CGExprConstant.cpp revision 64241fc930e0b2247e8c5b5af9d48d13c4bec8ae 
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/Support/Compiler.h"
26#include "llvm/Target/TargetData.h"
27using namespace clang;
28using namespace CodeGen;
29
30namespace  {
31
32class VISIBILITY_HIDDEN ConstStructBuilder {
33  CodeGenModule &CGM;
34  CodeGenFunction *CGF;
35
36  bool Packed;
37
38  unsigned NextFieldOffsetInBytes;
39
40  unsigned LLVMStructAlignment;
41
42  std::vector<llvm::Constant *> Elements;
43
44  ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
45    : CGM(CGM), CGF(CGF), Packed(false), NextFieldOffsetInBytes(0),
46    LLVMStructAlignment(1) { }
47
48  bool AppendField(const FieldDecl *Field, uint64_t FieldOffset,
49                   const Expr *InitExpr) {
50    uint64_t FieldOffsetInBytes = FieldOffset / 8;
51
52    assert(NextFieldOffsetInBytes <= FieldOffsetInBytes
53           && "Field offset mismatch!");
54
55    // Emit the field.
56    llvm::Constant *C = CGM.EmitConstantExpr(InitExpr, Field->getType(), CGF);
57    if (!C)
58      return false;
59
60    unsigned FieldAlignment = getAlignment(C);
61
62    // Round up the field offset to the alignment of the field type.
63    uint64_t AlignedNextFieldOffsetInBytes =
64      llvm::RoundUpToAlignment(NextFieldOffsetInBytes, FieldAlignment);
65
66    if (AlignedNextFieldOffsetInBytes > FieldOffsetInBytes) {
67      assert(!Packed && "Alignment is wrong even with a packed struct!");
68
69      // Convert the struct to a packed struct.
70      ConvertStructToPacked();
71
72      AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
73    }
74
75    if (AlignedNextFieldOffsetInBytes < FieldOffsetInBytes) {
76      // We need to append padding.
77      AppendPadding(FieldOffsetInBytes - NextFieldOffsetInBytes);
78
79      assert(NextFieldOffsetInBytes == FieldOffsetInBytes &&
80             "Did not add enough padding!");
81
82      AlignedNextFieldOffsetInBytes = NextFieldOffsetInBytes;
83    }
84
85    // Add the field.
86    Elements.push_back(C);
87    NextFieldOffsetInBytes = AlignedNextFieldOffsetInBytes + getSizeInBytes(C);
88
89    if (Packed)
90      assert(LLVMStructAlignment == 1 && "Packed struct not byte-aligned!");
91    else
92      LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
93
94    return true;
95  }
96
97  bool AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
98                      const Expr *InitExpr) {
99    llvm::ConstantInt *CI =
100      cast_or_null<llvm::ConstantInt>(CGM.EmitConstantExpr(InitExpr,
101                                                           Field->getType(),
102                                                           CGF));
103    // FIXME: Can this ever happen?
104    if (!CI)
105      return false;
106
107    if (FieldOffset > NextFieldOffsetInBytes * 8) {
108      // We need to add padding.
109      uint64_t NumBytes =
110        llvm::RoundUpToAlignment(FieldOffset -
111                                 NextFieldOffsetInBytes * 8, 8) / 8;
112
113      AppendPadding(NumBytes);
114    }
115
116    uint64_t FieldSize =
117      Field->getBitWidth()->EvaluateAsInt(CGM.getContext()).getZExtValue();
118
119    llvm::APInt FieldValue = CI->getValue();
120
121    // Promote the size of FieldValue if necessary
122    // FIXME: This should never occur, but currently it can because initializer
123    // constants are cast to bool, and because clang is not enforcing bitfield
124    // width limits.
125    if (FieldSize > FieldValue.getBitWidth())
126      FieldValue.zext(FieldSize);
127
128    // Truncate the size of FieldValue to the bit field size.
129    if (FieldSize < FieldValue.getBitWidth())
130      FieldValue.trunc(FieldSize);
131
132    if (FieldOffset < NextFieldOffsetInBytes * 8) {
133      // Either part of the field or the entire field can go into the previous
134      // byte.
