CGExprConstant.cpp revision 14c598268ff7534d3753ae84eba9b8a81bf0bf8f 
1//===--- CGExprConstant.cpp - Emit LLVM Code from Constant 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 Constant Expr nodes as LLVM code.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "CodeGenModule.h"
16#include "CGCXXABI.h"
17#include "CGObjCRuntime.h"
18#include "CGRecordLayout.h"
19#include "clang/AST/APValue.h"
20#include "clang/AST/ASTContext.h"
21#include "clang/AST/RecordLayout.h"
22#include "clang/AST/StmtVisitor.h"
23#include "clang/Basic/Builtins.h"
24#include "llvm/Constants.h"
25#include "llvm/Function.h"
26#include "llvm/GlobalVariable.h"
27#include "llvm/Target/TargetData.h"
28using namespace clang;
29using namespace CodeGen;
30
31//===----------------------------------------------------------------------===//
32//                            ConstStructBuilder
33//===----------------------------------------------------------------------===//
34
35namespace {
36class ConstStructBuilder {
37  CodeGenModule &CGM;
38  CodeGenFunction *CGF;
39
40  bool Packed;
41  CharUnits NextFieldOffsetInChars;
42  CharUnits LLVMStructAlignment;
43  SmallVector<llvm::Constant *, 32> Elements;
44public:
45  static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
46                                     InitListExpr *ILE);
47  static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
48                                     const APValue &Value, QualType ValTy);
49
50private:
51  ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
52    : CGM(CGM), CGF(CGF), Packed(false),
53    NextFieldOffsetInChars(CharUnits::Zero()),
54    LLVMStructAlignment(CharUnits::One()) { }
55
56  void AppendField(const FieldDecl *Field, uint64_t FieldOffset,
57                   llvm::Constant *InitExpr);
58
59  void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
60                      llvm::ConstantInt *InitExpr);
61
62  void AppendPadding(CharUnits PadSize);
63
64  void AppendTailPadding(CharUnits RecordSize);
65
66  void ConvertStructToPacked();
67
68  bool Build(InitListExpr *ILE);
69  void Build(const APValue &Val, QualType ValTy);
70  llvm::Constant *Finalize(QualType Ty);
71
72  CharUnits getAlignment(const llvm::Constant *C) const {
73    if (Packed)  return CharUnits::One();
74    return CharUnits::fromQuantity(
75        CGM.getTargetData().getABITypeAlignment(C->getType()));
76  }
77
78  CharUnits getSizeInChars(const llvm::Constant *C) const {
79    return CharUnits::fromQuantity(
80        CGM.getTargetData().getTypeAllocSize(C->getType()));
81  }
82};
83
84void ConstStructBuilder::
85AppendField(const FieldDecl *Field, uint64_t FieldOffset,
86            llvm::Constant *InitCst) {
87
88  const ASTContext &Context = CGM.getContext();
89
90  CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset);
91
92  assert(NextFieldOffsetInChars <= FieldOffsetInChars
93         && "Field offset mismatch!");
94
95  CharUnits FieldAlignment = getAlignment(InitCst);
96
97  // Round up the field offset to the alignment of the field type.
98  CharUnits AlignedNextFieldOffsetInChars =
99    NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment);
100
101  if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) {
102    assert(!Packed && "Alignment is wrong even with a packed struct!");
103
104    // Convert the struct to a packed struct.
105    ConvertStructToPacked();
106
107    AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
108  }
109
110  if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) {
111    // We need to append padding.
112    AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
113
114    assert(NextFieldOffsetInChars == FieldOffsetInChars &&
115           "Did not add enough padding!");
116
117    AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
118  }
119
120  // Add the field.
121  Elements.push_back(InitCst);
122  NextFieldOffsetInChars = AlignedNextFieldOffsetInChars +
123                           getSizeInChars(InitCst);
124
125  if (Packed)
126    assert(LLVMStructAlignment == CharUnits::One() &&
127           "Packed struct not byte-aligned!");
128  else
129    LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
130}
131
132void ConstStructBuilder::AppendBitField(const FieldDecl *Field,
133                                        uint64_t FieldOffset,
134                                        llvm::ConstantInt *CI) {
135  const ASTContext &Context = CGM.getContext();
136  const uint64_t CharWidth = Context.getCharWidth();
137  uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
138  if (FieldOffset > NextFieldOffsetInBits) {
139    // We need to add padding.
140    CharUnits PadSize = Context.toCharUnitsFromBits(
141      llvm::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits,
142                               Context.getTargetInfo().getCharAlign()));
143
144    AppendPadding(PadSize);
145  }
146
147  uint64_t FieldSize = Field->getBitWidthValue(Context);
148
149  llvm::APInt FieldValue = CI->getValue();
150
151  // Promote the size of FieldValue if necessary
152  // FIXME: This should never occur, but currently it can because initializer
153  // constants are cast to bool, and because clang is not enforcing bitfield
154  // width limits.
155  if (FieldSize > FieldValue.getBitWidth())
156    FieldValue = FieldValue.zext(FieldSize);
157
158  // Truncate the size of FieldValue to the bit field size.
159  if (FieldSize < FieldValue.getBitWidth())
160    FieldValue = FieldValue.trunc(FieldSize);
161
162  NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
163  if (FieldOffset < NextFieldOffsetInBits) {
164    // Either part of the field or the entire field can go into the previous
165    // byte.
166    assert(!Elements.empty() && "Elements can't be empty!");
167
168    unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset;
169
170    bool FitsCompletelyInPreviousByte =
171      BitsInPreviousByte >= FieldValue.getBitWidth();
172
173    llvm::APInt Tmp = FieldValue;
174
175    if (!FitsCompletelyInPreviousByte) {
176      unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
177
178      if (CGM.getTargetData().isBigEndian()) {
179        Tmp = Tmp.lshr(NewFieldWidth);
180        Tmp = Tmp.trunc(BitsInPreviousByte);
181
182        // We want the remaining high bits.
183        FieldValue = FieldValue.trunc(NewFieldWidth);
184      } else {
185        Tmp = Tmp.trunc(BitsInPreviousByte);
186
187        // We want the remaining low bits.
