Commit b40a4c55 authored by Bill Wendling's avatar Bill Wendling
Browse files

Merging r182266: 

------------------------------------------------------------------------
r182266 | rnk | 2013-05-20 07:02:37 -0700 (Mon, 20 May 2013) | 13 lines

Implement __declspec(selectany) under -fms-extensions

selectany only applies to externally visible global variables.  It has
the effect of making the data weak_odr.

The MSDN docs suggest that unused definitions can only be dropped at
linktime, so Clang uses weak instead of linkonce.  MSVC optimizes away
references to constant selectany data, so it must assume that there is
only one definition, hence weak_odr.

Reviewers: espindola

Differential Revision: http://llvm-reviews.chandlerc.com/D814
------------------------------------------------------------------------

llvm-svn: 182337
parent e3589dfa

clang/include/clang/Basic/Attr.td

+4 −0
Original line number Diff line number Diff line
@@ -948,6 +948,10 @@ def ForceInline : InheritableAttr { 
  let Spellings = [Keyword<"__forceinline">];

}



def SelectAny : InheritableAttr {

  let Spellings = [Declspec<"selectany">];

}



def Win64 : InheritableAttr {

  let Spellings = [Keyword<"__w64">];

}

clang/include/clang/Basic/DiagnosticSemaKinds.td

+2 −0
Original line number Diff line number Diff line
@@ -1948,6 +1948,8 @@ def warn_weak_identifier_undeclared : Warning< 
  "weak identifier %0 never declared">;

def err_attribute_weak_static : Error<

  "weak declaration cannot have internal linkage">;

def err_attribute_selectany_non_extern_data : Error<

  "'selectany' can only be applied to data items with external linkage">;

def warn_attribute_weak_import_invalid_on_definition : Warning<

  "'weak_import' attribute cannot be specified on a definition">,

  InGroup<IgnoredAttributes>;

clang/lib/CodeGen/CodeGenModule.cpp

+7 −1
Original line number Diff line number Diff line
@@ -1900,7 +1900,13 @@ CodeGenModule::GetLLVMLinkageVarDefinition(const VarDecl *D, 
    return llvm::Function::DLLImportLinkage;

  else if (D->hasAttr<DLLExportAttr>())

    return llvm::Function::DLLExportLinkage;

  else if (D->hasAttr<WeakAttr>()) {

  else if (D->hasAttr<SelectAnyAttr>()) {

    // selectany symbols are externally visible, so use weak instead of

    // linkonce.  MSVC optimizes away references to const selectany globals, so

    // all definitions should be the same and ODR linkage should be used.

    // http://msdn.microsoft.com/en-us/library/5tkz6s71.aspx

    return llvm::GlobalVariable::WeakODRLinkage;

  } else if (D->hasAttr<WeakAttr>()) {

    if (GV->isConstant())

      return llvm::GlobalVariable::WeakODRLinkage;

    else

clang/lib/Sema/SemaDecl.cpp

+9 −0
Original line number Diff line number Diff line
@@ -4638,6 +4638,15 @@ static void checkAttributesAfterMerging(Sema &S, NamedDecl &ND) { 
      ND.dropAttr<WeakRefAttr>();

    }

  }



  // 'selectany' only applies to externally visible varable declarations.

  // It does not apply to functions.

  if (SelectAnyAttr *Attr = ND.getAttr<SelectAnyAttr>()) {

    if (isa<FunctionDecl>(ND) || !ND.isExternallyVisible()) {

      S.Diag(Attr->getLocation(), diag::err_attribute_selectany_non_extern_data);

      ND.dropAttr<SelectAnyAttr>();

    }

  }

}



/// Given that we are within the definition of the given function,

clang/lib/Sema/SemaDeclAttr.cpp

+13 −0
Original line number Diff line number Diff line
@@ -4683,6 +4683,16 @@ static void handleForceInlineAttr(Sema &S, Decl *D, const AttributeList &Attr) { 
    S.Diag(Attr.getLoc(), diag::warn_attribute_ignored) << Attr.getName();

}



static void handleSelectAnyAttr(Sema &S, Decl *D, const AttributeList &Attr) {

  if (!checkMicrosoftExt(S, Attr))

    return;

  // Check linkage after possibly merging declaratinos.  See

  // checkAttributesAfterMerging().

  D->addAttr(::new (S.Context)

             SelectAnyAttr(Attr.getRange(), S.Context,

                           Attr.getAttributeSpellingListIndex()));

}



//===----------------------------------------------------------------------===//

// Top Level Sema Entry Points

//===----------------------------------------------------------------------===//
@@ -4909,6 +4919,9 @@ static void ProcessInheritableDeclAttr(Sema &S, Scope *scope, Decl *D, 
  case AttributeList::AT_ForceInline:

    handleForceInlineAttr(S, D, Attr);

    break;

  case AttributeList::AT_SelectAny:

    handleSelectAnyAttr(S, D, Attr);

    break;



  // Thread safety attributes:

  case AttributeList::AT_GuardedVar: