CGExprConstant.cpp revision a7e6845660f91ec611427e1db842780e1ec12bdb 
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 "CGObjCRuntime.h"
17#include "CGRecordLayout.h"
18#include "clang/AST/APValue.h"
19#include "clang/AST/ASTContext.h"
20#include "clang/AST/RecordLayout.h"
21#include "clang/AST/StmtVisitor.h"
22#include "clang/Basic/Builtins.h"
23#include "llvm/Constants.h"
24#include "llvm/Function.h"
25#include "llvm/GlobalVariable.h"
26#include "llvm/Target/TargetData.h"
27using namespace clang;
28using namespace CodeGen;
29
30//===----------------------------------------------------------------------===//
31//                            ConstStructBuilder
32//===----------------------------------------------------------------------===//
33
34namespace {
35class ConstStructBuilder {
36  CodeGenModule &CGM;
37  CodeGenFunction *CGF;
38
39  bool Packed;
40  unsigned NextFieldOffsetInBytes;
41  unsigned LLVMStructAlignment;
42  std::vector<llvm::Constant *> Elements;
43public:
44  static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
45                                     InitListExpr *ILE);
46
47private:
48  ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
49    : CGM(CGM), CGF(CGF), Packed(false), NextFieldOffsetInBytes(0),
50    LLVMStructAlignment(1) { }
51
52  bool AppendField(const FieldDecl *Field, uint64_t FieldOffset,
53                   llvm::Constant *InitExpr);
54
55  void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
56                      llvm::ConstantInt *InitExpr);
57
58  void AppendPadding(uint64_t NumBytes);
59
60  void AppendTailPadding(uint64_t RecordSize);
61
62  void ConvertStructToPacked();
63
64  bool Build(InitListExpr *ILE);
65
66  unsigned getAlignment(const llvm::Constant *C) const {
67    if (Packed)  return 1;
68    return CGM.getTargetData().getABITypeAlignment(C->getType());
69  }
70
71  uint64_t getSizeInBytes(const llvm::Constant *C) const {
72    return CGM.getTargetData().getTypeAllocSize(C->getType());
73  }
74};
75
76bool ConstStructBuilder::
77AppendField(const FieldDecl *Field, uint64_t FieldOffset,
78            llvm::Constant *InitCst) {
79  uint64_t FieldOffsetInBytes = FieldOffset / 8;
80
81  assert(NextFieldOffsetInBytes <= FieldOffsetInBytes
82         && "Field offset mismatch!");
83
84  unsigned FieldAlignment = getAlignment(InitCst);
85
86  // Round up the field offset to the alignment of the field type.
87  uint64_t AlignedNextFieldOffsetInBytes =
88    llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment);
89
90  if (AlignedNextFieldOffsetInBytes > FieldOffsetInBytes) {
91    assert(!Packed && "Alignment is wrong even with a packed struct!");
92
93    // Convert the struct to a packed struct.
94    ConvertStructToPacked();
95
96    AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
97  }
98
99  if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) {
100    // We need to append padding.
101    AppendPadding(FieldOffsetInBytes - NextFieldOffsetInBytes);
102
103    assert(NextFieldOffsetInBytes == FieldOffsetInBytes &&
104           "Did not add enough padding!");
105
106    AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
107  }
108
109  // Add the field.
110  Elements.push_back(InitCst);
111  NextFieldOffsetInBytes = AlignedNextFieldOffsetInBytes +
112                             getSizeInBytes(InitCst);
113
114  if (Packed)
115    assert(LLVMStructAlignment == 1 && "Packed struct not byte-aligned!");
116  else
117    LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
118
119  return true;
120}
121
122void ConstStructBuilder::AppendBitField(const FieldDecl *Field,
123                                        uint64_t FieldOffset,
124                                        llvm::ConstantInt *CI) {
125  if (FieldOffset > NextFieldOffsetInBytes * 8) {
126    // We need to add padding.
127    uint64_t NumBytes =
128      llvm::RoundUpToAlignment(FieldOffset -
129                               NextFieldOffsetInBytes * 8, 8) / 8;
130
131    AppendPadding(NumBytes);
132  }
133
134  uint64_t FieldSize =
135    Field->getBitWidth()->EvaluateAsInt(CGM.getContext()).getZExtValue();
136
137  llvm::APInt FieldValue = CI->getValue();
138
139  // Promote the size of FieldValue if necessary
140  // FIXME: This should never occur, but currently it can because initializer
141  // constants are cast to bool, and because clang is not enforcing bitfield
142  // width limits.
143  if (FieldSize > FieldValue.getBitWidth())
144    FieldValue.zext(FieldSize);
145
146  // Truncate the size of FieldValue to the bit field size.
147  if (FieldSize < FieldValue.getBitWidth())
148    FieldValue.trunc(FieldSize);
149
150  if (FieldOffset < NextFieldOffsetInBytes * 8) {
151    // Either part of the field or the entire field can go into the previous
152    // byte.
