Cherry pick fix for warning and compilation errors (#1849) (#1947)

Author: timmiesmith

include/oneapi/dpl/pstl/execution_impl.h

@@ -106,25 +106,25 @@ __select_backend(oneapi::dpl::execution::parallel_unsequenced_policy, _IteratorT
 namespace __ranges
 {
 
-::oneapi::dpl::__internal::__serial_tag<std::false_type>
+inline ::oneapi::dpl::__internal::__serial_tag<std::false_type>
 __select_backend(oneapi::dpl::execution::sequenced_policy)
 {
     return {};
 }
 
-::oneapi::dpl::__internal::__serial_tag<std::true_type> //vectorization allowed
+inline ::oneapi::dpl::__internal::__serial_tag<std::true_type> //vectorization allowed
 __select_backend(oneapi::dpl::execution::unsequenced_policy)
 {
     return {};
 }
 
-::oneapi::dpl::__internal::__parallel_tag<std::false_type>
+inline ::oneapi::dpl::__internal::__parallel_tag<std::false_type>
 __select_backend(oneapi::dpl::execution::parallel_policy)
 {
     return {};
 }
 
-::oneapi::dpl::__internal::__parallel_tag<std::true_type> //vectorization allowed
+inline ::oneapi::dpl::__internal::__parallel_tag<std::true_type> //vectorization allowed
 __select_backend(oneapi::dpl::execution::parallel_unsequenced_policy)
 {
     return {};

include/oneapi/dpl/pstl/hetero/dpcpp/parallel_backend_sycl_radix_sort.h

@@ -816,11 +816,11 @@ __parallel_radix_sort(oneapi::dpl::__internal::__device_backend_tag, _ExecutionP
     else if (__n <= 4096 && __wg_size * 4 <= __max_wg_size)
         __event = __subgroup_radix_sort<_RadixSortKernel, __wg_size * 4, 16, __radix_bits, __is_ascending>{}(
             __exec.queue(), ::std::forward<_Range>(__in_rng), __proj);
-    // In __subgroup_radix_sort, we request a sub-group size via _ONEDPL_SYCL_REQD_SUB_GROUP_SIZE_IF_SUPPORTED
-    // based upon the iters per item. For the below cases, register spills that result in runtime exceptions have
-    // been observed on accelerators that do not support the requested sub-group size of 16. For the above cases
-    // that request but may not receive a sub-group size of 16, inputs are small enough to avoid register
-    // spills on assessed hardware.
+    // In __subgroup_radix_sort, we request a sub-group size of 16 via _ONEDPL_SYCL_REQD_SUB_GROUP_SIZE_IF_SUPPORTED
+    // for compilation targets that support this option. For the below cases, register spills that result in
+    // runtime exceptions have been observed on accelerators that do not support the requested sub-group size of 16.
+    // For the above cases that request but may not receive a sub-group size of 16, inputs are small enough to avoid
+    // register spills on assessed hardware.
     else if (__n <= 8192 && __wg_size * 8 <= __max_wg_size && __dev_has_sg16)
         __event = __subgroup_radix_sort<_RadixSortKernel, __wg_size * 8, 16, __radix_bits, __is_ascending>{}(
             __exec.queue(), ::std::forward<_Range>(__in_rng), __proj);

include/oneapi/dpl/pstl/hetero/dpcpp/parallel_backend_sycl_radix_sort_one_wg.h

@@ -30,8 +30,7 @@ template <typename... _Name>
 class __radix_sort_one_wg_kernel;
 
 template <typename _KernelNameBase, uint16_t __wg_size = 256 /*work group size*/, uint16_t __block_size = 16,
-          ::std::uint32_t __radix = 4, bool __is_asc = true,
-          uint16_t __req_sub_group_size = (__block_size < 4 ? 32 : 16)>
+          std::uint32_t __radix = 4, bool __is_asc = true>
 struct __subgroup_radix_sort
 {
     template <typename _RangeIn, typename _Proj>
@@ -164,9 +163,12 @@ struct __subgroup_radix_sort
                 auto __counter_lacc = __buf_count.get_acc(__cgh);
 
                 __cgh.parallel_for<_Name...>(
-                    __range,
-                    ([=](sycl::nd_item<1> __it)[[_ONEDPL_SYCL_REQD_SUB_GROUP_SIZE_IF_SUPPORTED(__req_sub_group_size)]] {
-                        union __storage { _ValT __v[__block_size]; __storage(){} } __values;
+                    __range, ([=](sycl::nd_item<1> __it) [[_ONEDPL_SYCL_REQD_SUB_GROUP_SIZE_IF_SUPPORTED(16)]] {
+                        union __storage
+                        {
+                            _ValT __v[__block_size];
+                            __storage() {}
+                        } __values;
                         uint16_t __wi = __it.get_local_linear_id();
                         uint16_t __begin_bit = 0;
                         constexpr uint16_t __end_bit = sizeof(_KeyT) * ::std::numeric_limits<unsigned char>::digits;