Reference count crate_inherent_implss return value.

The repeated cloning of the result in `inherent_impls` queries has quite an impact on crates with many inherent trait implementations.

Author: hugwijst

src/librustc/ty/query/mod.rs

@@ -291,7 +291,8 @@ define_queries! { <'tcx>
  /// Gets a complete map from all types to their inherent impls.
  /// Not meant to be used directly outside of coherence.
  /// (Defined only for LOCAL_CRATE)
- [] fn crate_inherent_impls: crate_inherent_impls_dep_node(CrateNum) -> CrateInherentImpls,
+ [] fn crate_inherent_impls: crate_inherent_impls_dep_node(CrateNum)
+ -> Lrc<CrateInherentImpls>,
 
  /// Checks all types in the krate for overlap in their inherent impls. Reports errors.
  /// Not meant to be used directly outside of coherence.

src/librustc_typeck/coherence/inherent_impls.rs

@@ -31,7 +31,7 @@ use syntax_pos::Span;
 /// On-demand query: yields a map containing all types mapped to their inherent impls.
 pub fn crate_inherent_impls<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
  crate_num: CrateNum)
- -> CrateInherentImpls {
+ -> Lrc<CrateInherentImpls> {
  assert_eq!(crate_num, LOCAL_CRATE);
 
  let krate = tcx.hir.krate();
@@ -42,7 +42,7 @@ pub fn crate_inherent_impls<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
  }
  };
  krate.visit_all_item_likes(&mut collect);
- collect.impls_map
+ Lrc::new(collect.impls_map)
 }
 
 /// On-demand query: yields a vector of the inherent impls for a specific type.