3 files changed, 6 insertions, 9 deletions
diff --git a/src/librustc_metadata/encoder.rs b/src/librustc_metadata/encoder.rs
index 1b208a512e2..e40a3057a95 100644
--- a/src/librustc_metadata/encoder.rs
+++ b/src/librustc_metadata/encoder.rs
@@ -1414,7 +1414,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
         let mut all_impls: Vec<_> = visitor.impls.into_iter().collect();
 
         // Bring everything into deterministic order for hashing
-        all_impls.sort_unstable_by_key(|&(trait_def_id, _)| {
+        all_impls.sort_by_cached_key(|&(trait_def_id, _)| {
             tcx.def_path_hash(trait_def_id)
         });
 
@@ -1422,7 +1422,7 @@ impl<'a, 'b: 'a, 'tcx: 'b> IsolatedEncoder<'a, 'b, 'tcx> {
             .into_iter()
             .map(|(trait_def_id, mut impls)| {
                 // Bring everything into deterministic order for hashing
-                impls.sort_unstable_by_key(|&def_index| {
+                impls.sort_by_cached_key(|&def_index| {
                     tcx.hir.definitions().def_path_hash(def_index)
                 });
 
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index e89b5a7fc1b..76a14cf44f2 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -21,6 +21,7 @@
 #![feature(macro_lifetime_matcher)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
+#![feature(slice_sort_by_cached_key)]
 #![feature(specialization)]
 #![feature(rustc_private)]
 
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index c1a7f20feff..9ca7d1a372b 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -1151,13 +1151,9 @@ impl<'a> ModuleData<'a> {
 
     fn for_each_child_stable<F: FnMut(Ident, Namespace, &'a NameBinding<'a>)>(&self, mut f: F) {
         let resolutions = self.resolutions.borrow();
-        let mut resolutions = resolutions.iter().map(|(&(ident, ns), &resolution)| {
-                                                    // Pre-compute keys for sorting
-                                                    (ident.name.as_str(), ns, ident, resolution)
-                                                })
-                                                .collect::<Vec<_>>();
-        resolutions.sort_unstable_by_key(|&(str, ns, ..)| (str, ns));
-        for &(_, ns, ident, resolution) in resolutions.iter() {
+        let mut resolutions = resolutions.iter().collect::<Vec<_>>();
+        resolutions.sort_by_cached_key(|&(&(ident, ns), _)| (ident.name.as_str(), ns));
+        for &(&(ident, ns), &resolution) in resolutions.iter() {
             resolution.borrow().binding.map(|binding| f(ident, ns, binding));
         }
     }