CGExprConstant.cpp revision dbd920c7758e6dfb678a8f503fb14ba97c26f23a 
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::Constant::getNullValue(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(CGF->getLLVMContext());
266        if (NumBytes > 1)
267          Ty = llvm::ArrayType::get(Ty, NumBytes);
268
269        llvm::Constant *Padding = llvm::Constant::getNullValue(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        QualifiedDeclRefExpr *DRE = cast<QualifiedDeclRefExpr>(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 *VisitCastExpr(CastExpr* E) {
450    switch (E->getCastKind()) {
451    case CastExpr::CK_ToUnion: {
452      // GCC cast to union extension
453      assert(E->getType()->isUnionType() &&
454             "Destination type is not union type!");
455      const llvm::Type *Ty = ConvertType(E->getType());
456      Expr *SubExpr = E->getSubExpr();
457
458      llvm::Constant *C =
459        CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
460      if (!C)
461        return 0;
462
463      // Build a struct with the union sub-element as the first member,
464      // and padded to the appropriate size
465      std::vector<llvm::Constant*> Elts;
466      std::vector<const llvm::Type*> Types;
467      Elts.push_back(C);
468      Types.push_back(C->getType());
469      unsigned CurSize = CGM.getTargetData().getTypeAllocSize(C->getType());
470      unsigned TotalSize = CGM.getTargetData().getTypeAllocSize(Ty);
471
472      assert(CurSize <= TotalSize && "Union size mismatch!");
473      if (unsigned NumPadBytes = TotalSize - CurSize) {
474        const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext);
475        if (NumPadBytes > 1)
476          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
477
478        Elts.push_back(llvm::Constant::getNullValue(Ty));
479        Types.push_back(Ty);
480      }
481
482      llvm::StructType* STy =
483        llvm::StructType::get(C->getType()->getContext(), Types, false);
484      return llvm::ConstantStruct::get(STy, Elts);
485    }
486    case CastExpr::CK_NullToMemberPointer:
487      return CGM.EmitNullConstant(E->getType());
488
489    case CastExpr::CK_BaseToDerivedMemberPointer: {
490      Expr *SubExpr = E->getSubExpr();
491
492      const MemberPointerType *SrcTy =
493        SubExpr->getType()->getAs<MemberPointerType>();
494      const MemberPointerType *DestTy =
495        E->getType()->getAs<MemberPointerType>();
496
497      const CXXRecordDecl *BaseClass =
498        cast<CXXRecordDecl>(cast<RecordType>(SrcTy->getClass())->getDecl());
499      const CXXRecordDecl *DerivedClass =
500        cast<CXXRecordDecl>(cast<RecordType>(DestTy->getClass())->getDecl());
501
502      if (SrcTy->getPointeeType()->isFunctionProtoType()) {
503        llvm::Constant *C =
504          CGM.EmitConstantExpr(SubExpr, SubExpr->getType(), CGF);
505        if (!C)
506          return 0;
507
508        llvm::ConstantStruct *CS = cast<llvm::ConstantStruct>(C);
509
510        // Check if we need to update the adjustment.
511        if (llvm::Constant *Offset = CGM.GetCXXBaseClassOffset(DerivedClass,
512                                                               BaseClass)) {
513          llvm::Constant *Values[2];
514
515          Values[0] = CS->getOperand(0);
516          Values[1] = llvm::ConstantExpr::getAdd(CS->getOperand(1), Offset);
517          return llvm::ConstantStruct::get(CGM.getLLVMContext(), Values, 2,
518                                           /*Packed=*/false);
519        }
520
521        return CS;
522      }
523    }
524
525    default: {
526      // FIXME: This should be handled by the CK_NoOp cast kind.
527      // Explicit and implicit no-op casts
528      QualType Ty = E->getType(), SubTy = E->getSubExpr()->getType();
529      if (CGM.getContext().hasSameUnqualifiedType(Ty, SubTy))
530          return Visit(E->getSubExpr());
531      return 0;
532    }
533    }
534  }
535
536  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
537    return Visit(DAE->getExpr());
538  }
539
540  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
541    std::vector<llvm::Constant*> Elts;
542    const llvm::ArrayType *AType =
543        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
544    unsigned NumInitElements = ILE->getNumInits();
545    // FIXME: Check for wide strings
546    // FIXME: Check for NumInitElements exactly equal to 1??
