Don't perform the more complex analysis for debug builds

Author: ohadravid

compiler/rustc_mir_transform/src/copy_prop.rs

@@ -59,22 +59,26 @@ impl<'tcx> crate::MirPass<'tcx> for CopyProp {
         }
         .visit_body_preserves_cfg(body);
 
-        if any_replacement {
-            let move_data = MoveData::gather_moves(body, tcx, |_| true);
+        debug!(?head_storage_to_check);
 
-            let maybe_uninit = MaybeUninitializedPlaces::new(tcx, body, &move_data)
-                .iterate_to_fixpoint(tcx, body, Some("mir_opt::copy_prop"))
-                .into_results_cursor(body);
+        if any_replacement {
+            // Debug builds have no use for the storage statements, so avoid extra work.
+            let storage_to_remove = if tcx.sess.emit_lifetime_markers() {
+                let move_data = MoveData::gather_moves(body, tcx, |_| true);
 
-            debug!(?head_storage_to_check);
+                let maybe_uninit = MaybeUninitializedPlaces::new(tcx, body, &move_data)
+                    .iterate_to_fixpoint(tcx, body, Some("mir_opt::copy_prop"))
+                    .into_results_cursor(body);
 
-            let storage_to_remove = {
                 let mut storage_checker =
                     StorageChecker { maybe_uninit, head_storage_to_check, storage_to_remove };
 
                 storage_checker.visit_body(body);
 
                 storage_checker.storage_to_remove
+            } else {
+                // Conservatively remove all storage statements for the head locals.
+                head_storage_to_check
             };
             StorageRemover { tcx, storage_to_remove }.visit_body_preserves_cfg(body);