@@ -2389,6 +2389,11 @@ impl<D: Decoder> Decodable<D> for EncodedMetadata {
23892389
23902390#[ instrument( level = "trace" , skip( tcx) ) ]
23912391pub fn encode_metadata ( tcx : TyCtxt < ' _ > , path : & Path , ref_path : Option < & Path > ) {
2392+ // Since encoding metadata is not in a query, and nothing is cached,
2393+ // there's no need to do dep-graph tracking for any of it.
2394+ tcx. dep_graph . assert_ignored ( ) ;
2395+ 2396+ // Generate the metadata stub manually, as that is a small file compared to full metadata.
23922397 if let Some ( ref_path) = ref_path {
23932398 let _prof_timer = tcx. prof . verbose_generic_activity ( "generate_crate_metadata_stub" ) ;
23942399
@@ -2401,11 +2406,14 @@ pub fn encode_metadata(tcx: TyCtxt<'_>, path: &Path, ref_path: Option<&Path>) {
24012406 is_stub : true ,
24022407 } ) ;
24032408 header. position . get ( )
2404- } ) ;
2409+ } )
24052410 }
24062411
2412+ let _prof_timer = tcx. prof . verbose_generic_activity ( "generate_crate_metadata" ) ;
2413+ 24072414 let dep_node = tcx. metadata_dep_node ( ) ;
24082415
2416+ // If the metadata dep-node is green, try to reuse the saved work product.
24092417 if tcx. dep_graph . is_fully_enabled ( )
24102418 && let work_product_id = WorkProductId :: from_cgu_name ( "metadata" )
24112419 && let Some ( work_product) = tcx. dep_graph . previous_work_product ( & work_product_id)
@@ -2422,12 +2430,6 @@ pub fn encode_metadata(tcx: TyCtxt<'_>, path: &Path, ref_path: Option<&Path>) {
24222430 return ;
24232431 } ;
24242432
2425- let _prof_timer = tcx. prof . verbose_generic_activity ( "generate_crate_metadata" ) ;
2426- 2427- // Since encoding metadata is not in a query, and nothing is cached,
2428- // there's no need to do dep-graph tracking for any of it.
2429- tcx. dep_graph . assert_ignored ( ) ;
2430- 24312433 if tcx. sess . threads ( ) != 1 {
24322434 // Prefetch some queries used by metadata encoding.
24332435 // This is not necessary for correctness, but is only done for performance reasons.
@@ -2441,6 +2443,8 @@ pub fn encode_metadata(tcx: TyCtxt<'_>, path: &Path, ref_path: Option<&Path>) {
24412443 ) ;
24422444 }
24432445
2446+ // Perform metadata encoding inside a task, so the dep-graph can check if any encoded
2447+ // information changes, and maybe reuse the work product.
24442448 tcx. dep_graph . with_task (
24452449 dep_node,
24462450 tcx,
@@ -2461,7 +2465,7 @@ pub fn encode_metadata(tcx: TyCtxt<'_>, path: &Path, ref_path: Option<&Path>) {
24612465 ) ;
24622466
24632467 root. position . get ( )
2464- } ) ;
2468+ } )
24652469 } ,
24662470 None ,
24672471 ) ;
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