C++ CodeGenModule类代码示例

// maybeUpdateRTTILinkage - Will update the linkage of the RTTI data structures
// from available_externally to the correct linkage if necessary. An example of
// this is:
//
//   struct A {
//     virtual void f();
//   };
//
//   const std::type_info &g() {
//     return typeid(A);
//   }
//
//   void A::f() { }
//
// When we're generating the typeid(A) expression, we do not yet know that
// A's key function is defined in this translation unit, so we will give the
// typeinfo and typename structures available_externally linkage. When A::f
// forces the vtable to be generated, we need to change the linkage of the
// typeinfo and typename structs, otherwise we'll end up with undefined
// externals when linking.
static void 
maybeUpdateRTTILinkage(CodeGenModule &CGM, llvm::GlobalVariable *GV,
                       QualType Ty) {
  // We're only interested in globals with available_externally linkage.
  if (!GV->hasAvailableExternallyLinkage())
    return;

  // Get the real linkage for the type.
  llvm::GlobalVariable::LinkageTypes Linkage = getTypeInfoLinkage(CGM, Ty);

  // If variable is supposed to have available_externally linkage, we don't
  // need to do anything.
  if (Linkage == llvm::GlobalVariable::AvailableExternallyLinkage)
    return;

  // Update the typeinfo linkage.
  GV->setLinkage(Linkage);

  // Get the typename global.
  SmallString<256> OutName;
  llvm::raw_svector_ostream Out(OutName);
  CGM.getCXXABI().getMangleContext().mangleCXXRTTIName(Ty, Out);
  Out.flush();
  StringRef Name = OutName.str();

  llvm::GlobalVariable *TypeNameGV = CGM.getModule().getNamedGlobal(Name);

  assert(TypeNameGV->hasAvailableExternallyLinkage() &&
         "Type name has different linkage from type info!");

  // And update its linkage.
  TypeNameGV->setLinkage(Linkage);
}

static void initializeForBlockHeader(CodeGenModule &CGM, CGBlockInfo &info,
                    llvm::SmallVectorImpl<llvm::Type*> &elementTypes) {
  ASTContext &C = CGM.getContext();

  // The header is basically a 'struct { void *; int; int; void *; void *; }'.
  CharUnits ptrSize, ptrAlign, intSize, intAlign;
  llvm::tie(ptrSize, ptrAlign) = C.getTypeInfoInChars(C.UInt32Ty);
  llvm::tie(intSize, intAlign) = C.getTypeInfoInChars(C.Int32Ty);

  // Are there crazy embedded platforms where this isn't true?
  assert(intSize <= ptrSize && "layout assumptions horribly violated");

  CharUnits headerSize = ptrSize;
  if (2 * intSize < ptrAlign) headerSize += ptrSize;
  else headerSize += 2 * intSize;
  headerSize += 2 * ptrSize;

  info.BlockAlign = ptrAlign;
  info.BlockSize = headerSize;

  assert(elementTypes.empty());
  llvm::Type *i8p = CGM.getTypes().ConvertType(C.UInt32Ty);
  llvm::Type *intTy = CGM.getTypes().ConvertType(C.Int32Ty);
  elementTypes.push_back(i8p);
  elementTypes.push_back(intTy);
  elementTypes.push_back(intTy);
  elementTypes.push_back(i8p);
  elementTypes.push_back(CGM.getBlockDescriptorType());

  assert(elementTypes.size() == BlockHeaderSize);
}

static bool CheckElementalArguments(CodeGenModule &CGM, const FunctionDecl *FD,
                                    llvm::Function *Fn, bool &HasThis) {
  // Check the return type.
  QualType RetTy = FD->getReturnType();
  if (RetTy->isAggregateType()) {
    CGM.Error(FD->getLocation(), "the return type for this elemental "
                                 "function is not supported yet");
    return false;
  }

  // Check each parameter type.
  for (unsigned I = 0, E = FD->param_size(); I < E; ++I) {
    const ParmVarDecl *VD = FD->getParamDecl(I);
    QualType Ty = VD->getType();
    assert(!Ty->isIncompleteType() && "incomplete type");
    if (Ty->isAggregateType()) {
      CGM.Error(VD->getLocation(), "the parameter type for this elemental "
                                   "function is not supported yet");
      return false;
    }
  }

  HasThis = isa<CXXMethodDecl>(FD) && cast<CXXMethodDecl>(FD)->isInstance();

  // At this point, no passing struct arguments by value.
  unsigned NumArgs = FD->param_size();
  unsigned NumLLVMArgs = Fn->arg_size();

  // There is a single implicit 'this' parameter.
  if (HasThis && (NumArgs + 1 == NumLLVMArgs))
    return true;

  return NumArgs == NumLLVMArgs;
}

CodeGenVTables::CodeGenVTables(CodeGenModule &CGM)
  : CGM(CGM), ItaniumVTContext(CGM.getContext()) {
  if (CGM.getTarget().getCXXABI().isMicrosoft()) {
    // FIXME: Eventually, we should only have one of V*TContexts available.
    // Today we use both in the Microsoft ABI as MicrosoftVFTableContext
    // is not completely supported in CodeGen yet.
    MicrosoftVTContext.reset(new MicrosoftVTableContext(CGM.getContext()));
  }
}

