CGExprConstant.cpp revision 85b4521e34dcd4a0a4a1f0819e1123128e5a3125 
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 "clang/AST/APValue.h"
18#include "clang/AST/ASTContext.h"
19#include "clang/AST/RecordLayout.h"
20#include "clang/AST/StmtVisitor.h"
21#include "clang/Basic/Builtins.h"
22#include "llvm/Constants.h"
23#include "llvm/Function.h"
24#include "llvm/GlobalVariable.h"
25#include "llvm/Target/TargetData.h"
26using namespace clang;
27using namespace CodeGen;
28
29namespace  {
30class ConstStructBuilder {
31  CodeGenModule &CGM;
32  CodeGenFunction *CGF;
33
34  bool Packed;
35
36  unsigned NextFieldOffsetInBytes;
37
38  unsigned LLVMStructAlignment;
39
40  std::vector<llvm::Constant *> Elements;
41
42  ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
43    : CGM(CGM), CGF(CGF), Packed(false), NextFieldOffsetInBytes(0),
44    LLVMStructAlignment(1) { }
45
46  bool AppendField(const FieldDecl *Field, uint64_t FieldOffset,
47                   const Expr *InitExpr) {
48    uint64_t FieldOffsetInBytes = FieldOffset / 8;
49
50    assert(NextFieldOffsetInBytes <= FieldOffsetInBytes
51           && "Field offset mismatch!");
52
53    // Emit the field.
54    llvm::Constant *C = CGM.EmitConstantExpr(InitExpr, Field->getType(), CGF);
55    if (!C)
56      return false;
57
58    unsigned FieldAlignment = getAlignment(C);
59
60    // Round up the field offset to the alignment of the field type.
61    uint64_t AlignedNextFieldOffsetInBytes =
62      llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment);
63
64    if (AlignedNextFieldOffsetInBytes > FieldOffsetInBytes) {
65      assert(!Packed && "Alignment is wrong even with a packed struct!");
66
67      // Convert the struct to a packed struct.
68      ConvertStructToPacked();
69
70      AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
71    }
72
73    if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) {
74      // We need to append padding.
75      AppendPadding(FieldOffsetInBytes - NextFieldOffsetInBytes);
76
77      assert(NextFieldOffsetInBytes == FieldOffsetInBytes &&
78             "Did not add enough padding!");
79
80      AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
81    }
82
83    // Add the field.
84    Elements.push_back(C);
85    NextFieldOffsetInBytes = AlignedNextFieldOffsetInBytes + getSizeInBytes(C);
86
87    if (Packed)
88      assert(LLVMStructAlignment == 1 && "Packed struct not byte-aligned!");
89    else
90      LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
91
92    return true;
93  }
94
95  bool AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
96                      const Expr *InitExpr) {
97    llvm::ConstantInt *CI =
98      cast_or_null<llvm::ConstantInt>(CGM.EmitConstantExpr(InitExpr,
99                                                           Field->getType(),
100                                                           CGF));
101    // FIXME: Can this ever happen?
102    if (!CI)
103      return false;
104
105    if (FieldOffset > NextFieldOffsetInBytes * 8) {
106      // We need to add padding.
107      uint64_t NumBytes =
108        llvm::RoundUpToAlignment(FieldOffset -
109                                 NextFieldOffsetInBytes * 8, 8) / 8;
110
111      AppendPadding(NumBytes);
112    }
113
114    uint64_t FieldSize =
115      Field->getBitWidth()->EvaluateAsInt(CGM.getContext()).getZExtValue();
116
117    llvm::APInt FieldValue = CI->getValue();
118
119    // Promote the size of FieldValue if necessary
120    // FIXME: This should never occur, but currently it can because initializer
121    // constants are cast to bool, and because clang is not enforcing bitfield
122    // width limits.
123    if (FieldSize > FieldValue.getBitWidth())
124      FieldValue.zext(FieldSize);
125
126    // Truncate the size of FieldValue to the bit field size.
