpler to both
721  // default-initialize fields and skip over unnamed fields.
722  unsigned CurInitVal = 0;
723  for (RecordDecl::field_iterator Field = SD->field_begin(),
724                               FieldEnd = SD->field_end();
725       Field != FieldEnd; ++Field) {
726    // We're done once we hit the flexible array member
727    if (Field->getType()->isIncompleteArrayType())
728      break;
729
730    if (Field->isUnnamedBitfield())
731      continue;
732
733    // Don't emit GEP before a noop store of zero.
734    if (CurInitVal == NumInitElements && Dest.isZeroed() &&
735        CGF.getTypes().isZeroInitializable(E->getType()))
736      break;
737
738    // FIXME: volatility
739    LValue FieldLoc = CGF.EmitLValueForFieldInitialization(DestPtr, *Field, 0);
740    // We never generate write-barries for initialized fields.
741    FieldLoc.setNonGC(true);
742
743    if (CurInitVal < NumInitElements) {
744      // Store the initializer into the field.
745      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc,
746                                 Field->getType());
747    } else {
748      // We're out of initalizers; default-initialize to null
749      EmitNullInitializationToLValue(FieldLoc, Field->getType());
750    }
751
752    // If the GEP didn't get used because of a dead zero init or something
753    // else, clean it up for -O0 builds and general tidiness.
754    if (FieldLoc.isSimple())
755      if (llvm::GetElementPtrInst *GEP =
756            dyn_cast<llvm::GetElementPtrInst>(FieldLoc.getAddress()))
757        if (GEP->use_empty())
758          GEP->eraseFromParent();
759  }
760}
761
762//===----------------------------------------------------------------------===//
763//                        Entry Points into this File
764//===----------------------------------------------------------------------===//
765
766/// GetNumNonZeroBytesInInit - Get an approximate count of the number of
767/// non-zero bytes that will be stored when outputting the initializer for the
768/// specified initializer expression.
769static CharUnits GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
770  E = E->IgnoreParens();
771
772  // 0 and 0.0 won't require any non-zero stores!
773  if (isSimpleZero(E, CGF)) return CharUnits::Zero();
774
775  // If this is an initlist expr, sum up the size of sizes of the (present)
776  // elements.  If this is something weird, assume the whole thing is non-zero.
777  const InitListExpr *ILE = dyn_cast<InitListExpr>(E);
778  if (ILE == 0 || !CGF.getTypes().isZeroInitializable(ILE->getType()))
779    return CGF.getContext().getTypeSizeInChars(E->getType());
780
781  // InitListExprs for structs have to be handled carefully.  If there are
782  // reference members, we need to consider the size of the reference, not the
783  // referencee.  InitListExprs for unions and arrays can't have references.
784  if (const RecordType *RT = E->getType()->getAs<RecordType>()) {
785    if (!RT->isUnionType()) {
786      RecordDecl *SD = E->getType()->getAs<RecordType>()->getDecl();
787      CharUnits NumNonZeroBytes = CharUnits::Zero();
788
789      unsigned ILEElement = 0;
790      for (RecordDecl::field_iterator Field = SD->field_begin(),
791           FieldEnd = SD->field_end(); Field != FieldEnd; ++Field) {
792        // We're done once we hit the flexible array member or run out of
793        // InitListExpr elements.
794        if (Field->getType()->isIncompleteArrayType() ||
795            ILEElement == ILE->getNumInits())
796          break;
797        if (Field->isUnnamedBitfield())
798          continue;
799
800        const Expr *E = ILE->getInit(ILEElement++);
801
802        // Reference values are always non-null and have the width of a pointer.