135      assert(!Elements.empty() && "Elements can't be empty!");
136
137      unsigned BitsInPreviousByte =
138        NextFieldOffsetInBytes * 8 - FieldOffset;
139
140      bool FitsCompletelyInPreviousByte =
141        BitsInPreviousByte >= FieldValue.getBitWidth();
142
143      llvm::APInt Tmp = FieldValue;
144
145      if (!FitsCompletelyInPreviousByte) {
146        unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
147
148        if (CGM.getTargetData().isBigEndian()) {
149          Tmp = Tmp.lshr(NewFieldWidth);
150          Tmp.trunc(BitsInPreviousByte);
151
152          // We want the remaining high bits.
153          FieldValue.trunc(NewFieldWidth);
154        } else {
155          Tmp.trunc(BitsInPreviousByte);
156
157          // We want the remaining low bits.
158          FieldValue = FieldValue.lshr(BitsInPreviousByte);
159          FieldValue.trunc(NewFieldWidth);
160        }
161      }
162
163      Tmp.zext(8);
164      if (CGM.getTargetData().isBigEndian()) {
165        if (FitsCompletelyInPreviousByte)
166          Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
167      } else {
168        Tmp = Tmp.shl(8 - BitsInPreviousByte);
169      }
170
171      // Or in the bits that go into the previous byte.
172      Tmp |= cast<llvm::ConstantInt>(Elements.back())->getValue();
173      Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
174
175      if (FitsCompletelyInPreviousByte)
176        return true;
177    }
178
179    while (FieldValue.getBitWidth() > 8) {
180      llvm::APInt Tmp;
181
182      if (CGM.getTargetData().isBigEndian()) {
183        // We want the high bits.
184        Tmp = FieldValue;
185        Tmp = Tmp.lshr(Tmp.getBitWidth() - 8);
186        Tmp.trunc(8);
187      } else {
188        // We want the low bits.
189        Tmp = FieldValue;
190        Tmp.trunc(8);
191
192        FieldValue = FieldValue.lshr(8);
193      }
194
195      Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
196      NextFieldOffsetInBytes++;
197
198      FieldValue.trunc(FieldValue.getBitWidth() - 8);
199    }
200
201    assert(FieldValue.getBitWidth() > 0 &&
202           "Should have at least one bit left!");
203    assert(FieldValue.getBitWidth() <= 8 &&
204           "Should not have more than a byte left!");
205
206    if (FieldValue.getBitWidth() < 8) {
207      if (CGM.getTargetData().isBigEndian()) {
208        unsigned BitWidth = FieldValue.getBitWidth();
209
210        FieldValue.zext(8);
211        FieldValue = FieldValue << (8 - BitWidth);
212      } else
213        FieldValue.zext(8);
214    }
215
216    // Append the last element.
217    Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
218                                              FieldValue));
219    NextFieldOffsetInBytes++;
220    return true;
221  }
222
223  void AppendPadding(uint64_t NumBytes) {
224    if (!NumBytes)
225      return;
226
227    const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
228    if (NumBytes > 1)
229      Ty = llvm::ArrayType::get(Ty, NumBytes);
230
231    llvm::Constant *C = llvm::UndefValue::get(Ty);
232    Elements.push_back(C);
233    assert(getAlignment(C) == 1 && "Padding must have 1 byte alignment!");
234
235    NextFieldOffsetInBytes += getSizeInBytes(C);
236  }
237
238  void AppendTailPadding(uint64_t RecordSize) {
239    assert(RecordSize % 8 == 0 && "Invalid record size!");
240
241    uint64_t RecordSizeInBytes = RecordSize / 8;
242    assert(NextFieldOffsetInBytes <= RecordSizeInBytes && "Size mismatch!");
243
244    unsigned NumPadBytes = RecordSizeInBytes - NextFieldOffsetInBytes;
245    AppendPadding(NumPadBytes);
246  }
247
248  void ConvertStructToPacked() {
249    std::vector<llvm::Constant *> PackedElements;
250    uint64_t ElementOffsetInBytes = 0;
251
252    for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
253      llvm::Constant *C = Elements[i];
254
255      unsigned ElementAlign =
256        CGM.getTargetData().getABITypeAlignment(C->getType());
257      uint64_t AlignedElementOffsetInBytes =
258        llvm::RoundUpToAlignment(ElementOffsetInBytes, ElementAlign);
259
260      if (AlignedElementOffsetInBytes > ElementOffsetInBytes) {
261        // We need some padding.