547    if (NumInitElements > 0 &&
548        (isa<StringLiteral>(ILE->getInit(0)) ||
549         isa<ObjCEncodeExpr>(ILE->getInit(0))) &&
550        ILE->getType()->getArrayElementTypeNoTypeQual()->isCharType())
551      return Visit(ILE->getInit(0));
552    const llvm::Type *ElemTy = AType->getElementType();
553    unsigned NumElements = AType->getNumElements();
554
555    // Initialising an array requires us to automatically
556    // initialise any elements that have not been initialised explicitly
557    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
558
559    // Copy initializer elements.
560    unsigned i = 0;
561    bool RewriteType = false;
562    for (; i < NumInitableElts; ++i) {
563      Expr *Init = ILE->getInit(i);
564      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
565      if (!C)
566        return 0;
567      RewriteType |= (C->getType() != ElemTy);
568      Elts.push_back(C);
569    }
570
571    // Initialize remaining array elements.
572    // FIXME: This doesn't handle member pointers correctly!
573    for (; i < NumElements; ++i)
574      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
575
576    if (RewriteType) {
577      // FIXME: Try to avoid packing the array
578      std::vector<const llvm::Type*> Types;
579      for (unsigned i = 0; i < Elts.size(); ++i)
580        Types.push_back(Elts[i]->getType());
581      const llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
582                                                            Types, true);
583      return llvm::ConstantStruct::get(SType, Elts);
584    }
585
586    return llvm::ConstantArray::get(AType, Elts);
587  }
588
589  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
590    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
591  }
592
593  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
594    return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
595  }
596
597  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
598    const llvm::VectorType *VType =
599        cast<llvm::VectorType>(ConvertType(ILE->getType()));
600    const llvm::Type *ElemTy = VType->getElementType();
601    std::vector<llvm::Constant*> Elts;
602    unsigned NumElements = VType->getNumElements();
603    unsigned NumInitElements = ILE->getNumInits();
604
605    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
606
607    // Copy initializer elements.
608    unsigned i = 0;
609    for (; i < NumInitableElts; ++i) {
610      Expr *Init = ILE->getInit(i);
611      llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
612      if (!C)
613        return 0;
614      Elts.push_back(C);
615    }
616
617    for (; i < NumElements; ++i)
618      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
619
620    return llvm::ConstantVector::get(VType, Elts);
621  }
622
623  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
624    return CGM.EmitNullConstant(E->getType());
625  }
626
627  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
628    if (ILE->getType()->isScalarType()) {
629      // We have a scalar in braces. Just use the first element.
630      if (ILE->getNumInits() > 0) {
631        Expr *Init = ILE->getInit(0);
632        return CGM.EmitConstantExpr(Init, Init->getType(), CGF);
633      }
634      return CGM.EmitNullConstant(ILE->getType());
635    }
636
637    if (ILE->getType()->isArrayType())
638      return EmitArrayInitialization(ILE);
639
640    if (ILE->getType()->isStructureType())
641      return EmitStructInitialization(ILE);
642
643    if (ILE->getType()->isUnionType())
644      return EmitUnionInitialization(ILE);
645
646    if (ILE->getType()->isVectorType())
647      return EmitVectorInitialization(ILE);
648
649    assert(0 && "Unable to handle InitListExpr");
650    // Get rid of control reaches end of void function warning.
651    // Not reached.
652    return 0;
653  }
654
655  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
656    assert(!E->getType()->isPointerType() && "Strings are always arrays");
657
658    // This must be a string initializing an array in a static initializer.
659    // Don't emit it as the address of the string, emit the string data itself
660    // as an inline array.
661    return llvm::ConstantArray::get(VMContext,
662                                    CGM.GetStringForStringLiteral(E), false);
663  }
664
665  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
666    // This must be an @encode initializing an array in a static initializer.
667    // Don't emit it as the address of the string, emit the string data itself
668    // as an inline array.
669    std::string Str;
670    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
671    const ConstantArrayType *CAT = cast<ConstantArrayType>(E->getType());
672
673    // Resize the string to the right size, adding zeros at the end, or
674    // truncating as needed.
675    Str.resize(CAT->getSize().getZExtValue(), '\0');
676    return llvm::ConstantArray::get(VMContext, Str, false);
677  }
678
679  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
680    return Visit(E->getSubExpr());
681  }
682
683  // Utility methods
684  const llvm::Type *ConvertType(QualType T) {
685    return CGM.getTypes().ConvertType(T);
686  }
687
688public:
689  llvm::Constant *EmitLValue(Expr *E) {
690    switch (E->getStmtClass()) {
691    default: break;
692    case Expr::CompoundLiteralExprClass: {
693      // Note that due to the nature of compound literals, this is guaranteed
694      // to be the only use of the variable, so we just generate it here.