188        FieldValue = FieldValue.lshr(BitsInPreviousByte);
189        FieldValue = FieldValue.trunc(NewFieldWidth);
190      }
191    }
192
193    Tmp = Tmp.zext(CharWidth);
194    if (CGM.getTargetData().isBigEndian()) {
195      if (FitsCompletelyInPreviousByte)
196        Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
197    } else {
198      Tmp = Tmp.shl(CharWidth - BitsInPreviousByte);
199    }
200
201    // 'or' in the bits that go into the previous byte.
202    llvm::Value *LastElt = Elements.back();
203    if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt))
204      Tmp |= Val->getValue();
205    else {
206      assert(isa<llvm::UndefValue>(LastElt));
207      // If there is an undef field that we're adding to, it can either be a
208      // scalar undef (in which case, we just replace it with our field) or it
209      // is an array.  If it is an array, we have to pull one byte off the
210      // array so that the other undef bytes stay around.
211      if (!isa<llvm::IntegerType>(LastElt->getType())) {
212        // The undef padding will be a multibyte array, create a new smaller
213        // padding and then an hole for our i8 to get plopped into.
214        assert(isa<llvm::ArrayType>(LastElt->getType()) &&
215               "Expected array padding of undefs");
216        llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
217        assert(AT->getElementType()->isIntegerTy(CharWidth) &&
218               AT->getNumElements() != 0 &&
219               "Expected non-empty array padding of undefs");
220
221        // Remove the padding array.
222        NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements());
223        Elements.pop_back();
224
225        // Add the padding back in two chunks.
226        AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1));
227        AppendPadding(CharUnits::One());
228        assert(isa<llvm::UndefValue>(Elements.back()) &&
229               Elements.back()->getType()->isIntegerTy(CharWidth) &&
230               "Padding addition didn't work right");
231      }
232    }
233
234    Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
235
236    if (FitsCompletelyInPreviousByte)
237      return;
238  }
239
240  while (FieldValue.getBitWidth() > CharWidth) {
241    llvm::APInt Tmp;
242
243    if (CGM.getTargetData().isBigEndian()) {
244      // We want the high bits.
245      Tmp =
246        FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth);
247    } else {
248      // We want the low bits.
249      Tmp = FieldValue.trunc(CharWidth);
250
251      FieldValue = FieldValue.lshr(CharWidth);
252    }
253
254    Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
255    ++NextFieldOffsetInChars;
256
257    FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth);
258  }
259
260  assert(FieldValue.getBitWidth() > 0 &&
261         "Should have at least one bit left!");
262  assert(FieldValue.getBitWidth() <= CharWidth &&
263         "Should not have more than a byte left!");
264
265  if (FieldValue.getBitWidth() < CharWidth) {
266    if (CGM.getTargetData().isBigEndian()) {
267      unsigned BitWidth = FieldValue.getBitWidth();
268
269      FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth);
270    } else
271      FieldValue = FieldValue.zext(CharWidth);
272  }
273
274  // Append the last element.
275  Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
276                                            FieldValue));
277  ++NextFieldOffsetInChars;
278}
279
280void ConstStructBuilder::AppendPadding(CharUnits PadSize) {
281  if (PadSize.isZero())
282    return;
283
284  llvm::Type *Ty = CGM.Int8Ty;
285  if (PadSize > CharUnits::One())
286    Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
287
288  llvm::Constant *C = llvm::UndefValue::get(Ty);
289  Elements.push_back(C);
290  assert(getAlignment(C) == CharUnits::One() &&
291         "Padding must have 1 byte alignment!");
292
293  NextFieldOffsetInChars += getSizeInChars(C);
294}
295
296void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) {
297  assert(NextFieldOffsetInChars <= RecordSize &&
298         "Size mismatch!");
299
300  AppendPadding(RecordSize - NextFieldOffsetInChars);
301}
302
303void ConstStructBuilder::ConvertStructToPacked() {
304  SmallVector<llvm::Constant *, 16> PackedElements;
305  CharUnits ElementOffsetInChars = CharUnits::Zero();
306
307  for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
308    llvm::Constant *C = Elements[i];
309
310    CharUnits ElementAlign = CharUnits::fromQuantity(
311      CGM.getTargetData().getABITypeAlignment(C->getType()));
312    CharUnits AlignedElementOffsetInChars =
313      ElementOffsetInChars.RoundUpToAlignment(ElementAlign);
314
315    if (AlignedElementOffsetInChars > ElementOffsetInChars) {
316      // We need some padding.
317      CharUnits NumChars =
318        AlignedElementOffsetInChars - ElementOffsetInChars;
319
320      llvm::Type *Ty = CGM.Int8Ty;
321      if (NumChars > CharUnits::One())
322        Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity());
323
324      llvm::Constant *Padding = llvm::UndefValue::get(Ty);
325      PackedElements.push_back(Padding);
326      ElementOffsetInChars += getSizeInChars(Padding);
327    }
328
329    PackedElements.push_back(C);
330    ElementOffsetInChars += getSizeInChars(C);
331  }
332
333  assert(ElementOffsetInChars == NextFieldOffsetInChars &&
334         "Packing the struct changed its size!");
335
336  Elements.swap(PackedElements);
337  LLVMStructAlignment = CharUnits::One();
338  Packed = true;
339}
340
341bool ConstStructBuilder::Build(InitListExpr *ILE) {
342  RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
343  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
344
345  unsigned FieldNo = 0;
346  unsigned ElementNo = 0;
347  const FieldDecl *LastFD = 0;
348  bool IsMsStruct = RD->hasAttr<MsStructAttr>();
349
350  for (RecordDecl::field_iterator Field = RD->field_begin(),
351       FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
352    if (IsMsStruct) {
353      // Zero-length bitfields following non-bitfield members are
354      // ignored:
355      if (CGM.getContext().ZeroBitfieldFollowsNonBitfield((*Field), LastFD)) {
356        --FieldNo;
357        continue;
358      }
359      LastFD = (*Field);
360    }
361
362    // If this is a union, skip all the fields that aren't being initialized.