262        uint64_t NumBytes =
263          AlignedElementOffsetInBytes - ElementOffsetInBytes;
264
265        const llvm::Type *Ty = llvm::Type::getInt8Ty(CGM.getLLVMContext());
266        if (NumBytes > 1)
267          Ty = llvm::ArrayType::get(Ty, NumBytes);
268
269        llvm::Constant *Padding = llvm::UndefValue::get(Ty);
270        PackedElements.push_back(Padding);
271        ElementOffsetInBytes += getSizeInBytes(Padding);
272      }
273
274      PackedElements.push_back(C);
275      ElementOffsetInBytes += getSizeInBytes(C);
276    }
277
278    assert(ElementOffsetInBytes == NextFieldOffsetInBytes &&
279           "Packing the struct changed its size!");
280
281    Elements = PackedElements;
282    LLVMStructAlignment = 1;
283    Packed = true;
284  }
285
286  bool Build(InitListExpr *ILE) {
287    RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
288    const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
289
290    unsigned FieldNo = 0;
291    unsigned ElementNo = 0;
292    for (RecordDecl::field_iterator Field = RD->field_begin(),
293         FieldEnd = RD->field_end();
294         ElementNo < ILE->getNumInits() && Field != FieldEnd;
295         ++Field, ++FieldNo) {
296      if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
297        continue;
298
299      if (Field->isBitField()) {
300        if (!Field->getIdentifier())
301          continue;
302
303        if (!AppendBitField(*Field, Layout.getFieldOffset(FieldNo),
304                            ILE->getInit(ElementNo)))
305          return false;
306      } else {
307        if (!AppendField(*Field, Layout.getFieldOffset(FieldNo),
308                         ILE->getInit(ElementNo)))
309          return false;
310      }
311
312      ElementNo++;
313    }
314
315    uint64_t LayoutSizeInBytes = Layout.getSize() / 8;
316
317    if (NextFieldOffsetInBytes > LayoutSizeInBytes) {
318      // If the struct is bigger than the size of the record type,
319      // we must have a flexible array member at the end.
320      assert(RD->hasFlexibleArrayMember() &&
321             "Must have flexible array member if struct is bigger than type!");
322
323      // No tail padding is necessary.
324      return true;
325    }
326
327    uint64_t LLVMSizeInBytes = llvm::RoundUpToAlignment(NextFieldOffsetInBytes,
328                                                        LLVMStructAlignment);
329
330    // Check if we need to convert the struct to a packed struct.
331    if (NextFieldOffsetInBytes <= LayoutSizeInBytes &&
332        LLVMSizeInBytes > LayoutSizeInBytes) {
333      assert(!Packed && "Size mismatch!");
334
335      ConvertStructToPacked();
336      assert(NextFieldOffsetInBytes == LayoutSizeInBytes &&
337             "Converting to packed did not help!");
338    }
339
340    // Append tail padding if necessary.
