explain

src/intrinsics/mod.rs

@@ -275,6 +275,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
                     _ => bug!(),
                 };
                 let res = this.wrapping_binary_op(op, &a, &b)?;
+                // `wrapping_binary_op` already called `generate_nan` if necessary.
                 this.write_immediate(*res, dest)?;
             }