CodeGenModule.cpp

    //
    // This happens if there is a prototype for a function
    // (e.g. "int f()") and then a definition of a different type
    // (e.g. "int f(int x)").  Start by making a new function of the
    // correct type, RAUW, then steal the name.
    GlobalDeclMap.erase(getMangledName(D));
    llvm::Function *NewFn = cast<llvm::Function>(GetAddrOfFunction(GD, Ty));
    NewFn->takeName(OldFn);
    
    // If this is an implementation of a function without a prototype, try to
    // replace any existing uses of the function (which may be calls) with uses
    // of the new function
    if (D->getType()->isFunctionNoProtoType()) {
      ReplaceUsesOfNonProtoTypeWithRealFunction(OldFn, NewFn);
      OldFn->removeDeadConstantUsers();
    }
    
    // Replace uses of F with the Function we will endow with a body.
    if (!Entry->use_empty()) {
      llvm::Constant *NewPtrForOldDecl = 
        VMContext.getConstantExprBitCast(NewFn, Entry->getType());
      Entry->replaceAllUsesWith(NewPtrForOldDecl);
    }
    
    // Ok, delete the old function now, which is dead.
    OldFn->eraseFromParent();
    
    Entry = NewFn;
  }
  
  llvm::Function *Fn = cast<llvm::Function>(Entry);

  CodeGenFunction(*this).GenerateCode(D, Fn);

  SetFunctionDefinitionAttributes(D, Fn);
  SetLLVMFunctionAttributesForDefinition(D, Fn);
  
  if (const ConstructorAttr *CA = D->getAttr<ConstructorAttr>())
    AddGlobalCtor(Fn, CA->getPriority());
  if (const DestructorAttr *DA = D->getAttr<DestructorAttr>())
    AddGlobalDtor(Fn, DA->getPriority());
}

void CodeGenModule::EmitAliasDefinition(const ValueDecl *D) {
  const AliasAttr *AA = D->getAttr<AliasAttr>();
  assert(AA && "Not an alias?");

  const llvm::Type *DeclTy = getTypes().ConvertTypeForMem(D->getType());
  
  // Unique the name through the identifier table.
  const char *AliaseeName = AA->getAliasee().c_str();
  AliaseeName = getContext().Idents.get(AliaseeName).getName();

  // Create a reference to the named value.  This ensures that it is emitted
  // if a deferred decl.
  llvm::Constant *Aliasee;
  if (isa<llvm::FunctionType>(DeclTy))
    Aliasee = GetOrCreateLLVMFunction(AliaseeName, DeclTy, GlobalDecl());
  else
    Aliasee = GetOrCreateLLVMGlobal(AliaseeName,
                                    VMContext.getPointerTypeUnqual(DeclTy), 0);

  // Create the new alias itself, but don't set a name yet.
  llvm::GlobalValue *GA = 
    new llvm::GlobalAlias(Aliasee->getType(),
                          llvm::Function::ExternalLinkage,
                          "", Aliasee, &getModule());
  
  // See if there is already something with the alias' name in the module.
  const char *MangledName = getMangledName(D);
  llvm::GlobalValue *&Entry = GlobalDeclMap[MangledName];
  
  if (Entry && !Entry->isDeclaration()) {
    // If there is a definition in the module, then it wins over the alias.
    // This is dubious, but allow it to be safe.  Just ignore the alias.
    GA->eraseFromParent();
    return;
  }
  
  if (Entry) {
    // If there is a declaration in the module, then we had an extern followed
    // by the alias, as in:
    //   extern int test6();
    //   ...
    //   int test6() __attribute__((alias("test7")));
    //
    // Remove it and replace uses of it with the alias.
    