341    AppendTailPadding(Layout.getSize());
342
343    assert(Layout.getSize() / 8 == NextFieldOffsetInBytes &&
344           "Tail padding mismatch!");
345
346    return true;
347  }
348
349  unsigned getAlignment(const llvm::Constant *C) const {
350    if (Packed)
351      return 1;
352
353    return CGM.getTargetData().getABITypeAlignment(C->getType());
354  }
355
356  uint64_t getSizeInBytes(const llvm::Constant *C) const {
357    return CGM.getTargetData().getTypeAllocSize(C->getType());
358  }
359
360public:
361  static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
362                                     InitListExpr *ILE) {
363    ConstStructBuilder Builder(CGM, CGF);
364
365    if (!Builder.Build(ILE))
366      return 0;
367
368    llvm::Constant *Result =
369      llvm::ConstantStruct::get(CGM.getLLVMContext(),
370                                Builder.Elements, Builder.Packed);
371
372    assert(llvm::RoundUpToAlignment(Builder.NextFieldOffsetInBytes,
373                                    Builder.getAlignment(Result)) ==
374           Builder.getSizeInBytes(Result) && "Size mismatch!");
375
376    return Result;
377  }
378};
379
380class VISIBILITY_HIDDEN ConstExprEmitter :
381  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
382  CodeGenModule &CGM;
383  CodeGenFunction *CGF;
384  llvm::LLVMContext &VMContext;
385public:
386  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
387    : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
388  }
389
390  //===--------------------------------------------------------------------===//
391  //                            Visitor Methods
392  //===--------------------------------------------------------------------===//
393
394  llvm::Constant *VisitStmt(Stmt *S) {
395    return 0;
396  }
397
398  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
399    return Visit(PE->getSubExpr());
400  }
401
402  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
403    return Visit(E->getInitializer());
404  }
405
406  llvm::Constant *EmitMemberFunctionPointer(CXXMethodDecl *MD) {
407    assert(MD->isInstance() && "Member function must not be static!");
408
409    const llvm::Type *PtrDiffTy =
410      CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
411
412    llvm::Constant *Values[2];
413
414    // Get the function pointer (or index if this is a virtual function).
415    if (MD->isVirtual()) {
416      int64_t Index = CGM.getVtableInfo().getMethodVtableIndex(MD);
417
418      Values[0] = llvm::ConstantInt::get(PtrDiffTy, Index + 1);
419    } else {
420      llvm::Constant *FuncPtr = CGM.GetAddrOfFunction(MD);
421
422      Values[0] = llvm::ConstantExpr::getPtrToInt(FuncPtr, PtrDiffTy);
423    }
424
425    // The adjustment will always be 0.
426    Values[1] = llvm::ConstantInt::get(PtrDiffTy, 0);
427
428    return llvm::ConstantStruct::get(CGM.getLLVMContext(),
429                                     Values, 2, /*Packed=*/false);
430  }
431
432  llvm::Constant *VisitUnaryAddrOf(UnaryOperator *E) {
433    if (const MemberPointerType *MPT =
434        E->getType()->getAs<MemberPointerType>()) {
435      QualType T = MPT->getPointeeType();
436      if (T->isFunctionProtoType()) {
437        DeclRefExpr *DRE = cast<DeclRefExpr>(E->getSubExpr());
438
439        return EmitMemberFunctionPointer(cast<CXXMethodDecl>(DRE->getDecl()));
440      }
441
442      // FIXME: Should we handle other member pointer types here too,
443      // or should they be handled by Expr::Evaluate?
444    }
445
446    return 0;
447  }
448
449  llvm::Constant *VisitBinSub(BinaryOperator *E) {
450    // This must be a pointer/pointer subtraction.  This only happens for
451    // address of label.
452    if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) ||
453       !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext())))
454      return 0;
455
456    llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(),
457                                               E->getLHS()->getType(), CGF);
458    llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(),
459                                               E->getRHS()->getType(), CGF);
460
461    const llvm::Type *ResultType = ConvertType(E->getType());
462    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
463    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
464
465    // No need to divide by element size, since addr of label is always void*,
466    // which has size 1 in GNUish.