153    assert(!Elements.empty() && "Elements can't be empty!");
154
155    unsigned BitsInPreviousByte =
156      NextFieldOffsetInBytes * 8 - FieldOffset;
157
158    bool FitsCompletelyInPreviousByte =
159      BitsInPreviousByte >= FieldValue.getBitWidth();
160
161    llvm::APInt Tmp = FieldValue;
162
163    if (!FitsCompletelyInPreviousByte) {
164      unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
165
166      if (CGM.getTargetData().isBigEndian()) {
167        Tmp = Tmp.lshr(NewFieldWidth);
168        Tmp.trunc(BitsInPreviousByte);
169
170        // We want the remaining high bits.
171        FieldValue.trunc(NewFieldWidth);
172      } else {
173        Tmp.trunc(BitsInPreviousByte);
174
175        // We want the remaining low bits.
176        FieldValue = FieldValue.lshr(BitsInPreviousByte);
177        FieldValue.trunc(NewFieldWidth);
178      }
179    }
180
181    Tmp.zext(8);
182    if (CGM.getTargetData().isBigEndian()) {
183      if (FitsCompletelyInPreviousByte)
184        Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
185    } else {
186      Tmp = Tmp.shl(8 - BitsInPreviousByte);
187    }
188
189    // 'or' in the bits that go into the previous byte.
190    llvm::Value *LastElt = Elements.back();
191    if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt))
192      Tmp |= Val->getValue();
193    else {
194      assert(isa<llvm::UndefValue>(LastElt));
195      // If there is an undef field that we're adding to, it can either be a
196      // scalar undef (in which case, we just replace it with our field) or it
197      // is an array.  If it is an array, we have to pull one byte off the
198      // array so that the other undef bytes stay around.
199      if (!isa<llvm::IntegerType>(LastElt->getType())) {
200        // The undef padding will be a multibyte array, create a new smaller
201        // padding and then an hole for our i8 to get plopped into.
202        assert(isa<llvm::ArrayType>(LastElt->getType()) &&
203               "Expected array padding of undefs");
204        const llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
205        assert(AT->getElementType()->isIntegerTy(8) &&
206               AT->getNumElements() != 0 &&
207               "Expected non-empty array padding of undefs");
208
209        // Remove the padding array.
210        NextFieldOffsetInBytes -= AT->getNumElements();
211        Elements.pop_back();
212
213        // Add the padding back in two chunks.
214        AppendPadding(AT->getNumElements()-1);
215        AppendPadding(1);
216        assert(isa<llvm::UndefValue>(Elements.back()) &&
217               Elements.back()->getType()->isIntegerTy(8) &&
218               "Padding addition didn't work right");
219      }
220    }
221
222    Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
223
224    if (FitsCompletelyInPreviousByte)
225      return;
226  }
227
228  while (FieldValue.getBitWidth() > 8) {
229    llvm::APInt Tmp;
230
231    if (CGM.getTargetData().isBigEndian()) {
232      // We want the high bits.
233      Tmp = FieldValue;
234      Tmp = Tmp.lshr(Tmp.getBitWidth() - 8);
235      Tmp.trunc(8);
236    } else {
237      // We want the low bits.
238      Tmp = FieldValue;
239      Tmp.trunc(8);
240
241      FieldValue = FieldValue.lshr(8);
242    }
243
244    Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
245    NextFieldOffsetInBytes++;
246
247    FieldValue.trunc(FieldValue.getBitWidth() - 8);
248  }
249
250  assert(FieldValue.getBitWidth() > 0 &&
251         "Should have at least one bit left!");
252  assert(FieldValue.getBitWidth() <= 8 &&
253         "Should not have more than a byte left!");
254
255  if (FieldValue.getBitWidth() < 8) {
256    if (CGM.getTargetData().isBigEndian()) {
257      unsigned BitWidth = FieldValue.getBitWidth();
258
259      FieldValue.zext(8);
260      FieldValue = FieldValue << (8 - BitWidth);
261    } else
262      FieldValue.zext(8);
263  }
264
265  // Append the last element.
266  Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
267                                            FieldValue));
268  NextFieldOffsetInBytes++;
269}
270
271void ConstStructBuilder::AppendPadding(uint64_t NumBytes) {
272  if (!NumBytes)
273    return;
274
275  const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
276  if (NumBytes > 1)
277    Ty = llvm::ArrayType::get(Ty, NumBytes);
278
279  llvm::Constant *C = llvm::UndefValue::get(Ty);
280  Elements.push_back(C);
281  assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!");
282
283  NextFieldOffsetInBytes += getSizeInBytes(C);
284}
285
286void ConstStructBuilder::AppendTailPadding(uint64_t RecordSize) {
287  assert(RecordSize % 8 == 0 && "Invalid record size!");
288
289  uint64_t RecordSizeInBytes = RecordSize / 8;
290  assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!");
291
292  unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes;
293  AppendPadding(NumPadBytes);
294}
295
296void ConstStructBuilder::ConvertStructToPacked() {
297  std::vector<llvm::Constant *> PackedElements;
298  uint64_t ElementOffsetInBytes = 0;
299
300  for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
301    llvm::Constant *C = Elements[i];
302
303    unsigned ElementAlign =
304      CGM.getTargetData().getABITypeAlignment(C->getType());
305    uint64_t AlignedElementOffsetInBytes =
306      llvm::RoundUpToAlignment(ElementOffsetInBytes, ElementAlign);
307
308    if (AlignedElementOffsetInBytes > ElementOffsetInBytes) {
309      // We need some padding.