    Entry->replaceAllUsesWith(VMContext.getConstantExprBitCast(GA,
                                                          Entry->getType()));
    Entry->eraseFromParent();
  }
  
  // Now we know that there is no conflict, set the name.
  Entry = GA;
  GA->setName(MangledName);

  // Set attributes which are particular to an alias; this is a
  // specialization of the attributes which may be set on a global
  // variable/function.
  if (D->hasAttr<DLLExportAttr>()) {
    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      // The dllexport attribute is ignored for undefined symbols.
      if (FD->getBody())
        GA->setLinkage(llvm::Function::DLLExportLinkage);
    } else {
      GA->setLinkage(llvm::Function::DLLExportLinkage);
    }
  } else if (D->hasAttr<WeakAttr>() || 
             D->hasAttr<WeakImportAttr>()) {
    GA->setLinkage(llvm::Function::WeakAnyLinkage);
  }

  SetCommonAttributes(D, GA);
}

/// getBuiltinLibFunction - Given a builtin id for a function like
/// "__builtin_fabsf", return a Function* for "fabsf".
llvm::Value *CodeGenModule::getBuiltinLibFunction(unsigned BuiltinID) {
  assert((Context.BuiltinInfo.isLibFunction(BuiltinID) ||
          Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID)) && 
         "isn't a lib fn");
  
  // Get the name, skip over the __builtin_ prefix (if necessary).
  const char *Name = Context.BuiltinInfo.GetName(BuiltinID);
  if (Context.BuiltinInfo.isLibFunction(BuiltinID))
    Name += 10;
  
  // Get the type for the builtin.
  ASTContext::GetBuiltinTypeError Error;
  QualType Type = Context.GetBuiltinType(BuiltinID, Error);
  assert(Error == ASTContext::GE_None && "Can't get builtin type");

  const llvm::FunctionType *Ty = 
    cast<llvm::FunctionType>(getTypes().ConvertType(Type));

  // Unique the name through the identifier table.
  Name = getContext().Idents.get(Name).getName();
  // FIXME: param attributes for sext/zext etc.
  return GetOrCreateLLVMFunction(Name, Ty, GlobalDecl());
}

llvm::Function *CodeGenModule::getIntrinsic(unsigned IID,const llvm::Type **Tys,
                                            unsigned NumTys) {
  return llvm::Intrinsic::getDeclaration(&getModule(),
                                         (llvm::Intrinsic::ID)IID, Tys, NumTys);
}

llvm::Function *CodeGenModule::getMemCpyFn() {
  if (MemCpyFn) return MemCpyFn;
  const llvm::Type *IntPtr = TheTargetData.getIntPtrType();
  return MemCpyFn = getIntrinsic(llvm::Intrinsic::memcpy, &IntPtr, 1);
}

llvm::Function *CodeGenModule::getMemMoveFn() {
  if (MemMoveFn) return MemMoveFn;
  const llvm::Type *IntPtr = TheTargetData.getIntPtrType();
  return MemMoveFn = getIntrinsic(llvm::Intrinsic::memmove, &IntPtr, 1);
}

llvm::Function *CodeGenModule::getMemSetFn() {
  if (MemSetFn) return MemSetFn;
  const llvm::Type *IntPtr = TheTargetData.getIntPtrType();
  return MemSetFn = getIntrinsic(llvm::Intrinsic::memset, &IntPtr, 1);
}

static void appendFieldAndPadding(CodeGenModule &CGM,
                                  std::vector<llvm::Constant*>& Fields,
                                  FieldDecl *FieldD, FieldDecl *NextFieldD,
                                  llvm::Constant* Field,
                                  RecordDecl* RD, const llvm::StructType *STy) {
  // Append the field.
  Fields.push_back(Field);
  
  int StructFieldNo = CGM.getTypes().getLLVMFieldNo(FieldD);
  
  int NextStructFieldNo;
  if (!NextFieldD) {
    NextStructFieldNo = STy->getNumElements();
  } else {
    NextStructFieldNo = CGM.getTypes().getLLVMFieldNo(NextFieldD);
  }
  
  // Append padding
  for (int i = StructFieldNo + 1; i < NextStructFieldNo; i++) {
    llvm::Constant *C = 
      CGM.getLLVMContext().getNullValue(STy->getElementType(StructFieldNo + 1));
    
