CGExprConstant.cpp revision 875ab10245d3bf37252dd822aa1616bb0a391095 
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    return CGM.getCXXABI().EmitMemberFunctionPointer(MD);
459  }
460
461  llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) {
462    if (const MemberPointerType *MPT =
463        E->getType()->getAs<MemberPointerType>()) {
464      QualType T = MPT->getPointeeType();
465      DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr());
466
467      NamedDecl *ND = DRE->getDecl();
468      if (T->isFunctionProtoType())
469        return EmitMemberFunctionPointer(cast<CXXMethodDecl>(ND));
470
471      // We have a pointer to data member.
472      return CGM.EmitPointerToDataMember(cast<FieldDecl>(ND));
473    }
474
475    return 0;
476  }
477
478  llvm::Constant *VisitBinSub(BinaryOperator *E) {
479    // This must be a pointer/pointer subtraction.  This only happens for
480    // address of label.
481    if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) ||
482       !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext())))
483      return 0;
484
485    llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(),
486                                               E->getLHS()->getType(), CGF);
487    llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(),
488                                               E->getRHS()->getType(), CGF);
489
490    const llvm::Type *ResultType = ConvertType(E->getType());
491    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
492    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
493
494    // No need to divide by element size, since addr of label is always void*,
495    // which has size 1 in GNUish.
496    return llvm::ConstantExpr::getSub(LHS, RHS);
497  }
498
499  llvm::Constant *VisitCastExpr(CastExpr* E) {
500    switch (E->getCastKind()) {
501    case CastExpr::CK_ToUnion: {
502      // GCC cast to union extension
503      assert(E->getType()->isUnionType() &&
504             "Destination type is not union type!");
505      const llvm::Type *Ty = ConvertType(E->getType());
506      Expr *SubExpr = E->getSubExpr();
507
508      llvm::Constant *C =
509        CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
510      if (!C)
511        return 0;
512
513      // Build a struct with the union sub-element as the first member,
514      // and padded to the appropriate size
515      std::vector<llvm::Constant*> Elts;
516      std::vector<const llvm::Type*> Types;
517      Elts.push_back(C);
518      Types.push_back(C->getType());
519      unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
520      unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty);
521
522      assert(CurSize <= TotalSize && "Union size mismatch!");
523      if (unsigned NumPadBytes = TotalSize - CurSize) {
524        const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext);
525        if (NumPadBytes > 1)
526          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
527
528        Elts.push_back(llvm::UndefValue::get(Ty));
529        Types.push_back(Ty);
530      }
531
532      llvm::StructType* STy =
533        llvm::StructType::get(C->getType()->getContext(), Types, false);
534      return llvm::ConstantStruct::get(STy, Elts);
535    }
536    case CastExpr::CK_NullToMemberPointer:
537      return CGM.getCXXABI().EmitNullMemberFunctionPointer(
538                                   E->getType()->getAs<MemberPointerType>());
539
540    case CastExpr::CK_BaseToDerivedMemberPointer: {
541      Expr *SubExpr = E->getSubExpr();
542
543      llvm::Constant *C =
544        CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
545      if (!C) return 0;
546
547      return CGM.getCXXABI().EmitMemberFunctionPointerConversion(C, E);
548    }
549
550    case CastExpr::CK_BitCast:
551      // This must be a member function pointer cast.
552      return Visit(E->getSubExpr());
553
554    default: {
555      // FIXME: This should be handled by the CK_NoOp cast kind.
556      // Explicit and implicit no-op casts
557      QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType();
558      if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy))
559        return Visit(E->getSubExpr());
560
561      // Handle integer->integer casts for address-of-label differences.
562      if (Ty->isIntegerType() && SubTy->isIntegerType() &&
563          CGF) {
564        llvm::Value *Src = Visit(E->getSubExpr());
565        if (Src == 0) return 0;
566
567        // Use EmitScalarConversion to perform the conversion.