467    return llvm::ConstantExpr::getSub(LHS, RHS);
468  }
469
470  llvm::Constant *VisitCastExpr(CastExpr* E) {
471    switch (E->getCastKind()) {
472    case CastExpr::CK_ToUnion: {
473      // GCC cast to union extension
474      assert(E->getType()->isUnionType() &&
475             "Destination type is not union type!");
476      const llvm::Type *Ty = ConvertType(E->getType());
477      Expr *SubExpr = E->getSubExpr();
478
479      llvm::Constant *C =
480        CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
481      if (!C)
482        return 0;
483
484      // Build a struct with the union sub-element as the first member,
485      // and padded to the appropriate size
486      std::vector<llvm::Constant*> Elts;
487      std::vector<const llvm::Type*> Types;
488      Elts.push_back(C);
489      Types.push_back(C->getType());
490      unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
491      unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty);
492
493      assert(CurSize <= TotalSize && "Union size mismatch!");
494      if (unsigned NumPadBytes = TotalSize - CurSize) {
495        const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext);
496        if (NumPadBytes > 1)
497          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
498
499        Elts.push_back(llvm::UndefValue::get(Ty));
500        Types.push_back(Ty);
501      }
502
503      llvm::StructType* STy =
504        llvm::StructType::get(C->getType()->getContext(), Types, false);
505      return llvm::ConstantStruct::get(STy, Elts);
506    }
507    case CastExpr::CK_NullToMemberPointer:
508      return CGM.EmitNullConstant(E->getType());
509
510    case CastExpr::CK_BaseToDerivedMemberPointer: {
511      Expr *SubExpr = E->getSubExpr();
512
513      const MemberPointerType *SrcTy =
514        SubExpr->getType()->getAs<MemberPointerType>();
515      const MemberPointerType *DestTy =
516        E->getType()->getAs<MemberPointerType>();
517
518      const CXXRecordDecl *BaseClass =
519        cast<CXXRecordDecl>(cast<RecordType>(SrcTy->getClass())->getDecl());
520      const CXXRecordDecl *DerivedClass =
521        cast<CXXRecordDecl>(cast<RecordType>(DestTy->getClass())->getDecl());
522
523      if (SrcTy->getPointeeType()->isFunctionProtoType()) {
524        llvm::Constant *C =
525          CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
526        if (!C)
527          return 0;
528
529        llvm::ConstantStruct *CS = cast<llvm::ConstantStruct>(C);
530
531        // Check if we need to update the adjustment.
532        if (llvm::Constant *Offset = CGM.GetCXXBaseClassOffset(DerivedClass,
533                                                               BaseClass)) {
534          llvm::Constant *Values[2];
535
536          Values[0] = CS->getOperand(0);
537          Values[1] = llvm::ConstantExpr::getAdd(CS->getOperand(1), Offset);
538          return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2,
539                                           /*Packed=*/false);
540        }
541
542        return CS;
543      }
544    }
545
546    case CastExpr::CK_BitCast:
547      // This must be a member function pointer cast.
548      return Visit(E->getSubExpr());
549
550    default: {
551      // FIXME: This should be handled by the CK_NoOp cast kind.
552      // Explicit and implicit no-op casts
553      QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType();
554      if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy))
555        return Visit(E->getSubExpr());
556
557      // Handle integer->integer casts for address-of-label differences.
558      if (Ty->isIntegerType() && SubTy->isIntegerType() &&
559          CGF) {
560        llvm::Value *Src = Visit(E->getSubExpr());
561        if (Src == 0) return 0;
562
563        // Use EmitScalarConversion to perform the conversion.
564        return cast<llvm::Constant>(CGF->EmitScalarConversion(Src, SubTy, Ty));
565      }
566
567      return 0;
568    }
569    }
570  }
571
572  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
573    return Visit(DAE->getExpr());
574  }
575
576  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
577    std::vector<llvm::Constant*> Elts;
578    const llvm::ArrayType *AType =
579        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
580    unsigned NumInitElements = ILE->getNumInits();
581    // FIXME: Check for wide strings
582    // FIXME: Check for NumInitElements exactly equal to 1??
583    if (NumInitElements > 0 &&
584        (isa<StringLiteral>(ILE->getInit(0)) ||
585         isa<ObjCEncodeExpr>(ILE->getInit(0))) &&
586        ILE->getType()->getArrayElementTypeNoTypeQual()->isCharType())
587      return Visit(ILE->getInit(0));
588    const llvm::Type *ElemTy = AType->getElementType();
589    unsigned NumElements = AType->getNumElements();
590
591    // Initialising an array requires us to automatically
592    // initialise any elements that have not been initialised explicitly
593    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
594
595    // Copy initializer elements.
596    unsigned i = 0;
597    bool RewriteType = false;
598    for (; i < NumInitableElts; ++i) {
599      Expr *Init = ILE->getInit(i);
600      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
601      if (!C)
602        return 0;
603      RewriteType |= (C->getType() != ElemTy);
604      Elts.push_back(C);
605    }
606
607    // Initialize remaining array elements.
608    // FIXME: This doesn't handle member pointers correctly!
609    for (; i < NumElements; ++i)
610      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
611
612    if (RewriteType) {
613      // FIXME: Try to avoid packing the array
614      std::vector<const llvm::Type*> Types;
615      for (unsigned i = 0; i < Elts.size(); ++i)
616        Types.push_back(Elts[i]->getType());
617      const llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
618                                                            Types, true);
619      return llvm::ConstantStruct::get(SType, Elts);
620    }
621
622    return llvm::ConstantArray::get(AType, Elts);
623  }
624
625  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
626    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
627  }
628
629  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
630    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
631  }
632
633  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
634    const llvm::VectorType *VType =
635        cast<llvm::VectorType>(ConvertType(ILE->getType()));
636    const llvm::Type *ElemTy = VType->getElementType();
637    std::vector<llvm::Constant*> Elts;
638    unsigned NumElements = VType->getNumElements();
639    unsigned NumInitElements = ILE->getNumInits();
640
641    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
642
643    // Copy initializer elements.
644    unsigned i = 0;
645    for (; i < NumInitableElts; ++i) {
646      Expr *Init = ILE->getInit(i);
647      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
648      if (!C)
649        return 0;
650      Elts.push_back(C);
651    }
652
653    for (; i < NumElements; ++i)
654      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
655
656    return llvm::ConstantVector::get(VType, Elts);
657  }
658
659  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
660    return CGM.EmitNullConstant(E->getType());
661  }
662
663  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
664    if (ILE->getType()->isScalarType()) {
665      // We have a scalar in braces. Just use the first element.
666      if (ILE->getNumInits() > 0) {
667        Expr *Init = ILE->getInit(0);
668        return CGM.EmitConstantExpr(Init, Init->getType(), CGF);
669      }
670      return CGM.EmitNullConstant(ILE->getType());
671    }
672
673    if (ILE->getType()->isArrayType())
674      return EmitArrayInitialization(ILE);
675
676    if (ILE->getType()->isStructureType())
677      return EmitStructInitialization(ILE);
678
679    if (ILE->getType()->isUnionType())
680      return EmitUnionInitialization(ILE);
681
682    if (ILE->getType()->isVectorType())
683      return EmitVectorInitialization(ILE);
684
685    assert(0 && "Unable to handle InitListExpr");
686    // Get rid of control reaches end of void function warning.
687    // Not reached.
688    return 0;
689  }
690
691  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
692    assert(!E->getType()->isPointerType() && "Strings are always arrays");
693
694    // This must be a string initializing an array in a static initializer.
695    // Don't emit it as the address of the string, emit the string data itself
696    // as an inline array.
697    return llvm::ConstantArray::get(VMContext,
698                                    CGM.GetStringForStringLiteral(E), false);
699  }
700
701  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
702    // This must be an @encode initializing an array in a static initializer.
703    // Don't emit it as the address of the string, emit the string data itself
704    // as an inline array.
705    std::string Str;
706    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
707    const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
708
709    // Resize the string to the right size, adding zeros at the end, or
710    // truncating as needed.
711    Str.resize(CAT->getSize().getZExtValue(), '\0');
712    return llvm::ConstantArray::get(VMContext, Str, false);
713  }
714
715  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
716    return Visit(E->getSubExpr());
717  }
718
719  // Utility methods
720  const llvm::Type *ConvertType(QualType T) {
721    return CGM.getTypes().ConvertType(T);
722  }
723
724public:
725  llvm::Constant *EmitLValue(Expr *E) {
726    switch (E->getStmtClass()) {
727    default: break;
728    case Expr::CompoundLiteralExprClass: {
729      // Note that due to the nature of compound literals, this is guaranteed
730      // to be the only use of the variable, so we just generate it here.
731      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
732      llvm::Constant* C = Visit(CLE->getInitializer());
733      // FIXME: "Leaked" on failure.
