Provide default MetadataLoader

compiler/rustc_codegen_cranelift/src/lib.rs

@@ -28,7 +28,7 @@ use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_codegen_ssa::CodegenResults;
 use rustc_errors::ErrorReported;
 use rustc_middle::dep_graph::{WorkProduct, WorkProductId};
-use rustc_middle::middle::cstore::{EncodedMetadata, MetadataLoader};
+use rustc_middle::middle::cstore::EncodedMetadata;
 use rustc_session::config::OutputFilenames;
 use rustc_session::Session;
 
@@ -163,10 +163,6 @@ impl CodegenBackend for CraneliftCodegenBackend {
         }
     }
 
-    fn metadata_loader(&self) -> Box<dyn MetadataLoader + Sync> {
-        Box::new(rustc_codegen_ssa::back::metadata::DefaultMetadataLoader)
-    }
-
     fn target_features(&self, _sess: &Session) -> Vec<rustc_span::Symbol> {
         vec![]
     }

compiler/rustc_codegen_llvm/src/lib.rs

@@ -248,10 +248,6 @@ impl CodegenBackend for LlvmCodegenBackend {
         target_features(sess)
     }
 
-    fn metadata_loader(&self) -> Box<MetadataLoaderDyn> {
-        Box::new(rustc_codegen_ssa::back::metadata::DefaultMetadataLoader)
-    }
-
     fn codegen_crate<'tcx>(
         &self,
         tcx: TyCtxt<'tcx>,

compiler/rustc_codegen_ssa/src/traits/backend.rs

@@ -63,7 +63,14 @@ pub trait CodegenBackend {
         None
     }
 
-    fn metadata_loader(&self) -> Box<MetadataLoaderDyn>;
+    /// The metadata loader used to load rlib and dylib metadata.
+    ///
+    /// Alternative codegen backends may want to use different rlib or dylib formats than the
+    /// default native static archives and dynamic libraries.
+    fn metadata_loader(&self) -> Box<MetadataLoaderDyn> {
+        Box::new(crate::back::metadata::DefaultMetadataLoader)
+    }
+
     fn provide(&self, _providers: &mut Providers) {}
     fn provide_extern(&self, _providers: &mut Providers) {}
     fn codegen_crate<'tcx>(