Unify alignPtrTo implementation (#2275)

common/src/KokkosKernels_Utils.hpp

@@ -1527,41 +1527,18 @@ struct array_sum_reduce {
   }
 };
 
-/* Several alternatives were considered for SYCL, including
-
-unsigned int f1(unsigned int i, unsigned int align)
-{
-    return ((i + align - 1) / align * align);
-}
-
-unsigned int f2(unsigned int i, unsigned int align)
-{
-    return (i + align - 1) & (-align);
-}
-
-f1 should be equivalent to the below, but it produces incorrect results on SYCL
-f2 is how GCC does std::align, but it also produces incorrect results on SYCL
-possibly alignof(T) is not a power-of-2 on SYCL? Or a compiler error.
-*/
-#if defined(KOKKOS_ENABLE_SYCL)
 template <typename T, typename InPtr>
-KOKKOS_INLINE_FUNCTION T *alignPtrTo(InPtr p) {
-  std::uintptr_t ptrVal = reinterpret_cast<std::uintptr_t>(p);
-  while (ptrVal % alignof(T)) {
-    ++ptrVal;
-  }
-  return reinterpret_cast<T *>(ptrVal);
-}
-#else
-template <typename T, typename InPtr>
-KOKKOS_INLINE_FUNCTION T *alignPtrTo(InPtr p) {
+KOKKOS_INLINE_FUNCTION T *alignPtrTo(InPtr *p) {
   // ugly but computationally free and the "right" way to do this in C++
-  std::uintptr_t ptrVal = reinterpret_cast<std::uintptr_t>(p);
+  const std::uintptr_t ptrVal = reinterpret_cast<std::uintptr_t>(p);
   // ptrVal + (align - 1) lands inside the next valid aligned scalar_t,
   // and the mask produces the start of that scalar_t.
-  return reinterpret_cast<T *>((ptrVal + alignof(T) - 1) & (~(alignof(T) - 1)));
+  const std::uintptr_t ptrValNew =
+      (ptrVal + alignof(T) - 1) & (~(alignof(T) - 1));
+  return reinterpret_cast<T *>(
+      reinterpret_cast<char *>(const_cast<std::remove_cv_t<InPtr> *>(p)) +
+      (ptrValNew - ptrVal));
 }
-#endif
 
 }  // namespace Impl
 }  // namespace KokkosKernels