568        return cast<llvm::Constant>(CGF->EmitScalarConversion(Src, SubTy, Ty));
569      }
570
571      return 0;
572    }
573    }
574  }
575
576  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
577    return Visit(DAE->getExpr());
578  }
579
580  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
581    unsigned NumInitElements = ILE->getNumInits();
582    if (NumInitElements == 1 &&
583        (isa<StringLiteral>(ILE->getInit(0)) ||
584         isa<ObjCEncodeExpr>(ILE->getInit(0))))
585      return Visit(ILE->getInit(0));
586
587    std::vector<llvm::Constant*> Elts;
588    const llvm::ArrayType *AType =
589        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
590    const llvm::Type *ElemTy = AType->getElementType();
591    unsigned NumElements = AType->getNumElements();
592
593    // Initialising an array requires us to automatically
594    // initialise any elements that have not been initialised explicitly
595    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
596
597    // Copy initializer elements.
598    unsigned i = 0;
599    bool RewriteType = false;
600    for (; i < NumInitableElts; ++i) {
601      Expr *Init = ILE->getInit(i);
602      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
603      if (!C)
604        return 0;
605      RewriteType |= (C->getType() != ElemTy);
606      Elts.push_back(C);
607    }
608
609    // Initialize remaining array elements.
610    // FIXME: This doesn't handle member pointers correctly!
611    for (; i < NumElements; ++i)
612      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
613
614    if (RewriteType) {
615      // FIXME: Try to avoid packing the array
616      std::vector<const llvm::Type*> Types;
617      for (unsigned i = 0; i < Elts.size(); ++i)
618        Types.push_back(Elts[i]->getType());
619      const llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
620                                                            Types, true);
621      return llvm::ConstantStruct::get(SType, Elts);
622    }
623
624    return llvm::ConstantArray::get(AType, Elts);
625  }
626
627  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
628    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
629  }
630
631  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
632    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
633  }
634
635  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
636    return CGM.EmitNullConstant(E->getType());
637  }
638
639  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
640    if (ILE->getType()->isScalarType()) {
641      // We have a scalar in braces. Just use the first element.
642      if (ILE->getNumInits() > 0) {
643        Expr *Init = ILE->getInit(0);
644        return CGM.EmitConstantExpr(Init, Init->getType(), CGF);
645      }
646      return CGM.EmitNullConstant(ILE->getType());
647    }
648
649    if (ILE->getType()->isArrayType())
650      return EmitArrayInitialization(ILE);
651
652    if (ILE->getType()->isRecordType())
653      return EmitStructInitialization(ILE);
654
655    if (ILE->getType()->isUnionType())
656      return EmitUnionInitialization(ILE);
657
658    // If ILE was a constant vector, we would have handled it already.
659    if (ILE->getType()->isVectorType())
660      return 0;
661
662    assert(0 && "Unable to handle InitListExpr");
663    // Get rid of control reaches end of void function warning.
664    // Not reached.
665    return 0;
666  }
667
668  llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) {
669    if (!E->getConstructor()->isTrivial())
670      return 0;
671
672    QualType Ty = E->getType();
673
674    // FIXME: We should not have to call getBaseElementType here.
675    const RecordType *RT =
676      CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
677    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
678
679    // If the class doesn't have a trivial destructor, we can't emit it as a
680    // constant expr.
681    if (!RD->hasTrivialDestructor())
682      return 0;
683
684    // Only copy and default constructors can be trivial.
685
686
687    if (E->getNumArgs()) {
688      assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
689      assert(E->getConstructor()->isCopyConstructor() &&
690             "trivial ctor has argument but isn't a copy ctor");
691
692      Expr *Arg = E->getArg(0);
693      assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
694             "argument to copy ctor is of wrong type");
695
696      return Visit(Arg);
697    }
698
699    return CGM.EmitNullConstant(Ty);
700  }
701
702  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
703    assert(!E->getType()->isPointerType() && "Strings are always arrays");
704
705    // This must be a string initializing an array in a static initializer.
706    // Don't emit it as the address of the string, emit the string data itself
707    // as an inline array.