127    if (FieldSize < FieldValue.getBitWidth())
128      FieldValue.trunc(FieldSize);
129
130    if (FieldOffset < NextFieldOffsetInBytes * 8) {
131      // Either part of the field or the entire field can go into the previous
132      // byte.
133      assert(!Elements.empty() && "Elements can't be empty!");
134
135      unsigned BitsInPreviousByte =
136        NextFieldOffsetInBytes * 8 - FieldOffset;
137
138      bool FitsCompletelyInPreviousByte =
139        BitsInPreviousByte >= FieldValue.getBitWidth();
140
141      llvm::APInt Tmp = FieldValue;
142
143      if (!FitsCompletelyInPreviousByte) {
144        unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
145
146        if (CGM.getTargetData().isBigEndian()) {
147          Tmp = Tmp.lshr(NewFieldWidth);
148          Tmp.trunc(BitsInPreviousByte);
149
150          // We want the remaining high bits.
151          FieldValue.trunc(NewFieldWidth);
152        } else {
153          Tmp.trunc(BitsInPreviousByte);
154
155          // We want the remaining low bits.
156          FieldValue = FieldValue.lshr(BitsInPreviousByte);
157          FieldValue.trunc(NewFieldWidth);
158        }
159      }
160
161      Tmp.zext(8);
162      if (CGM.getTargetData().isBigEndian()) {
163        if (FitsCompletelyInPreviousByte)
164          Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
165      } else {
166        Tmp = Tmp.shl(8 - BitsInPreviousByte);
167      }
168
169      // Or in the bits that go into the previous byte.
170      Tmp |= cast<llvm::ConstantInt>(Elements.back())->getValue();
171      Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
172
173      if (FitsCompletelyInPreviousByte)
174        return true;
175    }
176
177    while (FieldValue.getBitWidth() > 8) {
178      llvm::APInt Tmp;
179
180      if (CGM.getTargetData().isBigEndian()) {
181        // We want the high bits.
182        Tmp = FieldValue;
183        Tmp = Tmp.lshr(Tmp.getBitWidth() - 8);
184        Tmp.trunc(8);
185      } else {
186        // We want the low bits.
187        Tmp = FieldValue;
188        Tmp.trunc(8);
189
190        FieldValue = FieldValue.lshr(8);
191      }
192
193      Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
194      NextFieldOffsetInBytes++;
195
196      FieldValue.trunc(FieldValue.getBitWidth() - 8);
197    }
198
199    assert(FieldValue.getBitWidth() > 0 &&
200           "Should have at least one bit left!");
201    assert(FieldValue.getBitWidth() <= 8 &&
202           "Should not have more than a byte left!");
203
204    if (FieldValue.getBitWidth() < 8) {
205      if (CGM.getTargetData().isBigEndian()) {
206        unsigned BitWidth = FieldValue.getBitWidth();
207
208        FieldValue.zext(8);
209        FieldValue = FieldValue << (8 - BitWidth);
210      } else
211        FieldValue.zext(8);
212    }
213
214    // Append the last element.
215    Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
216                                              FieldValue));
217    NextFieldOffsetInBytes++;
218    return true;
219  }
220
221  void AppendPadding(uint64_t NumBytes) {
222    if (!NumBytes)
223      return;
224
225    const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
226    if (NumBytes > 1)
227      Ty = llvm::ArrayType::get(Ty, NumBytes);
228
229    llvm::Constant *C = llvm::UndefValue::get(Ty);
230    Elements.push_back(C);
231    assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!");
232
233    NextFieldOffsetInBytes += getSizeInBytes(C);
234  }
235
236  void AppendTailPadding(uint64_t RecordSize) {
237    assert(RecordSize % 8 == 0 && "Invalid record size!");
238
239    uint64_t RecordSizeInBytes = RecordSize / 8;
240    assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!");
241
242    unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes;
243    AppendPadding(NumPadBytes);
244  }
245
246  void ConvertStructToPacked() {
247    std::vector<llvm::Constant *> PackedElements;
248    uint64_t ElementOffsetInBytes = 0;
249
250    for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
251      llvm::Constant *C = Elements[i];
252
253      unsigned ElementAlign =
254        CGM.getTargetData().getABITypeAlignment(C->getType());
255      uint64_t AlignedElementOffsetInBytes =
256        llvm::RoundUpToAlignment(ElementOffsetInBytes, ElementAlign);
257
258      if (AlignedElementOffsetInBytes > ElementOffsetInBytes) {
259        // We need some padding.
