[SYCL][NFC] Use reducer-access helper function instead of deduction guide (#8411)

The use of deduction guides in the `ReducerAccess` helper class causes
problems when building with a compiler that does not support them. This
commit changes the implementation to use a helper function instead.

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

Author: steffenlarsen

sycl/include/sycl/reduction.hpp

@@ -200,9 +200,11 @@ template <typename ReducerT> class ReducerAccess {
   ReducerT &MReducerRef;
 };
 
-// Deduction guide to simplify the use of ReducerAccess.
-template <typename ReducerT>
-ReducerAccess(ReducerT &) -> ReducerAccess<ReducerT>;
+// Helper function to simplify the use of ReducerAccess. This avoids the need
+// for potentially unsupported deduction guides.
+template <typename ReducerT> auto getReducerAccess(ReducerT &Reducer) {
+  return ReducerAccess<ReducerT>{Reducer};
+}
 
 /// Use CRTP to avoid redefining shorthand operators in terms of combine
 ///
@@ -283,7 +285,7 @@ template <class Reducer> class combiner {
       auto AtomicRef = sycl::atomic_ref<T, memory_order::relaxed,
                                         getMemoryScope<Space>(), Space>(
           address_space_cast<Space, access::decorated::no>(ReduVarPtr)[E]);
-      Functor(std::move(AtomicRef), ReducerAccess{*reducer}.getElement(E));
+      Functor(std::move(AtomicRef), getReducerAccess(*reducer).getElement(E));
     }
   }
 
@@ -956,7 +958,7 @@ struct NDRangeReduction<reduction::strategy::local_atomic_and_atomic_cross_wg> {
         // Work-group cooperates to initialize multiple reduction variables
         auto LID = NDId.get_local_id(0);
         for (size_t E = LID; E < NElements; E += NDId.get_local_range(0)) {
-          GroupSum[E] = ReducerAccess(Reducer).getIdentity();
+          GroupSum[E] = getReducerAccess(Reducer).getIdentity();
         }
         workGroupBarrier();
 
@@ -969,7 +971,7 @@ struct NDRangeReduction<reduction::strategy::local_atomic_and_atomic_cross_wg> {
         workGroupBarrier();
         if (LID == 0) {
           for (size_t E = 0; E < NElements; ++E) {
-            ReducerAccess{Reducer}.getElement(E) = GroupSum[E];
+            getReducerAccess(Reducer).getElement(E) = GroupSum[E];
           }
           Reducer.template atomic_combine(&Out[0]);
         }
@@ -1019,7 +1021,7 @@ struct NDRangeReduction<
         // reduce_over_group is only defined for each T, not for span<T, ...>
         size_t LID = NDId.get_local_id(0);
         for (int E = 0; E < NElements; ++E) {
-          auto &RedElem = ReducerAccess{Reducer}.getElement(E);
+          auto &RedElem = getReducerAccess(Reducer).getElement(E);
           RedElem = reduce_over_group(Group, RedElem, BOp);
           if (LID == 0) {
             if (NWorkGroups == 1) {
@@ -1030,7 +1032,7 @@ struct NDRangeReduction<
               Out[E] = RedElem;
             } else {
               PartialSums[NDId.get_group_linear_id() * NElements + E] =
-                  ReducerAccess{Reducer}.getElement(E);
+                  getReducerAccess(Reducer).getElement(E);
             }
           }
         }
@@ -1053,7 +1055,7 @@ struct NDRangeReduction<
           // Reduce each result separately
           // TODO: Opportunity to parallelize across elements.
           for (int E = 0; E < NElements; ++E) {
-            auto LocalSum = ReducerAccess{Reducer}.getIdentity();
+            auto LocalSum = getReducerAccess(Reducer).getIdentity();
             for (size_t I = LID; I < NWorkGroups; I += WGSize)
               LocalSum = BOp(LocalSum, PartialSums[I * NElements + E]);
             auto Result = reduce_over_group(Group, LocalSum, BOp);
@@ -1143,7 +1145,7 @@ template <> struct NDRangeReduction<reduction::strategy::range_basic> {
       for (int E = 0; E < NElements; ++E) {
 