    Fields.push_back(C);
  }
}

static llvm::StringMapEntry<llvm::Constant*> &
GetConstantCFStringEntry(llvm::StringMap<llvm::Constant*> &Map,
                         const StringLiteral *Literal,
                         bool TargetIsLSB,
                         bool &IsUTF16,
                         unsigned &StringLength) {
  unsigned NumBytes = Literal->getByteLength();

  // Check for simple case.
  if (!Literal->containsNonAsciiOrNull()) {
    StringLength = NumBytes;
    return Map.GetOrCreateValue(llvm::StringRef(Literal->getStrData(), 
                                                StringLength));
  }

  // Otherwise, convert the UTF8 literals into a byte string.
  llvm::SmallVector<UTF16, 128> ToBuf(NumBytes);
  const UTF8 *FromPtr = (UTF8 *)Literal->getStrData();
  UTF16 *ToPtr = &ToBuf[0];
        
  ConversionResult Result = ConvertUTF8toUTF16(&FromPtr, FromPtr + NumBytes, 
                                               &ToPtr, ToPtr + NumBytes,
                                               strictConversion);
  
  // Check for conversion failure.
  if (Result != conversionOK) {
    // FIXME: Have Sema::CheckObjCString() validate the UTF-8 string and remove
    // this duplicate code.
    assert(Result == sourceIllegal && "UTF-8 to UTF-16 conversion failed");
    StringLength = NumBytes;
    return Map.GetOrCreateValue(llvm::StringRef(Literal->getStrData(), 
                                                StringLength));
  }

  // ConvertUTF8toUTF16 returns the length in ToPtr.
  StringLength = ToPtr - &ToBuf[0];

  // Render the UTF-16 string into a byte array and convert to the target byte
  // order.
  //
  // FIXME: This isn't something we should need to do here.
  llvm::SmallString<128> AsBytes;
  AsBytes.reserve(StringLength * 2);
  for (unsigned i = 0; i != StringLength; ++i) {
    unsigned short Val = ToBuf[i];
    if (TargetIsLSB) {
      AsBytes.push_back(Val & 0xFF);
      AsBytes.push_back(Val >> 8);
    } else {
      AsBytes.push_back(Val >> 8);
      AsBytes.push_back(Val & 0xFF);
    }
  }

  IsUTF16 = true;
  return Map.GetOrCreateValue(llvm::StringRef(AsBytes.data(), AsBytes.size()));
}

llvm::Constant *
CodeGenModule::GetAddrOfConstantCFString(const StringLiteral *Literal) {
  unsigned StringLength = 0;
  bool isUTF16 = false;
  llvm::StringMapEntry<llvm::Constant*> &Entry =
    GetConstantCFStringEntry(CFConstantStringMap, Literal, 
                             getTargetData().isLittleEndian(),
                             isUTF16, StringLength);
  
  if (llvm::Constant *C = Entry.getValue())
    return C;
  
  llvm::Constant *Zero = getLLVMContext().getNullValue(llvm::Type::Int32Ty);
  llvm::Constant *Zeros[] = { Zero, Zero };
  
  // If we don't already have it, get __CFConstantStringClassReference.
  if (!CFConstantStringClassRef) {
    const llvm::Type *Ty = getTypes().ConvertType(getContext().IntTy);
    Ty = VMContext.getArrayType(Ty, 0);
    llvm::Constant *GV = CreateRuntimeVariable(Ty, 
                                           "__CFConstantStringClassReference");
    // Decay array -> ptr
    CFConstantStringClassRef =
      VMContext.getConstantExprGetElementPtr(GV, Zeros, 2);
  }
  
  QualType CFTy = getContext().getCFConstantStringType();
  RecordDecl *CFRD = CFTy->getAsRecordType()->getDecl();

  const llvm::StructType *STy = 
    cast<llvm::StructType>(getTypes().ConvertType(CFTy));

  std::vector<llvm::Constant*> Fields;
  RecordDecl::field_iterator Field = CFRD->field_begin();

  // Class pointer.
  FieldDecl *CurField = *Field++;
  FieldDecl *NextField = *Field++;
  appendFieldAndPadding(*this, Fields, CurField, NextField,
                        CFConstantStringClassRef, CFRD, STy);
  
  // Flags.
  CurField = NextField;
  NextField = *Field++;
  const llvm::Type *Ty = getTypes().ConvertType(getContext().UnsignedIntTy);
  appendFieldAndPadding(*this, Fields, CurField, NextField,
                        isUTF16 ? llvm::ConstantInt::get(Ty, 0x07d0)
                                : llvm::ConstantInt::get(Ty, 0x07C8), 
                        CFRD, STy);
    
  // String pointer.
  CurField = NextField;
  NextField = *Field++;
  llvm::Constant *C = VMContext.getConstantArray(Entry.getKey().str());

  const char *Sect, *Prefix;
  bool isConstant;
  llvm::GlobalValue::LinkageTypes Linkage;
  if (isUTF16) {
    Prefix = getContext().Target.getUnicodeStringSymbolPrefix();
    Sect = getContext().Target.getUnicodeStringSection();
    // FIXME: why do utf strings get "l" labels instead of "L" labels?
    Linkage = llvm::GlobalValue::InternalLinkage;
    // FIXME: Why does GCC not set constant here?
    isConstant = false;
  } else {
    Prefix = ".str";
    Sect = getContext().Target.getCFStringDataSection();
    Linkage = llvm::GlobalValue::PrivateLinkage;
    // FIXME: -fwritable-strings should probably affect this, but we
    // are following gcc here.
    isConstant = true;
  }
  llvm::GlobalVariable *GV = 
    new llvm::GlobalVariable(getModule(), C->getType(), isConstant, 
                             Linkage, C, Prefix);
  if (Sect)
    GV->setSection(Sect);
  if (isUTF16) {
    unsigned Align = getContext().getTypeAlign(getContext().ShortTy)/8;
    GV->setAlignment(Align); 
  }
  appendFieldAndPadding(*this, Fields, CurField, NextField,
                        VMContext.getConstantExprGetElementPtr(GV, Zeros, 2),
                        CFRD, STy);
  
  // String length.
  CurField = NextField;
  NextField = 0;
  Ty = getTypes().ConvertType(getContext().LongTy);
  appendFieldAndPadding(*this, Fields, CurField, NextField,
                        llvm::ConstantInt::get(Ty, StringLength), CFRD, STy);
  
  // The struct.
  C = llvm::ConstantStruct::get(STy, Fields);
  GV = new llvm::GlobalVariable(getModule(), C->getType(), true, 
                                llvm::GlobalVariable::PrivateLinkage, C, 
                                "_unnamed_cfstring_");
  if (const char *Sect = getContext().Target.getCFStringSection())
    GV->setSection(Sect);
  Entry.setValue(GV);
  
  return GV;
}

/// GetStringForStringLiteral - Return the appropriate bytes for a
/// string literal, properly padded to match the literal type.
std::string CodeGenModule::GetStringForStringLiteral(const StringLiteral *E) {
  const char *StrData = E->getStrData();
  unsigned Len = E->getByteLength();

  const ConstantArrayType *CAT =
    getContext().getAsConstantArrayType(E->getType());
  assert(CAT && "String isn't pointer or array!");
  
  // Resize the string to the right size.
  std::string Str(StrData, StrData+Len);
  uint64_t RealLen = CAT->getSize().getZExtValue();
  
  if (E->isWide())
    RealLen *= getContext().Target.getWCharWidth()/8;
  
  Str.resize(RealLen, '\0');
  
  return Str;
}

/// GetAddrOfConstantStringFromLiteral - Return a pointer to a
/// constant array for the given string literal.
llvm::Constant *
CodeGenModule::GetAddrOfConstantStringFromLiteral(const StringLiteral *S) {
  // FIXME: This can be more efficient.
  return GetAddrOfConstantString(GetStringForStringLiteral(S));
}

