Emit global references with constant initializers as constants. Fixes PR5585.

The standard actually says that such references should have internal linkage,
but gcc doesn't do that, so we probably can't get away with it.

llvm-svn: 95577

clang/lib/CodeGen/CodeGenModule.cpp

@@ -783,7 +783,7 @@ CodeGenModule::CreateRuntimeFunction(const llvm::FunctionType *FTy,
 }
 
 static bool DeclIsConstantGlobal(ASTContext &Context, const VarDecl *D) {
-  if (!D->getType().isConstant(Context))
+  if (!D->getType().isConstant(Context) && !D->getType()->isReferenceType())
     return false;
   if (Context.getLangOptions().CPlusPlus &&
       Context.getBaseElementType(D->getType())->getAs<RecordType>()) {

clang/test/CodeGenCXX/const-init.cpp

@@ -2,11 +2,11 @@
 
 // CHECK: @a = global i32 10
 int a = 10;
-// CHECK: @ar = global i32* @a
+// CHECK: @ar = constant i32* @a
 int &ar = a;
 
 void f();
-// CHECK: @fr = global void ()* @_Z1fv
+// CHECK: @fr = constant void ()* @_Z1fv
 void (&fr)() = f;
 
 struct S { int& a; };