260        uint64_t NumBytes =
261          AlignedElementOffsetInBytes - ElementOffsetInBytes;
262
263        const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
264        if (NumBytes > 1)
265          Ty = llvm::ArrayType::get(Ty, NumBytes);
266
267        llvm::Constant *Padding = llvm::UndefValue::get(Ty);
268        PackedElements.push_back(Padding);
269        ElementOffsetInBytes += getSizeInBytes(Padding);
270      }
271
272      PackedElements.push_back(C);
273      ElementOffsetInBytes += getSizeInBytes(C);
274    }
275
276    assert(ElementOffsetInBytes == NextFieldOffsetInBytes &&
277           "Packing the struct changed its size!");
278
279    Elements = PackedElements;
280    LLVMStructAlignment = 1;
281    Packed = true;
282  }
283
284  bool Build(InitListExpr *ILE) {
285    RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
286    const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
287
288    unsigned FieldNo = 0;
289    unsigned ElementNo = 0;
290    for (RecordDecl::field_iterator Field = RD->field_begin(),
291         FieldEnd = RD->field_end();
292         ElementNo < ILE->getNumInits() && Field != FieldEnd;
293         ++Field, ++FieldNo) {
294      if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
295        continue;
296
297      if (Field->isBitField()) {
298        if (!Field->getIdentifier())
299          continue;
300
301        if (!AppendBitField(*Field, Layout.getFieldOffset(FieldNo),
302                            ILE->getInit(ElementNo)))
303          return false;
304      } else {
305        if (!AppendField(*Field, Layout.getFieldOffset(FieldNo),
306                         ILE->getInit(ElementNo)))
307          return false;
308      }
309
310      ElementNo++;
311    }
312
313    uint64_t LayoutSizeInBytes = Layout.getSize() / 8;
314
315    if (NextFieldOffsetInBytes > LayoutSizeInBytes) {
316      // If the struct is bigger than the size of the record type,
317      // we must have a flexible array member at the end.
318      assert(RD->hasFlexibleArrayMember() &&
319             "Must have flexible array member if struct is bigger than type!");
320
321      // No tail padding is necessary.
322      return true;
323    }
324
325    uint64_t LLVMSizeInBytes = llvm::RoundUpToAlignment(NextFieldOffsetInBytes,
326                                                        LLVMStructAlignment);
327
328    // Check if we need to convert the struct to a packed struct.
329    if (NextFieldOffsetInBytes <= LayoutSizeInBytes &&
330        LLVMSizeInBytes > LayoutSizeInBytes) {
331      assert(!Packed && "Size mismatch!");
332
333      ConvertStructToPacked();
334      assert(NextFieldOffsetInBytes == LayoutSizeInBytes &&
335             "Converting to packed did not help!");
336    }
337
338    // Append tail padding if necessary.
