Introduce FunctionDecl::getFirstDeclaration() and VarDecl::getFirstDeclaration().

For multiple redeclarations they return the first one.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@75602 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index fe9885e..5ef0c09 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -358,12 +358,16 @@
   return Def? Def->getInit() : 0;
 }
 
-Decl *VarDecl::getPrimaryDecl() const {
-  const VarDecl *Prim = this;
-  while (Prim->getPreviousDeclaration())
-    Prim = Prim->getPreviousDeclaration();
+const VarDecl *VarDecl::getFirstDeclaration() const {
+  const VarDecl *First = this;
+  while (First->getPreviousDeclaration())
+    First = First->getPreviousDeclaration();
 
-  return const_cast<VarDecl *>(Prim);
+  return First;
+}
+
+Decl *VarDecl::getPrimaryDecl() const {
+  return const_cast<VarDecl *>(getFirstDeclaration());
 }
 
 //===----------------------------------------------------------------------===//
@@ -577,12 +581,16 @@
   }
 }
 
-Decl *FunctionDecl::getPrimaryDecl() const {
-  const FunctionDecl *Prim = this;
-  while (Prim->getPreviousDeclaration())
-    Prim = Prim->getPreviousDeclaration();
+const FunctionDecl *FunctionDecl::getFirstDeclaration() const {
+  const FunctionDecl *First = this;
+  while (First->getPreviousDeclaration())
+    First = First->getPreviousDeclaration();
 
-  return const_cast<FunctionDecl *>(Prim);
+  return First;
+}
+
+Decl *FunctionDecl::getPrimaryDecl() const {
+  return const_cast<FunctionDecl *>(getFirstDeclaration());
 }
 
 /// getOverloadedOperator - Which C++ overloaded operator this