363    if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
364      continue;
365
366    // Don't emit anonymous bitfields, they just affect layout.
367    if (Field->isUnnamedBitfield()) {
368      LastFD = (*Field);
369      continue;
370    }
371
372    // Get the initializer.  A struct can include fields without initializers,
373    // we just use explicit null values for them.
374    llvm::Constant *EltInit;
375    if (ElementNo < ILE->getNumInits())
376      EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++),
377                                     Field->getType(), CGF);
378    else
379      EltInit = CGM.EmitNullConstant(Field->getType());
380
381    if (!EltInit)
382      return false;
383
384    if (!Field->isBitField()) {
385      // Handle non-bitfield members.
386      AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit);
387    } else {
388      // Otherwise we have a bitfield.
389      AppendBitField(*Field, Layout.getFieldOffset(FieldNo),
390                     cast<llvm::ConstantInt>(EltInit));
391    }
392  }
393
394  return true;
395}
396
397void ConstStructBuilder::Build(const APValue &Val, QualType ValTy) {
398  RecordDecl *RD = ValTy->getAs<RecordType>()->getDecl();
399  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
400
401  if (CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
402    unsigned BaseNo = 0;
403    for (CXXRecordDecl::base_class_iterator Base = CD->bases_begin(),
404         BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) {
405      // Build the base class subobject at the appropriately-offset location
406      // within this object.
407      const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl();
408      CharUnits BaseOffset = Layout.getBaseClassOffset(BD);
409      NextFieldOffsetInChars -= BaseOffset;
410
411      Build(Val.getStructBase(BaseNo), Base->getType());
412
413      NextFieldOffsetInChars += BaseOffset;
414    }
415  }
416
417  unsigned FieldNo = 0;
418  const FieldDecl *LastFD = 0;
419  bool IsMsStruct = RD->hasAttr<MsStructAttr>();
420
421  for (RecordDecl::field_iterator Field = RD->field_begin(),
422       FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
423    if (IsMsStruct) {
424      // Zero-length bitfields following non-bitfield members are
425      // ignored:
426      if (CGM.getContext().ZeroBitfieldFollowsNonBitfield((*Field), LastFD)) {
427        --FieldNo;
428        continue;
429      }
430      LastFD = (*Field);
431    }
432
433    // If this is a union, skip all the fields that aren't being initialized.
434    if (RD->isUnion() && Val.getUnionField() != *Field)
435      continue;
436
437    // Don't emit anonymous bitfields, they just affect layout.
438    if (Field->isUnnamedBitfield()) {
439      LastFD = (*Field);
440      continue;
441    }
442
443    // Emit the value of the initializer.
444    const APValue &FieldValue =
445      RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo);
446    llvm::Constant *EltInit =
447      CGM.EmitConstantValue(FieldValue, Field->getType(), CGF);
448    assert(EltInit && "EmitConstantValue can't fail");
449
450    if (!Field->isBitField()) {
451      // Handle non-bitfield members.
452      AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit);
453    } else {
454      // Otherwise we have a bitfield.
455      AppendBitField(*Field, Layout.getFieldOffset(FieldNo),
456                     cast<llvm::ConstantInt>(EltInit));
457    }
458  }
459}
460
461llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) {
462  RecordDecl *RD = Ty->getAs<RecordType>()->getDecl();
463  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
464
465  CharUnits LayoutSizeInChars = Layout.getSize();
466
467  if (NextFieldOffsetInChars > LayoutSizeInChars) {
468    // If the struct is bigger than the size of the record type,
469    // we must have a flexible array member at the end.
470    assert(RD->hasFlexibleArrayMember() &&
471           "Must have flexible array member if struct is bigger than type!");
472
473    // No tail padding is necessary.
474  } else {
475    // Append tail padding if necessary.
476    AppendTailPadding(LayoutSizeInChars);
477
478    CharUnits LLVMSizeInChars =
479      NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
480
481    // Check if we need to convert the struct to a packed struct.
482    if (NextFieldOffsetInChars <= LayoutSizeInChars &&
483        LLVMSizeInChars > LayoutSizeInChars) {
484      assert(!Packed && "Size mismatch!");
485
486      ConvertStructToPacked();
487      assert(NextFieldOffsetInChars <= LayoutSizeInChars &&
488             "Converting to packed did not help!");
489    }
490
491    assert(LayoutSizeInChars == NextFieldOffsetInChars &&
492           "Tail padding mismatch!");
493  }
494
495  // Pick the type to use.  If the type is layout identical to the ConvertType
496  // type then use it, otherwise use whatever the builder produced for us.
497  llvm::StructType *STy =
498      llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(),
499                                               Elements, Packed);
500  llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty);
501  if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) {
502    if (ValSTy->isLayoutIdentical(STy))
503      STy = ValSTy;
504  }
505
506  llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements);
507
508  assert(NextFieldOffsetInChars.RoundUpToAlignment(getAlignment(Result)) ==
509         getSizeInChars(Result) && "Size mismatch!");
510
511  return Result;
512}
513
514llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
515                                                CodeGenFunction *CGF,
516                                                InitListExpr *ILE) {
517  ConstStructBuilder Builder(CGM, CGF);
518
519  if (!Builder.Build(ILE))
520    return 0;
521
522  return Builder.Finalize(ILE->getType());
523}
524
525llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
526                                                CodeGenFunction *CGF,
527                                                const APValue &Val,
528                                                QualType ValTy) {
529  ConstStructBuilder Builder(CGM, CGF);
530  Builder.Build(Val, ValTy);
531  return Builder.Finalize(ValTy);
532}
533
534
535//===----------------------------------------------------------------------===//
536//                             ConstExprEmitter
537//===----------------------------------------------------------------------===//
538
539/// This class only needs to handle two cases:
540/// 1) Literals (this is used by APValue emission to emit literals).
541/// 2) Arrays, structs and unions (outside C++11 mode, we don't currently
542///    constant fold these types).