/// GetAddrOfConstantStringFromObjCEncode - Return a pointer to a constant
/// array for the given ObjCEncodeExpr node.
llvm::Constant *
CodeGenModule::GetAddrOfConstantStringFromObjCEncode(const ObjCEncodeExpr *E) {
  std::string Str;
  getContext().getObjCEncodingForType(E->getEncodedType(), Str);

  return GetAddrOfConstantCString(Str);
}


/// GenerateWritableString -- Creates storage for a string literal.
static llvm::Constant *GenerateStringLiteral(const std::string &str, 
                                             bool constant,
                                             CodeGenModule &CGM,
                                             const char *GlobalName) {
  // Create Constant for this string literal. Don't add a '\0'.
  llvm::Constant *C = CGM.getLLVMContext().getConstantArray(str, false);
  
  // Create a global variable for this string
  return new llvm::GlobalVariable(CGM.getModule(), C->getType(), constant, 
                                  llvm::GlobalValue::PrivateLinkage,
                                  C, GlobalName);
}

/// GetAddrOfConstantString - Returns a pointer to a character array
/// containing the literal. This contents are exactly that of the
/// given string, i.e. it will not be null terminated automatically;
/// see GetAddrOfConstantCString. Note that whether the result is
/// actually a pointer to an LLVM constant depends on
/// Feature.WriteableStrings.
///
/// The result has pointer to array type.
llvm::Constant *CodeGenModule::GetAddrOfConstantString(const std::string &str,
                                                       const char *GlobalName) {
  bool IsConstant = !Features.WritableStrings;

  // Get the default prefix if a name wasn't specified.
  if (!GlobalName)
    GlobalName = ".str";

  // Don't share any string literals if strings aren't constant.
  if (!IsConstant)
    return GenerateStringLiteral(str, false, *this, GlobalName);
  
  llvm::StringMapEntry<llvm::Constant *> &Entry = 
    ConstantStringMap.GetOrCreateValue(&str[0], &str[str.length()]);

  if (Entry.getValue())
    return Entry.getValue();

  // Create a global variable for this.
  llvm::Constant *C = GenerateStringLiteral(str, true, *this, GlobalName);
  Entry.setValue(C);
  return C;
}

/// GetAddrOfConstantCString - Returns a pointer to a character
/// array containing the literal and a terminating '\-'
/// character. The result has pointer to array type.
llvm::Constant *CodeGenModule::GetAddrOfConstantCString(const std::string &str,
                                                        const char *GlobalName){
  return GetAddrOfConstantString(str + '\0', GlobalName);
}

/// EmitObjCPropertyImplementations - Emit information for synthesized
/// properties for an implementation.
void CodeGenModule::EmitObjCPropertyImplementations(const 
                                                    ObjCImplementationDecl *D) {
  for (ObjCImplementationDecl::propimpl_iterator 
         i = D->propimpl_begin(), e = D->propimpl_end(); i != e; ++i) {
    ObjCPropertyImplDecl *PID = *i;
    
    // Dynamic is just for type-checking.
    if (PID->getPropertyImplementation() == ObjCPropertyImplDecl::Synthesize) {
      ObjCPropertyDecl *PD = PID->getPropertyDecl();

      // Determine which methods need to be implemented, some may have
      // been overridden. Note that ::isSynthesized is not the method
      // we want, that just indicates if the decl came from a
      // property. What we want to know is if the method is defined in
      // this implementation.
      if (!D->getInstanceMethod(PD->getGetterName()))
        CodeGenFunction(*this).GenerateObjCGetter(
                                 const_cast<ObjCImplementationDecl *>(D), PID);
      if (!PD->isReadOnly() &&
          !D->getInstanceMethod(PD->getSetterName()))
        CodeGenFunction(*this).GenerateObjCSetter(
                                 const_cast<ObjCImplementationDecl *>(D), PID);
    }
  }
}

/// EmitNamespace - Emit all declarations in a namespace.
void CodeGenModule::EmitNamespace(const NamespaceDecl *ND) {
  for (RecordDecl::decl_iterator I = ND->decls_begin(), E = ND->decls_end();
       I != E; ++I)
    EmitTopLevelDecl(*I);
}