339    AppendTailPadding(Layout.getSize());
340
341    assert(Layout.getSize() / 8 == NextFieldOffsetInBytes &&
342           "Tail padding mismatch!");
343
344    return true;
345  }
346
347  unsigned getAlignment(const llvm::Constant *C) const {
348    if (Packed)
349      return 1;
350
351    return CGM.getTargetData().getABITypeAlignment(C->getType());
352  }
353
354  uint64_t getSizeInBytes(const llvm::Constant *C) const {
355    return CGM.getTargetData().getTypeAllocSize(C->getType());
356  }
357
358public:
359  static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
360                                     InitListExpr *ILE) {
361    ConstStructBuilder Builder(CGM, CGF);
362
363    if (!Builder.Build(ILE))
364      return 0;
365
366    llvm::Constant *Result =
367      llvm::ConstantStruct::get(CGM.getLLVMContext(),
368                                Builder.Elements, Builder.Packed);
369
370    assert(llvm::RoundUpToAlignment(Builder.NextFieldOffsetInBytes,
371                                    Builder.getAlignment(Result)) ==
372           Builder.getSizeInBytes(Result) && "Size mismatch!");
373
374    return Result;
375  }
376};
377
378class ConstExprEmitter :
379  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
380  CodeGenModule &CGM;
381  CodeGenFunction *CGF;
382  llvm::LLVMContext &VMContext;
383public:
384  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
385    : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
386  }
387
388  //===--------------------------------------------------------------------===//
389  //                            Visitor Methods
390  //===--------------------------------------------------------------------===//
391
392  llvm::Constant *VisitStmt(Stmt *S) {
393    return 0;
394  }
395
396  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
397    return Visit(PE->getSubExpr());
398  }
399
400  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
401    return Visit(E->getInitializer());
402  }
403
404  llvm::Constant *EmitMemberFunctionPointer(CXXMethodDecl *MD) {
405    assert(MD->isInstance() && "Member function must not be static!");
406
407    const llvm::Type *PtrDiffTy =
408      CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
409
410    llvm::Constant *Values[2];
411
412    // Get the function pointer (or index if this is a virtual function).
413    if (MD->isVirtual()) {
414      uint64_t Index = CGM.getVtableInfo().getMethodVtableIndex(MD);
415
416      // The pointer is 1 + the virtual table offset in bytes.
417      Values[0] = llvm::ConstantInt::get(PtrDiffTy, (Index * 8) + 1);
418    } else {
419      llvm::Constant *FuncPtr = CGM.GetAddrOfFunction(MD);
420
421      Values[0] = llvm::ConstantExpr::getPtrToInt(FuncPtr, PtrDiffTy);
422    }
423
424    // The adjustment will always be 0.
425    Values[1] = llvm::ConstantInt::get(PtrDiffTy, 0);
426
427    return llvm::ConstantStruct::get(CGM.getLLVMContext(),
428                                     Values, 2, /*Packed=*/false);
429  }
430
431  llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) {
432    if (const MemberPointerType *MPT =
433        E->getType()->getAs<MemberPointerType>()) {
434      QualType T = MPT->getPointeeType();
435      if (T->isFunctionProtoType()) {
436        DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr());
437
438        return EmitMemberFunctionPointer(cast<CXXMethodDecl>(DRE->getDecl()));
439      }
440
441      // FIXME: Should we handle other member pointer types here too,
442      // or should they be handled by Expr::Evaluate?
443    }
444
445    return 0;
446  }
447
448  llvm::Constant *VisitBinSub(BinaryOperator *E) {
449    // This must be a pointer/pointer subtraction.  This only happens for
450    // address of label.
451    if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) ||
452       !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext())))
453      return 0;
454
455    llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(),
456                                               E->getLHS()->getType(), CGF);
457    llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(),
458                                               E->getRHS()->getType(), CGF);
459
460    const llvm::Type *ResultType = ConvertType(E->getType());
461    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
462    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
463
464    // No need to divide by element size, since addr of label is always void*,
465    // which has size 1 in GNUish.