CGNVCUDARuntime::CGNVCUDARuntime(CodeGenModule &CGM) : CGCUDARuntime(CGM) {
  CodeGen::CodeGenTypes &Types = CGM.getTypes();
  ASTContext &Ctx = CGM.getContext();

  IntTy = Types.ConvertType(Ctx.IntTy);
  SizeTy = Types.ConvertType(Ctx.getSizeType());

  CharPtrTy = llvm::PointerType::getUnqual(Types.ConvertType(Ctx.CharTy));
  VoidPtrTy = cast<llvm::PointerType>(Types.ConvertType(Ctx.VoidPtrTy));
}

CGNVCUDARuntime::CGNVCUDARuntime(CodeGenModule &CGM)
    : CGCUDARuntime(CGM), Context(CGM.getLLVMContext()),
      TheModule(CGM.getModule()) {
  CodeGen::CodeGenTypes &Types = CGM.getTypes();
  ASTContext &Ctx = CGM.getContext();

  IntTy = CGM.IntTy;
  SizeTy = CGM.SizeTy;
  VoidTy = CGM.VoidTy;

  CharPtrTy = llvm::PointerType::getUnqual(Types.ConvertType(Ctx.CharTy));
  VoidPtrTy = cast<llvm::PointerType>(Types.ConvertType(Ctx.VoidPtrTy));
  VoidPtrPtrTy = VoidPtrTy->getPointerTo();
}

/// Given that we're currently at the end of the translation unit, and
/// we've emitted a reference to the v-table for this class, should
/// we define that v-table?
static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM,
                                                   const CXXRecordDecl *RD) {
  // If we're building with optimization, we always emit v-tables
  // since that allows for virtual function calls to be devirtualized.
  // If the v-table is defined strongly elsewhere, this definition
  // will be emitted available_externally.
  //
  // However, we don't want to do this in -fapple-kext mode, because
  // kext mode does not permit devirtualization.
  if (CGM.getCodeGenOpts().OptimizationLevel && !CGM.getLangOpts().AppleKext)
    return true;

  return !CGM.getVTables().isVTableExternal(RD);
}

static void setThunkProperties(CodeGenModule &CGM, const ThunkInfo &Thunk,
                               llvm::Function *ThunkFn, bool ForVTable,
                               GlobalDecl GD) {
  CGM.setFunctionLinkage(GD, ThunkFn);
  CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
                                  !Thunk.Return.isEmpty());

  // Set the right visibility.
  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
  setThunkVisibility(CGM, MD, Thunk, ThunkFn);

  if (CGM.supportsCOMDAT() && ThunkFn->isWeakForLinker())
    ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
}

static void EmitOMPAlignedClause(CodeGenFunction &CGF, CodeGenModule &CGM,
                                 const OMPAlignedClause &Clause) {
  unsigned ClauseAlignment = 0;
  if (auto AlignmentExpr = Clause.getAlignment()) {
    auto AlignmentCI =
        cast<llvm::ConstantInt>(CGF.EmitScalarExpr(AlignmentExpr));
    ClauseAlignment = static_cast<unsigned>(AlignmentCI->getZExtValue());
  }
  for (auto E : Clause.varlists()) {
    unsigned Alignment = ClauseAlignment;
    if (Alignment == 0) {
      // OpenMP [2.8.1, Description]
      // If no optional parameter is specified, implementation-defined default
      // alignments for SIMD instructions on the target platforms are assumed.
      Alignment = CGM.getTargetCodeGenInfo().getOpenMPSimdDefaultAlignment(
          E->getType());
    }
    assert((Alignment == 0 || llvm::isPowerOf2_32(Alignment)) &&
           "alignment is not power of 2");
    if (Alignment != 0) {
      llvm::Value *PtrValue = CGF.EmitScalarExpr(E);
      CGF.EmitAlignmentAssumption(PtrValue, Alignment);
    }
  }
}

static void setThunkVisibility(CodeGenModule &CGM, const CXXMethodDecl *MD,
                               const ThunkInfo &Thunk, llvm::Function *Fn) {
  CGM.setGlobalVisibility(Fn, MD);

  if (!CGM.getCodeGenOpts().HiddenWeakVTables)
    return;

  // If the thunk has weak/linkonce linkage, but the function must be
  // emitted in every translation unit that references it, then we can
  // emit its thunks with hidden visibility, since its thunks must be
  // emitted when the function is.

