[SYCL] overlooked const extract bits (#4770)

Signed-off-by: Chris Perkins <chris.perkins@intel.com>

Author: cperkinsintel

sycl/include/sycl/ext/oneapi/sub_group_mask.hpp

@@ -142,7 +142,7 @@ struct sub_group_mask {
 
   template <typename Type, size_t Size,
             typename = sycl::detail::enable_if_t<std::is_integral<Type>::value>>
-  void extract_bits(marray<Type, Size> &bits, id<1> pos = 0) {
+  void extract_bits(marray<Type, Size> &bits, id<1> pos = 0) const {
     size_t cur_pos = pos.get(0);
     for (auto &elem : bits) {
       if (cur_pos < size()) {

sycl/test/extensions/sub_group_mask.cpp

@@ -88,10 +88,15 @@ int main() {
   b_const.extract_bits(r2bc, 16);
   assert(r2 == 128);
   assert(r2bc == 128);
+
   b[31] = true;
-  sycl::marray<char, 6> r3{-1};
+  const auto b_const2{b};
+  sycl::marray<char, 6> r3{-1}, r3bc{-1};
   b.extract_bits(r3, 14);
+  b_const2.extract_bits(r3bc, 14);
   assert(r3[0] == 1 && r3[1] == 2 && r3[2] == 2 && !r3[3] && !r3[4] && !r3[5]);
+  assert(r3bc[0] == 1 && r3bc[1] == 2 && r3bc[2] == 2 && !r3bc[3] && !r3bc[4] &&
+         !r3bc[5]);
   int ibits = 0b1010101010101010101010101010101;
   b.insert_bits(ibits);
   for (size_t i = 0; i < 32; i++) {