543class ConstExprEmitter :
544  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
545  CodeGenModule &CGM;
546  CodeGenFunction *CGF;
547  llvm::LLVMContext &VMContext;
548public:
549  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
550    : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
551  }
552
553  //===--------------------------------------------------------------------===//
554  //                            Visitor Methods
555  //===--------------------------------------------------------------------===//
556
557  llvm::Constant *VisitStmt(Stmt *S) {
558    return 0;
559  }
560
561  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
562    return Visit(PE->getSubExpr());
563  }
564
565  llvm::Constant *
566  VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) {
567    return Visit(PE->getReplacement());
568  }
569
570  llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
571    return Visit(GE->getResultExpr());
572  }
573
574  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
575    return Visit(E->getInitializer());
576  }
577
578  llvm::Constant *VisitCastExpr(CastExpr* E) {
579    Expr *subExpr = E->getSubExpr();
580    llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF);
581    if (!C) return 0;
582
583    llvm::Type *destType = ConvertType(E->getType());
584
585    switch (E->getCastKind()) {
586    case CK_ToUnion: {
587      // GCC cast to union extension
588      assert(E->getType()->isUnionType() &&
589             "Destination type is not union type!");
590
591      // Build a struct with the union sub-element as the first member,
592      // and padded to the appropriate size
593      SmallVector<llvm::Constant*, 2> Elts;
594      SmallVector<llvm::Type*, 2> Types;
595      Elts.push_back(C);
596      Types.push_back(C->getType());
597      unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
598      unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(destType);
599
600      assert(CurSize <= TotalSize && "Union size mismatch!");
601      if (unsigned NumPadBytes = TotalSize - CurSize) {
602        llvm::Type *Ty = CGM.Int8Ty;
603        if (NumPadBytes > 1)
604          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
605
606        Elts.push_back(llvm::UndefValue::get(Ty));
607        Types.push_back(Ty);
608      }
609
610      llvm::StructType* STy =
611        llvm::StructType::get(C->getType()->getContext(), Types, false);
612      return llvm::ConstantStruct::get(STy, Elts);
613    }
614
615    case CK_LValueToRValue:
616    case CK_AtomicToNonAtomic:
617    case CK_NonAtomicToAtomic:
618    case CK_NoOp:
619      return C;
620
621    case CK_Dependent: llvm_unreachable("saw dependent cast!");
622
623    // These will never be supported.
624    case CK_ObjCObjectLValueCast:
625    case CK_ARCProduceObject:
626    case CK_ARCConsumeObject:
627    case CK_ARCReclaimReturnedObject:
628    case CK_ARCExtendBlockObject:
629      return 0;
630
631    // These don't need to be handled here because Evaluate knows how to
632    // evaluate them in the cases where they can be folded.
633    case CK_ToVoid:
634    case CK_Dynamic:
635    case CK_LValueBitCast:
636    case CK_NullToMemberPointer:
637    case CK_DerivedToBaseMemberPointer:
638    case CK_BaseToDerivedMemberPointer:
639    case CK_UserDefinedConversion:
640    case CK_ConstructorConversion:
641    case CK_CPointerToObjCPointerCast:
642    case CK_BlockPointerToObjCPointerCast:
643    case CK_AnyPointerToBlockPointerCast:
644    case CK_BitCast:
645    case CK_ArrayToPointerDecay:
646    case CK_FunctionToPointerDecay:
647    case CK_BaseToDerived:
648    case CK_DerivedToBase:
649    case CK_UncheckedDerivedToBase:
650    case CK_MemberPointerToBoolean:
651    case CK_VectorSplat:
652    case CK_FloatingRealToComplex:
653    case CK_FloatingComplexToReal:
654    case CK_FloatingComplexToBoolean:
655    case CK_FloatingComplexCast:
656    case CK_FloatingComplexToIntegralComplex:
657    case CK_IntegralRealToComplex:
658    case CK_IntegralComplexToReal:
659    case CK_IntegralComplexToBoolean:
660    case CK_IntegralComplexCast:
661    case CK_IntegralComplexToFloatingComplex:
662    case CK_PointerToIntegral:
663    case CK_PointerToBoolean:
664    case CK_NullToPointer:
665    case CK_IntegralCast:
666    case CK_IntegralToPointer:
667    case CK_IntegralToBoolean:
668    case CK_IntegralToFloating:
669    case CK_FloatingToIntegral:
670    case CK_FloatingToBoolean:
671    case CK_FloatingCast:
672      return 0;
673    }
674    llvm_unreachable("Invalid CastKind");
675  }
676
677  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
678    return Visit(DAE->getExpr());
679  }
680
681  llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
682    return Visit(E->GetTemporaryExpr());
683  }
684
685  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
686    unsigned NumInitElements = ILE->getNumInits();
687    if (NumInitElements == 1 && ILE->getType() == ILE->getInit(0)->getType() &&
688        (isa<StringLiteral>(ILE->getInit(0)) ||
689         isa<ObjCEncodeExpr>(ILE->getInit(0))))
690      return Visit(ILE->getInit(0));
691
692    llvm::ArrayType *AType =
693        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
694    llvm::Type *ElemTy = AType->getElementType();
695    unsigned NumElements = AType->getNumElements();
696
697    // Initialising an array requires us to automatically
698    // initialise any elements that have not been initialised explicitly
699    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
700
701    // Copy initializer elements.
702    std::vector<llvm::Constant*> Elts;
703    Elts.reserve(NumInitableElts + NumElements);
704
705    bool RewriteType = false;
706    for (unsigned i = 0; i < NumInitableElts; ++i) {
707      Expr *Init = ILE->getInit(i);
708      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
709      if (!C)
710        return 0;
711      RewriteType |= (C->getType() != ElemTy);
712      Elts.push_back(C);
713    }
714
715    // Initialize remaining array elements.
716    // FIXME: This doesn't handle member pointers correctly!