466    return llvm::ConstantExpr::getSub(LHS, RHS);
467  }
468
469  llvm::Constant *VisitCastExpr(CastExpr* E) {
470    switch (E->getCastKind()) {
471    case CastExpr::CK_ToUnion: {
472      // GCC cast to union extension
473      assert(E->getType()->isUnionType() &&
474             "Destination type is not union type!");
475      const llvm::Type *Ty = ConvertType(E->getType());
476      Expr *SubExpr = E->getSubExpr();
477
478      llvm::Constant *C =
479        CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
480      if (!C)
481        return 0;
482
483      // Build a struct with the union sub-element as the first member,
484      // and padded to the appropriate size
485      std::vector<llvm::Constant*> Elts;
486      std::vector<const llvm::Type*> Types;
487      Elts.push_back(C);
488      Types.push_back(C->getType());
489      unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
490      unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty);
491
492      assert(CurSize <= TotalSize && "Union size mismatch!");
493      if (unsigned NumPadBytes = TotalSize - CurSize) {
494        const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext);
495        if (NumPadBytes > 1)
496          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
497
498        Elts.push_back(llvm::UndefValue::get(Ty));
499        Types.push_back(Ty);
500      }
501
502      llvm::StructType* STy =
503        llvm::StructType::get(C->getType()->getContext(), Types, false);
504      return llvm::ConstantStruct::get(STy, Elts);
505    }
506    case CastExpr::CK_NullToMemberPointer:
507      return CGM.EmitNullConstant(E->getType());
508
509    case CastExpr::CK_BaseToDerivedMemberPointer: {
510      Expr *SubExpr = E->getSubExpr();
511
512      const MemberPointerType *SrcTy =
513        SubExpr->getType()->getAs<MemberPointerType>();
514      const MemberPointerType *DestTy =
515        E->getType()->getAs<MemberPointerType>();
516
517      const CXXRecordDecl *BaseClass =
518        cast<CXXRecordDecl>(cast<RecordType>(SrcTy->getClass())->getDecl());
519      const CXXRecordDecl *DerivedClass =
520        cast<CXXRecordDecl>(cast<RecordType>(DestTy->getClass())->getDecl());
521
522      if (SrcTy->getPointeeType()->isFunctionProtoType()) {
523        llvm::Constant *C =
524          CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
525        if (!C)
526          return 0;
527
528        llvm::ConstantStruct *CS = cast<llvm::ConstantStruct>(C);
529
530        // Check if we need to update the adjustment.
531        if (llvm::Constant *Offset = CGM.GetCXXBaseClassOffset(DerivedClass,
532                                                               BaseClass)) {
533          llvm::Constant *Values[2];
534
535          Values[0] = CS->getOperand(0);
536          Values[1] = llvm::ConstantExpr::getAdd(CS->getOperand(1), Offset);
537          return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2,
538                                           /*Packed=*/false);
539        }
540
541        return CS;
542      }
543    }
544
545    case CastExpr::CK_BitCast:
546      // This must be a member function pointer cast.
547      return Visit(E->getSubExpr());
548
549    default: {
550      // FIXME: This should be handled by the CK_NoOp cast kind.
551      // Explicit and implicit no-op casts
552      QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType();
553      if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy))
554        return Visit(E->getSubExpr());
555
556      // Handle integer->integer casts for address-of-label differences.
557      if (Ty->isIntegerType() && SubTy->isIntegerType() &&
558          CGF) {
559        llvm::Value *Src = Visit(E->getSubExpr());
560        if (Src == 0) return 0;
561
562        // Use EmitScalarConversion to perform the conversion.
563        return cast<llvm::Constant>(CGF->EmitScalarConversion(Src, SubTy, Ty));
564      }
565
566      return 0;
567    }
568    }
569  }
570
571  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
572    return Visit(DAE->getExpr());
573  }
574
575  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
576    std::vector<llvm::Constant*> Elts;
577    const llvm::ArrayType *AType =
578        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
579    unsigned NumInitElements = ILE->getNumInits();
580    // FIXME: Check for wide strings
581    // FIXME: Check for NumInitElements exactly equal to 1??
582    if (NumInitElements > 0 &&
583        (isa<StringLiteral>(ILE->getInit(0)) ||
584         isa<ObjCEncodeExpr>(ILE->getInit(0))) &&
585        ILE->getType()->getArrayElementTypeNoTypeQual()->isCharType())
586      return Visit(ILE->getInit(0));
587    const llvm::Type *ElemTy = AType->getElementType();
588    unsigned NumElements = AType->getNumElements();
589
590    // Initialising an array requires us to automatically
591    // initialise any elements that have not been initialised explicitly
592    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
593
594    // Copy initializer elements.
