Merge the two loops in internalize_symbols.

Because they have a lot of overlap.

compiler/rustc_monomorphize/src/partitioning.rs

@@ -486,21 +486,7 @@ fn internalize_symbols<'tcx>(
     mono_item_placements: FxHashMap<MonoItem<'tcx>, MonoItemPlacement>,
     internalization_candidates: FxHashSet<MonoItem<'tcx>>,
 ) {
-    if codegen_units.len() == 1 {
+    let single_codegen_unit = codegen_units.len() == 1;
-        // Fast path for when there is only one codegen unit. In this case we
-        // can internalize all candidates, since there is nowhere else they
-        // could be used from.
-        for cgu in codegen_units {
-            for (item, linkage_and_visibility) in cgu.items_mut() {
-                if !internalization_candidates.contains(item) {
-                    // This item is no candidate for internalizing, so skip it.
-                    continue;
-                }
-                *linkage_and_visibility = (Linkage::Internal, Visibility::Default);
-            }
-        }
-        return;
-    }
 
     // For each internalization candidates in each codegen unit, check if it is
     // used from outside its defining codegen unit.
@@ -512,6 +498,8 @@ fn internalize_symbols<'tcx>(
                 // This item is no candidate for internalizing, so skip it.
                 continue;
             }
+
+            if !single_codegen_unit {
                 debug_assert_eq!(mono_item_placements[item], home_cgu);
 
                 if let Some(user_items) = cx.usage_map.get_user_items(*item) {
@@ -529,6 +517,7 @@ fn internalize_symbols<'tcx>(
                         continue;
                     }
                 }
+            }
 
             // If we got here, we did not find any uses from other CGUs, so
             // it's fine to make this monomorphization internal.