[SYCL][COMPAT] Specialize reverse_bits for nvptx (intel#15805)

This uses a ptx instruction to specialize `syclcompat::bit_reverse` for
NVPTX backend.

---------

Signed-off-by: JackAKirk <[email protected]>

Author: JackAKirk

sycl/include/syclcompat/util.hpp

@@ -162,6 +162,13 @@ inline double cast_ints_to_double(int high32, int low32) {
 template <typename T> inline T reverse_bits(T a) {
   static_assert(std::is_unsigned<T>::value && std::is_integral<T>::value,
                 "unsigned integer required");
+#if defined(__NVPTX__)
+  if constexpr (sizeof(T) == 4) {
+    unsigned result;
+    asm volatile("brev.b32 %0, %1;" : "=r"(result) : "r"(a));
+    return result;
+  }
+#endif // __NVPTX__
   if (!a)
     return 0;
   T mask = 0;