  // This follows CodeGenModule::setTypeVisibility; see the comments
  // there for explanation.

  if ((Fn->getLinkage() != llvm::GlobalVariable::LinkOnceODRLinkage &&
       Fn->getLinkage() != llvm::GlobalVariable::WeakODRLinkage) ||
      Fn->getVisibility() != llvm::GlobalVariable::DefaultVisibility)
    return;

  if (MD->getExplicitVisibility())
    return;

  switch (MD->getTemplateSpecializationKind()) {
  case TSK_ExplicitInstantiationDefinition:
  case TSK_ExplicitInstantiationDeclaration:
    return;

  case TSK_Undeclared:
    break;

  case TSK_ExplicitSpecialization:
  case TSK_ImplicitInstantiation:
    if (!CGM.getCodeGenOpts().HiddenWeakTemplateVTables)
      return;
    break;
  }

  // If there's an explicit definition, and that definition is
  // out-of-line, then we can't assume that all users will have a
  // definition to emit.
  const FunctionDecl *Def = 0;
  if (MD->hasBody(Def) && Def->isOutOfLine())
    return;

  Fn->setVisibility(llvm::GlobalValue::HiddenVisibility);
}

static bool shouldEmitVTableThunk(CodeGenModule &CGM, const CXXMethodDecl *MD,
                                  bool IsUnprototyped, bool ForVTable) {
  // Always emit thunks in the MS C++ ABI. We cannot rely on other TUs to
  // provide thunks for us.
  if (CGM.getTarget().getCXXABI().isMicrosoft())
    return true;

  // In the Itanium C++ ABI, vtable thunks are provided by TUs that provide
  // definitions of the main method. Therefore, emitting thunks with the vtable
  // is purely an optimization. Emit the thunk if optimizations are enabled and
  // all of the parameter types are complete.
  if (ForVTable)
    return CGM.getCodeGenOpts().OptimizationLevel && !IsUnprototyped;

  // Always emit thunks along with the method definition.
  return true;
}

/// Given that we're currently at the end of the translation unit, and
/// we've emitted a reference to the vtable for this class, should
/// we define that vtable?
static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM,
                                                   const CXXRecordDecl *RD) {
  // If vtable is internal then it has to be done.
  if (!CGM.getVTables().isVTableExternal(RD))
    return true;

  // If it's external then maybe we will need it as available_externally.
  return shouldEmitAvailableExternallyVTable(CGM, RD);
}

void VBTableInfo::EmitVBTableDefinition(
    CodeGenModule &CGM, const CXXRecordDecl *RD,
    llvm::GlobalVariable::LinkageTypes Linkage) const {
  assert(RD->getNumVBases() && ReusingBase->getNumVBases() &&
         "should only emit vbtables for classes with vbtables");

  const ASTRecordLayout &BaseLayout =
    CGM.getContext().getASTRecordLayout(VBPtrSubobject.getBase());
  const ASTRecordLayout &DerivedLayout =
    CGM.getContext().getASTRecordLayout(RD);

  SmallVector<llvm::Constant *, 4> Offsets;

  // The offset from ReusingBase's vbptr to itself always leads.
  CharUnits VBPtrOffset = BaseLayout.getVBPtrOffset();
  Offsets.push_back(
      llvm::ConstantInt::get(CGM.IntTy, -VBPtrOffset.getQuantity()));

  // These are laid out in the same order as in Itanium, which is the same as
  // the order of the vbase iterator.
  for (CXXRecordDecl::base_class_const_iterator I = ReusingBase->vbases_begin(),
       E = ReusingBase->vbases_end(); I != E; ++I) {
    const CXXRecordDecl *VBase = I->getType()->getAsCXXRecordDecl();
    CharUnits Offset = DerivedLayout.getVBaseClassOffset(VBase);
    assert(!Offset.isNegative());
    // Make it relative to the subobject vbptr.
    Offset -= VBPtrSubobject.getBaseOffset() + VBPtrOffset;
    Offsets.push_back(llvm::ConstantInt::get(CGM.IntTy, Offset.getQuantity()));
  }

  assert(Offsets.size() ==
         cast<llvm::ArrayType>(cast<llvm::PointerType>(GV->getType())
                               ->getElementType())->getNumElements());
  llvm::ArrayType *VBTableType =
    llvm::ArrayType::get(CGM.IntTy, Offsets.size());
  llvm::Constant *Init = llvm::ConstantArray::get(VBTableType, Offsets);
  GV->setInitializer(Init);

  // Set the correct linkage.
  GV->setLinkage(Linkage);

  // Set the right visibility.
  CGM.setTypeVisibility(GV, RD, CodeGenModule::TVK_ForVTable);
}

CodeGenTypes::CodeGenTypes(CodeGenModule &cgm)
  : CGM(cgm), Context(cgm.getContext()), TheModule(cgm.getModule()),
    TheDataLayout(cgm.getDataLayout()),
    Target(cgm.getTarget()), TheCXXABI(cgm.getCXXABI()),
    CodeGenOpts(cgm.getCodeGenOpts()),
    TheABIInfo(cgm.getTargetCodeGenInfo().getABIInfo()) {
  SkippedLayout = false;
}

CharUnits swiftcall::getNaturalAlignment(CodeGenModule &CGM, llvm::Type *type) {
  // For Swift's purposes, this is always just the store size of the type
  // rounded up to a power of 2.
  auto size = (unsigned long long) getTypeStoreSize(CGM, type).getQuantity();
  if (!isPowerOf2(size)) {
    size = 1ULL << (llvm::findLastSet(size, llvm::ZB_Undefined) + 1);
  }
  assert(size >= CGM.getDataLayout().getABITypeAlignment(type));
  return CharUnits::fromQuantity(size);
}