717    llvm::Constant *fillC;
718    if (Expr *filler = ILE->getArrayFiller())
719      fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF);
720    else
721      fillC = llvm::Constant::getNullValue(ElemTy);
722    if (!fillC)
723      return 0;
724    RewriteType |= (fillC->getType() != ElemTy);
725    Elts.resize(NumElements, fillC);
726
727    if (RewriteType) {
728      // FIXME: Try to avoid packing the array
729      std::vector<llvm::Type*> Types;
730      Types.reserve(NumInitableElts + NumElements);
731      for (unsigned i = 0, e = Elts.size(); i < e; ++i)
732        Types.push_back(Elts[i]->getType());
733      llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
734                                                            Types, true);
735      return llvm::ConstantStruct::get(SType, Elts);
736    }
737
738    return llvm::ConstantArray::get(AType, Elts);
739  }
740
741  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
742    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
743  }
744
745  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
746    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
747  }
748
749  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
750    return CGM.EmitNullConstant(E->getType());
751  }
752
753  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
754    if (ILE->getType()->isArrayType())
755      return EmitArrayInitialization(ILE);
756
757    if (ILE->getType()->isRecordType())
758      return EmitStructInitialization(ILE);
759
760    if (ILE->getType()->isUnionType())
761      return EmitUnionInitialization(ILE);
762
763    return 0;
764  }
765
766  llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) {
767    if (!E->getConstructor()->isTrivial())
768      return 0;
769
770    QualType Ty = E->getType();
771
772    // FIXME: We should not have to call getBaseElementType here.
773    const RecordType *RT =
774      CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
775    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
776
777    // If the class doesn't have a trivial destructor, we can't emit it as a
778    // constant expr.
779    if (!RD->hasTrivialDestructor())
780      return 0;
781
782    // Only copy and default constructors can be trivial.
783
784
785    if (E->getNumArgs()) {
786      assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
787      assert(E->getConstructor()->isCopyOrMoveConstructor() &&
788             "trivial ctor has argument but isn't a copy/move ctor");
789
790      Expr *Arg = E->getArg(0);
791      assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
792             "argument to copy ctor is of wrong type");
793
794      return Visit(Arg);
795    }
796
797    return CGM.EmitNullConstant(Ty);
798  }
799
800  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
801    return CGM.GetConstantArrayFromStringLiteral(E);
802  }
803
804  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
805    // This must be an @encode initializing an array in a static initializer.
806    // Don't emit it as the address of the string, emit the string data itself
807    // as an inline array.
808    std::string Str;
809    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
810    const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
811
812    // Resize the string to the right size, adding zeros at the end, or
813    // truncating as needed.
814    Str.resize(CAT->getSize().getZExtValue(), '\0');
815    return llvm::ConstantDataArray::getString(VMContext, Str, false);
816  }
817
818  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
819    return Visit(E->getSubExpr());
820  }
821
822  // Utility methods
823  llvm::Type *ConvertType(QualType T) {
824    return CGM.getTypes().ConvertType(T);
825  }
826
827public:
828  llvm::Constant *EmitLValue(APValue::LValueBase LVBase) {
829    if (const ValueDecl *Decl = LVBase.dyn_cast<const ValueDecl*>()) {
830      if (Decl->hasAttr<WeakRefAttr>())
831        return CGM.GetWeakRefReference(Decl);
832      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
833        return CGM.GetAddrOfFunction(FD);
834      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
835        // We can never refer to a variable with local storage.
836        if (!VD->hasLocalStorage()) {
837          if (VD->isFileVarDecl() || VD->hasExternalStorage())
838            return CGM.GetAddrOfGlobalVar(VD);
839          else if (VD->isLocalVarDecl()) {
840            assert(CGF && "Can't access static local vars without CGF");
841            return CGF->GetAddrOfStaticLocalVar(VD);
842          }
843        }
844      }
845      return 0;
846    }
847
848    Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>());
849    switch (E->getStmtClass()) {
850    default: break;
851    case Expr::CompoundLiteralExprClass: {
852      // Note that due to the nature of compound literals, this is guaranteed
853      // to be the only use of the variable, so we just generate it here.
854      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
855      llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(),
856                                               CLE->getType(), CGF);
857      // FIXME: "Leaked" on failure.
858      if (C)
859        C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
860                                     E->getType().isConstant(CGM.getContext()),
861                                     llvm::GlobalValue::InternalLinkage,
862                                     C, ".compoundliteral", 0, false,
863                          CGM.getContext().getTargetAddressSpace(E->getType()));
864      return C;
865    }
866    case Expr::StringLiteralClass:
867      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
868    case Expr::ObjCEncodeExprClass:
869      return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
870    case Expr::ObjCStringLiteralClass: {
871      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
872      llvm::Constant *C =
873          CGM.getObjCRuntime().GenerateConstantString(SL->getString());
874      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
875    }
876    case Expr::PredefinedExprClass: {
877      unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
878      if (CGF) {
879        LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E));
880        return cast<llvm::Constant>(Res.getAddress());
881      } else if (Type == PredefinedExpr::PrettyFunction) {
882        return CGM.GetAddrOfConstantCString("top level", ".tmp");
883      }
884
885      return CGM.GetAddrOfConstantCString("", ".tmp");
886    }
887    case Expr::AddrLabelExprClass: {
888      assert(CGF && "Invalid address of label expression outside function.");
889      llvm::Constant *Ptr =
890        CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
891      return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
892    }
893    case Expr::CallExprClass: {
894      CallExpr* CE = cast<CallExpr>(E);
895      unsigned builtin = CE->isBuiltinCall();
896      if (builtin !=
897            Builtin::BI__builtin___CFStringMakeConstantString &&
898          builtin !=
899            Builtin::BI__builtin___NSStringMakeConstantString)
900        break;
901      const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
902      const StringLiteral *Literal = cast<StringLiteral>(Arg);
903      if (builtin ==
904            Builtin::BI__builtin___NSStringMakeConstantString) {
905        return CGM.getObjCRuntime().GenerateConstantString(Literal);
906      }
907      // FIXME: need to deal with UCN conversion issues.
908      return CGM.GetAddrOfConstantCFString(Literal);
909    }
910    case Expr::BlockExprClass: {
911      std::string FunctionName;
912      if (CGF)
913        FunctionName = CGF->CurFn->getName();
914      else
915        FunctionName = "global";
916
917      return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
918    }
919    case Expr::CXXTypeidExprClass: {
920      CXXTypeidExpr *Typeid = cast<CXXTypeidExpr>(E);
921      QualType T;
922      if (Typeid->isTypeOperand())
923        T = Typeid->getTypeOperand();
924      else
925        T = Typeid->getExprOperand()->getType();
926      return CGM.GetAddrOfRTTIDescriptor(T);
927    }
928    }
929
930    return 0;
931  }
932};
933
934}  // end anonymous namespace.
