Merge dead bb pruning and unreachable bb deduplication.

compiler/rustc_mir_transform/src/remove_unneeded_drops.rs

@@ -38,7 +38,7 @@ impl<'tcx> MirPass<'tcx> for RemoveUnneededDrops {
         // if we applied optimizations, we potentially have some cfg to cleanup to
         // make it easier for further passes
         if should_simplify {
-            simplify_cfg(tcx, body);
+            simplify_cfg(body);
         }
     }
 }