Readd copy ctor

Signed-off-by: Larsen, Steffen <[email protected]>

Author: steffenlarsen

sycl/doc/extensions/experimental/sycl_ext_oneapi_device_global.asciidoc

@@ -335,6 +335,19 @@ The object of type `T` is initialized from the `args` parameter pack using list
 
 `T` must be trivially destructible.
 
+// --- ROW BREAK ---
+a|
+[source,c++]
+----
+constexpr device_global(const device_global &other);
+----
+|
+Available if `PropertyListT::has_property<device_image_scope_key>() == false`.
+
+Constructs a `device_global` object, and implicit storage for `T` in the global address space on each device that may access it.
+
+The storage on each device for `T` is initialized with a copy of the storage in `other`.
+
 // --- ROW BREAK ---
 a|
 [source,c++]

sycl/include/sycl/ext/oneapi/device_global/device_global.hpp

@@ -226,6 +226,9 @@ class
   // Inherit the base class' constructors
   using detail::device_global_base<T, property_list_t>::device_global_base;
 
+  constexpr device_global(const device_global &DG)
+      : base_t(static_cast<const base_t &>(DG)) {}
+
   device_global(const device_global &&) = delete;
   device_global &operator=(const device_global &) = delete;
   device_global &operator=(const device_global &&) = delete;

sycl/test/extensions/device_global/device_global_copy_negative.cpp

@@ -10,11 +10,11 @@ namespace oneapiext = sycl::ext::oneapi::experimental;
 using device_image_properties =
     decltype(oneapiext::properties{oneapiext::device_image_scope});
 
-// expected-error@+2 {{call to implicitly-deleted copy constructor of}}
+// expected-error@sycl/ext/oneapi/device_global/device_global.hpp:* {{call to deleted constructor}}
 oneapiext::device_global<const int, device_image_properties> DGInit1{3};
 oneapiext::device_global<const int, device_image_properties> DGCopy1{DGInit1};
 
-// expected-error@+2 {{call to implicitly-deleted copy constructor of}}
+// expected-error@sycl/ext/oneapi/device_global/device_global.hpp:* {{call to deleted constructor}}
 oneapiext::device_global<int, device_image_properties> DGInit2{3};
 oneapiext::device_global<int, device_image_properties> DGCopy2{DGInit2};