935
936llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D,
937                                                CodeGenFunction *CGF) {
938  if (const APValue *Value = D.evaluateValue())
939    return EmitConstantValue(*Value, D.getType(), CGF);
940
941  // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a
942  // reference is a constant expression, and the reference binds to a temporary,
943  // then constant initialization is performed. ConstExprEmitter will
944  // incorrectly emit a prvalue constant in this case, and the calling code
945  // interprets that as the (pointer) value of the reference, rather than the
946  // desired value of the referee.
947  if (D.getType()->isReferenceType())
948    return 0;
949
950  const Expr *E = D.getInit();
951  assert(E && "No initializer to emit");
952
953  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
954  if (C && C->getType()->isIntegerTy(1)) {
955    llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
956    C = llvm::ConstantExpr::getZExt(C, BoolTy);
957  }
958  return C;
959}
960
961llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
962                                                QualType DestType,
963                                                CodeGenFunction *CGF) {
964  Expr::EvalResult Result;
965
966  bool Success = false;
967
968  if (DestType->isReferenceType())
969    Success = E->EvaluateAsLValue(Result, Context);
970  else
971    Success = E->EvaluateAsRValue(Result, Context);
972
973  if (Success && !Result.HasSideEffects)
974    return EmitConstantValue(Result.Val, DestType, CGF);
975
976  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
977  if (C && C->getType()->isIntegerTy(1)) {
978    llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
979    C = llvm::ConstantExpr::getZExt(C, BoolTy);
980  }
981  return C;
982}
983
984llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
985                                                 QualType DestType,
986                                                 CodeGenFunction *CGF) {
987  switch (Value.getKind()) {
988  case APValue::Uninitialized:
989    llvm_unreachable("Constant expressions should be initialized.");
990  case APValue::LValue: {
991    llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
992    llvm::Constant *Offset =
993      llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity());
994
995    llvm::Constant *C;
996    if (APValue::LValueBase LVBase = Value.getLValueBase()) {
997      // An array can be represented as an lvalue referring to the base.
998      if (isa<llvm::ArrayType>(DestTy)) {
999        assert(Offset->isNullValue() && "offset on array initializer");
1000        return ConstExprEmitter(*this, CGF).Visit(
1001          const_cast<Expr*>(LVBase.get<const Expr*>()));
1002      }
1003
1004      C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase);
1005
1006      // Apply offset if necessary.
1007      if (!Offset->isNullValue()) {
1008        llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Int8PtrTy);
1009        Casted = llvm::ConstantExpr::getGetElementPtr(Casted, Offset);
1010        C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
1011      }
1012
1013      // Convert to the appropriate type; this could be an lvalue for
1014      // an integer.
1015      if (isa<llvm::PointerType>(DestTy))
1016        return llvm::ConstantExpr::getBitCast(C, DestTy);
1017
1018      return llvm::ConstantExpr::getPtrToInt(C, DestTy);
1019    } else {
1020      C = Offset;
1021
1022      // Convert to the appropriate type; this could be an lvalue for
1023      // an integer.
1024      if (isa<llvm::PointerType>(DestTy))
1025        return llvm::ConstantExpr::getIntToPtr(C, DestTy);
1026
1027      // If the types don't match this should only be a truncate.
1028      if (C->getType() != DestTy)
1029        return llvm::ConstantExpr::getTrunc(C, DestTy);
1030
1031      return C;
1032    }
1033  }
1034  case APValue::Int: {
1035    llvm::Constant *C = llvm::ConstantInt::get(VMContext,
1036                                               Value.getInt());
1037
1038    if (C->getType()->isIntegerTy(1)) {
1039      llvm::Type *BoolTy = getTypes().ConvertTypeForMem(DestType);
1040      C = llvm::ConstantExpr::getZExt(C, BoolTy);
1041    }
1042    return C;
1043  }
1044  case APValue::ComplexInt: {
1045    llvm::Constant *Complex[2];
1046
1047    Complex[0] = llvm::ConstantInt::get(VMContext,
1048                                        Value.getComplexIntReal());
1049    Complex[1] = llvm::ConstantInt::get(VMContext,
1050                                        Value.getComplexIntImag());
1051
1052    // FIXME: the target may want to specify that this is packed.
1053    llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
1054                                                  Complex[1]->getType(),
1055                                                  NULL);
1056    return llvm::ConstantStruct::get(STy, Complex);
1057  }
1058  case APValue::Float: {
1059    const llvm::APFloat &Init = Value.getFloat();
1060    if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf)
1061      return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt());
1062    else
1063      return llvm::ConstantFP::get(VMContext, Init);
1064  }
1065  case APValue::ComplexFloat: {
1066    llvm::Constant *Complex[2];
1067
1068    Complex[0] = llvm::ConstantFP::get(VMContext,
1069                                       Value.getComplexFloatReal());
1070    Complex[1] = llvm::ConstantFP::get(VMContext,
1071                                       Value.getComplexFloatImag());
1072
1073    // FIXME: the target may want to specify that this is packed.
