message: Use popcount only on x86.
diff: @@ -61,7 +61,7 @@ impl SmallBitmap {
  self.0 == 0
  }
  - #[target_feature(enable = "popcnt")]
  + #[cfg_attr(target_arch = "x86", target_feature(enable = "popcnt"))]
  unsafe fn present_fast(&self) -> usize {
  self.0.count_ones() as usize
  }
  @@ -79,7 +79,7 @@ impl SmallBitmap {
  /// Get the sparse array index from a level index
  #[inline]
  - #[target_feature(enable = "popcnt")]
  + #[cfg_attr(target_arch = "x86", target_feature(enable = "popcnt"))]
  unsafe fn get_index_sparse_fast(&self, b: LevelIndex) -> ArrayIndex {
  let mask = b.mask();
  if self.0 & mask == 0 {
  @@ -95,7 +95,7 @@ impl SmallBitmap {
  }
  #[inline]
  - #[target_feature(enable = "popcnt")]
  + #[cfg_attr(target_arch = "x86", target_feature(enable = "popcnt"))]
  unsafe fn get_sparse_pos_fast(&self, b: LevelIndex) -> ArrayIndex {
  let mask = b.mask();
  ArrayIndex::create((self.0 & (mask - 1)).count_ones() as usize)
  