Auto merge of #115657 - Zoxc:source-span-avoid-query, r=cjgillot

Avoid a `source_span` query when encoding Spans into query results

This avoids a `source_span` query when encoding `Span`s into query results. It's not sound to execute queries here as the query caches can be locked and the dep graph is no longer writable.

r? `@cjgillot`

compiler/rustc_incremental/src/persist/save.rs

@@ -47,18 +47,6 @@ pub fn save_dep_graph(tcx: TyCtxt<'_>) {
         }
 
         join(
-            move || {
-                sess.time("incr_comp_persist_result_cache", || {
-                    // Drop the memory map so that we can remove the file and write to it.
-                    if let Some(odc) = &tcx.query_system.on_disk_cache {
-                        odc.drop_serialized_data(tcx);
-                    }
-
-                    file_format::save_in(sess, query_cache_path, "query cache", |e| {
-                        encode_query_cache(tcx, e)
-                    });
-                });
-            },
             move || {
                 sess.time("incr_comp_persist_dep_graph", || {
                     if let Err(err) = tcx.dep_graph.encode(&tcx.sess.prof) {
@@ -73,6 +61,20 @@ pub fn save_dep_graph(tcx: TyCtxt<'_>) {
                     }
                 });
             },
+            move || {
+                // We execute this after `incr_comp_persist_dep_graph` for the serial compiler
+                // to catch any potential query execution writing to the dep graph.
+                sess.time("incr_comp_persist_result_cache", || {
+                    // Drop the memory map so that we can remove the file and write to it.
+                    if let Some(odc) = &tcx.query_system.on_disk_cache {
+                        odc.drop_serialized_data(tcx);
+                    }
+
+                    file_format::save_in(sess, query_cache_path, "query cache", |e| {
+                        encode_query_cache(tcx, e)
+                    });
+                });
+            },
         );
     })
 }

compiler/rustc_middle/src/query/on_disk_cache.rs

@@ -896,7 +896,7 @@ impl<'a, 'tcx> Encodable<CacheEncoder<'a, 'tcx>> for Span {
         }
 
         if let Some(parent) = span_data.parent {
-            let enclosing = s.tcx.source_span(parent).data_untracked();
+            let enclosing = s.tcx.source_span_untracked(parent).data_untracked();
             if enclosing.contains(span_data) {
                 TAG_RELATIVE_SPAN.encode(s);
                 (span_data.lo - enclosing.lo).to_u32().encode(s);