803        if (Field->getType()->isReferenceType())
804          NumNonZeroBytes += CGF.getContext().toCharUnitsFromBits(
805              CGF.getContext().Target.getPointerWidth(0));
806        else
807          NumNonZeroBytes += GetNumNonZeroBytesInInit(E, CGF);
808      }
809
810      return NumNonZeroBytes;
811    }
812  }
813
814
815  CharUnits NumNonZeroBytes = CharUnits::Zero();
816  for (unsigned i = 0, e = ILE->getNumInits(); i != e; ++i)
817    NumNonZeroBytes += GetNumNonZeroBytesInInit(ILE->getInit(i), CGF);
818  return NumNonZeroBytes;
819}
820
821/// CheckAggExprForMemSetUse - If the initializer is large and has a lot of
822/// zeros in it, emit a memset and avoid storing the individual zeros.
823///
824static void CheckAggExprForMemSetUse(AggValueSlot &Slot, const Expr *E,
825                                     CodeGenFunction &CGF) {
826  // If the slot is already known to be zeroed, nothing to do.  Don't mess with
827  // volatile stores.
828  if (Slot.isZeroed() || Slot.isVolatile() || Slot.getAddr() == 0) return;
829
830  // C++ objects with a user-declared constructor don't need zero'ing.
831  if (CGF.getContext().getLangOptions().CPlusPlus)
832    if (const RecordType *RT = CGF.getContext()
833                       .getBaseElementType(E->getType())->getAs<RecordType>()) {
834      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
835      if (RD->hasUserDeclaredConstructor())
836        return;
837    }
838
839  // If the type is 16-bytes or smaller, prefer individual stores over memset.
840  std::pair<CharUnits, CharUnits> TypeInfo =
841    CGF.getContext().getTypeInfoInChars(E->getType());
842  if (TypeInfo.first <= CharUnits::fromQuantity(16))
843    return;
844
845  // Check to see if over 3/4 of the initializer are known to be zero.  If so,
846  // we prefer to emit memset + individual stores for the rest.
847  CharUnits NumNonZeroBytes = GetNumNonZeroBytesInInit(E, CGF);
848  if (NumNonZeroBytes*4 > TypeInfo.first)
849    return;
850
851  // Okay, it seems like a good idea to use an initial memset, emit the call.
852  llvm::Constant *SizeVal = CGF.Builder.getInt64(TypeInfo.first.getQuantity());
853  CharUnits Align = TypeInfo.second;
854
855  llvm::Value *Loc = Slot.getAddr();
856  const llvm::Type *BP = llvm::Type::getInt8PtrTy(CGF.getLLVMContext());
857
858  Loc = CGF.Builder.CreateBitCast(Loc, BP);
859  CGF.Builder.CreateMemSet(Loc, CGF.Builder.getInt8(0), SizeVal,
860                           Align.getQuantity(), false);
861
862  // Tell the AggExprEmitter that the slot is known zero.
863  Slot.setZeroed();
864}
865
866
867
868
869/// EmitAggExpr - Emit the computation of the specified expression of aggregate
870/// type.  The result is computed into DestPtr.  Note that if DestPtr is null,
871/// the value of the aggregate expression is not needed.  If VolatileDest is
872/// true, DestPtr cannot be 0.
873///
874/// \param IsInitializer - true if this evaluation is initializing an
875/// object whose lifetime is already being managed.
876//
877// FIXME: Take Qualifiers object.
878void CodeGenFunction::EmitAggExpr(const Expr *E, AggValueSlot Slot,
879                                  bool IgnoreResult) {
880  assert(E && hasAggregateLLVMType(E->getType()) &&
881         "Invalid aggregate expression to emit");
882  assert((Slot.getAddr() != 0 || Slot.isIgnored()) &&
883         "slot has bits but no address");
884
885  // Optimize the slot if possible.