708    return llvm::ConstantArray::get(VMContext,
709                                    CGM.GetStringForStringLiteral(E), false);
710  }
711
712  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
713    // This must be an @encode initializing an array in a static initializer.
714    // Don't emit it as the address of the string, emit the string data itself
715    // as an inline array.
716    std::string Str;
717    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
718    const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
719
720    // Resize the string to the right size, adding zeros at the end, or
721    // truncating as needed.
722    Str.resize(CAT->getSize().getZExtValue(), '\0');
723    return llvm::ConstantArray::get(VMContext, Str, false);
724  }
725
726  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
727    return Visit(E->getSubExpr());
728  }
729
730  // Utility methods
731  const llvm::Type *ConvertType(QualType T) {
732    return CGM.getTypes().ConvertType(T);
733  }
734
735public:
736  llvm::Constant *EmitLValue(Expr *E) {
737    switch (E->getStmtClass()) {
738    default: break;
739    case Expr::CompoundLiteralExprClass: {
740      // Note that due to the nature of compound literals, this is guaranteed
741      // to be the only use of the variable, so we just generate it here.
742      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
743      llvm::Constant* C = Visit(CLE->getInitializer());
744      // FIXME: "Leaked" on failure.
745      if (C)
746        C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
747                                     E->getType().isConstant(CGM.getContext()),
748                                     llvm::GlobalValue::InternalLinkage,
749                                     C, ".compoundliteral", 0, false,
750                                     E->getType().getAddressSpace());
751      return C;
752    }
753    case Expr::DeclRefExprClass: {
754      ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
755      if (Decl->hasAttr<WeakRefAttr>())
756        return CGM.GetWeakRefReference(Decl);
757      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
758        return CGM.GetAddrOfFunction(FD);
759      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
760        // We can never refer to a variable with local storage.
761        if (!VD->hasLocalStorage()) {
762          if (VD->isFileVarDecl() || VD->hasExternalStorage())
763            return CGM.GetAddrOfGlobalVar(VD);
764          else if (VD->isBlockVarDecl()) {
765            assert(CGF && "Can't access static local vars without CGF");
766            return CGF->GetAddrOfStaticLocalVar(VD);
767          }
768        }
769      }
770      break;
771    }
772    case Expr::StringLiteralClass:
773      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
774    case Expr::ObjCEncodeExprClass:
775      return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
776    case Expr::ObjCStringLiteralClass: {
777      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
778      llvm::Constant *C =
779          CGM.getObjCRuntime().GenerateConstantString(SL->getString());
780      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
781    }
782    case Expr::PredefinedExprClass: {
783      unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
784      if (CGF) {
785        LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E));
786        return cast<llvm::Constant>(Res.getAddress());
787      } else if (Type == PredefinedExpr::PrettyFunction) {
788        return CGM.GetAddrOfConstantCString("top level", ".tmp");
789      }
790
791      return CGM.GetAddrOfConstantCString("", ".tmp");
792    }
793    case Expr::AddrLabelExprClass: {
794      assert(CGF && "Invalid address of label expression outside function.");
795      llvm::Constant *Ptr =
796        CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
797      return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
798    }
799    case Expr::CallExprClass: {
800      CallExpr* CE = cast<CallExpr>(E);
801      unsigned builtin = CE->isBuiltinCall(CGM.getContext());
802      if (builtin !=
803            Builtin::BI__builtin___CFStringMakeConstantString &&
804          builtin !=
805            Builtin::BI__builtin___NSStringMakeConstantString)
806        break;
807      const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
808      const StringLiteral *Literal = cast<StringLiteral>(Arg);
809      if (builtin ==
810            Builtin::BI__builtin___NSStringMakeConstantString) {
811        return CGM.getObjCRuntime().GenerateConstantString(Literal);
812      }
813      // FIXME: need to deal with UCN conversion issues.
814      return CGM.GetAddrOfConstantCFString(Literal);
815    }
816    case Expr::BlockExprClass: {
817      std::string FunctionName;
818      if (CGF)
819        FunctionName = CGF->CurFn->getName();
820      else
821        FunctionName = "global";
822
823      return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
824    }
825    }
826
827    return 0;
828  }
829};
830
831}  // end anonymous namespace.