310      uint64_t NumBytes =
311        AlignedElementOffsetInBytes - ElementOffsetInBytes;
312
313      const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
314      if (NumBytes > 1)
315        Ty = llvm::ArrayType::get(Ty, NumBytes);
316
317      llvm::Constant *Padding = llvm::UndefValue::get(Ty);
318      PackedElements.push_back(Padding);
319      ElementOffsetInBytes += getSizeInBytes(Padding);
320    }
321
322    PackedElements.push_back(C);
323    ElementOffsetInBytes += getSizeInBytes(C);
324  }
325
326  assert(ElementOffsetInBytes == NextFieldOffsetInBytes &&
327         "Packing the struct changed its size!");
328
329  Elements = PackedElements;
330  LLVMStructAlignment = 1;
331  Packed = true;
332}
333
334bool ConstStructBuilder::Build(InitListExpr *ILE) {
335  RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
336  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
337
338  unsigned FieldNo = 0;
339  unsigned ElementNo = 0;
340  for (RecordDecl::field_iterator Field = RD->field_begin(),
341       FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
342
343    // If this is a union, skip all the fields that aren't being initialized.
344    if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
345      continue;
346
347    // Don't emit anonymous bitfields, they just affect layout.
348    if (Field->isBitField() && !Field->getIdentifier())
349      continue;
350
351    // Get the initializer.  A struct can include fields without initializers,
352    // we just use explicit null values for them.
353    llvm::Constant *EltInit;
354    if (ElementNo < ILE->getNumInits())
355      EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++),
356                                     Field->getType(), CGF);
357    else
358      EltInit = CGM.EmitNullConstant(Field->getType());
359
360    if (!EltInit)
361      return false;
362
363    if (!Field->isBitField()) {
364      // Handle non-bitfield members.
365      if (!AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit))
366        return false;
367    } else {
368      // Otherwise we have a bitfield.
369      AppendBitField(*Field, Layout.getFieldOffset(FieldNo),
370                     cast<llvm::ConstantInt>(EltInit));
371    }
372  }
373
374  uint64_t LayoutSizeInBytes = Layout.getSize() / 8;
375
376  if (NextFieldOffsetInBytes > LayoutSizeInBytes) {
377    // If the struct is bigger than the size of the record type,
378    // we must have a flexible array member at the end.
379    assert(RD->hasFlexibleArrayMember() &&
380           "Must have flexible array member if struct is bigger than type!");
381
382    // No tail padding is necessary.
383    return true;
384  }
385
386  uint64_t LLVMSizeInBytes = llvm::RoundUpToAlignment(NextFieldOffsetInBytes,
387                                                      LLVMStructAlignment);
388
389  // Check if we need to convert the struct to a packed struct.
390  if (NextFieldOffsetInBytes <= LayoutSizeInBytes &&
391      LLVMSizeInBytes > LayoutSizeInBytes) {
392    assert(!Packed && "Size mismatch!");
393
394    ConvertStructToPacked();
395    assert(NextFieldOffsetInBytes <= LayoutSizeInBytes &&
396           "Converting to packed did not help!");
397  }
398
399  // Append tail padding if necessary.
400  AppendTailPadding(Layout.getSize());
401
402  assert(Layout.getSize() / 8 == NextFieldOffsetInBytes &&
403         "Tail padding mismatch!");
404
405  return true;
406}
407
408llvm::Constant *ConstStructBuilder::
409  BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF, InitListExpr *ILE) {
410  ConstStructBuilder Builder(CGM, CGF);
411
412  if (!Builder.Build(ILE))
413    return 0;
414
415  llvm::Constant *Result =
416  llvm::ConstantStruct::get(CGM.getLLVMContext(),
417                            Builder.Elements, Builder.Packed);
418
419  assert(llvm::RoundUpToAlignment(Builder.NextFieldOffsetInBytes,
420                                  Builder.getAlignment(Result)) ==
421         Builder.getSizeInBytes(Result) && "Size mismatch!");
422
423  return Result;
424}
425
426
427//===----------------------------------------------------------------------===//
428//                             ConstExprEmitter
429//===----------------------------------------------------------------------===//
430
431class ConstExprEmitter :
432  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
433  CodeGenModule &CGM;
434  CodeGenFunction *CGF;
435  llvm::LLVMContext &VMContext;
436public:
437  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
438    : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
439  }
440
441  //===--------------------------------------------------------------------===//
442  //                            Visitor Methods
443  //===--------------------------------------------------------------------===//
444
445  llvm::Constant *VisitStmt(Stmt *S) {
446    return 0;
447  }
448
449  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
450    return Visit(PE->getSubExpr());
451  }
452
453  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
454    return Visit(E->getInitializer());
455  }
456
457  llvm::Constant *EmitMemberFunctionPointer(CXXMethodDecl *MD) {
458    assert(MD->isInstance() && "Member function must not be static!");
459
460    MD = MD->getCanonicalDecl();
461
462    const llvm::Type *PtrDiffTy =
463      CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
464
465    llvm::Constant *Values[2];
466
467    Values[0] = CGM.GetCXXMemberFunctionPointerValue(MD);
468
469    // The adjustment will always be 0.
