MIR inlining: allow backends to opt-in to inlining intrinsics

Author: RalfJung

src/lib.rs

@@ -98,7 +98,7 @@ use rustc_middle::ty::TyCtxt;
 use rustc_middle::util::Providers;
 use rustc_session::Session;
 use rustc_session::config::{OptLevel, OutputFilenames};
-use rustc_span::Symbol;
+use rustc_span::{Symbol, sym};
 use rustc_target::spec::{Arch, RelocModel};
 use tempfile::TempDir;
 
@@ -311,6 +311,10 @@ impl CodegenBackend for GccCodegenBackend {
     fn target_config(&self, sess: &Session) -> TargetConfig {
         target_config(sess, &self.target_info)
     }
+
+    fn fallback_intrinsics(&self) -> Vec<Symbol> {
+        vec![sym::type_id_eq]
+    }
 }
 
 fn new_context<'gcc, 'tcx>(tcx: TyCtxt<'tcx>) -> Context<'gcc> {