         // Copy the element to local memory to prepare it for tree-reduction.
-        LocalReds[LID] = ReducerAccess{Reducer}.getElement(E);
+        LocalReds[LID] = getReducerAccess(Reducer).getElement(E);
 
         doTreeReduction(WGSize, LID, false, Identity, LocalReds, BOp,
                         [&]() { workGroupBarrier(); });
@@ -1218,8 +1220,8 @@ struct NDRangeReduction<reduction::strategy::group_reduce_and_atomic_cross_wg> {
 
         typename Reduction::binary_operation BOp;
         for (int E = 0; E < NElements; ++E) {
-          ReducerAccess{Reducer}.getElement(E) = reduce_over_group(
-              NDIt.get_group(), ReducerAccess{Reducer}.getElement(E), BOp);
+          getReducerAccess(Reducer).getElement(E) = reduce_over_group(
+              NDIt.get_group(), getReducerAccess(Reducer).getElement(E), BOp);
         }
         if (NDIt.get_local_linear_id() == 0)
           Reducer.atomic_combine(&Out[0]);
@@ -1267,15 +1269,15 @@ struct NDRangeReduction<
         for (int E = 0; E < NElements; ++E) {
 
           // Copy the element to local memory to prepare it for tree-reduction.
-          LocalReds[LID] = ReducerAccess{Reducer}.getElement(E);
+          LocalReds[LID] = getReducerAccess(Reducer).getElement(E);
 
           typename Reduction::binary_operation BOp;
           doTreeReduction(WGSize, LID, IsPow2WG,
-                          ReducerAccess{Reducer}.getIdentity(), LocalReds, BOp,
-                          [&]() { NDIt.barrier(); });
+                          getReducerAccess(Reducer).getIdentity(), LocalReds,
+                          BOp, [&]() { NDIt.barrier(); });
 
           if (LID == 0) {
-            ReducerAccess{Reducer}.getElement(E) =
+            getReducerAccess(Reducer).getElement(E) =
                 IsPow2WG ? LocalReds[0] : BOp(LocalReds[0], LocalReds[WGSize]);
           }
 
@@ -1343,7 +1345,7 @@ struct NDRangeReduction<
       typename Reduction::binary_operation BOp;
       for (int E = 0; E < NElements; ++E) {
         typename Reduction::result_type PSum;
-        PSum = ReducerAccess{Reducer}.getElement(E);
+        PSum = getReducerAccess(Reducer).getElement(E);
         PSum = reduce_over_group(NDIt.get_group(), PSum, BOp);
         if (NDIt.get_local_linear_id() == 0) {
           if (IsUpdateOfUserVar)
@@ -1482,7 +1484,7 @@ template <> struct NDRangeReduction<reduction::strategy::basic> {
       for (int E = 0; E < NElements; ++E) {
 
         // Copy the element to local memory to prepare it for tree-reduction.
-        LocalReds[LID] = ReducerAccess{Reducer}.getElement(E);
+        LocalReds[LID] = getReducerAccess(Reducer).getElement(E);
 
         doTreeReduction(WGSize, LID, IsPow2WG, ReduIdentity, LocalReds, BOp,
                         [&]() { NDIt.barrier(); });
@@ -1756,7 +1758,7 @@ void reduCGFuncImplScalar(
   size_t LID = NDIt.get_local_linear_id();
 
   ((std::get<Is>(LocalAccsTuple)[LID] =
-        ReducerAccess{std::get<Is>(ReducersTuple)}.getElement(0)),
+        getReducerAccess(std::get<Is>(ReducersTuple)).getElement(0)),
    ...);
 
   // For work-groups, which size is not power of two, local accessors have
@@ -1807,7 +1809,7 @@ void reduCGFuncImplArrayHelper(bool Pow2WG, bool IsOneWG, nd_item<Dims> NDIt,
   for (size_t E = 0; E < NElements; ++E) {
 
     // Copy the element to local memory to prepare it for tree-reduction.
-    LocalReds[LID] = ReducerAccess{Reducer}.getElement(E);
+    LocalReds[LID] = getReducerAccess(Reducer).getElement(E);
 
     doTreeReduction(WGSize, LID, Pow2WG, Identity, LocalReds, BOp,
                     [&]() { NDIt.barrier(); });