832
833llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
834                                                QualType DestType,
835                                                CodeGenFunction *CGF) {
836  Expr::EvalResult Result;
837
838  bool Success = false;
839
840  if (DestType->isReferenceType())
841    Success = E->EvaluateAsLValue(Result, Context);
842  else
843    Success = E->Evaluate(Result, Context);
844
845  if (Success && !Result.HasSideEffects) {
846    switch (Result.Val.getKind()) {
847    case APValue::Uninitialized:
848      assert(0 && "Constant expressions should be initialized.");
849      return 0;
850    case APValue::LValue: {
851      const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
852      llvm::Constant *Offset =
853        llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext),
854                               Result.Val.getLValueOffset().getQuantity());
855
856      llvm::Constant *C;
857      if (const Expr *LVBase = Result.Val.getLValueBase()) {
858        C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
859
860        // Apply offset if necessary.
861        if (!Offset->isNullValue()) {
862          const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext);
863          llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type);
864          Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1);
865          C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
866        }
867
868        // Convert to the appropriate type; this could be an lvalue for
869        // an integer.
870        if (isa<llvm::PointerType>(DestTy))
871          return llvm::ConstantExpr::getBitCast(C, DestTy);
872
873        return llvm::ConstantExpr::getPtrToInt(C, DestTy);
874      } else {
875        C = Offset;
876
877        // Convert to the appropriate type; this could be an lvalue for
878        // an integer.
879        if (isa<llvm::PointerType>(DestTy))
880          return llvm::ConstantExpr::getIntToPtr(C, DestTy);
881
882        // If the types don't match this should only be a truncate.
883        if (C->getType() != DestTy)
884          return llvm::ConstantExpr::getTrunc(C, DestTy);
885
886        return C;
887      }
888    }
889    case APValue::Int: {
890      llvm::Constant *C = llvm::ConstantInt::get(VMContext,
891                                                 Result.Val.getInt());
892
893      if (C->getType()->isIntegerTy(1)) {
894        const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
895        C = llvm::ConstantExpr::getZExt(C, BoolTy);
896      }
897      return C;
898    }
899    case APValue::ComplexInt: {
900      llvm::Constant *Complex[2];
901
902      Complex[0] = llvm::ConstantInt::get(VMContext,
903                                          Result.Val.getComplexIntReal());
904      Complex[1] = llvm::ConstantInt::get(VMContext,
905                                          Result.Val.getComplexIntImag());
906
907      // FIXME: the target may want to specify that this is packed.
908      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
909    }
910    case APValue::Float:
911      return llvm::ConstantFP::get(VMContext, Result.Val.getFloat());
912    case APValue::ComplexFloat: {
913      llvm::Constant *Complex[2];
914
915      Complex[0] = llvm::ConstantFP::get(VMContext,
916                                         Result.Val.getComplexFloatReal());
917      Complex[1] = llvm::ConstantFP::get(VMContext,
918                                         Result.Val.getComplexFloatImag());
919
920      // FIXME: the target may want to specify that this is packed.
921      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
922    }
923    case APValue::Vector: {
924      llvm::SmallVector<llvm::Constant *, 4> Inits;
925      unsigned NumElts = Result.Val.getVectorLength();
926
927      for (unsigned i = 0; i != NumElts; ++i) {
928        APValue &Elt = Result.Val.getVectorElt(i);
929        if (Elt.isInt())
930          Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
931        else
932          Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
933      }
934      return llvm::ConstantVector::get(&Inits[0], Inits.size());
935    }
936    }
937  }
938
939  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
940  if (C && C->getType()->isIntegerTy(1)) {
941    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
942    C = llvm::ConstantExpr::getZExt(C, BoolTy);
943  }
944  return C;
945}
946
947static void
948FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T,
949                             std::vector<llvm::Constant *> &Elements,
950                             uint64_t StartOffset) {
951  assert(StartOffset % 8 == 0 && "StartOffset not byte aligned!");
952
953  if (!CGM.getLangOptions().CPlusPlus ||
954      !CGM.getCXXABI().RequiresNonZeroInitializer(T))
955    return;
956
957  if (const ConstantArrayType *CAT =
958        CGM.getContext().getAsConstantArrayType(T)) {
959    QualType ElementTy = CAT->getElementType();
960    uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy);
961
962    for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) {
963      FillInNullDataMemberPointers(CGM, ElementTy, Elements,
964                                   StartOffset + I * ElementSize);
965    }
966  } else if (const RecordType *RT = T->getAs<RecordType>()) {
967    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
968    const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
969
970    // Go through all bases and fill in any null pointer to data members.
