Minor comment cleanups.

lib/frontend/src/ssa.rs

@@ -422,8 +422,8 @@ where
         let mut preds = Vec::new();
         mem::swap(&mut preds, &mut self.predecessors_mut(dest_ebb));
         for &(pred, last_inst) in preds.iter() {
-            // For undef value  and each predecessor we query what is the local SSA value
-            // corresponding to var and we put it as an argument of the branch instruction.
+            // For each predecessor, we query what is the local SSA value corresponding
+            // to var and we put it as an argument of the branch instruction.
             let (pred_val, mut local_side_effects) =
                 self.use_var(dfg, layout, jts, temp_arg_var, ty, pred);
             pred_values = match pred_values {