message: Add comment to explain manual optimization
diff: @@ -44,6 +44,9 @@ impl SbTag {
  impl PartialEq for SbTag {
  fn eq(&self, other: &Self) -> bool {
  + // The codegen for the derived Partialeq is bad here and includes a branch.
  + // Since this code is extremely hot, this is optimized here.
  + // https://github.com/rust-lang/rust/issues/49892
  self.as_u64() == other.as_u64()
  }
  }
  