695      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
696      llvm::Constant* C = Visit(CLE->getInitializer());
697      // FIXME: "Leaked" on failure.
698      if (C)
699        C = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
700                                     E->getType().isConstant(CGM.getContext()),
701                                     llvm::GlobalValue::InternalLinkage,
702                                     C, ".compoundliteral", 0, false,
703                                     E->getType().getAddressSpace());
704      return C;
705    }
706    case Expr::DeclRefExprClass:
707    case Expr::QualifiedDeclRefExprClass: {
708      NamedDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
709      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
710        return CGM.GetAddrOfFunction(FD);
711      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
712        // We can never refer to a variable with local storage.
713        if (!VD->hasLocalStorage()) {
714          if (VD->isFileVarDecl() || VD->hasExternalStorage())
715            return CGM.GetAddrOfGlobalVar(VD);
716          else if (VD->isBlockVarDecl()) {
717            assert(CGF && "Can't access static local vars without CGF");
718            return CGF->GetAddrOfStaticLocalVar(VD);
719          }
720        }
721      }
722      break;
723    }
724    case Expr::StringLiteralClass:
725      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
726    case Expr::ObjCEncodeExprClass:
727      return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
728    case Expr::ObjCStringLiteralClass: {
729      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
730      llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(SL);
731      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
732    }
733    case Expr::PredefinedExprClass: {
734      // __func__/__FUNCTION__ -> "".  __PRETTY_FUNCTION__ -> "top level".
735      std::string Str;
736      if (cast<PredefinedExpr>(E)->getIdentType() ==
737          PredefinedExpr::PrettyFunction)
738        Str = "top level";
739
740      return CGM.GetAddrOfConstantCString(Str, ".tmp");
741    }
742    case Expr::AddrLabelExprClass: {
743      assert(CGF && "Invalid address of label expression outside function.");
744      unsigned id =
745          CGF->GetIDForAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
746      llvm::Constant *C =
747            llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), id);
748      return llvm::ConstantExpr::getIntToPtr(C, ConvertType(E->getType()));
749    }
750    case Expr::CallExprClass: {
751      CallExpr* CE = cast<CallExpr>(E);
752      if (CE->isBuiltinCall(CGM.getContext()) !=
753            Builtin::BI__builtin___CFStringMakeConstantString)
754        break;
755      const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
756      const StringLiteral *Literal = cast<StringLiteral>(Arg);
757      // FIXME: need to deal with UCN conversion issues.
758      return CGM.GetAddrOfConstantCFString(Literal);
759    }
760    case Expr::BlockExprClass: {
761      std::string FunctionName;
762      if (CGF)
763        FunctionName = CGF->CurFn->getName();
764      else
765        FunctionName = "global";
766
767      return CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
768    }
769    }
770
771    return 0;
772  }
773};
774
775}  // end anonymous namespace.
776
777llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
778                                                QualType DestType,
779                                                CodeGenFunction *CGF) {
780  Expr::EvalResult Result;
781
782  bool Success = false;
783
784  if (DestType->isReferenceType())
785    Success = E->EvaluateAsLValue(Result, Context);
786  else
787    Success = E->Evaluate(Result, Context);
788
789  if (Success) {
790    assert(!Result.HasSideEffects &&
791           "Constant expr should not have any side effects!");
792    switch (Result.Val.getKind()) {
793    case APValue::Uninitialized:
794      assert(0 && "Constant expressions should be initialized.");
795      return 0;
796    case APValue::LValue: {
797      const llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
798      llvm::Constant *Offset =
799        llvm::ConstantInt::get(llvm::Type::getInt64Ty(VMContext),
800                               Result.Val.getLValueOffset());
801
802      llvm::Constant *C;
803      if (const Expr *LVBase = Result.Val.getLValueBase()) {
804        C = ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
805
806        // Apply offset if necessary.
807        if (!Offset->isNullValue()) {
808          const llvm::Type *Type =
809            llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
810          llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, Type);
811          Casted = llvm::ConstantExpr::getGetElementPtr(Casted, &Offset, 1);
812          C = llvm::ConstantExpr::getBitCast(Casted, C->getType());
813        }
814
815        // Convert to the appropriate type; this could be an lvalue for
816        // an integer.
817        if (isa<llvm::PointerType>(DestTy))
818          return llvm::ConstantExpr::getBitCast(C, DestTy);
819
820        return llvm::ConstantExpr::getPtrToInt(C, DestTy);
821      } else {
822        C = Offset;
823
824        // Convert to the appropriate type; this could be an lvalue for
825        // an integer.