886  CheckAggExprForMemSetUse(Slot, E, *this);
887
888  AggExprEmitter(*this, Slot, IgnoreResult).Visit(const_cast<Expr*>(E));
889}
890
891LValue CodeGenFunction::EmitAggExprToLValue(const Expr *E) {
892  assert(hasAggregateLLVMType(E->getType()) && "Invalid argument!");
893  llvm::Value *Temp = CreateMemTemp(E->getType());
894  LValue LV = MakeAddrLValue(Temp, E->getType());
895  EmitAggExpr(E, AggValueSlot::forAddr(Temp, LV.isVolatileQualified(), false));
896  return LV;
897}
898
899void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
900                                        llvm::Value *SrcPtr, QualType Ty,
901                                        bool isVolatile) {
902  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
903
904  if (getContext().getLangOptions().CPlusPlus) {
905    if (const RecordType *RT = Ty->getAs<RecordType>()) {
906      CXXRecordDecl *Record = cast<CXXRecordDecl>(RT->getDecl());
907      assert((Record->hasTrivialCopyConstructor() ||
908              Record->hasTrivialCopyAssignment()) &&
909             "Trying to aggregate-copy a type without a trivial copy "
910             "constructor or assignment operator");
911      // Ignore empty classes in C++.
912      if (Record->isEmpty())
913        return;
914    }
915  }
916
917  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
918  // C99 6.5.16.1p3, which states "If the value being stored in an object is
919  // read from another object that overlaps in anyway the storage of the first
920  // object, then the overlap shall be exact and the two objects shall have
921  // qualified or unqualified versions of a compatible type."
922  //
923  // memcpy is not defined if the source and destination pointers are exactly
924  // equal, but other compilers do this optimization, and almost every memcpy
925  // implementation handles this case safely.  If there is a libc that does not
926  // safely handle this, we can add a target hook.
927
928  // Get size and alignment info for this aggregate.
929  std::pair<CharUnits, CharUnits> TypeInfo =
930    getContext().getTypeInfoInChars(Ty);
931
932  // FIXME: Handle variable sized types.
933
934  // FIXME: If we have a volatile struct, the optimizer can remove what might
935  // appear to be `extra' memory ops:
936  //
937  // volatile struct { int i; } a, b;
938  //
939  // int main() {
940  //   a = b;
941  //   a = b;
942  // }
943  //
944  // we need to use a different call here.  We use isVolatile to indicate when
945  // either the source or the destination is volatile.
946
947  const llvm::PointerType *DPT = cast<llvm::PointerType>(DestPtr->getType());
948  const llvm::Type *DBP =
949    llvm::Type::getInt8PtrTy(getLLVMContext(), DPT->getAddressSpace());
950  DestPtr = Builder.CreateBitCast(DestPtr, DBP, "tmp");
951
952  const llvm::PointerType *SPT = cast<llvm::PointerType>(SrcPtr->getType());
953  const llvm::Type *SBP =
954    llvm::Type::getInt8PtrTy(getLLVMContext(), SPT->getAddressSpace());
955  SrcPtr = Builder.CreateBitCast(SrcPtr, SBP, "tmp");
956
957  if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
958    RecordDecl *Record = RecordTy->getDecl();
959    if (Record->hasObjectMember()) {
960      CharUnits size = TypeInfo.first;
961      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
962      llvm::Value *SizeVal = llvm::ConstantInt::get(SizeTy, size.getQuantity());
963      CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
964                                                    SizeVal);
965      return;
966    }
967  } else if (getContext().getAsArrayType(Ty)) {
968    QualType BaseType = getContext().getBaseElementType(Ty);
969    if (const RecordType *RecordTy = BaseType->getAs<RecordType>()) {
970      if (RecordTy->getDecl()->hasObjectMember()) {
971        CharUnits size = TypeInfo.first;
972        const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
973        llvm::Value *SizeVal =
974          llvm::ConstantInt::get(SizeTy, size.getQuantity());
975        CGM.getObjCRuntime().EmitGCMemmoveCollectable(*this, DestPtr, SrcPtr,
976                                                      SizeVal);
977        return;
978      }
979    }
980  }
981
982  Builder.CreateMemCpy(DestPtr, SrcPtr,
983                       llvm::ConstantInt::get(IntPtrTy,
984                                              TypeInfo.first.getQuantity()),
985                       TypeInfo.second.getQuantity(), isVolatile);
986}
987