470    Values[1] = llvm::ConstantInt::get(PtrDiffTy, 0);
471
472    return llvm::ConstantStruct::get(CGM.getLLVMContext(),
473                                     Values, 2, /*Packed=*/false);
474  }
475
476  llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) {
477    if (const MemberPointerType *MPT =
478        E->getType()->getAs<MemberPointerType>()) {
479      QualType T = MPT->getPointeeType();
480      DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr());
481
482      NamedDecl *ND = DRE->getDecl();
483      if (T->isFunctionProtoType())
484        return EmitMemberFunctionPointer(cast<CXXMethodDecl>(ND));
485
486      // We have a pointer to data member.
487      return CGM.EmitPointerToDataMember(cast<FieldDecl>(ND));
488    }
489
490    return 0;
491  }
492
493  llvm::Constant *VisitBinSub(BinaryOperator *E) {
494    // This must be a pointer/pointer subtraction.  This only happens for
495    // address of label.
496    if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) ||
497       !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext())))
498      return 0;
499
500    llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(),
501                                               E->getLHS()->getType(), CGF);
502    llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(),
503                                               E->getRHS()->getType(), CGF);
504
505    const llvm::Type *ResultType = ConvertType(E->getType());
506    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
507    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
508
509    // No need to divide by element size, since addr of label is always void*,
510    // which has size 1 in GNUish.
511    return llvm::ConstantExpr::getSub(LHS, RHS);
512  }
513
514  llvm::Constant *VisitCastExpr(CastExpr* E) {
515    switch (E->getCastKind()) {
516    case CastExpr::CK_ToUnion: {
517      // GCC cast to union extension
518      assert(E->getType()->isUnionType() &&
519             "Destination type is not union type!");
520      const llvm::Type *Ty = ConvertType(E->getType());
521      Expr *SubExpr = E->getSubExpr();
522
523      llvm::Constant *C =
524        CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
525      if (!C)
526        return 0;
527
528      // Build a struct with the union sub-element as the first member,
529      // and padded to the appropriate size
530      std::vector<llvm::Constant*> Elts;
531      std::vector<const llvm::Type*> Types;
532      Elts.push_back(C);
533      Types.push_back(C->getType());
534      unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
535      unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty);
536
537      assert(CurSize <= TotalSize && "Union size mismatch!");
538      if (unsigned NumPadBytes = TotalSize - CurSize) {
539        const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext);
540        if (NumPadBytes > 1)
541          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
542
543        Elts.push_back(llvm::UndefValue::get(Ty));
544        Types.push_back(Ty);
545      }
546
547      llvm::StructType* STy =
548        llvm::StructType::get(C->getType()->getContext(), Types, false);
549      return llvm::ConstantStruct::get(STy, Elts);
550    }
551    case CastExpr::CK_NullToMemberPointer:
552      return CGM.EmitNullConstant(E->getType());
553
554    case CastExpr::CK_BaseToDerivedMemberPointer: {
555      Expr *SubExpr = E->getSubExpr();
556
557      const MemberPointerType *SrcTy =
558        SubExpr->getType()->getAs<MemberPointerType>();
559      const MemberPointerType *DestTy =
560        E->getType()->getAs<MemberPointerType>();
561
562      const CXXRecordDecl *DerivedClass =
563        cast<CXXRecordDecl>(cast<RecordType>(DestTy->getClass())->getDecl());
564
565      if (SrcTy->getPointeeType()->isFunctionProtoType()) {
566        llvm::Constant *C =
567          CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
568        if (!C)
569          return 0;
570
571        llvm::ConstantStruct *CS = cast<llvm::ConstantStruct>(C);
572
573        // Check if we need to update the adjustment.
574        if (llvm::Constant *Offset =
575            CGM.GetNonVirtualBaseClassOffset(DerivedClass,
576                                             E->path_begin(),
577                                             E->path_end())) {
578          llvm::Constant *Values[2];
579
580          Values[0] = CS->getOperand(0);
581          Values[1] = llvm::ConstantExpr::getAdd(CS->getOperand(1), Offset);
582          return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2,
583                                           /*Packed=*/false);
584        }
585
586        return CS;
587      }
588    }
589
590    case CastExpr::CK_BitCast:
591      // This must be a member function pointer cast.
592      return Visit(E->getSubExpr());
593
594    default: {
595      // FIXME: This should be handled by the CK_NoOp cast kind.
596      // Explicit and implicit no-op casts
597      QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType();
598      if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy))
599        return Visit(E->getSubExpr());
600
601      // Handle integer->integer casts for address-of-label differences.
