merge hasCLanguageLinkage and isExternC. Keep the shorter name.

I added hasCLanguageLinkage while fixing some language linkage bugs some
time ago so that I wouldn't have to check all users of isExternC. It turned
out to be a much longer detour than expected, but this patch finally
merges the two again. The isExternC function now implements just the
standard notion of having C language linkage.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@175119 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 42 deletions

diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 5c489273d2..433e76767c 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -1217,20 +1217,20 @@ SourceRange VarDecl::getSourceRange() const {
 
 template<typename T>
 static LanguageLinkage getLanguageLinkageTemplate(const T &D) {
-  // Language linkage is a C++ concept, but saying that everything in C has
+  // C++ [dcl.link]p1: All function types, function names with external linkage,
+  // and variable names with external linkage have a language linkage.
+  if (!isExternalLinkage(D.getLinkage()))
+    return NoLanguageLinkage;
+
+  // Language linkage is a C++ concept, but saying that everything else in C has
   // C language linkage fits the implementation nicely.
   ASTContext &Context = D.getASTContext();
   if (!Context.getLangOpts().CPlusPlus)
     return CLanguageLinkage;
 
-  // dcl.link 1: All function types, function names with external linkage, and
-  // variable names with external linkage have a language linkage.
-  if (!isExternalLinkage(D.getLinkage()))
-    return NoLanguageLinkage;
-
-  // dcl.link 4: A C language linkage is ignored in determining the language
-  // linkage of the names of class members and the function type of class member
-  // functions.
+  // C++ [dcl.link]p4: A C language linkage is ignored in determining the
+  // language linkage of the names of class members and the function type of
+  // class member functions.
   const DeclContext *DC = D.getDeclContext();
   if (DC->isRecord())
     return CXXLanguageLinkage;
@@ -1248,20 +1248,6 @@ LanguageLinkage VarDecl::getLanguageLinkage() const {
   return getLanguageLinkageTemplate(*this);
 }
 
-bool VarDecl::isExternC() const {
-  if (getLinkage() != ExternalLinkage)
-    return false;
-
-  const DeclContext *DC = getDeclContext();
-  if (DC->isRecord())
-    return false;
-
-  ASTContext &Context = getASTContext();
-  if (!Context.getLangOpts().CPlusPlus)
-    return true;
-  return DC->isExternCContext();
-}
-
 VarDecl *VarDecl::getCanonicalDecl() {
   return getFirstDeclaration();
 }
@@ -1780,24 +1766,6 @@ LanguageLinkage FunctionDecl::getLanguageLinkage() const {
   return getLanguageLinkageTemplate(*this);
 }
 
-bool FunctionDecl::isExternC() const {
-  if (getLinkage() != ExternalLinkage)
-    return false;
-
-  if (getAttr<OverloadableAttr>())
-    return false;
-
-  const DeclContext *DC = getDeclContext();
-  if (DC->isRecord())
-    return false;
-
-  ASTContext &Context = getASTContext();
-  if (!Context.getLangOpts().CPlusPlus)
-    return true;
-
-  return isMain() || DC->isExternCContext();
-}
-
 bool FunctionDecl::isGlobal() const {
   if (const CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(this))
     return Method->isStatic();
@@ -2466,7 +2434,7 @@ unsigned FunctionDecl::getMemoryFunctionKind() const {
     return Builtin::BIstrlen;
 
   default:
-    if (hasCLanguageLinkage()) {
+    if (isExternC()) {
       if (FnInfo->isStr("memset"))
         return Builtin::BImemset;
       else if (FnInfo->isStr("memcpy"))