734      if (C)
735        C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
736                                     E->getType().isConstant(CGM.getContext()),
737                                     llvm::GlobalValue::InternalLinkage,
738                                     C, ".compoundliteral", 0, false,
739                                     E->getType().getAddressSpace());
740      return C;
741    }
742    case Expr::DeclRefExprClass: {
743      NamedDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
744      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
745        return CGM.GetAddrOfFunction(FD);
746      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
747        // We can never refer to a variable with local storage.
748        if (!VD->hasLocalStorage()) {
749          if (VD->isFileVarDecl() || VD->hasExternalStorage())
750            return CGM.GetAddrOfGlobalVar(VD);
751          else if (VD->isBlockVarDecl()) {
752            assert(CGF && "Can't access static local vars without CGF");
753            return CGF->GetAddrOfStaticLocalVar(VD);
754          }
755        }
756      }
757      break;
758    }
759    case Expr::StringLiteralClass:
760      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
761    case Expr::ObjCEncodeExprClass:
762      return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
763    case Expr::ObjCStringLiteralClass: {
764      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
765      llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(SL);
766      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
767    }
768    case Expr::PredefinedExprClass: {
769      // __func__/__FUNCTION__ -> "".  __PRETTY_FUNCTION__ -> "top level".
770      std::string Str;
771      if (cast<PredefinedExpr>(E)->getIdentType() ==
772          PredefinedExpr::PrettyFunction)
773        Str = "top level";
774
775      return CGM.GetAddrOfConstantCString(Str, ".tmp");
776    }
777    case Expr::AddrLabelExprClass: {
778      assert(CGF && "Invalid address of label expression outside function.");
779      llvm::Constant *Ptr =
780        CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
781      return llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
782    }
783    case Expr::CallExprClass: {
784      CallExpr* CE = cast<CallExpr>(E);
785      if (CE->isBuiltinCall(CGM.getContext()) !=
786            Builtin::BI__builtin___CFStringMakeConstantString)
787        break;
788      const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
789      const StringLiteral *Literal = cast<StringLiteral>(Arg);
790      // FIXME: need to deal with UCN conversion issues.
791      return CGM.GetAddrOfConstantCFString(Literal);
792    }
793    case Expr::BlockExprClass: {
794      std::string FunctionName;
795      if (CGF)
796        FunctionName = CGF->CurFn->getName();
797      else
798        FunctionName = "global";
799
800      return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
801    }
802    }
803
804    return 0;
805  }
806};
807
808}  // end anonymous namespace.
809
810llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
811                                                QualType DestType,
812                                                CodeGenFunction *CGF) {
813  Expr::EvalResult Result;
814
815  bool Success = false;
816
817  if (DestType->isReferenceType())
818    Success = E->EvaluateAsLValue(Result, Context);
819  else
820    Success = E->Evaluate(Result, Context);
821
822  if (Success) {
823    assert(!Result.HasSideEffects &&
824           "Constant expr should not have any side effects!");
825    switch (Result.Val.getKind()) {
826    case APValue::Uninitialized:
827      assert(0 && "Constant expressions should be initialized.");
828      return 0;
829    case APValue::LValue: {
830      const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
831      llvm::Constant *Offset =
832        llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext),
833                               Result.Val.getLValueOffset());
834
835      llvm::Constant *C;
836      if (const Expr *LVBase = Result.Val.getLValueBase()) {
837        C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
838
839        // Apply offset if necessary.
840        if (!Offset->isNullValue()) {
841          const llvm::Type *Type = llvm::Type::getInt8PtrTy(VMContext);
842          llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type);
843          Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1);
844          C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
845        }
846
847        // Convert to the appropriate type; this could be an lvalue for
848        // an integer.
849        if (isa<llvm::PointerType>(DestTy))
850          return llvm::ConstantExpr::getBitCast(C, DestTy);
851
852        return llvm::ConstantExpr::getPtrToInt(C, DestTy);
853      } else {
854        C = Offset;
855
856        // Convert to the appropriate type; this could be an lvalue for
857        // an integer.
858        if (isa<llvm::PointerType>(DestTy))
859          return llvm::ConstantExpr::getIntToPtr(C, DestTy);
860
861        // If the types don't match this should only be a truncate.
862        if (C->getType() != DestTy)
863          return llvm::ConstantExpr::getTrunc(C, DestTy);
864
865        return C;
866      }
867    }
868    case APValue::Int: {
869      llvm::Constant *C = llvm::ConstantInt::get(VMContext,
870                                                 Result.Val.getInt());
871
872      if (C->getType() == llvm::Type::getInt1Ty(VMContext)) {
873        const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
874        C = llvm::ConstantExpr::getZExt(C, BoolTy);
875      }
876      return C;
877    }
878    case APValue::ComplexInt: {
879      llvm::Constant *Complex[2];
880
881      Complex[0] = llvm::ConstantInt::get(VMContext,
882                                          Result.Val.getComplexIntReal());
883      Complex[1] = llvm::ConstantInt::get(VMContext,
884                                          Result.Val.getComplexIntImag());
885
886      // FIXME: the target may want to specify that this is packed.
887      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
888    }
889    case APValue::Float:
890      return llvm::ConstantFP::get(VMContext, Result.Val.getFloat());
891    case APValue::ComplexFloat: {
892      llvm::Constant *Complex[2];
893
894      Complex[0] = llvm::ConstantFP::get(VMContext,
895                                         Result.Val.getComplexFloatReal());
896      Complex[1] = llvm::ConstantFP::get(VMContext,
897                                         Result.Val.getComplexFloatImag());
898
899      // FIXME: the target may want to specify that this is packed.
900      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
901    }
902    case APValue::Vector: {
903      llvm::SmallVector<llvm::Constant *, 4> Inits;
904      unsigned NumElts = Result.Val.getVectorLength();
905
906      for (unsigned i = 0; i != NumElts; ++i) {
907        APValue &Elt = Result.Val.getVectorElt(i);
908        if (Elt.isInt())
909          Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
910        else
911          Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
912      }
913      return llvm::ConstantVector::get(&Inits[0], Inits.size());
914    }
915    }
916  }
917
918  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
919  if (C && C->getType() == llvm::Type::getInt1Ty(VMContext)) {
920    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
921    C = llvm::ConstantExpr::getZExt(C, BoolTy);
922  }
923  return C;
924}
925
926static inline bool isDataMemberPointerType(QualType T) {
927  if (const MemberPointerType *MPT = T->getAs<MemberPointerType>())
928    return !MPT->getPointeeType()->isFunctionType();
929
930  return false;
931}
932
933llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
934  // No need to check for member pointers when not compiling C++.
935  if (!getContext().getLangOptions().CPlusPlus)
936    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
937
938  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
939
940    QualType ElementTy = CAT->getElementType();
941
942    // FIXME: Handle arrays of structs that contain member pointers.
943    if (isDataMemberPointerType(Context.getBaseElementType(ElementTy))) {
944      llvm::Constant *Element = EmitNullConstant(ElementTy);
945      uint64_t NumElements = CAT->getSize().getZExtValue();
946      std::vector<llvm::Constant *> Array(NumElements);
947      for (uint64_t i = 0; i != NumElements; ++i)
948        Array[i] = Element;
949
950      const llvm::ArrayType *ATy =
951        cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
952      return llvm::ConstantArray::get(ATy, Array);
953    }
954  }
955
956  if (const RecordType *RT = T->getAs<RecordType>()) {
957    const RecordDecl *RD = RT->getDecl();
958    // FIXME: It would be better if there was a way to explicitly compute the
959    // record layout instead of converting to a type.
960    Types.ConvertTagDeclType(RD);
961
962    const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
963    if (Layout.containsMemberPointer()) {
964      assert(0 && "FIXME: No support for structs with member pointers yet!");
965    }
966  }
967
968  // FIXME: Handle structs that contain member pointers.
969  if (isDataMemberPointerType(T))
970    return llvm::Constant::getAllOnesValue(getTypes().ConvertTypeForMem(T));
971
972  return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
973}
974