971    for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
972         E = RD->bases_end(); I != E; ++I) {
973      if (I->isVirtual()) {
974        // FIXME: We should initialize null pointer to data members in virtual
975        // bases here.
976        continue;
977      }
978
979      const CXXRecordDecl *BaseDecl =
980      cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
981
982      // Ignore empty bases.
983      if (BaseDecl->isEmpty())
984        continue;
985
986      // Ignore bases that don't have any pointer to data members.
987      if (!CGM.getCXXABI().RequiresNonZeroInitializer(BaseDecl))
988        continue;
989
990      uint64_t BaseOffset = Layout.getBaseClassOffset(BaseDecl);
991      FillInNullDataMemberPointers(CGM, I->getType(),
992                                   Elements, StartOffset + BaseOffset);
993    }
994
995    // Visit all fields.
996    unsigned FieldNo = 0;
997    for (RecordDecl::field_iterator I = RD->field_begin(),
998         E = RD->field_end(); I != E; ++I, ++FieldNo) {
999      QualType FieldType = I->getType();
1000
1001      if (!CGM.getCXXABI().RequiresNonZeroInitializer(FieldType))
1002        continue;
1003
1004      uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo);
1005      FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset);
1006    }
1007  } else {
1008    assert(T->isMemberPointerType() && "Should only see member pointers here!");
1009    assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
1010           "Should only see pointers to data members here!");
1011
1012    uint64_t StartIndex = StartOffset / 8;
1013    uint64_t EndIndex = StartIndex + CGM.getContext().getTypeSize(T) / 8;
1014
1015    llvm::Constant *NegativeOne =
1016      llvm::ConstantInt::get(llvm::Type::getInt8Ty(CGM.getLLVMContext()),
1017                             -1ULL, /*isSigned=*/true);
1018
1019    // Fill in the null data member pointer.
1020    for (uint64_t I = StartIndex; I != EndIndex; ++I)
1021      Elements[I] = NegativeOne;
1022  }
1023}
1024
1025llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
1026  if (!getLangOptions().CPlusPlus ||
1027      !getCXXABI().RequiresNonZeroInitializer(T))
1028    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
1029
1030  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
1031
1032    QualType ElementTy = CAT->getElementType();
1033
1034    llvm::Constant *Element = EmitNullConstant(ElementTy);
1035    unsigned NumElements = CAT->getSize().getZExtValue();
1036    std::vector<llvm::Constant *> Array(NumElements);
1037    for (unsigned i = 0; i != NumElements; ++i)
1038      Array[i] = Element;
1039
1040    const llvm::ArrayType *ATy =
1041      cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
1042    return llvm::ConstantArray::get(ATy, Array);
1043  }
1044
1045  if (const RecordType *RT = T->getAs<RecordType>()) {
1046    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1047    const llvm::StructType *STy =
1048      cast<llvm::StructType>(getTypes().ConvertTypeForMem(T));
1049    unsigned NumElements = STy->getNumElements();
1050    std::vector<llvm::Constant *> Elements(NumElements);
1051
1052    const CGRecordLayout &Layout = getTypes().getCGRecordLayout(RD);
1053
1054    // Go through all bases and fill in any null pointer to data members.
1055    for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
1056         E = RD->bases_end(); I != E; ++I) {
1057      if (I->isVirtual()) {
1058        // FIXME: We should initialize null pointer to data members in virtual
1059        // bases here.