602      if (Ty->isIntegerType() && SubTy->isIntegerType() &&
603          CGF) {
604        llvm::Value *Src = Visit(E->getSubExpr());
605        if (Src == 0) return 0;
606
607        // Use EmitScalarConversion to perform the conversion.
608        return cast<llvm::Constant>(CGF->EmitScalarConversion(Src, SubTy, Ty));
609      }
610
611      return 0;
612    }
613    }
614  }
615
616  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
617    return Visit(DAE->getExpr());
618  }
619
620  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
621    unsigned NumInitElements = ILE->getNumInits();
622    if (NumInitElements == 1 &&
623        (isa<StringLiteral>(ILE->getInit(0)) ||
624         isa<ObjCEncodeExpr>(ILE->getInit(0))))
625      return Visit(ILE->getInit(0));
626
627    std::vector<llvm::Constant*> Elts;
628    const llvm::ArrayType *AType =
629        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
630    const llvm::Type *ElemTy = AType->getElementType();
631    unsigned NumElements = AType->getNumElements();
632
633    // Initialising an array requires us to automatically
634    // initialise any elements that have not been initialised explicitly
635    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
636
637    // Copy initializer elements.
638    unsigned i = 0;
639    bool RewriteType = false;
640    for (; i < NumInitableElts; ++i) {
641      Expr *Init = ILE->getInit(i);
642      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
643      if (!C)
644        return 0;
645      RewriteType |= (C->getType() != ElemTy);
646      Elts.push_back(C);
647    }
648
649    // Initialize remaining array elements.
650    // FIXME: This doesn't handle member pointers correctly!
651    for (; i < NumElements; ++i)
652      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
653
654    if (RewriteType) {
655      // FIXME: Try to avoid packing the array
656      std::vector<const llvm::Type*> Types;
657      for (unsigned i = 0; i < Elts.size(); ++i)
658        Types.push_back(Elts[i]->getType());
659      const llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
660                                                            Types, true);
661      return llvm::ConstantStruct::get(SType, Elts);
662    }
663
664    return llvm::ConstantArray::get(AType, Elts);
665  }
666
667  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
668    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
669  }
670
671  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
672    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
673  }
674
675  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
676    return CGM.EmitNullConstant(E->getType());
677  }
678
679  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
680    if (ILE->getType()->isScalarType()) {
681      // We have a scalar in braces. Just use the first element.
682      if (ILE->getNumInits() > 0) {
683        Expr *Init = ILE->getInit(0);
684        return CGM.EmitConstantExpr(Init, Init->getType(), CGF);
685      }
686      return CGM.EmitNullConstant(ILE->getType());
687    }
688
689    if (ILE->getType()->isArrayType())
690      return EmitArrayInitialization(ILE);
691
692    if (ILE->getType()->isRecordType())
693      return EmitStructInitialization(ILE);
694
695    if (ILE->getType()->isUnionType())
696      return EmitUnionInitialization(ILE);
697
698    // If ILE was a constant vector, we would have handled it already.
699    if (ILE->getType()->isVectorType())
700      return 0;
701
702    assert(0 && "Unable to handle InitListExpr");
703    // Get rid of control reaches end of void function warning.
704    // Not reached.
705    return 0;
706  }
707
708  llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) {
709    if (!E->getConstructor()->isTrivial())
710      return 0;
711
712    QualType Ty = E->getType();
713
714    // FIXME: We should not have to call getBaseElementType here.
715    const RecordType *RT =
716      CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
717    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
718
719    // If the class doesn't have a trivial destructor, we can't emit it as a
720    // constant expr.
721    if (!RD->hasTrivialDestructor())
722      return 0;
723
724    // Only copy and default constructors can be trivial.
725
726
727    if (E->getNumArgs()) {
728      assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
729      assert(E->getConstructor()->isCopyConstructor() &&
730             "trivial ctor has argument but isn't a copy ctor");
731
732      Expr *Arg = E->getArg(0);
733      assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
734             "argument to copy ctor is of wrong type");
735
736      return Visit(Arg);
737    }
738
739    return CGM.EmitNullConstant(Ty);
740  }
741
742  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
743    assert(!E->getType()->isPointerType() && "Strings are always arrays");
744
745    // This must be a string initializing an array in a static initializer.
746    // Don't emit it as the address of the string, emit the string data itself
747    // as an inline array.
748    return llvm::ConstantArray::get(VMContext,
749                                    CGM.GetStringForStringLiteral(E), false);
750  }
751
752  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
753    // This must be an @encode initializing an array in a static initializer.
754    // Don't emit it as the address of the string, emit the string data itself
755    // as an inline array.
756    std::string Str;
757    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
758    const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
759
760    // Resize the string to the right size, adding zeros at the end, or
761    // truncating as needed.
762    Str.resize(CAT->getSize().getZExtValue(), '\0');
763    return llvm::ConstantArray::get(VMContext, Str, false);
764  }
765
766  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
767    return Visit(E->getSubExpr());
768  }
769
770  // Utility methods
771  const llvm::Type *ConvertType(QualType T) {
772    return CGM.getTypes().ConvertType(T);
773  }
774
775public:
776  llvm::Constant *EmitLValue(Expr *E) {
777    switch (E->getStmtClass()) {
778    default: break;
779    case Expr::CompoundLiteralExprClass: {
780      // Note that due to the nature of compound literals, this is guaranteed
781      // to be the only use of the variable, so we just generate it here.