595    unsigned i = 0;
596    bool RewriteType = false;
597    for (; i < NumInitableElts; ++i) {
598      Expr *Init = ILE->getInit(i);
599      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
600      if (!C)
601        return 0;
602      RewriteType |= (C->getType() != ElemTy);
603      Elts.push_back(C);
604    }
605
606    // Initialize remaining array elements.
607    // FIXME: This doesn't handle member pointers correctly!
608    for (; i < NumElements; ++i)
609      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
610
611    if (RewriteType) {
612      // FIXME: Try to avoid packing the array
613      std::vector<const llvm::Type*> Types;
614      for (unsigned i = 0; i < Elts.size(); ++i)
615        Types.push_back(Elts[i]->getType());
616      const llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
617                                                            Types, true);
618      return llvm::ConstantStruct::get(SType, Elts);
619    }
620
621    return llvm::ConstantArray::get(AType, Elts);
622  }
623
624  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
625    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
626  }
627
628  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
629    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
630  }
631
632  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
633    const llvm::VectorType *VType =
634        cast<llvm::VectorType>(ConvertType(ILE->getType()));
635    const llvm::Type *ElemTy = VType->getElementType();
636    std::vector<llvm::Constant*> Elts;
637    unsigned NumElements = VType->getNumElements();
638    unsigned NumInitElements = ILE->getNumInits();
639
640    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
641
642    // Copy initializer elements.
643    unsigned i = 0;
644    for (; i < NumInitableElts; ++i) {
645      Expr *Init = ILE->getInit(i);
646      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
647      if (!C)
648        return 0;
649      Elts.push_back(C);
650    }
651
652    for (; i < NumElements; ++i)
653      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
654
655    return llvm::ConstantVector::get(VType, Elts);
656  }
657
658  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
659    return CGM.EmitNullConstant(E->getType());
660  }
661
662  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
663    if (ILE->getType()->isScalarType()) {
664      // We have a scalar in braces. Just use the first element.
665      if (ILE->getNumInits() > 0) {
666        Expr *Init = ILE->getInit(0);
667        return CGM.EmitConstantExpr(Init, Init->getType(), CGF);
668      }
669      return CGM.EmitNullConstant(ILE->getType());
670    }
671
672    if (ILE->getType()->isArrayType())
673      return EmitArrayInitialization(ILE);
674
675    if (ILE->getType()->isRecordType())
676      return EmitStructInitialization(ILE);
677
678    if (ILE->getType()->isUnionType())
679      return EmitUnionInitialization(ILE);
680
681    if (ILE->getType()->isVectorType())
682      return EmitVectorInitialization(ILE);
683
684    assert(0 && "Unable to handle InitListExpr");
685    // Get rid of control reaches end of void function warning.
686    // Not reached.
687    return 0;
688  }
689
690  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
691    assert(!E->getType()->isPointerType() && "Strings are always arrays");
692
693    // This must be a string initializing an array in a static initializer.
694    // Don't emit it as the address of the string, emit the string data itself
695    // as an inline array.
696    return llvm::ConstantArray::get(VMContext,
697                                    CGM.GetStringForStringLiteral(E), false);
698  }
699
700  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
701    // This must be an @encode initializing an array in a static initializer.
702    // Don't emit it as the address of the string, emit the string data itself
703    // as an inline array.
704    std::string Str;
705    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
706    const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
707
708    // Resize the string to the right size, adding zeros at the end, or
709    // truncating as needed.
710    Str.resize(CAT->getSize().getZExtValue(), '\0');
711    return llvm::ConstantArray::get(VMContext, Str, false);
712  }
713
714  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
715    return Visit(E->getSubExpr());
716  }
717
718  // Utility methods
719  const llvm::Type *ConvertType(QualType T) {
720    return CGM.getTypes().ConvertType(T);
721  }
722
723public:
724  llvm::Constant *EmitLValue(Expr *E) {
725    switch (E->getStmtClass()) {
726    default: break;
727    case Expr::CompoundLiteralExprClass: {
728      // Note that due to the nature of compound literals, this is guaranteed
729      // to be the only use of the variable, so we just generate it here.
730      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
731      llvm::Constant* C = Visit(CLE->getInitializer());
732      // FIXME: "Leaked" on failure.