1060        continue;
1061      }
1062
1063      const CXXRecordDecl *BaseDecl =
1064        cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
1065
1066      // Ignore empty bases.
1067      if (BaseDecl->isEmpty())
1068        continue;
1069
1070      // Ignore bases that don't have any pointer to data members.
1071      if (!getCXXABI().RequiresNonZeroInitializer(BaseDecl))
1072        continue;
1073
1074      // Currently, all bases are arrays of i8. Figure out how many elements
1075      // this base array has.
1076      unsigned BaseFieldNo = Layout.getNonVirtualBaseLLVMFieldNo(BaseDecl);
1077      const llvm::ArrayType *BaseArrayTy =
1078        cast<llvm::ArrayType>(STy->getElementType(BaseFieldNo));
1079
1080      unsigned NumBaseElements = BaseArrayTy->getNumElements();
1081      std::vector<llvm::Constant *> BaseElements(NumBaseElements);
1082
1083      // Now fill in null data member pointers.
1084      FillInNullDataMemberPointers(*this, I->getType(), BaseElements, 0);
1085
1086      // Now go through all other elements and zero them out.
1087      if (NumBaseElements) {
1088        llvm::Constant *Zero =
1089          llvm::ConstantInt::get(llvm::Type::getInt8Ty(getLLVMContext()), 0);
1090
1091        for (unsigned I = 0; I != NumBaseElements; ++I) {
1092          if (!BaseElements[I])
1093            BaseElements[I] = Zero;
1094        }
1095      }
1096
1097      Elements[BaseFieldNo] = llvm::ConstantArray::get(BaseArrayTy,
1098                                                       BaseElements);
1099    }
1100
1101    for (RecordDecl::field_iterator I = RD->field_begin(),
1102         E = RD->field_end(); I != E; ++I) {
1103      const FieldDecl *FD = *I;
1104
1105      // Ignore bit fields.
1106      if (FD->isBitField())
1107        continue;
1108
1109      unsigned FieldNo = Layout.getLLVMFieldNo(FD);
1110      Elements[FieldNo] = EmitNullConstant(FD->getType());
1111    }
1112
1113    // Now go through all other fields and zero them out.
1114    for (unsigned i = 0; i != NumElements; ++i) {
1115      if (!Elements[i])
1116        Elements[i] = llvm::Constant::getNullValue(STy->getElementType(i));
1117    }
1118
1119    return llvm::ConstantStruct::get(STy, Elements);
1120  }
1121
1122  assert(T->isMemberPointerType() && "Should only see member pointers here!");
1123  assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
1124         "Should only see pointers to data members here!");
1125
1126  // Itanium C++ ABI 2.3:
1127  //   A NULL pointer is represented as -1.
1128  return llvm::ConstantInt::get(getTypes().ConvertTypeForMem(T), -1ULL,
1129                                /*isSigned=*/true);
1130}
1131
1132llvm::Constant *
1133CodeGenModule::EmitPointerToDataMember(const FieldDecl *FD) {
1134
1135  // Itanium C++ ABI 2.3:
1136  //   A pointer to data member is an offset from the base address of the class
1137  //   object containing it, represented as a ptrdiff_t
1138
1139  const CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(FD->getParent());
1140  QualType ClassType =
1141    getContext().getTypeDeclType(const_cast<CXXRecordDecl *>(ClassDecl));
1142
1143  const llvm::StructType *ClassLTy =
1144    cast<llvm::StructType>(getTypes().ConvertType(ClassType));
1145
1146  const CGRecordLayout &RL =
1147    getTypes().getCGRecordLayout(FD->getParent());
1148  unsigned FieldNo = RL.getLLVMFieldNo(FD);
1149  uint64_t Offset =
1150    getTargetData().getStructLayout(ClassLTy)->getElementOffset(FieldNo);
1151
1152  const llvm::Type *PtrDiffTy =
1153    getTypes().ConvertType(getContext().getPointerDiffType());
1154
1155  return llvm::ConstantInt::get(PtrDiffTy, Offset);
1156}
1157