782      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
783      llvm::Constant* C = Visit(CLE->getInitializer());
784      // FIXME: "Leaked" on failure.
785      if (C)
786        C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
787                                     E->getType().isConstant(CGM.getContext()),
788                                     llvm::GlobalValue::InternalLinkage,
789                                     C, ".compoundliteral", 0, false,
790                                     E->getType().getAddressSpace());
791      return C;
792    }
793    case Expr::DeclRefExprClass: {
794      ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
795      if (Decl->hasAttr<WeakRefAttr>())
796        return CGM.GetWeakRefReference(Decl);
797      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
798        return CGM.GetAddrOfFunction(FD);
799      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
800        // We can never refer to a variable with local storage.
801        if (!VD->hasLocalStorage()) {
802          if (VD->isFileVarDecl() || VD->hasExternalStorage())
803            return CGM.GetAddrOfGlobalVar(VD);
804          else if (VD->isBlockVarDecl()) {
805            assert(CGF && "Can't access static local vars without CGF");
806            return CGF->GetAddrOfStaticLocalVar(VD);
807          }
808        }
809      }
810      break;
811    }
812    case Expr::StringLiteralClass:
813      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
814    case Expr::ObjCEncodeExprClass:
815      return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
816    case Expr::ObjCStringLiteralClass: {
817      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
818      llvm::Constant *C =
819          CGM.getObjCRuntime().GenerateConstantString(SL->getString());
820      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
821    }
822    case Expr::PredefinedExprClass: {
823      unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
824      if (CGF) {
825        LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E));
826        return cast<llvm::Constant>(Res.getAddress());
827      } else if (Type == PredefinedExpr::PrettyFunction) {
828        return CGM.GetAddrOfConstantCString("top level", ".tmp");
829      }
830
831      return CGM.GetAddrOfConstantCString("", ".tmp");
832    }
833    case Expr::AddrLabelExprClass: {
834      assert(CGF && "Invalid address of label expression outside function.");
835      llvm::Constant *Ptr =
836        CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
837      return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
838    }
839    case Expr::CallExprClass: {
840      CallExpr* CE = cast<CallExpr>(E);
841      unsigned builtin = CE->isBuiltinCall(CGM.getContext());
842      if (builtin !=
843            Builtin::BI__builtin___CFStringMakeConstantString &&
844          builtin !=
845            Builtin::BI__builtin___NSStringMakeConstantString)
846        break;
847      const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
848      const StringLiteral *Literal = cast<StringLiteral>(Arg);
849      if (builtin ==
850            Builtin::BI__builtin___NSStringMakeConstantString) {
851        return CGM.getObjCRuntime().GenerateConstantString(Literal);
852      }
853      // FIXME: need to deal with UCN conversion issues.
854      return CGM.GetAddrOfConstantCFString(Literal);
855    }
856    case Expr::BlockExprClass: {
857      std::string FunctionName;
858      if (CGF)
859        FunctionName = CGF->CurFn->getName();
860      else
861        FunctionName = "global";
862
863      return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
864    }
865    }
866
867    return 0;
868  }
869};
870
871}  // end anonymous namespace.
872
873llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
874                                                QualType DestType,
875                                                CodeGenFunction *CGF) {
876  Expr::EvalResult Result;
877
878  bool Success = false;
879
880  if (DestType->isReferenceType())
881    Success = E->EvaluateAsLValue(Result, Context);
882  else
883    Success = E->Evaluate(Result, Context);
884
885  if (Success && !Result.HasSideEffects) {
886    switch (Result.Val.getKind()) {
887    case APValue::Uninitialized:
888      assert(0 && "Constant expressions should be initialized.");
889      return 0;
890    case APValue::LValue: {
891      const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
892      llvm::Constant *Offset =
893        llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext),
894                               Result.Val.getLValueOffset().getQuantity());
895
896      llvm::Constant *C;
897      if (const Expr *LVBase = Result.Val.getLValueBase()) {
898        C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
899
900        // Apply offset if necessary.
901        if (!Offset->isNullValue()) {
902          const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext);
903          llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type);
904          Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1);
905          C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
906        }
907
908        // Convert to the appropriate type; this could be an lvalue for
909        // an integer.
910        if (isa<llvm::PointerType>(DestTy))
911          return llvm::ConstantExpr::getBitCast(C, DestTy);
912
913        return llvm::ConstantExpr::getPtrToInt(C, DestTy);
914      } else {
915        C = Offset;
916
917        // Convert to the appropriate type; this could be an lvalue for
918        // an integer.
919        if (isa<llvm::PointerType>(DestTy))
920          return llvm::ConstantExpr::getIntToPtr(C, DestTy);
921
922        // If the types don't match this should only be a truncate.