733      if (C)
734        C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
735                                     E->getType().isConstant(CGM.getContext()),
736                                     llvm::GlobalValue::InternalLinkage,
737                                     C, ".compoundliteral", 0, false,
738                                     E->getType().getAddressSpace());
739      return C;
740    }
741    case Expr::DeclRefExprClass: {
742      NamedDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
743      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
744        return CGM.GetAddrOfFunction(FD);
745      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
746        // We can never refer to a variable with local storage.
747        if (!VD->hasLocalStorage()) {
748          if (VD->isFileVarDecl() || VD->hasExternalStorage())
749            return CGM.GetAddrOfGlobalVar(VD);
750          else if (VD->isBlockVarDecl()) {
751            assert(CGF && "Can't access static local vars without CGF");
752            return CGF->GetAddrOfStaticLocalVar(VD);
753          }
754        }
755      }
756      break;
757    }
758    case Expr::StringLiteralClass:
759      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
760    case Expr::ObjCEncodeExprClass:
761      return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
762    case Expr::ObjCStringLiteralClass: {
763      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
764      llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(SL);
765      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
766    }
767    case Expr::PredefinedExprClass: {
768      unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
769      if (CGF) {
770        LValue Res = CGF->EmitPredefinedFunctionName(Type);
771        return cast<llvm::Constant>(Res.getAddress());
772      } else if (Type == PredefinedExpr::PrettyFunction) {
773        return CGM.GetAddrOfConstantCString("top level", ".tmp");
774      }
775
776      return CGM.GetAddrOfConstantCString("", ".tmp");
777    }
778    case Expr::AddrLabelExprClass: {
779      assert(CGF && "Invalid address of label expression outside function.");
780      llvm::Constant *Ptr =
781        CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
782      return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
783    }
784    case Expr::CallExprClass: {
785      CallExpr* CE = cast<CallExpr>(E);
786      if (CE->isBuiltinCall(CGM.getContext()) !=
787            Builtin::BI__builtin___CFStringMakeConstantString)
788        break;
789      const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
790      const StringLiteral *Literal = cast<StringLiteral>(Arg);
791      // FIXME: need to deal with UCN conversion issues.
792      return CGM.GetAddrOfConstantCFString(Literal);
793    }
794    case Expr::BlockExprClass: {
795      std::string FunctionName;
796      if (CGF)
797        FunctionName = CGF->CurFn->getName();
798      else
799        FunctionName = "global";
800
801      return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
802    }
803    }
804
805    return 0;
806  }
807};
808
809}  // end anonymous namespace.
810
811llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
812                                                QualType DestType,
813                                                CodeGenFunction *CGF) {
814  Expr::EvalResult Result;
815
816  bool Success = false;
817
818  if (DestType->isReferenceType())
819    Success = E->EvaluateAsLValue(Result, Context);
820  else
821    Success = E->Evaluate(Result, Context);
822
823  if (Success && !Result.HasSideEffects) {
824    switch (Result.Val.getKind()) {
825    case APValue::Uninitialized:
826      assert(0 && "Constant expressions should be initialized.");
827      return 0;
828    case APValue::LValue: {
829      const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
830      llvm::Constant *Offset =
831        llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext),
832                               Result.Val.getLValueOffset());
833
834      llvm::Constant *C;
835      if (const Expr *LVBase = Result.Val.getLValueBase()) {
836        C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
837
838        // Apply offset if necessary.
839        if (!Offset->isNullValue()) {
840          const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext);
841          llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type);
842          Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1);
843          C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
844        }
845
846        // Convert to the appropriate type; this could be an lvalue for
847        // an integer.
848        if (isa<llvm::PointerType>(DestTy))
849          return llvm::ConstantExpr::getBitCast(C, DestTy);
850
851        return llvm::ConstantExpr::getPtrToInt(C, DestTy);
852      } else {
853        C = Offset;
854
855        // Convert to the appropriate type; this could be an lvalue for
856        // an integer.
