Save metadata among work products.

Author: cjgillot

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -520,6 +520,7 @@ pub(crate) fn start_async_codegen<B: ExtraBackendMethods>(
 
 fn copy_all_cgu_workproducts_to_incr_comp_cache_dir(
     sess: &Session,
+    metadata: &EncodedMetadata,
     compiled_modules: &CompiledModules,
 ) -> FxIndexMap<WorkProductId, WorkProduct> {
     let mut work_products = FxIndexMap::default();
@@ -530,6 +531,14 @@ fn copy_all_cgu_workproducts_to_incr_comp_cache_dir(
 
     let _timer = sess.timer("copy_all_cgu_workproducts_to_incr_comp_cache_dir");
 
+    if let Some(path) = metadata.path() {
+        if let Some((id, product)) =
+            copy_cgu_workproduct_to_incr_comp_cache_dir(sess, "metadata", &[("rmeta", path)])
+        {
+            work_products.insert(id, product);
+        }
+    }
+
     for module in compiled_modules.modules.iter().filter(|m| m.kind == ModuleKind::Regular) {
         let mut files = Vec::new();
         if let Some(object_file_path) = &module.object {
@@ -2059,8 +2068,11 @@ impl<B: ExtraBackendMethods> OngoingCodegen<B> {
 
         sess.dcx().abort_if_errors();
 
-        let work_products =
-            copy_all_cgu_workproducts_to_incr_comp_cache_dir(sess, &compiled_modules);
+        let work_products = copy_all_cgu_workproducts_to_incr_comp_cache_dir(
+            sess,
+            &self.metadata,
+            &compiled_modules,
+        );
         produce_final_output_artifacts(sess, &compiled_modules, &self.output_filenames);
 
         // FIXME: time_llvm_passes support - does this use a global context or

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -2205,6 +2205,8 @@ fn prefetch_mir(tcx: TyCtxt<'_>) {
 pub struct EncodedMetadata {
     // The declaration order matters because `mmap` should be dropped before `_temp_dir`.
     mmap: Option<Mmap>,
+    // The path containing the metadata, to record as work product.
+    path: Option<Box<Path>>,
     // We need to carry MaybeTempDir to avoid deleting the temporary
     // directory while accessing the Mmap.
     _temp_dir: Option<MaybeTempDir>,
@@ -2216,16 +2218,21 @@ impl EncodedMetadata {
         let file = std::fs::File::open(&path)?;
         let file_metadata = file.metadata()?;
         if file_metadata.len() == 0 {
-            return Ok(Self { mmap: None, _temp_dir: None });
+            return Ok(Self { mmap: None, path: None, _temp_dir: None });
         }
         let mmap = unsafe { Some(Mmap::map(file)?) };
-        Ok(Self { mmap, _temp_dir: temp_dir })
+        Ok(Self { mmap, path: Some(path.into()), _temp_dir: temp_dir })
     }
 
     #[inline]
     pub fn raw_data(&self) -> &[u8] {
         self.mmap.as_deref().unwrap_or_default()
     }
+
+    #[inline]
+    pub fn path(&self) -> Option<&Path> {
+        self.path.as_deref()
+    }
 }
 
 impl<S: Encoder> Encodable<S> for EncodedMetadata {
@@ -2249,7 +2256,7 @@ impl<D: Decoder> Decodable<D> for EncodedMetadata {
             None
         };
 
-        Self { mmap, _temp_dir: None }
+        Self { mmap, path: None, _temp_dir: None }
     }
 }