// EmitLinkageSpec - Emit all declarations in a linkage spec.
void CodeGenModule::EmitLinkageSpec(const LinkageSpecDecl *LSD) {
  if (LSD->getLanguage() != LinkageSpecDecl::lang_c) {
    ErrorUnsupported(LSD, "linkage spec");
    return;
  }

  for (RecordDecl::decl_iterator I = LSD->decls_begin(), E = LSD->decls_end();
       I != E; ++I)
    EmitTopLevelDecl(*I);
}

/// EmitTopLevelDecl - Emit code for a single top level declaration.
void CodeGenModule::EmitTopLevelDecl(Decl *D) {
  // If an error has occurred, stop code generation, but continue
  // parsing and semantic analysis (to ensure all warnings and errors
  // are emitted).
  if (Diags.hasErrorOccurred())
    return;

  // Ignore dependent declarations.
  if (D->getDeclContext() && D->getDeclContext()->isDependentContext())
    return;
  
  switch (D->getKind()) {
  case Decl::CXXMethod:
  case Decl::Function:
    // Skip function templates
    if (cast<FunctionDecl>(D)->getDescribedFunctionTemplate())
      return;
      
    // Fall through
        
  case Decl::Var:
    EmitGlobal(GlobalDecl(cast<ValueDecl>(D)));
    break;

  // C++ Decls
  case Decl::Namespace:
    EmitNamespace(cast<NamespaceDecl>(D));
    break;
    // No code generation needed.
  case Decl::Using:
  case Decl::ClassTemplate:
  case Decl::FunctionTemplate:
    break;
  case Decl::CXXConstructor:
    EmitCXXConstructors(cast<CXXConstructorDecl>(D));
    break;
  case Decl::CXXDestructor:
    EmitCXXDestructors(cast<CXXDestructorDecl>(D));
    break;

  case Decl::StaticAssert:
    // Nothing to do.
    break;

  // Objective-C Decls
    
  // Forward declarations, no (immediate) code generation.
  case Decl::ObjCClass:
  case Decl::ObjCForwardProtocol:
  case Decl::ObjCCategory:
  case Decl::ObjCInterface:
    break;

  case Decl::ObjCProtocol:
    Runtime->GenerateProtocol(cast<ObjCProtocolDecl>(D));
    break;

  case Decl::ObjCCategoryImpl:
    // Categories have properties but don't support synthesize so we
    // can ignore them here.
    Runtime->GenerateCategory(cast<ObjCCategoryImplDecl>(D));
    break;

  case Decl::ObjCImplementation: {
    ObjCImplementationDecl *OMD = cast<ObjCImplementationDecl>(D);
    EmitObjCPropertyImplementations(OMD);
    Runtime->GenerateClass(OMD);
    break;
  } 
  case Decl::ObjCMethod: {
    ObjCMethodDecl *OMD = cast<ObjCMethodDecl>(D);
    // If this is not a prototype, emit the body.
    if (OMD->getBody())
      CodeGenFunction(*this).GenerateObjCMethod(OMD);
    break;
  }
  case Decl::ObjCCompatibleAlias: 
    // compatibility-alias is a directive and has no code gen.
    break;

  case Decl::LinkageSpec:
    EmitLinkageSpec(cast<LinkageSpecDecl>(D));
    break;

  case Decl::FileScopeAsm: {
    FileScopeAsmDecl *AD = cast<FileScopeAsmDecl>(D);
    std::string AsmString(AD->getAsmString()->getStrData(),
                          AD->getAsmString()->getByteLength());
    
    const std::string &S = getModule().getModuleInlineAsm();
    if (S.empty())
      getModule().setModuleInlineAsm(AsmString);
    else
      getModule().setModuleInlineAsm(S + '\n' + AsmString);
    break;
  }
   
  default: 
    // Make sure we handled everything we should, every other kind is a
    // non-top-level decl.  FIXME: Would be nice to have an isTopLevelDeclKind
    // function. Need to recode Decl::Kind to do that easily.
    assert(isa<TypeDecl>(D) && "Unsupported decl kind");
  }
}