SYCL Updates, master branch (2020.08.14.)

I wrote a long and nice description about this. And then GitLab completely died under me, and forgot the whole text that I wrote.

So screw it. One of the updates is here to get rid of these sort of warnings while compiling Athena with DPC++:

In file included from /data/projects/athena-gpu/athena/Control/StoreGate/src/ActiveStoreSvc.cxx:6:
In file included from /data/projects/athena-gpu/athena/Control/StoreGate/StoreGate/StoreGateSvc.h:22:
In file included from /data/projects/athena-gpu/athena/Control/StoreGate/StoreGate/tools/SGImplSvc.h:54:
In file included from /data/projects/athena-gpu/athena/Control/StoreGate/StoreGate/SGIterator.h:18:
In file included from /data/projects/athena-gpu/athena/Control/SGTools/SGTools/DataProxy.h:431:
In file included from /data/projects/athena-gpu/athena/Control/SGTools/SGTools/DataProxy.icc:16:
In file included from /data/projects/athena-gpu/athena/Control/AthenaKernel/AthenaKernel/StorableConversions.h:15:
In file included from /data/projects/athena-gpu/athena/Control/AthenaKernel/AthenaKernel/DataBucket.h:129:
/data/projects/athena-gpu/athena/Control/AthenaKernel/AthenaKernel/DataBucket.icc:186:18: warning: ISO C++ requires the name after '::~' to be found in the same scope as the name before '::~' [-Wdtor-name]
SG::DataBucket<T>::~DataBucket()
~~~~~~~~~~~~~~~~~^~
                 ::DataBucket
1 warning generated.

The other update is necessary to make DPC++ not freak out about multi-versioned functions. (See: https://github.com/intel/llvm/issues/2128)

Pinging @ssnyder.

Control/AthenaKernel/AthenaKernel/DataBucket.icc

@@ -55,7 +55,7 @@ void db_free_ptr (T* ptr, std::true_type)
 ///////////////////////////////////////////////////////////////////////////////
 // CONSTRUCTORS
 ///////////////////////////////////////////////////////////////////////////////
-template <typename T> 
+template <typename T>
 SG::DataBucket<T>::DataBucket(T* data)
   : m_ptr(data)
 {
@@ -77,7 +77,7 @@ SG::DataBucket<T>::DataBucket(std::unique_ptr<U> data)
 {
 }
 
-template <typename T> 
+template <typename T>
 SG::DataBucket<T>::DataBucket(SG::DataObjectSharedPtr<T> data)
   : m_ptr(data.detach())
 {
@@ -86,11 +86,11 @@ SG::DataBucket<T>::DataBucket(SG::DataObjectSharedPtr<T> data)
 ///////////////////////////////////////////////////////////////////////////////
 // DATAOBJECT
 ///////////////////////////////////////////////////////////////////////////////
-template <typename T> 
-const CLID& SG::DataBucket<T>::clID() const {return classID();}  
+template <typename T>
+const CLID& SG::DataBucket<T>::clID() const {return classID();}
 
-template <typename T> 
-const CLID& SG::DataBucket<T>::classID() { 
+template <typename T>
+const CLID& SG::DataBucket<T>::classID() {
   typedef typename std::remove_pointer<T>::type BareTp;
   typedef typename std::remove_const<BareTp>::type BareT;
   return ClassID_traits<BareT>::ID();
@@ -105,7 +105,7 @@ const CLID& SG::DataBucket<T>::classID() {
  * @param irt To be called if we make a new instance.
  * @param isConst True if the object being converted is regarded as const.
  */
-template <typename T> 
+template <typename T>
 void*
 SG::DataBucket<T>::cast (CLID clid,
                          IRegisterTransient* irt /*= 0*/,
@@ -150,7 +150,7 @@ SG::DataBucket<T>::cast (CLID clid,
  * @param irt To be called if we make a new instance.
  * @param isConst True if the object being converted is regarded as const.
  */
-template <typename T> 
+template <typename T>
 void* SG::DataBucket<T>::cast (const std::type_info& tinfo,
                                IRegisterTransient* irt /*= 0*/,
                                bool isConst /*= true*/)
@@ -182,8 +182,13 @@ void* SG::DataBucket<T>::cast (const std::type_info& tinfo,
   return 0;
 }
 
-template <typename T> 
-SG::DataBucket<T>::~DataBucket()
+// The DataBucket descructor is put into an explicit namespace scope to get rid
+// of a pesky warning from DPC++. Unfortunately Clang has an issue with the
+// class name having a scope declaration on the destructor for some reason.
+namespace SG {
+
+template <typename T>
+DataBucket<T>::~DataBucket()
 {
   // Delete any copies.
   vec_t::iterator end = m_cnvcopies.end();
@@ -198,6 +203,8 @@ SG::DataBucket<T>::~DataBucket()
     SG::db_free_ptr(m_ptr, tag());
 }
 
+} // namespace SG
+
 
 namespace {
 
@@ -228,4 +235,3 @@ void SG::DataBucket<T>::lock()
 {
   call_lock (m_ptr, typename std::is_polymorphic<T>::type());
 }
-