923        if (C->getType() != DestTy)
924          return llvm::ConstantExpr::getTrunc(C, DestTy);
925
926        return C;
927      }
928    }
929    case APValue::Int: {
930      llvm::Constant *C = llvm::ConstantInt::get(VMContext,
931                                                 Result.Val.getInt());
932
933      if (C->getType()->isIntegerTy(1)) {
934        const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
935        C = llvm::ConstantExpr::getZExt(C, BoolTy);
936      }
937      return C;
938    }
939    case APValue::ComplexInt: {
940      llvm::Constant *Complex[2];
941
942      Complex[0] = llvm::ConstantInt::get(VMContext,
943                                          Result.Val.getComplexIntReal());
944      Complex[1] = llvm::ConstantInt::get(VMContext,
945                                          Result.Val.getComplexIntImag());
946
947      // FIXME: the target may want to specify that this is packed.
948      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
949    }
950    case APValue::Float:
951      return llvm::ConstantFP::get(VMContext, Result.Val.getFloat());
952    case APValue::ComplexFloat: {
953      llvm::Constant *Complex[2];
954
955      Complex[0] = llvm::ConstantFP::get(VMContext,
956                                         Result.Val.getComplexFloatReal());
957      Complex[1] = llvm::ConstantFP::get(VMContext,
958                                         Result.Val.getComplexFloatImag());
959
960      // FIXME: the target may want to specify that this is packed.
961      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
962    }
963    case APValue::Vector: {
964      llvm::SmallVector<llvm::Constant *, 4> Inits;
965      unsigned NumElts = Result.Val.getVectorLength();
966
967      for (unsigned i = 0; i != NumElts; ++i) {
968        APValue &Elt = Result.Val.getVectorElt(i);
969        if (Elt.isInt())
970          Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
971        else
972          Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
973      }
974      return llvm::ConstantVector::get(&Inits[0], Inits.size());
975    }
976    }
977  }
978
979  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
980  if (C && C->getType()->isIntegerTy(1)) {
981    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
982    C = llvm::ConstantExpr::getZExt(C, BoolTy);
983  }
984  return C;
985}
986
987static void
988FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T,
989                             std::vector<llvm::Constant *> &Elements,
990                             uint64_t StartOffset) {
991  assert(StartOffset % 8 == 0 && "StartOffset not byte aligned!");
992
993  if (!CGM.getTypes().ContainsPointerToDataMember(T))
994    return;
995
996  if (const ConstantArrayType *CAT =
997        CGM.getContext().getAsConstantArrayType(T)) {
998    QualType ElementTy = CAT->getElementType();
999    uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy);
1000
1001    for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) {
1002      FillInNullDataMemberPointers(CGM, ElementTy, Elements,
1003                                   StartOffset + I * ElementSize);
1004    }
1005  } else if (const RecordType *RT = T->getAs<RecordType>()) {
1006    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1007    const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
1008
1009    // Go through all bases and fill in any null pointer to data members.
1010    for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1011         E = RD->bases_end(); I != E; ++I) {
1012      if (I->isVirtual()) {
1013        // FIXME: We should initialize null pointer to data members in virtual
1014        // bases here.
1015        continue;
1016      }
1017
1018      const CXXRecordDecl *BaseDecl =
1019      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1020
1021      // Ignore empty bases.
1022      if (BaseDecl->isEmpty())
1023        continue;
1024
1025      // Ignore bases that don't have any pointer to data members.
1026      if (!CGM.getTypes().ContainsPointerToDataMember(BaseDecl))
1027        continue;
1028
1029      uint64_t BaseOffset = Layout.getBaseClassOffset(BaseDecl);
1030      FillInNullDataMemberPointers(CGM, I->getType(),
1031                                   Elements, StartOffset + BaseOffset);
1032    }
1033
1034    // Visit all fields.
1035    unsigned FieldNo = 0;
1036    for (RecordDecl::field_iterator I = RD->field_begin(),
1037         E = RD->field_end(); I != E; ++I, ++FieldNo) {
1038      QualType FieldType = I->getType();
1039
1040      if (!CGM.getTypes().ContainsPointerToDataMember(FieldType))
1041        continue;
1042
1043      uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo);
1044      FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset);
1045    }
1046  } else {
1047    assert(T->isMemberPointerType() && "Should only see member pointers here!");
1048    assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
1049           "Should only see pointers to data members here!");
1050
1051    uint64_t StartIndex = StartOffset / 8;
1052    uint64_t EndIndex = StartIndex + CGM.getContext().getTypeSize(T) / 8;
1053
1054    llvm::Constant *NegativeOne =
1055      llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()),
1056                             -1ULL, /*isSigned=*/true);
1057
1058    // Fill in the null data member pointer.
1059    for (uint64_t I = StartIndex; I != EndIndex; ++I)
1060      Elements[I] = NegativeOne;
1061  }
1062}
1063
1064llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
1065  if (!getTypes().ContainsPointerToDataMember(T))
1066    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
1067
1068  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
1069
1070    QualType ElementTy = CAT->getElementType();
1071
1072    llvm::Constant *Element = EmitNullConstant(ElementTy);
1073    unsigned NumElements = CAT->getSize().getZExtValue();
1074    std::vector<llvm::Constant *> Array(NumElements);
1075    for (unsigned i = 0; i != NumElements; ++i)
1076      Array[i] = Element;
1077
1078    const llvm::ArrayType *ATy =
1079      cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
1080    return llvm::ConstantArray::get(ATy, Array);
1081  }
1082
1083  if (const RecordType *RT = T->getAs<RecordType>()) {
1084    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1085    const llvm::StructType *STy =
1086      cast<llvm::StructType>(getTypes().ConvertTypeForMem(T));
1087    unsigned NumElements = STy->getNumElements();
1088    std::vector<llvm::Constant *> Elements(NumElements);
1089
1090    const CGRecordLayout &Layout = getTypes().getCGRecordLayout(RD);
1091
1092    // Go through all bases and fill in any null pointer to data members.
1093    for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1094         E = RD->bases_end(); I != E; ++I) {
1095      if (I->isVirtual()) {
1096        // FIXME: We should initialize null pointer to data members in virtual
1097        // bases here.
1098        continue;
1099      }
1100
1101      const CXXRecordDecl *BaseDecl =
1102        cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1103
1104      // Ignore empty bases.
1105      if (BaseDecl->isEmpty())
1106        continue;
1107
1108      // Ignore bases that don't have any pointer to data members.
1109      if (!getTypes().ContainsPointerToDataMember(BaseDecl))
1110        continue;
1111
1112      // Currently, all bases are arrays of i8. Figure out how many elements
1113      // this base array has.
1114      unsigned BaseFieldNo = Layout.getNonVirtualBaseLLVMFieldNo(BaseDecl);
1115      const llvm::ArrayType *BaseArrayTy =
1116        cast<llvm::ArrayType>(STy->getElementType(BaseFieldNo));
1117
1118      unsigned NumBaseElements = BaseArrayTy->getNumElements();
1119      std::vector<llvm::Constant *> BaseElements(NumBaseElements);
1120
1121      // Now fill in null data member pointers.
1122      FillInNullDataMemberPointers(*this, I->getType(), BaseElements, 0);
1123
1124      // Now go through all other elements and zero them out.
1125      if (NumBaseElements) {
1126        llvm::Constant *Zero =
1127          llvm::ConstantInt::get(llvm::Type::getInt8Ty(getLLVMContext()), 0);
1128
1129        for (unsigned I = 0; I != NumBaseElements; ++I) {
1130          if (!BaseElements[I])
1131            BaseElements[I] = Zero;
1132        }
1133      }
1134
1135      Elements[BaseFieldNo] = llvm::ConstantArray::get(BaseArrayTy,
1136                                                       BaseElements);
1137    }
1138
1139    for (RecordDecl::field_iterator I = RD->field_begin(),
1140         E = RD->field_end(); I != E; ++I) {
1141      const FieldDecl *FD = *I;
1142
1143      // Ignore bit fields.
1144      if (FD->isBitField())
1145        continue;
1146
1147      unsigned FieldNo = Layout.getLLVMFieldNo(FD);
1148      Elements[FieldNo] = EmitNullConstant(FD->getType());
1149    }
1150
1151    // Now go through all other fields and zero them out.
1152    for (unsigned i = 0; i != NumElements; ++i) {
1153      if (!Elements[i])
1154        Elements[i] = llvm::Constant::getNullValue(STy->getElementType(i));
1155    }
1156
1157    return llvm::ConstantStruct::get(STy, Elements);
1158  }
1159
1160  assert(T->isMemberPointerType() && "Should only see member pointers here!");
1161  assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
1162         "Should only see pointers to data members here!");
1163
1164  // Itanium C++ ABI 2.3:
1165  //   A NULL pointer is represented as -1.
1166  return llvm::ConstantInt::get(getTypes().ConvertTypeForMem(T), -1ULL,
1167                                /*isSigned=*/true);
1168}
1169
1170llvm::Constant *
1171CodeGenModule::EmitPointerToDataMember(const FieldDecl *FD) {
1172
1173  // Itanium C++ ABI 2.3:
1174  //   A pointer to data member is an offset from the base address of the class
1175  //   object containing it, represented as a ptrdiff_t
1176
1177  const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(FD->getParent());
1178  QualType ClassType =
1179    getContext().getTypeDeclType(const_cast<CXXRecordDecl *>(ClassDecl));
1180
1181  const llvm::StructType *ClassLTy =
1182    cast<llvm::StructType>(getTypes().ConvertType(ClassType));
1183
1184  const CGRecordLayout &RL =
1185    getTypes().getCGRecordLayout(FD->getParent());
1186  unsigned FieldNo = RL.getLLVMFieldNo(FD);
1187  uint64_t Offset =
1188    getTargetData().getStructLayout(ClassLTy)->getElementOffset(FieldNo);
1189
1190  const llvm::Type *PtrDiffTy =
1191    getTypes().ConvertType(getContext().getPointerDiffType());
1192
1193  return llvm::ConstantInt::get(PtrDiffTy, Offset);
1194}
1195