1074    llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
1075                                                  Complex[1]->getType(),
1076                                                  NULL);
1077    return llvm::ConstantStruct::get(STy, Complex);
1078  }
1079  case APValue::Vector: {
1080    SmallVector<llvm::Constant *, 4> Inits;
1081    unsigned NumElts = Value.getVectorLength();
1082
1083    for (unsigned i = 0; i != NumElts; ++i) {
1084      const APValue &Elt = Value.getVectorElt(i);
1085      if (Elt.isInt())
1086        Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
1087      else
1088        Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
1089    }
1090    return llvm::ConstantVector::get(Inits);
1091  }
1092  case APValue::AddrLabelDiff: {
1093    const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS();
1094    const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS();
1095    llvm::Constant *LHS = EmitConstantExpr(LHSExpr, LHSExpr->getType(), CGF);
1096    llvm::Constant *RHS = EmitConstantExpr(RHSExpr, RHSExpr->getType(), CGF);
1097
1098    // Compute difference
1099    llvm::Type *ResultType = getTypes().ConvertType(DestType);
1100    LHS = llvm::ConstantExpr::getPtrToInt(LHS, IntPtrTy);
1101    RHS = llvm::ConstantExpr::getPtrToInt(RHS, IntPtrTy);
1102    llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS);
1103
1104    // LLVM is a bit sensitive about the exact format of the
1105    // address-of-label difference; make sure to truncate after
1106    // the subtraction.
1107    return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType);
1108  }
1109  case APValue::Struct:
1110  case APValue::Union:
1111    return ConstStructBuilder::BuildStruct(*this, CGF, Value, DestType);
1112  case APValue::Array: {
1113    const ArrayType *CAT = Context.getAsArrayType(DestType);
1114    unsigned NumElements = Value.getArraySize();
1115    unsigned NumInitElts = Value.getArrayInitializedElts();
1116
1117    std::vector<llvm::Constant*> Elts;
1118    Elts.reserve(NumElements);
1119
1120    // Emit array filler, if there is one.
1121    llvm::Constant *Filler = 0;
1122    if (Value.hasArrayFiller())
1123      Filler = EmitConstantValue(Value.getArrayFiller(),
1124                                 CAT->getElementType(), CGF);
1125
1126    // Emit initializer elements.
1127    llvm::Type *CommonElementType = 0;
1128    for (unsigned I = 0; I < NumElements; ++I) {
1129      llvm::Constant *C = Filler;
1130      if (I < NumInitElts)
1131        C = EmitConstantValue(Value.getArrayInitializedElt(I),
1132                              CAT->getElementType(), CGF);
1133      if (I == 0)
1134        CommonElementType = C->getType();
1135      else if (C->getType() != CommonElementType)
1136        CommonElementType = 0;
1137      Elts.push_back(C);
1138    }
1139
1140    if (!CommonElementType) {
1141      // FIXME: Try to avoid packing the array
1142      std::vector<llvm::Type*> Types;
1143      Types.reserve(NumElements);
1144      for (unsigned i = 0, e = Elts.size(); i < e; ++i)
1145        Types.push_back(Elts[i]->getType());
1146      llvm::StructType *SType = llvm::StructType::get(VMContext, Types, true);
1147      return llvm::ConstantStruct::get(SType, Elts);
1148    }
1149
1150    llvm::ArrayType *AType =
1151      llvm::ArrayType::get(CommonElementType, NumElements);
1152    return llvm::ConstantArray::get(AType, Elts);
1153  }
1154  case APValue::MemberPointer:
1155    return getCXXABI().EmitMemberPointer(Value, DestType);
1156  }
1157  llvm_unreachable("Unknown APValue kind");
1158}
1159
1160llvm::Constant *
1161CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) {
1162  assert(E->isFileScope() && "not a file-scope compound literal expr");
1163  return ConstExprEmitter(*this, 0).EmitLValue(E);
1164}
1165
1166llvm::Constant *
1167CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) {
1168  // Member pointer constants always have a very particular form.
1169  const MemberPointerType *type = cast<MemberPointerType>(uo->getType());
1170  const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl();
1171
1172  // A member function pointer.
1173  if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl))
1174    return getCXXABI().EmitMemberPointer(method);
1175
1176  // Otherwise, a member data pointer.
1177  uint64_t fieldOffset = getContext().getFieldOffset(decl);
1178  CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset);
1179  return getCXXABI().EmitMemberDataPointer(type, chars);
1180}
1181
1182static void
1183FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T,
1184                             SmallVectorImpl<llvm::Constant *> &Elements,
1185                             uint64_t StartOffset) {
1186  assert(StartOffset % CGM.getContext().getCharWidth() == 0 &&
1187         "StartOffset not byte aligned!");
1188
1189  if (CGM.getTypes().isZeroInitializable(T))
1190    return;
1191
1192  if (const ConstantArrayType *CAT =
1193        CGM.getContext().getAsConstantArrayType(T)) {
1194    QualType ElementTy = CAT->getElementType();
1195    uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy);
1196
1197    for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) {
1198      FillInNullDataMemberPointers(CGM, ElementTy, Elements,
1199                                   StartOffset + I * ElementSize);
1200    }
1201  } else if (const RecordType *RT = T->getAs<RecordType>()) {
1202    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1203    const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
1204
1205    // Go through all bases and fill in any null pointer to data members.
1206    for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1207         E = RD->bases_end(); I != E; ++I) {
1208      if (I->isVirtual()) {
1209        // Ignore virtual bases.
1210        continue;
1211      }
1212
1213      const CXXRecordDecl *BaseDecl =
1214      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1215
1216      // Ignore empty bases.
1217      if (BaseDecl->isEmpty())
1218        continue;
1219
1220      // Ignore bases that don't have any pointer to data members.
1221      if (CGM.getTypes().isZeroInitializable(BaseDecl))
1222        continue;
1223
1224      uint64_t BaseOffset = Layout.getBaseClassOffsetInBits(BaseDecl);
1225      FillInNullDataMemberPointers(CGM, I->getType(),
1226                                   Elements, StartOffset + BaseOffset);
1227    }
1228
1229    // Visit all fields.
1230    unsigned FieldNo = 0;
1231    for (RecordDecl::field_iterator I = RD->field_begin(),
1232         E = RD->field_end(); I != E; ++I, ++FieldNo) {
1233      QualType FieldType = I->getType();
1234
1235      if (CGM.getTypes().isZeroInitializable(FieldType))
1236        continue;
1237
1238      uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo);
1239      FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset);
1240    }
1241  } else {
1242    assert(T->isMemberPointerType() && "Should only see member pointers here!");
1243    assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
1244           "Should only see pointers to data members here!");
1245
1246    CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset);
1247    CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T);
1248
1249    // FIXME: hardcodes Itanium member pointer representation!