826        if (isa<llvm::PointerType>(DestTy))
827          return llvm::ConstantExpr::getIntToPtr(C, DestTy);
828
829        // If the types don't match this should only be a truncate.
830        if (C->getType() != DestTy)
831          return llvm::ConstantExpr::getTrunc(C, DestTy);
832
833        return C;
834      }
835    }
836    case APValue::Int: {
837      llvm::Constant *C = llvm::ConstantInt::get(VMContext,
838                                                 Result.Val.getInt());
839
840      if (C->getType() == llvm::Type::getInt1Ty(VMContext)) {
841        const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
842        C = llvm::ConstantExpr::getZExt(C, BoolTy);
843      }
844      return C;
845    }
846    case APValue::ComplexInt: {
847      llvm::Constant *Complex[2];
848
849      Complex[0] = llvm::ConstantInt::get(VMContext,
850                                          Result.Val.getComplexIntReal());
851      Complex[1] = llvm::ConstantInt::get(VMContext,
852                                          Result.Val.getComplexIntImag());
853
854      // FIXME: the target may want to specify that this is packed.
855      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
856    }
857    case APValue::Float:
858      return llvm::ConstantFP::get(VMContext, Result.Val.getFloat());
859    case APValue::ComplexFloat: {
860      llvm::Constant *Complex[2];
861
862      Complex[0] = llvm::ConstantFP::get(VMContext,
863                                         Result.Val.getComplexFloatReal());
864      Complex[1] = llvm::ConstantFP::get(VMContext,
865                                         Result.Val.getComplexFloatImag());
866
867      // FIXME: the target may want to specify that this is packed.
868      return llvm::ConstantStruct::get(VMContext, Complex, 2, false);
869    }
870    case APValue::Vector: {
871      llvm::SmallVector<llvm::Constant *, 4> Inits;
872      unsigned NumElts = Result.Val.getVectorLength();
873
874      for (unsigned i = 0; i != NumElts; ++i) {
875        APValue &Elt = Result.Val.getVectorElt(i);
876        if (Elt.isInt())
877          Inits.push_back(llvm::ConstantInt::get(VMContext, Elt.getInt()));
878        else
879          Inits.push_back(llvm::ConstantFP::get(VMContext, Elt.getFloat()));
880      }
881      return llvm::ConstantVector::get(&Inits[0], Inits.size());
882    }
883    }
884  }
885
886  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
887  if (C && C->getType() == llvm::Type::getInt1Ty(VMContext)) {
888    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
889    C = llvm::ConstantExpr::getZExt(C, BoolTy);
890  }
891  return C;
892}
893
894static inline bool isDataMemberPointerType(QualType T) {
895  if (const MemberPointerType *MPT = T->getAs<MemberPointerType>())
896    return !MPT->getPointeeType()->isFunctionType();
897
898  return false;
899}
900
901llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
902  // No need to check for member pointers when not compiling C++.
903  if (!getContext().getLangOptions().CPlusPlus)
904    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
905
906  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
907
908    QualType ElementTy = CAT->getElementType();
909
910    // FIXME: Handle arrays of structs that contain member pointers.
911    if (isDataMemberPointerType(Context.getBaseElementType(ElementTy))) {
912      llvm::Constant *Element = EmitNullConstant(ElementTy);
913      uint64_t NumElements = CAT->getSize().getZExtValue();
914      std::vector<llvm::Constant *> Array(NumElements);
915      for (uint64_t i = 0; i != NumElements; ++i)
916        Array[i] = Element;
917
918      const llvm::ArrayType *ATy =
919        cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
920      return llvm::ConstantArray::get(ATy, Array);
921    }
922  }
923
924  if (const RecordType *RT = T->getAs<RecordType>()) {
925    const RecordDecl *RD = RT->getDecl();
926    // FIXME: It would be better if there was a way to explicitly compute the
927    // record layout instead of converting to a type.
928    Types.ConvertTagDeclType(RD);
929
930    const CGRecordLayout &Layout = Types.getCGRecordLayout(RD);
931    if (Layout.containsMemberPointer()) {
932      assert(0 && "FIXME: No support for structs with member pointers yet!");
933    }
934  }
935
936  // FIXME: Handle structs that contain member pointers.
937  if (isDataMemberPointerType(T))
938    return llvm::Constant::getAllOnesValue(getTypes().ConvertTypeForMem(T));
939
940  return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
941}
942