857        if (isa<llvm::PointerType>(DestTy))
858          return llvm::ConstantExpr::getIntToPtr(C, DestTy);
859
860        // If the types don't match this should only be a truncate.
861        if (C->getType() != DestTy)
862          return llvm::ConstantExpr::getTrunc(C, DestTy);
863
864        return C;
865      }
866    }
867    case APValue::Int: {
868      llvm::Constant *C = llvm::ConstantInt::get(VMContext,
869                                                 Result.Val.getInt());
870
871      if (C->getType() == llvm::Type::getInt1Ty(VMContext)) {
872        const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
873        C = llvm::ConstantExpr::getZExt(C, BoolTy);
874      }
875      return C;
876    }
877    case APValue::ComplexInt: {
878      llvm::Constant *Complex[2];
879
880      Complex[0] = llvm::ConstantInt::get(VMContext,
881                                          Result.Val.getComplexIntReal());
882      Complex[1] = llvm::ConstantInt::get(VMContext,
883                                          Result.Val.getComplexIntImag());
884
885      // FIXME: the target may want to specify that this is packed.
886      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
887    }
888    case APValue::Float:
889      return llvm::ConstantFP::get(VMContext, Result.Val.getFloat());
890    case APValue::ComplexFloat: {
891      llvm::Constant *Complex[2];
892
893      Complex[0] = llvm::ConstantFP::get(VMContext,
894                                         Result.Val.getComplexFloatReal());
895      Complex[1] = llvm::ConstantFP::get(VMContext,
896                                         Result.Val.getComplexFloatImag());
897
898      // FIXME: the target may want to specify that this is packed.
899      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
900    }
901    case APValue::Vector: {
902      llvm::SmallVector<llvm::Constant *, 4> Inits;
903      unsigned NumElts = Result.Val.getVectorLength();
904
905      for (unsigned i = 0; i != NumElts; ++i) {
906        APValue &Elt = Result.Val.getVectorElt(i);
907        if (Elt.isInt())
908          Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
909        else
910          Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
911      }
912      return llvm::ConstantVector::get(&Inits[0], Inits.size());
913    }
914    }
915  }
916
917  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
918  if (C && C->getType() == llvm::Type::getInt1Ty(VMContext)) {
919    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
920    C = llvm::ConstantExpr::getZExt(C, BoolTy);
921  }
922  return C;
923}
924
925static inline bool isDataMemberPointerType(QualType T) {
926  if (const MemberPointerType *MPT = T->getAs<MemberPointerType>())
927    return !MPT->getPointeeType()->isFunctionType();
928
929  return false;
930}
931
932llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
933  // No need to check for member pointers when not compiling C++.
934  if (!getContext().getLangOptions().CPlusPlus)
935    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
936
937  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
938
939    QualType ElementTy = CAT->getElementType();
940
941    // FIXME: Handle arrays of structs that contain member pointers.
942    if (isDataMemberPointerType(Context.getBaseElementType(ElementTy))) {
943      llvm::Constant *Element = EmitNullConstant(ElementTy);
944      uint64_t NumElements = CAT->getSize().getZExtValue();
945      std::vector<llvm::Constant *> Array(NumElements);
946      for (uint64_t i = 0; i != NumElements; ++i)
947        Array[i] = Element;
948
949      const llvm::ArrayType *ATy =
950        cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
951      return llvm::ConstantArray::get(ATy, Array);
952    }
953  }
954
955  if (const RecordType *RT = T->getAs<RecordType>()) {
956    const RecordDecl *RD = RT->getDecl();
957    // FIXME: It would be better if there was a way to explicitly compute the
958    // record layout instead of converting to a type.
959    Types.ConvertTagDeclType(RD);
960
961    const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
962    if (Layout.containsMemberPointer()) {
963      assert(0 && "FIXME: No support for structs with member pointers yet!");
964    }
965  }
966
967  // FIXME: Handle structs that contain member pointers.
968  if (isDataMemberPointerType(T))
969    return llvm::Constant::getAllOnesValue(getTypes().ConvertTypeForMem(T));
970
971  return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
972}
973