1250    llvm::Constant *NegativeOne =
1251      llvm::ConstantInt::get(CGM.Int8Ty, -1ULL, /*isSigned*/true);
1252
1253    // Fill in the null data member pointer.
1254    for (CharUnits I = StartIndex; I != EndIndex; ++I)
1255      Elements[I.getQuantity()] = NegativeOne;
1256  }
1257}
1258
1259static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
1260                                               llvm::Type *baseType,
1261                                               const CXXRecordDecl *base);
1262
1263static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
1264                                        const CXXRecordDecl *record,
1265                                        bool asCompleteObject) {
1266  const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
1267  llvm::StructType *structure =
1268    (asCompleteObject ? layout.getLLVMType()
1269                      : layout.getBaseSubobjectLLVMType());
1270
1271  unsigned numElements = structure->getNumElements();
1272  std::vector<llvm::Constant *> elements(numElements);
1273
1274  // Fill in all the bases.
1275  for (CXXRecordDecl::base_class_const_iterator
1276         I = record->bases_begin(), E = record->bases_end(); I != E; ++I) {
1277    if (I->isVirtual()) {
1278      // Ignore virtual bases; if we're laying out for a complete
1279      // object, we'll lay these out later.
1280      continue;
1281    }
1282
1283    const CXXRecordDecl *base =
1284      cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
1285
1286    // Ignore empty bases.
1287    if (base->isEmpty())
1288      continue;
1289
1290    unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base);
1291    llvm::Type *baseType = structure->getElementType(fieldIndex);
1292    elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
1293  }
1294
1295  // Fill in all the fields.
1296  for (RecordDecl::field_iterator I = record->field_begin(),
1297         E = record->field_end(); I != E; ++I) {
1298    const FieldDecl *field = *I;
1299
1300    // Fill in non-bitfields. (Bitfields always use a zero pattern, which we
1301    // will fill in later.)
1302    if (!field->isBitField()) {
1303      unsigned fieldIndex = layout.getLLVMFieldNo(field);
1304      elements[fieldIndex] = CGM.EmitNullConstant(field->getType());
1305    }
1306
1307    // For unions, stop after the first named field.
1308    if (record->isUnion() && field->getDeclName())
1309      break;
1310  }
1311
1312  // Fill in the virtual bases, if we're working with the complete object.
1313  if (asCompleteObject) {
1314    for (CXXRecordDecl::base_class_const_iterator
1315           I = record->vbases_begin(), E = record->vbases_end(); I != E; ++I) {
1316      const CXXRecordDecl *base =
1317        cast<CXXRecordDecl>(I->getType()->castAs<RecordType>()->getDecl());
1318
1319      // Ignore empty bases.
1320      if (base->isEmpty())
1321        continue;
1322
1323      unsigned fieldIndex = layout.getVirtualBaseIndex(base);
1324
1325      // We might have already laid this field out.
1326      if (elements[fieldIndex]) continue;
1327
1328      llvm::Type *baseType = structure->getElementType(fieldIndex);
1329      elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
1330    }
1331  }
1332
1333  // Now go through all other fields and zero them out.
1334  for (unsigned i = 0; i != numElements; ++i) {
1335    if (!elements[i])
1336      elements[i] = llvm::Constant::getNullValue(structure->getElementType(i));
1337  }
1338
1339  return llvm::ConstantStruct::get(structure, elements);
1340}
1341
1342/// Emit the null constant for a base subobject.
1343static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
1344                                               llvm::Type *baseType,
1345                                               const CXXRecordDecl *base) {
1346  const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base);
1347
1348  // Just zero out bases that don't have any pointer to data members.
1349  if (baseLayout.isZeroInitializableAsBase())
1350    return llvm::Constant::getNullValue(baseType);
1351
1352  // If the base type is a struct, we can just use its null constant.
1353  if (isa<llvm::StructType>(baseType)) {
1354    return EmitNullConstant(CGM, base, /*complete*/ false);
1355  }
1356
1357  // Otherwise, some bases are represented as arrays of i8 if the size
1358  // of the base is smaller than its corresponding LLVM type.  Figure
1359  // out how many elements this base array has.
1360  llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType);
1361  unsigned numBaseElements = baseArrayType->getNumElements();
1362
1363  // Fill in null data member pointers.
1364  SmallVector<llvm::Constant *, 16> baseElements(numBaseElements);
1365  FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base),
1366                               baseElements, 0);
1367
1368  // Now go through all other elements and zero them out.
1369  if (numBaseElements) {
1370    llvm::Constant *i8_zero = llvm::Constant::getNullValue(CGM.Int8Ty);
1371    for (unsigned i = 0; i != numBaseElements; ++i) {
1372      if (!baseElements[i])
1373        baseElements[i] = i8_zero;
1374    }
1375  }
1376
1377  return llvm::ConstantArray::get(baseArrayType, baseElements);
1378}
1379
1380llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
1381  if (getTypes().isZeroInitializable(T))
1382    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
1383
1384  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
1385    llvm::ArrayType *ATy =
1386      cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
1387
1388    QualType ElementTy = CAT->getElementType();
1389
1390    llvm::Constant *Element = EmitNullConstant(ElementTy);
1391    unsigned NumElements = CAT->getSize().getZExtValue();
1392
1393    if (Element->isNullValue())
1394      return llvm::ConstantAggregateZero::get(ATy);
1395
1396    SmallVector<llvm::Constant *, 8> Array(NumElements, Element);
1397    return llvm::ConstantArray::get(ATy, Array);
1398  }
1399
1400  if (const RecordType *RT = T->getAs<RecordType>()) {
1401    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1402    return ::EmitNullConstant(*this, RD, /*complete object*/ true);
1403  }
1404
1405  assert(T->isMemberPointerType() && "Should only see member pointers here!");
1406  assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
1407         "Should only see pointers to data members here!");
1408
1409  // Itanium C++ ABI 2.3:
1410  //   A NULL pointer is represented as -1.
1411  return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
1412}
1413
1414llvm::Constant *
1415CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) {
1416  return ::EmitNullConstant(*this, Record, false);
1417}
1418