Provide a default provide* implementation for CodegenBackend

Both cg_llvm and cg_clif don't override it. cg_spirv does override it,
so it needs to be preserved.

Author: bjorn3

compiler/rustc_codegen_cranelift/src/lib.rs

@@ -29,7 +29,6 @@ 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::ty::query::Providers;
 use rustc_session::config::OutputFilenames;
 use rustc_session::Session;
 
@@ -168,9 +167,6 @@ impl CodegenBackend for CraneliftCodegenBackend {
         Box::new(rustc_codegen_ssa::back::metadata::DefaultMetadataLoader)
     }
 
-    fn provide(&self, _providers: &mut Providers) {}
-    fn provide_extern(&self, _providers: &mut Providers) {}
-
     fn target_features(&self, _sess: &Session) -> Vec<rustc_span::Symbol> {
         vec![]
     }

compiler/rustc_codegen_llvm/src/lib.rs

@@ -252,9 +252,6 @@ impl CodegenBackend for LlvmCodegenBackend {
         Box::new(rustc_codegen_ssa::back::metadata::DefaultMetadataLoader)
     }
 
-    fn provide(&self, _providers: &mut ty::query::Providers) {}
-    fn provide_extern(&self, _providers: &mut ty::query::Providers) {}
-
     fn codegen_crate<'tcx>(
         &self,
         tcx: TyCtxt<'tcx>,

compiler/rustc_codegen_ssa/src/traits/backend.rs

@@ -64,8 +64,8 @@ pub trait CodegenBackend {
     }
 
     fn metadata_loader(&self) -> Box<MetadataLoaderDyn>;
-    fn provide(&self, _providers: &mut Providers);
-    fn provide_extern(&self, _providers: &mut Providers);
+    fn provide(&self, _providers: &mut Providers) {}
+    fn provide_extern(&self, _providers: &mut Providers) {}
     fn codegen_crate<'tcx>(
         &self,
         tcx: TyCtxt<'tcx>,